Afterbay Reservoir Lining
Award
Small Project
Description
The Afterbay Reservoir Lining Project successfully resolved long-standing seepage issues that had been causing significant water losses for the Berrenda Mesa Water District. The reservoir was losing more than 1,200 acre-feet annually to deep percolation into a saline aquifer. These losses resulted in major operational inefficiencies and financial impacts for local growers.
To address the issue, the project expanded the reservoir to a capacity of 254 acre-feet and lined it with high-density polyethylene (HDPE) to eliminate seepage. District crews excavated over 140,000 cubic yards of unsuitable material during regrading efforts. The project also included construction of a temporary inlet canal weir, a lined bypass channel capable of conveying 150 cubic feet per second, and a culvert crossing to maintain site access during construction.
One of the most critical achievements of the project was its ability to maintain water deliveries during construction. In response to unforeseen subgrade conditions, a bypass channel was designed and implemented mid-project to ensure uninterrupted water supply during peak irrigation demand. This adaptation prevented potential crop loss for the District’s customers.
The completed project now provides 67 acre-feet of additional storage and eliminates annual water losses valued at approximately $800,000. It significantly improves water supply reliability and operational flexibility, while reducing long-term maintenance costs. The project stands as an excellent example of responsive engineering, strategic planning, and successful implementation of infrastructure improvements in California’s agricultural heartland.
Branch
