Contra Costa Canal Replacement – Segment 5B
The 48-mile Contra Costa Canal is an aqueduct in California’s East Bay region originally built in the 1930s and 1940s to convey water for agricultural and industrial use. It continues to be a critical artery that diverts water from the Sacramento-San Joaquin Delta to municipal, commercial, and industrial customers, serving nearly 500,000 residents in the surrounding communities. The Contra Costa Canal Replacement project aims to modernize the aging infrastructure by piping the first four miles of the canal from its origin at the Rock Slough, which was previously earthen and unlined. More than 14,000 feet of the canal have been replaced since the multi-phase project began in 2009. Segment 5B replaces an additional 6,394 feet of the canal with 120-inch reinforced concrete pipe (RCP) provided by Northwest Pipe Company.
The large-diameter RCP was manufactured at our steel and concrete pipe facility in nearby Tracy, California. Our team utilizes a unique vertical vibration casting process that creates a highly dense and durable concrete pipe with a smooth interior surface. Each piece of 120-inch pipe utilizes two reinforced cages, an inner and outer cage, and has an 11-inch-thick concrete wall. The pieces are 15 feet in length and weigh 75,000 pounds each. Northwest Pipe Company manufactured 426 pieces in total to support Segment 5B of this major infrastructure replacement project.
To construct the pipeline, contractor Sukut Construction, LLC unwatered the existing canal and installed 165 dewatering wells, lowering the water table to negative 18 feet to accommodate the 10-foot diameter RCP. Crews are using a 330-ton crawler crane to install the pipe, backfilling the first 2.5 feet of trench with native CDF (controlled density fill made up of soil-cement slurry), and topping with native soil. In addition to the 6,394 LF pipeline, Sukut is constructing a 6,500 LF access road and a 27-foot tall concrete access structure.
By piping unlined portions of the 80+ year old aqueduct with RCP, this project resolves a number of concerns about the aging canal’s mounting maintenance costs, structural integrity, reliability, and public safety. The new concrete pipeline reduces water loss caused by seepage or evaporation, while also providing a durable and high-strength structure better equipped to protect water supplies from earthquakes or landslides. Enclosing the canal also helps mitigate water quality and life safety concerns associated with open waterways in areas with pedestrian and vehicular traffic. Finally, the concrete pipeline offers improved stormwater management and flooding control along the canal and a permanent infrastructure solution that is more aligned with the region’s future planned development goals.
Project Installation Photos Courtesy of Sukut Construction, LLC