You’d be forgiven for thinking the only tunnels in the south-west region of the United States are those illegally carved from Mexico under the border to Arizona or southern California. This area does not see many large tunnelling programs.

However, that status quo has been interrupted in the past few years as underground construction in Austin, Texas, and potential projects in Dallas are creating opportunities in the region.

Rudy Renda, principal with Southland Contracting, based out of Fort Worth, says, “It’s a unique market right now because typically there is not a lot of tunnel activity on a large scale down in the southwest.”

He explains further, “this hasn’t been a traditional tunnel market. It’s been sporadic over time.” He adds, “A lot of the tunnels that are done in mixed face conditions. They are a little bit more challenging and that’s what you have in Houston, the Dallas Fort Worth area and some of these other regions.”

But it’s not the case in central Texas where there is good, hard solid rock that lends itself to tunnelling, he points out. In particular, Austin is in the various stages of underground construction for a flood protection program, a new water treatment plant and a wastewater tunnel.

The city’s Waller Creek Tunnel is being built to protect the downtown from damaging and dangerous flash flooding and is expected to complete in 2014. This USD 146.5M project will build a mile-(1.6km)- long tunnel along Waller Creek with an inlet facility at a local park and an outlet in Lady Bird Lake.

Also expected to complete in 2014 is the city’s new Water Treatment Plant Four (WTP4), worth USD 508M. This project includes the 10.5km long Jollyville Transmission Main to carry treated water to a local reservoir. Packaged separately is the raw water system at Lake Travis, which includes two tunnels each of roughly 4,000ft (1,220m) in length.

In the Dallas-Forth Worth area a 150-mile (241km) pipeline, with diameters varying between 66in and 108in (1.7 to 2.7m) is being planned to increase water supply to the region. The Integrated Pipeline Project is a partnership of the Tarrant Regional Water District and the City of Dallas, which selected six engineering teams in late 2010 to begin designing the pipeline in sections.

This pipeline will run from Lake Palestine to Lake Benbrook, with connections to local reservoirs, and will include five pump stations. Tunnel construction is expected at several major crossings along the alignment, although depths for these proposed underground areas will be determined at a later date.

R.W. Beck, supported by AECOM, is the program management consultant for the project. And the client is using a concept engineering team of CDM, Freese and Nichols to prepare 10 per cent preliminary engineering, which is expected to complete in late 2011. The project’s scheduling calls for construction to begin in mid 2013.

Looking to neighboring states like Arizona, Oklahoma and New Mexico, there isn’t much work. Renda says, “There is some tunnel activity in the Tucson [Arizona] area. There is some small-scale tunnel work, but not tunnel projects, more ancillary work to a cut and cover operation. It doesn’t compare to what’s happening in Austin or Dallas right now.”

In Nevada there is the Lake Mead Intake No. Three project, outside of Las Vegas. The Southern Nevada Water Authority (SNWA) is building a 4.5km tunnel under the lake. During three separate incidents in 2010, excavations on the starter tunnel hit a fault and flooded. In early 2011 the design-build contractor, Vegas Tunnel Constructors, a JV of Impreglio and S.A. Healy, worked with SNWA to realign the starter tunnel. The 23.5ft (7m) diameter TBM by Herrenknecht that will mine the intake tunnel has been waiting at the job site since 2009, and is expected to launch this year.

A JV of Renda Contracting and Southland Contracting is excavating the connection from the intake tunnel to the pump station. There is a 320ft (97.5m) tunnel to the VTC excavations and a 2,500ft (762m) tunnel to the pump station in the other direction. These are both being excavated by drill and blast.


The old and new starter tunnels at Lake Mead Intake No. Three