The Athabasca River flows from the Columbia Glacier of the Columbia Icefield in Jasper National Park in Alberta.

The crossing includes one 1,350 metre and one 1,200 metre 900 mm DR11 HDPE pipes installed by horizontal directional drilling (HDD). The Regional Municipality of Wood Buffalo (RMWB) Project Team consisting of Stantec Consulting Ltd., Complete Crossings Inc. (CCI), Thurber Engineering Ltd., Consun Construction and Direct Horizontal Drilling Inc., encountered major challenges that had to be overcome to allow the project to proceed successfully.

The geological conditions included gas pockets detected during the geotechnical investigations resulting in the need to implement significant gas mitigation strategies such as installing surface casing and grant rotating heads most commonly used in the oil and gas drilling industry. The rig location was also equipped with a 24 hour gas monitoring system to ensure the safety of teams involved. The fractured limestone layers near the river surface also presented concerns for possible drilling mud releases to the surface or into the river. Large setbacks from the river banks and a drill depth of over 40 metres under the river bottom were employed to accommodate the concerns. The large depths resulted in the need to perform a wet product pipe pull, the pipe was filled with water to overcome buoyancy effects. Furthermore, the Athabasca River is heavily scrutinised by the environmental agencies and First Nations, so a full scale turbidity monitoring program had to be included from the onset of drilling operations.

HDD contractors generally work in the highly risk oriented world of major oil and gas exploration, where the oil and gas companies accept high levels of risk. The HDD companies normally pass any risk of drilling on to their clients. In contrast, municipalities do not usually assume project risk as they work with public funds in strictly controlled budgets. The challenge to merge the two environments required a detailed Risk Assessment Program be undertaken to identify the specific risks, responsibilities, mitigative measures as well as the potential value of the risk occurrence. The process allowed the RMWB to assign specific contingency amount to account for their portion of the risk.

One major challenge occurred when, just prior to the start of construction, a major construction conflict with the adjacent major highway upgrade required the design team to design an alternative river crossing route in a matter of weeks. Significant rights-of-way and work space challenges had to be overcome as numerous landowners and conflicts presented themselves very late in the design process.

The significant risks identified for the project necessitated the implementation of a 24 hour per day full scale drilling monitoring program which was provided by CCI. This program provided the RMWB with the assurance that all drilling related mitigation strategies were implemented and confirmed throughout the construction period. With the logistical issues surmounted, the various risks identified and mitigation strategies implemented, the project was launched in June 2009 and the final line pull completed in early November.

Overcoming obstacles underground

Direct Horizontal Drilling had to overcome many obstacles on this project. The first obstacle that had to be dealt with was the potential of encountering pockets of high pressure methane gas. This was completed with the installation of surface casing, a grant rotating head and stand alone monitors.

The next challenge was the pilot hole guidance across the river. With very little land in which to set a surface tracking coil, a barge was used as a base for a solenoid beacon system to track the drill head across the water. In the end, it was the combination of tracking systems and azimuth heading calculations that guided the drilling head to a successful punch out.

When the reaming was complete there was a wire attached to the first HDPE product line pipe, as it was being installed, which was to act as ranging wire for the Para Track II guidance tracking for the second pilot hole. With the ranging wire in the first hole the guidance technician was able to tell distance and direction from this hole while drilling the second pilot hole to ensure adequate separation.

The final challenge was buoyancy control. With the product line being made of HDPE, buoyancy water was to be added to the inside of the pipe to reduce the positive forces while it was being pulled into the hole. To overcome the challenge of delivering water to the leading end of the product pipe, a four inch HDPE pipe was pulled inside the 36 inch product line. Continuous operation was required to keep the fill water from freezing during the sub zero temperatures.

To conclude, both product lines were pulled in successfully, safely and with minimal pull forces.