The Sound Transit Board of Directors awarded the construction contract for the Sounder D-to-M Streets Track and Signal project to MidMountain Contractors Inc. The project will build a new commuter rail line from East D to South M Streets in Tacoma.

Work on the contract began in late September. When complete, the D-to-M Streets track will connect with the M-to-Lakewood segment, extending Sounder south line service from Tacoma Dome Station to Bridgeport Way in Lakewood. Service to Lakewood will begin in 2012.

MidMountain, headquartered in Kirkland, Wash., submitted a bid of $40.8 million, $25.6 million below the Sound Transit engineer’s estimate.