Simple Solutions Turn Complex on Large Sites
Apr 1, 2001 12:00 PM, By EC&M Staff
Trying to make changes in a plant that serves a large and changing network of buildings can result in multiple headaches. One mail order prescription company's attempt to provide more power to one of its locations led electrical contractors down a path with many twists. When Express Scripts, Maryland Heights, Mo., needed to increase power to an area being converted into a print center, the company contracted Bell Electrical Contractors, Maryland Heights, Mo., for the job.
“This project seemed pretty straightforward at first. It was just a situation where we needed to increase the service size,” says Tom Barker, a project manager with Bell. “It was a 480/277V 3-phase 4-wire service, 200A. We needed to increase it to 400A. We just needed to install a second panel, and it would be done in parallel.”
Barker and his crew needed to install the new panel 200 ft from the meter, and because the building housed other tenants, the conduit from the panel to the meter couldn't run through the building. Aesthetic concerns prevented Barker from attaching the conduit to the outside of the building. Barker finally decided to bury the conduit outside. He considered trenching, but this presented another problem: The concrete ramp of a delivery dock stretched nearly 40 ft from the building in the area between the panel and the meter. Trenching around it would mean saw-cutting concrete slabs. Directional boring seemed to be the last option. A hole bored beneath the ramp would provide a path through which the conduit could be pulled.
Barker called St. Louis-based Collins & Hermann, a subcontractor with a directional boring rig. Because of limited space, Barker decided to use Bore-Gard, a modified standard schedule 40 PVC “stick pipe” developed by Carlon of Cleveland. This UL-listed conduit, designed specifically for directional boring applications, would provide a fast joining method that wouldn't require glue.
Collins & Hermann cut holes in the asphalt patching at the bore end and at the pull end. They bored the hole about 5 ft beneath the footings of the concrete ramp. Once the bore head entered the pit at the other end, workers switched the bore head for a 6½-in. backreamer, and the conduit was hooked with a pull head. Then, they pulled the conduit through the hole.
According to Glen Marstall, facilities manager for Express Scripts, the job was done well within the critical timeframe and cost less than the budgeted amount for the project. Shrewd responses to mounting complexities had saved the day.
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