Approved April 23, 1992, by the WEF Executive Committee

Some stormwater discharges are contributing to the pollution of the nation's waterways. Municipal stormwater systems and urban and rural nonpoint runoff are all potential contributors to water quality problems in receiving waters. Given the regulatory differences required to address both point and nonpoint sources of stormwater under current federal law, this statement focuses on needed improvements in how point source discharges are addressed. It should be noted, however, that stormwater discharges ultimately should be addressed as part of an overall watershed approach which considers all sources of potential water quality impairment.

The current EPA stormwater permitting and control program will affect hundreds of thousands of municipal and industrial facilities, a number greater than all the facilities permitted under the NPDES during the last 20 years. However, technologies are just now beginning to be adapted specifically for point source stormwater control. As cost-effective technologies are adapted or developed, intensive research and analysis is needed to determine the extent and magnitude of stormwater discharges and the impact they are having on the water environment.

Strategy
Municipal and industrial point source stormwater discharges should be addressed under the authority of the National Pollutant Discharge Elimination System (NPDES). The permitting process, however, must take into account the inherent difference between conventional discharges and stormwater discharges. Innovative methods for reducing the potential administrative burden must be considered, including the use of general permits to the greatest extent possible. Discharge-specific permits should be limited only to those discharges which are having a quantifiable and significant adverse impact on receiving water quality.

Additional investigations must be conducted to obtain scientifically valid data on which to base legally defensible and environmentally sound permit terms and conditions. This data acquisition effort already is under way in many locations.

Until defensible and justifiable permit terms and conditions are developed, control measures should consist of cost-effective and reasonable Best Management Practices. Costly structural modification requirements and long-term intensive control programs should be deferred until any adverse impacts of specific stormwater discharges on receiving waters can be assessed and the water quality improvement of proposed control measures on such discharges quantified.

If it is determined that stormwater discharges are having an unacceptable impact on the environment, and that further control measures are necessary, the following factors should be considered in developing specific controls:

• Environmental benefit
• Feasibility of implementation
• Cost-effectiveness
• Timing of implementation

Preference should be given to control measures at a given site which have the greatest environmental benefit for the least economic impact. States must have sufficient flexibility to implement control requirements which meet federal mandates while taking into consideration local and regional water quality characteristics. For example, the discharge of nutrient-laden stormwater into a certain receiving water may cause an adverse environmental impact, and require more stringent controls, than a similar discharge into another watershed.

Problems Associated with Stormwater Assessment and Controls
A key problem which complicates the assessment and control of stormwater discharges and their associated impacts is their great diversity. Stormwater varies according to geography, duration, and intensity of the storm event, ambient environmental conditions along the course of stormwater runoff, and the condition of receiving waters impacted by the runoff. This inherent variability makes it difficult to define "typical" or "standard" stormwater discharges, or to develop standardized means of assessing their impacts. A range of conditions, as opposed to a single means of assessment, should therefore be established. This would allow for more realistic assessment of variable stormwater discharges, and help ensure that stormwater control programs reflect the actual nature of the problem.

Existing water quality assessment criteria and techniques designed to measure problems associated with conventional municipal and industrial discharges should not be relied upon to assess stormwater impacts. These conventional discharges are qualitatively and quantitatively predictable in contrast to stormwater discharges, and usually occur in locations where monitoring equipment can be feasibly sited. Techniques which take into account the characteristics of the receiving water after the storm event (i.e., increased stream flow and short-term acute discharges of toxics) should be used for assessing stormwater impacts.

It should be noted that one monitoring and assessment technique currently being considered for stormwater discharges, whole effluent toxicity (WET) testing, typically is conducted over a period of days, whereas most storm events last only a few hours. Another proposed technique, biological monitoring, can be used to measure long-term stormwater impacts, but only if suitable data from non-affected waters are available for comparison. These techniques should only be used where site-specific analysis indicates they are applicable. Widescale, indiscriminate application of these techniques as part of a regulatory monitoring program is not recommended.

Current Regulatory Program
Current court-imposed deadlines for issuance of stormwater regulations have left EPA, the states, industry, and municipalities struggling to comply with permit application requirements. To satisfy the requirements of the court, EPA issued regulations prior to development of a comprehensive and coherent method for implementing the subsequent permit program.

Many states, municipal agencies, and industries have moved to implement these programs even though the application filing and sampling requirements are poorly understood. Inadequate funding has exacerbated the confusion and delays. Potential permittees need clearer and more detailed instructions, guidelines, and explanations regarding permit conditions and sampling requirements. Congress should provide EPA with the authority and resources to implement this program in a clear and understandable fashion. This includes working with all affected parties to develop a permit application process which is feasible and realistic.

Time is needed to develop scientifically valid and defensible monitoring and control requirements which address the unique nature of stormwater. Initial monitoring results should be used as the basis for a long-term database, which can then be utilized in setting permit requirements once sufficient and scientifically valid information is available.

Conclusion
In order to ensure that dwindling resources are expended where they will have the most impact, we should seek to define the extent of the stormwater problem, identify those areas which are experiencing adverse impacts, and develop site-specific control programs to address the problem in those areas. This approach should be developed to reflect the enormity of the permitting burden associated with point source discharges of stormwater and should carefully weigh the environmental impacts of stormwater discharges in the context of the other national environmental priorities.