City of Seattle ($350,000 civil penalty) and King County ($400,000 civil penalty) agreed to implement combined sewer overflow control plans costing approximately $600 million and $860 million respectively, reducing CSO discharges to Puget Sound by 99%, with completion deadlines of 2025 and 2030.

City of Seattle and King County — $1.46 Billion CSO Consent Decree (2013)

Outcome: City of Seattle and King County agreed to pay a combined $750,000 in civil penalties and implement combined sewer overflow long-term control plans totaling approximately $1.46 billion in capital investment — $600 million for Seattle by December 31, 2025 and $860 million for King County by December 31, 2030 — reducing CSO discharges to Puget Sound by approximately 99%.

The City of Seattle and King County, Washington, operated combined sewer systems that discharged untreated combined sewage to Puget Sound, Elliott Bay, the Duwamish River, Lake Washington, and other waterways of the Pacific Northwest through combined sewer overflow outfalls during wet weather events. Violations included unauthorized CSO discharges, sanitary sewer overflows from separate sanitary sewer systems, NPDES permit effluent limit exceedances, and wastewater treatment plant bypasses. These violations affected the environmental health of Puget Sound, one of the most ecologically sensitive estuaries in the United States.

The settlement, announced April 16, 2013, required King County to pay a $400,000 civil penalty and Seattle to pay a $350,000 civil penalty, with the combined $750,000 split between the federal government and the State of Washington. King County was required to implement its Long Term Control Plan by December 31, 2030, at an estimated capital cost of approximately $860 million, reducing CSO discharges by approximately 95% to 99%. Seattle was required to implement its LTCP by December 31, 2025, at an estimated cost of approximately $600 million, achieving approximately 99% CSO reduction.

Both consent decrees permitted green infrastructure projects as alternatives to conventional gray infrastructure (storage tunnels and treatment facilities) where green infrastructure measures could achieve equivalent environmental outcomes. This provision reflected EPA's evolving policy favoring integrated green-gray infrastructure approaches in Pacific Northwest and other cities with permeable soils and opportunities for stormwater infiltration and retention.

Primary Source: Seattle, Washington and King County, Washington Settlement | US EPA