Pro-Tec’s Slide Rail System played a critical role in the underground installation of a 30,000-gal. (113,560 L) tank to supply diesel fuel for emergency power generators used by the University of Michigan Hospital at Ann Arbor. On-the-job challenges included tight quarters, buried water lines, and noise and vibration sensitive constraints.
“First of all, we had to install the huge tank underground in a confined area, next to a paved road on one side, the property line close by on another, and adjacent to 30-inch diameter underground water pipe lines. And we were in a ’Quiet Zone.’ To accommodate the big tank, we needed to open a clear span excavation measuring 64 feet long, 17 feet wide and 24 feet deep,” said Doug Miller of Fransted Construction, Concord, MI.
“Because of the tight quarters, we originally figured on driving tight sheeting around the perimeter of the excavation. In addition to slow response by the sheeting contractor, we found out that the vibration that would be generated by driving sheeting was not acceptable to hospital personnel performing life saving micro surgical procedures,” Miller said.
Excavating and installation of the slide rail system was handled by a Cat 365 with a 3-cu.-yd. (2.2 cu m) bucket. The Pro-Tec slide rail system consisted of posts and panels that move independently of each other.
Initially, panels and posts were installed in a shallow pilot cut. They were then pushed down simultaneously as soil was removed. The triple-track posts allowed the panels to telescope from the top down. The entire system was installed in two and a half days.
Removal was accomplished in less than one day. Posts and panels were raised incrementally from the bottom up as backfilling and compaction took place.
To provide a clear span large enough to accommodate the tank, walers with tiebacks to the vertical spreader posts were used along both sides of the excavation.
All things considered, Miller felt the Pro-Tec slide rail system contributed considerable savings in both time and materials over alternate tight sheeting methods.