Five toe drains and five associated weir boxes located at the O'Neill Forebay Dam will be modified, and the pipes will be replaced. The toe drains scheduled for maintenance are identified as 132.45, 132.7, 132.8, 134.75, and 40.80. Each toe drain consists of up to two, 24-inch corrugated metal pipes that lead from the interior of the Dam to a cement weir box. These weir boxes are currently too large to accurately measure the amount of water seeping from the Dam and the metal pipes are rusting. To prevent further degradation of the pipes, and to regain the ability to measure water that, by design, seeps from the Dam, the Department of Water Resources’ (DWR) San Luis Field Division (SLFD) will pothole using a vacuum trailer to locate the corrugated metal pipes. SLFD will then use hand tools to remove the wood lids on the existing weir boxes and a backhoe to lower a fiberglass weir box into each of the cement weir boxes. Hand tools will be used to secure the fiberglass weir boxes to the cement weir boxes. SLFD will then use a backhoe to dig up to ten trenches with maximum dimensions of 5 feet wide by 10 feet deep by 50 feet long to expose the rusting pipes. The pipes will be removed, new 12-inch or 15-inch diameter plastic pipes will be installed, and the trenches will be backfilled. Hand tools will be used to attach the new pipes to the weir boxes. This work is necessary to preserve the physical integrity of the O’Neill Forebay Dam and to accurately measure seepage.