Feature by Joe Schrank, PE, PEng, Alper Ucak, PhD, PE, Matt Bartlett, PE, and Sam Swartz, PE
Our new Tunnel Rehabilitation and Inspection Practice Group (TRIP) will support tunnel inspection and rehabilitation projects across the company. McMillen Jacobs has a long history of providing asset management, design, and construction management for tunnel inspection and rehab projects in all our underground markets. Recognizing that different regions have traditionally focused on certain types of tunnel inspections and rehabilitation (such as highway, water supply, wastewater, rail transit, and freight railroad), we formed TRIP to centralize our resources and share our available expertise across regions in order to better serve our clients and find solutions to rehab and inspection challenges. Below is a summary of recent client solutions in key markets.
Rail. McMillen Jacobs has provided engineering and construction services to the US rail market for over 35 years, and we are well known for our expertise in railroad tunnel repair and clearance improvement. Our projects range in size and complexity from rock fall mitigation and drainage improvements, to double-stack expansion including relining existing tunnels with construction occurring in short work windows. We have helped railroad clients efficiently move their projects from feasibility through design and construction. Projects include the Coos Bay Rail Line Tunnels Rehabilitation in Oregon; Q-3 (Windham) Tunnel Rehabilitation in Montana; Allegheny Tunnel Icing Shields in Pennsylvania; and Harpers Ferry Tunnel Clearance Improvement in Maryland.
Elk Creek Tunnel Rehab Project (2014): Shotcrete application for permanent ground support
Transportation. We have performed several tunnel rehab projects for the Oregon Department of Transportation over the past 10 years including inspections, alternatives analyses, design, and resident engineering. The 1,110-foot-long (338 m) Elk Creek Tunnel project (near Elkton) included pattern rock dowel installation to mitigate occasional rockfall and stabilize the crown, application of fiber-reinforced shotcrete to encase unlined portions of the tunnel, and concrete hardening of existing tunnel sidewalls. The Elk Creek tunnel is part of a critical link to the Oregon Coast, and closure would have required a 60-mile (97 km) detour. Therefore, all work was performed at night between 7 p.m. and 5 a.m. The project was successfully completed on-time and on-budget.
The Cornell Road Tunnels Rehab for the Portland Bureau of Transportation is similar to the Elk Creek Tunnel project. It consists of 500-foot-long (152 m) and 250-foot-long (76 m) tunnels in the northwest hills of Portland, Oregon. The project will remove deteriorated sections of the existing cast-in-place concrete lining and replace them with structural steel and fiber reinforced shotcrete. Shotcrete will then be applied full perimeter to both tunnels to reduce maintenance and improve service life and aesthetics. Construction is scheduled to start in the late summer.
Tiber Creek Trunk Sewer after rehabilitation work is completed (single barrel in foreground; double barrel in background)
Wastewater. As part of the DC Clean Rivers Project in Washington DC, a 122-foot-long (37 m) portion of the 100+ year-old Tiber Creek Trunk Sewer was rehabilitated with a reinforced shotcrete liner. This large-diameter sewer was heavily cracked and previously stabilized with temporary steel bents. McMillen Jacobs designed a permanent repair that improved hydraulic flow and provided continuous support during construction. Access for personnel and equipment was limited to a single 36-inch-diameter (915 mm) manhole opening. Our design accounted for this constraint and consisted of a two-pass, 6-inch-thick (150 mm) shotcrete liner. The first pass created shotcrete arches between the steel bents so they could be removed, while the second pass resulted in a smooth 6-inch-thick section over the entire length of the repair. The American Shotcrete Association honored the Tiber Creek Trunk Sewer Rehabilitation Project with the 2018 Outstanding Underground Project Award.
Water. McMillen Jacobs Associates was engaged as a subconsultant by Greeley and Hansen to provide tunnel repair and replacement for the 1.5-mile-long (2.4 km) Tiawah Tunnel near Tulsa, Oklahoma. This water tunnel was built in the 1920s by drill-and-blast and cut-and-cover methods. It has a 7-foot-diameter (2.1 m) horseshoe-shaped cast-in-place concrete liner. A portion of the liner required extensive repairs and an increase in reinforcement (where the tunnel transitioned from rock to soil). Replacement for this portion used cut-and-cover methods, with reinforced concrete pipe and cast-in-place concrete transition structures, and low-strength grout backfill. In-tunnel repairs, including patching and void filling, were performed during a short work outage.
These are just a few of the many tunnel inspection and rehabilitation projects we have worked on over the years across our rail, transportation, wastewater, and water markets. Future Segments issues will spotlight individual tunnel inspection and rehab projects in more depth.