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SUB-PROBLEMS INCLUDING LEADING TO IMPAIRMENT AND BEST PRACTICES FOR NON-HAZARDOUS WASTE DISPOSAL AND HAZARDOUS WASTE DISPOSAL USING UNDERGROUND INJECTION WELLS

(See endnotes 61, 64)

An underground injection well is a dug or mechanically constructed hole in the ground that is deeper than it is wide and is used for depositing fluid including hazardous wastes and also carbon dioxide into isolated areas typically far below the Earth’s surface. This means of disposal started in the 1930s and was used to remove salt water which was present during the drilling for crude oil. This process became even more common in the 1950s when chemical companies began depositing industrial waste into deep wells. In 2010, the EPA finished issuing regulations for geological sequestration of carbon dioxide.

There are at least six ways in which fluids injected underground in wells can migrate into the underground source of drinking water. They are:

  • 1. Migration through the injection well casing
  • 2. Migration through the annulus (void between concentric cylinders) between the casing and the drilled hole
  • 3. Migration from the injection horizon through the confining zone
  • 4. Vertical migration through wells which have been improperly abandoned or completed
  • 5. Lateral migration from an injection zone into a protected area
  • 6. Injection of the fluids above the underground source of drinking water or directly into it

Over half of the liquid hazardous waste and a large amount of the non-hazardous industrial liquid waste in the United States are put into underground injection wells. There are six types of underground injection wells that are regulated to protect the groundwater supply. They are:

  • Class I—Industrial and municipal waste disposal wells (See endnote 60)
  • Class II—Oil and gas-related wells
  • Class III—Mining wells
  • Class IV—Shallow hazardous and radioactive injection wells
  • Class V—Shallow injection wells which do not fit in the other four categories and may either be hazardous or non-hazardous
  • Class VI—Geological sequestration wells
 
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