Design and construction procurement for the Amtrak Hudson Tunnel project

The Gateway Trans-Hudson Partnership (GTHP), a joint venture of WSP USA, Inc., AECOM USA, Inc, and STV Incorporated, is providing preliminary engineering services to Amtrak for the Hudson Tunnel project as well as supporting the NEPA process for getting the record of decision (ROD). This preliminary engineering design effort by GTHP includes geotechnical exploration and laboratory testing, design of structures, tunnel contract packaging and procurement planning.

The Hudson Tunnel Project includes the construction of a new Hudson River Tunnel system and rehabilitation of the existing North River Tunnel. The new tunnel system will be constructed south of the existing North River Tunnel, from North Bergen under the Palisades to Hoboken in New Jersey, below the Hudson River, and connecting directly to Penn Station in New York (Fig. 1). The tunnel system is configured as two single-track tubes, intermediate ventilation shafts and cross passages in compliance with NFPA- 130 requirements. The adjacent surface alignment west of the Palisades will be constructed on viaducts, embankment and retained fills.

The existing North River Tunnel (Fig. 2) consists of two single-track, electrified rail tunnels extending from tunnel portals Completed in 1910 by the Pennsylvania Railroad, the tunnel opened at the same time as Penn Station and the four, single-track, East River tunnels that connect Penn Station to Queens and onto Long Island and New England, respectively. Both tunnels in the existing North River Tunnel were inundated with brackish river water during Superstorm Sandy (Fig. 3), resulting in the cancellation of all Amtrak and NJ Transit service into New York City for five days. After the brackish water was removed from the tunnels, the residual chlorides and sulfates have had on-going detrimental impacts on the interior concrete and rail systems.

The poor condition of the tunnels following Superstorm Sandy as well as their continuous high level of use, has highlighted the lack of a trans-Hudson River operational flexibility necessary to conduct routine maintenance and state of good repair to ensure continued Northeast Corridor (NEC) operations into Penn Station at existing peak period operating levels. Any emergency or routine maintenance in the tunnels requires outages that disrupt service for hundreds of thousands of passengers each day. An extended disruption, caused by natural or manmade disaster, would result in local, regional and national economic impacts. The susceptibility of the region to natural disasters and condition of this critical asset drives the urgency to strengthen resiliency of this river crossing. The Hudson Tunnel Project is focused on tunnel resiliency and redundancy essential to reducing the risk associated with dependency on the centuryold tunnel. Once the new Hudson River Tunnel is commissioned, the existing North River Tunnel will be rehabilitated and modernized. This will include renewal of the tunnel facilities, including benchwalls, catenary, communications and signals; fire and life safety; drainage facilities, as well as maintenance and emergency egress features. The existing ballasted track and drainage systems will be removed and replaced with a direct fixation track system.

The cancelled Access to the Region’s Core (ARC) Project (2010) included surface alignments and tunnels through New Jersey, under the Hudson River and into Manhattan to a new station cavern connecting to Penn Station. Most of the ARC New Jersey alignment has been utilized by the Hudson Tunnel project. This includes the surface works and Palisades Tunnels that have identical alignments as the ARC project. However, the new tunnel project Hudson River and Manhattan section alignments now differ from ARC along with a direct Penn Station connection.

The ARC Project had several construction packages where contracts had been already awarded or had been advertised and/or ready for award. Utilizing the knowledge and information that was collected during the ARC project, GTHP has utilized previous information and design and adjusted and revised contract packages previously awarded and incorporating whatever changes have been required for the new tunnel alignment.

Project location and anticipated subsurface conditions

Site development and manmade obstructions. Much of the New Jersey project area is set within the largely undeveloped, low-lying Hackensack Meadowlands. The area on the east side of Frank R. Lautenberg Station is characterized by major transportation infrastructure, including the New Jersey Turnpike and the NEC, and transmission towers. Industrial facilities such as the PSE&G Generating Station and warehouses and distribution centers are located north and south of the NEC. East of the Tonnelle Avenue arterial, the municipalities of North Bergen, Union City and Hoboken are characterized by a mix of low- and high-rise residential developments, commercial corridors and varying degrees of industrial activities.

The Hoboken and Weehawken area has increased residential development since the ARC Project was cancelled, in particular adjacent to the Hoboken Shaft area. In Hoboken, the tunnel alignment crosses two at-grade tracks of the Hudson Bergen Light Rail (HBLR) for a distance of about 121 m (400 ft). The electrified tracks were constructed in 2004. A new PSE&G substation was constructed in 2016, south of the HBLR at 19th Street adjacent to the tunnel alignment.

In Manhattan, the project alignment crosses below a heliport, Hudson River Park, 12th Avenue, West 30th Street, the elevated Highline urban park and new major development above the extensive rail yards west of Penn Station. The existing Manhattan Bulkhead (Fig. 4) was built in the 1870s and consists of timber piles, concrete blocks and stone rip-rap structure approximately 45 m (150 ft) in width. The North River Tunnels were mined through the Bulkhead piles and rip-rap by using Greathead Shields with compressed air. The new tunnel alignment requires a tunnel excavation to mine through the lower portion of the Bulkhead where timber piles and rip-rap structure will be encountered. Additionally, there are three other significant underground obstacles that will need to be addressed east of the Manhattan Bulkhead: 1) abandoned concrete-filled pipe piles of the former West Side Highway, 2) a NYCDEP interceptor sewer supported by steel piles underneath 12th Avenue and 3) a NYCDEP combined sewer anticipated to be supported on timber piles underneath West 30th Street.

Anticipated ground conditions

The Hudson Tunnel project is located within the Appalachian Highlands U.S. physiographic division. The project crosses two distinct physiographic provinces. The New Jersey portion of the project region is located within the Piedmont Lowlands section of the Piedmont physiographic province, a broad lowland interrupted by long, northeast-trending ridges and uplands. The most prominent physiographic feature in the eastern part of the section is the Palisades, a north-south topographic ridge near the Hudson River that rises above the surrounding lowlands of the Meadowlands.

The New York portion of the project region is located within the Manhattan Prong of the New England Upland section of the New England physiographic province. Topography is largely controlled by bedrock geology. Manhattan’s elongate ridges trend generally northeast.

The Hudson River portion of the project region is located between the Piedmont physiographic province to the west and the New England physiographic province to the east.

New Jersey Surface Alignment ground conditions

Five soil strata are identified in the New Jersey Surface Alignment section: Stratum F (fill), Stratum O (peat and organic soils), Stratum S (sand/silt and sand), Stratum C (varved silt/clay) and Stratum G (glacial till). The Stratum C can be further divided into two substrata, Stratum C1, an over-consolidated stiff layer.

From Tonnelle Avenue to the east toe of the Palisades, two soil strata are identified, Stratum F (fill) and Stratum G (glacial till). From the east toe of the Palisades to the Hoboken Shaft, all five soil strata are present.

Palisades Tunnels ground conditions. The Palisades Tunnels will be excavated and bored mainly in the igneous Palisades Diabase. There is also a limited section of Lockton Formation and Stockton Sandstone. The diabase is generally fresh to slightly weathered. Tunneling rock mass quality classifies from poor to good with the latter predominant.

The Lockatong is encountered at the eastern edge of the Palisades sill and typically consists of a silty argillite, laminated mudstone, very fine-grained sandstone and siltstone and minor silty limestone. Where the Palisades Diabase sill intruded into the Lockatong Formation, it thermally metamorphosed the rock into a brittle, black, very fine-grained hornfels. Further eastward and entering the Hoboken Shaft, the Stockton Sandstone is encountered. It consists of sandstone with conglomerate and siltstone lenses. Tunneling rock quality rock mass quality is classified as very poor to poor.

The Palisades tunnels will be mined in full-face rock with generally anticipated low ground water inflows although there are some faulted zones. Hudson River Tunnel ground conditions. In most of the Hoboken area there is fill underlain by a peaty and organic soil (O). It consists of fibrous peat mixed with dark gray, organic clay. The material is very soft to soft and classified as OH, Pt, CH and ML. Varying amounts of silt and sand are also present within this deposit. Methane gas is anticipated in this stratum.

In the Hoboken land section of the tunnel, estuarine deposits (designated E) is the primary soil stratum through which the Hudson River Tunnels will be excavated. The deposit consists of gray, silty clay to sandy silt with estimated thickness ranging from several feet to more than 61 m (200 ft). Stratum E is generally classified as high-plasticity clays (CH); however, high-plasticity silts (MH), low-plasticity clays (CL), and lowplasticity silts (ML) are also present.

Small shells and organics have been encountered at various depths within Stratum E. Organic content is typically less than 5 percent. In some locations, Stratum S locally underlies Stratum E with thickness ranging from 0.6 to 2.4 m (2 to 8 ft) and can be classified as very loose to dense silty sand (SM) or sandy silt (ML).

Glacial deposits (G) are present and will be encountered on a limited basis. The (G) soils are a heterogeneous mix of soils generally classified as CL, ML, SP, SM, SP-SM, GP, GM, GP-GM. The glacial deposits are typically reddish brown, brown or gray sands and consist of varying amounts of clay, silt, sand and gravel. Boulders are also present. Consistency and density ranges from stiff to hard and medium dense to very dense, respectively.

Parts of the Hudson River Tunnel alignment are in bedrock of different formations. Within the tunnel excavation, the Stockton Sandstone is present for about 25 percent of the entire alignment. The rock mass quality is generally rated poor to very poor. As the alignment progresses, eastward toward the Manhattan shore line, the rock type changes to Manhattan Schist. However, rock will not be encountered there since the alignment is shallow.

Mixed-face tunneling will be encountered at several locations in the Hoboken area as the tunnels proceed eastward toward the River. Approximately 1,400 feet of the tunnels, as they approach New York, have less than one diameter of ground cover in soft weak Stratum E soils. Additional design and construction considerations are required for this low cover section.

Manhattan Tunnel ground conditions. The overburden soil in the Manhattan area consists of fill materials (F) overlying saturated estuarine deposits (Stratum E), silt and clay (Stratum C), and glacial deposits (Stratum G). The overburden soils consist primarily of very soft to medium stiff clays and silts and very loose to medium dense silty sands. The glacial deposits are stiffer and denser and have the potential to contain cobbles and boulders. The overburden soils are highly compressible and will respond to minor changes in stress, such as construction surcharge loads, changes in pore pressure (due to dewatering or lowering of the ground water table from inflows into open excavations), or other changes from the initial in situ stress state. Mined tunnel excavations by non-TBM methods in estuarine deposits will require heavy support of excavation walls due to the low strength and high compressibility characteristics of these deposits. During excavation it will also be necessary to use some form of external ground treatment to stabilize the tunnel face and supplement the excavation support systems.

Hudson Tunnel Project contract packaging development

Multiple contract packages are planned for the Hudson Tunnel Project, including contracts covering tunneling, other major underground work, civil work, and, and follow-on typical finish works consisting of internal concrete, track work, rail systems, ventilation systems and fan plant structures. The packaging plan, currently under development, will be based on several factors, including

• Project funding strategy and expected cash flow
• Types of construction and skill sets involved
• Potential contract size and attractiveness to industry
• Schedule optimization
• Contract interface risk
• Opportunities for contractor innovation
• Timing for availability of real estate / easements
• Third party / stakeholder constraint, including permitting requirements.

Contract scope components (building blocks) to be organized with some combination into the final contract packages include the following.

NJ Surface alignment. The proposed NJ Surface Alignment scope component extends from Allied Interlocking, located east of County Road in Secaucus to the Tonnelle Avenue in North Bergen, just west of the Palisades Tunnel Portal. The double track configuration will be constructed on retained embankment, aerial viaduct structure and bridge structure over the Secaucus Road and the New York Susquehanna and Western and Conrail freight tracks. This scope also includes the construction of drainage culverts, access roadways, foundations for overhead catenary structures, security fencing, access stairways and platforms for signal and communication systems structures.

Tonnelle Avenue Overhead Bridge. This work componentwas already well under construction as a small first contract when the ARC Project was cancelled. Resumption of this work will require further excavation of the abutment walls that were previously completed and reestablishing the bearing area for the precast concrete deck beams.

This scope component also includes excavation of the backfill that was placed within the track alignment area between the abutment walls when the ARC Project work as suspended in 2010. A new drainage system needs to be installed to handle storm water in the overhead bridge area, and existing utilities below the roadway will need to be relocated.mining operation.

Palisades and Hudson River Tunnels. This major tunneling scope component consists of two TBM drives from the NJ Tonnelle Avenue Portal on the west side of the Palisades, through the Hoboken Shaft (future NJ fan plant site), under the Hudson River and into Manhattan terminating at the 12th Avenue Shaft (future fan plant). Major elements of this scope component are:

• Palisades portal works.
• TBM power substation.
• Hard rock TBM excavation for Palisades tunnels.
• Construction of the Hoboken shaft.
• Hybrid (rock, soft ground) TBM excavation for Hudson River Tunnels.
• Pre-excavation ground treatment in the River section with low ground cover.
• Nine cross-passages in rock; six cross passages in soft ground utilizing ground freezing.

Preparatory work for the TBM operation includes the construction of a temporary TBM power substation, stabilization of the rock face supporting Paterson Plank Road in North Bergen, NJ above the excavation of the approach to the Palisades Tunnels to establish starting line and grade for the TBM and assembly of one or two hard rock TBMs with trailing gear and supporting logistics at the Tonnelle Avenue Portal.

The Palisades Tunnels section, primarily stable rock, runs from the western slope of the Palisades to the Hoboken Shaft whereby the TBMs will be received. This shaft will also be utilized as a future ventilation shaft. The tunnels have the option to be supported using either single-pass pre-cast concrete segments, or a twopass lining system with temporary support and a follow-on permanent support of castin- place concrete with a waterproof membrane system. The number of hard rock TBMs and the selection of the tunnel lining alternative will be left to the contractor. The Hoboken Shaft excavation will utilize slurry walls through the overburden to rock, and drill-and-blast methods to excavate the rock to the required shaft base. During shaft construction, strict ground water control will be required to prevent pore pressure changes in the highly compressible soils that would result in large settlements to nearby utilities, roadways and residences. At the shaft TBM breakout, a combination of jet grouting and rock mass rock grouting is planned.

The Hudson Tunnels segment includes all work necessary to complete two TBM tunnel drives between the Hoboken Shaft and the 12th Avenue Shaft in Manhattan. These tunnel drives include full-face rock, mixed-face and soft ground conditions. Because of the variable and range of ground conditions, the TBMs are expected to be hybrids with pressurized-face capabilities, with earth pressure balance technology most applicable. The contractor could propose to utilize the two hybrid TBMs to first excavate the Palisades tunnels with perhaps some TBM cutterhead modifications done at the Hoboken Shaft following the Palisades rock tunnel excavations before proceeding eastward under the River.

The Hudson TBMs will be removed at the 12th Avenue shaft. The last several hundred feet of tunnel would be excavated though controlled low strength cementitious backfill of previously constructed sequential excavation method (SEM) tunnels extending from the River edge, under 12th Avenue and into the 12th Avenue Shaft. This SEM section will handle the removal of numerous obstructions.

For the Hudson Tunnels, preparatory work for the TBM operation includes a temporary TBM power substation (if not shared with the Palisades Tunnel section), underpinning of Willow Avenue Bridge in Hoboken and some ground treatment to protect sensitive structures located in the Hoboken mixed-face areas. Some of the sensitive structures are buried highvoltage cables and the HBLRT light rail.

A section of the River tunnel, toward the New York side, has low ground cover in weak soils, resulting in potential buoyancy issues and face stability concerns during TBM mining. Hence, prior to TBM arrival in this area, ground improvement installation (in the wet) placed within a temporary containment cofferdam is needed, see Fig. 5. The current preferred ground improvement method is deep soil mixing (DSM).

Cross passages will be provided for emergency egress between tunnels and to house some mechanical and electrical equipment. The 15 cross passages for the Palisades and Hudson Tunnels will be excavated and supported using two different methods, depending on the existing soil or rock conditions.

Cross passages in rock are anticipated to be mined excavations by SEM with drill-and-blast techniques. Temporary ground support (e.g., rock dowels, shotcrete) would be used. Permanent ground support would consist of either shotcrete or cast-in-place concrete, with a waterproof membrane.

Cross passages in the soft ground or soil areas will be pre-stabilized using horizontal ground freezing techniques. Excavation would be SEM with shotcrete/ lattice girders as temporary support. These cross passages would also be permanently supported with cast-in-place concrete or shotcrete with a waterproof membrane.

Manhattan Tunnels. This scope component entails much work centered around SEM tunnels through obstructions, shaft excavation, major ground stabilization measures and underpinning. All these works occur in very poor ground conditions where excavations need to be strictly controlled to mitigate ground settlements. Major work elements are:

• Construction of the 12th Avenue Shaft using slurry walls and ground improvement.
• Ground stabilization primarily by ground freezing and construction of SEM tunnels (westward) between the 12th Avenue Shaft and the Manhattan Bulkhead at the waterfront area including filling the tunnels with controlled lowstrength cementitious backfill.
• Ground stabilization primarily by jet grouting and construction of SEM tunnels (eastward) under West 30th St running from the 12th Avenue Shaft to connect with West Rail Yard (Hudson Yard) Tunnels north of West 30th Street.
• Installation of a permanent tunnel lining, castin- place concrete with a waterproof membrane system for the eastward West 30th St running SEM tunnels.
• Building a temporary bypass for the large 100-year old two cell storm sewer running along West 30th Street directly over the tunnel alignment and then finishing with a new permanent sewer structure after the tunnels are completed.
• Several utility underpinning and reconstruction/ relocations in West 30th Street and 12th Avenue areas.
• Demolition of existing structures on the 12th Avenue Shaft site (Block 675 Lot 1).

The 12th Avenue Shaft excavation will utilize slurry walls in soil overburden. Overburden consists of fill underlain by weak highly compressible silts and clays. Deeper below the shaft invert are glacial deposits and rock. During shaft construction, strict ground water control will be required to prevent the surrounding highly compressible soils from reacting to pore water pressure drops, which would result in large settlements to nearby utilities, roadways and buildings. Temporary construction flood gates will also be installed in the 12th Avenue Shaft.

Ground conditions for each SEM tunnel segment will consist of fill materials underlain by weak soft clays and silts.

The Manhattan Bulkhead is founded on timber piles with cobbles and rip-rap fill. Prior to excavation through the pile/rip-rap/cobbles, permeation grouting would be done to facilitate follow-on ground stabilization by filling rip-rap voids and locking riprap/ cobbles in-place. Ground stabilization is planned as ground freezing. More than 115 timber piles are expected to be encountered in each tunnel crossing of the Bulkhead.

Heading west from the 12th Avenue Shaft, SEM tunnels will be utilized to remove the steel H pile foundations of a large NYCDEP sewer below the northbound side of 12th Avenue, replacing them with an underpinning structure. In addition, abandoned West Side Highway concrete filled pipe piles will be removed. Ground improvement will be required prior to all SEM tunneling in this latter area due to poor ground conditions. However, ground stabilization in this area is planned as jet grouting.

Connection to A-Yard. The scope for making the connection to the Amtrak’s existing A-Yard track network on the west side of Penn Station New York includes construction of a cut and cover tunnel under 10th Avenue with temporary utility support and permanent reconstruction; the track reconfigurations in A-Yard with associated underpinning of several support columns for the overlying building at 450 West 33rd Street (Brookfield Building); construction of the A-Yard Fan Plant structure under the Brookfield Building; and installation of flood gates on the east side of 10th Avenue.

NJ fan plant and internal tunnel concrete. Construction of the Hoboken Fan Plant will follow the completion of the Palisades and Hudson River Tunnels, including the fan plant building structure and building mechanical, electrical and plumbing facilities.

The internal concrete finish work required for the Hudson River and Palisades Tunnels consists of the high and low benches, the tunnel invert, the sidewall ventilation duct wall, cross passage finish work and construction of the open cut section between Tonnelle Avenue and the Palisades Tunnel Portal.

Railroad systems

Traction power. Traction power facilities will be constructed in accordance with well-established railroad installation procedures. Each element of construction will be based on previously installed facilities. Critical constructability issues that will require refinement include the scheduling of outages with Amtrak for the connection to the existing transmission network and for the modifications required at the existing Amtrak substations.

Overhead catenary system. The project will include the installation of a complete overhead catenary system, including the supporting structures, for the entire alignment from the New Jersey surface section to A-Yard in Manhattan. It is assumed that all new catenary structures will be installed by the contractor. Amtrak forces will perform the connections to the existing NEC system at Allied Interlocking and in A-Yard.

Modification of the existing Amtrak catenary structures will need to be done as part of the Amtrak force account effort. Staging plans will need to be established with Amtrak to establish nighttime and/ or weekend schedules to work at the connections and adjacent to existing tracks.

Signal work. Signal construction will follow closely after the track bed is installed. A trough for the signals and communications cables will be installed along the full extent of the NJ surface contract. Platforms will also be constructed along the NJ surface alignment for the new signals and communication structures for controlling the new Allied Interlocking.

Embedded conduits in the tunnel sections as part of the appropriate tunnel finish concrete work. Cables will be pulled into the embedded conduits or laid in the trough as part of the railroad systems work. The signal equipment installation can coincide with work on other disciplines such as electric traction and communications.

Final connections of all new signal and communications equipment are expected to be performed by the Amtrak forces.

Track work. Ballasted track construction will be consistent with common local practice. Direct fixation track construction in the tunnel sections will be based on a resilient tie design. All special trackwork materials for the new Allied interlocking will be contract procured but installed by Amtrak forces.

Fan plant MEP and electrical substation installations. The Hoboken Fan Plant, 12th Avenue Fan Plant and A-Yard Fan Plant will all be fitted out and equipped in combination to ensure system compatibility. This scope component will also include provisioning of emergency power generators at the Hoboken and 12th Avenue Fan Plants and electrical power substations to supply operating power to the fan plants.

General project schedule

The start of construction will depend on when the Project will receive a Record of Decision for the environmental review process and the availability of the required funding is secured. Once construction is underway, the project has an overall timeline of approximately eight years. After the new Hudson Tunnels are operational, the existing North River Tunnels will be taken out of service one at time for complete rehabilitation, with that work expected to be approximately three years later. At that point, Amtrak will have four tunnels in reliable operating condition, which will make possible an increase of passenger capacity with the completion of other key projects that are part of the overall Gateway Program, including an expansion of Penn Station in New York.

Conclusion

There is an urgent need for a reliable and redundant back-up for the aging existing North River Tunnels crossing the Hudson River into New York. These existing tunnels are critical to the need for reliable rail transportation and the economic well-being of the Northeastern United Sates. When the new tunnels to be constructed under the Amtrak Hudson Tunnel Project are completed and operational, they will allow the existing tunnels to be taken out of service for complete rehabilitation to resolve their on-going structural and systems deterioration issues.

The Amtrak Hudson Tunnel Project construction is expected to be covered by a multiple contract packaging plan that is currently under development. The packaging plan will be configured to be attractive to the construction industry, reduce interface risk, and provide opportunities for contractor innovation.