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SAHM User`s Manual - Sacramento Stormwater Quality Partnership

1. PERLND No CEPS SURS UZS IFWS LZS AGWS GWVS 1 0 00 0 00 0 15 0 00 4 00 0 05 0 00 2 0 00 0 00 0 15 0 00 4 00 0 05 0 00 3 0 00 0 00 0 15 0 00 4 00 0 05 0 00 4 0 00 0 00 0 15 0 00 4 00 0 05 0 00 5 0 00 0 00 0 15 0 00 4 00 0 05 0 00 6 0 00 0 00 0 15 0 00 4 00 0 05 0 00 7 0 00 0 00 0 15 0 00 4 00 0 05 0 00 8 0 00 0 00 0 15 0 00 4 00 0 05 0 00 9 0 00 0 00 0 15 0 00 4 00 0 05 0 00 10 0 00 0 00 0 15 0 00 4 00 0 05 0 00 11 0 00 0 00 0 15 0 00 4 00 0 05 0 00 12 0 00 0 00 0 15 0 00 4 00 0 05 0 00 13 0 00 0 00 0 15 0 00 4 00 0 05 0 00 14 0 00 0 00 0 15 0 00 4 00 0 05 0 00 15 0 00 0 00 0 15 0 00 4 00 0 05 0 00 16 0 00 0 00 0 15 0 00 4 00 0 05 0 00 17 0 00 0 00 0 15 0 00 4 00 0 05 0 00 18 0 00 0 00 0 15 0 00 4 00 0 05 0 00 19 0 00 0 00 0 15 0 00 4 00 0 05 0 00 20 0 00 0 00 0 15 0 00 4 00 0 05 0 00 21 0 00 0 00 0 15 0 00 4 00 0 05 0 00 22 0 00 0 00 0 15 0 00 4 00 0 05 0 00 23 0 00 0 00 0 15 0 00 4 00 0 05 0 00 24 0 00 0 00 0 15 0 00 4 00 0 05 0 00 25 0 00 0 00 0 15 0 00 4 00 0 05 0 00 26 0 00 0 00 0 15 0 00 4 00 0 05 0 00 27 0 00 0 00 0 15 0 00 4 00 0 05 0 00 28 0 00 0 00 0 15 0 00 4 00 0 05 0 00 29 0 00 0 00 0 15 0 00 4 00 0 05 0 00 30 0 00 0 00 0 15 0 00 4 00 0 05 0 00 31 0 00 0 00 0 15 0 00 4 00 0 05 0 00 32 0 00 0 00 0 15 0 00 4 00 0 05 0 00 33 0 00 0 00 0 15 0 00 4 00 0 05 0 00 34 0 00 0 00 0 15 0 00 4 00 0 05 0 00 35 0 00 0 00 0 15 0 00 4 00 0 05 0 00 36 0 00 0 00 0 15 0
2. Orifice Diameter Height Infiltration Number in ft 1 2 LID Toolbox 3 Pond Volume at Riser Head ac ft 692 Show Pond Table Open Table Initial Stage f a Commercial Toolbox Tide Gate Time Series Demand Move Elements Determine Outlet With Tide Gate Q 4 I Use Tide Gate g Tide Gate Elevation ff 0 Downstream Connection Gece lean Overflow Elevation ft 0 Iterations 0 EM T Boa i Thu 1 50p default 0 Finish Mitigated alley The final pond dimensions bottom length bottom width effective pond depth and side slopes and outlet structure information riser height riser diameter riser weir type weir notch height and width and orifice diameter and height are shown on the trapezoidal pond screen to the right of the Schematic grid NOTE If Auto Pond selects a bottom orifice diameter smaller than the smallest diameter allowed by the local municipal permitting agency then the user has the option of specifying a minimum allowable bottom orifice diameter even if this size diameter is too large to meet flow duration criteria for this element Additional mitigating BMPs may be required to meet local hydromodification control 28 SAHM Guidance Document December 2013 requirements Please see Appendix C or consult with local municipal permitting agency for more details For manual sizing inform
3. Upstream Storage Area Length ft Maximum Depth of Ponding ft Primary Exit 1 Structure Secondary Exit 2 Structure Control Stucture H Control Stucture H Riser Height ft fo y Riser Height ft b Riser Diameter fi o H Riser Diameter in jo H RiserType Fia H Riser Type fia H Pro Elements Diameter Height Orifice Diameter Height LID Toolbox aa T in fh Ces Cte A 2h dh 4 3 de a Commercial Toolbox Volume at Top of Storage area ac ft 000 Show Splitter Table OpenTable r Move Elements Initial Stage ft 0 N eg Save xy Load xy x 2o y fg The flow splitter divides the runoff and sends it to two difference destinations The splitter has a primary exit exit 1 and a secondary exit exit 2 The user defines how the flow is split between these two exits The user can define a flow control structure with a riser and one to three orifices for each exit The flow control structure works the same way as the pond outlet structure with the user setting the riser height and diameter the riser weir type flat rectangular notch V notch or Sutro and the orifice diameter and height For more information on riser notch options and orifices see discussion in OUTLET STRUCTURE CONFIGURATIONS section 90 SAHM Guidance Document December 2013 File Edit Vi
4. Move Elements Run Predeveloped iE p 4 Run Mitigated 3 Ages KE 10 Acres f Clear All Gave xy Loadxy Import Basin Location 5 Select By a Go x Bo i Hat The exit from this land use basin will be selected as our point of compliance for the Pre project scenario Right click on the basin element and highlight Connect to Point of Compliance the point of compliance is defined as the project location at which the runoff from both the Pre project scenario and the Mitigated scenario are compared The Point of Compliance screen will be shown for Pre project Basin 1 The POC Point of Compliance outlet has been checked for both surface runoff and interflow shallow subsurface flow These are the two flow components of stormwater runoff Do not check the groundwater box unless there is observed and documented base flow on the project site Element Basin 1 POC Outlet WV Surface Flow JV Interflow Groundwater Select POC ADD Connect Click the Connect button in the low right corner to connect this point of compliance to the Pre project basin 14 SAHM Guidance Document December 2013 File Edit View Help Summary Report amp FIELET I FICER Subbasin Name Basin 1 Surface Flows To Area in Basin Available Pervious Acres gt D Grass Mod 1 2 fl E Pevoustoisi OT tes imperious Til Bd Aces Basina Dd es Deselect Z
5. PERLND No Soil Type Land Cover Land Slope 1 A Grass Flat 0 1 2 A Grass Moderate 1 2 3 A Grass Steep 2 5 4 A Grass Very Steep gt 5 5 A Agricultural Flat 0 1 6 A Agricultural Moderate 1 2 7 A Agricultural Steep 2 5 8 A Agricultural Very Steep gt 5 9 A Urban Flat 0 1 10 A Urban Moderate 1 2 11 A Urban Steep 2 5 12 A Urban Very Steep gt 5 13 A Trees Flat 0 1 14 A Trees Moderate 1 2 15 A Trees Steep 2 5 16 A Trees Very Steep gt 5 17 B Grass Flat 0 1 18 B Grass Moderate 1 2 19 B Grass Steep 2 5 20 B Grass Very Steep gt 5 21 B Agricultural Flat 0 1 22 B Agricultural Moderate 1 2 23 B Agricultural Steep 2 5 24 B Agricultural Very Steep gt 5 25 B Urban Flat 0 1 26 B Urban Moderate 1 2 27 B Urban Steep 2 5 28 B Urban Very Steep gt 5 29 B Trees Flat 0 1 30 B Trees Moderate 1 2 31 B Trees Steep 2 5 32 B Trees Very Steep gt 5 33 C Grass Flat 0 1 34 C Grass Moderate 1 2 35 C Grass Steep 2 5 36 C Grass Very Steep gt 5 37 C Agricultural Flat 0 1 46 SAHM Guidance Document December 2013 38 C Agricultural Moderate 1 2 39 C Agricultural Steep 2 5 40 C Agricultural Very Steep gt 5 41 C Urban Flat 0 1 42 C Urban Moderate 1 2 43 C Urban Steep 2 5 44 C Urban Very Steep gt 5 45
6. Pond drawdown retention time is computed on the Analysis screen NOTE This information is not required for basic sizing of the flow duration facility but can assist the user in determining the overall suitability of the mitigated design in meeting additional related requirements for treating stormwater runoff and minimizing risk of vector mosquito breeding problems See page 133 for more descriptions of this SAHM feature and Appendix C for discussion and references for these requirements Click on the Stage tab at the bottom to get the Mitigated pond stage time series 31 SAHM Guidance Document December 2013 File Edit View Help Summary Report Ose sae LEELEE TAA LEICA Flow Frequence Drawdown H LID Points Table Analyze datasets Compact WDM 1001 Trapezoidal Pond 1 STAGE Mitigated Duration Bounds JOO Minimum Z Maximum I Seasonal Durations mm dd saose Mbasa Fon r Ev Eros Click on the tab labeled Drawdown This is where the pond drawdown retention time results will be shown 32 SAHM Guidance Document December 2013 File Edit View Help Summary Report Dae te lo last ABSHEA Os SeBE D 2 O All Datasets Flow Stage Precip Evap POC1 Select the pond you want to analyze for drawdown retention time in this example there is only one pond Trapezoidal Pond 1 by clicking on the dataset and highlighting it 33 SAHM Guidance Document Decemb
7. The In Ground Infiltration Planter Box element is located in the LID Toolbox All of the LID Toolbox elements can be viewed and selected by clicking on the LID Toolbox bar An in ground planter allows stormwater to enter the planter above ground and then infiltrate through the soil and gravel storage layers before exiting through a discharge pipe Water can also infiltrate into the native soil beneath the planter For the purpose of flow control the discharge from the pipe should not exceed the pre project discharge from the project site for the flow duration range specified by In Ground Infiltration Planter the local jurisdiction In SAHM the in ground planter is represented by a specialized application of the bioretention swale element 111 SAHM Guidance Document December 2013 The in ground infiltration planter dimensions and parameters are Planter Length ft Length of planter box Planter Bottom Width ft Width of planter box Freeboard ft Additional storage height above top of riser Effective Total Depth ft Planter height from bottom of planter to top of riser plus freeboard Soil Layer 1 Type Select from Soil Type pulldown menu Soil Layer 1 ft Planter soil layer depth Soil Layer 2 Type Select from Soil Type pulldown menu usually gravel Soil Layer 2 ft Planter gravel layer depth Underdrain Diameter ft Planter underdrain pipe diameter set to zero if no underdrain is incl
8. NOTE See Appendix C or consult Orifice Diameter Height fh with the local municipal permitting ra aa E S a A Reis F 7 0 agency for additional considerations i dem ad m A x f se Wetted Surface Area sidewalls ry 0 regarding infiltration and Total Vole tated act Total Volume Through Riser ac ft Pond Volume at Riser Head ac ft 0 determination of the appropriate Toae Through Facility act 0 00 Show Pond Table Open Tabe infiltration reduction factor ieee Size Infiltration Pond Target 100 The user clicks on the Infiltration option Tee Time Series Demand p es gt Determine Outlet With Tide Gate arrow to change infiltration from NO to F use Tide Gate H H Tide Gate Elevation ft 0 Ss Downstream Connection YES This activates the infiltration ee e input options measured infiltration rate infiltration reduction factor and whether or not to allow infiltration through the wetted side slopes walls The infiltration reduction factor is a multiplier for the measured infiltration rate and should be less than one It is the same as the inverse of a safety factor For example a safety factor of 2 is equal to a reduction factor of 0 5 Infiltration occurs only through the bottom of the facility if the wetted surface area option is turned off Otherwise the entire wetted surface area is used for infiltration After the model
9. Auto Pond Quick Pond Facility Dimension Diagram Facility Dimensions Outlet Structure Data Facility Bottom Elevation ft Fier Hearst e E Eitens Riser Diameter in D H Bottom Width f noa RE E Effective Depth ft Notch Type Left Side Slope H V Bottom Side Slope H V Right Side Slope HAV Top Side Slope H V Orifice Diameter Height Number in m 1 Co oe aE 3 ce coe Disconnect POC Pond Volume at Riser Head ac ft 0 Cee ETE Show Pond Table Open Tabe initial Stege P Find Element Cut Element Copy Element Paste Element Delete Element Duplicate Predeveloped Save Element Load Element Run Predeveloped Run Mitigated Clear All Commercial Toolbox Import Basin Location Right click on the trapezoidal pond element to connect the pond s outlet to the point of compliance Highlight Connect to Point Of Compliance and click 21 SAHM Guidance Document December 2013 File Edit View Help Summary Report De e se ie S g M Mitigated wE AS 5 apezoidal Pond 1 Mitigated Facility Name asea Facility Type CACEN Or SMO ETERA Outlet 2 Outlet 3 Downstream Connections I Precipitation Applied to Facility Evaporation Applied to Facility Facility Dimensions Facility Bottom Elevation ft Bottom Length ft Bottom Width ft Effective Depth ft Auto Pond Quick Pond Facility Dimension Diagram _Outlet Struct
10. Flows To Trapezoidal Pond 1 LID Toolbox Commercial Toolbox Move Elements 4 Sy Save xy Load xy SAHM uses time series of precipitation evaporation and runoff stored in its database HSPF WDM file The user has the option to create or use an external time series file in SAHM This may be a time series of flow values created by another HSPF model An example is offsite runoff entering a project site If this offsite runoff is in an existing WDM file and is the same period as SAHM data and the same simulation time step hourly then it can be linked to SAHM model using the Time Series element To link the external time series to SAHM the user clicks on the Choose WDM button and identifies the external WDM file The external WDM s individual time series files are shown in the Time Series Out box The selected input dataset is the time series that will be used by SAHM 92 SAHM Guidance Document December 2013 STAGE STORAGE DISCHARGE TABLE File Edit View Help Summary Report DEH tee AHGHEA Or SBE Stslalelst Sham fete Z Trapezoid pod ooo ooo Loo Stage Storage Dschrge Infilt u ft ER acre ft cfs cfs H C Pre Project 000000 044444 088889 133333 EG 222222 266667 T a le le kk l 355556 400000 444444 488889 533333 577778 622222 666667 Agia bral 755556 800000 844444 8
11. Vault 1 If an analysis point i d then the EI is use user must select the SE 1000 time series Set up using Analysis Points Set up using POC numbers for the post unmit volume and 233 SAHM Guidance Document December 2013 the post mit volume based on the elements names The post mit volume will be from Outlet 1 except when using the Flow Splitter threshold option then the post mit volume will be from Outlet 2 If the POC number is then the user should select time series 501 for the pre volume 701 for the post unmit volume and 801 for the post mit volume These time series are based on the element names selected by the user 234 SAHM Guidance Document December 2013 Compost amended soil In the Pre Project scenario the Pre volume is modeled using a Basin element containing the drainage area of the pre project land use A point of compliance POC is assigned by the user to the Basin element Only surface runoff and interflow are connected to the POC In the Mitigated scenario the Unmitigated volume is modeled using a Basin element consisting of both impervious area and any pervious area draining to a compost amended soil represented by the Bioretention element For this element a separate POC is not needed to record the Unmitigated volume If an analysis point is used instead of a POC then there must be a conveyance element for example a Channel element imme
12. Sl Mitigated 801 for the post mit Run Scenario 7 volume These time Basic Elements series are based on the element names in Selected by the user E CO Pre Project pan A Mitigated If an analysis point is used then the user must select the 1000 time series numbers for the post unmit volume and the post 1 mit volume based on the elements names The post mit volume will be from Outlet 1 Set up using Analysis Points Set up using POC 240 SAHM Guidance Document December 2013 Sand Filter In the Pre Project scenario the Pre volume is modeled using a Basin element containing the drainage area of the pre project land use A point of compliance POC is assigned by the user to the Basin element Only surface runoff and interflow are connected to the POC In the Mitigated scenario the Unmitigated volume is modeled using a Basin element consisting of both impervious area and any pervious area draining to a Sand Filter element For this element a separate POC is not needed to record the Unmitigated volume If an analysis point is used instead of a POC then there must be a conveyance element for example a Channel element immediately upstream of the Sand Filter element The upstream conveyance element must include an analysis point to record the Unmitigated volume In the Mitigated scenario the sand filter Mitigated volume can be re
13. To save the project click on File in the upper left corner and select Save As 37 SAHM Guidance Document December 2013 M i Windows8_0S C gt ProgramData SAHM projects v Search projects Organize v New folder l SkyDrive Name Date modified Type gt default 2 27 2010 4 58 PM whm Document Libraries S default 0 2 27 2010 5 58 PM whm Document B Documents d Music Pictures E Videos 28 Homegroup A Doug Computer i Windows8_0S C Local Disk E a Hide Folders Select a file name and save the SAHM project file Note that the project file name will automatically be given the file extension whm The user can exit SAHM and later reload the project file with all of its information by going to File Open 38 SAHM Guidance Document December 2013 10 Exit SAHM Edit View Help Summary Report Facility Name lapesisFendt Fociiy Type aesae Outlet 1 ASHE Oe AI EIEE Outlet 2 Outlet 3 Downstream Connections PEE Bn Bd I Precipitation Applied to Facility 7 vena applet Fas Facility Dimensions Facility Bottom Elevation ft Bottom Length ft Bottom Width ft Effective Depth ft Left Side Slope HAV Bottom Side Slope HV Right Side Slope H V Top Side Slope HAV Infiltration Tide Gate Time Series Demand C Ar Pond _ouickPond _ Facility Dimension Diagram _ _Outlet Structure Data Ris
14. Drawdown LUD Points Table Analyze datasets Compact WDM 1 San Diego Pan Evap Duration Bounds 2 Rancho C OT Minimum 2 Maximum Seasonal Durations mm dd 22 From Alameda irrigation dsn 24 501 1 flow tigated flow 1000 Trapezoidal Pond 1 ALL OUTLETS Mitigated 1001 Trapezoidal Pond 1 STAGE Mitigated Start Date e Al Datasets Flow Stage J Precip Evap POC1 EndDate The user can calculate LID points by selecting the LID Points Table tab 138 SAHM Guidance Document December 2013 File Edit View Help Summary Report Del s2e ELEERI EI FICER Lop for Lat zn SS Be 5 LID Points Table x a LID Measures Pre Pre Vol PostUnmitElementName Post Post Unmit Post Mit Element Name Post Mit Postmit LID Pts Time ac ft Unmit Vol Time Vol Series Time _ ac ft Series ac ft Series LID points are calculated based on the following equation 200 Post Unmit Vol Post Mit Vol Post Unmit Vol Pre Vol where Post Unmit Vol the volume of the post development unmitigated runoff for the entire simulation period Post Mit Vol the volume of the post development mitigated runoff for the entire simulation period Pre Vol the volume of the pre project runoff for the entire simulation period The goal is for the entire project to have a LID points total of at least 100 points 139 SAHM Guidance Document December 2013 File Edit Vi
15. If the green roof is connected to a downstream element or is selected as a point of compliance the user should make sure that the groundwater runoff is included Unlike the other drainage area elements basin element etc the green roof groundwater always contributes to the total runoff The green roof groundwater has nowhere else to go 110 SAHM Guidance Document December 2013 IN GROUND INFILTRATION PLANTER BOX ELEMENT File Edit View Help Summary Report Der tiy oc CA ASHES Oe S I EILEAS is Facility Name Outlet2 Outlet3 C Pre Project Downstream Connection E Facility Type ox E Miioated PU Quick Planter 5 7 Size Infiltration Planter Maximum Planter Area ac Underdrain Diameter ft Target fio H Orifice Diameter in Planter Box Dimensions Planter Length ft Planter Bottom Width ft Freeboard ft Effective Total Depth ft Material Layers for Planter Depth ft Outlet Structure Data Riser Height Above Planter surface ft 9 H Riser Diameter in Native Infiltration Native Infiltration in hr Total Volume Through Facility ac ft Commercial Toolbox Total Volume Through Riser ac t Total Volume Infiltrated ac ft Percent Infiltrated Flow Through Underdrain ac ft Move Elements gt N Percent Through Underdrain Ke Show Planter Table OpenTable H La S Planter Volume at Riser Head ac ft 000 Save xy Load xy
16. SAHM Guidance Document December 2013 File Edit View Zoom Help DSH te BASUEN Ose Saulo Surface Area in Basin A Grass Flat 0 1 E PerviousTotal impens Tol O Aeee BasnTai Ae DeselectZero SeletBy co The final screen will look like the above screen The basin information screen on the right will show that Basin 1 surface and interflow flows to Trapezoidal Pond 1 groundwater is not connected 126 SAHM Guidance Document December 2013 ANALYSIS SCREEN SAM Bape AHBSHE OR Ose 8B EER 2 O Durations Drawdown LID Points Table ze datasets Compact WDM Duration Bounds 22 From Alameda irrigation dsn 24 501 POC 1 Predeveloped flow 701 Inflow to POC 1 Mitigated i 801 POC 1 Mitigated fow I Seasonal Durations mm dd 1000 Trapezoidal Pond 1 ALL OUTLETS Mitigated 1001 Trapezoidal Pond 1 STAGE Mitigated Stat Date o All Datasets Flow _ Stage Precip Evap POC1 End Date BSS The Analysis tool bar button third from the left brings up the Analysis screen where the user can look at the results of the Pre project and Mitigated scenarios The Analysis screen allows the user to analyze and compare flow durations flow frequency drawdown times hydrographs and compute LID points 127 SAHM Guidance Document December 2013 File Edit View Help Summary Report Cae se ABSHaBR Os SEES D 2 0 Durations Drawdown Hydrograph LID Points Table Analyze datasets C
17. Grid Scale 200 ft Set Area 12220 013 sa ft Grid X Ey det Slope im 1 Grid 33 fft The Grid X J dt Slope Zz 1 Grid ft default side slope value is 3 3 1 The side slopes can be individually changed by right clicking on the specific side which changes the line color from black to red and then entering the individual side slope value in the slope text box The grid scale can be changed by entering a new value in the grid scale box The default value is 200 feet PondPad Controls and Numbers Clear The Clear button clears all of the lines on the grid Line The Line button allows the user to draw new lines with the mouse Point The Point button allows the user to move individual points to alter the pond shape and size Sq Ft Converts the computed pond area from square feet to acres and back Grid Scale Changes the length of a grid line Default grid scale is 200 feet Grid X Horizontal location of the mouse pointer on the grid 0 is the upper left corner Grid Y Vertical location of the mouse pointer on the grid 0 is the upper left corner Area Top area of the pond either in square feet or acres Slope Side slope of the selected line side of the pond 65 SAHM Guidance Document December 2013 GRAVEL TRENCH BED ELEMENT File Edit View Help Summary Report Oeh tse ZABSGHUER Oe SeEa Schematic fete ies Gravel Trench Bed 1 Mitigate
18. Top Side Slope H V 0 zero for vertical infiltration basin pond sides Riser Height ft Height of infiltration basin pond overflow pipe above basin pond soil surface Riser Diameter in Infiltration basin pond overflow pipe diameter Infiltration Yes infiltration into the underlying native soil Measured Infiltration Rate in hr Native soil infiltration rate Use Wetted Surface Area sidewalls Yes if infiltration through the basin pond side slopes is allowed If infiltration is used then the user should consult the Infiltration discussion on page 79 SAHM includes automated sizing of the infiltration basin pond based on a user set target infiltration percentage After the target percentage is set then the user can click on the Size Infiltration Basin button SAHM will iterate to determine the infiltration basin pond length and width needed to meet the target infiltration percentage NOTE See Appendix C or consult with the local municipal permitting agency for additional considerations regarding infiltration and determination of the appropriate infiltration reduction factor An infiltration basin pond receives precipitation on and evaporation from the basin pond surface 117 SAHM Guidance Document December 2013 INFILTRATION TRENCH ELEMENT File Edit View Help Summary Report ELLEKE SB EIRA Facility Name Outlet 1 Outlet 2 Outlet 3 Downstream Connection 8 Bd Facility Type iit Tech Maximum Facil
19. 75 SAHM Guidance Document December 2013 The physical configuration of the outlet structure should include protection for the riser and orifices to prevent clogging of the outlet from debris or sediment Various outlet configurations are shown below They have been reproduced from Volume III of the Stormwater Management Manual for Western Washington which has more information on the subject 76 SAHM Guidance Document December 2013 removable watertight coupling or flange 2 min y amp min F plate welded to elbow with orifice as specified ELBOW RESTHI R DETAIL me NTS NOTES 1 Use a minimum of a 54 diameter type 2 catch basin 2 Outlet Capacity 100 Year developed peak flow 3 Metal Parts Corrosion resistant Non Galvanized parts perferred Galvanized pipe parts to have asphalt treatment 1 4 Frame and ladder or steps offset so A Cleanout gate is visible from top B Ctimb down space is clear of riser and cleanout gate C Frame is clear of curb 5 It metal outlet pipe connects to cement concrete pipe outlet pipe to have smooth O D equal to concrete pipe I D less 1 4 6 Provide at least one 3 X 090 inches support bracket anchored to concrete wall maximum 3 0 vertical spacing 7 Locate elbow restrictor s as necessary to provide minimum clearance as shown 8 Locate additional ladder rungs in structures used as access to tanks or vaults to allow access when catch basin
20. Names selected by the user gt Lo AA Mitigated A Mitigated Run Scenario Basic Elements If an analysis point is used then the user must select the 1000 time series numbers for the post unmit volume and the post mit volume based on Set up using Analysis Points Set up using POC the elements names The post mit volume will be from Outlet 1 242 SAHM Guidance Document December 2013 Stormwater Planter Infiltration In the Pre Project scenario the Pre volume is modeled using a Basin element containing the drainage area of the pre project land use A point of compliance POC is assigned by the user to the Basin element Only surface runoff and interflow are connected to the POC In the Mitigated scenario the Unmitigated volume is modeled using a Basin element consisting of both impervious area and any pervious area draining to an In Ground Infiltration Planter Box element For this element a separate POC is not needed to record the Unmitigated volume If an analysis point is used instead of a POC then there must be a conveyance element for example a Channel element immediately upstream of the Infiltration Planter Box element The upstream conveyance element must include an analysis point to record the Unmitigated volume In the Mitigated scenario the stormwater planter Mitigated volume can be represented modeled using the In Ground Infilt
21. Pass Pass Pass Pass Pass Evap POC 1 pocz Pass All Datasets Flow Stage Pass Pass Pass Pass Pass Pass In addition increasing the size of the underdrain diameter to 9 inches 0 75 ft and the underdrain orifice diameter to 8 inches results in a bioretention facility that passes the flow duration criteria Additional adjustments probably can be made to the bioretention area dimensions and the underdrain orifice diameter if needed 216 SAHM Guidance Document December 2013 APPENDIX G LID POINTS TABLE PROJECT EXAMPLES The LID Points Table allows the user to calculate the number of LID points that can be gained by reducing post development mitigated runoff volume Reduction of post development mitigated runoff volume is generally accomplished by increasing infiltration and or evapotranspiration LID points are calculated based on the following equation 200 Post Unmit Vol Post Mit Vol Post Unmit Vol Pre Vol where Post Unmit Vol the volume of the post development unmitigated runoff for the entire simulation period Post Mit Vol the volume of the post development mitigated runoff for the entire simulation period Pre Vol the volume of the pre project runoff for the entire simulation period The goal is for the entire project to have a LID points total of at least 100 points The following LID measures are included in the LID Points Table 1 Disconnected Pavement 2 D
22. Porous Pavement listing in the Available Impervious Coverages to represent and model porous pavement areas Instead use the Porous Pavement element see page The impervious lateral basin is similar to the standard basin except that the surface runoff from the lateral impervious basin goes to another adjacent lateral basin impervious or pervious rather than directly to a conveyance system or stormwater facility By definition the impervious lateral basin contains only impervious land types Pervious area is handled separately with the pervious lateral basin Lateral Basin The user selects the impervious lateral basin land type by checking the appropriate box on the Available Impervious Coverages screen This information is automatically placed in the Impervious IMPLND Type box above Once entered the land type can be changed by clicking on the Change button on the right The user enters the number of acres represented by the lateral impervious basin land type 51 SAHM Guidance Document December 2013 If the lateral impervious basin contains two or more impervious land use types then the user should create a separate lateral I basin for each To model parking lot runoff dispersion onto adjacent lawn connect the Lateral I Basin the parking lot to the Lateral Basin the lawn In the model s calculations surface runoff from the parking lot is added to the surface of the lawn urban vegetation The total runoff will then di
23. Porous pavement includes porous or permeable asphalt or concrete and grid lattice systems non concrete and paving blocks The use of any of these LID options requires that certain minimum standards and requirements are met related to subgrade geotextile material separation or bottom filter layer base material wearing layer drainage conveyance acceptance testing and surface maintenance Porous pavement can be represented by the porous pavement element if the following three conditions are met The infiltration rate of the porous pavement is greater than the peak rainfall rate 2 The infiltration rate of the porous pavement is greater than the underlying native soil 3 There is subgrade layer of crushed rock gravel between the porous pavement and the native soil 106 SAHM Guidance Document December 2013 The porous pavement element also called permeable pavement is an impervious basin element that drains directly to storage layer similar to a gravel trench bed The porous pavement element dimensions and parameters are Pavement Length ft Roadway length Pavement Bottom Width ft Roadway width Effective Total Depth ft Height from bottom of porous pavement subgrade to top of pavement plus at least 0 5 feet extra Bottom Slope ft ft Gravel layer slope or grade The effective volume factor is a value between zero and 1 00 It is only used when the bottom slope is greater than 2 The effective volume fac
24. SAHM Guidance Document December 2013 Cohension water porosity soil pore space in micropores Gravitational water porosity soil pore space in macropores in the lower and groundwater layers of the soil column Upper gravitation water porosity soil pore space in macropores in the upper layer of the soil column Upper zone storage factor portion of the water stored in macropores in the upper soil layer which will not surface discharge but will percolate evaporate or transpire Lower zone storage factor portion of the water stored in micropores in the lower soil layer which will not gravity drain but will evaporate or transpire NOTE Due to permit restrictions on infiltration for stormwater treatment measures in areas of high groundwater consult with the local municipal permitting agency regarding any project conditions that might involve using this element 84 SAHM Guidance Document December 2013 CHANNEL ELEMENT File Edit View Help Summary Report Oem se ABS6HUEB ES Oe 8 ai Sele as Schematic fete ies Channel 1 Mitigated Facility Name annel 1 Outlet 1 Outlet 2 Outlet 3 Downstream Connection 0 0 0 Facility Type Channel F Use X Sections Quick Channel Clean and Suagnr O03 joa Facility Dimension Diagram _ vt I Browse for file Channel Dimensions General Channel Data Channel Bottom width ft Channel Length ft Manning n coefficient
25. Z M Bias Stees Move Elements PerviousT otal p 4 Impervious Total fi KE g gt Basin Total fl Save xy Load xy Deselect Zero Select By Sa Fri 12 32p default 0 Finish Mitigated is 4 The easiest way to compare different land use scenarios is to place all of them on the same Schematic Editor screen grid in the Mitigated scenario Each basin can then represent a different land use scenario Because the LID scenario generator only compares runoff volume there is no need to do any routing through a conveyance system or stormwater facility For this example the three basins are assigned the following land uses Basin 1 1 acre A Grass Flat Basin 2 1 acre D Agriculture Moderate Basin 3 1 acre Impervious Flat The user should assign a different POC point of compliance to each basin for the LID analysis 148 SAHM Guidance Document December 2013 File Edit Yiew Help Summary Report Oe swe LEALI Ours aad ol folie eS UD Scensio Generator LID Posts Table POC To Analyze P H Arend gt PERLNO NAME AGrass Fiai 0 1 IMPLNO NAME ai Fa 1232p detoud Ol Finish Mitgsted Click on the Compute LID Base Data button to generate the LID analysis data and summarize the surface runoff interflow groundwater preci
26. of the 2 year flow and the upper threshold of 100 of the 10 year value can be changed 11 SAHM Guidance Document December 2013 4 Use the tool bar immediately above the map to move to the 5 Scenario Editor Click on the General Project Information button The General Project Information button will bring up the Schematic Editor The schematic editor screen contains two scenarios Pre Project and Mitigated Set up first the Pre project scenario and then the Mitigated scenario Check the Pre project scenario box Left click on the Basin element under the Elements heading The Basin element represents the project drainage area It is the upper left element Select any grid cell preferably near the top of the grid and left click on that grid The land use basin will appear in that grid cell 12 File Edit View Zoom Help Ded tae lo kel lal lal Run Scenario Basic Elements SSS EEH Pro Elements LID Toolbox Commercial Toolbox Move Wi CE Load xy SAHM Guidance Document December 2013 File Edit View Help Summary Report Cee sae ASHER Ors wae DERASNS 5 Schematic fe is Basi SSeS Subbasin Name fo sd lg Mitigated Area in Basin I Show Only Selected Hun Scena Available Pervious Acres Available Impervious Acres a A Grass Flat 0 1 P Imperv Flat 0 1 MI A Grass Mod 1 2 Imperv Mod 1 2 I AGrass Steep 2 5 I Imperv St
27. total depth bottom slope and left and right side slopes j l AE Sy s The material layers represent the gravel rock layers and their design characteristics thickness and porosity Quick Trench will instantly create a gravel trench bed with default values without Layer 1 Layer 2 Layer 3 Bottom Width checking it for compliancy with flow duration criteria 66 SAHM Guidance Document December 2013 The gravel trench bed input information Trench Length ft Trench bed length Trench Bottom Width ft Trench bed bottom width Effective Total Depth ft Height from bottom of trench bed to top of riser plus at least 0 5 feet extra Bottom Slope of Trench ft ft Must be non zero Left Side Slope ft ft H V ratio of horizontal distance to vertical 0 zero for vertical trench bed sides Right Side Slope ft ft H V ratio of horizontal distance to vertical 0 zero for vertical trench bed sides Infiltration Rate in hr Trench bed gravel or other media infiltration rate Layer Thickness ft Trench top media layer depth Layer Porosity Trench top media porosity Layer 2 Thickness ft Trench middle media layer depth Layer 2 is optional Layer 2 Porosity Trench middle media porosity Layer 3 Thickness ft Trench bottom media layer depth Layer 3 is optional Layer 3 Porosity Trench bottom media porosity Riser Height ft Height of trench overflow pipe above trench surface Riser
28. 0 0024318 Theta 0 00004715 Theta 2 YoverH Headr NotchBottom Headr Coef a b Headr c Headr 2 q Coef Tan Theta 2 Headr 5 2 73 SAHM Guidance Document December 2013 These equations are provided from the Washington State Department of Ecology s 2005 Stormwater Management Manual for Western Washington The outlet designs are shown below They have been reproduced from Volume III of the Stormwater Management Manual for Western Washington which has more information on the subject a CA VEGF CAVETR CVZ AW Tip Aha hb distance from hydraulic grade fine at the 2 year flow of the outflow pipe to the overflow elevation x Figure 3 20 Simple Orifice The diameter of the orifice is calculated from the flow The orifice equation is often useful when expressed as the orifice diameter in inches 36 880 d Th equation 5 where d orifice diameter inches Q flow cfs h hydraulic head ft 74 SAHM Guidance Document December 2013 SECTION NTS Figure 3 21 Rectangular Sharp Crested Weir Q C L 0 2H H 7 equation 6 where Q flow cfs C 3 27 0 40 H P ft H P are as shown above L length ft of the portion of the riser circumference as necessary not to exceed 50 percent of the circumference D inside riser diameter ft Note that this equation accounts for side contractions by subtracting 0 1H from L for each side of the notch weir
29. 0 05 10 2 0 2 0 0 00 0 00 0 05 11 2 0 2 0 0 00 0 00 0 05 12 2 0 2 0 0 00 0 00 0 05 13 2 0 2 0 0 00 0 00 0 05 14 2 0 2 0 0 00 0 00 0 05 15 2 0 2 0 0 00 0 00 0 05 16 2 0 2 0 0 00 0 00 0 05 17 2 0 2 0 0 00 0 00 0 05 18 2 0 2 0 0 00 0 00 0 05 19 2 0 2 0 0 00 0 00 0 05 20 2 0 2 0 0 00 0 00 0 05 21 2 0 2 0 0 00 0 00 0 05 22 2 0 2 0 0 00 0 00 0 05 23 2 0 2 0 0 00 0 00 0 05 24 2 0 2 0 0 00 0 00 0 05 25 2 0 2 0 0 00 0 00 0 05 26 2 0 2 0 0 00 0 00 0 05 27 2 0 2 0 0 00 0 00 0 05 28 2 0 2 0 0 00 0 00 0 05 29 2 0 2 0 0 00 0 00 0 05 30 2 0 2 0 0 00 0 00 0 05 31 2 0 2 0 0 00 0 00 0 05 32 2 0 2 0 0 00 0 00 0 05 33 2 0 2 0 0 00 0 00 0 05 34 2 0 2 0 0 00 0 00 0 05 35 2 0 2 0 0 00 0 00 0 05 36 2 0 2 0 0 00 0 00 0 05 37 2 0 2 0 0 00 0 00 0 05 38 2 0 2 0 0 00 0 00 0 05 39 2 0 2 0 0 00 0 00 0 05 40 2 0 2 0 0 00 0 00 0 05 41 2 0 2 0 0 00 0 00 0 05 42 2 0 2 0 0 00 0 00 0 05 43 2 0 2 0 0 00 0 00 0 05 44 2 0 2 0 0 00 0 00 0 05 164 SAHM Guidance Document December 2013 45 2 0 2 0 0 00 0 00 0 05 46 2 0 2 0 0 00 0 00 0 05 47 2 0 2 0 0 00 0 00 0 05 48 2 0 2 0 0 00 0 00 0 05 49 2 0 2 0 0 00 0 00 0 05 50 2 0 2 0 0 00 0 00 0 05 51 2 0 2 0 0 00 0 00 0 05 52 2 0 2 0 0 00 0 00 0 05 53 2 0 2 0 0 00 0 00 0 05 54 2 0 2 0 0 00 0 00 0 05 55 2 0 2 0 0 00 0 00 0 05 56 2 0 2 0 0 00 0 00 0 05 57 2 0 2 0 0 00 0 00 0 05 58 2 0 2 0 0 00 0 00 0 05 59 2 0 2 0 0 00 0 00 0 05 60 2 0 2 0 0 00 0 00 0 05 61 2 0
30. 0 60 0 60 0 60 0 70 0 75 0 75 0 75 0 75 0 75 0 75 0 65 0 60 62 0 60 0 60 0 60 0 70 0 75 0 75 0 75 0 75 0 75 0 75 0 65 0 60 63 0 60 0 60 0 60 0 70 0 75 0 75 0 75 0 75 0 75 0 75 0 65 0 60 64 0 60 0 60 0 60 0 70 0 75 0 75 0 75 0 75 0 75 0 75 0 65 0 60 177 SAHM Guidance Document December 2013 This page is intentionally left blank 178 SAHM Guidance Document December 2013 APPENDIX B DEFAULT SAHM HSPF IMPERVIOUS PARAMETER VALUES The default SAHM HSPF impervious parameter values are found in SAHM file defaultpers uci HSPF parameter values in SAHM have been adjusted for the different soil land cover and land slope categories of Sacramento County based on the professional judgment and experience of Clear Creek Solutions HSPF modelers in northern California HSPF parameter documentation is found in the document Bicknell B R J C Imhoff J L Kittle Jr T H Jobes and A S Donigian Jr 2001 Hydrological Simulation Program Fortran User s Manual for Version 12 AQUA TERRA Consultants Mountain View CA Table 1 SAHM Impervious Land Types IMPLND No IMPLND Name Land Slope 1 Impervious Flat 0 1 2 Impervious Moderate 1 2 3 Impervious Steep 2 5 4 Impervious Very Steep gt 5 Table 2 SAHM HSPF Impervious Parameter Values Part I IMPLND No LSUR SLSUR NSUR RETSC 1 100 0 01 0 05 0 100 2 100 0 02 0 05 0 100 3 1
31. 00 0 15 0 17 0 20 4 400 0 00 0 00 0 15 0 17 0 20 5 400 0 00 0 00 0 15 0 17 0 20 6 400 0 00 0 00 0 15 0 17 0 20 7 400 0 00 0 00 0 15 0 17 0 20 8 400 0 00 0 00 0 15 0 17 0 20 9 400 0 00 0 00 0 15 0 17 0 20 10 400 0 00 0 00 0 15 0 17 0 20 11 400 0 00 0 00 0 15 0 17 0 20 12 400 0 00 0 00 0 15 0 17 0 20 13 400 0 00 0 00 0 15 0 17 0 20 14 400 0 00 0 00 0 15 0 17 0 20 15 400 0 00 0 00 0 15 0 17 0 20 16 400 0 00 0 00 0 15 0 17 0 20 17 400 0 00 0 00 0 15 0 17 0 20 18 400 0 00 0 00 0 15 0 17 0 20 19 400 0 00 0 00 0 15 0 17 0 20 20 400 0 00 0 00 0 15 0 17 0 20 21 400 0 00 0 00 0 15 0 17 0 20 22 400 0 00 0 00 0 15 0 17 0 20 23 400 0 00 0 00 0 15 0 17 0 20 24 400 0 00 0 00 0 15 0 17 0 20 25 400 0 00 0 00 0 15 0 17 0 20 26 400 0 00 0 00 0 15 0 17 0 20 27 400 0 00 0 00 0 15 0 17 0 20 28 400 0 00 0 00 0 15 0 17 0 20 29 400 0 00 0 00 0 15 0 17 0 20 30 400 0 00 0 00 0 15 0 17 0 20 31 400 0 00 0 00 0 15 0 17 0 20 32 400 0 00 0 00 0 15 0 17 0 20 33 400 0 00 0 00 0 15 0 17 0 20 34 400 0 00 0 00 0 15 0 17 0 20 35 400 0 00 0 00 0 15 0 17 0 20 36 400 0 00 0 00 0 15 0 17 0 20 37 400 0 00 0 00 0 15 0 17 0 20 38 400 0 00 0 00 0 15 0 17 0 20 39 400 0 00 0 00 0 15 0 17 0 20 40 400 0 00 0 00 0 15 0 17 0 20 41 400 0 00 0 00 0 15 0 17 0 20 42 400 0 00 0 00 0 15 0 17 0 20 43 400 0 00 0 00 0 15 0 17 0 20 44 400 0 00 0 00 0 15 0 17 0 20 168 SAHM Guidance Document December 2013 45 400 0 00 0 00 0 15 0
32. 00 2 50 8 1 0 10 0 00 4 00 0 20 4 00 2 50 9 1 0 10 0 00 4 00 0 20 4 00 2 50 10 1 0 10 0 00 4 00 0 20 4 00 2 50 11 1 0 10 0 00 4 00 0 20 4 00 2 50 12 1 0 10 0 00 4 00 0 20 4 00 2 50 13 1 0 10 0 00 4 00 0 20 4 00 2 50 14 1 0 10 0 00 4 00 0 20 4 00 2 50 15 1 0 10 0 00 4 00 0 20 4 00 2 50 16 1 0 10 0 00 4 00 0 20 4 00 2 50 17 1 0 10 0 00 4 00 0 20 4 00 2 50 18 1 0 10 0 00 4 00 0 20 4 00 2 50 19 1 0 10 0 00 4 00 0 20 4 00 2 50 20 1 0 10 0 00 4 00 0 20 4 00 2 50 21 1 0 10 0 00 4 00 0 20 4 00 2 50 22 1 0 10 0 00 4 00 0 20 4 00 2 50 23 1 0 10 0 00 4 00 0 20 4 00 2 50 24 1 0 10 0 00 4 00 0 20 4 00 2 50 25 1 0 10 0 00 4 00 0 20 4 00 2 50 26 1 0 10 0 00 4 00 0 20 4 00 2 50 27 1 0 10 0 00 4 00 0 20 4 00 2 50 28 1 0 10 0 00 4 00 0 20 4 00 2 50 29 1 0 10 0 00 4 00 0 20 4 00 2 50 30 1 0 10 0 00 4 00 0 20 4 00 2 50 31 1 0 10 0 00 4 00 0 20 4 00 2 50 32 1 0 10 0 00 4 00 0 20 4 00 2 50 33 1 0 10 0 00 4 00 0 20 4 00 2 50 34 1 0 10 0 00 4 00 0 20 4 00 2 50 35 1 0 10 0 00 4 00 0 20 4 00 2 50 36 1 0 10 0 00 4 00 0 20 4 00 2 50 37 1 0 10 0 00 4 00 0 20 4 00 2 50 38 1 0 10 0 00 4 00 0 20 4 00 2 50 39 1 0 10 0 00 4 00 0 20 4 00 2 50 40 1 0 10 0 00 4 00 0 20 4 00 2 50 41 1 0 10 0 00 4 00 0 20 4 00 2 50 42 1 0 10 0 00 4 00 0 20 4 00 2 50 43 1 0 10 0 00 4 00 0 20 4 00 2 50 44 1 0 10 0 00 4 00 0 20 4 00 2 50 170 SAHM Guidance Document December 2013 45 1 0 10 0 00 4 00 0 20 4 00
33. 17 0 20 46 400 0 00 0 00 0 15 0 17 0 20 47 400 0 00 0 00 0 15 0 17 0 20 48 400 0 00 0 00 0 15 0 17 0 20 49 400 0 00 0 00 0 15 0 17 0 20 50 400 0 00 0 00 0 15 0 17 0 20 51 400 0 00 0 00 0 15 0 17 0 20 52 400 0 00 0 00 0 15 0 17 0 20 53 400 0 00 0 00 0 15 0 17 0 20 54 400 0 00 0 00 0 15 0 17 0 20 55 400 0 00 0 00 0 15 0 17 0 20 56 400 0 00 0 00 0 15 0 17 0 20 57 400 0 00 0 00 0 15 0 17 0 20 58 400 0 00 0 00 0 15 0 17 0 20 59 400 0 00 0 00 0 15 0 17 0 20 60 400 0 00 0 00 0 15 0 17 0 20 61 400 0 00 0 00 0 15 0 17 0 20 62 400 0 00 0 00 0 15 0 17 0 20 63 400 0 00 0 00 0 15 0 17 0 20 64 400 0 00 0 00 0 15 0 17 0 20 MELEV Mean surface elevation of the land segment feet BELV Base elevation for active groundwater feet GWDATM Datum for the groundwater elevation feet PCW Cohesion Water Porosity fraction PGW Gravitational Water Porosity fraction UPGW Upper Gravitational Water porosity fraction 169 SAHM Guidance Document December 2013 Table 6 SAHM HSPF Pervious Parameter Values Part V PERLND No STABNO SRRC SREXP IFWSC DELTA UELFAC LELFAC 1 1 0 10 0 00 4 00 0 20 4 00 2 50 2 1 0 10 0 00 4 00 0 20 4 00 2 50 3 1 0 10 0 00 4 00 0 20 4 00 2 50 4 1 0 10 0 00 4 00 0 20 4 00 2 50 5 1 0 10 0 00 4 00 0 20 4 00 2 50 6 1 0 10 0 00 4 00 0 20 4 00 2 50 7 1 0 10 0 00 4 00 0 20 4
34. 2 0 0 00 0 00 0 05 62 2 0 2 0 0 00 0 00 0 05 63 2 0 2 0 0 00 0 00 0 05 64 2 0 2 0 0 00 0 00 0 05 INFEXP Infiltration Exponent INFILD Infiltration ratio maximum to mean DEEPFR Fraction of groundwater to deep aquifer or inactive storage BASETP Base flow from groundwater Evapotranspiration fraction AGWETP Active Groundwater Evapotranspiration fraction 165 SAHM Guidance Document December 2013 Table 4 SAHM HSPF Pervious Parameter Values Part III PERLND No CEPSC UZSN NSUR INTFW IRC LZETP 1 see Table 8 0 35 0 25 2 00 0 50 see Table 9 2 see Table 8 0 33 0 25 1 90 0 48 see Table 9 3 see Table 8 0 32 0 25 1 80 0 45 see Table 9 4 see Table 8 0 30 0 25 1 60 0 40 see Table 9 5 see Table 8 0 35 0 20 2 00 0 50 see Table 9 6 see Table 8 0 33 0 20 1 90 0 48 see Table 9 7 see Table 8 0 32 0 20 1 80 0 45 see Table 9 8 see Table 8 0 30 0 20 1 60 0 40 see Table 9 9 see Table 8 0 35 0 25 1 50 0 40 see Table 9 10 see Table 8 0 33 0 25 1 45 0 38 see Table 9 11 see Table 8 0 32 0 25 1 30 0 37 see Table 9 12 see Table 8 0 30 0 25 1 20 0 35 see Table 9 13 see Table 8 0 45 0 35 2 25 0 60 see Table 9 14 see Table 8 0 42 0 35 2 20 0 58 see Table 9 15 see Table 8 0 40 0 35 2 10 0 55 see Table 9 16 see Table 8 0 35 0 35 2 00 0 50 see Table 9 17 see Table 8 0 35 0 25 1 50 0 50 see Table 9 18 see T
35. 2 50 46 1 0 10 0 00 4 00 0 20 4 00 2 50 47 1 0 10 0 00 4 00 0 20 4 00 2 50 48 1 0 10 0 00 4 00 0 20 4 00 2 50 49 1 0 10 0 00 4 00 0 20 4 00 2 50 50 1 0 10 0 00 4 00 0 20 4 00 2 50 51 1 0 10 0 00 4 00 0 20 4 00 2 50 52 1 0 10 0 00 4 00 0 20 4 00 2 50 53 1 0 10 0 00 4 00 0 20 4 00 2 50 54 1 0 10 0 00 4 00 0 20 4 00 2 50 55 1 0 10 0 00 4 00 0 20 4 00 2 50 56 1 0 10 0 00 4 00 0 20 4 00 2 50 57 1 0 10 0 00 4 00 0 20 4 00 2 50 58 1 0 10 0 00 4 00 0 20 4 00 2 50 59 1 0 10 0 00 4 00 0 20 4 00 2 50 60 1 0 10 0 00 4 00 0 20 4 00 2 50 61 1 0 10 0 00 4 00 0 20 4 00 2 50 62 1 0 10 0 00 4 00 0 20 4 00 2 50 63 1 0 10 0 00 4 00 0 20 4 00 2 50 64 1 0 10 0 00 4 00 0 20 4 00 2 50 STABNO User s number for the FTABLE in the FTABLES block which contains the outflow properties from the surface storage SRRC Surface Runoff Recession Constant per hour SREXP Surface Runoff Exponent IFWSC Maximum Interflow Storage Capacity when the groundwater elevation is greater than the upper influence elevation inches DELTA groundwater tolerance level used to determine transition between regions when high water table conditions are being simulated UELFAC multiplier on UZSN which gives the upper zone capacity LELFAC multiplier on LZSN which gives the lower zone capacity 171 SAHM Guidance Document December 2013 Table 7 SAHM HSPF Pervious Parameter Values Part VI
36. 20 0 18 63 0 15 0 15 0 15 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 18 64 0 15 0 15 0 15 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 18 175 SAHM Guidance Document December 2013 Table 9 SAHM HSPF Pervious Parameter Values Monthly Lower Zone Evapotranspiration PERLND No JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 1 0 40 0 40 0 40 0 45 0 50 0 55 0 55 0 55 0 55 0 55 0 45 0 40 2 0 40 0 40 0 40 0 45 0 50 0 55 0 55 0 55 0 55 0 55 0 45 0 40 3 0 40 0 40 0 40 0 45 0 50 0 55 0 55 0 55 0 55 0 55 0 45 0 40 4 0 40 0 40 0 40 0 45 0 50 0 55 0 55 0 55 0 55 0 55 0 45 0 40 5 0 50 0 50 0 50 0 55 0 60 0 65 0 65 0 65 0 65 0 65 0 55 0 50 6 0 50 0 50 0 50 0 55 0 60 0 65 0 65 0 65 0 65 0 65 0 55 0 50 7 0 50 0 50 0 50 0 55 0 60 0 65 0 65 0 65 0 65 0 65 0 55 0 50 8 0 50 0 50 0 50 0 55 0 60 0 65 0 65 0 65 0 65 0 65 0 55 0 50 9 0 50 0 50 0 50 0 60 0 65 0 65 0 65 0 65 0 65 0 65 0 55 0 50 10 0 50 0 50 0 50 0 60 0 65 0 65 0 65 0 65 0 65 0 65 0 55 0 50 11 0 50 0 50 0 50 0 60 0 65 0 65 0 65 0 65 0 65 0 65 0 55 0 50 12 0 50 0 50 0 50 0 60 0 65 0 65 0 65 0 65 0 65 0 65 0 55 0 50 13 0 60 0 60 0 60 0 70 0 75 0 75 0 75 0 75 0 75 0 75 0 65 0 60 14 0 60 0 60 0 60 0 70 0 75 0 75 0 75 0 75 0 75 0 75 0 65 0 60 15 0 60 0 60 0 60 0 70 0 75 0 75 0 75 0 75 0 75 0 75 0 65 0 60 16 0 60 0 60 0 60 0 70 0 75 0 75 0 75 0 75 0 75 0 75 0 65 0 60 17 0 40 0
37. 27 SAHM Guidance Document December 2013 solution has been found and the Mitigated flow duration values in red are as close as possible to the Pre project flow duration values in blue The user may continue to manually optimize the pond by manually changing pond dimensions and or the outlet structure configuration Manual optimization is explained in more detail on page 55 After making these changes the user should click on the Optimize Pond button to check the results and see if Auto Pond can make further improvements File Edit View Help Summary Report 22 es jassa oo oe a a a Shemale fete Trapezoidal Pond 1 Mitigated SCENARIOS Facility Name Trapezoidal Pond 1 Facility Type Trapezoidal Pond Outlet 1 Outlet 2 Outlet 3 pete C Pre Project Downstream Connections 0 0 0 Bid Miiaates IM Precipitation Applied to Facility ciak QuickPond _ M Evaporation Applied to Facility Facility Dimension Diagram Run Scenario s A r Facility Dimensions Facility Bottom Elevation ft Bottom Length ft Bottom Width ft Outlet Structure Data Riser Height ft 3 Riser Diameter in 7g Riser Type Notched rf Effective Depth ft Notch Type Rectangular 24 Left Side Slope H V Notch Height f 7269 4 Bottom Side Slope H V Notch Width ft aa H Right Side Slope H V Top Side Slope HAV Basic Elements
38. 3 Downstream Connections 0 0 0 I Precipitation Applied to Facility Auto Pond Quick Pond IV Evaporation Applied to Facility Facility Dimension Diagram Facility Dimensions Outlet Structure Data Facility Bottom Elevation ft Riser Height ft B H Bottom Length ft 28 Riser Diameter in 7g 4 Bottom Width ft 28 Riser Type Notched Effective Depth ft Notch Type PEESI Standard Import Features HSPF Input File Import Export Import Existing Input File Perlnds From LID Toolbox Select Datasets ElHI1 pan Diego Pan Even Commercial Toolbox 501 POC 1 Prede fl inflow to POC 1 Mitigated 1801 POC 1 Mitigated flow 1000 Trapezoidal Pond 1 ALL OUTLETS Mitigated IMPORT DATASI 1001 Trapezoidal Pond 1 STAGE Mitigated l l 11002 Trapezoidal Pond 1 OUTLET 1 Mitigated 11003 Trapezoidal Pond 1 OUTLET 2 Mitigated Start Date End Date EE Save xy Load xy 1961 10 01 00 00 2004709730 24 00 Timestep Out Boa Fri 8 58a Example 1 Finish Mitigated The list of available time series datasets will be shown The user can select the start and end dates for the data they want to export The time step hourly daily monthly yearly can also be specified If the user wants daily monthly or yearly data the user is given the choice of either selecting the maximum minimum or the sum of the hourly v
39. 40 0 40 0 45 0 50 0 55 0 55 0 55 0 55 0 55 0 45 0 40 18 0 40 0 40 0 40 0 45 0 50 0 55 0 55 0 55 0 55 0 55 0 45 0 40 19 0 40 0 40 0 40 0 45 0 50 0 55 0 55 0 55 0 55 0 55 0 45 0 40 20 0 40 0 40 0 40 0 45 0 50 0 55 0 55 0 55 0 55 0 55 0 45 0 40 21 0 50 0 50 0 50 0 55 0 60 0 65 0 65 0 65 0 65 0 65 0 55 0 50 22 0 50 0 50 0 50 0 55 0 60 0 65 0 65 0 65 0 65 0 65 0 55 0 50 23 0 50 0 50 0 50 0 55 0 60 0 65 0 65 0 65 0 65 0 65 0 55 0 50 24 0 50 0 50 0 50 0 55 0 60 0 65 0 65 0 65 0 65 0 65 0 55 0 50 25 0 50 0 50 0 50 0 60 0 65 0 65 0 65 0 65 0 65 0 65 0 55 0 50 26 0 50 0 50 0 50 0 60 0 65 0 65 0 65 0 65 0 65 0 65 0 55 0 50 27 0 50 0 50 0 50 0 60 0 65 0 65 0 65 0 65 0 65 0 65 0 55 0 50 28 0 50 0 50 0 50 0 60 0 65 0 65 0 65 0 65 0 65 0 65 0 55 0 50 29 0 60 0 60 0 60 0 70 0 75 0 75 0 75 0 75 0 75 0 75 0 65 0 60 30 0 60 0 60 0 60 0 70 0 75 0 75 0 75 0 75 0 75 0 75 0 65 0 60 31 0 60 0 60 0 60 0 70 0 75 0 75 0 75 0 75 0 75 0 75 0 65 0 60 176 SAHM Guidance Document December 2013 32 0 60 0 60 0 60 0 70 0 75 0 75 0 75 0 75 0 75 0 75 0 65 0 60 33 0 40 0 40 0 40 0 45 0 50 0 55 0 55 0 55 0 55 0 55 0 45 0 40 34 0 40 0 40 0 40 0 45 0 50 0 55 0 55 0 55 0 55 0 55 0 45 0 40 35 0 40 0 40 0 40 0 45 0 50 0 55 0 55 0 55 0 55 0 55 0 45 0 40 36 0 40 0 40 0 40 0 45 0 50 0 55 0 55 0 55 0 55 0 55 0 45 0 40 37 0 50 0 50 0 50 0 55 0 60 0 65 0 65
40. C Trees Flat 0 1 46 C Trees Moderate 1 2 47 C Trees Steep 2 5 48 C Trees Very Steep gt 5 49 D Grass Flat 0 1 50 D Grass Moderate 1 2 51 D Grass Steep 2 5 52 D Grass Very Steep gt 5 53 D Agricultural Flat 0 1 54 D Agricultural Moderate 1 2 55 D Agricultural Steep 2 5 56 D Agricultural Very Steep gt 5 57 D Urban Flat 0 1 58 D Urban Moderate 1 2 59 D Urban Steep 2 5 60 D Urban Very Steep gt 5 61 D Trees Flat 0 1 62 D Trees Moderate 1 2 63 D Trees Steep 2 5 64 D Trees Very Steep gt 5 The user does not need to know or keep track of the HSPF PERLND number That number is used only for internal tracking purposes The user inputs the number of acres of appropriate basin land use information Pervious land use information is in the form of soil land cover and land slope For example A Grass Flat means NRCS soil type A native grass vegetative cover and flat 0 1 land slope There are four basic soil types A well infiltrating soils B moderate infiltrating soils and C poor infiltrating soils and D really poor infiltrating soils There are four basic land cover categories grass agricultural land urban vegetation lawns flowers planted shrubs and trees Land slope is divided into flat O 1 moderate 1 2 steep 2 5 and very steep gt 5 47 SAHM Guidance Document December 2013 HSPF parameter values in SAHM have been adjust
41. DMAIE Surface Interflow Groundwater Flows To a T Area in Basin Available Pervious Acres Available Impervious Acres A oe eee i perv Mod 1 2 ESA E L le Bove Elna PerviousTotal B Acres Impervious Total EE A Basin Tatal 4 Acres DessecZeo Select By NNN o DMA 1A 36 acres drains into the upstream channel reach Channel 1 DMA 1B 70 acres drains into the downstream channel reach Channel 2 Channel 2 discharges at the point of compliance POC 1 DMA 1C 154 acres also drains to POC 1 but is not connected to Channel 2 because it is sufficiently close to the POC that routing the DMA 1C runoff through the length of Channel 2 would not be accurate We will set up all three pre project DMAs before running the pre project scenario 201 SAHM Guidance Document December 2013 File Edit View Help Summary Report Del jee AgH4HaxH i m e A a e z Schematic ex SSD Table 1 Pre Project SCENARIOS a Facility Name Existing Pond Flows To ut M Pre Project M Precipitation Applied eid Mitigated Facility Type S5D TABLE FE a gt Manual Infiltration jun Scenario f Existing Pond Basic Elements cL Load File Browse Be Stage Computed Add Layer E Se Area Storage a gemm 1 Sta
42. December 2013 45 5 00 0 055 400 0 01 3 0 0 92 46 4 90 0 050 400 0 02 3 0 0 92 47 4 85 0 045 400 0 05 3 0 0 92 48 4 80 0 035 350 0 10 3 0 0 92 49 4 40 0 030 400 0 01 3 0 0 92 50 4 35 0 028 400 0 02 3 0 0 92 51 4 30 0 025 400 0 05 3 0 0 92 52 4 20 0 020 350 0 10 3 0 0 92 53 5 00 0 030 400 0 01 3 0 0 92 54 4 95 0 028 400 0 02 3 0 0 92 55 4 90 0 025 400 0 05 3 0 0 92 56 4 80 0 020 350 0 10 3 0 0 92 57 4 45 0 020 400 0 01 3 0 0 92 58 4 40 0 018 400 0 02 3 0 0 92 59 4 35 0 015 400 0 05 3 0 0 92 60 4 25 0 010 350 0 10 3 0 0 92 61 5 00 0 040 400 0 01 3 0 0 92 62 4 95 0 035 400 0 02 3 0 0 92 63 4 90 0 030 400 0 05 3 0 0 92 64 4 80 0 020 350 0 10 3 0 0 92 LZSN Lower Zone Storage Nominal inches INFILT Infiltration inches per hour LSUR Length of surface flow path feet SLSUR Slope of surface flow path feet feet KVARY Variable groundwater recession AGWRC Active Groundwater Recession Constant per day 163 SAHM Guidance Document December 2013 Table 3 SAHM HSPF Pervious Parameter Values Part II PERLND No INFEXP INFILD DEEPFR BASETP AGWETP 1 2 0 2 0 0 00 0 00 0 05 2 2 0 2 0 0 00 0 00 0 05 3 2 0 2 0 0 00 0 00 0 05 4 2 0 2 0 0 00 0 00 0 05 5 2 0 2 0 0 00 0 00 0 05 6 2 0 2 0 0 00 0 00 0 05 7 2 0 2 0 0 00 0 00 0 05 8 2 0 2 0 0 00 0 00 0 05 9 2 0 2 0 0 00 0 00
43. E A EA r maA Commercial Toolbox Be For the developed mitigated scenario we will be sizing the stormwater mitigation facilities to meet the HMP flow duration requirements It is easiest to do this one DMA atatime We will start with DMA 1 206 SAHM Guidance Document December 2013 File Edit View Help Summary Report Dee see ABSGHUBA Os SREBlDO0 5 iA Facility Name DMA1Pond Facil Outlet 1 oi I Downstream Connections ie I Precipitation Applied to Faciity Auto Pond _ P E Facility Dimengj e Facility Dimensions Facility Bottom Elevation tt RiserHeight ft o H Riser Diameter fin 0 H E Miigated Jm Bottom Length ft i Bottom Width t arrere Riser Type Fiat 4 a Effective Depth ft eee Left Side Slope HAV Bottom Side Slope HAV Right Side Slope H V eps Sea iy Orifice Diameter Height Infiltration Number in 1 Comal coe 4 2 ome ceed 3 ee tie Pond Volume at Riser Head ac ft 0 Show Pond Table OpenTable 4 Tide Gate Time Series Demand In DMA the two open channels remain and will now drain to a stormwater detention pond The grass and agricultural land has been converted to urban vegetation lawn flowers and shrub irrigated landscaping and impervious areas roads roofs sidewalks etc Everything drains to DMA 1 Pond The discharge from DMA 1 Pond is the mitigated POC 1 We can now size DMA 1 Pond using the Auto
44. Edit View Help Summary Report Deh Be 2 asum AS reise Automatic Pond Adjuster SCENARIOS GH C Pre Project A Mitigated Run Scenario Predeveloped m 0 1 min lt 2 10 min gt 10 min Fast Thorough Pond Depth incl 1 ft freeboard gft Pond length to width ratio 1 to1 Pond Side Slopes 3 tol Bottom Length 123 982273 ft Bottom Width 123 982273 ft Volume at riser head 1 327 acre ft 4 39 Mitigated 3 40 Basic Elements FLOW cfs Choose Outlet Structure 1 orifice amp rectangular notch hd 1 40 Progress Performing iteration 3 of an estimated 300 0 40 E 4 10E 3 10E 2 10E 1 1 10 100 el Optimize Pond Accept pond Close LID Toolbox Percent Time Exceeding Show Pond Table Open Table Initial Stage f Commercial Toolbox Tide Gate Time Series Demand Determine Outlet With Tide Gate F Use Tide Gate Tide Gate Elevation ft 0s Downstream Connection 7 Overflow Elevation ft 0S Iterations es Move Elements 7N 268 Save xy Load xy xB ta l a Thu 1 50p default 0 Finish Mitigated 2 BU v 4 Flow duration results are shown in the plots above The vertical axis shows the range of flows from 25 of the 2 year flow 0 40 cfs to the 10 year flow 4 39 c
45. High Flow Threshold for POC 1 10 year PRE PROJECT LAND USE Name Basin 1 Bypass No GroundWater No Pervious Land Use Acres D Grass Mod 1 2 10 Pervious Total 10 Impervious Land Use Acres Impervious Total 0 Basin Total 10 Element Flows To Surface Interflow Groundwater Scroll down the Text Report or the PDF Report screen to see all of the results 36 SAHM Guidance Document December 2013 9 Save project Edit View Help Summary Report Ctrl N LID Toolbox Severs Loy Facility Name Facility Type sc Thu t 50p defaut0 Finish Mig v LEECGEKTI A I EIEE Outlet 1 Outlet 2 Outlet 3 Downstream Connections EEE p BD 7 Precipitation Applied to Facility QuickPond_ Evaporation Applied to Facility Facility Dimension Diagram Facility Dimensions _ Outlet Structure Data Riser Height ft B H Facility Bottom Elevation tt Bottom Length ft Riser Diameter in fg H Bottom Width ft Riser Type Notched H Effective Depth ft Notch Type Rectangular 24 Left Side Slope HAV Notch Height 0 7263 Notch Width ft Ma H Bottom Side Slope H V Right Side Slope H V Orifice Diameter Height Number in ft Top Side Slope H V Infiltration NOH 2 Ho H 3 fH lie Pond Volume at Riser Head ac ft 692 Show Pond Table OpenTable 4 Initial Stage f ai Tide Gate Time Series Demand
46. Internet access only required for downloading SAHM not required for executing SAHM Pentium 3 or faster processor desirable Color monitor desirable Before Starting the Program Knowledge of the site location Knowledge of the actual distribution of existing site soil by category A B C or D Knowledge of the actual distribution of existing and proposed site land cover by category grass agricultural land urban or trees Knowledge of the actual distribution of existing and proposed site topography by category flat moderate steep or very steep slope Knowledge of the planned distribution of the proposed development buildings streets sidewalks parking lawn areas overlying the soil categories Knowledge of conveyance systems both existing and planned and the drainage area to each Knowledge of where Point of Compliance POC comparisons will be made SAHM Guidance Document December 2013 SAHM OVERVIEW The SAHM software architecture and methodology is the same as that developed for BAHM Bay Area Hydrology Model SDHM San Diego Hydrology Model SOHM South Orange Hydrology Model and WWHM and uses HSPF as its computational engine Like BAHM SDHM SOHM and WWHM SAHM is a tool that generates flow duration curves for the pre and post project condition and then sizes a flow duration control pond basin or vault and outlet structure to match the pre project curve The software package consists of a user fri
47. Lateral flow basins No Yes Dry Well Dry Well Yes Yes Interceptor Trees Basin No Yes Porous Pavement Porous Pavement No Yes Green Roof Green Roof No Yes Capture and Re use Vault Yes Yes Compost Amended Soil Bioretention Yes Yes Bioretention Bioretention Yes Yes combination of Constructed Wetland Basin elements Yes Yes Detention Basin Trapezoidal Pond Yes Yes Infiltration Basin Infiltration Basin Yes Yes Sand Filter Sand Filter Yes Yes Stormwater Planter Flow Flow Through Planter Through Box Yes Yes Stormwater Planter Infiltration Infiltration Planter Box Yes Yes Vegetated Swale Channel Yes Yes Vegetated Filter Strip Bioretention Yes Yes Proprietary Devices SSD Table Yes Yes BMP Treatment Trains Multiple elements Yes No Yes requires the addition of an upstream conveyance element No if disconnected impervious surfaces interceptor trees porous pavement or green roof is included in the treatment train 250
48. Run Scenario Underdrain Used Underdrain Diameter ft 0 lt Offsettin Basic Elements R SVation ft 0 Orifice Diameter in o fo fd Swale Dimensions Flow Through Underdrain ac ft 0 Swale Length ft 0 000 Total Outflow ac ft 0 Swale Bottom Width ft 0 000 Percent Through Underdrain 0 Freeboard ft 0 000 Facility Dimension Diagram diry 0 000 Outlet Structure Data Effective Total Depth ft 0 Riser Outlet Structure 4 Bottom slope of Swale ft t 0 000 Outlet Structure Data Top and Bottom side slope ft ft 0 000 Riser Height Above Swale surface ft 9 H Left Side Slope H V Right Side Slope H Material Layers Use of the simple swale can result in insufficient storage in the soil layers due to little or no discharge from an underdrain or no native infiltration Please insure that you have sufficient discharge LID Toolbox Commercial Toolbox 0 KSat Safety Factor 3 fo fo None C2 4 Show Swale Table OpenTable lt 4 Move Elements Swale Volume at Riser Head ac ft 000 e aay Native Infiltration Ves H Total Volume Intiltrated ac ft 0 t 4 Measured Infiltration Rate in hr 0 E Total Volume Through Riser ac ft 0 Reduction Factor infilt factor 1 a Total Volume Through Facilityfac ft 0 _Save xy Load xy Use Wetted Surface Area sidewalls Ng 24 Percent Infitrated 0 There is a simple swale option It is c
49. Slope H v 3 Top Side Slope H V 3 Orifice Diameter Height Infiltration Nomi Number in ft LID Toolbox Original text based report Report opens in Wordpad Formatted report with charts in pdf format Report opens in pdf viewer Commercial Toolbox PDF Report IV Draft Report Landuse Report Original text based report Move Elements CHE Save xy Load xy xa Hl i Yy 4 Thu 1 50p default 0 Finish Mitigated Original text based report Parameter Report Click on the Reports tool bar button fourth from the left to select the Report options table Selecting Text Report will generate a project report in Microsoft Word RTF format with all of the project information and results Selecting PDF Report will generate a project report in Adobe Acrobat PDF format with all of the project information and results The Landuse Report produces a list of the land use information contained in the project The Parameter Report lists any HSPF parameter value changes made by the user 35 SAHM Guidance Document December 2013 SAHM PROJECT REPORT Project Name default 0 Site Name Site Address City Report Date 12 5 2013 Gage RANCHO C Data Start 1961 10 01 Data End 2004 03 30 Precip Scale 0 94 Version 2013 12 03 Low Flow Threshold for POC 1 25 Percent of the 2 Year
50. Slope of Channel ft Ft Left Side Slope HZ Right Side Slope H V Maximum Channel Depth ft Infiltration NO 5 Pro Elements LID Toolbox Commercial Toolbox Show Channel Table penTabe Save xy Load xy x B ah The Channel element allows the user to route runoff from a basin or facility through an open channel to a downstream destination The channel cross section is represented by a trapezoid and is used with Manning s equation to calculate discharge from the channel If a trapezoid does not accurately represent the cross section then the user should represent the channel with an independently calculated SSD Table element or use the Use X Sections option The user inputs channel bottom width channel length channel bottom slope channel left and right side slopes maximum channel depth and the channel s roughness coefficient Manning s n value NATURAL CHANNEL The user can select channel type and associated Manning s n from a table list directly above the Channel Dimension information or directly input the channel s Manning s n value Bottom Width 85 SAHM Guidance Document December 2013 The channel is used to represent a natural or artificial open channel through which water is routed It can be used to connect a basin to a pond or a pond to a pond or multiple channels ca
51. Table 8 0 32 0 35 0 75 0 55 see Table 9 48 see Table 8 0 30 0 35 0 65 0 50 see Table 9 49 see Table 8 0 30 0 25 0 70 0 50 see Table 9 50 see Table 8 0 28 0 25 0 65 0 48 see Table 9 51 see Table 8 0 27 0 25 0 60 0 45 see Table 9 52 see Table 8 0 25 0 25 0 50 0 40 see Table 9 53 see Table 8 0 30 0 20 0 70 0 50 see Table 9 54 see Table 8 0 28 0 20 0 65 0 48 see Table 9 55 see Table 8 0 27 0 20 0 60 0 45 see Table 9 56 see Table 8 0 25 0 20 0 50 0 40 see Table 9 57 see Table 8 0 30 0 25 0 50 0 40 see Table 9 58 see Table 8 0 28 0 25 0 48 0 38 see Table 9 59 see Table 8 0 27 0 25 0 45 0 37 see Table 9 60 see Table 8 0 25 0 25 0 35 0 35 see Table 9 61 see Table 8 0 35 0 35 0 80 0 60 see Table 9 62 see Table 8 0 33 0 35 0 78 0 58 see Table 9 63 see Table 8 0 32 0 35 0 75 0 55 see Table 9 64 see Table 8 0 30 0 35 0 65 0 50 see Table 9 CEPSC Interception storage inches UZSN Upper Zone Storage Nominal inches NSUR Surface roughness Manning s n INTFW Interflow index IRC Interflow Recession Constant per day LZETP Lower Zone Evapotranspiration fraction 167 SAHM Guidance Document December 2013 Table 5 SAHM HSPF Pervious Parameter Values Part IV PERLND No MELEV BELV GWDATM PCW PGW UPGW 1 400 0 00 0 00 0 15 0 17 0 20 2 400 0 00 0 00 0 15 0 17 0 20 3 400 0 00 0
52. The POC number should be the same as for the Pre Project scenario If the POC number is 1 then the user should select time series 501 for the pre volume 701 for the post unmit volume and 801 for the post mit volume These time series are based on the element names selected by the user 225 SAHM Guidance Document December 2013 Dry wells In the Pre Project scenario the Pre volume is modeled using a Basin element containing the drainage area of the pre project land use A point of compliance POC is assigned by the user to the Basin element Only surface runoff and interflow are connected to the POC In the Mitigated scenario the Unmitigated volume is modeled using a Basin element consisting of both impervious area and any pervious area draining to a dry well For this element a separate POC is not needed to record the Unmitigated volume If an analysis point is used instead of a POC then there must be a conveyance element for example a Channel element immediately upstream of the Dry Well element The upstream conveyance element must include an analysis point to record the Unmitigated volume In the Mitigated scenario the dry well Mitigated volume can be modeled using any one of the following SAHM elements Trapezoidal Pond Irregular Pond Vault Gravel Trench SSD Table Infiltration Basin Infiltration Trench or Dry Well Regardless of which of these elements is selected infiltration into the native soil should be turned on a
53. The higher settings increase the amount 80 SAHM Guidance Document December 2013 of optimization The highest setting farthest right will size the most efficient smallest pond but will result in longer computational time Pond Depth Pond depth is the total depth of the pond and should include at least one foot of freeboard above the riser The pond s original depth will be used when optimizing an existing pond changing the value in the Pond Depth text box will override any previous set depth value The default depth is 4 feet Pond Length to Width Ratio This bottom length to width ratio will be maintained regardless of the pond size or orientation The default ratio value is 1 0 Pond Side Slopes Auto Pond assumes that all of the pond s sides have the same side slope The side slope is defined as the horizontal distance divided by the vertical A typical side slope is 3 3 feet horizontal to every foot vertical The default side slope value is 3 Choose Outlet Structure The user has the choice of either 1 orifice and rectangular notch or 3 orifices If the user wants to select another outlet structure option then the pond must be manually sized Create Pond This button creates a pond when the user does not input any pond dimensions or outlet structure information Any previously input pond information will be deleted Optimize Pond This button optimizes an existing pond It cannot be used if the user has not already
54. Time Series is the runoff time series number for the SAHM element selected in column 4 This Post Unmit Time Series number is selected by the user from a drop down box of options The Post Unmit Time Series number will be a 700 time series number if using a POC If the element has an analysis point then the number will be a 1000 time series number The sixth column Post Unmit Vol ac ft is the total post development unmitigated runoff volume for the entire multi year simulation period for the selected element This 140 SAHM Guidance Document December 2013 runoff volume is calculated when the Calculate button at the bottom of the table is clicked by the user The seventh column Post Mit Element Name is the SAHM mitigated scenario element that is generating the mitigated runoff volume For each LID measure the user selects the appropriate element name from the column s drop down box to produce the mitigated runoff volume The eighth column Post Mit Time Series is the runoff time series number for the SAHM element selected in column 7 This Post Mit Time Series number is selected by the user If the LID element has a POC then the number will be a 800 time series number if the element has an analysis point then the number will be a 1000 time series number The ninth column Post Mit Vol ac ft is the total post development mitigated runoff volume for the entire multi year simulation period for the selected element This runoff volum
55. a Basin element consisting of both impervious area and any pervious area draining to BMP treatment train The Unmitigated volume should be based on the previous described unmitigated conditions depending on the LID measures included in the BMP treatment train If an analysis point is used instead of a POC then there must be a conveyance element for example a Channel element immediately upstream of the start of the treatment train series of elements The upstream conveyance element must include an analysis point to record the Unmitigated volume In the Mitigated scenario the treatment train total Mitigated volume can be based on the flow exiting the most downstream LID element A point of compliance POC is assigned by the user to the surface and underdrain if any discharge Outlet 1 of the element to compute the Mitigated volume The POC number should be the same as for the Pre Project scenario 247 SAHM Guidance Document December 2013 File Edit View Help Summary Report Cem eB lop fa a et I Ba z Schematic SCENARIOS Set up using Analysis Points File Edit View Help Summary Report Deh tee a en SSEn E Schematic JC Pre Project A Mitigated Save w Load xy Set up using POC 248 If the POC number is 1 then the user must select time series 501 for the pre volume 701 for the post unmit volume and 801 for the post mit volume These time serie
56. a time of the mitigated post project scenario to get an idea of how often the discharge that corresponds to the maximum allowed drain time would be exceeded during warmer months when mosquito development times are shortest 185 SAHM Guidance Document December 2013 This page is intentionally left blank 186 SAHM Guidance Document December 2013 APPENDIX D SAHM REVIEWER CHECKLIST SAHM Reviewer Checklist Yes No Received SAHM project WHM and WH2 files Received SAHM WDM WDM file Received SAHM report file Project WHM file loads okay Project location matches location on SAHM screen Pre project scenario runs okay Mitigated scenario runs okay Compare SAHM Report screen with report file a Project location descriptions match b Precipitation gages match c Precipitation scales match d Flow frequency results match e All flow duration values PASS f Any pervious PERLND land use changes g Any impervious IMPLND land use changes h Any scaling factor changes i Any duration criteria changes j pond dimensions match k pond outlet structure info matches 9 SAHM pond dimensions match drawings 10 Infiltration set to YES for infiltration pond 11 Total SAHM drainage area matches drainage maps drawings 12 Mitigated drainage area s match Pre project 13 Pre project vegetation correct 14 Mitigated land use areas correct 15 Routing correct 16 Check facility drawdown if inclu
57. as the target for the Mitigated scenario compliance The model will accept any land use for this scenario Mitigated is defined as the developed land use with mitigation measures as selected by the user Mitigated is used for sizing stormwater control and water quality facilities The runoff from the Mitigated scenario is compared with the Pre project scenario runoff to determine compliance with flow duration criteria File Edit View Zoom Help keta pi Pre Project Ta C Mitigated LID Toolbox Commercial Toolbox Move Elements 4 Sy Save xy Load xy x Y Below the scenario boxes are the Elements Each element represents a specific feature basin pond etc and is described in more detail in the following section 43 SAHM Guidance Document December 2013 SCHEMATIC EDITOR File Edit View Help Summary Report Osh see ABSUEesAlO sr ds aes Hisaiast SCENARIOS Subbasin Name El x 2 Surface Interflow Groundwater onivess Flows To j fi C1 Mitigated Area in Basin I Show Only Selected Run Scenario Available Pervious Acres Available Impervious Acres Eja A Grass Flat 0 1 Imperv Flat 0 1 M AGrassMod 1 2 I Imperv Mod 1 2 I A Grass Steep 2 5 I Impery Steep 2 5 I AGrassVSteep gt 5 M Imperv VSteep gt 5 I AAaric Flat 0 1 7 Porous Pavement I AAgric Mod 1 2 I AAgr
58. be moved up down left or right using the Move Elements arrow buttons The grid coordinates from one project can be saved Save x y and used for new projects Load x y 44 SAHM Guidance Document December 2013 BASIN ELEMENT File Edit View Help Summary Report Cee te cape ee Hisaiast SCENARIOS Subbasin Name El x 2 Surface Interflow Groundwater onivess Flows To j fi C1 Mitigated Area in Basin I Show Only Selected Run Scenario Available Pervious Acres Available Impervious Acres Eja A Grass Flat 0 1 Imperv Flat 0 1 M AGrassMod 1 2 I Imperv Mod 1 2 I A Grass Steep 2 5 I Impery Steep 2 5 I AGrassVSteep gt 5 M Imperv VSteep gt 5 I AAaric Flat 0 1 7 Porous Pavement I AAgric Mod 1 2 I AAgric Steep 2 5 M AAgicVSteeph5 Pro Elements I AUrban Flat 0 1 C AUibanMod 2 I A Urban Steep 2 5 I AUrbanVSteep gt 5 LID Toolbox I ATrees Flat 0 1 I A Trees Mod 1 2 I ATrees Steep 2 5 I ATrees VSteep gt 5 I B Grass Flat 0 1 Commercial Toolbox B Grass Mod 1 2 z BiGrass Steepi25 Basic Elements Move Elements PerviousT otal 10 Actes 4p Impervious Total o Actes KEJ g2 Basin Total 0 Actes Save xy Load xy DeselectZe
59. categories of Sacramento County based on the professional judgment and experience of Clear Creek Solutions HSPF modelers in northern California HSPF parameter documentation is found in the document Bicknell B R J C Imhoff J L Kittle Jr T H Jobes and A S Donigian Jr 2001 Hydrological Simulation Program Fortran User s Manual for Version 12 AQUA TERRA Consultants Mountain View CA 159 SAHM Guidance Document December 2013 Table 1 SAHM Pervious Land Types PERLND No Soil Type Land Cover Land Slope 1 A Grass Flat 0 1 2 A Grass Moderate 1 2 3 A Grass Steep 2 5 4 A Grass Very Steep gt 5 5 A Agricultural Flat 0 1 6 A Agricultural Moderate 1 2 7 A Agricultural Steep 2 5 8 A Agricultural Very Steep gt 5 9 A Urban Flat 0 1 10 A Urban Moderate 1 2 11 A Urban Steep 2 5 12 A Urban Very Steep gt 5 13 A Trees Flat 0 1 14 A Trees Moderate 1 2 15 A Trees Steep 2 5 16 A Trees Very Steep gt 5 17 B Grass Flat 0 1 18 B Grass Moderate 1 2 19 B Grass Steep 2 5 20 B Grass Very Steep gt 5 21 B Agricultural Flat 0 1 22 B Agricultural Moderate 1 2 23 B Agricultural Steep 2 5 24 B Agricultural Very Steep gt 5 25 B Urban Flat 0 1 26 B Urban Moderate 1 2 27 B Urban Steep 2 5 28 B Urban Very Steep gt 5 29 B Tr
60. created a pond Accept Pond This button will stop the Auto Pond routine at the last pond size and discharge characteristics that produce a pond that passes the flow duration criteria Auto Pond will not stop immediately if the flow duration criteria have not yet been met The bottom length and width and volume at riser head will be computed by Auto Pond they cannot be input by the user Auto Vault and Auto Tank operate the same way as Auto Pond There are some situations where Auto Pond or Auto Vault will not work If the soil type is A or B then the flow duration lower threshold will be very small This is result in a very small bottom orifice and a very large storage volume In these situations it is recommended not to use Auto Pond but to infiltrate as much water as possible and manually size the facility In addition there can be situations where complex routing conditions upstream of the pond make it difficult or impossible for Auto Pond to determine which land use will be 81 SAHM Guidance Document December 2013 contributing runoff to the pond For these situations the pond will have to be manually sized Go to page 55 to find information on how to manually size a pond or other HMP facility NOTE If Auto Pond selects a bottom orifice diameter smaller than the smallest diameter allowed by the local municipal permitting agency then additional mitigating BMPs may be required to meet local hydromodification control requi
61. duration facilities 2 Stormwater that is detained also undergoes water quality treatment through settling and or infiltration of pollutants The focus of water quality management is reducing mean annual loads and typical concentrations of pollutants in receiving waters so treatment design focuses on typical storms which contain the bulk of annual runoff volume Stormwater permits and guidance documents describe the local design criteria for volume based treatment measures which apply to a wider range of projects than the hydromodification management requirements Recommended drawdown times for detention structures are typically at least 48 hours but not to exceed 96 hours 3 Flood control design is intended to control peak flows for large sized storms with expected recurrence intervals such as 25 50 or 100 years Flood control facilities typically require capture and detention of a specified volume of stormwater which then is discharged out at flows that can be safely conveyed by downstream channels without undue risk of flooding Although many factors affect the drawdown time the suggestions below may help SAHM users in evaluating these other requirements If flow duration control is required for a project site it is recommended that the design process start with by using SAHM to obtain a preliminary design for the flow duration pond vault or tank Then check the performance of the facility for vector control concerns and against trea
62. h A 8 e E E 6 H J x t M N p a R 1 501 POC 1 Predeveloped flow 801 POC 1 Mitigated flow 10 1 1561 1 760317 1 697474 10 1 1962 0 8212938 1 198515 4 10 2 1969 0 1754018 90 4097468 5 10 3 1564 1 865081 Lina 6 10 1 1965 0 069804713 0 3730958 7 10 1 1 6 12s 2 065922 10 1 1967 0 863584 03533664 9 10 1 1968 1 760137 1 33299 0 10 1 1369 1409654 1 69805 10 1 1870 2 098128 2 395049 1 w m 0 001533361 90 3259206 wn 4 084505 2 007262 4 10 1 1973 1 292186 08171957 s 10 1 1974 ssesses oasa 16 10 1 1975 0 001893251 029279764 10 31 197 000189778 0 203825 10 1 1977 1 95625 Osr 10 3 1978 0 907523 0407487 10 1 1979 3 093839 1 580475 10 2 1900 0 3420355 OSIS 2 10 1 1981 3 41682 2 880896 a 10 1 1382 431737 3 573781 2s 10 3 1983 1612885 1841709 25 10 1 1984 00 9257534 ins 2 10 3 1985 6 506509 6 14605 7 10 1 1986 0 7465193 0 4056348 28 10 1 1987 1357323 04087365 23 10 1 1988 2 206153 1 302888 x0 20 2 2989 1 722651 2 068126 a 0 1 1990 1215948 LANTI R IW 2 535847 2 508104 33 10 1 1992 1 980862 1515152 x w a 0 9530066 CAITE 3 10 1 1984 7 173828 7 402658 36 20 1 1995 445506 3 219771 3 10 1 1996 5 577405 4 768275 Sheet G Gi Graphs that are copied to Windows Clipboard can then be pasted into a Microsoft Excel spreadsheet with the individual plotted values shown in the spreadsheet 137 SAHM Guidance Document December 2013 LID POINTS TABLE SAI Bape File Edit View Help Summary Report DEH the IABSUE Rl Os S BEER o 2 O
63. horizontal distance to vertical 0 zero for vertical sides Top refers to the uphill end of the bioretention facility bottom to the downhill end Left Side Slope ft ft H V ratio of horizontal distance to vertical 0 zero for vertical swale sides Right Side Slope ft ft H V ratio of horizontal distance to vertical 0 zero for vertical swale sides The input information required for the vertical orifice plus overflow option is Vertical Orifice Diameter inches diameter of vertical opening below the weir Vertical Orifice Elevation inches vertical distance from the top of the amended soil surface to the bottom of the vertical orifice Width of Over road Flow feet weir street length must be greater than zero Diagram of bioretention with vertical orifice plus overflow Width of Over road Flow Over road Flooding Freeboard Native Soil Effective Total Depth Underdrain Native Soil Native Soil The material layer inputs are Layer Thickness feet depth of amended soil Type of amended soil 24 different soil types are included the user can also create their own soil type using the Edit Soil Type button 101 SAHM Guidance Document December 2013 Note that there can be a maximum of three different amended soil layers Infiltration to the native soil can be turned on by setting Native Infiltration to YES The parameters for native soil infiltration are Measured Infiltration Rate inches
64. immediately upstream of the Bioretention element The upstream conveyance element must include an analysis point to record the Unmitigated volume In the Mitigated scenario the vegetated filter strip Mitigated volume can be represented modeled using the Bioretention element If infiltration to the native soil is allowed then infiltration should be turned on and an infiltration rate input by the user A point of compliance POC is assigned by the user to the surface and underdrain if any discharge Outlet 1 of the Bioretention element to compute the Mitigated volume The POC number should be the same as for the Pre Project scenario Fae EAC Vicu Licks Simanen Revere File Edit View Help Summary Report If the POC number Os t ee Ook ae is 1 then the user lel lla must select time Partin ee series 501 for the SCENARIOS SCENARIOS pre volume 701 for BO Oy pre Prciect ree a RoR the post unmit tnaed gt RAT Miigates volume and 801 Run Scenario TF for the post mit volume These time series are gt based on the element names selected by the user If an analysis point is used then the user must select the 1000 time series numbers for the Set up using Analysis Points Set up using POC post unmit volume and the post mit volume based on the elements names The post mit volume will be from Outlet 1 245 SAHM Guidance Document December 2013 Proprietary De
65. is filled with water Figure 3 17 Flow Restrictor TEE T11 SAHM Guidance Document December 2013 watertigi coupling Bs A NOTES emh outlet capacity 100 year developed peak flow metal parts corrosion resistant steat parts plate welded galvanized and asphalt coated to elbow with 8 max catch basin type 2 minimum 72 diameter orifice as Ea ELBOW RESTRICTOR DETAIL orifices sized and located as required with NTS lowest orifice a minimum of 2 from base Figure 3 18 Flow Restrictor Baffle Riser protection structures Diagrams courtesy of Washington State Department of Ecology 78 SAHM Guidance Document December 2013 Infiltration of stormwater runoff is a TL a Te recommended solution if certain Facility Name Trapezoidal Pond 1 Facility Type _ Trapezoidal Pond Outlet 1 Outlet 2 Outlet 3 conditions are met These conditions Downstream Connections a a ii A il I Precipitation Applied to Facility Auto Pond Quick Pond include a soils report testing 17 ESSER AEST ER Paci DimensianiDiaaram i i Facility Dimensions utlet Structure Data groundwater protection pre settling ass anaes Deiat Secure Data and appropriate construction Bottom Length h Reena ge Bottom Width ft Riser Type Fal techniques Etecive Depth 4 Notch Type Left Side Slope H V Bottom Side Slope H V Rights s op Side Slope H V
66. of Channel ft ft 0 005 la M A Grass Flat 0 1 Maximum Interflow Storage Capacity 4 Left Side Slope H V 0 LID Toolbox tl A Grass Mod 1 2 Right Side Slope H V 0 M AGrass Steep 2 5 Maximum Channel Depth ft 7 A Grass VSteep gt 5 4 Agric Flat 0 1 AAgric Mad 1 2 AAaric Steep 2 5 A Agric VSteep gt 5 A Urban Flat 0 1 Commercial Toolbox Show Wetland Table Open Tabe Move Elements 4 4 Save xy Load xy x Go y ap Accept The High Groundwater Wetpond element is a complex element that should only be used in special applications by advanced SAHM users The purpose of the high groundwater wetpond element is to model hydrologic conditions where high groundwater rises to the surface or near the surface and reduces the ability of water to infiltrate into the soil The element can be used to represent wetland conditions with surface ponding where the discharge from the wetland is via a surface release The user is given the choice of using either a natural channel berm weir or control structure to determine the release characteristics The element provides default values for some of the parameters especially as they relate to high groundwater The user should be fully familiar with these parameters and the appropriate values for their site prior to attempting to use this element The high groundwater parameter definitions are shown below 83
67. slope of Swale ft ft Outlet Structure Data Top and Bottom side slope ft t f Riser Height Above Swale surface f Jo 4 Left Side Slope H V d Riser Diameter fn o 4 Right Side Slope H V Riser Type Flat H Material Layers for Swal LID Toolbox Layer Layer d Depth ft 0 000 0 Soil Layer 1 GRAVEL Soil Layer 2 GRAVEL Orifice Diameter Height Soil Layer 3 GRAVEL Number in t Commercial Toolbox 0 H Edit Soil Types fo ay KSat Safety Factor o None 2 Cc 4 Show Swale Table Open Tab WMbbeline at Riser Head Move Elements oF a Native Infiltration No lt 4 Save xy Load xy a y x N The bioretention dimensions are specified below Swale Length ft length dimension of bioretention surface bottom Swale Bottom Width ft width dimension BIORETENTION SWALE of bioretention surface bottom Freeboard ft depth of surface ponding above riser height Effective Depth Effective Total Depth ft the total depth of the amended soil layer s plus riser i height plus freeboard effective total depth Bottom Length is computed by SAHM Pervious Pipe 98 SAHM Guidance Document December 2013 Bottom Slope of Swale ft ft the slope of the swale length must be greater than zero Top and Bottom Side Slopes ft ft H V ratio of ho
68. soil is allowed then infiltration should be turned on and an infiltration rate input by the user A point of compliance POC is assigned by the user to the surface discharge Outlet 1 of the Trapezoidal Pond element to compute the Mitigated volume The POC number should be the same as for the Pre Project scenario Ese EAE View Glen li Sunumany Report File Edit View Help Summary Report If the POC number Ose se Oe tae is 1 then the user le ke ea En S h EAE must select time z Schematic rH Schematic series 501 for the SCENARIOS HE C Fre Project A Mitigated Run Scenario SCENARIOS pre volume 701 for a Pre Project the post unmit m I mitigated volume and 801 Run Scenario TT for the post mit Base emer volume These time series are based on the element names selected by the user Basic Elements If an analysis point is used then the Pe hd user must select the 1000 time series Set up using Analysis Points Set up using POC numbers for the post unmit volume and the post mit volume based on the elements names The post mit volume will be from Outlet 1 LID Toolbox 239 SAHM Guidance Document December 2013 Infiltration Basin In the Pre Project scenario the Pre volume is modeled using a Basin element containing the drainage area of the pre project land use A point of compliance POC is assigned by the user to the Bas
69. soil layer depth Top Soil Layer Porosity Dry well soil porosity Gravel Sand Layer Thickness ft Dry well gravel layer depth Gravel Sand Layer Porosity Dry well gravel porosity Native Infiltration Yes infiltration into the underlying native soil Measured Infiltration Rate in hr Native soil infiltration rate If infiltration is used then the user should consult the Infiltration discussion on page 79 SAHM includes automated sizing of the dry well based on a user set target infiltration percentage After the target percentage is set then the user can click on the Size Dry Well button SAHM will iterate to determine the dry well length and width needed to meet the target infiltration percentage NOTE See Appendix C or consult with the local municipal permitting agency for additional considerations regarding infiltration and determination of the appropriate infiltration reduction factor Note that the dry well is covered there is no precipitation on or evaporation from the dry well 121 SAHM Guidance Document December 2013 POINT OF COMPLIANCE SAHM allows for multiple points of compliance maximum of 59 in a single project A point of compliance is defined as the location at which the Pre project and Mitigated flows will be analyzed for compliance with the flow control standard le Edit View Help Summary Report Fi Dw amp amp ABSUER Os SB EE D 2 J Schematic fe e jis ig Trapezoidal Pond 1 Mitigated
70. the orifice whichever is smaller Head conditions are determined by computing the saturation level of the lowest soil layer first Once the lowest soil layer is saturated and flow begins then the gravity head is considered to be at the saturation level of the lowest soil layer Once the lowest soil layer is saturated completely then the head will include the gravity head from the next soil layer above until gravity head from all soil layers is included Gravity head from ponding on the surface is included in the orifice calculations only if all of the intervening soil layers are saturated 3 There is native infiltration but no underdrain Discharge infiltration into the native soil is computed based a user entered infiltration rate in units of inches per hour Specific head conditions are not used in determining infiltration into the native soil Any impact due to head on the infiltration rate is considered to be part of the determination of the native soil infiltration rate Because it is possible to have a maximum of three soil layers each modeled layer must overcome matric head before infiltration to the native soil can begin Once matric head is overcome by gravity head for all modeled layers then infiltration begins at a 190 SAHM Guidance Document December 2013 maximum rate determined either by the ability of the water to move through the soil layers or by the ability of the water to infiltrate into the native soil whichever is limitin
71. the pond is covered The pond bottom elevation can be set to an elevation other than zero if the user wants to use actual elevations All pond stage values are relative to the bottom elevation Negative bottom elevations are not allowed The pond effective depth is the pond height including freeboard above the pond bottom It is not the actual elevation of the top of the pond Pond side slopes are in terms of horizontal distance over vertical A standard 3 1 H V side slope would be given a value of 3 A vertical side slope has a value of 0 The pond bottom is assumed to be flat The pond outlet structure consists of a riser and zero to three orifices The riser has a height typically one foot less than the effective depth and a diameter The riser can have either a flat top or a weir notch cut into the side of the top of the riser The notch can be either rectangular V shaped or a Sutro weir More information on the riser weir shapes and orifices is provided later in this manual After the pond is given dimensions and outlet information the user can view the resulting stage storage discharge table by clicking on the Open Table arrow in the lower right corner of the pond information screen This table hydraulically defines the pond s characteristics 54 SAHM Guidance Document December 2013 The user can use either Auto Pond to size a pond or can manually size a pond Follow the following steps for manual sizing a pond usi
72. the treatment standard percentage If the value is less than the treatment standard percentage then the user should increase the size of the sand filter dimensions and or change the outlet structure The sand filter input information Bottom Length ft Sand filter bottom length Bottom Width ft Sand filter bottom width Effective Depth ft Height from bottom of sand filter to top of riser plus at least 0 5 feet extra Left Side Slope ft ft H V ratio of horizontal distance to vertical 0 zero for vertical sand filter sides Bottom Side Slope ft ft H V ratio of horizontal distance to vertical 0 zero for vertical sand filter sides Right Side Slope ft ft H V ratio of horizontal distance to vertical 0 zero for vertical sand filter sides Top Side Slope ft ft H V ratio of horizontal distance to vertical 0 zero for vertical sand filter sides Riser Height ft Height of sand filter overflow pipe above sand filter surface Riser Diameter in Sand filter overflow pipe diameter Riser Type options Flat or Notched Notch Type Rectangular V Notch or Sutro For a rectangular notch Notch Height feet distance from the top of the weir to the bottom of the notch Notch Width feet width of notch cannot be larger than the riser circumference For more information on riser notch options and orifices see discussion in OUTLET STRUCTURE CONFIGURATIONS section Infiltration Yes infiltration through the filte
73. the watershed rainfall interception infiltration runoff and stream flows and affect the supply and transport of sediment in the stream system The change in runoff characteristics from a watershed caused by changes in land use conditions is called hydrograph modification or simply hydromodification As the total area of impervious surfaces increases in previously undeveloped areas infiltration of rainfall decreases causing more water to run off the surface as overland flow at a faster rate Storms that previously didn t produce runoff under rural conditions can produce erosive flows The increase in the volume of runoff and the length of time that erosive flows occur ultimately intensify sediment transport causing changes in sediment transport characteristics and the hydraulic geometry width depth slope of channels The larger runoff durations and volumes and the intensified erosion of streams can impair the beneficial uses of the stream channels Regulatory Context The California Regional Water Quality Control Board Water Board requires stormwater programs to address the increases in runoff rate and volume from new and redevelopment projects where those increases could cause increased erosion of receiving streams Phase 1 municipal stormwater permits in Sacramento County contain requirements to develop and implement hydromodification management plans HMPs and to implement associated management measures Development of the Sacram
74. to 1 and the outlet structure configuration default 1 orifice and riser with rectangular notch weir 24 SAHM Guidance Document December 2013 To optimize the pond design and create the smallest pond possible move the Automatic Pond Adjuster pointer from the left to the right A Trapezoidal Pond 1 Automatic Pond Adjuster _ a Predeveloped OT min lt 210min gt 10 mine E Mitigated Fast Thorough Pond Depth incl 1 ft freeboard ft Pond length to width ratio 1 tol Pond Side Slopes 3 tol Bottom Length ft Bottom Width ft Volume at riser head acre ft Choose Outlet Structure 1 orifice amp rectangular notch had Progress The pond does not yet have any dimensions Click the Create Pond button to create initial pond dimensions which will be the starting point for Auto Pond s automated optimization process to calculate the pond size and outlet structure dimensions Running Auto Pond automates the following SAHM processes 1 the hourly Pre project runoff is computed for the 30 50 years of record it varies depending on the rain gage used 2 the Pre project runoff flood frequency is calculated based on the partial duration peak flows 3 the range of flows is selected for the flow duration lower threshold of 25 for this example of the 2 year peak to the 10 year peak 4 this flow range is divided into 100 increments and 5
75. to Facility boxes should not be checked 62 SAHM Guidance Document December 2013 IRREGULAR POND ELEMENT File Edit View Help Summary Report Oem te Aa6HU2E Osea SCENARIOS Pre Project DARASA Schematic ECE gt Mitigated Run Scenario Basic Elements LID Toolbox Commercial Toolbox Move Elements 3 Save xy Load xy yo Hl Be Facility Name Irregular Pond 1 Facility Type Irregular Pond Outlet 1 Outlet 2 Outlet 3 Downstream Connections 0 o 0 I Precipitation Applied to Facility M Evi iig Facility Bottom Elevation ft 0 Outlet Structure Effective Depth f Gab a e Riser Diameter in jo H Riser Type Fiat H Notch Type Orifice Diameter Height Number in fy 1 ce Cel 4 2 Cel oe 4 36 dbo 4 Pond Volume at Riser Head ac ft 0 Show Pond Table Initial Stage ft Use Tide Gate Open Table 0 No H id An irregular pond is any pond with a shape that differs from the rectangular top of a trapezoidal pond An irregular pond has all of the same characteristics of a trapezoidal pond but its shape must be defined by the user The Auto Pond option is not available for an irregular sh
76. x a A green roof is roof covered with vegetation and a growing medium typically an engineered soil mix Green roofs are not always green and are also known as vegetated roofs or eco roofs The advantage of a green roof is its ability to store some runoff on the plants surfaces and in the growing medium Evapotranspiration by the plants and from the growing medium reduces the total runoff Runoff movement through the growing medium slows down the runoff and reduces peak discharge during storm events 109 SAHM Guidance Document December 2013 support panel thermal insulation vapour control layer structural support The typical cross section of a green roof is shown above The dimensions and parameters to adjust to represent a green roof are Green Area ac Size of the green roof Depth of Material in Growing media soil depth Slope of Rooftop ft ft Roof surface slope Vegetative Cover Type of vegetation on green roof choices are ground cover shrubs or trees Length of rooftop ft Length of the longest runoff path to reach a roof drain Default input values are automatically included with the element They should be changed to reflect actual roof conditions The green roof surface area automatically receives rainfall and produces evapotranspiration The green roof surface area should be excluded from the basin element s total surface area
77. 0 Native Infiltration N0 lt 4 The bioretention will include an underdrain but no infiltration to the native soil The outlet structure will be a riser Six inches 0 5 ft of ponding will occur on the surface before there is overflow into the riser All flow through the material layers exits through the underdrain The underdrain discharge rate is controlled by the underdrain orifice We will start with an underdrain orifice of 4 inches 212 SAHM Guidance Document December 2013 File Edit View Help Summary Report Dee sae AASEN Ose Saul DO D eles es BM 503 POC 3 Predeveloped f 803 POC 3 Mitigated flow Facility FAILED duration standard for 1 f Flow cfs Predev Mit Percentage Pass Fail 559 278 Fail 523 264 Fail 490 253 Fail 465 237 Fail 438 228 Fail 413 217 Fail 384 208 Fail 370 197 Fail 350 189 Fail 330 184 Fail 315 178 Fail 296 174 Fail 286 163 Fail 268 Fail 254 Fail 249 Fail Durations Drawdown Hydrograph LID Points Table i Boa Fe Analyze datasets Compact WDM 215 Fail 199 Fail 191 Fail 184 Fail 177 Fail 161 Fail 153 Pass 143 Fail 139 Pass 137 Pass All Datasets il 129 Pass 123 Pass All time series related to precipitation e 121 Pass 119 Pass 115 Pass Pass FLOW cfs 10E 3 10E 2 E11 10 Percent Time Exceeding 0 O OOO IIINADAHD WO Od ob ob The flow duration results for POC 3 sh
78. 0 Post Unmit Vol Post Mit Vol Post Unmit Vol Pre Vol 223 SAHM Guidance Document December 2013 Guidance for how each LID measure should be represented in SAHM is described below Note that the analysis point numbers and the POC numbers used in the examples below are for representative purposes only for each individual project start with POC 1 and add POCs only as needed Use analysis points where POCs are not needed NOTE If a channel element is added solely to provide an analysis point location for LID points calculation purposes as described below then use the channel element Quick Channel option and increase the default channel length from 500 feet to 2500 feet if the total contributing area is less than 100 acres and to 12 500 feet for areas equal to or greater than 100 acres The use of these channel lengths will minimize the changes in volume and frequency results introduced by the addition of the channel element to the model for LID points calculation purposes 224 SAHM Guidance Document December 2013 Disconnect impervious surfaces These LID measures can be disconnected pavement alternative driveways disconnected roof drains or any other impervious surface that drains onto a pervious surface prior to discharging into a stormwater conveyance system Disconnected impervious surfaces must use POCs in the Mitigated scenario The unmitigated impervious element must be a Lateral Flow Impervious Area element
79. 0 Top Side Slope H V o Orifice Diameter Height rapezoi Automatic Pond Adjuster J i Predeveloped LID Toolbox a Ot min lt 210min gt 10 mine I Mitigated Fast Thorough Pond Depth incl 1 ft freeboard 4 ft Pond length to width ratio 1 to 1 Pond Side Slopes 3 to1 Commercial Toolbox Bottom Length ft Bottom Width ft Volume at riser head acre ft Choose Outlet Structure 1 orifice amp rectangular notch hd Move ry Ka g gt Progress Save xy Load xy Create Pond Optimize Pond Accept pond Close Auto Pond automatically creates a pond size and designs the outlet structure to meet the flow duration criteria The user can either create a pond from scratch or optimize an existing pond design Auto Pond requires that the Pre project and Mitigated basins be defined prior to using Auto Pond Clicking on the Auto Pond button brings up the Auto Pond window and the associated Auto Pond controls Auto Pond controls Automatic Pond Adjuster The slider at the top of the Auto Pond window allows the user to decide how thoroughly the pond will be designed for efficiency The lowest setting 0 1 min at the left constructs an initial pond without checking the flow duration criteria The second setting to the right creates and sizes a pond to pass the flow duration criteria however the pond is not necessarily optimized
80. 0 0 10 0 10 0 10 0 10 0 10 0 11 0 12 40 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 41 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 42 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 43 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 44 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 45 0 15 0 15 0 15 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 18 46 0 15 0 15 0 15 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 18 47 0 15 0 15 0 15 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 18 48 0 15 0 15 0 15 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 18 49 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 50 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 51 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 52 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 53 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 54 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 55 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 56 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 57 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 58 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 59 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 60 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 61 0 15 0 15 0 15 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 18 62 0 15 0 15 0 15 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0
81. 0 65 0 65 0 65 0 55 0 50 38 0 50 0 50 0 50 0 55 0 60 0 65 0 65 0 65 0 65 0 65 0 55 0 50 39 0 50 0 50 0 50 0 55 0 60 0 65 0 65 0 65 0 65 0 65 0 55 0 50 40 0 50 0 50 0 50 0 55 0 60 0 65 0 65 0 65 0 65 0 65 0 55 0 50 41 0 50 0 50 0 50 0 60 0 65 0 65 0 65 0 65 0 65 0 65 0 55 0 50 42 0 50 0 50 0 50 0 60 0 65 0 65 0 65 0 65 0 65 0 65 0 55 0 50 43 0 50 0 50 0 50 0 60 0 65 0 65 0 65 0 65 0 65 0 65 0 55 0 50 44 0 50 0 50 0 50 0 60 0 65 0 65 0 65 0 65 0 65 0 65 0 55 0 50 45 0 60 0 60 0 60 0 70 0 75 0 75 0 75 0 75 0 75 0 75 0 65 0 60 46 0 60 0 60 0 60 0 70 0 75 0 75 0 75 0 75 0 75 0 75 0 65 0 60 47 0 60 0 60 0 60 0 70 0 75 0 75 0 75 0 75 0 75 0 75 0 65 0 60 48 0 60 0 60 0 60 0 70 0 75 0 75 0 75 0 75 0 75 0 75 0 65 0 60 49 0 40 0 40 0 40 0 45 0 50 0 55 0 55 0 55 0 55 0 55 0 45 0 40 50 0 40 0 40 0 40 0 45 0 50 0 55 0 55 0 55 0 55 0 55 0 45 0 40 51 0 40 0 40 0 40 0 45 0 50 0 55 0 55 0 55 0 55 0 55 0 45 0 40 52 0 40 0 40 0 40 0 45 0 50 0 55 0 55 0 55 0 55 0 55 0 45 0 40 53 0 50 0 50 0 50 0 55 0 60 0 65 0 65 0 65 0 65 0 65 0 55 0 50 54 0 50 0 50 0 50 0 55 0 60 0 65 0 65 0 65 0 65 0 65 0 55 0 50 55 0 50 0 50 0 50 0 55 0 60 0 65 0 65 0 65 0 65 0 65 0 55 0 50 56 0 50 0 50 0 50 0 55 0 60 0 65 0 65 0 65 0 65 0 65 0 55 0 50 57 0 50 0 50 0 50 0 60 0 65 0 65 0 65 0 65 0 65 0 65 0 55 0 50 58 0 50 0 50 0 50 0 60 0 65 0 65 0 65 0 65 0 65 0 65 0 55 0 50 59 0 50 0 50 0 50 0 60 0 65 0 65 0 65 0 65 0 65 0 65 0 55 0 50 60 0 50 0 50 0 50 0 60 0 65 0 65 0 65 0 65 0 65 0 65 0 55 0 50 61
82. 00 0 05 0 05 0 095 4 100 0 10 0 05 0 090 LSUR Length of surface flow path feet for impervious area SLSUR Slope of surface flow path feet feet for impervious area NSUR Surface roughness Manning s n for impervious area RETSC Surface retention storage inches for impervious area Table 3 SAHM HSPF Impervious Parameter Values Part II IMPLND No RETS SURS 1 0 00 0 00 2 0 00 0 00 3 0 00 0 00 4 0 00 0 00 RETSC Initial surface retention storage inches for impervious area SURS Initial surface runoff inches for impervious area 179 SAHM Guidance Document December 2013 This page is intentionally left blank 180 SAHM Guidance Document December 2013 APPENDIX C ADDITIONAL GUIDANCE FOR USING SAHM Scope and Purpose This appendix includes guidance and background information that are not incorporated into the SAHM software but which the user needs to know in order to use SAHM for designing projects in the participating jurisdictions The three main topic areas in this appendix are flagged in the main guidance documentation text by specially formatted notes under the SAHM elements or software features to which they are related Appendix C Topic Relevant Sections in Guidance documentation Infiltration Reduction Factor Infiltration page 79 applicable when specifying characteristics of a facility pond vault tank some LID elements if yes is selected as the Infilt
83. 00 4 00 0 05 0 00 37 0 00 0 00 0 15 0 00 4 00 0 05 0 00 38 0 00 0 00 0 15 0 00 4 00 0 05 0 00 39 0 00 0 00 0 15 0 00 4 00 0 05 0 00 40 0 00 0 00 0 15 0 00 4 00 0 05 0 00 41 0 00 0 00 0 15 0 00 4 00 0 05 0 00 42 0 00 0 00 0 15 0 00 4 00 0 05 0 00 43 0 00 0 00 0 15 0 00 4 00 0 05 0 00 44 0 00 0 00 0 15 0 00 4 00 0 05 0 00 172 SAHM Guidance Document December 2013 45 0 00 0 00 0 15 0 00 4 00 0 05 0 00 46 0 00 0 00 0 15 0 00 4 00 0 05 0 00 47 0 00 0 00 0 15 0 00 4 00 0 05 0 00 48 0 00 0 00 0 15 0 00 4 00 0 05 0 00 49 0 00 0 00 0 15 0 00 4 00 0 05 0 00 50 0 00 0 00 0 15 0 00 4 00 0 05 0 00 51 0 00 0 00 0 15 0 00 4 00 0 05 0 00 52 0 00 0 00 0 15 0 00 4 00 0 05 0 00 53 0 00 0 00 0 15 0 00 4 00 0 05 0 00 54 0 00 0 00 0 15 0 00 4 00 0 05 0 00 55 0 00 0 00 0 15 0 00 4 00 0 05 0 00 56 0 00 0 00 0 15 0 00 4 00 0 05 0 00 57 0 00 0 00 0 15 0 00 4 00 0 05 0 00 58 0 00 0 00 0 15 0 00 4 00 0 05 0 00 59 0 00 0 00 0 15 0 00 4 00 0 05 0 00 60 0 00 0 00 0 15 0 00 4 00 0 05 0 00 61 0 00 0 00 0 15 0 00 4 00 0 05 0 00 62 0 00 0 00 0 15 0 00 4 00 0 05 0 00 63 0 00 0 00 0 15 0 00 4 00 0 05 0 00 64 0 00 0 00 0 15 0 00 4 00 0 05 0 00 CEPS Initial interception storage inches SURS Initial surface runoff inches UZS Initial Upper Zone Storage inches IFWS Initial interflow inches LZS Initial Lower Zone Storage inches AGWS Initial Active Groundwater storage inch
84. 2 19 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 20 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 21 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 22 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 23 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 24 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 25 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 26 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 27 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 28 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 29 0 15 0 15 0 15 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 18 30 0 15 0 15 0 15 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 18 31 0 15 0 15 0 15 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 18 174 SAHM Guidance Document December 2013 32 0 15 0 15 0 15 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 18 33 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 34 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 35 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 36 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 37 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 38 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 39 0 12 0 12 0 12 0 11 0 1
85. 4 Show Swale a0R migs Swale Volume at Riser Head ac tt ORG Native Infiltration yes Total Volume Infiltrated ac ft Measured Infiltration Rate in hr Total Volume Through Riser ac ft teed Mitigated Move Elements 5 TA Reduction Factor infilt factor J Total Volume Through Facility ac ft Save ny Load xy Use Wetted Surface Area sidewalls a Percent Infitrated xa tt te iP If native infiltration is turned on then native infiltration will start when if Water starts to fill the underdrain if an underdrain is used Water enters the amended soil Gif Use Wetted Surface Area sidewalls is set to YES 3 Water saturates the amended soil layer s to 2 3rds of the total amended soil depth if there is no underdrain and Wetted Surface Area is set to NO or 103 SAHM Guidance Document December 2013 fal SAHM File Edit View Help Summary Report Dee Se 4Aug4be ol foe Le z SREMA a S Bio Swale 1 Mitigated EJ SCENARIOS Facility Name Bio Swale 1 Outlet 1 Outlet 2 Outlet 3 i Pre Project 0 o o 7 Facility Type Bioretention Swale A Miioated Use simple swale Quick Swale
86. 5 0 105 400 0 02 3 0 0 92 3 4 70 0 100 400 0 05 3 0 0 92 4 4 60 0 090 350 0 10 3 0 0 92 5 5 50 0 110 400 0 01 3 0 0 92 6 5 45 0 105 400 0 02 3 0 0 92 7 5 40 0 100 400 0 05 3 0 0 92 8 5 30 0 090 350 0 10 3 0 0 92 9 4 70 0 060 400 0 01 3 0 0 92 10 4 65 0 055 400 0 02 3 0 0 92 11 4 60 0 050 400 0 05 3 0 0 92 12 4 50 0 040 350 0 10 3 0 0 92 13 5 50 0 120 400 0 01 3 0 0 92 14 5 45 0 115 400 0 02 3 0 0 92 15 5 40 0 110 400 0 05 3 0 0 92 16 5 30 0 100 350 0 10 3 0 0 92 17 4 70 0 065 400 0 01 3 0 0 92 18 4 65 0 060 400 0 02 3 0 0 92 19 4 60 0 055 400 0 05 3 0 0 92 20 4 50 0 050 350 0 10 3 0 0 92 21 5 40 0 065 400 0 01 3 0 0 92 22 5 35 0 060 400 0 02 3 0 0 92 23 5 30 0 055 400 0 05 3 0 0 92 24 5 20 0 050 350 0 10 3 0 0 92 25 4 60 0 050 400 0 01 3 0 0 92 26 4 55 0 045 400 0 02 3 0 0 92 27 4 50 0 040 400 0 05 3 0 0 92 28 4 40 0 030 350 0 10 3 0 0 92 29 5 40 0 075 400 0 01 3 0 0 92 30 5 35 0 070 400 0 02 3 0 0 92 31 5 30 0 065 400 0 05 3 0 0 92 32 5 20 0 055 350 0 10 3 0 0 92 33 4 50 0 045 400 0 01 3 0 0 92 34 4 45 0 043 400 0 02 3 0 0 92 35 4 40 0 040 400 0 05 3 0 0 92 36 4 30 0 035 350 0 10 3 0 0 92 37 5 00 0 045 400 0 01 3 0 0 92 38 4 90 0 043 400 0 02 3 0 0 92 39 4 85 0 040 400 0 05 3 0 0 92 40 4 80 0 035 350 0 10 3 0 0 92 41 4 45 0 035 400 0 01 3 0 0 92 42 4 40 0 030 400 0 02 3 0 0 92 43 4 35 0 025 400 0 05 3 0 0 92 44 4 25 0 015 350 0 10 3 0 0 92 162 SAHM Guidance Document
87. 88889 933333 977778 022222 066667 eialielral 155556 200000 244444 288889 333333 377778 422222 466667 Serko 555556 918274 920724 923178 925635 928095 930558 933025 935495 937968 940444 942924 945407 947893 950383 952876 955372 957871 960374 962880 965389 967901 970417 972936 975458 977983 980512 983044 985579 988118 990660 993205 995793 998305 000860 003418 005979 000000 040867 081842 122927 164121 205424 246837 288360 329992 371735 413588 455550 497624 539808 582102 624508 667024 709652 752391 795241 838203 881277 924463 967760 011170 054692 098327 142074 185934 229907 273993 2318192 362504 406930 451470 496123 000000 049832 070473 086312 099664 111428 122064 131844 140947 149497 157583 165275 172624 179673 186455 192999 199329 205464 211420 217214 222856 228360 233734 238987 244127 249161 254095 258936 263687 268355 272942 277454 281894 286264 290569 294811 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 000000 wa Pd Mitigated R
88. ANTER BOX ELEMENT 0 ccsscsssesssceseceeeeeceeeceseeeseenaes 114 INFILTRATION BASIN ELEMENT 0000 cee ecccsceceeeceseesseceeecseseacesceeseeeaeenaeenaeeaee 116 INFILTRATION TRENCH ELEMENT cccccsssssscstecosesssosseracesorenssonsenscsaeeraceaaes 118 DRY WELL BREMEN Ti ooo Ge at Sees aan Gee 120 vii POINT OF COMPLIANCE prcne aran T E N GTE 122 CONNECTING ELEMEN TS cca osc ccnaaconatcpntasieidian ceca a a a e a 124 AINALSY SIS SCREEN kertin aea AAA A A ARAE E 127 FLOW DURATION ee a a a i dey e devodwes 129 FLOW FREQUENCY scroadcconnuconandiei n Anun eaten OR AAE Ai 132 DRAWDOW N a e p e E A ane 133 HYDROGRAPHS rriena eia a E a wlecundabopeds 134 LID POINTS TABLE ceaintcasesynaseasbataacs o e AATE E EAR RN ees 138 REPORTS SCREEN ccrndan dnn aa RO a Ra a an e 143 TOOES SCREEN verfio raa n a a a g a a aria 145 LIDANALYSIS SCREEN E a e n A A A A N a 147 OPTIONS Srna a a aA E E E REN N ANS 153 DURA RIONCRITERIA aip A a tte sens a e ca aes EG 155 SCALING FACTORS oiio EAE E R A A EA 157 APPENDIX A DEFAULT SAHM HSPF PERVIOUS PARAMETER VALUES 159 APPENDIX C ADDITIONAL GUIDANCE FOR USING SAHM ccc cc ee eeeees 181 Infiltration Reduction FactOr cccccccccccccccssesescsccccceccssssssceccccssssssussesccesssssusesssesccesseees 181 Flow Duration Outlet Structures Practical Design Considerations cceeee 182 Drawdown time and treatment vector CONSIGELATIONS cccesseeeesecccccesesseeese
89. D Notch Type a Left Side Slope HAV 0 Bottom Side Slope H V 0 Right Side Slope H v eo Pro Elements Top Side Slope HA a Orifice Diameter Height Infiltration No y Number in ft 1 Ab 4 E e ee 4 LID Toolbox 2 ee 1 ee Pond Volume at Riser Head ac ft 0 Show Pond Table Open Tabe lt 4 Initial Stage fi Commercial Toolbox Tide Gate Time Series Demana Move Elements Determine Outlet With Tide Gate K 4 IF Use Tide Gate g2 Tide Gate Elevation ft fo Downstream Connection X ea Toad Overflow Elevation ff fo Iterations fo E bi va a 5 The point of compliance is shown on the pond element as a small box with the letter A and number 1 in the bar chart symbol in the lower right corner The letter A stands for Analysis and designates that this is an analysis location where flow and stage will be computed and the output flow and stage time series will be made available to the user The number 1 denotes that this is POC 1 You can have an analysis location without having a point of compliance at the same location but you cannot have a point of compliance that is also not an analysis location 23 SAHM Guidance Document December 2013 6 Sizing the pond File Edit View Help Summary Report Os e ABSHE SOs SBS oO 5 Trapezoidal Pond 1 Mitigated Facility Name TrepezoidalPond 1 i TETEE Downstream Co
90. December 2013 Bioretention In the Pre Project scenario the Pre volume is modeled using a Basin element containing the drainage area of the pre project land use A point of compliance POC is assigned by the user to the Basin element Only surface runoff and interflow are connected to the POC In the Mitigated scenario the Unmitigated volume is modeled using a Basin element consisting of both impervious area and any pervious area draining to a Bioretention element For this element a separate POC is not needed to record the Unmitigated volume If an analysis point is used instead of a POC then there must be a conveyance element for example a Channel element immediately upstream of the Bioretention element The upstream conveyance element must include an analysis point to record the Unmitigated volume In the Mitigated scenario the bioretention Mitigated volume can be represented modeled using the Bioretention element If infiltration to the native soil is allowed then infiltration should be turned on and an infiltration rate input by the user A point of compliance POC is assigned by the user to the surface and underdrain if any discharge Outlet 1 of the Bioretention element to compute the Mitigated volume The POC number should be the same as for the Pre Project scenario Fae RCN Vicu Licks Simranen Reror File Edit View Help Summary Report If the POC number DEH see AEE is 1 then the user ede must select time T ee serie
91. Diagram Basic Elements Facility Dimensions Pavement Length ft 2080 Pavement Bottom width ft 209 Effective Total Depth ft 3 5 Bottom slope ft ft 0 01 Overflow Data Ponding Depth Above Pavement ft 01 Ei Fifective Valine Factor n Post Mit Porous Pavement 229 SAHM Guidance Document December 2013 In the Mitigated scenario the Mitigated volume is modeled with a Porous Pavement element A point of compliance POC is assigned by the user to the surface and underdrain if any discharge Outlet 1 of the Porous Pavement element to compute the Mitigated volume The POC number should be the same as for the Pre Project scenario If the POC number is 7 then the user should select time series 507 for the pre volume 808 for the post unmit volume and 807 for the post mit volume These time series are based on the element names selected by the user 230 SAHM Guidance Document December 2013 Green roof In the Pre Project scenario the Pre volume is modeled using a Basin element containing the drainage area of the pre project land use A point of compliance POC is assigned by the user to the Basin element Only surface runoff and interflow are connected to the POC In the Mitigated scenario the Unmitigated volume is modeled using a Basin element consisting of impervious area equal to the size of the green roof area This impervious area will be in a separate Basi
92. Diameter in Trench overflow pipe diameter Riser Type options Flat or Notched Notch Type Rectangular V Notch or Sutro For a rectangular notch Notch Height feet distance from the top of the weir to the bottom of the notch Notch Width feet width of notch cannot be larger than the riser circumference For more information on riser notch options and orifices see discussion in OUTLET STRUCTURE CONFIGURATIONS section Native Infiltration Yes infiltration into the underlying native soil Measured Infiltration Rate in hr Native soil infiltration rate Infiltration Reduction Factor 1 Native soil infiltration rate safety factor see page 79 Use Wetted Surface Area sidewalls Yes if infiltration through the trench side slopes is allowed If infiltration is used then the user should consult the Infiltration discussion on page 79 NOTE See Appendix C or consult with the local municipal permitting agency for additional considerations regarding infiltration and determination of the appropriate infiltration reduction factor Gravel trench bed receives precipitation on and evaporation from the trench surface The Precipitation Applied to Facility and Evaporation Applied to Facility boxes should be checked 67 SAHM Guidance Document December 2013 Note a gravel trench bed is assumed to fill with stormwater from the bottom of the trench to the top By comparison a bioretention facility fills from the surface down to th
93. Gate F Use Tide Gate Tide Gate Elevation fi Overflow Elevation ft m Auto Vault Quick Vault I Fixed Width For Auto Vault Facility Dimension Diagram_ Outlet Structure Data Riser Height ft 0 Riser Diameter in 0 Riser Type Notch Type Orifice Number in ft H o Flat Diameter Height 1 fo H 2h Hh 3 Hh Vault Volume at Riser Head ac ft Show Vault Table Initial Stage ff 0 Downstream Connection z Iterations Open Table 000 E m The storage vault has all of the same characteristics of the trapezoidal pond except that the user does not specify the side slopes by definition they are zero and the vault is assumed to have a lid no precipitation or evaporation Auto Vault and Quick Vault work the same way as Auto Pond and Quick Pond Go to page 55 to find information on how to manually size a vault or other HMP facility Vault input information Bottom Length ft Vault bottom length Bottom Width ft Vault bottom width Effective Depth ft Vault height from vault bottom to top of riser plus at least 0 5 feet extra Riser Height ft Height of overflow pipe above vault bottom 59 DEPTH VAULT SAHM Guidance Document December 2013 Riser Diameter in Vault overflow pipe diameter Riser Type options Flat or Notched Notch Type Rectangular V Notch or Sutro For a rectangular notch Notch Height feet distanc
94. In the Pre Project scenario the Pre volume is File Edit View Help Summary Report i ie Osi tee modeled using a Basin element containing ie the drainage area of the pre project land use ees Sa A point of compliance POC is assigned by ie the user to the Basin element Only surface SCENARIOS LH O Pre Project e ia v Mitigated Run Scenario runoff and interflow are connected to the POC Basic Elements Hasa demm gemd Pro Elements In the Mitigated scenario the Unmitigated volume is modeled using a Lateral Flow Impervious Area element which contains the impervious areas that are disconnected from the stormwater conveyance system and directed to runoff onto adjacent pervious areas A POC is not required for the Lateral Flow Impervious Area element When a POC is used at the downstream LID element then a POC is not required for the Lateral Flow Impervious Area element to record the Unmitigated volume When using a POC at the LID element the inflowing Unmitigated volume is automatically saved for future calculations In the Mitigated scenario the Mitigated volume is modeled with a Lateral Flow Impervious Area element connected to a Lateral Flow Soil Basin element A point of compliance POC is assigned by the user to the Lateral Flow Soil Basin element representing the LID measure Only surface runoff and interflow are connected to the POC to compute the Mitigated volume
95. M Mitigated Area in Basin IV Show Only Selected Ansci rr Available Pervious Acres Available Impervious Acres IV CTrees Flat 0 1 2 M Impery Flat 0 1 8 Basic Elements Post Mit Basin 20 Interceptor Trees 80 Impervious 22 SAHM Guidance Document December 2013 In the Mitigated scenario the Mitigated volume is modeled with a Basin element consisting of both impervious area and tree area A point of compliance POC is assigned by the user to the Basin element to compute the Mitigated volume Only surface runoff and interflow are connected to the POC The POC number should be the same as for the Pre Project scenario If the POC number is 5 then the user should select time series 505 for the pre volume 806 for the post unmit volume and 805 for the post mit volume These time series are based on the element names selected by the user 228 SAHM Guidance Document December 2013 Porous pavement In the Pre Project scenario the Pre volume is modeled using a Basin element containing the drainage area of the pre project land use A point of compliance POC is assigned by the user to the Basin element Only surface runoff and interflow are connected to the POC In the Mitigated scenario the Unmitigated volume is modeled using a Basin element consisting of impervious area equal to the size of the porous pavement area This impervious area will be in a separate Basin element added
96. M have been adjusted for the different soil land cover and land slope categories based on the professional judgment and experience of Clear Creek Solutions HSPF modelers in northern California For this example we will assume that the Pre project land use is 10 acres of D soil with grass vegetation on a moderate slope 1 2 13 SAHM Guidance Document December 2013 File Edit View Help Summary Report Dee tae a EACE N Ore aa E m X ol let Ba z GE baii SCENARIOS Subbasin Name Bain 5 Surface Interflow Groundwater Flows To Area in Basin I Show Only Selected Connect To Element Available Pervious Acres Available Impervious Acres A ETrees Mod 1 22 I Imperv Flat 0 1 o Basin 1 F CTrees Steep 2 5 I Imperv Mod 1 2 0 IM CTreesVSteep gt 5 Imperv Steep 2 5 0 Element Option List pFlat O 1 M ImperwVSteep gt 5 0 Porous Pavement 0 Connect to Point Of Compliance l Analyze Disconnect Element Disconnect POC Pro Elements Compute Recharge Find Element LID Toolbox Cut Element Copy Element Paste Element Delete Element Duplicate Predeveloped Commercial Toolbox SSeS e ele sesers eers elses Save Element Load Element
97. POC 1 Developed 1A 1B 1C Other Total Total drainage area 260 ac 36 70 144 10 260 soil cover slope C urban moderate 60 ac 31 29 60 D urban moderate 40 ac 40 40 impervious flat 150 ac 5 70 75 150 pond 10 10 10 Total drainage area 260 ac 36 70 144 10 260 DMA 2 East Area Drains to POC 2 Developed 2A 2B Pond Other Total Total drainage area 83 ac 15 57 5 6 83 soil cover slope C urban moderate 1 ac 1 0 1 D grass moderate 3 ac 0 0 3 3 lateral to impervious grass moderate ac 0 0 3 3 impervious moderate 71 ac 14 57 71 existing pond 1 ac 0 0 1 1 new pond 4 ac 4 4 Total drainage area 83 ac 15 57 5 6 83 DMA 3 South Area Drainsto POC3 Developed Total drainage area 127 ac soil cover slope C urban moderate 7 ac green roof flat 1 ac impervious flat 82 ac permeable pavement moderate 30 ac bioretention flat 7 ac Total drainage area 127 ac The development project is going to convert mostly agricultural land into a commercial and residential subdivision There is an existing pond in DMA 2 that will be included in the final development The development will also include porous pavement DMA 3 198 SAHM Guidance Document December 2013 lateral flow dispersion DMA 2 green roof DMA 3 and bioretention DMA 3 in addition to stormwater ponds detention basins in DMAs and 2 File Edit View Help Summary Report Oe te Agel Site Information Site Name Address City Precip Factor Ma
98. Pond option 207 SAHM Guidance Document December 2013 a SAHM Example Complex File Edit View Zoom Help AGSU A Oe SMES 0 Outlet 1 Outlet 3 Connections EEE Quick Pond _ Facility Dimension Diagram enone _ Outlet Structure Data Flevation f O RriserHeishe it p H fo Riser Diameter in a H J Riser Type Notched Predeveloped Mitigated oa foE 4 106 3 10E 2 10E 1 Percent Time Exceeding sever Lost We have now sized the DMA 1 Pond 208 SAHM Guidance Document December 2013 amp EEEE Os SEES DO 0 i Surface Interflow AA Mitigatec Lateral Area ac 2 Eje A SSA Ew For DMA 2 we are including 3 acres of parking that sheet flows onto 3 acres of lawn grass before entering the existing pond on site We use the lateral flow basins to represent the parking and lawn areas for this situation All of the runoff eventually drains to the stormwater detention pond at POC 2 209 SAHM Guidance Document December 2013 a SAHM Example Complex fle gdt View Zoom Help Ose 2a Kasum Oe SORE 000 Predeveloped Mitigated 10E3 WWE s Percent Time Exceeding We use Auto Pond to size DMA 2 Pond 210 SAHM Guidance Document December 2013 DMA 3 has a combination of land uses including porous pavement and a l acre green roof Everything drains to the bioretention facility we will have to size the bioretention
99. Sacramento Area Hydrology Model SAHM Guidance Document Clear Creek Solutions Inc www clearcreeksolutions com December 2013 ii To download the Sacramento Area Hydrology Model and the electronic version of this document please go to www clearcreeksolutions com downloads If you have questions about SAHM or its use please contact Clear Creek Solutions Inc 360 943 0304 8 AM 5 PM Pacific time iii End User License Agreement End User Software License Agreement Agreement By clicking on the Accept Button when installing the Sacramento Area Hydrology Model SAHM Software or by using the Sacramento Area Hydrology Model Software following installation you your employer client and associates collectively End User are consenting to be bound by the following terms and conditions If you or User do not desire to be bound by the following conditions click the Decline Button and do not continue the installation process or use of the Sacramento Area Hydrology Model Software The Sacramento Area Hydrology Model Software is being provided to End User pursuant to a sublicense of a governmental licensee of Clear Creek Solutions Inc Pursuant to the terms and conditions of this Agreement End User is permitted to use the Sacramento Area Hydrology Model Software solely for purposes authorized by participating municipal county or special district member agencies of signatory programs which are organized on a co
100. Slope H V ratio of horizontal distance to vertical 0 zero for vertical pond sides Riser Height ft Height of overflow pipe above pond bottom Riser Diameter in Pond overflow pipe diameter Riser Type options Flat or Notched Notch Type Rectangular V Notch or Sutro For a rectangular notch Notch Height feet distance from the top of the weir to the bottom of the notch Notch Width feet width of notch cannot be larger than the riser circumference For more information on riser notch options and orifices see discussion in OUTLET STRUCTURE CONFIGURATIONS section Infiltration Yes infiltration into the underlying native soil Measured Infiltration Rate in hr Native soil infiltration rate Infiltration Reduction Factor 1 Native soil infiltration rate safety factor see page 79 55 SAHM Guidance Document December 2013 Use Wetted Surface Area sidewalls Yes if infiltration through the pond side slopes is allowed If infiltration is used then the user should consult the Infiltration discussion on page 79 NOTE See Appendix C or consult with the local municipal permitting agency for additional considerations regarding infiltration and determination of the appropriate infiltration reduction factor A pond receives precipitation on and evaporation from the pond surface The Precipitation Applied to Facility and Evaporation Applied to Facility boxes should be checked 56 SAHM Guidance Document Decemb
101. Time Series Demand The stage area and storage are automatically copies into the SSD Table To get the discharge column we click on Not Used in column 4 and select Manual 203 SAHM Guidance Document December 2013 File Edit View Help Summary Report D MELEE TAA FEIE Facility Name Faciiy Type SBT _ Runscenerio __ Basic Elements EB rz SEA eJ __ ProElements ey i LID Toolbox Commercial Toolbox Be Tide Gate Time Series Demand We connect the discharge from the DMA 2 existing pond and the runoff from DMA 2B to POC 2 204 SAHM Guidance Document December 2013 BEALE M Or A EEA Subbasin Name MAS Surface Interflow Flows To Area in Basin Available Pervious Acres Available Impervious Acres Imperv Mod 1 2 j LID Toolbox D Agric Flat 0 1 L M Daira J eseis dove Elements PerviousT otal Imperious Toth B Ace Bain Toit aT Ae DeselectZero Select By co L The input for DMA 3 is added along with a channel element Channel 3 It doesn t matter where DMA 3 and Channel 3 are placed on the grid as long as Channel 3 is connected to the correct POC in this example POC 3 We run the pre project scenario by clicking on the Run Scenario button and when the pre project scenario finishes we go to the mitigated scenario grid 205 SAHM Guidance Document December 2013 File Edit View Zoom Help
102. To ES E I Precipitation Applied aa ae F Bvepatendpied Facility TypelSSD TABLE Maral infitation LoadFile Browse Aid gO sae acas e3 Not usea not uses not UNY niot usos not Uses Jsed E LID Toolbox Commercial Toolbox Be Tide Gate Time Series Demand To use column 4 Discharge or column 5 Discharge or Infiltration click on Not Used at the top of the column and select the appropriate input Manual means that the input is from the external SSD file just loaded Outlet Structure gives the user the option of inputting the outlet configuration data riser height diameter notch orifice information and having SAHM compute the discharge for the corresponding stage values 96 SAHM Guidance Document December 2013 BIORETENTION RAIN GARDEN ELEMENT File Edit View Help Summary Report Dee e HEEE h m eA Pa a Schematic Bio Swale 1 Mitigated SCENARIOS Facility Name Outlet 1 Outlet 2 Outlet 3 Bites C Pre Project Downstream Connection 0 0 o BA Miigated il Type Bioretention Swale Use simple swale Quick Swale Run Scenario F Underdrain Used Basic Elements Swale Bottom Elevation ft Swale Dimensions Flow Through Underdrain ac ft Ea Swale Length ft 0 000 Total Outflow ac ft oe Swale Bottom Width ft 0 000 Bio Swale 1 Freebo
103. Types PERLNDs Check only one A Grass Flat 0 1 A Grass Mod 1 2 A Grass Steep 2 5 A Grass VSteep gt 5 A Aaric Flat 0 1 AAaric Mod 1 2 A Agric Steep 2 5 A Agric VSteep gt 5 Commercial Toolbox el M AlUrban Flat 0 1 LID Toolbox WA Aaa aa Accept Cancel Move Elements PN ty Save xy Load xy 2 S x Y Runoff dispersion from impervious surfaces onto adjacent pervious land can be modeled using pervious and impervious lateral basins For example runoff from an impervious parking lot can sheet flow onto an adjacent lawn prior to draining into a stormwater conveyance system This action slows the runoff and allows for some limited infiltration into the pervious lawn soil prior to discharging into a conveyance system The pervious lateral basin is similar to the standard basin except that the runoff from the lateral basin goes to another adjacent lateral basin impervious or pervious rather than directly to a conveyance system or stormwater facility By definition the pervious lateral basin contains only a single pervious land type Impervious area is handled separately with the impervious lateral basin Lateral I Basin The user selects the pervious lateral basin land type by checking the appropriate box on the Available Soil Types Tools screen This information is automatically placed in the Soil PERLND Type box abo
104. able 8 0 33 0 25 1 45 0 48 see Table 9 19 see Table 8 0 32 0 25 1 40 0 45 see Table 9 20 see Table 8 0 30 0 25 1 20 0 40 see Table 9 21 see Table 8 0 35 0 20 1 50 0 50 see Table 9 22 see Table 8 0 33 0 20 1 45 0 48 see Table 9 23 see Table 8 0 32 0 20 1 40 0 45 see Table 9 24 see Table 8 0 30 0 20 1 20 0 40 see Table 9 25 see Table 8 0 35 0 25 1 00 0 40 see Table 9 26 see Table 8 0 33 0 25 0 90 0 38 see Table 9 27 see Table 8 0 32 0 25 0 80 0 37 see Table 9 28 see Table 8 0 30 0 25 0 60 0 35 see Table 9 29 see Table 8 0 45 0 35 2 00 0 60 see Table 9 30 see Table 8 0 42 0 35 1 90 0 58 see Table 9 31 see Table 8 0 40 0 35 1 80 0 55 see Table 9 32 see Table 8 0 35 0 35 1 50 0 50 see Table 9 33 see Table 8 0 30 0 25 0 70 0 50 see Table 9 34 see Table 8 0 28 0 25 0 65 0 48 see Table 9 35 see Table 8 0 27 0 25 0 60 0 45 see Table 9 36 see Table 8 0 25 0 25 0 50 0 40 see Table 9 37 see Table 8 0 30 0 20 0 70 0 50 see Table 9 38 see Table 8 0 28 0 20 0 65 0 48 see Table 9 39 see Table 8 0 27 0 20 0 60 0 45 see Table 9 40 see Table 8 0 25 0 20 0 50 0 40 see Table 9 41 see Table 8 0 30 0 25 0 50 0 40 see Table 9 42 see Table 8 0 28 0 25 0 48 0 38 see Table 9 43 see Table 8 0 27 0 25 0 45 0 37 see Table 9 44 see Table 8 0 25 0 25 0 35 0 35 see Table 9 166 SAHM Guidance Document December 2013 45 see Table 8 0 35 0 35 0 80 0 60 see Table 9 46 see Table 8 0 33 0 35 0 78 0 58 see Table 9 47 see
105. alues Click the Export button The user provides a file name and the format or type of file The file type can be ASCII text comma delimited Access database recharge SWMM or WWHM Click Save to save the exported time series file 4 UL Windows8_0S C ProgramData gt SAHM gt projects v Search projects Organize New folder la SkyDrive A Name z Date modified Type nfile 12 6 20138 58AM_ Text Document Libraries E Documents a Music Pictures E Videos e amp Homegroup PA Doug 1 Computer i Windows8_OS C a Local Disk E v Hourly X SUM AVG d Export Close File name Outflow Comma Di csv Hide Folders Access Database mdb Recharge rcg SWMM swm WWHM zwm 146 SAHM Guidance Document December 2013 LID ANALYSIS SCREEN File Edit View Help Summary Report DW tee ff N ABS6HESA Or SER hi o o OGAR SIA LID Scenario Generator LID Points Table LRE O Pre Project S POC To Analyze ff H annual 4 gA Mitigated Run Scenario Basic Elements nim Pro Elements LID Toolbox Commercial Toolbox Move llanats M Units of Inches 7 Close 7N I Units of Acre Ft Kal Na Tide Gate Elevation ft 0 Downstream Connection v i Overflow Elevation ft 0 Iterations 0 Save xy Load xy rE g p Y E I gt Fri 8 58 Example 1 Fini
106. amended 25 n n x Soil Layer 2 Sandy loam z Soil Layer 3 GRAVEL Edit Soil Types aaa Quick Swale Underdrain Diameter ft 05 Offset in Orifice Diameter in Flow Through Underdrain ac ft Total Outflow ac ft Percent Through Underdrain Facility Dimension Diagram Riser Outlet Structure fa Outlet Structure Data Riser Height Above Swale surface ft 9 5 H Riser Diameter in 35 24 Riser Type Notched H Rectangular H Notch Height ft o H Notch Width ft ct 4 Orifice Diameter Height Number in o eae E 2h Ah 4 3h Ah HA Show Swale Table OpenTable H Swale Volume at Riser Head ac ft 41 541 We can double the bioretention area from 7 acres to 14 acres We remove 7 acres of urban landscaping in DMA 3 to compensate for the increase in the bioretention area size 215 SAHM Guidance Document December 2013 File Edit View Help Summary Report eE IE CICE TIA I FILEE CERAS a 503 POC 3 Predeveloped The Facility PASSED 803 POC 3 Mitigated flow Flow cfs Predev Mit Percentage Pass Fail Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Durations Flow Frequency Drawdown Hydrograph LID Points Table pa Analyze datasets Compact WDM S Pass FLOW cfs y 10E 3 10E 2 10E 1 1 10 Percent Time Exceeding 4 4 4 5 5 5 6 6 6 7 7 7 8 8 8 9 9 Pass Pass Pass
107. an 1 day Ponds may have drain times in excess of the allowed maximum This can occur when a pond has a small bottom orifice If this is not acceptable then the user needs to change the pond outlet configuration manually run the Mitigated scenario and repeat the analyze stage computations A situation may occur where it is not possible to have both an acceptable pond drawdown retention time and meet the flow duration criteria NOTE The flow duration criteria take precedence unless the user is instructed otherwise by Appendix C or the local municipal permitting agency 133 SAHM Guidance Document December 2013 HYDROGRAPHS SAH Bape File Edit View Help Summary Report Cee se IABSHER Oe SB BERD 20 olla Sas Durations Drawdown A p Hydrograph up Analyze datasets Compact WDM Gan Diego fan Ere Duration Bounds i rea T 22 From Alameda igation den 24 JOO Minimum 2 Maximum Seasonal Durations mm dd tigated flow 1000 Trapezoidal Pond 1 ALL OUTLETS Mitigated 1001 Trapezoidal Pond 1 STAGE Mitigated Start Date Al Datasets Flow Stage J Precip Evap POC1 EndDate The user can graph plot any or all time series data by selecting the Hydrograph tab 134 SAHM Guidance Document December 2013 File Edit View Help Summary Report Oeil e MELEE MTAA E lee l F m Add Data File Previous Plots I Record Plots 1 San Diego Pan Evap 2 Rancho C Start Date 1961 10 01 00 00 Aaa te
108. ap Controls aas lt 4 gt SAHM selects the appropriate rain gage record and precipitation multiplication factor for the project site from the available long term hourly precipitation records provided by Sacramento County Sacramento County has four long term hourly precipitation records Elk Grove Natomas Orangevale and Rancho Cordova For this example we will use the Rancho Cordova rain gage with a precipitation factor of 0 944 The value of 0 944 is based on county isohyetal information provided by Sacramento County GIS The hourly precipitation data will be multiplied by this value to represent the actual precipitation at the project site 9 SAHM Guidance Document December 2013 The site name address and city information are optional This information is not used by SAHM but will be included in the project report summary 3 Select the lower threshold value for the flow duration analysis The default lower threshold value for the flow duration analysis is 25 of the 2 year flow File Edit ar Help Summary Report D H Toolbar tak EA ka Status Bar First Steps Site Information Site Name Address City Precip Factor Map Controls aas lt p To view the flow duration lower and upper threshold values select View Options 10 SAHM Guidance Document December 2013 cH Xe CEEI Osean Restore Defaults If appropriate the default SAHM flow duration lower threshold of 25
109. aped pond Go to page 55 to find information on how to manually size an irregular pond or other HMP facility To create the shape of an irregular pond the user clicks on the Open PondPad button This allows the user to access the PondPad interface see below 63 SAHM Guidance Document December 2013 PondPad Interface AASEN Os SB EE D OO E Pond 1 Mitigated acility Name lmeoularPond 1 Facility Type Outlet 1 Outlet 2 Outlet 3 Downstream Connections Precipitation Applied to Facility I Evaporation Applied to Facility Facility Dimensions Facility Bottom Elevation ft Outlet Structure Effective Depth ft Riser Height ft D y Riser Diameter in Doy Riser Type Fa H Notch Type The PondPad interface is a grid on which the user can specify the outline of the top of the pond and the pond s side slopes 64 SAHM Guidance Document December 2013 The user selects the line button second from the top on the upper left corner of the PondPad screen Once the line button is turned on the user moves the mouse over the grid to locate the pond s corner points The user does this in a clockwise direction to outline the pond s top perimeter The user can select individual points by clicking on the point button immediately below the line button Once selected any individual point can be moved or repositioned Grid Scale 200 ft Set Area 12206 186 sa ft
110. ard ft 0 000 Facility Dimension Diagram ge Over toad Flooding ft 2 000 Effective Total Depth ft 0 Riser Outlet Structure H J Bottom slope of Swale ft ft 0 000 Outlet Structure Data Top and Bottom side slope ft ft 0 000 Riser Height Above Swale surface ft fo H Left Side Slope HAV 0 000 Riser Diameter fn o 4 Right Side Slope HAV 0 000 Riser Type Fiat H Material Layers for Swale LID Toolbox Layer Layer2 Layer 3 Depth ft 000 i o Soil Layer 1 GRAVEL Soil Layer 2 GRAVEL Orifice Diameter Height Soil Layer 3 GRAVEL Number in t Commercial Toolbox Edta 1 fo 10 EditSoil Types it Soil Types 2 1 fo 2 KSat Safety Factor 3 fo 4 fo J None C2 Cc 4 Show Swale Table OpenTable lt 1 Move Elements Swale Volume at Riser Head ac ft 000 Q EN Native Infiltration o 4 lt g Save xy Load xy E Hoa B I The bioretention element is also known as a rain garden A bioretention facility is a depression in which the native soils have been excavated and replaced with amended or engineered soil On the surface of the bioretention facility there is either a riser with a discharge pipe or a weir controls the surface discharge from the bioretention Ponding of stormwater runoff is allowed encouraging it to infiltrate into the amended soil Infiltration from the amended soil to the native soil is al
111. ass Pass Pass Pass Pass Pass Pass Pass Pass FLOW cfs 10E 3 10E 2 1064 1 10 Percent Time Exceeding Analyze datasets Compact WDM 801 POC 1 Mitigated flo All Datasets Flow Stage Precip Evap J o o o o o o o o o o o o o o o 1 Durations Drawdown Hydrograph LID Points Table a 2 as a 1 2 ri z 1 1 1 re 2 1 z The flow duration plot for both Pre project and Mitigated flows will be shown along with the specific flow values and number of times Pre project and Mitigated flows exceeded those flow values The Pass Fail on the right indicates whether or not at that flow level the flow control standard criteria were met and the pond passes at that flow level in this example from 25 of the 2 year flow to the 10 year If not a Fail is shown a single Fail fails the pond design A maximun ratio of 110 is allowed for flows between the lower and upper thresholds for no more than 10 of the 100 flow levels listed in the flow duration table on the right of the flow duration plot 30 SAHM Guidance Document December 2013 File Edit View Help Summary Report Oem 28 AaSHBs Oe SEER olen Wes Durations Flow Frequency Drawdown Hydrograph LID Points Table Analyze datasets Compact WDM 1001 Trapezoidal Pond 1 STAGE Mitigated Duration Bounds O0 Minimum f2 Maximum I Seasonal Durations mm dd statbae m ow Pie Jee Jpoct Eeoae
112. ation see page 55 7 Review analysis File Edit View Help Summary Report Dee te AaS6HBs Os SBE 4 MM 501 POC 1 Predeveloped The Facility PASSED 801 POC 1 Mitigated flow FLOW cfs 10E 3 10E 2 1064 1 10 Percent Time Exceeding Durations Flow Frequency Drawdown Hydrograph LID Points Table Analyze datasets Compact WDM ji C 1 Predev low 801 POC 1 Mitigat All Datasets Flow Stage Precip Evip 0 0 0 0 oO 0 0 0 0 0 o 0 0 0 0 1 1 i I ja 1 1 ja 1 z 1 1 1 pb 1 1 1 1 1 The Analysis tool bar button third from the left brings up the Analysis screen where the user can look at the results Each time series dataset is listed in the Analyze Datasets box in the lower left corner To review the flow duration analysis at the point of compliance select the POC 1 tab at the bottom and make sure that both the 501 POC 1 Pre project flow and 801 POC 1 Developed flow are highlighted 29 SAHM Guidance Document December 2013 File Edit View Help Summary Report Dee te ABSGHEs Os SB FICE wlelien Ses 501 POC 1 Predeveloped The Facility PASSED 801 POC 1 Mitigated flow Flow cfs Predev Mit Percentage Pass Fail 4032 836 Pass 4435 568 Pass 4838 Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass P
113. ayer 1 Thickness ft Infiltration trench soil layer depth Layer 1 Porosity Infiltration trench soil porosity Riser Height ft Height of infiltration trench overflow pipe above trench soil surface If a weir is preferred instead of a riser then set the riser height to the weir height and set the riser diameter to the weir length Riser Diameter in Infiltration trench overflow pipe diameter Native Infiltration Yes infiltration into the underlying native soil Measured Infiltration Rate in hr Native soil infiltration rate If infiltration is used then the user should consult the Infiltration discussion on page 79 SAHM includes automated sizing of the infiltration trench based on a user set target infiltration percentage After the target percentage is set then the user can click on the Size Infiltration Trench button SAHM will iterate to determine the infiltration trench length and width needed to meet the target infiltration percentage NOTE See Appendix C or consult with the local municipal permitting agency for additional considerations regarding infiltration and determination of the appropriate infiltration reduction factor The infiltration trench receives precipitation on and evaporation from the trench surface 119 SAHM Guidance Document December 2013 DRY WELL ELEMENT File Edit View Help Summary Report ASHER Ossau Oooo Facility Name Outlet 1 Downstream Connection a p Facility Type Maximum Fac
114. cm hr K hydraulic conductivity of the porous medium cm hr h total hydraulic head cm z elevation cm The total head h is the sum of the matric head y and the gravity head z h y z Equation 4 Substituting for h yields K a Equation 5 Z 193 SAHM Guidance Document December 2013 Hydraulic conductivity and matric head vary with soil moisture content These values can be computed by solving the Van Genuchten s equation Equation 6 for both values Note that w 0 when the soil is saturated Van Genuchten Equation to calculate total head Mn h 1 l 1 EZ Equation 6 where A total hydraulichead a constant SE effective saturation m constant n constant and z elevation head Effective saturation SE can be computed using the following Van Genuchten equation Van Genuchten Equation to calculate effective saturation 0 6 l SE Equation 7 0 1 ay where water content 0 residual water content porosity a constant y 1 n constant 1 m constant 1 a A 1 A pore size distribution index Y bubbling pressure y pressure head h z h total hydraulic head z elevation head and SE effective saturation Ignoring z elevation head results in h hm matric head Evapotranspiration is an important component of the bioretention facility s hydrologic processes Evapotranspiration removes water from bioretention surface ponding and the
115. ct area of 470 acres with three locations where stormwater flows off of the project area and into adjacent stream and stormwater conveyance systems Using an Excel spreadsheet we will identify the pre project and developed land use for the area draining to each of the points of compliance POCs Pre project SAHM Complex Project Example Total Project Area 470 DMA 1 North Area Drains to POC 1 Pre project 1A 1B 1C Total Total drainage area 260 ac 36 70 154 260 soil cover slope C grass steep 6 ac 6 0 0 6 C agriculture moderate 160 ac 30 60 70 160 D grass moderate 9 ac 0 9 0 9 D agriculture flat 82 ac 0 0 82 82 impervious moderate 3 ac 0 1 2 3 Total drainage area 260 ac 36 70 154 260 DMA 2 East Area Drains to POC 2 Pre project 2A 2B Pond Total Total drainage area 83 ac 21 61 1 83 soil cover slope C grass steep 1 ac 1 0 1 C agriculture moderate 48 ac 9 39 48 D grass moderate 1 ac 1 0 1 D agriculture flat 32 ac 10 22 32 existing pond 1 ac 0 0 1 1 Total drainage area 83 ac 21 61 1 83 DMA 3 South Area Drains to POC3 Pre project Total drainage area 127 ac soil cover slope C grass steep 1 5 ac C agriculture moderate 28 ac 197 SAHM Guidance Document December 2013 D grass moderate 0 D agriculture flat 96 impervious moderate 1 5 Total drainage area 127 ac ac ac ac Developed SAHM Complex Project Example Total Project Area 470 DMA 1 North Area Drains to
116. d SCENARIOS a Facility Name Gravel Trench Bed 1 Outlet 1 Outlet 2 Outlet 3 i Pre Project Downstream Connection 0 0 0 a a Facility Type Gravel Trench Bed I Precipitation Applied to Facility Quick Trench Run Scenario Facility Dimension Diagram Basic Elements Facility Dimensions Outlet Structure Data Trench Length ft 0 3 3 Trench Bottom width O piser Hesar o mmm Gravel Trench Bed 1 Effective Total Depth ft 0 pear Diameter in 0 Bottom slope ft ft 0 Bisel ype Flat g Left Side Slope HAV 0 NEOUS Right Side Slope H V 0 Material Layers for Trench Bed Layer 1 Thickness ft 0 Orifice Diameter Height Layer 1 porosity 0 1 0 Number in ft LID Toolbox Layer 2 Thickness ft 0 t hk H Layer 2 porosity 0 1 0 2 fo oo 4 Layer 3 Thickness ft 0 3 fo 0 H Layer 3 porosity 0 1 0 Infiltration moy Trench Volume at Riser Head ac ft 000 Commercial Toolbox Show Trench OpenTable H Initial Stage Ft 0 Move Elements rN 37 Save xy Load xy a ee 2 ai By 4 The gravel trench bed is used to spread and infiltrate runoff but also can have one or more surface outlets represented by an outlet structure with a riser and multiple orifices sips GRAVEL TRENCH BED The user specifies the trench length bottom width
117. d precipitation multiplication factor for the project site from the available long term hourly precipitation records provided by Sacramento County Sacramento County has four long term hourly precipitation records Elk Grove Natomas Orangevale and Rancho Cordova These long term hourly precipitation records and corresponding evaporation records are also used in the Sacramento BMP Sizing Calculator The user can provide site information optional The site name and address will help to identify the project on the Report screen and in the printed report provided to the local municipal permitting agency The user locates the project site on the map screen by using the mouse and left clicking at the project site location Right clicking on the map re centers the view The and buttons zoom in and out respectively The cross hair button zooms out to the full county view The arrow keys scroll the map view 42 SAHM Guidance Document December 2013 GENERAL PROJECT INFORMATION SCREEN The project screen contains all of the information about the project site for the two land use scenarios Pre project land use conditions and the Mitigated developed land use conditions To change from one scenario to another check the box in front of the scenario name in the upper left corner of the screen Pre project is defined as the existing land cover conditions prior to any new land use development Runoff from the Pre project scenario is used
118. ded a Used POC Mitigated stage b Drawdown times okay 17 Options set to default values 18 Other issues SAHM submittal APPROVED INIAM R O NM 187 SAHM Guidance Document December 2013 Below is a complete list of the files produced by SAHM Project file WHM Project back up file WH2 text file Project database file WDM HSPF WDM binary file Project report file RTF Microsoft Word rich text file format Project report file PDF portable document format Project HSPF input file UCI HSPF text file Project HSPF message file MES HSPF text file Project HSPF PERLND output file L61 HSPF text file Project HSPF RCHRES output file L62 HSPF text file Project HSPF data output file DAT HSPF text file Project HSPF error file ERROR FIL HSPF text file Note Only the project file is needed to run or check a model SAHM will create the additional files as needed 188 SAHM Guidance Document December 2013 APPENDIX E BIORETENTION MODELING METHODOLOGY The bioretention swale element is also known as a landscape swale or rain garden The SAHM bioretention swale element is a special conveyance feature with unique characteristics The element uses the HSPF hydraulic algorithms to route runoff but the HSPF routing is modified to represent the two different flow paths that runoff can take The routing is depe
119. development unmitigated runoff time series for each LID measure and cannot add two or more time series together to get the total post development unmitigated volume SCENARIOS LID Toolbox Use of a POC instead of an analysis point will solve this point The POC automatically will generate the total post development unmitigated runoff time series from all of the upstream elements without the need for analysis points As described above when using a POC for a LID measure a post development unmitigated time series with a 700 series number for unmitigated flows entering the LID measure will be automatically created and stored in the SAHM data management file SAHM LID POINTS TABLE In the SAHM LID Points Table shown above the first column LID Measures is a user input column that lists all of the LID measure elements used in the LID points calculations The user can type into column one any name to identify the LID measure The second column Pre Time Series is the runoff time series number for the SAHM element selected in column 1 This Pre Time Series number is selected by the user from a drop down list If the element has a POC then the number will be a 500 time series number if the element has an analysis point then the number will be a 1000 time series number The third column Pre Vol ac ft is the total predevelopment runoff volume for the entire multi year simulation period for the
120. diately upstream of the compost amended soil Bioretention element The upstream conveyance element must include an analysis point to record the Unmitigated volume In the Mitigated scenario the compost amended soil Mitigated volume can be represented modeled using the Bioretention element If infiltration to the native soil is allowed then infiltration should be turned on and an infiltration rate input by the user A point of compliance POC is assigned by the user to the surface and underdrain if any discharge Outlet 1 of the Bioretention element to compute the Mitigated volume The POC number should be the same as for the Pre Project scenario File Edit View Help Summary Report File Edit View Help Summary Report If the POC number Dee se DOS e is then the user lel must select time T areen series 501 for the SCENARIOS pre volume 701 for a Pre Project the post unmit AHA Miigated volume and 801 Run Scenario for the post mit volume These time series are gt based on the element names selected by the user GH C Pre Project AA Mitigated If an analysis point LID Toolbox Hade is used then the a user must select the 1000 time series Set up using Analysis Points Set up using POC numbers for the post unmit volume and the post mit volume based on the elements names The post mit volume will be from Outlet 1 235 SAHM Guidance Document
121. distribution for all three land use scenarios side by side 150 SAHM Guidance Document December 2013 The bottom red is the surface runoff Above in yellow is interflow then green for groundwater and blue for evaporation Basin 1 Scenario 1 is an A soil with grass land cover on a flat slope and produces the least amount of surface runoff red and interflow yellow the sum of surface and interflow is the total stormwater runoff and the largest amount of groundwater green and evapotranspiration blue Basin 2 is a D soil with agriculture land cover on a moderate slope it produces more surface runoff red and interflow interflow than Basin 1 Basin 3 is impervious and produces the largest amount of surface runoff red and the smallest amount of evaporation blue A maximum of seven scenarios can be graphed at one time 151 SAHM Guidance Document December 2013 This page is intentionally left blank 152 SAHM Guidance Document December 2013 OPTIONS Doe AE KA P File Edit s Help Summary Report Toolbar eal Bg amp Status Bar First Steps Site Information Site Name Address City Precip Factor Map Controls aga lt p Options can be accessed by going to View Options 153 SAHM Guidance Document December 2013 1 Restore Defaults This will bring up the Options screen and the ability to modify the built in default duration criteria f
122. e bottom 68 SAHM Guidance Document December 2013 SAND FILTER ELEMENT File Edit View Help Summary Report Dao tege IABSGHUE SR Os I FILEE h DCRRARKSA 5 Schematic fella es ae BL lus SCENARIOS a Facility Name Sand Filter 1 Outlet 1 Outlet 2 Outlet 3 Downstream Connections 0 0 0 Facility Type Sand Filter I7 Precipitation Applied to Facility Quick Filter vE i Facility Dimension Diagram Facility Dimensions Outlet Structure Data Bottom Length ft 0 A A Bottom Width ft 0 Beer toote 0 a Sand Filter 1 Effective Depth ft 0 Bizet Diemetec e l Left Side Slope HAV 0 Piser oe E F Bottom Side Slope HV O niyen Right Side Slope H V 0 Top Side Slope HV 0 Infiltration Fes 4 Orifice Diameter Height Hydraulic Conductivity in hr 0 Number in ft LID Toolbox l 1 CS oI Filter material depth ft fo o H 2 b 4h 4 Total Volume Filtrated ac ft 0 3 lo H 0 E Total Volume Through Riser ac ft 0 Total Volume acti 0 Filter Storage Volume at Riser Head ac ft 000 Commercial Toolbox Percent Filtered 0 Show Filter Table Open Tabe Size Infiltration Basin Initial Stage ft 0 Target 100 Move Elements ef Sy Save xy Load xy xa ee E A Ei gt The sand filter is a water quality facility It does not infiltrat
123. e from the top of the weir to the bottom of the notch Notch Width feet width of notch cannot be larger than the riser circumference For more information on riser notch options and orifices see discussion in OUTLET STRUCTURE CONFIGURATIONS section Infiltration Yes infiltration into the underlying native soil Measured Infiltration Rate in hr Native soil infiltration rate Infiltration Reduction Factor 1 Native soil infiltration rate safety factor see page 79 Use Wetted Surface Area sidewalls Yes if infiltration through the vault sides is allowed If infiltration is used then the user should consult the Infiltration discussion on page 79 NOTE See Appendix C or consult with the local municipal permitting agency for additional considerations regarding infiltration and determination of the appropriate infiltration reduction factor A vault is usually covered and does not receive precipitation on and evaporation from the vault surface The Precipitation Applied to Facility and Evaporation Applied to Facility boxes should not be checked unless the vault top is open to the atmosphere 60 SAHM Guidance Document December 2013 TANK ELEMENT File Edit View Help Summary Report Dae 2 e IABSHE SR Or SM OR D 2 O X Schematic D Tank 1 Mitigated Ea Facility Name Facility Type Outlet 1 Outlet 2 Outlet 3 C Fre Project Downstream Connection 0 o jo a Z Mitigated T Precip
124. e is calculated when the Calculate button at the bottom of the table is clicked by the user Column 10 is the LID points value calculated for each individual LID measure selected by the user when the Calculate button at the bottom of the table is clicked by the user The LID points equation is 200 Post Unmit Vol Post Mit Vol Post Unmit Vol Pre Vol Note Click on the Calculate button only after all of the user input has been provided for columns 1 2 4 5 7 and 8 Guidance for how each LID measure should be represented in SAHM is described in Appendix G 141 SAHM Guidance Document December 2013 This page is intentionally left blank 142 SAHM Guidance Document December 2013 REPORTS SCREEN we SAHM Example 1 File Edit View Help Summary Report Doe Ed amp Bastian ABSUHS Oe Sam Gs m m k E aN N Agric fete Trapezoidal Pond 1 Mitigated E SCENARIO a Facility Name Trapezoidal Pond 1 Facility Type Trapezoidal Pond Outlet 1 Outlet 2 Outlet 3 Pre Project Downstream Connections 0 0 0 Mitigated IV Precipitation Applied to Facility Auto Pond Quick Pond Buns I Evaporation Applied to Facility Facility Dimension Diagram un scenaro n z a ae Sea Outlet Structure Data acility Bottom Elevation ft 0 Riser Height ft pm ad Bottom Length ft 90 668814 Riser Diameter in 7g H Bottom Width ft 9066881426 eae z 5 x Original t
125. e mouse pointer pull the other end of the line down to the trapezoidal pond and click on the pond This will bring up the From Basin to Conveyance screen As with the Pre project scenario we want to only connect the surface flow and the interflow shallow subsurface runoff from the basin to the pond Click OK 19 SAHM Guidance Document December 2013 File Edit View Help Summary Report De sae BASHEN Ose SOBER ooo j 5 Facility Name Tasesa Facility Type Outlet 1 Outlet 2 Outlet 3 Downstream Connections Bn Bd igat Precipitation Applied to Facility AutaPond QuickPond 1 Evaporation Applied to Faciity Facility Dimension Diagram Facility Dimensions Outlet Structure Data Facility Bottom Elevation ft Fier Heh p24 ABE poogen Riser Diameter in p H Bottom Width ft ao e Es Eifective Dert j Notch Type r Left Side Slope HAV E ae Bottom Side Slope H V Right Side Slope H V Pro Elements ToP Ske Sora HA Orifice Diameter Height 5 Infiltration Number in ft 1 cee e 2 Cee H 3 cee 1 ole Pond Volume at Riser Head ac ft 0 Show Pond Table Open Tabe Initial Stage f P Commercial Toolbox Tide Gate Time Series Demand A line will connect the land use basin to the pond 20 SAHM Guidance Document December 2013 JASEN Ossau DO D 5 Facility Name arsa Pmd 1 Facility Type Outlet 1 Outlet 2 Outlet 3 Downstream Connections
126. e native soil Infiltration Reduction Factor between 0 and 1 1 Native soil infiltration rate safety factor see page 79 Use Wetted Surface Area sidewalls YES or NO YES allows infiltration to the native soil through the sidewalls of the swale otherwise all infiltration is through the bottom only If infiltration is used then the user should consult the Infiltration discussion on page 79 99 SAHM Guidance Document December 2013 NOTE See Appendix C or consult with the local municipal permitting agency for additional considerations regarding infiltration and determination of the appropriate infiltration reduction factor Vertical orifice plus overflow ee eae EE File Edit View Help Summary Report ee FA ABG4HUE E Oe 5S Oak Schematic fo S je Bio Swale 1 Mitigated ae ee Facility Name Bio Swale 1 Outlet 1 Outlet 2 Outlet 3 DRE CO Pre Project Downstream Connection 0 0 0 Facility Type Bioretention Swal Ped Mitigated ty Typ F Use simple swale Quick Swale Run Scenario F Underdrain Used Basic Elements Swale Bottom Elevation ft 0 Swale Dimensions Flow Through Underdrain ac ft 0 Swale Length ft 0 000 low ac tt Swale Bottom Width ft 0 000 Bio Swale 1 Freeboard ft 0 0 Facility Dimension Diagram Over toad Fl
127. e runoff but is used to filter runoff through a medium and send it downstream It can also have one or more surface outlets represented by an outlet SAND FILTER structure with a riser and multiple orifices The user must specify the facility dimensions bottom length and width effective depth and side slopes The hydraulic conductivity of the sand filter and the filter material depth are also needed to size the sand filter default values are 1 0 inch per hour and 1 5 feet respectively EFFECTIVE DEPTH ss Se ee BOTTOM LENGTH FILTER MATERIAL DEPTH 69 SAHM Guidance Document December 2013 NOTE When using the sand filter element check with Appendix C or the local municipal permitting agency to determine the required treatment standard percent of the total runoff volume treated by the sand filter The filter discharge is calculated using the equation Q K I A where Q is the discharge in cubic feet per second cfs K equals the hydraulic conductivity inches per hour For sand filters K 1 0 in hr Sand is the default medium If another filtration material is used then the design engineer should enter the appropriate K value supported by documentation and approval by the reviewing authority Design of a sand filter requires input of facility dimensions and outlet structure characteristics running the sand filter scenario and then checking the volume calculations to see if the Percent Filtered equals or exceeds
128. e the point of compliance has been selected the element is modified on the E s Bt ev Hep summam Report i E A IERA Schematic screen to include a small box with the letter A for Analysis in the lower right corner This identifies the outlet from this element as a point of compliance The number 1 next to the letter A is ansema the number of the POC POC 1 ES LID Toolbox 123 SAHM Guidance Document December 2013 CONNECTING ELEMENTS File Edit View Help Summary Report Dee se ABSHE OR Os SORT O0 Subbasin Name A Designate as Bypass for POC Surface Interflow Groundwater Flows To Area in Basin able Pervious Acres Available Impervious Acres Element SEES List od Impery Flat 0 1 Connect To Element Connect to Point Of Compliance Analyze ala Disconnect Element ERWA Disconnect POC w i Compute Recharge E Find Element f Cut Element E Paste Element Delete Element Duplicate Predeveloped Save Element Load Element a il oobice Run Predeveloped Basin Total DeselectZero SelectBy cc Elements are connected by right clicking on the upstream element in this example Basin 1 and selecting and then left clicking on the Connect To Element option By doing so SAHM extends a line from the upstream element to wherever the user wants to connect that element 124 SAHM Guidance Document December 2013 File Edit View Help Summary Repo
129. eceesseees 183 APPENDIX D SAHM REVIEWER CHECKLIST ccc c cc cccccececececececesecsceeecs 187 APPENDIX E BIORETENTION MODELING METHODOLOGY cee 189 APPENDIX F SAHM COMPLEX PROJECT EXAMPLE 0 ccc cece cc cccccccecececececeeees 197 APPENDIX G LID POINTS TABLE PROJECT EXAMPLES oee 217 viii SAHM Guidance Document December 2013 INTRODUCTION TO SAHM SAHM is the Sacramento Area Hydrology Model SAHM is based on the WWHM Western Washington Hydrology Model stormwater modeling platform WWHM was originally developed for the Washington State Department of Ecology More information about WWHM can be found at www clearcreeksolutions com More information can be found about the Washington State Department of Ecology s stormwater management program and manual at www ecy wa gov programs waq stormwater manual html Clear Creek Solutions is responsible for SAHM and the SAHM guidance documentation This guidance documentation is organized so as to provide the user an example of a standard application using SAHM described in Quick Start followed by descriptions of the different components and options available in SAHM The Tips and Tricks section presents some ideas of how to incorporate LID Low Impact Development facilities and practices into the SAHM analysis Appendices A and B provide a full list of the HSPF parameter values used in SAHM Appendix C contains additional guidance and recommendations by the stormwater p
130. ed for the different soil land cover and land slope categories based on the professional judgment and experience of Clear Creek Solutions HSPF modelers in northern California SAHM HSPF soil parameter values take into account the hydrologic effects of land development activities that result from soil compaction Impervious areas are divided into two different slopes see Table 2 Impervious areas include roads roofs driveways sidewalks and parking The slope categories are the same as for pervious areas flat moderate steep and very steep Table 2 SAHM Impervious Land Types IMPLND No IMPLND Name Land Slope 1 Impervious Flat 0 1 2 Impervious Moderate 1 2 3 Impervious Steep 2 5 4 Impervious Very Steep gt 5 The user does not need to know or keep track of the HSPF IMPLND number That number is used only for internal tracking purposes 48 SAHM Guidance Document December 2013 LATERAL BASIN ELEMENT Pervious File Edit View Help Summary Report Dee e 4 amp AA Schematic Lateral Basin 1 Pre Project EJ Element Name Lateral Basin 1 SCENARIOS Runoff Type Surface Interflow Groundwater BB V Pre Project Downstream Connection 0 0 0 a Element Type Lateral Pervious Flow Basin Soil PERLND Type Change Run Scenario Lateral Area ac 0 O Mitigated Lateral Basi Tools B Available Soil
131. eep 2 5 I AGrassVSteep gt 5 I Imperv VSteep gt 5 I AAaric Flat 0 1 J Porous Pavement I AAatic Mod 1 22 M AAgicStesp25 I AAagticVSteep gt 5 IF AUrban Flat 0 1 F AUrban Mod 1 22 I AUrban Steep 2 5 I AUrbanVSteep 5 I A Trees Flat 0 12 I A Trees Mod 1 2 I ATrees Steep 2 5 I ATreesNSteep gt 5 I B Grass Flat 0 1 I B Grass Mod 1 2 z BiGrass Steepi25 JH 3 Surface Interflow Groundwater E Pre Project Flows To Basic Elements PerviousTotal Acres Impervious Total Actes Basin Total Actes Deselect Zero Select By Go xa virza To the right of the grid is the land use information associated with the landuse basin element Select the appropriate soil land cover and land slope for the Pre project scenario Soils are based on NRCS general categories A B C and D Land cover is based on the native vegetation for the Pre project area and the planned vegetation for the planned development Mitigated scenario The SAHM land cover categories are grass agricultural land urban vegetation lawns flowers and planted shrubs and trees Land slope is divided into flat 0 1 moderate 1 2 steep 2 5 and very steep gt 5 HSPF parameter values in SAH
132. ees Flat 0 1 30 B Trees Moderate 1 2 31 B Trees Steep 2 5 32 B Trees Very Steep gt 5 33 C Grass Flat 0 1 34 C Grass Moderate 1 2 35 C Grass Steep 2 5 36 C Grass Very Steep gt 5 37 C Agricultural Flat 0 1 38 C Agricultural Moderate 1 2 39 C Agricultural Steep 2 5 40 C Agricultural Very Steep gt 5 41 C Urban Flat 0 1 42 C Urban Moderate 1 2 43 C Urban Steep 2 5 160 SAHM Guidance Document December 2013 44 C Urban Very Steep gt 5 45 C Trees Flat 0 1 46 C Trees Moderate 1 2 47 C Trees Steep 2 5 48 C Trees Very Steep gt 5 49 D Grass Flat 0 1 50 D Grass Moderate 1 2 51 D Grass Steep 2 5 52 D Grass Very Steep gt 5 53 D Agricultural Flat 0 1 54 D Agricultural Moderate 1 2 55 D Agricultural Steep 2 5 56 D Agricultural Very Steep gt 5 57 D Urban Flat 0 1 58 D Urban Moderate 1 2 59 D Urban Steep 2 5 60 D Urban Very Steep gt 5 61 D Trees Flat 0 1 62 D Trees Moderate 1 2 63 D Trees Steep 2 5 64 D Trees Very Steep gt 5 161 SAHM Guidance Document December 2013 Table 2 SAHM HSPF Pervious Parameter Values Part I PERLND No LZSN INFILT LSUR SLSUR KVARY AGWRC 1 4 80 0 110 400 0 01 3 0 0 92 2 4 7
133. element for each type of pond and stormwater control facility The pond element shown above is for a trapezoidal pond This is the most common type of stormwater pond A trapezoidal pond has dimensions bottom length and width depth and side slopes and an outlet structure consisting of a riser and one or more orifices to control the release of stormwater from the pond A trapezoidal pond includes the option to infiltrate runoff if the soils are appropriate and there is sufficient depth to the underlying TRAPEZOIDAL POND 53 SAHM Guidance Document December 2013 groundwater table The user has the option to specify that different outlets be directed to different downstream destinations although usually all of the outlets go to a single downstream location Auto Pond will automatically size a trapezoidal pond to meet the required flow duration criteria Auto Pond is available only in the Mitigated scenario Quick Pond can be used to instantly add pond dimensions and an outlet configuration without checking the pond for compliancy with flow duration criteria Quick Pond is sometimes used to quickly create a scenario and check the model linkages prior to sizing the pond Multiple clicks on the Quick Pond button incrementally increase the pond size The user can change the default name Trapezoidal Pond 1 to another more appropriate name if desired Precipitation and evaporation must be applied to the pond unless
134. endly graphical interface with screens for input of pre project and post project conditions an engine that automatically loads appropriate parameters and meteorological data and runs continuous simulations of site runoff to generate flow duration curves a module for sizing or checking the control measure to achieve the hydromodification control standard and a reporting module The HSPF hydrology parameter values used in SAHM are based on best professional judgment using our experience with calibrated watersheds in other parts of California SAHM uses the Sacramento County long term hourly precipitation data records selected to represent Sacramento County rainfall patterns SAHM computes stormwater runoff for a site selected by the user SAHM runs HSPF in the background to generate a hourly runoff time series from the available rain gage data over a number of years Stormwater runoff is computed for both pre project and post project land use conditions Then another part of the SAHM routes the post project stormwater runoff through a stormwater control facility of the user s choice SAHM uses the pre project peak flood values from an annual series of individual peak events to compute the pre project 2 year through 25 year flood frequency values The post project runoff 2 year through 25 year flood frequency values are computed at the outlet of the proposed stormwater facility The model routes the post project runoff through the stormwater facil
135. ent the pavement layer and two subgrade layers and their design characteristics thickness and porosity The subgrade layers Sublayer 1 and Sublayer 2 are available to provide storage prior to discharge through infiltration to the native soil or discharge via an underdrain 107 SAHM Guidance Document December 2013 Quick Pavement will create a porous pavement feature with default values without checking it for compliancy with flow duration standards The porous pavement surface area automatically receives rainfall and produces evapotranspiration Due to this model input the porous pavement surface area should be excluded from the basin element s total surface area If ponding is not allowed then the ponding depth above pavement value should be set to zero 108 SAHM Guidance Document December 2013 GREEN ROOF ELEMENT SSS SSS File Edit View Help Summary Report Cel e AZABSSHER Or S aEe ol fel la Schematic Element Name Runoff Type Surface Interflow Groundwater Downstream Connection o 0 0 Element Type Green Roof Soil PERLND Type Green ECO ROOF Green Area ac o Depth of Material in 4 Slope of Rooftop ft ft 0 001 Vegetative Cover Ground Cover X 50 Length of Rooftop ft SCENARIOS Pro Elements LID Toolbox Commercial Toolbox m Move Elements 4 ey Save xy Loadxy
136. ento Area Hydrology Model The concept of designing a flow duration control facility is relatively new and as described above requires the use of a continuous simulation hydrologic model To facilitate this design approach Clear Creek Solutions CCS has created a user friendly automated modeling and flow duration control facility sizing software tool adapted from its Western Washington Hydrology Model WWHM The WWHM was developed in 2001 for the Washington State Department of Ecology to support Ecology s Stormwater Management Manual for Western Washington and assist project proponents in complying with the Western Washington hydromodification control requirements The Sacramento Area Hydrology Model SAHM is adapted from WWHM Version 4 but has been modified to represent Sacramento County hydrology and enhanced to be able to size other types of control measures and low impact development LID techniques for flow reduction as well SAHM is a useful tool in the design process but must be used in conjunction with local design guidance to ensure compliance for specific projects The reader should refer to Appendix C and local stormwater program guidance for additional information and suggestions for using the SAHM Acknowledgements The following individuals are acknowledged for their contributions to the development of SAHM and guidance documentation e Doug Beyerlein Joe Brascher and Gary Maxfield of Clear Creek Solutions Inc f
137. er 2013 circumference length of opening sized for 100 yr flow overflow W S for secondary inlet Provide vertical bars in frame 4 O C _SECTION a a_ See also the separate verfiow NTS structure shown in Figure 2 7 SECTION B B has 2 options L e_n ai eae F T Piua CATENA 1 ff reek linino NTS Figure 3 10 Typical Detention Pond Sections 57 SAHM Guidance Document December 2013 NOTE The detention pond section diagram shows the general configuration used in designing a pond and its outlet structure This diagram is from the Washington State Department of Ecology s 2005 Stormwater Management Manual for Western Washington Consult with your local municipal permitting agency on specific design requirements for your project site 58 SAHM Guidance Document December 2013 VAULT ELEMENT File Edit View Help Summary Report Cel e DOLARLA Schematic SCENARIOS Facility Name H CO Pre Project tigated Run Scenario Basic Elements Effective Depth ft Pro Elements Infiltration LID Toolbox Commercial Toolbox Move vi fy Save xy Load xy Downstream Connection 0 Precipitation Applied to Facility Vault 1 Mitigated Vault 1 Outlet 1 Outlet 2 Outlet 3 0 0 NOH Tide Gate Time Series Demand Determine Outlet With Tide
138. er 2013 File Edit View Help Summary Report Doel e AEA EE ol hel la P Analysis ES Drawdown Analysis 001 Trapezoidal Pond 1 STAGE Mitigated Pond Trapezoidal Pond 1 Stage feet Percent of Total Run Time 1 NVA NVA 2 N A N A 3 N A N A 4 NYA N A 5 N A N A Max Stage 3 533514 Drawdown Time dd hh mm ss Less than 1 day Pond drains in less than 1 days Durations Flow Frequency Drawdown Hydrograph LID Points Table Analyze datasets Compact WDM japezoidal Pond 1 STAGE Mitigated Duration Bounds 0 01 Minimum f2 Maximum Seasonal Durations mm dd Start Date All Datasets Flow Stage Precip Evap Poci End Date Click on the Analyze Stage button and the computed pond stages pond water depths are summarized and reported in terms of drain retention time in days For this example the maximum stage computed during the entire 30 50 year simulation period is 3 53 feet This maximum stage has a drawdown time less than 1 day Ponds may have drain times in excess of the allowed maximum of hours This can occur when a pond has a small bottom orifice If this is not acceptable then the user needs to change the pond outlet configuration manually run the Mitigated scenario and repeat the analyze stage computations A situation may occur where it is not possible to have bot
139. er Height p H Riser Diameter in fg 4 Riser Type Notched H Notch Type Rectangular Notch Height a 72ga Notch width ft gg H Orifice Diameter Height Number in ft 1 Basil el 2 mS 3 Cm cet Pond Volume at Riser Head acf 692 Show Pond Table OpenTable Initial Stage e To exit SAHM click on File in the upper left corner and select Exit Or click on the X in the red box in the upper right hand corner of the screen 39 SAHM Guidance Document December 2013 This page is intentionally left blank 40 SAHM Guidance Document December 2013 MAIN SCREENS SAHM has six main screens These main screens can be accessed through the buttons shown on the tool bar above or via the View menu The six main screens are Map Information General Project Information Analysis Reports Tools LID Low Impact Development Analysis Each is discussed in more detail in the following sections 41 SAHM Guidance Document December 2013 MAP INFORMATION SCREEN File Edit View Help Summary Report Dag x e z o De a et a Sacramento Site Information Site Name Address City Gage Precip Factor Map Controls aas lt A gt The Map Screen contains county information The precipitation gage and precip factor are shown to the right of the map They are based on the project site location SAHM selects the appropriate rain gage record an
140. ero Select By ao After the point of compliance has been added to the land use basin the basin element will change A small box with a bar chart graphic and a number will be shown in the lower right corner of the basin element This small POC box identifies this basin as a point of compliance The number is the POC number e g POC 1 15 SAHM Guidance Document December 2013 5 Set up the Mitigated scenario sa 2B ASUmM Os S L EIA Subbasin Name M Designate as Bypass for POC Surface Interflow Groundwater Flows To H d l MI Miti Area in Basin Available Pervious Acres Available Impervious Acres Imperv Flat 0 13 Ue Commercial Toolbox l PerviousTotal ines Toal DO Jaee Banta D jae eselect Zero Select By m co First check the Mitigated scenario box and place a land use basin element on the grid 16 SAHM Guidance Document December 2013 File Edit View Help Summary Report Dee se PELLEM Os SEER D2 GO Subbasin Name Basn i Designate as Bypass for POC Surface Interflow Groundwater Flows To Area in Basin I Show Only Selected Available Pervious Acres Available Impervious Acres alr Cna E Ipew OTR G Imperv Mod 1 2 gt L D Urban Mod 1 27 le PerviousT otal Impervious Total Basin Total Save xy Load xy ee Select By co For the Mitigated land use we have 4 5 acres of D soil urban vegetatio
141. es GWVS Initial Groundwater Vertical Slope feet feet 173 SAHM Guidance Document December 2013 Table 8 SAHM HSPF Pervious Parameter Values Monthly Interception Storage inches PERLND No JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 1 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 2 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 3 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 4 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 5 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 6 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 7 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 8 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 9 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 10 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 12 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 0 11 13 0 15 0 15 0 15 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 18 14 0 15 0 15 0 15 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 18 15 0 15 0 15 0 15 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 18 16 0 15 0 15 0 15 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 20 0 18 17 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 12 18 0 12 0 12 0 12 0 11 0 10 0 10 0 10 0 10 0 10 0 10 0 11 0 1
142. ess than or equal to 110 for flow levels values between the lower threshold 25 of the 2 year flow in this example and upper threshold 10 year flow Only a maximum of 10 of the 100 flow levels values may exceed 100 all other flow levels values must be 100 or less If the percentage value does not exceed these rules then the Pass Fail column shows a Pass for that flow level If they are exceeded then a Fail is shown A single Fail and the facility fails the flow duration criteria The facility overall Pass Fail is listed at the top of the flow duration table File Edit View Help Summary Report Deh te z ele es Am Durations Flow Frequency Drawdown ooranh LID Points Table Analyze datasets Compact WDM 1 San Diego Pan Evap Duration Bounds 2 Rancho C 0 01 Minimum B Maximum 22 From Alameda irrigation dsn 24 0 Seasonal Durations mm dd 1000 Trapezoidal Pond 1 ALL OUTLETS Mitigated 1001 Trapezoidal Pond 1 STAGE Mitigated Start Date All Datasets Flow J Stage J Precip Evap J POC 1 J End Date Sz The user also has the option of computing a duration curve for any of the data sets listed with user defined lower and upper limits The default minimum and maximum duration bounds are 0 01 and 2 0 but these can be changed by the user to any appropriate values for example the minimum can be changed to zero 130 SAHM Guidance Document December 2013 Duration anal
143. etland basin Mitigated volume can be represented modeled using a combination of SAHM elements This combination of elements reproduces the combined effect of the constructed wetland basin s forebay open water zone wetland zone and outlet zone The forebay can be represented modeled using the Trapezoidal Pond Irregular Pond Vault or SSD Table element The open water zone can be represented modeled using the Trapezoidal Pond Irregular Pond Vault or SSD Table element The wetland zone can be represented modeled using the Bioretention element The outlet zone can be represented modeled using the Trapezoidal Pond Irregular Pond or SSD Table element If infiltration to the native soil is allowed in any one of these zones then infiltration should be turned on and an infiltration rate input by the user A point of compliance POC is assigned by the user to the surface discharge Outlet 1 of the outlet zone element to compute the Mitigated volume The POC number should be the same as for the Pre Project scenario 237 SAHM Guidance Document December 2013 File Edit View Help Summary Report File Edit View Help Summary Report If the POC number oa amp EOE amp is 1 then the user OES IRIENSES ekl ISE must select time Schematic eee series 501 for the pre volume 701 for the post unmit volume and 801 for the post mit volume These time series are based on the element names selected by the user If an anal
144. ew Help Summary Report Ds AMSRa MR Os SEER DO0 Facility Name Downstream Connection Sximum Depth of Panding ft Primary Exit 1 Structure Secondary Exit 2 Structure Flow Threshold H Flow Threshold cfs 5 LID Toolbox Commercial Toolbox Volume at Top of Storage area ac ft 000 Show Splitter Table OpenTable H Initial Stage ft Save xy Load xy x Le The second option is that the flow split can be based on a flow threshold The user sets the flow threshold value cfs for exit 1 at which flows in excess of the threshold go to exit 2 For example if the flow threshold is set to 5 cfs then all flows less than or equal to 5 cfs go to exit 1 Exit 2 gets only the excess flow above the 5 cfs threshold total flow minus exit 1 flow 91 SAHM Guidance Document December 2013 TIME SERIES ELEMENT File Edit View Help Summary Report De se 4aSks De Sim LE DSAAS S Schematic ET S Time Series 1 Mitigated i a Name Time Series 1 SCENARIOS LRE O Pre Project AA Miigated Run Scenario Time Series Out Choose WDM C ProgramData SAHM projects Example 1 wdm 1 San Diego Pan Evap ancho C Basic Elements 22 From Alameda irrigation dsn 24 501 POC 1 Predeveloped flow 701 _ Inflow to POC 1 Mitigated 801 POC 1 Mitigated flow 1000 Trapezoidal Pond 1 ALL OUTLETS Mitigated 1001_Trapezoidal Pond 1 STAGE Mitigated
145. ew Help Summary Report Oem S aE LE op Fo it Lee SS Analysis 33 Results 5 LID Points Table LID Measures Pre Pre Vol PostUnmitElementName Post Post Unmit Post Mit Element Name Post Mit Postmit LID Pts Time ac ft Unmit Vol Time l Series Time ac ft Series ac ft Series Dry Wells 501 113 0 Basin 1 701 365 8 Trapezoidal Pond 1 801 1827 144 86 Total 144 86 Duratio Analyze dat All Datasets v port Close In the first column the user selects the LID Measure from a drop down box The user then selects each LID element for which LID points will be calculated The second column Pre Time Series is the runoff time series number for the SAHM element selected in column 1 This Pre Time Series number is selected by the user If the element has a POC then the number will be a 500 time series number if the element has an analysis point then the number will be a 1000 time series number The third column Pre Vol ac ft is the total predevelopment runoff volume for the entire multi year simulation period for the selected element This runoff volume is calculated when the Calculate button at the bottom of the table is clicked by the user The fourth column Post Unmit Element Name is the SAHM mitigated scenario element that is generating the unmitigated runoff volume The fifth column Post Unmit
146. ext based report Report opens in Wordpad Formatted report with charts in pdf format Report opens in pdf viewer PDF Report LID Toolbox M Draft Report Original text based report Landuse Report Commercial Toolbox Original text based report a Parameter Report Move Elements ey Save xy Load xy JE 7 Y j gt Fri 8 58a Example 1 Finish Mitigated Bel Click on the Reports tool bar button fourth from the left to select the Report options table Selecting Text Report will generate a project report in Microsoft Word RTF format with all of the project information and results Selecting PDF Report will generate a project report in Adobe Acrobat PDF format with all of the project information and results The Landuse Report produces a list of the land use information contained in the project The Parameter Report lists any HSPF parameter value changes made by the user 143 SAHM Guidance Document December 2013 SAHM PROJECT REPORT Project Name Example 1 Site Name Site Address City Report Date 12 6 2013 Gage RANCHO C Data Start 1961 10 01 Data End 2004 09 30 Precip Scale 0 94 Version 2013 12 03 Low Flow Threshold for POC 1 25 Percent of the 2 Year High Flow Threshold for POC 1 10 year PRE PROJECT LAND USE Name Basin 1 Bypass No GroundWater No Pervious Land Use Acres D G
147. for the i PreProject post unmit volume Bd Mitigated and 801 for the post mit volume These time series are based on the element names selected by the user ARSA a Schematic SCENARIOS G CO Pre Project Lina v Mitigated Run Scenario Run Scenario Basic Elements Basic Elements Pro Elements E LID Toolbox Pa dh a Ein If an analysis point is used then the user must select the 1000 time series numbers for the post unmit volume and the post mit volume based on Set up using Analysis Points Set up using POC the elements names The post mit volume will be from Outlet 1 244 SAHM Guidance Document December 2013 Vegetated Filter Strip In the Pre Project scenario the Pre volume is modeled using a Basin element containing the drainage area of the pre project land use A point of compliance POC is assigned by the user to the Basin element Only surface runoff and interflow are connected to the POC In the Mitigated scenario the Unmitigated volume is modeled using a Basin element consisting of both impervious area and any pervious area draining to a vegetated filter strip represented by the Bioretention element For this element a separate POC is not needed to record the Unmitigated volume If an analysis point is used instead of a POC then there must be a conveyance element for example a Channel element
148. fs The horizontal axis is the percent of time that flows exceed a flow value Plotting positions on the horizontal axis typical range from 0 0001 to 1 as explained below For the entire 30 to 50 year simulation period depending on the period of record of the precipitation station used all of the hourly time steps are checked to see if the flow for 26 SAHM Guidance Document December 2013 that time step is greater than the minimum flow duration criteria value 0 40 cfs in this example For a 50 year simulation period there are approximately 400 000 hourly values to check Many of them are zero flows The 25 of the Pre project 2 year flow value is exceeded less than 1 of the total simulation period This check is done for both the Pre project flows shown in blue on the screen and the Mitigated flows shown in red If all of the Mitigated flow duration values in red are to the left of the Pre project flow duration values in blue then the pond mitigates the additional erosive flows produced by the development If the Mitigated flow duration values in red are far to the left of the Pre project flow duration values in blue then the pond can be made smaller and still meet the flow duration criteria a Sacramento Area Hydrology Model File Edit View Help Summary Report Osea s 8 Augua6n8 ol ellen Ee Scher Automatic Pond Adjuster 0 1 min lt 2 10 min gt 10 min Fast Thorough Pond Depth incl 1
149. ft freeboard gft Pond length to width ratio 1 tot Pond Side Slopes 3 tol Bottom Length poeses1a2 ft Bottom Width 20 6688142 ft Volume at riser head 692 acre ft Trapezoidal Pond 1 a SCENARIOS GOH C Pre Project AA Mitigated Run Scenario Predeveloped Mitigated 4 39 Basic Elements 2 40 Autopond Finished FLOW cfs Choose Outlet Structure 1 orifice amp rectangular notch iv 1 40 Progress Pond Computed MfoE 4 10E 3 10E 2 ioei 1 10 100 Create Pond Optimize Pond Accept pond Close LID Toolbox Percent Time Exceeding Show Pond Table OpenTable Initial Stage fi Commercial Toolbox Tide Gate Time Series Demand Determine Outlet With Tide Gate F Use Tide Gate Tide Gate Elevation ff 0 Downstream Connection z Overflow Elevation ff 0 Iterations 0 Move fell Lge aay Save xy Load xy x Bo va Ha i Thu 1 50p default 0 Finish Mitigated L EM lx 4 Auto Pond goes through an iteration process by which it changes the pond dimensions and outlet configuration then instructs SAHM to again compute the resulting Mitigated runoff compare flow durations and decide if it has made the results better or worse This iteration process continues until Auto Pond finally concludes that an optimum
150. g 4 There is both an underdrain and native infiltration Underdrain flow and native infiltration are computed as discussed above However there is one other limitation to consider In the case where the flow through the soil layer is less than the sum of the discharge through the underdrain and the native infiltration then the flow through the soil layer becomes the limiting flow and must be divided between the native infiltration and the underdrain This division is done based on the relative discharge rates of each Note that wetted surface area can be included in the discharge calculations by adding the infiltration through the wetted surface area to the lower soil layer and the upper surface layer individually This is done by computing the portion of the wetted surface area that is part of the upper surface layer and computing the infiltration independently from the portion of the wetted surface area that is part of the lower soil layers There are several equations used to determine water movement from the surface of the bioretention facility through the soil layers and into an underdrain or native infiltration The water movement process can be divided into three different zones 1 Surface ponding and infiltration into the top soil layer soil layer 1 2 Percolation through the subsurface layers 3 Underdrain flow and native infiltration 191 SAHM Guidance Document December 2013 The modified Green Ampt equation Equation 1 c
151. ge ft acres acre Not Used Not Used Not Used Not Used Not Used 1 2 J EA DE E Pro Elements _5 pm E6 8 E LID Toolbox 70 11 12 S Commercial Toolbox Tide Gate Time Series Demand Determine Outlet With Tide Gate Move Elements F Use Tide Gate 4 Tide Gate Elevation ft fo Downstream Connection tes Overflow Elevation ft 0 Iterations 0 Save xy Load xy Intitial Stage f x _ gt ve l Malley The runoff from DMA 2A flows to the DMA 2 existing pond The DMA 2 existing pond can be represented by the SSD Table element The SSD Stage Storage Discharge Table allows us to input the stage storage discharge relationship for any routing element We can create the SSD Table values in an Excel spreadsheet Elevation ft Stage ft Surface Area ac Storage Volume ac ft Discharge cfs 54 00 0 00 1 00 0 00 0 00 55 00 1 00 1 00 1 00 3 20 56 00 2 00 1 00 2 00 9 05 57 00 3 00 1 00 3 00 16 63 58 00 4 00 1 00 4 00 25 60 59 00 5 00 1 00 5 00 35 78 60 00 6 00 1 00 6 00 47 03 We copy the stage surface area storage volume and discharge values excluding the headings into an Excel CSV comma delimited file to import into SAHM The elevation column is not needed and is not included 202 SAHM Guidance Document December 2013 File Edit View Help Summary Report B A ERA ABSGUEA Or A E EILERA Facility Name Flows To Tide Gate
152. h an acceptable pond drawdown retention time and meet the flow duration criteria NOTE See Appendix C or the local municipal permitting agency for an overview of other requirements that may apply regarding drawdown time and suggestions for addressing situations where it is not possible to meet all drawdown retention time guidelines and also meet the flow duration criteria The guidance documentation assumes that the flow duration criteria take precedence unless the user is instructed otherwise by the local municipal permitting agency 34 SAHM Guidance Document December 2013 8 Produce report Sacramento Area Hydrology Model ASHES Os SEER B Trapezoidal Pond 1 Mitigated Ee Facility Name _ Trapezoidal Pond 1 Facility Type Trapezoidal Pond Outlet 1 Outlet 2 Outlet 3 Downstream Connections p p p I Precipitation Applied to Facility Auto Pond Quick Pond V Evaporation Applied to Facility Facility Dimension Diagram Facility Dimensions Outlet Structure Data Facility Bottom Elevation Ft 0 Riser Height ft Bo Bottom Lenat ft 90 66881428 Riser Diameter in 7g e RE 90 66881 428 Riser Type Notched zal pa n epth ft 4 Notch Type Rectangular Left see HA 3 Notch Height ft 0 726 Bottom Side Slope H V 3 Notch width t Ma H a sil Right Side
153. he in ground infiltration planter except that water is not allowed to infiltrate into the native soil underlying the gravel layer of the planter This is due to the native soil having poor infiltration capacity As with the in ground planter stormwater enters the planter above ground and then infiltrate through the soil and gravel storage layers before exiting through a discharge pipe Flow through Planter For the purpose of flow control the discharge from the pipe should not exceed the pre project discharge from the project site for the flow duration range specified by the local jurisdiction 114 SAHM Guidance Document December 2013 In SAHM the flow through planter is represented by a specialized application of the bioretention swale element The flow through planter dimensions and parameters are Planter Length ft Length of planter box Planter Bottom Width ft Width of planter box Freeboard ft Additional storage height above top of riser Effective Total Depth ft Planter height from bottom of planter to top of riser plus freeboard Soil Layer 1 Type Select from Soil Type pulldown menu Soil Layer 1 ft Planter soil layer depth Soil Layer 2 Type Select from Soil Type pulldown menu usually gravel Soil Layer 2 ft Planter gravel layer depth Underdrain Diameter ft Planter underdrain pipe diameter set to zero if no underdrain is included Orifice Diameter in Planter underdrain pipe orifice d
154. iameter set to zero if no underdrain is included Riser Height Above Planter Surface ft Height of planter overflow pipe above planter soil surface Riser Diameter in Planter overflow pipe diameter The only difference between an in ground infiltration planter and a flow through planter is whether or not native infiltration is allowed 115 SAHM Guidance Document December 2013 INFILTRATION BASIN ELEMENT File Edit View Help Summary Report DSH ee BEA EE MTAA EA AA Schematic a L SCENARIOS Facility Name Infilt Basin 1 Outlet 1 Outlet 2 Outlet 3 J C Pre Project Downstream Connections 0 0 E Facility Type IMP Infiltration Basin Maximum Facility Area ac 0 Quick Infiltration Basin Run Scenario Facility Dimensions Bottom Length ft Bottom Width ft Effective Depth ft Left Side Slope HAV Bottom Side Slope H V Right Side Slope H V Top Side Slope H V Outlet Structure Data Riser Height ft fo yH Riser Diameter in Infiltration ves H Measured Infiltration Rate in hr 0 H Use Wetted Surface Area sidewalls Mo H Sid Mitigated Basic Elements LID Toolbox Total Volume Infiltrated ac ft 0 Total Volume Through Riser ac ft 0 Total Volume Through Facility ac ft 0 00 Commercial Toolbox Percent Infiltrated 0 Pond Volume at Riser Head ac ft 0 Show Facility Table O
155. ic Steep 2 5 M AAgicVSteeph5 Pro Elements I AUrban Flat 0 1 C AUibanMod 2 I A Urban Steep 2 5 I AUrbanVSteep gt 5 LID Toolbox I ATrees Flat 0 1 I A Trees Mod 1 2 I ATrees Steep 2 5 I ATrees VSteep gt 5 I B Grass Flat 0 1 Commercial Toolbox B Grass Mod 1 2 z BiGrass Steepi25 Basic Elements Move Elements PerviousT otal 10 Actes 4p Impervious Total o Actes KEJ g2 Basin Total 0 Actes Save xy Load xy DeselectZero Select By Go x 2 Yi The project screen also contains the Schematic Editor The Schematic Editor is the grid to the right of the elements This grid is where each element is placed and linked together The grid using the scroll bars on the left and bottom expands as large as needed to contain all of the elements for the project All movement on the grid must be from the top of the grid down The space to the right of the grid will contain the appropriate element information To select and place an element on the grid first left click on the specific element in the Elements menu and then drag the element to the selected grid square The selected element will appear in the grid square The entire grid can
156. ified Line 9 specifies how many cross section values station and elevation there are in the input file In this example the number is 8 The user can specify up to a maximum of 50 cross section values Line 10 identifies the top of bank for both the right and left side of the channel In this example the top of bank is at values 3 80 0 24 0 and 6 94 0 24 0 This means that all elevations below 24 0 are in the channel and use the channel s Manning s n value of 0 04 and all elevations above 24 0 are in the floodplain and use the floodplain s Manning s n value of 0 10 The transition elevations 24 0 do not have to be identical for both the left and right banks but they should at least be close Below Line 10 are the eight lines of cross section values listing first station feet and then elevation feet The station is cumulative distance from an arbitrary datum at the left edge of the floodplain looking upstream The first station value does not have to be zero The elevation value corresponds to the specific station value The channel must have the lowest elevation values The channel bottom does not have to be flat it can be V shaped with a single value representing the deepest location 88 SAHM Guidance Document December 2013 If there are multiple cross sections the user would add another set of data starting with Line 9 after the last cross section value Note The final stage storage discharge table created by th
157. ility Area ac 0 _Calculate Dry Well Facility Dimensions 1 Diy Well Length ft Ew 5 Bry Well 1 Dry Well Bottom Width ft fe i Material Layers for Dry Well Reservoir Thickness ft Top Soil Layer Thickness ft Top Soil Layer Porosity 0 1 b Gravel Sand Layer Thickness ft Gravel S and Layer Porosity 0 1 Infiltration ms 4 Infiltration Rate inhr fo 4 Total Volume Infiltrated ac ft 0 Total Volume Through Riser ac ft 0 Total Volume Through Facility ac ft 0 Percent Infiltrated 0 Dry Well Volume at Riser Head ac ft 000 Show Dry Well Table OpenTable 24 The Dry Well element is located in the LID Toolbox All of the LID Toolbox elements can be viewed and selected by clicking on the LID Toolbox bar A dry well is similar to the in ground infiltration planter except that there is no bottom discharge pipe or underdrain Water must infiltrate into the native soil underlying the gravel layer of the planter The native soil must have sufficient infiltration capacity to infiltrate all of the stormwater In SAHM the dry well is represented by a specialized application of the gravel trench element 120 SAHM Guidance Document December 2013 The dry well dimensions and parameters Dry Well Length ft Length of well Dry Well Width ft Width of well Reservoir Thickness ft Depth of open water storage Top Soil Layer Thickness ft Dry well
158. in element Only surface runoff and interflow are connected to the POC In the Mitigated scenario the Unmitigated volume is modeled using a Basin element consisting of both impervious area and any pervious area draining to an Infiltration Basin element For this element a separate POC is not needed to record the Unmitigated volume If an analysis point is used instead of a POC then there must be a conveyance element for example a Channel element immediately upstream of the Infiltration Basin element The upstream conveyance element must include an analysis point to record the Unmitigated volume In the Mitigated scenario the infiltration basin Mitigated volume can be represented modeled using any one of the following SAHM elements Trapezoidal Pond Irregular Pond Vault Gravel Trench SSD Table Infiltration Basin or Infiltration Trench Infiltration to the native soil should be turned on and an infiltration rate input by the user A point of compliance POC is assigned by the user to the surface and underdrain if any discharge Outlet 1 of the Infiltration Basin element to compute the Mitigated volume The POC number should be the same as for the Pre Project scenario File Edit View Help Summary Report File Edit View Help Summary Report If the POC number is aACEL D D eee 1 then the user must le M B bea select time series 501 cx Schematic for the pre volume SCENARIOS 701 for the post al Pre Project unmit volume and m
159. ion Outlet Structures Practical Design Considerations Low flow Orifice Sizing The diameter of the low flow bottom orifice is an important design parameter for flow duration facilities since flows discharged through this outlet should be at or below the project threshold for controlled flows Qcp However maintenance and or other practical considerations may dictate a practical limit to how small this orifice may be which may be larger than the optimal theoretical diameter determined by Auto Pond As an example the SWMMWW specifies a minimum orifice diameter of 0 5 inches for flow restrictor assemblies that are within protective enclosures that screen out large particles and also have 1 2 ft of sump below the orifice to allow for some sediment accumulation While the user can manually set a minimum size for the low flow orifice doing so before running Auto Pond is not recommended as this may impair the program s ability to optimize the pond configuration The following general approach is suggested for designing a pond when there is a small value for the low end of the flow matching range 1 First estimate the minimum pond volume allowing Auto Pond to freely determine the diameter and placement of all orifices 182 SAHM Guidance Document December 2013 2 Then manually accept all of the pond settings except low flow orifice diameter Set the low flow orifice to the desired minimum size after consulting the local municipal permi
160. ions based on Pre project flow frequency or 2 durations based on user defined flow values If using durations based on user defined flow values click on that option and input the lower and upper flow values The default pass fail threshold is 110 for the flows between the lower threshold 25 155 SAHM Guidance Document December 2013 of the 2 year and the upper threshold 10 year flow The duration criteria can be changed for a single point of compliance Click on the Update button once all of the changes have been made To return to the default values click on the Restore Defaults button 156 SAHM Guidance Document December 2013 SCALING FACTORS Paint of Compliance Restore Defaults The user has the ability to change the scaling factor for pan evaporation The default value is 1 00 NOTE Any change in default scaling factors requires approval by the local municipal permitting agency Click on the Update button once all of the changes have been made To return to the default values click on the Restore Defaults button 157 SAHM Guidance Document December 2013 This page is intentionally left blank 158 SAHM Guidance Document December 2013 APPENDIX A DEFAULT SAHM HSPF PERVIOUS PARAMETER VALUES The default SAHM HSPF pervious parameter values are found in SAHM file defaultpers uci HSPF parameter values in SAHM have been adjusted for the different soil land cover and land slope
161. ired to meet HMP requirements Specific control measures from the August 2013 Stormwater Quality Design Manual for the Sacramento Region are listed in Table 1 along with the appropriate SAHM model element Table 1 Control Measures and Equivalent SAHM Elements Control Measure SAHM Element Underground Storage Vault or Tank Porous Pavement Porous Pavement Disconnected Pavement Lateral Impervious Basin to Lateral Pervious Basin Alternative Driveways Porous Pavement Disconnected Roof Drains Lateral Impervious Basin to Lateral Pervious Basin Interceptor Trees Land use Basin Green Roof Green Roof Capture and Re Use Vault or Tank Dry Well Dry Well or Pond with infiltration or Gravel Trench Compost Amended Soil Bioretention Constructed Wetland Basin Pond to Bioretention to Pond Detention Basin Trapezoidal Pond or Irregular Pond Infiltration Basin Infiltration Basin or Pond with infiltration Infiltration Trench Infiltration Trench or Gravel Trench with infiltration Sand Filter Sand Filter Stormwater Planter Flow Through Flow Through Planter Box Stormwater Planter Infiltration Infiltration Planter Box Vegetated Swale Channel Vegetated Filter Strip Bioretention Proprietary Devices SSD Table Note The Sacramento Stormwater Quality Partnership Stormwater Quality Design Manual and the City and County of Sacramento Drainage Manual Volume IT SAHM Guidance Docume
162. is method should be checked to make sure that the table s stage storage and discharge values meet the criteria specified below 1 Stage feet must start at zero and increase with each row The incremental increase does not have to be consistent 2 Storage acre feet must start at zero and increase with each row Storage values should be physically based on the corresponding depth and surface area but SAHM does not check externally generated storage values 3 Discharge cfs must start at zero Discharge does not have to increase with each row It can stay constant or even decrease Discharge cannot be negative Discharge should be based on the outlet structure s physical dimensions and characteristics but SAHM does not check externally generated discharge values 4 Surface area acres is only used if precipitation to and evaporation from the facility are applied If any of these criteria are violated SAHM will produce an error message If that occurs the cross section values station and elevation will need to be adjusted to produce a stage storage discharge table that meets the above criteria 89 SAHM Guidance Document December 2013 FLOW SPLITTER ELEMENT File Edit View Help Summary Report DW te ABSUBR Ose Sanaa oh al fe Sia Schematic so a je S low Splitter E ENARE a Facility Name Downstream Connection HC Pre Project Both Exits Primary Exit 1 Secondary Exit 2 Trapezoidal Pond 1 Channel 1
163. is run and flow is routed through the infiltration facility the total volume infiltrated total volume through the riser total volume through the facility and percent infiltrated are reported on the screen If the percent infiltrated is 100 then there is no surface discharge from the facility The percent infiltrated can be less than 100 as long as the surface discharge does not exceed the flow duration criteria The user can set an infiltration target 100 or less and SAHM will iterate to size the facility to meet that target infiltration total 79 SAHM Guidance Document December 2013 File Edit View Help Summary Report DH tae FABGHE SE Os 8S BES ob fo at SS n Schematic fe vente Trapezoidal Pond 1 Mitigated SCENARIOS E a Facility Name Trapezcidal Pond 1 Facility Type Trapezoidal Pond Outlet 1 Quilo Outlet 3 OH O Pre Project Downstream Connections 0 2 L m a Z Miioated Precipitation Applied to Facility A I Evaporation Applied to Facility Run Scenario ili Fi ji Facility Dimensions Basic Elements Facility Bottom Elevation ft 0 Riser Height ft Eei Bottom Lendhi i 0 Riser Diameter in 0 SCD Width ft 0 Riser Type fia H Effective Depth ft 0 Notch Type Left Side Slope H V 0 Bottom Side Slope HZ 0 Right Side Slope H V
164. itation Applied to Facility Auto Tank Quick Tank Facility Dimension Diagram Run Scenario es 3 Facility Dimensions Outlet Structure Data Facility Bottom Elevation ft 0 ane Tank Type es n ae Diameter ft e Gio Diameter fin o a Length ft 0 Riser Type Flat Notch Type Infiltration Ino H Orifice Diameter Height Number in ft 1 20 Abe 4 LID Toolbox dio oe ea Tank Volume at Riser Head ac ft 0 Show Tank Table OpenTabe H Intitial Stacie f J Commercial Toolbox Tide Gate Time Series Demand Determine Outlet With Tide Gate Use Tide Gate Move Elements Tide Gate Elevation jo Downstream Connection wy Ql N Overflow Elevation f 0 iterations am Save xy Load xy A storage tank is a cylinder placed on its side The user specifies the tank s diameter and length The tank element includes Auto Tank automatic tank sizing routine Or the user can manually size the tank to meet the flow duration criteria Go to page 55 to find information on how to TANK manually size a tank or other HMP facility CIRCULAR There is a Quick Tank option that creates a tank but does not check for compliance with the flow duration criteria DIAMETER Tank input information Tank Type Circular or Arched LENGTH 61 SAHM Guidance Document December 2013 For Circular Diameter ft Tank diameter Length ft Tank length For A
165. itigated volume The POC number should be the same as for the Pre Project scenario File Edit View Help Summary Report File Edit View Help Summary Report If the POC number is Cee see Ok t de 1 then the user must le M ba select time series 501 z Schematic for the pre volume SEM 701 for the post unmit N volume and 801 for AEE viostea the post mit volume Ringe em These time series are based on the element names selected by the SSD Tabe User H CO Pre Project EAM Mitigated Basic Elements If an analysis point is used then the user must select the 1000 time series numbers for the post unmit volume and the post Set up using Analysis Points Set up using POC mit volume based on the elements names The post mit volume will be from Outlet 1 246 SAHM Guidance Document December 2013 BMP Treatment Trains BMP treatment trains are a collection of BMPs in series For example a treatment train could be disconnected roof drains discharging across lawns to a bioretention cell to an infiltration basin In the Pre Project scenario the Pre volume is modeled using a Basin element containing the drainage area of the pre project land use A point of compliance POC is assigned by the user to the Basin element Only surface runoff and interflow are connected to the POC In the Mitigated scenario the Unmitigated volume is modeled using
166. ity As with the pre project peak flow values partial duration post project flow values are selected by the model to compute the developed 2 year through 25 year flood frequency The pre project 2 year peak flow is multiplied by a percentage 25 or 45 percent depending on location to set the lower limit of the erosive flows in accordance with the current HMP performance criteria The pre project 10 year peak flow is the upper limit A comparison of the pre project and post project flow duration curves is conducted for 100 flow levels between the lower limit and the upper limit The model counts the number of hourly intervals that pre project flows exceed each of the flow levels during 2 SAHM is based on WWHM Version 4 3 The actual flood frequency calculations are made using the Weibull flood frequency equation SAHM Guidance Document December 2013 the entire simulation period The model does the same analysis for the post project mitigated flows Low impact development LID best management practices BMPs have been recognized as opportunities to reduce and or eliminate stormwater runoff at the source before it becomes a problem They include compost amended soils bioretention porous pavement green roofs rain gardens and vegetated swales All of these approaches reduce stormwater runoff SAHM can be used to determine the magnitude of the reduction from each of these practices and the amount of stormwater detention storage still requ
167. ity Area ac Quick Trench Facility Dimensions Trench Length ft Trench Bottom Width ft Berm Height ft Material Layer for Trench Layer 1 Thickness ft Layer 1 porosity 0 1 Infiltration Infiltration Rate in hr Total Volume Infiltrated ac ft Total Volume Through Riser ac ft Total Volume Through Facility ac ft Percent Infiltrated Outlet Structure Data Riser Height ft te Riser Diameter in 0 Trench Volume at Riser Head ac ft 000 Show Trench Table OpenTable H Size Infiltration Trench The Infiltration Trench element is located in the LID Toolbox All of the LID Toolbox elements can be viewed and selected by clicking on the LID Toolbox bar An infiltration trench is similar to the dry well There is no bottom discharge pipe or underdrain Water must infiltrate into the native soil underlying the gravel layer of the planter The native soil must have sufficient infiltration capacity to infiltrate all of the stormwater In SAHM the infiltration trench is Infiltration Trench represented by a specialized application of the gravel trench element The infiltration trench dimensions and parameters are Trench Length ft Infiltration trench length 118 SAHM Guidance Document December 2013 Trench Bottom Width ft Infiltration trench width Berm Height ft Height above top of trench at which overflow occurs one foot above riser height L
168. l Channel Data Channel Bottom width ft aamen o Merinoncosticen fp Slope of Channel ft ft Left Side Slope HV Right Side Slope H V Memu Chanel Dep 9 Infiltration Ino H Show Channel Table OpenTable If the Use X Sections option is selected then the user is required to create a cross section input file outside of SAHM Note This option uses the XS2 program to create the channel s stage storage discharge table 87 SAHM Guidance Document December 2013 The text file should be created in the following format Line 1 RCH130 FTB starts in B Channel D WordPad column 1 Lines 2 4 end in column 5 File Edit Yiew Insert Format Help It recommends that the user copies the first four lines exactly as they are Deh 66 me i RCH130 FTB Line 5 lists first the upstream elevation 130 of the channel and then the 6 downstream elevation The upstream 10 elevation value ends in column 7 the 200 178 downstream in column 17 0 2 0 04 0 1 Line 6 is the length of the channel in 1 miles the value must be between 8 column 1 and column 10 3 6 0 0 32 0 Line 7 is the Manning s n roughness P 5 P values for first the channel and then 84 0 18 0 the floodplain The first value must be 92 0 18 0 between column 1 and column 10 the 94 0 24 0 second value between 11 and 20 200 0 26 0 300 0 32 0 Line 8 specifies how many cross sections are used to define the channel For this example only one is spec
169. ma 2 Basinimp 1022 8 GreenRoof 103 4 Capture and re use 1031 Basin Imp 1052 24 Vault Compost amended soil 1042 Basin Imp Grass 1052 15 Bioretention Bioretention 1058 12 Basinimp Grass 1034 36 Bioretention 1044 28 Calculate Close NOTE Each LID measure must be identified in SAHM as an analysis point or point of compliance POC to be available for the LID Points Table calculations 219 SAHM Guidance Document December 2013 File Edit View Help Summary Report Ose se Swale Bottom E Swale Dimensi Swale Length ft Swale Bottom Width I Freeboard ft Over toad Flooding ft Effective Total Depth Connect To Element Connect to Point Of Compliance Paste Element Delete Element Duplicate Predeveloped Save Element aaa Run Predeveloped Run Mitigated Clear All Import Basin Location The user has the choice of defining the LID measure as either an analysis point Analyze or a point of compliance Connect to Point of Compliance 220 SAHM Guidance Document December 2013 If Analyze is selected then the element will be labeled with a small A in the lower right corner If Connect to Point of Compliance is selected then the element will be labeled with a box containing an A plus the POC number in the example below the POC number is 1 Analysis Point Point of Compliance In the LID Points Table the anal
170. manually File Edit View Help Summary Report D a AHBSHUB SOs 8 LEIER So aor WY ETETE Facility Name Porous Pavement 1 Outlet 1 Outlet 2 Outlet 3 i Pre Project Downstream Connection Surface Swale 1 0 0 a Facility Type Porous Pavement M Mitigated PaE ae Quick Pavement Run Scenario Facility Dimension Diagram Basic Elements Facility Dimensions Overflow Data A pen Pavement Length ft Pavement Bottom Width ft Ponding Depth Above Pavement ft oo H bel Effective Total Depth ft Bottom slope ft ft z Effective Volume Factor Pro Elements Layers for Porous Pavement Pavement Thickness t 0 5 Diameter Height H Pavement porosity 0 1 0 28 in ft LID Toolbox Sublayer 1 Thickness ft Wnderdrain A Sublayer 1 porosity 0 1 04 Sublayer 2 Thickness ft Sublayer 2 porosity 0 1 Infiltration Ino Storage Volume at Top of Pavement ac ft 61 920 Commercial Toolbox EA Show Pavement Table Open Table H Initial Stage ft ce Move Elements xa Y bo__ a Fri 4 12p Example Complex Finish Mitigated iy The porous pavement area is 30 acres The total area draining to the bioretention is 120 acres including the porous pavement area The general rule of thumb is that the bioretention area must be at least 5 of the total area draining to it We star
171. must use the following units Stage feet Surface Area acres Storage acre feet Discharge cubic feet per second cfs A fifth column can be used to create a second discharge cfs This second discharge can be infiltration or a second surface discharge 94 SAHM Guidance Document December 2013 Certain rules apply to the SSD Table whether it is created inside or outside of SAHM These rules are 1 Stage feet must start at zero and increase with each row The incremental increase does not have to be consistent 2 Storage acre feet must start at zero and increase with each row Storage values should be physically based on the corresponding depth and surface area but SAHM does not check externally generated storage values 3 Discharge cfs must start at zero Discharge does not have to increase with each row It can stay constant or even decrease Discharge cannot be negative Discharge should be based on the outlet structure s physical dimensions and characteristics but SAHM does not check externally generated discharge values 4 Surface area acres is only used if precipitation to and evaporation from the facility are applied To input an externally generated SSD Table first create and save the table outside of SAHM Use the Browse button to locate and load the file into SAHM 95 SAHM Guidance Document December 2013 File Edit View Help Summary Report Del tae ASSUE SOs SMER DA0 Facility Name Rows
172. n moderate slope 3 acres of impervious flat slope 2 5 acres of impervious moderate slope We will add a trapezoidal pond downstream of the basin The impervious land categories include roads roofs sidewalks parking and driveways All are modeled the same except that steeper slopes have less surface water retention storage prior to the start of surface runoff 17 SAHM Guidance Document December 2013 Osa e ASHER Os 6 MEE oD 2 o Subbasin Name Ban i 7 Designate as Bypass for POC Surface Interflow Groundwater Flows To Area in Basin Available Pervious Acres Available Impervious v v Acres M ImperwSteep252 fo M ImpewWSteep gt 5 Jo M PorousPavement Jo LID Toolbox Paste Element Delete Element SESE SSE EEE 3 Save Element Load Element Run Predeveloped Run Mitigated Clear All Select By co The trapezoidal pond element is placed below the basin element on the grid Right click on the basin and select Connect To Element A green line will appear with one end connected to the basin 18 SAHM Guidance Document December 2013 ASHES Ose Se EILERA Subbasin Name Bsn 1 Designate as Bypass for POC Surface Interflow Groundwater Flows To Ey E Area in Basin Available Pervious Acres Available Impervious Acres L D Urban Mod 1 2 le PeviousTo BT Aas imperious Toal B5 Aces BeinTost Dd aes Deselect Zero SelectBy With th
173. n element added to the model for the sole purpose of providing the Unmitigated volume for the LID Points calculations otherwise this element does not need to be in the model Because as described above this is a situation where the unmitigated runoff volume is not automatically generated in the model and additional model input is required and a separate POC is needed to record the Unmitigated volume We suggest a POC number one greater than that selected for the Pre Project scenario Note that analysis points cannot be used for green roofs File Edit View Help Summary Report Oa e YZAOSUBsA Ose SO eaak h D eA a Ban a Schematic a SCENARIOS Subbasin Name in I Designate as Bypass for POC ey DPteProject Surface Interflow Groundwater gaiis Flows To BA Miiticated i Area in Basin IZ Show Only Selected Available Pervious Acres Available Impervious Acres Impery Flat 0 1 1 Run Scenario Basic Elements Post Unmit Basin 100 Impervious File Edit View Help Summary Report Ose se ASHE Os Sai 5 Element Name Green Roof 1 Runoff Type Surface Interflow Groundwater BEE C Pre Project Downstream Connection 0 0 0 fi Element Type Green Roof EA Mitgsted Soil PERLND Type Gieen ECO ROOF Green Area fac Depth of Material in 4 Slope of Rooftop ft ft Vegetative C
174. n linked together Channel input information Channel Bottom Width ft Open channel bottom width Channel Length ft Open channel length Manning s n coefficient Open channel roughness coefficient user menu selected or input Slope of Channel ft ft Open channel bottom slope Left Side Slope of Channel ft ft H V ratio of horizontal distance to vertical 0 zero for vertical channel sides Right Side Slope of Channel ft ft H V ratio of horizontal distance to vertical 0 zero for vertical channel sides Maximum Channel Depth ft Height from bottom of channel to top of channel bank Infiltration Yes infiltration into the underlying native soil Measured Infiltration Rate in hr Native soil infiltration rate Infiltration Reduction Factor 1 Native soil infiltration rate safety factor see page 79 Use Wetted Surface Area sidewalls Yes if infiltration through the channel side slopes is allowed If infiltration is used then the user should consult the Infiltration discussion on page 79 NOTE See Appendix C or consult with the local municipal permitting agency for additional considerations regarding infiltration and determination of the appropriate infiltration reduction factor 86 SAHM Guidance Document December 2013 Basic Elements 7a a IABSUBR Os SEED 0 Facility Name Downstream Connection Facility Type Clean and Straight 0 030 rt Channel Dimensions oeeie Genera
175. n the layer that first becomes saturated is determined by which layer is more restrictive This is determined by using Darcy s equation to compute flux for each layer at the current level of saturation The layer with the more restrictive flux is the layer that becomes saturated for that time step The next time step the same comparison is made The rate and location of water discharging from the soil layer is determined by the discharge conditions selected by the user There are four possible combinations of discharge conditions 1 There is no discharge from the subsurface layers except for evapotranspiration This means that there is no underdrain and there is no infiltration into the native soil Which this discharge condition is unlikely we still need to be able to model it 2 There is an underdrain but no native infiltration Discharge from the underdrain is computed based on head conditions for the underdrain The underdrain is configured to have an orifice It is possible for the orifice to be the same diameter as the underdrain With a maximum of three soil layers determining head conditions for the orifice is complicated Each modeled layer must overcome matric head before flow through the underdrain can begin Once matric head is overcome by gravity head for all of the layers then the underdrain begins to flow The flow rate is determined based on the ability of the water to move through the soil layers and by the discharge from
176. n values is shown on the left the flow values on the right The flow duration flow range is from the lower threshold flow frequency value 25 of the 2 year value in this example to the upper threshold flow frequency value 10 year value As shown in the flow duration table to the right of the flow duration curves this flow range is divided into approximately 100 levels flow values The division of the flow range into a large number of levels is important to make sure that the erosive flows do not increase between the lower threshold 25 of the 2 year flow in this example and the 2 year flow frequency value and between increasing flow frequency levels 3 year 4 year 5 year etc The majority of the erosive flows occur between the lower threshold flow value and the 2 year flow frequency value It is important to divide the flow levels in that range into multiple level steps to not miss any occasions when the mitigated flows exceed the pre project flows 129 SAHM Guidance Document December 2013 For each flow level value SAHM counts the number of times that the flow at the Point of Compliance for the Pre project scenario Predev exceeds that specific flow level value It does the same count for the Mitigated scenario flow Mit The total number of counts is the number of simulated hours that the flow exceeds that specific flow level value The Percentage column is the ratio of the Dev count to the Predev count This ratio must be l
177. nd an infiltration rate input by the user A point of compliance POC is assigned by the user to the surface discharge Outlet 1 of the selected element to compute the Mitigated volume The POC number should be the same as for the Pre Project scenario File Edit View Help Summary Report File Edit View Help Summary Report Ded tse Dem 22 ical oe isl Schematic SCENARIOS KRE CO Pre Project A Miigated a BEA Mitigated O Fre Project SCENARIOS Run Scenario Basic Elements Pro Elements LID Toolbox SS Schematic Dry Well 2 Set up using Analysis Points Set up using POC 226 If the POC number is 3 then the user must select time series 503 for the pre volume 703 for the post unmit volume and 803 for the post mit volume These time series are based on the element names selected by the user If an analysis point is used then the user must select the 1000 time series numbers for the post unmit volume and the post mit volume based on the elements names The post mit volume will be from Outlet 1 SAHM Guidance Document December 2013 Interceptor trees In the Pre Project scenario the Pre volume is modeled using a Basin element containing the drainage area of the pre project land use A point of compliance POC is assigned by the user to the Basin element Only surface runoff and interflow are co
178. ndent on the inflow to the swale and the swale soil capacity to absorb additional runoff HSPF Special Actions is used to check the swale soil capacity to determine the appropriate routing option A bioretention swale is a swale in which the native soils have been excavated and replaced with amended soil At the downstream end of the swale a weir or riser controls the surface discharge from the swale and detains runoff encouraging it to infiltrate into the amended soil Infiltration from the amended soil to the native soil is also possible depending on the properties of the native soil Swales can include an underdrain pipe The amended soil placed in the swale is assumed to have storage capacity equal to its porosity and volume Runoff infiltrates from the surface of the swale to the amended soil at an infiltration rate set by the user The infiltration rate cannot exceed the available storage capacity of the amended soil The available storage capacity is determined each time step by HSPF Special Actions Once the amended soil is saturated then water has the opportunity to infiltrate into the underlying native soil at the native soil s infiltration rate The native soil infiltration is input by the user and is assumed to be constant throughout the year Inflow to the swale can exceed the amended soil infiltration rate When this occurs the extra water ponds on the surface of the swale The extra water can then infiltrate into the soil during the
179. next time step or can flow out of the swale through its surface outlet if the ponding exceeds the surface outlet s storage Runoff in both the surface storage and amended soil storage is available for evapo transpiration Surface storage evapotranspiration is set to the potential evapo transpiration the amended soil evapotranspiration pan evaporation factor is set to 0 50 to reflect reduced evapotranspiration from the amended soil In the amended soil water movement through the soil column is dependent on soil layer characteristics and saturation rates for different discharge conditions Consider a simple two layered bioretention facility designed with two soil layers with different characteristics As water enters the facility at the top it infiltrates into the soil based on the modified Green Ampt equation Equation 1 The water then moves through the top soil layer at the computed rate determined by Darcy s and Van Genuchten s equations As the soil approaches field capacity i e gravity head is greater than matric head we can determine when water will begin to infiltrate into the second 189 SAHM Guidance Document December 2013 layer lower layer of the soil column This occurs when the matric head is less than the gravity head in the first layer top layer Since the two layers have different soil characteristics water will move through the two layers at different rates Once both layers have achieved field capacity the
180. ng an outlet configuration with one orifice and a riser with rectangular notch this is usually the most efficient design 1 Input a bottom orifice diameter that allows a discharge equal to the lower threshold e g 25 of 2 year Pre project flow for a stage equal to 2 3rds the height of the riser This discharge can be checked by reviewing the pond s stage storage discharge table 2 Input a riser rectangular notch height equal to 1 3 of the height of the riser Initially set the riser notch width to 0 1 feet 3 Run Pre project and Mitigated scenarios 4 Goto Analysis screen and check flow duration results 5 If pond passes flow duration criteria then decrease pond dimensions 6 If pond fails flow duration criteria then change in order of priority bottom orifice diameter riser notch width pond dimensions 7 Iterate until there is a good match between Pre project and Mitigated flow duration curves or fatigue sets in Pond input information Bottom Length ft Pond bottom length Bottom Width ft Pond bottom width Effective Depth ft Pond height from pond bottom to top of riser plus at least 0 5 feet extra Left Side Slope H V ratio of horizontal distance to vertical 0 zero for vertical pond sides Bottom Side Slope H V ratio of horizontal distance to vertical O zero for vertical pond sides Right Side Slope H V ratio of horizontal distance to vertical 0 zero for vertical pond sides Top Side
181. nmit Vol ac ft is the total post development unmitigated runoff volume for the entire multi year simulation period for the selected element This runoff volume is calculated when the Calculate button at the bottom of the table is clicked by the user following the input of all of the table information The seventh column Post Mit Element Name is the SAHM mitigated scenario element that is generating the mitigated runoff volume This is one of the LID measures included in the model For each LID measure the user types in the appropriate element name to produce the mitigated runoff volume The eighth column Post Mit Time Series is the runoff time series number for the SAHM element selected in column 7 This Post Mit Time Series number is selected by the user If the LID element has a POC then the number will be a 800 time series number if the element has an analysis point then the number will be a 1000 time series number The ninth column Post Mit Vol ac ft is the total post development mitigated runoff volume for the entire multi year simulation period for the selected element This runoff volume is calculated when the Calculate button at the bottom of the table is clicked by the user following the input of all of the table information Column 10 is the LID points value calculated for each individual LID measure selected by the user when the Calculate button at the bottom of the table is clicked by the user The LID points equation is 20
182. nnected to the POC In the Mitigated scenario the Unmitigated volume is modeled using a Basin element consisting of impervious area This will be a separate Basin element added to the model for the sole purpose of providing the Unmitigated volume for the LID Points calculations otherwise this element does not need to be in the model Because as described above this is a situation where the unmitigated runoff volume is not automatically generated in the model and additional model input is required and a separate POC is needed to record the Unmitigated volume We suggest a POC number one greater than that selected for the Pre Project scenario Note that analysis points cannot be used for interceptor trees File Edit View Help Summary Report Deh se UELLE TIALE ol el ed EN Se 2 Schematic 5 Basin 3 Mitigated a SCENARIOS Subbasin Name Em I Designate as Bypass for POC yy 7 Surface Interflow Groundwater Biotin ss Flows To ied Miioated i Area in Basin M Show Only Selected Run Scenario i Available Pervious Acres Available Impervious Acres ImpervFlat 0 1 Basic Elements File Edit View Help Summary Report Dad e AERLE TAAI FIE oll et Se Schematic z in g Subbasin Name Post Mit I Designate as Bypass for POC py D Fre Proiect Surface Interflow Groundwater al Flows To ee Ag
183. nnections 0 F Precipitation Applied to Facilty F Evaporation Applied to Facility Facility Dimension agram Facility Dimensions ot Str Facility Bottom Elevation ft Riser Height ty 2 Bottom Length ft Riser Diameter in Q H Bottom Width ft D Risertype pa Effective Depth ft GR Notch Type l Left Side Slope HAV b Bottom Side Slope HAV ec Right Side Slope HAV ec Top Side Slope HV Orifice Diameter Height Infiltration No H Number in t Automatic Pond Adjuster EEE 0 1 min lt 2 10 min gt 10 min Fast TI Pond Depth incl 1 ft freeboard Pond length to width ratio tol Pond Side na tol Bottom Length __ Bottom Width Volume at riser head acre ft Hs Predeveloped I Mitigated Choose Outlet Structure 1 orifice amp rectangular notch Progress A p Create Pond Optimize Pond _ Close A trapezoidal stormwater pond can be sized either manually or automatically using Auto Pond For this example Auto Pond will be used Go to page 55 to find more information about how to manually size a pond or other HMP facility Click on the Auto Pond button and the Auto Pond screen will appear The user can set the pond depth default 4 feet pond length to width ratio default 1 to 1 pond side slopes default 3
184. nswer is to the standard method The standard method will always be more accurate than the simple swale 105 SAHM Guidance Document December 2013 POROUS PAVEMENT ELEMENT File Edit View Help Summary Report Cee e ABSHE SR Os Seat IOS eis cx Schematic See avement 1 Mitigat SCENARIOS Facility Name Porous Pavement 1 E Outlet 1 Outlet 2 Outlet 3 A C Pre Project Downstream Connection 0 0 o Facility Type Porous Pavement dM Miiiasted aoe Quick Pavement Run Scenario Facility Dimension Diagram Basic Elements Porous Pavement 1 Facility Di 2 acility Dimensions Ovariow Data Pavement Length ft 0 3 z Pavement Bottom Width ft 0 Ponding Depth Above Pavement ft fil Effective Total Depth ft 0 Bottom slope ft ft 0 Effective Volume Factor 0 Pro Elements Layers for Porous Pavement Pavement Thickness ft 0 Diameter Height Pavement porosity 0 1 0 in ft LID Toolbox Sublayer 1 Thickness ft 0 Underdrain fo y fo Sublayer 1 porosity 0 1 0 Sublayer 2 Thickness ft 0 Sublayer 2 porosity 0 1 0 Infiltration ino Storage Volume at Top of Pavement ac ft 000 Commercial Toolbox Show Pavement Table Open Table 4 Initial Stage ft 0 Move Elements 4 2g Save xy Load xy vi HH ui ny
185. nt December 2013 Hydrology should be consulted to make sure that SAHM solutions are consistent with city and county design specifications SAHM Guidance Document December 2013 This page is intentionally left blank SAHM Guidance Document December 2013 QUICK START Quick Start very briefly describes the steps to quickly size a stormwater detention pond using SAHM New users should read the descriptions of the SAHM screens elements and analysis tools before going through the steps described below 1 Open SAHM SAHM will open with a map of Sacramento County at a Bile f t yen Help Summary Report Dg ike NAS EOI SAHM Guidance Document December 2013 File Edit View Help Summary Report Cee tae LEA El The map controls can be used to enlarge a specific area on the street map layer This option helps to locate the specific project site When the street map layer is enlarged a sufficient amount the individual street names are shown on the map SAHM Guidance Document December 2013 2 Select the project site location Locate the project site on the map Use the map controls to magnify a portion of the map if needed Select the project site by left clicking on the map location A red square will be placed on the map identifying the project site File Edit View Help Summary Report Deh gige zi ol DRRRS Sacramento SS Site Information Site Name Address M
186. ntage After the target percentage is set then the user can click on the Size Infiltration Planter button SAHM will iterate to determine the planter length and width needed to meet the target infiltration percentage 113 SAHM Guidance Document December 2013 FLOW THROUGH PLANTER BOX ELEMENT File Edit View Help Summary Report Ose te SCENARIOS Commercial Toolbox Move Elements 5 Facility Name IABSUER Or SEES 2 Outlet 2 Outlet 3 Downstream Connection 0 0 Facility Type Size Planter Box Quick Planter Optimize Maximum Planter Box Area ac 0 Underdrain Diameter ft Orifice Diameter in Planter Box Dimensions Planter Length ft Planter Bottom Width ft Freeboard ft tals jc Effective Total Depth ft Material Layers for Planter Sandy Loam bd Gravel z Outlet Structure Data Riser Height Above Planter surface ft Riser Diameter in Eie Co Show Planter Table Open Table H 000 Planter Volume at Riser Head ac ft Flow Through Underdrain ac ft Total Outflow ac ft Percent Through Underdrain 0 0 0 39 Save xy Load xy x 2o__ Y 2 The Flow Through Planter Box element is located in the LID Toolbox All of the LID Toolbox elements can be viewed and selected by clicking on the LID Toolbox bar A flow through planter is similar to t
187. nveys water proportionally to the depth of amended soil saturation When the amended soil is fully saturated the underdrain pipe is at full capacity Discharge from the underdrain pipe is controlled by the underdrain orifice diameter File Edit View Help Summary Report Dw amp aE L e 5 Schematic IEJ jem Bio Swale 1 Mitigated SCENARIOS Facility Name Bio Swale 1 Outlet 1 Outlet 2 Outlet 3 ae Pre Project Downstream Connection 0 0 0 Facility Type Bioretention Swale F Use simple swale Quick Swale Run Scenario M Underdrain Used Underdrain Diameter ft Basic Elements Swale Bottom Elevation ft Orifice Diameter in Swale Dimensions Flow Through Underdrain ac ft Swale Length ft T000 Total Outflow ac ft Swale Bottom Width ft 0 000 Percent Through Underdrain Freeboard ft 0 000 Facility Dimension Diagram Over toad Flooding ft 0 000 Outlet Structure Data Effective Total Depth ft o Riser Outlet Structure Bottom slope of Swale ft ft 0 000 Outlet Structure Data Top and Bottom side slope ftt 0 000 Riser Height Above Swale surface ft Jo H Left Side Slope H V 0 000 Riser Diameter in 9 4 Right Side Slope H V 0 000 Riser Type Fiat 4 Material Layers for Swale LID Toolbox Layer Layer2 Layer3 0 000 0 0 GRAVEL GRAVEL Orifice Diameter Height GRAVEL Number in ft Commercial Toolbox 1 fo 4 Edit Soil Types 2 fp ah KSat Safety Factor 0 4 2 C
188. o Riser Outlet Structure a Bottom slope of Swale ft ft 0 000 Outlet Structure Data Pro Elements Top and Bottom side slope t ft 0 000 Riser Height Above Swale surface t 9 4 Left Side Slope H V 0 000 Riser Diameter fin fo 4 Right Side Slope H V 0 000 RiserType Flat H cS Material Layers for Swale LID Toolbox Layer Layer2 Layer 3 Depth ft 0 000 0 o Soil Layer 1 GRAVEL Soil Layer 2 GRAVEL Soil Layer 3 GRAVEL Orifice Diameter Height Number in ft Lolle Commercial Toolbox TEE 1 fo fo Yp rs it S01 es 2 0 0 ma KSat Safety Factor 3h dhe C Noe C2 C4 Show Swale Table OpenTable m Move Elements Swale Volume at Riser Head ac ft 000 ORG Native Infiltration N0 4 Save xy Load xy xo y fs ai E 102 SAHM Guidance Document December 2013 To use the underdrain click the Underdrain Used box and input an underdrain pipe diameter feet underdrain outlet orifice diameter inches and the offset or height above the bottom of the lowest amended soil layer The amended soil layer fills with stormwater from the top on down to where it can drain to the native soil if Native Infiltration is set to YES and or the underdrain pipe if Underdrain Used box is checked Water enters the underdrain when the amended soil becomes saturated down to the top of the underdrain The underdrain pipe fills and co
189. oad such a table to SAHM program 93 SAHM Guidance Document December 2013 SSD TABLE ELEMENT File Edit View Help Summary Report Deol e 4ug6g8 i In 2 Schematic J i SD Table 1 Mitigated SCENARIOS Facility Name SSD Table 1 Flows To T Precipitation Applied Facility Type SSD TABLE re I Manual Infiltration Load File Browse A M Stage Computed Add Layer Ai St Stage ft fase Gaon Not Used Not Used Not Used Not Used Not Used Pro Elements LID Toolbox N Commercial Toolbox Tide Gate Time Series Demand Determine Outlet With Tide Gate Move Elements Use Tide Gate 4 Tide Gate Elevation fi 0 Downstream Connection v g Overflow Elevation ft 0 Iterations 0 Save xy Load xy Intitial Stage ft 0 J k The SSD Table is a stage storage discharge table externally produced by the user and is identical in format to the stage storage discharge tables generated internally by SAHM for ponds vaults tanks and channels The easiest way to create a SSD Table outside of SAHM is to use a spreadsheet with a separate column for stage surface area storage and discharge in that order Save the spreadsheet file as a comma delimited file A text file can also be created if more convenient The SSD Table
190. ompact WDM 1 San Diego Pan Evap p Duration Bounds 3 22 Fom lat worn A JOO Minimum 2 Maximum ea POT el a J Seasonal Durations mm dd Spezoidal Pond 1 STAGE Mitigated StatDate 7 q All Datasets Stage Precip Evap POC1 The user can analyze all time series datasets or just flow stage precipitation evaporation or point of compliance POC flows by selecting the appropriate tab below the list of the different datasets available for analysis 128 SAHM Guidance Document December 2013 FLOW DURATION SAM Bample File Edit View Help Summary Report Dae e z ET WdE 8 Ose Bea A 501 POC 1 Predeveloped The Facility PASSED 201 POC 1 Mitigated flow Flow cfs Predev Mit Percentage Pass Fail 857 836 Pass 770 568 Pass 706 501 Pass 652 463 Pass 589 420 Pass 549 381 Pass 495 345 Pass 461 320 Pass 432 303 Pass 384 285 Pass 361 265 Pass 251 Pass 237 Pass 228 Pass 207 Pass 193 Pass 184 Pass 167 Pass 158 Pass 152 Pass 144 Pass 134 Pass 128 Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass Pass FLOW cfs 0 40 Oa 1064 103 102 1064 1 10 Percent Time Exceeding EAB OSs ompact WDM P Drawdown Hydrograph LID Points Table All Datasets Flow J Stage J Precip Evap A PPPPPPPPPPPPPPPPPPPOOOODODOOO00000000 Flow duration at the point of compliance POC 1 is the most common analysis A plot of the flow duratio
191. omputationally much faster than the standard bioretention swale Before using the simple swale option read the note on the screen and the information below to understand the limitations of the simple swale Note that the message about sufficient discharge refers to the surface discharge when surface ponding is filled to overflowing In this situation the model has to have outlet information to know how to discharge the excess water Increasing freeboard and or riser diameter are two ways to ensure sufficient discharge The standard bioretention swale routine checks the available amended soil storage and compares it with the inflow rate Because of the check done each time step simulations using bioretention elements take much longer than simulations not using bioretention elements Simulations that normally take only seconds may take multiple minutes when one or more bioretention elements are added depending on the computational speed of the computer used One solution to this problem is to use the simple bioretention swale option check the Use Simple Swale box The simple bioretention swale does not check for volume It is less accurate than the standard swale Tests have shown that the simple swale option should 104 SAHM Guidance Document December 2013 only be used when the swale area and volume is relatively small compared to the contributing basin area If in doubt model the bioretention both ways and see how close the simple a
192. ontrols the infiltration rate into the top soil layer f K fi eee Equation 1 f soil surface infiltration rate cm hr soil porosity of top soil layer 0 soil moisture content of top soil layer g suction head at the wetting front cm F soil moisture content of the top soil layer cm d surface ponding depth cm K hydraulic conductivity based on saturation of top soil layer cm hr K relative hydraulic conductivity can be computed using the following Van Genuchten approximation equation Van Genuchten approximation of relative hydraulic conductivity Equation 2 where K relative hydraulic conductivity K Saturated hydraulic conductivity 6 water content 0 residual water content porosity a constant n constant m constant A few issues arise when dealing with multiple subsurface soil layers The K value used in Equation 1 must be computed from the top soil layer Infiltration into the upper soil layer must not exceed the lesser of the maximum percolation rates for each of the soil layers Finally the rate of percolation of the top layer may be reduced because the layer or layers beneath the top layer cannot accept the percolation flux because of existing saturation levels 192 SAHM Guidance Document December 2013 Water storage and movement through the three subsurface layers will be computed using Darcy s equation as shown below q K Equation 3 z Where q Darcy flux
193. ooding ft Effective Total Depth ft Vertical Orifice Overflow Bottom slope of Swale ft ft 0 000 Outlet Configuration Data Top and Bottom side slope ft ft 000 Vertical Orifice diameter in 0 000 Left Side Slope H Vertical Orifice Elevation in 0 000 Right Side Slope HAV i Width of overroad flow ft 0 000 Material Layers for Swale LID Toolbox Layer Layer2 Layer3 Depth ft 0 000 0 o Soil Layer 1 GRAVEL v Soil Layer 2 GRAVEL Soil Layer 3 GRAVEL Tal Commercial Toolbox ees Ji Edit Soil Types KSat Safety Factor F z None C2 C4 Show Swale Table OpenTable prc arne Swale Volume at Riser Head ac ft 000 lt e Native Infiltration N0 lt 4 eae xy Load sy i oy ve A a ST I The bioretention dimensions are specified below Swale Length ft length dimension of bioretention surface bottom Swale Bottom Width ft width dimension of bioretention surface bottom Freeboard ft Height from top of vertical orifice to weir Over road Flooding feet height above weir must be greater than zero Effective Total Depth ft the total depth of the amended soil layer s plus vertical orifice elevation plus vertical orifice diameter plus freeboard plus over road flooding height effective total depth is computed by SAHM 100 SAHM Guidance Document December 2013 Bottom Slope of Swale ft ft the slope of the swale length must be greater than zero Top and Bottom Side Slopes ft ft H V ratio of
194. or development of WWHM BAHM and SAHM and preparation of the SAHM guidance documentation e Scott Taylor Richard Lucera and Remi Candaele of RBF Consulting for providing SAHM meteorological data maps and technical specifications 1 Washington State Department of Ecology 2001 Stormwater Management Manual for Western Washington Volume III Hydrologic Analysis and Flow Control Design BMPs Publication No 99 13 Olympia WA vi TABLE OF CONTENTS Bnd User License A preement ssc i ie acts E eaten eet tes iv FOREWORD poroi oratia EE E A E A E e ea Ret aoc ae oes v Effects of Hy dromodinc aio seeen a E A eee tines v RES Wl ALOT O O A a O eae v Development of the Sacramento Area Hydrology Model eccceeecceeeseeeeeseeeeeneeeeeees v ACKMOWIEASEMENES nenecese n ae i g E ESEE aaka a Ra oah vi INTRODUC HON TO SAHM oirne a n a tee e a e e aE 1 SAHM OVERVIEW ademe ie o o ie ase Rae aoi r et Geshu Paes eS 3 QUICKSTART A tee T E T 7 MAIN SCREENS areata Ten aE A ETa A REE E EATE TN AK L ATEEN 41 MAP INFORMATION SCREEN a a a A snas equ aAA AARAA SEINES 42 GENERAL PROJECT INFORMATION SCREEN ccesssceesceseeeeeceseceaecaeeeneeseeees 43 SCHEMATIC EDITOR yisiacisusicnsvshseateisetuacds lasdaeciounedeayesdoaatisnteanss deabadeiserede eta jeaaliswieonss 44 BASIN ELEIMEN cacutecor tas teie a a anciacnis aan tee santas tesla aks T 45 LATERAL BASIN ELEMENT Pervious c ccsccssssessssresoceenessscrsetanesansonsenneeneee
195. or flow duration matching and scaling factors for climate variables 154 SAHM Guidance Document December 2013 DURATION CRITERIA Options Duration Criteria Scaling Factors Point of Compliance Durations Based on Predeveloped Flow Frequency G Analyze Durations for 25 percent of the 2yr to the 10 yr X Durations Based on User Defined Flow Values Analyze Durations for 0 efs to 0 cfs Pass Fail threshold Altering the flow duration criteria will change the mitigation requirements for the selected point of compliance only These changes will impact all duration analysis related to the POC including automatic facility sizing and any flow duration analysis tun on this specific POC Restore Defaults The flow duration criteria are 1 Ifthe post development flow duration values exceed any of the pre project flow levels between the lower threshold the default is 25 of the two year and the upper threshold 100 of the ten year pre project peak flow values more than 10 percent of the time 110 Percent Threshold then the flow duration standard has not been met 2 If appropriate the lower threshold can be changed by the user from 25 percent to 45 percent of the two year pre project peak flow value 3 If more than 10 percent of the flow duration levels exceed the 100 percent threshold then the flow duration standard has not been met The user can conduct the duration analysis using either 1 durat
196. over Length of Rooftop ft Post Mit Green Roof 231 SAHM Guidance Document December 2013 In the Mitigated scenario the Mitigated volume is modeled with a Green Roof element A point of compliance POC is assigned by the user to the Green Roof element to compute the Mitigated volume A point of compliance POC is assigned by the user to the surface runoff interflow and groundwater of the Green Roof element Note for the Green Roof element groundwater must be included in the POC runoff volume this is not true for any other element The POC number should be the same as for the Pre Project scenario If the POC number is 9 then the user should select time series 509 for the pre volume 810 for the post unmit volume and 809 for the post mit volume These time series are based on the element names selected by the user 232 SAHM Guidance Document December 2013 Capture and re use In the Pre Project scenario the Pre volume is modeled using a Basin element containing the drainage area of the pre project land use A point of compliance POC is assigned by the user to the Basin element Only surface runoff and interflow are connected to the POC In the Mitigated scenario the Unmitigated volume is modeled using a Basin element consisting of both impervious area and any pervious area draining to a capture and re use storage facility For this element a separate POC is not needed to
197. ow duration pond or the top 181 SAHM Guidance Document December 2013 layer of a bioretention facility However a safety factor is also used to account for uncertainties in the available estimate of in situ infiltration rates The SMMWW notes that its suggested CF values which range from 2 to 4 represent an average degree of long term facility maintenance TSS reduction through pretreatment and site variability in the subsurface conditions and that increases or decreases to these factors should be considered for unusual situations Suggested safety factors in other texts and guidance generally range from 1 to 4 Sacramento County stormwater permits may require some form of tracking and verification for treatment and hydromodification facilities In addition designers should not be overly conservative in selecting a very high safety factor since this might lead to over controlled lower post project flows and an increased risk of causing impacts from deposition or sedimentation in the receiving channels In the absence of other guidance it is suggested that the SAHM Infiltration Reduction Factor not be less than 0 25 or greater than 0 5 Note Sacramento County stormwater programs may also restrict the use of infiltration for treatment purposes in certain conditions since the flow duration facilities are also performing some treatment designers should discuss treatment measure design with the applicable jurisdiction Flow Durat
198. ow that too much water is discharged at the lower end of the flow duration curve This discharge is controlled by the underdrain orifice Our assumed underdrain orifice diameter of 4 inches is too large We will reduce it to 2 inches and try again 213 SAHM Guidance Document December 2013 File Edit View Help Summary Report Ose see ABSHE SR Os SOBER 9 00 lysis 503 POC 3 Predeveloped 803 POC 3 Mitigated flow FLOW cfs 10E 3 106 2 10E1 10 100 Percent Time Exceeding Durations Drawdown Hydrograph LID Points Table Analyze datasets Compact WDM Evap POC1 All Datasets Flow Changing the size of the underdrain orifice did not change the flow duration results That means that too much water is going through the riser and the bioretention area is too small 214 SAHM Guidance Document December 2013 File Edit View Help Summary Report B A IEA BEL EE TAA ERRA EEH LID Toolbox Commercial Toolbox Facility Name Outlet 1 Outlet 2 Downstream Connection SSS ay Facility Type F Use simple swale M UnderdrainUsed Swale Bottom Elevation ff 0 Swale Dimensions Seah m Swale Bottom Width ft Bs Freeboard ft Over road Flooding ft a Effective Total Depth ft k3 Bottom slope of Swale ft Ft Top and Bottom side slope ft ft Left Side Slope HAV Right Side Slope HAV ooo Material Layers for Swale Layer Layer2 Layer 3 Deni S ny mea SollLayer1
199. p Controls aas lt 4p The project site is in the northwestern part of the county The Natomas precipitation record will be used with a precipitation multiplication factor of 1 00 199 SAHM Guidance Document December 2013 Run Scenario Basic Elements LID Toolbox Commercial Toolbox gt Move Elements N Ey Save xy Load x y The project is going to include a large number of elements so to show more elements on the schematic grid at one time we use the Zoom feature to double 2X the number of grid cells We will start with DMA 1 Because of the size of this DMA 260 acres the stormwater travel time and the existence of agricultural drainage ditches we will include two channel reaches to provide routing time between the upstream end of the DMA and the downstream POC We are using a one hour time step so the routing time through each channel reach should equal approximately one hour Also because of the large size of the drainage areas we see evidence of groundwater flowing into the existing conveyance systems as base flow Therefore we include groundwater in our point of compliance calculations and add it to surface runoff and interflow shallow sub surface runoff to calculate the total stormwater runoff 200 SAHM Guidance Document December 2013 dit View He SH te ASHE A Ose S MEE DO O SubbasinName
200. pen Tabe 4 Size Infiltration Basin miea Target 100 4 Save xy Load xy Move Elements gt The Infiltration Basin element is located in the LID Toolbox All of the LID Toolbox elements can be viewed and selected by clicking on the LID Toolbox bar An infiltration basin pond allows stormwater to enter the basin pond above ground and then infiltrate through the bottom of the basin pond before exiting through a discharge pipe Water can also infiltrate into the native soil beneath the basin pond For the purpose of flow control the discharge from the pipe should not exceed the pre project discharge from the project site for the flow duration range specified by the local jurisdiction Infiltration Basin Pond In SAHM the infiltration basin pond is represented by a specialized application of the trapezoidal pond element 116 SAHM Guidance Document December 2013 The infiltration basin pond dimensions and parameters are Bottom Length ft Infiltration basin pond length Bottom Width ft Infiltration basin pond width Effective Depth ft Infiltration basin height from basin pond bottom to top of riser plus at least 0 5 feet extra Left Side Slope H V 0 zero for vertical infiltration basin pond sides Bottom Side Slope H V 0 zero for vertical infiltration basin pond sides Right Side Slope H V 0 zero for vertical infiltration basin pond sides
201. per hour infiltration rate of the native soil Infiltration Reduction Factor between 0 and 1 1 Native soil infiltration rate safety factor see page 79 Use Wetted Surface Area sidewalls YES or NO YES allows infiltration to the native soil through the sidewalls of the swale otherwise all infiltration is through the bottom only If infiltration is used then the user should consult the Infiltration discussion on page 79 NOTE See Appendix C or consult with the local municipal permitting agency for additional considerations regarding infiltration and determination of the appropriate infiltration reduction factor File Edit View Help Summary Report Osh sae ELEERI ob oe a Le Sb z Schematic Emme e Bio Swale 1 Mitigated SCENARIOS a Facility Name Bio Swale 1 Outlet 3 C Fre Project j Downs ion 0 0 ef ity Type Bioretention Swale ged Mitgsted F Use simple swale Quick Swale Run Scenario d Underdrain Diameter ft 0 Offset in Basic Elements Swale Bottom Elevation ft 0 Orifice Diameter in b f ic Dimensions Flow Through Underdrain ac ft 0 Ed B ES Swale Lent 0 000 Total Outflow ac ft Sem Swale Bottom Width ft o 9 Bio Swale 1 Freeboard ft 0 000 Facility Dimension Diagram Z A Over road Flooding ft 0 000 Outlet Structure Data P Effective Total Depth ft
202. pitation evaporation and total runoff for all of the basins The results will be shown for each basin in terms of its POC For Basin 1 1 acre of A Grass Flat the distribution of the precipitation is Surface runoff 0 104 inches per year Interflow 1 139 inches per year Groundwater 3 721 inches per year Evaporation 13 633 inches per year The sum of the surface runoff interflow active groundwater evaporation equals 18 59 inches per year The precipitation at this site equals 18 50 inches per year The difference is due to the depletion of the initial groundwater storage To look at the other basins click on the Select POC To arrow and select the basin of interest The LID analysis results can be presented in terms of either inches per year or acre feet per year by checking the appropriate box in the lower right portion of the LID analysis screen 149 SAHM Guidance Document December 2013 XB AOS esl Ov ds aeG 000 Low Impact Development Scenario Generator UD Scenario Generator LID Ports Table POC To Analyze P Arend H To compare the different scenarios side by side in a graphical format click on the Water Balance Chart button gasusm Ow sans Low Impact Development Scenario Generator UD Scene Ganasstor UO Tatie SAMO POC Te Analyze F H Fma Teas EPN The water balance chart graphically displays the runoff
203. presented modeled using the Sand Filter element Infiltration through the sand filter continues downstream unless diverted off line A point of compliance POC is assigned by the user to the surface discharge Outlet 1 and the infiltrated discharge Outlet 2 of the Sand Filter element to compute the Mitigated volume The POC number should be the same as for the Pre Project scenario ieee Fae Ed View Si Help i Surnmary Report File Edit View Help Summary Report If the POC number Oem se Os e is 1 then the user OAE CMa must select time eater m See series 501 for the SCENARIOS SCENARIOS pre volume 701 for DO Peroa PPE i Pre Project the post unmit AA AT mitigated volume and 801 Run Scenario FAA for the post mit ie volume These time series are based on the element names selected by the user If an analysis point is used then the user must select the 1000 time series numbers for the post unmit volume and the post mit volume based on the elements names The post mit volume will be from All Outlets the sum of Outlet 1 and Outlet 2 Set up using Analysis Points Set up using POC 241 SAHM Guidance Document December 2013 Stormwater Planter Flow Through In the Pre Project scenario the Pre volume is modeled using a Basin element containing the drainage area of the pre project land use A point of compliance POC is assigned by the
204. r ah esel End Date 2004 09 30 24 00 Plot Hydrograph 43 1000 Trapezoidal Pond 1 ALL OUTLETS Mitigated 1001 Trapezoidal Pond 1 STAGE Mitigated Copy to WDM DSN to Copy The Create Graph screen is shown and the user can select the time series to plot the time interval yearly monthly daily or hourly and type of data peaks average or volume The following numbering system is used for the flow time series 500 599 Pre project flow Pre project scenario 700 799 Inflow to the POC Mitigated runoff entering the BMP facility 800 899 POC flow Mitigated flow exiting the BMP facility The selected time series are shown in color To graph the selected time series the user clicks on the Graph button 135 SAHM Guidance Document December 2013 Annual Max Peak Values Flow cfs S01 POC 1 Penceewtepes tow BOL POC 1 Anand tow In this example the hydrograph shows the yearly maximum peak flow values for each time series for the entire simulation period from 1964 through 2004 The graph can be saved copied to Windows Clipboard or printed 136 SAHM Guidance Document December 2013 Qa e Re Book Excet 0 EE oe rem auvon romas Daa REVEW vew oases Oy tein P R Xar Taia In las Ee Sites Genel E p Noms Bad Good Sie Sx fg ZAutosum ay it B Copy lt pr P Dinane OTUS E DAt ESE tS cele Cm ERE e oee e on ol Chipboard J ter a Abgrmerd 3 Nember 3 yes ch toeng a at
205. r authorized representatives be liable for any damages whatsoever including without limitation to damages for loss of business profits loss of business information business interruption and the like arising out of the use of or inability to use this program even if Clear Creek Solutions Inc has been advised of the possibility of such damages Software Copyright by Clear Creek Solutions Inc 2005 2013 All Rights Reserved iv FOREWORD The Sacramento Area Hydrology Model SAHM is a tool for analyzing the hydromodification effects of land development projects and sizing solutions to mitigate the increased runoff from these projects This section of the guidance documentation provides background information on the definition and effects of hydromodification and relevant findings from technical analyses conducted in response to regulatory requirements It also summarizes the current Hydromodification Management Standard and general design approach for hydromodification control facilities which led to the development of the SAHM Effects of Hydromodification Urbanization of a watershed modifies natural watershed and stream processes by altering the terrain modifying the vegetation and soil characteristics introducing pavement and buildings installing drainage and flood control infrastructure and altering the condition of stream channels through straightening deepening and armoring These changes affect hydrologic characteristics in
206. r material Hydraulic Conductivity in hr Filtration rate through the sand filter Filter material depth ft Depth of sand filter material for runoff filtration 70 SAHM Guidance Document December 2013 Sand filter receives precipitation on and evaporation from the sand filter surface The Precipitation Applied to Facility and Evaporation Applied to Facility boxes should be checked 71 SAHM Guidance Document December 2013 OUTLET STRUCTURE CONFIGURATIONS The trapezoidal pond vault tank irregular pond gravel trench bed and sand filter all use a riser for the outlet structure to control discharge from the facility ASSHER Ose OM BE D 20 Riser Diameter Auto Pond __ Quick Pond Facility Dimension Diagram Facility Dimensions Outlet Structure Data Facility Bottom Elevation ft E Riser Height ft fo 4 Bottom Length ft Riser Diameter in o H Bottom Width f E RiserType Fiat 4 Effective Depth ft Notch Type Left Side Slope H V Bottom Side Slope HAV Right Side Slope HAV Top Side Slope HA A Orifice Diameter Height Infiltration 7 Number in ft 1 cee Oe 2 fe p 3 Hh j Pond Volume at Riser Head ac ft 0 Show Pond Table OpenTable H Initial Stage ft art The riser is a vertical pipe with a height above pond bottom typically one foot less than the effective depth The user specifies the riser height and diameter The riser can have up to three round o
207. rank largest event m 1 N number of years a 1 b 0 Probability 1 Tr The return period value Tr is used in SAHM to determine the 2 year 5 year 10 year and 25 year peak flow values If necessary the 2 year 5 year 10 year and 25 year values are interpolated from the Tr values generated by Weibull 132 SAHM Guidance Document December 2013 DRAWDOWN SAM Bcemple File Edit View Help Summary Report Ce e Awe lola Drawdown Analysis Select analysis for 1001 Trapezoidal Pond 1 STAGE Mitigated Trapezoidal Pond 1 Drain Time days Stage feet Percent of Total Run Time 1 N A N A 2 N A Na 3 INZA 4 N A 5 N A Max Stage 3 533514 Drawdown Time dd hh mm ss Less than 1 day Pond drains in less than 1 days Durations J Flow Frequend Drawdown Hydjjaraph LID Points Table J Analyze datasets Compact WDM 1001 Trapezoidal Pond 1 STAGE Mitigated Duration Bounds 0 01 Minimum 2 Maximum I Seasonal Durations mm dd Start Date All Datasets Flow Stage Precip Evap POC1 End Date The drawdown screen is used to compute pond stages water depths These stages are summarized and reported in terms of drain retention time in days For this example the maximum stage computed during the entire 30 50 year simulation period is 3 53 feet This maximum stage has a drawdown time of less th
208. rass Mod 1 2 10 Pervious Total 10 Impervious Land Use Acres Impervious Total 0 Basin Total 10 Element Flows To Surface Interflow Groundwater Scroll down the Text Report or the PDF Report screen to see all of the results 144 SAHM Guidance Document December 2013 TOOLS SCREEN File Edit View Help S Dael sae EIGERT AA Bk D OO le fra jal Pond 1 Mitigated Facility Name Trapez Pon Facility Type Outlet 1 Outlet 2 Outlet 3 Downstream Connections isl T Precipitation Applied to Faciity AutoPond __QuickPond _ F Evaporation Applied to Facil Facility Dimension Diagram Facility Dimensions Outlet Structure Data Facility Bottom Elevation ft DB RiserHeioht tt pH Bottom Length ft Riser Diameter in fig H Bottom Width ft Riser Type Notched Effective Depth ft Notch Type Rectanaula The Tools screen is accessed with the Tools tool bar second from the right The two major purposes of the Tools screen are 1 To allow users to view SAHM HSPF PERLND parameter values The parameter values are locked and cannot be changed by the user 2 To allow users to export time series datasets To export a time series dataset click on the Export Dataset box 145 SAHM Guidance Document December 2013 File Edit View Help Summary Report De se CACEN TAA E EILEEN ies Trapezoidal Pond 1 Mitigated Facility Name Trapezoidal Pond 1 Facility Type Trapezoidal Pond Outlet 1 Outlet 2 Outlet
209. ration Planter Box element Infiltration is turned on and an infiltration rate must be input by the user A point of compliance POC is assigned by the user to the surface and underdrain if any discharge Outlet 1 of the Infiltration Planter Box element to compute the Mitigated volume The POC number should be the same as for the Pre Project scenario File Edit View Help Summary Report File Edit View Help Summary Report If the POC number is oot tae Coe e 1 then the user must ell lel lla et SS Bal select time series 501 Saat for the pre volume SCENARIOS 701 for the post EHD Pie Project unmit volume and a 801 for the post mit volume These time series are based on the element names infitPlanter Selected by the user Schematic SCENARIOS peste C Pre Project bes 7 Mitigated Run Scenario A Mitigated Run Scenario Basic Elements Hasa Ees Sama DEH If an analysis point is Pio Elements used then the user a must select the 1000 time series numbers for the post unmit volume and the post mit volume based on the elements names Set up using Analysis Points Set up using POC The post mit volume will be from Outlet 1 Basic Elements Pro Elements LID Toolbox ae es Pil 243 SAHM Guidance Document December 2013 Vegetated Swale In the Pre Project scenario the Pre volume is modeled u
210. ration option Flow Duration Outlet Structures Outlet Structure Configurations pages 72 78 includes sizing of low flow orifice and applicable when specifying characteristics of a alternative configurations flow duration facility Drawdown drain time for flow duration Drawdown Analysis screen page 133 facilities This guidance was originally created by the stormwater programs of Alameda Santa Clara and San Mateo counties Please consult with the local municipal permitting agency for additional considerations Additional guidance and references are also discussed at the end of this appendix Infiltration Reduction Factor The Western Washington Hydrology Model included this factor to reflect the requirement in the Stormwater Management Manual for Western Washington SMMWW to incorporate a Correction Factor CF to determine long term infiltration rates the inverse of the CF is the Infiltration Reduction Factor in SAHM The SMMWW gives three methods for determining CF 1 a table providing empirical correlations between long term infiltration rates and USDA Soil Textural Classification 2 ASTM gradation testing at full scale infiltration facilities or 3 In situ infiltration tests preferably using a Pilot Infiltration Test specified in an appendix of the SMMWW Application of a CF or safety factor attempts to account for clogging and the reduction in infiltration over time which might apply to the bottom of a fl
211. rched Height ft Tank height Width ft Tank width at widest point Length ft Tank length Riser Height ft Height of overflow pipe above tank bottom must be less than tank diameter or height Riser Diameter in Tank overflow pipe diameter Riser Type options Flat or Notched Notch Type Rectangular V Notch or Sutro For a rectangular notch Notch Height feet distance from the top of the weir to the bottom of the notch TANK Notch Width feet width of notch cannot be ARCHED larger than the riser circumference ua For more information on riser notch options and HEIGHT orifices see discussion in OUTLET STRUCTURE CONFIGURATIONS section LENGTH Infiltration Yes infiltration into the underlying native soil Measured Infiltration Rate in hr Native soil infiltration rate Infiltration Reduction Factor 1 Native soil infiltration rate safety factor see page 79 Use Wetted Surface Area sidewalls Yes if infiltration through the tank sides is allowed If infiltration is used then the user should consult the Infiltration discussion on page 79 NOTE See Appendix C or consult with the local municipal permitting agency for additional considerations regarding infiltration and determination of the appropriate infiltration reduction factor A tank is covered and does not receive precipitation on and evaporation from the tank surface The Precipitation Applied to Facility and Evaporation Applied
212. record the Unmitigated volume If an analysis point is used instead of a POC then there must be a conveyance element for example a Channel element immediately upstream of the capture and re use storage facility element The upstream conveyance element must include an analysis point to record the Unmitigated volume In the Mitigated scenario the capture and re use storage facility can be represented modeled using any one of the following SAHM elements Vault Tank SSD Table or Flow Splitter Regardless of the element selected re use should be represented by the infiltration option or in the case of the Flow Splitter by the second outlet Infiltration should be turned on and an infiltration rate input by the user equal to the expected re use A point of compliance POC is assigned by the user to the surface discharge Outlet 1 of the selected element to compute the Mitigated volume The POC number should be the same as for the Pre Project scenario File Edit View Help Summary Report File Edit View Zoom Help If the POC number Oe te D CE e aLa is 1 then the user ie le w BSAA E must select time cH Schematic a E Schematic series 501 for the SCENARIOS SCENARIOS pre volume 701 for DE O Pre Project REO Pre Project the post unmit oe Miigated volume and 801 AERE REEERE rr for the post mit Basic Elements Basic Elements volume These time series are based on the element names selected by the user
213. rected to a stormwater conveyance system by the user Note The Sacramento Design Manual includes a restriction that the maximum allowable ratio of impervious lateral flow basin area to pervious soil flow basin area is 2 to 1 52 SAHM Guidance Document December 2013 TRAPEZOIDAL POND ELEMENT a i ee es ABSGH SOs SBE DO D File Edit View Help Summary Report Oel t e W C Pre Project DEZ Mitigated Run Scenario Basic Elements LID Toolbox Commercial Toolbox sts Save xy Load xy is Facility Name Trape Downstream Connections Bd Precipitation Applied to Facility Evaporation Applied to Faciliyg Facility Dimensions Facility Bottom Elevation ft Bottom Length ft Bottom Width ft Effective Depth ft Left Side Slope H V Bottom Side Slope HV Right Side Slope HV Top Side Slope H V Infiltration Tide Gate Time Series Demana Auto Pond Quick Pond Facility Dimension Diagram Outlet Structure Data Riser Heitt g H Riser Diameter in D H Riser Type Flat H Notch Type Orifice Diameter Height Number in i 1 cee oe 1 2 ot cel 3 D oe Pond Volume at Riser Head ac ft 0 Show Pond Table OpenTable 4 Initial Stage f SS Determine Outlet With Tide Gate F Use Tide Gate Tide Gate Elevation f 0 Downstream Connection oct Overflow Elevation ft 0 kterations In SAHM there is an individual
214. rements Please see Appendix C or consult with local municipal permitting agency for more details For manual sizing information see page 55 82 SAHM Guidance Document December 2013 HIGH GROUNDWATER WETLAND ELEMENT File Edit View Help Summary Report De e o 46g i oe ac ee SS a z Schematic 5 Wetpond 1 Mitigated fe Element Name Wetpond 1 Designate as Bypass for F SCENARIOS Runoff Type Surface Interflow Groundwater O Pre Project Downstream Connection 0 0 0 gs Element Type High Groundwater wetland ied Mitigated SoilPERLND Type Change Run Scenario High Groundwater Area ac 0 Average Depth of Surface Pondinafft 1 Basic Elements High Groundwater Outlet Defined by Natural Channel Mean Surface Elevation ft 400 Base Groundwater Elevation ft 0 Channel Type Deep Groundwater Elevation ft 0 Typical Wetland 0 1 Cohesion Water porosity 0 1 0 15 Channel Tos gt B Gravitational Water porosity 0 1 0 17 General Channel Data n Available Soil Types PERLNDs Upper Gravitation Water porosity 0 1 0 2 Channel Bottom width ft o Upper Zone Storage Factor 4 Channel Length ft 0 Check only one Lower Zone Storage Factor 25 Manning n coefficient 0 1 Surface Runoff Recession Constant 0 1 Slope
215. rifices The bottom orifice is usually located at the bottom of the pond and or above any dead storage in the facility The user can set the diameter and height of each orifice The user specifies the riser type as either flat or notched The weir notch can be either rectangular V notch or a Sutro weir The shape of each type of weir is shown below Top Vidth P Vidth Rectangular Notch V Notch T2 SAHM Guidance Document December 2013 By selecting the appropriate notch type the user is then given the option to enter the appropriate notch type dimensions Riser and orifice equations used in SAHM are provided below Headr the water height over the notch orifice bottom q discharge Riser Head Discharge Head water level above riser q 9 739 Riser Diameter Head 1 5 Orifice Equation q 3 782 Orifice Diameter 2 SQRT Headr Rectangular Notch b NotchWidth 1 0 2 Headr where b gt 0 8 q 3 33 b Headr 1 5 Sutro Wh Top Width Bottom Width Top Width Notch Height Headr Wd Bottom Width Wh the difference between the bottom and top widths Ql rectangular notch q where Notch Width Wh Q2 rectangular notch q where Notch Width Wd q Q1 Q2 2 V Notch Notch Bottom height from bottom of riser to bottom of notch Theta Notch Angle a 2 664261 0 0018641 Theta 0 00005761 Theta 2 b 0 48875 0 003843 Theta 0 000092124 Theta 2 c 0 3392
216. rizontal distance to vertical 0 zero for vertical sides Top refers to the uphill end of the bioretention facility bottom to the downhill end Left Side Slope ft ft H V ratio of horizontal distance to vertical 0 zero for vertical swale sides Right Side Slope ft ft H V ratio of horizontal distance to vertical 0 zero for vertical swale sides The input information required for the riser outlet structure is Riser Height above Swale Surface feet depth of surface ponding before the riser is overtopped Riser Diameter inches diameter of the stand pipe Riser Type Flat or Notched Notch Type Rectangular V Notch or Sutro For a rectangular notch Notch Height feet distance from the top of the weir to the bottom of the notch Notch Width feet width of notch cannot be larger than the riser circumference For more information on riser notch options and orifices see discussion in OUTLET STRUCTURE CONFIGURATIONS section The material layer inputs are Layer Thickness feet depth of amended soil Type of amended soil 24 different soil types are included the user can also create their own soil type using the Edit Soil Type button Note that there can be a maximum of three different amended soil layers Infiltration to the native soil can be turned on by setting Native Infiltration to YES The parameters for native soil infiltration are Measured Infiltration Rate inches per hour infiltration rate of th
217. ro Select By Go xa vE NOTE Do not use the Porous Pavement listing in the Available Impervious column to represent and model porous pavement areas Instead use the Porous Pavement element see page The Basin element represents a drainage area that can have any combination of soils land cover and land slopes A basin produces three types of runoff 1 surface runoff 2 interflow and 3 groundwater Surface runoff is defined as the overland flow that quickly reaches a conveyance system Surface runoff mainly comes from impervious surfaces Interflow is shallow subsurface flow produced by pervious land categories and varies based on soil characteristics and how these characteristics are altered by land development practices Groundwater is the subsurface flow that typically does not enter a stormwater conveyance system but provides base flow directly to streams and rivers 45 SAHM Guidance Document December 2013 The user can specify where each of these three types of runoff should be directed The default setting is for the surface runoff and interflow to go to the stormwater facility groundwater should not be connected unless there is observed base flow occurring in the drainage basin Table 1 shows the different pervious land types represented in the Basin element Table 1 SAHM Pervious Land Types
218. rograms that have sponsored the SAHM development Appendix D is a checklist for use by SAHM project reviewers Appendix E documents the bioretention modeling methodology used in SAHM Appendix F demonstrates how to set up a complex project with multiple stormwater mitigation facilities and multiple points of compliance Appendix G provides detailed instructions on how to set up projects for the LID Points Table calculations Throughout the guidance documentation notes using this font sans serif italic alert the user to actions or design decisions for which guidance must be consulted that is external to the SAHM software either provided in Appendix C of this guidance documentation or by the local municipal permitting agency Purpose The purpose of SAHM is to size hydromodification management or flow control facilities to mitigate the effects of increased runoff peak discharge duration and volume from proposed land use changes that impact natural streams wetlands and other water courses SAHM provides e A uniform methodology for Sacramento County e An easy to use software package SAHM Guidance Document December 2013 SAHM is based on Continuous simulation hydrology HSPF Actual long term recorded precipitation data Actual long term recorded pan evaporation data Existing vegetation for pre project conditions Regional HSPF parameters Computer Requirements Windows 2000 XP Vista 7 8 with 300 MB uncompressed hard drive space
219. rt Oe amp ASHES Ose SEED OG Subbasin Name Basn 1 Designate as Bypass for POC Surface Interflow Groundwater Flows To HEE Area in Basin IT Show Only Selected Available Pervious Acres Available Impervious Acres AF CiibanFia o1 A a M CUibansteepi252 fo M ImpewSteepi25 fa M Cilibanvsteep5 fo M ImpewNSteepp5 0 M Cresta a M PorousPavement Jo M CireesMod 2 Jo M Crees Steeni25 J0 F Crees vSteep5 0 M Dasta fo M DGrassMod 2 fa I Drass Steepi252 I DiGrass Steep gt 5 r DAgicFiat 01 r DAgicMod 1 2 r DAgicSteep 25 JD O iF DAgicWsteesb5 Jo r Dotnata a fs Zir DiibanSteepi25 0 PevvsTotal EBT Aes Impervious Tol B5 Aces BesinTotal 0 Ases DeselectZero_ Select By G0 The user extends the connection line to the downstream element in this example a pond and left clicks on the destination element This action brings up the From Basin to Conveyance box that allows the user to specify which runoff components to route to the downstream element Stormwater runoff is defined as surface flow interflow Both boxes should be checked Groundwater should not be checked for the standard land development mitigation analysis Groundwater should only be checked when there is observed and documented base flow occurring from the upstream basin After the appropriate boxes have been checked click the OK button 125
220. ry Wells 3 Interceptor Trees 4 Porous Pavement 5 Green Roof 6 Capture and Re use 7 Compost Amended Soil 8 Bioretention 9 Disconnected Driveways 10 Disconnected Roof Drains 11 Constructed Wetland Basin 12 Detention Basin 13 Infiltration Basin 14 Sand Filter 15 Stormwater Planter Flow Through 16 Stormwater Planter Infiltration 17 Vegetated Swale 18 Vegetated Filter Strip 19 Proprietary Devices 217 SAHM Guidance Document December 2013 20 BMP Treatment Trains That said SAHM allows any measure to be included in the LID points calculations and the user can type the name of the LID measure in the LID Points Table There can be more than one of each of type of LID measure SAHM individually tracks the runoff volume for each as long as it is an analysis point or point of compliance Only surface runoff and interflow are included in the calculations groundwater is not included except for the green roof LID Table 1 is an example of the proposed LID Points Table included in SAHM Following the table is the additional that explains how to set up and model 218 SAHM Guidance Document December 2013 Table 1 SAHM LID Points Table xU LID Table LID Measures i Post Mit Element Name Post Mit Post mit LID Pts Disconnect impervious surfaces Lateral Flow Pervious a E Interceptor trees aa ee 24 _ Basin Imp Trees Porous pavement Basin Imp 808 20 Porous Pavement Green root fo
221. s 49 LATERAL I BASIN ELEMENT Impervious ce eseescesceseeeeecnaeeeeeeseeseneeenaeens 51 TRAPEZOIDAL POND ELEMENT ccccsssscrsssesonsessceseveotecssersconsesacensrenssonsenseoseess 53 VAULT ELEMENT nhani iiin a ai A EA 59 TANK ELEMEN DU cg cages ineen iana S A T E E Ea 61 IRREGULAR POND ELEMENT i areae a a acne A 63 GRAVEL TRENCH BED ELEMENT wisscsssccusceusesacdasessaceaspeveeacasnevaata seveneuarenseetisaucedes 66 SAND FILTER EGEMEN T inspisere n eene aa seisde 69 OUTLET STRUCTURE CONFIGURATIONS eniciisness cucssuns vatenessvncosevseeianessivexeeaswaranaye 12 INFILTRATION seinne saree n atraia saaa aks ASAE ARAE IAE EAA E A ETRE AEE ETER 79 AUTO POND cirera i n e E E rea Nees E T E ee on ter Ue ea ee ere nee 80 HIGH GROUNDWATER WETLAND ELEMENT eceecceseeseeneeeeeeeeeeteeeeeeneeeeees 83 CHANNEL ELEMEN Te a ys sous tustas vie anscouy toad cenvaedeeay aaa AEA AATA 85 FLOW SPLITTER ELEMENT ptosis ieste eiste aaee tos etsien acs eisi 90 TIME SERIES ELEMENT rennaises natisa e E R aa 92 STAGE STORAGE DISCHARGE TABLE cceescessesseceseeseeeeceeneeseeeseceaecnceeneeseeess 93 SSD TABLEELEMEN Durie eiu e a a a ea h 94 BIORETENTION RAIN GARDEN ELEMENT ccccesccssesseeeeeeseeeeeceaeeneeeaeeseeerees 97 POROUS PAVEMENT ELEMENT i irestore sisis seesi gtestr etisi enas iiaiai 106 GREEN ROOF ELEMENT roteert ee e age r E a Sine 109 IN GROUND INFILTRATION PLANTER BOX ELEMENT 0 eeceeeeeeeeteeeteeeee 111 FLOW THROUGH PL
222. s 501 for the SCENARIOS SCENARIOS pre volume 701 for BO Oy pre Prciect ree a RoR the post unmit tnaed gt RAT Miigates volume and 801 Run Scenario TF for the post mit volume These time series are gt based on the element names selected by the user If an analysis point is used then the user must select the 1000 time series numbers for the post unmit volume and the post mit volume based on Set up using Analysis Points Set up using POC the elements names The post mit volume will be from Outlet 1 236 SAHM Guidance Document December 2013 Constructed Wetland Basin In the Pre Project scenario the Pre volume is modeled using a Basin element containing the drainage area of the pre project land use A point of compliance POC is assigned by the user to the Basin element Only surface runoff and interflow are connected to the POC In the Mitigated scenario the Unmitigated volume is modeled using a Basin element consisting of both impervious area and any pervious area draining to a Bioretention element For this element a separate POC is not needed to record the Unmitigated volume If an analysis point is used instead of a POC then there must be a conveyance element representing the forebay of the constructed wetland basin The upstream conveyance element must include an analysis point to record the Unmitigated volume In the Mitigated scenario the constructed w
223. s are based on the element names selected by the user If an analysis point is used then the user must select the 1000 time series numbers for the post unmit volume and the post mit volume based on the elements names The post mit volume will be from Outlet 1 SAHM Guidance Document December 2013 SUMMARY Note that the POC numbers used in the examples above are for representative purposes only for each individual project start with POC 1 and add POCs only as needed After all of the LID measures are input to the LID Points Table the user then clicks on the Calculate button to instruct SAHM to compute the appropriate runoff volumes and calculate LID points The LID points for each LID measure are shown along with the total LID points for the project If needed the user can then make changes to the Mitigated scenario input rerun the Mitigated scenario model and recalculate the LID points until the results are satisfactory Table 2 summarizes the LID measures and associated SAHM elements that can be used in the LID point calculations As noted above some LID measures are required to use a Point of Compliance POC for the volume calculations Other LID measures can use either an Analysis Point or a POC 249 SAHM Guidance Document December 2013 Table 2 LID Measure Summary LID Measure SAHM Element Analysis Point POC Disconnect Impervious Surfaces
224. s that could clog the outlet Orifices can also be placed on a tee section or a vertical baffle within the same type of enclosure An alternative configuration is a flat headwall with orifices and or notches protected by racks or gratings This may be fabricated from a large steel plate similar in construction to the extended detention outlets specified in the Denver Colorado manual referenced below This alternative outlet can be simulated in the SAHM as a very large diameter standpipe where the width of the top notch is equal to the overflow width at the top of the plate between its supports Drawdown time and treatment vector considerations Flow duration control facilities are designed to detain stormwater on site for an extended period of time The drawdown time is a concern to designers in relation to three areas of design besides hydromodification management 1 Standing water for extended periods provides a potential habitat in which mosquitoes can breed Sacramento stormwater programs work with their local mosquito abatement or vector control agencies to develop guidelines for stormwater facility design these generally recommend that design detention times 183 SAHM Guidance Document December 2013 not exceed 96 hours Provisions for access and inspection by vector control personnel are also required Contact the local permitting agency for details of local vector control provisions which apply to both treatment measures and flow
225. selected element This runoff volume is calculated when the Calculate button at the bottom of the table is clicked by the user following the input of all of the table information 222 SAHM Guidance Document December 2013 The fourth column Post Unmit Element Name is the SAHM mitigated scenario element that is generating the unmitigated runoff volume For mitigated scenario elements where the unmitigated runoff is coming from an upstream element or elements for example two basin elements discharging to a bioretention element connected to an element with a POC the user should type in an appropriate name For mitigated scenario elements using an analysis point then the upstream element name should be input by the user For the mitigated scenario elements where the unmitigated runoff volume is not automatically generated in the model porous pavement green roof and interceptor trees additional model input is required see below For porous pavement green roof and interceptor trees the user types in the appropriate unmitigated element name The fifth column Post Unmit Time Series is the runoff time series number for the SAHM element selected in column 4 This Post Unmit Time Series number is selected by the user from a drop down box of options The Post Unmit Time Series number will be a 700 time series number if using a POC If the element has an analysis point then the number will be a 1000 time series number The sixth column Post U
226. sh Mitigated ivi The LID tool bar button farthest on the right brings up the Low Impact Development Scenario Generator screen The LID analysis screen has two options LID Scenario Generator and LID Points Table The LID Scenario Generator can be used to compare the amount of runoff from different land types and combinations By clicking on the Compute LID Base Data the user can quickly see how changing the land use affects surface runoff interflow groundwater and evapotranspiration NOTE The LID Scenario Generator works only in the Mitigated scenario 147 SAHM Guidance Document December 2013 File Edit View Help Summary Report Deseo IABSHEB SR Ose Se OE DO O Basin 3 Mitigat Subbasin Name Basn 3 Designate as Bypass for POC Surface Interflow Groundwater Flows To P T Area in Basin I Show Only Selected Available Pervious Acres Available Impervious Acres a A Grass Flat 0 1 Imperv Flat 0 1 I A Grass Mod 1 2 I Impery Mod 1 2 I AGrass Steep 2 5 I Imperv Steep 2 5 M AGrassVSteepp 5 M ImpenWSteep gt 5 I AAaric Flat 0 1 I Porous Pavement I AAgric Mod 1 2 7 I AAgic Steep 2 5 ol I RAgicNSteesbs4 0 Pro Elements I AUrban Flat 0 1 0 r Aena o _ P AUrban Steep 2 5 cs I AlutbanVSteep gt 5 LID Toolbox I ATrees Flat 0 1 J A Trees Mod 1 2 F AlreesSteepi25 I AtreesVSteep gt 5 7 B Grass Flat 0 1 Commercial Toolbox F BGrassMod 1 2 e
227. sing a Basin element containing the drainage area of the pre project land use A point of compliance POC is assigned by the user to the Basin element Only surface runoff and interflow are connected to the POC In the Mitigated scenario the Unmitigated volume is modeled using a Basin element consisting of both impervious area and any pervious area draining to a vegetated swale represented by the Channel element For this element a separate POC is not needed to record the Unmitigated volume If an analysis point is used instead of a POC then there must be a conveyance element for example an upstream Channel element immediately upstream of the vegetated swale Channel element The upstream conveyance element must include an analysis point to record the Unmitigated volume In the Mitigated scenario the vegetated swale Mitigated volume can be represented modeled using the Channel element If infiltration to the native soil is allowed then infiltration should be turned on and an infiltration rate input by the user A point of compliance POC is assigned by the user to the surface and underdrain if any discharge Outlet 1 of the Channel element to compute the Mitigated volume The POC number should be the same as for the Pre Project scenario File Edit View Help Summary Report File Edit View Help Summary Report If the POC number Dal eee Dw st is 1 then the user le must select time Cee series 501 for the pre SCENARIOS volume 701
228. so possible depending on the properties of the native soil Bioretention also can include an underdrain pipe Note a bioretention facility fills from the surface down to the bottom By comparison a gravel trench bed is assumed to fill with stormwater from the bottom of the trench to the top This makes a difference in how quickly water reaches the underdrain and the native soil and exits the bioretention amended soil via either discharge route The user can select one of two outlet configurations 1 Riser outlet structure 2 Vertical orifice overflow 97 SAHM Guidance Document December 2013 The user is required to enter the following information about the bioretention facility depending on the outlet configuration selected Riser outlet structure File Edit View Help Summary Report Del se 4a608 d m Ds ol ld el Si z Schematic lt a S Bio Swale 1 Mitigated SCENARIOS Facility Name _ Outlet 1 Outlet 2 Outlet 3 i Pre Project Downstream Connection 0 0 0 Facility Type Bioretention Swale F Use simple swale Quick Swale Run Scenario F Underdrain Used gt AE Mitigated Basic Elements Swale Bottom Elevation ft Swale Dimensions Flow Through Underdrain ac ft Swale Length ft 0 000 Total Swale Bottom Width ft Freeboard ft Facility Dimension Diagram Over toad Flooding ft Effective Total Depth ft Riser Outlet Structure Bottom
229. soil column during non storm periods The routine will satisfy potential evapo transpiration PET demands in the same sequence as implemented in HSPF 1 Water available from vegetation interception storage 2 Water available from surface ponding 194 SAHM Guidance Document December 2013 3 Water available from the bioretention soil layers top layer first Water will be removed from vegetation interception storage and surface ponding and the bioretention soil layers starting at the top layer down to the rooting depth at the potential rate Water is taken from the soil layers below the rooting depth based on a percentage factor to be determined Without this factor there will be no way to remove water from below the rooting depth once it becomes completely saturated 195 SAHM Guidance Document December 2013 This page is intentionally left blank 196 SAHM Guidance Document December 2013 APPENDIX F SAHM COMPLEX PROJECT EXAMPLE A complex project site with multiple stormwater mitigation facilities and multiple points of compliance can easily be modeled with SAHM The key to successful stormwater modeling of a complex project site is to approach the modeling in a systematic way The following is an example of how that can be done in SAHM It is important to first lay out what the project area looks like prior to development and then with the proposed new development For this example we will assume that we have a large proje
230. ss SCENARIOS Pal peciity Name Facility Type Outlet 1 Outlet 2 Outlet 3 or Downstream Connections a AAE Mitioatea M Precipitation Applied to Facility Auto Pond Quick Pond IV Evaporation Applied to Facility Facility Dimension Diagram Facility Dimensions Outlet Structure Data BES ete Facility Bottom Elevation fi Outlet Structure Data nA Da Poom eenah t Riser Diameter fin gp H Bottom Width ft Riser Type Fa Effective Depth ft Kahte Left Side Slope H V Bottom Side Slope H V Right Side Slope H V Pio Elements Top Side Siope HA Orifice Diameter Height Infiltration Number in ft 1 He _4 2 M one Run Scenario J 5 oole 5 5 LID Toolbox Joan a Element Trapezoidal Pond 1 POC Outlet SelectPOC ADD Pond Volume at Riser Head ac ft 0 M Dutlet1 Show Pond Table OpenTable 4 Initial Stage fi Commercial Toolbox Tide Gate Time Series Demand Move Elements gt r Determine Outlet With Tide Gate F Use Tide Gate Tide Gate Elevation ff fo Downstream Connection X Overflow Elevation ft 0 Iterations fo The point of compliance is selected by right clicking on the element at which the compliance analysis will be made In the example above the point of compliance analysis will be conducted at the outlet of the trapezoidal pond 122 SAHM Guidance Document December 2013 Onc
231. t with a bioretention surface area of 7 acres In the model rain falls directly on the porous pavement green roof and the bioretention areas so these acreages are not included in the DMA 3 basin total area 211 SAHM Guidance Document December 2013 File Edit View Help Summary Report Del sae ELLEKS EILERA Facility Name Outlet 1 Outlet 2 Outlet 3 Downstream Connection oo Facility Type eine F Use simple swale Quick Swale Underdrain Used Underdrain Diameter ft 05 Offset in Swale Bottom Elevation f 0 Orifice Diameter in p 0 Swale Dimensions Flow Through Underdrain ac ft 0 iz Se Ze Swale Length ft Total Dutflow ac tt 0 Swale Bottom Width ft Percent Through Underdrain 0 Freeboard ft poo Facility Dimension Diagram Over toad Flooding ft aco Riser Outlet Structure a Effective Total Depth ft Bottom slope of Swale ft ft Outlet Structure Data Top and Bottom side slope t t Riser Height Above Swale surface f 9 5 Left Side Slope H V Riser Diameter in 35 H Right Side Slope H V joo RiserType Fist ad Material Layers for Swale Layer Layer2 Layer 3 Devin Eon LO Soil Layer 1 Amended 25ih gt Soil Layer 2 Sandy loam Orifice Diameter Height Soil Layer 3 amave y o Number in ft Edit Soil Types 1g Hb H _Edit Soil Types 2p Abi KSat Safety Factor 30 de 4 None C2 4 Show Swale Table OpenTable Swale Volume at Riser Head ac ft 20 77
232. the number of hourly Pre project flow values that exceed each flow increment level Pre project flow duration are counted to create the flow duration curves and accompanying tabular results Next SAHM computes the post project runoff in the Mitigated scenario and routes the runoff through the pond But before the runoff can be routed through the pond the pond must be given dimensions and an outlet configuration Auto Pond uses a set of rules based on the Pre project and Mitigated scenario land uses to give the pond an initial set of dimensions and an initial outlet orifice diameter and riser the riser is given a default rectangular notch This information allows SAHM to compute a stage storage discharge table for the pond 29 SAHM Guidance Document December 2013 With this initial pond stage storage discharge table SAHM 1 routes the hourly post project runoff through the pond for the 30 50 years of record to create to the Mitigated flow time series 2 counts the number of hourly Mitigated flow values that exceed each flow increment level this is the Mitigated flow duration and 3 computes the ratio of Mitigated flow values to Pre project flow values for each flow increment level comparing the Pre project and Mitigated flow duration results If any of the 100 individual ratio values is greater than allowed by the flow duration criteria then the pond fails to provide an appropriate amount of mitigation and needs to be resized
233. tment and or flood control design criteria as appropriate The latter are both based on the concept of a single empirical design storm which does not directly correspond to the flow duration approach using frequency analysis in a long term simulation Stormwater treatment design requires the use of volume based runoff coefficients which although similar in concept to runoff coefficients used for flood control are determined differently Runoff coefficients used for flood control were derived for large storms with some conservatism built in to estimates of peak flow rates and water surface elevations Runoff coefficients for stormwater treatment have been adjusted to reflect runoff from small storms where a greater percentage of the rainfall is held within the catchment Vector Management If the maximum allowed drawdown is seldom or never exceeded over the simulation period then likelihood of mosquito breeding in the facility is very low and the design for the pond vault or tank does not need to be modified If a maximum allowed drawdown time is exceeded then the system may need to be redesigned to reduce the drawdown time The designer should consider additional reductions in impervious area and or LID elements to help reduce the facility size 184 SAHM Guidance Document December 2013 To evaluate the frequency and distribution of larger events in more detail use the Hydrograph tool page 134 to plot monthly peaks for several years at
234. to the model for the sole purpose of providing the Unmitigated volume for the LID Points calculations otherwise this element does not need to be in the model Because as described above this is a situation where the unmitigated runoff volume is not automatically generated in the model and additional model input is required and a separate POC is needed to record the Unmitigated volume We suggest a POC number one greater than that selected for the Pre Project scenario Note that analysis points cannot be used for porous pavement File Edit View Help Summary Report Daw amp ica KEETA oo aa el Sa RP 5 Schematic SCENARIOS Subbasin Name Post Unmit I Designate as Bypass for POC Y O Pre Proj Surface Interflow Groundwater aes Flows To gt eed M Mitigated Area in Basin F Show Only Selected Available Pervious Acres Available Impervious Acres M Impery Flat 0 1 10 Run Scenario Basic Elements Post Unmit Basin 100 Impervious File Edit View Help Summary Report Dae 28 AbBSHEA Ose SO BBG d d o e A e N es 5 Schematic D Porous Pavement 1 Mitigated E SCENARIOS Facility Name Porous Pavement 1 Outlet 1 Outlet 2 Outlet 3 pated C Pre Project Downstream Connection 0 0 0 a Miigated Facility Type Porous Pavement Quick Pavement Run Scenario Facility Dimension
235. tor is the fraction ratio of the average maximum water depth behind a check dam in the gravel layer Sublayer 1 compared to the maximum gravel layer depth Sublayer 1 For example if the average maximum water height is 6 and the gravel depth is 9 then the Effective Volume Factor 0 67 6 9 The effective volume factor is multiplied by the Sublayer 1 storage volume to determine the actual maximum volume available for stormwater storage before the check dam is overtopped and the water in the gravel layer depth Sublayer 1 proceeds to a downstream conveyance facility Pavement Thickness ft Porous pavement layer depth Pavement Porosity Porous pavement porosity Layer 1 Thickness ft Subgrade gravel layer depth Layer Porosity Subgrade gravel porosity Layer 2 Thickness ft Sand layer depth if appropriate Layer 2 Porosity Sand porosity Ponding Depth Above Pavement ft Height at which sheet flow occurs on the pavement Underdrain Diameter in Set to zero if there is no underdrain Underdrain Height ft Height of the bottom of the underdrain above the bottom layer Native Infiltration Yes infiltration into the underlying native soil Measured Infiltration Rate in hr Native soil infiltration rate Infiltration Reduction Factor 1 Native soil infiltration rate safety factor see page 79 If infiltration is used then the user should consult the Infiltration discussion on page 79 The porous pavement layers repres
236. tting agency 3 Manually run the mitigated scenario as described on page 55 and review the Analysis screen to check if the revised mitigated flow still passes the flow duration criteria for curve matching If so proceed with the pond design using the revised outlet 4 If the revised design shows Fail scoring at one or more flow levels excess flow durations may be reduced somewhat by reducing the depth of the pond which lowers the head above the orifice SWMMWW recognizes a practical minimum of 3 feet of live storage if pond shallowing is required at the minimum orifice size As an alternative further mitigation can be applied to the low flow orifice flow by adding an additional infiltration measure downstream This can be sized either approximately by estimating an average excess flow from the orifice or with the help of SAHM by returning to the screen for the Pond characteristics and specifying a different Downstream Connection for the bottom orifice which is then connected to an additional element With this revision to the post project scenario the Point of Compliance for the system would then be located at the downstream end of the additional low flow mitigation Alternative Outlet Configurations SAHM has two default types of outlet configurations multiple orifice or orifice plus weir notch based on a standpipe riser structure The entire standpipe is usually within a cylindrical enclosure or manhole to exclude trash and larger particle
237. uded Orifice Diameter in Planter underdrain pipe orifice diameter set to zero if no underdrain is included Riser Height Above Planter Surface ft Height of planter overflow pipe above planter soil surface Riser Diameter in Planter overflow pipe diameter Native Infiltration Yes infiltration into the underlying native soil Measured Infiltration Rate in hr Native soil infiltration rate If infiltration is used then the user should consult the Infiltration discussion on page 79 NOTE See Appendix C or consult with the local municipal permitting agency for additional considerations regarding infiltration and determination of the appropriate infiltration reduction factor 112 SAHM Guidance Document December 2013 File Edit View Help Summary Report Ded e AaGSa e Oe SMES 00 k Vv 3 z Size Infiltration Planter Planter Bottom Width ft Freeboard ft Effective Total Depth ft Material Layers for Planter i Soil Layer 1 Salse eel f f Outlet Structure Data Riser Height Above Planter surface h 0 ie Tota Volume Through Facility ac t Total Volume Through Riser ac ft Total Volume Infitrated fact Percent Infiltrated Flow Through Underdrain ac tt Percent Through Underdrain Show Planter Table Open Table a Planter Volume at Riser Head ac ft 000 SAHM includes automated sizing of the planter box based on a user set target infiltration perce
238. un Scenario Basic Elements LID Toolbox Commercial Toolbox r Move Elements T 33 Save xy Load xy Bo yva H j j j i j ji ji j jdi jM Mi M oOooooooooooeoceoco0ccoc0ce00cocsd MPeReEocoooooceooccocooococcoccocCocceocoocoocococococCCoCS H k H k ee eee ee eoOoOoOoOoooooooeocoocecocececce0coecs ee o o E o o E E o E E o A E o E B o ao B E o E o E o A o R o o E o oo B E o E o o E E o E o ieee EE eee eee e eee eee AVES EID The stage storage discharge table hydraulically represents any facility that requires stormwater routing The table is automatically generated by SAHM when the user inputs storage facility dimensions and outlet structure information SAHM generates 91 lines of stage surface area storage surface discharge and infiltration values starting at a stage value of zero facility bottom height and increasing in equal increments to the maximum stage value facility effective depth When the user or SAHM changes a facility dimension for example bottom length or an orifice diameter or height the model immediately recalculates the stage storage discharge table The user can input to SAHM a stage storage discharge table created outside of SAHM To use a stage storage discharge table created out of SAHM the SSD Table element is required See the SSD Table element description below for more information on how to l
239. unty wide basis for implementation of stormwater discharge permits issued by the California Regional Water Quality Control Board under the National Pollutant Discharge Elimination System The End User is not permitted to use the Sacramento Area Hydrology Model Software for any other purpose than as described above End User shall not copy distribute alter or modify the Sacramento Area Hydrology Model Software The SAHM incorporates data on soils climate and geographical features to support its intended uses of identifying site appropriate modeling parameters incorporating user defined inputs into long term hydrologic simulation models of areas within the County of Sacramento and assisting design of facilities for flow duration control as described in the accompanying documentation These data may not be adequate for other purposes such as those requiring precise location measurement or description of geographical features or engineering analyses other than those described in the documentation This program and accompanying documentation are provided as is without warranty of any kind The entire risk regarding the performance and results of this program is assumed by End User Clear Creek Solutions Inc and the governmental licensee or sublicensees disclaim all warranties either expressed or implied including but not limited to implied warranties of program and accompanying documentation In no event shall Clear Creek Solutions Inc o
240. ure Data RiserHeight R o H Riser Diameter in o H Riser Type Fa H Notch Type T Left Side Slope H V ESNEA Bottom Side Slope H V Right Side Slope H V TPE A Orifice Diameter Height Infiltration Number in ft 1f He oH 2 i _ UD Toolbox a a a 3 cert cine Pond Volume at Riser Head ac ft 0 Show Pond Table OpenTable gt Initial Stage P Commercial Toolbox Tide Gate Time Series Demand I The Point of Compliance screen will be shown for the pond The pond has one outlet by default The outflow from the pond will be compared with the Pre project runoff The point of compliance is designated as POC 1 SAHM allows for a maximum of 59 points of compliance in a single project Click on the Connect button 22 SAHM Guidance Document December 2013 File Edit View Help Summary Report Oeil s 8 ABSGUEBR Ossau oooO z Schematic a e jis S Trapezoidal Pond 1 Mitigated SCENARIOS a Facility Name Trapezoidal Pond 1 Facility Type Outlet 1 Outlet 2 Outlet 3 DPP Downstream Connections EEEE Bn a Z Mitigated IV Precipitation Applied to Facility Auto Pond Quick Pond il Facility Dimension Diagram Run Scenario Outlet Structure Data Basic Elements Facility Bottom Elevation ft 0 Fes Henne n E 5 Bottom Length ft 0 Ree Deen e m e Bottom width ft o Riser Type m E Effective Depth ft
241. user to the Basin element Only surface runoff and interflow are connected to the POC In the Mitigated scenario the Unmitigated volume is modeled using a Basin element consisting of both impervious area and any pervious area draining to a Flow Through Planter Box element For this element a separate POC is not needed to record the Unmitigated volume If an analysis point is used instead of a POC then there must be a conveyance element for example a Channel element immediately upstream of the Flow Through Planter Box element The upstream conveyance element must include an analysis point to record the Unmitigated volume In the Mitigated scenario the stormwater planter Mitigated volume can be represented modeled using the Flow Through Planter Box element Infiltration to the native soil is not allowed A point of compliance POC is assigned by the user to the surface and underdrain discharge Outlet 1 of the Flow Through Planter Box element to compute the Mitigated volume The POC number should be the same as for the Pre Project scenario File Edit View Help Summary Report File Edit View Help Summary Report If the POC number 1S Cee se Ose tee 1 then the user must aly E S h AnA E SS hu select time series Schematic Schematic 501 for the p re SCENARIOS SCENARIOS volume 701 for the RE Pre Proect fy FE Pie Proiect post unmit volume nl nl and 801 for the post mit volume These time series are based on the element FTPianier
242. ve Once entered the land type can be changed by clicking on the Change button on the right 49 SAHM Guidance Document December 2013 The user enters the number of acres represented by the lateral basin land type If the lateral basin contains two or more pervious land use types then the user should create a separate lateral basin for each Note The Sacramento Design Manual includes a restriction that the maximum allowable ratio of impervious lateral flow basin area to pervious soil flow basin area is 2 to 1 50 SAHM Guidance Document December 2013 LATERAL I BASIN ELEMENT Impervious File Edit View Help Summary Report Ose sae 4 DARASE Schematic sz Lateral Basin 1 Pre Project Element Name Lateral Basin 1 Runoff Type Surface Interflow Groundwater Pre Project Downstream Connection 0 0 0 SCENARIOS Element Type Lateral Impervious Flow Basin Impervious IMPLND Type change a flea Mitigated Run Scenario Lateral Area ac 0 Basic Elements Lateral Flow IMPLND E Available Impervious coverages IMPLNDs Check only one Impery Flat 0 1 Imperv Mod 1 2 Impery Steep 2 5 Imperv VSteep gt 5 Porous Pavement LID Toolbox ieee Commercial Toolbox Move Elements N Sy Save xy Load xy x Bo Y fa NOTE Do not use the
243. vices In the Pre Project scenario the Pre volume is modeled using a Basin element containing the drainage area of the pre project land use A point of compliance POC is assigned by the user to the Basin element Only surface runoff and interflow are connected to the POC In the Mitigated scenario the Unmitigated volume is modeled using a Basin element consisting of both impervious area and any pervious area draining to a proprietary device represented by the SSD Stage Storage Discharge Table element For this element a separate POC is not needed to record the Unmitigated volume If an analysis point is used instead of a POC then there must be a conveyance element for example a Channel element immediately upstream of the SSD Table element The upstream conveyance element must include an analysis point to record the Unmitigated volume In the Mitigated scenario the proprietary device Mitigated volume can be represented modeled using the SSD Table element as long as the operation of the device can be described in a table consisting of stage water depth in units of feet water surface area in units of acres storage volume in units of acre feet and discharge cfs If infiltration to the native soil is allowed then a fifth column of infiltration flow to the native soil cfs is required A point of compliance POC is assigned by the user to the surface and underdrain if any discharge Outlet 1 of the SSD Table element to compute the M
244. ysis is done for the entire 12 months of every year in the modeling period of record However if the user wants to compute the durations for only a portion of a year the Seasonal Duration option can be used The user inputs a start date mm dd and an end date mm dd For example if the user is interested in a duration analysis of only summer flows the start date can be set to 06 21 and the end date input as 09 22 Then using the user defined minimum and maximum duration bounds SAHM will compute the duration analysis for that summer season as defined by the user 131 SAHM Guidance Document December 2013 FLOW FREQUENCY File Edit View Help Summary Report Osi tee EA GE M Os Sana Plow Frequency Cumulative Probability m Flow cfs Predeveloped Mitigated yik tg tx x Ha x x x REX AIOE 10 20 30 50 70 80 9 9 98 9999 5 100 Durations Flow Frequency Dravgjown Hydrograph J LID Points Table J Analyze datasets DM All Datasets Flow J Stage J Precip J Evap F REN RPONOFRWOWUDRFOORRFPRONEHFORFOROOF RREROOMNRFRFWNOKRDODDOOONONKFHFONORFORE Flow frequency plots are shown on the left and the 2 5 10 and 25 year frequency values are on the right Flow frequency calculations are based on selecting annual flow values and ranking them by their Weibull Plotting Position The Weibull Plotting Position formula is Tr N a m b where Tr return period years m
245. ysis point is used then the user must select the 1000 time series numbers for the post unmit volume and the post mit ra volume based on ey the elements i names The post Save xy Load xy unmit volume will l l be from All Set up using Analysis Points Set up using POC Outlets The post mit volume will be from Outlet 1 238 SAHM Guidance Document December 2013 Detention Basin In the Pre Project scenario the Pre volume is modeled using a Basin element containing the drainage area of the pre project land use A point of compliance POC is assigned by the user to the Basin element Only surface runoff and interflow are connected to the POC In the Mitigated scenario the Unmitigated volume is modeled using a Basin element consisting of both impervious area and any pervious area draining to an element representing the detention basin For this element a separate POC is not needed to record the Unmitigated volume If an analysis point is used instead of a POC then there must be a conveyance element for example a Channel element immediately upstream of the Infiltration Basin element The upstream conveyance element must include an analysis point to record the Unmitigated volume In the Mitigated scenario the bioretention Mitigated volume can be represented modeled using any one of the following SAHM elements Trapezoidal Pond Irregular Pond Vault or SSD Table If infiltration to the native
246. ysis points have numbers in the thousand range 1001 and above The POCs have numbers less than 1000 and are determined based on the POC number and the type of time series represented All predevelopment time series are in the 500 range for example 501 is the predevelopment runoff for POC 1 All post development unmitigated time series are in the 700 range for unmitigated flows entering the LID measure for example 701 is the post development unmitigated runoff for POC 1 All post development mitigated time series are in the 800 range for mitigated flows exiting the LID measure for example 801 is the post development mitigated runoff for POC 1 221 SAHM Guidance Document December 2013 Analysis points only can be used in situations where the runoff volume is going from one conveyance element to the next In all other situations a POC must be used For example a POC must be used when two or more elements provide runoff to a downstream LID measure see example below EErEE In this situation an analysis point would be ocd see needed for each of the upstream channel le m Ban elements to save the post development z unmitigated runoff time series from each to the SAHM data management file The two post K C Pre Project e e EN ne development unmitigated runoff time series would need to be added together to calculate the total post development unmitigated volume However the LID Points Table requires a single post

SAHM User`s Manual - Sacramento Stormwater Quality Partnership

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