Abandoning a Brick-Lined Dug Well
A farm owner wants to abandon a 36-inch-diameter hand-dug well that is 30 ft deep with a brick liner. The well is 60 ft from the proposed replacement well, 70 ft from a septic tank, and 50 ft from an absorption field. It is located in a low spot that ponds after rain. The well contains debris, a broken pump rod, and 8 ft of standing water. The driller proposes to pull the debris, dump five 80-lb bags of bentonite chips into the well, and cap it with a concrete slab at grade. The replacement well is to be drilled 2 weeks later.
1. Is the proposed abandonment method adequate? What does the Code require for a large-diameter dug well?
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No. The proposal is unlikely to produce a proper seal. A 36-inch well 30 ft deep has a volume of about 212 cubic feet, or roughly 7.9 cubic yards. Five 80-lb bags of bentonite chips are only 400 lb and a small fraction of the volume; chips can bridge on debris or the brick liner and leave voids. The debris and broken rod must first be removed, and the well should be disinfected before sealing. For a large-diameter dug well, the lower portion is typically filled with clean, graded granular material to a point above the water level, and the upper portion is sealed with a low-permeability grout such as neat cement or bentonite slurry. The seal must extend to the surface and be mounded to shed water. A concrete slab at grade in a ponding area is not sufficient surface protection. The abandonment must be recorded and reported.
2. Evaluate the separation distances between the old and new wells and the septic features. Does abandonment timing matter?
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The replacement well at 60 ft from the old dug well is not automatically prohibited by the old well, but 70 ft from the septic tank meets the 50-ft minimum and 50 ft from the absorption field fails the 75-ft minimum. The replacement well location is therefore unacceptable regardless of how well the old well is abandoned. The driller should relocate the replacement well or have the drainfield relocated or re-evaluated by the local authority. Timing matters because the old well is an open contamination pathway; it should be properly abandoned before or during replacement-well construction, not left open while the new well is completed. The old well should not be used as a disposal point for drilling fluids or debris.
3. What documentation and surface protection should follow the abandonment?
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The driller should record the well location, diameter, depth, static water level, debris removed, fill and seal materials, volumes, and top-of-seal elevation, and submit the required abandonment or well-construction report to the state and local health authority. The finished seal should be mounded above grade so ponded water drains away, and the site should be graded to prevent ponding. If the brick liner is left in place, it should be perforated or removed at the seal zone if needed to ensure a continuous grout column and no bridging. The owner should be given the record and advised not to excavate or disturb the sealed area. A proper abandonment protects the replacement well and the aquifer from surface contamination.