Denny Way/Lake Union CSO King County Department of Natural Resources
HWA GeoSciences Inc. performed preliminary geotechnical studies for the entire project and final design studies for two of the three sections the project. HWA’s final design studies include explorations and geotechnical analyses for design of five 72-inch diameter or larger tunnels that will connect to the Mercer Street Tunnel. At the western end of the project, two 96-inch-diameter tunnels will be 55 to 60 feet deep and about 400 feet long, A 72-inch-diameter tunnel will also be constructed along a similar route at a shallower depth. Two 72-inch diameter tunnels at the eastern end of the Mercer Street Tunnel will be 780 and 1,730 feet long. All five tunnels will be well below the ground water level in permeable soils, and three of the five tunnels may encounter cobbles, boulders, old piles and buried logs and debris that pose serious potential problems for construction. HWA developed design and construction recommendations for the proposed tunnels as well as associated access pits and portals. This work included preparation of Geotechnical Data Reports, Geotechnical Baseline Reports (GBRs) and/or Geotechnical Design Reports for all of the tunnels. HWA also assisted in probabilistic risk analyses and provided geotechnical consultation for the Mercer Street Tunnel. In addition to the geotechnical engineering studies, HWA performed pumping tests at five locations to evaluate dewatering conditions along the Mercer Street Tunnel as well as the five smaller tunnels. HWA provided monitoring services and consultation during installation of the 72-inch-diameter shallow bore-and-jack tunnel beneath the BNSF railroad tracks and for pile driving, dewatering, vibration evaluation and other portions of the Elliott West pipelines portion of the project.
Other Notable Projects:
King County Conveyance System Improvements King County Department of Natural Resources
Swamp Creek Trunk Sewer Extension King County Department of Natural Resources
North Creek Diversion King County Department of Natural Resources
Tolt Pipeline No. 2, Phase IV Seattle Public Utilities
Seattle-Tacoma Intertie EIS Seattle Public Utilities
Columbia Slough Consolidation Conduit City of Portland
HWA GeoSciences Inc. performed preliminary geotechnical studies for the entire project and final design studies for two of the three sections the project. HWA’s final design studies include explorations and geotechnical analyses for design of five 72-inch diameter or larger tunnels that will connect to the Mercer Street Tunnel. At the western end of the project, two 96-inch-diameter tunnels will be 55 to 60 feet deep and about 400 feet long, A 72-inch-diameter tunnel will also be constructed along a similar route at a shallower depth. Two 72-inch diameter tunnels at the eastern end of the Mercer Street Tunnel will be 780 and 1,730 feet long. All five tunnels will be well below the ground water level in permeable soils, and three of the five tunnels may encounter cobbles, boulders, old piles and buried logs and debris that pose serious potential problems for construction. HWA developed design and construction recommendations for the proposed tunnels as well as associated access pits and portals. This work included preparation of Geotechnical Data Reports, Geotechnical Baseline Reports (GBRs) and/or Geotechnical Design Reports for all of the tunnels. HWA also assisted in probabilistic risk analyses and provided geotechnical consultation for the Mercer Street Tunnel. In addition to the geotechnical engineering studies, HWA performed pumping tests at five locations to evaluate dewatering conditions along the Mercer Street Tunnel as well as the five smaller tunnels. HWA provided monitoring services and consultation during installation of the 72-inch-diameter shallow bore-and-jack tunnel beneath the BNSF railroad tracks and for pile driving, dewatering, vibration evaluation and other portions of the Elliott West pipelines portion of the project.