Grouting, Sealing, and Abandonment
This domain tests the seal: the material that keeps surface water and shallow contamination out of the annulus, and the procedure that takes an unused well permanently out of service. Expect grout material selection, placement method, volume checks, and abandonment standards.
Grout materials and mixing
- Approved seals are typically neat cement, cement-bentonite blends, and bentonite slurry, mixed to the density the rule specifies. Mix by the book and record the batch; a thin slurry is a failed seal even if it looks full.
- Grout must fill the annular space continuously from the bottom of the casing up, and the surface seal must be finished to grade.
Placement
- Place grout by tremie or positive displacement from the bottom up. Never pour from the top and never allow free-fall through standing water; that bridges and dilutes.
- Compare volume actually pumped with calculated annular volume. A large shortfall means a void or a bridge; treat it before you leave the site.
Abandonment
- Pull the pump and wiring, remove obstructions, disinfect, then fill with approved grout or specified material, seal the top, and restore grade. Flowing artesian wells need a seal designed to hold pressure.
- File the abandonment record and give the owner documentation.
Worked example
A 6-inch hole with 4.5-inch outside-diameter casing, 100 feet of annulus to seal. Area equals 0.7854 times (0.5 squared minus 0.375 squared), about 0.086 square feet, times 100 feet equals 8.6 cubic feet, or roughly 64 gallons. Add 10 to 20 percent for loss and order about 75 gallons. If only 40 gallons go in, stop and investigate.
Traps that cost marks
- Grouting only the top portion instead of the full required interval.
- Dumping grout from the surface.
- No volume cross-check and no record of gallons used.
- Leaving an abandoned well unsealed or undocumented.