California is home to two deep pocket projects for the tunnelling industry, a new network for high-speed rail and a series of twin tunnels for water conveyance. Both projects have seen a number of hurdles on their way to execution.

There are also projects for wastewater and public transit, up and down the coast. While mega projects eek forward, hotly in contention there is other, voter-approved, work to be done underground.

BDCP
Bringing water from the San Francisco Bay, south to the Sacramento-San Joaquin Delta, the controversial Bay Delta Conservation Plan (BDCP) will require more than 30 miles (48.3km) of tunnelling.

The state, acting through The California Environmental Quality Act, has selected Alternative 4 as its preferred project out of the 15 options, many of which include tunnelling.

Alternative 4 includes twin-bore TBM-driven tunnels of up to 40ft id, 30-miles long (initially 35 miles), 150ft (45.7m) underground. There are two other, smaller tunnels: one single-bore with a 20ft (6.1m) id connecting two intakes expanding to 29ft (8.8m) id to connect with an intermediate forebay, approximately 47,400ft (14,450m) long.

Another 20ft id single-bore tunnel between a third intake and a second intermediate forebay, approximately 24,900ft long. Both of these tunnels will each have a launch, retrieval and vent shaft. Last December lead state and federal agencies have extended the public comment period for the Draft BDCP and the Draft EIR/EIS by 60 days, to this month.

CHSRA
The California High Speed Rail Authority (CHSRA) is responsible for creating the first high-speed rail system in the nation. It estimates by 2029, the system will run from San Francisco to the Los Angeles basin in under three hours at speeds capable of over 200 miles (322km) per hour. The system will eventually extend to Sacramento and San Diego, totaling 800 miles (1,290km). On April 4, the CHSRA issued an RFP to five firms for Construction Package 2-3, a designbuild contract for more than 60 miles including bridges, culverts, trenches and tunnels, utility relocations, aerial structures, grade separations, security and drainage. This is the project’s second significant construction package, and is worth USD 1.5bn to USD 2bn.

California Subway
Both San Francisco and Los Angeles, two of California’s largest cities by population, have subway tunnel projects underway. In San Francisco, TBMs are currently excavating the Central Subway extension project (page 25). And sometime next year TBM work will also start in Los Angeles (page 30). There is a plethora of construction work for public transportation in the Los Angeles metro region, thanks to a voter-approved tax increase in 2008. At least three of these projects require underground construction.

Seattle Light Rail
Tunnelling is expected to start this year in Seattle for the city’s next extension to its light rail system. A majority of the Northgate Link Extension comprises twin tunnels, 3.6 miles (5km) of the 4.2-mile (6.76km) line, starting at the University of Washington Station. Contractor JCM Northlink LLC, (a joint venture of Jay Dee Contractors, Frank Collucio Construction Company and Michaels Corporation) will use two TBMs for the drive, and will also dig two underground stations and excavate 23 cross-passages.

The Sound Transit Board approved the Northgate Link Extension tunnel construction contract on July 25 worth USD 440M, and it is the largest construction contract the client has ever awarded. JCM had also mined the light rail tunnels between downtown Seattle and Capitol Hill Station as part of Sound Transit’s University Link project.

The first TBM, a completely refurbished Hitachi Zosen EPBM, is scheduled to be launched from the northern Maple leaf Portal site this month. This is the TBM previously used by the JCM JV on the ULINK U230 Contract. A joint venture of CH2M HILL and Jacobs have a seven-year construction management contract with client Sound Transit worth USD 75.5M.

Bencor Corporation of America, a wholly-owned subsidiary of Layne Christensen Company, is building slurry walls for one of the line’s stations and should be finished by this July. Two separate contracts will finish each underground station. The contract for Roosevelt Station Finishes (Contract N150) is being procured using the GC/ CM project delivery method. Hoffman Construction Company is now under contract for Pre-construction services. Contract N140, for U District Station Finishes, is also being procured using the GC/CM delivery method. A Preconstruction services contract should be awarded for N140 in June this year.

Another contract will construct the remaining elevated mile of light rail. Contract N160 will be for construction of the elevated station at Northgate Mall and approximately one mile (1.6km) of elevated guideway. This contract is in the final design stage.

Jacobs Associates is responsible for tunnel design and design for support of excavation for the stations. Shannon & Wilson is involved on the project for geotechnical work, and Parsons Brinckerhoff is the lead designer for the aerial guideway and the aerial station at Northgate.

Water works
Like many cities in the US, Honolulu is dealing with aging sewer infrastructure and sewer overflows. To replace an outdated sewer and meet a consent decree, the City and County of Honolulu awarded some USD 175M in contracts for the Kaneohe-Kailua gravity sewer tunnel project to the joint venture group of Southland Contracting, Inc., and Mole Construction, and local management firm Bowers + Kubota, last fall.

The new 3-mile- (4.8km-) long wastewater tunnel with an inside diameter of 10ft (3m) is being constructed by TBM through the former caldera of an extinct volcano. Work also includes three shafts and installation of a 10ft (3m), 3in (76.2mm) fiberglass pipe with the annulus backfilled with low density cellular concrete.

Geology along the alignment is approximately 90 per cent basalt, and a 10 per cent soils. Bencor Corporation of America recently announced it has secured a contract for jet grouting on the Kaneohe-Kailua tunnel, as well as constructing two deep shafts with slurry walls. Wilson Okamoto Corporation, based in Honolulu, prepared the design the Kaneohe-Kailua project, with sub-consultant Jacobs Associates.