On most any day, people are out playing soccer on the fields of Waterloo, Ontario. Soccer is a serious business that cannot be disrupted by something as mundane as replacing sewer pipes. With that in mind, Harry Cosford of Swiss Hill Landscaping took on the job of installing new sewer lines beside a city soccer field. While installing the underground pipes, he had to avoid delaying the games.
The job consisted of replacing 400 feet of four-inch sewer piping along the western end of the field. The site included the soccer field, underground water lines that could not be disturbed, and bad soil conditions. The ground had been filled in with imported soils that contained rocks and concrete.
Boring beats trenching. The traditional trench-and-replace method could not meet Cosford’s goals. He chose the same trenchless technique that the city of Waterloo was already using to replace underground pipes–using a piercing tool for lateral connection bores to replace sewer lines. The work had so impressed Cosford that he knew it was the only way to do the job.
Although piercing tools were introduced in Europe more than 30 years ago, the tools had not been used often to install the type of gravity sewers Waterloo needed. The Grundomat Tool by TT Technologies, however, was up to the task at the soccer field.
Despite less than ideal conditions, the Grundomat tool bored through on the correct trajectory and exited on target each time. The 5 3/4-inch tool created three bores, one at 100 feet and two at 150 feet. They were completed in two days. The speed was about 1.5 feet per minute, so the total boring time amounted to less than five hours. Traditional trenching would have taken several days.
Head design pushes job forward. The Grundomat boring machine, with its reciprocating stepped-cone head, hit the target. Unlike the cone-shaped heads on most piercing tools, the Grundomat pneumatic piercing tool provides fast and accurate horizontal boring in a variety of soil conditions, according to the manufacturer.
Smooth operators. Piercing tools perform underground horizontal bores with little or no surface disturbance. They can be launched directly into a slope, such as a railway bed or a highway bed, and exit on the other side of the rails or road, leaving traffic flow uninterrupted. The procedure is cheaper than trenching because it requires less crew and equipment. There’s no resurfacing or repair of the rail or road, either. In applications such as the soccer field job, small entrance and exit pits are prepared to launch and retrieve the tool.
Piercing tools are being used to install or repair sewer and water lines, cable, and electrical conduits. The tools are available in many sizes to fit most applications. The Grundomat tool alone comes in 10 sizes. The tool can create a bore with the pipe inserted later, or the pipe or conduit can be pulled in behind the tool with a pipe pulling adaptor. Pipe pushing adaptors are available for installing the pipe after the bore has been made.
The high cost of trenching, laying pipe, and then resurfacing areas is convincing owners and contractors that horizontal boring is often a better option. Contractors who have invested in piercing tools have found that they pay for themselves after just a few jobs.
“Using a Grundomat tool was a cheaper alternative compared to the open trench method,” Cosford says. “Plus I didn’t want to rip up the playing field.”
Constructor, March 1995, Page 30