Langley Pond Dam Rehabilitation
The objective was to demolish and remove the existing concrete spillway structure. Construct new labyrinth crested reinforced concrete chute spillway. Flatten, improve, and armor existing 1800' long earthen dam. Install new SCB (soil-cement-bentonite) cutoff wall which was constructed through the approximate centerline of the embankment to reduce seepage and control gradients through the sandy embankment and foundation soils. Excavate and install new outlet channel. Install pedestrian bridge across dam. Install 54" resilient wedge gate valves with 54" DIP bypass piping (x2). The proposed chute spillway will have staged labyrinth-crested weir. The labyrinth-crested weir will have 6-½ cycles consisting of two (2) stages. Stage 1 will consist of 4 cycles that have an overall weir length on the order of 663 ft. Stage 2 will consist of 2-1/2 cycles that have an overall weir length on the order of 416 ft. Stage 2, in combination with stage 1, will aid in the discharge of flows for less frequent storm events, to include 50% of the PMF.