Combined Sewer System Long Term Control Plan - DC Water

Existing Conditions
and plans to consider the adoption of the new bacteria standard in its WQS at its next triennial
review scheduled for late 2002 or early 2003. Therefore, e-coli concentrations have been
monitored and modeled as part of the LTCP development effort to evaluate the performance of
alternatives in relation to this potential new standard.
2.4.2 EPA Combined Sewer Overflow (CSO) Control Policy
The EPA first issued requirements for control of CSOs with publication of a Control Strategy in
September 1989. In April 1994, the agency issued its CSO Control Policy designed to elaborate on
the Strategy and to expedite compliance with the requirements of the CWA. The purpose of the
policy is to coordinate the planning, selection, design and implementation of CSO management
practices and controls, to meet the requirements of the CWA and to involve the public fully during
the decision-making process.
The policy is framed around the principal elements as follows:
Implementation of minimum technology-based CSO controls; and
Development of long-term CSO control plans which evaluate alternatives for attaining
compliance with the CWA, including compliance with water quality standards and
protection of designated uses, and modifications to the standards if warranted.
CSO policy became law with the passage of the Wet Weather Water Quality Act of 2000 in
December 2000. EPA implements the CSO Control Policy through the NPDES Permit Program.
2.4.2.1 Minimum Technology-Based CSO Controls
Minimum requirements for technology-based controls have been developed by EPA for combined
sewer systems. These requirements are included in EPA’s list of “Nine Minimum Controls” (NMC)
which are summarized as follows:
1. Proper operation and regular maintenance programs for the sewer system and the CSOs;
2. Maximize use of the collection system for storage;
3. Review and modification of pretreatment requirements to assure CSO impacts are
minimized;
4. Maximize flow to the POTW (public owned treatment works) for treatment;
5. Prohibition of CSOs during dry weather;
6. Control of solid and floatable materials in CSOs;
7. Pollution prevention;
8. Public notification to ensure that the public receives adequate notification of CSO
occurrences and CSO impacts; and
9. Monitoring to effectively characterize CSO impacts and the efficacy of CSO controls.
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