[Code of Federal Regulations]
[Title 40, Volume 22]
[Revised as of July 1, 2007]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR146.5]

[Page 766-767]
 
                   TITLE 40--PROTECTION OF ENVIRONMENT
 
         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
 
PART 146_UNDERGROUND INJECTION CONTROL PROGRAM: CRITERIA AND STANDARDS--Table 
 
                      Subpart A_General Provisions
 
Sec. 146.5  Classification of injection wells.

    Injection wells are classified as follows:
    (a) Class I. (1) Wells used by generators of hazardous waste or 
owners or operators of hazardous waste management facilities to inject 
hazardous waste beneath the lowermost formation containing, within one 
quarter (\1/4\) mile of the well bore, an underground source of drinking 
water.
    (2) Other industrial and municipal disposal wells which inject 
fluids beneath the lowermost formation containing, within one quarter 
mile of the well bore, an underground source of drinking water.
    (3) Radioactive waste disposal wells which inject fluids below the 
lowermost formation containing an underground source of drinking water 
within one quarter mile of the well bore.
    (b) Class II. Wells which inject fluids:
    (1) Which are brought to the surface in connection with conventional 
oil or natural gas production and may be commingled with waste waters 
from gas plants which are an integral part of production operations, 
unless those waters are classified as a hazardous waste at the time of 
injection.
    (2) For enhanced recovery of oil or natural gas; and
    (3) For storage of hydrocarbons which are liquid at standard 
temperature and pressure.
    (c) Class III. Wells which inject for extraction of minerals 
including:
    (1) Mining of sulfur by the Frasch process;
    (2) In situ production of uranium or other metals. This category 
includes only in-situ production from ore bodies which have not been 
conventionally mined. Solution mining of conventional mines such as 
stopes leaching is included in Class V.
    (3) Solution mining of salts or potash.
    (d) Class IV. (1) Wells used by generators of hazardous waste or of 
radioactive waste, by owners or operators of hazardous waste management 
facilities, or by owners or operators of radioactive waste disposal 
sites to dispose of hazardous waste or radioactive waste into a 
formation which within one quarter (\1/4\) mile of the well contains an 
underground source of drinking water.
    (2) Wells used by generators of hazardous waste or of radioactive 
waste, by owners or operators of hazardous waste management facilities, 
or by owners or operators of radioactive waste disposal sites to dispose 
of hazardous waste or radioactive waste above a formation which within 
one quarter (\1/4\) mile of the well contains an underground source of 
drinking water.
    (3) Wells used by generators of hazardous waste or owners or 
operators of hazardous waste management facilities to dispose of 
hazardous waste, which cannot be classified under Sec. 146.05(a)(1) or 
Sec. 146.05(d) (1) and (2) (e.g., wells used to dispose of hazardous 
wastes into or above a formation which contains an aquifer which has 
been exempted pursuant to Sec. 146.04).
    (e) Class V. Injection wells not included in Class I, II, III, or 
IV. Specific types of Class V injection wells are also described in 40 
CFR 144.81. Class V wells include:
    (1) Air conditioning return flow wells used to return to the supply 
aquifer the water used for heating or cooling in a heat pump;
    (2) Cesspools including multiple dwelling, community or regional 
cesspools, or other devices that receive wastes which have an open 
bottom and sometimes have perforated sides. The UIC requirements do not 
apply to single family residential cesspools nor to non-residential 
cesspools which receive solely sanitary wastes and have the capacity to 
serve fewer than 20 persons a day.
    (3) Cooling water return flow wells used to inject water previously 
used for cooling;
    (4) Drainage wells used to drain surface fluid, primarily storm 
runoff, into a subsurface formation;

[[Page 767]]

    (5) Dry wells used for the injection of wastes into a subsurface 
formation;
    (6) Recharge wells used to replenish the water in an aquifer;
    (7) Salt water intrusion barrier wells used to inject water into a 
fresh water aquifer to prevent the intrusion of salt water into the 
fresh water;
    (8) Sand backfill and other backfill wells used to inject a mixture 
of water and sand, mill tailings or other solids into mined out portions 
of subsurface mines whether what is injected is a radioactive waste or 
not.
    (9) Septic system wells used to inject the waste or effluent from a 
multiple dwelling, business establishment, community or regional 
business establishment septic tank. The UIC requirements do not apply to 
single family residential septic system wells, nor to non-residential 
septic system wells which are used solely for the disposal of sanitary 
waste and have the capacity to serve fewer than 20 persons a day.
    (10) Subsidence control wells (not used for the purpose of oil or 
natural gas production) used to inject fluids into a non-oil or gas 
producing zone to reduce or eliminate subsidence associated with the 
overdraft of fresh water;
    (11) Radioactive waste disposal wells other than Class IV;
    (12) Injection wells associated with the recovery of geothermal 
energy for heating, aquaculture and production of electric power.
    (13) Wells used for solution mining of conventional mines such as 
stopes leaching;
    (14) Wells used to inject spent brine into the same formation from 
which it was withdrawn after extraction of halogens or their salts;
    (15) Injection wells used in experimental technologies.
    (16) Injection wells used for in situ recovery of lignite, coal, tar 
sands, and oil shale.

[45 FR 42500, June 24, 1980, as amended at 46 FR 43161, Aug. 27, 1981; 
47 FR 4999, Feb. 3, 1982; 64 FR 68573, Dec. 7, 1999]