HDD Helps to Expand a Municipal Water System in Thunder Bay, Ontario
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 createdthrough the amalgamation of the former Cities of Port Arthur and Fort William.The amalgamation brought with it the requirement to join two completely separatewater supply and delivery systems into one common operation.
Thisprocess has been on going for several decades and with the recent decision toutilize a single water source to supply the entire city, a large number ofinfrastructure projects have been initiated to complete this task. The City ofThunder Bay is bordered on its south side by the Kamanistiquia River. Thelocation of this river presented an obstacle for the installation of a 30-in.diameter water line, which would supply water to a newly constructed waterreservoir located approximately 2.5 miles south of the City. An engineeringinvestigation was done to determine the feasibility of crossing the river at therequired location utilizing horizontal directional drilling (HDD).
Theengineering study confirmed the suitability of directional drilling for both thesoils encountered and ability to provide adequate entry and exit locationswithin the project alignment and easements. Upon completion of the tenderingprocess, LTL Contracting Ltd. in conjunction with LTL Directional DrillingServices Ltd., both based in Thunder Bay, were awarded the contract to install1,300 ft of 30-in. diameter water main by HDD.
LTL Contracting Ltd.,founded 25 years ago, specializes in water main installations and municipalinfrastructure including sewer systems, lagoon construction and remoteconstruction requiring the development of ice road for access, air lifting ofequipment and personnel and utilization of barge services in remote areas ofHudson Bay. LTL Directional Drilling Service Ltd. was founded four years ago tomeet the growing needs of municipal water and sewer systems for a trenchlessalternative to traditional open-cut methods of installation.
During latefall 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 upthe drill and recycling system on the north side of the river, situated 65 ftabove 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 ftfrom the river’s edge.
Directly along the east side of the bore, Highway61 and the bridge over the Kamanistiquia River provided the first barrier. Theprovincial Ministry of Transportation had great concerns over safety andrestricted access to the worksite. Therefore access and the drill lay down areaon the north side of the river was gained through a cemetery.
It waswith 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 thenarrow corridors of the cemetery to its lay down area on the edge of thecemetery.
The south side access was strictly limited to vehicles on a timedschedule and restricted to regular movements of vehicles such as float trucks,vacuum excavators etc. Each of these movements would require preplanning andcoordination with the Ministry of Transportation.
As expected, thecemetery was particularly a sensitive area to work in and around. Severalfunerals took place throughout the cemetery and directly adjacent to theworksite. To respect the family members and friends of the deceased, the projectwas temporarily halted, with all equipment shut down and work crews removed fromthe site prior to arrival of the funeral precession. This did create significantdelays and additional work restarting equipment and scheduling personnel, but itwas 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 quicklychanged as the crew approached the river. Along the north river edge, boreholelogs and soil samples showed a drastic change in soil. Large areas of loose tovery loose medium and course-grained sands were encountered. During review ofthis area, the sand proved to contain few fines and was unstable. This was ofmost concern and the mud program was focused on this area of the bore. As thesampling program proceeded southward across the river, silts became present inthe sand and the borepath would then pass through silty clays prior to exiting.Baroid Industrial Drilling Products provided great assistance with the planningof the bore and mud program including onsite monitoring of the program duringthe bore. This was essential given the sandy conditions encountered.
Correct project setup was crucial. LTL had a confined working space inthe cemetery and limited access to the exit pit, which meant vacuum trucks couldnot freely access the site. The mud management plan was therefore a key factorin project setup. To transfer drilling muds from the receiving pit, LTLinstalled two mud transfer lines under the river from the exit pit to a mudcontainment pond at the drill. These two lines were installed by HDD, as opposedto simply laying the lines aboveground. This was required to provide freezeprotection as temperatures during the project were dropping well below freezing.It would have been difficult to prevent two 1,300-ft transfer pipes fromfreezing if they had been placed aboveground.
LTL crews started drillingon Nov. 22, 2004. Temperatures at this time were ranging from 41 to –13 F andwith the frigid conditions, extreme precautions were taken to ensure allequipment, pumps and muds continued to function and flow. This included heatingand insulation protection of the recycler, drill rods, mud transfer piping andtooling. As mud flow into the mud containment pond slowed, ice quickly formingon the surface was a constant reminder on how critical it was to maintain ourheating systems. The initial 12-in. pilot bore proceeded slower than anticipatedmainly due to steering difficulties encountered in soil regions with loosematerial even at depths of 26 ft below river bottom. Upon completion of thepilot bore, the hole was opened in two intervals prior to final product pullback.
With no further drilling problems encountered, preparations weremade to install the product pipe. This included final fusing of pipe segmentsand moving the product into place on the south side. With minimal clearing oftrees ample space was available for assembly of the product pipe prior to finalpull back.
With the product pipe being installed, crews were kept busymaintaining the pit pumps, tooling and mud transfer piping from freezing astemperatures overnight were dipping below –4 F. Pullback proceeded as scheduleduntil freezing temperatures and equipment fatigue slowed the supply of mud tothe recycler. With approximately 330 ft left to pull back, a temporary shutdownof the drill was required to repair the mud pumps and mix new batches of mudwhile the recycling operation was put back in operation. After a one-hour shutdown, LTL attempted to pull the product pipe with no success. With pullbackpressures exceeding its capacity to pull, the crews were forced to push from theother end of the pipe. With two large excavators and one large loader already onthe south side to handle the product pipe, LTL had a quick turnaround time tosetup both excavators and the loader to assist the drill with freeing of theproduct pipe.
Once free and moving again, pullback pressures droppedsignificantly, allowing the drill to complete the pullback within 12 hours fromthe start time. Vermeer Sales and Service was onsite at this time and providedexcellent assistance in maintaining the drill during tough operating and coldweather conditions. It was the dedication of the LTL crews, combined with strongsupport from its suppliers that lead to the success of this project.
