Liquid Waste Disposal
Drilling for oil and gas produces both liquid and solid waste that must be disposed of. The liquid waste from this industry is considered a “Class II waste” according to the US EPA. Aquifers are places underground capable of holding or transmitting groundwater. To dispose of Class II waste, operators are granted aquifer exemptions, by the EPA based on the state’s recommendations. The term “exemption,” specifically, refers to the Safe Drinking Water Act, which protects underground sources of drinking water (USDWs).
Therefore, these exemptions grant oil and gas operators the right to contaminate groundwaters, albeit many of the groundwater formations used for disposal in Class II wells are very deep.
Aquifer Exemption Criteria
There are several qualifiers for a USDW to be granted exempt from the Safe Drinking Water Act. Aquifer exemptions are granted for underground formations that are not currently used as a source of drinking water and meet one of the following criteria:
- The formation contains commercially producible minerals or hydrocarbons;
- The formation is so deep that recovery of water for drinking water purposes is economically or technologically impractical; or,
- The formation is so contaminated that it would be economically or technologically impractical to render the water fit for human consumption.
- In some states, aquifer exemptions are not approved for formations with Total Dissolved Solids (TDS*) equal to or less than 3,000 mg/l TDS.
If an underground formation qualifies for an exemption, it does not mean that groundwater cannot be used for drinking water, just that it is not currently a source of drinking water. The most precarious criteria requirement, therefore, is the determination that a USDW is simply not “economically viable” or it is “technologically impractical,” meaning that the cost of drilling a groundwater well to the depth of the aquifer (under the condition of the current need for water) may make the investment impractical. In the near future, this water may be needed and highly valued, however.
TDS = Total dissolved solids are inorganic salts (e.g. calcium, magnesium, potassium, sodium, bicarbonates, chlorides, and sulfates), as well as some organic matter, dissolved in water.
The Lay of the Land
Below, we have put together a map of aquifer exemptions in the U.S. Click on the dots and shaded areas to learn more about a particular aquifer.
Map of all aquifer exemptions in the U.S.
By Kyle Ferrar, Western Program Coordinator, FracTracker Alliance