There are three main steps to identifying threats to drinking water

1) Identify and map vulnerable areas

There are four types of vulnerable areas that need to be delineated:

1. Wellhead Protection Areas (WHPAs): areas where water travels through the ground to a municipal well

2. Intake Protection Zones (IPZs): areas around municipal surface water intakes

3. Highly Vulnerable Aquifers (HVAs): areas that are more susceptible to contamination moving from the surface into the groundwater

4. Significant Groundwater Recharge Areas (SGRAs): areas where larger amount os water go into the ground instead of flowing directly into creeks, rivers or lakes

2) Determine where threats may exist

There are 21 of different types of threat activities that can affect drinking water quality under the Clean Water Act:

1. The establishment, operation or maintenance of a waste disposal site within the meaning of Part V of the Environmental Protection Act.
2. The establishment, operation or maintenance of a system that collects, stores, transmits, treats or disposes of sewage. Why are septic systems a threat to drinking water?
3. The application of agricultural source material to land.
4. The storage of agricultural source material.
5. The management of agricultural source material.
6. The application of non-agricultural source material to land.
7. The handling and storage of non-agricultural source material.
8. The application of commercial fertilizer to land.
9. The handling and storage of commercial fertilizer.
10. The application of pesticide to land.
11. The handling and storage of pesticide.
12. The application of road salt.
13. The handling and storage of road salt.
14. The storage of snow.
15. The handling and storage of fuel. Why is fuel a threat to drinking water?
16. The handling and storage of a dense non-aqueous phase liquid. Why are DNAPLs a threat to drinking water?
17. The handling and storage of an organic solvent.
18. The management of runoff that contains chemicals used in the de-icing of aircraft.
19. An activity that takes water from an aquifer or a surface water body without returning the water taken to the same aquifer or surface water body.
20. An activity that reduces the recharge of an aquifer.
21. The use of land as livestock grazing or pasturing land, an outdoor confinement area or a farm-animal yard.

 3) Calculate threat levels