CHALLENGING SEWER REHABILITATION OF THE 96-INCH DIAMETER EASTSIDE INTERCEPTOR

Abstract

King County needed to rehabilitate approximately 3,900 lineal feet (LF) of severely corroded 96-inch diameter reinforced concrete pipe located in Renton, WA. The existing pipe, constructed in 1964, is installed in an urban area between Boeing’s 737 commercial airline facility and a mixed use development. King County completed an alternatives analysis and selected Linabond as the rehabilitation technology in order to maintain capacity. The rehabilitation process requires workers to be in the pipe to apply the Linabond coating. This is accomplished from work platforms constructed in the pipe with live flow conveyed under the platform. During design of the project, Carollo completed a Flow Bypass Study to analyze existing flows in the interceptor and to develop a plan to bypass up to 45 million-gallons-per-day (mgd) during low-flow summer months. Historical data showed that flows remain under 45 mgd 98% of the time. The bypass plan included provisions in the design that allowed for working under live flow conditions while providing the capability to remove all essential personnel and equipment from within the pipe during emergency high flow conditions. The bypass plan also included the preparation of a flow management plan that included coordination efforts of three wastewater treatment plants and two offsite operations groups, in addition to the project team to manage flows entering the project area. This paper will look at the risk management aspects addressed in preparing the bypass sewer plan, including construction footprint constraints, operational agreements, traffic impacts, and community mitigation measures for both noise and odor during construction.