Award of Excellence: Aurora College Site Remediation

CATEGORY: ENVIRONMENTAL

EBA ENGINEERING CONSULTANTS

In 1996, a large heating oil spill was uncovered during routine excavation work at the Thebacha Campus of Aurora College in Fort Smith, Northwest Territories. It was considered possible that as much as 100,000 litres of heating fuel had been released from an underground storage tank over 20 years.

The quantity of leaked heating fuel was high enough for separate-phase liquid hydrocarbon to pool on the water table and spread beneath the college’s Trades Building. It was also moving down towards a nearby roadway, Raven Crescent, which has buried utilities and adjacent residential properties. Over three hectares was affected by the contamination.

There was concern over the potential health impact on students and staff using the Trades Building and on the nearby residents. Several public meetings were held to inform the users, residents and the general public about site conditions and alternative solutions before a remediation program was finally selected and implemented.

EBA developed the environmental remediation management plan for Public Works and Services of the Government of the Northwest Territories. The two key objectives were to halt the movement of the heating fuel in the groundwater towards the residential area, and to remediate hydrocarbon-impacted soil in accordance with the Territory’s regulations. Over 5,000 square metres of surface area had to be excavated.

Excavating below the water table in permeable soils was a major challenge in terms of replacing the soil and operating equipment safely. The difficulty was overcome by installing a large grid of small vacuum well-points that intersect and overlap, rather than a few larger wells. With over 700 well points, the project is the largest vacuum well point system installed in the Northwest Territories. The size and location of the project meant that much of the equipment had to be mobilized from outside the jurisdiction, including the water treatment technology, groundwater control measures, and some heavy equipment.

The location of the campus provided an on-the-job work opportunity for 20 technology students of the Thebacha Campus Heavy Equipment Program who provided much of the labour related to earth-moving equipment. Eight trainees worked full days, six days a week throughout the summer of 2001. Upon completing the program, all the trainees seeking work were hired for full-time work at diamond mines in recognition of the experience they had gained with heavy equipment during the Fort Smith remediation project.

Treating the extracted groundwater on-site to meet the town of Fort Smith’s sewer use criteria posed a challenge stemming from uncertainties in the hydrocarbon concentration. Project-specific criteria were established in consultation with the town, and all the extracted water had to meet the criteria before being released into the town’s sewer and lagoon treatment systems.

Water treatment and soil remediation

A water treatment system was configured that included a commercial oil-water separator (TORR) that was originally developed for treating oily marine ballast. This was its first use for a site remediation project in Western and Northern Canada, and the system gave a high degree of assurance. The water quality was monitored on site using immunoassay equipment to test the hydrocarbon concentrations. On-site reporting within one hour enabled the operators to make rapid adjustments to the treatment system or store excess water if necessary. The on-site results were subsequently verified in a laboratory.

The excavation and remediation of ground adjacent to the Trades Building also involved dewatering from beneath the building. Upon completion of the excavation work, groundwater monitoring wells that had been constructed through the Trades Building floor showed a great reduction in readily mobile heating fuel. The presence of a small amount of heating fuel was expected as groundwater levels returned to their original levels, and the situation is currently being monitored. Pre- and post-construction dewatering control point surveys on the building indicated no detectable ground settlement.

The involvement of Fort Smith residents, as well as the ready availability of project information, were important aspects of the project. Up to 10 casual labour staff (including several local residents) were employed at different times. This was viewed as an important benefit to the community, as information about the project was freely available through their direct work, as well as through the ongoing public consultations.

Site remediation was successfully concluded in September 2001 followed by a two-year monitoring program. The project had a total budget during 2001 of under $1.5 million. EBA estimated that without the participation of Aurora College trainees, the budget would have been over $4 million. The College benefited because the project provided funding for a new excavator that continues to be used for training.

EBA also provided technical data on ground-effect heat pump technology. Aurora College elected to install the heat-exchange piping while the final remediation was going on and the excavated ground was still being de-watered and accessible. This is the first implementation of ground-effect heat exchange technology for classroom and office space cooling in the Northwest Territories.

Name of project: Aurora College Site Remediation

Other key players: BC Research, Groundwater Control Systems, Earth (Canada) Corp., Enviro-Test Laboratories, Donald Sutherland, P.Eng.