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(HELP) Model - Environmental Laboratory

1. v kinematic viscosity of water 1 14 x 10 cm7 sec at 15 C C proportionality constant replaced in Equation A 6 by a function of the porosity d particle diameter cm approximated for nonuniform particles by Equation A 7 Darcy s proportionality constant is dependent on the shape and packing of the soil grains Freeze and Cherry 1979 Since porosity represents an integrated measure of the packing arrangement in a porous media the following semi empirical uniform pore size equation relating Darcy s proportionality constant and porosity was developed by Kozeny Carman Freeze and Cherry 1979 cc 00 o iv ad m 1 80x104 where K saturated hydraulic conductivity cm sec g acceleration due to gravity 981 cm sec v kinematic viscosity of water 1 14 x 10 cm sec at 15 C n total porosity geometric mean soil particle diameter mm computed by Equation A 7 The original Kozeny equation was obtained from a theoretical derivation of Darcy s Law where the porous media was treated as a bundle of capillary tubes Bear 1972 Carman introduced an empirical coefficient to Kozeny s equation to produce the semi empirical Kozeny Carman equation Brutsaert 1967 The Kozeny Carman s equation reported in Freeze and Cherry 1979 was altered to allow the mean particle size to be entered in millimeters Freeze and Cherry 1979 indicated that the particle diameter of a non uniform soil can be described usin
2. DATA FILES PRECIPITATION TEMPERATURE amp SOLAR RADIATION DATA Figure 4 Schematic of Weather Data Module 4 5 1 Weather Data File Selection The first screen in the weather data module is the Weather Data File Editing screen A schematic of this screen is shown in Figure 5 On this screen the user may enter file names of existing files to select previously generated HELP Version 3 files for editing or leave the file names blank to create new data One file name for each of the four types of weather data to be edited is needed The DOS path may be specified if different from the active or default drive and subdirectory such as C HELP3 DATA The following gives file naming and extension information as displayed on the screen 47 WEATHER DATA FILES TO EDIT PROCEED TO WEATHER DATA ENTRY amp EDITING Figure 5 Schematic of Weather Data File Editing Screen User Specified Data Type DOS Path Drive and or Subdirectory File Name Precipitation D4 Temperature D7 Solar radiation D13 Evapotranspiration DII Any valid DOS name that the user desires up to eight characters is acceptable The HELP program supplies the extension This convention must be always remembered when selecting file names for editing saving or converting data from other sources However when typing a file name on this screen the user should not enter the extension because the program automatically assigns the p
3. The program provides the user with a maximum LAI value typical of the location selected if the value entered by the user cannot be supported without irrigation because of low rainfall or a short growing season This statement should be considered only as a warning The maximum LAI for bare ground is zero For a poor stand of grass the LAI could approach 1 0 for a fair stand of grass 2 0 for a good stand of grass 3 5 and for an excellent stand of grass 5 0 The LAI for dense stands of trees and shrubbery would also approach 5 The program is largely insensitive to values above 5 If 13 the vegetative species limit plant transpiration such as succulent plants the maximum LAI value should be reduced to a value equivalent of the LAI for a stand of grass that would yield a similar quantity of plant transpiration Most landfills would tend to have at best a fair stand of grass and often only a poor stand of grass because landfills are not designed as ideal support systems for vegetative growth Surface soils are commonly shallow and provide little moisture storage for dry periods Many covers may have drains to remove infiltrated water quickly reducing moisture storage Some covers have liners near the surface restricting root penetration and causing frequent saturation of the surface soil which limits oxygen availability to the roots Some landfills produce large quantities of gas which if uncontrolled reduces the oxygen availability in the
4. The second screen in the weather data module is entitled Precipitation Temperature and Solar Radiation From this screen the user can select methods for creating the precipitation data file D4 the temperature data file D7 and the solar radiation data file D13 A schematic of the main options available on this screen are shown in Figure 7 In Version 3 of the HELP model all of the weather data need not be generated by the same method For example the user can enter the precipitation data using the synthetic weather generator the temperature data using data from a NOAA data file and solar radiation from an ASCII file Seven options are available for entering temperature and solar radiation data Under the precipitation data there are the same seven plus a default option Figures 8 9 and 10 show the possible options Default Precipitation If the default precipitation option Customary Units Only is selected the program will prompt the user with the list of states having default data The HELP model provides default precipitation values for the list of cities in Table 1 To select a state move the cursor to the desired state name and press Enter At this time the program prompts the user with the list of cities in the selected state for which default precipitation data is available Similarly the city can be selected by moving the cursor to the desired city and pressing Enter The user can return to the Precipitation Temperatur
5. mass of water M per mass of soil M The two can be related to each other by knowing the dry bulk density p dry bulk specific gravity I of the soil ratio of dry bulk density to water density p wet bulk density wet bulk specific gravity I of the soil ratio of wet bulk density to water density 0 w P wlTy 2 P 0 Ww Pup _ w d 3 l w p l w 3 6 GEOMEMBRANE CHARACTERISTICS The user can assign geomembrane liner characteristics vapor diffusivity saturated hydraulic conductivity to a layer using the default option the user defined soil option or the manual option Saturated hydraulic conductivity for geomembranes is defined in terms of its equivalence to the vapor diffusivity The porosity field capacity wilting point and intial moisture content are not needed for geomembranes Table 4 shows the default characteristics for 12 geomembrane liners The user assigns default soil characteristics to a layer simply by specifying the appropriate geomembrane liner texture number The user defined option accepts user specified geomembrane liner characteristics for layers assigned textures greater than 42 Manual geomembrane liner characteristics can be assigned any texture greater than 42 Regardless of the method of specifying the geomembrane soil characteristics the program also requires values for geomembrane liner thickness pinhole density installation defect density geomembrane placement quality and the
6. program will examine each row for completeness for the type of layer described for example the program will insure that a placement quality was entered for all geomembrane liners layer type 4 It will also check for the appropriateness of the values for example it will insure that the porosity is greater than the field capacity If there are no violations or warnings the program will write OK to the right of the option otherwise the program will list the problems and then write BAD to the right of the option Similarly the user can check for violations in the ordering of the layers from top to bottom based on the layer types specified by selecting the Verify Layer Arrangement option This option will check the nine rules for ordering of layers for example the program will insure that the top layer is not a liner This option operates in the same manner as the verification options Another available option on this screen is to review the user defined soil textures that were used in the landfill profile for inclusion in or deletion from the library of user defined soil textures Upon selecting this option the program lists all of the non zero user defined soil textures used in the profile and allows the user to enter or edit a name to describe the material in the user soil library Then after entering the names or labels the user should tag all of the soil textures to be included in the library with a Y in the column of cells under the
7. s 1950 series parallel coefficient of permeability model assumes that the porous media is equivalent to a number of parallel portions each with a different hydraulic conductivity and each with uniform pore size The hydraulic conductivity of each portion is obtained from the assumption of a bundle of capillary tubes parallel to the direction of flow The media is fractured at a normal plane with two resulting faces which are then rejoined after some random displacement Brutsaert 1967 Rawls et al 1982 fit Equation A 9 using geometric mean values for Brooks Corey parameters to saturated hydraulic conductivity values from their data base and obtained a good correlation between these and predicted values Rawls et al 1982 and Rawls et al 1983 subsequently recommended using an a constant of 21 cm sec However Rawls et al 1982 fit Equation A 9 to data presented by other researchers and obtained saturated hydraulic conductivities that overpredicted the data by three to four times Although conservative these results re emphasize the fact that empirical equations are not meant to replace laboratory or field measured data A 4 VEGETATED SATURATED HYDRAULIC CONDUCTIVITY If the saturated hydraulic conductivity of a soil or waste layer is not selected from the HELP default data base the program will not adjust the saturated hydraulic conductivity to account for root penetration by surface vegetation Therefore the user must adjust the
8. CONTENTS continued Page 3 4 Landfill Profile and Layer Descriptions 04 5 26 3 5 SOILCBAPAacteristeS s obese Dot edt nr her RU Oe PRE SER ES Ae Ste 29 3 6 Geomembrane Characteristics llle 33 Str See arcte tse S andene es eq Ee bove ER ERE da SEN ee 35 3 8 Overview of Modeling Procedure S 2o vs eo 3E AS bare RS AS is 36 3 9 Assumptions and Limitations llle 37 3 91 Solution Methods S etu bee RE x x eR ee Eee eS 37 392 Limits of Application 21 5 nA IESUS 39 4 PROGRAM INPUT iss xe X IS HERREN ex SL Ehe oe op 42 A ils Introd com 24 c6 ecoute ui v eo ioa et Is bot D Gc DNE Eta Mode 42 4 2 Dennions and Rules esci wx Xie OC eere du E RE 42 4 3 Program Structure pencetus Sopas sol Sc p ND 49 RE eru NOU alb Obr t Dg as 45 AA Mam Menu isse c RR REAPER REA URSI MERE Ea 45 4S Weather Data 3 tesoty wes SH yA git are ae x And ed oda est oe at EN 47 4 5 1 Weather Data File Selection llle 47 4 5 2 Evapotranspiration ET Data llle 49 4 5 3 Precipitation Temperature and solar Radiation Data 2 6 dreaded vere X Ge Has 51 ADA Saving Weather Data 9245 9 act X bik nei ed v Sine go Res 60 4 6 Soil and Design Data esse Es RE xU EUER hoe ew a 62 4 6 1 Soil and Design Data File Selection 24 62 4 6 2 Landfill General Information 00 5 64 4 6 3 Landfill Layer Design iiu oss ERG RAE PR US S 65 4 6 4 Runoff Curve Number 2 us ex UE ek
9. Clay 0 03454 Silt A 7 8 where d geometric mean soil particle diameter mm Percent silt and clay should be determined using a grain size distribution chart and grain sizes defined by the U S Department of Agriculture USDA textural soil classification system see para A 2 2 Kozeny Carman s equation coupled with Shiozuwa and Campbell s equation for mean diameter was applied to soils data provided by Lane and Washburn 1946 These data included void ratio and grain size distribution curves for three soils composed of differing degrees of silt and sand The saturated hydraulic conductivity predicted by Kozeny Carman s equation was compared with laboratory data provided by Lane and Washburn 1946 This comparison indicated that Kozeny Carman s saturated hydraulic conductivity equation coupled with Shiozuwa and Campbell s mean diameter equation can overpredict measured values by one to two orders of magnitude Although conservative these results reemphasize the fact that semi empirical equations are not meant to replace laboratory or field measured data Numerous other empirical equations with limited application have been developed to estimate saturated hydraulic conductivity from the physical properties of soils For example Freeze and Cherry 1979 Holtz and Kovacs 1981 and Lambe and Whitman 1969 presented various forms of Allen Hazen s equation for determining the saturated hydraulic conductivity of silt sand a
10. Ellwood R B and Greene D S 1990 Hydraulic characteristics of municipal refuse Journal of Geotechnical Engineering 116 4 539 553 US Environmental Protection Agency 1985 Covers for uncontrolled hazardous waste sites EPA 540 2 85 002 Hazardous Waste Engineering Research Laboratory Cincinnati OH 529 pp US Environmental Protection Agency 1988 Guide to technical resources for the design of land disposal facilities EPA 625 6 88 018 Risk Reduction Engineering Laboratory Cincinnati OH 63 pp US Environmental Protection Agency 1989 Technical guidance document Final covers for hazardous waste landfills and surface impoundments EPA 530 SW 89 047 Office of Solid Waste and Emergency Response Washington D C 39 pp 84 APPENDIX A CALCULATING SOIL WASTE AND MATERIAL PROPERTIES A 1 BACKGROUND The HELP program requires values for the total porosity field capacity wilting point and saturated hydraulic conductivity of each layer of soil waste or other material in a landfill profile These values can be selected from a list of default materials provided by the HELP program Table 4 or specified by the user User specified values can be measured estimated or calculated using empirical or semi empirical methods presented in this appendix Selecting the HELP values from default materials or calculating them based on empirical or semi empirical techniques are not intended to replace laboratory or field
11. John Wiley and Sons New York 745 pp Rawls W J and Brakensiek D L 1982 Estimating soil water retention from soil properties Journal of the Irrigation and Drainage Division 108 IR2 166 171 Rawls W J and Brakensiek D L 1985 Prediction of soil water properties for hydrologic modelling Proceedings of watershed management in the eighties B Jones and T J Ward ed American Society of Civil Engineers New York 293 299 Rawls W J Brakensiek D L and Saxton K E 1982 Estimation of soil water properties Transactions of the American Society of Agricultural Engineers 25 5 1316 1320 Rawls W J Brakensiek D L and Soni B 1983 Agricultural management effects on soil water processes part I Soil water retention and green and ampt infiltration parameters Transactions of the American Society of Agricultural Engineers 26 6 1747 1757 Shiozawa S and Campbell G S 1991 On the calculation of mean particle diameter and standard deviation from sand silt and clay fractions Soil Science 152 6 427 431 Shirazi M A and Boersma L 1984 A unifying quantitative analysis of soil texture Soil Science Society of America Journal 48 1 142 147 A 9 Shirazi M A Boersma L and Hart J W 1988 A unifying quantitative analysis of soil texture Improvement of precision and extension of scale Soil Science Society of America Journal 52 1 181 190 Springer E P
12. ROUEN REA 73 4 6 5 Verifying and Saving Soil and Design Data 75 AT Execu ns the Simmulatiol 2 02298 4 xh wee DENS USE S ede JJ AS Miewine Results ss eheu Wem REN RR Rex e d 79 49 Prnting Results 4 vo LCS ERES EI EIER IU REIR ae N 79 4 10 Displaying Guidance 22 sull pn ra RR ER RE RES 8l 4 Lb Quite HEEP ee ts d eer Iovi eui Meg qr eir ame a 8l REFERENCES 4l iaa de wd weed RR XE kx el XOU d edd CN Ae Seta 82 BIBLIOGRAPHY 65 ni eua te eR GR CR GUI DR I e ei Pe dtu Res 84 APPENDIX A Calculating Soil Waste and Material Properties Al vii NY OQ ta A W oo 10 11 12 13 14 15 16 17 18 19 20 FIGURES Page Schematic of Landfill Profile Illustrating Typical Landfill Features 24 443 0a eye tie orania arag aa SEARS SiG 7 Relation between SCS Curve Number and Default Soil Texture Number for Various Levels of Vegetation 36 ERM ati Men o Loo doe S eo ws ma he toes ar hee qus 46 Schematic of Weather Data Module l l 47 Schematic of Weather Data File Editing Screen 48 Schematic of Evapotranspiration Data Screen 50 Schematic of Precipitation Temperature and Solar Radiation Sereen 22e ud epu eei ieR4d4 ena Le 22 Precipitation Options 24 so RE Foret ee edie bt kd Ex E Seed R3 22 Temperature OpHODS e uk org xe onem ato a d RE ns 53 Solat Radiation Opus eek ex tee RR Ye eh AE ON RUE eae x 54 Weather Data File Saving Screen O
13. SAVE heading Similarly the user should tag all of the soil textures to be deleted from or not included in the library with a N in the column of cells under the SAVE heading To complete the additions and deletions to the library the user should press F10 to cancel the additions and deletions and return to the 75 Verification and Saving screen the user should press Ese or F9 If the user selects the Save Soil and Design Data option the program automatically checks for possible violation of rules or errors in the soil and design data This checking encompasses verification of presence arrangement and values entered for the general landfill information the landfill profile and layer data and the runoff curve number information The program scans through the three landfill profile spreadsheets of layer data one layer at a time and reports the errors as they are encountered If any violations or inconsistencies are found the program displays them on multiple screens The user should press Enter or Page Down to proceed through the screens and reach the File Saving screen where the data can be saved in a file If the user wishes to return to Verification and Saving screen press Esc Upon reaching the File Saving screen the user can return to the verification and input screens to correct violations by editing the data To return press Page Up successively until the desired screen is reached On the other hand the user can still
14. TYPE EXECUTION FILES SELECTION INPUT AND OUTPUT FILES EXECUTE SIMULATION SELECTION OF SIMULATION PERIOD OUTPUT TYPES PROCEED TO NEXT SCREEN OR RUN SIMULATION RETURN TO PREVIOUS SCREEN Figure 18 Schematic of Execute Simulation Option directory by entering the name of that directory in the column labeled DIRECTORY and on the same row as the file type of interest To select a file from the list of displayed files move the cursor to the file and select it by pressing Enter This transfers control back to the previous screen and the name of the file just selected will be displayed in the proper cell The user can exit the list of files screen without selecting a file by pressing the Esc key Once file names have been selected the user can proceed to the next screen of the execution module by pressing Page Down or F10 If the output file already exists the user is prompted with a warning indicating that this file already exists The program then asks whether the file should be overwritten If the user answers N the program moves the cursor to the output file name cell so that the user can enter a new file name If the user answers Y the program proceeds to the Output Selection screen Before displaying the next screen the program reads the weather data files to determine the maximum allowable simulation period Output Selection On this screen the user selects the units of the HELP model outpu
15. Waterways Experiment Station Vicksburg MS 72 pp Schroeder P R Dozier T S Zappi P A McEnroe B M Sjostrom J W and Peyton R L 1994 The hydrologic evaluation of landfill performance HELP model Engineering documentation for version 3 EPA 600 8 94 xxx US Environmental Protection Agency Cincinnati OH 105 pp USDA Soil Conservation Service 1985 Chapter 9 hydrologic soil cover complexes National engineering handbook section 4 hydrology US Government Printing Office Washington D C 11 pp 83 BIBLIOGRAPHY Darilek G T Laine D L and Parra J O 1989 The electrical leak location method geomembrane liners Development and applications Geosynthetics 59 Conference Proceedings San Diego CA 456 466 Giroud J P and Bonaparte R 1989 Leakage through liners constructed with geomembranes part I Geomembrane liners Geotextiles and Geomembranes 8 1 27 67 Giroud J P and Bonaparte R 1989 Leakage through liners constructed with geomembranes part II Composite liners Geotextiles and Geomembranes 8 2 71 111 Giroud J P Khatami A and Badu Tweneboah K 1989 Evaluation of the rate of leakage through composite liners Geotextiles and Geomembranes 8 4 337 340 McEnroe B M and Schroeder P R 1988 Leachate collection in landfills Steady case Journal of the Environmental Engineering Division 114 5 1052 1062 Oweis I S Smith D A
16. combination causes the program to delete a layer from the list of layers For example to delete the layer on line 3 the user should move the cursor to line 3 hold the Alt key down and press D The program will delete all information on line 3 and will shift the layers on lines 4 to 20 upward one line i e layer on line 4 moves to line 3 layer on line 5 moves to line 4 etc and line 20 becomes a blank line The user is cautioned that the deleted layer cannot be recovered without quitting and losing all changes F9 or Esc The copy command allows the user to place a layer that is identical to another layer on another line For example to copy the layer on line 7 to line 2 move the cursor to line 7 and press the Alt C combination then move the cursor to line 2 and press the Alt A combination This action will cause the program to insert a layer with values the same as those formerly found at line 7 above the layer formerly found at line 2 The layers formerly at and below line 2 will be moved downward one line The user may obtain the same result after the Alt C combination by moving to line 1 and pressing the combination Alt B The move command allows the user to move a layer from one row on the screens of layer data to another row For example to move the layer on line 3 above the layer on line 6 move the cursor to line 3 press the Alt M combination and move the cursor to line 6 and press the Alt A combination This action will cause t
17. curve numbers for rangeland soils Annual meeting of the American society of agricultural engineers Pacific northwest region Kennewick WA USDA ARS Paper Number PNR 84 203 13 pp Brooks R H and Corey A T 1964 Hydraulic properties of porous media Hydrology Papers 3 Colorado State University Fort Collins CO 27 pp Brutsaert W 1967 Some methods of calculating unsaturated permeability Transactions of the American Society of Agricultural Engineers 10 3 400 404 A 8 Childs E C and Collis George N 1950 The permeability of porous material Proceeding of the Royal Society 201 Section A Freeze R A and Cherry J A 1979 Groundwater Prentice Hall Englewood Cliffs NJ 604 pp Gupta S C and Larson W E 1979 Estimating soil water retention characteristics from particle size distribution organic matter percent and bulk density Water Resources Research 15 6 1633 1635 Holtz R D and Kovacs W D 1981 An introduction to geotechnical engineering Prentice Hall Englewood Cliffs NJ 733 pp Lambe T W and Whitman R V 1969 Soil mechanics John Wiley and Sons New York 553 pp Lane K S and Washburn D E 1946 Capillary tests by capillarimeter and by soil filled tubes Proceedings of the twenty sixth annual meeting of the Highway Research Board Washington D C 460 473 Perloff W H and Baron W 1976 Soil mechanics principles and applications
18. depth equal to the expected average root depth would tend to yield a low estimate of evapotranspiration and a high estimate of drainage through the evaporative zone An evaporative depth should be specified for bare ground to account for direct evaporation from the soil this depth would be a function of the soil type and vapor and heat flux at the surface The depth of capillary draw to the surface without vegetation or to the root zone may be only several inches in gravels in sands the depth may be about 4 to 8 inches in silts about 8 to 18 inches and in clays about 12 to 60 inches Rooting depth is dependent on many factors species moisture availability maturation soil type and plant density In humid areas where moisture is readily available near the surface grasses may have rooting depth of 6 to 24 inches In drier areas the rooting depth is very sensitive to plant species and to the depth to which moisture is stored and may range from 6 to 48 inches The evaporative zone depth would be somewhat greater than the rooting depth The local Agricultural Extension Service office can provide information on characteristic rooting depths for vegetation in specific areas Maximum leaf area index The user must enter a maximum value of leaf area index LAI for the vegetative cover LAI is defined as the dimensionless ratio of the leaf area of actively transpiring vegetation to the nominal surface area of the land on which the vegetation is growing
19. edge of the screen the user should move the cursor to line 29 hold the Alt key down and press A The result of this action is that a blank cell is inserted above line 29 and the program shifts the year on line 29 and all the years below it one line downward i e year on line 29 moves to line 30 year on line 30 moves to line 31 etc and line 29 will be a blank line for the user to enter the value for 57 the new year To add a year directly below a certain year for example below the year on line 5 the user should move the cursor to line 5 hold the Alt key down and press B The result of this action is that a blank cell is inserted below line 5 and the program shifts the year on line 6 and all the years below it one line downward i e year on line 6 moves to line 7 year on line 7 moves to line 8 etc and line 6 will be a blank cell for the user to enter the value of the new year The Alt D combination causes the program to delete a year from the list of years For example to delete the year on line 15 the user should move the cursor to line 15 hold the Alt key down and press D The program will delete information on line 15 and will shift the years on lines 16 to 100 upward one line i e year on line 16 moves to line 15 year on line 17 moves to line 16 etc and cell on line 100 becomes an empty cell The user is cautioned that the deleted year cannot be recovered without quitting and losing all changes F9 or Esc The o
20. generated data Default and calculated values are suitable for planning purposes parametric studies and design comparisons but are not recommended for accurate water balance predictions The default and calculated values are for water retention and flow therefore leachate is assumed to behave the same as water The effects of macropores resulting from poor construction practices burrowing animals desiccation cracks etc are not taken into account in the calculation of the properties or in the default values but the saturated hydraulic conductivity of the surface soil described by the default values is modified for grassy vegetation A 2 EMPIRICAL METHOD The empirical method for calculating HELP program user defined values employs empirical equations reported by Brakensiek et al 1984 and Springer and Lane 1987 to determine soil water retention parameters field capacity and wilting point and an empirical equation developed by Kozeny Carman to determine saturated hydraulic conductivity The total porosity and percent sand silt and clay of each layer is the minimum data required to calculate user defined values using this method A 2 1 Total Porosity Total porosity is a measure of the volume of void water and air space in the bulk volume of porous media At 100 percent saturation total porosity is equivalent to the volumetric water content of the media volume of water per total volume of media or Water Volume A 1 Total
21. grass 3 0 for a maximum LAI of 2 fair stand of grass 4 2 for a maximum LAI of 3 3 good stand of grass and 5 0 for a maximum LAI of 5 excellent stand of grass The manual option requires values for porosity field capacity wilting point and saturated hydraulic conductivity These and related soil properties are defined below Soil Water Storage Volumetric Content the ratio of the volume of water in a soil to the total volume occupied by the soil water and voids Total Porosity the soil water storage volumetric content at saturation fraction of total volume 3l Field Capacity the soil water storage volumetric content after a prolonged period of gravity drainage from saturation corresponding to the soil water storage when a soil exerts a soil suction of 1 3 bar Wilting Point the lowest soil water storage volumetric content that can be achieved by plant transpiration or air drying that is the moisture content where a plant will be permanently wilted corresponding to the soil water storage when a soil exerts a soil suction of 15 bars Saturated Hydraulic Conductivity the rate at which water drains through a saturated soil under a unit pressure gradient Porosity field capacity and wilting point are all dimensionless numbers between 0 and 1 Porosity must be greater than field capacity which in turn must be greater than the wilting point The wilting point must be greater than zero The values for porosity field capac
22. liners When a barrier soil liner or a geomembrane liner is not placed directly below the lowest drainage layer all drainage layers below the lowest liner are treated as vertical percolation layers Thus no lateral drainage is computed for the bottom section of the landfill 66 7 The top layer may not be a barrier soil liner 8 The top layer may not be a geomembrane liner 9 The profile can contain no more than a total of five barrier soil liners and geomembrane liners The program checks for rule violations only at the time the user saves the data Therefore to reduce the time involved in evaluating a landfill the user is encouraged to design a proper layer sequence before saving the data In the second column which has the heading Layer Thickness the user should enter the thickness of each layer in the landfill profile even for the geomembrane liner in inches or cm The values must be greater than zero a blank cell is taken as a value of zero Again during data verification the program checks for layer thickness of zero and issues a violation statement when the user tries to save the data In the third column the user should enter the soil texture number of the soil that forms the layer The 4 possible options for the user to enter soil texture numbers are 1 Select from a list of default textures for 42 soils wastes geomembranes geosynthetics and other materials 2 Select from a library of user defined textures t
23. of the area that is sloped in a manner that would permit drainage off the surface The runoff estimates predicted by the model are equal to the computed runoff by the curve number method times this percent The difference between the computed runoff and the actual runoff is added to the infiltration Next the user must select the method of moisture content initialization that is whether or not the user wishes to specify the initial moisture storage If the user answers N no to this question the program assumes near steady state values and then runs the first year of the simulation to improve the initialization to steady state The soil water contents at the end of this year of initialization are taken as the initial values for the simulation period The program then runs the complete simulation starting again at the beginning of the first year of weather data The results for the initialization period are 64 not reported However if the user answers Y yes the user is requested to enter the amount of water or snow water on the surface in the units selected Later the user should enter the initial moisture content of each layer as explained in the next section 4 6 3 Landfill Layer Data The next step in the soil and design data module is to input the design specifications of the landfill profile one layer at a time Layer data are entered in three screens These screens have a spreadsheet layout where each row represents a layer Fig
24. or Metric Units The program will generate from 1 to 100 years of daily precipitation data stochastically for the selected location using a synthetic weather generator The precipitation data will have approximately the same statistical characteristics as the historic data at the selected location If desired the user can enter normal mean monthly precipitation values for the specific location to improve the statistical characteristics of the resulting daily values The user is advised to enter normal mean monthly precipitation values if the project site is located more than a few miles from the city selected from Table 3 or if the land use or topography varies between the site and city The daily values will vary from month to month and from year to year and will not equal the normal values entered The same data is produced every time the option is used for a given location The data required by the synthetic weather generator are Location select from a list of 139 U S cities in Table 3 e Number of years of data to be generated e Normal mean monthly precipitation Optional default values are available 3 Create Edit Precipitation Option Customary or Metric Units Under the Create option the user may enter from 1 to 100 years of daily precipitation data manually The years which need not be consecutive can be entered in any order The user may add or delete years of data or rearrange the order of the years of data This same option can
25. presented below More details are given in the following sections about specific data requirements for each option Option 1 on the main menu is Enter Edit Weather Data This module permits the user to read evapotranspiration precipitation temperature and solar radiation data files and then review edit and save the data or create new files There are four primary screens in this module they are a file selection screen evapotranspiration data screen a screen that controls the method used for specifying precipitation temperature and solar radiation data and a screen for saving weather data files Several options are available for specifying precipitation temperature and solar radiations data These vary from using default data for precipitation only to synthetic and other user defined data sources such as NOAA Tape Climatedata ASCII data HELP Version 2 data and Canadian Climatological data Data may also be entered manually Default and synthetic weather data generation is performed by selecting the city of interest from a list of cities and specifying optional additional data Option 2 on the main menu is Enter Edit Soil and Design Data This module allows the user to read an already existing soil and design data file and then review edit and save the data or create a new data file There are eight primary screens in the soil and design data module they are a file selection screen a landfill general information screen three
26. saturated hydraulic conductivity in the top half of the evaporative zone The program A 7 adjusts the default values using the following equation developed by regressing changes in infiltration resulting from vegetation K 1 0 0 5966 LAI 0 132659 LAI 0 1123454 LAI 0 04777627 LAI 0 004325035 LAI K A 10 where K vegetated saturated hydraulic conductivity in top half of evaporative zone cm sec LAI leaf area index unitless K unvegetated saturated hydraulic conductivity in top half of evaporative zone cm sec A 5 CONCLUSIONS The HELP program user defined values for total porosity field capacity wilting point and saturated hydraulic conductivity can be conservatively calculated using empirical or semi empirical methods presented in this appendix Total porosity percent sand silt and clay and particle diameter are the minimum data required to calculate user defined values using the empirical method Total porosity and Brooks Corey parameters are the minimum data required for the semi empirical method Where available comparisons with measured values re emphasized the fact that neither of these methods is intended to replace laboratory or field generated data A 6 REFERENCES Bear J 1972 Dynamics of fluids in porous media American Elsevier Publishing Company New York 764 pp Brakensiek D L Rawls W J and Stephenson G R 1984 Modifying SCS hydrologic soil groups and
27. screens for entering design soil and geomembrane liner data by layers a screen for entering a runoff curve number a data verification screen and a screen for saving the soil and design data file Input screens associated with this module provide 45 1 ENTER EDIT WEATHER DATA 2 ENTER EDIT SOIL AND DESIGN DATA 3 EXECUTE SIMULATION czmsz 2 Ps gt eo PRINT RESULTS 5 DISPLAY GUIDANCE Figure 3 HELP3 Main Menu cells for entering project title system of units initial soil conditions landfill area layer design information such as layer type thickness soil texture drainage characteristics geomembrane liner information and runoff curve number information including the ability to adjust the curve number a function of surface slope and length At the end of this module the user may request that the data be checked for possible violation of the design rules explained in Section 3 Under this module the HELP model verifies the design data soil and geomembrane liner properties and layer arrangement Option 3 on the main menu is Execute Simulation In this option the user defines the data files to be used in running the simulation component of the HELP model and selects the output frequency and simulation duration desired from execution In this option the user can also view the list of files available and can make file selections from these lists Option 4 on the main menu is View Results This option allows the
28. sources with several different formats HELP Version 3 represents a significant advancement over the input techniques of Version 2 Users of the HELP model should find HELP Version 3 easy to use and should be able to use it for many purposes such as preparing and editing landfill profiles and weather data Version 3 facilitates use of metric units international applications and designs with geosynthetic materials This report should be cited as follows Schroeder P R Aziz N M Lloyd C M and Zappi P A 1994 The Hydrologic Evaluation of Landfill Performance HELP Model User s Guide for Version 3 EPA 600 R 94 168a September 1994 U S Environmental Protection Agency Office of Research and Development Washington DC This report was submitted in partial fulfillment of Interagency Agreement Number DW21931425 between the U S Environmental Protection Agency and the U S Army Engineer Waterways Experiment Station Vicksburg MS This report covers a period from November 1988 to June 1994 and work was completed as of June 1994 CONTENTS Page DISCUAIMERS 3d Oso sa oon NO aa a a ane qa dB Oe ODE aera s ii FOREWORD C 2d ake a a let a a a a Mat totale te a LT iii ABSTRACT iud Grd ee Dev eI Ce abo Be a a ee e iv FIGURES 453 dac ER e Aa aude hee teh E hee Read viii TABLES aea Ta e De ue armas A Er ftd woe E fedes ix ACKNOWLEDGMENTS e 41 45 reat yo eon Si ach CERRO NOS RE rca X i INTRODUCTION A c5 Teama droga dedi ede RP QU
29. text files could be imported into other software such as word processors and printed in the format desired 79 VIEW SELECT RESULTS FILE MAIN MENU DISPLAY FILE Figure 19 Schematic of View Results Option Similarly the output in total or part can be printed within the Viewing Option using the LIST program and blocking sections to be printed 4 10 DISPLAYING GUIDANCE PRINT SELECT RESULTS FILE Figure 20 Schematic of Print Results Option 80 On line help is provided throughout the program However option 6 on the main menu gives an overview of the HELP program as well as general criteria for landfill design and guidance on using the model Most of this user guide is displayed in this option and the guidance refers to figures and tables in this guide In addition the on line guidance uses the same section numbering as this guide 4 11 QUITTING HELP Option 7 on the main menu is to quit the HELP program and return to DOS 81 REFERENCES Arnold J G Williams J R Nicks A D and Sammons N B 1989 SWRRB A basin scale simulation model for soil and water resources management Texas A amp M University Press College Station TX 142 pp Breazeale E and McGeorge W T 1949 A new technic for determining wilting percentage of soil Soil Science 68 371 374 Brooks R H and Corey A T 1964 Hydraulic properties of porous media Hydrology Papers 3 Colorado State Universit
30. the primary liner are a geosynthetic drainage net and a sand layer that serve as drainage layers for leachate collection The drain layers composed of sand are typically at least 1 ft thick and have suitably spaced perforated or open joint drain pipe embedded below the surface of the liner The leachate collection drainage layer serves to collect any leachate that may percolate through the waste layers In this case where the liner is solely a geomembrane a drainage net may be used to rapidly drain leachate from the liner avoiding a significant buildup of head and limiting leakage The liners are sloped to prevent ponding by encouraging leachate to flow toward the drains The net effect is that very little leachate should percolate through the primary liner and virtually no migration of leachate through the bottom composite liner to the natural formations below Taken as a whole the drainage layers geomembrane liners and barrier soil liners may be referred to as the leachate collection and removal system drain liner system and more specifically a double liner system PRECIPITATION EVAPOTRANSPIRATION F VEGETATION RUNOFF We ye VERTICAL PERCOLATION LAVER TOPSOIL meumanond N x 2 LATERAL DRAINAGE LAYER SAND LATERAL DRAINAGE FROM COVER 8 K s S GEOMEMBRANE LINER SLOPE Y S 4 BARRIER SOIL LAYER CLAY PERCOLATION ux C AA RR l VERTICAL y X 8
31. the yearly total precipitation column since this total is computed by the program after the daily data for the year is entered If the user reaches this screen from the precipitation option on the Precipitation Temperature and Solar Radiation screen the user will only be able to move within the column under precipitation Similarly if the user reaches this screen from the temperature data option then only movement in the temperature column is permitted and analogously for the solar radiation option To enter a new year of daily values the user should move the cursor to a empty cell type in the year and press Enter The program will display the daily data screen on which the daily values are entered The user can return to the yearly data screen by pressing F10 to retain the data to a temporary file or by pressing Esc to abandon the created data The user can enter up to 100 years of daily data The yearly data screen can only display 20 rows at a time The user however can move the cursor to the bottom of the screen and then cursor down to move to the next row until the hundredth row is displayed Similarly the user can move the cursor upward to display the rows in the spreadsheet that are not shown on the screen if any To move down 20 rows press Page Down and to move up 20 rows press Page Up To reach the last row press End and to go to the first row press Home To edit an existing year of daily values the user must first cre
32. 0 years The model cannot simulate a capillary break or unsaturated lateral drainage 39 The model has limits on the arrangement of layers in the landfill profile Each layer must be described as being one of four types vertical percolation layer lateral drainage layer barrier soil liner or geomembrane liner The model does not permit a vertical percolation layer to be placed directly below a lateral drainage layer A barrier soil liner may not underlie another barrier soil liner Geomembranes cannot envelop a barrier soil liner and barrier soil liners cannot envelop a geomembrane The top layer may not be a liner If a liner is not placed directly below the lowest lateral drainage layer the lateral drainage layers in the lowest subprofile are treated by the model as vertical percolation layers No other restrictions are placed on the order of the layers The lateral drainage equation was developed for the expected range of hazardous waste landfill design specifications Permissible ranges for slope of the drainage layer are 0 to 50 percent Due to dimensionless structure of the lateral drainage equation there are no practical limits in the maximum drainage length Several interrelations must exist between the soil characteristics of a layer and of the soil subprofile The porosity field capacity and wilting point can theoretically range from 0 to 1 units of volume per volume however the porosity must be greater than the field capacity an
33. 10 Fine Copper Slag 0 375 0 055 0 020 4 1x10 Drainage Net 0 6 cm 0 850 0 010 0 005 3 3x10 Moderately Compacted Continued 29 30 31 32 33 34 x 30 TABLE 4 continued DEFAULT SOIL WASTE AND GEOSYNTHETIC CHARACTERISTICS Saturated Classification Total Field Wilting Hydraulic Porosity Capacity Point Conductivity 35 High Density Polyethylene HDPE 2 0x10 6 Low Density Polyethylene 4 0x10 8 3 LDPE i Polyvinyl Chloride PVC 2 0x10 3 Butyl Rubber EE 39 Chlorinated Polyethylene CPE 40 Hypalon or Chlorosulfonated Polyethylene CSPE 3 0x10 41 Ethylene Propylene Diene Monomer EPDM m roe L3 concluded 2 0x10 3 0x10 user defined soil option accepts non default soil characteristics for layers assigned soil type numbers greater than 42 This is especially convenient for specifying characteristics of waste layers User specified soil characteristics can be assigned any soil type number greater than 42 When a default soil type is used to describe the top soil layer the program adjusts the saturated hydraulic conductivities of the soils in the top half of the evaporative zone for the effects of root channels The saturated hydraulic conductivity value is multiplied by an empirical factor that is computed as a function of the user specified maximum leaf area index Example values of this factor are 1 0 for a maximum LAI of 0 bare ground 1 8 for a maximum LAI of 1 poor stand of
34. CII file to the HELP format Each year of ASCII daily solar radiation data should be stored in a separate file The program will convert the first 365 or 366 values excess data will be ignored Inadequate data will yield an error This option should also be used to convert data from spreadsheet format by first printing each year of solar radiation to individual print files The following data are required for this option e Location 23 e Files containing ASCII data e Years 6 HELP Version 2 Data Option Customary Units Version 3 of the HELP model converts solar radiation data prepared for use in Version 2 of the HELP model Schroeder et al 1988b into the HELP Version 3 format This option requires the following data Location e File containing HELP Version 2 data 7 Canadian Climatological Data Option Metric Units The HELP model converts Canadian Climatological Data Surface in compressed or uncompressed diskette formats into the HELP Version 3 format Conversion is available only for hourly global solar radiation values The input requirements are e Location Canadian Climatological Data file containing years of hourly global solar radiation values NOTE Canadian Climatological Data for most locations are readily available in publications of the Environment Canada Atmospheric Environment Service Canadian Climate Centre Data Management Division 4905 Dufferin Street Downsview Ontario Canada M3H 5T4 3 3 SOIL A
35. Cell Each input cell is set to a given width depending on the type of information expected to be entered in that cell The cursor will be initially located on the first character space of the cell The left and right arrow keys may be used to move the cursor to different spaces within the cell If a value is typed in the first space of the cell the cell contents will be deleted To delete a character move the cursor to the character location and then press the Delete key or move the cursor to the space that is to the right of the character and then press the Backspace key A character can be inserted between characters in an input cell by moving the cursor to the desired position and then pressing the Insert key The Insert key will shift all characters that are at and to the right of the cursor one position to the right 6 Terminating At any time during the session the user may press the F9 key to quit without saving changes return to the main menu or exit the program The Esc key and the Ctrl Break keys will end some options and allow you to continue with other operations The F10 key is used to save the data or proceed If necessary the user can terminate input or execution by rebooting Ctrl Alt Del keys resetting or turning off the computer however the user is discouraged from terminating a run in these manners because some of the data may be lost 7 On Line Help On line help is available to the user from any cell location on the scr
36. ICO Albuquerque Roswell NEW YORK Albany Buffalo New York Syracuse NORTH CAROLINA Asheville Charlotte Greensboro Raleigh NORTH DAKOTA Bismarck Williston OHIO Cleveland Columbus Toledo OKLAHOMA Oklahoma City Tulsa OREGON Burns Meachem Medford Pendleton Portland Salem Sexton Summit PENNSYLVANIA Philadelphia Pittsburgh RHODE ISLAND Providence SOUTH CAROLINA Charleston Columbia SOUTH DAKOTA Huron Rapid City TENNESSEE Chattanooga Knoxville Memphis Nashville TEXAS Abilene Amarillo Austin Brownsville Corpus Christi Dallas El Paso Galveston Houston San Antonio Temple Waco UTAH Milford Salt Lake City VIRGINIA Norfolk Richmond WASHINGTON Olympia Spokane Stampede Pass Walla Walla Yakima WEST VIRGINIA Charleston WISCONSIN Green Bay Lacrosse Madison Milwaukee WYOMING Cheyenne 17 4 NOAA Tape Precipitation Option Customary Units The option will convert the 6 NOAA Summary of Day daily precipitation data written to diskette in ASCII print as on tape format into the format used by Version 3 of the HELP model The following data are required for this option e Location e NOAA ASCII print file of Summary of Day daily precipitation data in as on tape format NOTE Daily precipitation data and normal mean monthly precipitation values for most locations are readily available in publications or on diskette from NOAA Information on climatological data sources can be obt
37. L amp DESIGN DATA FILE Figure 16 Schematic of Runoff Curve Number Information Screen Options The user should refer to the HELP model documentation for Version 3 for the techniques used in the computation of the curve number based on slope and slope length The value of the slope must be input in percent and slope length must be input in the units indicated If the top layer in the landfill is obtained from the default soil material 73 textures the soil texture number for that layer will be displayed in the appropriate cell on the screen The user can solicit help on the vegetation cover by pressing the F2 key The only valid entries for the vegetation are 1 through 5 according to the following 1 Bare ground 2 Poor stand of grass 3 Fair stand of grass 4 Good stand of grass 5 Excellent stand of grass If the user selects the option that requires the HELP model to compute the curve number the program first calculates the SCS runoff curve number for landfills with mild surface slopes 2 to 5 percent based on the vegetation type and the soil texture on the top layer if one of the default soil material textures is selected soil texture types 1 through 18 20 and 22 through 29 in the same manner as Version 2 Schroeder et al 1988b HELP Version 3 then adjusts the SCS runoff curve number based on the surface slope and the length of the slope 4 6 5 Verifying and Saving Soil and Design Data Pressing F10 anywhere in th
38. LP model Schroeder et al 1988b into the HELP Version 3 format This option requires the following data Location e File containing HELP Version 2 data Canadian Climatological Data Option Metric Units The HELP model converts Canadian Climatological Data Surface in compressed or uncompressed diskette formats into the HELP Version 3 format Conversion is available only for daily mean temperature values The following data are required by this option 21 e Location e Canadian Climatological Data file containing years of daily mean temperature values NOTE Canadian Climatological Data for most locations are readily available in publications of the Environment Canada Atmospheric Environment Service Canadian Climate Centre Data Management Division 4905 Dufferin Street Downsview Ontario Canada M3H 5T4 3 2 4 Solar Radiation Data 1 Synthetic Solar Radiation Option Customary or Metric Units The program will generate from 1 to 100 years of daily solar radiation data stochastically for the selected location The synthetic generation of daily solar radiation values is a strong function of precipitation and as such the user must first specify the precipitation Generation of solar radiation data is limited to the number of years of precipitation data available The synthetic solar radiation data will have approximately the same statistical characteristics as the historic data at the selected location If desired the user can
39. ND DESIGN DATA REQUIREMENTS The user may enter soil data by using the default soil material textures option the user defined soil texture option or a manual option If the user selects a default soil texture the program will display porosity field capacity wilting point and hydraulic conductivity values of the soil that is stored as default There are 42 default soil material textures If user defined soil textures are selected the program will display the porosity field capacity wilting point and hydraulic conductivity of the selected soil from the user defined soil texture data file In the manual soil texture option the user must specify values for the soil parameters General data requirements for all options are listed below Detailed explanations are given in Sections 3 4 through 3 9 3 3 1 Landfill General Information 1 Project title 24 Landfill area Customary or Metric Percentage of landfill area where runoff is possible Method of initialization of moisture storage user specified or program initialized to near steady state Initial snow water storage optional needed when moisture storage is user specified 3 3 2 Layer Data l Layer type Four types of layers are permitted 1 vertical percolation 2 lateral drainage 3 barrier soil liner and 4 geomembrane liner Layer thickness Customary or Metric Soil texture e Select from 42 default soil material textures to get the following data Porosi
40. PERCOLATION WASTE g LAYER 3 Y 3 q l2 3 LATERAL DRAINAGE LAYER SAN D LATERAL DRAINAGE N m n LEACHATE COLLECTION 3 5 7 LATERAL DRAINAGE NET 3 SIS IAZ LEAKAGE GEOMEMBRANE LINER LATERAL DRAINAGE X LATERAL DRAINAGE SAND ZZ GE DETECTION E LAYER a S x 3 uM Di a Sjn A RNG E 8 S PIPE MAXIMUM BARRIER SOIL LINER DRAINAGE I DISTANCE CLAY PERCOLATION LEAKAGE Figure 1 Schematic of Landfill Profile Illustrating Typical Landfill Features 7 After the landfill is closed the leachate collection and removal system serves basically in a back up capacity However while the landfill is open and waste is being added these components constitute the principal defense against contamination of adjacent areas Thus care must be given to their design and construction Day to day operation of a modern sanitary landfill calls for wastes to be placed in relatively thin lifts compacted and covered with soil each day Thus wastes should not remain exposed for more than a few hours Although the daily soil cover serves effectively to hide the wastes and limit the access of nuisance insects and potential disease vectors it is of limited value for preventing the formation of leachate Thus even though a similar procedure can be used for hazardous wastes the drainage liner system must function well throughout and after the active life of the landfill When the capacity of the landfill is reached the wa
41. Porosity Total Volume A 1 Total porosity can be calculated by developing a solid liquid and air phase relationship of each layer This relationship can be calculated using the water content on a weight basis and density wet or dry of a sample Introductory geotechnical engineering textbooks such as Holtz and Kovacs 1981 and Perloff and Baron 1976 provide detail guidance for determining phase relationships Total porosity is also related to void ratio ratio of void volume to solid volume by the following equation Void Ratio A 2 1 Void Ratio Total Porosity A 2 2 Soil Water Retention Field capacity is the volumetric water content of a soil or waste layer at a capillary pressure of 0 33 bars Field capacity is also referred to as the volumetric water content of a soil remaining following a prolonged period of gravity drainage Wilting point is the volumetric water content of a soil or waste layer at a capillary pressure of 15 bars Wilting point is also referred to as the lowest volumetric water content that can be achieved by plant transpiration The general relation among soil moisture retention parameters and soil texture class is shown below 0 60 DRAINABLE POROSITY 0 40 ABL PLANT AVAIL ER CAPACIT 0 30 0 20 WATER CONTENT VOL VOL 0 10 0 00 SAND SANDY LOAM SILTY CLAY SILTY CLAY LOAM LOAM LOAM CLAY Figure A 21 General Relation Among Soil Moisture Retention Properties
42. RE US erm es 1 lb Back SrOund v2 ense eV Doe Rates eee eaters Sud are dA 1 1 2 MOVERVIEW oiseau oo goes ond Dae mt Pik eee ek oe Re eee ee eee 3 1 3 System and Operating Documentation llle 3 1 3 1 Computer Equipment 2 4 22 ERR BER YS 3 1 9 2 R qg ted LALA WATE Le aci erp RN e d enean EE 3 1 3 3 Software Requirements 1 bini 848 bie uos X ERR Ex 4 2 BASIC LANDFILL DESIGN CONCEPTS lesen 5 Z2 BaOESPOUD 912230 2 EAE edunt Sect buses eS Har d ede 5 2 2 Leachate Production s a os oer AUF ada Ro NP UE NOR I dou e e d 5 2 3 Design for Leachate Conwoll ox vex YE ERE Reb RE See Bee 6 3 PROGRAM DEFINITIONS OPTIONS AND LIMITATIONS 9 Jal Antroduchion 1222322932346 ee eee sb eom dees E EAST ue vede 9 3 2 Weather Data Requirements len ex a ee 2a hee Ve Gas Yes 9 3 2 1 Evapotranspiration Data i See ee ee eR E 9 2 2 2 Precipitation Dabo oe 3 94 dase Ber ed d Se EG S OS RA 14 3 2 3 Temperature Data ss ks binge ce Ride oe Ae eee eee wed 19 3 2 4 Solar Radiation Data 2 Av ovars entered eae ge eae bee ee 22 3 3 Soil and Design Data Requirements 00000 ee aes 24 3 3 1 Landfill General Information 0008 24 309 2 cbayer Palas weeds uus e Do Acci tabs aed S e Md e 25 3 3 3 Lateral Drainage Layer Design Data 25 3 3 4 Geomembrane Liner Data Sos uc rue eee m ped o dos 26 3 3 5 Runoff Curve Number Information 26 vi
43. THE HYDROLOGIC EVALUATION OF LANDFILL PERFORMANCE HELP MODEL USER S GUIDE FOR VERSION 3 by Paul R Schroeder Cheryl M Lloyd and Paul A Zappi Environmental Laboratory U S Army Corps of Engineers Waterways Experiment Station Vicksburg Mississippi 39180 6199 and Nadim M Aziz Department of Civil Engineering Clemson University Clemson South Carolina 29634 0911 Interagency Agreement No DW21931425 Project Officer Robert E Landreth Waste Minimization Destruction and Disposal Research Division Risk Reduction Engineering Laboratory Cincinnati Ohio 45268 RISK REDUCTION ENGINEERING LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U S ENVIRONMENTAL PROTECTION AGENCY CINCINNATI OHIO 45268 DISCLAIMER The information in this document has been funded wholly or in part by the United States Environmental Protection Agency under Interagency Agreement No DW21931425 to the U S Army Engineer Waterways Experiment Station It has been subjected to the Agency s peer and administrative review and it has been approved for publication as an EPA document Mention of trade names or commercial products does not constitute endorsement or recommendation for use il FOREWORD Today s rapidly developing and changing technologies and industrial products and practices frequently carry with them the increased generation of materials that if improperly dealt with can threaten both public health and the environment Abandoned was
44. The program however displays guidance information on the evaporative zone depth for that location depending on the vegetative cover The user must enter a value of the evaporative zone depth that is appropriate for the landfill design location top soil and vegetation See Section 3 for detailed guidance The user must also enter a value for the maximum leaf area index for the site If the value entered is greater than the default maximum allowable value based on the climate for the selected city the program will display that value only as a guidance to the user The user is not forced to change the entered value If the user decides to edit the name of the city or state the program will erase the 50 guidance information Guidance is provided only for cities that are selected from the list obtained by pressing F5 The location of the landfill being evaluated is likely to be some distance from all of the listed cities In this case the user has the option to select a city that has an similar climate and edit the values to improve the data or to simply enter the information manually The bottom line of the Evapotranspiration Data screen provides additional help information Once all data are entered the user can move on to another screen by pressing Page Up or Page Down return to the main menu by pressing F9 or proceed to save the evapotranspiration data by pressing F10 4 5 3 Precipitation Temperature and Solar Radiation Data
45. a File Saving screen Several secondary screens may appear during the session depending on the action taken by the user On line help screens are always available for display by pressing F1 or F2 The individual primary screens and their secondary screens of this module are discussed below Figure 12 shows a schematic of the soil and design data module SOIL amp DESIGN DATA FILE FOR ENTER EDIT SOIL amp DESIGN DATA LANDFILL GENERAL EDITING INFORMATION E33 SHEETS OF LANDFILL PROFILE DESIGN Eu SOIL DESIGN AND E4 TEXTURES DATA oue FILE VERIFY DATA Eu SAVE RUNOFF CURVE NUMBER INFORMATION Figure 12 Schematic of Soil and Design Data Module 4 6 1 Soil and Design Data File Selection The first screen in the soil and design module is the Soil and Design Data File Editing screen A schematic of this screen is shown in Figure 13 On this screen the user may enter the file name of an existing file to select a previously generated HELP Version 3 file for editing or leave the file name blank to create new data When selecting a file to be edited the user may specify the DOS path if different from the default drive and subdirectory such as C HELP3 DATA The default directory is initially displayed in the directory cell on the screen If the user specifies a drive or a directory that does not exist the program will display respectively Invalid Drive or Invalid Directory and repl
46. aces the content with the default directory The soil and design data file may have any valid DOS name of up to 8 characters If the user enters an illegal file name the program displays Bad File Name and clears the file name If the user specifies a file name that does not exist the program displays File Not Found and clears the file name 62 The program adds an extension of D10 to the file name As such the user should not specify the extension in HELP Version 3 whenever entering a file name for editing or saving SOIL amp DESIGN DATA FILE TO EDIT PROCEED TO SOIL amp DESIGN DATA ENTRY amp EDITING Figure 13 Soil and Design Data File Editing Screen Options As shown in Figure 13 the user may obtain a listing of all soil and design data files that reside on the directory currently specified in the directory cell by pressing F4 Up to 120 data files can be displayed on the screen The name of the current directory where these files are located is also displayed To change to another directory the user should enter the name of that directory in the column labeled DIRECTORY To select a file from the list of displayed files move the cursor to the file and select it by pressing Enter This transfers control back to the previous screen and the name of the file just selected will be displayed in the proper cell The user can exit the list of files screen without selecting a file by pressing F4 again or Esc When
47. ained from the National Climatic Data Center NCDC NOAA Federal Building Asheville NC 28801 704 259 0682 Climatedata Precipitation Option Customary Units The program will convert daily precipitation data from an ASCII print file prepared by the Climatedata CD ROM data base program into the format used by Version 3 of the HELP model The Climatedata format is used by other CD ROM state and regional data bases and therefore those files can also be converted by this option For example the State of California and the Midwest Climatic Data Consortium used this same format The following data are required for this option Location e Climatedata prepared file containing daily precipitation data NOTE Hydrosphere Data Products Inc sells NOAA Summary of the Day precipitation data in a 4 disc CD ROM data base called Climatedata one disc for each of four U S regions Information on Climatedata is available from Hydrosphere 1002 Walnut Suite 200 Boulder CO 80302 800 949 4937 ASCII Precipitation Option Customary or Metric Units The HELP model converts daily precipitation data in an ASCII file to the HELP format Each year of ASCII precipitation data should be stored in a separate file The first 365 or 366 values will be converted excess data will be ignored Inadequate data will yield an error This option should also be used to convert data from spreadsheet format by first printing each year of precipi
48. alues is presented in Section 3 Version 3 of the HELP program is started by typing HELP3 from the DOS prompt in the directory where the program resides The program starts by displaying a title screen a preface a disclaimer and then the main menu The user moves from the title screen to the main menu by striking any key such as the space bar Upon reaching the main menu the user can select any of seven options The program automatically solicits input from the user based on the option selected In general the HELP model requires the following data some of which may be selected from the default values Units Location Weather data file names Evapotranspiration information Precipitation data Temperature data Solar radiation data Soil and design data file name General landfill and site information Landfill profile and soil waste geomembrane data SCS runoff curve number information piper pres m m 4 2 DEFINITIONS AND RULES There are a few fundamental rules regarding the input facility that a user must keep in mind when using the model These rules should be followed to move around the screens and to move within the same screen Below are some definitions and rules 1 Screens A screen in the HELP user interface as used in this report is a single screen of information These screens are divided into three categories 42 e Input Screen a screen on which the user can input data e Selection Screen a screen from which the
49. and Lane L J 1987 Hydrology component parameter estimation Chapter 6 simulation of production and utilization of rangelands SPUR documentation and user guide J R Wight and J W Skiles eds ARS 63 US Department of Agriculture Agricultural Research Service 372 pp Williams R D Ahujam L R and Naney J W 1992 Comparison of methods to estimate soil water characteristics from soil texture bulk density and limited data Soil Science 153 3 172 184 A 10
50. and Soil Texture Class Brakensiek et al 1984 and Springer and Lane 1987 reported the following empirical equations which were developed using data from natural soils with a wide range of sand 5 70 percent and clay 5 60 percent content Field Capacity 0 1535 0 0018 Sand 0 0039 Clay A 3 0 1943 Total Porosity Wilting Point 0 0370 0 0004 Sand 0 0044 Clay A 4 0 0482 Total Porosity Sand and clay percentages should be determined using a grain size distribution chart and particle sizes defined by the U S Department of Agriculture textural soil classification system According to this system sand particles range in size from 0 05 mm to 2 0 mm silt particles from 0 002 mm to 0 05 mm and clay particles are less than 0 002 mm Numerous other equations relating field capacity and wilting point to soil textural properties have been developed Most of these equation were developed using site specific data However Gupta and Larson 1979 developed empirical equations for field capacity and wilting point using data from separate and mixed samples of dredged sediment and soil from 10 geographic locations in eastern and central United States Rawls and Brakensiek 1982 and Rawls et al 1982 also developed empirical equations by fitting the Brooks and Corey s 1964 soil water retention equation to soil water retention and matrix potential data from 500 natural soils in 18 states Rawls 1982 eq
51. and less than 0 0001 cm sec 1 Perfect Assumes perfect contact between geomembrane and adjacent soil that limits drainage rate no gap sprayed on seal between membrane and soil formed in place 2 Excellent Assumes exceptional contact between geomembrane and adjacent soil that limits drainage rate typically achievable only in the lab or small field lysimeters 3 Good Assumes good field installation with well prepared smooth soil surface and geomembrane wrinkle control to insure good contact between geomembrane and adjacent soil that limits drainage rate 4 Poor Assumes poor field installation with a less well prepared soil surface and or geomembrane wrinkling providing poor contact between geomembrane and adjacent soil that limits drainage rate resulting in a larger gap for spreading and greater leakage 5 Worst Case Assumes that contact between geomembrane and adjacent soil does not limit drainage rate resulting in a leakage rate controlled only by the hole 6 Geotextile separating geomembrane liner and drainage limiting soil Assumes leakage spreading and rate is controlled by the in plane transmissivity of the geotextile separating the geomembrane and the adjacent soil layer that would have otherwise limited the drainage This quality would not normally be used with a geosynthetic clay liner GCL as the controlling soil layer Upon wetting the bentonite swells and extrudes into the geotextile filling its voids and red
52. ate and or read weather data If the data were previously saved the user should specify the existing data file Weather Data File Editing screen immediately after selecting the Enter Edit Weather Data option from the main menu The HELP model reads the data from the edit file and stores it in a temporary file Upon entering the create edit option the program displays the list of years for precipitation the total annual precipitation for each year and a list of years for the temperature and solar radiation data To edit move the cursor to the year that is to be edited and press Enter The program will display the daily data screen and 55 the user may type over any values that need to be edited The operation of the yearly data spreadsheet and the daily data spreadsheet is the same when editing existing data or when creating new data After entering or editing years of daily weather data the user can return to the Precipitation Temperature and Solar Radiation screen to exercise other weather data options To retain the newly created or edited years of daily weather data the user should press F10 from the yearly data screen the program will then replace the existing temporary data file containing all of the years of data for that type of weather data To lose the newly entered or edited daily data the user should press F9 or Esc the program will retain the previously existing temporary data file containing the values of that type of wea
53. ation of site selection surface grading transpiration from vegetation soil evaporation drainage through the sand and the low hydraulic conductivity of the barrier soil liner serves effectively to minimize leachate production from external water Added effectiveness is gained by the use of geomembrane liners in the cap in conjunction with the barrier soil liner The cap should be no more permeable than the leachate collection and removal system so that the landfill will not gradually fill and overflow into adjacent areas following abandonment of the landfill This phenomenon is sometimes referred to as the bathtub effect SECTION 3 PROGRAM DEFINITIONS OPTIONS AND LIMITATIONS 3 1 INTRODUCTION The HELP program was developed to provide landfill designers and regulators with a tool for rapid economical screening of alternative designs The program may be used to estimate the magnitudes of various components of the water budget including the volume of leachate produced and the thickness of water saturated soil head above liners The results may be used to compare the leachate production potential of alternative designs to select and size appropriate drainage and collection systems and to size leachate treatment facilities The program uses weather climatic soil and design data to generate daily estimates of water movement across into through and out of landfills To accomplish this objective and compute a water balance daily precipi
54. be used to edit the daily values of any year of data commonly this is used to add severe storm events such as the 25 year 24 hour precipitation event The data required are e Location One or more years of daily precipitation data 16 TABLE 3 CITIES FOR SYNTHETIC PRECIPITATION DATA ALABAMA Birmingham Mobile Montgomery ARIZONA Flagstaff Phoenix Yuma ARKANSAS Fort Smith Little Rock CALIFORNIA Bakersfield Blue Canyon Eureka Fresno Mt Shasta San Diego San Francisco COLORADO Colorado Springs Denver Grand Junction Pueblo CONNECTICUT Windsor Locks DELAWARE Wilmington DISTRICT OF COLUMBIA Washington FLORIDA Jacksonville Miami Tallahassee Tampa GEORGIA Atlanta Augusta Macon Savannah IDAHO Boise Pocatello ILLINOIS Chicago INDIANA Evansville Fort Wayne Indianapolis IOWA Des Moines Dubuque KANSAS Dodge City Topeka Wichita KENTUCKY Covington Lexington Louisville LOUISIANA Baton Rouge New Orleans Shreveport MAINE Caribou Portland MARYLAND Baltimore MASSACHUSETTS Boston Nantucket MICHIGAN Detroit Grand Rapids MINNESOTA Duluth Minneapolis MISSISSIPPI Jackson Meridian MISSOURI Columbia Kansas City St Louis MONTANA Billings Great Falls Havre Helena Kalispell Miles City NEBRASKA Grand Island North Platte Scottsbluff NEVADA Elko Las Vegas Reno Winnemucca NEW HAMPSHIRE Concord Mt Washington NEW JERSEY Newark NEW MEX
55. composition reactions and initial moisture content however it is largely governed by the amount of external water entering the landfill Thus a key first step in controlling leachate migration is to limit production by preventing to the extent feasible the entry of external water into the waste layers A second step is to collect any leachate that is produced for subsequent treatment and disposal Techniques are currently available to limit the amount of leachate that migrates into adjoining areas to a virtually immeasurable volume as long as the integrity of the landfill structure and leachate control system is maintained 2 3 DESIGN FOR LEACHATE CONTROL A schematic profile view of a somewhat typical hazardous waste landfill is shown in Figure 1 The bottom layer of soil may be naturally existing material or it may be hauled in placed and compacted to specifications following excavation to a suitable subgrade In either case the base of the landfill should act as a liner with some minimum thickness and a very low hydraulic conductivity or permeability Treatments may be used on the barrier soil to reduce its permeability to an acceptable level As an added factor of safety an impermeable synthetic membrane may be placed on the top of the barrier soil layer to form a composite liner Immediately above the bottom composite liner is a leakage detection drainage layer to collect leakage from the primary liner in this case a geomembrane Above
56. d as vertical percolation layers Lateral drainage layers e g Layers 2 6 7 and 9 in Figure 1 are layers directly above liners that are designed to promote drainage laterally to a collection and removal system Vertical flow in a lateral drainage layer is modeled in the same manner as a vertical percolation layer but saturated lateral drainage is allowed The saturated hydraulic conductivity specified for a lateral drainage layer should be in the lateral direction downslope for anisotropic materials A lateral drainage layer may be underlain by only another lateral drainage layer or a liner The drainage slope specified for a lateral drainage should be the slope of the surface of the liner underlying the drainage layer in the direction of flow the maximum gradient for a section of liner in a single plane and may range from 0 to 50 percent The drainage length specified for a lateral drainage layer is the length of the horizontal projection of a representative flow path from the crest to the collector rather than the distance along the slope For slopes of less than 10 percent the difference is negligible The drainage length must be greater than zero but does not have a practical upper limit Recirculation is permitted from lateral drainage layers directly above a liner where 0 to 100 percent of the drainage collected can be recirculated and redistributed in a user specified vertical percolation or lateral drainage layer Barrier soil liners
57. d the field capacity must be greater than the wilting point Initial soil moisture storage must be greater than or equal to the wilting point and less than or equal to the porosity The initial moisture content of liners must be equal to the porosity and the liners remain saturated The field capacity and wilting point values are not used for barrier soil liners Values for porosity field capacity and wilting point are not needed for geomembranes Values for the leaf area index may range from 0 for bare ground to 5 for an excellent stand of grass Detailed recommendations for leaf area indices and evaporative depths are given in the program The default values for the evaporation coefficient are based on experimental results The basis for the calculation of these default values is described by Schroeder et al 1994 The model imposes upper and lower limits of 5 1 and 3 3 so as not to exceed the range of experimental data Surface runoff from adjacent areas does not run onto the landfill and the physical characteristics of the landfill specified by the user remain constant over the modeling period No adjustments are made for the changes that occur in these characteristics as the landfill ages Additionally the program cannot model the filling process within a single simulation Aging of materials and staging of the landfill operation must be modeled by successive simulations Default Soil Characteristics The HELP model contains default valu
58. diation losses heat loss at night A frozen soil model has been added to improve infiltration and runoff predictions in cold regions The unsaturated vertical drainage model has also been improved to aid in storage computations Input and editing have been further simplified with interactive full screen menu driven input techniques In addition the HELP Version 3 model provides a variety of methods for specifying precipitation temperature and solar radiation data Now data from the most commonly available government and commercial sources can be imported easily Moreover data used in HELP Version 2 can still be used with minimum user effort Specifying weather data manually and editing previously entered weather data can be easily done by using built in spreadsheet facilities The use of data files in Version 3 is much simpler and more convenient than HELP Version 2 because data are saved permanently in user defined file names at a user specified location Similarly the user has more flexibility to define units for every type of data needed to run the HELP model Finally Version 3 of the HELP model provides on line help at every step of the data preparation process Although applicable to most landfill applications the HELP model was developed specifically to perform hazardous and municipal waste disposal landfill evaluations as required by RCRA Hazardous waste disposal landfills generally should have a liner to prevent migration of was
59. dson C W and Wright D A 1984 WGEN A model for generating daily weather variables ARS 8 USDA Agricultural Research Service 83 pp Ruffner J A 1985 Climates of the states National Oceanic and Atmospheric 82 Administration narrative summaries tables and maps for each state volume 1 Alabama New Mexico and volume 2 New York Wyoming and territories Gale Research Company Detroit MI 758 pp and 1572 pp Schroeder P R and Gibson A C 1982 Supporting documentation for the hydrologic simulation model for estimating percolation at solid waste disposal sites HSSWDS Draft Report US Environmental Protection Agency Cincinnati OH 153 pp Schroeder P R Gibson A C and Smolen M D 1984 The hydrologic evaluation of landfill performance HELP model volume IL documentation for version 1 EPA 530 SW 84 010 US Environmental Protection Agency Cincinnati OH 256 pp Schroeder P R Peyton R L McEnroe B M and Sjostrom J W 1988 The hydrologic evaluation of landfill performance HELP model Volume III User s guide for version 2 Internal Working Document EL 92 1 Report 1 US Army Engineer Waterways Experiment Station Vicksburg MS 87 pp Schroeder P R McEnroe B M Peyton R L and Sjostrom J W 1988 The hydrologic evaluation of landfill performance HELP model Volume IV Documentation for version 2 Internal Working Document EL 92 1 Report 2 US Army Engineer
60. e If the user answers Y for all of the files the program will overwrite the files complete the saving process and return to the main menu If the user answers N for any file the program will interrupt the saving return to the SAVE column and change the tag to N The user can then change the tag back to Y rename the file and restart the saving by pressing F10 or Page Down The program provides other options listed on the File Saving screen to enable the user to return the weather data entry screens Page Up or to return to the main menu without saving the data F9 The user must be cautioned that the F9 option will cause all the data created if any to be lost Figure 11 shows the available options PROCEED WITH SAVING RETURN TO WEATHER DATA ENTRY amp EDITING Figure 11 Weather Data File Saving Screen Options 4 6 SOIL AND DESIGN DATA 61 This module is selected from the main menu by pressing 2 Enter Edit Soil and Design While in this module the user will be able to enter site information a landfill profile layer design data characteristics of soils geomembranes and other materials and SCS runoff curve number information The primary screens in this module are the Soil and Design Data File Editing screen Landfill General Information screen three Landfill Profile Design and Layer Data screens Runoff Curve Number Information screen Verification and Saving screen and Soil and Design Dat
61. e and Solar Radiation screen from either list by pressing Esc By doing so neither a city nor a state is considered selected However once a city is selected the program reads the five years of default precipitation data for the selected city The usefulness of the default precipitation option is limited since it contains only five years of precipitation data It is additionally limiting since these five years may be dry or wet years and may not be representative of the site in question The following options are available for entering Precipitation Temperature and Solar Radiation data 51 PRECIPITATION TEMPERATURE amp SOLAR RADIATION DATA PRECIPITATION TEMPERATURE SOLAR RADIATION OPTIONS OPTIONS OPTIONS EVAPO TRANSPIRATION DATA VERIFY amp SAVE WEATHER DATA FILES Figure 7 Schematic of Precipitation Temperature and Solar Radiation Screen DEFAULT SYNTHETIC DATA YEAR RE E SELECTION NOAA TAPE CLIMATEDATA ASCII HELP 2 CANADIAN Figure 8 Precipitation Options CREATE EDIT PRECIPITATION 52 Synthetic The second available method for entering precipitation data is to use the synthetic weather generator Customary or Metric Units This is the first method on the screen for entering temperature and solar radiation data This option can be selected for temperature and solar radiation only if the user has previously entered precipitation data since the synthetic weather generator requ
62. e g Layers 4 and 11 in Figure 1 are intended to restrict vertical drainage percolation leakage These layers should have saturated hydraulic conductivities substantially lower than those of the other types of layers Liners are assumed to be saturated at all times but leak only when there is a positive head on the top surface of the liner The percolation rate depends upon the depth of water saturated soil head above the base of the liner the thickness of the liner and the saturated hydraulic conductivity The saturated hydraulic conductivity specified for a barrier soil liner should be its value for passing the expected permeant in the vertical direction for anisotropic materials The program allows only downward saturated flow in barrier soil liners Evapotranspiration and lateral drainage are not permitted from a liner Thus any water moving into a liner will eventually percolate through the liner In Version 3 composite liners are modeled as two layers a geomembrane liner and a barrier soil liner as shown in Figure 1 27 Geomembrane liners e g Layers 3 8 and 10 in Figure 1 are virtually impermeable synthetic membranes that reduce the area of vertical drainage percolation leakage to a very small fraction of the area located near manufacturing flaws and installation defects punctures tears and faulty seaming A small quantity of vapor transport across the membrane also occurs and can be modeled by specifying the vapor diffusivity a
63. e soil and design option transfers control to the Verification and Saving screen This screen provides the user with several options verify landfill general design data verify soil layer geomembrane properties verify layer arrangement review save user defined soil textures and save soil and design data The user can select any of these options by moving the cursor to the option and pressing Enter Figure 17 shows the verify and save soil and design data options The user can verify the data before attempting to save the data by exercising the first three options on the Verification and Saving screen These options are available mainly for the convenience of the new user since experienced users will be familiar with data requirements and the data will always be verified before saving To check the data entered on the general landfill and runoff information screens the user should select the first option Verify Landfill General Information Design Data If there are no violations or warnings the program will write OK to the right of the option otherwise the program will list the problems and then write BAD to the right of the option The user can check the layer descriptions the values on a row of the third screens 74 VERIFY VERIFY DATA amp SAVE amp SAVE DATA USER SOIL TEXTURES Figure 17 Verify and Save Soil and Design Data Options of layer data by selecting the Verify Soil Layer Geomembrane Properties option The
64. e the tag back to Y rename the file and restart the saving by pressing F10 or Page Down The program provides other options listed on the File Saving screen to provide the means for the user to display a directory of existing soil and design data files F4 to return to the data entry screens Page Up or to return to the main menu without saving the data F9 The user must be cautioned that the F9 option will cause all the data created if any to be lost Figure 17 shows the available options 4 7 EXECUTING THE SIMULATION 76 Option 3 on the main menu is Execute Simulation This option is composed of two primary screens Execution Files File Management screen and Output Selection screen and is shown schematically in Figure 18 Execution Files This screen is used to define the weather and soil and design data files that contain the data to be used in the HELP model simulation Six files must be specified to run HELP model The input data files required are a precipitation data file a temperature data file a solar radiation data file an evapotranspiration data file and a soil and design data file and for output the HELP model requires one file on which the results are to be written The user must enter the file names without extension since the HELP model recognizes the following extensions for the various types of files D4 for precipitation data D7 for temperature data D11 for evapotranspiration data D13 for s
65. ects on the environment Recently public attention has been focused on a special class of materials commonly referred to as hazardous wastes The chemical and physical diversity environmental persistence and acute and chronic detrimental effects on human plant and animal health of many of these substances are such that great care must be exercised in their disposal Hazardous wastes are produced in such large quantities and are so diverse that universally acceptable disposal methods have yet to be devised However for the present disposal or storage in secure landfills is usually a prudent approach The current state of the art is an extension of sanitary landfill technology using very conservative design criteria Some important basic principles and concepts of landfill design are summarized below Specific emphasis is given to disposal of hazardous materials but the discussion is also applicable to ordinary sanitary landfills 2 2 LEACHATE PRODUCTION Storage of any waste material in a landfill poses several potential problems One problem is the possible contamination of soil groundwater and surface water that may occur as leachate produced by water or liquid wastes moving into through and out of the landfill migrates into adjacent areas This problem is especially important when hazardous wastes are involved because many of these substances are quite resistant to biological or chemical degradation and thus are expected to persist in thei
66. ed layer where the cursor is positioned Alt D deletes the highlighted layer where the cursor is positioned Alt M tags the highlighted layer where the cursor is positioned to be moved to another location to be designated using the cursor and Alt A or Alt B Alt C tags the highlighted layer where the cursor is positioned to be copied to another location to be designated using the cursor and Alt A or Alt B To add a new layer directly above a certain layer for example above the layer on line 6 shown on the left edge of the screen the user should move the cursor to line 6 hold the A t key down and press A The result of this action is that a blank line is inserted above the layer that was at line 6 and the program shifts the layer on line 6 and all the layers below it one line downward i e layer on line 6 moves to line 7 layer on line 7 moves to line 8 etc and line 6 will be a blank line for the user to enter the values for the new layer To add a layer right below a certain layer for example below the layer on line 5 the user should move the cursor to line 5 hold the A t key down and press B The result of this action is that a blank line is inserted below line 5 and the program shifts the layer on line 6 and all the layers below it one line downward i e layer on line 6 moves to line 7 layer on line 7 moves to line 8 etc and line 6 will be a blank cell for the user to enter the value of the new layer 71 The Alt D
67. een By pressing F1 information about the operations and purpose of the screen is displayed and by pressing F2 specific technical assistance for the highlighted cell is displayed Note that the on line help screens contain sections from this User s Guide and that the figures and tables mentioned on the screens are located in this document The F3 key displays various functions of keystrokes Other specific information of the input screen is listed in menu line s at the bottom of screen 8 System of Units Throughout the HELP program the user is required to select a system of units The HELP model allows the user to use either the customary system of units a mixture of U S Customary and metric units traditionally used in landfill design and in Version 2 of the HELP model or the Metric SI system of units The user is not restricted to the same system for all data types for example the soil and design data can be in one system of units and the weather data can be in the other system Moreover it is not necessary for all types of weather data to have the same system of units i e evapotranspiration data can be in the Metric system of units while precipitation data is in customary units the solar radiation data can be in customary units while temperature data is in Metric units and so on Appropriate units are displayed in proper locations to keep the user aware of which units should be used for each data entry Consistency in units is only r
68. en is shown in Figure 6 The two methods for entering this data are the manual option and the default option Manual Option This option requires the user to enter all evapotranspiration data manually The user should first specify a location in the form of a city state and latitude followed by the evaporative zone depth the maximum leaf area index the Julian dates of the start planting and end harvest of the growing season the annual average wind speed and quarterly average relative humidities in percentages for the entered location Default Option 49 EVAPO TRANSPIRATION DATA CITIES FOR DEFAULT DATA SELECTION VERIFY amp SAVE WEATHER DATA FILES PRECIPITATION TEMPERATURE amp SOLAR RADIATION DATA Figure 6 Schematic of Evapotranspiration Data Screen This option takes advantage of an available list of cities for which default values are provided for most of the evapotranspiration data guidance information is available for the rest of the data This option is triggered from any input cell on the Evapotranspiration Data screen by pressing F5 and selecting a location state and city from a displayed list of locations This list of cities is the same as that in Table 3 Once a city is selected the program automatically displays values in the appropriate input cells for the city state latitude growing season dates wind speed and the four quarterly humidity values for that location
69. enter the latitude for the specific location to improve the computation of potential solar radiation and the resulting daily values The user is advised to enter the latitude if the project site is more than 50 miles north or south of the city selected from Table 1 The data required by the synthetic weather generator are Location select from a list of 183 U S cities in Table 1 e Number of years of data to be generated e Years of daily precipitation values Latitude optional default value is available 2 Create Edit Solar Radiation Option Customary or Metric Units Under the create option the user may enter up to 100 years of daily solar radiation data manually The years which need not be consecutive can be entered in any order The user may add or delete years of data or rearrange the order of the years of data This same option can be used to edit the daily values of any year of data The input requirements are e Location e One or more years of daily solar radiation data 22 3 5 NOAA Tape Solar Radiation Option Customary Units This option will convert the NOAA Surface Airways Hourly solar radiation data written to diskette in ASCII print as on tape format into the format used by Version 3 of the HELP model The following data are required for this option e Location e NOAA ASCII print file of Surface Airways Hourly solar radiation data in as on tape format NOTE Daily temperature mean or maximum and mi
70. entered the program reads the data from the specified file and converts it to the HELP Version 3 format Climatedata This option allows the user to enter daily precipitation or temperature data to the HELP model from Climatedata Customary Units Only If this option is selected the user must enter the city and state for the site and the Climatedata file name Note that for temperature data two file names are requested one for the maximum temperature file and the other for the minimum temperature file The Climatedata file should have been created by exporting or printing the CD ROM data to an ASCII print file This same format is used by data bases other than Climatedata and therefore these data bases can be converted using this same option Example Climatedata files are included with the HELP program BIRM PRC for precipitation BIRM MAX for maximum temperature and BIRM MIN for minimum temperature When entering the Climatedata file name the user should include the DOS path if the file location is different than the default directory file name and extension The user can abandon the entry of this data by pressing Esc Once valid information is entered the program reads the data from the specified file and converts it to the HELP Version 3 format ASCII Data This option allows the user to enter daily weather data to the HELP model from ASCII data files Customary or Metric Units The ASCII data set is composed of li
71. equired within each data type 4 5 PROGRAM STRUCTURE 44 The flow or logic of the input facility of the HELP program may be viewed as a tree structure The tree structure consists of nodes where new branches of the tree are started The first node is called the trunk root or parent node and the terminal nodes of the tree are called leaves All components nodes of the tree structure in the HELP model are screens that have different functions as defined previously with the trunk node being the Main Menu During an input session the user should reach the leaf node if all the data for a given branch module are entered Some of the nodes screens are common to more than one branch The user must return to the node where the branch started in order to go to another branch These movements can be accomplished with the special keys discussed above such as Page Up Page Down F9 F10 etc 4 4 MAIN MENU At the beginning of each run the Main Menu is displayed A schematic of the main menu in Figure 3 shows the seven available modules branches Selection from the main menu is made by either moving the cursor to the desired module or by pressing the number of that option Once a selection is made program control transfers into an environment specific to that option and cannot transfer to another main menu option without exiting that environment to the main menu and then selecting another option A brief description of each main menu option is
72. er Information screen is shown in Figure 16 This screen is composed of three options that can be used to specify the runoff curve number The first option is to use an user specified curve number that the HELP model will use without modification The second option is to request the HELP model to modify a user specified curve number according to the surface slope and surface slope length In the third option the user requests a HELP model computed runoff curve number based on surface slope slope length soil texture of the top layer in the landfill profile and vegetation To select one of these three options the user should move the cursor to the desired option and press Enter This action will cause the program to transfer control down to the box for the option selected For each option the user must input all required information Although the user can move from one box to the other use Tab and Shift Tab keys care should be taken to insure that the desired method is the one that will be used by HELP The HELP model uses that option in which data was last entered this option is marked by a small arrow in front of the option RUNOFF CURVE NUMBER INFORMATION COMPUTE CURVE NUMBER BASED ON SOIL TEXTURE SLOPE SLOPE LENGTH AND VEGETATION MODIFY CURVE NUMBER FOR SLOPE AND SLOPE LENGTH USER SPECIFIED CURVE NUMBER PgUp SHEETS OF LAYER DATA LANDFILL GENERAL INFO VERIFY amp SAVE SOI
73. er below the second liner system the leakage detection drainage layer Layer 9 to the base of the lowest liner Layer 11 The program allows up to five liner systems and therefore five subprofiles plus an additional subprofile of vertical percolation layers below the bottom liner system The program models the flow of water through one subprofile at a time from top to bottom with the percolation or leakage from one subprofile serving as the inflow to the underlying subprofile 3 5 SOIL CHARACTERISTICS The user can assign soil characteristics to a layer using the default option the user defined soil option or the manual option Table 4 shows the default characteristics for 42 soil material types The soil texture types are classified according to two standard systems the U S Department of Agriculture textural classification system and the Unified Soil Classification System The default characteristics of types 1 through 15 are typical of surficial and disturbed agricultural soils which may be less consolidated and more aerated than soils typically placed in landfills Breazeale and McGeorge 1949 England 1970 Lutton et al 1979 Rawls et al 1982 Clays and silts in landfills would generally be compacted except within the vegetative layer which might be tilled to promote vegetative growth Untilled vegetative layers may be more compacted than the loams listed in Table 4 Soil texture types 22 through 29 are compacted soils Type 18 is re
74. er should include the DOS path if the file location is different than the default directory file name and extension The user can abandon the entry of this data by pressing Esc Once valid information is entered the program reads the data from the specified file and converts it to the HELP Version 3 format Canadian This option allows the user to enter weather data to the HELP model from a Canadian Climatological Data Surface file Metric Units Only If this option is selected the user must enter the city and state for the site and the Canadian Climatological Data file name The precipitation and mean temperature data files should contain daily values written in either compressed or uncompressed diskette format The solar radiation data file should contain hourly global solar radiation values also written in either compressed or uncompressed diskette format Example Canadian data files are included with the HELP program CAN4 DAT and CCAN4 DAT for precipitation CAN7 DAT and CCAN7 DAT for temperature and CANI3 DAT and CCAN13 DAT for solar radiation When entering the Canadian data file name the user should include the DOS path if the file location is different than the default directory file name and extension The user can abandon the entry of this data by pressing Esc Once valid information is entered the program reads the data from the specified file and converts it to the HELP Version 3 format 4 5 4 Saving Weather Data During t
75. es of soil characteristics based on soil texture class The documentation for Version 3 describes the origin of these default values 40 Schroeder et al 1994 Recommended default values for LAI and evaporative depth based on thick loamy top soils are given in the program Manual Soil Characteristics The HELP model computes values for the three Brooks Corey parameters as described in the documentation for Version 3 Schroeder et al 1994 based on the values for porosity field capacity and wilting point Soil Moisture Initialization The soil moisture of the layers may be initialized by the user or the program When initialized by the program the process consists of three steps The first step sets the soil moisture of all layers except barrier soil liners equal to field capacity and all barrier soil liners to porosity saturation In the second step the program computes a soil moisture for each layer below the top barrier soil liner These soil moisture contents are computed to yield an unsaturated hydraulic conductivity equal to 85 percent of the lowest effective saturated hydraulic conductivity of the all liner systems above the layer including consideration for the presence of a synthetic geomembrane liner If the unsaturated hydraulic conductivity is less than 1 x 10 cm sec and if the computed soil moisture is greater than field capacity the soil moisture is set to equal computed soil moisture instead of the field capacity The t
76. except that it is not intercepted by vegetation The free available water is used to compute the runoff by the SCS rainfall runoff relationship The interception is the measure of water available to evaporate from the surface Interception in excess of the potential evaporation is added to infiltration Surface evaporation is then computed Potential evaporation from the surface is first applied to the interception any excess is applied to the snowmelt then to the snowpack and finally to the groundmelt Potential evaporation in excess of the evaporation from the surface is applied to the soil column and plant transpiration The snowmelt and rainfall that does not run off or evaporate is assumed to infiltrate into the landfill along with any groundmelt that does not evaporate The first subsurface processes considered are soil evaporation and plant transpiration from the evaporative zone of the upper subprofile A vegetative growth model accounts for the daily growth and decay of the surface vegetation The other subsurface processes are modeled one subprofile at a time from top to bottom using a design dependent time step ranging from 30 minutes to 6 hours A storage routing procedure is used to redistribute the soil water among the modeling segments that comprise the subprofile This procedure accounts for infiltration or percolation into the subprofile and evapotranspiration from the evaporative zone Then if the subprofile contains a liner the prog
77. f a wide variety of landfill designs The primary purpose of the model is to assist in the comparison of design alternatives as judged by their water balances The model applicable to open partially closed and fully closed sites is a tool for both designers and permit writers This report explains how to use Version 3 of the HELP model Section provides background and overview of the model and lists software and hardware requirements Section 2 describes basic landfill design and liquids management concepts Section 3 presents definitions options and limitations for input parameters as well as detailed guidance for selecting their input values Section 4 provides detailed instructions on how to enter input run the simulation and view or print output Appendix A provides assistance for estimating material properties for moisture retention and saturated hydraulic conductivity The user interface or input facility is written in the Quick Basic environment of Microsoft Basic Professional Development System Version 7 1 and runs under DOS 2 1 or higher on IBM PC and compatible computers The HELP program uses an interactive and a user friendly input facility designed to provide the user with as much assistance as possible in preparing data to run the model The program provides weather and soil data file management default data sources interactive layer editing on line help and data verification and accepts weather data from the most commonly used
78. f low rainfall or a short growing season This statement should be considered only as a warning The maximum LAI for bare ground is zero For a poor stand of grass the LAI could approach 1 0 for a fair stand of grass 2 0 for a good stand of grass 3 5 and for an excellent 10 TABLE 1 CITIES FOR EVAPOTRANSPIRATION DATA AND SYNTHETIC TEMPERATURE AND SOLAR RADIATION DATA ALABAMA GEORGIA MICHIGAN NEW YORK Birmingham Atlanta Detroit Albany Mobile Augusta East Lansing Buffalo Montgomery Macon Grand Rapids Central Park ALASKA Savannah Sault Sainte Marie Ithaca Annette Watkinsville MINNESOTA New York Bethel HAWAII Duluth Syracuse Fairbanks Honolulu Minneapolis NORTH CAROLINA ARIZONA IDAHO St Cloud Asheville Flagstaff Boise MISSISSIPPI Charlotte Phoenix Pocatello Jackson Greensboro Tucson ILLINOIS Meridian Raleigh Yuma Chicago MISSOURI NORTH DAKOTA ARKANSAS East St Louis Columbia Bismarck Fort Smith INDIANA Kansas City Williston Little Rock Evansville St Louis OHIO CALIFORNIA Fort Wayne MONTANA Cincinnati Bakersfield Indianapolis Billings Cleveland Blue Canyon IOWA Glasgow Columbus Eureka Des Moines Great Falls Put in Bay Fresno Dubuque Havre Toledo Los Angeles KANSAS Helena OKLAHOMA Mt Shasta Dodge City Kalispell Olkahoma City Sacramento Topeka Miles City Tulsa San Diego Wichita NEBRASKA OREGON San Francisco KENTUCKY Grand Island Astoria Santa Maria Covington North Platte Burns COLORADO Lexington Omaha Meacham Colorado Springs Lo
79. g a mean particle size diameter Shirazi and Boersma 1984 A 4 indicated that geometric rather than arithmetic statistical properties are advocated for describing soil samples The reason in part is that there is a wide range of particle sizes in a natural soil sample making the geometric scale much more suitable than the arithmetic scale Therefore the mean particle diameter in Kozeny Carman s equation reported in Freeze and Cherry 1979 was identified as the geometric mean soil particle diameter Shirazi et al 1988 and Shiozawa and Campbell 1991 indicated that bimodal models describe particle grain size curves more accurately than unimodal models However analysis performed by Shiozawa and Campbell 1991 on six Washington state soils exhibiting varying sand silt and clay fractions indicated that the unimodal model accurately predicted the geometric mean soil particle diameter in all soils tested Therefore Shiozawa and Campbell 1991 developed an equation for geometric mean soil particle diameter by using the unimodal model developed by Shirazi and Boersma 1984 using geometric mean particles sizes based on the USDA classification system as recommended by Shirazi et al 1988 and assuming that the soil was composed entirely of clay silt and sand Shiozawa and Campbell s 1991 equation was altered to relate percent silt and clay to the particle diameter resulting in the following equation d exp 1 151 0 07713
80. h 5 The program is largely insensitive to values above 5 If the vegetative species limit plant transpiration such as succulent plants the maximum LAI value should be reduced to a value equivalent of the LAI for a stand of grass that would yield a similar quantity of plant transpiration Most landfills would tend to have at best a fair stand of grass and often only a poor stand of grass because landfills are not designed as ideal support systems for vegetative growth Surface soils are commonly shallow and provide little moisture storage for dry periods Many covers may have drains to remove infiltrated water quickly reducing moisture storage Some covers have liners near the surface restricting root penetration and causing frequent saturation of the surface soil which limits oxygen availability to the roots Some landfills produce large quantities of gas which if uncontrolled reduces the oxygen availability in the rooting zone and therefore limits plant growth The program produces values for the Julian dates starting and ending the growing season the annual average wind speed and the quarterly average relative humidity for the location The values for the growing season should be checked carefully to agree with the germination and harvesting end of seasonal growth dates for your type of vegetation For example grasses in southern California would germinate in the fall when the rains occur and die off in late spring when the soil moistu
81. hat were previously saved and numbered by the user up to 100 such textures are allowed 3 Enter a new soil texture number that can be used again in this design and that can later be saved in the library of user defined textures material properties must also be entered manually for this texture 4 Leave the texture number blank and enter the material properties manually Default Soil Material Textures Default soil material textures have numbers from 1 to 42 and are listed in Table 4 The user can either type the soil texture number or press F6 to select a texture from the list of default textures If the user enters a default soil material texture number manually the program automatically assigns the default values for porosity field capacity wilting point and hydraulic conductivity to the layer On the other hand the user may press F6 to obtain the list of soil textures on a separate screen On the soil texture screen the user can move the cursor to the desired texture or press Page Down to display the rest of the default soil textures After cursoring to the desired texture press Enter to select it At this time program control returns to layer spreadsheet screen and displays the selected soil texture number along with the porosity field capacity wilting point and hydraulic conductivity in appropriate cells Notice that the only information available for the 67 default geomembrane liners is the hydraulic conductivity liner vapo
82. he creation of the weather data explained above the data are saved in temporary files To save the data to permanent files the user must press F10 from the primary screens Once the F10 key is pressed the program verifies that all the data have been entered If any of the data is incomplete the program displays a list of the problem areas The user can return to the primary screens to complete the data or continue to save the incomplete data After displaying the deficiencies the program displays the Weather Data File Saving screen Here the user may save all or only some of the four weather types or completely abandon the save option The user should tag each type of data to 60 be saved by entering a Y in the SAVE column and those not to be saved by entering a N in the SAVE column Default file names are displayed in appropriate locations on this screen these are the same names as used in Version 2 At this time the user may enter new file names for any or all of the four types of weather data See Section 4 5 1 for file naming convention used in HELP If the file already exists the program will display File Already Exists after entering the name After replacing all file names of interest the user should press F10 or Page Down to complete the saving to the requested file names If files already exists for any of the file names as they would for the default names the program will ask the user about overwriting each existing fil
83. he initial values for the simulation period The program then runs the complete simulation starting again from the beginning of the first year of data The results for the initialization period are not reported To improve initialization to steady state moisture storage the user should replace thick vertical percolation and lateral drainage layers that are below the evaporative zone and above the saturated zone above liners with thin layers Then run the simulation for a number of years until steady state is approximated The final dimensionless water storage values after nearing steady state should then be specified as the initial water contents in your actual simulation using the true dimensions of the layers 32 The initial moisture content of municipal solid waste is a function of the composition of the waste reported values for fresh wastes range from about 0 08 to 0 20 vol vol The average value is about 0 12 vol vol for compacted municipal solid waste If using default waste texture 19 where 75 of the volume is inactive the initial moisture content should be that of only the active portion 25 of the values reported above The soil water storage or content used in the HELP model is on a per volume basis 8 volume of water V per total bulk soil water and air soil volume V V V V which is characteristic of practice in agronomy and soil physics Engineers more commonly express moisture content on a per mass basis w
84. he layer on line 3 to be deleted and be placed directly above the layer on line 6 This will cause line 4 to move up one line to line 3 line 5 to move to line 4 and line 3 to move to line 5 the other lines will be unchanged The user may obtain the same result after the Alt M combination by moving to line 5 and pressing the combination Alt B The Esc key can be used to quit the move and copy functions after pressing Alt M or Alt C and before pressing Alt A or Alt B By editing the data as discussed above the user may arrange the order of the layers and run the model to test several possible configurations If the user has 20 lines completely filled with layers and then decides to add or copy a layer the layer that is already in line 20 will disappear and cannot be recovered Therefore care must be taken not to add layers that will cause the loss of the layers at the bottom of the spreadsheet When all the layers of the profile are entered press Page Down from the third layer spreadsheet to proceed with the rest of the soil and design data entry Pressing Page Up from the first layer spreadsheet passes control to the Landfill General Information screen 4 6 4 Runoff Curve Number The Runoff Curve Number Information screen may be reached from the third layer spreadsheet by pressing Page Down or from the Landfill General Information Screen 42 by pressing Page Up A schematic of the options associated with the Runoff Curve Numb
85. he program computes an effective gradient for saturated flow through the lower segment This permits vertical percolation or lateral drainage layers to be arranged without restrictions on their properties as long as they perform as their layer description implies and not as liners The model assumes that a the soil moisture retention properties and unsaturated hydraulic conductivity can be calculated from the saturated hydraulic conductivity and limited soil moisture retention parameters porosity field capacity and wilting point and b the soil moisture retention properties fit a Brooks Corey relation Brooks et al 1964 defined by the three soil moisture retention parameters Upon obtaining the Brooks Corey parameters the model assumes that the unsaturated hydraulic conductivity relation with soil moisture is well described by the Campbell equation The model does not explicitly compute flow by differences in soil suction soil suction gradient and as such does not model the draw of water upward by capillary drying This draw of water upward is modeled as an extraction rather than transport of water upward Therefore it is important that the evaporative zone depth be specified as the depth of capillary drying Drainage downward by soil suction exerted by dry soils lower in the landfill profile is modeled as Darcian flow for any soil having a relative moisture content greater than the lower soils The drainage rate is equal to the 38 unsa
86. hird step in the initialization consists of running the model for one year of simulation using the first year of climate data and the initial soil moisture values selected in the second step At the end of this year of initialization the soil moisture values existing at that point are reported as the initial soil moisture values The simulation is then restarted using the first year of climate data Synthetic Temperature and Solar Radiation Values The synthetically generated temperature and solar radiation values are assumed to be representative of the climate at the site Synthetic daily temperature is a function of normal mean monthly temperature and the occurrence of rainfall Synthetic daily solar radiation is a function of latitude occurrence of rainfall average daily dry day solar radiation and average daily wet day solar radiation 41 SECTION 4 PROGRAM INPUT 4 1 INTRODUCTION This section describes the procedures and options available to input data execute the model and obtain results The discussion includes general input information some definitions and rules the program structure and detailed explanations of the options reached from the Main Menu Guidance is given throughout the section for selecting the most appropriate values in certain situations but the main purpose of this section is to describe the mechanics of using the user interface Detailed guidance on the definitions of input parameters and selection of their v
87. hout modification 2 User specified curve number modified for surface slope and slope length 3 Curve number computed by HELP program based on surface slope slope length default soil texture and quantity of vegetative cover 3 4 LANDFILL PROFILE AND LAYER DESCRIPTIONS The HELP program may be used to model landfills with up to twenty layers of materials soils geosynthetics wastes or other materials Figure 1 shows a typical landfill profile with eleven layers The program recognizes four general types of layers 1 Vertical percolation layers 2 Lateral drainage layers 3 Barrier soil liners 26 4 Geomembrane liners It must be noted that correct classification of layers is very important because the program models the flow of water through the four types of layers in different ways Flow in a vertical percolation layer e g Layers 1 and 5 in Figure 1 is by unsaturated vertical drainage downward due to gravity drainage upward flux due to evapotranspiration is modeled as an extraction The rate of gravity drainage percolation in a vertical percolation layer is a function of soil moisture and soil parameters The saturated hydraulic conductivity specified for a vertical percolation layer should be in the vertical direction for anisotropic materials The main role of a vertical percolation layer is to provide moisture storage Waste layers and layers designed to support vegetation and provide evaporative storage are normally designate
88. ically placement quality 6 would not be used with a geosynthetic clay liner GCL despite the presence of a geotextile since upon wetting the clay extrudes through the geotextile and provides intimate contact with the geomembrane 70 After completing input for one layer the user can go back to the first spreadsheet and enter information for other layers Page Up and Page Down are used to move backward and forward between spreadsheets The user may also input values on one spreadsheet completely filling it and move on to the next spreadsheet filling in the information for the layers entered in the first spreadsheet and so on No blank rows be left in the spreadsheet between layers however if the user does leave some blank lines the program will not save these as layers Layer Editing While entering or editing the properties of the layers in the landfill defined in the three spreadsheets of layer data the user has the option to add a layer to the profile delete a layer move a layer to another location in the profile or copy a layer to another location When using these layer editing functions the program operates simultaneously on all three screens of layer data This is done by using the following key combinations Alt A adds inserts a layer either new being moved or being copied above the highlighted layer where the cursor is positioned Alt B adds inserts a layer either new being moved or being copied below the highlight
89. information The first value that must be entered is the number of years of synthetic data to be generated The rest of the information on the screen is optional For precipitation the user can elect to use the default normal mean monthly precipitation values provided by the HELP program or to enter normal mean monthly precipitation values to be used in generating the synthetic precipitation for that location For temperature the user has the option to use the default normal mean monthly temperature values provided by the HELP program or to enter normal mean monthly temperature values to be used in generating the synthetic temperature for that location Users are encouraged to enter their own normal mean monthly values especially if the landfill is not located at the selected city The program uses the normal mean monthly data to adjust the data generated by the synthetic weather generator If the user decides not to use the default values the program will transfer control to the normal mean monthly data option under the User heading At this time the user must input values for January through December A blank cell for a given month will be recorded as zero and the user must be careful not to leave a cell without an entry A zero entry however is a valid entry For solar radiation the optional value is the latitude for the location The default latitude of the selected city will be displayed but the user is encouraged to enter the latitude of the act
90. ires precipitation values for generating both temperature and solar radiation By selecting the synthetic data option the program prompts the user with a list of states for which it has synthetic weather data coefficients Again the user can move the cursor to the appropriate state and press Enter to obtain the list of cities in that state for which synthetic data can be generated From this list the user can select the city where the project is located or a city with a climate similar to the project location Selection is accomplished by moving the cursor to the selection cell highlighting the desired city and pressing Enter At any time the user may abandon the input for the synthetic weather generator by pressing Esc the program will return to the Precipitation Temperature and Solar Radiation screen without loss of previously entered data Once a city is selected the program displays another screen called Synthetic Precipitation Data Synthetic Temperature Data or Synthetic Solar Radiation Data On this screen the city and state are displayed and the user is asked to provide additional SYNTHETIC OPTIONAL DATA YEAR RECORDS AND RATY SELECTION MEAN MONTHLY TEMPERATURE CONVERT AND IMPORT DATA CREATE EDIT NOAA TAPE TEMPERATURE CONVERT AND CLIMATEDATA IMPORT DATA CONVERT AND ASCII IMPORT DATA CONVERT AND HELP 2 IMPORT DATA CONVERT AND CANADIAN IMPORT DATA Figure 9 Temperature Options 53
91. ity and wilting point are not used for liners except for initializing the soil water storage of liners to the porosity value The soil moisture retention properties of a layer should be adjusted downward if some volume of the layer does not participate in the drainage and storage of infiltrated water This condition commonly exists in shallow layers of municipal solid waste because municipal solid waste is very heterogeneous and poorly compacted The plastics in the waste also channels the drainage limits the spreading of infiltration and restricts the wetting of the waste and therefore the storage Default soil texture number 19 provides adjusted retention values for a municipal solid waste with significant channeling it assumes that only 25 percent of the volume is actively involved in drainage and storage of infiltration As the values were computed by multiplying the values for municipal solid waste default texture number 18 by 0 25 the initial soil water content would also be multiply by 0 25 The HELP user has the option of specifying the initial volumetric water storage content of all layers except liners Liners are assumed to remain saturated at all times If the user chooses not to specify initial water contents the program estimates values near steady state and then runs one year of initialization to refine the estimates before starting the simulation The soil water contents at the end of this year of initialization are taken as t
92. kette in ASCII print as on tape format into the format used by Version 3 of the HELP model The program will accept either mean daily temperature or daily maximum and minimum temperature values If maximum and minimum temperatures are used the program averages the two to compute the daily mean temperature value If mean temperature values are used the same file is specified as the maximum and minimum temperature files The following data are required for this option e Location e NOAA ASCII print file of Summary of Day data file containing years of daily maximum temperature values or daily mean temperature values in as on tape format e NOAA ASCII print file of Summary of Day data file containing years of daily minimum temperature values or daily mean temperature values in as on tape format NOTE Daily temperature mean or maximum and minimum data and normal mean monthly temperature values for most locations are readily available in publications or on diskette from NOAA Information on climatological data sources can be obtained from the National Climatic Data Center NOAA Federal Building Asheville NC 28801 704 259 0682 4 Climatedata Temperature Option Customary Units The program will convert daily maximum and minimum temperature data from ASCII print files prepared by the ClimatedataTM CD ROM data base program into the daily mean 20 5 6 temperature data file format used by Version 3 of the HELP model The Clima
93. layers low permeability barrier soils and synthetic geomembrane liners may be modeled The program was developed to conduct water balance analysis of landfills cover systems and solid waste disposal and containment facilities As such the model facilitates rapid estimation of the amounts of runoff evapotranspiration drainage leachate collection and liner leakage that may be expected to result from the operation of a wide variety of landfill designs The primary purpose of the model is to assist in the comparison of design alternatives as judged by their water balances The model applicable to open partially closed and fully closed sites is a tool for both designers and permit writers 1 1 BACKGROUND The HELP program Versions 1 2 and 3 was developed by the U S Army Engineer Waterways Experiment Station WES Vicksburg MS for the U S Environmental Protection Agency EPA Risk Reduction Engineering Laboratory Cincinnati OH in response to needs in the Resource Conservation and Recovery Act RCRA and the Comprehensive Environmental Response Compensation and Liability Act CERCLA better known as Superfund as identified by the EPA Office of Solid Waste Washington DC HELP Version 1 Schroeder et al 1984 represented a major advance beyond the Hydrologic Simulation on Solid Waste Disposal Sites HSSWDS program Perrier and Gibson 1980 Schroeder and Gibson 1982 which was also developed at WES The HSSWDS model simulated on
94. ly the cover system did not model lateral flow through drainage layers and handled vertical drainage only in a rudimentary manner The infiltration percolation and evapotranspiration routines were almost identical to those used in the Chemicals Runoff and Erosion from Agricultural Management Systems CREAMS model which was developed by Knisel 1980 for the U S Department of Agriculture USDA The runoff and infiltration routines relied heavily on the Hydrology Section of the National Engineering Handbook USDA Soil Conservation Service 1985 Version 1 of the HELP model incorporated a lateral subsurface drainage model and improved unsaturated drainage and liner leakage models into the HSSWDS model In addition the HELP model provided simulation of the entire landfill including leachate collection and liner systems Version 2 Schroeder et al 1988 represented a great enhancement of the capabilities of the HELP model The WGEN synthetic weather generator developed by the USDA Agricultural Research Service ARS Richardson and Wright 1984 was added to the model to yield daily values of precipitation temperature and solar radiation This replaced the use of normal mean monthly temperature and solar radiation values and improved the modeling of snow and evapotranspiration Also a vegetative growth model from the Simulator for Water Resources in Rural Basins SWRRB model developed by the ARS Arnold et al 1989 was merged into the HELP
95. model to calculate daily leaf area indices Modeling of unsaturated hydraulic conductivity and flow and lateral drainage computations were improved Accuracy was increased with the use of double precision Default soil data were improved and the model permitted use of more layers and initialization of soil moisture content Input and editing were simplified Output was clarified and standard deviations were reported In Version 3 the HELP model has been greatly enhanced beyond Version 2 The number of layers that can be modeled has been increased The default soil material texture list has been expanded to contain additional waste materials geomembranes geosynthetic drainage nets and compacted soils The model also permits the use of a user built library of soil textures Computation of leachate recirculation between soil layers and groundwater drainage into the landfill have been added Moreover HELP Version 3 accounts for leakage through geomembranes due to manufacturing defects pinholes and installation defects punctures tears and seaming flaws and by vapor diffusion through the liner The estimation of runoff from the surface of the landfill has been improved to account for large landfill surface slopes and slope lengths The snowmelt model has been replaced with an energy based model the Priestly Taylor potential evapotranspiration model has been replaced with a Penman method incorporating wind and humidity effects as well as long wave ra
96. mounts of runoff evapotranspiration drainage leachate collection and liner leakage that may be expected to result from the operation of a wide variety of landfill designs The primary purpose of the model is to assist in the comparison of design alternatives The model is a tool for both designers and permit writers E Timothy Oppelt Director Risk Reduction Engineering Laboratory iii ABSTRACT The Hydrologic Evaluation of Landfill Performance HELP computer program is a quasi two dimensional hydrologic model of water movement across into through and out of landfills The model accepts weather soil and design data and uses solution techniques that account for the effects of surface storage snowmelt runoff infiltration evapotranspiration vegetative growth soil moisture storage lateral subsurface drainage leachate recirculation unsaturated vertical drainage and leakage through soil geomembrane or composite liners Landfill systems including various combinations of vegetation cover soils waste cells lateral drain layers low permeability barrier soils and synthetic geomembrane liners may be modeled The program was developed to conduct water balance analysis of landfills cover systems and solid waste disposal and containment facilities As such the model facilitates rapid estimation of the amounts of runoff evapotranspiration drainage leachate collection and liner leakage that may be expected to result from the operation o
97. nd gravel soils Rawls and Brakensiek 1985 also A 5 presented an equation for determining the saturated hydraulic conductivity of soils with varying degrees of sand 5 70 percent and clay 5 60 percent A 3 SEMI EMPIRICAL METHOD A 3 1 The semi empirical method for determining the HELP program user defined values employs a theoretical equation developed by Brooks and Corey 1964 to determine soil water retention parameters field capacity and wilting point and a semi empirical equation developed by Brutsaert 1967 and Rawls et al 1982 to calculate saturated hydraulic conductivity The total porosity residual volumetric water content pore size distribution index and bubbling pressure of each layer are the minimum data required to calculate the user defined values for this method As previously mentioned total porosity can be calculated using Equation A 1 or A 2 Soil Water Retention The HELP program does not allow the user to define the Brooks Corey parameters residual volumetric water content pore size distribution index and bubbling pressure of the soil waste or barrier layers therefore if these data are available the user must first calculate field capacity and wilting point using Brooks and Corey s 1964 water retention equation M S A 8 gt 6 v where 0 volumetric water content field capacity or wilting point unitless 0 residual saturation volumetric water content unitless total p
98. nderlain by a liner with a lateral drainage collection and removal system The primary purpose of a vertical percolation layer is to provide moisture storage as such top soil layers and waste layers are often vertical percolation layers 2 A layer of moderate to high permeability material that is underlain by a liner with a lateral drainage collection and removal system is classified as a lateral drainage layer The layer drains vertically primarily as unsaturated flow and laterally as a saturated flow 3 A layer of low permeability soil designed to limit percolation leakage is classified 4 as a barrier soil liner The layer drains only vertically as a saturated flow A geomembrane synthetic flexible membrane liner designed to restrict vertical drainage and limit leakage is classified as a geomembrane liner Leakage is modeled as vapor diffusion and leakage through small manufacturing defects and installation flaws While the HELP program is quite flexible there are some basic rules regarding the arrangement of layers in the profile that must be followed l 2 A vertical percolation layer may not be underlying a lateral drainage layer A barrier soil liner may not be underlying another barrier soil liner A geomembrane liner may not be placed directly between two barrier soil liners A geomembrane liner may not be underlying another geomembrane liner A barrier soil liner may not be placed directly between two geomembrane
99. nds somewhat below the depth of root penetration because of capillary suction to the roots The depth specified should be characteristic of the maximum depth to which the moisture changes near the surface due to drying over the course of a year typically occurring during peak evaporative demand or when peak quantity of vegetation is present Setting the evaporative depth equal to the expected average root depth would tend to yield a low estimate of evapotranspiration and a high estimate of drainage through the evaporative zone An evaporative depth should be specified for bare ground to account for direct evaporation from the soil this depth would be a function of the soil type and vapor and heat flux at the surface The depth of capillary draw to the surface without vegetation or to the root zone may be only several inches in gravels in sands the depth may be about 4 to 8 inches in silts about 8 to 18 inches and in clays about 12 to 60 inches Maximum leaf area index Guidance is available for the selected location The user must enter a maximum value of leaf area index for the vegetative cover Leaf area index LAI is defined as the dimensionless ratio of the leaf area of actively transpiring vegetation to the nominal surface area of the land on which the vegetation is growing The program provides the user with a maximum LAI value typical of the location selected if the value entered by the user cannot be supported without irrigation because o
100. nently saved in a library of user defined textures A library of up to 100 soil textures may be saved in a user defined soil texture data file The creation and addition of textures to this file are explained in Section 4 6 5 of this User s Guide The third method is to select a user defined texture that was previously saved in the library If this library of user defined soil textures exists the user can display the list of available textures for selection by pressing F7 Selecting a user defined soil texture for a given layer is identical to that of selecting a default soil material textures the user should move the cursor to the desired soil texture and press Enter At this point program control returns to the layer spreadsheet and displays soil texture values porosity field capacity wilting point and hydraulic conductivity of the selected soil in the layer row where F7 was pressed Also in the same manner as in default soil material textures the user can simply type the number of the user defined soil texture in Soil Texture No column of the first screen of the layer spreadsheets and the program will automatically obtain the soil characteristics for that soil texture and place them in the proper location on the layer spreadsheet Whenever F7 is pressed control transfers to the user defined soil textures To move among pages of soil textures press Page Up and Page Down To make a selection press Enter and to return to the layer sp
101. nes of data whose values are separated by a blank s a comma or other non numeric symbol If this option is selected the user must enter the city and state for the site the units of the data in the ASCII files The user can abandon the entry of this data by pressing Esc Once valid information is entered the program then asks for the file name and year of the ASCII data set one year at a time Each file should contain only one year of daily values for a particular type of data either precipitation mean temperature or solar radiation Example ASCII data files are included with the HELP program RAIN 1 and RAIN 2 for precipitation TEMP 1 and TEMP 2 for temperature and SOLAR 1 and 59 SOLAR 2 for solar radiation When entering the ASCII data file name the user should include the DOS path if the file location is different than the default directory file name and extension In order to return from this option to the Precipitation Temperature and Solar Radiation screen press Esc HELP 2 This option allows the user to enter weather data to the HELP model Version 3 from a data file used in the HELP model Version 2 Customary Units Only If this option is selected the user must enter the city and state for the site and the HELP Version 2 data file name Example HELP 2 data files are included with the HELP program ALA4 for precipitation ALA7 for temperature and ALA13 for solar radiation When entering the HELP 2 data file name the us
102. ng the necessary values in the second spreadsheet screen of layer data the user should press Page Down to go to the third and last screen of layer data Pressing Page Up will return to the first spreadsheet of layer data allowing the user to edit the previously entered values Again on the third spreadsheet screen the layer type of all layers in the profile are displayed to aid in positioning data on the screen Geomembrane Liner Design All of the entries on third screen of layer data pertain to geomembrane liner properties such as geomembrane liner pinhole density geomembrane liner installation defect density geomembrane liner placement quality and associated geotextile transmissivity if present Values must be entered for each geomembrane liner layer type 4 in the profile Guidance on estimating the pinhole and installation defect density as well as definitions for these parameters is provided in Section 3 The placement quality options are also described in Section 3 and are presented below The geotextile transmissivity should be specified only when a placement quality of 6 is used In the third column of cells the user should input the geomembrane liner placement quality The HELP program recognizes the following six types of placement quality 1 Perfect contact 2 Excellent contact 3 Good field placement 4 Poor field placement 5 Bad contact worst case 6 Geotextile separating geomembrane liner and controlling soil layer Typ
103. nimum data and normal mean monthly temperature values for most locations are readily available in publications or on diskette from the NOAA Information on climatological data sources can be obtained from the National Climatic Data Center NOAA Federal Building Asheville NC 28801 704 259 0682 Climatedata Solar Radiation Option Customary Units The program will convert the Surface Airways ASCII print files of daily average solar radiation data into a daily solar radiation data file of the format used by HELP Version 3 It is anticipated that this option may also work with some other data sources as they become available The following data are required for this option Location Surface Airways prepared file containing years of daily solar radiation data NOTE EarthInfo Inc sells NOAA Surface Airways daily global solar radiation data in a 12 disc CD ROM data base called Surface Airways as part of their NOAA data base three discs for each of four U S regions Information on Surface Airways is available from EarthInfo Inc 5541 Central Avenue Boulder CO 80301 2846 303 938 1788 Hydrosphere Inc is also developing a CD ROM data base of NOAA Surface Airways data as part of their Climatedata Information on Climatedata is available from Hydrosphere 1002 Walnut Suite 200 Boulder CO 80302 800 949 4937 ASCII Solar Radiation Option Customary or Metric Units The HELP model converts daily solar radiation data in an AS
104. ny Central Park Ithaca New York Syracuse NORTH CAROLINA Greensboro NORTH DAKOTA Bismarck OHIO Cincinnati Cleveland Columbus Put in Bay OKLAHOMA Oklahoma City Tulsa OREGON Astoria Medford Portland PENNSYLVANIA Philadelphia Pittsburgh RHODE ISLAND Providence SOUTH CAROLINA Charleston SOUTH DAKOTA Rapid City TENNESSEE Knoxville Nashville TEXAS Brownsville Dallas El Paso Midland San Antonio UTAH Cedar City Salt Lake City VERMONT Burlington Montpelier Rutland VIRGINIA Lynchburg Norfolk WASHINGTON Pullman Seattle Yakima WISCONSIN Madison WYOMING Cheyenne Lander PUERTO RICO San Juan 15 e Location NOTE The user should be aware of the limitations of using the default historical precipitation data None of the 102 locations for which data are available may be representative of the study site because rainfall is spatially very variable In addition the 5 years for which default data are available 1974 1978 in most cases may not be typical but were unusually wet or dry The user should examine the rainfall and determine how representative it is of normal wet and dry years at the study site In addition simulations should be run for more than five years to determine long term performance of the landfill using if necessary another precipitation input option to examine the design under the range of possible weather conditions 2 Synthetic Precipitation Option Customary
105. o is an inappropriate value Trailing decimal points are not required on input because the program automatically knows whether to treat a value as an integer or a floating point variable For example if a user wishes to enter the number nine either 9 9 or 9 00 is acceptable provided the input cell is wide enough 3 Selection Cells These are cells that are used to select from a list of options Selection cells highlight one item at a time An item option must be highlighted before it can be selected Selection is made by pressing the Enter key 4 Moving Between Cells The user can move from one input screen to another by pressing the Page Down key for the next screen or Page Up key for the previous screen in the loop of primary or secondary screens Input screens are arranged in a loop format such that if the Page Down key is pressed from the last input screen the control will return to the first screen and vice versa The up and down arrows are used to move up and down through the cells of a screen If the up arrow is pressed from the first cell on the screen control will transfer to the last cell on the same screen and vice versa The Tab and Shift Tab keys can be used to move to the right and to the left respectively among input and selection cells that are located on the same line In addition the left and right arrows may be used to move between 43 selection cells that are located on the same line 5 Moving Within an Input
106. olar radiation data D10 for soil and design data OUT for the output When the program initially displays the Execution Files File Management screen the program lists the default directory name in each cell in the directory column and the file names of each type of data that were used in the last simulation The user should enter the directory if different than the default directory for each type of file If an invalid directory is entered the program displays the message Invalid Directory and replaces the directory with the default directory If user enters a file name that could not be found on the specified directory then the program displays the message File Not Found and erases the file name As shown in Figure 18 the user may obtain a list of all files that reside on the current directory by pressing F4 When the user presses F4 the program obtains a directory of all files that pertain to the type of file at the cell where F4 was pressed For example if F4 was pressed from the temperature file cell the program will display the list of files with extension D7 that reside on the current directory displayed in temperature file row Up to 120 data files for any file type can be displayed on a separate screen The name of the current directory where these files are located is also displayed The user can obtain the list of data files with the same extension that are available in another valid 77 LIST FILES OF SPECIFIC DATA
107. on with Location Specific Guidance Customary and Metric Units This option uses the data provided by the HELP model for selected U S cities The cities are listed in Table 1 The data needed for this option are e Location e Evaporative zone depth Guidance is available for the selected location based on a thick layer of loamy soil with a grassy form of vegetation Clayey soils would generally have larger evaporative zone depths since it exerts greater capillary suction analogously sandy soils would have smaller evaporative depths Shrubs and trees with tap roots would have larger evaporative zone depths than the values given in the guidance The user must specify an evaporative zone depth and can use the guidance along with specific design information to select a value The program does not permit the evaporative depth to exceed the depth to the top of the topmost liner Similarly the evaporative zone depth would not be expected to extend very far into a sand drainage layer The evaporative zone depth must be greater than zero The evaporative zone depth is the maximum depth from which water may be removed by evapotranspiration The value specified influences the storage of water near the surface and therefore directly affects the computations for evapotranspiration and runoff Where surface vegetation is present the evaporative depth should at least equal the expected average depth of root penetration The influence of plant roots usually exte
108. only a portion of a weather file for future use to rearrange the years of data to repeat the same year s of data for a longer simulation period or to insert years of data into an existing file These options are performed using the functions to add insert a year above or below an existing year in the list of years delete a year move a year to a position above or below an existing year in the list of years or copy a year to a position above or below an existing year in the list of years The options are performed only on the type of data precipitation temperature or solar radiation highlighted when the create edit option was selected This is done by using the following key combinations of functions Alt A adds inserts a year either new being moved or being copied above the highlighted year where the cursor is positioned Alt B adds inserts a year either new being moved or being copied below the highlighted year where the cursor is positioned Alt D deletes the highlighted year where the cursor is positioned Alt M tags the highlighted year where the cursor is positioned to be moved to another location to be designated using the cursor and Alt A or Alt B Alt C tags the highlighted year where the cursor is positioned to be copied to another location to be designated using the cursor and Alt A or Alt B To add a new year directly above a certain year for example above the year on line 29 Line numbering is shown on the left
109. or Alt C and before pressing Alt A or Alt B By editing the data as discussed above the user is actually arranging the order of the precipitation data of the years Actual rearranging of data in the data file however takes place only after the user presses F10 NOAA Tape Data This option allows the user to enter data to the HELP model from a NOAA data set 58 Customary Units Only If this option is selected the user must enter the city and state for the site and the NOAA file name For the precipitation and temperature options the NOAA data file should contain daily Summary of Day data written in as on tape format Note that for temperature data two file names are requested one for the maximum temperature and the other for the minimum temperature If the user has only a mean temperature data file the mean temperature data file name should be entered for both maximum and minimum temperature data file names For the solar radiation option the NOAA data file should contain hourly Surface Airways data written in as on tape format Example NOAA data files are included with the HELP program PC49215A PRN for precipitation MX49215A PRN for maximum temperature and MN49215A PRN for minimum temperature When entering the NOAA file name the user should include the DOS path if the file location is different than the default directory file name and extension The user can abandon the entry of this data by pressing Esc Once valid information is
110. orosity unitless pore size distribution index unitless w capillary pressure bars at field capacity 0 33 or wilting point 15 0 WV bubbling pressure bars The volumetric water content in Equation A 8 is by definition equivalent to field capacity at a capillary pressure of 0 33 bar and is equivalent to wilting point at a capillary pressure of 15 bars The HELP program will use the calculated field capacity and wilting point values to recalculate the Brooks Corey parameters however because the program estimates the residual saturation water content from the wilting point before using Equation A 8 to calculate the other Brooks Corey parameters the program values will differ slightly from the laboratory data A 6 A 3 2 Saturated Hydraulic Conductivity Brutsaert 1967 derived a saturated hydraulic conductivity relation by substituting Brooks Corey s water retention equation into the Childs and Collis George 1950 series parallel coefficient of permeability integral Rawls et al 1982 and 1983 presented the following form of Brutsaert s 1967 equation 0 2 2 pog ru o A 9 i CA A 1 A 2 where K saturated hydraulic conductivity cm sec a constant representing the effects of various fluid constants and gravity 21 cm sec total porosity unitless 0 residual volumetric water content unitless WV bubbling pressure cm pore size distribution index unitless Childs and Collis George
111. patible personal computers PC under the DOS environment 1 3 2 Required Hardware The following IBM compatible CPU 8088 80286 80386 or 80486 hardware is required 1 Monitor preferably color EGA or better 2 Floppy disk drive 5 25 inch double sided double or high density or 3 5 inch double sided double or high density 3 Hard disk drive or a second floppy disk drive 4 400k bytes or more of available RAM memory 5 8087 80287 80387 or 80486 math co processor 6 Printer if a hard copy is desired 1 3 3 Software Requirements The user must use Microsoft or compatible Disk Operating Systems MS DOS Version 2 10 or a higher version The user interface executable module was compiled and linked with Microsoft Basic Professional Development System 7 1 Other executable components were compiled with the Ryan McFarland FORTRAN Version 2 42 The Microsoft Basic Professional Development System and Ryan McFarland FORTRAN compiler are not needed to run the HELP Model SECTION 2 BASIC LANDFILL DESIGN CONCEPTS 2 1 BACKGROUND Over the past 20 to 30 years the sanitary landfill has come to be widely recognized as an economic and effective means for disposal of municipal and industrial solid wastes Today modern methods of landfill construction and management are sufficiently developed to ensure that even large volumes of such materials can be handled and disposed of in such a way as to protect public health and minimize adverse eff
112. pe is already appearing In the first column of cells the saturated hydraulic conductivity must be specified in the appropriate units cm sec If the soil texture selected was a default soil material texture or a user defined soil texture the saturated hydraulic conductivity will be displayed in this column Remember that changing the saturated hydraulic conductivity causes the soil texture number on the previous screen to revert to zero in the same manner as changing any of the other material characteristics porosity field capacity or wilting point Drainage Layer Design Information on lateral drainage layer design must be entered manually for each lateral drainage layer directly above the liner regardless of the method used to enter soil textures The required information is the drainage length drainage layer slope recirculation percentage and recirculation destination These parameters are found in the second through fifth column of cells on the second spreadsheet screen of layer data These columns are used only for the lateral drainage layers directly above the liner data placed in rows for other layers will be ignored during execution The second column of cells on this second screen of layer data is for entering the maximum drainage length of lateral drainage layers which is the length of the horizontal projection of the flow path down the slope of a liner to the water leachate collection system This length must be greater than zero In
113. presentative of typical municipal solid waste that has been compacted type 19 is the same waste but it accounts for 65 percent of the waste being in dead zones not contributing to drainage and storage Soil types 16 and 17 denote very well compacted clay soils that might be used for barrier soil liners The user assigns default soil characteristics to a layer by specifying the appropriate number for the material type The 29 TABLE 4 DEFAULT SOIL WASTE AND GEOSYNTHETIC CHARACTERISTICS Saturated Classification Total Field Wilting Hydraulic Porosity Capacity Point Conductivity mem CH 0 398 0 244 0 136 1 2x10 0 464 0 310 0 187 6 4x10 0 471 0 342 0 210 42x10 SiCL 0 430 0 321 0 221 3 3x10 CoS S FS LS LFS SL FSL L SiL SCL CL SC SiC C Az 0 479 0 371 0 251 2 5x10 CH 0 475 0 378 0 265 1 7x10 p UA 16 0 427 0 418 0 367 1 0x107 17 Bentonite Mat 0 6 cm 0 750 0 747 0 400 3 0x10 oo Municipal Waste 900 Ib yd or 312 kg m 0 671 0 292 0 077 1 0x10 Municipal Waste channeling and dead zones 0 168 0 073 0 019 1 0x10 Drainage Net 0 5 cm 0 850 0 010 0 005 1 0x10 19 20 21 N N 0 419 0 307 0 180 1 9x10 0 461 0 360 0 203 9 0x10 N U N ON tA NIN N Coal Burning Electric Plant Fly Ash 0 541 0 187 0 047 5 0x10 Coal Burning Electric Plant Bottom Ash 0 578 0 076 0 025 4 1x10 Municipal Incinerator Fly Ash 0 450 0 116 0 049 1 0x
114. ptions 4 61 Schematic of Soil and Design Data Module 62 Soil and Design Data File Editing Screen Options 63 Schematic of Landfill General Information Screen 64 Schematic of Landfill Layer Data pce 9 2 6 acd Ret SOE NEG RY 66 Schematic of Runoff Curve Number Information Screen OpHGHS 4 5 fs Gah hie be He ee Shee Ree ee Se teehee 73 Verify and Save Soil and Design Data Options 75 Schematic of Execute Simulation Option 06 78 Schematic of View Results Option 0 000002 eee 80 Schematic of Print Results Option 00 5 80 viii TABLES Cities For Evapotranspiration Data and Synthetic Temperature and Solar Radiation Data Cities For Default Historical Precipitation Data Cities For Synthetic Precipitation Data 04 Default Soil Waste and Geosynthetic Characteristics 11 15 17 ACKNOWLEDGMENTS The support of the project by the Waste Minimization Destruction and Disposal Research Division Risk Reduction Engineering Laboratory U S Environmental Protection Agency Cincinnati OH and the Headquarters U S Army Corps of Engineers Washington DC through Interagency Agreement No DW21931425 is appreciated In particular the authors wish to thank the U S EPA Project Officer Mr Robert Landreth for his long standing support The draf
115. r diffusivity If the user changes any of the four soil properties obtained for a default soil material texture the program automatically resets the soil texture number to 0 The user can then assign the values a new soil texture number that is not used in either the list of default or previously saved user defined textures if the user wishes to save the material characteristics for future use As mentioned above default soil material textures are obtained by pressing F6 and are available on all three screens To move from one screen of default soil material textures to another the user should press Page Up or Page Down To return to the layer spreadsheet without making a selection press Esc A selection is made only by moving the cursor to the desired soil texture and pressing Enter User Defined Soil Texture In Version 3 of the HELP model the user has three options to specify material characteristics in addition to selecting soil textures from the default list One method is to enter all of the material characteristics manually without specifying a soil texture number This method is used when the user does not wish to save these characteristics for use again in this simulation or future simulations The second method which allows the user to assign a new soil texture number to the manually entered values for the soil properties is used when the same characteristics are to be used in future simulations and the characteristics are to be perma
116. r original form for many years perhaps even for centuries Given this possibility hazardous waste landfills should be designed to prevent any waste or leachate from ever moving into adjacent areas This objective is beyond the capability of current technology but does represent a goal in the design and operation of today s landfills The HELP model has been developed specifically as a tool to be used by designers and regulatory reviewers for selecting practical designs that minimize potential contamination problems In the context of a landfill leachate is described as liquid that has percolated through the layers of waste material Thus leachate may be composed of liquids that originate from a number of sources including precipitation groundwater consolidation initial moisture storage and reactions associated with decomposition of waste materials The chemical quality of leachate varies as a function of a number of factors including the quantity produced the original nature of the buried waste materials and the various chemical and biochemical reactions that may occur as the waste materials decompose In the absence of evidence to the contrary most regulatory agencies prefer to assume that any leachate produced will contaminate either ground or surface waters in the light of the potential water quality impact of leachate contamination this assumption appears reasonable The quantity of leachate produced is affected to some extent by de
117. ram computes the head on the liner The head on the liner is then used to compute the leakage percolation through the liner and if lateral drainage is permitted above the top of the liner the lateral drainage to the collection and removal system 3 9 ASSUMPTIONS AND LIMITATIONS 3 9 1 Solution Methods The modeling procedures documented in the previous section are necessarily based on many simplifying assumptions Generally these assumptions are reasonable and consistent with the objectives of the program when applied to standard landfill designs However some of these assumptions may not be reasonable for unusual designs The major assumptions and limitations of the program are summarized below Runoff is computed using the SCS method based on daily amounts of rainfall and snowmelt The program assumes that areas adjacent to the landfill do not drain onto the 37 landfill The time distribution of rainfall intensity is not considered The program cannot be expected to give accurate estimates of runoff volumes for individual storm events on the basis of daily rainfall data However because the SCS rainfall runoff relation is based on considerable daily field data long term estimates of runoff should be reasonable The SCS method does not explicitly consider the length and slope of the surface over which overland flow occurs This limitation has been removed by developing and implementing into the HELP input routine a procedure for computing c
118. re is depleted This contrasts with a typical growing season which would start in the spring and end in the fall 2 Manual Option Customary and Metric Units The data needed for this option are 12 Location Evaporative zone depth The user must specify an evaporative zone depth and can use the guidance given under the default option along with specific design information to select a value The program does not permit the evaporative depth to exceed the depth to the top of the topmost barrier soil layer Similarly the evaporative zone depth would not be expected to extend very far into a sand drainage layer The evaporative zone depth must be greater than zero The evaporative zone depth is the maximum depth from which water may be removed by evapotranspiration The value specified influences the storage of water near the surface and therefore directly affects the computations for evapotranspiration and runoff Where surface vegetation is present the evaporative depth should at least equal the expected average depth of root penetration The influence of plant roots usually extends somewhat below the depth of root penetration because of capillary suction to the roots The depth specified should be characteristic of the maximum depth to which the moisture changes near the surface due to drying over the course of a year typically occurring during peak evaporative demand or when peak quantity of vegetation is present Setting the evaporative
119. re than a total of five barrier soil liners and geomembrane liners The HELP model does not permit two barrier soil liners to be adjacent to each other If a design has two soil layers adjacent to each other that would be expected to act as a single liner and both soils will remain nearly saturated and contribute significantly to the head loss and restriction of vertical drainage then the thickness of the two layers should be summed and an effective saturated hydraulic conductivity should be computed for the combined liner The effective saturated hydraulic conductivity should be computed as follows 28 T T T K e e En Sc b v K K i i Ki j where K effective saturated hydraulic conductivity of combined liner T effective thickness of combined liner T thickness of liner soil i K saturated hydraulic conductivity of liner soil i n number of liner soils in the combined liner For computational purposes the soil profile is partitioned into subprofiles Subprofiles are defined in relation to the location of the liners The first top subprofile shown on Figure 1 extends from the landfill surface to the bottom of the highest liner system bottom of the composite liner Layer 4 upper barrier soil layer The second subprofile extends from the top of the layer Layer 5 below the bottom of the first liner system to the base of the second liner system Layer 8 The third bottom subprofile extends from the top of the lay
120. readsheet without making a selection press Esc The values entered for the moisture storage parameters in columns 4 through 7 of the first screen of layer spreadsheets are interrelated In column 4 the porosity must be greater than zero but less than 1 In column 5 the field capacity must be between zero 68 and 1 but must be smaller than the porosity In column 6 the wilting point must be greater than zero but less than the field capacity In column 7 the initial moisture content must be greater than or equal to the wilting point and less than or equal to the porosity If the user had indicated on the Landfill General Information screen that the program should specify initial moisture content for the soil layers the program will ignore all input in column 7 As such the user does not need to enter data in this column On the other hand if the user had indicated that the user wishes to specify the initial moisture content these values must be entered manually An empty cell is interpreted as zero for initial moisture violating the rules If the layer is a liner the program during execution automatically sets the initial water content equal to the porosity of the layer The program will detect violations of these values and will report them to the user during verifications when the data is to be saved to a file The second screen of layer spreadsheets can be obtained by pressing Page Down On this sheet the user will notice that the layer ty
121. ready to proceed to enter new data or edit existing data the user should press Page Down or F10 The program then reads the data file to be edited if a file is specified and proceeds to the Landfill General Information screen If a new data set is to be created file name left blank the program initializes the soil and design data and then asks for the system of units to be used throughout the module Customary or Metric Proper units are displayed throughout the module for entries that require units 63 4 6 2 Landfill General Information The second input screen in the soil and design data module is the Landfill General Information screen Figure 14 shows the screen and its branches as a schematic By moving the cursor to the appropriate cell the user can enter new information or edit the information that was read from the edit file The first entry is the project title which is only used for identification of the simulation LANDFILL GENERAL INFORMATION amp DESIGN DATA EDIT RUNOFF CURVE NUMBER Figure 14 Schematic of Landfill General Information Screen The second entry on this screen is the landfill area The units of the area are displayed next to the input cell according to the system of units selected The user should enter the area in acres for Customary units or in hectares for Metric units The third entry is for the percent of area where runoff is possible This variable specifies the portion
122. riginal temporary file is replaced only when the changes are finally retained by pressing F10 from the yearly data screen The copy command allows the user to place a year that 1s identical to another year on another line For example to copy the year on line 70 to line 5 move the cursor to line 70 and press the A t C combination then move the cursor to line 5 and press the Alt A combination At this point the user must specify a value for the new year the value must be different from the value of any other year in the data set for that type of weather data This action will cause the new value for the year to appear on line 5 but the daily values will be the same as those found for the year copied and previously found in line 70 The user may obtain the same result after the Alt C combination by moving to line 4 and pressing the combination Alt B The move command allows the user to move one year from one location on the yearly data screen to another For example to move the year on line 32 above the year on line 56 move the cursor to line 32 press the Alt M combination and move the cursor to line 56 and press the Alt A combination This action will cause the year on line 32 to be deleted and be placed directly above the year on line 56 The user may obtain the same result after the Alt M combination by moving to line 55 and pressing the combination Alt B The Esc key can be used to quit the move and copy functions after pressing Alt M
123. rooting zone and therefore limits plant growth Dates starting and ending the growing season The start of the growing season is based on mean daily temperature and plant species Typically the start of the growing season for grasses is the Julian date day of the year when the normal mean daily temperature rises above 50 to 55 degrees Fahrenheit The growing season ends when the normal mean daily temperatures falls below 50 to 55 degrees Fahrenheit In cooler climates the start and end would be at lower temperatures and in warmer climates at higher temperatures Data on normal mean daily temperature is available from Climates of the States Ruffner 1985 and the Climatic Atlas of the United States NOAA 1974 In locations where the growing season extends year round the start of the growing season should be reported as day 0 and the end as day 367 The values for the growing season should be checked carefully to agree with the germination and harvesting end of seasonal growth dates for your type of vegetation For example grasses in southern California would germinate in the fall when the rains occur and die in late spring when the soil moisture is depleted This contrasts with a typical growing season which would start in the spring and end in the fall Normal average annual wind speed This data is available from NOAA annual climatological data summary Climates of the States Ruffner 1985 and the Climatic Atlas of the United Sta
124. roper extension to the file according to the weather types The current directory is displayed on the screen The user may obtain a listing of all data files that reside on the current directory by pressing F4 By pressing F4 the program obtains a directory of all files that pertain to the weather data cell from which F4 was pressed For example if F4 was pressed from the temperature file cell the program will display the list of files with an extension of D7 that reside on the currently specified directory Up to 120 data files for any weather data type can be displayed on the screen The name of the current directory where these files are located is also displayed To obtain the data files pertaining to the weather information needed that reside in another directory the user should type in the name of a valid drive and 48 subdirectory in the Directory column and then press F4 for the list of files in that subdirectory To display a directory for another type of data move the cursor to the row for that data type and repeat the process listed above To select a file from the list of displayed files move the cursor to the desired file name and press Enter This action transfers control back to the previous screen and the name of the file just selected will be displayed in the proper cell The user can exit the Data Files screen without selecting a file by pressing the Esc key If the user wants to enter the file name in the file cell the u
125. s conservatively assumed that the head on the holes can be represented by the average head across the entire liner and can be estimated from the soil moisture storage and that the liner underlies the entire area of the landfill The lateral drainage model is based on the assumption that the saturated depth profile is characteristic of the steady state profile for the given average depth of saturation As such the model assumes that the lateral drainage rate for steady state drainage at a given average depth of saturation is representative of unsteady lateral drainage rate for the same average saturated depth In actuality the rate would be somewhat larger for periods when the depth is building and somewhat smaller for periods when the depth is falling Steady drainage implies that saturated conditions exist above the entire surface of the liner agreeing with the assumptions for leakage through liner systems The model assumes the vegetative growth and decay can be characterized by a vegetative growth model developed for crops and perennial grasses In addition it is assumed that the vegetation transpires water shades the surface intercepts rainfall and reduces runoff in similar quantities as grasses or as an adjusted equivalence of LAI 3 0 2 Limits of Application The model can handle water routing through or storage in up to twenty soil or waste layers as many as five liner systems may be employed The simulation period can range from 1 to 10
126. s considered by the program to indicate a value of zero for that day A zero is a valid entry The program keeps track of leap years and adjusts the month and day at the top of the spreadsheet accordingly Since there are 37 lines with each line containing 10 days of data there will be empty cells at the end of line 37 in the spreadsheet These cells are ignored by the program If the user decides to quit entering data in the daily spreadsheet and return to the yearly spreadsheet the user should press the Esc key By doing so whatever data were entered on the daily data sheet will be lost the previously existing data will be retained To exit the daily spreadsheet and retain the data entered on that sheet the user should press F10 Note that the F10 key will retain the data in a temporary file only and not 56 in any previously selected file A separate temporary file is maintained for each year of daily data Once the user returns to the yearly weather sheet more years can be entered or edited and the daily values for these years can be input on the daily sheet in the same manner described above After exiting the precipitation spreadsheet by pressing F10 and upon returning to the yearly sheet the annual total precipitation for that year is computed and displayed next to the year Editing Data on Yearly Data Screen Besides selecting years for creating or editing daily data the user has the options on the yearly data screen to select
127. s the saturated hydraulic conductivity of the geomembrane Geomembranes leak only when there is a positive head on the top surface of the liner The leakage rate depends on the depth of saturated soil head above the liner the saturated hydraulic conductivity of the drainage limiting soil layer adjacent to the membrane the contact between the membrane and the adjacent drainage limiting soil layer geomembrane properties and the size and number of holes in the geomembrane liner Aging of geomembranes is not considered While the HELP program is quite flexible there are some basic rules that must be followed regarding the arrangement of layers in the profile 1 A vertical percolation layer may not be underlying a lateral drainage layer 2 A barrier soil liner may not be underlying another barrier soil liner 3 A geomembrane liner may not be placed directly between two barrier soil liners 4 A geomembrane liner may not be underlying another geomembrane liner 5 A barrier soil liner may not be placed directly between two geomembrane liners 6 When a barrier soil liner or a geomembrane liner is not placed directly below the lowest drainage layer all drainage layers below the lowest liner are treated as vertical percolation layers Thus no lateral drainage is computed for the bottom section of the landfill 7 The top layer may not be a barrier soil liner 8 The top layer may not be a geomembrane liner 9 The profile can contain no mo
128. save the data now and make corrections at a later time if there were violations However it should not be expected that the HELP model will provide meaningful answers for such data Soil and design data are saved in a file specified on the Soil and Design Data File Saving screen The program displays the default file name DATA10 for saving in the default directory DATA10 is the same name for the soil and design data as used in Version 2 except that Version 3 adds an extension of D10 to the specified soil and design data file name To save the data the user should enter Y in the Save column Then the user should specify the directory in which to save the file If the directory cannot be found the program responds Invalid Directory and replaces it with the default directory After the directory the user should enter the file name no extension or period If the file already exists the program will display File Already Exists After entering the file name the user should press F10 or Page Down to complete the saving to the requested file name If the file already exists as the default file would the program will ask whether the user wishes to have the existing file overwritten If the user answers Y the program will overwrite the file complete the saving process and return to the main menu If the user answers N the program will interrupt the saving return to the SAVE column and change the tag to N The user can then chang
129. ser must first enter the correct directory name If an invalid directory is entered the program will displayed the message Invalid Directory and replace the entered directory name with the default directory name where the program was started The user then has another opportunity to enter the correct directory name If the program cannot find the file name as entered the message File Not Found will be displayed The previously entered file name is erased and the user has another opportunity to enter a correct file name Pressing Page Down causes the program to read the valid data files selected and then proceeds to the first weather data entry screen 4 5 2 Evapotranspiration ET Data The evapotranspiration data requirements are listed in Section 3 and are entered to the program from the Evapotranspiration Data screen This screen contains all information required by the HELP model to construct the evapotranspiration data file D11 If the user specified an edit file name for the evapotranspiration data the contents of the file will be displayed in the appropriate cells on this screen The user can move the cursor to any cell to edit its contents However if no file was selected as an edit file then data must be specified by the user First the user must select the system of units to be used for the evapotranspiration data which may be entered in customary or metric units as explained in a previous section A schematic of this scre
130. sses and subsurface processes The surface processes modeled are snowmelt interception of rainfall by vegetation surface runoff and surface evaporation The subsurface processes modeled are evaporation from soil profile plant transpiration unsaturated vertical drainage barrier soil liner percolation geomembrane leakage and saturated lateral drainage 100 ARE pnovse 80 r oo aps Re x g 60 F NS co 5 Cn z em x er XL i KS ce amp gt id p o 40 e o 20 Oo 1 3 5 7 9 11 13 15 CoS FS LFS FSL SiL cL sc c SOIL TEXTURE NUMBER Figure 2 Relation between SCS Curve Number and Default Soil Texture Number for Various Levels of Vegetation 36 Daily infiltration into the landfill is determined indirectly from a surface water balance Infiltration is assumed to equal the sum of rainfall surface storage and snowmelt minus the sum of runoff additional storage in snowpack and evaporation of surface water No liquid water is assumed to be held in surface storage from one day to the next except in the snowpack or when the top soil is saturated and runoff is not permitted Each day the free available water for infiltration runoff or evaporation from water on the surface is determined from the surface storage discharge from the snowpack and rainfall Snowfall is added to the surface snow storage which is depleted by either evaporation or melting Snowmelt is added to the free available water and is treated as rainfall
131. ste cells may be covered with a cap or final cover typically composed of four distinct layers as shown in Figure 1 At the base of the cap is a drainage layer and a liner system layer similar to that used at the base of the landfill Again a geomembrane liner would normally be used in conjunction with the barrier soil liner for hazardous waste landfill but has been used less frequently in municipal waste landfills The top of the barrier soil layer is graded so that water percolating into the drainage layer will tend to move horizontally toward some removal system drain located at the edge of the landfill or subunit thereof A layer of soil suitable for vegetative growth is placed at the top of final cover system to complete the landfill A 2 ft thick layer of soil having a loamy silty nature serves this purpose well The upper surface is graded so that runon is restricted and infiltration is controlled to provide moisture for vegetation while limiting percolation through the topsoil Runoff is promoted but controlled to prevent excessive erosion of the cap The vegetation used should be selected for ease of establishment in a given area promotion of evapotranspiration and year round protection from erosion The root system should not penetrate disrupt or desiccate the upper liner system Layers 3 and 4 Grasses are usually best for this purpose however local experts should be consulted to aid in selection of appropriate species The combin
132. t the number of years to simulate and the output frequency The user may use a maximum of 100 years of simulation provided that weather data are available for that many years If the weather 78 data in the selected files have a different number of years the HELP model allows the simulation period to be no larger than the minimum number of years available in any of the daily weather data files If the simulation period selected is smaller than the maximum allowable period the program will use the years of weather data starting at the top of the files The rest of the information available on this screen is for selecting the type of optional output desired daily monthly or annual The user may select any all or none of the available options The program will always write the summary output to the output file as well as a description of the input data In order to select additional or different output frequencies move the cursor to the desired output frequency and type Y Once all execution files and output frequency data are selected the user should press Page Down or F10 to start the simulation To move back to the Execution Files screen press Page Up 4 8 VIEWING RESULTS Option 4 on the main menu is to view the results of execution This option is used to browse through the output file before printing Figure 19 is a schematic of this option The program displays the View Results screen The user should enter the desired direc
133. t version of this document was prepared at Clemson University by Dr Nadim M Aziz the author of the HELP Version 3 user interface under contract with the USEPA Risk Reduction Engineering Laboratory and the USAE Waterways Experiment Station The final version of this document was prepared at the USAE Waterways Experiment Station by Dr Paul R Schroeder and Ms Cheryl M Lloyd Appendix A was written by Mr Paul A Zappi The figures used in the report were prepared by Messrs Jimmy Farrell and Christopher Chao The report and user interface were reviewed by Messrs Elba A Dardeau Jr and Daniel E Averett This report has not been subjected to the EPA review and therefore the contents do not necessarily reflect the views of the Agency and no official endorsement should be inferred SECTION 1 INTRODUCTION The Hydrologic Evaluation of Landfill Performance HELP computer program is a quasi two dimensional hydrologic model of water movement across into through and out of landfills The model accepts weather soil and design data and uses solution techniques that account for the effects of surface storage snowmelt runoff infiltration evapotranspiration vegetative growth soil moisture storage lateral subsurface drainage leachate recirculation unsaturated vertical drainage and leakage through soil geomembrane or composite liners Landfill systems including various combinations of vegetation cover soils waste cells lateral drain
134. tation is partitioned into surface storage snow snowmelt interception runoff infiltration surface evaporation evapotranspiration from soil subsurface moisture storage liner leakage percolation and subsurface lateral drainage to collection removal and recirculation systems This section discusses data requirements nomenclature important assumptions and limitations and other fundamental information needed to run the program The program documentation report Schroeder et al 1994 contains detailed explanations of the solution techniques employed and the computer programs The HELP program requires three general types of input data weather data soil data and design data A summary of input options and data requirements is presented in this section Section 4 provides step by step input instructions 3 2 WEATHER DATA REQUIREMENTS The weather data required in the HELP model are classified into four groups evapotranspiration precipitation temperature and solar radiation data The HELP user may enter weather data using several options depending on the type of weather data being considered The requirements for each weather data type are listed below The units used are also listed next to each data type and or variable Customary units are based on the US Customary units and Metric implies SI units 3 2 1 Evapotranspiration Data The evapotranspiration data can be entered in one of two ways 1 Default Evapotranspiration Opti
135. tation to individual print files The following data are required for this option e Location 18 e Files containing ASCII data e Years 7 HELP Version 2 Data Option Customary Units Version 3 of the HELP model converts precipitation data prepared for use in Version 2 of the HELP model Schroeder et al 1988b into the HELP Version 3 format This option requires the following data Location File containing HELP Version 2 data 6 Canadian Climatological Data Option Metric Units The HELP model converts Canadian Climatological Data Surface in compressed or uncompressed diskette formats into the HELP Version 3 format The following data are required by this option Location e Canadian Climatological Data file containing years of daily precipitation values NOTE Canadian Climatological Data for most locations are readily available in publications of the Environment Canada Atmospheric Environment Service Canadian Climate Centre Data Management Division 4905 Dufferin Street Downsview Ontario Canada M3H 5T4 3 2 3 Temperature Data 1 Synthetic Temperature Option Customary or Metric Units The program will generate from 1 to 100 years of temperature data stochastically for the selected location The synthetic generation of daily temperature values is a weak function of precipitation and as such the user must first specify the precipitation Generation of temperature data is limited to the number of years of precipita
136. te from the landfill a final cover to minimize the production of leachate following closure careful controls of runon and runoff and limits on the buildup of leachate head over the liner to no more than 1 ft The HELP model is useful for predicting the amounts of runoff drainage and leachate expected for reasonable designs as well as the buildup of leachate above the liner However the model should not be expected to produce credible results from input unrepresentative of landfills 1 4 OVERVIEW The principal purpose of this User s Guide is to provide the basic information needed to use the computer program Thus while some attention must be given to definitions descriptions of variables and interpretation of results only a minimal amount of such information is provided Detailed documentation providing in depth coverage of the theory and assumptions on which the model is based and the internal logic of the program is also available Schroeder et al 1994 Potential HELP users are strongly encouraged to study the documentation and this User s Guide before attempting to use the program to evaluate a landfill design Additional documentation concerning the sensitivity of program inputs application of the model and verification of model predictions are under development 1 3 SYSTEM AND OPERATING DOCUMENTATION 1 3 1 Computer Equipment The model entitled The Hydrologic Evaluation of Landfill Performance HELP was written to run on IBM com
137. te sites and accidental releases of toxic and hazardous substances to the environment also have important environmental and public health implications The Risk Reduction Engineering Laboratory assists in providing an authoritative and defensible engineering basis for assessing and solving these problems Its products support the policies programs and regulations of the Environmental Protection Agency the permitting and other responsibilities of State and local governments and the needs of both large and small businesses in handling their wastes responsibly and economically This report presents guidance on the use of the Hydrologic Evaluation of Landfill Performance HELP computer program The HELP program is a quasi two dimensional hydrologic model for conducting water balance analysis of landfills cover systems and other solid waste containment facilities The model accepts weather soil and design data and uses solution techniques that account for the effects of surface storage snowmelt runoff infiltration evapotranspiration vegetative growth soil moisture storage lateral subsurface drainage leachate recirculation unsaturated vertical drainage and leakage through soil geomembrane or composite liners Landfill systems including various combinations of vegetation cover soils waste cells lateral drain layers low permeability barrier soils and synthetic geomembrane liners may be modeled The model facilitates rapid estimation of the a
138. tedata format is also used by other CD ROM state and regional data bases and therefore those files can also be converted by this option For example the State of California and the Midwest Climatic Data Consortium used this same format The following data are required for this option Location e Climatedata prepared file containing daily maximum temperature data e Climatedata prepared file containing daily minimum temperature data NOTE Hydrosphere Data Products Inc sells NOAA Summary of the Day daily temperature data in a 4 disc CD ROM data base called Climatedata one disc for each of four U S regions Information on Climatedata is available from Hydrosphere 1002 Walnut Suite 200 Boulder CO 80302 800 949 4937 ASCII Temperature Option Customary or Metric Units The HELP model converts daily mean temperature data in an ASCII file to the HELP format Each year of ASCII temperature data should be stored in a separate file The program will convert the first 365 or 366 values excess data will be ignored Inadequate data will yield an error This option should also be used to convert data from spreadsheet format by first printing each year of temperature to individual print files The following data are required for this option Location e Files containing ASCII data e Years HELP Version 2 Data Option Customary Units Version 3 of the HELP model converts temperature data prepared for use in Version 2 of the HE
139. tes NOAA 1974 Normal average quarterly relative humidity This data is available from NOAA annual climatological data summary Climates of the States Ruffner 1985 and the Climatic Atlas of the United States NOAA 1974 3 2 2 Precipitation Data 1 Default Precipitation Option Customary Units The user may select 5 years of historical precipitation data for any of the 102 U S cities listed in Table 2 The input needed for this option is 14 TABLE 2 CITIES FOR DEFAULT HISTORICAL PRECIPITATION DATA ALASKA Annette Bethel Fairbanks ARIZONA Flagstaff Phoenix Tucson ARKANSAS Little Rock CALIFORNIA Fresno Los Angeles Sacramento San Diego Santa Maria COLORADO Denver Grand Junction CONNECTICUT Bridgeport Hartford New Haven FLORIDA Jacksonville Miami Orlando Tallahassee Tampa West Palm Beach GEORGIA Atlanta Watkinsville HAWAII Honolulu IDAHO Boise Pocatello ILLINOIS Chicago East St Louis INDIANA Indianapolis IOWA Des Moines KANSAS Dodge City Topeka KENTUCKY Lexington LOUISIANA Lake Charles New Orleans Shreveport MAINE Augusta Bangor Caribou Portland MASSACHUSETTS Boston Plainfield Worcester MICHIGAN East Lansing Sault Sainte Marie MINNESOTA St Cloud MISSOURI Columbia MONTANA Glasgow Great Falls NEBRASKA Grand Island North Omaha NEVADA Ely Las Vegas NEW HAMPSHIRE Concord Nashua NEW JERSEY Edison Seabrook NEW MEXICO Albuquerque NEW YORK Alba
140. ther data prior to entering the create edit option Daily Data Screen Upon selecting or specifying a year from the yearly data screen the program displays the daily data screen a spreadsheet for entering daily data This spreadsheet consists of 10 columns and 37 rows The spreadsheet contains information on the file name the year month and day This information is displayed at the top of the spreadsheet The day and month are continuously updated as the user moves from one cell to another The first day is considered January 1 and the last day is December 31 The spreadsheet is divided into two parts the first part being rows 1 through 19 and the second part rows 20 through 37 The user can move the cursor to the bottom of the screen and cursor down to move to the next row until the 37th row is displayed Similarly the user can move the cursor upward to display any rows in the spreadsheet that are not shown To move from the upper to the lower portions of the spreadsheet and vice versa press Page Down and Page Up respectively To reach the last cell in the spreadsheet press End and to return to the first cell press Home The user should input values one day at a time without leaving empty cells between months For example the first month January will extend to the first cell or column in the fourth row The values for the first day in February should start in column 2 of row 4 no empty cells are left between months An empty cell i
141. third column of cells the user should enter the drain slope in percent This slope is the maximum gradient of the surface of the liner at the base of the lateral drainage layer this is the slope along the flow path In Version 3 the HELP program allows leachate drainage recirculation to be simulated The amount of leachate lateral drainage to be recirculated from a given layer should be entered as a percent of the layer s drainage in the fourth column of cells The layer to which this leachate drainage should be recirculated should be entered on the same row in the fifth column of cells The value entered is the number of the layer receiving recirculation Layer numbers are those numbers displayed on the left side of the screen These numbers are through 20 and refer to the order of the layers in the profile The 69 HELP model does not allow leachate recirculation to a liner Version 3 of the HELP model also allows the user to specify subsurface inflow into the landfill from a groundwater source The amount of subsurface inflow into each layer should be entered in the last column of the second spreadsheet of layer data and is considered to be a steady flow rate into the landfill at the layer where the inflow value is entered If subsurface inflow is specified for the bottom layer the program will assume no leakage through the bottom of the landfill For most landfills the inflows will be zero and this column can be left blank After enteri
142. tion data available The synthetic temperature data will have approximately the same statistical characteristics as the historic data at the selected location If desired the user can enter normal mean monthly temperature values for the specific location to improve the statistical characteristics of the resulting daily values The user is advised to enter normal mean monthly temperature values if the project site is located more than 100 miles from the city selected from Table 1 or if the difference in elevation between the site and the city is more than 500 feet The data required by the synthetic weather generator are Location select from a list of 183 U S cities in Table 1 19 2 3 e Number of years of data to be generated e Years of daily precipitation values e Normal mean monthly temperature Optional default values are available Create Edit Temperature Option Customary or Metric Units Under the create option the user may enter up to 100 years of daily temperature data manually The years which need not be consecutive can be entered in any order The user may add or delete years of data or rearrange the order of the years of data This same option can be used to edit the daily values of any year of data The data required are Location One or more years of daily temperature data NOAA Tape Temperature Option Customary Units This option will convert the NOAA Summary of Day daily temperature data written to dis
143. tory and file name The file name can be selected from a list of files by pressing F4 After selecting the file press Page Down or F10 to display the selected file The viewing function uses the LIST program written by Vernon D Buerg and instructions on its use are available on screen by typing or FI To display other types of files first enter the extension of the file of interest then the directory and the file name To return to the main menu press Page Down or F10 4 9 PRINTING RESULTS Option 5 on the main menu is used to print the output file Figure 20 is a schematic of this option The program displays the Print Results screen The user should enter the desired directory and file name The file name can be selected from a list of files by pressing F4 After selecting the file press Page Down or F10 to print the selected file The print function uses the DOS PRINT command and instructions on its use are available in a DOS manual The output file is 80 characters wide for all output options except daily output which can be up to 132 characters wide When printing output with daily results it may be necessary to select a compressed font on your printer before printing to avoid wrapping or loss of output To print other types of files first enter the extension of the file of interest then the directory and the file name To return to the main menu press Page Down or F10 Alternatively the output file or any data file which are ASCII
144. transmissivity of geotextiles separating geomembranes and drainage limiting soils These parameters are defined below 33 Pinhole Density the number of defects diameter of hole equal to or smaller than geomembrane thickness hole estimated as 1 mm in diameter in a given area generally resulting from manufacturing flaws such as polymerization deficiencies Installation Defect Density the number of defects diameter of hole larger than the geomembrane thickness hole estimated as 1 cm in area per acre resulting primarily from seaming faults and punctures during installation Geotextile Transmissivity the product of the in plane saturated hydraulic conductivity and thickness of the geotextile The density of pinholes and installation defects is a subject of speculation Ideally geomembranes would not have any defects If any were known to exist during construction the defects would be repaired However geomembranes are known to leak and therefore reasonably conservative estimates of the defect densities should be specified to determine the maximum probable leakage quantities The density of defects has been measured at a number of landfills and other facilities and reported in the literature These findings provide guidance for estimating the defect densities Typical geomembranes may have about 0 5 to 1 pinholes per acre 1 to 2 pinholes per hectare from manufacturing defects The density of installation defects is a function of the q
145. turated hydraulic conductivity computed as a function of the soil moisture content As such the rate is assumed to be independent of the pressure gradient Leakage through barrier soil liners is modeled as saturated Darcian flow Leakage is assumed to occur only as long as there is head on the surface of the liner The model assumes that the head driving the percolation can be represented by the average head across the entire liner and can be estimated from the soil moisture storage It is also assumed that the liner underlies the entire area of the landfill and conservatively that when leakage occurs the entire area of the landfill leaks The model does not consider aging or drying of the liner and therefore the saturated hydraulic conductivity of the liner does not vary as a function of time Geomembranes are assumed to leak primarily through holes The leakage passes through the holes and spreads between the geomembrane and soil until the head is dissipated The leakage then percolates through the soil at the rate dependent on the saturated hydraulic conductivity and the pressure gradient Therefore the net effect of a geomembrane is to reduce the area of percolation through the liner system The program assumes the holes to be uniformly distributed and the head is distributed across the entire liner The model does not consider aging of the liner and therefore the number and size of the holes do not vary as a function of time In addition it i
146. ty in vol vol Field capacity in vol vol Wilting point in vol vol Saturated hydraulic conductivity cm sec e Select from user built soil texture library to get the following data Porosity in vol vol Field capacity in vol vol Wilting point in vol vol Saturated hydraulic conductivity cm sec Enter the following data for manual soil texture descriptions Porosity in vol vol Field capacity in vol vol Wilting point in vol vol Saturated hydraulic conductivity cm sec Initial volumetric soil water content storage in vol vol optional needed when initial moisture storage is user specified Rate of subsurface inflow to layer Customary or Metric 3 3 3 Lateral Drainage Layer Design Data 25 1 Maximum drainage length Customary or Metric 2 Drain slope percent 3 Percentage of leachate collected from drainage layer that is recirculated 4 Layer to receive recirculated leachate from drainage layer 3 3 4 Geomembrane Liner Data 1 Pinhole density in geomembrane liner Customary or Metric 2 Geomembrane liner installation defects Customary or Metric 3 Geomembrane liner placement quality six available options 4 Geomembrane liner saturated hydraulic conductivity vapor diffusivity cm sec 5 Geotextile transmissivity cm sec optional when placed with geomembrane 3 3 5 Runoff Curve Number Information Three methods are available to define a SCS AMC II runoff curve number 1 User specified curve number used wit
147. ual landfill location to obtain better solar radiation values Create Edit If the user selects the create edit option Customary or Metric Units for manually OPTIONAL SYNTHETIC DATA g Alt YEAR CREATE EDIT RECORDS AND am SELECTION CONVERT AND IMPORT DATA SOLAR PRESENTLY RADIATION CUIMATEBATS UNAVAILABLE CONVERT AND IMPORT DATA NOAA TAPE ASCII CONVERT AND nee IMPORT DATA CONVERT AND CANADIAN IMPORT DATA Figure 10 Solar Radiation Options 54 entering or editing precipitation temperature and or solar radiation data the program prompts the user with a request to enter the city and state of the location and the units that will be used for entering the data manually These requests appear on the same screen as Precipitation Temperature and Solar Radiation screen and will be filled in with information when editing an existing data file The user may press the Esc key to abandon the entry of this information and return to the selection of another weather data option Once the location and units are specified the program displays the yearly data screen Yearly Data Screen This screen is like a spreadsheet that has four columns Two of these columns are for the precipitation data and one column each is for temperature and solar radiation The first column is for the year for which the precipitation data is to be entered and the second column is for total annual precipitation The user cannot access
148. uality of installation testing materials surface preparation equipment and QA QC program Representative installation defect densities as a function of the quality of installation are given below for landfills being built today with the state of the art in materials equipment and QA QC In the last column the frequency of achieving a particular installation quality is given The estimates are based on limited data but are characteristic of the recommendations provided in the literature Installation Defect Density Frequency Quality number per acre percent Excellent Up to 1 10 Good 1 to 4 40 Fair 4 to 10 40 Poor 10 to 20 10 Higher defect densities have been reported for older landfills with poor installation operations and materials however these high densities are not characteristic of modern practice The user must also enter the placement quality of the geomembrane liner if pinholes or installation defects are reported There are six different possible entries for the geomembrane liner placement quality The program selects which equation will be used to compute the geomembrane based on the placement quality specified and the saturated hydraulic conductivity of the lower permeability soil drainage limiting soil adjacent to 34 the geomembrane The program has different equations for three ranges of saturated hydraulic conductivity greater than or equal to 0 1 cm sec less than 0 1 and greater than or equal to 0 0001 cm sec
149. uations are not applicable to soils subjected to compactive efforts Williams et al 1992 concluded that equations used to predict water contents based on texture and bulk density alone provided poorer estimates of water content with large errors at some capillary pressures in comparison with models that incorporate even one known value of water content HELP users generally do not have adequate information to use models that require unsaturated water content information therefore Equations A 3 and A 4 are used to calculate the water retention of soil and waste layers A 2 3 Saturated Hydraulic Conductivity Saturated hydraulic conductivity sometimes referred to as the coefficient of permeability is used as a constant in Darcy s law governing flow through porous media Hydraulic conductivity is a function of media properties such as the particle size void ratio composition fabric and degree of saturation and the kinematic viscosity of the fluid moving through the media Saturated hydraulic conductivity is used to describe flow through porous media where the void spaces are filled with a wetting fluid e g water Permeability unlike saturated hydraulic conductivity is solely a function of media A 3 properties Henri Darcy s experiments resulted in the following equation for hydraulic conductivity Freeze and Cherry 1979 K d cq A 5 v where K hydraulic conductivity cm sec g acceleration due to gravity 981 cm sec
150. ucing its transmissivity below the point where it can contribute significantly to spreading of leakage GCL s when properly placed tend to have intimate contact with the geomembrane Harpur et al 1993 3 7 SITE CHARACTERISTICS The user must also supply a value of the Soil Conservation Service SCS runoff curve number for Antecedent Moisture Condition II AMC II or provide information so that a curve number can be computed Unlike Version 2 of the HELP model Version 3 accounts for surface slope effects on curve number and runoff In Version 3 of the HELP model there are three different options by which a curve number can be obtained 1 A curve number defined by the user 35 2 A curve number defined by the user and modified according to the surface slope and slope length of the landfill 3 A curve number is computed by the HELP model based on landfill surface slope slope length soil texture of the top layer and the vegetative cover Some general guidance for selection of runoff curve numbers is provided in Figure 2 USDA Soil Conservation Service 1985 Two of the options account for surface slope The correlation between surface slope conditions and curve number were developed for slopes ranging from 1 percent to as high as 50 percent and for slope lengths ranging from 50 feet to 2000 feet 3 8 OVERVIEW OF MODELING PROCEDURE The hydrologic processes modeled by the program can be divided into two categories surface proce
151. uisville Scottsbluff Medford Denver LOUISIANA NEVADA Pendleton Grand Junction Baton Rouge Elko Portland Pueblo Lake Charles Ely Salem CONNECTICUT New Orleans Las Vegas Sexton Summit Bridgeport Shreveport Reno PENNSYLVANIA Hartford MAINE Winnemucca Philadelphia New Haven Augusta NEW HAMPSHIRE Pittsburgh Windsor Locks Bangor Concord RHODE ISLAND DELAWARE Caribou Mt Washington Providence Wilmington Portland Nashua SOUTH CAROLINA DISTRICT OF COLUMBIA MARYLAND NEW JERSEY Charleston Washington Baltimore Edison Columbia FLORIDA MASSACHUSETTS Newark SOUTH DAKOTA Jacksonville Boston Seabrook Huron Miami Nantucket NEW MEXICO Rapid City Orlando Plainfield Albuquerque TENNESSEE Tallahassee Worchester Roswell Chattanooga Tampa Knoxville West Palm Beach Memphis Nashville Continued 11 TABLE 1 continued CITIES FOR EVAPOTRANSPIRATION DATA AND SYNTHETIC TEMPERATURE AND SOLAR RADIATION DATA TEXAS UTAH WASHINGTON WISCONSIN Abilene Cedar City Olympia Green Bay Amarillo Milford Pullman Lacrosse Austin Salt Lake City Seattle Madison Brownsville VERMONT Spokane Milwaukee Corpus Christi Burlington Stampede Pass WYOMING Dallas Montpelier Walla Walla Cheyenne El Paso Rutland Yakima Lander Galveston VIRGINIA WEST VIRGINIA PUERTO RICO Houston Lynchburg Charleston San Juan Midland Norfolk San Antonio Richmond Temple Waco Concluded stand of grass 5 0 The LAI for dense stands of trees and shrubbery would also approac
152. ure 15 shows the three spreadsheets and their associated screens The first row of cells on the screens is the uppermost layer in the landfill Each column of cells on the screens represents a variable or a property of the layer or its material Variable names are listed in the first two rows of the screen and the third row contains the units of that variable if any Every highlighted cell is associated with a highlighted property heading of a column and a highlighted layer number row label The user should enter the value of the specified property for the corresponding layer All entries must obey certain rules which are discussed below 3 SHEETS LAYER SOIL PROPERTIES SHEET 1 m DRAIN F1 PROPERTIES SHEET 2 F3 DEFAULT E6 SOIL GEOMEMBRANE TEXTURES PROPERTIES SHEET 3 F7 USER SOIL TEXTURES F9 SAVE SOIL amp DESIGN DATA PgDn PROCEED TO NEXT SCREEN PgUp RETURN TO PREVIOUS SCREEN Figure 15 Schematic of Landfill Layer Data Layer Type The user should input layer type in the first column of the spreadsheet The four layer types and their associated code numbers that the program recognizes are vertical percolation 1 lateral drainage 2 barrier soil liner 3 and geomembrane liner 4 These are defined as follows 1 A layer of moderate to high permeability material that drains vertically primarily as unsaturated flow is classified as a vertical percolation layer as long as it is not u
153. urve numbers that take into consideration the effect of slope and slope length The limitation however remains on the user specified curve number the first method This limitation is not a concern provided that the slope and slope length of the landfill do not differ dramatically from those of the test plots upon which the SCS method is based Use of the SCS method probably underestimates runoff somewhat where the overland flow distance is very short or the slope is very steep or when the rainfall duration is very short and the intensity is very high The HELP model assumes Darcian flow by gravity influences through homogeneous soil and waste layers It does not consider explicitly preferential flow through channels such as cracks root holes or animal burrows but allows for vertical drainage through the evaporative zone at moisture contents below field capacity Similarly the program allows vertical drainage from a layer at moisture contents below field capacity when the inflow would occupy a significant fraction of the available storage capacity below field capacity The drainage rate out of a segment is assumed to equal the unsaturated hydraulic conductivity of the segment corresponding to its moisture content provided that the underlying segment is not a liner and is not saturated In addition to these special cases the drainage rate out of a segment can be limited by the saturated hydraulic conductivity of the segment below it When limited t
154. user selects an entry from a list On line Help Screen a screen where assistance is provided General assistance on the interface is displayed by pressing the FJ key technical assistance by pressing the F2 key and key operations by pressing the F3 key This terminology is used throughout this section Each module consists of two types of screens primary and secondary Primary screens are main screens that form a loop for each option of HELP Secondary screens are displayed from the primary screens as part of the input process These screens can be input screens or selection screens 2 Input Cells When the program highlights a number of spaces called an input cell throughout this section an input from the user is expected At any input cell the user has one of several options enter the data requested accept existing value seek on line help or select one of the menu items listed at the bottom of the screen Each cell is associated with a variable that is used directly or indirectly in the HELP model Therefore every effort must be made to assign a value to each cell when applicable The user may input the value the first time around or return to the cell at a later time during the program session If an input cell is left blank a value of zero will be assigned to the corresponding variable If zero is not an appropriate answer to the question it will produce erroneous results The program will warn the user when a blank or zer
155. user to browse through the output file and examine the results of the run after executing the program Option 5 is Print Results and Option 6 is Display Guidance on general landfill design procedures and on the HELP model itself containing much of the text of this user s guide Finally Option 7 is used to Quit running the model and return to DOS 46 In the following sections detailed explanations of the main menu options are presented and methods of data entry to the program and various options are discussed 4 55 WEATHER DATA As mentioned above this module is selected from the main menu by pressing 1 Enter Edit Weather Data A schematic of this module is shown in Figure 4 In this module the user can specify all of the weather data evapotranspiration precipitation temperature and solar radiation required to run the model The four primary screens in this module are Weather Data File Editing Evapotranspiration Data Precipitation Temperature and Solar Radiation Data and Weather Data File Saving Several secondary screens may appear during the session depending upon the action taken by the user On line help screens are always available for display by pressing FI or F2 The individual primary screens and their secondary screens of this module are discussed below WEATHER DATA FILES FOR EDITING ENTER EDIT WEATHER DATA EVAPO TRANSPIRATION DATA VERIFY amp SAVE WEATHER
156. y Fort Collins CO 27 pp England C B 1970 Land capability A hydrologic response unit in agricultural watersheds ARS 41 172 USDA Agricultural Research Service 12 pp Harpur W A Wilson Fahmy R F and Koerner R M 1993 Evaluation of the contact between geosynthetic clay liners and geomembranes in terms of transmissivity Proceeedings of GRI Seminar on Geosynthetic Liner Systems Geosynthetic Research Institute Drexel University Philadelphia PA 143 154 Knisel W J Jr Editor 1980 CREAMS A field scale model for chemicals runoff and erosion from agricultural management systems volumes I II and III USDA SEA Conservation Research Report 26 643 pp Lutton R J Regan G L and Jones L W 1979 Design and construction of covers for soil waste landfills EPA 600 2 79 165 US Environmental Protection Agency Cincinnati OH 249 pp National Oceanic and Atmospheric Administration 1974 Climatic atlas of the United States US Department of Commerce Environmental Science Services Administration Nation Climatic Center Ashville NC 80 pp Perrier E R and Gibson A C 1980 Hydrologic simulation on solid waste disposal sites EPA SW 868 US Environmental Protection Agency Cincinnati OH 111 pp Rawls W J Brakensiek D L and Saxton K E 1982 Estimation of soil water properties Transactions of the American Society of Agricultural Engineers 25 5 1316 1320 Richar

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