On the Job: Sonic Rescue Rigs Complete Geotheral Grid
March 1, 2010
While students at the new Woodward Hill Elementary School in Surrey, B.C., score goals on their soccer field, the geothermal grid that lies directly beneath will quietly be heating their school and helping to save the environment.
“Geothermal is a good idea for new schools as well as retrofitting for old schools,” says Bill Fitzgerald, general manager of Sonic Drilling Ltd., the Vancouver-based company contracted to rescue the project from some challenging ground conditions. “A school geothermal grid shouldn’t need replacing for 50 years to 70 years, and it pays for itself quite quickly – after that, you’ve got free energy.”
But, before the school could take advantage of those savings, the system first had to be installed – a total of 120 vertical holes, drilled to a depth of 180 feet each, with pipe running all the way back to the mechanical room in the new school.
TR3 Geological Services, based in Abbotsford, B.C., won the tender to install the grid during the summer of 2009 under what would be the brand-new school’s all-weather soccer field. Unfortunately, Mother Nature had other plans. With the field already compacted for the installation of the soccer surface, a rainstorm hit (in an otherwise dry summer on the West Coast) forcing the fines in the soil to vibrate up to the surface and turning the field into a giant, squishy marsh.
With the ground composition, a conventional drill rig worked the site, but spent far too long trying to drill through and install the loops. With the clock ticking on an expected school opening, there was only one way to save the day – bring in two sonic rescue rigs. “The sonic drills did the work six times as fast,” claims Rick Saari, president and owner of TR3. “The two sonics drilled four to six holes a day, and they are the only rigs that could do that in the specified time.”
With the geothermal grid now in place, Saari says, “the school will save 30 percent to 50 percent on its heating costs, and it could be higher depending on how they built it. I know they put in a large heat-recovery ventilator that will help the building retain the heat. This is more for the operating cost-savings. And the technology is not rocket science; it’s been around since the turn of the century.”
Modern sonic drilling technology was pioneered and developed by Canadian engineer Ray Roussy, president of the Sonic Drill Corp. and Sonic Drilling Ltd. Today, sonic rigs are in use all over the world in a myriad of applications.
Although a sonic drill rig looks much like a conventional air or mud rotary drill rig, a big difference can be found in the drill head, which is slightly larger and uses proprietary technology to transmit vibrations and power through a drill string. The energy produced liquefies overburden and bedrock, and pushes the material up and away from the drill pipe. This enables a sonic drill to achieve improved penetration rates without the use of drilling mud. That means reducing on-site time and, in doing so, reducing the per-foot project costs.
Geothermal applications have caught on in a big way in the last few years for both commercial and residential development. TR3 has completed a number of geothermal fields for schools in Ontario, and Saari suspects British Columbia will be doing many more in the future with the environmental advantages and cost savings.
For the Woodward Hill Elementary School project, general contractor Envoy Construction Services Ltd. aimed for a gold Canadian Leadership in Energy and Environmental Design (LEED) standard. Certain features and equipment help contractors accumulate points for either bronze, sliver, gold or platinum ratings. The energy efficiency of geothermal adds considerably to achieving the gold standard, and TR3 increased the total score by ensuring no drilling water or mud was left at the site.
As Saari explains, throughout the process, all the water was recycled, filtered and reused by the drills after passing through a mud-recycling device. The filtered, air-dried mud and sand also were reused as part of the backfill in the manifold trenches.
Although this was not the cleanest or easiest job, the school’s geothermal installation was saved by the bell when the two sonic rescue rigs completed it on schedule.