|Client:||SNC Lavalin Nexacor|
|Services:||Emergency response and remedial oversight|
XCG was retained by SNC Lavalin Nexacor, on behalf of Bell Canada, to provide engineering services to support the underground fuel storage tank replacement and remediation activities at the Bell Mobility facility (facility) located at 70 Queen Elizabeth Boulevard in Toronto, Ontario (site).
The purpose of the tank replacement and remediation activities were to remediate diesel fuel-related impacts to soil and groundwater resulting from an accidental release of diesel fuel during refuelling activities at the site; and to replace the 25,000-litre UST located north of, and adjacent to, the northeast corner of the site building. The release resulted in approx. 6,000 litres of diesel fuel discharging into the gravel backfill and bedding of the above-noted UST. The release occurred on February 10, 2009 and emergency procedures commenced on February 10, 2009 to contain the spill and recover as much diesel fuel as possible.
Emergency response procedures were supervised by XCG. The removal of spilled diesel fuel and groundwater (short-term remedial measures) continued until remedial construction commenced in order to create and maintain an inward groundwater gradient to limit migration of impacts.
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Investigation & Remediation
XCG developed a work plan and completed a soil and groundwater investigation including test pits, boreholes and groundwater monitoring wells, to determine the magnitude and extent of diesel fuel-related impacts to soil and groundwater resulting from the accidental release. Based on the results of the investigation, XCG completed a review of options to address soil and groundwater impacts related to the release of the diesel fuel. The preferred option was the removal of the existing tank, excavation, removal and disposal of impacted backfill, bedding, and soil and installation of a new tank and selected components from the existing tank installation.
XCG completed detailed design and specifications, based on Bell Guidelines, for the replacement UST and appurtenances. XCG provided tender and construction administration, and, construction inspection for the preferred remedial option. This included liaison with the Technical Standards & Safety Authority to secure the required approvals.
During the remedial construction activities, XCG identified that the UST excavation was completed with a concrete base slab and the vertical sidewalls of the excavation were reinforced with a low strength asphaltic concrete. As a result, a trench box was installed within the excavation to manage potential safety issues related to slope stability during construction.
A supplementary remediation program was recommended based on the limited soil excavation due to the condition of the UST excavation, and the native geology comprised of fracture bedrock in the shallow subsurface. During installation of the new UST, four remediation wells were installed in the corners of the excavation. Subsequent to completion of the new UST installation, XCG collected baseline groundwater samples from the monitoring wells. Following completion of the baseline groundwater sampling, oxygen release compound (ORC®) filter socks by Regenesis were installed in each of the four remediation wells. Monitoring was continued for approximately 6 months until laboratory analytical results indicated that impacts were confirmed to be below the respective MOE groundwater quality criteria.
Subsequent to the completion of all activities XCG prepared a remedial action plan report summarizing all of the work completed at the facility related to the accidental release of diesel fuel.