After an extensive process to advance the planning and engineering of the Phase II Project, VTA has progressed the next key project efforts, such as the awarding of project contracts, advancement of design, and the start of early construction activities. In May 2022, VTA awarded the Tunnel and Trackwork contract to the joint venture of Kiewit Shea Traylor (KST). Utility relocations, site preparation, building demolition, and soil testing will be the first construction activities to take place at the various work areas. These early work construction activities are key to ensuring that the tunneling and heavy construction of the future stations can proceed on time.
The Tunnel's Path
VTA’s BART Silicon Valley Phase II Extension Project includes the construction of a tunnel that will be approximately five-miles long. Tunnel construction will begin south of the Santa Clara Station within Newhall Yard and run underneath I-880 and the Caltrain tracks. It will be launched from what is referred to as the West Portal. From there, the tunnel will continue southeast and cross under the western side of the Caltrain tracks at Emory Street and then continue under Stockton Avenue and curve east before reaching Diridon Station. From Diridon Station, the tunnel will continue under Santa Clara Street for approximately one-mile to the future Downtown San José Station. It will then curve northeast near 27th Street and Santa Clara Street to the future 28th Street/Little Portugal Station. From there, the tunnel will continue northeast under US 101 to McKee Road where it will run parallel to the highway until it surfaces at the East Portal, near Las Plumas Avenue and Marburg Way.
Tunneling Construction
Construction of the subway tunnel is within the Tunnel and Trackwork contract (Contract Package 2). The tunnel will be constructed as a single, large diameter tunnel, commonly referred to as Single-Bore, and will contain two independent track ways, one for each direction of travel. The tunnel will be excavated by a Tunnel Boring Machine (TBM). The TBM is an electrically powered machine that removes soil, rocks, and debris to create the underground tunnel. It features a cutter-head, which rotates to dig through soil and rock. Excavated material is removed through a conveyor system within the machine. The TBM will be able to excavate and build approximately 30 to 40 feet of the tunnel per day on average. At the stations, mining techniques will be used to excavate the underground connections between the tunnel and stations (which contain the boarding platforms). Tunneling is expected to occur 24 hours a day, up to 7 days a week to excavate and support the five-mile tunnel.
How a Tunnel Boring Machine (TBM) Operates
A Tunnel Boring Machine (TBM) will remove soil from the tunnel itself, keeping the street above intact. The TBM includes a cutter-head, which rotates to dig through soil and rock. The excavated material will then be removed through a conveyor system within the machine. TBM boring speeds vary greatly, depending on the size and length of the tunnel, the geological conditions, and many other factors. The following video demonstrates how TBMs work.
Check back in mid-2024 to learn more about naming the TBM!
Construction at VTA’s Newhall Yard and West Portal
Background and Purpose
The West Portal is the launching point for the Tunnel Boring Machine (TBM) that will dig the project tunnel, which will span five-miles between Brokaw Road and I-880. The West Portal is located along a construction site that crosses between the City of Santa Clara and City of San José. The West Portal refers to the overall construction site where many support facilities are located as well as the specific shaft that the TBM will enter the ground.
In preparation for construction, VTA proactively developed a plan to outline the modifications to access and circulation in and within the station areas during construction. This plan is referred to as the Construction Transportation Management Plan (CTMP). The goal is to maintain site conditions that allow for efficient construction while minimizing impacts to the community to the extent feasible. To develop the CTMP, VTA and the Contractor engaged in regular coordination with key stakeholders including the Cities of San José and Santa Clara, PayPal Park, and adjacent businesses and developments within the construction area. Watch the video of the March 2023 Public Meeting to learn more about the CTMP and early construction at the West Portal. Future CTMPs will be drafted for the other constructions areas as more details about the construction means and methods are developed.
Read the West Portal Early Works CTMP and watch previous City Council meetings where it was approved:
- City of San José approval (5/23/2023)
- City of Santa Clara approval - final CTMP (6/6/2023)
- City of San José approval - final CTMP (8/15/2023)
Construction Elements On-Site
The West Portal serves as the assembly and eventual launching point for the TBM and, accordingly, the area will house many large support structures.
The site at West Portal hosts several important elements:
- During operation, the West Portal itself, also known as the TBM shaft, will also remove excavated soil out of the tunnel so that tunnel lining segments will be brought into the tunnel and installed
- The tunnel lining factory and tunnel lining storage is where tunnel lining segments will be fabricated and stored. The lining segments will be placed in the tunnel as soil is removed to create a structurally sound tube underground. One ring of the tunnel is comprised of nine segments; up to six rings per day will be installed
- The Grout Plant is also integral to the lining of the tunnel. Grout will be used to seal the tunnel lining segments in place as the TBM advances
- The Excavated Materials Bin is where the excavated soils from the tunnel will be stored until hauled offsite to be repurposed or disposed of
- A noise curtain will be constructed along the west side of the site to reduce noise from construction activities. The contractor will determine the exact length of the curtain to ensure they meet the noise mitigation requirements
Early Work Construction Activities
VTA will conduct several activities within an initial phase of preparing the site for tunneling operations called Early Work Construction, including:
- Constructing on-site access points, designated crew parking, and office space
- Excavating the portal and establishing the excavated materials bin
- Constructing and operating the facilities needed to produce the tunnel lining
- Assembling the tunnel boring machine (TBM) required to create the tunnel
What Are the Project’s Working Hours?
Construction activities at the Newhall Yard and West Portal for early work construction activities will be single shift only (6 AM to 6 PM working hours and 6 AM to 4 PM hauling hours, including Saturdays).
Working hours will increase when the excavation of the portal begins, requiring double shifted work hours and hauling hours (6 AM to 4 AM including Saturdays and lasting 22 hours per day). We expect that these 22-hour work shifts will last 15 months. After this portion of construction activities is complete, hauling shifts will return to 12 hours and on-site work hours will last 22 hours per day. The working hours for when the TBM is operational have yet to be determined.
Where Will the Dirt Go?
Excavated material removed from the tunnel is referred to as muck. The excavated material will be temporarily stored within VTA’s construction staging area and may be reused as fill material or loaded onto trucks for reuse or disposal. Muck removed during tunnel excavation will require a large number of dump trucks. As such, VTA will coordinate with the City of Santa Clara and City of San José to determine the most direct and least disruptive routes to transport the muck.
What Will the Site Be Used for in the Future?
Once the tunnel construction is complete, the project will begin construction of the Newhall Maintenance Facility and the Santa Clara BART Station. The Newhall Maintenance Facility is a key component of the Phase II extension, as it allows for end-of-line maintenance and storage of BART vehicles. Without this facility, BART trains would need to return to the East Bay at the end of service each day.
Within the Maintenance Facility there will be a BART train maintenance shop, train car wash, maintenance and engineering offices, a yard and control tower, and other support facilities. Most maintenance activities will occur inside enclosed buildings, resulting in minimal noise from trains. The operations at the yard and maintenance facility will commence with passenger service of the Project.
After an extensive process to advance the planning and engineering of the Phase II Project, VTA has progressed the next key project efforts, such as the awarding of project contracts, advancement of design, and the start of early construction activities. In May 2022, VTA awarded the Tunnel and Trackwork contract to the joint venture of Kiewit Shea Traylor (KST). Utility relocations, site preparation, building demolition, and soil testing will be the first construction activities to take place at the various work areas. These early work construction activities are key to ensuring that the tunneling and heavy construction of the future stations can proceed on time.
The Tunnel's Path
VTA’s BART Silicon Valley Phase II Extension Project includes the construction of a tunnel that will be approximately five-miles long. Tunnel construction will begin south of the Santa Clara Station within Newhall Yard and run underneath I-880 and the Caltrain tracks. It will be launched from what is referred to as the West Portal. From there, the tunnel will continue southeast and cross under the western side of the Caltrain tracks at Emory Street and then continue under Stockton Avenue and curve east before reaching Diridon Station. From Diridon Station, the tunnel will continue under Santa Clara Street for approximately one-mile to the future Downtown San José Station. It will then curve northeast near 27th Street and Santa Clara Street to the future 28th Street/Little Portugal Station. From there, the tunnel will continue northeast under US 101 to McKee Road where it will run parallel to the highway until it surfaces at the East Portal, near Las Plumas Avenue and Marburg Way.
Tunneling Construction
Construction of the subway tunnel is within the Tunnel and Trackwork contract (Contract Package 2). The tunnel will be constructed as a single, large diameter tunnel, commonly referred to as Single-Bore, and will contain two independent track ways, one for each direction of travel. The tunnel will be excavated by a Tunnel Boring Machine (TBM). The TBM is an electrically powered machine that removes soil, rocks, and debris to create the underground tunnel. It features a cutter-head, which rotates to dig through soil and rock. Excavated material is removed through a conveyor system within the machine. The TBM will be able to excavate and build approximately 30 to 40 feet of the tunnel per day on average. At the stations, mining techniques will be used to excavate the underground connections between the tunnel and stations (which contain the boarding platforms). Tunneling is expected to occur 24 hours a day, up to 7 days a week to excavate and support the five-mile tunnel.
How a Tunnel Boring Machine (TBM) Operates
A Tunnel Boring Machine (TBM) will remove soil from the tunnel itself, keeping the street above intact. The TBM includes a cutter-head, which rotates to dig through soil and rock. The excavated material will then be removed through a conveyor system within the machine. TBM boring speeds vary greatly, depending on the size and length of the tunnel, the geological conditions, and many other factors. The following video demonstrates how TBMs work.
Check back in mid-2024 to learn more about naming the TBM!
Construction at VTA’s Newhall Yard and West Portal
Background and Purpose
The West Portal is the launching point for the Tunnel Boring Machine (TBM) that will dig the project tunnel, which will span five-miles between Brokaw Road and I-880. The West Portal is located along a construction site that crosses between the City of Santa Clara and City of San José. The West Portal refers to the overall construction site where many support facilities are located as well as the specific shaft that the TBM will enter the ground.
In preparation for construction, VTA proactively developed a plan to outline the modifications to access and circulation in and within the station areas during construction. This plan is referred to as the Construction Transportation Management Plan (CTMP). The goal is to maintain site conditions that allow for efficient construction while minimizing impacts to the community to the extent feasible. To develop the CTMP, VTA and the Contractor engaged in regular coordination with key stakeholders including the Cities of San José and Santa Clara, PayPal Park, and adjacent businesses and developments within the construction area. Watch the video of the March 2023 Public Meeting to learn more about the CTMP and early construction at the West Portal. Future CTMPs will be drafted for the other constructions areas as more details about the construction means and methods are developed.
Read the West Portal Early Works CTMP and watch previous City Council meetings where it was approved:
- City of San José approval (5/23/2023)
- City of Santa Clara approval - final CTMP (6/6/2023)
- City of San José approval - final CTMP (8/15/2023)
Construction Elements On-Site
The West Portal serves as the assembly and eventual launching point for the TBM and, accordingly, the area will house many large support structures.
The site at West Portal hosts several important elements:
- During operation, the West Portal itself, also known as the TBM shaft, will also remove excavated soil out of the tunnel so that tunnel lining segments will be brought into the tunnel and installed
- The tunnel lining factory and tunnel lining storage is where tunnel lining segments will be fabricated and stored. The lining segments will be placed in the tunnel as soil is removed to create a structurally sound tube underground. One ring of the tunnel is comprised of nine segments; up to six rings per day will be installed
- The Grout Plant is also integral to the lining of the tunnel. Grout will be used to seal the tunnel lining segments in place as the TBM advances
- The Excavated Materials Bin is where the excavated soils from the tunnel will be stored until hauled offsite to be repurposed or disposed of
- A noise curtain will be constructed along the west side of the site to reduce noise from construction activities. The contractor will determine the exact length of the curtain to ensure they meet the noise mitigation requirements
Early Work Construction Activities
VTA will conduct several activities within an initial phase of preparing the site for tunneling operations called Early Work Construction, including:
- Constructing on-site access points, designated crew parking, and office space
- Excavating the portal and establishing the excavated materials bin
- Constructing and operating the facilities needed to produce the tunnel lining
- Assembling the tunnel boring machine (TBM) required to create the tunnel
What Are the Project’s Working Hours?
Construction activities at the Newhall Yard and West Portal for early work construction activities will be single shift only (6 AM to 6 PM working hours and 6 AM to 4 PM hauling hours, including Saturdays).
Working hours will increase when the excavation of the portal begins, requiring double shifted work hours and hauling hours (6 AM to 4 AM including Saturdays and lasting 22 hours per day). We expect that these 22-hour work shifts will last 15 months. After this portion of construction activities is complete, hauling shifts will return to 12 hours and on-site work hours will last 22 hours per day. The working hours for when the TBM is operational have yet to be determined.
Where Will the Dirt Go?
Excavated material removed from the tunnel is referred to as muck. The excavated material will be temporarily stored within VTA’s construction staging area and may be reused as fill material or loaded onto trucks for reuse or disposal. Muck removed during tunnel excavation will require a large number of dump trucks. As such, VTA will coordinate with the City of Santa Clara and City of San José to determine the most direct and least disruptive routes to transport the muck.
What Will the Site Be Used for in the Future?
Once the tunnel construction is complete, the project will begin construction of the Newhall Maintenance Facility and the Santa Clara BART Station. The Newhall Maintenance Facility is a key component of the Phase II extension, as it allows for end-of-line maintenance and storage of BART vehicles. Without this facility, BART trains would need to return to the East Bay at the end of service each day.
Within the Maintenance Facility there will be a BART train maintenance shop, train car wash, maintenance and engineering offices, a yard and control tower, and other support facilities. Most maintenance activities will occur inside enclosed buildings, resulting in minimal noise from trains. The operations at the yard and maintenance facility will commence with passenger service of the Project.