The Austin (Texas) Water Utility recently awarded an important underground utility project to Layne Heavy Civil Inc., headquartered in Fairburn, Ga. Layne is in the process of installing 17,500 linear ft of 54-in. diameter cement coated pipe, mostly in joints 50 ft long.
The Martin Hill Water Transmission Main will provide water for the Northwest and North quadrants of the City of Austin. It is part of the city’s Strategic Water Facility Plan and, when completed, will connect the Martin Hill Reservoir to existing city water pipelines. The Martin Hill Reservoir is the largest steel potable water tank in the United States and can hold more than 35 million gallons of fresh water.
The majority of the main is being installed via open-cut excavation. However, many stretches of pipe installation are being installed 15 to 20 ft deep and require a series of long trench boxes to accommodate the 50-ft lengths of pipe while keeping the crews safe in the trench.
“Layne originally requested 8-ft tall trench boxes with arches on the end,” explains Mike Ciotta, Regional Sales Manager at Efficiency Shoring and Supply’s Dallas/Ft. Worth Branch Office. Efficiency Shoring and Supply rented and supported all the trench safety equipment and shoring for the project.
Continues Ciotta, “However, it was so difficult maneuvering the 50-ft joints of pipe, Layne decided they needed 10-ft tall boxes. We didn’t have any long, 10-ft-tall trench shields left in our yard, but because we’re [manufacturer] Efficiency Production’s factory-direct branch, we were able to get a 10-ft by 32-ft box built and shipped here to Austin, so there was no downtime on the project.”
There were also instances where Layne needed to tunnel the water main — under a busy intersection for 960 linear ft of the 72-in. casing pipe and under railroad tracks for another 379 linear ft of 72-in. line. These instances require up to 45-ft deep tunnel shafts to be excavated and shored; but because of the versatility of the Efficiency trench shields, Layne was able to reutilize the trench boxes to shore the tunneling pits.
In total, more than 25 large trench shields were utilized by Layne, including Efficiency trench boxes sized 10 ft by 32 ft, 10 ft by 24 ft, 10 ft by 16 ft, 8 ft by 16 ft, plus two spreader arches. Layne also had road plate and a 12-yd Stone Mizer bedding box filled with clean loose rock for backfill. Layne’s heavy equipment for the project includes:
- John Deere 870G excavator with a 4-yd bucket for the main trench digging
- John Deere 470G excavator for moving the back shield and backfilling the trench
- John Deere 844 loader to unload the 22,000-lb steel pipe
- John Deere 644 loader hauling bedding stone to the stone mizer
- Trencor rock trencher for pre trenching in the limestone rock areas
Installing the mammoth pipe in the trench boxes is a bit of a process. Two trench shields are used with high-clearance arch spreaders on abutted ends. That provides enough vertical clearance for the expert excavator operator and crew to thread the pipe into the boxes under the arches. The boxes are then shifted to protect the personnel in the trench who are filet welding the joints from inside the pipe.
“The boxes are working really well,” says Layne’s Fred Lester. “Right now, we’re on Section C of the three-part [Martin Hill Water Transmission Main] project. We’ve already got Efficiency working on the shoring plan for Sections A and B, where the ground will be more rock than soil.”
The project is contracted to be completed in early 2015; however, Lester says that they hope to be finished by later this fall 2014.
James McRay is the Director of Marketing and Media for Efficiency Production Inc. (www.efficiencyshoring.com). He can be reached at email@example.com. For more information on Layne Heavy Civil, visit www.layne.com.