Turner Valley Gas Plant
Risk Assessment: Approach of Choice
Early in 1998, a team of experts from O’Connor Associates Environmental Inc. came to the Turner Valley Gas Plant site and took a number of soil and groundwater samples which were tested at labs in the city.
It wasn’t an unusual occurrence at the site, the first natural gas plant in the province and a cornerstone of Alberta’s early oil and gas history. As residents in the area knew well, tests and reports of all kinds had been done there since 1985, when the plant was decommissioned following 65 years of being in business. Professionals came out and assessed contamination, monitored air quality, measured mercury in the soil, checked to see if there was seepage into the nearby Sheep River, and made remediation plans.
But the O’Connor team’s purpose was more than measuring contamination from left over oil and natural gas by-products: They were the advance guard of the reclamation and development plan, sent to uncover what were the remaining potential contaminants on site. They needed to determine who or what could be affected by the contaminants and how or what could be done to make the historic facility safe for staff and visitors.
In techno-speak, they were conducting a risk assessment for "receptors" at the site, with receptors being people, plants and animals.
"The risk assessment helped determine the least interventionist approach to conserving the site," Ian Clarke, the regional historic sites manager, says. "The other option would have been a total reclamation, getting rid of the buildings and so on. We were bound to clean it up."
A planning committee of a dozen people, including local residents, and municipal, provincial representatives, was struck to follow the risk assessment. It took 18 months to complete and followed the guidelines set out by Health Canada, Canadian Council of Ministers for the Environment, and the United States Environmental Protection Agency.
The process started with the environmental team identifying specific potential contaminants from samples and previous tests that could impact human and ecological health (assuming the removal of potential continuing sources of contamination like the underground storage tanks).
Since the site would be used as a tourist facility, commercial standards of exposure were chosen rather than residential ones, meaning data that was incorporated was based on being on the site during a working day, rather than living there all day and night.
The team took groundwater samples from north of the condensate tanks, east of the scrubbing plant, in the ditch north of the office/lab building, and south of the welding shop. Soil samples were taken from the bagging plant, the west boundary of the Sulphur Block, and southeast of the site’s storage tank complex.
What the team found was that most of the industrial contaminants were not at dangerous levels, but total volatile hydrocarbons (TVH), total extractable hydrocarbons (TEH), and mercury levels in some of the onsite soil were higher than acceptable norms.
The main way people would come into contact with TVH and TEH would be by inhaling them while indoors. The Risk Assessment determined people and animals like voles and rabbits could come into contact with mercury through direct skin contact, ingesting soil contaminated with it, or inhaling mercury fumes.
Once complete, the assessment morphed into a risk management plan which outlined six major items that needed resolution before opening the site to full-time staff and the public. Topping the list was getting rid of any damaged material that contained asbestos, which can cause serious diseases in the lungs and other organs through prolonged contact.
The next highest priority would be to physically clean up the site and remove hazards like broken glass and unsecured ladders, and biohazards like animal and bird dung.
Minimizing potential exposure to mercury inside the buildings and in soil on certain parts of the gas plant was third and fourth on the list. Minimizing exposure to soil high in TVH and TEH followed.
Finally, the team said exposure to sulphur-soaked soil and investigation of lead-based paint should be looked after, and aesthetic concerns around the groundwater seeps required attention before opening the full facility as an historic site.
The risk management plan offered long-term as well as immediate actions, including implementing an annual monitoring program to ensure that site conditions didn’t deteriorate over time.
For the residents of the Turner Valley area and for Albertans in general, both the risk assessment and the risk management plans were vital steps toward ensuring a safe historic site.
