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Coolidge Generating Station

WSP USA provided engineering design and construction management for the Coolidge Generation Station in Arizona.


The Coolidge Generation Station is a 512-megawatt simple cycle peaking power plant that uses 12 combustion turbine generators with evaporative cooling power augmentation. It is one of the largest peaking plants in the U.S. The plant was designed for daily start/stop peaking operations and is able to operate continuously, if needed, consistent with permitted water supply availability. It is also capable of providing a utility operating reserve through rapid 10-minute startup capability.

The plant is capable of operating at ambient temperatures as high as 122 degrees Fahrenheit (50 degrees Celsius) to deal with the Arizona climate. It is also able to operate during extreme winter conditions by employing anti-icing systems. The combustion turbine generators use pipeline-quality natural gas as the fuel source. Water for the plant is supplied from new on-site wells, and plant wastewater will be discharged to on-site lined evaporation ponds for disposal.

WSP was engaged, in joint venture, to develop the plant under an engineer-procure-construct (EPC) contract. The firm provided all engineering services, including civil, structural, mechanical, electrical, and control systems engineering. The firm also provided engineering support during construction, and developed start-up and operating procedures for the plant. Coolidge was completed ahead of schedule and under budget.