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. (5,334 m) of 54 in. (137 cm) diameter cement coated pipe, mostly in joints 50 ft. (15 m) 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. (4.6 to 6 m) deep and require a series of long trench boxes to accommodate the 50 ft. (15 m) lengths of pipe while keeping the crews safe in the trench.
"Layne originally requested eight foot tall trench boxes with arches on the end," said Mike Ciotta, regional sales manager of Efficiency Shoring & Supply’s Dallas/Ft. Worth branch office. Efficiency Shoring & Supply rented and supported all the trench safety equipment and shoring for the project.
"However, it was so difficult maneuvering the 50 foot joints of pipe, Layne decided they needed 10 foot tall boxes. We didn’t have any long 10 foot 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 by 32 foot box built and shipped here to Austin, so there was no down time on the project," Ciotta continued.
There also were instances where Layne needed to tunnel the water main: Under a busy intersection for 960 linear ft. (293 m) of the 72 in. (183 cm) casing pipe; and under railroad tracks for another 379 linear ft. (115.5 m) of 72 in. (183 cm) line. These instances required up to 45 ft. (13.7 m) 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 on rent to shore the tunneling pits.
In total, more than 25 large trench shields were utilized by Layne. Layne also had road plate and a 12 yd. (11 m) Stone Mizer bedding box filled with clean loose rock for backfill. Layne’s heavy equipment for the project includes:
• John Deere 870G with a 4 yd. (3.7 m) bucket for the main trench digging
• John Deere 470G for moving the back shield and backfilling the trench
• John Deere 844 loader to unload the 22,000 lb. (9,979 kg) steel pipe
• John Deer 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 hi-clearance arch spreaders on abutted ends. That provides enough vertical clearance for the 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," said 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," Lester added.
The project is contracted to be completed in early 2015, however, Lester said that they hope to be finished by later this fall, 2014.
Layne Heavy Civil delivers sustainable solutions to government agencies and industrial clients by performing design and build services of critical water and wastewater treatment facilities and pipeline installation.
For more information, visit www.layne.com.
For more information on Efficiency Shoring & Supply, call 800/220-8707 or visit www.efficiencyshoring.com.
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