Water Wells - What to Do Before the Flood

After the spring flooding of 1996 numerous rural residents noted problems with their well water. Problems which included unpleasant taste or odour, cloudiness and even some contamination which only became evident after water quality testing. Generally, the source of these problems was identified as either runoff from a livestock area, overflow of a domestic septic system, the silty nature of flood water and possibly herbicide/pesticide residues from adjacent fields.

While there are techniques which can rehabilitate a well affected by surface flood water, there are steps which a homeowner should follow to minimize any potential impacts. See article - Water Wells - What to do after the flood.

Here is a checklist for safeguarding your water well from flood water contamination:

1. Ensure that the land surrounding the well is sloped away so that surface water flows away rather than towards the well. This may involve extending the well casing above ground level and some minor dike building or sandbagging. You may need to consider protecting the area over the water line between the well and the house as an recent or improperly backfilled trench may represent a preferred flow path for the flood water to the the well casing.
2. Ensure there has been no settling of the soil or a cavity developed around the outside of the well casing where surface water is able to flow down. A local water well driller can provide information on commercial sources for fine bentonite chips which can be used to make an impervious seal around the well casing.
3. Ensure the well has a tight fitting water proof cap. This may be as simple as wrapping the well casing with durable sheet plastic and duct tape to form a water tight seal. Most wells have caps with vent holes which are required for proper operation. If the well is not used for the duration of the flood event then these vent holes should be plugged. Otherwise, a tube, which would extend above flood level, should be attached to the vent hole. When sealing the well cap, remember that it will need to be removable in order to allow future servicing of the well. v
4. Ensure that livestock wastes are removed from the flood prone area and that household septic systems are pumped empty prior to the onset of flooding. Caution is required when emptying fibreglass or plastic septic tanks that are not anchored. They should be refilled with clean water to prevent floating under high water table conditions. Also, any toxic substances such as pesticides, fertilizers or herbicides should be removed from the flood prone area.
5. Raise or remove any non-submersible mechanical or electrical equipment that is installed in a dry well pump pit and may be at risk from surface flooding or a rising water table.
6. Ensure that any stand-by or abandoned (unused) wells in the area are also protected. Any abandoned well is an environmental liability and should be permanently sealed to ensure it will not act as a point source of groundwater pollution now or in the future. Flood waters entering an abandoned well can contaminate the aquifer that you and your neighbours draw water from. Additional information on sealing abandoned water well will be covered in a future article, or contact your local PFRA or Manitoba Water Services Board Office.

There is no guarantee that, even if you follow this checklist, you are not going to have problems with your well water after the flooding. It is important that the water is tested at least for total coliform bacteria (prices range from $26.75 to $45.00 at Envirotest Labs and Norwest Labs) before using it for domestic water supply. You may want to boil your drinking water until you are sure it is safe for consumption.