Lansdowne Wellhead Protection Area Study
The village of Lansdowne is located northeast of Gananoque in the Township of Leeds and the Thousand Islands.
Water is supplied to the village by two wells that were drilled in 1974. This water is treated at an on-site treatment system operated by the Ontario Clean Water Agency (OCWA).
Purpose of the Study
The purpose is to determine where the water that supplies the village of Lansdowne comes from and how quickly it reaches the wells. The study also examines how the groundwater in the vicinity of these wells is affected by nearby land uses and land practices.
As part of the study, Wellhead Protection Areas (WHPAs) around the wells are calculated. Recommendations on what needs to be done to protect the drinking water source will be developed as part of the source protection plan.
Who is Doing the Work?
Phases 1 and 2 of the study were done by Malroz Engineering Inc. The final phase is being done by Intera Engineering Ltd. under the direction of the Cataraqui Region Conservation Authority. The Township of Leeds and the Thousand Islands, the Leeds Grenville and Lanark Health District Unit, and the Ontario Clean Water Agency are also providing input to the study as part of a technical advisory group.
Wellhead Protection Areas
A wellhead is the physical structure of the well that is located above the ground. A wellhead protection area (WHPA) is the area around the wellhead where land uses and activities have the potential to affect the quality of water that flows into the well.
The study methods for determining wellhead protection areas are prescribed by the Ontario Ministry of Environment (MOE).
A WHPA is determined by mapping the geology and groundwater levels surrounding the wellhead and using this information to create a mathematical model. The model is used to predict the speed at which the groundwater is flowing toward the well and from which direction, depending on how much water is being pumped at the municipal well supply.
Using this model, a series of zones are drawn based on the time it would take groundwater and contaminants to travel to the wellhead. The zones are as follows:
- Zone A is a 100 metre radius around the wellhead
- Zone B is the five year time of travel to the wellhead
- Zone C is the ten year time of travel to the wellhead
- Zone D is the 25 year time of travel to the wellhead
- Zones E and F are drawn to account for potential groundwater under the direct influence of surface water (GUDI) designation. (Zones E and F don't apply to every wellhead.)
Once these zones are mapped, the vulnerability of the aquifer (the underground area that contains the groundwater) can be assessed. If an aquifer allows water to move through it quickly, like through sand, gravel or fractured rock, then it is highly vulnerable.
Vulnerability scores are calculated based on how easily contaminants can reach the aquifer. The more vulnerable the aquifer and the closer proximity to the well, the higher the vulnerability score. 
A generic illustration of a wellhead protection area is provided below.
Study Methods
The first step in examining the area surrounding the Lansdowne wells was to gather information about the geology and hydrogeology of the area. Existing studies were reviewed and these were supplemented by more detailed field work.
Five boreholes were drilled to improve the geology information available about the Lansdowne area. This information was used to improve the data for a mathematical groundwater flow model known as MODFLOW.
From this information we were able to map the different zones within the Lansdowne wellhead protection area and assess the vulnerability of these zones to contamination.
The next stage is to identify any potential sources of contamination to Lansdowne's drinking water source and any water quality issues at the wells. Scores are then produced for any potential sources of contamination and additional information is gathered on those sources that are considered to be significant.
This information will be used to develop a source protection plan. This plan will contain recommendations to protect the source of Lansdowne's drinking water.
Study Completion
The study is scheduled to be completed in early 2010. A public open house was held on November 24, 2009 to share the draft study findings and obtain public input.
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