Technical Insights by Water Market Leads David Crouthamel, GE, Bade Sozer, PhD, PE
Water is one of the world’s most valuable resources, and its conveyance, distribution, and disposal are a major concern for clients across the world facing aging structures, population growth, and environmental challenges. McMillen Jacobs has been providing innovative design and construction management of new water conveyance tunnels and rehabilitation projects for more than 65 years, with over 120 water tunnels and pipelines across the United States, Canada, Australia, and New Zealand just in the last 15 years. We serve our clients/owners, contractors, and other AE firms by all delivery services—including Construction Management at Risk (CMAR), Design-Build (DB), Design-Bid-Build (DBB).
McMillen Jacobs has over 250 staff with a focus on underground engineering, complemented by diversified experience and exceptional skills in geotechnical contract documents, hydrogeology, the New Austrian Tunnelling Method (NATM), tunnel boring machines (TBMs), contract packaging, alternative delivery, tunnel rehabilitation and inspection, seismic pipe modeling, trenchless methods, among others. Our underground-focused portfolio runs the gamut, from large-diameter tunnels and chambers to small-diameter force mains and pipelines, and includes cut-and-cover, drill-and-blast, TBM, and trenchless excavation methods. For more information on our various water tunnel projects, visit our company’s Underground/Tunneling Water webpage.
Three of our recent projects across North America highlight our capabilities:
Project: Rondout-West Branch Bypass Tunnel
Client: New York City Department of Environmental Protection (NYCDEP)
This signature project, which is under construction, includes a bypass tunnel around the leaking segment of the Rondout-West Branch Tunnel (RWBT), which has carried 50% of New York City’s water supply since 1940s. The challenges for the project included high head conditions under the Hudson River, an existing live tunnel with 1,200 feet (366 m) of head at 1,750 feet (533 m) away, bypass excavation through faulted and fractured rock, and installation and drainage of the steel interliner with a reinforced concrete final lining.
The connection to the RWBT will be performed during an outage in 2022 and will include unwatering that tunnel for the first time since 1957, inspection, and grouting repairs as well as bypass to the RWBT connection and concrete plugs. McMillen Jacobs has been actively involved with the project since the planning phase in 2012 and has been providing design services to the NYCDEP for initial support, TBM, segmental lining, final lining, grouting, design of pressure tunnel linings, and liner failure analysis, and will support the NYCDEP during connection for RWBT inspections and lining repairs.
RWBT Bypass Tunnel Alignment
Project: Mountain Tunnel Improvements Project
Client: San Francisco Public Utilities Commission (SFPUC)
The century-old, 18.9-mile-long (30.4 km) Mountain Tunnel is a key component of the Hetch Hetchy Reservoir regional water system. McMillen Jacobs is the Engineer-of-Record (EOR) for this rehabilitation project. As part of the project, we will participate in five yearly planned outages, starting in 2021. The tunnel is a critical water supply conveyance, so outages are restricted to two months or less depending on available storage resources. Therefore, direct work on the tunnel can only be conducted during planned outages. The rehabilitation of the tunnel includes repairs and contact grouting of the lining, tunnel ground support enhancement, and water cut-off. New components include a Flow Control Facility housed in a new shaft and bypass tunnel, with valving to control flow through the tunnel and enhance operational reliability, and extension of a siphon beneath the Tuolumne River. The work for this project is anticipated to be completed in 2026.
Mountain Tunnel Improvements Project
Project: Port Mann Main Water Supply Tunnel
Client: Metro Vancouver
This project will provide a seismically resilient, larger diameter drinking water conduit to replace an existing shallow Fraser River crossing near Vancouver, British Columbia, Canada. McMillen Jacobs is the EOR and provided engineering design services during construction. The project includes two 65-meter-deep (213 ft) shafts to launch and retrieve a 3.5-meter-diameter (11.5 ft) TBM driven through a 1-kilometer-long (0.6 mi) tunnel. Ground conditions were challenging in dense, highly variable glacial till to silty clay with up to 6 bar of hydrostatic pressure. The tunnel initial support utilized bolted and gasketed segments and a final lining using a steel lining. The primary challenges for this project were the variable soil conditions, no surface access except the two shafts, and high external head for a relatively small-diameter TBM.
The next Metro Vancouver water conveyance project is the Second Narrows Water Supply Tunnel, located between North Vancouver and Burnaby, BC. Similar to the Port Mann project, it will provide increased seismic resiliency and capacity for Metro Vancouver’s water distribution system. This project is currently under construction, with substantial completion anticipated by 2023. See the July 2021 Segments project update for more information.
Lowering of Port Mann TBM from the North Shaft