|For T&B's tank installation project, an unobstructed opening of more than 55 feet was made pssible by utilizing Efficiency's Parallel Beam cross-trench support design.|
St. Francis Hospital in Indianapolis is in the midst of a $265-million expansion. When completed by mid-2010, the hospital campus will include a new emergency room, six-story inpatient tower, surgical suites, and additional space for support services.
As part of this huge expansion, Tonn and Blank (T&B) Construction Co., headquartered in Michigan City, IN (the construction subsidiary of the Sisters of St. Francis Health Services Inc.), installed a 30,000-gallon fiberglass fuel tank measuring 47 feet long and 12 feet in diameter. The tank will be used to fuel the hospital's backup generators.
On a busy hospital campus such as St. Francis, a project such as this was not going to be easy or routine. The excavation site was located about six feet from the hospital, and had very limited access and many surrounding obstacles to contend with, including a loading bay dock directly along one side that had to stay open throughout the excavation and installation process, and newly installed electrical banks just a few feet on the other side of the excavation site. Excavators and other equipment could only access the site from two sides.
Shoring the excavation to T&B's strict safety standards was going to be a huge challenge.
Providing A Solution
Tonn and Blank Foreman Stan Burnside contacted Jim Wright, branch manager at United Rentals Trench Safety in Indianapolis, to discuss shoring. "After looking at the specs of the project, I could see that our options were very limited," says Wright. "I contacted Scott Moreland, United Rental Trench Safety's product install and shoring specialist, to discuss all of our options."
"Vibration restrictions at the hospital eliminated the option of using vibratory hammer-installed sheeting and bracing," says Wright. "Also, installing a beam and plate or lagging system was off the table due to the two-week schedule given to complete the project. When it was all said and done, a Slide Rail Shoring System really was the best option for the tank installation; it was the most cost-effective system for the job."
After designing a Slide Rail Shoring plan, Wright and Moreland called Efficiency Production in Mason, MI — a manufacturer and engineering specialist of Slide Rail Systems — for proposal drawings for a three-bay, four-sided Multi-Bay Slide Rail System that would allow T&B to completely shore an unobstructed pit 56 feet long and 16 feet wide on the ends to a depth of 16 feet.
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 feet by 50 feet with Efficiency's ClearSpan System; or in a linear Multi-Bay configuration to install length of pipe over 40 feet.
For T&B's tank installation project, an unobstructed opening of more than 55 feet was made possible utilizing Efficiency's Parallel Beam cross-trench support design incorporating external ClearSpan waler I-beams.
"When Jim (Wright) first suggested Slide Rail, I was a bit skeptical because I wasn't at all familiar with it, and it didn't sound anything like other shoring systems I've used," says Burnside. "But, Jim did a great job explaining to me what it is, its advantages and how it works."
Slide Rail Overcomes Difficult Ground Conditions
Tonn and Blank has an exceptional safety record for all of their construction projects, and Slide Rail was a perfect fit for their strict requirements. 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. The panels and posts are then pushed 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 and safe for workers to be in the excavation throughout the entire installation or removal process.
T&B began the excavation by first cutting a pilot hole on the end nearest to the hospital about 6 feet deep, and laying in an 8-foot-tall, 20-foot-wide panel. Eighteen-foot-long Slide Rail corner posts were then set on both ends of the panel by sliding the posts outside slotted rail down a "T-track" welded on the ends of the panels. Two more 8-foot panels were installed perpendicular to the first panel, this time by sliding the panels' T-tracks down the corner posts' other set of outside slotted rails — 90 degrees to the first.
The excavation's ground conditions were unique and challenging, as along one side electrical banks had been recently installed and the soil was almost entirely heavily-saturated fill sand. Water almost immediately began flowing into the pilot hole and would need to be controlled by pumps while installing the Slide Rail components. Installing the system was also challenging because the side with sand was very unstable, but directly across the pit was hard-packed clay (next to the loading bay area).
After the three panels were set in a 'U' shape, footprinting the first 'bay,' T&B brought in the first Parallel Beam-Linear Post Assembly and set them on the ends of the open panels. This cross-trench support is unique to Efficiency's system, and is designed with special parallel beams that pin-in-place standard trench shield spreader pipes. The parallel beams have rollers that allow them to be removed, creating a completely unobstructed, shored excavation.
To reach 16 feet deep, the panels and posts were pushed incrementally until a depth of 8 feet was accomplished, then more 8-foot-tall panels were installed into the posts' inside open-face rails, which then were pushed incrementally until the entire first bay was at grade. The second and third bays were installed in a similar manner as the first. After the entire system was at grade, leveled and laid with stone backfill, T&B poured-in-place the tank's concrete foundation.
To assist T&B with the initial Slide Rail installation, Efficiency Production sent their Slide Rail Systems Manager Greg Ross to the site. "It's always interesting to see the reaction of contractors the first time they use Slide Rail," says Ross. "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 as they are 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."
After the ClearSpan waler beams were secured in the integrated brackets that slide down the outside face of the linear posts, the three parallel beam-spreader assemblies were removed for the tank set. The result was an unobstructed pit that was 56 feet long and was able to accommodate the 47-foot-long tank. The tank was set with a crane and backfilled with stone, while the Slide Rail components were pulled incrementally from the ground as the backfill progressed.