Agency says inactive extraction sites may pose threat to drinking water
By Rob O’Flanagan Guelph Mercury Mar 02 2011
GUELPH — The Ontario Ministry of the Environment is being asked to consider certain activities related to the rehabilitation of sand, gravel and stone extraction sites as potential threats to drinking water.
Under the Clean Water Act, the Lake Erie Source Protection Region develops water protection plans for the entire Grand River watershed, which includes the Speed and Eramosa rivers in Guelph and local aquifers. The agency’s reach also includes Kettle Creek, Catfish Creek and Long Point Region watersheds.
“Really what we are asking the ministry to consider and look at is very specific activities that are happening after an aggregate operation is closed,” said Martin Keller, the agency’s source protection program manager. “What we’re asking is that they look at the post-extraction phase.”
Last year, the Lake Erie Source Protection Region committee requested the ministry identify as a drinking water threat all aggregate operations that go below the water table and penetrate the protective layer over an aquifer. That would include sites like Guelph’s Dolime quarry and a number of others in the area. The ministry rejected that request.
Now the committee is asking the ministry to look at identifying post-extraction as a threat. If approved, new policies would be developed around how rehabilitation is monitored and carried out.
Keller explained that the environment ministry has identified a series of “prescribed drinking water threats.” Among them are a number related to water quality issues, including regulations on the storage of fuel, the use of agricultural fertilizers and chemicals, pesticide application, waste disposal and septic systems.
Post-extraction aggregate sites in vulnerable areas of a municipal drinking water system are a potential threat to our water, he said. Water ponds in the sites can allow the introduction of contaminants into the groundwater system.
As well, there is the potential for contaminated fill material to be placed in the sites during reclamation work – fill containing hauled sewage, municipal, industrial or petroleum refining waste. Chloride, cyanide, arsenic, metals and pesticides are potential contaminants.
Heather Malcolmson, the ministry’s manager of source protection planning, said the ministry is “currently evaluating the activity to determine whether or not we can assign what we call a hazard rating,” she said, explaining that such a rating is assigned as a measure of an activity’s threat to drinking water. She said that within the 19 prescribed drinking water threats, there are about 1,400 circumstances “under which an activity can be a drinking water threat.”
“We are in the midst of doing that evaluation,” she said, speaking of the post-extraction aggregate issue. “We haven’t completed it yet. We are certainly considering it.”
Keller said active aggregate operations generally pump water out of the site, removing the likelihood of contaminants entering aquifers.
“Once the pumping stops, in those cases where the extraction is below the water table, that water table is then more exposed to any specific contaminants potentially reaching that aquifer, because of the reversal of the flow particularly in regards to ponding,” he explained. “With any contaminants that are in that pond, there is a higher likelihood that those things actually can reach the aquifer and close-by wells.”
Adding post-extraction aggregate sites to the list of drinking water threats “would open the door to look at potential policies that would mitigate the risks,” Keller added. An example of a future requirement may be to place a liner in aggregate site ponds to help prevent contamination