Marathon Drilling, Greely, Ontario, Canada, is leading the way for trenchless technology in Canada, as well as North America. The company was formed in 1981 to serve the needs of the oil and gas pipeline industry, specifically drilling services, in eastern Canada. The first trenchless service offerings were added a few years later in 1984.
According to Marathon Drilling president David McPhedran, trenchless technology has become a big part of the company. “Trenchless has had explosive growth with Marathon Drilling. If you look at 1995, for example, our trenchless services and our drilling services were probably at about 50-50 in terms of revenue share. Go back a few more years to 1990, and it was more 60-40 in favor of drilling services,” he said. “Now jump ahead to 2009 and trenchless technology represents about 90 percent of our volume. During that time, our vertical drilling operations have continued to grow at a small, but steady pace. The trenchless technology side has really exploded.”
It Takes a Contractor
On a whole, the growth of trenchless in North America has been remarkable over the last several decades, but it has taken a commitment to education by trenchless contractors and equipment manufactures to establish the technology in the first place and then grow it. Marathon Drilling is a primary example of a contractor that has made the investment and effort to bring trenchless to the forefront of the construction industry.
“We have been a real advocate of trenchless technology. We’re out there every single day, looking at conventional construction designs and trying to change them, modify them with trenchless solutions, to get them approved,” McPhedran said. “If we see a road crossing that may be open-cut or a creek crossing project designed using non-trenchless or conventional technologies, we try to have it changed. We try to promote the industry and promote education and exposure to it. So I think our role, very much like all the other trenchless technology companies that exist, has been to be real pioneers of change, bringing on new solutions.”
For Marathon Drilling, however, that effort has paid off. Considered one of the leading trenchless contractors in Canada, the company continues to expand the reach of trenchless. One trenchless method in particular that Marathon Drilling employs regularly is pneumatic pipe ramming.
As Versatile as a Hammer: Pipe Ramming
Trenchless pipe installation through ramming is a basic process. A pneumatic hammer is attached to the rear of the casing or pipe. The ramming tool, which is basically an encased piston, drives the pipe through the ground with repeated percussive blows. A cutting shoe is sometimes welded to the front of the lead casing to help reduce friction and cut through the soil. Bentonite or polymer lubrication can also be used to help reduce friction during ramming operations.
According to pipe ramming specialist Rick Melvin from trenchless equipment manufacturer TT Technologies, Aurora, Ill., several options are available for ramming various lengths of pipe. “While pipe ramming may be a simple process, just like a hammer, a pipe rammer is very versatile and effective. You can install an entire length of pipe at once,” he said. “For longer runs, one section at a time can be installed. In that case, the ramming tool is removed after each section is in place and a new section is welded onto the end of the newly installed section. Depending on the size of the installation, spoil from inside the casing can be removed with compressed air, water, an auguring system or other types of earthmoving equipment.”
Ramming requires minimal working depths and can be used for horizontal, vertical and angled applications. Ramming is also ideal for installations under roads and rail lines because it displaces the soil without creating voids or slumps. While some methods have trouble with rock or boulder-filled soils, pipe ramming can accommodate boulders and rocks as large as the casing itself during the process. That spoil can be removed after the installation is complete.
Transmission Line Slick-Bore
Slick-boring is a ramming method that is conducive to transmission pipeline installation and is also utilized extensively by Marathon Drilling. During the slick-bore process, a bore pipe is installed under a roadway or rail line. The new transmission product pipe is then welded to the back end of an installed bore pipe. A winch is connected to the lead end of the bore pipe and is used to pull the casing out. As the bore pipe is removed, the product pipe is pulled into place. In this scenario, the bore pipe is installed with a pneumatic pipe rammer.
Slick-boring limits the amount of stress placed on the product pipe, which is of concern to project owners. The bore pipe ultimately takes the brunt of impact from the ramming in tough soil conditions and spoil cleanout.
Typically, crews have a sufficient amount of room on either side of the road or rail crossing to facilitate ramming and slick-boring operations. This also allows them to install longer sections of pipe. But even in tighter working areas, crews are still able to ram in the bore pipe section by section and install the product pipe section by section.
Marathon Drilling recently completed a 270-ft, 26-in. diameter slick-bore pipe ram for Union Gas. “The project began as a standard jack-and-bore. However, because of heavy boulder obstruction, the slick-bore method was employed to complete the installation,” said Marathon Drilling project manager Tyler Gordon. “This was very effective and product pipe was installed without issue. We have crews perform slick-bore installations on a regular basis for various pipeline projects.”
Large Diameter Ramming
A recent pipe ram for an on-grade sewer main installation in Ottawa Ontario, highlights the capability of the pipe ramming process. Marathon Drilling crews used a Grundoram Taurus from TT Technologies to install a 72-in. diameter casing, online and grade, 72 ft under a road to accommodate a gravity sewer main. “The ram was under a very busy road and under a 24-in. diameter high-pressure water main. And because of the depth, we were about 25 ft deep, the ability to open-cut without wiping out the entire roadway and totally disrupting traffic wasn’t possible,” said McPhedran.
“Ramming tools, in general, are capable of installing 4- through 144-in. diameter pipe and steel casings. At 24 in. in diameter, the Grundoram Taurus, which Marathon is currently using, is the world’s second largest pipe rammer. The Grundoram Apollo at 32 in. in diameter is the world’s largest ramming tool,” Melvin said. “Casing diameters up to 147 in. have been successfully installed using this larger scale ramming equipment.”
Marathon drilling crews not only had to face a challenging installation, temperature on the project hovered around 30 degrees below zero. McPhedran said, “It was ugly. It was extremely cold.”
After completing pit construction, the first 10-ft section of pipe was lowered into position. The connection between a 24-in. diameter Grundoram Taurus and the 72-in. diameter casing was made using a standard 72-in. ramming gear. A 72-in. ram cone was connected to the pipe and reduced the overall diameter to 30 in. A 24-in. ram cone made the final connection to the tool. The entire configuration was secured with tensioning chains and the tool was connected to the air compressor.
“Ramming went smoothly and once the first section of pipe was in place, we removed the ramming tool from the casing, lowered the next 10-ft joint into the pit and welded it to the back end of the casing that we had just installed,” Gordon said. “That process continued until the entire length of casing was successfully rammed in.”
Crews then set to work cleaning the spoil from the casing. According to McPhedran, some of the boulders were so large that they needed to be removed one at a time with chains and cables. After the spoil was removed, the concrete sewer main was inserted into the 72-in. diameter casing. Marathon crews built bulkheads on top of the concrete pipe to the top of the casing to hold the main in place. The space was then filled with cementitious grout.
One of the biggest factors in the future growth of trenchless is the general public and, according McPhedran, the time is ripe for trenchless. “The one driving factor in the growth of trenchless technology is the overall growth of our communities, our cities. They’ve become denser, there are more roads, more homes, driveways, people, the things that make it more challenging to complete construction projects utilizing conventional excavation techniques,” he said. “A big thing today is reducing the socio-economic impact on taxpayers. They don’t want the road ripped up. It delays them from getting things done during the course of a day. It affects business, and business today can’t afford lost or downtime. It’s never made up again. So they don’t want that road detoured or that highway delayed.”
Jim Schill is a technical writer, based in Mankato, Minn.