LTL Group Thunder Bay, Ontario, Canada

The City of Thunder Bay, situated on the rugged north shore of Lake Superior, is home for approximately 130,000 residents. In 1970, the City was created through the amalgamation of the former Cities of Port Arthur and Fort William. The amalgamation brought with it the requirement to join two completely separate water supply and delivery systems into one common operation.

This process has been on  going for several decades and with the recent decision to utilize a single water source to supply the entire city, a large number of infrastructure projects have been initiated to complete this task. The City of Thunder Bay is bordered on its south side by the Kaministiquia River. The location of this river presented an obstacle for the installation of a 30-in. diameter water line, which would supply water to a newly constructed water reservoir located approximately 2.5 miles south of the City. An engineering investigation was done to determine the feasibility of crossing the river at the required location utilizing horizontal directional drilling (HDD).

The engineering study confirmed the suitability of directional drilling for both the soils encountered and ability to provide adequate entry and exit locations within the project alignment and easements. Upon completion of the tendering process, LTL Contracting Ltd. in conjunction with LTL Directional Drilling Services Ltd., both based in Thunder Bay, were awarded the contract to install 1,300 ft of 30-in. diameter water main by HDD.

LTL Contracting Ltd., founded 25 years ago, specializes in water main installations and municipal infrastructure including sewer systems, lagoon construction and remote construction requiring the development of ice road for access, air lifting of equipment and personnel and utilization of barge services in remote areas of Hudson Bay. LTL Directional Drilling Service Ltd. was founded four years ago to meet the growing needs of municipal water and sewer systems for a trenchless alternative to traditional open-cut methods of installation.

During late fall 2004, LTL crews commenced work on the installation of 1,300 ft of 30-in. diameter HDPE. Planning proved to be the most critical phase of the project, given several restrictions with site access and setup. The plan was to set up the drill and recycling system on the north side of the river, situated 65 ft above river level, and drill the pilot bore directly south across the river, approximately 26 ft below the river bottom and exiting on the south side 230 ft from the river's edge. Directly along the east side of the bore, Highway 61 and the bridge over the Kaministiquia River provided the first barrier. The provincial Ministry of Transportation had great concerns over safety and restricted access to the worksite. Therefore access and the drill lay down area on the north side of the river was gained through a cemetery.

It was with great care and consideration that LTL mobilized a Vermeer D150x300 drill, 6,000-gal Tri-Flo mud recycler, pumps, drill rods and drilling muds through the narrow corridors of the cemetery to its lay down area on the edge of the cemetery. The south side access was strictly limited to vehicles on a timed schedule and restricted to regular movements of vehicles such as float trucks, vacuum excavators etc. Each of these movements would require preplanning and coordination with the Ministry of Transportation.

As expected, the cemetery was particularly a sensitive area to work in and around. Several funerals took place throughout the cemetery and directly adjacent to the worksite. To respect the family members and friends of the deceased, the project was temporarily halted, with all equipment shut down and work crews removed from the site prior to arrival of the funeral precession. This did create significant delays and additional work restarting equipment and scheduling personnel, but it was also necessary.

The planned borepath would pass through a variety of soil types. The north side of the river consisted of silt and silty clay, which quickly changed as the crew approached the river. Along the north river edge, borehole logs and soil samples showed a drastic change in soil. Large areas of loose to very loose medium and coarse-grained sands were encountered. During review of this area, the sand proved to contain few fines and was unstable. This was of most concern and the mud program was focused on this area of the bore. As the sampling program proceeded southward across the river, silts became present in the sand and the borepath would then pass through silty clays prior to exiting. Baroid Industrial Drilling Products provided great assistance with the planning of the bore and mud program including onsite monitoring of the program during the bore. This was essential given the sandy conditions encountered.

Correct project setup was crucial. LTL had a confined working space in the cemetery and limited access to the exit pit, which meant vacuum trucks could not freely access the site. The mud management plan was therefore a key factor in project setup. To transfer drilling muds from the receiving pit, LTL installed two mud transfer lines under the river from the exit pit to a mud containment pond at the drill. These two lines were installed by HDD, as opposed to simply laying the lines aboveground. This was required to provide freeze protection as temperatures during the project were dropping well below freezing. It would have been difficult to prevent two 1,300-ft transfer pipes from freezing if they had been placed aboveground.

LTL crews started drilling on Nov. 22, 2004. Temperatures at this time were ranging from 41 to -13 F and with the frigid conditions, extreme precautions were taken to ensure all equipment, pumps and muds continued to function and flow. This included heating and insulation protection of the recycler, drill rods, mud transfer piping and tooling. As mud flow into the mud containment pond slowed, ice quickly forming on the surface was a constant reminder on how critical it was to maintain our heating systems. The initial 12-in. pilot bore proceeded slower than anticipated mainly due to steering difficulties encountered in soil regions with loose material even at depths of 26 ft below river bottom. Upon completion of the pilot bore, the hole was opened in two intervals prior to final product pull back.

With no further drilling problems encountered, preparations were made to install the product pipe. This included final fusing of pipe segments and moving the product into place on the south side. With minimal clearing of trees ample space was available for assembly of the product pipe prior to final pull back.

With the product pipe being installed, crews were kept busy maintaining the pit pumps, tooling and mud transfer piping from freezing as temperatures overnight were dipping below -4 F. Pullback proceeded as scheduled until freezing temperatures and equipment fatigue slowed the supply of mud to the recycler. With approximately 330 ft left to pull back, a temporary shutdown of the drill was required to repair the mud pumps and mix new batches of mud while the recycling operation was put back in operation. After a one-hour shut down, LTL attempted to pull the product pipe with no success. With pullback pressures exceeding its capacity to pull, the crews were forced to push from the other end of the pipe. With two large excavators and one large loader already on the south side to handle the product pipe, LTL had a quick turnaround time to setup both excavators and the loader to assist the drill with freeing of the product pipe.

Once free and moving again, pullback pressures dropped significantly, allowing the drill to complete the pullback within 12 hours from the start time. Vermeer Sales and Service was onsite at this time and provided excellent assistance in maintaining the drill during tough operating and cold weather conditions. It was the dedication of the LTL crews, combined with strong support from its suppliers that lead to the success of this project.

Jamie Geils, C.E.T., is co-founder of LTL Directional Drilling Services, Thunder Bay, Ontario, Canada.