Doubling Down on Trenchless Methods
Contractor uses two different trenchless tools in Arizona gas main replacement project
Contractor uses two different trenchless tools in Arizona gas main replacement project
By Jim Schill
While it is often assumed that individual methods of trenchless installation tools and technology compete for projects, that’s not always the case. Many times, on many projects, several pieces of trenchless equipment can be used in harmony with greater results.
On a recent gas main and service replacement project, Underground Construction Co. Inc., a Quanta Services Company headquartered in Benicia, Calif., was able to effectively employ two different trenchless methods. The project was completed at a golf course retirement community in Sun City West, Ariz.
Underground Construction Superintendent Ernesto Gonzalez explained, “The gas mains and services providing natural gas to the customers were installed in the backyards between the homeowners’ properties and the golf course fairways for this development. They were deteriorating and required replacement.”
New mains were installed in the street, Gonzalez said, and the new gas services needed to be installed from the new mains to the homes. “The old system was in the back easements and the new system was being placed in streets in front of the homes. This would also provide easier access.”
The compact directional drill was an ideal choice for the longer service installations in tight work conditions
Underground Construction crews initially began the project using Grundomat horizontal boring tools from trenchless equipment manufacturer TT Technologies, based in Aurora, Ill.
“Ground conditions were extremely dry, hard and tight,” noted George Mallakis, a trenchless technology specialist with TT Technologies. “In addition, crews had to contend with very narrow workspaces, hardscape, trees, and vegetation between homes to reach the home’s gas meter.” According to Mallakis, open cut was dismissed as too slow and “would cause much disruption and difficulties with the restoration of the beautiful and unique landscapes.”
The piercing tool was a good choice for this project, he said. “Longer runs were proving very time consuming. So Underground Construction reached out for additional, more productive solutions.”
80 Years in the Business
Underground Construction Co. has completed gas transmission and distribution projects throughout the United States and has over 80 years of utility and construction experience including gas and electrical structures, fiber optics, fueling facilities, and municipal utilities. In addition, the company has spent over 50 years working in refineries and on heavy engineering construction projects. Over the years, the utility contractor has installed 4-inch to 36-inch gas transmission lines, and gas distribution lines from 1/2 to 16 inches.
During this time, the company has achieved an impressive safety record, which is the result of a sound safety program, continuous training, education, hard work and discipline. A lot of that happens daily at the jobsite.
Gonzalez said, “We meet every day and go through a job hazard analysis. That helps makes sure that everyone is on the same page and we’re working safely and efficiently.”
Underground Construction Company used a combination of piercing tools and compact directional drilling on a difficult gas main and service line replacement project.
Horizontal Boring Tool Power
Piercing tools are some of the most versatile trenchless tools available. The tool can be used in a wide variety of trenchless applications. According to Mallakis, it is hard to match the productivity and capability. “Obviously [our piercing tools] can be used as a boring tool,” he said, “but when you factor in that they can also be used as a ramming tool and a pipe bursting tool, it is easy to see how effective this piece of trenchless equipment actually is.” Piercing tools are used in water, gas, sewer, electrical, telecom and FTTH applications, he noted. “In addition, for shorter boring projects, like the ones Underground Construction is using them for, they are very economical on a cost-per-foot basis.”
Installing conduit or HDPE sleeves with the piercing tool can be accomplished in several ways. Mallakis said, “Often, the piercing tool will pull in some type of poly line or tape during the bore. Once the run is complete, the conduit is pulled in with the poly line.” Sometimes after the bore is done, he added, the HDPE sleeve is attached to the front of the piercing tool and installed by backing the tool out through the borehole. “Sometimes you can pull it in with the tool’s air hose after the bore,” he said. “There are many options and accessories available but in Underground Construction’s case, the gas customer required a sleeving to be installed for the bore. Then, the actual gas carrier pipe was installed by simply sliding it inside of the sleeve.”
Arizona Project by the Numbers
For the project in Arizona, approximately 10,000 lf of new 3-inch mainline sleeving needed to be installed. Once in place, 2-inch HDPE gas mains were inserted. In addition, approximately 8,000 lf of new 1 1/2-inch service sleeving also needed to be installed, which equals about 120 home service laterals. Once the conduit was installed, 1-inch gas service lines would be inserted.
“For services from across the street, lengths ranged anywhere from 125 feet to 50 feet depending on the distance from the house or where the meter was located,” Gonzalez said.
“The ground conditions were rocky and difficult to work in,” he recalled. The tools allowed for trenchless installation of the gas services, avoiding costly open cut restoration and inconvenience to the homeowners. But due to the extremely dry and hard soils, the tools would take 2-3 hours to install the new service.
According to Mallakis, the horizontal boring tools did their job and were very accurate and reliable in these tough conditions. “The Underground Construction crews did a great job of using their experience, skills and ingenuity to use multiple tools at the same time from the same launch pits to install more than one service at a time, doubling their production,” he said. “[This was] very clever on their part!”
To try to improve production for the longer service installations in tough, narrow working conditions, Underground Construction’s Area Manager Jim Dillon asked Mallakis to bring in a compact directional drill. “We worked out a schedule to get our 4X out and give it a try,” he said. TT Technologies Compact Directional Drilling Specialist Mark Schneider provided on-site support and helped get the Underground Construction drill crew familiar with the compact directional drilling rig.
Utilizing the trenchless methods helped lessen the impact to the homeowners and reduced restoration costs.
Compact HDD Pulls Its Weight
According to Schneider, much progress has been made in the function and capability of compact directional drills and they are defined by various criteria. He said, “The amount of pullback is also a way to define or categorize directional drills. Ones under 20,000 lbs of pullback are sometimes placed in the compact category; sometimes it’s under 10,000 lbs. The Grundodrill 4X at 9,800 lbs of pullback and thrust is definitely in the compact category.”
They are also relatively lightweight and smaller-than-standard sized drill rigs, he said. “They can work in tight, residential areas. They also tend to be about 36 inches wide so they can fit through a standard yard gate.”
Portability is another factor, he added. “Most compact drills can be legally towed behind a 1-ton truck.”
For this project, it was not only the ability of the compact drill to deliver the power crews needed to overcome the difficult soils that made it an ideal choice, it was the fact the drill could work effectively in small, confined, residential areas.
Gonzalez explained, “For some of the service, we backed the drill up to the house and drilled from the house to the street. But depending on the particular layout we sometimes had to bore from the street to the house. The size of the machine was important. Sometimes we needed to get into backyards and that access is narrow. A small machine really helps in a situation like that.”
Schneider said, “The crew was very positive and made it work. Instead of the two to three hours to install new gas services, they were able to install the gas services with the compact drill in about an hour. The crews mostly used the drill for longer runs and continued to use the horizontal boring tools for the shorter runs.”
The entire project took three and a half months from start to finish. Underground Construction crews completed the final connections with the residences and performed all restoration work as well.
“When you face underground conditions that consist of hard, tough soils and tight spaces, there is no substitute for using the appropriate trenchless tools and methods in combination with the best contractors and equipment manufacturers with experienced technical support,” said Mallakis. It reduces cost and time for completions between 30 and 50 percent, he estimated. “Not to mention the reduced impact on the homeowners’ beautiful and personal home landscapes.” UP
the Author: Jim Schill is a technical writer based in Mankato, Minn.