The Sound Transit Board of Directors today authorized the award of the construction contract for the Sounder D-to-M Streets Track and Signal project to low bidder 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 is anticipated to begin 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 $40,823,190, $25.6 million below the Sound Transit engineer’s estimate of $66,423,687.