The Yolo County Flood Control and Water Conservation District provides irrigation delivery to 195,000 acres in Yolo County through a 150-mile network of open canals. The Alder Canal conveyed water from the north side of Cache Creek to the southside by way of a 60” siphon pipeline. Due to shallow burial depth and aging pipe material, the siphon periodically sustained damage during winter floods that required repairs. Unfortunately, during the initial months of the 2019 irrigation season, the siphon catastrophically failed and YCFCWCD immediately initiated an emergency declaration to construct a replacement. Repairs to the siphon restored 50% capacity, but replacement was needed to prevent further loss of delivery service and costly crop damage.

We collaborated with District staff and their selected contractor in a design-build approach to expedite the design and implementation of a superior design featuring a 900-foot-long, twin 54” Class III reinforced concrete pipe encased in concrete, reinforced concrete inlet structure with emergency spill outlet, and a riprapped outlet. Pipe burial depths ranged from 6- 24 feet below the ground surface. Strategic engineering and construction solutions were required to enable replacement adjacent to the active and fragile siphon. Diversion of the active Creek and managing of shallow groundwater required significant dewatering and trench shoring measures. Full capacity irrigation deliveries were resumed in 2020.