The science of gravel extraction
Photo by Jason Teakle, Brant News
Nick Greenacre is researching the effects of gravel extraction below the water table in relation to a proposed 600-acre gravel pit to be located on both sides of Watts Pond Road north of Paris.
Conducting independent research into the effects of gravel extraction on groundwater resources is keeping a County of Brant resident busy as companies seek to open gravel pits in the municipality.
Nick Greenacre, a retired lecturer in environmental health at the Liverpool School of Tropical Medicine in England and former head of the Regional Network Centre for Water and Waste Management in East Africa, is researching the effects of gravel extraction below the water table in relation to a proposed 600-acre gravel pit to be located on both sides of Watts Pond Road north of Paris.
The issue has come to the forefront in Paris as a group of residents known as the Concerned Citizens of Brant work to fight the pit proposal, put forward by Dufferin Aggregates.
A second 500-acre pit is being proposed for near Burford by CBM Aggregates, a division of St. Marys Cement. The pit proposed by Dufferin is located near a municipal water source for the town of Paris. CBM's proposed pit is located near private wells, but not a municipal water source.
Greenacre said that although chemicals are not used in gravel extraction, pesticide residues left in the ground as a result of agricultural practices have the potential to contaminate groundwater during extraction.
"The excavation of the source pond creates a transport pathway directly into the aquifer for any pollutants washed from the aggregate," Greenacre said. "While aggregate extraction may not introduce pesticides, the washing of extracted aggregate in a closed-loop system can release pesticide residues or other contaminants already in the aggregate."
The Concerned Citizens of Brant have spent months fighting the planned Dufferin Aggregates operation and have asked the Ontario Environmental Commissioner's office to review the company's licence – granted by the Ministry of Natural Resources in 1974 – to be reviewed. The group is expected to receive an answer to its request by early March.
Greenacre said residue of a pesticide commonly sprayed on crops grown in the County of Brant – atrazine – poses a potential risk to groundwater sources located in close proximity to the planned Watts Pond Road pit.
"The potential risk is there and that is why (atrazine) is banned in other countries," Greenacre said. "There was no acknowledgement or awareness of some of these pesticides (when Dufferin Aggregates received a licence from the MNR for the operation in 1974). The potential for aggregate washing to release previously absorbed pesticide residues directly into a drinking water aquifer needs to be included as a specific potential threat covered by specific regulation and binding policies."
In a letter to Greenacre from the Ontario Ministry of the Environment, a MOE spokesperson says provincial legislation addresses residual contamination resulting from past activity, but not current activity that could compound past contamination.
"If residual contamination in the environment was to pose a risk to sources of drinking water, there is a mechanism to address this under the (Ontario) Clean Water Act," the letter says. "The act includes a class of threats called conditions that represent contamination that has resulted from past activities. This approach addresses the contamination itself – rather than an activity that happens to be taking place in, on or around the site."
Kevin Mitchell, land development and geology manager with Dufferin Aggregates said the company has been regularly sampling groundwater at the Watts Pond Road site for about 25 years.
"Dufferin Aggregates has a groundwater monitoring program which includes water quality sampling of ground and surface water at the site," Mitchell said. "This groundwater monitoring program has been in place since 1988, providing extensive baseline data and will continue during the operation of the pit."
Mitchell said the company does not anticipate negative impacts on groundwater at the Watts Pond Road site and gravel extraction below the water table will not occur if deemed a threat.
"The washing of aggregate is not anticipated to impact groundwater," Mitchell said. "There are currently naturally occurring ponds that are connected to the groundwater table within the Paris pit site. Based on our own experience at Dufferin Aggregates – and that of the aggregate industry in Ontario – washing aggregates is currently done at locations across the watershed in Ontario without incident.
"There is no known example of an aggregate operation resulting in groundwater contamination of a municipal water supply. We remain committed to constant evaluation and review and below water table extraction will not occur if these programs determine it cannot be done safely."
Mitchell said the results of groundwater tests are shared with all interested parties.
"The results of the monitoring are shared with the County of Brant, Ministry of the Environment, Ministry of Natural Resources and the Grand River Conservation Authority," Mitchell said. "In addition, the County of Brant has their own groundwater monitoring program which is required by their permit to take water for the municipal wells. To date, there is no indication of any impacts.
"The source water protection plans that are being developed across the province will also address groundwater concerns as many aggregate operations in Ontario exist within well-head protection areas. We anticipate the source water protection plan will have recommendations for our site and we are committed to working with the approval agencies to implement them."
Groundwater testing programs in place will allow the company to compare results once extraction begins at the Watts Pond Road site, Mitchell said.
"The Dufferin groundwater monitoring program and the County of Brant groundwater monitoring program include actual water quality data from wells on the Paris pit site and in the surrounding area. When the Paris pit operations commence, the monitoring programs will continue and the results will be compared to the base data to determine if the operation of the Paris pit has had any influence."
Read more about CBM's proposed pit by clicking here.