Cogswell Dam

Dam in Los Angeles County, California

34°14′41″N 117°57′55″W / 34.24472°N 117.96528°W / 34.24472; -117.96528Opening date1935; 89 years ago (1935)Owner(s)Los Angeles County Department of Public WorksDam and spillwaysType of damRock-filledImpoundsWest Fork San Gabriel RiverHeight266 ft (81 m)Height (foundation)280 ft (85 m)^[1]Length585 ft (178 m)Spillway capacity59,900 cu ft/s (1,700 m³/s)^[1]ReservoirCreatesCogswell ReservoirTotal capacity12,234 acre⋅ft (15,090,000 m³)Catchment area38.4 sq mi (99 km²)Surface area146 acres (59 ha)

Cogswell Dam is a rockfill dam on the West Fork of the San Gabriel River in Los Angeles County, California. It is located in the San Gabriel Mountains, northeast of Mount Wilson, and within the Angeles National Forest.

It forms Cogswell Reservoir, which has a capacity of 8,969 acre-feet (11,063,000 m³).^[2]

The dam serves mainly for flood control in conjunction with San Gabriel Dam and Morris Dam downstream. San Gabriel Dam lies 13 miles (21 km) downstream.^[3]

Construction

Bonds for the dam's construction were issued in 1924. Construction began in March 1932 and was completed in April 1934, at a total cost of US$3,127,762.^[3]

The rock-fill dam, built by the Los Angeles County Flood Control District, is 585 feet (178 m) long, 266 feet (81 m) tall (measured from the stream bed), 18 feet (5.5 m) wide at the top, and contains 1,044,945 cubic yards (798,918 m³) of material. Its crest is 2,412 feet (735 m) above sea level and 27 feet (8.2 m) above the certified water storage elevation.^[2]

The dam rests on crystalline granite bedrock. The buttress is 750 feet (230 m) thick at the base, and the height from foundation to crest is 285 feet (87 m). There are concrete cutoff walls and a concrete facing slab on the dam's upstream side.^[3]

References

^ ^a ^b [1] ^{[dead link]}
^ ^a ^b "Dams Within the Jurisdiction of the State of California (A-G)" (PDF). California Department of Water Resources. Archived from the original (PDF) on 2012-03-09. Retrieved September 30, 2012.
^ ^a ^b ^c "Cogswell Dam" (PDF). Dpwftp.cp.la.ca.us. Retrieved November 18, 2012.^{[permanent dead link]}