St. Francis Hospital in Indianapolis, Ind., is in the midst of a $265 million expansion. When completed by mid-year 2010, the Indianapolis hospital campus will have 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 Company headquartered in Michigan City, Ind., (The construction subsidiary of the Sisters of St. Francis Health Services Inc.) is installing a 30,000-gal. (113,562 L) fiberglass fuel tank measuring 47 ft. (14.3 m) long, and 12 ft. (3.7 m) 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 6 ft. (1.8 m) 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 excavating and installation process, and newly installed electrical banks just a few feet away, 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.
United Rentals Trench Safety Provides Solution
Tonn and Blank Foreman Stan Burnside contacted Jim Wright, branch manager of 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,” said 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,” continued 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, Mich. — a leading manufacturer and engineering specialist of slide rail systems — for proposal drawings for a three bay, 4-sided Multi-Bay slide rail system that would allow T&B to completely shore an unobstructed pit 56 ft. (17 m) long, 16 ft. (4.9 m) wide on the ends, down to a depth of 16 ft.
Parallel Beam Cross-Trench Design Fits in 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 versatile 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 over 40 ft. (12 m). For T&B’s tank installation project, an unobstructed opening of more than 55 ft. (16.8 m) 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,” said Burnside. “But, Jim did a great job explaining to me what it is, its advantages, and how it works.”
Safe Choice for Strict Requirements
T&B has an exceptional safety record for all 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 — 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 and safe for workers to be in the excavation throughout the entire installation or removal process.
Overcoming Difficult Ground Conditions
T&B began the excavation by first cutting a pilot hole on the end nearest to the hospital about 6 ft. deep, and laying in an 8-ft. (2.4 m) tall, 20-ft. (6.1 m) wide panel. Eighteen-ft. (5.5 m) 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 to the ends of the panels. Two more 8-ft. 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 which are 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 also was challenging because the side with sand was very unstable, but directly across the pit was hard-packed clay (next to the loading bay area). Fortunately, Efficiency’s slide rail is designed to work in both types of soil conditions, even when both are present on the same excavation project.
After the three panels were set in a “U” shape, foot-printing 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 which allow them to be removed, creating a completely unobstructed, shored excavation.
To reach 16 ft. deep, the panels and posts are pushed incrementally until a depth of 8 ft. is accomplished. Then, more 8-ft. tall panels are installed into the posts’ inside open-face rails, which are pushed incrementally until the entire first bay is at grade. The second and third bays are installed in a similar manner as the first.
After the entire system was at grade, level, and stone backfill laid; T&B poured-in-place the tank’s concrete foundation.
(James McRay is the director of marketing and media, Efficiency Production Inc. For more information, call 800/552-8800 or e-mail [email protected].)
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