When drilling in a residential area around some of the nation's largest gas pipelines, there's no question that safety comes first. One utility contractor working to preserve these pipelines has created a process to help ensure both his crews and the residents aren't placed in danger.
Matt Kelly, co-owner of Ballard Utilities Construction LLC, knows the ins and outs of horizontal directional drilling (HDD). He has been in the industry since 1990, and his knowledge explains one of the reasons Ballard Utilities Construction was hired by Williams Gas Pipeline — Transco for a major cathodic protection project.
Williams Gas Pipeline delivers clean-burning natural gas from production areas to millions of Americans' local utilities. The company, headquartered in Tulsa, Okla., operates more than 15,000 miles of interstate natural gas pipelines. Its three natural gas transportation units deliver about 12 percent of the natural gas consumed in the United States. Transco, one of the natural gas transportation units, comprises 10,500 miles of pipeline that service cities along the East Coast, including Atlanta and New York City.
To preserve these major gas pipelines, Ballard Utilities Construction of Anderson, S.C., will install cathodic protection, which prevents corrosion of the steel pipelines. Cathodic protection involves installing cables of AnodeFlex, which transmit a current onto the gas pipeline so it can repel corrosion. Because it is a more active metal, the AnodeFlex cable attracts the corrosion away from the steel gas pipeline so it corrodes first.
This year, Ballard Utilities Construction will install cathodic protection for 110,000 feet of gas pipeline. In Fairfax, Va., Kelly's crews are installing the protection for four major gas mains, including two 30-inch, a 36-inch and a 42-inch pipe. Because much of the work in and around the city occurs in residential areas, Kelly uses a fleet of Vermeer® NAVIGATOR® HDD units to drill around obstacles. "We're in a housing area where everyone's backyards are built right on top of the gas pipelines. And in everyone's backyard there is either a chain-link or wood fence, and they have sheds and swimming pools," he says. "The only way to come through these areas is to bore everything."
To determine which sections of the pipeline are in need of cathodic protection, Williams Gas Pipeline regularly performs ground readings and takes soil samples, Kelly says. In the Fairfax residential area, Kelly's crews are installing two 1-1/2-inch AnodeFlex cables that will run parallel between the 36-inch and 42-inch gas pipelines. The number of AnodeFlex cables that are placed depends on several factors, including the amount of corrosion coverage needed and the space between the pipelines.
For this portion of the project, which costs $4.5 million, Ballard Utilities Construction chose to use three of its five Vermeer HDD units — a D24x40a and two D18x22 machines. The company also owns two D16x20a HDD units, which they are using in Anderson for power line installation jobs.
In working around such large gas pipelines, Kelly considers safety first and foremost. The large gas pipelines run parallel to the homes, many of which are as close as 10 feet away.
"We have to get production, but production comes second to safety," he says. "You're talking about a pipeline that's 800 pounds of pressure."
Before drilling begins, Kelly has a four-member layout crew work two weeks ahead to locate and pothole the gas pipelines and other utilities. The workers probe every 50 feet to monitor if they are still following the route of the gas pipelines. They also measure in between the pipelines and mark the centerline with white paint so HDD operators can hold that line when boring. "And then every single utility that crosses these pipelines, I make them dig to it," he says. "They measure it and then mark on a wooden stake what kind of utility it is and how deep it's buried."
Once the layout crew has finished locating a section, it provides the HDD crew with a utility log sheet.
Kelly says some utility contractors may initially consider a layout crew to be too costly. But his theory is that "drill rigs don't make money when operators have to stop to pothole a utility because they don't know how deep it is."
It's a proven fact that the layout crew has improved the HDD crews' production rates. In fact, Kelly says there have been a couple of instances when the HDD crew has bored so fast that it's actually caught up to the layout crew, requiring him to add more workers to the layout crew.
Even though the layout crew has helped make the job go more smoothly, the job hasn't come without other obstacles.
Much of the 110,000 feet Ballard Utilities Construction must drill requires going through red shale rock. To tackle the hard ground conditions, Kelly says his HDD operators use either a TriHawk® drill head or bear claw drill head. So far the layers of rock have greatly varied from area to area.
"Sometimes you can get 2 feet or 3 feet of good dirt and then you get into a soft layer of that shale, which you can get good steer out of with a bear claw. But some of it's too hard and we have to use the TriHawk drill head to carve it out," he says.
In addition to boring under the Reston National Golf Course in Reston, Va., Kelly's crews also must cross under creeks that are surrounded by solid granite rock. For those harder conditions that can't be drilled through with a regular drill head, Kelly says he plans to use the Vermeer RockFire® rock-drilling system.
With most of the shale rock, Kelly says his crews typically must do two prereams. However, in softer ground conditions, they have been able to drill out 500 feet without needing to preream.
Because the AnodeFlex cables are wrapped with a mesh sock filled with a fine carbon slag powder, the HDD crews must be especially careful when pulling back the cables. Applying too much pressure or allowing it to drag through the shale rock can tear a hole in the mesh sock, which would then make the AnodeFlex cable ineffective. "The cable won't be able to provide cathodic protection without the carbon slag around it," Kelly says. "If the mesh sock is torn and the cable touches dirt, it will burn out."
To successfully pull back the AnodeFlex cables, Ballard Utilities Construction uses a 6-inch or 8-inch backreamer along with POLY-BORE and BORE-GEL drilling fluids. Kelly says his two D18x22 HDD machines have worked well on this project because they're small and easy to maneuver in residential areas, but powerful enough to drill through the shale rock. Crews use the D24x40a when needing additional power to complete longer bores in harder shale rock.
In the red shale rock, Kelly says each of his three HDD crews has been averaging between 600 feet and 800 feet per day. "These are good production rates, especially considering the soil conditions," he says.
Ballard Utilities Construction has been providing utility installation for more than 40 years. Like Williams Gas Pipeline — Transco, Ballard Utilities Construction believes that safety should never be compromised. This may be one reason why they fully grasp the significance of the job they were hired to do.
"What we're doing out here is probably the most important preventive maintenance Williams Gas Pipeline — Transco could do for this pipeline," Kelly says.