Problem Solved: Underground Piping Installation Poses Unique Challenge
Our project managers oversee projects related to the commercial side of the business here at General Heating and Air Conditioning. In our new “Problem Solved” series, several of our project managers will share a challenge they encountered on the job and how they were able to provide their client with a solution. Today, Eric Smithback shares his story.
The Dane County Highway Facility and Medical Examiner’s building on the east side of Dane County utilizes waste heat from the Dane County Landfill across Highway AB. At the landfill, generators produce electricity by burning methane gas produced by decomposing landfill materials. The byproduct of generating this electricity is a lot of heat. As part of the construction of the Dane County East Campus, the plan called for installing over 1,300 feet of 6 inch and 4 inch pre-insulated piping underground in order to move 205 degree water from generators at the landfill to heat each of the new buildings. However, in order to get the water from the generators to the new buildings, it had to go under Highway AB.
Underground piping installation is nothing new to General Heating and Air Conditioning as we have installed miles of pipe for geothermal heat exchange piping. The unique aspect of this project was the fact that Highway AB is a truck route in Dane County, meaning that a shut down or detour requires extreme coordination.
We explored many options to complete the work without shutting down the road. The obvious answer was to bore under the road. But, the amount of sand and gravel on site meant that two smaller casings could not be bored next to each other without collapsing the bores. The preferred option was to directionally drill a single 90 foot long, 36 inch diameter casing that would carry two pipes under the road using a miniature version of a tunnel boring machine. The problem with this approach, other than cost, is that sometimes in sandy soils workers are required to crawl through the casing and hand dig the hole because the rotation of the drill head would cause the hole to collapse in front of the casing. This approach would expose our subcontractor’s labor force to a huge safety risk and coupled with the high cost, this approach was not approved.
The Best Outcome
The project team all agreed that the only realistic solution was to shut down the road. For about 16 hours on a Friday night, our subcontractors cut the pavement, dug a 16 foot deep trench, and drug 151 foot sections of pipe into the trench. Our subcontractors then sand bedded and backfilled the trench before repaving the road. This took a great deal of coordination between the county, project team, and General Heating and Air Conditioning, but in the end the task was completed on schedule to the satisfaction of all parties involved.