For any tunnel project, gaining access to the underground is a critical – if sometimes overlooked – component. The building of vertical shafts is the most common method of getting men and material into and out of the tunnel, but shaft construction is no easy matter due to challenging soils, the presence of groundwater, conflicting utilities and risk of settlement to adjacent structures.

In one recent project, contractor James W. Fowler Co. (JWF) introduced new shaft construction technology to the United States. JWF, an experienced heavy civil and tunneling contractor based in Dallas, Ore., used a Herrenknecht vertical shaft machine (VSM) as part of the Ballard Siphon Replacement project for King County’s Wastewater Treatment Division in Seattle, Wash.