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Healthy Waters: Well Decommissioning & Upgrade Program ?Well Head Protection Zones

It has been identified through the Walkerton Inquiry and Source Protection Planning Initiatives that improperly maintained and abandoned water wells are a potential source of contamination to groundwater supplies and require attention. Unused or poorly maintained water wells provide a direct link from the land surface to the water bearing subsurface zones that represent the source water for other wells and streams in the area.

These poorly maintained water wells could allow surface runoff to flow directly down to local and regional aquifers, often carrying organic wastes, fertilizers and other chemical residues, such as pesticides and petroleum products into the groundwater. Once a groundwater source is contaminated it can be harmful to drink the water from wells tapping these sources.

Well Head Protection Area
Bowmanville Marsh Photo: Canadian Wildlife Service

Many residents in Durham Region depend on municipal wells to supply water for their many domestic needs. The Region of Durham recently completed a number of wellhead protection studies for all municipal wells as part of the Groundwater Studies to define the area of lands around each municipal wells or well fields, for which groundwater protection measures are to be applied. Many residents in small Communities in Durham Region depend on municipal wells to supply water for their domestic needs. These studies involved the following components:

  • Detailed 3-dimensional modeling to delineate the capture areas
  • Definition of wellhead protection areas (WHPA) for each well
  • Inventory of the contaminant sources within each WHPA; and
  • Management Plan for each WHPA

Wellhead Protection Area for a typical municipal well with Capture Zone - 50 day to 25 year Time of Travel (TOT)

The size of capture zones for each well is directly related to pumping rate at each municipal well, local geology, hydrogeology, and hydraulic properties of the water-bearing zones (aquifer) and confining layers (aquitards). Capture zones, often described in Time of Travel (TOT), indicate how long it takes for the groundwater to arrive at the municipal well. Under the Wellhead Protection Area Studies the following capture zones were identified.

WHPAís require more diligent source protection, as these wells supply water to many area residents. With source protection being the first barrier in a multi-barrier system, the intent is to prevent contamination of groundwater supplies at the source. Under the Regions Wellhead Protection Program, a number of privately owned wells that are located within the wellhead protection zones have been identified. Where it is recognized that many of these wells may be in use and or in excellent condition, some may be in questionable condition and in need of an upgrade or may need to be decommissioned. Poorly maintained and abandoned wells within these areas represent a potential threat to the aquifers that serve the Regionís municipal wells.

With the support from Lake Simcoe, Kawartha, Ganaraska, and Toronto and Region Conservation Authorities, CLOCA has extended its stewardship efforts toward the decommissioning/upgrade of wells located within the Regionís Wellhead Protection Areaís. This program aims to assist the Region and area residents in the protection of their groundwater supplies from potential contamination by providing well owners with grant assistance to upgrade or decommission unused wells. It specifically targets privately owned domestic wells within Durham Regionís wellhead protection zones.


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