In an area where wells penetrate more than one water-bearing layer, contaminants may reach the ground water zone of the old well and then travel on to other portions of the aquifer. If the contamination connects with another abandoned well, it could impact other aquifers and threaten operating wells and water supply sources. Abandoned dug wells typically do not lead to a contamination risk for deep aquifers, but their wide diameter, usually 3 feet to 5 feet, creates a physical safety hazard for construction equipment, in addition to the danger to people and animals that may be injured falling into the well.
Landowners should find the location of any old or out-of-service wells. Clues to the location of these wells include:
- Pipes sticking out of the ground
- Small buildings that may have been a well house
- Depressions in the ground
- The presence of concrete vaults or pits (perhaps covered by lumber or metal plates)
- Out-of-use windmills (wind pumps) are likely to be located near an old well
- Other clues and information can be obtained from:
- Old maps, plans and property title documents
- Information from neighbors
- Additions to an old home: In the past, wells commonly were constructed in basements or under porches to keep the water pumps from freezing and to ease access in the winter.
- Water utility history: What was the source of water for the home before utility water was available?
Once a well is determined to have no current use or potential future use, a water well contractor should be contacted to give advice about the most appropriate well decommissioning method. The water well professional will have knowledge of well decommissioning code requirements. Wells should be sealed from the bottom up. In most cases, only well contractors have the right equipment to do this. Any pumps, pipes, related equipment or blockage should be removed from the well so that it may be filled-in and sealed properly.
Approved backfilling and well-sealing procedures vary from state to state. They generally require the use of special sealing material, usually cement-bentonite grout or bentonite clay chips. The use of straight Portland cement usually is discouraged because cement shrinks in volume during curing, which creates very small fractures and gaps through which water may continue to penetrate.
In most cases, homeowners are required to notify their local Department of Environmental Protection or Water Quality Division to document the decommissioning of the well. Homeowners are urged to contact these environmental agencies to learn what procedures are required in their region.
For more information on ground water and wells, well owners are encouraged to visit www.privatewell.com and click on “ground water information.”