Abandoned water wells pose a hazard, and are potential sources of contamination for groundwater. If you have an abandoned well on your property, you should take steps to plug or fill in the well to prevent accidents from occurring. Landowners can fill shallow water wells themselves by following the proper guidelines. In some cases, the county may help a landowner to fill in these wells. County authorities are naturally reluctant to come on private land where their equipment may damage water lines, gas lines, electric lines, or sewer lines. However, if you have an abandoned well, contact your commissioner or the groundwater conservation district office and see if they can help if you do not have the means to do so yourself.
Groundwater Districts are encouraging the State to make available more money to assist landowners in filling and plugging abandoned wells. A deep water well can be plugged by removing the casing, if possible, and cementing and/or using bentonite clay to fill the penetration to the surface, from the bottom up. Contact the PCGCD office if you have any questions about abandoned water wells.
An abandoned well is a direct conduit from the surface to the aquifer below. Contaminants that enter the well are introduced directly into the aquifer with no opportunity for natural filtration by soils or geologic materials. If a contamination incident occurs with a concentrated chemical, the potential for health threatening levels in the underlying aquifer is high. This puts other wells in the aquifer at risk, particularly those wells on the same property or those that are close to the abandoned well. Just one gallon of 2,4-D herbicide can contaminate about three to four million gallons of water. In terms of groundwater, approximately that much water would be held in the upper three feet of an aquifer over a 20-acre area.
A well open to more than one aquifer will allow water to migrate out of a zone with higher pressure head and enter a zone with lower pressure head. In many areas of Texas, deep aquifers are under high pressures and are extremely salty. When the casing from a high pressure well deteriorates and the well is abandoned without proper plugging, continual upward flow of salty water from the deeper aquifer will cause contamination of the shallower freshwater aquifer. Also, any pollutants that occur in one zone can migrate to another zone through the well.
For more information: http://abandonedwell.tamu.edu/