Edmonton’s EPCOR Utilities installs electrical vaults
on “easy” street with Efficiency Slide Rail

Installing utilities 20 ft. deep in a densely urban area is a daunting task even for the most experienced underground contractor. EPCOR Utilities, Inc. of Edmonton, Alberta– one of Canada's top providers of energy and energy-related services and products–is installing 17 new electrical vaults as deep as 20 ft. for the first time.

Mountainview Systems provides guidance to first-time deep excavators
“They needed to start at the very beginning, including choosing the right shoring system,” says Craig Gilbert of Mountainview Systems Ltd., Canada’s leading supplier of trench shielding and shoring equipment. Gilbert worked with EPCOR’s project manager, Mark Mathon, to come up with a shoring plan that would work for the unique and challenging situation, yet still be affordable and relatively easy for the utility company to install.

Gilbert consulted with Mike West, Vice President of Engineering at Efficiency Production, Inc. – the country’s leading manufacturer of trench shielding and shoring equipment. With the assistance of Efficiency’s engineering department which provided detailed drawings and specifications, Mountainview proposed utilizing Efficiency Production's universal Slide Rail System.

“There were three things that sold EPCOR on Efficiency’s Slide Rail System; the first was that it was more economical than sheeting, plus much faster to install and remove,” says Gilbert. “(EPCOR) is on a tight schedule, wanting to get one vault installed a week, so that was pretty important. Plus it’s just a very easy system to use once you get the hang of it.”

“The (slide rail system) is working really well. A dream, really,” says Mathon. “The toughest of the excavations so far was a deep 20 ft. pit in a tight spot, and there was no problem putting in or taking out the shoring system.”

“Dig and Push” system reduces over-excavation
Efficiency’s Universal Slide Rail is a component shoring system comprised of steel panels (similar to trench shield sidewalls) and vertical steel posts. The versatile system can be used in a variety of configurations, such as small four-sided pits; large unobstructed working pits as big as 50 x 50 ft. with Efficiency’s ClearSpan™ System; or in a linear Multi-Bay configuration to install length of pipe over 40 ft.

EPCOR is utilizing slide rail in a two-bay, 4-Sided Multi-Bay Configuration with the patented waler system which provides a larger unobstructed area for installing tanks, vaults, and other structures.

Slide Rail is installed simultaneously as the trench or pit is excavated by sliding the panels into integrated rails on the posts–either double or triple rails depending on needed depth–then pushing the panels and posts incrementally down to grade as the pit is dug; a process commonly referred to as a “dig and push” system.

Slide Rail is unique in that it is installed and removed incrementally, which allows the trench to be properly shored throughout the entire installation or removal process, maximizing the stability of the surrounding ground, and allowing the trench to be open for a longer period of time. Plus, EPCOR is continuously reusing the same slide rail components for each installation, which is a huge cost savings.

Downtown Edmonton to benefit from back-up power supply
The new vaults are part of a bigger project to provide a back-up feed and redundancy power to Downtown Edmonton from the north. The $20 million sub-project involves 17 separate, deep excavations to install the electrical conduit and personnel accessible vaults over a 13 mile area of northern Edmonton. Each excavation poses it’s own unique challenges and has varying site conditions, including overhead power lines in the utility right-of-way. Installation depths range from approximately 12-20 ft. deep in very urban, congested spots.

Each vault is 28 ft. long, about 9.5 (3 m) wide, and about 10 ft. (2 m) high with 10 in. thick pre-cast concrete walls and cap. Together, the six piece vault weighs approximately 155,000 lbs. The vaults are manufactured by LaFarge Concrete of Edmonton, Alberta.

Unobstructed clearance for vault made easy with Efficiency Slide Rail
“The biggest problem was finding a system that would allow us to put in a big slab of concrete at the bottom of the excavation, so we couldn’t use a system that had (immovable) spreader bars,” says Janelle McKenzie, Electrical Engineer for EPCOR. “The Efficiency system with the external walers was exactly what we needed.”

Efficiency’s Slide Rail System provides an advantage over other manufacturer’s slide rail because their multi-bay slide rail configuration utilizes unique parallel beams that incorporate into the vertical linear posts and pin-in-place standard trench box spreaders as cross-members. The parallel beams have rollers, and when horizontal walers and sacrificial members are utilized, the entire parallel beam assembly can be easily removed resulting in an unobstructed clearance to the shored excavation.

Mountainview Systems supplied all the slide rail components and Efficiency Production sent their Senior Slide Rail Installer, Greg Ross, to assist with the initial installation. “Greg was great; a big help,” adds McKenzie “He came on site and immediately was able to trouble-shoot a small problem we had on our initial install.”

The slide rail system components included four, 24 ft. vertical corner posts and one set of 24 ft. linear posts; and 5 in. thick, 16 ft. long, 8 ft. and 4 ft. tall slide rail panels. The system was engineered to incorporate a 40 ft. long W24x162 I-beam held against the outside of the vertical posts in specially designed brackets that slide down the outside of the linear posts. Sacrificial beams were placed at the bottom of the linear posts below grade, to eliminate the potential of deflection when the cross-member assembly was removed. The resulting 33 ft. wide unobstructed working pit can easily accommodate the 26 ft. long concrete vault.

EPCOR is using a Kamatsu 300 excavator to install and remove the slide rail components. “The shoring goes in real well. We were wondering how it would go together as it’s a lot different than watching the video; but we discovered very quickly that it was not that hard,” McKenzie concludes. “We’re able to get it entirely installed within just two days, so we’re on schedule for one vault a week.”

The project began in mid-April and is expected to be completed by mid-September, 2007.
EPCOR Utilities Inc. builds, owns and operates power plants, electrical transmission and distribution networks, water and wastewater treatment facilities and infrastructure in Canada and the United States. EPCOR has been named one of Canada’s Top 100 employers for seven consecutive years, and is headquartered in Edmonton, Alberta.

Mountainview Systems Ltd. provides Alberta and British Columbia contractors, surveyors and municipalities with quality products and services designed to increase productivity and lower costs, while maintaining the highest level of accuracy.

Efficiency Production, Inc., “America’s Trench Box Builder™,” provides the widest selection of standard and custom trench shielding and shoring systems in the United States and Canada. Efficiency’s versatile products are designed specifically for safe and cost effective installation of utility systems and infrastructure improvements. All products are P.E. certified to meet regulatory standards.

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EPCOR Utilities, Inc. of Edmonton, Alberta– one of Canada's top providers of energy and energy-related services and products–is installing 17 new electrical vaults as deep as 20 ft. for the first time to service downtown Edmonton.

EPCOR is utilizing Efficiency Production Slide Rail System in a two-bay, 4-Sided Multi-Bay Configuration with the patented waler system which provides a larger unobstructed area for installing tanks, vaults, and other structures. The shoring equipment were rented from Mountainview Systems Ltd. Pictured in the excavation is EPCOR Electrical Engineer Janelle McKenzie.

Efficiency’s Slide Rail in a multi-bay configuration utilizes unique parallel beams that incorporate into the vertical posts and pin-in-place standard trench box spreaders as cross-members. The parallel beams have rollers, and when horizontal walers and sacrificial members are utilized, the entire cross-member apparatus can be easily removed resulting in an unobstructed clearance to the shored excavation.

Each vault is 28 ft. long, about 9.5 (3 m) wide, and about 10 ft. (2 m) high with 10 in. thick pre-cast concrete walls and cap. Together, the six piece vault weighs approximately 155,000 lbs. The vaults are manufactured by LaFarge Concrete of Edmonton, Alberta.