The components of the SWQMP are designed to address a range of stormwater pollution sources. Program components include methods and practices for identifying and managing sources of pollutants to the storm sewer system from construction sites, commercial and residential areas, industrial activities, and non-stormwater discharges (also called "illicit connections") entering the storm sewer system. Urban stormwater pollutant sources are to be located and controlled through ordinances, local programs, etc. to reduce the pollutants discharged from their system to the maximum extent practicable.
In the development of the SWQMP, the local governments are responsible for determining the types of control measures that are most appropriate for their specific needs. This allows flexibility for the municipalities to tailor their stormwater management programs to the needs and priorities of their jurisdictional areas. The various municipalities will have similarity in their programs due to the state's emphasis on pollution prevention and source reduction methods for stormwater management.
While the emphasis will be on these methods, the municipalities will be able to select the specific methods that best fit their needs to produce an effective and efficient stormwater management program. DEM will continue to have oversight over the programs to assure that they are adequately addressing stormwater needs.
It should be mentioned that the industries and municipalities currently covered by the NPDES stormwater requirements represent Phase I of the federal stormwater control program. The Clean Water Act requirements for regulating stormwater discharges approached the problem on a priority basis with emphasis on high risk areas in the initial stages of the stormwater program.
The second step in the federal program involves a review of those areas that are not covered under Phase I (industries and municipalities) to determine which areas should be covered under Phase II of the program. It is apparent that additional areas will be covered under Phase II, and the U. S. EPA is currently working on reports to congress outlining additional areas and activities that may require coverage under Phase II of the federal stormwater program. In addition, reauthorization of the Clean Water Act is anticipated to include provisions which will impact coverage under the NPDES stormwater programs and other related areas.
On the state level, DEM is stressing a need to look at priority areas and areas where urban water quality problems exist in targeting where stormwater coverage may apply under Phase II. It is also anticipated that the experience gained through the existing municipal NPDES stormwater programs can be utilized to stream-line the application process and program development for future municipalities that may be covered. The use of monitoring and reporting information from the currently covered municipalities will be an invaluable tool in assessing the most efficient and effective methods of controlling stormwater problems on the local level.
Stormwater Pollution Prevention Plans
As part of the NPDES permit requirements, all facilities will be required to prepare a Stormwater Pollution Prevention Plan (SPPP) to reduce and prevent pollution in the receiving water from the stormwater discharge. An SPPP consists of five parts: 1) a Site Plan; 2) a Stormwater Management Plan; 3) a Spill Prevention and Response Plan; 4) a Preventive Maintenance and Good Housekeeping Program; and 5) Training Programs to educate and train all employees in reducing stormwater pollution. The measures in the stormwater management system should work together in a systematic way to eliminate, remove or reduce stormwater pollutants in a reliable and cost-effective manner. Industrial facilities must make Stormwater Pollution Prevention Plans available to municipalities.
Methods to Estimate Pollutant Loading
Estimating pollutant loading is important to meet criteria for the protection of a stream or other water body. Newer water quality management plans are written to control the total daily load of pollutants entering the receiving water from all sources rather than the concentration of pollutants from only point source discharges. As the newer rules are phased in, developments, industrial sites, municipalities and any other NPDES permit holder must control the loading of pollutants their discharge adds to the water. There are several methods for estimating pollutant loading.
A simple method is to compute the total flow of runoff from a site, find (from a reference work) the average pollutant concentration in the stormwater, and multiply the two numbers to obtain the total mass of pollutant in the stormwater discharge. This technique should have adequate accuracy for small drainage areas if the concentrations and other values for the stormwater volume are properly chosen.
Other computational methods include various techniques of calculating the total flow from the drainage area using computer models. Values of pollutant concentration or loading coefficients (pounds or kilograms of pollutant per acre or hectare) for pollutants can then be used to calculate an estimate for the pollutant loading. There are a number of computer models available to evaluate stormwater flows and pollutant loading. These models usually require advanced computer skills and sophisticated measurements to yield reliable results. Advantages of such computational methods are that long records of hydrologic data may be used to compute the stormwater volumes and pollutant loadings, which may increase accuracy, and loadings may be predicted for hypothetical storms or longer periods of time. Also, computational methods are inexpensive, flexible and can be used to predict the loadings with differing controls once the initial set-up and calibration are done. However, calibration of models can require extensive effort and the methods are still dependent on the experience and judgment of the user in choosing values needed for the models.
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