Disinfecting Water Wells Flooded By Harvey

Recent rainfall that caused flooding in low areas around here and massive flooding to many places to the south, can cause contamination of water wells.
If water gets above the entrance to the well, you need to assume that the water in it is contaminated. Bacteria from the floodwater can infect, what was once clean groundwater, and make it unsuitable for drinking, cooking, and even bathing until you have cleaned it up.
If the well is shallow, has been flooded by surface water, or is in an unconfined aquifer, pump it out to remove any potential contaminants. Pump out at least 3 well volumes of water from a faucet near the wellhead. At a minimum, pump the well for at least 1 hour before beginning the disinfection process.
Remove the plug or screen on the well cap to access the inside well casing. Turn off electric power to the pump and remove the well cap.
Prepare a solution of bleach and water, and pour the solution into the top of the well. The amount of bleach depends on the depth of water in the well and the diameter of the well casing, which is a steel or plastic pipe placed in a well to maintain the well opening and to serve as the lining to the well.
There is a method of determining how much bleach to add to your well that would take too much time here to describe. So, to simplify, a typical 8-inch casing diameter with unknown standing water depth would require 3 gallons of household bleach.
Recirculate the water by connecting a hose to a faucet and spraying the water back into the well for at least 10 minutes.
Open every faucet in the system and let the water run until the smell of chlorine can be detected.
Close all the faucets and seal the top of the well. Drain all water heaters to allow the chlorinated water to circulate through the hot water system also. Flush out household plumbing, including the water heater. Make sure the water is clear and free of sediment.
Allow the chlorinated water to stand in the system for at least 12 hours, preferably 24 hours.
The next day, operate the pump by turning on all faucets, beginning with those outside, and flushing out the water until there is no chlorine odor.
After disinfection, have the well water tested by a certified laboratory to make sure there is no bacterial contamination (especially E. coli). Out best friend to help us is the Angelina & Neches River Authority (ANRA).
The ANRA’s mission is to conserve, store, control, preserve, use, and distribute of all waters in the Neches River Basin. They also test homeowner’s well water!
The cost is only $22. You’ll need to stop by the ANRA office at 210 Lufkin Avenue, located directly across from the front steps of the Angelina County Courthouse.
Go there first to get a sterile bottle that will ensure your water sample isn’t contaminated by the very container you use. Following their instructions, bring your water sample back for the test.
Well disinfection does not eliminate hydrocarbons (fuels, oils), pesticides, heavy metals, or other types of contamination. If you suspect such contamination, the water will require special testing and treatment. Again, the good folks at the ANRA will be able to answer your questions or direct you to another laboratory that can. For more information, you can call them at 936.633.7527 or email treeves@anra.org.


Cary Sims
Cary Sims
Cary Sims is the County Extension Agent for agriculture and natural resources for Angelina County. His email address is cw-sims@tamu.edu

Educational programs of the Texas AgriLife Extension Service are open to all people without regard to race, color, sex, disability, religion, age, or national origin.

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