Hubbard Construction Company recently completed the installation of two 24 in. (61 cm) butterfly valves off a 36 in. (91 cm) methane gas trunk line. The trunk line was located about 25 ft. (7.6 m) below grade. The water table was approximately 10 ft. (3 m).
The two butterfly valve taps were just a small part of the Orange County (Florida) Landfill Cell 10 Expansion project. But the installation challenges were anything but small, according to the contractor.
“We were fighting water the whole time,” said Hubbard Project Engineer Javier Saldana. “We used as many as eight submersible pumps at each of the two locations, and it still took a week and a half to get each location dry enough to tap in the valves.”
However, getting rid of the water was only the first challenge. Keeping the excavation open and safe for installation personnel to work in the trench was the second, bigger challenge.
Tight-Sheeting Not An Option
Tight sheeting is typically the technique of choice for shoring when excessive water is present. But sheeting was not an option in this instance. Instead, the contractor turned to the Slide Rail Shoring System.
“Using sheeting would have cost $350,000 or more,” said Saldana. “Plus, we’d need special permits and special engineering, and vibrating in sheets could loosen the new berm and damage the new liner causing even more damage.”
Instead, Saldana and Project Manager Robert Tanksley contacted Efficiency Production — a manufacturer of Slide Rail Systems and other trench safety equipment — for information on its Slide Rail System.
“We watched their video, studied their installation manual; all the information they provided us,” explained Saldana. “And we got onsite assistance from Professional Shoring and Supply right here in Orlando.”
Dig and Push
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, such as small four-sided pits; large unobstructed working pits as big as 50 by 50 ft. (15 by 15 m) with Efficiency’s ClearSpan System; or in a linear Multi-Bay configuration to install length of pipe over 40 ft. (12 m).
Slide Rail is installed simultaneously as the trench or pit is excavated by sliding the panels into integrated rails on the posts — an outside slotted rail first, then an open-face rail on the inside — 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. Efficiency Production offers an open-face rail design on its Slide Rail posts.
Custom Sheeting Guide Frame Panel
Hubbard rented from Professional Shoring, a two-bay 4-sided Multi-Bay configured system which incorporated sheeting guide frame panels that integrate into the slide rail system by replacing an inside panel with the guide frame. The custom sheeting guide frame allows KD-750 sheeting to be installed deeper into the excavation. It can be placed tightly around or next to the existing pipe.
It was the first time the HCC crew had used Slide Rail, but it met all their expectations.
“We loved the system,” said Saldana. “When we first got to the site, we were apprehensive never having used it before, but Efficiency’s Greg [Ross, Slide Rail manager] and Rod [Austin, Slide Rail specialist] did a great job of teaching us how to use the system properly. We were very impressed at how quickly and easily the system went in, and came out of the ground.”
“It’s always interesting to see the reaction of contractors the first time they use Slide Rail,” Ross said. “The first day, they usually are intrigued on how and if it’s going to work; the second day, there is usually a bit of consternation as they have to overcome unexpected ground conditions trying to put the system in one piece at a time; but by the third day, they really get the hang of it, and they really start to figure out that this is a great system.”
Hubbard had the Slide Rail System on rent for two months, and its team got the first valve installed a week ahead of schedule, which allowed ample time to complete the work at the second bay. Hubbard used a Cat 450 excavator and Komatsu JJ4 front loader to excavate at each location. The pipe crew installing the valve and new 24 in. (61 cm) HDPE pipe were Alliance Contracting, located in St. Cloud, Fla.
Working with Saldana on Hubbard’s portion of the $23.6 million Orange County Landfill Cell 10 Expansion project were Project Superintendent Todd Andrepont, Pipe Foreman Paul Brannock, and Tanksley.
Founded in 1920, Hubbard is Florida’s largest heavy civil construction company with yearly revenues of more than $300 million. The scope of Hubbard’s work includes complex highway projects, site development, paving, utility and drainage systems, surveying, RAP and hot mix sales, and state of the art bridge building.
With offices in Orlando, Jacksonville, and Tampa, Professional Shoring and Supply is an official Efficiency Production Inc. trench shielding and shoring equipment distributor. All products are P.E. certified to meet OSHA standards.
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