WET WEATHER WATER QUALITY STANDARDS FOR CSO IMPACTED WATERS

The 1998 USEPA National Water Quality Inventory Report to Congress indicated that urban and agricultural wet weather sources are the most significant causes of impairment to our Nation's rivers and streams. However, these “impairments” are typically assessed in the reference to water quality standards developed in the context of historical efforts to control dry weather wastewater sources. Therefore, the significance of wet weather impairments and the need for costly controls is under debate. This issue has been especially controversial for municipalities that are required to control wet weather combined sewer overflows (CSOs). This paper explores the issue of wet weather water quality standards for CSO impacted waters, provides an overview of the obstacles to undertaking and completing the water quality standards review and revision (WQSRR) process, and includes a summary of the steps that EPA and other organizations are taking to support scientifically sound and regulatory compliant WQSRRs.

In 1994 EPA published the Natural Combined Sewer Overflow policy. The policy established nine minimum controls as a technology requirement plus additional controls as needed to meet water quality standards. The policy also required that water quality standards be reviewed and revised for applicability to wet weather CSO conditions. As of 1999 only two such reviews had been undertaken, and Congress directed EPA to provide guidance and assistance to support the WQSRR process. In the Spring of 1999, EPA conducted several stakeholder listening sessions to get feedback from environmental groups, municipalities, state and regional EPA regulato rs and others on the WQSRR process. EPA used these sessions to define central issues and prepare a preliminary outline of needed guidance. This information was then critically reviewed in September of 1999 by an Expert Stakeholder Panel convened jointly by EPA and WEF. Wet weather CSO and water quality standards issues were further reviewed at a WEFTEC preconference workshop in October of 1999.

This paper explores the background of this issue, the obstacles identified by stakeholders and the process EPA has been using for developing the required guidance. The pivotal controversial issues have been identified and discussed. The final EPA guidance is targeted for Fall 2000 and will be presented and discussed in Session 16 at the WEFTEC 2000 conference presentation.