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Agreement to formalize King County’s long-term pollution control plan


King County Executive Dow Constantine will sign an agreement with federal regulators for completion of work to protect local waterways from stormwater and wastewater pollution.


King County Executive Dow Constantine will sign an agreement with federal regulators for completion of work to protect local waterways from stormwater and wastewater pollution.

“Over the past 30 years, King County has made great strides in reducing the volume of discharges that flow into Puget Sound and other waterways from a combination of sewer overflows and polluted stormwater,” said Executive Constantine. “With this agreement, we affirm our commitment to the Clean Water Act, and to completion of our long-term pollution control plan.”

With unanimous approval from the King County Council, Executive Constantine today signed legislation that enables final agreement on a consent decree with the U.S. Environmental Protection Agency (EPA) to control overflows of stormwater mixed with sewage that still occur in older parts of Seattle during heavy rains.

“Puget Sound, and our local waterways, will be cleaner for future generations due to King County’s continuing commitment to reduce pollutants by controlling combined sewer overflows,” said Councilmember Larry Phillips, Chair of the Regional Water Quality Committee. “King County’s efforts over the past four decades have reduced the amount of sewage spilled in King County’s waterways from 20-30 billion gallons per year to less than 800 million gallons, and the approved plan will further reduce that to ensure an average of no more than one CSO event per year.”

The negotiation of terms with federal regulators began in 2007 with an EPA audit. The consent decree enforces the County Council-approved schedule to complete nine CSO control projects to control the remaining 14 uncontrolled sites at an estimated cost of $711 million (in 2010 dollars), and imposes requirements around documenting program progress.

King County had already committed to limiting combined sewer overflows to one per year at each outfall by 2030 through its adopted policies and a 2011 Agreement with the Department of Ecology.

Since the 1970s, King County has successfully reduced volumes of untreated discharges and uncontrolled CSOs in area waterways by more than 90 percent.

“Today’s proposed agreement signals a new era in protecting Seattle-area waters from sewer overflows," said Dennis McLerran, EPA Regional Administrator in Seattle. “Once final, this plan will give King County unprecedented flexibility to better manage its storm water and waste water using the most cost effective and protective technologies available today."

Acting Department of Ecology Director Polly Zehm said, “We appreciate the county’s commitment to fulfilling its clean water act and state responsibilities. The county CSO control projects will further protect public health for citizens of King County, and aquatic life in Seattle’s urban waterways.”

CSOs occur in older parts of Seattle where storm drains are connected to the sewer system. During heavy rain events when sewers are full, sewage mixed with stormwater discharges into local water bodies which prevents sewage backups in homes and businesses.

The consent decree is a legal settlement with the U.S. Department of Justice and EPA that ensures the County’s current CSO control plan developed to meet the state Department of Ecology’s requirements is implemented and completed. The CSO control plan was recently updated by King County’s Wastewater Treatment Division and approved by the King County Council in September 2012.

The consent decree preserves the planning updates approved by the King County Council in September that include expediting Lower Duwamish River area projects and evaluating greater use of Green Stormwater Infrastructure for CSO control. It also gives the County the flexibility to better sequence CSO projects and integrate them with other water quality improvements to attain greater environmental benefits.

The consent decree also assesses a $400,000 penalty for past water quality permit compliance problems which are primarily attributed to two of the County’s four satellite CSO treatment plants in Seattle.

Because the plants operate only during severe storms when stormwater fills sewer lines to capacity, operational issues are challenging to diagnose and repair. Corrective measures are in the works, or have already completed, on problems that led to permit compliance problems that have not resulted in any threats to local water quality or public health.

King County’s overall environmental record for its wastewater treatment plants in Seattle and Renton is excellent, with each plant meeting its effluent discharge requirements for more than a decade.

EPA is pursuing a national strategy to put numerous utilities under a consent decree, including King County’s wastewater utility. These utilities are typically in older, larger cities in the Northeastern, Midwestern and Northwestern parts of the country, where stormwater is managed by discharging it directly to the sanitary sewer system, which can lead to water quality issues when sewers overflow.

The City of Seattle has also negotiated a consent decree to control combined sewer overflows in its wastewater system.  

Once the state and national governments approve and sign the decree, it will be lodged in federal court. The Department of Justice will then provide a 30-day public comment period.

Additional information about King County’s CSO Control Program is available at


Note to editors and reporters: Visit the WTD Newsroom, a portal to information for the news media about the Wastewater Treatment Division, King County Department of Natural Resources and Parks.



Residents enjoy clean water and a healthy environment thanks to King County's wastewater treatment program. The county’s Wastewater Treatment Division protects public health and water quality by serving 17 cities, 17 local sewer districts and more than 1.5 million residents in King, Snohomish and Pierce counties. The regional clean-water agency has been preventing water pollution for nearly 50 years.