Abandonment and Decommissioning of Wells
Abandonment and Decommissioning of Wells
This domain tests whether you can close a well so it never becomes a vertical conduit between aquifers or a pathway for surface contamination. Abandonment is a construction activity with records, not a bulldozer task.
Core requirements
- Abandonment is performed under the well construction rules by a licensed driller, with notice and filing to the regulatory authority and a record of what was placed where.
- The well must be sealed so each water-bearing zone is isolated and the borehole is impermeable from the bottom up. Filling with sand, gravel, or drill cuttings is not abandonment.
- Full-length grouting - neat cement, cement-bentonite, or high-solids bentonite - placed by tremie from the bottom up is the standard. Where casing cannot be removed, perforate or cut it at intervals so grout can pass behind it, then pressure-grout.
- Flowing artesian wells must be controlled and sealed until flow stops; uncontrolled artesian head wastes water and cross-connects aquifers.
- Cut off or remove casing below grade, cap or seal the top, restore the surface so the site drains, and permanently record the location.
Worked example
A 400-ft well with 6-inch casing to 200 ft and open hole below. Plan: tremie grout the open hole from 400 to 200 ft, then seal the casing interior or annulus so the entire borehole is sealed. Open-hole volume: area = π/4 × (6/12)² = 0.196 ft²; × 200 ft = 39 ft³; with 1.5 excess for voids = 59 ft³. Neat cement yields about 1.18 ft³ per 94-lb sack, so roughly 50 sacks, plus the casing seal. Document volumes, methods, and top of seal.
Traps
- Sand or gravel fill only, or gravel left opposite a fresh-water zone.
- Grout dumped from the surface, bridging and leaving voids.
- Leaving casing open at the surface because "it's capped."
- No abandonment record, which becomes a liability when the parcel is sold or redeveloped.