The start of construction on a new maintenance facility marks a major milestone for Sound Transit and the agency’s effort to extend light rail from Seattle to outlying communities.

Sound Transit broke ground April 4 on its Operations and Maintenance Facility East, designed to service and house light-rail vehicles for North Link extensions to Northgate and Lynnwood and for vehicles designed for Federal Way and Redmond.

Hensel Phelps Construction Co. was chosen as the design-build team in May 2017 and tasked with the facility's design, permitting and construction. The company worked with the city of Bellevue on the master development plan entitlements that include planning for the site’s surplus property. Sound Transit expects to issue a request for proposals to seek a master developer for this transit-oriented development by the end of 2018.

Sound Transit worked with the City of Bellevue and community partners to incorporate opportunities for transit-oriented development at the facility. Sound Transit officials hope to integrate the site with new housing, office and retail projects as part of the Spring District. Approximately 1.1 million sq ft of space will open to transit-oriented development when the facility completes by the end of 2020.

Beginning in 2019 and continuing through 2023, Sound Transit’s light rail vehicle fleet will expand from its current 62 vehicles to 214. The new facility will accommodate the inspection, service, maintenance, storage and deployment of up to 96 light rail vehicles on top of the 104-vehicle capacity at the existing Forest Street facility in Seattle. Sound Transit expects the east facility to start storing light rail vehicles in 2020, the same time the Seattle facility reaches capacity.

The Bellevue facility will run nonstop, employing up to 250 full-time employees. It will include 14 service bays; a cleaning and wash bay; shop areas; parts storage; office space; and on-site parking. Sound Transit plans to pursue a minimum of LEED silver certification for the facility.

Follow Tim Newcomb on Twitter at @tdnewcomb.