Well Decommissioning and Test Hole Abandonment
There are numerous benefits to decommissioning abandoned wells on your property and is an important action to protect the ground water resources below the property. The vital importance of proper well management cannot be stressed enough. The safety of your family, the integrity of Ground Water sources and the future success of your farming operation could be in jeopardy unless proper steps are taken.
See “Related Documents,” outlining the general procedures for decommissioning both large diameter bored wells and small diameter drilled wells.
Test Hole Abandonment
Contamination of ground water resources has not been a major problem in most parts of Saskatchewan, due in large to the forgiving nature of the geology. The surficial glacial tills have served to protect this resource by intercepting most of the contamination and holding it until it can be naturally broken down into non-harmful products. It also follows that if this protective shield can remove harmful products, then it also will be that much more difficult to clean up after contamination occurs.
Any time a hole is completed, an avenue for contamination is opened. For this reason, abandonment of test holes and the decommissioning of wells is critical if we are to protect this vital resource.
Saskatchewan’s Ground Water Regulations state that, “when a test hole is abandoned without well completion, the driller shall immediately seal and fill this test hole with suitable uncontaminated material in a manner so as to prevent the detrimental vertical movement of water in the hole.”
Dry Auger Test Holes
If no suitable formation is encountered, then the test hole should be filled with the material removed using the auger to compress the fill. A bentonite plug should be placed at the top 2 feet to prevent any surface contamination from entering the hole.
If a formation is encountered and a well is to be completed at this site within a reasonable time, then a 2-foot seal of bentonite should be placed before leaving the test hole site.
If a sand or gravel layer is encountered and no well is to be completed at this site, then the hole should be filled with the material removed during drilling. This material (containing as much clay as is available) should be compressed with the auger and the bentonite plug should extend to the 10-foot level.
If more than one formation is encountered and no well is to be completed, then an attempt must be made to seal the hole to prevent vertical movement between formations. This would mean that the hole should be plugged with bentonite from below the lowest formation to above the highest formation. To accomplish this, bentonite pellets must be used and slowly added to fill the total depth of the hole. An alternative would be to mix a high solids mud and pump the hole full from the bottom to the top.
Rotary Test Holes
If no suitable formation is encountered, then the test hole should be filled with the material removed. A bentonite plug should be placed at the top 2 feet to prevent any surface contamination from entering the hole.
If a sand or gravel layer is encountered and no well is to be completed at this site, then bentonite or a high solids mud should be used to fill the hole.