November 26, 2009

FEATURE | Demolition & environmental engineering

Assessment tool helps keep costs down in remediation of Quebec fuel depot

JEAN SORENSEN

correspondent

VANCOUVER

An assessment tool which provides civil, geotechnical and environmental consulting services internationally, combined with super oxygenated water process, led to a low-cost, efficient and natural means of remediating a 40-year-old Quebec-based former petroleum depot.

Known as GoldSET and designed by Golder Associates, the application and technology won recognition at the Canadian Urban Institute’s 2009 Canadian Brownfields conference held in Vancouver recently. Golder Associates received a Brownie Award in the category of sustainable remediation technologies and technological innovation.

The Victoriaville petroleum depot, used for four decades but shut down in 1980, had consisted of above-ground storage tanks and associated piping, loading platform and warehouse plus a nearby storm water sewer line.

The centrally located site was needed for housing. The challenge was finding an economical yet effective way of reducing years of contamination, mainly centred in a 1,500 square meter area.

“The best remedial option had to be chosen by the Golder team,” said Robert Noel de Tilly, remediation specialist in the Montreal office.

The quickest solution would have been simply excavation and trucking out the soil but it would also increase the environmental footprint of the clean-up and disrupted the natural eco-systems in place on the site.

Golder deployed GoldSET instead, a computer program which considers a triple bottom line (financial, social and economic) to evaluate different remediation processes. It helps identify optimal solutions for decision-making based on the principles of sustainable development. The chosen remediation process had to address two issues: the hydrocarbons in the soil plus mitigate any water seepage from contaminated sites into a nearby sewer line.

GoldSET found removing the contaminated soil, aside from the sustainability drawbacks, was a quick but costly fix when weighed against the land value.

GoldSET identified another more feasible option. It was a slower process but super-oxygenated water, a bio-remediation treatment, realized the best triple line objectives.

Super oxygenated water treatment worked with the natural ground elements on site to remove contamination. “It is low cost technology and low in energy consumption and it is an insitu treatment,” said Noel de Tilly. “You treat the soil in place.” The soil is not excavated, even for treating on site as some processes allow, thus reducing trucking costs. Super-oxygenated water is a process of enriching of the oxygen content in a water line and then injecting this highly oxygenated liquid into wells, which allow it to seep into the contaminated ground.

Normally, water has 7-8 PPM of oxygen but super-oxygenated water increases the content to 40 PPM. The oxygen increases the bacterial activity normally found in the ground causing it to multiply. The bacteria then devour the hydrocarbon residuals as food. “They can break down the hydrocarbon chain until there is no chain,” he said. The Golder installed system (which included an oxygenation station plus piping) feeds into 20 evenly-spaced wells throughout the contaminated area.

To contain the ground water plume from going into a nearby sewer, they installed a pumping system in front of the line and it prevented any run-off with contaminates entering the sewer. “That would be a further cost to the client,” said Noel de Tilly.

The super oxygenated water remedition system has been in place for a year generating optimum results while there has been no contamination of the sewer within that period. Once the oxygenation has been complete, Noel de Tilly said, this system – which preserves natural ecosystems on site – can easily be removed and the site can progress towards development.

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