With high-profile projects under way in California providing improvements for intercity transportation networks – namely the Central Subway project in San Francisco and the Regional Connector, Westside/Purple Line Extension and Crenshaw/LAX projects in Los Angeles — the state itself is also busy planning upgrades to its intercity rail network. Through the California High-Speed Rail Authority, the state is moving closer to building the United States’ first high-speed rail network.
When completed, trains will travel between San Francisco and Los Angeles at speeds of more than 200 miles per hour, completing the journey in less than three hours. Future plans include connections to other major metropolitan areas, including Sacramento and San Diego. Eventually, the system will total 800 miles with stations in as many as 24 cities across California.
A high-speed rail network boasts many advantages for the state, including easing congestion along already strained vehicular arteries and reducing greenhouse gas emissions. With airports also operating at capacity and the state’s population expected to continue to rise significantly, it is apparent that simply maintaining the existing transportation infrastructure was not an option. Additionally, the building of the network over the coming years will provide a steady stream of revenue and jobs for the construction industry.
Tunnels will play a key role in delivery of the program where the alignment traverses challenging mountainous terrain associated the California Coast Range in Northern California and the Tehachapi and San Gabriel Mountain ranges in Southern California.
The roots for high-speed rail in California date back to the 1980s when planning studies evaluated a network in Southern California. The idea gained a broader scope in the 1990s as a state-commissioned study verified the feasibility of a statewide high-speed rail system. In 1996, the California High-Speed Rail Authority was created, and in 2008 the state passed a $9.95 billion bond measure to authorize funding. Additional funding came through the American Recovery and Reinvestment Act (ARRA) of 2009 and through the state’s Greenhouse Gas Reduction Fund (also known as Cap and Trade).
In 2015, state dignitaries celebrated a ground-breaking ceremony in downtown Fresno as a plan decades in the making took a major step toward being a reality. Currently more than 100 miles of the alignment is under construction running through California’s Central Valley and this segment forms the backbone of the San Francisco-to-Los Angeles route. From there, the line will be extended northward to San Francisco and southward to Los Angeles, with a goal of completing Phase 1 by 2029. Phase 2 currently calls for an extension of the Central Valley line north to Sacramento, and an extension from Los Angeles eastward through the Inland Empire and then southward to San Diego.
Phase 1 comprises three main sections: the Central Valley section (Madera to Bakersfield); the Silicon Valley to Central Valley (San Jose to Merced/Madera); and Southern California (Bakersfield to Burbank). Between San Jose and San Francisco and Burbank and Los Angeles/Anaheim, the California High-Speed Rail Authority plans to use a blended operations strategy partnering with commuter rail systems like Caltrain (serving the San Francisco Bay area) and Metrolink (serving Southern California). Upgrades will be required on those systems to accommodate high-speed rail operations.
The Central Valley line serves one of the fastest-growing population centers in the state. It is broken into three main design-build construction packages that are currently under construction. They include:
Construction Package 1 — CP 1 covers a 29-mile stretch from north of Madera to south of Fresno. The contract was awarded in 2013 to a joint venture of Tutor Perini/Zachary/Parsons with a bid of $985 million.
Construction Package 2-3 — CP 2-3 extends 60 miles from the end of CP 1 through Tulare and to a point near the Kern County line. The contract was awarded in 2015 to a joint venture of Dragados/Flatiron/Shimmick with a bid of $1.23 billion.
Construction Package 4 — CP 4 extends 22 miles from near the Kern County Line to a point north of Bakersfield. The contract was awarded this year to California Rail Builders (Ferrovial Agroman US Corp.) with a bid of $348 million.
Most of the alignment in the Central Valley will be at-grade with some trench and aerial structure (viaduct) sections. The Central Valley section will be used as a test track for the system before beginning revenue operations.
Future contracts include a Rail Infrastructure contract (RI 1) which will be awarded to install track and operating systems and a Rolling Stock contract to provide trainsets with two initial prototype vehicles to begin testing in 2021 on the test track in the Central Valley and start revenue operations in the Silicon Valley to Central Valley segment in 2025.
While the Central Valley section does not include much in the way of underground construction, that is likely to change significantly when the Authority embarks on its northern and southern extensions.
To the north, the alignment from San Jose to Merced/Madera – dubbed “Silicon Valley to Central Valley” — traverses the Pacheco Pass in the Diablo Mountains of the California Coast Range. The 24-mile stretch through Pacheco Pass will include up to 12 miles of tunnels, according to WSP/Parsons Brinckerhoff’s Steve Klein, the Tunneling Manager for the program.
Environmental and engineering work is currently under way, including geotechnical studies and the vetting of alternatives, and current plans include five tunneled sections ranging in length from 3,000 ft to 5 miles long. Four of the five tunnel sections range from 2 to 5 miles long, and these tunnels may be suitable for TBM tunneling methods. Twin tunnels in a single track configuration would be about 28 ft in diameter (ID). In the shorter tunnel section, the sequential excavation method (SEM) may be a viable approach, although in the design-build contracting method envisioned for these construction contracts, the contractor will be able to determine the preferred tunneling method.
Depth of cover in the Pacheco Pass tunnels ranges from 200 to 800 ft and challenging geologic methods are anticipated including Franciscan Formation greywacke and mélange and interbedded sedimentary rocks from the Great Valley Sequence. Both of these formations have been intensely fractured, deformed, and sheared due to past tectonic activity
Because of the amount of tunneling and the impact on the overall project schedule, the Pacheco Pass section will be the first construction contract awarded along the Silicon Valley to Central Valley route. Plans are to issue a RFQ for this section by the end of the year and proceed with a design-build procurement next year. Follow on contracts will be awarded connecting the western end of Pacheco Pass to San Jose and Madera/Merced to the eastern end of Pacheco Pass. The combined cost of these three sections is on the order of $6.5 to $8 billion.
There will be several other tunnel sections on the route from Bakersfield to Burbank. In this stretch, the alignment traverses the Tehachapi Mountains and then the San Gabriel Mountains.
In the Tehachapi’s, plans call for nine tunneled sections, ranging in length from 1,500 ft to roughly 2 miles. Four of the tunnels are a half-mile long or less and may be most economically constructed using SEM, while the longer tunnels may be constructed using TBMs. Again, design-build contracts will likely be issued, so the contractor will have the final decision on construction methods. Depth of cover in this area ranges from 150 to 500 ft and geologic conditions consist mainly of variably weathered granitic rocks.
The San Gabriel Mountains section are where some of the most significant tunnels are located. There are still three alternatives being considered, which would include anywhere from two to seven tunnels. One alternative being considered includes a 20-mile tunnel. Depth of cover in this area ranges from several hundred feet to over 2,000 ft. A complex arrangement of sedimentary, granitic, and metamorphic rocks is anticipated in this area, including soft ground conditions, old alluvium in some areas. Most of these tunnels will be below the groundwater table, adding additional challenges.
The Bakersfield to Burbank section is scheduled to open by 2029, completing Phase 1 of the project. The 2016 Business Plan adopted for the HSR program has established a program estimate for Phase 1, from San Francisco to Los Angeles of $64.2 billion.
Jim Rush is editor and publisher of TBM: Tunnel Business Magazine.
SIDEBAR – Building Big in California: The ‘Water Fix’
The California High-Speed Rail network is not the only tunneling megaproject on horizon. When you’re talking about big tunneling projects, it doesn’t getting much bigger than the “California Water Fix” — the project that would take water from the Sacramento-San Joaquin Delta region and deliver them via massive tunnels to existing pumps near Tracy, California, that feed the California Aqueduct.
Key components of the program include a series of water conveyance tunnels that will allow for transport of up to 9,000 cfs of water directly from the Sacramento River to the major export pumping plants in the south end of the Delta. The components of this program will replace the current water diversion activities that rely on a series of improved channels and canals to move the water southward in the Delta.
The program consists of three river intake structures, approximately 10 miles of 29-ft and 40-ft ID tunnels, and approximately 60 miles of 40-ft ID main conveyance tunnels, and a 9,000 cfs pumping facility located at the terminus of the main tunnels. The main conveyance tunnels will be configured in a parallel twin bore arrangement, with tunnel invert depth of averaging approximately 150 ft below ground surface. In addition to launching and receiving shafts, a series of ventilation/access shafts will be constructed along each tunnel reach.
Current conceptual engineering efforts have been completed to support the environmental impact documents that are being circulated for public comment as part of the EIR/EIS process. The EIR/EIS is expected to be completed in fall 2016, and tunnel design is anticipated to commence in early 2018 with the first tunnel contracts being advertised for construction bids in mid-2020. Subsequent tunnel construction packages will be advertised on approximate 6-month intervals following the first contract award. Approximately five to six tunnel construction contracts will be awarded under this program. It is currently anticipated the facilities will be operational by 2033.
However, as big as the tunnel project is — $15.5 billion according to a Sept. 6, 2016, report in The Sacramento Bee — it is just as controversial. Environmentalists are concerned about the impacts on the natural waterways, including the Sa Francisco Bay which receives Delta waters. Additionally, there is a concern about whether users of the water in Southern California and the Central Valley (the agricultural center) will have increased access to water from the Delta.
Proponents say that the project would actually protect endangered fish species in the Delta by using more environmentally intakes, and will help increase the reliability and the security of the California Aqueduct, which is a vital piece of infrastructure for millions of Californians.TBM Online - 2017