Contractor Bores, Pours in Excavation Using Slide Rail System

Sat February 27, 2010
James McRay

South Bend, Ind., like so many other big communities, is in the midst of storm-sewer separation upgrades. For many cities, that can mean miles of new pipe or upgrading utilities. And with these separation projects occurring inside the city limits in most cases, it’s usually very congested around excavation sites and frequently not easily accessible.

When these pits need to be very deep, safety of workers and construction personnel becomes of utmost importance. A safe, reliable shoring system is a critical factor in bidding the work, but tried-and-true trench shields or sloping are almost immediately ruled out as a viable option.

Traditionally, deep excavations usually meant driving tight-sheeting; a cumbersome, expensive, long, and loud operation. In the past couple of years, however, “slide rail” has become the new system of choice for deep digging contractors.

“It’s in a really tight spot in a narrow street in a residential area,” said Todd Bell, vice president of Woodruff & Sons Inc. Contractors, of the Twyckenham Drive excavation site. Woodruff was the low bidder on a portion of the sewer separation project installing 72 in. (183 cm) diameter RCP storm sewer and outfall into the St. Joseph River. The Michigan City, Ind., contractor also is pouring-in-place a 12 by 12 ft. (3.6 by 3.6 m) drop-assembly structure, while boring in the pipe from the same excavation pit.

“On one side of the pit, the system is only 3 or 4 feet from a structure,” Bell added.

With an obviously challenging excavation ahead of them, Bell contacted Efficiency Production Inc. — a manufacturer of Slide Rail Systems and trench shoring equipment.

“This is the second time we’ve used Efficiency’s slide rail in two years. Last year we used it on an excavation project in Michigan City,” added Bell. “We really like [their system].”

Efficiency’s Slide Rail Engineers and CAD technicians quickly drew up a custom designed system that would work for Woodruff’s heavily congested site conditions, and reach a final grade of 35 ft. (10.7 m) deep.

“Actually, we’ve designed and installed a number of Slide Rail Systems for contractors that go 35 feet deep or more,” said Greg Ross, Efficiency’s manager of slide rail systems, who was on site for the initial installation. “It’s just one of many shoring challenges we’ve overcome with our slide rail.”

“It’s really cost effective, especially compared to sheeting,” added Bell. “On our last project, I’d say we saved about 10 to 20 percent by using slide rail instead of sheeting; and we can keep our own guys working, rather than hiring a sheet piling company or driving sheet piling ourselves.”

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. (15.2 by 15.2 m) with Efficiency’s ClearSpan System; or in a linear Multi-Bay configuration to install length of pipe more than 40 ft. (12 m).

Woodruff is utilizing a two-bay, 4-Sided Multi-Bay Configuration, which provides a larger unobstructed area for installing tanks, vaults, and other structures. For Woodruff’s installation project, an unobstructed opening of more than 28 ft. (8.5 m) was made possible utilizing Efficiency’s parallel beam cross-trench support design incorporating external ClearSpan waler I-beams.

The biggest challenge for Woodruff, however, wasn’t the inside dimension of the pit, but rather the depth. Slide Rail is installed simultaneously as the trench or pit is excavated by sliding the panels into integrated rails on the posts. Efficiency offers a triple-rail post that incorporates an outside slotted rail and two inside “open-faced” rails. The open face design helps eliminate the system binding as it is dug and pushed into place because the inside panels have a little “slack.”

In addition Woodruff also utilized Efficiency’s Shore-Trak sheeting guide frame, which integrates into the slide rail system, replacing an inside panel, and allows sheeting to be installed on one end much deeper into the excavation. This allowed Woodruff to use 24 ft. (7.3 m) lengths of KD-6 Sheeting, rather than more difficult-to-handle 36 ft. (11 m) tall sheets.

The sheeting was perfect for boring the 72 in. (183 cm) diameter pipe, which was handled by boring specialists L.J. Keefe, out of Mt. Prospect, Ill. Abonmarche Consultants were the engineering firm for the project.

The $4.2 million project began in November 2009 and is scheduled to be completed by November 2010.

Woodruff & Sons Inc. is a multi-faceted construction company with a history of work in sanitary sewer installation, water transmission, storm drainage improvement, as well as many other excavation related projects. With two locations in Florida and headquartered in Michigan City, Ind., it is a state licensed general contractor, underground utility and excavation contractor, and class V fire sprinkler contractor.

James McRay is the director of marketing and media for Efficiency Production Inc. He can be reached at 800/552-8800; jmcray@efficiencyproduction.com.