SBUs, Auger Boring Equipment Play Critical Role In Pipeline Expansion

November 2008 Vol. 63 No. 11

At 260 miles long, Arizona’s Phoenix Expansion Project is a giant in the making.

The natural gas pipeline snakes through challenging terrain and protected lands including two national forests. The most difficult thing about this project has been the terrain: going under rivers, 30-foot side cuts into mountains and very steep slopes,” said Eric Pickett, project engineer for Price Gregory Services, one of two main contractors working on the pipeline. The path of the line, selected to minimize environmental impact, has also required dozens of crossings utilizing both cut and cover and trenchless excavation.

Geological conditions range from soft soils to cobbles to hard rock, requiring auger boring, HDD and rock cutting heads called Robbins Small Boring Units. “The conditions are highly variable. The ground we are working in can change from cemented cobbles, to non cemented ground with little warning,” said Tom Vandyke, president of contractor T&D Services, Inc. Both contractors – T&D Services Inc. of Murrieta, CA, and Price Gregory Services Inc. of Houston – have successfully utilized Small Boring Units on a total of 24 crossings in both hard rock and mixed ground. “The Robbins SBU is one of the few machines we’ve found that will work regardless of the conditions,” continued Vandyke.

Project overview

The Phoenix Expansion Project is being constructed by Transwestern Pipeline Company to service a booming population expected to grow by 38 percent within the next 30 years. By the end of 2008, the pipeline will provide 500 million cubic feet per day of natural gas and will fuel several new power plants in the region, increasing power output from 80,000 GWh in 2008 to 120,000 GWh by 2024.

Gas will be pumped into the Phoenix area using a pre existing 2,400 mile long supply chain of pipelines extending from West Texas and Oklahoma to New Mexico, Arizona and the California border. Much of the gas will come from the Rocky Mountain Basin, as well as the San Juan Basin in northwestern New Mexico and southern Colorado.

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