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Salt Cavern Closure
- Once a cavern has been filled with waste, the cavern would
be sealed and the borehole plugged with cement.
- Plugs would be placed above and below water-bearing zones
to isolate those zones permanently.
- Once sealed, the cavern would be subject to a number of post-closure
processes.
Post-Closure Processes
- With time, the volume of a salt cavern would decrease because
of salt creep (i.e., salt surrounding the waste-filled cavern
would deform and flow into the cavern because it is at a higher
pressure than the waste).
- The pressure in the cavern would increase because of its reduced
volume and through warming by the surrounding salt mass.
- Differential settling and compaction of the waste material
would occur.
- Chemical reactions could occur in the waste material.
- Gas production could occur in the cavern:
- bacterial degradation of the waste
- corrosion natural degassing of the surrounding salt
- Although salt is highly impermeable, under the extreme pressures
found at cavern depth, it may become slightly permeable to the
extent that some of the built up cavern pressure can release
into the surrounding salt formation.
- DOE funded the Solution Mining Research Institute (SMRI) to
develop a bibliography of papers and reports on cavern closure
and abandonment.
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