In 2020, SWPB worked on a project to replace the guard gate stem at the Nilan North Dam, the stem was bent and prevented operation of the gate. Nilan East Dam stem guides were also replaced as preventative maintenance. Water is delivered through the dam by the operation of two gates, a guard gate and an operating gate. The guard gate is upstream of the operating gate and is typically kept open while the operating gate is used to regulate flow out of the reservoir. The guard gate is typically only closed to allow for inspection of the outlet conduit and the operating gate. Since the gate stem guide replacement in 2020, the Nilan East Dam guard gate hasn’t properly sealed, we are proposing to place a small temporary coffer dam upstream of the Nilan East Dam and dewater the area to facilitate safe entry into the outlet conduit to diagnose and fix the ongoing guard gate sealing issue.