Vulnerable Areas

A wellhead is the part of the well that is above ground. A WHPA is the area around a wellhead that contributes to a municipal drinking water source.

Water can carry contaminants as it infiltrates the ground and flows down to an aquifer. Aquifers are areas where groundwater water fills cracks in bedrock or spaces between grains of sand, gravel, or dirt. Human activity in a WHPA can impact the quality and/or quantity of groundwater in an aquifer.

Scientists study how and where water moves through the ground. They also use models to calculate vulnerability scores in WHPAs. These scores represent the risk of an activity posing a threat to a drinking water source. Factors include the type of aquifer, soil type, topography (the rise and fall of the land) and pumping rates. WHPAs closest to a well typically have a higher vulnerability score. This is because there is less time for contaminants to break down before they reach the well.

Source protection plan policies manage drinking water threats in WHPAs.

Types of WHPAs

• WHPA-A: 100-metre radius around the wellhead
• WHPA-B: 2-year travel time for groundwater (and potential contaminants) to reach the well
• WHPA-C: 5-year travel time for groundwater (and potential contaminants) to reach the well
• WHPA-D: 25-year travel time for groundwater (and potential contaminants) to reach the well
• WHPA-E: 2-hour travel time from surface to aquifer.

An IPZ is an area around a surface water intake pipe that contributes to a drinking water source.

Surface water can carry contaminants to an intake pipe. Human activity in an IPZ can impact the quality and/or quantity of water flowing to an intake pipe.

Scientists study how and where surface water flows on the surface of the ground. They also use models to calculate vulnerability scores in WHPAs. These scores represent the risk of an activity posing a threat to a drinking water source. Factors include the type and size of a watercourse size and depth and size of the intake pipe. IPZs closest to an intake pipe typically have a higher vulnerability score. This is because there is less time water treatment plan operators to take action to preventative action.

Source protection plan policies manage drinking water threats in IPZs.

Types of IPZs

• IPZ-1: immediate area around an intake pipe and 1km upstream
• IPZ-2: area upstream of IPZ-1 from which water can flow to the intake pipe in two hours or less.
• IPZ-3: all areas that contribute surface water to the IPZ-2.

SGRAs are areas known to replenish an aquifer. They include sand and gravel deposits. Municipalities should consider SGRAs when making decision on planner matters. They may request more information or studies to ensure a drinking water source is not put at risk.

HVAs are areas which make an aquifer susceptible to contamination. This includes fractured bedrock or sand and gravel deposits. Municipalities should consider HVAs when making decision on planner matters. They may request more information or studies to ensures proposed development does not put a drinking water source at risk.