The Beacon Hill segment of the Link Light Rail Central Line consists of about one mile of twin 18.9-foot diameter transit tunnels; a deep underground binocular station with twin 550-foot long by 36-foot diameter platform tunnels; one deep main and one deep ancillary ventilation and emergency egress shaft; a headhouse at the top of each shaft; a west portal box structure beneath Interstate 5 (I-5); and an east portal box structure for access to Rainier Valley.

The twin tunnels were constructed with an earth pressure balance tunnel boring machine and precast, gasketed, bolted concrete segmental liner, resulting in less than ¼ inch of surface settlement.

Shannon & Wilson provided geotechnical exploration and design input for conceptual, preliminary, and final design for the Beacon Hill project segment. We also prepared and reviewed geotechnical portions of the plans and specifications, and assisted with construction management (CM) and monitoring of portal and tunnel construction.