CSO Basin 34 (I-90) Stormwater Mitigation/Separation Facility

The City of Seattle is requesting bids for construction of the CSO Basin 34 (I-90) Stormwater Mitigation/Separation Facility, with proposals due September 29, 2026. The project addresses combined sewer overflow management in the Basin 34 drainage area along the I-90 corridor.

The scope encompasses a diversion structure, stormwater lift station, four modular wetland stormwater treatment systems, four Type 2 deep drywells, five catch basins, approximately 200 linear feet of stormwater forcemain pipe with valve vault and appurtenances, 380 linear feet of stormwater pipe of varying sizes, 250 square yards of HMA pavement, 123 linear feet of sidewalk and driveways, sundry utility adjustments, and related miscellaneous items. Work requires coordination with existing utility systems and compliance with applicable city, state, and federal regulations governing stormwater management and environmental protection. Technical requirements, design standards, and construction specifications are detailed in the Scopes of Work document (2018052.pdf).

No contract value, contract term, incumbent contractor, set-aside or preference program, evaluation criteria, or pre-bid meeting information is provided in the posting.