NPDES Permits

A National Pollutant Discharge Elimination System (NPDES) permit is the Clean Water Act authorization, from EPA or an approved State, for a point source that discharges pollutants to waters of the United States; the program also reaches treatment works treating domestic sewage, unless their sludge requirements sit in certain other permits (40 CFR 122.1(b)(1), (2), 122.2).

What puts a property on this record

The regulation says who must apply, not which sites are listed.

• Duty to apply. Anyone discharging or proposing to discharge pollutants without an effective permit must apply, unless covered by a general permit, excluded under section 122.3, or discharging into a privately owned treatment works the Director has not required to apply; where one person owns a facility and another operates it, the operator applies (40 CFR 122.21(a)(1), (b)).
• Point source. A point source is "any discernible, confined, and discrete conveyance" that does or may discharge pollutants, such as a pipe, ditch or well; agricultural storm water runoff and irrigation return flows are not point sources (40 CFR 122.2). A discharge includes surface runoff collected or channelled by man, but not pollutants an indirect discharger sends to a publicly owned treatment works, which need no NPDES permit (40 CFR 122.2, 122.3(c)).
• Stormwater. A discharge made up entirely of storm water needs a permit only in the cases listed, among them storm water associated with industrial activity and, since October 1, 1994, small construction activity, subject to the exclusions and waivers the section sets out (40 CFR 122.26(a)(1)(ii), (a)(9)(i)(B)). The industrial term reaches conveyances "directly related to manufacturing, processing or raw materials storage areas at an industrial plant", including, for the listed categories, "areas where industrial activity has taken place in the past and significant materials remain and are exposed to storm water" (40 CFR 122.26(b)(14)).

What a listing shows, and what it does not

The regulation does not say what a listing holds. Applicants other than publicly owned and other treatment works treating domestic sewage, vessels and pesticide applicators give the activities that need the permit and the facility's other environmental permits, with a map reaching one mile past the property boundaries that shows the facility's discharge structures and hazardous waste facilities and the wells where its fluids are injected underground (40 CFR 122.21(f)). With exceptions for some construction, oil and gas, and mining discharges, an industrial storm water applicant for an individual permit also maps each area, past or present, where significant materials were stored or disposed of outdoors, and gives what it knows of "significant leaks or spills of toxic or hazardous pollutants" in the three years before applying (40 CFR 122.26(c)(1)(i)(A), (D)).

The permittee reports monitoring results on discharge monitoring reports or the Director's sludge forms, and "shall report any noncompliance which may endanger health or the environment" orally within 24 hours of learning of it and in writing within 5 days, an unanticipated bypass or an upset that exceeds an effluent limitation among them; the Director may waive the written report for those if the oral one came in time (40 CFR 122.41(l)(4)(i), (l)(6)).

A site without a permit may still discharge: into a publicly owned treatment works as an indirect discharger, or, for storm water alone, where an industrial facility shelters all its materials and activities from it and meets the section's conditions for a no exposure certification (40 CFR 122.3(c), 122.26(g)).

In a Phase I ESA

NPDES records are not a standard source of Table 2, and Table 3, the standard's examples of additional records, does not name them (E1527-21, 8.2.2, Table 2, 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 initial site assessments for the type of transaction involved, under local good commercial and customary practice (E1527-21, 8.2.4).

Before the site visit, the owner, the key site manager if one is identified, and the user if not the owner are asked whether documents such as NPDES and other wastewater permits exist (E1527-21, 10.8, 10.8.1), and the visit looks at wastewater and stormwater leaving or entering the subject property, and at drains, sumps, pits, ponds and lagoons (E1527-21, 9.4.21, 9.4.22, 9.4.26).

For a permit at the subject property, the answer turns on what is discharged and from which process, where outfalls, drains and storage areas lie, and what the reports and applications in the file record of exceedances, bypasses, spills and past storage areas. Where they show a release that left hazardous substances or petroleum products present or likely present at the subject property, the condition is listed in the Conclusions as a recognized environmental condition (REC) unless judged a de minimis condition or a historical REC, 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). See pit, pond or lagoon on the subject property.

A listing of the subject property, or of another site inside the approximate minimum search distance, gets the professional's judgment on its significance (E1527-21, 8.1.10). See adjoining or nearby property.

What the federal rule says

The inquiry rule does not name discharge permits. For the subject property, its list includes:

Records of activities, conditions, or incidents likely to cause or contribute to releases or threatened releases as defined in § 312.1(c)

40 CFR 312.26(b)(2), edition revised as of July 1, 2025

Its examples include records and permits for landfills, storage tanks and hazardous waste handlers, and spill reporting records (40 CFR 312.26(b)(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

Applications and reports go to the Director: the Regional Administrator or, under an approved State program, normally the State Director (40 CFR 122.2, 122.21(a)(1), 122.41(k)(1)). The permittee keeps monitoring records, report copies and application data for at least 3 years, counted from each sample, measurement, report or application, and sewage sludge monitoring records for at least five years; the Director may lengthen the period (40 CFR 122.41(j)(2)). For EPA's public compliance records of direct dischargers, see ECHO.

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.