Garco Construction Inc., of Spokane, says it has won an $8 million contract to renovate and construct additions to the maintenance facility at Wanapum Dam, on the Columbia River in Central Washington.

Garco has started site work for the project, which is on the east side of the dam, about 150 miles southwest of Spokane, says Colin McGlocklin, a project manager for Garco. The project is scheduled to be completed in June 2013, he says.

Under the contract, Garco will demolish the interior of a 43,000-square-foot metal structure, leave the structural steel intact, replace the metal wall panels, and install insulated metal roofing, McGlocklin says.

The contractor also will construct a 14,200-square-foot mezzanine and erect a 12,000-square-foot addition on the west side of the structure, he says.

The structure houses a large fabrication shop, McGlocklin says. "This is where they work on parts for the dam," he says.

Bernardo Wills Architects PC, of Spokane, designed the project.

Wanapum Dam, a 49-year-old hydroelectric project, has 10 turbines with total generating capacity of 1,038 megawatts. A megawatt is roughly the amount of power consumed by 750 homes.

The Ephrata, Wash.-based Grant County Public Utility District operates the dam, which is near Vantage, Wash., and also the Priest Rapids Dam, another hydroelectric project, which is 18 miles downstream.