The Ministry of the Environment (MOE) is asking Dufferin Wind Power to seal the foundations of more than 300 utility poles to guard against possible groundwater contamination in Melancthon and Amaranth.
The Ontario Energy Board (OEB) approved Dufferin Wind’s plan to construct a 230 kV transmission line from its 49-turbine wind farm in Melancthon to Amaranth last year.
Earlier this summer, however, the MOE asked Dufferin Wind to revise its construction blueprint.
Ministry officials made that request after a local resident argued some utility pole foundations Dufferin Wind was constructing could act as conduits for surface water pollutants to enter the groundwater supply.
A memo written to municipal officials by Gary Tomlinson, senior environmental officer in the MOE’s Guelph office, identifies “it is possible that it can happen,” although he noted utility pole foundations aren’t particularly efficient pathways for large quantities of water.
“There is a small but nonetheless actual potential for surface water to travel to and possibly into the fractured limestone bedrock,” Tomlinson wrote. “That scenario is certainly concerning.”
The primary source of potable water in the area is found within the aquifer of the relatively shallow limestone bedrock underneath where Dufferin Wind’s transmission line is being built.
MOE spokesperson Lindsay Davidson said the retaining structures, or caissons, used by Dufferin Wind lend to the accumulation of surface water in and around the bases of the utility poles.
As a result, Dufferin Wind spokesperson Connie Roberts said the company agreed to “address the remote possibility” these caissons could transfer surface pollutants, such as fertilizers, into the bedrock in the event of heavy rain run-off or flooding.
“The mitigation actions by Dufferin Wind Power show an abundance of caution to prevent a very unlikely event,” she said in an email.
“We can find no other instance in the province of Ontario of another power installation that is taking the same precautionary measures.”
Dufferin Wind will seal all of its utility poles with bases that end within 2.5 metres of the limestone bedrock.
The remedial work will consist of installing a benonite clay seal both inside and outside of caissons, according to Tomlinson’s memo.
The MOE has given Dufferin Wind until Sept. 15 to complete the sealing program.
More than 300 utility poles, including 216 in Melancthon and 91 in Amaranth, will undergo the remedial work.
“The areas around the poles will be graded and drained to prevent the pooling of water around the poles and to direct water away from the pole bases,” Davidson said in an email.
“The ministry continues to routinely monitor the construction phase of the project to ensure compliance.”
Prior to the MOE’s request, Roberts noted Dufferin Wind’s transmission line construction plan had already received provincial approval.
As she explained, all the company’s utility poles currently adhere to provincial standards.
The mitigation measures agreed to by Dufferin Wind merely “go above and beyond” those provincial standards and regulations, Roberts added.
So, how did the MOE’s oversight fail to see this caisson conduit possibility?
For starters, Tomlinson wrote the utility pole construction plan was approved by the OEB.
He also noted that neither the MOE’s review of Dufferin Wind’s wind farm application or subsequent approval by the Environmental Review Tribunal identified it as a possibility.
“The concept of a utility pole providing a potential conduit for surface water into bedrock aquifers was not previously identified by this Ministry or any proponent,” Tomlinson wrote.
“(The MOE) foresees no additional requirements beyond existing programs currently in place.”
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