Water Wells - What to Do After the Flood

As the flood waters of 1997 recede affected residents will begin to reoccupy their homes and businesses. While it is natural to focus on repairing and rehabilitating the flood damage that we can see, there may be damages that are not readily apparent. Potential contamination of water wells by flood water is an example of this hidden damage. While this contamination may be associated with an unpleasant taste, odour, or cloudiness of the well water, some contamination will only become evident after water quality testing.

Most groundwater aquifers receive the majority of their recharge from a spring snow melt. Under normal conditions this recharge percolates through the soil profile, which can attenuate most potential contamination. Under flood conditions surface water may enter directly into the aquifer via the well itself, an old abandoned well, or some other nearby excavation, bypassing the natural filtering process. Flood water quality testing by Manitoba Environment has indicated that any fertilizer and pesticide contaminants are diluted to insignificant concentrations because of the large volume of flood water. Therefore, any testing and rehabilitation efforts should be focussed on potential bacterial contamination.

While the majority of water wells are likely unaffected, each homeowner should take certain steps to ensure their well water is safe for human consumption. As a first step, water from all wells in the flooded area should be tested for quality. In order to do this, you should obtain a bacterial sample bottle from your local municipal office or public health officer. Manitoba Environment has aranged for pick up and drop off points within the flooded area. No charge is applied for bacterial analyses. Results are expected to be available within 48 hours. The attached Table lists the Pick-up/Drop-off locations.

Until the bacterial analysis shows the water to be safe, all water for human consumption should be boiled. If the bacterial analysis indicates that your well has some level of contamination, then the well should be chlorinated and retested. Chlorination is a procedure used to disinfect a water well contaminated with bacteria. It is also part of regular maintenance to extend the productive life of a well.

The following is a based on the procedure recommended by Manitoba Agriculture (similar to that recommended by Manitoba Emergency Management Organization) for chlorination of a well before it is put back into use:

1. Pumps other than submersible pumps should have the electrical motor and wiring cleaned and thoroughly dried out. The best procedure is to take the motor to a repair shop where it can be properly dried, cleaned and serviced. Submersible pump switches, control boxes and wiring must be cleaned and dried, but the motor need not be serviced.
   
   Remember that a water well has electrical components of its own. While these well related electrical component are often located in the home, many are located in other buildings or even inside the well cribbing. If your home has been flooded, you will need an electrician to inspect all wiring, ensure that the electrical components of your water well pump and distribution systems are included. If your home was not flooded but the area around the well was, you may need to have the electrical components related to the well inspected.
2. Thoroughly clean the well, removing all floating debris. Scrub or hose foreign material from the well casing.
3. Pump the well until the water is clear. Store enough water to meet household needs for about eight hours. Turn off your water heater as chlorination is less effective in warmer water.
4. Pump 300 gallons (1350 litres) of water into a clean storage container close to the wellhead. Remember anything that has been in this storage container previously can contaminate your well. Therefore, a clean poly tank or a pickup truck box lined with a new plastic sheet may be your best option.
5. Pour 2 gallons (9 litres) of unscented household laundry bleach (5.25 % chlorine) into the well.
6. Allow water to return to a non-pumping level in the well.
7. Pour 2 gallons (9 litres) of household laundry bleach into the 300 gallons of water stored close to the wellhead. Siphon this mixture into the well. This procedure is essential, as it forces chlorinated water out of the bottom of the well and into the aquifer.
8. Open each hydrant, faucet, etc. in the distribution system and let the water run until it has a chlorine odour at the outlet.
9. Leave the chlorinated water in the distribution system for at least eight hours.
10. Bypass the water softner, filters and other treatment devices. Remove aerators from faucets.
11. Using an outside faucet run water until the chlorine odour is gone and the water is clear. Waste water does not harm hardy plants but should not be used for flowers or other tender species. Do not pump the waste water into the septic tank as large amounts of chlorine may harm it.
12. Run each fixture until the chlorine odour is gone and water is clear.
13. Backwash all water filters and softeners, also flush the hot-water tank.
14. Obtain a bacterial sample bottle from your local pick-up/drop-off location, follow the instructions on the bottle to collect a sample and return it for bacterial analysis.
15. Until a bacterial analysis indicates the water to be safe for human consumption, all water should be boiled if it is for human consumption.

If your well was unaffected by flood water, you may still wish to collect a water sample and disinfect your distribution system as a precaution. This would involve the same procedure as noted above, except that steps 4 and 7 could be omitted.

Experience has shown that not all of the wells will have flood-related contamination. Some may have had problems prior to flooding and are now detected. Also, it is unlikely that all affected water wells will be satisfactory after a single treatment. Once a well has been chlorinated, it should be tested one or two weeks after treatment. If the bacteria are found with this second test, the well needs to be shock chlorinated and tested again. If you have problems at any point in this process, PFRA will have staff and equipment available to assist you. You can get assistance by contacting you Rural Municipality Office or a PFRA Office.