King County Metro delivers major improvements to Atlantic Base Yard Facility

King County Metro is improving infrastructure at the Atlantic Base Yard Facility to support the storage of its growing fleet as well as the replacement, maintenance and upkeep of the bus yard.

The project will replace all concrete paving and underground infrastructure, including storm drainage, sanitary sewer, industrial waste, and buried power lines, as well as rehabilitating underground storage tanks. Additionally, the existing overhead catenary system will be upgraded to support the expanding electric trolley fleet.

The construction is estimated to cost $45 million and will be delivered by Granite Construction in multiple phases to ensure the uninterrupted operation of bus service operating from the Atlantic Base. The majority of the work will occur during normal business hours with intermittent nighttime work. This work is expected to be completed by 2028.

Atlantic Base was expanded to store 200 trolley buses between 1979 and 1980. To accommodate this, the parking lot was constructed of Portland cement concrete panel (PCCP) and 4 to 6 inches of gravel base. Existing concrete panels are typically 17 by 22 feet, with some built in 1979 and the rest earlier. Several areas were repaired or replaced as part of the base’s regular maintenance program, and in several areas concrete panels have been overlaid with asphalt concrete, mainly along the perimeters of the site.

In 2016, King County Metro contracted engineers to assess and monitor the conditions of the facilities. From these assessments, a Transit Facilities Conditions Needs Report identified capital improvements needed at the Atlantic Base parking lot. The report recommended removing and replacing concrete panels in the bus parking areas of the Atlantic Base Site trolley yard in coordination with utility replacement projects.

Source: King County Metro