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Tunnels The HNTB Companies Infrastructure Solutions

Revolutionizing the way tunnels are designed HNTB’s tunnel experts leverage their insight, expertise, and an unsurpassed level of technical excellence to deliver innovative, revolutionizing tunnel solutions tailored specifically to our client’s unique needs. Our long and proven history in planning, program management, design, construction management and technical services for tunnel and complex underground structures has resulted in a number of award-winning projects on some of the country’s most challenging programs for transportation infrastructure.

Tom Lantos Tunnels California

John F. Kennedy Airport Redevelopment Program New York, New York Courtesy: PANYNJ 3

East Link Extension King County, Washington

Expertise •

Soft ground tunnels

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Rock tunnels

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Caverns

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Shafts

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SEM/NATM

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Cut-and-cover structures

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Immersed tunnels

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Micro-tunneling and pipe jacking

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Tunnel condition survey, inspection and rehabilitation

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Geotechnical engineering

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Rock mechanics and engineering geology

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Geotechnical and geophysical investigations

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GDR, GIR and GBR

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Liner design

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Excavation support

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Underpinning, support and protection of existing structures

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Settlement analysis and mitigation

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Ground/structure interaction

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Seismic design and seismic retrofit of tunnels

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Geotechnical and structural instrumentation

Services

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Ground improvement

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Planning

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Geohydrology/groundwater modeling

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Design

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Dewatering

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Project management

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Waterproofing

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Tunnel, underground and structural engineering

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Blast design and monitoring

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Fire life safety

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Geotechnical engineering

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Tunnel ventilation

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Geology/hydrogeology

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SES and CFD analyses

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Construction management & engineering

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Feasibility and alternative analysis

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Tunnel Inspection

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Program management

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Instrumentation and monitoring

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Tunnel rehabilitation

Construction management and resident engineering

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Ventilation and fire life safety

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Operations and maintenance

Underground construction and engineering services

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Risk management

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Peer and value engineering review

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Constructability/construction phasing

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Visualization and 4-D virtual construction

HNTB’s capabilities cover a broad range of services and expertise that help our clients and communities meet their goals.

Istanbul Strait Road Tunnel Construction Istanbul, Turkey

Setting the Standard of Excellence At HNTB, our client is the focus. Our approach centers on the client’s needs, discovering the critical and defining solutions that work in the short and long term. We pride ourselves on taking a vision and turning it into reality. Through collaboration, HNTB is consistently setting a new standard of how tunneling projects are designed, delivered and managed.

Presidio Parkway San Francisco, California Services: Design

When Doyle Drive became structurally and seismically deficient, the California Transportation Department and the San Francisco County Transportation Authority led the effort to replace a 1.6-mile segment of Route 101 with a new Presidio Parkway that would be safer for traffic and serve as a regional gateway. HNTB served as lead designer and provided construction design services for Phase II of California’s first private-public partnership (PPP) alternative delivery project. The design included a high viaduct, completing the US 1 interchange, and designing three new cut-andcover tunnels, four low viaduct structures, and a new diamond interchange. By concealing large sections of the highway in tunnels and tucking the tunnels into the area’s natural contours, passengers have unobstructed sightlines of the bay. With its combination of bay muds and shallow aquifers, the unstable soil was prone to liquefication and incapable of supporting the parkway’s viaducts, tunnels and retaining walls. The team used cemented deep soil mixing to strengthen the ground, which creates columnar grids of soil and grout strong enough to support the structural loads. Thanks to the innovation used in designing infrastructure for high-seismicity areas, the Presidio Parkway can withstand a magnitude 8.3 earthquake, the maximum consideration for the region.

Istanbul Strait Road Tunnel Crossing Istanbul, Turkey Services: Independent design review and analyses, constructability and schedule improvements, risk mitigation The Istanbul Strait Road Tunnel Crossing connects the European and Asian sides of Istanbul, Turkey, by a road tunnel under the Bosphorus Strait, one of the world’s busiest waterways. The 44.29-diameter, 3-mile, single-bore, large-diameter TBM tunnel houses a double-decked lane configuration. It is the centerpiece of a 9-mile mobility-enhancing project that also includes twin New Austrian Tunneling Method tunnels and cut-and-cover tunnels. Recommendations for the interior structures and the final tunnel liner increased the structure’s safety, expedited the construction schedule, enhanced constructability, fire-life safety, ventilation facilities and operational functions during various incident events. Specific activities included: • Meeting Turkish technical and design requirements as well as specified American and European standards and codes • Reviewing and verifying geotechnical parameters • Conducting detailed pre-, mid- and post-construction seismic analyses to ensure minimal ground movement and maximum stability/safety • Recommended funding models for future Turkish infrastructure projects

Work performed on this project helped advance the worldwide tunneling industry’s knowledge of large-bore tunnels, proving they are a realistic, reliable mobility solution even in the most challenging environments.

Baltimore and Potomac Tunnel Rehabilitation

Seeking to increase safety and service,

Maryland

existing B&P Tunnel and constructing a new

Amtrak is modernizing and transforming a 4-mile section of the NEC by rehabilitating the higher-speed tunnel through Baltimore. The new

Services: Project management

tunnel will link Baltimore Pennsylvania Station with points south, improving connectivity

With no fire and life safety system, excessive

throughout the region.

water infiltration, a deteriorating structure and a sinking floor, this 1873-built tunnel, a

HNTB helped Amtrak get both tunnel projects

significant component of Amtrak’s Northeast

shovel-ready by providing preliminary

Corridor (NEC), required costly maintenance.

engineering support, project controls, design

South of Baltimore, the NEC’s four tracks

reviews, value engineering and coordination

narrowed down to two, creating a bottleneck

of the National Environmental Policy Act

as trains approached the Baltimore and

process. The public involvement team

Potomac (B&P) Tunnel. As a result, the

added value to the project by educating

750,000 passengers who used the corridor

the community about the planned major

daily often suffered through delays and

construction and holding collaborative meetings

unreliable trip times.

with transportation officials in Baltimore, Philadelphia and New York City.

SR 99 Alaskan Way Tunnel Seattle, Washington Services: Design of large diameter single bore tunnel, tunnel approaches (open cut, cut and cover), permanents structures and facilities, tunnel road and facility systems including tunnel ventilation and fire life safety systems, construction management, testing and commissioning Completing the State Route 99 Tunnel in 2019 was a transformative event in Seattle’s storied transportation history and a breakthrough for the worldwide tunneling industry. The tunnel creates a fast, convenient north-south option for motorists who want to bypass traffic congestion in the central business district while pushing the limits of size and safety. At 57.3 feet in diameter, the colossal tunnel winds for 2 miles under downtown, carrying two southbound lanes stacked atop two northbound lanes. It is the world’s longest continuous machine-based tunnel in soft ground and one of the world’s safest. The design incorporates numerous world-class safety and seismic features: • A tunnel liner system designed to meet stringent seismic load and water proofing requirements • State-of-the-art ventilation, fire detection and suppression systems • Completely pressurized emergency egress system with independent ventilation system • Security system with closed-circuit TVs • ITS with variable message signs Skilled tunneling expertise helped mitigate construction and third-party risks while setting a new standard for innovative, creative and safe tunneling solutions under densely populated cities.

Tom Lantos Tunnels San Mateo County, California Services: Tunnel design, hydrology/hydraulics, geotechnical engineering, plans, specifications preparation, construction cost estimating, soil-structure interaction, ventilation design, lighting design, system design, tunnel lining and portal design, tunnel designer’s field liaison during construction, engineering support during construction California’s Devil’s Slide is a dangerous stretch of coastline highway plagued by land slippages and rockslides, initiating closures for months and creating lengthy detours for commuters. Supported by public vote, the California Department of Transportation elected to bypass the troublesome roadway with the first highway tunnels constructed in the seismically prone state since 1964. The twin 4,200-foot tunnels satisfied a highly involved and environmentally conscious public and overcame challenges that included: • 10 variable rock formations • Mixed ground conditions • Significant groundwater • A high potential for seismic activity • Two endangered species Knowing the tunnels’ length and ground conditions were not conducive to tunnel boring machine techniques, HNTB introduced Caltrans to the New Austrian Tunneling Method. The NATM is a sequential excavation and support tunnel-mining technique that facilitated unprecedented in-field collaboration and set a standard for future tunnel designers and contractors.

East Link Extension King County, Washington Services: Project management, design-build support, civil, structural, environmental and station final design, value engineering and design, optimization studies, utility relocation, financial tracking, risk analysis, stakeholder coordination, contract procurement documents, design support during construction, developer coordination, public involvement activities, engineering systems integration, maintenance of traffic, project controls HNTB is leading a joint venture to deliver final design of the South Bellevue to Overlake Transit Center portion of Sound Transit’s East Link Extension project. The 7.2mile double-track route takes the light-rail line under downtown Bellevue via a third-of-a-mile-long tunnel, excavated using the sequential excavation method. The JV project team determined SEM was the most cost-effective approach after conducting a tunnel method study. The study was part of a value engineering effort that saved Sound Transit $39 million and eliminated surface impact and disruption associated with the cut-and-cover method previously proposed. Under SEM, conventional equipment removes soil in small sections. Crews support the excavated areas with spray-applied concrete, then apply waterproofing and construct the center wall and final concrete lining. The tunnel finishes and the adjacent station work were delivered under a heavy civil/construction management package. Excavation began in 2017 and was completed five months early in August 2020, keeping the project on schedule despite COVID-19 delays.

Sound Transit’s U-Link Light Rail Extension Seattle, Washington Services: Lead designer The University Link project takes the existing light rail terminus at Pine Street and extends it more than 3 miles north to the university via twin-bore, soft-ground tunnels. HNTB, part of the integrated joint-venture team, was contract lead for the design of the I-5 undercrossing and the live transit tunnel connection. To support I-5’s massive underground retaining walls during excavation, HNTB designed four structural concrete boxes that held the partially demolished retaining walls in place while the tunnel boring machine mined through the boxes. Applying high-level technical understanding and innovative box solution, the walls deformation stayed well within criteria limits during excavation. As an added benefit, the U-Link extension finished ahead of schedule and significantly below budget. Today, this successful project provides passengers a 24-minute time savings by taking the underground route that proves tunneling is a viable solution for improving mobility in dense urban areas.

O’Hare Airport Tunnel Network Chicago, Illinois Services: Design When one of the world’s busiest airports wants to transform the passenger experience and increase airport capabilities, it calls on the aviation and tunneling experts at HNTB to help renew the original 1944 O’Hare International Airport into a modern, efficient, accessible international gateway. The Terminal Area Plan features a new O’Hare Global Terminal and two new satellite concourses. HNTB will design the heavy infrastructure components, including a central tunnel system that will convey passengers, utilities and baggage from the Global Terminal to the satellite concourses. The 3/4 mile tunnel system will be excavated and constructed using cut and cover methods and be designed to support both the current aircraft fleet as well as future heavier aircraft.

Elizabeth River Tunnels South Hampton Roads region of Virginia Services: Construction quality control, testing and inspection The Virginia Department of Transportation and Elizabeth River Crossings groups recognized the need for a solution to the increase of traffic congestion and travel delays brought on by population increases over the last 50 years. The project’s complexity required a combination of expertise covering roadways, bridges, large mechanical and electrical systems, intelligent traffic systems and extensive tunnels design. By establishing a successful working relationship with VDOT on other projects, HNTB removed a level of complexity to the Elizabeth River Tunnels project by tapping into the vast knowledge of VDOT public-private partnership design guidelines and existing awareness of VDOT construction procedures. Through collaboration and innovation, the new Midtown Tunnel eliminated two-way traffic in existing tunnels, extended the adjacent freeway, improved connecting interchanges and currently saves nearly a million monthly travelers 30 minutes a day in commuting time.

Minneapolis-St. Paul International Airport Light Rail Transit Tunnels and Lindbergh Station Minneapolis-St. Paul, Minnesota Services: Design, construction services It was a clear choice to extend light rail service to Minneapolis-St. Paul International Airport which would provide a seamless connection to downtown Minneapolis and the Mall of America. However, MSP had little surface area to accommodate a light-rail extension. The new infrastructure project would need to be built underground — without disrupting airport operations. The Metropolitan Airport Commission turned to HNTB’s combined aviation and tunnel expertise to lead design and construction services. As the Hiawatha Line approached the airport, it would enter a cut-and-cover portal, descend 65 feet into parallel 1.7-mile tunnels and connect to the underground station. The 21-feet-in-diameter twin tunnels were excavated with a tunnel boring machine. This was the fastest, safest method for excavating without interrupting airport operations. Burrowing below two operational runways and four operational taxiways, through sandstone, limestone and glacial till, the TBM completed its mission in 14 months. To ensure the tunnels could support the load of the large aircraft above, HNTB lined the structures with heavy reinforced precast concrete segments. After the two tubes were in place, construction began on Lindbergh Station, a 40-foot-high, 63-foot-wide and 300-foot-long grand hall, dug out of sandstone and lined with precast concrete.

San Francisco BART Station San Mateo County, California Services: Structural, architectural and civil design, construction phasing Expanding the Bay Area Rapid Transit (BART) system 8 miles from Colma City Station to the San Francisco International Airport was a master class in overcoming challenges. The complex alignment successfully navigated multiple cities, cemeteries, neighborhoods, endangered species habitats, a regional shopping center and an operating railroad. The project also included 6.1 miles of subway, 1.2 miles of at-grade trackway and more than a mile of complex aerial bridge structures.

The northern portion of the heavy rail line in Colma City was constructed using a cut-andcover approach. The southern half runs parallel to the Caltrain corridor, which remained in service throughout construction. The final stretch is an elevated section that ties into the airport’s Millbrae Station. The extension offers a convenient alternative for travelers, reduces airport congestion, and links to the airport and downtown San Francisco for transit-dependent commuters while meeting strict seismic requirements.

Washington Dulles International Airport Tunnel Dulles, Virginia Services: Design In 1999, the Metropolitan Washington Airports Authority (MWAA) launched Dulles Development, an enormous capital improvement program that included a new loop tunnel system. The tunnel system was built under the airfield and would house an automated people mover that would shuttle passengers safely and efficiently between the airport’s three busiest terminals. At nearly 5-miles long, the multi-tunnel system would include an underground guideway, four stations, a new baggage handling system, underground tugs, utilities, pedestrians and maintenance. Based on the location of the tunnel segments, HNTB employed not one but three tunnel mining techniques. MWAA favored cut-and-cover construction for the tunnel segments, where access did not disrupt airfield operations. The New Austrian Tunneling Method and tunnel boring machines were used for burrowing under active taxiways and concourses.

VTA’s BART Silicon Valley Phase II Extension Project

underground stations (28th Street/Little Portugal, Downtown San José, and Diridon), one groundlevel station (Santa Clara),a train maintenance and storage facility, and additional emergency egress and ventilation facilities.

Santa Clara County, California Services: Program management, planning, design management and conceptual engineering, scope, cost and schedule development, funding strategy and federal funding grant application, program information controls systems, transit-oriented joint development analysis and coordination, design-build procurement document development The Santa Clara Valley Transportation Authority’s Bay Area Rapid Transit to Silicon Valley Phase II Extension is a six-mile, four-station extension of BART from Berryessa/North San José Station (opened 2020) through downtown San José to the City of Santa Clara. The Phase II Project is planned to include an approximately five-mile subway, three

Not only will modern tunnel boring machine construction technology be used for the first time on the BART system, but the project will be utilizing a large diameter single-bore tunnel sized to house both guideways and the station platforms at the three underground stations. This will be the first application of large diameter single-bore tunneling technology for transit in the U.S. Beginning in downtown San José, the tunnel will travel 5 miles under highways, residential and industrial areas, city streets, rivers and creeks and through a fault zone before surfacing in Santa Clara. The VTA will design, construct and own the asset. BART will operate the service and maintain the facilities. This extension provides a safe, efficient, world-class mass transit system that links to local, state, regional, national and international transportation modes.

West Seattle to Ballard Link Extension Seattle, Washington Services: Design When it comes to successfully delivering tunnels under downtown Seattle, no firm has more experience than HNTB. The firm was the lead designer and engineer-of-record for Seattle’s SR 99 Tunnel and is assisting Sound Transit with two lightrail extension projects — both of which require urban tunneling expertise.

In total, HNTB will help shape more than 3.5 miles of tunnel and six stations to be excavated and constructed under Seattle’s central business district and densely populated neighborhoods, with additional tunnel alternatives being considered for Ballard and West Seattle. When completed, the project will add 12 miles to Sound Transit’s light rail transit system and connect major population and employment centers in the region.

As part of the West Seattle and Ballard extensions, Sound Transit plans to construct a second downtown transit tunnel for the Ballard Extension, connecting the West Seattle Extension to an existing facility under Seattle.

Metro K Line Los Angeles, California Services: Lead designer, principal engineer As part of the Walsh-Shea Corridor Constructors designbuild team, HNTB served as lead designer and principal engineer for the Lost Angeles County Metropolitan Transportation’s (Metro) K Line, which links to two other Metro lines — the E Line and the C Line. The project provides a vital mobility alternative to the underserved residents and businesses of South Los Angeles. Crucial elements to the K line project were the three cut-and-cover tunnels as well as the mile of twin bored tunnels. For the complex underground structural components to meet stringent seismic design requirements, HNTB and Arup North America each completed independent designs then collaborated to reconcile differences for the bored tunnel, the underground stations and the cut-and-cover tunnel structures.

NYC Under-River Tunnel Assessment and Rehabilitation New York, New York Services: Project and construction management In 2012, Superstorm Sandy sent millions of gallons of seawater surging into tunnels under the Hudson and East rivers in New York City. Major flooding rendered the tunnels inoperable for days, crippling mobility into and out of Manhattan. Needing an accurate picture of the tunnels’ conditions and necessary repairs, the New York City Transit Authority and Amtrak selected HNTB to assess the near- or potentially long-term damage to the under-river rail

and structural systems. The team of technical, geotechnical and hydrology experts used stateof-the-art scanning technology, producing clear photogrammetric, laser and infrared images of the damage. The X-ray-like scans revealed chlorides and sulfates from the seawater had caused and were still contributing to the corrosion and cracking of key tunnel components. Following the damage assessment, HNTB developed a document detailing its findings and repair recommendations. Bringing the tunnels back to preflood conditions would require removing all delaminated and loose concrete, pressure washing to remove corrosive substances and replacing bench walls, tunnel ballast and rail systems. The rapid response and high-tech scans enabled both owners to gain an accurate and comprehensive understanding of the tunnels’ conditions so they could make informed decisions and move their tunnels into construction quickly.

North 27th Street Inline Sewer System Tunnel Milwaukee, Wisconsin Services: Preliminary and final design and construction services To help reduce the number of overflows every time the metro area received heavy rainfall, the Milwaukee Metropolitan Sewerage District needed a depth of expertise. HNTB provided the range of disciplines necessary to help the district analyze all options, gain public buy-in of the preferred alternative, design the solution and ensure its accurate construction. Preliminary engineering analysis included hydraulic modeling of the geographic area, a thorough assessment of geotechnical issues and cost analysis of near-surface storage, satellite treatment facilities and tunnel storage. HNTB’s preliminary design report contained 30 percent tunnel plans and specifications, a preliminary geotechnical baseline report that analyzed variable ground conditions, high water pressure, groundwater cut-off and complex grouting. The MMSD chose a 2-mile-long storage tunnel with vertical access shafts. Excavated by a rock ground tunnel boring machine, the freshly bored tunnel would have a 21-foot finished diameter and hold 27 million gallons of combined stormwater and sewage. During final design, HNTB completed the tunnel’s plans and specifications, developed easement drawings, legal descriptions and acquisition plat, provided geotechnical data and baseline reports and conducted a traffic control analysis.

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