By Brad Herron
The Eagle
Springwood Developments unveiled its 333-page remedial action plan (RAP) to bring the former-Domtar site up to an environmentally-commercial standard at an open house at the Cochrane RancheHouse June 18.
The 45-acre site in downtown Cochrane was used by Domtar for over 20 years, from 1963 to 1987, to treat railway ties with coal tar, creosote and pentachlorophenol, commonly known as PCP. When Domtar ceased operations at the facility, extensive contamination was found both along the surface and in the groundwater.
Now, more than two decades later, there is a plan to remediate the surface area of the property, beginning as early as this summer.
Gordon Johnson, a consultant with WorleyParsons Komex, explained that contaminated surface material will be remediated through the use of biological-stabilization technology.
Contaminated dirt, most of which was affected by drippings from treated material, will be moved into large piles, tarped and exposed to active bacteria which, given the right conditions and nutrients, eliminate the contamination during the summer months.
“This stuff is designed to resist treatment, it’s stubborn, but the compounds that tend to go into the environment are the lighter, more soluble ones and remediation has proven to be the most successful on those compounds,” Johnson said.
Philippe Gingras, the project manager from Biogénie, compared the process to industrial composting.
The deeply-contaminated source area, the former pit where creosote, along with other chemicals were poured directly onto the ground, will be treated the same way.
While the contamination on most of the site extends into the ground less than a metre, the source contamination has migrated into the groundwater system. The surface dirt in the Special Management Area (SMA), will be removed, subjected to the bio-stabilization techniques, then put back.
Dirt that goes back in may be contaminated, but its “contamination potential is reduced,” Johnson said.
“The treatment process tends to reduce the concentration of soluble materials, the volatile materials that are riskier than the heavy creosote that are apt to stick to the rocks and stay put,” he added.
Three types of groundwater contamination exist on the site: a dissolved contaminant that moves with water, creosote that has mixed with a carrier fluid (diesel fuel) which floats on top of groundwater, and heavier creosote and tar mixture that sit along the rock bed and moves very slowly.
“It’s not practical to remove it — it may not be possible to remove it, at least not conventionally,” Johnson said about the contaminated groundwater. “So, the idea is to maintain this area separate.”
Springwood will continue to monitor the groundwater contamination on the site. Domtar is controlling the groundwater hydraulically through the use of wells, pipes and trenches underground.
A south trench was built in 1986, followed by a west trench in 1990 and the Griffin Road trench in 2002. The entire system, which included two hydraulic barrier wells and a new ground water treatment plan were installed between 2002 and 2005. The treatment system is designed to recover non-aqueous phase liquid, commonly known as NAPL, and separate suspended particulate from the groundwater.
Martha Walton, a lead consultant from San Francisco, Calif., who has co-ordinated remediation projects across the United States and Canada, said the long-term key will be to remove the “heart of the problem in the original source area.”
Once the remediation project is completed, much of the SMA will be capped by pavement to allow for future remediation. A cover of asphalt will also change the dynamics of the water table, and ultimately cause the amount of local groundwater to shrink, further slowing the leeching of contaminants into groundwater. Springwood plans to not allow any use of groundwater on the property.
The SMA was recently subdivided by council. This area will contain no commercial development, and instead be used for roads and parking. It is owned by Cochrane Properties, but leased to Springwood which will take long-term liability insurance on the property.
Before bio-stabilization starts, the target area, much of which is gravel, will be put through a one-inch screening to sort dirt from rock. The rock, which is less likely to harbour contaminants, will be crushed into gravel for asphalt. This includes piles that have previously been certified as clean soil by Alberta Environment.
Residents will notice work is taking place even if it’s out of view, as the work site will smell.
“It smells like creosote obviously, but I don’t anticipate it will be anything close to when the actual cooking process was being done by Domtar,” Gingras said.
Measures will be installed to mitigate potential health hazards. The outer fence will be maintained throughout construction to keep both people and wildlife off the site and particulate sensors, both onsite and on the perimeter, will be installed for the public and employees.
Included in the remedial action plan is a concept plan dated Feb. 13, which is strictly on the southern half of the site, and calls for a 151,180- square foot major tenant building.
The same concept plan, which encompasses 28 acres of the project including the SMA, proposes 301,430 square feet of development and 1,609 parking stalls.
Nathan Boskers, Springwood’s project manager, said the remediation could take as little as 18 months to complete.
No development will occur until the entire site is remediated.
A copy of the plan is available at the Cochrane Environmental Action Committee’s website, www.cochrane-environment.org.