In an area of extensive flooding where infiltration of septic waste and chemicals can render groundwater unsafe to drink for days or even months depending on the extent of contamination and flow rate of groundwater. Essentially, the water will have to clear itself through natural attenuation (filtering by the soil and the contamination moving thorough the system). Your well may not be a safe source of water for many months after the flood, but in all likelihood it will recover. The well can become contaminated long after a storm when significant spill from up gradient can seep into the groundwater, flow down gradient and reach a well head. Waste water from malfunctioning septic tanks or chemicals seeping into the ground can contaminate the ground water even after the water was tested and found to be safe. If there was significant flooding, it is advised to respond to the immediate problem and then test the water periodically to verify the safety of drinking water.
The most likely occurrence if you were not dead on in the path of the hurricane and submerged underwater near a trucking depot, gas station or other industrial or commercial source of chemicals is that torrential rains have infiltrated your well and you have “dirty or brownish” water from surface infiltration. This is especially true if you have a well pit. Historically, it was common practice to construct a large diameter pit around a small diameter well. The pit was intended to provide convenient access to underground water line connections below the frost line. Unfortunately, wells pits tend to be unsanitary because they literally invite drainage into the well creating a contamination hazard to the water well system. Not having a sanitary cap on a well head is another likely source of surface infiltration.
Run your hoses (away from your septic system and down slope from your well) to clear the well. Run it for an hour or so and see if it runs clear. If not let it rest for 8-12 hours and run the hoses again. Several cycles should clear the well. What we are doing is pumping out any infiltration in the well area and letting the groundwater carry any contamination away from your well. In all likelihood the well will clear of obvious discoloration. Then disinfect your well. This is an emergency procedure that will kill any bacteria for 7 to 10 days. After 7 to 10 days you need to test your well for bacteria to make sure that it is safe. Testing the well for bacteria would determine if the water were safe to drink. A bacteria test checks for the presence of total coliform bacteria and fecal coliform bacteria. These bacteria are not normally present in deeper groundwater sources. They are associated with warm-blooded animals, so they are normally found in surface water and in shallow groundwater (less than 20-40 feet deep). Most bacteria (with the exception of fecal and e-coli) are not harmful to humans, but are used as indicators of the safety of the water.
Determine what type of well you have and how to pour the bleach into the well. Some wells have a sanitary seal which must be unbolted. Some well caps have an air vent or a plug that can be removed. On bored or dug well, the entire cover can simply be lifted off to provide a space for pouring the bleach into the well. Take one gallon of non-scented household liquid bleach and carefully pour about half the bottle down into the well casing using a funnel if necessary. For a typical 6 inch diameter well you need 2 cups of regular laundry bleach for each 100 foot of well depth to achieve about 200 parts per million chlorine concentration. Wear rubber gloves, old clothes and protective glasses to protect you from the inevitable splashes, and don't forget a bucket of bleach mixed with water to wash the well cap. After the bleach has been added, run water from an outside hose into the well casing until you smell chlorine coming from the hose (depending on the depth of your well and the recharge rate, this can take more than an hour) This step is important to mix the chlorine in the well. Then turn off the outside hose. Now go into the house and one bathroom and sink at a time, turn on all cold water faucets, until the chlorine odor is detected in each faucet, then shut it off and move on to the next sink, or bathroom (if you have an automatic ice maker turn it off and dump the ice. If you have a water treatment system, switch it to bypass before turning on the indoor faucets. Once the inside system has been done, go back to the outside spigots and run the hoses until you smell chlorine coming out. Warning if you have iron bacteria in your well, your water may turn completely rust colored. Do not panic it will flush out of the system, but do not use the hot water until the water runs clear or you will have to drain the hot water tank to prevent staining.
Wait 8 to 24 hours before turning the faucets back on. You may want to run the hoses until the water runs clear. It is important not to drink, cook, bath or wash with this water during the time period it contains high amounts of chlorine whose by products are a carcinogen. After at least 8 hours, run the water into a safe area where it will not kill your lawn, your trees or plants pollute lakes, streams or septic tanks. Run the water until there is no longer a chlorine odor. Turn the water off. The system should now be disinfected, and you can now use the water for 7 to 10 days when the effects of the disinfection wear off.
Unlike public water systems, private systems are entirely unregulated; consequently, the well testing, and treatment are the voluntary responsibility of the homeowner. Virginia Master Well Owner Network (VAMWON). volunteers can help simplify understanding the components of a well and private drinking water system. The VAMWON volunteers and agents can provide information and resource links for private well owners and inform Virginians dependent on private water systems about water testing, water treatment, and system maintenance. You can find your VAMWON volunteer neighbor through this link by entering your county in the search box.