Seattle and King County Agree to Reduce Sewer Overflows to Puget Sound

Aug. 27, 2009
EPA issued compliance orders Aug. 26 addressing Clean Water Act violations

The City of Seattle and King County have agreed to increase their efforts to protect Puget Sound from wastewater overflows during severe rainstorms, according to compliance orders issued Aug. 26 by the U.S. Environmental Protection Agency (EPA). 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.”

Seattle and King County have combined sewer systems, which carry wastewater and storm water 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-area waters.

The city of Seattle currently manages 92 combined sewer overflow locations and King County manages 38, each of which routinely discharge untreated water during heavy rain into Lake Union, Lake Washington, the Duwamish River and Puget Sound. In 2007, Seattle’s system overflowed approximately 249 times and King County’s system overflowed approximately 87 times.

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

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

City of Seattle Order
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 will also require 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 2012.

King County Order
The King County compliance order requires the county to submit a plan to observe and document CSO outfalls after a rainfall event to ensure there is no debris being discharged with the CSOs. The order also requires King County to upgrade their Elliot West CSO Treatment Plant to ensure proper treatment of overflows that may occur there during wet weather events. EPA expects King County to comply with the order by 2010.

Source: EPA