Oil and Gas Production Wastewater: Soil Contamination and Pollution Prevention

Table 4

US EPA injection well classification system.

Well class	Injection well description	Approximate inventory
Class I	Inject hazardous wastes beneath the lowermost USDW	500
	Inject industrial nonhazardous liquid beneath the lowermost USDW
	Inject municipal wastewater beneath the lowermost USDW
Class II	Dispose of fluids associated with the production of oil and natural gas	147,000
	Inject fluids for enhanced oil recovery
	Inject liquid hydrocarbons for storage
Class III	Inject fluids for the extraction of minerals	17,000
Class IV	Inject hazardous or radioactive waste into or above USDW, 40 sites
	This activity is banned. These wells can only inject as part of
	an authorized cleanup
Class V	Wells not included in the other classes. Inject nonhazardous liquid into or above a USDW	500,000 to >685,000

[52].