After the intake structure at Unit 4 of Horse Mesa Dam suffered a catastrophic failure in summer 2012 when a flow control wall collapsed, owner Salt River Project (SRP) began to make preparations to bring the facility—the largest source of hydroelectric power generation on the Salt River—back to life. A major hurdle, however, was the failure's location 160 ft below the lake's surface. That left just two options for the repair: draining a large majority of Apache Lake's 254,138-acre water capacity or utilizing saturation divers to complete the work.
SRP says it conducted a multitude of studies and research that made it clear that saturation divers could do the job more quickly, while also limiting the economic downside caused to local businesses by a reduction in lake levels.