Pilot-Tube Microtunneling Teams with Pipe Bursting

A major bottling plant in Newport News, Va., once again has utilized trenchless technologies as part of an $18 million expansion to manufacture its own plastic bottles and to replace an aging, broken drain under the floor inside the plant.

After having completed an innovative indoor microtunneling project at the plant in 2007, Trenchless Pipe Technologies Inc., Newport News, Va., was contacted by the plant manager to engineer the installation of a new 4-in. drain pipe to service the relocated recycling area, as well as the replacement of the existing 6-in. process water drain pipe servicing the batching and filling rooms.

David Martin, president of Trenchless Pipe Technologies Inc., realized that the open-cut method would not be a feasible option for the approximately 165 ft of new 4-in. pipe needed to drain the relocated recycling area because the pipe had to be routed through the warehouse to connect to the existing building’s drain pipe, which would have been a major disruption to the constant flow of daily forklift traffic, resulting in safety concerns, as well as lost production time for the plant.

While the job was in the early planning stages, Martin contacted David Crandall, vice president of sales and marketing with Icon Equipment Distributors Inc., East Brunswick, N.J. After having discussed the various challenges of the project and the relatively small diameter of the pipe, Martin and Crandall decided the method of choice would be to pilot tube micro bore the route, then pull the new pipe into place while simultaneously retrieving the pilot tubes. When Martin asked Crandall if Icon had ever done a pull back before, he stated, “No, we’ve never been approached to do anything quite like this but I’m excited about the challenge. I guarantee we can make it happen.”

Crandall recommended a Bohrtec BM 4001 Pilot Tube Guided Auger Boring Machine (GABM) with a maximum jacking force of 100 tons and a total length of 2.25 m plus pipe length, which he said would be more than suitable for the bore and pull back. Once Trenchless Pipe Technologies was awarded the job, the company arranged to send a Bohrtec GABM from Icon and contracted to have an application technician to assist with the job.

Prior to the start of the job, Martin collaborated with Crandall to fabricate an adaptor that would connect his pipe bursting head to the pilot tube. Martin stated, “The adaptor was crucial. Without a solid design, we wouldn’t have been able to get the approximately 165 ft of HDPE into place.”

The pipe selected for the job was 4-in., SDR 17 HDPE due to its flexibility and its high resistance to chemicals in liquids under 140 F. “We needed a very flexible pipe to negotiate the relatively steep reception pit. We would have ideally preferred a longer pit but we were limited by a block of wall at the back of the pit,” Martin said. “A high degree of chemical resistance was also needed due to the varying pH levels of the process water that would be flowing through the pipe. HDPE pipe made perfect sense in this application.”

Foreman Alphonso Herbin and equipment operator Andrew Dowd, both of Trenchless Pipe Technologies, led a four-person crew by first creating two pits that were approximately 165 ft apart and a third pit approximately midway between the first two for the installation of a floor clean out servicing the 4-in. drain pipe. The shored launch pit measured 16 ft long x 8 ft wide x 5 ft deep, while the clean out pit measured 3 ft long x 3 ft wide x 3.5 ft deep.

Due to the presence of the plant’s exterior wall, several block interior walls and racks of shelving filled with product along the intended route, it was not possible for engineers to establish surveyor marks for the GABM theodolite guidance system. Instead, Martin strung a line just below the bar joists of the building’s roof structure along the intended pipe route to establish a perfect 45-degree angle between the new drain pipe and the 8-in. building drain, ensuring a connection using a single 45-degree elbow.
The actual pilot tube micro boring part of the job began in monsoon-like conditions that lasted for two days, with Trenchless Pipe Technologies employees lowering the GABM into the launch pit with Icon technician Robert J. Langenbach and trainer Frank Stillor overseeing its placement and setup.

Once the GABM was in place inside the launch pit, the entire working area was covered with a waterproof awning to allow work to continue in the rain while pumps evacuated any water that entered the launch pit, thus staying on schedule for a three-day completion. One of the unique features of a Bohrtec GABM system is that it can operate in up to a 10-ft water table. “It was comforting to know that, if the torrential rainfall amounts combined with the minimal groundwater in the pit should exceed our pumping capabilities, we could still get pipe in the ground,” Martin said.

To eliminate the possibility of the concrete floor heaving inside the plan, the starting depth of the 4.5-in. diameter pilot tube was 24 in. below finished floor set on a 1 percent grade. There was only a 2-in. margin of error to make the connection because of the elevation of the existing building drain, therefore demanding a precise installation.

After the pilot tube boring phase commenced, the crew was excited to see that the first target — the cleanout pit — had been hit dead center and on grade. “Once we hit that first pit dead on, I knew we were going to be successful unless something unexpected happened, like a mechanical failure,” stated Martin.

Once the full length of pilot tubes had been installed to the reception pit, the crew removed the pilot head and installed the adaptor along with the bursting head. The crew then flooded the reception and cleanout pits, to reduce friction and began the pull back to completion in less than 1 1/2 hours. The entire job took a four-person crew less than two weeks to complete, while the pilot tube and pipe installation took three days.

To repair the approximately 75 ft of 6-in. broken process water pipe, Trenchless Pipe Technologies used a Hammerhead pipe burster and 6-in., SDR 17 HDPE pipe.

First, Martin used video pipe analysis, hydro jet pipe cleaning and vacuuming to determine the exact location of all of the branch connections and where the pipe had broken.

The most difficult aspect of the job was the time allotted for it — a mere 48 hours from start to finish, which required working around the clock.

In order to get ahead of schedule, all of the concrete floor saw cutting for access pits and the 80 ft of rerouted laboratory room drain pipes were completed on the weekend prior to the actual pipe bursting phase. The connection under the lab floor had to be eliminated due to excessive dust and confined working conditions.

Once all of the preliminary work was accomplished, the new pipe was pulled into place in less than two hours, allowing the job to be completed on time.

Martin said that the bottling company was “very satisfied with the outcome of both jobs, especially with the fact that they experienced no delays or lost production time.”
    
Tammy M. George is director of marketing for Trenchless Pipe Technologies Inc., which is based in Newport News, Va.