The second week of September, the US Drought Monitor reported 50 per cent of the US to be in drought conditions, specifically the D1 or moderate drought category. This concerned most of the states in the west, southwest and Midwest.

For much of the southwestern states, a region with a population of 50 million people that is quickly growing, drought is a familiar reality. The combination of shrinking water supplies and growing demand means various cities and municipalities are in the stages of planning and building tunnels to ensure water supply.

At Lake Mead in Las Vegas the Southern Nevada Water Authority (SNWA) has been working on a project to build a third intake since 2008. The project has included several tunnel contracts, with the addition of one more just this fall.

However, projections for the lake’s water levels indicate Intake 1 could be inoperable should the water levels drop another 40ft (12.1m), or below 1,065ft (325m) when water quality would be affected, according to SNWA. The US Bureau of Reclamation (BOR) reports the lake could drop another 30ft by 2015.

BOR also reports the lake could sink to 1,084ft (330.4m) by next fall – its lowest level since 2010 and 9ft (2.7m) from triggering a federal shortage declaration, reducing Nevada and Arizona’s available Colorado River water. SNWA is fast-tracking more tunnelling work, and issued a change order to the existing contract with Renda Pacific, which excavated 2,820ft (860m) worth of tunnels to eventually connect the forthcoming third intake, with Intake 2. New construction includes a 110ft (33.5m) vertical shaft from the bottom of the pump station at Intake 1 to the connector tunnels for Intakes 2 and 3. Vegas Tunnel Constructors, a joint venture of Impregilo and its subsidiary, S.A. Healy, is still tunnelling under Lake Mead for the construction of Intake 3, having realigned the starter tunnel after flood events slowed progress.


The San Francisco Public Utilities Commission (SFPUC) is spending USD 4.6bn to repair and replace components of the Hetch Hetchy Regional Water System. This includes the USD 313M Bay Tunnel of 5 miles (8km), for which a joint venture of Michels/Jay Dee/ Coluccio completed TBM excavation in January, six months ahead of schedule.

Meanwhile a Southland Contracting/ Tutor Perini joint venture has been excavating the 3.5-mile (5.6km) long New Irvington Tunnel parallel to the existing tunnel to transit water between the Sunol Valley and Fremont.

On October 8 the roadheader excavation crews made the project’s final breakthrough, and miners will prepare the new tunnel for installation of its steel pipe lining. SFPUC will take the existing tunnel out of service for maintenance and repair.

There is on-going and heated debate over the state’s Delta Tunnel project, the Bay Delta Conservation Plan (BDCP), which will convey water in tunnels approximately 150ft (45.7m) underground. This project could include up to 35-miles (56km) of tunnels, between 33ft and 35ft (10m and 1 0.6m) in diameter, beneath the Sacramento-San Joaquin Delta. The BDCP is currently developing its EIR/EIS and should enter the period of formal public comment late this year.


Flash flooding and an urban redevelopment program are two main drivers for the Waller Creek storm water bypass tunnel project in downtown Austin, Texas. The 5,600ft (1,707m) tunnel, approximately 22ft (6.7m) in diameter has been designed by a KBR/Espey joint venture, whose services included hydrology and hydraulic modelling and analysis. The project also includes, surface level inlet and outlet structures, and a water recirculation system to provide the necessary flood relief, and improve water quality during drought periods. Contractor S.J. Louis has completed excavation of the tunnel and is working on the concrete lining. Zachry Construction Corporation is building the outlet structure and Oscar Renda secured the contract for the inlet in November 2011. Waller Creek is scheduled to finish in 2014. The City of Austin’s water department has been building a new water treatment plant, which involves a number of tunnels.


The Charleston Water System (CWS) in South Carolina is replacing its aging sewer tunnels through a series of phases. Black & Veatch has been working on the design for the fifth phase, the West Ashley Sewer Tunnel and influent pump station, which will replace an existing section of tunnel.

CWS awarded a contract worth USD 50.8M for construction of the 1.6-mile tunnel to a JV of Southland and Oscar Renda. The excavation will be roughly 6 to 7ft (1.83 to 2.13m) with a final diameter of 54in (1.37m). Phase six, the West Ashley Tunnel Extension, is in preliminary planning, and has an estimated cost of USD 47M. Charleston is also working on a 4,000ft (1,220m) long drainage tunnel for stormwater, 80ft (24.4m) below Market Street. The Market Street Drainage Improvements Division II: Tunnels and Shafts contract includes the 10ft (3.05m) diameter tunnel, a 25ft (7.62m) diameter access shaft and three 54in (1.37m) drop shafts. The project design was done by Davis & Floyd and URS Corporation, the contractor is a joint venture between Triad Engineering and Midwest Mole, Black & Veatch is the construction manager.

MiaMi freeze

While not a water conveyance tunnel, it’s nearly impossible to discuss tunnelling in the south and not mention the 12.8M excavated diameter Port of Miami Tunnel (POMT) below Biscayne Bay in Miami. Design-build contractor Bouygues Civil Works Florida, as part of the MAT concessionaire, completed its westbound and final tunnel drive of 4,152ft (1,265.5m) on May 6. Excavation of the 4,186ft (1,276m) eastbound tunnel started in November 2011 with a breakthrough on July 31, 2012. In total the TBM installed 1,496 rings to line the highway tunnels. Bouygues is using a compact Brokk 400 to excavate the five cross passages, spaced roughly 500 to 700ft (152m to 213m) apart. The first, fourth and fifth cross passages have been pretreated with cutter soiling mixing panels. The two below the water required ground freezing, for which Nicholson construction installed a total of 44 freezing pipes for the brine, for approximately 40 days.

Cross passage excavation work started in late 2012. The Brokk 400 is being used with multiple attachments including an Atlas Copco hydraulic breaker, a Drum Cutter, a bucket attachment and a beam manipulator to install ribs in the cross passages. Substantial completion of the POMT project is expected in May 2014.