Silicon Valley, CA: Large Diameter Sewer Replacement and Rehabilitation – Design Challenges using Multiple Trenchless Methods and Lessons Learned during Construction

摘要

The City of Santa Clara (City) is located in the heart of California’s fast-growing Silicon Valley. The City owns and operates a 270-mile wastewater collection system. One of the City’s main trunk sewers, a 48-inch diameter pipe located in Trimble Road was heavily corroded and nearing the end of its useful life. The Trimble Road Trunk Sanitary Sewer Improvements Project was developed to replace and/or rehabilitate the aging pipeline. The Trimble Road sanitary trunk sewer is a major conveyance pipeline that carries approximately 12.5 MGD from the City’s collection system in Santa Clara through a City of San Jose (CSJ) main traffic artery, Trimble Road, before connecting into 54- and 78-inch diameter CSJ sewer interceptors that flow to the joint San Jose/Santa Clara treatment plant. A significant portion of the existing alignment requiring manhole rehabilitation is also located immediately adjacent to the San Jose International Airport (Airport). The project included pilot tube guided auger boring installation of a 48-inch sewer under the Santa Clara Valley Transportation Authority’s light rail tracks, installation of 4,400 feet of 48-inch diameter cured-in-place pipe (CIPP) within a heavily trafficked roadway and 1,625 feet of CIPP ranging in diameter from 8- to 33-inches near the Airport and beneath U.S. Highway 101, and rehabilitation of 33 manholes – some of which involved construction subject to Federal Aviation Administration regulations and restrictions. This paper will explore design challenges including: agency tunneling permit restrictions, significant and congested existing utility infrastructure, and substantial flow bypass for large-diameter CIPP installation as well as discuss lessons learned during construction.