There are only a few options available to a contractor when laying 72 in. (183 cm) pipe in 40 ft. (12.2 m) lengths.
If possible, open cut is the preferred method, but what does a contractor do when he wants to use a trench box?
Forty-foot lengths of pipe do not easily fit into most trench shields; they don’t even fit easily into two trench shields end-to-end. Such an extreme challenge requires an extreme shoring solution.
Up for the Challenge
S. J. Lewis Construction Inc. of Waite Park, MN, was recently awarded a $22 million contract from the City of Albuquerque, NM, to install a new raw water transmission line in Albuquerque which will divert water from the Rio Grande to a new water treatment plant that is scheduled for completion in 2008.
S. J. Lewis is subcontracting from Bradbury Stamm Construction of Albuquerque the installation of 17,500 linear ft. (5,334 m) of 72 in. (183 cm) diameter spiral-steel pipe in 40 ft. (12 m) lengths. Each pipe is cement lined, tape wrapped and mortared. One stick of pipe weighs 32,000 lbs. (14,515 kg).
In several areas along the pipeline’s progress, access is severally limited, especially where it runs along the right-a-way of Paseo Del Norte Highway. In this stretch, the pipeline trench needs to be cut vertical, mere feet from the road’s shoulder and very near adjacent buildings in some spots.
With the option of sloping and sheet piling (due to potential vibration damage) eliminated, a trench shielding system becomes the desired option.
S.J. Lewis Seeks Help
“For big pipe lengths, we frequently have used a combination of shorter trench boxes, sometimes abutted with arch spreaders,” said Kenny Zajac, S. J. Lewis’ project superintendent. “For this project, however, it’s so much faster and easier to have a complete open-span shield in order to lay the 40 foot-long pipe completely horizontal, with no obstructions, spreaders, or arches in the way. Essentially, we don’t have to adjust the angle of the pipe when we are laying it, or walk it under arches.”
In order to obtain a trench box that would meet the requirements of the project, S.J. Lewis contacted United Rental’s Trench Safety Division. United Rentals in turn contacted Efficiency Production Inc. — a trench shielding and shoring manufacturer headquartered in Mason, MI, that custom-engineers and designs shoring systems.
Efficiency Production Inc.
For Efficiency Production’s Vice President of Engineering, Mike West, the solution was to “build for them one of the largest, longest steel trench boxes that we have ever designed and manufactured.”
The result was the timely design, engineering, and production of a 50 ft. (15. 2 m) long, 10 ft. (3 m) high steel trench shield with 12 in. (30.5 cm) thick sidewalls. To accommodate the 6 ft. (1.8 m) diameter pipe, the box incorporates a five-pipe independent spreader system with 10 ft. (3 m) long, 10 in. (25 cm) schedule-120 steel spreader pipe with reinforced side-wall collar oversleeves.
The depth of the trench ranges between 15 to 17 ft. (4.6 to 5.2 m) in very fast-moving sandy soil.
The project also includes five highway bores involving 96 in. (244 cm) casing, which S. J. Lewis subcontracted.
Trench Box Works
“With the fast-moving sandy ground, many times a trench box is the only way to get the trench down to grade near adjacent structures, and certainly it keeps all the workers safe,” said Kevin Collins of Boyle Engineering — the project’s design engineering firm.
S. J. Lewis is using a Cat 385 excavator to set the pipe and handle the trench shield. A Komatsu PC 600 is used on the backend of the box for backfill and compaction.
Primary Contractor Bradbury Stamm’s Safety Director, John Brown, also had high praise for S. J. Lewis’ work installing pipe.
“With those 40 foot joints of pipe, there are spots were they just could not do this without that 50 foot trench box. It’s keeping adjacent buildings and roads from being seriously compromised, and they’re moving less dirt which saves them time and money,” Brown said.
New Water Supply
The Drinking Water Supply Project is one of six work projects in the Albuquerque Bernalillo County Water Utility Authority’s San Juan-Chama Drinking Water Project.
The project is necessary because Albuquerque’s current water system relies entirely on pumping groundwater from an underground aquifer; which is being seriously depleted.
San Juan-Chama will provide 70 percent of the metropolitan area’s future water. The job started in October 2005, and is scheduled to be completed by December 2006; however, Zajac is confident the pipeline will be completed ahead of schedule.
For more information on San-Juan Chama, visit www.sjcdrinkingwater.org.
S. J. Lewis was founded by James Schueller in 1983. They currently employ more than 400 people and specialize in underground utility work, specifically large diameter pipe installations. They are members of the National Utility Contractors Association and the Minnesota Water-Well Association.
Efficiency Production Inc. provides a wide selection of standard and custom engineered trench shielding and shoring systems. Efficiency’s products are designed specifically for safe and cost effective installation of utility systems and infrastructure improvements. All products are P.E. certified and engineered to comply with OSHA excavation and trenching standards.
(James McRay is the Media and Marketing Manager of Efficiency Production Inc.)