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DROPMIX User`s Manual

1. The third and final receiving water screen allows the user to supply information on the density of the receiving water environment Three density profiles are possible 1 Uniform Density Profile U 2 Linearly Varying Profile A and 3 Step or Pycnocline Profile B Densities may be specified directly or they may be computed based on user specified salinity and temperature data If densities are input directly and the Linearly Varying or Step profile is selected then the densities must refer to the surface and bottom densities In addition if the Step or Pycnocline profile is selected the user must indicate the distance from the bottom of the receiving water body to the location of the pycnocline If densities are computed the program user must supply the salinity in ppt and the temperature Specified and computed densities are in kg m Disposal Operations Data Disposal Operations Data refers to information which describes the density and velocity characteristics of the effluent and the geometry and orientation of the effluent discharge device Entering dredge disposal data is actually a two step process although the process appears seamless to the program user The first step is to supply general information describing the dredge disposal operation with the second step involving presenting data on the particular disposal case 1 e pipeline slurry hopper overflow etc There are two screens associated with the general disposal operat
2. if REGVAL gt 0 otherwise CLEGMZ no 4 WQSTD is automatically set to yes if CCC gt 0 otherwise WQSTD no Program Output The output provided by DROPMIX is currently given in text form and is essentially the output produced by the CORMIX routines Selected output reflecting a hopper overflow discharge case is shown in Table 3 4 CORIMX1 will supply more output than is shown below but most of this additional output is simply an echo of input data DROPMIX User s Manual Page 35 Table 3 4 Selected CORMIX Output CORMIX1 PREDICTION FILE 11111111111111111111111111111111111111111111111111111111111111111111111111111 CORNELL MIXING ZONE EXPERT SYSTEM Subsystem CORMIX1 Subsystem version Submerged Single Port Discharges CASE DESCRIPTION Site name label Example Problem Hopper Dredge Overflow Design case Hopper Dredge Overflowing into Estuary X Y Z COORDINATE SYSTEM ORIGIN is located at the surface and above the center of the port 1000 00 m from the RIGHT bank shore X axis points downstream Y axis points to left Z axis points downward NSTEP 5 display intervals per module BEGIN MOD101 DISCHARGE MODULE FLOW ESTABLISHMENT X Y Z S C B 0 00 0 00 1 00 1 0 0 250E 02 1 00 BEGIN MOD121 WEAKLY DEFLECTED PLUME IN CROSSFLOW Profile definitions B Gaussian 1 e 37 half width normal to trajectory S hydrodynamic centerline dilution C centerline concentration includes reaction effects if an
3. Figure 4 6 illustrates the case where Receiving Water Data and Disposal Operations Data have been supplied Note that information on the Project Title and Site Description and Mixing Zone Data has yet to be provided Input File Saving Menu The Input File Saving Menu is displayed if the user selects the Save data file to disk option from the Data Selection Menu This menu is nearly identical to the Input Data File Selection Menu as can be seen from Figure 4 7 In fact options 1 3 in the file saving menu operate identically to options 1 3 in the file selection menu The only difference between the two menus is the fourth option DROPMIX User s Manual Page 47 Automated Dredging and Disposal Alternatives Management System DROPMIX Dredging Operations Mixing Zone Model DROPMIX Data Selection Menu Fl Project Title and Site Description F2 Receiving Water Data F3 Disposal Operations Data F4 Mixing Zone Data F5 Save data file to disk Esc Return to DROPMIX Activity Selection Menu ACTIVE FILE C DROPMIX channel Sample Data File To Test Channel Velocity Computations Use T ana 4 keys to highlight option and then ENTER to select or press the selection key of the desired option Figure 4 6 Example of Existing Data Selecting this option will cause the active data file to be saved to disk If the file already exists and the file saving option is selected DROPM
4. Regardless of how the dredge material is excavated once the dredged material is removed it must be disposed of in some fashion There are three major alternatives for dredged material disposal 1 Open water disposal 2 Confined disposal and 3 Beneficial use With regard to environmental impacts of disposal on receiving waters the open water and confined disposal alternatives pose the greatest risk As a result they are described in greater detail in the following paragraphs DROPMIX User s Manual Page 4 Open Water Disposal Open water disposal is the act of placing dredged sediments within water bodies such as rivers lakes estuaries or oceans as shown in Figure 2 1 The dredged material may either be transported directly to the disposal site via a pipeline or the material may be shipped to the site and released from hopper dredges or barges The discarded material is discharged at or very near the surface of the receiving waters PIPELINE HOPPER BARGE PLACEMENT PLACEMENT PLACEMENT Figure 2 1 Open Water Dredge Disposal Methods Because dredged material is generally heavier than water sediment that is disposed of through open water means will usually sink to the bottom Material more dense than the receiving water is said to be negative buoyant Of course the material will not settle to the bottom directly below the point of discharge As shown in Figure 2 1 receiving water currents may transport the material some distance aw
5. 5 CDF Effluent Discharge Via Pipe 6 Containment Dike Leakage DROPMIX User s Manual Page 17 Given information describing the receiving water conditions the characteristics of the effluent and the manner in which it is disposed and general information on initial pollutant concentrations DROPMIX will determine the dilution characteristics of the effluent receiving water environment Program output includes the centerline concentration of a pollutant along the trajectory of the contaminant plume and the degree of lateral dispersion perpendicular to the plume trajectory DROPMIX utilizes the CORMIX suite of computer programs to analyze mixing Since discharges associated with dredging operations typically occur at or very near the surface a mirror image transformation is made Using a numerical preprocessing program a negatively buoyant surface discharge is converted to an equivalent positively buoyant bottom discharge This mirror image discharge is then analyzed by the CORMIX modules Modifications to the output routines in the CORMIX programs have been made so that program output is referenced to the surface The data required to perform a complete mixing zone simulation can essentially be subdivided into three categories 1 Data describing the receiving water environment 2 Data describing the effluent and its discharge mechanism 3 Data describing the mixing zone Each of the individual data requirements are described in grea
6. A L H 3 CDF Effluent Discharges DROPMIX assumes that direct effluent discharges not seepage from confined disposal facilities is either routed immediately to the receiving water through a single pipeline or is transported through a channel or side stream for ultimate disposal into the receiving waters In either case the velocity of the effluent is required in order to perform the mixing zone simulation For the case of CDF effluent disposal via a pipeline DROPMIX requires the program user to supply data on the discharge from the CDF and the diameter of the pipeline This information is used with the continuity equation to determine effluent velocity Discharge from a CDF will primarily be due to displacement of supernatant by the dredged discharge and can generally be assumed to be equal to the rate at which material is discharged into the CDF i e steady state conditions Use of the continuity equation shown in Eq 1 implies that the pipeline is flowing full during discharge events The velocity within a stream or open channel can also be found using the continuity equation The program user must supply the channel discharge and geometry For the case of a side stream the discharge within the waterway can be found from a hydrologic analysis of the CDF and any surrounding areas which contribute flow to the channel Two types of open channels are supported by the DROPMIX program 1 rectangular channels and 2 circular pipes For the
7. CORMIX output routines is necessary so that results can be referenced back to the original geometry of the surface or near surface discharge Purpose To address the processes inherent in removal transport disposal storage and general management of dredged material the U S Army Corps of Engineers Waterways Experiment Station USAEWES has developed a computer package that assists engineers planners and dredging operations managers in predicting the fate and behavior of dredged material The personal computer based package is called ADDAMS The Automated Dredging and Disposal Alternatives Management System Schroeder and Palermo 1990 ADDAMS consists of a number of individual computer programs each of which performs a unique function related to dredge material disposal or management One of the ADDAMS modules is the DROPMIX computer program This document serves as the User s Manual for the DROPMIX computer program This manual will provide the necessary guidance so that data files describing various dredge disposal operations can be created executed and interpreted Specifically the program is used to predict the fate and transport of dredged material discharges into a receiving water environment Results from the DROPMIX program typically consist of the physical limits of the mixing zone and the concentration of pollutants within the zone It is assumed that users of the ADDAMS family of programs are already familiar with dredging op
8. Requirements o oo ooooooooooo oo Page 50 Project Title and Site Description o o ooooooooo Page 52 Receiving Water Data lt 6 ki4648 rd a Pes Page 52 Disposal Operations Data 00000008 Page 53 Mixing Zone Dala ie siete a al a Page 54 Example Input Session 1 0 0 00 0 eee eee eee Page 55 REFERENCES ua da BYES Te eS Pa eee ed ees Page 59 Appendix A List of DROPMIX Files 0 002000 0 0 Page A 1 DROPMIX User s Manual Page iii Figure 2 1 Figure 2 2 Figure 2 3 Figure 2 4 Figure 2 5 Figure 2 6 Figure 3 1 Figure 3 2 Figure 3 3 Figure 3 4 Figure 3 5 Figure 3 6 Figure 3 7 Figure 3 8 Figure 3 9 Figure 4 1 Figure 4 2 Figure 4 3 Figure 4 4 Figure 4 5 Figure 4 6 Figure 4 7 Figure 4 8 Figure 4 9 List of Figures Open Water Dredge Disposal Methods Page 4 Examples Of Confined Disposal Facilities Page 5 Sewage Outfall Discharging Into A River Page 7 Example of a Pure Jet and a Pure Plume Page 8 Velocity and Concentration Profile In The Near Field Page 10 Example Of Buoyant Spreading Page 10 CORMIX Representation of a Natural Channel Cross Section ce 64 46 ava gb eae Wd waren ore Oh eee oe Page 16 Possible Receiving Water Density Profiles Page 18 Lateral Spreading Caused By Density Differences Page 21 Dike Leakage Case susu h
9. X Y Z point in the DROPMIX output corresponds to the centerline of the effluent trajectory Sea 11 XYZ where Sxyz The Dilution At Any Point P x y z Ci y The Concentration At Any Point P x y z C The Initial Pollutant Concentration DROPMIX User s Manual Page 38 Figure 3 8 Example of CORMIX X Y Z Coordinate System In addition if a toxic dilution zone or zone of initial dilution defined by the acute toxicity standard CMC or a mixing or chronic toxicity standard CCC is specified the DROPMIX program will indicate if the criterion has been met by printing messages shown below In this particular case the CMC value was 5 0 and the CCC value was 2 0 The concentration units are specified by the program user CMC HAS BEEN FOUND The pollutant concentration in the plume falls below CMC value of 0 500E 01 in the current prediction interval This is the extent of the TOXIC DILUTION ZONE WATER QUALITY STANDARD OR CCC HAS BEEN FOUND The pollutant concentration in the plume falls below water quality standard or CCC value of 0 200E 01 in the current prediction interval This is the spatial extent of concentrations exceeding the water quality standard or CCC value The point where the criterion maximum concentration CMC is met defines the limits of the toxic dilution zone For example in the output shown in Table 3 4 the pollutant concentration falls below the CMC somewhere between 1 95 to 3 04 meters
10. allows program output to be viewed and so on For each individual selection menu the ESC key can be used to exit the menu move to the next higher level menu Note that near the bottom of each selection menu the current data file name is displayed Also presented is a character string describing the currently loaded data file 1 Activity Selection Menu 2 Input Data File Selection Menu 3 Data Selection Menu 4 Input File Saving Menu 5 Execution Data File Selection Menu Activity Selection Menu The Activity Selection Menu shown in Figure 4 2 is the main DROPMIX menu where major program functions are initiated The first option F1 allows existing data files to be edited or new files to be created The second option F2 launches execution of the DROPMIX preprocessor immediately followed by the appropriate CORMIX module F3 will invoke the view or print output option This option will allow the CORMIX output file or any other ASCII file to be viewed through the LIST COM viewer The fourth option is to generate graphics which will allow a pictorial examination of the DROPMIX output Graphics for the DROPMIX program are unavailable at this time The fifth option is to configure hardware for graphics namely the monitor and printer Finally pressing the ESC key will terminate execution of the DROPMIX program Any of the program options may be initiated by pressing the appropriate function key or using the up or down arrow keys to highlight th
11. directly opposes the prevailing current Horizontal angles of 90 and 270 reflect cross flow conditions where the effluent is discharged perpendicular to the receiving water current Figure 3 5 illustrates the vertical and horizontal discharge angles used in the DROPMIX program Figure 3 5 Examples of Horizontal and Vertical Discharge Angles DROPMIX User s Manual Page 27 Pipeline Slurry Discharge The pipeline discharge case is simulated assuming a single port discharge followed by a multi port diffuser discharge Consequently the information needed to describe the orientation of the discharge mechanisms are the vertical and horizontal discharge angles of the pipeline and the vertical horizontal and diffuser axis angles describing the diffuser Figure 3 6 depicts the angles necessary to fully describe the orientation of the pipeline discharge case PIPELINE Figure 3 6 Pipeline Slurry Discharge Case Note in Figure 3 6 that the distance between the pipeline outlet and the diffuser DISTPD is needed This length represents the horizontal distance the effluent will travel before it strikes the bottom of the receiving water channel This distance may be found using vector analysis The composite velocity in the same direction as the effluent stream is a function of the effluent velocity the receiving water velocity and the horizontal and vertical discharge angles The expression below can be used to compute this velocity Un
12. dispersion plume The approach used to model pipeline discharges and subsequent bottom collapse induced mixing involves use of both the CORMIX1 and CORMIX2 modules That portion of the mixing from the mouth of the pipeline to the receiving water bottom is modeled using the CORMIX1 program within a mirror image framework Any subsequent mixing that occurs after the plume strikes the bottom is modeled assuming that the flow resembles flow though a multi port diffuser Thus the CORMIX2 module 1s used however in this case there is no mirror image transformation since the discharge originates at the bottom of the receiving water DROPMIX User s Manual Page 13 Hopper Overflow Discharges As mentioned previously a hopper barge may be allowed to overflow in order to increase the sediment load carried by the vessel This has proven to be an effective method for coarse grained sediments although for fine grained material the effectiveness of this approach is questionable USACE and USEPA 1992 When the barge overflows sediment laden water leaves the vessel and enters the receiving water Not only is the effluent likely to have a higher turbidity than the receiving water but because it has been in contact with the dredged material it may also have trace concentrations of heavy metals toxins or other pollutants Hopper barges typically overflow in an uncontrolled manner The flow may be over one or more sides of the vessel and generally resemble
13. downstream of the origin and 3 88 to 5 32 meters below the water surface Likewise the location where the criterion continuous concentration CCC has been satisfied defines the limits a water quality standard Again referring to Table 3 4 the water quality DROPMIX User s Manual Page 39 standard is met somewhere between 4 20 to 5 42 meters downstream of the discharge point and 6 76 to 8 20 meters below the receiving water surface The final zone is the regulatory mixing zone the limits of which the user identifies DROPMIX will also indicate the dilution and concentration at the limits of the regulatory mixing zone Not only will DROPMIX indicate the effluent trajectory centerline concentrations but it will also supply information describing the size of the effluent plume along its trajectory The quantity BV refers to the thickness of the contaminant plume while BH represents the half width of plume measured normal to the effluent centerline trajectory Figure 3 9 illustrates the usefulness of BV and BH in constructing a three dimensional representation of the contaminant plume Figure 3 9 Three Dimensional Representation of Contaminant Plume DROPMIX User s Manual Page 40 PART 4 USER S MANUAL Getting Started The DROPMIX component of ADDAMS is designed to run in the DOS environment on an IBM or compatible personal computer with 640 KB of RAM and a hard disk The program does not run in extended memory As a result app
14. extends out into the receiving water m and width is the maximum width of the disposal facility The equivalent dike length is found from Lize VYBI width 10 Recall that dike faces which oppose the flow should not be included in the analysis A list of the variables required to completely describe the dredged material disposal environment are provided in Table 3 2 DROPMIX User s Manual Page 31 Table 3 2 Description of Dredged Disposal Variables Name Data Required For Hopper Overflow Dike Leakage and Pipeline Discharge Case THETA Horizontal angle between effluent trajectory and receiving water current SIGMA Vertical angle between effluent trajectory and receiving water current HO Depth from surface to point of discharge HD Depth of receiving water at discharge location Diffuser Data For Dike Leakage and Pipeline Discharge Cases DITYPE Type of diffuser BETA Angle between diffuser discharge direction and diffuser axis GAMM Angle between diffuser axis and receiving water current A THETA2 Horizontal angle between diffuser effluent trajectory and receiving water current SIGMA2 Vertical angle between diffuser effluent trajectory and receiving water current Depth from surface to point of discharge for diffuser H02 D B Y DROPMIX User s Manual Page 32 Table 3 2 Cont Variable Name Description Channel Data For Open Channel Flow Case CHNTY Type of open channel Re
15. found at the centerline of the plume trajectory and lower concentrations normally exist at radial distances from the centerline Far Field Mixing Once the effluent momentum has sufficiently dissipated then the effluent is said to be in the far field and far field mixing processes further dilute the effluent pollutant concentration There are two mixing processes at work in the far field 1 buoyant spreading and 2 passive diffusion Buoyant spreading precedes diffusion and is caused by the relative density differences of the now mixed effluent and the receiving waters Doneker and Jirka 1990 indicate that four types of spreading may occur an example of which is shown in Figure 2 6 1 Spreading at the water surface 2 Spreading at the bottom 3 Spreading at a sharp internal density interface pycnocline or thermocline 4 Spreading at the terminal level However if the effluent is nonbuoyant or weakly buoyant or there are no pronounced density differences within the receiving water then buoyant spreading will not occur and any additional mixing beyond the near fieldwill be due entirely to passive diffusion In other words the turbulence associated with the receiving waters will cause DROPMIX User s Manual Page 10 Figure 2 5 Velocity and Concentration Profile In The Near Field Figure 2 6 Example Of Buoyant Spreading DROPMIX User s Manual Page 11 further dilution of the effluent Like near field mixing mixin
16. of continuous discharge is assumed to be valid With regard to the assumption of steady state flow flow through a pipeline or over a weir will not be truly steady due to minor variances in the flow rate However the time over which these variances occur is generally small compared to the time over which mixing occurs Thus the assumption of steady state flow is assumed to hold Not only is the flow presumed to be steady but the receiving water velocity is assumed to be uniform that is the velocity exhibits the same magnitude everywhere over its entire cross section Changes in receiving water velocities associated with tidal effects may be ignored since these occur over much longer periods of time than mixing occurs hours vs minutes Alternatively if long term mixing results are desired then it is possible to conduct a quasi steady analysis Typically in these cases the results from prior steady state analyses are used as boundary or initial conditions for subsequent analyses Mixing within the receiving water is assumed to be due solely to hydrodynamic processes In other words dilution of the effluent concentrations is assumed to be the result of the interactions between effluent and receiving water velocities densities and geometries The original CORMIX modules assume that the pollutant is a conservative species and that any physical chemical or biological reactions or decay processes do not exist However modifications to the
17. on the screen Instead each variable typically has a range over which it is acceptable If numeric data supplied by the program user falls outside the valid range then DROPMIX will display a warning message indicating such DROPMIX User s Manual Page 50 Each of the spreadsheet screens respond to the four keys listed at the bottom of the display ESC HOME PG UP and PG DN The ESC key returns control to the previous menu without any loss of data The HOME key permits the user to exit from the current data entry screen and return to the most recent menu again with no loss of data The PG UP Page Up key returns control to the most recent data entry screen while the PG DN Page Down key advances to the next data screen Generally speaking there are about two to three data screens for each major data item i e receiving water data disposal data mixing zone data The PG UP and PG DN keys can be used to navigate among the individual data screens As shown in Figure 4 9 descriptive information for the current screen is displayed at the top of each screen If the PG DN key is pressed while the last screen is displayed control will be transferred to the DROPMIX Data Selection Menu DROPMIX Data Requirements Each of the individual data items will be addressed in the following paragraphs However before proceeding to a description of the data items the general format of the DROPMIX data file will be discussed Table 4 3 shows the general
18. rectangular channel the channel width and depth of flow must be provided The product of these two quantities is the flow area which is used in the continuity equation to obtain the effluent velocity For circular pipes the pipe diameter and depth of flow are specified by the program user DROPMIX treats circular pipes flowing partially full as rectangular channels with comparable depths and cross sectional areas For a set of given pipe characteristics diameter and depth of flow one may determine a congruent rectangular channel by equating the area of both sections and solving for the depth of flow in the rectangular channel For a given discharge the equation below provides an expression for the flow depth in a rectangular channel which will have the same area and velocity as a pipe flowing partially full 2 ygs D cos sin 4 4B where Yan Depth of Flow in a Rectangular Channel m B Width of Rectangular Channel m DROPMIX User s Manual Page 24 D Pipe Diameter m 9 Central Angle rad cos 1 2y D y Depth of Flow in a Circular Pipe m Eq 4 will allow an equivalent depth in a rectangular channel y to be computed based on a pipeline that is flowing partially full at a depth of y However in order to compute y the width of the rectangular channel B which is not known must be supplied Consequently the program user must supply an assumed value for the rectangular channel bottom wi
19. specify either Manning s roughness n or Darcy Weisbach friction factor f If Manning s n is given then the preprocessor will convert it to an equivalent Darcy Weisbach friction factor 3 The following convention is adopted for density profiles U Uniform Density Profile A Linearly Varying Density Profile B Two Layer or Pycnocline Density Profile 4 The distance above the receiving water bottom where the pycnocline occurs must only be specified for a Two Layer or Pycnocline Density Profile Dredged Material Disposal Operations Data Dredged material disposal data generally refers to the physical characteristics of the discharged effluent and its discharge mechanism As mentioned earlier six dredged material disposal mechanisms can be analyzed with DROPMIX Although there is certain data that is unique to each discharge case the information required to describe the dredging operations environment is very similar to that of the receiving water Information needed to fully describe the disposal operations are 1 effluent density 2 effluent velocity 3 geometry of the effluent discharge device and 4 orientation of the effluent discharge mechanism with respect to the receiving water current Unlike the receiving water the dredge effluent is not allowed to have multiple densities The density of the effluent is initially assumed to be greater than the surface density of the receiving water so as to preserve negatively buoyant
20. the dike axis makes with the receiving water current must also be supplied However in lieu of directly supplying this information the program user may wish to enable automatic computation of the dike axis angle Hydraulic variables which must be supplied to the DROPMIX program include the rate at which effluent is discharged and the area of over which it is discharged For the pipeline slurry and single port hopper overflow or CDF discharge cases flow is routed through a single pipe For seepage through a porous dike conceptually flow is assumed to pass through a multi port diffuser where each port is assumed to have the same diameter Hence for these cases the diameter of the port must be supplied by the program user In the case of seepage through a CDF port diameters are automatically computed For hopper overflow cases where uncontrolled spillage over the sides occurs the flow length must be supplied The flow area is then found using weir formulas Finally for the side stream discharge case the flow area is determined based on user supplied channel geometry Mixing Zone Data Mixing zone data is furnished to DROPMIX through two data screens The first screen allows the user to enter a nine 9 character string which is used to specify the concentration units or if the user wishes the name of the pollutant The next data item supplied is the concentration of pollutant in the user specified units if units are provided A first order re
21. the vessel makes with the current DROPMIX automatically computes the remaining necessary discharge angles In certain discharge cases the barge may be moving as it releases dredged material This factor is considered by using vector analysis Using the horizontal discharge angle the vessel velocity can be decomposed into two components one component acting in the same direction as the receiving water and another component which is orthogonal to the receiving water direction A composite velocity acting in the same direction as the receiving water current is then found by adding the receiving water current to the velocity component acting in the same direction as the receiving water CDF Effluent Discharges The geometric information needed for direct discharges from a CDF are dependent upon how discharge from a confined disposal facility is modeled If flow is assumed to enter the receiving water from a single pipeline then only the vertical and horizontal discharge angles are needed Figure 3 5 portrays this information DROPMIX User s Manual Page 29 If CDF discharge is modeled as a channel or side stream discharge then three variables are needed to fully describe the orientation of the channel with respect to the receiving water The first variable is a horizonal angle that the channel centerline makes with the receiving water current The second variable is the slope of the receiving water bottom This quantity represents the chang
22. 1 Ay where U Effluent Velocity m s Q Effluent Discharge m s A Area Over Which Discharge Occurs m Pipeline Slurry Discharge Concerning effluent velocities the pipeline slurry discharge case requires data that quite possibly is the easiest of the six discharge cases to obtain The user must specify the flow rate through the pipeline Since pipeline discharges are most frequently used in hydraulic dredging operations the pipeline flow DROPMIX User s Manual Page 22 rate may assumed to be equal to the hydraulic dredge pumping rate The program user must also specify the diameter of the pipe The effluent velocity is then easily found by employing the continuity equation The pipeline slurry discharge case is simulated in DROPMIX as a combination of a single port discharge followed by a multi port diffuser discharge Consequently information describing the physical characteristics of the multi port diffuser must be provided Diffuser information includes the length of the diffuser the number of diffuser ports and the diameter of each port Hopper Overflow Discharges For the hopper overflow case the rate at which effluent leaves the barge is assumed to be equal to the pumping rate of the hydraulic dredge Hopper overflows resulting from mechanical dredging operations should not be simulated with the DROPMIX model Receiving water effects from barge scow or other vessel overflows are found assuming that effluent leav
23. DROPMIX User s Manual IDIRVALP I Prepared For Dr Paul R Schroeder U S Army Engineer Waterways Experiment Station Vicksburg MS 39180 Prepared By Don Chase Ph D P E Department of Civil amp Environmental Engineering University of Dayton Dayton OH 45469 November 1994 DROPMIX User s Manual Page i Table Of Contents PART 1 INTRODUCTION o i 36 4 524 449 ad RS ESS Page 1 Backgto nd e tr ata ta os a et Page 1 Purposesa est sua Woe dha a a E els e e dl de e eA ld o Page 2 O O O A EUS Page 2 PART 2 DREDGE DISCHARGE OPERATIONS AND THE MIXING ZONE Page 3 Dredeing Overview don e veh ete ARAS AOS a ee Page 3 Open Water Disposal 2 0 e ee eee o Page 4 Confined Disposal y a nados Batibo vee eh 4 Page 5 Effect Of Disposal On The Environment Page 6 Overview Of Hydrodynamic Mixing 0 008 Page 6 Near Pield MAS 24 a O02 eo eek A ees Page 9 Far Field Maxine ng 20 ge oe oe eR SEER ok OR Se aS Page 9 Application To Dredging Operations o oo ooo moco ooo Page 11 Dredge Discharge Mechanisms 0 00000 eee o Page 12 Pipeline Slurry Distharges so5 826s a ake lew Dee Page 12 Hopper Overflow Discharges o o ooooooooo oo Page 13 CDF Effluent Discharges sica ini Ohara sa ewe Ss Page 13 Seepage From Confined Disposal Facilities Page 14 PART 3 DATA REQUIREMENTS AND PROGRAM OUTPUT Page 15 Program Limitatio
24. ENTER to select or press the selection key of the desired option Figure 4 2 DROPMIX Activity Selection Menu Table 4 1 Discharge Cases and Appropriate CORMIX Module Discharge Case CORMIX Module Pipeline Slurry Discharges CORMIX1 amp CORMIX2 Hopper Overflow Discharge Single Port CORMIX1 CDF Effluent Discharge Via Channel Side Stream CORMIX3 CDF Effluent Discharge Via Pipe CORMIX1 Containment Dike Leakage CORMIX2 Hopper Overflow Discharge Weir Flow CORMIX2 DROPMIX User s Manual Page 43 appropriate CORMIX module has executed At this point the user may examine program output to determine the characteristics of the mixing zone However if the pipeline discharge case is selected then the interface program will automatically initiate execution of a postprocessor that combines CORMIX1 and CORMIX2 output into a single output file Once this has been accomplished then this simulation is complete Selection Menus There are a total of five menus in the DROPMIX program Each of the menus are listed below and are described in greater detail in subsequent paragraphs For each of the selection menus the up and down arrow keys and the function keys are used to invoke various program options and features For example referring to Figure 4 2 the Fl key is used to edit an existing data file or to create a new file the F2 key is used to initiate execution of the preprocessor and CORMIX modules the F3 key
25. ES 2D GEOMETRY CONTINUED SPAC PORTN D02 LD YB1 YB2 0 100E 00 0 171E 03 0 200E 00 0 343E 02 0 983E 03 0 102E 04 EFFLUE DISHARGE VARIABLES CHANNEL CHNTYP BO HO YO THETAB SIGMAC CHAN 0 000E 00 0 000E 00 0 000E 00 0 000E 00 0 000E 00 EFFLUE DISHARGE VARIABLES HYDRAULIC 00 Uo AO DO RHOO RE2D QOT2D 0 100E 01 0 318E 00 0 314E 01 0 200E 01 0 1004E 04 0 000E 00 0 10E 01 EFFLUE DISHARGE VARIABLES HYDRAULIC CONTINUED FRESHO TO co CUNITS KS KD F 0 000E 00 0 250E 02 ppm 0 000E 00 0 000E 00 IXING ZONE DATA CTOX CMC CCE CLEGMZ CLEGSP REGVAL WQS yes 0 500E 01 0 200E 01 yes width 0 140E 01 yes DIKE LEAKAGE CASE DATA IDKTYP IAUTO DWIDTH WLENGTH 0 0 0 2000E 03 0 3434E 02 DROPMIX User s Manual Page 52 Project Title and Site Description The first data item which will typically be entered is information describing the project title and site description Figure 4 10 shows the screen where narrative information identifying the particular dredge disposal project is provided A total of six lines each 60 characters long are supplied for narrative input The up and down arrow keys can be used to move among the six character lines Once narrative information has been typed the user should press the ENTER key to lock the data into memory gt TITLE INFORMATION SCREEN 1 OF1 Sample Data File To Test Channel Velocity Computations Title 1 Site Name Joe Engineer July 18 1994 Title 2 Site Description Ti
26. IX will indicate that the file exists and provides the program user the choice of saving the data file Any existing file that is saved to disk will be overwritten Automated Dredging and Disposal Alternatives Management System DROPMIX Dredging Operations Mixing Zone Model DROPMIX Input File Saving Menu Fl Enter name of file to be saved F2 Enter DOS path for data file Optional F3 Display directory of input data files F4 Save data in or to the active file Esc Return to DROPMIX data selection menu ACTIVE FILE C DROPMIX channel Sample Data File To Test Channel Velocity Computations Use T and 4 keys to highlight option and then ENTER to select or press the selection key of the desired option Figure 4 7 DROPMIX Input File Saving Menu DROPMIX User s Manual Page 48 DROPMIX provides some error detection before the data file is written to disk Under these circumstances the DROPMIX will notify the program user that an error has been discovered and will then transfer control back to the Data Selection Menu If no errors have been found then the current file will be written to the current directory At this point the ESC key may be pressed and program control will be transferred back to the Data Selection Menu Execution Data File Selection Menu Once the data file has been saved to disk the DROPMIX numerical engines may be executed As mentioned before th
27. PMIX Data File SITE DESCRIPTION Hopper Overflow Case SITNAM Example Problem Hopper Dredge Overflow Page 51 DESCRIPTION OF THE DISCHARGE CASE FOR CONSIDERATION CASE Hopper Dredge Overflowing into Estuary RUN CONTROL P pipeline B pipe2d C channel H hopp EFFTYP ROI NSTEP P 0 100E 04 0 500E 01 AMBIENT WATER VARIABLES GEOMETRIC CBOUND ICHREG BS HA no 0 100E 01 0 000E 00 0 100E AMBIENT WATER VARIABLES HYDRAULIC MAN F UA QA UW 0 150E 01 0 000E 00 0 300E 01 0 000E 00 0 500E 01 AMBIENT WATER VARIABLES WATER COLUMN STRCND RHOA HINT RHOAS RHOAB B 0 9900E 03 0 200E 01 0 1002E 04 0 1003E 04 AMBIENT WATER VARIABLES WATER COLUMN CONTINUED FRESHA TA TAS TAB F 0 000E 00 0 000E 00 0 000E EFFLUE DISHARGE VARIABLES GEOMETRIC CBANK DISTB DISTPD THETA SIGMA HO HD EF 0 100E 04 0 207E 02 0 900E 02 0 000E 00 0 100E 01 0 100E 02 FFLUE DISHARGE VARIABLES 2D GEOMETRY DITYPE BETA GAMMA THETA2 SIGMA2 HO2 AAP 0 900E 02 0 000E 00 0 900E 02 0 900E 02 0 100E 00 FFLUE DISHARGE VARIABL
28. a hopper barge Hydraulic dredges are generally used for loosely compacted materials that are easily disturbed As might be expected hydraulic dredges also transport large volumes of water through the slurry pipeline Because of the high water content associated with hydraulic dredging methods hopper dredges and scows used in these operations are occasionally filled past their rated volume and are allowed to overflow In such cases the heavy material will quickly settle to the bottom of the hopper while fine grained material is held in suspension The liquid that is allowed to overflow will typically have a specific gravity very close to water but may also have a high turbidity cloudy and possibly high concentrations of pollutants if the dredged sediment is contaminated Consequently environmental concerns may preclude the use of hopper overflow to increase sediment loads Mechanical dredges remove bottom material through mechanical or physical means The material is excavated using backhoes buckets draglines etc lifted out of the water and typically placed into a temporary storage facility Alternately dredge material may be placed directly into a permanent disposal facility if a suitable site can be found in close proximity to the dredge site Mechanical dredging activities exhibit the desirable characteristic of removing very little water with the excavated material Consequently excavated densities are very close to in situ densities
29. action constant and a surface heat exchange coefficient is also supplied from this screen DROPMIX User s Manual Page 55 The second screen allows the user to specify if a toxic dilution zone or a water quality standard exist This is accomplished by supplying a positive value for the Criterium Maximum Concentration CMC in which case a toxic dilution zone is assumed to exist In fact the limits of the toxic dilution zone are those areas where the pollutant concentration is higher than the CMC Similarly if the user supplies a positive value for the Criterium Continuous Concentration CCC then a water quality standard is assumed to apply At those locations where the pollutant concentration is higher than the CCC the water quality standard is violated Finally the limits of a regulatory mixing zone may be defined using distance width or area to indicate the extend of the zone Example Input Session Table 4 4 Receiving Water Data Value 1 ICHREG N A N A N A A S M I Not Required if CBOUND No 01 F10 2 Not Required if CBOUND No Low 0 0 m s Medium 2 0 m s High 15 Table 4 5 Dredge Disposal Operations Data Variable Minimum Maximum Units Default Format Notes Possible Values Name Value Value Value Left Right Fos o o F10 5 Data Required For Hopper Overflow Dike Leakage and Pipeline Slurry Discharge Case DITYPE Horizontal Discharge Angle Vertical Discharge Angle Diffuser Data For Dike Leakage and Pipe
30. arge Via Channel Side Stream 5 CDF Effluent Discharge Via Pipe 6 Containment Dike Leakage Pipeline Slurry Discharges A common disposal method particularly for open water disposal operations is to discharge dredged material through a pipeline Pipeline discharges of this sort are most commonly used in concert with hydraulic dredging operations The pipeline transports the dredged slurry a reasonable distance from the dredging site to a location where its deposition will not interfere with navigation or other uses of the water body Effluent from a pipeline will typically have a much higher concentration of suspended solids than the receiving water The effluent could also contain heavy metals toxins or other pollutants that have previously settled to the bottom of the dredged channel and adsorbed to the sediment When effluent discharges from a pipeline it will typically find its way to the bottom of the receiving water This may be accomplished by directing the outlet of the effluent pipe downwards towards the bottom of the receiving waters More likely however the nature of the negatively buoyant effluent will cause the material to sink to the bottom Regardless of the bottom forcing mechanism when the effluent plume strikes the bottom it will begin to disperse or fan out Furthermore the momentum associated with the sinking effluent could disturb dredged material which has previously settled to the bottom thus increasing the size of the
31. articular format for each of the individual data items which make up the DROPMIX data file can be found later in this chapter The first data item which is supplied by the program user is narrative information describing the dredging site and the project in general DROPMIX provides a total of six 6 60 character lines where specific information unique to the dredging project may be placed The first line of narrative information is displayed with the active file name at the bottom of every DROPMIX selection menu The second data item is information describing the receiving water environment Essential data which is entered here includes receiving water density velocity and geometry Part 3 of this manual provides a general description of the input data requirements for the receiving water Similarly selection of the third data item Disposal Operations Data will cause a series of screens to be displayed where data characterizing dredge disposal operations is provided Data of this type includes the dredge discharge effluent density and velocity and information on the type of disposal DROPMIX User s Manual Page 46 Automated Dredging and Disposal Alternatives Management System DROPMIX Dredging Operations Mixing Zone Model DROPMIX Data Selection Menu Fl Project Title and Site Description F2 Receiving Water Data F3 Disposal Operations Data F4 Mixing Zone Data F5 Save data file to disk Esc Ret
32. ay from the original discharge point In addition the density of the receiving water can also influence the movement of discharged material Finally the initial velocity associated with the effluent itself may play a role in the final resting place for disposed sediments The DROPMIX computer program can be used to identify the extent over which material discharged into open DROPMIX User s Manual Page 5 waters will migrate due to the receiving water environment and the nature of the open water disposal method Confined Disposal In some situations open water disposal of dredged material may not be feasible and the material must be stored in a confined disposal facility CDF Generally a confined disposal facility is a man made structure consisting of dikes which enclose a specific disposal area As shown in Figure 2 2 CDF s may either be located entirely on the shore upland adjacent to the shore nearshore or located away from the shore island Several very large man made islands are actually confined disposal facilities for dredged material Figure 2 2 Examples Of Confined Disposal Facilities Dredged material removed by hydraulic or mechanical means can be stored in a CDF However because of the high water content associated with hydraulic dredging methods storage volumes will be greater than if material were excavated using mechanical dredging methods DROPMIX User s Manual Page 6 Effect Of Disposal On The Envi
33. bing to the effects of the receiving water is also dependent upon the buoyancy density of the effluent Discharges that are lighter than water and hence move upwards through the water column are said to be positively buoyant The mixing that occurs in the immediate vicinity of the outfall is dependent upon the characteristics of the effluent and its discharge mechanism The area where the momentum buoyancy and outfall geometry control the shape and size of the discharge plume is termed the near field As the effluent plume rises the initial momentum and buoyancy is dissipated and the effects of the receiving water velocity and density become more pronounced In fact the plume may begin to bend and will eventually start to disperse due to turbulence associated with the receiving water The region where the characteristics of the effluent plume are governed by the receiving water environment is called the far field Once the far field region is encountered the velocity of the receiving water dominates and the effluent will in most cases begin to travel in a downstream direction In other words the receiving water current will begin to carry the effluent away For DROPMIX User s Manual Page 9 most practical problems the extent of the far field is much larger than that of the near field Of course the relative sizes of each field is dependent upon the particular discharge and receiving water characteristics but it is not uncommon for the
34. conditions This will typically result in the effluent continuing to sink to the receiving water bottom even after the initial effluent momentum is dissipated However it is possible that as the effluent plume migrates towards the bottom the density of the diluted effluent and the density of the surrounding water will converge Under these circumstances it is possible that the effluent plume will cease to move downward and will begin to disperse laterally in a direction parallel to the channel bottom as shown in Figure 3 3 CORMIX will model lateral spreading of this sort Within the DROPMIX program effluent density may be specified directly or computed based on user supplied data describing the effluent fluid density and the concentration and density of solids within the effluent DROPMIX User s Manual Page 21 Figure 3 3 Lateral Spreading Caused By Density Differences In addition to the effluent density DROPMIX requires the user to supply the velocity of the effluent exiting from the discharge mechanism In a practical sense the velocity of flow over the sides of a barge or through a dike pipeline or channel is rarely known What is typically known however is the effluent flow rate Consequently DROPMIX does not allow entry of effluent velocities Rather an effluent discharge rate is required and the program will convert the user provided flow rate into an equivalent velocity using the continuity equation shown below y amp
35. ctangular or Pipe Width of rectangular channel HO Depth of flow in open channel P HO YO Distance channel protrudes into waterway B THETA Slope of receiving water bottom SIGMAC Horizontal angle of discharge Hydraulic Data Required For All Four Cases Effluent discharge rate 0 Area over which effluent is discharge DO Diameter of single port discharge pipe Effluent density Reynolds number Total flow through dikes DROPMIX User s Manual Page 33 Mixing Zone Data The final bit of information required before DROPMIX can conduct a mixing zone simulation is data on initial pollutant concentrations and data on the mixing zone itself For the most part this data is not used in the mixing zone calculations Rather the information is used for information purposes in terms of indicating the limits of the mixing zone and other regulatory zones For example two pieces of mixing zone information required by DROPMIX are the criterion maximum concentration CMC and the criterion continuous concentration CCC The criterion maximum concentration CMC indicates the level of pollutant concentrations above which acute or lethal effects may occur To prevent potentially lethal concentrations of toxins the CMC must be met a short distance from the effluent discharge mechanism The limits of the zone where the pollutant concentration is higher than the CMC is termed the toxic dilution zone The U S Environmental Pro
36. dary Z coordinate ZL upper plume boundary Z coordinate S hydrodynamic average bulk dilution C average bulk concentration includes reaction effects if any Control volume inflow Xx Y Z S C B 5 42 0 00 8 20 14 7 0 170E 01 1 23 Control volume outflow X Y Z S C BV BH ZU ZL 13 20 0 00 10 00 25 00 100E 01 1 60 15 56 10 00 8 40 Cumulative travel time 17 sec END OF MOD132 LAYER BOUNDARY IMPINGEMENT UPSTREAM SPREADING BEGIN MOD141 BUOYANT AMBIENT SPREADING Profile definitions BV top hat thickness measured vertically BH top hat half width measured horizontally in Y direction ZU lower plume boundary Z coordinate ZL upper plume boundary Z coordinate S hydrodynamic average bulk dilution C average bulk concentration includes reaction effects if any Plume Stage 1 not bank attached X Y Z S C BV BH ZU ZL 13 20 0 00 10 00 25 00 100E 01 1 60 15 56 10 00 8 40 REGULATORY MIXING ZONE BOUNDARY In this prediction interval the plume distance meets or exceeds the regulatory value 1000 00 m DROPMIX User s Manual Page 37 Table 3 4 Concluded This is the extent of the REGULATORY MIXING ZONE 1010 56 0 00 10 00 69 90 357E 00 0 43 161 44 10 00 9 57 2007 92 0 00 10 00 166 8 0 150E 00 0 67 249 84 10 00 9 33 3005 28 0 00 10 00 345 7 0 723E 01 1 06 325 47 10 00 8 94 4002 64 0 00 10 00 621 50 402E 01 1 58 394 26 10 00 8 42 5000 00 0 00 10 00 1005 9 0 249E 01 2 19 458 33 10 00 7 81 Cumulative
37. density of the receiving water The density of the effluent The geometry of the receiving body of water O The geometry of the effluent discharge mechanism Discharges into a receiving stream may be subdivided into two fundamental classes a pure jet and a pure plume Fischer et al 1979 Holley and Jirka 1986 A pure jet occurs when the discharge into the receiving environment is caused solely by the momentum or velocity associated with the effluent A pure plume on the other hand has NO momentum affiliated with it Rather the movement into the receiving environment is due entirely to a difference in densities between the effluent and the receiving fluid 1 e one fluid is lighter than the other A large number of discharges are a combination of a pure jet and a pure plume Discharges where both momentum and buoyancy play a role in the shape and movement of the discharge plume are called buoyant jets or forced plumes Regardless of the mechanism by which effluent is introduced into the receiving environment the effluent will generally surge into the receiving fluid thereby forming a cloud or plume DROPMIX User s Manual Page 8 Figure 2 4 Example of a Pure Jet and a Pure Plume When effluent is released from a discharge mechanism pipe diffuser etc the momentum velocity affiliated with the effluent will typically dominate over the receiving water velocity Likewise the distance the effluent column travels before succum
38. directly or can be determined automatically by the program The next section provides details on diffuser lengths 5 where D Diffuser Port Diameter m Qr Cumulative Discharge Through Porous Dikes m s U Effluent Velocity 0 02 m s Np Number of Diffuser Ports 10 000 DROPMIX User s Manual Page 26 Dredge Discharge Orientation Data The final component of dredged material disposal data is the orientation of the discharge mechanism CORMIX requires information describing the positioning of the discharge mechanism in relation to the receiving water current Although the particular data which must be supplied is dependent upon the particular discharge case each of the six cases requires information describing the vertical and horizontal discharge angles The vertical discharge angle O is the angle in the X Z plane the effluent device centerline makes with the receiving water surface An angle of 0 reflects a discharge case where flow is parallel to the water surface A value of 90 indicates that flow is oriented vertically downwards whereas a value of 45 refers to the case where discharge is occurring upwards at an angle of 45 with the water surface The horizontal angle O is the angle in the X Y plane measured with respect to the receiving water current Thus an angle of 0 indicates a co flowing case where flow is parallel to the current while a value of 180 describes a counter flowing case i e flow
39. dth and compute the depth of flow accordingly The approach outlined above will insure that the velocity in the rectangular section is the same as the velocity in the circular pipe for the same effluent discharge rate This is key since effluent velocity and not effluent discharge is the critical parameter in evaluating receiving water quality effects Channels used to transport releases from upland CDF s to receiving waters may be natural or man made In either case it is quite possible that the channel will not exhibit a true rectangular shape Under these circumstances an equivalent rectangular cross section must be provided An analysis similar to the one described above can be used The cross sectional area of the actual channel and a rectangular channel are equated and solved assuming a fixed bottom width The solution will provide the flow depth such that both channels have the same velocity Seepage From Confined Disposal Facilities For the case of leakage from a confined disposal facility the user must specify the total discharge through all porous dikes which contribute flow to the receiving waters However this may not include each and every side of the facility At present CORMIX is unable to model counter flowing discharges that is discharges where the effluent direction is opposite the receiving water direction Figure 3 4 shows a three sided nearshore CDF used to store dredged material Of the three sides side A opposes the cu
40. e The CORMIX system consists of three separate modules 1 CORMIX1 2 CORMIX2 and 3 CORMIX3 The CORMIX1 module is used to examine submerged single port discharges the CORMIX2 model is used to address submerged multiport diffuser discharges and the CORMIX3 program is used to analyze surface discharges from channels The CORMIX model was originally developed to address bottom discharges with low suspended solids concentrations Such discharges are typically associated with municipal wastewater or industrial waste outfalls Dredged disposal operations on the other hand typically involve surface or near surface discharges with high suspended solids concentrations Consequently the existing CORMIX package is not directly applicable However CORMIX may be used if surface discharges from dredge disposal operations are made equivalent to the mirror image of bottom discharges This fundamental assumption is the foundation for the Dredging Operations Mixing Zone Model DROPMIX DROPMIX User s Manual Page 2 Instead of modifying the existing set of CORMIX programs to analyze surface or near surface discharges a separate computer program was developed Havis 1994 This preprocessor program takes data describing typical dredge discharge activities and transforms the information into an equivalent mirror image bottom discharge scenario with sedimentation As a result the existing CORMIX models are used However some slight modifications to the
41. e displayed at the bottom of the menu then the data filename can be directly specified by using option Enter name of data file to be used during execution Alternately option 3 can be selected causing all files ending in a DRI extension to be displayed on the screen The up and down arrow keys may then be used to highlight a particular file Pressing the ENTER key will select the file and make it active Selecting option four Execute DROPMIX with selected file will initiate the two step program execution process The active file displayed at the bottom of the screen will be the file used in the mixing zone analysis DROPMIX User s Manual Page 49 DROPMIX Data Entry Data is entered into the active file in a spreadsheet fashion A series of screens each containing a series of major data items is displayed and specific information is requested as shown in Figure 4 9 The up and down arrow keys and the TAB key may be used to move between the individual data items Once data for a particular item has been supplied the ENTER key must be pressed to lock the data into memory After the ENTER key is pressed the cursor automatically moves to the next data item gt RECEIVING WATER DATA SCREEN 1 OF 3 4 ENTER THE MEAN DEPTH OF THE RECEIVING WATER m 20 00 IS THE RECEIVING BODY OF WATER NARROW OR IS THE DISCHARGE Y LOCATION CLOSE TO A BOUNDARY Y or N Examples
42. e in receiving water bottom elevation from the point where the channel discharges to the point where the average receiving water depth is reached Finally the distance the channel protrudes out into the receiving water must be supplied Each of the geometric variables described above are shown in Figure 3 7 Figure 3 7 Channel Discharge Case Seepage From Confined Disposal Facilities The geometric description of the dike leakage case is somewhat more involved than the hopper overflow or CDF discharge cases due to the presence of multiple diffuser ports As before the vertical and horizontal discharge angles for the diffuser ports must be specified In addition the orientation of the dike itself in relation to the receiving water current must be provided Assuming that the individual discharge ports are perpendicular to the dike axis a relationship between the port discharge direction and dike axis angles exists as shown below DROPMIX User s Manual Page 30 y 6 8 where o Horizontal Discharge Angle deg y Dike Axis Angle deg For confined disposal facilities with multiple faces a single equivalent dike face is assumed to discharge effluent The user is required to supply the maximum distance the CDF extends out into the receiving water and the width of the facility DROPMIX will then compute the dike axis angle y using the following equation YB1 9 tan Width where YB1 is the maximum distance the CDF
43. e option and then pressing the ENTER key Input Data File Selection Menu Pressing the F1 key Build or edit input data file will summon the Input Data File Selection Menu as shown in Figure 4 3 As before the various program options can be invoked by pressing the pertinent function key or using the arrow keys to highlight the option and then pressing the ENTER key Pressing the ESC key will return control the DROPMIX Activity Selection Menu DROPMIX User s Manual Page 44 Automated Dredging and Disposal Alternatives Management System DROPMIX Dredging Operations Mixing Zone Model DROPMIX Input Data File Selection Menu Fl Enter name of input data file to be built or edited F2 Enter DOS path to data file storage location Optional F3 Display directory of input data files F4 Build or edit input data file Esc Return to DROPMIX Activity Selection Menu ACTIVE FILE C DROPMIX channel Sample Data File To Test Channel Velocity Computations Use T and 4 keys to highlight option and then ENTER to select or press the selection key of the desired option Figure 4 3 DROPMIX Input Data File Selection Menu The first option allows the name of the active data file to be entered Active files may either be existing files or new files that have yet to be created When this feature is used the line displaying the active or current data file will be hig
44. eiving waters are modeled by transforming the problem into an equivalent bottom discharge problem This is accomplished by creating a mirror image of the surface discharge problem using a preprocessor program Havis 1994 The preprocessor program generates a data file representing the equivalent bottom discharge case for the CORMIX model CORMIX analyzes the bottom discharge case to generate information on the mixing zone and pollutant plume This information includes the location and concentrations of effluent within the receiving waters The majority of effort required to transform a surface discharge case into an equivalent mirror image bottom discharge scenario is affiliated with the effluent and receiving water densities For the CORMIX routines receiving water density profiles are referenced to the receiving water bottom However for dredged material disposal density differences are referenced to the water surface Also the CORMIX programs reference step density changes to the bottom Once again a transformation must be made to reference any step changes to the surface DROPMIX User s Manual Page 12 Dredge Discharge Mechanisms Six types of surface or near surface discharges are accommodated by the DROPMIX program Each discharge case is described in greater detail in the following paragraphs 1 Pipeline Slurry Discharges 2 Hopper Overflow Discharge Single Port 3 Hopper Overflow Discharge Weir Flow 4 CDF Effluent Disch
45. erations Scope This document is subdivided into four parts Part 1 provides a brief introduction to the DROPMIX computer program Part 2 gives a more thorough discussion of dredged material disposal operations within the context of the DROPMIX program Part 3 provides a summary of the data requirements and Part 4 addresses the particular data format required by the DROPMIX program DROPMIX User s Manual Page 3 PART 2 DREDGE DISCHARGE OPERATIONS AND THE MIXING ZONE Dredging Overview Dredging is the act of removing or excavating sediments from the bottom of bodies of water and is typically performed in order to maintain navigable channels in inland and coastal waterways Maintaining such channels helps to promote commerce and national defense readiness The dredging process typically refers to the removal transport storage and placement or disposal of dredged material For any dredging project each element of the dredging process must be properly analyzed and designed and the various components which comprise the project must be carefully coordinated to insure a successful cost effective and environmentally safe completion of the project Sediment can be removed from the bottom of a waterway either through hydraulic or mechanical means Hydraulic dredges remove sediment in a liquid slurry form through use of a suction pump The sediment is then pumped from the dredging site to a disposal site or to a transportation vessel such as
46. es the vessel as 1 weir flow or 2 flow through a single pipe or port As mentioned previously hoppers are frequently allowed to overflow in order to increase the sediment load carried by the vessel Usually the overflow is uncontrolled that is flow is allowed to spill over one or more sides of the vessel In some cases however the overflow is captured and routed to a common point on the vessel where it is then discharged generally through a pipeline into the receiving waters For overflow discharged through a single port the velocity of the effluent is found using the continuity equation assuming that the port is a circular pipe As a result the user must supply the overflow rate and the diameter of the pipe DROPMIX can also simulate uncontrolled overflows assuming that the flow acts as weir flow Once again the continuity equation may be used to determine the effluent velocity however the unknown in this case is the area over which flow occurs If the overflow rate and the length over which flow occurs is known then the height or head above the weir can be found by the weir equation H y o Cy Lo where H Height of Effluent Above the Weir m Q Effluent Discharge m s L Hopper Overflow Length m C Weir Coefficient 1 88 Once the height above the weir is known then the flow area is simply the product of the overflow length L and the weir height as shown below DROPMIX User s Manual Page 23
47. format of the DROPMIX data file A constant pattern is maintained throughout the file As shown below a line of text numeric data is preceded by two lines of descriptive information The first line provides general information indicating the general use of the variables The next line of information contains the variable names of the individual data items The third and final line contains the values of the variables Each three line segment of data is separated by a blank line Definitions of the individual variables were given in Tables 3 1 through 3 3 Tables 4 4 through 4 6 provide information on the format and possible range of values for each data item AMBIENT WATER VARIABLES GEOMETRIC CBOUND ICHREG BS HA no 0 100E 01 0 000E 00 0 100E 02 AMBIENT WATER VARIABLES HYDRAULIC MANN F UA QA UW 0 150E 01 0 000E 00 0 300E 01 0 000E 00 0 500E 01 The format of the DROPMIX data file is the same regardless of the discharge case analyzed Although all data is read certain data which is applicable to a given discharge case is not used at all For example the two dimensional effluent discharge variables GAMMA SIGMA2 THETA2 etc are not used in any computations if a single port discharge case is analyzed Such an approach allows a consistent data file structure to be maintained regardless of the actual discharge case described by the data file DROPMIX User s Manual Table 4 3 Typical DRO
48. g within the far field will occur in a longitudinal direction parallel to the receiving water current and in a direction perpendicular to the current It is extremely important to point out that the geometry of the receiving water plays a major role in far field mixing since it is possible that the effluent may come in contact with and attach itself to the bank or receiving water bottom Application To Dredging Operations The description of hydrodynamic mixing presented above is valid for subaqueous bottom discharges that are commonly associated with point source emissions from industry or municipalities Dredging operations on the other hand involve discharges that occur at or very near the receiving water surface Fortunately the mixing behavior of negatively buoyant surface discharges can be fully described by the physics of positively buoyant bottom discharges The fundamental assumption which allows bottom discharges to be used to model surface discharges can be stated as follows Negatively Buoyant Surface Discharges The Mirror Image of Positively Buoyant Bottom Discharges In order for results to be meaningful however the boundary conditions of the surface discharge problem must be transformed to remain consistent with the equivalent boundary conditions for the bottom discharge problem This is the approach taken in the DROPMIX computer model The mixing characteristics of surface or near surface dredge related discharges into rec
49. hlighted and the program user will be able to type in any valid filename DROPMIX assumes that all data files end with a DRI extension As a result file extensions should not be provided If the file name supplied to DROPMIX is the name of a file that does not exist then the user will be given the option to create the file All data files are assumed to reside in the same directory as the DROPMIX subdirectory In order to manage the location of data files more effectively the current directory may be changed to a user supplied name This can be accomplished through the section menu option Enter DOS path to data file storage location If this option is used then a line near the bottom of the menu will be highlighted and the program user may type the name of any existing subdirectory The third menu option Display directory of input data files is a very convenient option that will display the eight letter DOS filename of every file ending in a DRI extension Figure 4 4 shows an example of the screen that will be presented if this menu item is selected It is possible that files displayed with this option may not be DROPMIX data files since every file ending with a DRI extension regardless of its origin or purpose will be displayed DROPMIX data files can be selected by using the up and down arrow keys to highlight the file of interest and then pressing the ENTER key This procedure will cause the selected file to become the active or cur
50. ie ie eee eo Bees Page 25 Examples of Horizontal and Vertical Discharge Angles a eh hake A RAS eed Page 26 Pipeline Slurry Discharge Case o o o o oooooocoooooo oo Page 27 Channel Discharge Case o a Ye do Page 29 Example of CORMIX X Y Z Coordinate System Page 38 Three Dimensional Representation of Contaminant Plume sevi ad oe A ee Bee ee Page 39 Interrelationship Between DROPMIX Modules Page 41 DROPMIX Activity Selection Menu Page 42 DROPMIX Input Data File Selection Menu Page 44 Display Directory of Input Data Files Screen Page 45 DROPMIX Data Selection Menu o oo oo ooocoo momo oo Page 46 Example of Existing Data se ii Wages Page 47 DROPMIX Input File Saving Menu Page 47 DROPMIX Execution Data File Selection Menu Page 48 Sample DROPMIX Spreadsheet For Data Entry Page 49 Figure 4 10 Project Title and Site Description Screen Page 52 DROPMIX User s Manual Page 1 PART 1 INTRODUCTION Background Each year several hundred million cubic yards of sediment are removed from rivers waterways ports and harbors within the United States The primary purpose of these dredging activities is to maintain inland and coastal navigation and coastal defense readiness Given the nature of dredging operations the processes involved in removing transporting storing and disposing dredged material
51. ions data The first screen requests input describing the particular discharge case the maximum distance over which the mixing simulation is modeled and the number of reporting intervals used in generating program output The dredged disposal discharge case may be one of six possible cases as shown below The maximum distance over which the plume is modeled represents the horizontal distance X direction over which computations will be carried out Finally the number of reporting intervals represents the number of locations where the plume centerline position will be determined and the pollutant concentration will be computed P Pipeline Slurry Discharges H Hopper Overflow Discharge Single Port W Hopper Overflow Discharge Weir Flow C CDF Effluent Discharge Via Channel Side Stream E CDF Effluent Discharge Via Pipe D Containment Dike Leakage The second general disposal operations screen allows information on the effluent density to be supplied Like the receiving water density the effluent density may either be specified directly or it can be computed based on user supplied data There is no density stratification allowed for the discharged effluent If the user wishes to compute effluent density then the salinity and temperature of the fluid portion of the effluent must be provided In addition the specific gravity and concentration of solids within the effluent must be furnished DROPMIX will then compute the ove
52. is is a two step process The first step is to execute the preprocessor which converts the data describing surface or near surface discharge conditions into an equivalent bottom discharge problem The second step is to run the appropriate CORMIX model using a separate data file created by the preprocessor which depicts bottom discharge conditions Once the DROPMIX modules have run to completion the output produced by CORMIX may be viewed Automated Dredging and Disposal Alternatives Management System DROPMIX Dredging Operations Mixing Zone Model DROPMIX Execution Data File Selection Menu Fl Enter name of data file to be used during execution F2 Enter DOS path to data file storage location Optional F3 Display directory of execution data files F4 Execute DROPMIX with selected file Esc Return to DROPMIX Activity Selection Menu ACTIVE FILE C DROPMIX channel Sample Data File To Test Channel Velocity Computations Use T and 4 keys to highlight option and then ENTER to select or press the selection key of the desired option Figure 4 8 DROPMIX Execution Data File Selection Menu The format of the Execution Data File Selection Menu is the same as the Input Data File Selection Menu and the Input File Saving Menu The first three options operate identically for all three menus Thus if one wishes to analyze a file different from the active fil
53. isrpp Ua cos a Ucos 6 DROPMIX User s Manual Page 28 where Upistpp Horizontal Effluent Velocity m s U Receiving Water Velocity m s Uo Effluent Velocity m s Vertical Discharge Angle rad O Horizontal Discharge Angle rad The time required for the effluent plume to travel from the pipeline to the receiving water bottom is found from Eq 7 Once the travel time is known it is multiplied by the composite velocity Upjstpp to find the distance traveled DISTPD t Usin H 7 where t Time For Effluent To Travel From Pipeline To Channel Bottom sec U Effluent Velocity m s Vertical Discharge Angle rad H Mean Receiving Water Depth at Discharge Location m Hopper Overflow For the hopper overflow case the only geometric information needed to fully describe the discharge orientation are the vertical and horizontal discharge angles and the distance below the water surface where effluent enters the receiving water If overflow is through a single port then the vertical angle is the angle the pipe makes with the water surface and the horizontal angle is the angle the pipeline makes with the receiving water current as shown in Figure 3 5 If on the other hand overflow is simulated as weir flow then the user must specify the vertical discharge angle and the angle the vessel makes with the receiving water current Typically for weir flow the vertical angle will be 90 Based on the angle
54. limits of the near field to be five percent or less of the far field The CORMIX set of programs will identify where the transition from the near field to the far field occurs Near Field Mixing A very short distance from the outfall mechanism the effluent will begin to mix with the receiving water As the effluent mixes with the receiving water the concentration of any pollutants present within the effluent will begin to decrease In other words the effluent will become diluted As might be expected the concentration of any pollutant will generally decrease as the distance from the mouth of the discharge mechanism increases In fact the dilution for a pure jet is linearly proportional to the distance from the discharge point For a pure plume the dilution varies with the distance squared Thus for a buoyant jet that is a discharge case that has both initial momentum and buoyancy the pollutant concentration will decrease with distance at a rate that varies between the rate for a pure jet and a pure plume Within the near field not only does the pollutant concentration decrease along the plume trajectory but the pollutant concentration also radiates outward perpendicular to the trajectory as illustrated in Figure 2 5 Generally the concentration profile exhibits a Gaussian or Normal probability distribution as it radiates outward from the trajectory centerline Regardless of the distance from the discharge point the maximum concentration can be
55. line Slurry Discharge Case UAP Dike Leakage Case AAP Slurry Case 360 0 degrees F10 5 Avoid Counter Discharges F10 5 90 Recommended ros Table 4 6 Mixing Zone Data Variable Minimum Maximum Units Default Notes Possible Values a ce EN Value cunts E D Distance W Width A Area DROPMIX User s Manual Page 59 REFERENCES Havis R N 1994 Mixing Zone Simulation Model For Dredge Overflow and Discharge Into Inland and Coastal Waters U S Army Corps of Engineers Waterways Experiment Station Vicksburg MS June 1994 Doneker R L and Jirka G H 1990 Expert System for Hydrodynamic Mixing Zone Analysis of Conventional and Toxic Submerged Single Port Discharges CORMIX1 U S Environmental Protection Agency Environmental Research Laboratory Athens GA February 1990 Schroeder P R and Palermo M R 1995 The Automated Dredging and Disposal Alternatives Management System ADDAMS Environmental Effects of Dredging Technical Note EEDP 06 12 U S Army Engineer Waterways Experiment Station Vicksburg MS Holley E R and Jirka G H 1986 Mixing In Rivers Technical Report E 86 11 U S Army Engineer Waterways Experiment Station Vicksburg MS Fischer H B List E J Koh R C Y Imberger J and Brooks N H 1979 Mixing in Inland and Coastal Waters Academic Press New York N Y U S Army Corps of Engineers and U S Environmental Protection Agency 1992 Evaluating Enviro
56. must be carefully managed to insure that dredging projects are completed in a cost effective and environmentally safe manner Of central concern in dredging operations is the impact of discharges on the receiving water environment As such the creation migration and dilution of a discharge plume is of considerable interest as is the size of a required mixing zone for adequate dilution A mixing zone is a limited volume of water that serves as a zone of initial dilution in the immediate vicinity of the point where material is discharged into the receiving waters Within this zone the quality of the receiving waters once mixed with the discharged effluent may not meet water quality criteria or standards otherwise applicable to the receiving water Most states limit the size of the mixing zone and hence the area where water quality standards may be violated to as small a size as practical For example 17 states restrict the size of the mixing zone in streams to 25 or less of the stream s cross sectional area USEPA 1990 Several mathematical models are available for estimating the growth and movement of discharge plumes caused by subaqueous emissions One of these models the Cornell Mixing Zone Expert System CORMIX was specifically developed to provide a predictive tool for conventional or toxic pollutant discharges into waterways The CORMIX model focuses on the geometry and dilution characteristics of the initial or near field mixing zon
57. nmental Effects of Dredged Material Management Alternatives A Technical Framework EPA842 B 92 008 November 1992 Appendix A Table A 1 List of DROPMIX Files Program Type of Description Name File DROPMIX DROPMIX interface program PREPRO Executable Preprocessor which converts surface discharge into mirror image bottom discharge HYDRO1 CORMIX 1 Single port bottom discharge model HYDRO2 CORMIX2 Multi port bottom discharge model HYDRO3 CORMIX3 Surface discharge model POSTPRO Postprocessor for pipeline discharge case
58. ns and Assumptions 00 Page 15 Input Data Requirements xl Gd oe oecd este eo wa Page 16 Receiving Water Data 2 2 24 eseg hc ken aa doe hes han Page 17 Dredged Material Disposal Operations Data Page 20 Pipeline Slurry Discharge ooooooocoocoooo oo Page 21 Hopper Overflow Discharges 0 0008 Page 22 CDF Fffluent Discharges 24 203 dl et he eae ne Page 23 Seepage From Confined Disposal Facilities Page 24 Dredge Discharge Orientation Data 4 Page 26 Pipeline Slurry Discharge 2 ach Se bad cia ee eee Page 27 Hopper Overlow nadas a by eas ea ae ae ee es Page 28 CDF Effluent Discharges 00 6634 ba eta Sd LS YRS wes Page 28 Seepage From Confined Disposal Facilities Page 29 Mixing Zone Data ca casada ata A os Page 33 PTOS DPI a eE sha tee hte ee eke Page 34 DROPMIX User s Manual Page 11 PARSE aos NS Se wok dt e Be Sew aes Page 40 Getting Started ts grita Hoe at hee Page 40 The DROPMIX Environment ocre wae a SO Page 40 Selection Men s LL EA 9 2a ERG OE AR A Page 43 Activity Selection Menus 44 S440 4444 42 hears ae es Page 43 Input Data File Selection Menu Page 43 Data Selection Ment Gps pa a et ieee KOS Re ee OR Page 45 Input File Saving Menu 40 44 E 3 Page 46 Execution Data File Selection Menu Page 48 DROPMIX Data ENY oiis a E gt ee Page 49 DROPMIX Data
59. of narrow waters are rivers and streams Lakes and coastal areas are not considered narrow INDICATE THE TYPE OF CHANNEL GEOMETRY S S STRAIGHT UNIFORM CHANNEL M MODERATELY MEANDERING NONUNIFORM CHANNEL I STRONGLY WINDING IRREGULAR CHANNEL Far field dispersion can be affected by the shape of the channel containing the receiving waters ENTER THE WIDTH OF THE RECEIVING WATER m 0 00 The width of the receiving water is used to determine if the disposal material adheres to the bank for waters which are bounded lt Esc gt Exit lt Home gt Main Menu lt Pg Up gt Previous Menu lt Pg Dn gt NEXTMenu Figure 4 9 Sample DROPMIX Spreadsheet For Data Entry DROPMIX data may either be numeric or text based Referring to Figure 4 9 an example of a text based variable is CBOUND which is used to indicate whether or not the body of receiving water is bounded Possible values for CBOUND are yes or no All valid entries for text based data are shown on the spreadsheet as illustrated by the INDICATE THE TYPE OF CHANNEL GEOMETRY data item However most of the DROPMIX data is numeric An example of a numeric data item is HA the mean depth of the receiving water assuming a rectangular channel Although in some cases typical values are provided valid entries for numerical data are not shown
60. ogram option An example of the Activity Selection Menu is shown in Figure 4 2 Once all data has been supplied and the file is saved then the interface program will generate a data file compatible with the numerical preprocessor When a DROPMIX simulation is requested the interface program will execute the preprocessor The preprocessor will take the data describing a surface or near surface discharge and transform it into an equivalent mirror image bottom discharge problem The preprocessor will then create a data file that will be read by the appropriate CORMIX model i e CORMIX1 CORMIX2 or CORMIX3 At this point control is transferred back to the interface program where the next step is to initiate execution of the appropriate CORMIX model Table 4 1 indicates which CORMIX modules are executed For the hopper overflow channel side stream discharge and containment facility leakage cases the simulation is complete after the DROPMIX User s Manual Page 42 Automated Dredging and Disposal Alternatives Management System DROPMIX Dredging Operations Mixing Zone Model DROPMIX Activity Selection Menu Fl Build or edit input data file F2 Execute DROPMIX F3 Print or view output F4 Generate graphics F5 Perform hardware configuration for graphics Esc Quit ACTIVE FILE C DROPMIX TEST TEST DAT A SAMPLE FILE Use T and 4 keys to highlight option and then
61. omputations to generate information describing the plume location plume geometry and pollutant concentration within the plume as a function of time Overview Of Hydrodynamic Mixing Consider a subaqueous outfall from a municipal wastewater treatment plant which discharges into a water body as shown in Figure 2 3 A number of questions regarding the discharge case can be asked How far will the plume of significant concentration move in the downstream direction How far will the plume exceeding water quality standards move laterally across the river s cross section What is the concentration of a specific pollutant 5 50 or even 500 meters downstream of the discharge point If the stream is only 15 meters wide and the mixing zone is restricted to 25 of the stream s width is this discharge case in compliance Clearly a myriad of questions regarding the geometric and pollutant characteristics of the discharge scenario can be asked not only by design engineers but by regulating agencies as well Fortunately such questions can be answered with the assistance of mathematical models such as CORMIX that have been specifically developed to address aqueous discharges of this sort The major variables needed to quantify the impact of the discharge on the receiving water include DROPMIX User s Manual Page 7 Figure 2 3 Sewage Outfall Discharging Into A River The velocity of the receiving water The velocity of the effluent The
62. ples of bounded channels include rivers streams or even narrow harbors Examples of unbounded channels include wide lakes estuaries and coastal areas In some cases it may not be clear whether the receiving water is bounded or unbounded Under these circumstances the program user should perform multiple simulations assuming bounded and unbounded conditions and make appropriate engineering decisions accordingly Receiving water geometry is also described by the average or mean depth and the bottom roughness As mentioned previously CORMIX assumes that the receiving water body can be characterized as a rectangular channel Thus the depth specified by the program user represents the depth of the rectangular section Bottom roughness values A y may be specified either in terms of Manning s n value or a Darcy Weisbach friction factor f Table 3 1 lists receiving water variable names and a brief description of their meaning Table 3 1 Description of Receiving Water Variables Name na MANN Manning s n for bottom roughness 2 Darcy Weisbach friction factor f for bottom roughness 2 y HINT Distance from bottom of water body where density step occurs 4 UA W DROPMIX User s Manual Page 20 Notes 1 If the receiving water body is unbounded then the degree of channel meandering and the width of the channel does not have to be specified These variables are only applicable to for bounded channels 2 The user must
63. program have incorporated first order reaction processes Havis 1994 Field studies suggest that results of CORMIX simulations accurately predict the mixing and the subsequent migration of contaminant plumes Doneker and Jirka 1990 DROPMIX User s Manual Page 16 CORMIX assumes that regardless of its natural cross section the receiving water body can be modeled as a rectangular channel as shown in Figure 3 1 For many artificial waterways and well channelized natural streams this assumption is clearly valid and hence selection of receiving water geometry channel width and depth is rather straightforward However for natural streams having irregular cross sectional geometry selection of this data is not as apparent Consequently engineering judgement plays a major role in identifying channel geometry The astute program user will conduct multiple simulations varying channel geometry to obtain an intuitive feel for the sensitivity between model input and output Figure 3 1 CORMIX Representation of a Natural Channel Cross Section Input Data Requirements The primary function of DROPMIX is to analyze mixing of effluent from dredging operations discharging into inland and coastal waterways and at ocean dumping sites The model can accommodate six discharge scenarios 1 Pipeline Slurry Discharges 2 Hopper Overflow Discharge Single Port 3 Hopper Overflow Discharge Weir Flow 4 CDF Effluent Discharge Via Channel Side Stream
64. rall effluent density with units in kg m DROPMIX User s Manual Page 54 Once the general disposal operations data has been supplied then specific information for the selected dredge disposal case may be supplied The particular information required for each discharge case is a function of the case itself but typically this data includes a description of the hydraulic and geometric characteristics of the discharge mechanism With regards to the geometric properties of the discharge mechanism DROPMIX requires the user to specify which bank LEFT or RIGHT is closest to the point of discharge In addition the distance from the bank to the discharge location must be furnished Finally the depth below the surface where the effluent enters the receiving water must also be provided These three items are used in part to establish the origin of the discharge scenario The depth to the bottom of the receiving water body at the point of discharge is also used in the DROPMIX computations and as such must be supplied by the program user The orientation of the discharge mechanism with respect to the receiving water current must also be supplied by the program user With the exception of the CDF seepage case this will only involve the vertical and horizontal discharge angles Any additional angles needed in the hydrodynamic computations are automatically determined by the DROPMIX program For the case of leakage through porous dikes the angle
65. rent file and as such it may be edited or used in program execution DROPMIX User s Manual Page 45 File Name Data Set Title BARGE SITE DESCRIPTION Hopper Overflow Case CHANNEL Sample Data File To Test Channel Velocity Computations D 1 Craney Island INPUT Sample Data File To Test Channel Velocity Computations JUNK JUNK DRI a SAMPLE FILE OUTPUT T 1 DATA FILE T 1 SITE DESCRIPTION EST Sample Data File Figure 4 4 Display Directory of Input Data Files Screen Option four Build or edit input data file is the feature that must be selected in order to edit an existing or create a new DROPMIX data file Selecting this option will cause control to transfer to the Data Selection Menu which will be discussed in greater detail in following paragraphs Pressing the ESC key will transfer control back to the DROPMIX Activity Selection Menu Data Selection Menu Selecting option four Build or edit input data file from the DROPMIX Input Data File Selection Menu will cause the DROPMIX Data Selection Menu to be displayed This menu is shown in Figure 4 5 Note that this menu provides the only avenue for saving data files Also note that as with the other menus the name and a brief description of the active file is displayed at the bottom of the screen Each of the menu items will be briefly discussed below The p
66. ronment Depending upon the means by which dredged material is disposed there can be varying degrees of impact on the receiving water environment For example if a hopper barge is allowed to overflow then effluent possibly contaminated probably highly turbid will enter the receiving water causing a degradation of water quality in the vicinity of the discharge point If on the other hand a pipeline is used in an open water disposal project then the quality of the receiving water in the vicinity of the discharge location and possibly at points further downstream will be affected perhaps more than in the hopper overflow case Albeit small even seepage from confined disposal facilities can impact the quality of the receiving waters When discharges into a receiving body are made a pollutant cloud or plume will form The discharge need not be toxic or highly polluted as suspended solids also degrade water quality The size location and movement of the plume and hence the impact on the receiving water can be estimated using the DROPMIX model In addition the program can be used to determine the extent of the mixing zone that is that area in the immediate vicinity of the discharge point where water quality parameters may exceed established criteria Information describing the receiving water environment the dredged material disposal method and the mixing zone is provided to the model The model will use this data in concert with numerical c
67. roximately 510 KB of RAM must be free or available for the program to successfully load and begin executing The amount of available memory can be determined by running the CHKDSK DOS utility DOS Version 4 0 and earlier or the MEM DOS utility DOS Version 5 0 and higher Consult a DOS manual for instructions on running the CHKDSK or MEM utilities There are no special hardware requirements so the program can be run on basically any personal computer with a hard disk regardless of the type of video card CGA EGA VGA SVGA amount of extended memory higher than 640 KB or presence of any other peripheral devices mouse printer CD ROM etc The total amount of hard disk space required by DROPMIX is approximately 1 5 MB At present the program does not support mouse usage The DROPMIX package can be installed by running the INSTALL program found on the floppy disk which contains the package This installation program will create a subdirectory on a user specified drive C D etc named DROPMIX and copy all pertinent files to the subdirectory All files supplied on the floppy disk have been compressed Consequently the installation routine must be run in order to uncompress the files A list and brief description of all files contained on the DROPMIX diskette is given in Appendix A The DROPMIX Environment The DROPMIX package actually consists of a number of individual computer programs including a user interface a numerical preproces
68. rrent whereas sides B and C do not Consequently the discharge supplied to the DROPMIX model must reflect the seepage through sides B and C It is the responsibility of the program user to supply accurate estimates of flow through the porous dike One possibility is to employ Darcy s Law or use flow nets to estimate leakage through the contributing sides of the facility Leakage through a porous dike is modeled with the CORMIX2 module assuming that flow through the dike behaves similarly to flow through a multi port diffuser As a result information describing the multi port diffuser must be provided namely the number of diffuser ports the diameter of the individual ports and the length of the diffuser It is assumed that each port has the same diameter Because of the wide variability in potential diffuser characterization and the somewhat unwieldy data requirements associated with diffuser depiction DROPMIX takes a simplistic approach when describing diffusers used to simulate dike leakage First the DROPMIX User s Manual Page 25 Receiving Water Current Confined Disposal Facility Figure 3 4 Dike Leakage Case number of diffuser ports is assumed to be 10 000 Secondly the velocity of the effluent seeping from a CDF is assumed to be 0 02 m s Using this information with the total leakage rate the diameter of the individual diffuser ports can be found from the equation below The length of the diffuser may be specified
69. s flow over a weir In some cases the flow over the sides is collected and routed to a common point where it is discharged through a single pipe When a hopper is used in conjunction with hydraulic dredge operations a steady state condition may assume to exist In other words the flow rate over the sides of the barge is equal to the rate at which sediment is pumped to the vessel The assumption of steady state conditions is made in the DROPMIX program for the hopper overflow case For the single port discharge hopper overflow is modeled using the CORMIX1 program whereas CORMIX2 is used for uncontrolled weir type discharges In both instances however a mirror image transformation is made CDF Effluent Discharges Confined disposal facilities are engineered structures and as such they are typically equipped with outlet devices that decant excess water generated by the hydraulic dredging process An example of such an outlet structure would be a culvert passing through the dike face Because the excess water comes in contact with the disposed material it is possible that the effluent has higher concentrations of suspended solids or other pollutants than the receiving water Usually the outlet structure represents a single point discharge and as a result the CORMIX1 module may be used For effluent discharges from confined disposal facilities via a single pipe DROPMIX uses the CORMIX1 module with a mirror image transformation For upland CDF s
70. sor several numerical engines and a numerical postprocessor The flowchart shown in Figure 4 1 depicts the interrelationship between the various DROPMIX components All of the programs which make up the DROPMIX package are written in FORTRAN 77 Due to the limited screen functions associated with standard FORTRAN most of the screen control operations are performed through the use of an Assembly language routine In addition because of FORTRAN s inability to communicate with DOS within a run time environment a number of DOS interactions and system calls are accomplished through use of a third party library The interface program is responsible for file management data entry preprocessor file generation program execution and results presentation Generally DROPMIX User s Manual Page 41 DROPMIX INTERFACE PROGRAM Pipeline Slurry Discharge Case Hopper Dredge Overflow Case Single Port Hopper Dredge Overflow Case Wier Overflow CDF Effluent Via Channel Sidestream CDF Effluent Via Pipe Containment Dike Leakage Case Figure 4 1 Interrelationship Between DROPMIX Modules speaking the interface program is the only component of the DROPMIX package that most users will run The interface program is a user friendly menu driven cursor controlled program that accepts all input necessary to conduct a complete mixing zone simulation The interface program consists of a series of screens each representing a different pr
71. tection Agency provides guidance on the limits of the toxic dilution zone if one exists USEPA 1985 A minimum effluent velocity of 3 m s is required to insure rapid near field so that toxic exposure to receiving water organisms is minimized Likewise EPA has specified three geometric criteria shown below which must also be met if a toxic dilution zone is specified CMC gt 0 Table 3 3 lists the mixing zone variables which must be supplied by the program user 1 The CMC must be met within 10 of the distance from the effluent outfall structure to the edge of the regulatory mixing zone in any spatial direction 2 The diluted concentration must be less than the CMC at a distance no more than 50 times the discharge length scale in any direction The discharge length scale is defined as the square root of the cross sectional area of the effluent discharge port 3 The CMC must be met within a distance of 5 times the local water depth inya horizontal direction For design purposes the local water depth may be defined as the depth which occurs under low flow conditions DROPMIX User s Manual Page 34 Table 3 3 Description of Mixing Zone Variables Name Specifies how regulatory mixing zone is defined Notes 1 CUNITS is a simple string variable and its contents have no bearing on the computations 2 CTOX is automatically set to yes if CMC gt 0 otherwise CTOX no 3 CLEGMZ is automatically set to yes
72. ter detail in the following paragraphs All data supplied to the DROPMIX program must be given in METRIC units Receiving Water Data There are three major data items which fully describe the receiving water environment 1 density 2 velocity and 3 geometry CORMIX will determine if an effluent plume comes in contact with or attaches to a boundary such as the bank of a river or the bottom of a lake Consequently information describing the presence of boundaries receiving water depths bottom roughnesses and degree of channel meandering are required Also required are the mean channel velocity and mean wind speed Finally data describing the receiving water density profile must be provided The receiving water may exhibit one of three density profiles 1 Uniform 2 Linearly varying or 3 a Two Layer or Pycnocline profile For the uniform profile the receiving water density is assumed to remain constant throughout its depth With the DROPMIX User s Manual Page 18 linear profile on the other hand density is assumed to vary linearly from the surface density to the bottom density as illustrated in Figure 3 2 The final density profile assumes a uniform two layer density separated by a step located a specified distance from the receiving water bottom Density information may be specified directly or computed by the program based on user specified depth salinity and temperature PBot Pot Uniform Linearly Step or Varying P
73. that is those structures that are not located adjacent to open waters the effluent is usually discharged into a receiving stream having little or no continuous flow In fact the discharge from the CDF may represent the greatest fraction of flow within the stream The stream in turn typically discharges into a much larger body of water such as a river estuary or ocean Like pipeline discharges hopper overflows and direct CDF discharges channel discharges can also degrade receiving water quality The CORMIX3 module is used to analyze channel or side stream discharges from upland containment facilities CORMIX3 was developed specifically to evaluate aqueous mixing of surface discharges and as a result no modifications of the discharge scenario is necessary DROPMIX User s Manual Page 14 Seepage From Confined Disposal Facilities When a confined disposal facility is used to store dredged material the material may initially have a high water content especially if used in hydraulic dredging operations Although the sediment may eventually dewater dry out a combination of factors including hydraulic gradients weight of the sediment and porosity of the dike will cause effluent to leak from the containment facility In addition infiltrated precipitation will recharge the zone of saturation such that leakage from the facility may continue long after the initial sediment moisture content has decreased Admittedly the flow or velocity thro
74. tle 3 Site Description Title 4 Description of the Discharge Case Title 5 Description of the Discharge Case Title 6 Description of the Discharge Case lt Esc gt Exit lt Home gt Main Menu lt Pg Up gt Previous Menu lt Pg Dn gt NEXT Menu Figure 4 10 Project Title and Site Description Screen Receiving Water Data The next major data item is the receiving water data Receiving water data utilizes three separate screens On the first screen the program user indicates the mean depth of the receiving waters and whether or not the receiving water body is bounded If the body of water is bounded then the user must supply the degree of channel meandering and the width of the channel Recall that CORMIX idealizes a natural channel as a rectangular section Thus the mean depth and channel width supplied from this screen represents values for the rectangular channel section The second receiving water data screen accepts input describing the bottom roughness of the channel Manning s n value or Darcy Weisbach friction factor f may be supplied to the program If Manning s n is provided then DROPMIX will convert the roughness to an equivalent Darcy Weisbach friction factor Typical values of Manning s n and Darcy Weisbach f are shown on the screen Also supplied through this screen is the mean receiving water velocity and the average wind speed DROPMIX User s Manual Page 53
75. travel time 9990 sec Simulation limit based on maximum specified distance 5000 00 m This is the REGION OF INTEREST limitation END OF MOD141 BUOYANT AMBIENT SPREADING CORMIX1 Submerged Single Port Discharges End of Prediction File 11111111111111111111111111111111111111111111111111111111111111111111111111111 As seen from the given output the majority of the DROPMIX output is contained in a series of tables that describe the changes in dilution S and concentration C over an X Y Z coordinate system In addition the horizontal widths BH and vertical thicknesses BV of the contaminant plume are provided A detailed description of the coordinate system and output variables are provided in the following paragraphs All DROPMIX output is referenced to an origin in a three dimensional Cartesian coordinate system As shown in Figure 3 8 the positive X direction points downstream in a direction parallel to the receiving water current the positive Y direction points towards to left bank looking downstream and the positive Z direction is oriented downwards The location of the origin is described in the CORMIX output and generally corresponds to the location of the effluent discharge mechanism For each coordinate point X Y Z a dilution and concentration is given The dilution at any point is simply the ratio of the initial concentration of effluent pollutant to the concentration at the point as shown in Eq 13 The location of the
76. ugh the CDF s porous dikes will be small and occur over very large distances compared to the other disposal cases described above Nonetheless the flow through the CDF can degrade water quality and as a result merits examination In DROPMIX flow through a porous dike is modeled assuming that the dike acts as a multi port diffuser Consequently the CORMIX2 module is used to predict pollutant concentrations within the receiving water DROPMIX User s Manual Page 15 PART 3 DATA REQUIREMENTS AND PROGRAM OUTPUT Program Limitations and Assumptions In order for CORMIX to accurately simulate subaqueous discharges the effluent must represent a continuous steady state discharge In addition steady state flow within the receiving water must exist Of course the condition of continuous flow is relative to the time over which mixing occurs For example a hopper overflow will not be truly continuous Operations and hence discharges into the receiving water will cease after the hoppers have filled However the duration over which overflow occurs on the order of hours is typically much larger than the duration over which initial dilution occurs on the order of minutes or even seconds Moreover the travel time within the regulatory mixing zone is typically less than one hour Furthermore a second barge may begin to overflow relatively shortly after the first barge thus preserving the assumption of continuous flow Consequently the assumption
77. urn to DROPMIX Activity Selection Menu ACTIVE FILE C DROPMIX channel Sample Data File To Test Channel Velocity Computations Use T and 4 keys to highlight option and then ENTER to select or press the selection key of the desired option Figure 4 5 DROPMIX Data Selection Menu mechanism and the orientation of the dredged disposal device with respect to the receiving waters Finally the user must supply information representing the mixing zone Specifically initial pollutant concentrations must be supplied In addition the presence and sizes of regulatory mixing zones must be provided After the program user has supplied all necessary information on the dredge disposal operations the data file may be saved to disk for subsequent analysis or future reference This is accomplished by selecting the fifth data selection menu item Save data file to disk If this item is selected then DROPMIX will transfer control to the Input File Saving Menu Finally the user may return to the Input Data File Selection Menu by pressing the ESC key If the Active File is an existing file then the symbol located between the function keys and the major data items will be replaced with a symbol thereby indicating that data for those items has been furnished Similarly if a new file is constructed the dash will be replaced by an asterisk once the individual data screens have been accessed and data supplied
78. y X Y Z S C B 0 00 0 00 1 00 1 00 250E 02 0 44 0 93 0 00 244 2 00 123E 02 0 60 195 0 00 3 88 3 90 636E 01 0 75 CMC HAS BEEN FOUND The pollutant concentration in the plume falls below CMC value of 0 500E 01 in the current prediction interval This is the extent of the TOXIC DILUTION ZONE 3 04 0 00 5 32 6 70 374E 01 0 91 4 20 0 00 6 76 10 30 244E 01 1 07 WATER QUALITY STANDARD OR CCC HAS BEEN FOUND The pollutant concentration in the plume falls below water quality standard or CCC value of 0 200E 01 in the current prediction interval This is the spatial extent of concentrations exceeding the water quality standard or CCC value 5 42 0 00 8 20 14 70 170E 01 1 23 Cumulative travel time 1 sec DROPMIX User s Manual Page 36 Table 3 4 Cont BEGIN MOD132 LAYER BOUNDARY IMPINGEMENT UPSTREAM SPREADING Vertical angle of layer ooundary impingement 49 80 deg Horizontal angle of layer boundary impingement 0 00 deg UPSTREAM INTRUSION PROPERTIES Upstream intrusion length 5 93 m X position of upstream stagnation point 0 52 m Thickness in intrusion region 1 60 m Half width at downstream end 15 56 m Thickness at downstream end Z 1 60 m Plume width as a function of position X 0 52 144 340 536 7 32 9 28 11 24 13 20 BH 0 00 588 832 10 19 11 76 13 15 14 41 15 56 Profile definitions BV top hat thickness measured vertically BH top hat half width measured horizontally in Y direction ZU lower plume boun
79. ycnocline Figure 3 2 Possible Receiving Water Density Profiles Receiving water velocity is specified directly by the program user It is assumed that information on channel velocities would be more readily available than data describing receiving water discharges The specified velocity represents the mean velocity acting uniformly over the width and depth of the receiving water body In addition the velocity is assumed to be constant over the duration of the simulation The mean wind speed must also be specified to account for mixing effects from wind induced turbulence DROPMIX allows users to indicate if the wind speed is low medium or high Depending upon the wind conditions specified by the program user DROPMIX will assign a value of 0 m s 2 m s or 15 m s respectively to the wind speed CORMIX has the ability to indicate if the effluent plume comes in contact with and attach to the receiving water banks or bottom Obviously the potential for bank contact and attachment is higher for narrow channels such as rivers and streams than for wider bodies of water e g lakes bays and coastal areas In addition diffusivity coefficients which control far field mixing differ for narrow and wide water courses DROPMIX User s Manual Page 19 Thus CORMIX requires information on whether the receiving water is bounded As the name implies a bounded channel is one where the receiving water channel is bounded on both sides by banks Exam

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