Drilled wells draw water from deep below the ground and are the source of drinking water for many households and communities throughout Vermont.
As a well is drilled, steel casing is inserted into the hole. This casing is secured 10 feet into bedrock. Drilling will continue deeper into bedrock until an adequate supply of water is discovered.
A different method is used if the well driller encounters gravel instead of bedrock.
Once the drilling is completed, a submersible water pump is installed in the well to pump water to the home. The well casing extends about 18 inches above the ground, it has a watertight well cap with a screened vent, and there is a conduit for the electrical wires for the pump close to the casing. (See diagram.)
Wells drilled since 1987 may have a metal tag with identifying numbers stamped into it. These numbers correspond to the well drillers report filed on this specific well.
Consider the following when planning to construct or improve a drilled well:
Before drilling, determine the location of all possible sources of contamination in the area. The well should be located uphill and as far as possible from them. Examples include leachfields, barnyards, livestock pastures, fuel tanks, roads, etc.
Do not situate the well in a floodplain or close to streams, ponds or wetlands. In some instances, you may want to hire a hydrogeologist to assist in this decision; in other instances, the well driller’s experience can be helpful. On small parcels of land where a permit may be required, the well location may already be specified in the permit.
Additional protection can be gained by having the driller grout the well. Grout is a mud-like mixture of concrete or clay that is pumped between the casing and the soil, forming a seal. This seal effectively prevents surface water from flowing down the outside edge of the casing so that no contamination will be able to enter the well hole.
After a well is drilled, repaired or serviced, it should be disinfected. Disinfection will ensure that any bacteria or viruses that may have gotten into the well during construction or other work are killed and flushed out of the plumbing system.
Liquid household bleach can be used to disinfect the well. Use one gallon of bleach per 350 feet of well depth. This solution should be left in the system 12 hours and then flushed out over several days using an outside faucet. See Guidelines for Disinfection for specific instructions. If the well water has iron or manganese present, disinfection could temporarily cause the water to change color (rust or grey).
After there is no longer any chlorine odor, arrange for a laboratory bacteria test. The test will determine whether coliform bacteria are present. These bacteria do not naturally live in well water; they are common in soil and are found in the intestines of warm blooded animals.
Their presence in your well indicates that water from the surface has entered your well. This means that there is a possibility, but not a certainty, that disease organisms can enter the well by the same route.
Your laboratory sample will be checked more specifically for the presence of fecal coliform (animal or human waste) if total coliform are found.
A properly constructed and maintained well and piping system should not have total coliform bacteria.
A bacterial test kit can be ordered from the public health laboratory by calling 802-863-7335 or, from within Vermont, 800-660-9997.
Do not drink water that is contaminated with bacteria until corrections are made to the well, the system is disinfected and a follow-up water sample shows that no coliform organisms are present. Boiling your water for one minute will make it safe for drinking, ice cubes, produce washing and teeth brushing.