Heavy Civil GC/CM Services for MDCSO Wet Weather Treatment Station

The contract pertains to the development of the Wet Weather Treatment Station (WWTS) at the mouth of the Duwamish River, a critical infrastructure project designed to treat combined sewer overflows (CSOs) before their discharge into the waterway. The scope encompasses the construction of a below-grade 4 million-gallon equalization basin, influent piping, screening, pumping systems, and a UV disinfection system utilizing ballasted sedimentation technology for solids removal. Additional work includes demolition of existing structures, shoring and excavation, soil management—including disposal of contaminated soils—and site surface improvements. The project also involves installing solids storage, odor control systems, instrumentation, and controls to ensure operational efficiency and environmental compliance. The procurement process is managed by King County, Washington, with a solicitation issued for Heavy Civil GC/CM (General Contractor/Construction Manager) services, with responses due by October 21, 2025. The contract size is estimated between 50 million and 150 million dollars. The process includes multiple addenda that update insurance requirements, emphasizing compliance with the Owner Controlled Insurance Program (OCIP) and specific coverage limits for professional liability, pollution, and other risks. The contractual documents comprise draft agreements for both preconstruction and construction phases, outlining scope, cost, schedule, and legal provisions, all governed by Washington State RCWs. The project emphasizes collaborative delivery, with a focus on safety, environmental stewardship, and adherence to regulatory standards, aiming for a comprehensive, integrated approach to constructing a state-of-the-art CSO treatment facility with an estimated project duration of over 124 months.