Frost fight

No matter where you live, underground utility installations get a lot more difficult when the ground freezes. However, the last several years have proven to be especially tough for Calgary contractors, ever since their traditional ground-thawing techniques of coal burning have been outlawed. In fact, the new rules have severely slowed most wintertime utility installations in the city, as contractors have struggled to find new ways to fight the frost.

No heavy equipment required. The Toasters could be moved around the job site by gripping and lifting the impact cages.

Perhaps no one has felt the effects as much as ATCO Gas, the area’s natural gas distributor. During December of 2010, Calgary’s Skyview Ranch development was in a bind to supply services to the new commercial buildings on its property. By this point all utilities were installed except for gas. Three commercial buildings urgently needed gas by Jan. 1, and several more buildings requested it soon thereafter. Christmas was rapidly approaching, so schedules were extremely tight. To complicate matters even more, frost had already formed in the ground.

SkyView Ranch is a four-year-old residential development in the northeast outskirts of Calgary. Consisting of mixed single-family and semi-detached houses, row houses and condominiums, the neighbourhood calls itself part of Calgary’s “New North.” The development is located outside the urban core of Calgary, just six kilometres aways from Calgary Airport, so the developer decided to add a commercial strip to the area including convenience stores, a gas station, a liquor store, restaurants, a dental clinic, a spa and a bar. The development was opening new show homes in February, so the developer was desperate to have the commercial amenities in place before then.

Several years ago, the frost might not have presented such a problem. Calgary’s utility contractors would have lain straw beds and used burning coals to thaw a path of frozen ground. Then, excavators could trench along the path for the gas lines. Despite the lack of sophistication, this method worked somewhat effectively. Nonetheless, the environmental concerns were too great for legislators, causing them to put a stop to the practice.

Safer than coal, more efficient than boilers and less awkward than trailers. Dunwald and Fleming started with 10 and now it has 30 Serious Toaster units.

The coal-burning ban created serious issues for everyone involved with underground utility work, including ATCO’s service contractor for the Skyview Ranch job. The contractor couldn’t bring large excavators in to rip through the frost – partly because of the heightened risk of damaging existing underground utility lines, but also because mini excavators were the only machines small enough to access the jobsite. Unfortunately, mini-excavators didn’t have the power to dig through frost, so without some method of heating the ground, the contractor couldn’t install the gas lines.

Not just any heating source would work for the Skyview Ranch, however. It needed to thaw ground as quickly as coal and straw – if not quicker – in order to make the deadline. Without an effective solution, the building tenants could have been forced to wait until spring to receive natural gas services. But since their contracts stated a Jan. 1 occupancy, delaying the process was simply not an option.

When it was determined that the service contractor simply did not have the tools or the time to complete the task, ATCO started considering other options. That’s when ATCO heard its seasoned mains-installation contractor, Dunwald and Fleming Enterprises, had recently purchased some infrared heating devices. The new technology promised to thaw ground faster than any other method, so ATCO quickly asked Dunwald and Fleming to step in and put the heaters to the test.

The new infrared heaters were Serious Toasters from Serious Thermal Products. Each Toaster measures only 10 feet long by two feet wide, but multiple units can be placed together in a series according to the route of the proposed trench. They are powered by propane and run from a 110-volt power source. Using targeted reflectors, the infrared technology of the Toasters efficiently directs heat into the ground with minimal heat loss. Thanks to these advantages, the units appeared to be an ideal solution for the Skyview Ranch job.

“We explored several options before finally finding the infrared heaters,” said Marv Dunwald, owner of Dunwald and Fleming, who struggled to identify alternatives to coal and straw. First, he tried glycol boiler systems to heat the ground, but they proved to be extremely inefficient for utility work. “There was so much heat loss that it would take three to four days just to thaw one foot of ground,” he said.

Next, Dunwald experimented with trailer-mounted units, which he found to be cumbersome. “A trailer only thaws about 12 feet at a time,” he said. “Plus, there are only about 10 units in all of Calgary, so nobody can get their hands on one.”

Upon discovering the Toasters, Dunwald ended his long, frustrating search and purchased 10 units. His plan for the Skyview Ranch job was to line all 10 of them up to thaw 100 feet of ground at a time. After one stretch of ground had thawed, he would move the Toasters ahead to start heating more frozen ground while his crew trenched the first 100 feet. The process would be repeated until 1,000 feet of ground had been thawed and trenched with gas lines installed and the dirt backfilled.

The infrared units provided a safe, quiet heat source, allowing Dunwald to place the Toasters against buildings and fences, and let them operate overnight without close supervision. “Glycol boilers would have been too noisy to operate overnight near residential areas,” said Dunwald, “and most other systems use open flames, which would have been a fire hazard on our jobsite.”

After Toasting, the ground was soft enough to dig carefully with a mini-excavator. “We could have used a shovel to dig,” Dunwald said.

It took approximately 24 hours for the Toasters to thaw one metre (deep enough to install the gas lines). That meant every morning when the crew got to the jobsite, they could move the Toasters, and the ground would be ready for trenching. “With coal and straw we would only thaw about one foot every 24 hours,” said Dunwald. “The infrared heat worked up to three times faster.”

Not only did the infrared heat system increase Dunwald’s productivity, but it also helped his crew work safely next to the existing utility lines. “We had the inside path, so we were constantly crossing our lines with other utilities,” he said. But, thankfully, the ground was thawed well enough that Dunwald didn’t have to be too forceful when trenching with his Yanmar mini excavator. “We could have used a shovel to dig,” he said.

The gas line installation spanned 10 days, and all buildings were ready to be occupied by the January deadline. Without the infrared heaters, Dunwald isn’t sure what would have happened. Consequently, both ATCO and the developer were fully enthused by Dunwald’s work. “The developer wanted to buy our Toasters on the spot,” Dunwald said.

His only regret was not having enough units to get the job done even faster. “We could have worked a lot quicker if we had more than 10 Toasters,” he said. “Then again, the same job might have taken us 30 days if we didn’t have any.”

Since working on the Skyview Ranch project, Dunwald has better prepared himself for future underground installations. He eventually purchased 20 more Toasters, giving him a total of 30. He’s used them on a variety of other jobs – both commercial and residential. “The Toasters have given us the upper hand in Calgary, and more work has started to flow our way,” Dunwald said.

With happy clients and an increasing workload, Dunwald is thankful for the infrared technology that allows him to trench during winter months. And the coal-burning ban that once hampered his business has finally provided a silver lining. Now that he offers services that no other contractor in Calgary can match, when it comes to underground utility installations, Dunwald definitely has the hot hand.