During a flood, there is an increased risk that drinking-water wells may become contaminated with bacteria or other micro-organisms. Any well-water system, whether deep or shallow, can become contaminated when flooding occurs.
Risk factors for well water
There is increased risk of contamination in well water when:
• groundwater sources are open to the surface because of shallowness and/or water-permeable soils such as sand, gravel or other non-water-tight materials;
• wells are located in pits or depressions where water has pooled;
• wells have unsealed casings that do not extend at least 30 centimetres (one foot) or more above the ground or have rusted casings;
• wells are located near unsealed abandoned wells;
• wells are near septic tanks or fields, barns, feed lots, sink holes or quarries;
• wells or groundwater sources are affected by changes in environmental conditions such as floods and heavy rains;
• other wells in close proximity are flooded and may be contaminated with bacteria; or
• water in the well changes in colour, clarity, taste or odour.
If a large sewage spill or other source of significant fecal contamination of the well is suspected, contact the Manitoba Office of Drinking Water in Winnipeg at 204-945-5762 or 204-945-8913.
When boiling is necessary
In flood-affected areas, it is advised that if well contamination is suspected, boil the water before using it or find an alternative supply of drinking water until flooding subsides and bacteria tests show it is safe to use. Boiling kills all micro-organisms (bacteria, viruses and parasites) that may be present in water.
Tap water from flood-affected wells cannot be used for drinking until it is properly sterilized by bringing it to rolling boil for one minute. This includes water used for:
• making ice,
• preparing any beverages including infant formula,
• cooking,
• washing fruits and vegetables, or
• brushing teeth.
If boiling water is not an option, use an alternate, safe supply of water such as bottled water.
Using water for other domestic purposes
Tap water from flood-affected wells can be used for:
• laundry,
• bathing, and
• washing dishes
Adults, teenagers and older children can use the water to shower but should avoid swallowing it. Toddlers and infants should be sponge bathed instead of bathing in a tub.
Testing well water
Well water should be tested for bacterial contamination after flooding has subsided. Drinking water should be boiled until test results confirm it is safe to drink.
Steps for testing well water
NOTE: The provincial government is waiving all fees for professional bacteriological testing of private drinking water wells affected by flooding until June 30.
• The presence of bacteria in the water sample indicates well-water contamination. Well water should be tested by a professional lab.
• Homeowners are responsible for collecting the water samples. A special water sample collection bottle is required and certain steps must be followed for bacterial analysis. Bottles for taking water samples, instructions for use and submission forms are available from participating rural municipality offices, Manitoba Water Stewardship and Conservation offices or directly from ALS Laboratory Group, 1329 Niakwa Road East, Unit 12, Winnipeg R2J 3T4, 204-255-9720 or 1‑800‑607-7555 (toll‑free), Monday to Friday, 8 a.m. to 4:30 p.m.
• It is very important to follow the instructions provided on the back of the laboratory sample submission form. If proper sampling procedures are not followed, the sample may be contaminated and produce false results.
• A special water sample collection bottle is required and certain steps must be followed in collecting a water sample for bacterial analysis. The laboratory will provide instructions for sampling, a special sample bottle and a submission form that must be filled out.
• Homeowners are responsible for collecting their own water samples. Carefully follow the instructions provided on the back of the laboratory’s sample submission form.
Submitting well-water samples
Sample bottles should be dropped off within 24 hours of collecting the water sample. To be eligible for the free testing, bottles must be clearly labelled 2009 Flood.
Sample bottles, including submission forms clearly indicating 2009 Flood, should be dropped off at:
• participating rural municipality offices before noon on Tuesdays, or
• at the ALS laboratory in Winnipeg at the address listed above.
Well restoration after flooding subsides
NOTE: This section applies to wells that have been overtopped, completely submerged or suffered structural damage and have major contamination, as opposed to wells that may have had a little seepage.
• Problems may arise if wells have been submerged by flood water. The well should be professionally assessed to determine how best to bring it back to a safe, useable condition.
• More extensive well restoration may be needed if wells have been structurally damaged, completely submerged or overtopped, or if flood water has been observed draining into the well. Flood water and sediment can damage pumps and their electrical components. All assessments, repairs and replacements should be done by qualified professionals. It may not be safe to turn on a pump until the well is cleaned out and all sediment and flood water are removed.
• Well owners who have suffered this type of problem should contact Groundwater Management at 204-945-3737 or 204‑945‑7425.
For more information on wells, well-water testing, disinfection and interpretation of water-testing results, contact:
• the Manitoba Office of Drinking Water in Winnipeg at 204-945-5762,
• the local drinking water officer,
• Health Links-Info Santé at 204-788-8200 or 1-888-315-9257 (toll-free), or go to www.manitoba.ca/drinkingwater or www.gov.mb.ca/health/publichealth/cmoh/water.html.
