Providing long-duration storage via a new pumped storage facility

Salt River Project – Pumped Storage

Salt River Project (SRP) is a community-based utility providing affordable and sustainable water and energy in central Arizona. Serving as their engineer, we are helping develop a new 20-gigawatt-hour (GWh) energy storage project using pumped storage hydropower (PSH) in alignment with SRP’s 2035 sustainability goals.

Located downstream from the Roosevelt Dam at Apache Lake, the PSH facility will be built in two phases and will provide flexible, long-duration energy storage. It will provide up to 2,000 megawatts (MWs) of electricity on demand for up to 10 hours using two reservoirs with an elevation difference of 1,400 feet (427 metres) to store electricity. When electricity demand is lower and SRP has excess power available, the turbines will spin backward to pump water to the upper reservoir. When power is needed, water will be released back to the lower reservoir through the turbines to produce electricity. No water is consumed—it simply goes back and forth.

This project marks a significant milestone in U.S. energy storage development. It is set to become the first large, pumped storage facility built nationally in 35 years and stands as the largest progressive design-build effort of its kind. The scale of geotechnical investigation underway is among the most extensive in the country.

Our collaboration with SRP extends back 25 years, focusing on their pumped storage and hydroelectric assets. This new facility will store enough excess energy to power up to 450,000 homes for 10 hours. This partnership supports SRP’s continued delivery of reliable, affordable water and power, reinforcing long-term energy resilience for Arizona.