Underground Injection Wells

An injection well is a well into which fluids are being injected. The federal underground injection control (UIC) rule, 40 CFR part 144, sorts injection wells into six classes, and every owner or operator of one must be authorized by permit or by rule (40 CFR 144.1(g), 144.3, 144.6). The owner or operator of a well authorized by rule gives inventory information about it to the program's Director, with exceptions the rule sets (40 CFR 144.26). The standard's table of standard sources does not name these records (E1527-21, 8.2.2, Table 2).

What puts a property on this record

The classes cover disposal below the lowermost formation holding, within a quarter mile of the well bore, an underground source of drinking water (Class I), fluids tied to oil and gas production and storage (Class II), injection to extract minerals (Class III), disposal of hazardous or radioactive waste into or above a formation that, within a quarter mile, holds an underground source of drinking water (Class IV), and geologic sequestration of carbon dioxide (Class VI) (40 CFR 144.6). The rule prohibits building or, past dates it sets, operating a Class IV well, except one that reinjects treated ground water into the formation it came from under a cleanup approved under CERCLA or RCRA (40 CFR 144.13(a), (c)).

Class V takes the injection wells in none of the other classes (40 CFR 144.6(e)). They are typically shallow wells that place fluids directly below the land surface; if the fluids qualify as hazardous waste under RCRA, the well is Class I or Class IV, not Class V (40 CFR 144.80(e)). The part's Class V examples include large-capacity cesspools, drainage wells mainly for storm runoff, septic system wells serving a multiple dwelling or business establishment, and:

Dry wells used for the injection of wastes into a subsurface formation;

40 CFR 144.81(5), edition revised as of July 1, 2025

A drywell is a well, other than an improved sinkhole or subsurface fluid distribution system, completed above the water table, and a cesspool is a drywell that receives untreated sanitary waste (40 CFR 144.3). Motor vehicle waste disposal wells receive or have received fluids from vehicle repair or maintenance (40 CFR 144.81(16)). The rule does not cover single family residential cesspools and septic systems, nor non-residential ones used solely for sanitary waste with the capacity to serve fewer than 20 persons a day (40 CFR 144.1(g)(2), 144.81(2), (9)). It does cover a well that a hazardous waste generator or facility uses to dispose of fluids containing hazardous waste, septic systems and cesspools included, whatever their capacity (40 CFR 144.1(g)(1)(iii)).

The inventory gives at least the facility's name and location, a legal contact, its ownership, and the nature, type and operating status of its injection wells (40 CFR 144.26(a), 144.83(a)(2)(i)). In a program EPA runs directly, owners of Class II enhanced recovery wells, Class IV wells and certain Class V wells also give each well's location, depth and construction and the nature of the fluids injected (40 CFR 144.26(b), 144.83(a)(2)(ii), (iii)). An owner or operator who fails to submit inventory information by the rule's deadline may not inject until it is submitted (40 CFR 144.26, 144.84(b)(4)).

New motor vehicle waste disposal wells and new cesspools are prohibited as of April 5, 2000. Large-capacity cesspools must be closed. An existing motor vehicle waste disposal well in a ground water protection area or other sensitive ground water area, or anywhere in a State that has not identified those areas, must be closed or permitted (40 CFR 144.84(b)(2), 144.85). A Class V well is closed so that no fluid with a contaminant moves into an underground source of drinking water where it may cause a drinking water violation or otherwise harm health, and soil, gravel, sludge, liquids or other materials taken from or beside it are managed under the rules that apply (40 CFR 144.12(a), 144.82(b)).

What a listing shows, and what it does not

The regulation does not say which wells are on any list. A Class V well authorized by rule needs no individual permit, so the lack of a permit does not show the lack of a well (40 CFR 144.84(a)). The systems the rule does not cover owe no inventory information under it (40 CFR 144.1(g)(2), 144.26). Outside the wells listed for programs EPA runs directly, the minimum inventory items the federal rule sets do not include what was injected; a Director may require more (40 CFR 144.26(a), 144.82(d), 144.83(a)(2), (b)). A State Director's annual program report includes an updated inventory of active underground injection operations (40 CFR 144.8(b)(2)(i)(C)); the regulation does not say whether a closed well stays on an inventory.

In a Phase I ESA

Table 3, the standard's examples of additional records, does not name these records (E1527-21, Table 3). Additional records are checked when the environmental professional judges them reasonably ascertainable, useful, accurate and complete enough for the purpose of the records review, and generally obtained in local practice for the kind of transaction (E1527-21, 8.2.4). Wells, dry wells and injection wells among them, septic systems or cesspools, and drains and sumps are site visit features (E1527-21, 9.4.21, 9.4.27, 9.4.28). Before the site visit, the owner, the key site manager and the user are asked whether underground injection permits and registrations of underground injection systems exist (E1527-21, 10.8, 10.8.1.4, 10.8.1.6).

For a well at the subject property, the answer turns on its class and status, what went into it and from which uses, whether it was closed and how, and what became of the material taken out. See septic system, cesspool or dry well and auto repair shop with lifts, floor drains and a separator. If the professional concludes that hazardous substances or petroleum products are present or likely present at the subject property because of a release or a likely one, or present under conditions posing a material threat of a future release, then unless judged a de minimis condition or a historical REC, the REC is listed in the Conclusions, and the professional should give an opinion on additional investigation, if any (E1527-21, 3.2.20, 3.2.39, 3.2.73, 12.7, 12.8).

A listing of the subject property, or of another site inside the approximate minimum search distance, from any source the assessment uses gets the professional's judgment on its significance (E1527-21, 8.1.10).

What the federal rule says

The inquiry rule (40 CFR part 312) does not mention injection wells. Among what the inquiry must seek to identify about the subject property:

Waste management and disposal activities that could have caused releases or threatened releases of hazardous substances;

40 CFR 312.20(e)(1)(iii), edition revised as of July 1, 2025

For a party seeking the liability protections that item stops at hazardous substances; the standard includes petroleum products (E1527-21, 1.1.2). The rule lets the procedures of E1527-21 be used to comply with its sections 312.23 through 312.31 (40 CFR 312.11(a)).

Where the record is kept

The Director is normally the state or tribal director where a program is approved, and the EPA Regional Administrator where EPA runs the program (40 CFR 144.3). The Director's annual reports are to be completed and available to the public within 60 days after the calendar year (40 CFR 144.8(c)(2)). A submitter may claim information given to EPA as confidential, but a claim for the name and address of a permit applicant or permittee, or for information on contaminants in drinking water, is denied (40 CFR 144.5).

This page is general reference for environmental professionals. It does not classify any property. ASTM E1527-21 is the standard and is not reproduced here; the judgment of the environmental professional on the facts governs.