hazardous waste landfills must also comply with inspections, monitoring, release
response plans, and closure and post-closure plans (e.g., monitoring leachate,
preventing storm water run on and run off).
Salt Formations, Caves, and Mines
Salt dome and bed formations, underground caves, and mines are geologic
repositories. The absence of flowing water within natural salt formations
prevents dissolution and the subsequent spreading of the waste products. Rooms
and caverns in the salt can be sealed, thus isolating the waste from the biosphere.
Surface Impoundments
Surface impoundments are natural topographic depressions, man-made
excavations, or diked areas formed primarily of earthen materials that are used
for temporary storage and/or for the treatment of liquid hazardous waste.
Examples include holding, storage, settling, aeration pits, ponds, and lagoons.
Hazardous waste surface impoundments are required to be constructed with a
double liner system, a leachate collection and removal system, and a leak
detection system.
PROS
■ Low initial startup and operating costs.
■ Built quickly, wastes can be retrieved, and, if lined, can store wastes for
long periods of time.CONS
■ Groundwater contamination.
■ VOC (Volatile Organic Compound) pollution.
■ Overflow if flooding occurs.
■ Earthquake issues.
■ Promotes waste production.Underground Deep Well Injection
An injection well stores fluid deep underground in geologically stable, porous
rock formations, such as sandstone or limestone, or into or below the shallow