Living on Karst
A Reference Guide for Landowners in Limestone Regions
Produced by the Cave Conservancy of the Virginias, June 1997
Water Well Tips
- Wells should be lined, or "cased," with welded lengths of steel pipe, which are grouted in place. Since the outside surface of the well casing is a direct conduit to the aquifer the top of the well should be surrounded by a concrete pad and tightly capped, or "sealed."
- Do not spread or store fertilizer, pesticides, petroleum products, or other chemicals in the zone around the well.
- The wellhead area should be landscaped so that standing water cannot accumulate around the well.
- Never pump a new limestone well at high rates (greater than 200 gallons per minute) unless aquifer tests have been conducted by a qualified hydrogeologist. In some areas, excessive pumping of karst wells has caused ground subsidence, sinkhole collapses, and de-watering of neighboring wells and ponds.
- Homeowners and prospective home buyers should be aware that water well samples required for new well permits and property transactions may be collected immediately after "shock" chlorination treatment to disinfect the well. Such samples will not reveal the actual concentration of bacteria and other constituents that may be present after the chlorine is pumped from the system. Re-testing is recommended.
- Abandoned wells, old hand-dug farm wells, and cisterns often represent direct connections between the surface and the karst aquifer. Abandoned wells should be properly plugged with clean rock (in the water zone) and sand-cement grout (to the surface) to prevent runoff from migrating directly to the groundwater. No wastes or debris should ever be disposed in a well or in karst features near any well.
- Test domestic wells for coliform bacteria, nitrates, and other suspected compounds at least annually, and keep a record of these as a "background" for evaluating any future pollution. Also record the dates that muddiness or low water level problems occur, as well as current and previous climatic conditions.
Local health departments regulate the practice of well abandonment.
- Well drillers are required to disinfect new wells with chlorine; attempts to use unapproved "cleansers" in this process have contaminated aquifers for great distances. Be sure your driller follows all applicable state permit guidelines for water well construction and development.
- Polluted and low-yielding wells can sometimes be rehabilitated by a skilled driller who can acidify the well; "seal off" a contaminated water zone with casing, packers, and grout; and re-drill the well to a cleaner water zone (if one exists). Consult with your neighbors about the depth and quality of their water wells, as well as local well drillers, the health department, and geologists before attempting to re-drill a water well.
- If contamination is suspected or is a threat, a specific study to map land use patterns and determine the direction and rate of groundwater movement may be necessary. The information from such studies could serve as the basis for long-term, local solutions to pollution. Contact your local health department or state environmental agency for the names of environmental consultants, non-profit organizations, universities, or watershed groups with experience in this area.