Well Abandonment and Sealing
What the exam tests
Abandonment and sealing test whether you can permanently remove a well from service without creating a vertical pathway between aquifers or a physical hazard. In New Jersey this is regulated work, not a bulldozer job.
Core rules
- An abandoned well must be sealed by a licensed well driller using an approved grout - neat cement, cement-bentonite, or bentonite - placed from the bottom of the well to land surface.
- Remove or perforate casing and obstructions so grout can fill the full borehole and annulus. A casing left open at the bottom can let grout fall away and leave a void.
- Use a tremie or pump to place grout from the bottom up; pouring from the top bridges and leaves gaps.
- Fill the annular space and any gravel pack that could transmit water. Where the well penetrates multiple aquifers, the seal must isolate each producing zone.
- Restore the surface and record the seal: well depth, casing size, grout type, volume, and date.
Worked example
A 200-foot, 6-inch steel-cased well is abandoned. The casing is sound but the screen is at 180-200 feet. Perforate the casing at 100 feet and near the bottom, wash the hole, and tremie grout from 200 feet to surface with a cement-bentonite mix. Calculate grout volume from the borehole and annular volumes, then verify the return at surface. Do not fill the well with sand and cap it: sand transmits water and does not seal the aquifer.
Traps
Sealing only the top 10 feet. Leaving casing in place without perforation so grout cannot reach the screen. Using bentonite chips in a water-filled hole without confirming they hydrate and settle. Failing to notify the property owner or to file the sealing record. Assuming a dry well does not need sealing - it can still be a pathway.