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 significant infrastructure project aimed at managing combined sewer overflows (CSOs) to improve water quality in the region. The scope encompasses the construction of a large below-grade equalization basin with a capacity of 4 million gallons, along with associated infrastructure such as influent piping, screening, pumping systems, solids handling, odor control, and advanced disinfection technology utilizing ultraviolet light. The project also involves demolition of existing structures, shoring, excavation, soil management—including disposal of contaminated soils—and site surface improvements. Key features include ballasted sedimentation technology for solids removal, UV disinfection systems, and comprehensive instrumentation and controls to ensure operational efficiency and environmental compliance. The procurement process is highly detailed, involving multiple addenda that update insurance requirements, project timelines, scope of work, and contractual terms. The solicitation, issued by King County, seeks a Heavy Civil General Contractor/Construction Manager (GC/CM) with an estimated project value ranging from 50 to 150 million dollars, with a focus on collaborative delivery and adherence to state procurement statutes. The process includes preconstruction and construction phases, with draft contracts outlining scope, cost, and project schedule, emphasizing early subcontracting, risk management, and integration of lean construction and Building Information Modeling (BIM) principles. The project is scheduled for completion by December 31, 2034, with a proposal deadline set for October 28, 2025, and aims to deliver a high-capacity, environmentally sustainable treatment facility to mitigate urban water pollution and enhance regional water management infrastructure.