Turner Valley Gas Plant Provincial Historic Site

Technical Clean-up Summaries

Learn about what has been done to help clean up the Turner Valley Gas Plant:

  • Asbestos

  • Containment System

  • Mercury

  • Risk Assessment

  • Sulphur

  • Asbestos

    Since the Turner Valley Gas Plant was first considered as a possible tourism destination, extensive asbestos abatement work has been carried out. In 1995, the cost of removing or containing it safely was estimated at $40,000 because the intent then was to open only four buildings to the public.

    By the time the abatement work was done in 2002, the scope had expanded to 20 buildings plus a number of stand-alone items such as pipes and vessels.

    Qualified contractors removed all seriously damaged asbestos, and where the damage was minor, wrapped it in aluminum or canvas, sealed it, and painted it so the plant would look as it had when it was last used.

    The job also included removing some mercury and cleaning up biohazards, such as bird droppings, that had collected while the buildings sat abandoned.

    The tab came in at $335,000, plus $22,000 for independent air monitoring and inspection.

    There’s plenty of asbestos remaining both inside and outside many buildings on the site. But according to Colin Wildgrube, senior building environment specialist for the technical services branch of Alberta Infrastructure and Transportation, as long as it remains undisturbed and undamaged, it poses no risk to visitors.

    For 25 years, the branch has been contributing the most up-to-date asbestos-handling procedures to the Alberta Asbestos Abatement Manual. It oversaw the removal and encapsulation of asbestos at the gas plant.

    The manual is available for download from the publications page of the Jobs, Skills, Training and Labour website (www.employment.alberta.ca) and typing "asbestos" into the search line. The manual specifies:

    • In buildings being altered or renovated, any materials having the potential for releasing asbestos fibres in the area of alteration or renovation must be encapsulated, enclosed or removed.
    • In buildings to be demolished, materials having the potential for releasing asbestos fibres must first be removed.

    Since 2002, an asbestos management plan--required for any site containing asbestos--has called for a thorough annual inspection, which is done in the early spring to make sure any possible damage is repaired and the entire site is in a safe, sealed condition before public tours start.

    "You could just keep rewrapping it. As long as it’s not severely damaged you could keep it indefinitely. There are lots of government buildings that have asbestos in them that are kept in good condition with a management plan." said Wildgrube.

    Culture department restoration officer Ron Johnson does the inspections and oversees any needed repairs. This year he found insulation that had peeled off a tank in a small auxiliary building that had never even been unlocked before and had the repairs made. "The whole point is to get everything in tiptop condition," Wildgrube says. "Right now we’re comfortable with what’s being done there and we have no concerns."

    Alberta Environment and the Calgary Health Region have advised that they have no concerns with asbestos at the site.

    Containment System

    Not to diminish the engineering elegance of the groundwater gathering and flood protection system newly installed at the historic Turner Valley Gas Plant . . . but it really is just a big bathtub, a $7-million, 15.4-hectare bathtub with a fancy drain.

    The project manager who built it says so.

    The price tag includes design, construction and any operating costs the structure incurs in the next two years. Its purpose is to channel all of the water that flows through and over the site of the decommissioned gas plant plus remove the hydrocarbons contaminating the soils and groundwater before the water spills into the Sheep River.

    At the same time this highly-engineered bathtub controls the flow of the water within the site, it protects against the river raging past each spring. The need for groundwater containment and cleaning became urgent when the Sheep River flooded three times in 2005. Torrents of water severely eroded the river bank and leached out hydrocarbons that had leaked from the plant long ago.

    The base of the bathtub is bedrock, which is a relatively impermeable shale in this area. It is walled on its downhill sides with bentonite, to separate the site from the river. Bentonite is a highly-absorbent Wyoming clay. When water is stirred into it, it swells dramatically and becomes impermeable. Excavation to build the bentonite wall so it could form a seal with the uneven bedrock reached as deeply as five metres below the soil surface.

    Just as a bathtub slants toward its drain, the sloping bedrock and the bentonite wall funnel all of the surface and groundwater into a state-of-the-art "treatment corridor" built at the lowest point adjoining the river. That "treatment corridor," a row of cleaning systems, removes the hydrocarbons so the water draining into the Sheep River is clean.

    It may actually be cleaner than water in the area has ever been. Historians say it was naturally occurring gas and oil seeps that attracted investors and led to the drilling of the Dingman 1 natural gas well, which blew in dramatically on May 14, 1914.

    The success of that and other wells gave birth to the energy industry in Alberta. The federal government has declared it a national historic site, and the provincial government has been working to reclaim the site and open it as a tourist attraction.

    The principles incorporated to channel and clean the water have been used in other places, says Bruce Dewar, Project Manager, Environment, Stantec Ltd., but this installation is innovative in the way it applies those principles to the complexities of the site, and in the combination of passive and active water treatment technologies.

    The complexities:

    • Separated from the gas plant property by only a chain link fence, there stands a Talisman Energy Inc. sour gas compressor station which is serviced by active high-pressure underground pipelines.
    • Utilities lines belonging to the Town of Turner Valley underlie Sunset Boulevard along the northern boundary of the gas plant site.
    • The bedrock, largely covered by a layer of gravel, is a series of three shale terraces rising unevenly 10 metres from the meander of the river, which forms a J as you face north. Shale is a common, fine-grained, sedimentary rock whose original constituents were clays or muds. Any fissuring tends to be parallel to the base layer. Shale is readily seen across the river on the south escarpment.

    The bedrock here is discharging water, contributing water into the groundwater rather than having water on top of it discharging water into the bedrock," Dewar says. "Different hydrostatic pressures make it discharge at different places. This is also contiguous bedrock. There are not a whole lot of cracks or fissures. It’s hard shale, relatively impermeable, very uniform."

    The total length of all the legs of bentonite dyking is approximately 750 metres. Because the Talisman battery station has live underground high-pressure gas production lines, Stantec could not excavate to encircle the whole gas plant property with bentonite. The engineering team chose to use weeping tile -- actually a perforated pipeline that water would drain into -- to demarcate the northern boundary.

    "We wanted to put it along the northern edge of the middle terrace, but we couldn’t excavate to the depth we wanted because of all the live lines there. If we moved it south would it really serve its purpose? So we talked to the Town, which owns utilities under Sunset Boulevard (to the north of the Talisman plant). The Town wanted to upgrade its utilities. We said if we go in and put the line under the road, we’ll help you and upgrade the utilities at the same time. We put it as deep as possible on the clay layer under the gravel, directly underneath their new sanitary line."

    The thinking is that it may well take a year for water to cross the site. Rate of flow depends on the amount of water in the ground, the amount of precipitation, and the kinds of soils. The general slope on the property is from south to north, in conjunction with the river.

    Using only gravity, the weeping tile and bentonite walls direct the water towards a three-stage "treatment corridor" which has been built with extra space available for any advances in technology that may yet be developed.

    Stage 1 is a skimmer that separates out the heavier hydrocarbons, the oils visible floating on the water -- F1s and F2s, in the jargon.

    Stage 2 is an air sparger. It is a grid of 5-cm pvc piping that pumps air into the water, like a fish tank aerator. Its purpose is to speed up the natural evaporation of any light hydrocarbons and add oxygen to support the growth of microbes which eat hydrocarbons. Among the light hydrocarbons may be low concentrations of benzene, toluene, ethylbenzene and xylene, which are known collectively as BTEX.

    The air sparger compartment contains "geotextile" curtains, made of a material which allows the water to pass through but catches the gas-gobbling microbes and any metals that precipitate out of the water, to stop them from flowing into the following compartment.

    Stage 3 contains two activated carbon filters, like an industrial version of a kitchen water filter. The carbon captures the polycyclic aromatic hydrocarbons, chemical compounds primarily formed by incomplete combustion of carbon-containing fuels, but also found within crude oil.

    "Water passes over the carbon matrix and any hydrocarbons not volatilized (evaporated) will preferentially stick to the carbon, versus staying in the water," Dewar says. "Carbon has binding sites, a million little cracks and crevices, and an ionic charge difference between particle and carbon" makes the particles adhere to the carbon.

    Tubs filled with brine sit on top of the carbon cells to force the water down through them and provide insulation against freezing. The corridor has been designed to work year-round; time will tell whether water flow is little enough that it can be shut down during the winter to save energy. It will be carefully monitored through the first two years to develop benchmarks.

    There’s also an insulated lid over the entire corridor, which will let in precipitation but serve to keep out wayward tourists, animals and autumn leaves.

    To accommodate varying conditions, valves at each end either passively or actively control the rate water moves through the corridor. Should spring floodwaters rise to the level of the outlet, a one-way valve will prevent river water from flowing backwards into the corridor.

    Remote instrumentation is in place to alert Stantec of any problems, and technicians visit periodically to collect water samples from the monitors stationed in each of the treatment corridor compartments.

    Sampling and analysis has shifted from every week to every four because initial results were excellent. Analysis, including for the various hydrocarbons and mercury, covers almost 80 characteristics (parameters is the jargon), from ionic balance to pH and turbidity. Results are measured against both the Canadian Drinking Water Guidelines and the Canadian Council of Ministers of the Environment Guidelines for the Protection of Aquatic Life. Monitoring will continue far into the future.

    Should reclamation of the plant and property be deemed adequate for the plant to be safe as a public venue, visitors will stroll the grounds on a blend of native grasses.

    The security fence is on the inside of the bentonite wall, so area residents will have access to a five- to six-metre-wide pathway along the top of the wall.

    Rafters floating down the river will see only the intimidating armour of riprap protecting the retaining wall, standing half a metre taller than the highest floodwaters reached in 2005.

    Mercury at the Plant – a Thing of the Past

    The Turner Valley Gas Plant was among the earliest gas processing facilities in Alberta. When Stantec went to the Plant in 2002 to help remediate the historic site, they knew mercury was present because of the mercury control switches in the dozens of gauges used throughout the complex.

    Little was known of the health hazards around mercury until the 1970s. It was spilled, workers breathed its vapours, and broken gauges were generally disposed of without containment.

    Higher levels of mercury have been found near the buildings on the gas plant site, rather than spread across the whole property.

    "The reason for that, we think, is that most of the mercury was used in pressure gauges inside the buildings," Stantec project manager Bruce Dewar says. "The thought is that when they’d break, workers would either chuck the mercury out the door or it would cling to their boots and they would track it out."

    After the gas plant closed in 1985, the Alberta government resolved to clean up the Turner Valley Gas Plant and open it as an historic site. Mercury remediation was high on the to do list.

    Mercury is considered a toxic substance, and studies done in the 1990s indicated there were certain "hot spots" at the plant that had to be cleaned up to reduce the risk to visitors and those who would staff the site.

    Intact mercury gauges were located, drained and disposed of in the Gasoline Plant, the Scrubbing Plant, and the Compressor Plant as part of initial plans to clean up the location in 1999.

    Stantec came in to refine the remediation process, focusing on contamination outside on the site, and inside the plant’s buildings.

    Using criteria established by Health Canada, Canadian Council of Ministers for the Environment, and the United States Environmental Protection Agency, the Stantec team took samples from inside buildings over the summer of 2002, and soil samples from along the tour pathway in the fall of 2003.

    Inside, the concern was around breathing in mercury vapours from residue left in the floor, walls and ceiling. Air sampling found elevated levels in the fractionating building, scrubbing plant, the compressor plant, the sulphur plant, and the gasoline plant.

    The buildings were mapped into grids of five-metre square sections, then vapour tests were taken at three different heights in every five-metre quadrant of each building.

    "What we were looking for was the potential for inhalation from different groups," Dewar says. "The waist level tests mimicked the average height of a child; samples taken around five feet off the ground were considered the average adult breathing space, and floor level was worst-case scenario, where mercury would be trapped in cracks in the floor."

    Dewar notes a vast majority of the tests showed no detectable mercury vapours. And the standard applied to the site was high: twice as stringent as the occupational health and safety standard created for commercial areas estimated for people working on site eight hours a day, five days a week.

    Coincidentally, while the tests were being completed, Alberta reduced its commercial exposure guidelines from 0.05 to 0.025 milligrams per cubic metre – the level that was followed in the gas plant remediation program from the beginning.

    The crews scrubbed the floor, and sealed all cracks in the concrete with silicone sealant to ensure any mercury residue was sealed in. The mercury vapour testing was completed again and it was found that all the areas were well below the eight hour exposure limit.

    Outside, soils showing mercury contamination were excavated to a depth of one to two feet, and the contaminated soil trucked to an Alberta Environment-approved landfill. The holes were backfilled with clean soil obtained from a local source.

    For the majority of the plant, site specific soil mercury guidelines (21 mg/kg) were followed. This guideline is similar to the industrial exposure guideline provided by the government. Surface soils showing mercury concentrations greater than this were excavated and removed from the site.

    The tour path was sampled every 25 meters for mercury contamination. On this area of the plant specifically the more stringent residential soil guideline of 6.6 mg/kg was applied to the soils. Surface soils along the path found to exceed 6.6 mg/kg were excavated, removed from site for disposal, and the holes backfilled with clean material.

    With mercury remediation contained to the most stringent guidelines, including the meeting of residential standards, proper disposal procedures and an ongoing management plan in place, mercury no longer poses a hazard at the site.

    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.

    Sulphur Disposal at the Plant

    Sulphur is essential to human and animal life. It is a key component in most proteins, and a minor constituent of fats, body fluids, and skeletal minerals. Each one of us contains a couple of grams of elemental sulphur for each kilogram we weigh.

    It is also an essential plant nutrient, required for protein synthesis and the formation of chlorophyll. It is necessary to all Alberta annual crop production, to varying degrees, and is very frequently added as a soil amendment, either in sulphate form or in elemental form. Canola plants, for instance, must have sulphur to develop fertile flowers; alfalfa roots need it to develop good nodules.

    The 16th most common element in the world, sulphur is a part of many foods, including asparagus, onion, garlic, mustard, eggs and cauliflower. It is used in arthritis supplements, and creams to treat acne and eczema.

    But, "too much of a good thing is not necessarily a good thing," says Bruce Dewar, Project Manager, Environment, Stantec Ltd., the contractor which oversaw the cleanup of the elemental sulphur left on and in the soil at the historic Turner Valley Gas Plant site after decades of sour natural gas production.

    "Elemental sulphur is benign, but when you add water it will slowly acidify the soils." That can lower the pH beyond what is good for plants, he says. "Winds can spread sulphur dust unless it is properly managed, making soils acidic and (harming) vegetation."

    Acidic water can also leach natural irons and other metals out of soil and carry them into rivers and underground aquifers.

    There was no risk to human or animal health from the powdered sulphur on the site, Dewar says, but the yellow patches were not aesthetically pleasing.

    The visible sulphur could have been a source of concern to visitors, should the historic site be made a tourist attraction. The general public is likely to know that breathing hydrogen sulphide in unrefined sour gas is dangerous, but may not know that elemental sulphur is harmless.

    Alberta Environment and Parks sets the standard for acceptable sulphur content in soils at four per cent and lays out procedures for managing it. For more information, download the Guidelines for the Remediation and Disposal of Sulphur Contaminated Solid Wastes.

    "The use/disposal plan chosen to manage waste materials must ensure environmental protection, accommodate human health needs, and make the best practicable use of sulphur," the guidelines say. "Recovery of sulphur should be the primary concern for dealing with waste material; in situ land surface treatment and land application should be used whenever possible; and landfilling should be used only as a last resort or if other options are inappropriate for the particular waste."

    Four per cent sulphur content roughly equates to the amount that would be visible. "We removed as much visible sulphur as we could get," Dewar says. "The rest was treated with proportional amounts of limestone, which neutralized any potential acid."

    The provincial guidelines specify the proportions for adding limestone (a mixture of calcium and magnesium carbonates) to sulphur-rich soil; how finely the limestone must be ground; and, how thoroughly the amendment must be mixed in. Stantec tested repeatedly to ensure guidelines were met, and, in fact, developed innovative tests just for this site because the hydrocarbons in the soil skewed the results from standard tests.

    If the sulphur-laden soil from the gas plant site had not been contaminated with anything else, it could have been spread on agricultural land and mixed with ground limestone to neutralize it, instead of being hauled to the landfill. Repeated applications of elemental sulphur are acceptable on agricultural land as long as there is time for soil bacteria to oxidize the sulphur into a sulphate form accessible to plants in between applications.

    The entire project cost $600,000, for everything from initial testing to soil removal and tipping fees at the landfill, to limestone amendment, to rehabilitation to restore the historic appearance of the site.

    Had the sulphur remediation not been done on the Turner Valley Gas Plant property in 2002, the excess would now be contained by the groundwater dyking and cleaning system installed in the spring of 2007 to remove hydrocarbons from the groundwater before it reaches the Sheep River.

    Last reviewed/revised: March 18, 2016