Emergency Sewer Force Main Rehabilitation in Valley Forge National Historic Park

摘要

Tredyffrin Township faced three catastrophic failures of a 30-inch prestressed concrete cylinder pipe (PCCP), the Wilson Road Sewage Force Main, between 2012 and 2014. The first failure resulted in a wastewater spill to Valley Creek. Second and third failures occurred just 42 days apart in the spring of 2014. Tredyffrin proactively entered into a voluntary consent decree to ensure a solution was reached in a timely manner given the complex stakeholder environment and threat of legal action from environmental groups.Assessment of the 18,000-ft. force main determined that external corrosion had degraded the strength of the wire inside the 30-inch PCCP, rendering the pipeline unable to handle the system's operating pressure. Working with the engineer CH2M on the project, the method of repair chosen was a thermoplastic close-fit lining system known commercially as Tite Liner®. The system is a high-density polyethylene liner that can provide a fully-structural solution when pulled into place inside the existing pipeline. The Tite Liner® system was engineered and custom made to be slightly larger than the host pipe and installed utilizing a proprietary roller compression system.United Pipeline Systems’ (United) installation method helped minimize disruption and expand system capacity within the Park’s limited jobsite footprint, while also offering low material costs and long installation sections. The lining portion of the project was completed over 3 months in 31 separate installations – on time and on budget – with zero safety incidents or wetlands impacts. This paper will highlight the rehabilitation method selection, project planning and installation.