Slide Rail Proves Best Choice for
Canadian Power Plant Construction

The Ontario, Canada, Power Authority (OPA) recently entered into an agreement for the construction of a new 1,005-megawatt natural gas-fired power plant. The plant, called the Greenfield Energy Centre, will be located in Courtright, St. Clair Township, near Sarnia, Ontario. The project will be owned by Greenfield Energy Centre, L.P., a partnership between Calpine Corp. and Mitsui & Co., Ltd. and will use modern, combined-cycle technology.

Overseeing the co-generation plant’s construction is Sandwell Engineering of Vancouver, British Columbia. The installation of the high-pressure water pipe for the turbine cooling system was subcontracted to Goodfellow Construction of Corunna, Ontario.

The high-pressure water pipe is part of a complicated closed-loop system that circulates the water that cools the gas-powered turbines.  The water is transmitted from a pump pit to branch pipes that are outside of the cooling tower’s main structure.  The water hits a “T-Pipe” where it is diverted north and south along a tapered main pipe that has a series of discharge leads at intervals along the pipe. The discharge leads transmit the water directly up to the top of the cooling tower where it heads to a series of turbines.

Tight Quarters require alternative to tight sheeting

This project was challenging because the main pressure pipeline outside the structure was installed 12 to 14 ft. deep, but only 1.5 ft. from the cooling tower’s concrete foundation!  This made shoring or shielding the pipeline trench extremely challenging, because the walls of the trench needed to be cut entirely vertical, and the stability of the adjacent soil maintained.  Therefore, some type of trench shielding system had to be found that would fit within the 1.5 ft. space.  Traditional tight sheeting was not an option because of the potential destabilization of the soil under the nearby structure foundation due to vibrating or piling sheeting into place.

Contractor seeks help from America’s leading trench shielding and shoring manufacturer

Needing a custom shoring solution, Goodfellow contacted Efficiency Production, Inc., the United States’ leading manufacturer of trench shielding and shoring.  “Someone had told me of the concept of Slide Rail and when I did an Internet search, I landed on Efficiency’s web site,” says Randy McKenney, Field Coordinator for Goodfellow Construction.

“After calling Efficiency, I talked at length with Greg Ross (Efficiency’s Slide Rail Installer and Sales Manager) and he sent me initial information, manuals, videos, and a proposal drawing; really everything I needed to bid on the project,” adds McKenney.  “Greg even came out to the job site to look at the conditions.  We were competing for the job against one other contractor who came in with no other shoring options other than open-cut, so I think the Slide Rail option helped us land the job,” he adds.

“Dig and Push” system ‘fits’ the bill

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 of infinite size with Efficiency’s ClearSpan™ System; or in a linear Multi-Bay configuration to install length of pipe as long as 40 ft.

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.

First time user says Slide Rail prevents two-month delay

The first step for Goodfellow was to install 120 ft. of 96 in. diameter cement-lined steel pipe starting from the pump pit to “outside” the cooling tower.  This section of pipe was installed before the tower’s foundation was begun, and Goodfellow elected to open cut and slope the trench.  That first 120 ft. ends at a T-vault which is just outside where the cement foundation of the building was to be laid by Hayman Construction Works, a cement company with whom Goodfellow was working as a joint venture.

As soon as Hayman began construction on the foundation, open-cutting was no longer an option for the north and south branch-pipeline trenches.  “They wanted to start that foundation on time, and if it were not for Slide Rail, the whole project would have been held up for at least two months while we installed the pipe branches,” says McKenney.

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, and always provides ‘active shoring,’ maximizing the stability of the surrounding ground.  This allowed Goodfellow to install Slide Rail 6 in. from the structure’s foundation!

McKenney adds that, “The Slide Rail System worked very well and was very consistent, which was critical as the pipe needed to go in exactly perpendicular to the outside of the tower structure.  Using Slide Rail for the first time there was a learning curve, but with Greg’s installation assistance, my crew picked it up fairly easily.”

      Goodfellow first installed the south branch pipeline 375 ft. from the center T-foundation. Each bell-spigot joint of pipe is 20 ft. long, and is welded inside with a cement diaper over the outside joint.  Eight ft. diameter pipe was installed near the T-Vault and tapered to 6 ft. diameter pipe at the end of the pipeline to maintain constant pressure.  Ten of the pipe sticks, including the T-vault, have prefabricated 3 ft. diameter chimneys which were installed at intervals on the pipeline for transmitting the water up to the top of the tower.

Once the south branch was completely installed, backfilled, and the Slide Rail components removed, Goodfellow began installing the north branch in the same manner.  The total pipeline outside the tower is 750 ft.

Goodfellow rented a seven-bay linear application Slide Rail System factory-direct from Efficiency Production.  The bays were 20 and 14 ft. long, and the linear posts 24 ft. tall.  They used 10 ft. spreader pipes on the 1 ft. wide x 7 ft. tall parallel beams for a total trench width of 12 ft.  The trench was excavated in Type-C, sandy-clay soils.

The new power plant is scheduled to go on-line in February 2008.  It is currently anticipated that the project will create up to 800 jobs during the construction period, and approximately 25-30 full-time permanent jobs during facility operations.  The Greenfield Energy Centre was selected for development through the Ontario Ministry of Energy's 2004 open and competitive RFP (request for proposal) process for new, clean energy.

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The high-pressure water pipe is part of a complicated closed-loop system that circulates the water that cools the gas-powered turbines.	The main pressure pipeline outside the structure was installed 12 to 14 ft. deep, but only 1.5 ft. from the cooling tower’s concrete foundation!
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, and always provides ‘active shoring,’ maximizing the stability of the surrounding ground. This allowed Goodfellow to install Slide Rail 6 in. from the structure’s foundation!