This paper presents a case study describing the design processes and construction results of an emergency size-forsize pipe burst replacement of an 8-inch vitrified clay pipe in Seattle, Washington. The existing combined sewer had a collapsed section of approximately 8 feet, causing a void above the sewer. The location of the void was within the embankment for the West Seattle Bridge, a major thoroughfare in and out of West Seattle, directly below the east bound lanes. The collapse had resulted in complete blockage and resultant surcharge of the combined line, and threatened a sanitary sewer overflow if not resolved. There was also major concern that the collapsed pipe and resulting void would propagate to the road deck and result in settlement of the West Seattle Bridge. As such, replacement of the pipeline was imminent and triggered Seattle Public Utilities (SPU) to seek professional consultation to evaluate the feasibility of using trenchless technologies to perform the replacement in-lieu of rerouting the sewer with open trenching. Staheli Trenchless Consultants worked hand-in-hand with SPU to develop risk profiles for feasible pipeline replacement methods, and the design team selected pipe bursting to achieve project goals while keeping construction costs and risk exposure to a minimum. Design and construction was challenging due to numerous site constraints and the necessity to burst a collapsed pipe under a thoroughfare that could not be shut down. Although the project was challenging and fast-tracked, the combined efforts of the design team and the contractor proved successful in replacing the collapsed pipe with minimal impact to adjacent residents and homeowners.
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