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Every year, King County prepares an annual report on its combined sewer overflow (CSO) control program for the Washington State Department of Ecology (Ecology).

These reports are required under the National Pollutant Discharge Elimination (NPDES) permit for King County’s West Point Treatment Plant in Seattle and WAC 173-245-090.1 .

In 2013 King County signed an agreement with the Environmental Protection Agency (EPA) and the Washington State Department of Ecology (Ecology). This agreement, called a “consent decree” also requires an annual report. With the agreement of EPA and Ecology the two annual reports are consolidated into one. This report meets the consent decree, state, and federal requirements.

Report Contents
1.0 Introduction
2.0 Programs to Meet EPA’s Nine Minimum Controls
3.0 CSO Control Measures Currently Underway
4.0 Summary of Rainfall and CSO Events
5.0 Summary of Consent Decree and NPDES Violations in 2019
6.0 Control Status of CSO Locations
7.0 Post-construction Monitoring
A Untreated CSO Events, January–December 2020
B Treated CSO Events, January–December 2020
C Alki Wet Weather Treatment Station Annual Report, January–December 2020
D Carkeek Wet Weather Treatment Station Annual Report, January–December 2020
E Elliott West Wet Weather Treatment Station Annual Report, January–December 2020
F Henderson/MLK Jr. Way Wet Weather Treatment System Annual Report, January–December 2020

Janice Johnson
CSO Control Program