Thermalito Afterbay Brood Pond 4 Culvert Rehab

The project will excavate and remove existing 36” corrugated metal pipe (CMP) and concrete headwall. CMP excavation trench will be 7-feet in depth and 6-feet in width. Replace existing headwall and metal culvert with two new 5-foot by 5-foot precast concrete headwalls with attached wingwalls and galvanized steel slide gates, and 22’ long by 36” diameter reinforced concrete pipe (RCP). The new culvert and headwalls will require an excavated trench with a 2:1 slope. The disturbed area will be mostly within the uplands and will be about 24’ wide by 30’ long. Estimated 1,860 cubic feet of material in total will be stockpiled on the west parking area, all stockpiled material will be reused to close the trench. Equipment staging will be on the access road to the west and east of the project area. If water surface elevations cannot be lowered below 128 feet, a coffer dam will be constructed. Construct 4-foot high, 9-foot-wide wall around work area on the Afterbay side of the dam. The coffer dam is made of an inflatable dual wall polyethylene tube that is filled with water. No in-water work will occur.