The directional drilling equipment routinely used for installing underground utilities is turning up in some unusual places as project and property owners become more aware of the benefits offered by the trenchless technology.
A good example is a recent project in Victoria, TX, where a compact horizontal directional drilling (HDD) unit was busy installing new power cable under the floors directly through the middle of Victoria Mall, a 675,800-sq.-ft. retail facility with 70 retail stores, specialty shops, and eating places.
The utility work was because of the expansion and complete remodeling of the single-level retail mall, owned by Hull Storey Retail Group, Augusta, GA.
The general contractor for the work, MK Marlow of Victoria, proposed jackhammering the terrazzo and saw cutting a 2-ft.-wide trench through concrete the length of the mall and through five side corridors, said Kyle Berg, the facility’s property manager.
However, Berg had seen the benefits of directional drilling when the method was used to relocate telephone and power cable in parking lots as part of a previous mall expansion.
“Sawing and hammering could be done only at night, the work would create a lot of dust that would have to be cleaned up before the next day’s business, and trenches would make cross traffic from store to store difficult,” Berg said.
So he suggested directional drilling as a practical alternative.
“At first there was concern about using HDD because of the risk of hitting buried lines or structural beams,” Berg continued. “After looking at the original plans, discussing HDD with the electrical contractor, Hall Electric of Victoria, and talking with drilling contractor 2M Road Bore in Victoria, we all agreed directional drilling could be done, allowing the installations to be made with minimal damage to the mall’s floor.”
Careful planning was needed before work could begin, said Brian Morris, co-owner of 2M Road Bore.
“Initially, I think the biggest concern was the possibility of interference with the drilling unit’s tracking equipment,” Morris recalled. “But after checking the mall out with the Subsite 750 tracking system we would use, we determined that we would be able to do the job.”
As planning proceeded, existing utilities were located and marked, and mall plans were studied to identify any other obstacles that might be encountered. Entry and exit points for each bore were established, and crew members determined where equipment would be brought into the mall.
Getting the drilling unit used on the project into the building was not a problem — the compact Ditch Witch JT2020 Mach 1 is only 50.5 in. wide (128 cm), 78 in. high (198 cm), and 203 in. long (516 cm). However, a truck for the machine’s supply of water for drilling fluid was too big to enter the building.
“We came up with the solution of mixing fluids outside the building using a Ditch Witch FM13 mixing system, transferring fluid to 250-gallon tote tanks, and bringing them in with a fork lift,” said Morris. “During drilling, we elevated the tank with the fork lift which provided positive pressure to bring fluid to the drilling unit.”
In addition to its compact size, Morris said the JT2020 was ideal for the job in other respects.
It’s rubber tracks allowed it to move easily over the floor without damaging it. It also is quite powerful for its size, developing 20,000 lb. (9,072 kg) of pullback, 2,200 ft. lb. of rotary torque, and spindle speeds to 150 rpm.
The route for the new cable was along the center of the mall, and because the conduit run was not continuous, five separate bores were made along 1,068 linear ft. of the hallway. Entry and exit pits were 18 by 48 in. (46 by 122 cm).
Pilot bores had to be precisely controlled, maintaining a depth of 18 in. (46 cm).
“And we had to stay within three inches of the centerline at all times, because the floor would be opened later to install floor plugs at specific locations to serve the kiosks and freestanding retail stands that would be placed in the wide aisle,” Morris continued.
Working from 9 p.m. to 9 a.m., the HDD portion of the project was completed in three days, including clean-up necessary to make the mall ready for the next business day.
The success of the trenchless HDD installations opened the door to using another trenchless procedure to place cable under floors of side corridors.
“We needed to make some short bores from entry points to locations of nearby floor plugs, but the distances were so short it was not practical to use the HDD machine for them,” explained Morris. “Ditch Witch of Houston dealer general manager Ronny Padgett suggested using a piercing tool and once we made the first installation, it was obviously the perfect choice.”
The crew used a 2.25-in. (5.7 cm) Ditch Witch PT20 pneumatic piercing tool to make 14 shots ranging in length from 15 to 50 ft. (4.6 to 15 m). The tool, placed in a starting pit and powered by an air compressor, pounds itself through the earth toward its exit point. Depths of the compaction bores ranged from 12 to 16 in. (30 to 41 cm).
“Prior to starting the tool, we aligned it with a laser,” Morris said. “It was not necessary to track the path.”
One 1.25-in. (3.2 cm) HDPE conduit for electrical cable was placed in the compaction bores.
All of the piercing tool installations were completed over two nights, including clean up.
“Trenchless construction proved to be very successful,” concluded mall property manager Berg. “Directional drilling was clean, less disruptive than saw cutting would have been, and saved time on our construction schedule.”
2M Road Bore is owned by Brian and Ronnie Morris. The company does oil field and gas line construction, and special projects such as the one at the mall.
“We often do jobs where we are able to show project owners and general contractors how they can avoid the disruption caused from excavation by using trenchless HDD methods,” said Morris. CEG