Santa Fe - Private domestic water well owners in San Juan County and other parts of New Mexico inundated by floodwater caused by recent heavy rain are being advised to take precautions. Flood water can be tainted by sewage leaked by flooded septic systems, or other contaminants, and the floodwater can contaminate water wells. For private domestic water well users whose wells have been inundated by the floodwater, the New Mexico Environment Department (NMED) recommends the following actions:
1. The well water should be vigorously boiled for 5 minutes before use for drinking, cooking, dishwashing or bathing, until a well water test shows no contamination.
2. The water well should be disinfected with the procedure detailed below.
3. After the disinfection procedure is complete, the well water should be tested for total and fecal coliform bacteria. Laboratories certified by NMED to test drinking water for bacteria are listed here
http://www.nmenv.state.nm.us/dwb/Labs/documents/Certifiedlablistforweb_062013.pdf
4. The well can be returned to normal domestic use after the test results show no bacterial contamination.
Disinfection Procedure
Unscented household bleach containing 5.25% chlorine can be used to disinfect wells. One gallon of bleach will treat up to an 8-inch diameter well containing 100 feet of water.
Avoid direct skin contact with bleach. Wear rubber gloves and goggles when handling bleach. If skin or eye contact occurs, flush immediately with clean water.
Mix 2 quarts of bleach in 10 gallons of water; pour into well.
Connect a garden hose to a nearby faucet and wash down the inside of the well.
Open each faucet and let water run until a strong chlorine odor is detected, then turn it off. Do this for each indoor and outdoor faucet and hydrant. Drain the water heater and let it refill with chlorinated water. If a strong odor is not detected at all outlets, add more chlorine to the well. Also flush the toilets.
Mix an additional 2 quarts of bleach in 10 gallons of water. Pour it into the well without pumping.
Allow chlorinated water to stand in the well and pipes for at least 8 hours (preferably 12 to 24 hours). It is important not to drink, cook, bathe or wash with this water during the time period --- it contains high amounts of chlorine.
Run water from outdoor faucets to waste (away from desirable vegetation) until the chlorine odor is slight or not detected at each faucet. Then run indoor faucets until there is no chlorine odor.
Minimize the amount of chlorinated water flowing into the septic tank.
Some chlorine may persist in the system for 7-10 days. Water with a slight chlorine smell should be usable for most purposes including drinking.
Documents attached to this release also provide useful information from the U.S. Environmental Protection Agency on what to do after a flood.