Tulloch Hydroelectric Project, 3rd Unit Addition, Phase 2 Construction

Work on the new third generating unit at Tulloch Lake and Dam in the Sierra foothills near Oakdale, California involved many facets of heavy construction. In order to install the new 6-megawatt generator, PrōVen’s crews had to remove over 15,000 cubic yards of solid granite, including an 80-foot deep shaft beneath the existing Tulloch Dam. Using both drill and shoot techniques and mechanical means, PrōVen’s crews were able to excavate the rock to create access to the new powerhouse addition and the vertical shaft in the rock necessary for installation of the 1650mm variable pitch Kaplan turbine. The existing 69″ low level outlet piping from the original dam was reconfigured into a bifurcated penstock to provide the flow to the new turbine assembly. During the shaft excavation for the turbine installation a cofferdam was designed and constructed by PrōVen to alleviate water intrusion from the river due to a previously unforeseen geologic condition. Construction of a three-story, reinforced concrete powerhouse structure to enclose the new generator facility with all required mechanical systems was performed by PrōVen’s own forces with electrical work being subcontracted to San Joaquin Electric from Stockton, California. All work was performed in compliance with strict environmental protection requirements for the Stanislaus River and without any lost-time accidents by PrōVen and their subcontractors.

Location: Tulloch Dam
Jamestown, California
Start Date: October 2009
Completion Date: November 2011, 815 calendar days
Contract Value: $12,655,731
Owner: South San Joaquin Irrigation District & Oakdale
Irrigation District Tri-Dam Project
Contract No. 2067-C2
Engineer: MWH