Stony Gorge Dam, a reinforced concrete Ambursen-type dam (concrete slab and buttress), was completed in 1928. It is 868 feet long at the crest, with a structural height of 139 feet. This project, performed by AECOM (legacy Shimmick), increased lateral support of the dam by adding diaphragm walls, additional struts and capital struts.
A 90-foot-high diaphragm wall was placed in each bay. The additional strut was a two-by-two strut located at the midpoint of the buttresses. At the top of the buttresses, capitals with struts spanned across each bay. In total, 45 bays were modified, requiring more than 7,000 cubic yards of concrete.
The project was completed in 2009.