The tunneling industry is thriving on the west coast. With public transportation in high demand, not to mention drinking water, there is work up and down the pacific coast. But it’s the region’s drastically varied terrain that makes many of these projects uniquely challenging.

To even contemplate the west coast’s market for tunneling, it’d be tough to avoid mentioning the Alaskan Way Viaduct replacement in Seattle. This 1.7 mile (2.7km) bored tunnel will have an excavated diameter of 58ft (17.7m) to accommodate its two-level design. In January, a joint venture of Dragados/Tutor Perini signed a USD 1.35bn design-build contract with the Washington State Department of Transportation (WSDOT). In April, WSDOT awarded Hatch Mott MacDonald a USD 11M contract for construction management. Following the project’s environmental review, expected this summer, the JV will begin final design and construction of the bored tunnel.

“Alaskan Way Viaduct is unique on a global platform, not just a North American platform,” says Randy Essex, executive vice president, Hatch Mott MacDonald. “Its 58ft (17.68m) diameter is 7ft (2.13m) larger than any TBM ever used before – that’s 30 per cent greater face area of a tunnel machine. It’s just a quantum leap in tunnelling technology and how we monitor what’s going on at the cutter head versus what’s going on in the immediate proximity of the tunneling machine.”

The project faces a more immediate challenge as local and state officials struggle to see eye-to-eye on the tunnel. The pro-tunnel governor of Washington and Seattle City Council have been pitted against the anti-tunnel mayor of Seattle, while two anti-tunnel groups have gathered enough signatures for two separate initiatives both dealing with the city’s right of way to be on an August ballot.

Seattle’s city attorney has sued one of the initiatives, saying both are not legal because they are being applied to administrative actions, not policy decisions. The city council is waiting to hear the court’s opinion on the first initiative before it takes any action on the second.

San Francisco
In San Francisco and the Bay area billions of dollars are being spent on infrastructure projects for transportation and water conveyance that are driving a strong demand for tunneling. One need not look past downtown San Francisco to see how vital transportation is to the Bay Area. The Transbay Joint Powers Authority is building the USD 4bn Transbay Transit Center, which it calls the ‘Grand Central Station of the west’. Located in downtown San Francisco, this terminal will connect 11 different transit systems, including BART, Caltrains, Greyhound, Muni, Amtrak and future high-speed rail. In addition to underground work needed for the terminal’s replacement, the project will extend underground rail operations.

Then there is the Central Subway that will require twin-bore tunnels, each 1.6 miles (2.6km) long, driven by two EPB TBMs. The San Francisco Municipal Transportation Agency released the contract, estimated to cost USD 225M, in March; bids were due on May 25.

Meanwhile, the San Francisco Public Utilities Commission (SFPUC) is undertaking its USD 4.6bn program to upgrade and repair the Hetch Hetchy Regional Water System. Totaling 86 construction projects, including three new tunnels, this work allows the commission to continue providing drinking water to its 2.5 million customers in the Bay Area in the event of a major earthquake. For example, a Southland/Tutor Perini JV is constructing the 3.5-mile New Irvington Tunnel to replace an existing tunnel that has reached the end of its life.

Los Angeles
There is also work in southern California for public transportation to enhance the Los Angeles Subway system. “LA County has a lot of money for improvements to the transit network in and around the county,” Essex says.

On the western side of the city, a project to expand the Purple Line identified a locally preferred alternative (LPA) in October 2010, to which the Federal Transit Administration has granted permission to begin preliminary engineering earlier this year. The 9-mile (14.48km) extension will include seven new stations and be built primarily underground using TBMs, and the Los Angeles County Metropolitan Transportation Authority (Metro) estimates it would cost USD 5.1bn if completed by 2022.

The Purple Line extension has become a point of contention for the Beverly Hills Unified School District (BHUSD), as the LPA requires tunneling beneath the district’s high school. The BHUSD had expressed its preference for an alignment that doesn’t tunnel under the school, and in May filed a petition with state courts demanding Metro release studies and technical documents for the district’s consultants to evaluate all proposed alignments.

Another transportation project in the pipeline, the Crenshaw Corridor, will extend 10 miles (16km) through Los Angeles, and provide a connection to LAX Airport. A Draft Environmental Impact Report has been completed for the light rail line, on which Hatch Mott MacDonald is providing design services. “Crenshaw is going to involve possibly one-third tunnel, maybe one-third at grade and then one-third at aerial construction. Those details are still being ironed out,” Essex says.

High-speed rail
While the republican governors of several states have passed up billions of dollars in federal money for high-speed rail, California has welcomed the idea with open arms. Voters approved a measure in 2008— presented by a bipartisan coalition—for USD 9.95bn in bonds to be issued to build a high-speed rail network for the state.

And once that is established, for Californians traveling between cities, the reduction in journey times alone will be drastic. “When you talk about the time savings, you’re really talking about quality of life,” Essex says.

“People who live in California are already paying high prices for quality of life. So they want to enhance that. To approve these bond issues—that are unprecedented in size for any state—the voters are basically saying ‘we want it, we’re willing to pay for it and in fact we’re willing to give up something else up to pay for it.’”

He makes an example of Los Angeles (a city that often conjures up imagery of endless traffic jams and smog) saying the public is willing to make these decisions because grid lock has reached a point where they know that building more highways is not a solution. Going underground is the only option.

Just last month California received another USD 300M for high-speed rail as one of 15 states to benefit from the USD 2bn chunk of federal funding Florida’s republican governor, Rick Scott, passed up on. This brings the state’s total federal and state funding to USD 6.33bn.

Some of that money has already been dedicated to engineering underground construction for the network. A joint venture lead by Parsons with Jacobs Associates is working on preliminary tunnel design for the Pacheco Pass in the northern part of the state. The California High Speed-Rail Authority (CHSRA) estimates five twin bore tunnels totaling some 63,800 linear feet (19.4km) will be needed through the mountain pass, ranging in length from 3,000ft to 26,000ft (0.91km to 7.9km). They will also be located in close proximity to several active earthquake faults. According to Jacobs Associates, geologic conditions vary from sandstone, siltstone, shale and conglomerate for the eastern tunnels to a chaotic mixture of sheared rocks in the Franciscan Complex melange for the western tunnels.

Looking to the southern end of the system, the CHSRA awarded two contracts to a joint venture of URS Corporation, Hatch Mott MacDonald and Arup in 2007 for engineering and environmental services.

The first contract, worth USD 120M, concerns the 193-mile (310km) segment running from Fresno to Palmdale. Under the second contract, worth USD 75M, the JV is working on the 61-mile (98km) segment of the rail line running from Los Angeles to Palmdale, California. “Between these two contracts we could be looking at 30 to 50 miles [48 to 80km] of twin bore high-speed rail tunnels,” Essex says.