SSH Joint Venture Creates $2.3B BART Silicon Valley Berryessa Extension
Threading a rail line through the congested corridor from Fremont, California, into Silicon Valley may have presented challenges to the design-build team, but as the Santa Clara Valley Transportation (VTA) regional Bay Area Rapid Transit (BART) Silicon Valley Berryessa Extension nears completion, the $2.3 billion project remains on budget and ahead of schedule.
The community has yearned for a regional transit service into Silicon Valley since the late 1990s. Santa Clara County, California, voters approved, in 2000, a 30-year, half-cent sales tax to pay for the extension. Studies showed extending the BART line to Milpitas, San Jose and Santa Clara offered an optimal option for relieving congestion on the north-south interstates.
"The extension will provide mobility alternatives to the highly congested Interstate 880 and Interstate 680 corridor," says Bernice Alaniz, Communications Director for the Santa Clara VTA. "The [San Francisco] Bay and hills preclude more asphalt. We wanted to encourage people to be more environmentally conscious, so we are providing a commute alternative."
The project is the largest public works project in Santa Clara County history. VTA oversees all aspects of the two-phased project. The first $2.3 billion, 10-mile phase runs from the future BART Warm Springs station in Fremont to just north of downtown San Jose.
VTA hired Skanska, Shimmick and Herzog (SSH) joint venture to design and build the project under a $772-million contract that included the track, line, systems and stations. The bid was $77 million less than engineers' estimates. The joint venture partners are Skanska of New York, Shimmick Construction of Oakland, California, and Herzog Contracting Corp. of St. Joseph, Missouri. Lockwood, Andrews & Newnam (LAN) of Houston and T.Y. Lin International Group of San Francisco designed the project for SSH.
"This is a high-profile project for the Bay area and I'm proud of being part of a project that will give the area another transportation choice," says Tim Schmidt, Deputy Design Manager with LAN.
For every $1 spent on construction, operations and maintenance, VTA estimates $4 to $10 will be reinvested into the region. That includes new businesses, offices and retail space; access to better paying jobs; and for employers, a larger labor pool and skill set, adding about 500,000 people, explains Alaniz.
"More than 40 percent of the parcels and property adjacent to the stations and beyond have turned over and started to be converted to higher-density housing units," says Brad Nystrom, Program Director with SSH. "There has been a tremendous amount of development activity surrounding the project."
Designing for a Tight Area
The new BART extension runs through a confined corridor, which created some design challenges, Schmidt reports. During the first 6 miles, the dual-track extension runs in the right-of-way parallel to the Union Pacific Railroad lines. Then the corridor is lined with homes, offices and businesses.
"It was a challenge trying to fit in the double track, and still leave room to build the project," Schmidt says.
About 6 miles of the line is at grade, with standard ballasted rail. Three miles is in a trench section, fully or partially below grade, and about 0.75 miles is aerial, over two existing roads and into one of the stations.
LAN divided the project into 31 design units, including grading, retaining walls, trenches and track, to create advance packages that let some of the work finish before all designs were finalized.
Vibrations were a concern in sections of the line. The team used floating track slabs, in which the slab floats on rubber pucks, in some of those areas and tire-derived aggregate, produced from recycled tires in others. The tire-derived aggregate is placed below the sub-ballast and ballast, wrapped in geotextile fabric and compressed. It also added sound walls along a portion of the line.
The rail line runs underneath or above the limited cross points for I-880 and I-680. The rail line, when operational, will not conflict with vehicular traffic.
SSH is a fully integrated joint venture. It broke the project into different teams based on discipline. It had a utilities, guideway, roadway, structures, track and station teams. By keeping the teams based on discipline, it gained the benefit of repetitive process and improved production, Nystrom explains.
During construction, SSH needed to keep the roadway traffic moving smoothly and had more than 300 traffic control plans.
"We approached the crossing areas a little differently," Nystrom says. "Instead of doing a typical bottom-up construction, we went for a top-down approach, which meant a shorter turnover time, six weeks or so, where we would excavate, put in the utilities, construct the road deck surface and put traffic back on top of it. Then we came back later and excavated underneath."
The vast majority of construction took place during the day to avoid disturbing people who were sleeping. While creating the trenches, SSH used specialized tools to press the sheet pile into place, rather than the usual pounding to reduce noise for nearby residents and businesses. The team also used variable moment hammers to control vibration and noise while installing and removing the sheet piling.
At each crossing, SSH aimed to avoid utility relocations whenever possible, since they can slow a project down and can take control of the schedule away from the construction team, Nystrom says.
"We did some pretty intensive utility investigation to determine where the utilities are and came up with some creative plans," Nystrom says. "For instance, we did a lift and lay for a major fiberoptic cable with hundreds of fiber pairs."
Relocating the cable would have taken six months. SSH noted slack in the line, so crews excavated 17-feet down, broke away the concrete, lifted the line about 15 feet into the bridge deck, placed a clamshell steel casing around it and cast it into the road surface.
Reflecting History in the Stations
The first phase includes two multimodal stations: Milpitas and Berryessa in San Jose. VTA worked with the communities, so the stations represent the history of those areas. Milpitas has an industrial theme and connects to a VTA light rail system and bus service. The Berryessa station enjoys an environmental theme to highlight the waterways in the area. It also provides access to bus service.
VBN Architects in Oakland, California, provided preliminary design for the street level Milpitas Station with below ground boarding, and FMG Architects of Oakland designed the at-grade Berryessa Station with elevated boarding. Anil Verma Associates, also of Oakland, handled the final design of both stations.
"These stations are signature architectural stations," Schmidt says. "They make a statement."
Both stations are a blend of structural steel, concrete, metal panels and glass. Both have a curved roof.
"These are not off-the-shelf buildings," Nystrom says. "All of the elements are unique. We have employed craftspeople and great subcontractors to support the project."
At the Berryessa station, as an environmental mitigation, crews had to reengineer Upper Penitencia Creek to eliminate flooding issues and eroding of property. Crews shored up the creek with trees removed from the station site, eliminated non-native plants, straightened the creek and created a flood plain.
The project is 80 percent complete, with testing and start up beginning. The team expects the rail service to open early in the fall of 2017.
"Positive delivery and the visible progress on schedule is very important to us delivering the next phase," Alaniz says. "We're setting the example for future infrastructure improvements."
The second $4 billion phase, was just given the green light by the Federal Transit Administration to enter the Project Development Phase of the Federal New Starts Funding Program. Phase II will continue on through San Jose, stop at Diridon Station, soon to become the largest transit hub in northern California, and end in Santa Clara. VTA owns the infrastructure and BART will operate and maintain the rail service.
"This is going to make a significant difference to the communities where we are working," Nystrom concluded.