Coolidge Dam Outlet Rehabilitation

Engineering services, Self-performed construction, Engineering during construction, Testing & commissioning
Peridot, AZ
USACE Albuquerque District
why it matters

Coolidge Dam is a primary source for providing irrigation water to farmland in the Peridot, Arizona community. The recent rehabilitation of the dam’s outlet and supporting structures was essential in ensuring the continued delivery of water to nearby communities. Completed six months ahead of schedule, and with zero recordable incidents, the project was a success. The current water levels at the dam are the highest since March 2017, highlighting the importance of the dam in maintaining water supply for agricultural purposes.

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Coolidge Dam is impressive in its unique design, which includes three vast domes and a crest length of 580 feet. The massive dam, once a source of hydroelectric power, now solely provides irrigation water for approximately 100,000 acres of farmland in nearby communities. Due to aging and deteriorating conditions, operations at the Coolidge Dam became inhibited, requiring refurbishment of the outlet gate trash racks, removal of two 8’ x 150’ cylinder gates, and demolition of two concrete vaults and penstocks in preparation for new 96” butterfly valves.

Serving as the general contractor, McMillen successfully and safely removed the two 150’ long x 8’ diameter 50-ton, steel isolation gates contained in each outlet tower by utilizing a specialty and custom-designed bridge crane system. This work also included dredging over 2,000 cubic yards of mud and concrete gunite surrounding the outlet towers. McMillen had to overcome unprecedented fluctuating reservoir levels to successfully complete the work. Following the gate demolition, McMillen procured and installed two new 96-inch inch butterfly isolation valves to new penstock spools. 

Additionally, designed, fabricated, and installed a new HPU system to regulate the new valves and existing regulating gates. The new system can operate remotely from a new master control building with a mile of underground conduit and fiber-optic installed by McMillen electrical crews. Our team was also responsible for designing, fabricating, and installing the circular bulkhead to seal and dewater the large-diameter penstocks. Other design services included fire protection, intrusion detection, and surveillance systems, as well as wiring diagrams and spillway access ladders.

We received an “Exceptional” rating from the U.S. Army Corps of Engineers.


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