SRD-SCE Agnew Dam Response

Flood control upgrades to the remote Agnew Dam outside of the Ansel Adams Wilderness Area. The Dam is located on Rush Creek, at an elevation of 8,499 feet above mean sea level (MSL) on the eastern slope of the Sierra Nevada mountain range, in Mono County, California. The Dam is located in the Inyo National Forest, fourteen miles upstream from Mono Lake, near the town of June Lake, CA. The Dam was constructed in 1916. It is a 30-foot high, 278-foot long concrete multiple arch dam. The Dam has five complete arches and two partial arches located at the ends. The project required sawcutting and removing two additional openings at the arches to allow for lowering the upstream water level during flood events. This was done following the Oroville Dam catastrophe. Penhall Crews headed to work each day in a 12 minute helicopter ride. Yes, a helicopter ride. The extremely remote location of the project required all employees, equipment and material to be flown in with passenger helicopters and a Skycrane helicopter, Sikorsky S-64. Two openings, 5’5” x 6’6” x 2’2” thick had to be sawcut into 4 pieces per opening to allow for removal with the Skycrane helicopter. The layout was first cut partial depth approx. 3/8” wide with a wall saw and followed up with a wire saw to attain a precise cut in the 26” concrete with no overcuts. All slurry had to be captured, collected and hauled off site in this environmentally sensitive location. All work was complete on schedule and without incident.