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05-662 Water pollution control planning (for UCT students, CIV530Z  is a programme of individual study on a specialized topic - examination by report/s and possibly an oral) is a graduate engineering course, comprising the six even-numbered modules below: 2. philosophy underlying public water pollution; 4. methods of developing area-wide pollution control plans and sustainable use plans in Ontario and elsewhere; 6. introduction to BMPs and the SLAMM model; 8.  introduction to the WASP model; 10. Urban litter in drainage systems;  12. examination of quantitative and non-quantitative information in the context of planning. No field trips are planned for Jan-Apr 2000. More info is provided in module 0.   

Current modules in this website are for January to April 2002.   

Module 6
Introduction to BMPs and the SLAMM Model

 Contents

Introduction
Abstract
History of Slamm and Typical Uses
SLAMM Computational Processes
Monte Carlo Simulation of Pollutants Strengths of Runoff from Various Urban Source Areas
Use of Slamm to Identify Pollutant Sources and to Evaluate Different Control Programs
Simple Workshop Example
Table 6. Example SLAMM Input File for “new mdr.dat”
SLAMM/SWMM Interface Program
How SSIP Works
References
Reading and links
Assignment A6

Introduction

Pedagogic note: This module examines the Source Loading and Management Model (SLAMM), especially as how it can examine combinations of source controls, development options, and outfall treatment. The model will be used in this module to examine “low impact development” (somewhat of a buzz word in the US) scenarios. Since the current version is completely written in Visual Basic, the Window’s interface allows efficient use, even for new users (but, please contact me for specific help, as needed). This module describes the SLAMM/SWMM Interface Program (SSIP) for completion, although it is not expected to be easily used by the students. The next version of SSIP, expected within the next few months, will be much more automated and user friendly, at least to users who are familiar with both SLAMM and SWMM.
 Source: This material was mostly extracted from a recent EPA research report:
 Pitt, R., M. Lilburn, S. Nix, S.R. Durrans, S. Burian, J. Voorhees, and J. Martinson Guidance Manual for Integrated Wet Weather Flow (WWF) Collection and Treatment Systems for Newly Urbanized Areas (New WWF Systems). U.S. Environmental Protection Agency. 612 pgs. December 1999. 

The most detail on SLAMM attributes (especially small storm hydrology and particulate washoff, to be covered in Module 7) is given in Pitt’s dissertation:
 Pitt, R. Small Storm Urban Flow and Particulate Washoff Contributions to Outfall Discharges, Ph.D. Dissertation, Civil and Environmental Engineering Department, University of Wisconsin, Madison, WI, November 1987. 

Much of the material presented here was developed for the Humber River basin in Toronto as part of my dissertation research and was included in the following report prepared for the Ontario Ministry of the Environment:
Pitt, R. and J. McLean. Humber River Pilot Watershed Project, Ontario Ministry of the Environment, Toronto, Canada. 483 pgs. June 1986.

Some of the material was presented in Pitt (1986), in a general description of the Wisconsin Nonpoint Source Program:
Pitt, R. “The Incorporation of Urban Runoff Controls in the Wisconsin Priority Watershed Program.”  In: Advanced Topics in Urban Runoff Research, (Edited by B. Urbonas and L.A. Roesner). Engineering Foundation and ASCE, New York. pp. 290-313. 1986.

SLAMM and its source area treatment capabilities have also been described at EPA Region V/NIPC conferences in Chicago, when some of the examples were prepared:
Pitt, R. and J. Voorhees. “Critical Source Area Controls in the SLAMM Water Quality Model.” A National Symposium: Assessing the Cumulative Impacts of Watershed Developments on Aquatic Ecosystems and Water Quality. U.S. EPA and Northeastern Illinois Planning Commission. Chicago, Illinois, March 1996.
Pitt, R. and J. Voohees. “The Source Loading and Management Model (SLAMM).” National Conference on Urban Runoff Management. U.S. EPA, Chicago, Ill. March 1993.

Various attributes of SLAMM have also been published in Volumes 6 through 8 of the proceedings of the stormwater user’s conference given annually in Toronto:

Pitt, R. and J. Lantrip. “Infiltration through disturbed urban soils.” In: Advances in Modeling the Management of Stormwater Impacts, Volume 8. (Edited by W. James). Computational Hydraulics International, Guelph, Ontario. 1999.

Pitt, R. “Small storm hydrology and why it is important for the design of stormwater control practices.” In: Advances in Modeling the Management of Stormwater Impacts, Volume 7. (Edited by W. James). Computational Hydraulics International, Guelph, Ontario and Lewis Publishers/CRC Press. 1998.

Pitt, R. “Unique Features of the Source Loading and Management Model (SLAMM).” In: Advances in Modeling the Management of Stormwater Impacts, Volume 6. (Edited by W. James). Computational Hydraulics International, Guelph, Ontario and Lewis Publishers/CRC Press. pp. 13 – 37. 1997.

Abstract

SLAMM was originally developed to better understand the relationships between sources of urban runoff pollutants and runoff quality. It has been continually expanded since the late 1970s and now includes a wide variety of source area and outfall control practices (infiltration practices, wet detention ponds, porous pavement, street cleaning, catchbasin cleaning, and grass swales). SLAMM is strongly based on actual field observations, with minimal reliance on pure theoretical processes that have not been adequately documented or confirmed in the field. SLAMM is mostly used as a planning tool, to better understand sources of urban runoff pollutants and their control.

Special emphasis has been placed on small storm hydrology and particulate washoff in SLAMM, common areas of misuse in the SWMM RUNOFF block. Many currently available urban runoff models have their roots in drainage design where the emphasis is with very large and rare rains. In contrast, stormwater quality problems are mostly associated with common and relatively small rains. The assumptions and simplifications that are legitimately used with drainage design models are not appropriate for water quality models. SLAMM therefore incorporates unique process descriptions to more accurately predict the sources of runoff pollutants and flows for the storms of most interest in stormwater quality analyses. However, SLAMM can be effectively used in conjunction with drainage design models to incorporate the mutual benefits of water quality controls on drainage design.

SLAMM has been used in many areas of North America and has been shown to accurately predict stormwater flows and pollutant characteristics for a broad range of rains, development characteristics, and control practices. As with all stormwater models, SLAMM needs to be accurately calibrated and then tested (verified) as part of any local stormwater management effort.

SLAMM is unique in many aspects. One of the most important aspects is its ability to consider many stormwater controls (affecting source areas, drainage systems, and outfalls) together, for a long series of rains. Another is its ability to accurately describe a drainage area in sufficient detail for water quality investigations, but without requiring a great deal of superfluous information that field studies have shown to be of little value in accurately predicting discharge results. SLAMM also applies stochastic analysis procedures to more accurately represent actual uncertainty in model input parameters in order to better predict the actual range of outfall conditions (especially pollutant concentrations). However, the main reason SLAMM was developed was because of errors contained in many existing urban runoff models. These errors were obvious when comparing actual field measurements to the solutions obtained from model algorithms.

In addition to the material presented in this module, a user’s guide is linked for using SLAMM, along with another link to a description for the source area and outfall controls incorporated in SLAMM.

History of Slamm and Typical Uses

The Source Loading and Management Model (SLAMM) was initially developed to more efficiently evaluate stormwater control practices. It soon became evident that in order to accurately evaluate the effectiveness of stormwater controls at an outfall, the sources of the pollutants or problem water flows must be known. SLAMM has evolved to include a variety of source area and end-of-pipe controls and the ability to predict the concentrations and loadings of many different pollutants from a large number of potential source areas. SLAMM calculates mass balances for both particulate and dissolved pollutants and runoff flow volumes for different development characteristics and rainfalls. It was designed to give relatively simple answers (pollutant mass discharges and control measure effects for a very large variety of potential conditions).               

SLAMM was developed primarily as a planning level tool, such as to generate information needed to make planning level decisions, while not generating or requiring superfluous information. Its primary capabilities include predicting flow and pollutant discharges that reflect a broad variety of development conditions and the use of many combinations of common urban runoff control practices. Control practices evaluated by SLAMM include detention ponds, infiltration devices, porous pavements, grass swales, catchbasin cleaning, and street cleaning. These controls can be evaluated in many combinations and at many source areas as well as the outfall location. SLAMM also predicts the relative contributions of different source areas (roofs, streets, parking areas, landscaped areas, undeveloped areas, etc.) for each land use investigated. As an aid in designing urban drainage systems, SLAMM also calculates correct NRCS curve numbers that reflect specific development and control characteristics. These curve numbers can then be used in conjunction with available urban drainage procedures to reflect the water quantity reduction benefits of stormwater quality controls.               

SLAMM is normally used to predict source area contributions and outfall discharges. However, SLAMM has been used in conjunction with a receiving water model (HSPF) to examine the ultimate receiving water effects of urban runoff (Ontario 1986).               

The development of SLAMM began in the mid 1970s, primarily as a data reduction tool for use in early street cleaning and pollutant source identification projects sponsored by the EPA’s Storm and Combined Sewer Pollution Control Program (Pitt 1979; Pitt and Bozeman 1982; Pitt 1984). Additional information contained in SLAMM was obtained during the EPA’s Nationwide Urban Runoff Program (NURP) (EPA 1983), especially the Alameda County, California (Pitt and Shawley 1982), the Bellevue, Washington (Pitt and Bissonnette 1984), and the Milwaukee (Bannerman, et al. 1983) projects. The completion of the model was made possible by the remainder of the NURP projects and additional field studies and programming support sponsored by the Ontario Ministry of the Environment (Pitt and McLean 1986), the Wisconsin Department of Natural Resources (Pitt 1986; Bannerman, et al. 1996; Legg, et al. 1996), and Region V of the U.S. Environmental Protection Agency. Early users of SLAMM included the Ontario Ministry of the Environment’s Toronto Area Watershed Management Strategy (TAWMS) study (Pitt and McLean 1986) and the Wisconsin Department of Natural Resources’ Priority Watershed Program (Pitt 1986). Many SLAMM user’s have incorporated the use of the model with a GIS (see Module 3) (Thum, et al. 1990; Kim, et al. 1993; Kim and Ventura 1993; Ventura and Kim 1993; Bachhuber 1996; Haubner and Joeres 1996). SLAMM can now be effectively used as a tool to enable watershed planners to obtain a better understanding of the effectiveness of different control practice programs.
A logical approach to stormwater management requires knowledge of the problems that are to be solved, the sources of the problem pollutants, and the effectiveness of stormwater management practices that can control the problem pollutants at their sources and at outfalls. SLAMM is designed to provide information on these last two aspects of this approach.             

SLAMM Computational Processes
Figure 1 illustrates the wide variety of development characteristics that affect stormwater quality and quantity. This figure shows a variety of drainage systems from concrete curb and gutters to grass swales, along with directly connected roof drainage systems and drainage systems that drain to pervious areas. “Development characteristics” define the magnitude of these drainage efficiency attributes, along with the areas associated with each surface type (road surfaces, roofs, landscaped areas, etc.). The use of SLAMM shows that these characteristics greatly affect runoff quality and quantity. Land use alone is usually not sufficient to describe these characteristics. The types of the drainage system (curbs and gutters or grass swales) and roof connections (directly connected or draining to pervious area), are probably the most important attributes affecting runoff characteristics. These attributes are not directly related to land use, but some trends are obvious: most roofs in strip commercial and shopping center areas are directly connected, and the roadside is most likely drained by curbs and gutters, for example. Different land uses, of course, are also associated with different levels of pollutant generation. For example, industrial areas usually have the greatest pollutant accumulations due to material transfer and storage, and heavy truck traffic.
 
 
Figure 1. Urban runoff source areas and drainage alternatives (Pitt 1986).
               
 Figure 2 shows how SLAMM considers a variety of pollutant and flow routings that may occur in urban areas. SLAMM routes material from unconnected sources to the drainage system directly or to adjacent directly connected or pervious areas which in turn drain to the collection system. Each of these areas has pollutant deposition mechanisms in addition to removal mechanisms associated with them. As an example, unconnected sources, which may include rooftops draining to pervious areas or bare ground and landscaped areas, are affected by regional air pollutant deposition (from point source emissions or from fugitive dust) and other aspects that would affect all surfaces. Pollutant losses from these unconnected sources are caused by wind removal and by rain runoff washoff which flow directly to the drainage system, or to adjacent areas. The drainage system may include curbs and gutters where there is limited deposition, and catch basins and grass swales which may remove substantial participates that are transported in the drainage system. Directly connected impervious areas include paved surfaces that drain directly to the drainage system. These source areas are also affected by regional pollutant deposition, in addition to wind removal and controlled removal processes, such as street cleaning. On-site storage is also important on paved surfaces because of the large amount of participate pollutants that are not washed-off, blown-off, or removed by direct cleaning (Pitt 1979; Pitt and Shawley 1982; Pitt 1984).
 
 
 
Figure 2. Pollutant deposition and removal at source areas (Pitt 1986).
 
 Figure 3 shows how SLAMM proceeds through the major calculations. There is a double set of nested loops in the analyses where runoff volume and suspended solids (particulate residue) are calculated for each source area and then for each rain. These calculations consider the affects of each source area control, in addition to the runoff pattern between areas. Suspended solids washoff and runoff volume from each individual area for each rain are summed for the entire drainage system. The effects of the drainage system controls (catch basins or grass swales, for example) are then calculated. Finally, the effects of the outfall controls are calculated.
  

Figure 3. SLAMM calculation flow chart.
 
SLAMM uses the water volume and suspended solids concentrations at the outfall to calculate the other pollutant concentrations and loadings. SLAMM keeps track of the portion of the total outfall suspended solids loading and runoff volume that originated from each source area. The suspended solids fractions are then used to develop
weighted loading factors associated with each pollutant. In a similar manner, dissolved pollutant concentrations and loadings are calculated based on the percentage of water volume that originates from each of the source areas within the drainage system.
               
SLAMM predicts urban runoff discharge parameters (total storm runoff flow volume, flow-weighted pollutant concentrations, and total storm pollutant yields) for many individual storms and for the complete study period. It has built-in Monte Carlo sampling procedures to consider many of the uncertainties common in model input values. This enables the model output to be expressed in probabilistic terms that more accurately represent the likely range of results expected.
 

Monte Carlo Simulation of Pollutants Strengths of Runoff from Various Urban Source Areas

Initial versions of SLAMM only used average concentration factors for different land use areas and source areas. This was satisfactory for predicting the event mean concentrations (EMC, as used by NURP, EPA 1983) for an extended period of time and in calculating the unit area loadings for different land uses. Figure 4 is a plot of the event mean concentrations at a Toronto test sites (Pitt and McLean 1986). The observed concentrations are compared to the SLAMM predicted concentrations for a long term simulation. All of the predicted EMC values are very close to the observed EMC values. However, in order to predict the probability distributions of the concentrations, it was necessary to include probability information for the concentrations found in the different source areas. Statistical analyses of concentration data (attempting to relate concentration trends to rain depths and season, for example) from these different source areas have not been able to explain all of the variation in concentrations that have been observed. The statistical analyses also indicate that most pollutant concentration values from individual source areas are distributed log-normally. Therefore, log-normally distributed random concentration values are used in SLAMM for these different areas. The result is much more reasonable predictions for concentration distributions at the outfall when compared to actual observed conditions. This provides more accurate estimates of criteria violations for different stormwater pollutants at an outfall for long continuous simulations.
 
 
 
Figure 4. Observed and modeled outfall pollutant concentrations – Emery (industrial site) (Pitt 1987).
 
Use of Slamm to Identify Pollutant Sources and to Evaluate Different Control Programs

Table 1 is a field sheet that has been developed to assist users of SLAMM describe test watershed areas. This sheet is mostly used to evaluate stormwater control retrofit practices in existing developed areas, and to examine how different new development standards effect runoff conditions. Much of the information on the sheet is not actually required to operate SLAMM, but is very important when considering additional control programs (such as public education and good housekeeping practices) that are not quantified by SLAMM. The most important information shown on this sheet is the land use, the type of the gutter or drainage system, and the method of drainage from roofs and large paved areas to the drainage system. The efficiency of drainage in an area, specifically if roof runoff or parking runoff drains across grass surfaces, can be very important when determining the amount of water and pollutants that enter the outfall system. Similarly, the presence of grass swales in an area may substantially reduce the amount of pollutants and water discharged. This information is therefore required to use SLAMM.
  
Table 1. Study Area Description Field Sheet
 
The areas of the different surfaces in each land use is also very important for SLAMM. Figure 5 is an example showing the areas of different surfaces for a medium density residential area in Milwaukee. As shown in this example, streets make up between 10 and 20 percent of the total area, while landscaped areas can make up about half of the drainage area. The variation of these different surfaces can be very large within a designated area. The analysis of many candidate areas may therefore be necessary to understand how effective or how consistent the model results may be for a general land use classification.
 
  
 
 
Figure 5. Source areas – Milwaukee medium density residential areas (without alleys) (Pitt 1987).
               
Tables 2 and Table 3 are coding sheets that have been prepared for SLAMM users. The information on these sheets is used by SLAMM to determine the concentrations and loadings from the different source areas and the effectiveness of different control practices. Table 2 shows general information describing the areas and the characteristics of source areas. More information is required for some source areas than others, based upon responses to questions. Table 3 contains the coding sheets to describe the types of control practices that are to be investigated using SLAMM in a specific watershed area. Control practices evaluated by SLAMM include infiltration trenches, seepage pits, disconnections of directly connected roofs and paved areas, percolation ponds, street cleaning, porous pavements, catchbasin cleaning, grass swales, and wet detention ponds. These devices can be used singly or in combination, at source areas or at the outfalls or, in the case of grass swales and catchbasins, within the drainage system. In addition, SLAMM provides a great deal of flexibility in describing the sizes and other design aspects for these different practices.

 Table 2a. SLAMM Site Characterization Data Coding Sheet (Pitt and Voorhees 1995)

Table 2b. SLAMM Site Characterization Data Coding Sheet (Pitt and Voorhees 1995)

Table 3a. SLAMM Control Device Data Sheet (Pitt and Voorhees 1995)

Table 3b. SLAMM Control Device Data Sheet (Pitt and Voorhees 1995)

Table 3c. SLAMM Control Device Data Sheet (Pitt and Voorhees 1995) 

Table 3d. SLAMM Control Device Data Sheet (Pitt and Voorhees 1995)

One of the first problems in evaluating an urban area for stormwater controls is the need to understand where the pollutants of concern are originating under different rain conditions. Figures 6 through 9 are examples for a typical medium density residential area (described in the previous coding sheets) showing the percentage of different pollutants originated from different major sources, as a function of rain depth. As an example, Figure 6 shows the areas where water is originating. For storms of up to about 0.1 inch in depth, street surfaces contribute about one-half to the total runoff to the outfall. This contribution decreased to about 20 percent for storms greater than about 0.25 inch in depth. This decrease in the significance of streets as a source of water is associated with an increase of water contributions from landscaped areas (which make up more than 75% of the area and have clayey soils). Similarly, the significance of runoff from driveways and roofs also starts off relatively high and then decreases with increasing storm depth. Figures 7, 8 and 9 are similar plots for suspended solids, phosphorus and lead. These show that streets contribute almost all of these pollutants for the smallest storms up to about 0.1 inch. The contributions from landscaped areas then become dominant. Figure 9 shows that the contributions of phosphates are more evenly distributed between streets, driveways, and rooftops for the small storms, but the contributions from landscaped areas completely dominate for storms greater than about 0.25 inch in depth. Obviously, these are just example plots and the source contributions would vary greatly for different land uses/development conditions, rainfall patterns, and the use of different source area controls.

Figure 6. Flow sources for example medium density residential area having clayey soils (Pitt and Voorhees 1995).

 A major use of SLAMM is to better understand the role of different sources of pollutants. As an example, to control suspended solids, street cleaning (or any other method to reduce the washoff of particulates from streets) may be very effective for the smallest storms, but would have very little benefit for storms greater than about 0.25 inches in depth. However, erosion control from landscaped surfaces may be effective over a wider range of storms. The following list shows the different control programs that were investigated in this hypothetical medium density residential area having clayey soils: 

• Base level (as built in 1961-1980 with no additional controls)
• Catchbasin cleaning
• Street cleaning
• Grass swales
• Roof disconnections
• Wet detention pond
• Catchbasin and street cleaning combined
• Roof disconnections and grass swales combined
• All of the controls combined

 This residential area, which was based upon actual Birmingham, Alabama, field observations for homes built between 1961 to 1980, has no controls, including no street cleaning or catchbasin cleaning. The use of catchbasin cleaning in the area, in addition to street cleaning was evaluated. Grass swale use was also evaluated, but swales are an unlikely retrofit option, and would only be appropriate for newly developing areas. However, it is possible to disconnect some of the roof drainages and divert the roof runoff away from the drainage system and onto grass surfaces for infiltration in existing developments. In addition, wet detention ponds can be retrofitted in different areas and at outfalls. Besides those controls examined individually, catchbasin and street cleaning controls combined were also evaluated, in addition to the combination of disconnecting some of the rooftops and the use of grass swales. Finally, all of the controls together were also examined.

The following list shows a general description of this hypothetical area:
               all curb and gutter drainage (in fair condition)
                70% of roofs drain to landscaped areas
                50% of driveways drain to lawns
                90% of streets are intermediate texture (remaining are rough)
                no street cleaning
                no catchbasins
 About one-half of the driveways currently drain to landscaped areas, while the other half drain directly to the pavement or the drainage system. Almost all of the streets are of intermediate texture, and about 10 percent are rough textured. As noted earlier, there currently is no street cleaning or catchbasin cleaning.

 The level of catchbasin use that was investigated for this site included 950 ft³ of total sump volume per 100 acres (typical for this land use), with a cost of about $50 per catchbasin cleaning. Typically, catch basins in this area could be cleaned about twice a year for a total annual cost of about $85 per acre of the watershed.               

Street cleaning could also be used with a monthly cleaning effort for about $30 per year per watershed acre. Light parking and no parking restrictions during cleaning is assumed, and the cleaning cost is estimated to be $80 per curb mile.               

Grass swale drainage was also investigated, assuming that swales could be used throughout the area, there could be 350 feet of swales per acre (typical for this land use), and the swales were 3.5 ft. wide. Because of the clayey soil conditions, an average infiltration rate of about 0.5 inch per hour was used in this analysis, based on many different double ring infiltrometer tests of typical soil conditions. Swales cost much less than conventional curb and gutter systems, but have an increased maintenance frequency. Again, the use of grass swales is appropriate for new development, but not for retrofitting in this area.               

Roof disconnections could also be utilized as a control measure by directing all roof drains to landscaped areas. The objective would be to direct all the roof drains to landscaped areas. Since 70 percent of the roofs already drain to the landscaped areas, only 30 percent could be further disconnected, at a cost of about $125 per household. The estimated total annual cost would be about $10 per watershed acre.               

An outfall wet detention pond suitable for 100 acres of this medium density residential area would have a wet pond surface of 0.5% of drainage area to provide about 90% suspended solids control. It would need 3 ft. of dead storage and live storage equal to runoff from 1.25” rain. A 90o V notch weir and 5 ft. wide emergency spillway could be used. No seepage or evaporation was assumed. The total annual cost was estimated to be about $ 130 per watershed acre.               

Figure 9 Dissolved phosphate sources for example medium density residential area having clayey soils (Pitt and Voorhees 1995).

Table 4 summarizes the SLAMM results for runoff volume, suspended solids, filterable phosphate, and total lead for 100 acres of this medium density residential area. The only control practices evaluated that would reduce runoff volume are the grass swales and roof disconnections. All of the other control practices evaluated do not infiltrate stormwater. Table 4 also shows the total annual average volumetric runoff coefficient (Rv) for these different options. The base level of control has an annual flow-weighted Rv of about 0.3, while the use of swales would reduce the Rv to about 0.1. Only a small reduction of Rv (less than 10 percent) would be associated with complete roof disconnections compared to the existing situation because of the large amount of roof disconnections that already occur. The suspended solids analyses shows that catchbasin cleaning alone could result in about 14 percent suspended solids reductions. Street cleaning would have very little benefit, while the use of grass swales would reduce the suspended solids discharges by about 60 percent. Grass swales would have minimal effect on the reduction of suspended solids concentrations at the outfall (they are primarily an infiltration device, having very little filtering benefits). Wet detention ponds would remove about 90 percent of the mass and concentrations of suspended solids. Similar observations can be made for filterable phosphates and lead.

Figure 10. Cost-effectiveness data for runoff volume reduction benefits (Pitt and Voorhees 1995).

Figure 11. Cost-effectiveness data for suspended solids reduction benefits (Pitt and Voorhees 1995).

Figure 12. Cost-effectiveness data for dissolved phosphate reduction benefits (Pitt and Voorhees 1995).

Figure 13. Cost-effectiveness data for total lead reduction benefits (Pitt and Voorhees 1995).

Figures 10 through 13 show the maximum percentage reductions in runoff volume and pollutants, along with associated unit removal costs. As an example, Figure 10 shows that roof disconnections would have a very small potential maximum benefit for runoff volume reduction and at a very high unit cost compared to the other practices. The use of grass swales could have about a 60 percent reduction at minimal cost. The use of roof disconnection plus swales would slightly increase the maximum benefit to about 65 percent, at a small unit cost. Obviously, the use of roof disconnections alone, or all controlled practices combined, are very inefficient for this example. For suspended solids control, catchbasin cleaning and street cleaning would have minimal benefit at high cost, while the use of grass swales would produce a substantial benefit at very small cost. However, if additional control is necessary, the use of wet detention ponds may be necessary at a higher cost. If close to 95 percent reduction of suspended solids were required, then all of the controls investigated could be used together, but at substantial cost. 

Simple Workshop Example

The following is a simple “hello world” SLAMM input file example. This will enable the user to become familiar with the input portions of the program, and can form a basis for simple modifications. Table 5 is the site characterization sheet for a 100 acre residential area, modeled after site surveys conducted in Madison, Wisconsin. The acreage is simply the percentage of each area in the surveyed neighborhoods. This enables relatively efficient “unit area” calculations, for annual discharge (ft³ of runoff/100 acre/study period) and yield (lb of SS/100 acre/study period). The study period is for March 1 to November 11, 1981, the non-snow period for the 1981 rain year (previously determined by the USGS to be a good representative year for Madison). The area is relatively simple, comprised of the following areas: 

 Total directly connected impervious area:                23.67
Total impervious area draining to lawns:                  13.24
Pervious areas:                                                     63.09 
As seen, this is a heavily developed area, with more than 35% pavement and roofs, and about 2/3 of that amount directly connected to the drainage system. 

The area could have been simplified further, if the on-street parking conditions did not vary. However, it is common to have several street areas separated by street texture. The area has street cleaning once a week, but there are no other controls. The street dirt loading at the beginning of the study period and the street dirt accumulation rates are being determined by the model. It may have been appropriate to designate a large loading (as much as 10,000 lb/curb-mile) as the initial loading, as the study period begins immediately after snowmelt, and large street dirt loadings remain on the street until removed by rains, street cleaning, or wind turbulence. The street cleaning frequency remains at once per week for the whole 9 month period. However, if a high loading occurs at the beginning of the study period, it would be reasonable to designate an intensive street cleaning program (about twice a week) for the first month, or so, of the study period, then tapering off (to about once per month) for residential areas. 

Only runoff volume and suspended solids are being modeled. Table 6 is the corresponding SLAMM input file, while Table 7 is an output file, showing the contributions of different source areas to runoff yield and suspended solids discharges for each of the modeled rains and summarized for the complete period. The output table is prepared by selecting “file” then “print” from the tool bar after the complete analysis is run. The dialog box is a report generator for selecting the specific information to be printed, or saved to a disk file. The saved file is a *.csv (comma separated file) that can be directly opened in Excel for further formatting and evaluation. In this example, the directly connected impervious areas (which comprise about 24% of the area, produce 83% of the annual runoff volume and 79% of the annual suspended solids discharge. The landscaped area (about 63% of the total area), only produces about 14% of the annual runoff and 20% of the annual suspended solids discharge. The relative contributions for each source area varies as the rain depth changes, so appropriate control measures can be examined in relationship to the contributing areas for the rain depth ranges of most interest. Obviously, something should be done about the large amounts of paved/roof areas that are being discharged directly to the drainage system (or across pavement and then to the drainage system). 

Table 6. Example SLAMM Input File for “new mdr.dat”

  Data file name:  C:\Program Files\WinSLAMM\new mdr.dat        SLAMM Version V8.0
    Rain file name:  C:\PROGRAM FILES\WINSLAMM\MADS5289.RAN      
    Particulate Solids Concentration file name:  C:\PROGRAM FILES\WINSLAMM\MADISON.PSC
    Runoff Coefficient file name:  C:\PROGRAM FILES\WINSLAMM\RUNOFF.RSV
    Particulate Residue Delivery file name:  C:\PROGRAM FILES\WINSLAMM\MADISON.PRR
    Pollutant Relative Concentration file name:  C:\PROGRAM FILES\WINSLAMM\MADISON7.PPD
 
                                                                  Seed for random number generator:   0
    Study period starting date:  03/01/81                         Study period ending date:  11/30/81
    Date:  01-25-2000                                             Time:  19:53:57
    Fraction of each type of Drainage System serving study area:
      1.  Grass Swales 0
      2.  Undeveloped roadside 0
          Curb and Gutters, `valleys', or sealed swales in:
           3.  Poor condition (or very flat) 0
           4.  Fair condition 0
           5.  Good condition (or very steep) 1
    Site information:  100 acre base file of single family homes for Madison, Wisconsin.  This is based on a 5 site review amounting to approximately 39 acres.  Does not include downtown Isthmus areas. No-snow season only.
 
                           |<===== Areas for each Source (acres) =====>|
                           Resi-   Institu- Commercial Industrial  Open
                          dential   tional     Areas      Areas   Spaces
Source Area                Areas    Areas                          Areas         Freeway Source Area                   Area (acres)
 
12345678901234567890123456789012345678901234567890123456789012345678901234567890
Roofs 1                    2.06      0.00      0.00      0.00      0.00          Pavd Lane & Shldr Area 1                0.00
Roofs 2                    12.23     0.00      0.00      0.00      0.00          Pavd Lane & Shldr Area 2                0.00
Roofs 3                    0.00      0.00      0.00      0.00      0.00          Pavd Lane & Shldr Area 3                0.00
Roofs 4                    0.00      0.00      0.00      0.00      0.00          Pavd Lane & Shldr Area 4                0.00
Roofs 5                    0.00      0.00      0.00      0.00      0.00          Pavd Lane & Shldr Area 5                0.00
Paved Parking/Storage 1    0.00      0.00      0.00      0.00      0.00          Large Turf Areas                        0.00
Paved Parking/Storage 2    0.00      0.00      0.00      0.00      0.00          Undeveloped Areas                       0.00
Paved Parking/Storage 3    0.00      0.00      0.00      0.00      0.00          Other Pervious Areas                    0.00
Unpaved Prkng/Storage 1    0.00      0.00      0.00      0.00      0.00          Other Directly Conctd Imp               0.00
Unpaved Prkng/Storage 2    0.00      0.00      0.00      0.00      0.00          Other Partially Conctd Imp              0.00
Playground 1               0.00      0.00      0.00      0.00      0.00                                                   --------
Playground 2               0.00      0.00      0.00      0.00      0.00          Total                                   0.00
Driveways 1                5.14      0.00      0.00      0.00      0.00
Driveways 2                1.01      0.00      0.00      0.00      0.00
Driveways 3                0.00      0.00      0.00      0.00      0.00
Sidewalks/Walks 1          3.73      0.00      0.00      0.00      0.00
Sidewalks/Walks 2          0.00      0.00      0.00      0.00      0.00
Street Area 1              3.92      0.00      0.00      0.00      0.00
Street Area 2              1.33      0.00      0.00      0.00      0.00
Street Area 3              7.49      0.00      0.00      0.00      0.00
Large Landscaped Area 1    0.00      0.00      0.00      0.00      0.00
Large Landscaped Area 2    0.00      0.00      0.00      0.00      0.00
Undeveloped Area           0.00      0.00      0.00      0.00      0.00
Small Landscaped Area 1    63.09     0.00      0.00      0.00      0.00
Small Landscaped Area 2    0.00      0.00      0.00      0.00      0.00
Small Landscaped Area 3    0.00      0.00      0.00      0.00      0.00
Isolated Area              0.00      0.00      0.00      0.00      0.00
Other Pervious Area        0.00      0.00      0.00      0.00      0.00
Other Dir Cnctd Imp Area   0.00      0.00      0.00      0.00      0.00
Other Part Cnctd Imp Area  0.00      0.00      0.00      0.00      0.00
                        --------  --------  --------  --------  --------
Total                   100.00    0.00      0.00      0.00      0.00
                                                               
 
Total of All Source Areas               100.00
                                        ---------
Total of All Source Areas
     less All Isolated Areas            100.00
                                        =========
 
                   Source Area Control Practice Information
Land Use:  Residential
   Roofs 1    Source area number:  1
         The roof is pitched
         The Source Area is directly connected or draining to a directly connected area
   Roofs 2    Source area number:  2
         The roof is pitched
         The Source Area is draining to a pervious area (partially connected impervious area)
         The SCS Hydrologic Soil Type is Clayey
         The building density is low
   Driveways 1    Source area number:  13
         The Source Area is directly connected or draining to a directly connected area
   Driveways 2    Source area number:  14
         The Source Area is draining to a pervious area (partially connected impervious area)
         The SCS Hydrologic Soil Type is Clayey
         The building density is low
   Sidewalks/Walks 1    Source area number:  16
         The Source Area is directly connected or draining to a directly connected area
   Street Area 1    Source area number:  18
            1.  Street Texture:  intermediate
            2.  Total study area street length (curb-miles):  2.133
            3.  Initial Street Dirt Loading (lbs/curb-mi):  default value
            4.  Street Dirt Accumulation:
                  Default value used
      Control Practice:  Street Cleaning
            1. Street cleaning schedule: 
                 Begin cleaning on: 04/15/81    Schedule: 1/week 
                 Final cleaning period ending date:  10/01/81
            2. Street cleaner productivity:  Default
            3. Parking density:  Extensive (long term)
            4. Parking controls imposed?  No
            5. Equation coefficient M (slope):   0.55
            6. Equation coefficient B (intercept):   280
   Street Area 2    Source area number:  19
            1.  Street Texture:  intermediate
            2.  Total study area street length (curb-miles):  0.73
            3.  Initial Street Dirt Loading (lbs/curb-mi):  default value
            4.  Street Dirt Accumulation:
                  Default value used
      Control Practice:  Street Cleaning
            1. Street cleaning schedule: 
                 Begin cleaning on: 04/15/81    Schedule: 1/week
                 Final cleaning period ending date:  10/01/81
            2. Street cleaner productivity:  Default
            3. Parking density:  Medium
            4. Parking controls imposed?  No
            5. Equation coefficient M (slope):   0.65
            6. Equation coefficient B (intercept):   220
   Street Area 3    Source area number:  20
            1.  Street Texture:  intermediate
            2.  Total study area street length (curb-miles):  4.076
            3.  Initial Street Dirt Loading (lbs/curb-mi):  default value
            4.  Street Dirt Accumulation:
                  Default value used
      Control Practice:  Street Cleaning
            1. Street cleaning schedule: 
                 Begin cleaning on: 04/15/81    Schedule: 1/week 
                 Final cleaning period ending date:  10/01/81
            2. Street cleaner productivity:  Default
            3. Parking density:  Light
            4. Parking controls imposed?  No
            5. Equation coefficient M (slope):   0.3
            6. Equation coefficient B (intercept):   450
   Small Landscaped Area 1    Source area number:  24
         The SCS Hydrologic Soil Type is Clayey
 
Pollutants to be Analyzed and Printed:
 
         Pollutant Name                Pollutant Type
         --------------                --------------           Solids                       Particulate

SLAMM/SWMM Interface Program

Introduction. The purpose of the SLAMM-SWMM Interface Program (SSIP) is to allow the user to replace SWMM’s RUNOFF Block with SLAMM. This allows SLAMM to provide the runoff and pollutant loads for input into the TRANSPORT or EXTRAN Blocks of SWMM, instead of using results from the RUNOFF Block. Using SLAMM better accounts for small storm processes and adds greater flexibility in evaluating source area flow and pollutant controls. The interface program manipulates the output from SLAMM so that it is acceptable for SWMM. The principal manipulation is to convert the event volumes and loads into event hydrographs and pollutographs. 

The version of the SLAMM-SWMM Interface Program presented here is Version 1. 1. This version has not reached the full potential envisioned for the program. This is discussed later. It is assumed that the reader is familiar with both SLAMM and SWMM and has the appropriate documentation. 

SSIP Version 1.0. An early version of the SLAMM-SWMM Integration Program was developed to work with SWMM Windows provided by the US Environmental Protection Agency (based on SWMM Version 4.3). This was used to create SSIP Version 1.1, which is deigned for use with all SWMM 4 sub-versions. 

SSIP Version 1.1. SSIP Version 1.1 takes hydrographs and pollutographs from SLAMM and partially prepares input hydrographs for use in the SWMM EXTRAN Block and input hydrographs and pollutographs for the SWMM TRANSPORT Block. However, at this time SSIP has only been tested in the preparation of hydrographs for SWMM EXTRAN. 

SLAMM currently has the option of producing source area hydrographs and pollutographs over continuous periods. Each location is produced as a separate file. The format for these files is as follows:

• First Line = subcatchment number (defined in SLAMM)
• Second Line = labels for each column in “quotation marks”, separated by commas
• Third Line = Values separated by commas, no spaces (e.g., time,flow,pollutant,pollutant,)
• NOTE: The time increments used in each file must be identical (e.g., 1, 1.5, 2, … must be the same for each file).

These files are converted into files appropriate for SWMM. However, at this time, the user must manually manipulate some of these converted files for actual use in SWMM. The SLAMM/SWMM Interface Program Version 1.1 is Windows-based and is programmed in Visual Basic. A new version is currently being prepared that will further minimize the needed user manipulation. 

How SSIP Works.

1. SSIP goes through each SLAMM hydrograph/pollutograph file, one at a time, in the directory chosen by the user. These files have the extension *.hyd. 

2. SSIP then creates the files for SWMM (*.hp1, *.hp2, and*.hp3 for TRANSPORT and *.hp4 for EXTRAN). 

3. Next, it reads the second hydrograph/pollutograph file and appends the information to the first files that were created. This will be done for all files with the extension *.hyd. So it is important that only the files desired are located in the directory. 

4. When there are no more SLAMM files left, the user gets a message that the file conversions are completed. 

Interface Program Instructions. The instructions below are illustrated with a series of files provided with the disk that accompanies this report. These files are referred to throughout this section in order to illustrate the process for executing SSIP and creating useable hydrograph files for SWMM EXTRAN. (Recall that this is the only application of SSIP that has been tested to date.) All of the needed SLAMM and SSIE files are installed in a single directory when the files are installed (from the attached disks having zipped filed). 

1 . The user begins by opening the file “Interface1.exe” provided on the disk. A series of dialog boxes will then appear. Instructions for each dialog box appear with that box. The dialog boxes are discussed below: 

• A start-up box. This box starts the program.

• A file location box (to identify where the SLAMM files are and where the SWMM files are to be placed.) At this time, SSIP seems to work best if all file operations (including the execution of SIPP) are carried out under the same directory. Set the SLAMM file locator to the directory to which you placed the contents of the supplied disk (this is where the SLAMM files are located). For this application there are three files, associated with each of three locations for which SLAMM produced hydrographs and pollutographs. These three locations will be input to SWMM. Set the SWMM file locator to the same directory.

• A SWMM Block selection box (i.e. for which SWMM Block files are to be produced). The TRANSPORT option has not been tested. Use only the EXTRAN option at this time. Select the EXTRAN option.

• A “process complete” box informing the user that the SWMM files have been created. 

2. Once the processing is complete, as many as four files (*.hp 1, *.hp2, and *.hp3 for TRANSPORT and *.hp4 for EXTRAN) will have been produced. These files need to be manually placed in a SWMM system input file produced by the user. (The term “system input file” is meant to describe the file that describes the drainage system.) An example system input file is included on the disk as “extrn001.run”. This file is associated with Example 1 in the SWMM EXTRAN Block users manual (Roesner, et al. 1988). Be sure it is on the directory you created on your hard drive. 

The SWMM system input file will need to be modified before SWMM can be executed. For the most part, this requires the user to modify and then merge the file created by SSIP with the SWMM system input file. Open the file named “usehp001.hp4” with any text editor. (The “001” indicates that this is the first time a file was created. If you repeated this operation, a file called “usehp002.hp4” would be produced.) Then do the following: 

• Remove the first line that simply says “3”.

• On the line labeled “K2”, replace the three alphanumeric labels (in quotes) with 82309, 80408, and 81009 (no quotes), respectively. These are the three locations in SWMM to which the SLAMM produced flows are being directed (see Example 1 in the SWMM EXTRAN users manual).

• Resave this file.

Open the example SWMM system input file “extrn001.run” with any text editor. Then do the following: 

• Optional: change the value 1440 to some other appropriate value. This is the number of time steps. The number of time steps multiplied by the computational time step length (the value 20 to the right of the number of time steps), in seconds, must be equal to or shorter than the time represented by the flow history provided by SLAMM. In this case, the example SLAMM files covers 365 hours, or 1,314,000 seconds. The hydrograph time step is 2.5 minutes. (The computational time step and the flow time step do not have to be the same.)

• Replace the lines labeled “K3” with the file “usehp001.hp4”. Be sure that the “$ENDPROGRAM” line is the last line in the resulting file. The K3 lines in EXTRAN are the hydrographs to input to the sewer system, with each line representing a different point in time.

• Resave this file.

3. Execute SWMM with the modified “extrn001.run” file. You can follow this process with any sub-version of SWMM Version 4.

Limitations and Caveats. SSIP takes all the SLAMM files from the directory chosen by the user and converts them. If there are SLAMM files (i.e., those with the extension *.HYD) in the directory chosen by the user that are not to be included in the conversion, it is suggested that the user delete or move these files before running the Interface Program. 

SSIP does not run on Windows NT because of file permissions. It is designed to run under Windows 95 or Windows 98. SSIP may work under other operating systems, but these have not been tested or supported. 

Future Versions. Work is continuing on making SSIP much more user friendly and efficient. In its present form, the user is far too involved in file manipulation. Future versions will also transfer information through the more efficient and automated interface mechanisms found in SWMM (see Section 2 of the SWMM user's manual, Huber, et al. 1988) rather than through the user-prepared system input files. Location matching will also be part of SSIP (as opposed to the manual matching done now). These changes will make the interface effort much more seamless for the user.

References

Bachhuber, J.A. “A decision making approach for stormwater management measures: A case example in the City of Waukesha, Wisconsin.” North American Water and Environment Congress. American Society of Civil Engineers. Reston, VA. C-184-1. 1996.

Bannerman, R., K. Baun, M. Bohn, P.E. Hughes, and D.A. Graczyk. Evaluation of Urban Nonpoint Source Pollution Management in Milwaukee County, Wisconsin, Vol. I. Grant No. P005432-01-5, PB 84-114164. US Environmental Protection Agency, Water Planning Division, November 1983.

Bannerman, R.T., A.D. Legg, and S.R. Greb. Quality of Wisconsin Stormwater, 1989-94. U.S. Geological Survey. Open-file report 96-458. Madison, WI. 26 pgs. 1996.

EPA (U.S. Environmental Protection Agency). Final Report for the Nationwide Urban Runoff Program. Water Planning Division, Washington, D.C., December 1983.

Haubner, S.M. and E.F. Joeres. “Using a GIS for estimating input parameters in urban stormwater quality modeling.” Water Resources Bulletin. Vol. 32, no. 6, pp. 1341 – 1351. December 1996.

Huber, W.C and R.E. Dickinson, Storm Water Management Model, Version 4, User’s Manual, EPA-600/3-88-001a, U.S. Environmental Protection Agency, Athens, Georgia, 1988.

Kim, K., P.G. Thum, and J. Prey. “Urban non-point source pollution assessment using a geographical information system.” Journal of Environmental Management. Vol. 39., no. 39, pp. 157 – 170. 1993.

Kim, K. and S. Ventura. “Large-scale modeling of urban nonpoint source pollution using a geographical information system.” Photogrammetric Engineering & Remote Sensing. Vol. 59, no. 10, pp. 1539 – 1544. October 1993.

Legg, A.D., R.T. Bannerman, and J. Panuska. Variation in the Relation of Rainfall to Runoff from Residential Lawns in Madison, Wisconsin, July and August 1995. U.S. Geological Survey. Water-resources investigations report 96-4194. Madison, Wisconsin. 11 pgs. 1996.

Ontario Ministry of the Environment. Humber River Water Quality Management Plan, Toronto Area Watershed Management Strategy. Toronto, Ontario, 1986.

Pitt, R. Demonstration of Nonpoint Pollution Abatement Through Improved Street Cleaning Practices. EPA-600/2-79-161, U.S. Environmental Protection Agency, Cincinnati, Ohio, August 1979.

Pitt, R. and M. Bozeman. Sources of Urban Runoff Pollution and Its Effects on an Urban Creek. EPA-600/S2-82-090, U.S. Environmental Protection Agency, Cincinnati, Ohio, December 1982.

Pitt, R. and G. Shawley. A Demonstration of Non-Point Source Pollution Management on Castro Valley Creek. Alameda County Flood Control and Water Conservation District (Hayward, CA) for the Nationwide Urban Runoff Program, U.S. Environmental Protection Agency, Water Planning Division, Washington, D.C., June 1982.

Pitt, R. Characterization, Sources, and Control of Urban Runoff by Street and Sewerage Cleaning. Contract No. R-80597012, U.S. Environmental Protection Agency, Office of Research and Development, Cincinnati, Ohio, 1984.

Pitt, R. and P. Bissonnette. Bellevue Urban Runoff Program, Summary Report. Storm and Surface Water Utility, Bellevue, Washington, November 1984.

Pitt, R. and J. McLean. Toronto Area Watershed Management Strategy Study - Humber River Pilot Watershed Project. Ontario Ministry of the Environment, Toronto, Ontario, June 1986.

Pitt, R. “Runoff controls in Wisconsin’s priority watersheds,” Conference on Urban Runoff Quality - Impact and Quality Enhancement Technology, Henniker, New Hampshire, Edited by B. Urbonas and L.A. Roesner, Proceedings published by the American Society of Civil Engineering, New York, June 1986.

Pitt, R. Small Storm Flow and Particulate Washoff Contributions to Outfall Discharges. Ph.D. dissertation, Department of Civil and Environmental Engineering, the University of Wisconsin - Madison, November 1987.

Pitt, R. and J. Voorhees. “Source loading and management model (SLAMM).” Seminar Publication: National Conference on Urban Runoff Management: Enhancing Urban Watershed Management at the Local, County, and State Levels. March 30 – April 2, 1993. Center for Environmental Research Information, U.S. Environmental Protection Agency. EPA/625/R-95/003. Cincinnati. Ohio. pp. 225-243. April 1995.

Roesner, L.A., J.A. Aldrich, and R.E. Dickinson, Storm Water Management Model, User's Manual, Version 4: Addendum I, EXTRAN, EPA-600/3-88-001b, U.S. Environmental Protection Agency, Cincinnati, Ohio, August, 1988.

Thum, P.G., S.R. Pickett, B.J. Niemann, Jr., and S.J. Ventura. “LIS/GIS: Integrating nonpoint pollution assessment with land development planning.” Wisconsin Land Information Newsletter. University of Wisconsin – Madison. Vol., no. 2, pp. 1 – 11. 1990.

Ventura, S.J. and K. Kim. “Modeling urban nonpoint source pollution with a geographical information system.” Water Resources Bulletin. Vol. 29, no. 2, pp. 189 – 198. April 1993.

Reading and links

• User’s Guide (appendix C)

• Controls in SLAMM (appendix D)

• SLAMM Download

Assignment A6 

Allow up to 12 h for reading, installing SLAMM and doing the basic analyses, and up to 6 h for writing your web page. It is important that you conduct the reading included in the links, as the above description of SLAMM is very basic and doesn’t describe the modeling process and attributes very thoroughly (especially in comparison to alternative models). 

1) Download and install SLAMM and do a simple “hello world” model run based on the example in the text (a 100 acre residential area). 

2) Modify the basic run for your area:

a) Modify the basic model run by describing the neighborhood where you live. Describe the surfaces in your area, using the acre values to represent the percentages of each surface, so the total area equals 100 ac. 

b) Select a rain series that may be similar to your area (Birmingham and Toronto have rain files included. Germany and South Africa may be grossly approximated by using rain files for areas having similar climates; sorry about that, but if you want, you can create local rain files for this assignment using the instructions in the User’s Guide. SLAMM is also a fair weather program, as it currently does not include snowmelt (or baseflows). For areas with very cold winters (having extended periods of snowpacks each winter), the model should only be run for the rain season. For other areas, long-term continuous simulations are possible using the complete rain files covering several decades. The following is a listing of the rain files included with the download program, including brief descriptions of the rain series included in each file (you notice there are no 2000 year dates, that is another story).

 c) run the modified SLAMM for your area, describing the annual total/average conditions for runoff volume and suspended solids, and describe the variability in individual events.

 3) Further modify your area to consider simple development alternatives (not very suitable for retro-fitting), especially features associated with “low impact development” (narrow streets, disconnected roof and pavement drainages, and grass swales should give you a good start). Compare this with a hard development using very wide streets (especially to accommodate on-street parking), and mostly directly connected pavement, and typical curb and gutter drainages.

 EXTRA: 4) In addition to using a rain file suitable for your area, also run your site descriptions using the special rain file “Bhamsrce.ran” which is an artificial series of rains starting with very small and short duration rains, to large and long duration rains. The depth/duration inter-relationship was developed for Birmingham, AL, conditions, and the durations could easily be modified, if you want, for more accurate local conditions. This file will enable you to more easily see where the flows and pollutants are originating for different types of rains, as the output is already sorted (an alternative would be to sort a regular output file by rain depth). Examine this information and recommend the types of stormwater controls, or other alternatives, that are most suitable. As an example, street cleaning only affects streets and pavement, and if these areas are not significant sources, then that control may not be very effective. Drainage system and outlet controls can obviously affect all flows, but are not targeted to critical source areas and have to be large to accommodate the combined flows from all areas.