A 60-inch-diameter, welded-steel pipe typically is not the type of utility buried 19 feet under the road median at the end of your driveway. It's the creation of the Point of the Mountain Aqueduct (POMA), a job that involves installation of 68,500 linear feet of a new drinking water pipeline that will run approximately 12 miles through Salt Lake City's heavily residential suburbs.
Installing the pipeline without having to close down access to entire neighborhoods has been made possible with the help of a custom-engineered shoring system: a linear-bay slide rail system from Efficiency Production Inc., Mason, Mich.
The component system comprises steel panels and posts. It is installed simultaneously as the trench or pit is excavated by pushing the posts and panels down to grade as the pit is dug; this process commonly is referred to as a “dig and push” system. In the linear or “bay” configuration used for this project, 11x1-foot parallel beams slide into the inside of linear posts and pin-in-place 6-feet-wide standard trench shield spreader pipes as cross members. With external walers attached to the linear posts with large C clamps, plus sacrificial timber at the bottom of the trench, the parallel beams can be removed to lay the 44-foot oversized sticks of pipe.
W.W. Clyde and Co., Springville, Utah—general contractor on the $64 million project—examined all types of shoring systems before opting for the slide rail system. “Efficiency's system is very well built—overbuilt, really—and everyone is always very safe laying pipe,” said Allan Schieb, construction manager for the POMA project.
As Clyde's pipe-laying crews progress through the suburbs, they are encountering many cross utilities, which slow their progress. Clyde is addressing the shoring needs around existing utilities with Efficiency's Shore-Trak system, which includes steel panel guide frames integrating into the slide rail system. Two-feet-wide steel panels slide through the guide frame and pin-in-place around the existing utilities. The contractor rented the Shore-Trak system from United Rentals-Trench Safety, Salt Lake City.
Clyde currently has six crews using about 250 feet of shoring equipment to install pipe simultaneously in different locations along existing easements through residential neighborhoods in Sandy and Draper, Utah. Each crew has two large 365/375 Caterpillar trackhoe excavators, and a medium Caterpillar 330 trackhoe. To dig inside the shoring, operators use smaller 1½- and 2¾-yard buckets on the machines.
Construction of POMA began in March 2005; when complete in 2007, it will deliver water to approximately 500,000 residents in the Salt Lake Valley. The pipeline will connect two water treatment plants and establish a critical link between the valley's major water distribution systems.
POMA is one of the Metropolitan Water District of Salt Lake and Sandy's most significant undertakings in 50 years. “The Point of the Mountain Aqueduct will assure that we meet all of the water needs for the Salt Lake Valley communities,” said Robyn Clayton, spokesperson for the Metro Water District. “We have seen tremendous growth in the area, and we are trying to be proactive to make sure water needs are met not only for the present, but for the future as well.”
— James McRay is media and marketing manager for Efficiency Production Inc.