Mountain Tunnel Improvements
This project for the San Francisco Public Utilities Commission involves 11 miles of rehabilitation of the 10-ft diameter, concrete-lined, horseshoe tunnel, which was completed in 1925. Work includes concrete lining repairs, contact grouting, water cut-off grouting, and the construction of a new 1,075-ft adit tunnel. The project designer is McMillen Jacobs Associates with AECOM as environmental consultant. Project design and environmental review has commenced, and both phases are anticipated to be completed at the end of 2019. Bidding is anticipated in late 2019 with construction from 2020 to 2026. The estimated cost is $130-140 million.


Interlake Tunnel
The Interlake Tunnel for the Monterey County Water Resources Agency comprises an 11,000-ft long, 10-ft diameter, gravity-flow tunnel and related structures that would divert water from Lake Nacimiento (Nacimiemto Reservoir) to Lake San Antonio (San Antonio Reservoir). COWI North America has been hired by the agency as Program Manager for the project. McMillen Jacobs Associates has been retained for preliminary engineering and design services for the projects. Tunnel design utilizing EPB single-pass lining technology is 60 percent complete as of January 2019. Design-build SOQ is scheduled for Q1 2020. Construction is scheduled to begin in Q3 2020 following a local election to secure project financing. The estimated project cost including the tunnel and spillway modification is approximately $123 million.


Delta Conveyance
The Department of Water Resources (DWR) in May began formal steps to withdraw proposed permits for the WaterFix project and begin a renewed environmental review and planning process for a smaller, single tunnel project that will protect a critical source of water supplies for California. The actions implement Governor Gavin Newsom’s direction earlier this year to modernize the state’s water delivery infrastructure by pursuing a smaller, single tunnel project through the Sacramento-San Joaquin Delta.

San Jose

BART Silicon Valley Extension
The $4.7 billion, 6-mile BART Silicon Valley Phase II Extension includes 5 miles tunnel constructed by a single, large-bore TBM on the order of 45-ft in diameter. The extension includes four stations (three underground). The overall project is a 16-mile extension of the Bay Area Rapid Transit system in the San Francisco Bay area. Construction is planned to start by 2021 with passenger service by 2026. A joint venture of HNTB and WSP agreed to a four-year, $88.3 million program management contract with the owner, Santa Clara Valley Transportation Authority (VTA).



Potomac River Tunnel Project
The Potomac River Tunnel is a component of DC Water’s long-term control plan (LTCP), also known as the DC Clean Rivers Project. The Consent Decree establishes schedules for construction of the Potomac River Tunnel and other CSO control facilities under the DC Clean Rivers Project, including a 2025 deadline to implement the project in its entirety. The Potomac River Tunnel will be located approximately 100 ft below ground. CSOs captured by the Potomac River Tunnel would be conveyed to the Blue Plains Advanced Wastewater Treatment Plant.



NE Corridor Superconducting Maglev
The Environmental Impact Statement (EIS) for the first leg of the Northeast Corridor Superconducting Maglev project is underway with the Draft EIS to be released in October 2019, and the Final EIS and Record of Decision anticipated in Summer/Fall 2020. The first leg comprises 60 km from Washington to Baltimore, approximately 75 percent of the alignment in tunnel, and two underground stations (Washington, BWI Airport) and one at-grade station (Baltimore). The total cost is over $10 billion. TBM tunneling is anticipated as a single bore with guideways (~$15M OD). As many as eight or nine TBMs are anticipated. Owner: TNEM/BWRR; Prime Consultant: WSP (formerly Louis Berger); Tunneling subconsultant: Gall Zeidler.


St. Louis

Project Clear Tunnels
Metropolitan St. Louis Sewer District (MSD) has begun an ambitious program called Project Clear, a multi-billion dollar investment addressing wastewater overflows. The system improvements include construction of nine tunnels to control sewer overflows.

Upcoming tunneling components of Project Clear include (Project, Construction Begin, Construction Cost Estimate, Tunnel Length, Tunnel Diameter):

  • Lower & Middle Des Peres Storage Tunnel, 2020, $631,000,000, 9 miles, 30 ft dia
  • Lower Meramec Tunnel, 2020, $170,000,000, 6.8 miles, 8 ft dia
  • River Des Peres Tributaries CSO Tunnel, 2024, $375,000,000, 12,144 ft, 20 ft dia
  • Upper River Des Peres CSO Storage Tunnel, 2028, $226,000,000, 8,976 ft, 24 ft dia


New York

Flushing Bay CSO
The New York City Department of Environmental Protection has begun drafting an RFP for design of 2.5-mile long, 25 million gallon CSO tunnel in Queens as part of a Long-Term Control Plan. The tunnel is expected to be 18-20 ft in diameter an estimated cost of between $670 million $829 million for the preferred alternative. Preliminary plans envision construction occurring from 2026 to 2035.

New York

Hudson Tunnel Project/Gateway
The Hudson Tunnel Project is a new two-track heavy rail tunnel along the Northeast Corridor from the Bergen Palisades in New Jersey to Manhattan that will directly serve Penn Station New York. It consists of three major elements: the Hudson Yards right-of-way preservation project, the Hudson Tunnel, and the rehabilitation and modernization of the existing North River tunnel.

A joint venture of WSP, AECOM and STV has been awarded the design contract. The tunnel portion of the contract, estimated at $13 billion, is envisioned to be a design-build contract including the Palisades Tunnel and Hudson Tunnel. Uncertainties regarding funding is impacting the schedule.

In June, both New Jersey and New York passed legislation to create the Gateway Development Commission, a bi-state entity that would oversee planning, finding and construction of the new tunnels and other affiliated projects.

New York

Second Avenue Subway – Phase 2
Design is underway for the Phase 2 of the second Avenue Subway. A joint venture of WSP and STV is working on the design for the project that extends the line northward from 96th Street to 125th Street – a total of 1.5 miles with three new stations. The alignment will use some existing tunnels originally built in the 1970s, in addition to new soft-ground TBM tunnels. The cost estimate for this phase of the project is $6 billion, with revenue service anticipated between 2027 and 2029.



NEORSD Project Clean Lake
Project Clean Lake for the Northeast Ohio Regional Sewer District (NEORSD) includes several major tunnel components to store and convey combined sewer overflows. The projects include:

  • Shoreline Storage Tunnel – 15,300 lf of 21-ft diameter soft ground CSO tunnel. It is anticipated to bid in 2021;
  • Shoreline Consolidation Sewer – 11,700 lf of 9.5-ft diameter soft ground tunnel. It is anticipated to bid in 2021;
  • Southerly Storage Tunnel – 18,340 lf of 23-ft diameter CSO tunnel. It is anticipated to bid in 2024;
  • Big Creek Storage Tunnel – 22,400 lf of 18-ft diameter CSO tunnel. It is anticipated to bid in 2029.



The Allegheny County Sanitary Authority (ALCOSAN) is designing a tunnel program to control combined sewer overflows (CSOs) as part of a consent decree with EPA. The $2.8 billion system improvement program is expected to include tunnel segments to store and treat overflows. The improvements are slated to be complete by 2026. The tunnels include: Ohio River Segment (1.9 miles, 12-14 ft in diameter, $84 million); Allegheny River Segment (3.6 miles, 12-14 ft in diameter, $136 million); and Monongahela River Segment (4.5 miles, 12-14 ft in diameter, $152 million). Additionally, the program will include interceptor and consolidation sewers, dewatering pump station and treatment plant improvements. To date, a formal agreement has not been reached, so plans are not finalized.


Pawtucket/East Providence

Pawtucket Tunnel
The Narragansett Bay Commission (NBC) has begun conceptual design for Phase 3 of its Combined Sewer Overflow Program, which includes the Pawtucket Tunnel (approximately 13,000 ft long, 28 ft in diameter and located in bedrock about 200 ft deep). The contract will include the launch and recovery shafts (which will become permanent access shafts), two to three drop shafts with connecting adits at existing outfall locations, and an underground pump station.

The program/construction manager for Phase III is Stantec and its teaming partner Pare Corporation. Construction of the Pawtucket Tunnel is anticipated to begin in late 2020 or early 2021.



Phase 2 Lake Travis Deep Water Intake
The Brushy Creek Regional Utility Authority (BCRUA) has embarked on a multiple year program to increase capacity and manage concerns associated with recent historic low water levels of Lake Travis. The program includes: a multiple level-screen deep water intake assembly and shaft extending about 70-ft below lake bottom; approximately 10,000-ft of 96-in. diameter tunnel to convey water by gravity from the intake to a new on-shore pump station (with a subterranean forebay, multiple individual pump wells and a 30 ft diameter wetwell extending about 300 ft below grade); and 3,000-ft of 84-in. diameter pressurized transmission tunnel. Final design is anticipated to begin in 2019, and construction is anticipated to begin in 2021 or 2022. BCRUA is currently acquiring easements for the project.


D2 Subway
Dallas Area Rapid Transit (DART) is well underway with planning and preliminary design of the D2 Subway, which will provide a second light rail alignment through downtown Dallas. The targeted opening date for the design-build project is 2024.

Thirty-four borings have been completed since 2016, providing data on conditions up to 120 ft below grade. These borings have revealed the rock types of Austin Chalk (limestone) and Barnett Shale (shale). Upon completion of soil and rock testing, additional evaluations will be performed to help DART determine the most appropriate method(s) to construct the tunnel, stations, and station access portals.

The project budget was $1.3 billion as of October 2016. The project includes 1.3 miles of alignment below grade (2 miles total) and three underground stations (four total).


Flood Control Tunnels
The Harris County Flood Control District is set to receive a federal grant of $320,000 to study the feasibility of building deep tunnels to divert storm water to the Houston Ship Channel, the Houston Chronicle reported on Feb. 20. The four-month study would determine whether the tunnels would be practical and cost-effective in the district’s flood-protection strategy. The district got a $2.5 billion flood bond approved last summer.

Discussions have the tunnels at least 20 ft diameter and 150 ft deep moving water from upstream bayous to the ship channel, in some cases a distance of 30 miles.

San Antonio

SAWS Tunnel
The San Antonio Water System (SAWS), a public utility owned by the City of San Antonio, Texas, is in the process of selecting a consultant for its W-6 Upper Segment: Hwy 90 to SW Military Drive Sewer Main Project.

The estimated $150 million project involves approximately 27,000 lf of 10-ft diameter tunnel to host the new 90-in. FRP gravity sewer pipe. The project also includes installation of about 2,300 lf of 60-in. gravity sewer pipe via open cut. The tunnel depth will vary along the alignment with depths of up to 130 ft. The project includes five launching/receiving shafts with additional smaller access shafts. Geotechnical data is being gathered as design proceeds.

This project is part of SAWS’ compliance with the EPA Consent Decree. The depth and extent of tunneling is beyond that of past sewer projects at SAWS.

The goal is to complete 100% Contract Documents by February 2020, so SAWS can advertise in March 2020. The objective is to award the construction contract in June 2020. Estimated construction duration is a maximum of 36 months.



AlexRenew Tunnel
Alexandria Renew Enterprises (AlexRenew) has put forth a plan to address the discharge of combined sewage to Alexandria, Virginia’s waterways that includes a storage and conveyance tunnel system. The Tunnel System is the largest component of the program with an estimated construction cost of $293 million and capital cost of $345 million. The tunnel is envisioned to be a 12-ft diameter, 11,500-ft long and 120-ft deep soft ground tunnel, with three shafts ranging from 35 to 50-ft in diameter. The Tunnel System and other controls need to be in place by July 1, 2025, per state law.

The tunnel will be procured via through a two-step, fixed-price, design-build. A Request for Qualifications (RFQ) was issued on June 7, 2019. The board expects to approve the contract in November 2020 with NTP in December 2020.

RELATED: Tunnel Construction Project Update

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