Summary

King County Executive Dow Constantine today proposed a long-term plan to control combined sewer overflows – one that reaffirms King County’s commitment to water quality while at the same time calling for a new science-based study to be carried out in parallel with top-priority combined sewer overflow projects over the next three years.

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King County Executive Dow Constantine today proposed a long-term plan to control combined sewer overflows – one that reaffirms King County’s commitment to water quality while at the same time calling for a new science-based study to be carried out in parallel with top-priority combined sewer overflow projects over the next three years.

“As we meet our obligations to control combined sewer overflows, we should take this opportunity to coordinate these projects with other watershed investments to make sure we are delivering the best outcomes for improving water quality and protecting public health” said Executive Constantine.

Combined sewer overflows, or CSOs, discharge a combination of wastewater and stormwater into rivers, lakes, and Puget Sound during heavy rains when sewers are full.

King County is required by state law to control its remaining uncontrolled CSOs to no more than one overflow event per year by 2030. To accomplish that, the Executive on June 15 sent the King County Council a plan to carry out nine new projects to control 14 uncontrolled CSOs that still exist in the oldest parts of Seattle.

A key element of the Executive’s proposal is the call for a new science-based water quality assessment and environmental benefit study to be carried out in parallel with top-priority CSO projects over the next three years.

“This proposal keeps us on track to address the remaining CSOs by 2030, while we learn more about the sources of pollutants and how our other actions to improve water quality, health, and habitat outcomes can be sequenced for the greatest benefit,” added Constantine.

Since the 1980s, King County has successfully controlled roughly half of its 38 CSOs, reducing volumes of uncontrolled CSOs in our waterways by more than 65 percent.

The nine new proposed projects are expected to be among the most complex and expensive, estimated to cost $711 million. The proposed plan is based on the input received during a public process in late 2011, and considers the program schedule, CSO control methods, potential neighborhood impacts and project sequence.

The proposal reflects stakeholder and public comments to:

• complete two projects in the Lower Duwamish River area sooner to coincide with federally-coordinated sediment cleanup;
• evaluate the use of Green Stormwater Infrastructure techniques to complement more traditional CSO control techniques;
• collaborate with the City of Seattle on projects to improve effectiveness and save money; and
• take steps to assess local waterbodies where CSOs discharge to provide the best outcomes for improving water quality.

The proposed study of water quality and environmental benefit would be guided by a new, integrated planning framework developed by the U.S. Environmental Protection Agency. An independent science panel would assess the findings and potential actions identified in the study. Federal, state, tribal, and environmental leaders would be invited to help frame the questions and make recommendations to meet water quality standards and integrate actions within the CSO discharge areas for the most benefit.

The goal of the proposed study is to inform decisions about the most effective, integrated set of actions to improve long-term water quality and protect public health in the CSO discharge areas. 

“As a region, we are poised to boost investments in combined sewer overflow control, clean up contaminated sediments in the Lower Duwamish, implement more stringent stormwater standards, and put salmon recovery plans into action,” said Executive Constantine. “While there is a lot of public support for each of these initiatives individually, we need to show how we can best integrate and sequence them to get the most for the public’s money.”

The King County Council is scheduled to act on the County’s CSO Control Program in September.

Learn more about King County’s CSO Control Program at

www.kingcounty.gov/csocontrol