Photo by Mark Defeo, Aerials on Demand

The $63-million project placed new rockfill buttresses on the upstream and downstream slopes of the dam, constructed internal drainage improvements, reinforced portions of the concrete core wall and raised the crest by 7 ft.

Photo by Jeff Axell

Built in the early 1900s near Yosemite National Park, this hydraulic earth-and-rock fill dam was in need of significant seismic upgrades. The $63-million project placed new rockfill buttresses on the upstream and downstream slopes of the dam, constructed internal drainage improvements, reinforced portions of the concrete core wall and raised the crest by 7 ft. The particularly challenging upstream buttress required GPS-controlled excavators to prep the foundation, providing a live Internet feed so engineers and inspectors could monitor subsurface conditions and accelerate the rigorous foundation acceptance process. The construction sequence for the upstream buttress took advantage of low lake levels to place fill, allowing for an early project completion.

Key Players

Contractor Kiewit Infrastructure West Co., Fairfield.

Owner Pacific Gas and Electric Co. (PG&E), San Francisco

Lead Design AMEC, Oakland

Engineers Sanders & Associates Geostructural Engineering, Granite Bay; Parsons, Pasadena

Subcontractors Drill Tech Drilling and Shoring, Antioch; California Drilling & Blasting Co., El Monte; The Dutra Group, Rio Vista; Gasch and Associates, Rancho Cordova; Cardno Entrix, Concord; Rain for Rent, San Joaquin