Seattle, King County Ordered to Stop Sewage Overflows to Puget Sound

EPA issued the orders to address violations of the two governments' federal Clean Water Act wastewater discharge permits.

“We know that sewer overflows regularly deliver harmful pollution to Puget Sound,” said Michelle Pirzadeh, EPA's acting regional administrator in Seattle. “What we are requiring of the city and county is clear. They must take steps to reduce the volume and frequency of overflows."

"We must make sure our treatment plants are doing their best to reduce the amount of untreated wastewater entering Puget Sound waters,” said Pirzadeh.

Seattle and King County have combined sewer systems, which carry wastewater and stormwater to a sewage treatment plant before being discharged into a nearby water body.

During heavy rainstorms, these systems can exceed their capacity and overflow. The extra water gets piped or pumped, with little or no treatment, directly into Puget Sound or its tributaries.

The City of Seattle currently manages 92 combined sewer overflow locations and King County manages 38, and neither government has stopped the routine discharge of untreated water during heavy rain into Lake Union, Lake Washington, the Duwamish River and Puget Sound.

King County's West Point Treatment Plant (Photo courtesy King County)

In 2007, Seattle's system overflowed 249 times and King County's system overflowed 87 times.

Each year, an estimated 1.94 billion gallons of untreated sewage and polluted runoff are discharged from Seattle and King County combined sewer overflow outfalls into Puget Sound and its tributary waters. This overflow can carry high levels of grease, petroleum and other chemicals from roadways and parking lots.

Both the city and county have already added some water storage capacity to their systems, which has reduced the volume of overflows.

The City's compliance order addresses wastewater discharge permit violations found during a March 2008 EPA investigation. The order requires the City of Seattle to prepare an overflow emergency response plan, a plan to ensure the collection system is cleaned in a more systematic way, and a plan to create more collection system storage to prevent some CSO overflows from discharging.

The order requires the City of Seattle to prepare a plan to reduce the number of basement backups and a plan to reduce the number of dry weather overflows. EPA expects the City of Seattle to be in compliance with the conditions of the compliance order by March 2012.

The King County compliance order requires the county to submit a plan to observe and document some of King County's combined sewer overflow outfalls after a rainfall event to ensure there is no debris being discharged.

The order also requires King County to upgrade its Elliot West Treatment Plant to ensure proper treatment of overflows that may occur there during wet weather vents. EPA expects King County to comply with the order by March 2010.

The Mercer/Elliott West tunnel storage and treatment system was brought online in May 2005 as a joint project with Seattle's East Lake Union CSO control projects. In 2008, the third full year of operation, there were four discharge events that released 53.1 million gallons.

King County provides wastewater treatment to 17 cities and 17 local sewer utilities, serving about 1.5 million people, including most urban areas of King County and parts of south Snohomish County and northeast Pierce County.

Copyright Environment News Service, ENS, 2009. All rights reserved.