Pipe Bursting Success in a Developed Neighborhood

The city of Pacifica, California, (city) is implementing a multi-year capital improvement program to eliminate capacity related sanitary sewer overflows (SSOs) by January 1, 2019, to comply with the San Francisco Regional Water Quality Control Board's (RWQCB’s) cease and desist order (CDO). The Pedro Point Neighborhood Sewer Rehabilitation Project is a key component of the capital improvement program (CIP) that included replacement of over 16,000 linear feet of 6-in, 8-in, and 10-in diameter vitrified clay pipe (VCP) with 8-in and 12-in diameter high density polyethylene (HDPE) pipe using pipe bursting. Several project challenges included: approximately 50% of the sewer mains are located within backyard easements; open trench in the narrow neighborhood roadways would require street closures impacting access to over 250 homes; the neighborhood elevation varies over 300 feet within the project limits and the steep roadway slopes makes open trench construction while maintaining public safety challenging; and the sanitary sewer mains cross both natural gas and potable water mains that would require careful excavation, potentially even hand excavation, potentially reducing the open trench production rates, and thereby extending the project schedule. Pipe bursting was chosen as the preferred construction method based on the city's previous positive experience, reducing roadway surface impacts, reducing potential impact to adjacent utilities, and higher anticipated pipe replacement production rate. The project was successful because of the following key activities: city maintenance staff interviews were performed during the design phase to document easement access requirements; implemented a detailed existing utility research and potholing effort to confirm location and depth of existing utilities; existing sewer main condition evaluated using closed circuit television (CCTV) to identify spot repairs; implemented a comprehensive public outreach to present long-term benefit to community; required all contractors to be prequalified; mandatory project bid walk through all backyard easements; and regular construction progress updates.