Shell Canada has several options for dealing with contamination caused by a leak at its Granville and West 41st gas station, according to the Ministry of Environment.
Options include doing nothing but monitoring contamination while it naturally degrades if the company demonstrates the plume is stable and not growing, said Mike Macfarlane, senior manager for the environment ministrys land remediation section.
Proactive options range from introducing chemicals into the plume by injection to enhance biodegradation, using vapour extraction systems to suck up ground water and running it through an afterburner to burn off the volatile, introducing pumping stations to make sure contamination doesnt migrate further or a combination of these measures.
Contamination was discovered when the station was being rebuilt in 2006. Testing since then revealed at least 78 neighbouring properties have been affected72 residential and six commercial ones. Much of the contamination is 60 feet below ground.
[Shell has] indicated it will be a combination [of measures], that they will be doing some component of risk management, but the early discussions are we should be seeing a plan maybe by the fall or the winter, Macfarlane said.
What Shell has to look at is what would be the effectiveness of each of those [options] given consideration of the substrates that theyre dealing withhow deep it is, the size of it. They have to evaluate the range of options that could be done and come up with a strategy they think is workable.
The area of contamination from the Granville and 41st source goes a half a block south along Granville and extends west towards Marguerite Street.
Reading numbers vary across the contamination area. Close to the service station the numbers are quite high and at the leading edge of the plume theyre delineating is fairly low. What theyre looking at is how much over the drinking water number they are. It ranges from near the service station at 10 times to 100 times the drinking water standard, whereas its quite lowtheyre at almost compliance with the drinking water number at the boundary, Macfarlane said.
Shell plans further drilling and testing in coming months to pin down the boundary of contamination. Macfarlane said the problem is not a major concern because the areas not currently being used for a drinking water supply.
Theres no risk associated with these levels or vapours that would come off the water table and migrate into indoor space, he added.
Companies arent fined for leaks, but non-compliance with regulations is an offense such as failure to file notice with the ministry for the start and completion of independent remediation of contamination.
Macfarlane said the length of time between the discovery of contamination in 2006 and the ongoing investigation of its limits is likely partly due Shells allocation of its financial resources and competition for drilling equipment.
Everybodys after the drill rigs. Theres a finite number of these around the province. Ive got one this week up at Cowichan doing drilling. So they have to do the same thing. Theyre booking time with consultants that do the work and the companies that have the equipment to do the investigation and remediation.
Theres no deadline for completing the work, unless its a high-risk situation, but the ministry asks for a schedule and tries to keep the company to it.
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