GM Mechanical, Inc., headquartered in Covington, Ohio, recently installed a 20,000 gal. (75,708 L) rainwater storage tank at Miami East High School in Casstown, Ohio. The 10 ft. (3 m) diameter, 38 ft. (11.6 m) long tank was installed about 15 ft. (4.6 m) deep. No big deal, right? Well, there was one tiny, little, impediment: the contractor installed the tank less than 5 ft. (1.5 m) from three existing structures, including a wall of the High School.
“Normally we sub-contract for site work like that, but there were problems with the original design for shoring,” said Jack Liddy, GM Mechanical’s project superintendent. “So we ended up installing the tank ourselves.”
Liddy contacted Efficiency Production Inc. — a leading manufacturer of trench shielding and shoring equipment — for assistance designing a shoring system that would fit into the very tight excavation area and still meet safety regulations.
After a careful examination of the blueprints, Efficiency sent Liddy proposal CAD drawings that detailed how a slide rail shoring system could and would work in the tank’s tight spot.
Efficiency’s universal slide rail is a component shoring system comprised of steel panels (similar to trench shield sidewalls) and vertical steel posts. The system can be used in a variety of configurations. Efficiency’s universal slide rail can be configured into small four-sided pits; an obstruction-free ClearSpan configuration; or in a Multi-Bay configuration to install large tanks and structures, or lengths of pipe over 40 ft. (12.2 m)
Slide rail is installed by sliding the panels into integrated rails on the posts, and 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” shoring system.
“We definitely liked the slide rail system; it worked great,” Liddy said. “If we had used any other shoring that required digging outside the system, we could have potentially undermined the integrity of adjacent building.”
Slide Rail is considered “active shoring,” which means that personnel and equipment can be safely in the hole throughout the entire installation and removal process. The system is installed simultaneously as the trench or pit is excavated, while over-cutting outside the system is entirely unnecessary. The individual component pieces can be handled with a standard size excavator, which means that excavation contractors can usually install the shoring system themselves.
Because this was the first time GM Mechanical had used Efficiency’s slide rail system, Efficiency sent out Shoring Specialist Rod Austen to assist with the initial installation.
“It was a very difficult spot to be digging,” said Austen. “What complicated things even further was that the excavator had access to the site from only one side,” Austen explained.
“[Austen] was very good at giving exact directions without giving too much information,” said Liddy. “And even after he left, he stayed available for any questions we had.”
GM Mechanical used a Cat 330 excavator with help from a front loader to dig the hole and install the slide rail system. They utilized a two bay, four-sided Multi-Bay configuration, which provides a larger unobstructed area for installing the tank.
“The original design for the slide rail was two equal size bays,” explained Liddy. “But because we only had access on one end, Rod changed up the equipment so we had a shorter end bay. This allowed our excavator to reach to the far side of the pit.”
GM Mechanical excavated and installed the slide rail shoring in two days. It took two days to install and hook-up the tank, then less than two days to remove the slide rail components.
Overall, Liddy was impressed with Efficiency’s slide rail system.
“This is not just for specialty work. I’d use it again anytime we need to put in a tank. It really helps reduce the amount of excavating necessary, and the amount of backfill that goes with it,” Liddy concluded.
GM Mechanical has been providing service in the Dayton and Columbus area since 1975. They are members of the Unified Group, a nationwide organization of commercial HVAC companies dedicated to the success of independent contractors and their customers. For more information, visit www.gmmec.com.
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