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[[File:General information page image.png|left|100px|alt=image]]
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The Source Loading and Management Model (WinSLAMM) is a proprietary stormwater quality model originally developed for the USGS for the evaluation of non-point pollution in urban areas and pollutant removal at water quality BMPs. WinSLAMM uses experimentally derived runoff coefficients to predict runoff and associated pollutant loading from a number of land use types. A unique feature in WinSLAMM is that within defined land use types (e.g., commercial, residential, etc.), the program tracks loading from many different types of source areas (e.g., roofs, parking lots, etc.) and further distinguishes source areas using source area parameters (e.g., is the roof flat or pitched? Does the roof drain to a pervious surface?, etc.). WinSLAMM provides this level of specificity so that unique runoff coefficient and pollutant loading assumptions can be applied to sources areas within land use types, allowing for refinement of runoff and pollutant loading results.
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WinSLAMM predicts pollutant removal at water quality BMPs based on correlation to experimental results (empirical) as well as modeling the generation and removal of particulates through sedimentation and filtration (physically based). By modeling hydraulic performance at BMPs and physically tracking the particle scale distribution (PSD) through BMPs, WinSLAMM is capable of modeling bypass from BMPs and is capable of predicting performance of BMPs in series (i.e., treatment trains). WinSLAMM is a continuous model which can produce results for long term simulations and produce results for individual rainfall events. It should be noted that WinSLAMM simulations are done in batch mode, which means that it is not modeling individual rainfall events in real-time, and accounting for antecedent moisture conditions for pervious runoff, the way that P8 does.
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WinSLAMM is a versatile program suitable for TMDL applications ranging from TMDL development, to demonstrating Waste Load Allocation (WLA) and permit compliance from individual municipal separate storm systems (MS4s). Download links for WinSLAMM and related documentation are provided below. As noted above, WinSLAMM is a proprietary model which needs to be licensed or purchased before use.
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*[http://www.winslamm.com/winslamm_updates.html Model download]
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*[http://www.winslamm.com/purchase.html Model purchase]
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*[http://www.winslamm.com/Select_documentation.html Model documentation]
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'''Note''': information provided in the following subsections does not reiterate or re-present information readily available in model documentation files. Instead, guidance provided in this document provides engineers and planners with recommendations for development of model inputs, provides guidance for interpreting and summarizing model results, provides supplementary information not included in model documentation, and provides examples showing how WinSLAMM can be used to demonstrate TMDL compliance.
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==Applicability to demonstrating WLA compliance==
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WinSLAMM is a continuous water quality model capable of summarizing runoff and associated [https://stormwater.pca.state.mn.us/index.php?title=Total_Suspended_Solids_(TSS)_in_stormwater total suspended solids] (TSS) and [https://stormwater.pca.state.mn.us/index.php?title=Phosphorus total phosphorus] (TP) generation, removal, and outflow loading from individual catchments, individual BMPs and junctions, or as a model wide summary. Additionally, because WinSLAMM models the particulate and pollutant particle-scale distribution through filtration and sedimentation BMPs and models hydraulic performance of BMPs based on watershed loading and BMP dimensions, the model is capable of accurately predicting pollutant removal through BMPs <span title="multiple BMPs that work together to remove pollutants utilizing combinations of hydraulic, physical, biological, and chemical methods"> '''in series'''</span> as well as predicting runoff and pollutant bypass from undersized <span title="a BMP that does not treat the full water quality volume"> '''undersized BMPs'''</span>. Due to this flexibility, WinSLAMM is capable of providing accurate pollutant removal estimates regardless of BMP network and subwatershed configuration, and is capable of demonstrating compliance to mass-based Water Quality Based Effluent Limits (WQBELs), concentration-based WQBELS, and areal-loading based WQBELS (e.g., lbs of TSS per acre per year) for both TSS and TP.
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==Model inputs==
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The following subsections outline data sources and special consideration related to model inputs, model setup, and model initialization. '''Note''': these subsections do not represent information readily available in [http://www.winslamm.com/Select_documentation.html Model documentation], but instead highlight data sources (e.g., spatial datasets), special consideration, and important notes for engineers and planners to consider while generating model inputs.
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===Current file data: parameter files===
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WinSLAMM requires a number of parameter files to generate runoff, particulate loading, and pollutant accumulation and washoff from source areas within each land use type. Each of the required parameters files is described briefly, below:
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*''Rain File'' (".RAN"): specifies rainfall event date, duration, and depth for the modeled period.
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*''Runoff Coefficient File'' (“.RSVX”): specifies the runoff coefficient (Rv) for each source area as a function of rainfall event depth.
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*''Particulate Solids Concentration File'' (“.PSCX”): specifies the particulate solids concentration (mg/L) for each source area as a function of rainfall depth.
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*''Source Area PSD and Peak to Average Flow Ratio File'' (“.CSV”): specifies the particle scale distribution (PSD) file (“.CPZ”) and the peak-to-average flow ratio for each source area.
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**''Particle Size Parameter Files'' (“.CPZ”): specifies the PSD for particulates generated from a WinSLAMM source area. Unique PSD “.CPZ” files can be applied to each source area.
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*''Street Delivery File'' (“.STD”, six (6) files): specifies the washoff coefficient for street textures as a function of rainfall depth. Note: unique street delivery files can be applied to road surface sources areas for each of the six (6) land use types.
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*''Pollutant Probability Distribution Files'' (“.PPDX”): specifies the particulate pollutant concentration associated with generated particulate (mg/kg) and the dissolved pollutant concentration (mg/L) for all modeled pollutant constituents from all source areas within each land use type.
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The Rain File (“.RAN”), which specifies rainfall events, duration, and depth for the modeled period, is regionally specific and should be developed for the study area. The [https://www.ncdc.noaa.gov/cdo-web/search National Oceanic and Atmospheric Administration] (NOAA) maintains a searchable database that can be used to search for hourly precipitation data based by city or geographic region (e.g., zip code). Local area airports (e.g., Minneapolis Saint Paul International Airport) are another resource that can be used to develop required precipitation data inputs. As described in model documentation, rainfall input “.RAN” files can be created within the Rainfall File Editor (“Utilities &rarr; Parameter Files &rarr; Rainfall Files”).
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The remaining parameter files (Runoff Coefficient File (“.RSVX”), Particulate Solids Concentration File (“.PSCX”), Source Area PSD and Peak to Average low Ratio File (“.CSV”), Particle Size Parameter Files (“.CPZ”), Street Delivery Files (“.STD”), and Pollutant Probability Distribution Files (“.PPDX”)) contain input values that must be generated from literature values, case studies, or water quality monitoring data. For this reason, default parameter files have been generated for several geographic locations across the United States and are provided in WinSLAMM documentation. Additionally, some state and local agencies have developed state-wide or regional WinSLAMM input parameter files. For this reason, it is recommended that the engineer or designer first determine if local or regional parameter files have been developed before utilizing default regional parameter files provided in the WinSLAMM model files. Figure 19 shows regional coverage of default WinSLAMM parameter files. As shown, the “Great Lakes” provides coverage of the majority of Minnesota and should be used if local or regional parameter files are not available for the study area.
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'''Special Consideration(s)''':<br>
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*The rainfall editor within WinSLAMM can be used to make Rain File(s) (“.RAN”) unique to the study area (“Utilities &rarr; Parameter Files &rarr; Rainfall Files”).
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*Parameter files can be viewed and edited from “Utilities &rarr; Parameter Files”.
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*Default parameter files unique to each “Parameter File Region” are included in WinSLAMM program files.
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===Current file data: job control===
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Job control parameters related to model run time are specified in the “Current File Data” window. Job control parameters are described briefly, below:
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*''Start Date / End Date'': specifies the start and stop date of simulation.
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*''Start / End of Winter'' (mm/dd): specifies the date range that represents winter conditions. Winter conditions impact how runoff is generated as well as particle accumulation and washoff from road surfaces.
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'''Special Consideration(s)''':<br>
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*The start date / end date must be within the date range in the Rain File (“.RAN”).
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*Model documentation files suggest a winter start and end date of December 3 (12/03) to March 21 (03/21) for the “Great Lakes” parameter file region.
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===Job control: pollutant selection===
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Accessed through the “Pollutants” tab on the main WinSLAMM model menu, the “Pollutant Selection” window defines which pollutant(s) included in the Pollutant Probability Distribution (“.PPDX”) file will be modeled and tracked in reported model outputs.
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'''Special Consideration(s)''':<br>
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*For phosphorus TMDLs, it is recommended that the “particulate”, “dissolved”, and “total” radial options be selected.
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*Only pollutants included in the selected Pollutant Probability Distribution File (“.PPDX”) file will be included in the “Pollutant Selection” window.
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===Job control: program options===
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Job control parameters and options related to output generation within WinSLAMM “Program Options” (“Tools &rarr; Program Options”) should be reviewed by the engineer or designer before performing model simulation. The “Program Options” window is separated into three tabs. A brief discussion of each of the “Program Options” tab is provided below:
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*''Default Current File Data'': specifies default parameter files applied to “Current File Data”
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*''Default Model Options'': specifies several job control parameters and options related to model output. The designer or engineer should review the “Default Time Increment (min)”, which defines the time increment used to route flow and pollutant hydrographs between control practices. Additionally, if outflow hydrographs or particle size distribution files are required, the “Create Hydrograph and Particle Size Distribution .csv Files” radial button should be selected.
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*''Default Output File Options'': specifies optional result outputs for each of eleven (11) control practices. Reporting options should be reviewed by the engineer or designer based on reporting information required and control practices modeled before performing model simulation.
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===Land use===
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Within WinSLAMM, drainage basins are modeled using one or more “land uses” (e.g., residential, commercial, etc.), which are represented by land use nodes within the model space. Within each land use, area is further delineated into “source areas” (e.g., roofs, sidewalks, etc.). Runoff and pollutant loading from drainage areas is impacted by the land use type, as well as the source area type. A complete list of land use and source area types in provided in Table 32. Finally, each source area type is further characterized by a “source area parameters”. For example, the “source area parameter” for a roof source area define whether the roof is pitched or flat, whether the roof drains onto a pervious or impervious surface, etc. Developing this detail of input parameters is possible for small, development-scale study areas, but is not feasible for larger study areas (e.g., municipal-scale study areas). For this reason, WinSLAMM has a number of default “Standard Land Uses” which can be applied to any of the six (6) land use types.

Revision as of 15:48, 15 August 2019

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The Source Loading and Management Model (WinSLAMM) is a proprietary stormwater quality model originally developed for the USGS for the evaluation of non-point pollution in urban areas and pollutant removal at water quality BMPs. WinSLAMM uses experimentally derived runoff coefficients to predict runoff and associated pollutant loading from a number of land use types. A unique feature in WinSLAMM is that within defined land use types (e.g., commercial, residential, etc.), the program tracks loading from many different types of source areas (e.g., roofs, parking lots, etc.) and further distinguishes source areas using source area parameters (e.g., is the roof flat or pitched? Does the roof drain to a pervious surface?, etc.). WinSLAMM provides this level of specificity so that unique runoff coefficient and pollutant loading assumptions can be applied to sources areas within land use types, allowing for refinement of runoff and pollutant loading results.

WinSLAMM predicts pollutant removal at water quality BMPs based on correlation to experimental results (empirical) as well as modeling the generation and removal of particulates through sedimentation and filtration (physically based). By modeling hydraulic performance at BMPs and physically tracking the particle scale distribution (PSD) through BMPs, WinSLAMM is capable of modeling bypass from BMPs and is capable of predicting performance of BMPs in series (i.e., treatment trains). WinSLAMM is a continuous model which can produce results for long term simulations and produce results for individual rainfall events. It should be noted that WinSLAMM simulations are done in batch mode, which means that it is not modeling individual rainfall events in real-time, and accounting for antecedent moisture conditions for pervious runoff, the way that P8 does.

WinSLAMM is a versatile program suitable for TMDL applications ranging from TMDL development, to demonstrating Waste Load Allocation (WLA) and permit compliance from individual municipal separate storm systems (MS4s). Download links for WinSLAMM and related documentation are provided below. As noted above, WinSLAMM is a proprietary model which needs to be licensed or purchased before use.

Note: information provided in the following subsections does not reiterate or re-present information readily available in model documentation files. Instead, guidance provided in this document provides engineers and planners with recommendations for development of model inputs, provides guidance for interpreting and summarizing model results, provides supplementary information not included in model documentation, and provides examples showing how WinSLAMM can be used to demonstrate TMDL compliance.

Applicability to demonstrating WLA compliance

WinSLAMM is a continuous water quality model capable of summarizing runoff and associated total suspended solids (TSS) and total phosphorus (TP) generation, removal, and outflow loading from individual catchments, individual BMPs and junctions, or as a model wide summary. Additionally, because WinSLAMM models the particulate and pollutant particle-scale distribution through filtration and sedimentation BMPs and models hydraulic performance of BMPs based on watershed loading and BMP dimensions, the model is capable of accurately predicting pollutant removal through BMPs in series as well as predicting runoff and pollutant bypass from undersized undersized BMPs. Due to this flexibility, WinSLAMM is capable of providing accurate pollutant removal estimates regardless of BMP network and subwatershed configuration, and is capable of demonstrating compliance to mass-based Water Quality Based Effluent Limits (WQBELs), concentration-based WQBELS, and areal-loading based WQBELS (e.g., lbs of TSS per acre per year) for both TSS and TP.

Model inputs

The following subsections outline data sources and special consideration related to model inputs, model setup, and model initialization. Note: these subsections do not represent information readily available in Model documentation, but instead highlight data sources (e.g., spatial datasets), special consideration, and important notes for engineers and planners to consider while generating model inputs.

Current file data: parameter files

WinSLAMM requires a number of parameter files to generate runoff, particulate loading, and pollutant accumulation and washoff from source areas within each land use type. Each of the required parameters files is described briefly, below:

  • Rain File (".RAN"): specifies rainfall event date, duration, and depth for the modeled period.
  • Runoff Coefficient File (“.RSVX”): specifies the runoff coefficient (Rv) for each source area as a function of rainfall event depth.
  • Particulate Solids Concentration File (“.PSCX”): specifies the particulate solids concentration (mg/L) for each source area as a function of rainfall depth.
  • Source Area PSD and Peak to Average Flow Ratio File (“.CSV”): specifies the particle scale distribution (PSD) file (“.CPZ”) and the peak-to-average flow ratio for each source area.
    • Particle Size Parameter Files (“.CPZ”): specifies the PSD for particulates generated from a WinSLAMM source area. Unique PSD “.CPZ” files can be applied to each source area.
  • Street Delivery File (“.STD”, six (6) files): specifies the washoff coefficient for street textures as a function of rainfall depth. Note: unique street delivery files can be applied to road surface sources areas for each of the six (6) land use types.
  • Pollutant Probability Distribution Files (“.PPDX”): specifies the particulate pollutant concentration associated with generated particulate (mg/kg) and the dissolved pollutant concentration (mg/L) for all modeled pollutant constituents from all source areas within each land use type.

The Rain File (“.RAN”), which specifies rainfall events, duration, and depth for the modeled period, is regionally specific and should be developed for the study area. The National Oceanic and Atmospheric Administration (NOAA) maintains a searchable database that can be used to search for hourly precipitation data based by city or geographic region (e.g., zip code). Local area airports (e.g., Minneapolis Saint Paul International Airport) are another resource that can be used to develop required precipitation data inputs. As described in model documentation, rainfall input “.RAN” files can be created within the Rainfall File Editor (“Utilities → Parameter Files → Rainfall Files”).

The remaining parameter files (Runoff Coefficient File (“.RSVX”), Particulate Solids Concentration File (“.PSCX”), Source Area PSD and Peak to Average low Ratio File (“.CSV”), Particle Size Parameter Files (“.CPZ”), Street Delivery Files (“.STD”), and Pollutant Probability Distribution Files (“.PPDX”)) contain input values that must be generated from literature values, case studies, or water quality monitoring data. For this reason, default parameter files have been generated for several geographic locations across the United States and are provided in WinSLAMM documentation. Additionally, some state and local agencies have developed state-wide or regional WinSLAMM input parameter files. For this reason, it is recommended that the engineer or designer first determine if local or regional parameter files have been developed before utilizing default regional parameter files provided in the WinSLAMM model files. Figure 19 shows regional coverage of default WinSLAMM parameter files. As shown, the “Great Lakes” provides coverage of the majority of Minnesota and should be used if local or regional parameter files are not available for the study area.

Special Consideration(s):

  • The rainfall editor within WinSLAMM can be used to make Rain File(s) (“.RAN”) unique to the study area (“Utilities → Parameter Files → Rainfall Files”).
  • Parameter files can be viewed and edited from “Utilities → Parameter Files”.
  • Default parameter files unique to each “Parameter File Region” are included in WinSLAMM program files.

Current file data: job control

Job control parameters related to model run time are specified in the “Current File Data” window. Job control parameters are described briefly, below:

  • Start Date / End Date: specifies the start and stop date of simulation.
  • Start / End of Winter (mm/dd): specifies the date range that represents winter conditions. Winter conditions impact how runoff is generated as well as particle accumulation and washoff from road surfaces.

Special Consideration(s):

  • The start date / end date must be within the date range in the Rain File (“.RAN”).
  • Model documentation files suggest a winter start and end date of December 3 (12/03) to March 21 (03/21) for the “Great Lakes” parameter file region.

Job control: pollutant selection

Accessed through the “Pollutants” tab on the main WinSLAMM model menu, the “Pollutant Selection” window defines which pollutant(s) included in the Pollutant Probability Distribution (“.PPDX”) file will be modeled and tracked in reported model outputs.

Special Consideration(s):

  • For phosphorus TMDLs, it is recommended that the “particulate”, “dissolved”, and “total” radial options be selected.
  • Only pollutants included in the selected Pollutant Probability Distribution File (“.PPDX”) file will be included in the “Pollutant Selection” window.

Job control: program options

Job control parameters and options related to output generation within WinSLAMM “Program Options” (“Tools → Program Options”) should be reviewed by the engineer or designer before performing model simulation. The “Program Options” window is separated into three tabs. A brief discussion of each of the “Program Options” tab is provided below:

  • Default Current File Data: specifies default parameter files applied to “Current File Data”
  • Default Model Options: specifies several job control parameters and options related to model output. The designer or engineer should review the “Default Time Increment (min)”, which defines the time increment used to route flow and pollutant hydrographs between control practices. Additionally, if outflow hydrographs or particle size distribution files are required, the “Create Hydrograph and Particle Size Distribution .csv Files” radial button should be selected.
  • Default Output File Options: specifies optional result outputs for each of eleven (11) control practices. Reporting options should be reviewed by the engineer or designer based on reporting information required and control practices modeled before performing model simulation.

Land use

Within WinSLAMM, drainage basins are modeled using one or more “land uses” (e.g., residential, commercial, etc.), which are represented by land use nodes within the model space. Within each land use, area is further delineated into “source areas” (e.g., roofs, sidewalks, etc.). Runoff and pollutant loading from drainage areas is impacted by the land use type, as well as the source area type. A complete list of land use and source area types in provided in Table 32. Finally, each source area type is further characterized by a “source area parameters”. For example, the “source area parameter” for a roof source area define whether the roof is pitched or flat, whether the roof drains onto a pervious or impervious surface, etc. Developing this detail of input parameters is possible for small, development-scale study areas, but is not feasible for larger study areas (e.g., municipal-scale study areas). For this reason, WinSLAMM has a number of default “Standard Land Uses” which can be applied to any of the six (6) land use types.

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