Decommissioning Wells for Safety
Posted: December 17, 2012
Decomissioning a well. A long tremie pipe is being used to grout the entire well bore after the casing has been pulled.
Pennsylvania has one of the largest rural populations of any state in the country, and most rural populations depend on private water systems for drinking water.
Homeowners may choose to abandon a well on their property if it is plagued with problems and they believe that a new well will provide a high-quality water supply. A well may also go unused if it does not provide an adequate yield and a new well is thought to provide a more abundant water supply.
Regardless of the reason that a well is no longer in use, it is very important for any unused well to be properly sealed (or decommissioned) by a qualified well driller. The goal of sealing a well properly is to restore the area to the same condition (or better) that existed before the original well was drilled. An unused well that is not properly sealed becomes a direct conduit for surface contamination to affect the surrounding groundwater supply. In certain situations an unused well that is not sealed properly can lead to mixing between aquifers of poor and good water quality. Besides the potential pollution that an unused well might cause, it can also be a physical hazard and sealing it properly will help to prevent injury. It is never acceptable for unused wells to be used for the disposal of any type of liquid or solid waste.
Pennsylvania currently has no statewide residential regulations regarding sealing wells. The procedures generally used in Pennsylvania are based on the recommendations of the National Ground Water Association.
The first step in properly decommissioning a private water well is to hire a qualified professional. Use special consideration if the well to be plugged is a flowing artesian well. In this situation, you should select a driller who has extensive experience in sealing an artesian well.
After a qualified driller is obtained, the following steps should be taken:
- Research must be done on the well. Any records on the well, including the well log or maintenance records, should be located and given to the contractor. If no records can be obtained, then a down-hole camera and other techniques can be used for the contractor to gather information about the well.
- Any material potentially hindering the proper sealing of a decommissioned well should be removed. In most situations, the well casing or liner should be removed from the borehole along with the pitless adapter, pump, screen, and any debris that has fallen into well.
- The well should be shock chlorinated (100 to 500 mg/L) to reduce the presence of bacteria and the chance that the sealed well might be a future source of bacteria for other wells in the area.
- A grout or cement material chosen by the contractor should be used to seal the hole. The sealing material must be introduced at the bottom of the borehole and filled up to the surface using a tremie or grout pipe, cement bucket, or dump bailer under pressure.
Methods and equipment used for the sealing should be selected based on recommendations from a qualified professional. And finally, information about the decommissioned well should be recorded by the contractor and a copy of the report given to both the homeowner and the state or local regulatory agency. More information about the National Ground Water Association and specific recommendations for well decommissioning can be found at www.wellowner.org or the Pennsylvania Department of Environmental Protection.