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In July 2018, King County’s Wastewater Treatment Division released the 2017 Annual CSO and Consent Decree Report.

Combined Sewer Overflows (CSOs) in King County exist in older Seattle neighborhoods like Magnolia, where one set of pipes carries both sewage and stormwater. When heavy rains fill the pipes, excess flows are released through a permitted outfall into Puget Sound. Once it is back in operations in late 2018, King County’s Magnolia Wet Weather Storage Facility will help reduce CSOs from the outfall off 32nd Avenue West to no more than one per year on a long-term average.

King County has provided regulators with a supplemental compliance plan and updates during the Magnolia remediation project. You can find a summary and list of CSOs in 2017 in the annual report .

This engineering report (facility plan) outlines improvements to the King County conveyance system serving the South Magnolia basin that are necessary to control CSOs in compliance with RCW 90.48.480 and WAC 173-245-020 (22).

This report is submitted in compliance with the first of three compliance schedule dates noted in Section S18 of the West Point Treatment Plant National Pollutant Discharge Elimination System permit (refer to page 53 of permit).

Final engineering report (facility plan), September 2011

Draft engineering report (facility plan), December 2010