Clean Water Act

The Clean Water Act (CWA) — formally the Federal Water Pollution Control Act of 1972 — established the basic structure for regulating discharges of pollutants into U.S. waters and set the national goal of making waters "fishable and swimmable." Its core mechanism is the National Pollutant Discharge Elimination System (NPDES): any facility discharging pollutants from a "point source" (a pipe, ditch, or defined conveyance) into navigable waters needs a permit. The Army Corps of Engineers separately administers Section 404 permits for dredge-and-fill activities that affect wetlands — a major regulatory tool that has been repeatedly contested over what waters qualify as "waters of the United States" (WOTUS). The Supreme Court's Sackett v. EPA (2023) decision substantially narrowed WOTUS, eliminating federal jurisdiction over wetlands that aren't continuously connected to navigable waters, removing protections for approximately half the nation's wetlands by some estimates. The CWA also authorizes citizen suits, allowing any person to sue polluters or EPA directly for enforcement failures — a provision that has generated significant environmental litigation and regulatory accountability.

Current Law (2026)

Legal Authority

• 33 U.S.C. § 1251 — Congressional declaration of goals (objective: restore and maintain the chemical, physical, and biological integrity of the Nation's waters; national goal to eliminate discharge of pollutants; interim goal of fishable/swimmable waters)
• 33 U.S.C. § 1311 — Effluent limitations (discharge of any pollutant by any person shall be unlawful except in compliance with the Act; technology-based limits for industrial dischargers and POTWs; Best Available Technology for toxics and non-conventional pollutants; Best Conventional Pollutant Control Technology for conventional pollutants)
• 33 U.S.C. § 1312 — Water quality related effluent limitations (more stringent limits when technology-based standards are insufficient to meet water quality standards)
• 33 U.S.C. § 1313 — Water quality standards (states adopt water quality standards for designated uses — drinking, recreation, aquatic life, agriculture; standards include numeric criteria for pollutants; Total Maximum Daily Loads for impaired waters)
• 33 U.S.C. § 1316 — National standards of performance (technology-based standards for new point sources in designated categories)
• 33 U.S.C. § 1317 — Toxic and pretreatment effluent standards (EPA sets standards for toxic pollutants; industrial users discharging to POTWs must meet pretreatment standards to prevent pass-through and interference)
• 33 U.S.C. § 1318 — Records, reports, and inspections (dischargers must maintain records, install monitoring equipment, sample effluent, and report results; EPA/states may enter and inspect facilities)
• 33 U.S.C. § 1319 — Enforcement (compliance orders, administrative penalties up to $25,000/day, civil penalties up to $68,445/day per violation, criminal penalties for negligent violations up to $25,000/day and 1 year imprisonment, knowing violations up to $50,000/day and 3 years, knowing endangerment up to $250,000 and 15 years)
• 33 U.S.C. § 1321 — Oil and hazardous substance liability (prohibition on discharge of oil or hazardous substances in harmful quantities; National Contingency Plan for removal; liability for cleanup costs and natural resource damages)
• 33 U.S.C. § 1341 — State certification (Section 401 — any applicant for a federal license or permit that may result in a discharge must obtain state certification that the discharge complies with state water quality standards)
• 33 U.S.C. § 1342 — NPDES permits (EPA or authorized states issue permits for point source discharges; permits contain technology-based and water quality-based effluent limits, monitoring requirements, and reporting conditions)
• 33 U.S.C. § 1344 — Section 404 wetlands permits (Army Corps issues permits for discharge of dredged or fill material into navigable waters including wetlands; EPA has veto authority under § 1344(c); nationwide permits for minor activities)
• 33 U.S.C. § 1362 — Definitions (navigable waters, point source, discharge, pollutant, person, municipality — foundational terms for CWA jurisdiction)
• 33 U.S.C. § 1365 — Citizen suits (any citizen may sue any person alleged to be in violation of an effluent standard or order, or sue EPA for failure to perform non-discretionary duties; 60-day notice requirement; attorneys' fees available)
• 33 U.S.C. § 1370 — State authority (states may adopt standards more stringent than federal; CWA does not preempt state water quality laws)

Implementing Regulations (CFR)

• 40 CFR Part 122 — NPDES Permit Program:

  • 40 CFR 122.21 — Application for a permit (content and submission requirements for individual NPDES permits)
  • 40 CFR 122.23 — Concentrated animal feeding operations (CAFOs) (NPDES requirements for large livestock operations)
  • 40 CFR 122.26 — Storm water discharges (permit requirements for municipal separate storm sewer systems and industrial/construction storm water)
  • 40 CFR 122.28 — General permits (coverage for categories of similar dischargers under a single permit)

• 40 CFR Part 117 — Determination of reportable quantities for hazardous substances:

  • Applicability to NPDES discharge permits; establishes reportable quantities for hazardous substances that trigger notification requirements when discharged into navigable waters

• 40 CFR Part 121 — State and tribal water quality certification:

  • Procedures for state and tribal certification programs under Clean Water Act § 401; certification that federally permitted discharges comply with state water quality standards; timelines and conditions for certification decisions

• 40 CFR Part 122 — NPDES Permit Program (additional provisions):

  • 40 CFR 122.24 — Concentrated aquatic animal production facilities (NPDES requirements for aquaculture facilities that meet production thresholds)
  • 40 CFR 122.23 — Concentrated animal feeding operations / CAFOs (defines CAFO categories — large, medium, small; establishes which operations are point sources requiring NPDES permits; sets requirements for nutrient management plans)

• 40 CFR Part 131 — Water Quality Standards (designated uses, water quality criteria, antidegradation policy, and state adoption/EPA approval procedures)

• 40 CFR Part 122 — NPDES Permit Program: Stormwater and New Source Provisions (the regulatory provisions governing stormwater discharge permitting — the fastest-growing component of the NPDES program, now covering millions of construction sites, municipalities, and industrial facilities):

  • § 122.26 — Stormwater discharges: the NPDES program covers stormwater runoff from three major categories: (1) municipal separate storm sewer systems (MS4s) — storm drain networks operated by cities, counties, and other local governments that convey stormwater directly to water bodies without treatment; (2) industrial storm water — runoff from industrial facilities exposed to precipitation at manufacturing, mining, and similar operations; (3) construction site runoff — earth-disturbing activities over 1 acre require an NPDES permit (or coverage under a general permit)
  • §§ 122.30–122.37 — Small MS4 storm water program: cities, towns, counties, and other government entities operating storm sewer systems in urbanized areas must obtain NPDES permit coverage; regulated MS4 operators must develop and implement a stormwater management program addressing six minimum control measures: (1) public education and outreach, (2) public participation/involvement, (3) illicit discharge detection and elimination, (4) construction site runoff control, (5) post-construction runoff control, and (6) pollution prevention/good housekeeping for municipal operations; the focus on illicit discharge detection (§ 122.34) is particularly important — storm sewer systems routinely receive illegal connections from sanitary sewers, industrial drains, and washing operations that are not authorized NPDES discharges; municipalities must map their storm systems and systematically detect and eliminate these connections
  • § 122.28 — General permits: NPDES permits can be issued as "individual permits" (facility-specific, negotiated conditions) or general permits covering a category of similar dischargers; most construction stormwater and small industrial stormwater is covered by EPA regional or state general permits rather than individual permits; operators "obtain coverage" by submitting a Notice of Intent (NOI) rather than a full permit application; general permit conditions apply uniformly to all covered operators; violation of a general permit's best management practices (BMPs) is a Clean Water Act violation even without a numeric effluent standard
  • § 122.29 — New sources and new dischargers: facilities that are "new sources" (constructing new capacity after the applicable ELG was promulgated) face NSPS (New Source Performance Standards) — the strictest technology-based limits — from day one of operation and cannot obtain variances available to existing sources for a 10-year period; identifying "new source" vs. "existing source" status is critical to permit compliance planning for facility expansions
  • § 122.21 — Permit application requirements: individual NPDES permit applications must include outfall location, receiving water identification, discharge monitoring data for all parameters that will be controlled, production data, and a description of pollution control measures; industrial facilities applying for first-time permits must conduct at minimum one set of effluent sampling under representative operating conditions to establish baseline discharge levels

• 40 CFR Part 131 — Water Quality Standards (34 sections — the EPA's framework governing how states develop, adopt, and revise water quality standards (WQS) that define the goals for their water bodies and set the upstream limit for all point source permit limits; WQS are the "ceiling" that NPDES permits must not exceed and the benchmark for TMDL development):

  • § 131.10 — Designation of uses: each state must specify appropriate uses (called "designated uses") for each water body or reach — examples: drinking water supply, primary contact recreation (swimming), secondary contact recreation (boating), fish consumption, aquatic life support, agricultural water supply, industrial water supply; states may not remove uses that were attained as of the Clean Water Act's effective date; states must conduct a use attainability analysis (UAA) before removing a use designation; the designated uses drive what criteria are required — a drinking water supply designation requires more stringent criteria than an industrial supply designation
  • § 131.11 — Criteria (the numeric or narrative limits that protect designated uses): states must adopt criteria sufficient to protect designated uses; criteria may be numeric (specific mg/L concentrations for specific pollutants — e.g., no more than 10 μg/L total dissolved copper) or narrative (e.g., "free from substances in amounts sufficient to be toxic to humans, animals, plants, or aquatic life"); EPA has published Quality Criteria for Water (commonly called the "Gold Book") as guidance on scientifically defensible numeric criteria for hundreds of pollutants; states may use EPA criteria directly, develop their own scientifically defensible criteria, or use a site-specific variant; where a state has not adopted numeric criteria, EPA publishes water quality criteria guidance that can be used to develop permit limits under § 131.11(b)(2); criteria must protect both human health (for fish consumption and drinking water) and aquatic life (both acute and chronic toxicity endpoints)
  • § 131.12 — Antidegradation policy and implementation methods (one of the most consequential but least-known CWA provisions): every state must have an antidegradation policy with three tiers: (1) existing use protection — regardless of the current classification, existing uses must be maintained and protected; no state may allow existing uses to be degraded by new or increased discharges; (2) high quality waters — waters currently meeting or exceeding criteria for their designated uses may only be degraded for "important economic or social development" in the area; (3) Outstanding National Resource Waters (ONRWs) — waters of exceptional quality (national parks, designated wilderness, ecologically significant waters) may receive no additional degradation; the antidegradation policy applies to all CWA regulatory programs — permits, §401 certifications, and 404 permits; it has become a significant litigation battleground as development projects seek to discharge into high-quality waters
  • § 131.14 — Variances: since 2015, states may adopt WQS variances — time-limited modifications of criteria for specific dischargers that cannot immediately meet the standard; variances allow continued operation during a compliance timeline rather than immediate shutdown; the discharger must demonstrate the criterion is not achievable due to factual circumstances (limits of pollution control technology, natural background conditions, or significant economic hardship); variances require EPA approval and must include a compliance schedule
  • § 131.20 — Mandatory triennial review: states must review their WQS every 3 years and revise them as appropriate; if a state's review concludes its standards are adequate, it must certify this to EPA; EPA may require revisions if a state fails to review or if EPA's scientific developments indicate existing criteria are not protective; the triennial review requirement has produced inconsistent compliance across states — some complete comprehensive reviews, others submit minimal certifications
  • § 131.21 — EPA approval: after a state adopts or revises WQS (through its state administrative process, with public comment), it must submit the revised standards to EPA; EPA reviews and either approves (effective 60 days after EPA receipt if not acted on) or disapproves within 60 days; EPA disapproval means the standard does not take effect and EPA must promptly develop a replacement; if EPA disapproves state WQS, the old (more protective) standards remain in effect until EPA promulgates replacements
  • § 131.22 — EPA promulgation: if a state does not adopt standards that EPA identifies as necessary to meet the Act's requirements, EPA may promulgate standards for the state; this is a backstop authority that EPA has used when states have failed to address specific pollutants (e.g., nutrient criteria, PFAS criteria) despite EPA's determination that existing standards are insufficient; EPA has promulgated WQS for a few states historically, primarily when state-federal disagreements over specific criteria reach an impasse; EPA promulgation of WQS is highly contentious and politically charged

  Water quality standards are the overlooked foundation of the entire Clean Water Act program. Every NPDES permit is derived from the WQS for the receiving water body; when the WQS sets the limit, the permit must include a water quality-based effluent limit (WQBEL) — often more stringent than the technology-based limit. The antidegradation policy (§ 131.12) has become particularly significant in Clean Water Act litigation: states and EPA increasingly use it to block permits for new or expanded dischargers into pristine streams, even when the discharger could meet all applicable technology-based limits. Recent rulemakings: 89 FR 35747 (May 2024) — EPA proposed rule strengthening antidegradation requirements and codifying requirements for PFAS-related WQS development; 59 FR 64344 (December 1994) — antidegradation provisions.

• 40 CFR Part 141 — National Primary Drinking Water Regulations (maximum contaminant levels for 90+ contaminants including lead, arsenic, PFAS, disinfection byproducts, and microbial contaminants; treatment technique requirements; monitoring and reporting; 196 sections)

• 40 CFR Part 130 — Water Quality Planning and Management (15 sections — the EPA's framework for how states develop, update, and implement their Water Quality Management (WQM) programs under CWA §§ 106, 205(j), 208, 303, and 305; this part is where TMDL requirements are operationalized):

  • § 130.7 — Total Maximum Daily Loads (TMDLs): when a water body is listed as "impaired" on the § 305(b) list (not meeting applicable water quality standards for its designated uses), the state must establish a TMDL — the maximum amount of a pollutant that the water body can receive while still meeting water quality standards; the TMDL is allocated among point sources (Wasteload Allocations), nonpoint sources (Load Allocations), and a margin of safety; once EPA approves a TMDL, NPDES permits for dischargers in the watershed must be updated to ensure compliance with the TMDL's wasteload allocation; the TMDL program has been one of the most significant drivers of Clean Water Act litigation — courts have forced states to develop TMDLs for thousands of impaired water segments, including entire systems like the Chesapeake Bay TMDL (the largest ever established, requiring nutrient reductions across six states and DC)
  • § 130.8 — Water quality report (§ 305(b)): states must report to EPA every two years on the quality of all waters in the state — whether each water body is supporting its designated uses; the § 305(b) report is the basis for the § 303(d) impaired waters list; the 305(b)/303(d) Integrated Report submitted every two years forms the national TMDL docket
  • § 130.10 — State submittals to EPA: states must regularly submit § 305(b) reports, annual § 205(j) certifications, and annual state work programs identifying priority water quality planning activities; EPA provides grant funding through §§ 106 and 205(j) to support state water quality management offices
  • § 130.12 — Coordination with NPDES: NPDES permits must not conflict with approved Water Quality Management plans under CWA § 208(e); the coordination requirement ensures that individual permit decisions are consistent with the broader regional pollution control strategy

  Part 130 is the regulatory foundation for the TMDL program — one of the most significant and contentious elements of modern Clean Water Act implementation. The Chesapeake Bay TMDL (2010) is the most prominent example: EPA set limits for nitrogen, phosphorus, and sediment across the 64,000-square-mile watershed, imposing wasteload allocations on thousands of point sources and requiring states to develop watershed implementation plans for nonpoint source reductions. No major amendments since 1985 promulgation.

• Effluent Limitation Guidelines (ELGs) — Industry-Specific Discharge Standards (40 CFR Parts 400–471): EPA publishes technology-based effluent limits for roughly 60 distinct industrial categories — from iron and steel to hospitals to poultry processing. Every ELG Part follows the same four-tier structure: BPT (Best Practicable Technology — the floor for existing direct dischargers, reflects average of the best-performing facilities); BAT (Best Available Technology Economically Achievable — tighter limits for toxic and non-conventional pollutants); NSPS (New Source Performance Standards — the strictest tier, applied to new facilities incorporating best available demonstrated technology from design); and PSES/PSNS (Pretreatment Standards for existing and new indirect dischargers — facilities discharging to POTWs rather than directly to navigable waters). Within each Part, the regulated industry is broken into subcategories reflecting differences in raw materials, processes, or wastewater characteristics, each with its own pollutant-specific numeric limits. Key ELG Parts include:

  • 40 CFR Part 408 — Canned and Preserved Seafood Processing (231 sections across 33 subcategories): effluent limits for catfish, shrimp (remote Alaskan, Northern, Southern non-breaded), salmon, herring, tuna, bottom fish, and shellfish (crab, dungeness/tanner crab, clams, scallops, oysters); wastewater from seafood processing contains high biochemical oxygen demand (BOD), total suspended solids (TSS), and oils/fats from fish processing operations; remote Alaskan subcategories (§§ 408.100–408.107) reflect the unique regulatory challenge of processing vessels and shore-based facilities without access to centralized treatment; inland facilities must meet categorical pretreatment standards when discharging to POTWs; the regulations expressly distinguish "breaded" vs. "non-breaded" shrimp subcategories because breading generates starch waste with different treatment requirements

  • 40 CFR Part 415 — Inorganic Chemicals Manufacturing (238 sections across 30 subcategories): effluent limits for producers of aluminum chloride, potassium compounds (potassium metal, potassium dichromate, potassium sulfate, potassium permanganate), sodium compounds (sodium bicarbonate, sodium dichromate, sodium silicate, sodium sulfite), chlorine and caustic soda (chlor-alkali), hydrofluoric acid, hydrogen peroxide, phosphoric acid, and other industrial inorganic chemicals; the subcategory structure reflects the enormous diversity of production processes — electrolytic processes (chlor-alkali) vs. thermal/chemical synthesis (potassium metal) vs. acid extraction (phosphoric acid) generate fundamentally different wastewater streams with different pollutant profiles; heavy metals (chromium, mercury from chlor-alkali mercury-cell plants), fluoride, and pH are the primary regulated pollutants; existing chlor-alkali mercury-cell facilities face strict mercury pretreatment limits

  • 40 CFR Part 420 — Iron and Steel Manufacturing Point Source Category (110 sections across 13 subcategories — EPA's effluent limitations guidelines for the integrated steel industry, covering every production stage from cokemaking through finished steel; one of the most complex ELGs because a single integrated steel mill may operate multiple subcategories simultaneously, each generating distinct pollutant-laden wastewater streams): The 13 subcategories follow the steel production sequence: Subpart A — Cokemaking: coal heated in coke ovens to produce metallurgical coke; by-product cokemaking generates ammonia-liquor wastewater (ammonia, cyanide, phenols — collectively known as 4-aminoantipyrine phenols or 4AAP), benzene from light-oil recovery, and coke-quench wastewater; the cokemaking pretreatment standards (PSES compliance date July 10, 1985) limit cyanide, ammonia, phenols (4AAP), benzene, and TSS; Subpart B — Sintering: iron ore fines agglomerated by heating before blast furnace charge; wet air pollution control scrubbers generate wastewater containing dioxins (particularly 2,3,7,8-TCDF), PAHs, TSS, and heavy metals; EPA established a PSES compliance date of October 17, 2005 for 2,3,7,8-TCDF (§ 420.28); Subpart C — Ironmaking: blast furnace operations converting iron ore to molten iron; blast furnace gas scrubber water is the primary wastewater stream, containing phenols, cyanide, zinc, ammonia-nitrogen, and high suspended solids; Subparts D–E — Steelmaking: basic oxygen furnace (BOF) and electric arc furnace (EAF) steelmaking; BOF scrubber water and EAF wet dust collector water contain iron oxides, zinc (from galvanized scrap in EAFs), and TSS; Subpart G — Hot Forming: hot rolling of steel into plate, sheet, strip, bars, and structural shapes using high-pressure scale-breaker water; scale-break wastewater contains iron scale and mill oil/grease; BPT and BAT limits require oil separation and scale pits before discharge; Subpart L — Cold Forming: cold rolling of steel sheet using rolling oils or emulsions as lubricants; cold rolling wastewater is primarily oil-in-water emulsion requiring oil skimming and treatment before discharge; Subpart M — Alkaline Cleaning: cleaning steel with alkaline solutions to remove scale, oil, and lubricants before further processing; alkaline cleaning wastewater contains oil/grease, TSS, and surfactants; Subpart N — Hot Coating: hot-dip galvanizing (zinc coating), Terne coating (lead-tin), and electrolytic tinning; galvanizing tank wastewater and rinse water contain zinc, lead, and TSS; regulated pollutants include zinc, lead, and TSS.

    Cross-cutting provisions: § 420.03 — "Water bubble": integrated steel mills that operate multiple subcategories may apply for alternative effluent limitations that treat the facility as a whole ("bubble"), comparing combined pollutant loads against summed subcategory limits — allowing flexibility to allocate treatment effort among wastewater streams; § 420.07 — pH: pH must be maintained between 6.0 and 9.0 in all process wastewater discharges across all subcategories; § 420.08 — Non-process wastewater and stormwater: non-contact cooling water and stormwater from steel mill yards may qualify for increased loading allowances because they are less contaminated than process contact water; § 420.06 — Removal credits for phenols: POTWs that can demonstrate removal of 4AAP phenols may grant removal credits to steel mills using them as pretreatment compliance offsets. The iron and steel ELG was last substantially revised in 2002 (67 FR 64216); EPA has announced plans to update the rule, particularly to address PFAS (from quenching and finishing operations), dioxins in sinter plant wastewater, and hexavalent chromium from cold finishing operations — making Part 420 a likely target for near-term ELG revision given the steel industry's environmental footprint and current trade and manufacturing policy emphasis.

  • 40 CFR Part 421 — Nonferrous Metals Manufacturing (199 sections across 28 subcategories): effluent limits for primary and secondary (recycled) production of aluminum (bauxite refining, primary aluminum smelting), copper, lead, zinc, tin, titanium, tungsten, columbium-tantalum, and precious metals (silver, gold); primary smelting operations generate wastewater containing dissolved metals (copper, zinc, cadmium, lead, arsenic), cyanide (gold leaching circuits), and pH extremes; secondary (scrap-based) smelting generates different wastewater characteristics requiring separate subcategory standards; wet scrubber blowdown from air pollution control (capturing stack gases) is a major wastewater source at primary smelters; pretreatment standards for indirect dischargers prevent toxic metals from passing through POTWs untreated and accumulating in sewage sludge

  • 40 CFR Part 405 — Dairy Products Processing (84 sections across 10 subcategories): effluent limits for receiving stations (raw milk collection), fluid milk processing, butter manufacturing, cottage cheese, natural cheese, condensed milk, dry milk, ice cream, and the condensed and dry whey subcategories; dairy wastewater has extremely high biochemical oxygen demand (BOD) from milk fat, lactose, and proteins — whey from cheese-making is among the most oxygen-demanding food processing streams; BPT/BAT limits target BOD5, TSS, and oil/grease; PSES/PSNS pretreatment standards govern facilities discharging to municipal sewage plants

  • 40 CFR Part 406 — Grain Mills (70 sections across 6 subcategories): effluent limits for corn wet milling (starch, corn syrup, corn oil, gluten feed), corn dry milling, wheat flour milling, bulgur wheat, rice milling, and animal feed manufacturing; corn wet milling is the highest-pollutant subcategory — steep liquor (the water used to soak corn kernels) and germ-separation wastewater generate high BOD and TSS; newer corn wet mills increasingly recycle steep liquor as animal feed rather than treating and discharging it; limits address BOD5, TSS, and oil/grease

  • 40 CFR Part 425 — Leather Tanning and Finishing (69 sections across 9 subcategories): effluent limits for hair pulp/chrome tan/retan-wet finishing, vegetable and retan wet finishing, specialty leather, and shearling production; regulated pollutants are unusually diverse — BOD, TSS, sulfide (from sodium sulfide used in hair unhairing), total chromium (from chrome tanning salts), ammonia-nitrogen, and pH; trivalent chromium from chrome tanning is the defining regulated pollutant; §425.03 specifies the potassium ferricyanide titration method for sulfide measurement; PSES (§425.04) requires chromium and sulfide removal before discharge to POTWs

  • 40 CFR Part 426 — Glass Manufacturing (83 sections across 5 subcategories): effluent limits for pressed and blown glass (tableware, cookware), glass containers (bottles and jars), flat glass (window and automotive), specialty glass (TV panels, optical), and insulation fiberglass; regulated pollutants include fluoride (added to glass batches for forming properties), boron (from borosilicate glass formulations), TSS, and oil/grease from forming lubricants; flat glass float-bath processes generate relatively clean wastewater; fiberglass manufacturing generates higher-pollutant streams containing fluoride and boron that require treatment before discharge

  • 40 CFR Part 432 — Meat and Poultry Products (74 sections across 12 subcategories): effluent limits for simple slaughterhouses, complex slaughterhouses with further processing, poultry slaughtering, poultry further processing, rendering, egg processing, and small slaughterhouse facilities; slaughterhouse wastewater contains blood, gut contents, grease, and fecal matter — generating high BOD, TSS, oil/grease, ammonia-nitrogen, and fecal coliform loads requiring aerobic biological treatment; rendering (converting inedible animal parts to fats and protein meal) produces the highest-strength wastewater stream; the Biden administration proposed significantly tighter BAT limits in 2023 that were withdrawn by EPA in September 2025 under the Trump administration, leaving limits that date substantially to the 1970s–1980s in place

  • 40 CFR Part 427 — Asbestos Manufacturing (74 sections): effluent limits for facilities that manufactured asbestos-based products — asbestos-cement pipe and sheet (pressure pipe, sewer pipe, flat sheets for construction), roofing products, paper products, pipeline wrap, and specialized subcategories for vapor absorption (asbestos used in chemical manufacturing processes) and wet dust collection (wash-water from asbestos manufacturing facilities); the primary regulated pollutant is asbestos fibers in process wastewater — asbestos manufacturing generates wet cutting, grinding, and forming operations that produce fiber-laden wastewater requiring filtration or settlement before discharge; TSS and pH are secondary regulated parameters; this is largely a legacy ELG — domestic asbestos manufacturing has nearly ceased following federal bans on most asbestos-containing products, but the regulations remain in place for any facilities still operating

  • 40 CFR Part 410 — Textile Mills (62 sections across 7 subcategories): effluent limits for wool scouring, wool finishing, low-water-use processes (dry spinning and non-aqueous fiber processing), woven fabric finishing, knit fabric finishing, carpet manufacturing, and stock/yarn/specialty fiber; textile wastewater is highly variable by fiber type and finishing process — wool processing uses sulfide-based desulfurization, synthetic fiber finishing uses surfactants and carriers, and dyeing operations introduce color and pH extremes; primary regulated pollutants are BOD5, COD, TSS, sulfide, total chromium, and pH; dyeing and printing operations are the most pollutant-intensive subcategories, generating colored effluent with high COD that conventional biological treatment can address but not fully solve; the EPA established separate subcategories for "low-water-use" textile processes that use little water and generate minimal wastewater, allowing exemptions from numeric effluent limits

  • 40 CFR Part 428 — Rubber Manufacturing (64 sections across 4 subcategories): effluent limits for tire and inner tube plants, general molded/extruded/fabricated rubber products, latex-dipped/extruded/molded rubber, and latex foam; tire manufacturing is largely a dry process (vulcanization in presses doesn't generate process wastewater) but water is used for cooling molds and in internal mixing — the resulting process water contains oils, rubber particles, and antioxidants; latex-based operations (gloves, balloons, foam) generate higher-volume, higher-pollutant wastewater from the aqueous latex dipping process; primary regulated pollutants for tire plants are BOD, TSS, and oil/grease; latex operations also generate ammonia from the preservatives used in natural latex compounding

  • 40 CFR Part 436 — Mineral Mining and Processing (64 sections across 7 subcategories): effluent limits for barite mining, fluorspar mining, salines from brine lakes, borax mining, potash mining, frasch sulfur (dissolved in hot water and pumped to surface), and a catch-all subcategory for other minerals including industrial minerals used in chemical manufacturing; mineral mining wastewater comes primarily from process water in crushing, grinding, and flotation operations — the water picks up dissolved minerals, total suspended solids, and pH extremes from the ore; barite (used as drilling mud weighting agent) and borax generate wastewater with high dissolved solids; frasch sulfur operations have relatively clean effluent because the process uses clean hot water; the primary challenge in mineral mining effluent control is managing total dissolved solids (TDS) and mining-specific contaminants (fluoride from fluorspar, borate from borax) that conventional biological treatment cannot address

  • 40 CFR Part 435 — Oil and Gas Extraction Point Source Category (25 sections across 4 subcategories — EPA's effluent limitations guidelines for wastewater generated at oil and gas wells and production operations; authority: 33 U.S.C. § 1251; covers the enormous volumes of produced water generated at oil and gas wells across four operating environments): Subpart A — Offshore subcategory (production platforms and drill rigs in OCS and state offshore waters): the basic offshore standard is a strict "no discharge of free oil" requirement — produced water may be discharged overboard only if it does not cause a visible sheen; BPT/BCT/BAT/NSPS all require this zero free-oil standard; synthetic-based drilling muds generate cuttings subject to a separate no-discharge standard — no synthetic-based mud cuttings may be discharged to navigable waters (they must be shipped to shore for disposal or reinjected); Subpart B — Onshore subcategory (§§ 435.30–435.34, wells in continental inland areas): the onshore standard effectively requires zero discharge of produced water to navigable waters — all produced water from onshore oil and gas wells must be injected underground (Class II UIC wells), evaporated in lined pits, or reused in oil field operations; the zero-discharge standard reflects that onshore produced water volumes are manageable for injection and that surface discharge would introduce brine, hydrocarbons, and naturally occurring radioactive materials (NORM, primarily radium-226 and radium-228) into inland waterways; PSES/PSNS (§§ 435.33–435.34) prohibit onshore producers from discharging produced water to POTWs that are not specifically designed and permitted for oil-field brine — effectively requiring injection for almost all onshore operations; Subpart C — Coastal subcategory (§§ 435.40–435.47, wells in coastal state territorial waters): coastal operations may discharge produced water through oil-water separators meeting defined treatment levels — BPT/BAT require that discharged produced water not exceed established oil and grease limits on a 24-hour composite sample basis; coastal pretreatment standards require removal of dispersed oil before any discharge to POTWs; Subpart D — Beneficial use subcategory (§ 435.50): produced water beneficially reused for livestock watering, crop irrigation, wildlife watering, or dust suppression is subject to a separate, less stringent standard reflecting that the beneficial use itself limits environmental exposure. The Part 435 onshore zero-discharge standard (§ 435.32) already applies to hydraulic fracturing operations — produced water from fracked wells must be injected or reused, not discharged to surface waters; EPA has been developing a separate ELG specifically addressing treatment requirements when fracking wastewater is sent to industrial wastewater treatment facilities, but that rulemaking remains pending.

  • 40 CFR Part 407 — Canned and Preserved Fruits and Vegetables Processing (53 sections across 8 subcategories): effluent limits for apple juice, apple products (applesauce, dried apples), citrus products, canned and frozen fruits, potato processing (french fries, chips, instant mashed potato), tomato products (ketchup, sauce, paste, juice), and canned and frozen vegetables; fruit and vegetable processing generates BOD5 and TSS from washing, blanching, peeling, and cooking operations — the biochemical oxygen demand comes from sugars, starches, and organic acids in the wastewater; potato processing is the highest-BOD subcategory because starch and sugar concentrations in wash and blanch water are very high; BPT limits reflect activated sludge biological treatment as the floor; PSES under § 407.14 governs facilities discharging to POTWs

  • 40 CFR Part 414 — Organic Chemicals, Plastics, and Synthetic Fibers (OCPSF) (51 sections): one of EPA's most complex ELGs — covers hundreds of different organic chemical manufacturing processes, plastics production (polyethylene, PVC, nylon, polypropylene), and synthetic fiber manufacturing (polyester, nylon, acrylic) under a two-subcategory structure: direct dischargers using end-of-pipe biological treatment (Subpart C — § 414.100) vs. direct dischargers not using biological treatment (Subpart B); OCPSF facilities generate process wastewater containing priority toxic pollutants — volatile organics (benzene, toluene, ethylbenzene, vinyl chloride), acid-extractable compounds (chlorophenols, nitrophenols), base-neutral compounds (naphthalene, acenaphthylene, PAHs), and toxic metals; toxic pollutant limits under § 414.101 are mass-based (mass per unit flow), derived from best available technology for each pollutant class; indirect dischargers (§ 414.111) face pretreatment standards to prevent toxic pollutants from passing through POTWs and contaminating sewage sludge; OCPSF is the ELG most likely to affect large chemical manufacturing complexes (Gulf Coast petrochemical facilities, Midwest plastics plants)

  • 40 CFR Part 418 — Fertilizer Manufacturing (46 sections across 6 subcategories): effluent limits for phosphate fertilizer production (phosphoric acid from wet-process phosphate rock digestion and from electric furnace), ammonia manufacturing, urea, ammonium nitrate, nitric acid, and mixed/blended fertilizer production; phosphate fertilizer production generates fluoride (from fluorapatite in phosphate rock), phosphorus, and TSS from wet scrubbers used to control fluoride air emissions — the scrubber wastewater is a major discharge point; BAT for phosphate operations is zero discharge through closed-loop recycling of process water; ammonia plants generate cooling water and process condensate with ammonia-nitrogen requiring stripping before discharge; ammonium nitrate and nitric acid production generate high nitrogen loads (nitrate, nitrite) that must be reduced before discharge or POTW introduction; fertilizer manufacturing near waterways historically contributed significant nutrient loads driving downstream eutrophication and hypoxia in receiving waters

  • 40 CFR Part 471 — Nonferrous Metals Forming and Metal Powders (61 sections across 10 subcategories): effluent limits for the cold and hot forming of nonferrous metals — rolling, drawing, extruding, and forging of lead, tin, bismuth, molybdenum, tungsten, nickel, cobalt, titanium, precious metals (gold, silver, platinum-group), zirconium/hafnium, and metal powders (produced from iron, steel, and nonferrous metals by reduction or atomization); forming operations use lubricants and coolants that must be separated from process wastewater before discharge; regulated pollutants: TSS, oil and grease, and dissolved heavy metals characteristic of the specific metal being formed (lead for lead-forming, cadmium for zinc alloys, nickel for nickel-cobalt alloys); the metal powders subcategory (§ 471.100–471.105) generates fine-particle wastewater from the spray-drying, reduction, and classification of metal powders; BAT limits for metals in forming wastewater require precipitation, sedimentation, and in some cases further polishing to achieve compliance

  • 40 CFR Part 467 — Aluminum Forming (45 sections across 6 subcategories): effluent limits for the rolling, drawing, extruding, and forging of aluminum and aluminum alloys — the world's most widely used nonferrous metal; subcategories reflect the type of lubricant used during forming: rolling with neat oils (hydrocarbon cutting oils without water dilution), rolling with emulsions (oil-water emulsions used for high-speed rolling), extrusion, forging, drawing and ironing, and drawing with neat oils; neat-oil subcategories generate higher-concentration wastewater from the oil itself; emulsion subcategories generate higher-volume, lower-concentration wastewater from emulsion bath maintenance; regulated pollutants are TSS, oil and grease, and aluminum — with limits expressed as mass per unit production (lbs per 1,000 lbs of aluminum processed); § 467.01 includes within scope "annealing, solution heat treating, aging, tempering, and similar processes that alter the metallurgical characteristics of the aluminum"; pretreatment standards under § 467.04 (PSES compliance date October 24, 1986) limit aluminum, chromium, cyanide, lead, nickel, and zinc discharged to POTWs

  • 40 CFR Part 440 — Ore Mining and Dressing (44 sections across 12 subcategories): effluent limits for hard-rock mining and ore beneficiation operations — the processing that separates ore minerals from waste rock before smelting; subcategories include iron ore, lead-zinc ore (§ 440.30), copper-lead-zinc-gold-silver-molybdenum ores (Subpart J, § 440.100), platinum ore (§ 440.110), titanium ore, tungsten ore, and coal refuse piles; mining wastewater sources are diverse: pit dewatering (groundwater pumped from open pits), mill discharge (wastewater from wet-grinding and flotation), and tailings pond overflow; regulated pollutants for metal ore operations include TSS (the dominant pollutant from crushing and grinding), total recoverable metals characteristic of the ore type (iron, copper, lead, zinc, cadmium, arsenic, manganese), and pH extremes from acid-generating sulfide ores; the NSPS for copper/lead/zinc/gold operations in Subpart J requires zero discharge of process wastewater — all mine drainage and mill effluent must be recycled; for existing operations, BPT allows limited discharge with TSS limits of 30 mg/L (daily average) and 50 mg/L (daily maximum); acid mine drainage from sulfide ore mining is a persistent challenge as pyrite oxidation in pit walls and tailings continues generating acidic, metal-laden water for decades after mining ends

  • 40 CFR Part 409 — Sugar Processing (37 sections across 2 subcategories — beet sugar and cane sugar): effluent limits for the extraction and refining of sucrose from sugar beets and sugarcane, two distinct industrial processes that both generate high-BOD wastewater but through different mechanisms; the beet sugar subcategory (Subpart A, §§ 409.10–409.17) covers the wet extraction process — beets are washed, sliced into thin strips (cossettes), and diffused with hot water to extract sugar; the resulting diffusion juice is highly concentrated in sugars, beet pulp solids, amino acids, and organic acids; wastewater from beet washing, pulp pressing, and condensate from evaporation are the principal discharge streams; BPT limits (§ 409.12) for beet sugar are expressed as pounds of BOD5 per ton of beets sliced; BAT limits (§ 409.13) tighten the BOD5 mass-load and add limits for COD; PSES pretreatment standards (§ 409.14) apply to beet sugar operations discharging to POTWs; NSPS (§ 409.15) and PSNS (§ 409.16) govern new facilities; BCT (§ 409.17) covers conventional pollutants for new and existing direct dischargers; the cane sugar subcategory covers the crushing and processing of sugarcane — cane is crushed, juice extracted, clarified, and evaporated; wastewater from cane washing and mill house operations contains high concentrations of BOD from sugarcane juice and bagasse (fibrous residue); sugar processing facilities are seasonal operations (beet processing in fall/winter; cane in harvest season), which complicates BOD treatment system design since biological treatment performance degrades when systems sit idle between campaigns; permit writers use production-normalized limits (lbs BOD5 per ton of product) to account for variability across facility scales

  • 40 CFR Part 424 — Ferroalloy Manufacturing Point Source Category (41 sections across 6 subcategories): effluent limits for the manufacturing of ferroalloys — metallic alloys of iron with one or more other metals (silicon, manganese, chromium, nickel, molybdenum, tungsten, vanadium, titanium) used in steel production; ferroalloy manufacturing uses submerged electric arc furnaces operating at extremely high temperatures; wastewater comes primarily from wet scrubbing systems used to capture furnace off-gases (fumes containing metal oxides and particulates) before atmospheric discharge; the scrubber water picks up dissolved and suspended metals, cyanide (from carbon electrodes and organic material), fluoride (from flux materials), pH extremes, and total suspended solids; subcategories reflect the specific alloy produced — ferrosilicon, silicon metal, high-carbon ferromanganese, silicomanganese, ferrochrome/charge chrome, and silicon-manganese-chrome; pretreatment standards (PSES/PSNS) are particularly important for ferroalloy manufacturers discharging to POTWs because the metals and cyanide in scrubber water can be acutely toxic to biological treatment organisms and accumulate in sewage sludge; primary regulated pollutants include TSS, total cyanide, total chromium, and pH; BPT and BAT limits were established in the early 1980s and have not been revised — they represent the technology baseline for an industry that has contracted significantly from its peak U.S. production levels

  • 40 CFR Part 439 — Pharmaceutical Manufacturing Point Source Category (40 sections across 5 subcategories): effluent limits for the manufacture of pharmaceutical products, organized by production process: (A) fermentation products (antibiotics like penicillin and streptomycin, steroids, vitamins, amino acids produced by fermentation of microorganisms in large tanks); (B) extraction products (hormones, vitamins, and compounds extracted from plant or animal materials through solvent extraction processes); (C) chemical synthesis products (synthetic drugs and intermediates manufactured through multi-step organic chemistry reactions); (D) mixing/compounding and formulation (final dosage forms — tablets, capsules, solutions — produced by combining active ingredients with excipients); and (E) research (laboratory-scale pharmaceutical research generating small-volume wastewater). Key regulated pollutants vary significantly by subcategory:

    • Fermentation (Subpart A): very high BOD from fermentation broth residues (spent fermentation media, mycelial cake); also TSS, COD, and some regulated priority pollutants in trace amounts from fermentation process chemicals; BPT/BAT limits for fermentation are among the most stringent food/bio-processing limits because fermentation wastewater can have BOD5 values of 10,000–100,000 mg/L before treatment
    • Chemical synthesis (Subpart C): the most toxics-intensive subcategory; regulated priority pollutants include halogenated organic solvents (methylene chloride, chloroform, trichloroethylene), benzene, toluene, and other organic compounds used as reaction solvents, carriers, and extractants; BAT and PSES/PSNS standards for synthetic pharmaceutical wastewater require source reduction and solvent recovery before end-of-pipe treatment; the priority toxic pollutant limits are set to ensure that pharmaceutical solvent discharges don't contribute to human health risks downstream
    • Research (Subpart E): exempt from most categorical limits — research-scale batch processes generating small volumes; generic NPDES best management practices apply The pharmaceutical ELG rulemaking was last substantially revised in 2003 (68 FR 12274); EPA proposed more comprehensive pharmaceutical effluent standards in subsequent years but has not finalized additional requirements, despite ongoing monitoring showing pharmaceutical active ingredients in rivers downstream from pharmaceutical manufacturing facilities and from POTW discharges receiving pharmaceutical wastewater.

  • 40 CFR Part 464 — Metal Molding and Casting Point Source Category (the ELG for foundry operations — aluminum, copper/brass/bronze, iron, steel, and zinc die-casting facilities that melt metal and pour it into molds, generating process wastewater contaminated with suspended solids, oil and grease, and toxic organic compounds used in mold releases and cooling systems):

    • § 464.11 — Subpart A (aluminum forming): BPT and BAT limits for aluminum casting wastewater; primary regulated pollutants are total suspended solids (TSS) and oil and grease from hydraulic fluids, lubricants, and mold-release agents; aluminum casting operations typically use wet scrubbers and quench water that picks up aluminum oxide particulates and petroleum-based lubricants; best practicable technology requires clarification plus skimming for oil/grease removal
    • § 464.32 — Subpart C (copper casting): BAT limits for brass and bronze foundries; copper casting uses chemical binders in sand molds that generate phenolic compounds and ammonia in rinse water; BAT requires treatment to remove these organics before discharge; indirect dischargers (facilities discharging to a POTW) are subject to pretreatment standards under Subpart C's PSES provisions (§ 464.36)
    • § 464.51 — Subpart E (iron casting): limits for gray iron, ductile iron, and malleable iron foundry wastewater; iron foundries generate the highest volumes of process water among casting subcategories; core making (sand and chemical binders shaped into mold inserts) generates wastewater with phenols and cresols from phenolic resin binders; BPT/BAT require settling plus biological or chemical treatment for organics; iron casting accounts for the majority of U.S. foundry output by tonnage
    • § 464.61 — Subpart F (steel casting): similar regulated pollutants to iron casting but with higher temperature wastewater from electric arc furnaces; steel casting facilities include investment casting (precision aircraft and industrial components) and sand casting; priority toxic organics from mold binders and release agents are regulated alongside conventional TSS and oil/grease parameters
    • § 464.71 — Subpart G (zinc die casting): die casting injects molten zinc at high pressure into metal dies with oil-based lubricants; quench water and die-lube rinse streams contain zinc, cadmium (a common zinc alloy contaminant), and petroleum hydrocarbons; PSES pretreatment standards for indirect dischargers require zinc removal before POTW discharge to prevent interference with municipal sludge quality

  Under Part 464, facilities have the option to monitor for total toxic organics (TTO) — the combined mass of 65 listed priority organic pollutants — or to demonstrate compliance through a toxic organic management plan (TOMP) that certifies use of oil/grease monitoring as a surrogate. The TOMP option reduces monitoring costs for foundries that can demonstrate their priority toxic organics come exclusively from petroleum lubricants tracked by the oil/grease parameter. Pretreatment compliance dates under PSES were established as October 31, 1988, for existing indirect dischargers. New source performance standards (NSPS) apply to new foundry construction and major modifications.

  • 40 CFR Part 437 — Centralized Waste Treatment (CWT) Point Source Category (the ELG for commercial hazardous and non-hazardous liquid waste treatment facilities — businesses that receive industrial wastewaters, sludges, and oily wastes from off-site generators and treat or recover value from them before discharging treated effluent; organized into four subcategories based on the primary waste stream processed):
    • § 437.10 (Subpart A — Metals): BPT, BAT, NSPS, PSES, and PSNS limits for CWT facilities treating metal-bearing wastes — wastewaters containing dissolved copper, zinc, cadmium, lead, chromium, nickel, silver, and other heavy metals from industrial processes; BAT limits for metals subcategory CWT facilities mirror the stringency applicable to direct metal-plating dischargers; PSES compliance deadline December 22, 2003; regulated parameters include antimony, arsenic, cadmium, chromium, cobalt, copper, lead, mercury, nickel, silver, thallium, zinc, and total toxic organics (TTO)
    • § 437.20 (Subpart B — Oils): limits for CWT facilities treating oily wastes — used lubricating oils, hydraulic fluids, metalworking fluids, and tank bottom sludge received from off-site industrial customers; primary regulated parameters are oil and grease, TSS, and TTO; BAT requires API separators plus dissolved air flotation (DAF) for oil-in-water emulsions; the oily waste subcategory covers the largest volume of CWT operations by liquid volume — used oil re-refining and recycling operations are the most common CWT facility type in this subcategory
    • § 437.30 (Subpart C — Organics): limits for CWT facilities treating organic liquid wastes — solvents, still bottoms, aqueous waste streams from organic chemical manufacturing, and contaminated groundwater from remediation sites; primary regulated parameters include volatile organic compounds (benzene, toluene, methylene chloride), semi-volatile compounds, and TTO; BAT for the organics subcategory requires air stripping or steam stripping for volatile organics plus carbon adsorption or biological treatment for residual organics before discharge
    • § 437.40 (Subpart D — Multiple Wastes): applies to CWT facilities that treat two or more of the waste types covered in Subparts A, B, and C; limits are determined on a flow-weighted average basis using the applicable subcategory standards; mixed-waste CWT facilities must track which portion of their influent falls under each subcategory and apply the corresponding limits proportionally to the combined discharge

  CWT facilities serve as the off-site treatment option for industrial generators that lack on-site wastewater treatment capacity. They are licensed by states under RCRA (for hazardous waste) or in some cases as commercial wastewater treatment facilities, and discharge under NPDES permits that incorporate Part 437 categorical limits. The Part 437 ELG was significantly revised in 2000 (65 FR 81241) following EPA's finding that many CWT facilities were discharging metals and organics at levels exceeding what on-site industrial treatment technologies would achieve — the 2000 revision tightened BAT and PSES standards, particularly for the metals subcategory, requiring additional treatment steps (chemical precipitation for metals, advanced separation for organics) beyond prior BPT-level requirements.

  • 40 CFR Part 465 — Coil Coating Point Source Category (the ELG for facilities that apply coatings — paints, primers, sealers, and chemical treatments — to continuous metal coil stock before it is cut, stamped, or formed into end products; major end-use markets include appliance skins, building panels, automotive parts, and beverage cans; primary wastewater pollutants are cyanide (from chemical conversion coating baths), chromium (from chromate rinse stages), and zinc (from galvanized substrate dissolution and zinc phosphate pretreatment); authority: 33 U.S.C. § 1311(b)):
    • § 465.10 (Subpart A — Steel Basis Material): BPT, BAT, and NSPS limits for coil coating lines processing bare cold-rolled steel and hot-rolled steel substrates; the coating process for steel coil involves alkaline cleaning, iron phosphate or zinc phosphate conversion coating, chromate rinse, and paint application; phosphate/chromate rinse wastewater is the primary regulated discharge stream; BPT limits for chromium (total) reflect lime precipitation achieving roughly 1 mg/L total chromium; BAT limits for zinc and cyanide reflect the same chemical precipitation plus pH adjustment achievable at well-controlled coil coating facilities; NSPS apply to new construction and major process modifications
    • § 465.20 (Subpart B — Galvanized Steel Basis Material): limits for coil coating lines processing zinc-coated (galvanized) steel, where the galvanizing layer itself contributes zinc to the process wastewater; the conversion coating bath interacts with the galvanized surface differently than bare steel, generating higher zinc loadings in the rinse water; BPT zinc limits for galvanized steel coil lines are set above the bare-steel BPT limit to reflect this additional zinc source while still requiring removal to the level achievable by clarification and chemical precipitation; chromate post-rinse on galvanized steel coils requires the same chromate treatment controls as bare steel
    • § 465.30 (Subpart C — Aluminum Basis Material): limits for coil coating of aluminum coil stock used in building panels, gutters, and roofing; aluminum coil coating uses chromic acid anodizing or chromate conversion coating to enhance paint adhesion; chromate conversion generates hexavalent chromium in rinse water — a more toxic and regulated form than the trivalent chromium predominant in steel coil processes; the hexavalent chromium presence in aluminum coil coating wastewater makes the Subpart C limits stricter on a unit-basis than Subparts A and B, requiring chemical reduction of Cr(VI) to Cr(III) before precipitation
    • §§ 465.04, 465.40 (Subpart D — Canmaking): limits for can manufacturing facilities that apply interior and exterior coatings to two-piece and three-piece beverage and food cans; the can coating process uses spray and roll application of FDA-compliant coatings in high-speed lines; cyanide is the critical regulated pollutant in the canmaking subcategory — used in cleaning baths for the can bodies — with § 465.03 requiring periodic cyanide analysis at the point of discharge; PSES pretreatment compliance for the canmaking subcategory was established March 10, 1988 under § 465.04(b), applying to indirect dischargers that send wastewater to POTWs

  Under Part 465, the full ELG tier structure applies: BPT (minimum for all existing direct dischargers), BAT (technology-based best available treatment for toxic pollutants), BCT (best conventional pollutant control for conventional parameters like TSS), NSPS (new source performance standards for new construction), PSES (pretreatment standards for existing indirect dischargers), and PSNS (pretreatment standards for new indirect dischargers). The original coil coating ELG was established in 1983 (48 FR 40,098) — reflecting 1980s-era best available technology. The primary pollutant controls required under BAT (chemical precipitation for metals, alkaline chlorination or thermal treatment for cyanide) remain standard practice; no major revision to the coil coating ELG has occurred since the 1980s, though EPA's 2020s ELG annual review has flagged the category for potential long-term reassessment given changes in coating chemistry (reduced chromate use, waterborne coatings replacing solvent-based formulas).

  • 40 CFR Part 469 — Electrical and Electronic Components Point Source Category (the ELG for semiconductor manufacturing and electronic component fabrication — facilities that manufacture integrated circuits, printed circuit boards, and electronic crystals, generating wastewater containing fluoride, TTO, copper, and pH extremes from etching, cleaning, and plating operations):
    • § 469.10 (Subpart A — Semiconductors): BPT, BAT, BCT, NSPS, PSES, and PSNS limits for semiconductor fabrication facilities; semiconductor manufacturing uses hydrofluoric acid (HF) for silicon wafer etching, generating fluoride-bearing wastewater as the primary pollutant of concern; BAT fluoride limit compliance date was November 8, 1985; TTO limits (covering volatile organics like acetone, isopropanol, methyl chloroform used in cleaning and photoresist stripping) apply to both direct dischargers and indirect dischargers (PSES); the TTO certification option (§ 469.13) allows facilities to certify that they have not used any of the listed TTO compounds in the 30 days prior to a discharge monitoring report, in lieu of analytical monitoring — reducing compliance costs for facilities that use only a limited set of organic solvents
    • § 469.20 (Subpart B — Electronic Crystals): limits for manufacturers of quartz crystals, silicon carbide, and other electronic crystals used in oscillators and frequency control devices; crystal manufacturing uses HF for etching and generates fluoride wastewater; BAT fluoride limit compliance date was also November 8, 1985; TTO PSES compliance for electronic crystals was July 1, 1984 (earlier than the semiconductor subcategory)
    • § 469.30 (Subpart C — Electroplating on Plastic): limits for electroplating operations on plastic substrates (decorative chrome plating on automotive trim, ABS plastic plating); this subcategory addresses the specific etching process for plastic — chromic acid etching generates hexavalent chromium wastewater in addition to the conventional electroplating metals; limits cover cyanide, total chromium (with hexavalent chromium as primary concern), copper, nickel, zinc, and TTO; cross-reference to 40 CFR Part 413 (Electroplating) for additional requirements

  The semiconductor ELG is notable in the context of current U.S. semiconductor policy: the CHIPS and Science Act (2022) is funding $52 billion in new U.S. semiconductor fabrication capacity, with major TSMC, Intel, Samsung, and Micron fabs under construction in Arizona, Ohio, and Idaho. Each new fab will require an NPDES permit incorporating Part 469 fluoride and TTO limits; state NPDES authorities in Arizona and Ohio are processing permit applications for facilities generating millions of gallons per day of high-purity rinse water contaminated with HF, copper, and photochemicals. Part 469's PSES compliance dates from the 1980s are grandfathered for existing facilities but NSPS applies in full to new fab construction — meaning the CHIPS Act fabs will face the strictest semiconductor ELG tier.

  • 40 CFR Part 455 — Pesticide Chemicals Point Source Category (the ELG for facilities that manufacture pesticide active ingredients — insecticides, herbicides, fungicides, and rodenticides — as opposed to formulation facilities that simply mix or package finished pesticide products; two subcategories cover the primary production types):
    • § 455.20 (Subpart A — Organic Pesticide Chemicals Manufacturing): BPT, BAT, BCT, NSPS, PSES, and PSNS limits for manufacturers of carbon-based pesticide active ingredients (organophosphate insecticides like chlorpyrifos and malathion, carbamate insecticides, organochlorine compounds, phenoxy herbicides like 2,4-D, and glyphosate); the primary regulated pollutants are COD (chemical oxygen demand), BOD5, TSS, and total organic active ingredients (TOAI) — the combined mass of all organic pesticide active ingredients in the wastewater; TOAI is the pesticide-specific analogue of TTO in other ELG categories; BAT requires end-of-pipe biological treatment (activated sludge) plus source reduction to minimize TOAI concentrations at the point of generation; PSES compliance deadline September 28, 1993 (§ 455.11)
    • § 455.40 (Subpart B — Organic Pesticide Chemicals Formulating, Packaging, and Repackaging): limits for facilities that do not manufacture pesticide active ingredients but instead receive them and blend, dilute, package, or repackage them into finished pesticide products; these formulation facilities generate relatively low-volume, high-concentration rinse water from equipment cleaning between batch runs; the primary regulated parameter is again TOAI from residuals left in mixing vessels, filling lines, and drums; formulation facilities are regulated as indirect dischargers (PSES/PSNS only) in most cases since they typically discharge to POTWs rather than directly to waterways; zero discharge of process wastewater is the BAT standard for most formulation operations — wastewater must be evaporated, reused as process water, or shipped offsite for disposal, not discharged to surface water

  Pesticide manufacturing wastewater is particularly challenging to treat because many pesticide active ingredients are specifically designed to be biologically active — they are toxic to microorganisms at low concentrations, which can inhibit the biological treatment processes (activated sludge) that are the basis of wastewater treatment plant operation. TOAI monitoring is required at the point of discharge; facilities that co-discharge with other industrial wastewater streams must demonstrate that pesticide concentrations in the combined effluent meet Part 455 limits. The EPA has proposed updating the pesticide ELG, noting that glyphosate manufacturing (the world's most widely applied herbicide by volume) generates wastewater with unique treatment challenges not fully addressed by the 1993-era standards.

  • 40 CFR Part 442 — Transportation Equipment Cleaning Point Source Category (28 sections across 4 subparts): effluent limits for facilities that clean the interior of tanks used to transport chemical, petroleum, and food-grade cargos — including tank trucks and intermodal tank containers (Subpart A), rail tank cars (Subpart B), tank barges and ocean/sea tankers (Subpart C), and food-grade transport tanks (Subpart D). This ELG addresses a niche but important wastewater source: chemical residues left in transport tanks are mobilized during interior cleaning with hot water, steam, and cleaning agents, generating washwater contaminated with the prior cargo's chemical constituents:
    • Subpart A — Tank Trucks and Intermodal Tank Containers (chemical/petroleum): BPT limits include BOD5, TSS, oil and grease (HEM), pH, and specific priority pollutants depending on cargo history; copper and mercury limits reflect the use of cleaning agents and the accumulation of trace metals from transported chemical cargos; BAT = NSPS (same numeric limits for existing and new sources), reflecting the achievability of well-controlled cleaning operations; PSES (§ 442.15) governs facilities discharging to POTWs — the primary concern is preventing petroleum and chemical residues from passing through treatment plants and entering receiving waters; the BAT/NSPS limits require segregation of first-rinse wastewater (highest concentration) from subsequent rinse water; zero discharge of cleaning chemicals not meeting effluent standards is required before discharge
    • Subpart B — Rail Tank Cars (chemical/petroleum): same pollutant categories as Subpart A with slightly different numeric limits reflecting the larger tank volumes and different cleaning practices used for railcars; rail tank car cleaning facilities discharge to both POTWs and directly to surface water; mercury limits are particularly stringent because mercury-bearing chemicals have historically been transported in rail tank cars that are cleaned at centralized tank car cleaning facilities
    • Subpart C — Tank Barges and Ocean/Sea Tankers: limits for shoreside facilities cleaning petroleum tanker and chemical tanker cargo tanks; oily ballast water and tanker cargo hold washwater discharged to shoreside reception facilities (rather than at sea) is subject to these limits; the BAT standard requires gravity separation plus flotation or other enhanced oil removal for petroleum cargo washwater; chemical tanker washwater may require additional treatment depending on the prior cargo
    • Subpart D — Food Grade Cargos: less stringent limits reflecting the relatively lower toxicity of food-grade cargo residues (edible oils, corn syrup, dairy, fruit juices) compared to chemical and petroleum cargos; BOD5, TSS, and oil/grease are the primary parameters; BAT reflects activated sludge biological treatment for high-BOD food-grade cleaning wastewater, which is essentially equivalent to food processing wastewater

  Tank cleaning is a specialized industrial sector — centralized commercial tank cleaning facilities accept trucks, railcars, and barge tanks from multiple customers, generating variable wastewater as different chemical residues are sequentially cleaned. The variability of prior cargo (a tank car previously carrying chlorinated solvents cleaned the same day as one carrying corn syrup) creates compliance challenges: sampling under representative conditions must account for this variability. No major Part 442 amendments since the original 1978 rule — the limits are among the oldest in EPA's ELG program.

  • 40 CFR Part 443 — Paving and Roofing Materials (Tars and Asphalt) Point Source Category (the ELG for facilities that manufacture asphalt-based products — paving materials, roofing products, and linoleum — generating process wastewater and stormwater runoff contaminated primarily with oil and grease from the petroleum-based raw materials; four subcategories reflect the distinct production processes and wastewater generation patterns within the asphalt industry; authority: 33 U.S.C. § 1251):
    • § 443.10 (Subpart A — Asphalt Emulsion): BPT, BAT, and NSPS limits for manufacturers of asphalt emulsion — liquid asphalt suspended in water using emulsifying agents, used for road surface treatment and chip seals; process wastewater is generated from equipment washing and rainwater runoff from the production area (oxidation towers, loading facilities); the regulated production area (§ 443.11 definition) is the zone within which process wastewater pollutants can accumulate; BPT limits for oil and grease are 0.02 kg/m³ maximum daily and 0.015 kg/m³ 30-day average for the combined process and stormwater runoff from the production area; BAT standards for the asphalt emulsion subcategory are equivalent to BPT, reflecting that no technology more stringent than clarification plus oil skimming has been demonstrated to be achievable for this dilute wastewater stream
    • § 443.20 (Subpart B — Asphalt Concrete): limits for asphalt concrete (also called hot-mix asphalt or HMA) facilities — plants that blend aggregate with liquid asphalt cement to produce paving material; most asphalt concrete facilities use dry-process operations that generate little or no process wastewater, but drum dryers and other equipment cleaning operations can generate oily wastewater; stormwater runoff from aggregate storage piles and paving material storage areas is the primary regulated discharge stream; BPT/BAT limits match Subpart A numeric values for oil and grease and pH
    • § 443.30 (Subpart C — Asphalt Roofing): limits for manufacturers of asphalt roofing products — fiberglass-mat and organic-felt-based shingles, roll roofing, and modified bitumen roofing membranes; the manufacturing process saturates felt or fiberglass mat with asphalt, applies granular surfacing material, and forms individual shingles or rolls; process wastewater from felt saturating operations, granule washing, and equipment cleaning contains oil and grease from the petroleum-based saturant; PSES (pretreatment standards for existing indirect dischargers) applies to roofing manufacturers that discharge to POTWs, requiring the same oil and grease removal achievable through gravity separation and skimming
    • § 443.40 (Subpart D — Linoleum and Printed Asphalt Felt): limits for manufacturers of linoleum floor covering and asphalt-saturated felt products used in roofing underlayment; linoleum production uses linseed oil and rosin as binders over a jute burlap backing, generating wastewater with biological oxygen demand (BOD) from the organic binders; asphalt-felt manufacturing parallels roofing felt production; this subcategory has the lowest effluent volumes of the four asphalt subcategories

  Part 443 reflects the production-area runoff control model used across asphalt industry ELGs: the regulated discharge is not a continuous process wastewater stream but the intermittent combination of equipment washwater and precipitation runoff from defined production zones. BPT/BAT achievability is demonstrated through collection sumps, retention ponds, oil-water separators, and skimmers — technology available at every asphalt plant. The original Part 443 ELG was established in 1975 (40 FR 31191) with a technical correction in 1995 (60 FR 33969); no major substantive revisions since 1995. Given the age of these standards, EPA's ongoing ELG review process periodically examines whether new analytical methods (for trace polycyclic aromatic hydrocarbons in asphalt runoff, which are known carcinogens) warrant a new rule, but no proposal has been issued as of 2026.

  • 40 CFR Part 411 — Cement Manufacturing (23 sections across 3 subcategories — nonleaching, leaching, and materials storage piles runoff): the ELG for a production process that is largely a dry operation at modern plants; Subpart A (nonleaching) covers dry-process cement kilns and wet-process kilns with closed-loop scrubber water recirculation — BPT/BAT standard for nonleaching facilities is zero discharge of process wastewater because all kiln gas scrubber water is recycled back into the process or raw material grinding; Subpart B (leaching) covers older wet-process kilns and operations with leaching aggregate storage — these facilities discharge process wastewater containing pH extremes, TSS from kiln dust carryover, and trace metals dissolved from the limestone and clinker feed; Subpart C (materials storage piles runoff) addresses stormwater runoff from limestone, clinker, and fly ash storage piles — requiring collection, pH adjustment, and TSS removal before discharge; the dominant environmental driver is pH: cement kiln scrubber water and clinker pile runoff can reach pH 12–13 because calcium hydroxide (lime) dissolves from the process materials; BPT/BAT for the leaching subcategory requires collection ponds plus pH neutralization; U.S. cement plants are ~95% dry-process, making the nonleaching zero-discharge standard the operative rule for virtually all domestic producers.

  • 40 CFR Part 422 — Phosphate Manufacturing (21 sections across 6 subcategories): effluent limits for the production of elemental phosphorus and phosphate compounds from phosphate rock; Subpart A (phosphorus production) covers electric furnace reduction of phosphate rock to elemental phosphorus — one of the most energy-intensive industrial processes; furnace off-gases (containing phosphorus vapor and other compounds) are scrubbed with water, generating wastewater containing dissolved phosphorus, fluoride (from fluorapatite in phosphate rock), and suspended solids from the quench process; elemental phosphorus in wastewater is highly toxic to aquatic life; BAT for phosphorus production is essentially zero discharge of process phosphorus through slag-granulating water recirculation; Subpart B (phosphorus consuming) covers production of phosphoric acid, phosphate salts (sodium hexametaphosphate, trisodium phosphate), and polyphosphates from elemental phosphorus — wastewater contains dissolved phosphates and fluoride at concentrations requiring treatment before discharge; Subpart D (defluorinated phosphate rock) covers thermal calcination of phosphate rock to remove fluoride for use as animal feed supplement — fluoride is the dominant regulated pollutant, with BPT requiring wet scrubber water recirculation and fluoride precipitation; Subpart E (defluorinated phosphoric acid) and Subpart F (sodium phosphates) cover further downstream processing; primary regulated pollutants across all subcategories: total phosphorus, fluoride, and TSS; PSES pretreatment standards govern the substantial fraction of phosphate producers discharging to POTWs rather than directly to waterways.

  • 40 CFR Part 458 — Carbon Black Manufacturing (23 sections across 4 subcategories — furnace process, thermal process, channel process, lamp process): effluent limits for manufacturing carbon black — the fine carbon particulate used as a reinforcing agent in tires and rubber products (roughly 70% of production) and as a pigment; Subpart A (furnace process) is the commercially dominant subcategory, covering 97%+ of U.S. carbon black production — heavy aromatic oils are combusted with limited air in a reactor to yield carbon black particles entrained in process gas; quench water and pelletizing water pick up carbon black particulates and oils from the process; BAT standard for furnace carbon black is zero discharge of process wastewater — all process water is recycled in closed loops; stormwater runoff from carbon black storage areas is regulated as the primary compliance challenge; Subpart B (thermal process) uses thermal decomposition of natural gas without combustion to produce coarser-particle carbon black — a cleaner process with lower water use; Subpart C (channel process) and Subpart D (lamp process) are largely obsolete production methods maintained in the ELG for historical completeness; the primary environmental concern at carbon black facilities is stormwater contaminated with fugitive carbon black dust — which, despite its insolubility, creates high TSS in runoff and contributes to receiving-water turbidity.

  • 40 CFR Part 463 — Plastics Molding and Forming (25 sections across 3 subcategories — contact cooling and heating water, cleaning water, and finishing water): the ELG covering the enormous plastics manufacturing industry where water contacts plastic materials during processing; Subpart A (contact cooling/heating water) is the dominant subcategory — injection molding, extrusion, blow molding, and thermoforming operations use water to cool or heat molds that are in direct contact with molten or softened plastic; the cooling water picks up plasticizers (including phthalates from PVC and flexible plastics), mold-release agents, and plastic particles; BPT limits address oil and grease and TSS; BAT for contact cooling water requires recirculation of cooling water and treatment (gravity separation, filtration) before any discharge; the production-based limit structure (§ 463.12) ties discharge limits to the average process water usage rate rather than a concentration-based standard, recognizing that facilities use widely varying water volumes for the same products; Subpart B (cleaning water) covers water used to clean molds, extruder barrels, mixing equipment, and finishing areas — cleaning wastewater contains higher concentrations of plasticizers, dyes, and processing chemicals than cooling water; Subpart C (finishing water) covers wet sanding, buffing, and surface treatment of plastic parts — generating wastewater with plastic particles and abrasives; most plastics processors are indirect dischargers (PSES governs), since standalone POTW connections are more economical than on-site treatment for the small volumes generated; total toxic organics (TTO) limits address phthalate plasticizers and other priority pollutants.

  • 40 CFR Part 466 — Porcelain Enameling (25 sections across 4 subcategories — steel, cast iron, aluminum, and copper basis materials): effluent limits for the porcelain enameling industry — facilities that fuse ground glass (ceramic frit) to metal surfaces by firing at 750–850°C to produce the glossy, corrosion-resistant coating on kitchen appliances (ranges, refrigerators), bathtubs and plumbing fixtures, cookware, signage, and industrial vessels; the environmental significance is the pretreatment process: before enamel can be applied, metal surfaces must be prepared by acid pickling (removing oxides), alkaline cleaning, and nickel or cobalt deposition (to improve enamel-to-metal adhesion); these surface preparation steps generate wastewater containing nickel, cobalt, chromium, alkaline pH, and dissolved metals from the pickling acid; PSES compliance date (§ 466.04) was November 25, 1985; regulated pollutants vary by substrate: Subpart A (steel) limits TSS, cyanide (from alkaline cleaning baths containing cyanide compounds), and metals including nickel, copper, and chromium; Subpart B (cast iron) has similar pollutants reflecting heavy acid descaling of cast iron surfaces; Subpart C (aluminum) uses chromate or anodize pretreatment, generating hexavalent chromium wastewater requiring chemical reduction before precipitation; Subpart D (copper) applies to artisan and specialty porcelain applications; BAT for all subcategories requires chemical precipitation of metals (hydroxide precipitation at controlled pH) and clarification; most U.S. porcelain enamelers discharge to POTWs, making PSES the operative compliance standard.

  • 40 CFR Part 417 — Soap and Detergent Manufacturing Point Source Category (129 sections across 19 subcategories): the ELG covering one of the oldest continuous-process industrial wastewater sources — facilities that manufacture soap and synthetic detergent products from animal fats, vegetable oils, and petrochemical feedstocks; the 19 subcategories track the distinct manufacturing processes rather than finished products, because each process generates wastewater with different pollutant characteristics requiring different treatment approaches: Soap subcategories (Subparts A–H): Subpart A (batch kettle saponification) — the traditional soap-making process in which fats and oils are heated with caustic soda in large kettles and "salted out" with brine; the spent lye (nigre) and glycerine-containing wastewater are the primary discharge streams, with high BOD and COD from residual glycerine and fatty acid soaps; BPT/BAT limits reflect activated sludge biological treatment as the baseline for the high-BOD saponification streams; Subpart B (fatty acid production by fat splitting) — fats hydrolyzed under high-pressure steam to release fatty acids and crude glycerine, generating high-BOD condensate streams and glycerine-bearing wash water; Subpart D and E (glycerine concentration and distillation) — evaporation and distillation of crude glycerine streams, generating condensates and vapor condensation wastewater with residual glycerine and salt; Subparts F, G, and H (soap flakes, bar soaps, and liquid soaps) — final product forming operations that generate rinse water, pan wash, and equipment cleaning streams primarily containing soap residuals (BOD and COD); Detergent sulfonation subcategories (Subparts I–N): these cover the industrial processes for manufacturing anionic surfactants — the active cleaning agents in synthetic detergents — by reacting fatty alcohols, alpha-olefins, or alkylbenzene feedstocks with sulfur trioxide (SO3), oleum (fuming sulfuric acid), sulfamic acid, or chlorosulfonic acid to produce sulfonate and sulfate salts; sulfonation processes require neutralization of the acidic sulfonate products and generate wastewater from scrubbing SO3 off-gases and equipment rinses containing dissolved organosulfonates, unreacted acids, and inorganic sulfate salts; because anionic surfactants are specifically designed to resist natural degradation (a property desirable for cleaning performance but problematic for wastewater treatment), surfactant concentration limits are emphasized in the pretreatment standards for indirect dischargers; Subpart P and S (liquid detergents and detergent bars) — product formulation operations combining active surfactants with builders (phosphates, silicates, zeolites), fillers, and other ingredients, generating equipment wash and batch rinse streams containing mixed surfactant/builder residuals and pH extremes from alkaline builder systems. Primary regulated pollutants across all soap and detergent subcategories: BOD5, COD, TSS, and oil and grease (from fat/oil raw materials); surfactant-specific limits apply in pretreatment standards for indirect dischargers to prevent foaming and surfactant passthrough at POTWs. The soap and detergent ELG was established in 1974 (39 FR 13372) with revisions in 1995 (60 FR 33954); the 1995 revision updated numeric limits reflecting BAT improvements in glycerine recovery and closed-loop condensate reuse.

These ELG Parts implement 33 U.S.C. § 1311(b) (technology-based effluent limitation requirements) and § 1317 (toxic pollutant standards). NPDES permit writers incorporate ELG limits directly into facility permits; facilities discharging above their applicable ELG limits are in violation of their NPDES permits and subject to enforcement regardless of receiving water conditions.

• 40 CFR Part 139 — Discharges Incidental to the Normal Operation of Vessels (EPA's national standards for the routine operational discharges from vessels operating in U.S. waters — implementing the Vessel Incidental Discharge Act (VIDA) of 2018, which directed EPA to develop uniform national standards replacing a patchwork of state permits; authority: 33 U.S.C. § 1251; the rule covers over 25 discharge types from vessels, each with its own performance standard):

  • § 139.10 — Ballast tanks: vessels equipped with ballast tanks must implement best management practices to minimize the introduction of invasive aquatic species; ballast water exchange (replacing coastal water with open-ocean water at least 200 miles offshore) is a baseline practice; VIDA directed EPA to establish technology-based standards for ballast water treatment systems; vessels operating in the Great Lakes and Hudson River face more stringent standards due to those systems' documented vulnerability to invasive species (zebra mussels, round gobies); vessels less than 1,600 gross tons and those that operate in a single Captain of the Port zone are excluded from certain ballast water requirements
  • § 139.11 — Bilges: bilgewater — water mixed with oil, lubricants, fuel drips, and residues that accumulates in the lowest part of a vessel's hull — may be discharged at sea only if oil content is 15 parts per million (ppm) or less when measured with an oily water separator and its monitoring device; discharge of bilgewater is prohibited in port, in Annex I special areas under MARPOL, and in the Great Lakes; vessels must maintain an Oil Record Book logging all bilge discharges; the 15 ppm limit is calibrated to the output of standard shipboard oily water separators (OWS) — a critical piece of equipment for any commercial or large recreational vessel that wants to avoid bilge pump-out fees in port
  • § 139.15 — Decks: deck washdown water and precipitation runoff may be discharged; the use of deck cleaning agents (detergents, degreasers) is prohibited in certain federally designated areas (marine sanctuaries, Annex V special areas) unless the products are certified as non-toxic, non-bioaccumulative, and biodegradable; vessels must prevent dry cargo residues, paint scrapings, and solid debris from entering the water during deck washing
  • § 139.18 — Exhaust gas emission control systems: exhaust gas scrubbers (EGCS, also called "scrubbers" or "washwater" systems) used by vessels to comply with SOx emission limits under MARPOL Annex VI may discharge washwater from open-loop scrubbers only if water quality standards are met; the scrubber washwater must meet pH (≥6.5), polycyclic aromatic hydrocarbons (PAHs), turbidity, and nitrate standards; discharge of open-loop scrubber washwater is prohibited in port, at anchor, and in many coastal waters of the U.S. and internationally — creating compliance pressure on vessels that retrofitted scrubbers expecting global discharge freedom
  • § 139.24 — Gray water: gray water (shower, laundry, galley sink wastewater) from vessels may be discharged underway but is prohibited in the Great Lakes, coastal waters of Alaska, and designated no-discharge zones; vessels over 400 gross tons must use gray water management practices (minimization, holding) when in port; commingled gray water/sewage is subject to sewage treatment requirements rather than the more permissive gray water standards

  Part 139 replaces the former Vessel General Permit (VGP) system operated under NPDES and codifies standards that were previously set by EPA permit guidance. The shift from a permit-based to a regulatory standard model under VIDA was intended to create nationally consistent requirements preempting the varied state-by-state permit conditions that had developed under the VGP (California and other coastal states had imposed conditions stricter than the EPA's general permit). Implementation of the VIDA standards was the subject of extended EPA rulemaking from 2018 through 2022; EPA published the final Part 139 rule in 2024 (89 FR 33784) with phased compliance dates for different vessel types and discharge categories. The Coast Guard enforces the Part 139 standards through port state control inspections and USCG vessel documentation requirements that track OWS maintenance and Oil Record Book entries.

• 40 CFR Part 230 — Section 404(b)(1) Guidelines for Specification of Disposal Sites for Dredged or Fill Material (49 sections across 10 subparts — the EPA's substantive environmental criteria that govern every Corps of Engineers permit decision under CWA § 404; these are not procedural rules but the analytical framework the Corps must apply when evaluating whether to issue a permit for discharging dredge or fill material into waters of the United States, including wetlands):

  • § 230.10 — Restrictions on discharge (the core restriction): a Section 404 permit may not be issued if: (1) a practicable alternative exists that would have less adverse impact on aquatic ecosystems (and the alternative does not have other significant environmental consequences); (2) the discharge will violate applicable water quality standards or toxic effluent standards; (3) the discharge would jeopardize listed threatened or endangered species or their critical habitat; or (4) the discharge would cause or contribute to significant degradation of waters of the United States; the "practicable alternative" analysis (§ 230.10(a)) is the most frequently contested provision — applicants must demonstrate they have no viable alternative site or design that avoids or minimizes wetlands impact
  • § 230.10(a) — Practicable alternatives: an alternative is "practicable" if it is available and capable of being done after taking into consideration cost, existing technology, and logistics; for projects not water-dependent (i.e., not requiring access to water to fulfill their basic purpose — shopping malls, parking lots, housing), there is a presumption that alternatives without aquatic site impacts exist unless the applicant demonstrates otherwise; for water-dependent projects (marinas, boat launches, irrigation structures), no such presumption applies; the presumption shift is critical — upland projects bear a much heavier burden to justify wetlands fill than facilities that inherently require water access
  • § 230.11 — Factual determinations: before granting a permit, the Corps must determine in writing the potential short- and long-term effects of the proposed discharge on physical and chemical characteristics (§§ 230.20–230.25), biological characteristics (§§ 230.30–230.34), and human use characteristics (§§ 230.50–230.56); the written determination creates an administrative record subject to judicial review
  • Subpart E — Potential Impacts on Special Aquatic Sites (§§ 230.40–230.45): certain wetland types receive extra scrutiny — sanctuaries and refuges, wetlands, mudflats, vegetated shallows, coral reefs, and riffle/pool complexes are designated "special aquatic sites" whose "values are recognized as being of more than ordinary importance"; discharges into special aquatic sites face a heightened practicable alternatives analysis and require specific factual findings on the site's special values before a permit can issue
  • Subpart H — Mitigation Requirements (§§ 230.70–230.77): Corps permits may require applicants to take measures to avoid, minimize, or compensate for aquatic resource impacts; the mitigation hierarchy — avoid first, minimize second, compensate last — governs permit conditions; compensatory mitigation (wetlands replacement) is the last resort, not a license to destroy aquatic resources if compensation is available
  • Subpart J — Compensatory Mitigation (§§ 230.91–230.98): the most recently revised subpart (2008); establishes standards for the three types of compensatory mitigation — mitigation banks (pre-constructed replacement wetlands that sell credits to permit applicants), in-lieu fee programs (permit applicants pay a fee to a program that undertakes mitigation on their behalf), and permittee-responsible mitigation (the applicant constructs and maintains the replacement wetlands itself); the mitigation bank structure is preferred because the credits are verified functional before being used; permit applicants and the Corps negotiate the amount of credit needed through a functional assessment of the impacted wetlands' ecological value

  Part 230 is the substantive spine of the Section 404 wetlands permitting program. It transforms the Corps' permit authority from an administrative process into an environmental analysis requirement: the Corps cannot grant a 404 permit without conducting the factual determinations in § 230.11, applying the practicable alternatives test in § 230.10(a), and documenting its findings. Environmental organizations regularly challenge 404 permits by arguing the Corps failed to properly apply the Part 230 guidelines — particularly the alternatives analysis and special aquatic site findings. After Sackett v. EPA (2023) significantly narrowed the definition of "waters of the United States," the scope of which wetlands trigger the Part 230 analysis is itself contested; the Corps and EPA issued revised WOTUS regulations in 2023 that were stayed pending further litigation.

  Recent rulemakings: 73 FR 19687 (April 2008) — the 2008 compensatory mitigation rule added Subpart J and established the current mitigation bank and in-lieu fee framework; the core Guidelines (Subparts A–G) were finalized in 1980 (45 FR 85344) and have not been comprehensively revised.

• 40 CFR Part 125 — Criteria and Standards for the National Pollutant Discharge Elimination System (58 sections): technical standards governing specific NPDES permit types beyond the standard effluent limitation framework. Key subparts:

  • Subpart M (§§ 125.120–125.124) — Ocean Discharge Criteria: EPA standards for point source discharges into territorial seas, contiguous zones, and oceans; NPDES permit writers must determine that proposed discharges will not cause "unreasonable degradation of the marine environment"; criteria for unreasonable degradation include irreparable harm, permanent changes to ecological characteristics, and impacts on human health; most ocean permits require a full site-specific analysis of dilution, mixing zones, and ecological effects before the Director may issue the permit
  • Subpart B (§§ 125.10–125.11) — Aquaculture Discharge Guidelines: NPDES permits may be issued for controlled aquaculture projects that deliberately introduce pollutants (fish feed, metabolic wastes) into water bodies to support regulated aquaculture production; the project must be intended to produce harvestable food fish and be controlled to prevent undue harm to the receiving water
  • Subpart I (§§ 125.80–125.89) — Cooling Water Intake Structures for New Facilities (CWA § 316(b)): new facilities using cooling water intake structures (CWIS) must implement location, design, construction, and capacity criteria to reduce impingement and entrainment of aquatic life to levels achievable by the best technology available; this addresses the fish mortality caused by large-scale cooling water withdrawal at power plants and industrial facilities
  • Subpart J (§§ 125.90–125.99) — Cooling Water Intake Structures for Existing Facilities (CWA § 316(b)): the 2014 rule requiring existing power plants, refineries, and other industrial facilities that withdraw ≥2 million gallons/day of cooling water to implement Best Technology Available (BTA) standards for minimizing impingement (fish trapped against intake screens) and entrainment (small fish and larvae pulled through cooling systems); the national impingement mortality standard requires that facilities limit impingement mortality to ≤24% of impinged fish on an annual average (§ 125.94(a)(2)(ii)) — facilities may achieve this through intake velocity reduction, fine mesh screens, traveling screens with fish return systems, or other approved technologies; entrainment standards are determined site-specifically by the NPDES permit Director based on a comprehensive entrainment characterization study; facilities serving critical grid reliability needs may seek extended compliance schedules

  The 316(b) cooling water regulations (Subparts I and J) represent one of the longest regulatory development histories in environmental law — the original § 316(b) was enacted in 1972, but comprehensive regulations for existing facilities were not finalized until 79 FR 48300 (August 2014) after extensive litigation. Power plants on major rivers and the Great Lakes operate some of the largest CWIS in the country — older nuclear and coal plants were designed around once-through cooling systems that withdraw and return enormous water volumes. The 2014 rule was upheld by the Second Circuit (Entergy Corp. v. Riverkeeper) after the Supreme Court's 2009 decision allowed cost-benefit analysis in 316(b) implementation.

• 40 CFR Part 503 — Standards for the Use or Disposal of Sewage Sludge (40 sections — the national biosolids rule governing what happens to the solid material removed from wastewater treatment — roughly 7 million dry tons produced annually; establishes pollutant limits, pathogen reduction requirements, and site management practices for land application, surface disposal, and incineration). Key provisions:

  • § 503.13 — Pollutant limits for land application: bulk sewage sludge and bagged biosolids products may not be applied to land if they exceed ceiling concentrations for 10 regulated pollutants — arsenic (75 mg/kg), cadmium (85 mg/kg), copper (4,300 mg/kg), lead (840 mg/kg), mercury (57 mg/kg), molybdenum (75 mg/kg), nickel (420 mg/kg), selenium (100 mg/kg), and zinc (7,500 mg/kg); additionally, "exceptional quality" biosolids meeting the stricter pollutant concentration limits and Class A pathogen requirements may be applied without site restrictions (they are effectively treated as fertilizer products)
  • § 503.15 / § 503.32 — Pathogen reduction: biosolids must meet either Class A (pathogens reduced to below detectable levels — achieved by pasteurization, extended thermophilic composting, or alkali treatment to pH ≥12; Class A can be land-applied without time restrictions and can be sold retail as fertilizer) or Class B (pathogens significantly reduced but not eliminated — achieved by anaerobic digestion, aerobic digestion, lime stabilization, or other approved processes; Class B requires site restrictions including 30-day waiting period before harvesting food crops, prohibition of public access, and animal grazing restrictions)
  • § 503.14 — Management practices for land application: bulk biosolids shall not be applied to agricultural land if likely to adversely affect threatened or endangered species; shall not be applied to wetlands or in a manner that causes pollutant runoff to surface water; buffer distances required from water bodies; and application must not exceed the agronomic rate (the nitrogen/phosphorus uptake capacity of the crop being grown) — the agronomic rate requirement prevents over-application that causes nutrient runoff
  • § 503.16 / § 503.17 — Monitoring and recordkeeping: monitoring frequency depends on quantity applied — facilities applying under 290 dry metric tons/year must test at least once per year; those applying over 1,500 dry metric tons/year must test at least four times per year; records must be retained for 5 years and include pollutant concentrations, pathogen treatment method, application site and quantity, and nutrient analysis
  • §§ 503.20–503.26 — Surface disposal: biosolids placed on a surface disposal site (monofill) face different requirements than land application — liner and leachate collection systems required for new units within 150 meters of a public water supply, over a sandy soil aquifer, or in a 100-year flood plain; pollutant loading limits prevent groundwater contamination
  • §§ 503.40–503.47 — Incineration: sewage sludge incinerators must meet total hydrocarbon (THC) and beryllium/mercury emissions limits; risk-specific concentrations (RSCs) for seven additional metals (arsenic, cadmium, chromium, lead, nickel) are calculated based on site-specific air dispersion modeling; facilities must monitor emissions through continuous emission monitors or stack testing at required intervals

  The Part 503 biosolids rule represents one of EPA's most science-intensive regulatory programs — the pollutant limits were derived from a risk assessment across the 14 most critical exposure pathways (direct soil contact, crop uptake, grazing animal intake, airborne dust, etc.). Land application is the dominant beneficial use — roughly 55% of biosolids are land-applied as crop fertilizer and soil amendment, displacing synthetic nitrogen and phosphorus fertilizers. The major emerging regulatory issue for Part 503 is PFAS (per- and polyfluoroalkyl substances): biosolids from wastewater treatment accumulate PFAS from consumer products and industrial discharges, and land-applied biosolids have contaminated farm soils and groundwater in several states. EPA proposed PFAS limits for biosolids as part of its broader PFAS Action Plan, but final rules have not yet been promulgated.

• 40 CFR Part 501 — State Sludge Management Program Regulations: while 40 CFR Part 503 establishes the federal biosolids standards, Part 501 provides the mechanism by which a state may obtain EPA approval to administer its own sewage sludge management program in lieu of the federal program. This state primacy framework for biosolids parallels the state NPDES primacy program under 40 CFR Part 123 — once EPA approves a state's sludge program, the state becomes the primary regulator for biosolids generated within its borders, with EPA retaining oversight and backstop authority. Key provisions:

  • § 501.11 — Program submission requirements: a state seeking to administer a sludge management program must submit to the EPA Regional Administrator at least three copies of a program submission that includes: (a) a program description explaining the proposed state program and its legal authorities; (b) a statement from the state Attorney General certifying that the state has the legal authority to administer the program and take enforcement action against violators; (c) a Memorandum of Agreement (MOA) with the EPA Regional Administrator specifying the division of responsibilities, inspection frequencies, data sharing, and how EPA will exercise its oversight and backstop enforcement functions; and (d) the full text of all state statutes, regulations, and policies that will govern the program
  • § 501.15 — Permitting requirements: state sludge programs must have legal authority to issue permits to POTWs (and other generators of significant quantities of biosolids) governing the management of sewage sludge, and to impose permit conditions at least as stringent as the Part 503 federal standards; states may be more stringent but not less stringent; state permits must address land application rates, monitoring, recordkeeping, and all pollutant and pathogen requirements equivalent to Part 503 — states cannot exempt their biosolids generators from the Class A/Class B pathogen standards or the pollutant concentration limits
  • § 501.16–501.17 — Compliance evaluation and enforcement authority: state programs must have authority to monitor compliance (inspections, record reviews, effluent and biosolids sampling), and must have enforcement tools that include: (a) authority to restrain immediately and effectively any person creating an imminent and substantial endangerment; (b) authority to sue in state court for civil penalties; and (c) authority to criminally prosecute willful or knowing violations; the enforcement authority must be substantially equivalent to EPA's own authority under the CWA
  • § 501.18 — EPA veto over state permits: even after program approval, EPA retains authority to object to any state-issued permit; if EPA objects in writing to a proposed permit, the state may not issue the permit as proposed; the Regional Administrator's objection authority ensures that EPA can prevent a state from issuing a biosolids permit that violates Part 503 standards even when the state's program has been approved
  • § 501.14 — Memorandum of Agreement: the MOA is the operational agreement between EPA and the state — it specifies what data the state must share with EPA (permit applications, monitoring reports, inspection reports), the frequency of EPA oversight inspections, how disputes between state and EPA will be resolved, and the procedures for EPA to take enforcement action when the state fails to act; the MOA is binding on both parties and is publicly available

  As of 2026, relatively few states have sought EPA approval for a state biosolids program under Part 501 — most states that regulate biosolids do so under their own state authority operating alongside (not instead of) the federal Part 503 standards. States with state biosolids primacy include several that have integrated biosolids permitting into their NPDES program approvals. The state primacy pathway is most valuable for states that want a fully integrated approach to POTW regulation — combining wastewater discharge (NPDES), pretreatment, and biosolids into a single state permit program. No major Part 501 amendments since original promulgation in 1989 — the state primacy framework has remained stable while Part 503 itself (the federal standards states must match) has been the subject of ongoing revisions.

• 40 CFR Part 403 — General Pretreatment Regulations for Existing and New Sources: the horizontal framework governing how industrial users (IUs) discharging wastewater to publicly owned treatment works (POTWs) must pretreat their discharges before they enter the municipal sewer system. The ELG rules (Parts 405–471) set the industry-specific numeric limits; Part 403 sets the procedural and institutional framework — the "rules of the pretreatment game" — for the entire system:

  • § 403.5 — National prohibited discharge standards: no IU may discharge to a POTW any pollutant that (1) causes pass-through (a discharge that exits the POTW's effluent in violation of its NPDES permit) or (2) causes interference (disrupts the POTW's treatment processes, including biological treatment organisms or biosolids disposal); specific prohibited categories include flammable/explosive materials above 10% of the lower explosive limit, corrosive waste below pH 5.0, pollutants causing POTW upset, solid or viscous pollutants causing obstructions, trucked or hauled pollutants except at designated receiving points, heat sufficient to inhibit biological treatment, petroleum oil exceeding a specific concentration, and trucked/hauled pollutants except at approved receiving facilities; these categorical prohibitions apply regardless of whether a categorical pretreatment standard exists for the IU's industry
  • § 403.6 — Categorical pretreatment standards: the numeric limits for specific industrial categories (ELGs — Parts 405-471) are incorporated into the pretreatment system; IUs regulated under a categorical standard must meet the Pretreatment Standards for Existing Sources (PSES) or Pretreatment Standards for New Sources (PSNS) applicable to their industry; categorical standards override local POTW limits to the extent the categorical standard is stricter; local limits (set by the POTW under § 403.5(c)) may be stricter than categorical standards but not weaker
  • § 403.8 — POTW pretreatment program requirements: large POTWs (treating 5 million gallons per day or more, or significant industrial users in smaller systems) must develop and implement an approved pretreatment program; the program must identify and control IUs discharging to the POTW, set local discharge limits where national standards are insufficient to prevent pass-through/interference, conduct inspections and sampling, and take enforcement action against noncompliant IUs; EPA or the state approves and oversees the POTW pretreatment program
  • § 403.12 — Reporting requirements: IUs subject to categorical pretreatment standards must submit baseline reports upon first being regulated (within 180 days), compliance reports after the compliance deadline (60 days), and periodic compliance reports (semi-annual); reports must certify compliance or identify the basis of non-compliance and the corrective schedule; the reporting framework is the industrial pretreatment system's backbone — it obligates IUs to self-monitor and self-report
  • §§ 403.16–403.17 — Upset and bypass: an IU may assert "upset" as a defense if it can demonstrate unintentional and temporary noncompliance caused by factors beyond its reasonable control (e.g., mechanical failure, raw material supply disruption) and the IU took immediate corrective action; "bypass" (intentional diversion of waste streams around treatment) is generally prohibited unless the bypass is unavoidable to prevent loss of life or severe property damage, and the POTW has been notified in advance; these provisions parallel the NPDES upset/bypass defenses for direct dischargers

  The General Pretreatment Program covers approximately 34,000 indirect industrial dischargers that send significant wastewater to publicly owned treatment plants. Pretreatment standards are the primary mechanism for preventing industrial toxic pollutants from undermining POTW operations and contaminating sewage sludge with heavy metals, organic toxics, and other pollutants that would restrict its beneficial use as biosolids. The program is administered jointly by EPA, states, and individual POTWs — creating a three-tier oversight structure where each level can impose stricter requirements than the tier above.

• 40 CFR Part 112 — Oil Pollution Prevention (Spill Prevention, Control, and Countermeasure Rule): one of the most broadly applicable environmental regulations in the United States, requiring any facility that stores oil in quantities above threshold amounts to prepare and implement a written Spill Prevention, Control, and Countermeasure (SPCC) Plan. The rule implements CWA § 311 and is administered by EPA to prevent oil discharges from reaching navigable waters or adjoining shorelines:

  • § 112.1 — Applicability: the SPCC rule applies to any onshore or offshore non-transportation facility that: (1) has a total aboveground oil storage capacity greater than 1,320 gallons, or a completely buried oil storage capacity greater than 42,000 gallons; and (2) could reasonably be expected to discharge oil in harmful quantities to navigable waters or adjoining shorelines; "oil" is broadly defined to include crude oil, fuel oil, sludge, oil refuse, diesel, kerosene, vegetable oil, animal fat, hydraulic fluid, lubricating oil, and other petroleum products; agricultural operations, manufacturing facilities, warehouses, marinas, fuel terminals, and many commercial buildings with backup generators are commonly subject to the rule
  • § 112.3 — SPCC Plan requirement: subject facilities must prepare a written SPCC Plan meeting the technical requirements of § 112.7; for facilities with aggregate aboveground oil storage capacity above 10,000 gallons (or facilities with a spill history), the Plan must be certified and signed by a licensed Professional Engineer (PE); facilities with total aboveground storage between 1,320 and 10,000 gallons and no spill history may self-certify their Plan; the Plan must be prepared and kept at the facility; the Plan is not submitted to EPA unless specifically requested
  • § 112.7 — General Plan requirements: the SPCC Plan must include: a facility description and oil storage inventory; a prediction of direction, rate of flow, and total quantity of oil that could reach navigable waters in the event of a spill; a description of secondary containment structures (earthen berms, concrete dikes, or impoundment basins) providing capacity for the largest single container plus precipitation run-on); inspection and testing procedures for storage tanks and secondary containment; training procedures for oil-spill response; and drainage control procedures; secondary containment for aboveground storage tanks must hold the capacity of the largest single tank in the containment area
  • § 112.5 — Amendment obligations: operators must review and update the SPCC Plan at least every 5 years, and must amend the Plan whenever there is a change in facility design, construction, operation, or maintenance that materially affects oil discharge potential; any spill in excess of reportable quantity thresholds triggers a required review and potential amendment; the PE must re-certify any amended Plan if the original required PE certification
  • § 112.20 — Facility Response Plans (FRPs): facilities that store oil in quantities that could cause "substantial harm" to navigable waters — defined as facilities with single tank capacity above one million gallons, or facilities located such that a worst-case discharge could reach navigable water — must prepare a Facility Response Plan (FRP) in addition to the SPCC Plan; the FRP must provide for a "worst-case discharge" scenario, identify a qualified individual to coordinate spill response, and provide for contracting with certified oil spill response organizations (OSROs); FRPs are submitted to EPA Regional Administrators

  The SPCC rule is one of the most widely applicable environmental regulations in the country — any facility storing significant quantities of oil must comply. Enforcement is primarily inspection-driven: EPA and state environmental agency inspectors check for SPCC Plans during facility inspections and after spills. Common violations include: failure to prepare an SPCC Plan, inadequate secondary containment (dike capacity insufficient for the largest tank), lack of PE certification for required Plans, failure to update Plans after changes, and inadequate inspection records. Penalties range up to $25,000 per day for civil violations and criminal penalties for willful violations. Recent rulemakings: 73 FR 74236 (December 2008) — comprehensive rule revision that streamlined compliance pathways for smaller farms and qualified facilities; 76 FR 21652 (April 2011) — further amendments for agricultural facilities.

• 40 CFR Part 129 — Toxic Pollutant Effluent Standards: EPA's regulations establishing specific effluent standards for six toxic pollutants regulated under CWA § 307(a) — the "§ 307 standards" which are distinct from the technology-based ELG limits in Parts 405-471 because they are set at levels necessary to protect public health, not based on the best available treatment technology. These are the CWA's most stringent water quality standards:

  • Coverage: the six substances regulated under § 307(a) toxic standards include: aldrin/dieldrin (chlorinated insecticides, now banned but persistent in the environment); DDT, DDE, and DDD (banned chlorinated insecticides with known endocrine disruption and carcinogenic effects); endrin (highly toxic chlorinated insecticide); toxaphene (complex chlorinated pesticide); benzidine (chemical intermediate used in dye manufacturing, a human carcinogen); and polychlorinated biphenyls (PCBs — banned industrial chemicals used in transformers and capacitors, still found in legacy discharges and sediments)
  • Standard-setting approach: unlike ELG limits (which are technology-based), § 307 standards must be set at levels necessary to "protect public health and welfare with an ample margin of safety"; this means the limits must account for bioaccumulation in the food chain, persistence in sediments, and potential carcinogenicity — factors that technology-based standards do not necessarily address; the six substances regulated under § 307 were selected specifically because they bioaccumulate, persist, and have been linked to cancer or reproductive harm in wildlife and humans
  • Zero discharge requirements: for some of the most toxic substances (aldrin/dieldrin, DDT/DDE/DDD, endrin, toxaphene, PCBs), the standards effectively require zero measurable discharge because any detectable level in receiving waters can contribute to bioaccumulation problems; this is technically achievable for most regulated industries because the substances are already banned or restricted in use — facilities discharging these compounds are typically dealing with legacy contamination in soil runoff, not active use
  • Relationship to NPDES permits: § 307(a) standards are incorporated directly into NPDES permits for any discharger that could reasonably discharge these substances; permit writers must ensure permit limits are at least as stringent as the § 307 standards; the standards preempt less stringent state water quality standards — states cannot allow these discharges at higher levels than § 307 standards even if their own water quality standards are less stringent

  Part 129 standards remain relevant despite the banned status of most regulated substances because legacy contamination continues — industrial sites, brownfields, and agricultural lands with historic DDT or PCB applications can still discharge these compounds in stormwater runoff or leachate. Any NPDES permit for a facility with potential exposure to these legacy substances must include Part 129 compliance analysis.

• 40 CFR Part 433 — Metal Finishing Point Source Category: EPA's effluent limitations guidelines (ELGs) and pretreatment standards for the metal finishing industry — one of the largest and most geographically dispersed categories of industrial wastewater dischargers in the United States. Metal finishing operations (electroplating, anodizing, etching, chemical milling, polishing, coating) generate wastewater containing heavy metals (chromium, nickel, zinc, copper, lead, cadmium, cyanide) that are toxic to aquatic life and human health. Key provisions:

  • § 433.10 — Applicability: covers plants performing any of six metal finishing operations (electroplating, electroless plating, anodizing, chemical etching and milling, printed circuit board manufacture, and other metal finishing on any basis material including steel, aluminum, copper, nickel, and plastics); exemptions apply to facilities regulated under other, more specific ELG categories (e.g., copper forming is regulated separately); the regulation reaches an estimated 45,000+ facilities nationwide
  • § 433.11 — Definitions: "TTO" (total toxic organics) is the key compliance metric — a sum of specific toxic organic compounds measured against a threshold; the cyanide measurement distinguishes "Cyanide, T" (total) from "Cyanide, A" (amenable to chlorination), with different limits applying to each
  • § 433.12 — Monitoring: in lieu of direct TTO monitoring, facilities may use a certification pathway — certifying that they have implemented toxic organic management plans that prevent TTO discharge above the threshold; this compliance flexibility reduces routine monitoring burden while maintaining accountability through periodic facility records review
  • § 433.13 — Best Practicable Technology (BPT) limits: numeric limits for conventional and non-conventional pollutants using BPT — the minimum floor for existing sources; BPT limits for metal finishing cover cadmium, chromium (total and hexavalent), copper, lead, nickel, silver, zinc, TTO, and cyanide
  • § 433.14 — Best Available Technology (BAT) limits: more stringent than BPT for toxic pollutants; BAT limits for hexavalent chromium, cyanide, and TTO reflect the best performing facilities; BAT drives facilities toward closed-loop systems, chrome reduction, and cyanide oxidation rather than end-of-pipe treatment alone
  • § 433.15 — Pretreatment Standards for Existing Sources (PSES): numeric limits for metal finishing facilities that discharge to POTWs (indirect dischargers) rather than directly to surface waters; PSES limits are designed to protect POTWs and biosolids from toxic metal contamination that would pass through biological treatment; PSES effectively extends the CWA's metal finishing controls to the thousands of facilities discharging to municipal sewers

  Part 433 is one of the oldest and most economically significant ELG categories — metal finishing was among the first industries regulated under the CWA's effluent guidelines program in the 1980s. The regulation covers everything from small job shops electroplating hardware parts to large facilities producing precision aerospace and electronics components. The chromium and cyanide limits have driven widespread adoption of chrome reduction systems (reducing hexavalent Cr to trivalent Cr before treatment) and cyanide oxidation processes across the industry. Recent rulemakings: No major Part 433 amendments in the past 10 years — the rule's numeric limits date to 1983 (48 FR 32462) and have not been significantly updated; EPA has initiated reconsideration of metal finishing ELGs periodically but no final revision has been issued.

• 40 CFR Part 430 — Pulp, Paper, and Paperboard Point Source Category (96 sections across 12 subcategories — EPA's effluent limitations guidelines for the U.S. paper industry, one of the largest industrial water users in the country; the paper industry's defining regulatory history is the 1998 "Cluster Rules," a landmark combined NESHAP/ELG rulemaking that effectively ended the use of elemental chlorine in pulp bleaching, eliminating the primary source of dioxins and chlorinated organic compounds in pulp mill wastewater):

  • § 430.01 — Adsorbable organic halides (AOX): Part 430 introduces AOX — a bulk measurement of chlorinated organic compounds formed when chlorine-based bleaching chemicals react with lignin in wood pulp — as the primary regulated pollutant distinguishing the pulp and paper ELG from other industries; chlorinated organics include trace levels of dioxins and furans (particularly 2,3,7,8-TCDD and 2,3,7,8-TCDF), which bioaccumulate in fish tissue and prompted the 1998 rulemaking
  • § 430.03 — Best Management Practices (BMPs): direct and indirect dischargers must implement BMPs for spent pulping liquor (the concentrated organic-laden "black liquor" from the kraft pulping process, which must be recovered and combusted rather than discharged), soap (crude tall oil soap skimmed from black liquor evaporation), and turpentine (volatile organic compounds recovered from kraft pulping); spill prevention and containment programs are required for all subcategories
  • Subpart B — Bleached Papergrade Kraft and Soda (the largest subcategory by volume, covering the dominant U.S. pulp production process): the 1998 Cluster Rules established BAT limits requiring that kraft mills either eliminate chlorine dioxide bleaching or achieve AOX discharge levels not exceeding 0.623 kg AOX/air-dried metric ton of product (daily maximum); the rule effectively drove the industry to "elemental chlorine-free" (ECF) bleaching using chlorine dioxide instead of molecular chlorine, which reduces AOX and eliminates dioxin formation; BOD and TSS limits are also established for direct dischargers; PSES/PSNS require AOX pretreatment to avoid passing chlorinated organics through POTWs untreated
  • Subpart G — Mechanical Pulp (groundwood, thermomechanical, chemi-thermomechanical pulp): produced by grinding or refining wood without chemical pulping; no chlorine bleaching, so no AOX concern; primary regulated pollutants are BOD and TSS from wood fiber losses and resin acid-containing process water; mechanical mills have much higher fiber losses to wastewater than chemical mills
  • Subpart L — Tissue, Filter, Non-Woven, and Paperboard From Purchased Pulp (secondary fiber conversion): facilities that convert purchased market pulp or wastepaper into tissue, specialty papers, or paperboard without pulping; wastewater is primarily from wet forming processes and finishing; BOD and TSS are regulated but at lighter limits than kraft mills because purchased-pulp converters don't carry the pulping chemical loads

  The 1998 Cluster Rules (63 FR 18504, April 15, 1998) — simultaneously establishing Part 430 BAT/NSPS limits and NESHAP standards under the Clean Air Act for kraft mill air emissions — are considered among EPA's most significant industrial regulatory achievements. By requiring elemental chlorine-free bleaching, they drove a 95%+ reduction in AOX discharges and essentially eliminated dioxin in pulp mill effluent measured against 1980s baseline levels. The U.S. pulp and paper industry spent billions on process changes. Today, kraft mill effluent monitoring still tracks dioxin/furan levels in receiving water fish tissue through EPA's National Study of Chemical Residues in Lake Fish Tissue. Recent rulemakings: No major Part 430 amendments since the 1998 Cluster Rules; EPA has conducted ELG reviews but has not initiated a new Part 430 rulemaking.

• 40 CFR Part 429 — Timber Products Processing Point Source Category (94 sections across 14 subcategories — EPA's effluent limitations guidelines for wood products manufacturing operations that generate process wastewater from mechanical processing of logs and timber, including sawmilling, plywood manufacturing, hardboard and particleboard production, wood preserving, and wet wood storage):

  • Sawmills and Planing Mills (Subpart K): the largest employment category in the timber products sector; wastewater comes from log flume water, dewatering operations, and wet dust collection; primary pollutants are BOD and TSS from bark leachate (bark contains tannins that create high-BOD wastewater and characteristic brown color) and wood fiber losses; BPT and BAT limits target BOD and TSS; NSPS requires zero discharge of log flume water at new sawmills where log flotation can be eliminated
  • Veneer and Plywood (Subparts B and C): veneer dryer condensate contains methanol, acetaldehyde, and other volatile organics from wood drying; plywood manufacturing uses formaldehyde-based resins (urea-formaldehyde, phenol-formaldehyde) that may appear in press condensate; regulated pollutants include BOD, TSS, and for veneer operations, COD (chemical oxygen demand) from the condensate streams; BAT for veneer operations limits COD in dryer condensate
  • Wet Storage (Subpart L — log ponds and chip storage): logs stored in water ponds or sprayed with water to prevent checking generate highly colored, high-BOD leachate from bark extraction; primary pollutants are BOD, TSS, and color; NSPS for wet storage prohibits the discharge of debris (floating bark, wood chips) to surface waters — the only quantitative zero-discharge standard in Part 429; BAT limits apply to pH and TSS in log-pond overflow
  • Wood Furniture and Fixture Production (Subpart P): facilities with water wash spray booths (used to control overspray from furniture finishing operations) generate wastewater containing lacquers, varnishes, pigments, and solvents; regulated pollutants include BOD, TSS, and oil/grease; this is the most technologically diverse subcategory — manufacturers have moved substantially to waterborne coatings and UV-cure finishes to reduce spray booth wastewater generation

  Part 429's subcategories cover a highly fragmented industry — there are thousands of sawmills, planing mills, and wood products manufacturers across the Pacific Northwest, Southeast, and Great Lakes regions. The regulated pollutants (BOD, TSS, color, resin acids) are generally amenable to conventional biological treatment and settling, making compliance achievable for modern facilities. Legacy issues include pentachlorophenol (PCP) and creosote contamination at former wood-treating sites — these are addressed under Superfund and RCRA corrective action rather than Part 429 ELG limits, which address ongoing process discharges. Sawmill wastewater's high color can cause aesthetic impairment in receiving streams even at BOD/TSS levels within permit limits — states sometimes impose color limits beyond the federal ELG through water quality-based effluent limits (WQBELs) in NPDES permits. Recent rulemakings: The original Part 429 rule dates to 1974; EPA conducted an ELG review in 2017 concluding no revision was warranted; the rule remains essentially unchanged for most subcategories.

• 40 CFR Part 133 — Secondary Treatment Regulation: the minimum effluent quality standards that all publicly owned treatment works (POTWs — municipal sewage treatment plants) must achieve under CWA § 301 (33 U.S.C. § 1311). Part 133 defines "secondary treatment" as a specific level of performance rather than a process — any treatment technology that achieves these numerical standards qualifies:

  • § 133.102 — Secondary treatment standards: POTWs must achieve (and maintain on a rolling average basis) — BOD5 (5-day biochemical oxygen demand): 30-day average ≤30 mg/L; 7-day average ≤45 mg/L; Suspended Solids (SS): 30-day average ≤30 mg/L; 7-day average ≤45 mg/L; pH: must remain between 6.0 and 9.0 at all times; additionally, the percent removal requirement mandates that BOD5 and SS each be reduced by at least 85% from raw sewage influent levels — the 85% removal standard and the 30 mg/L concentration standard must both be met, whichever is more stringent
  • § 133.103 — Special considerations: combined sewer systems (which collect both sanitary sewage and stormwater in the same pipe) may be physically incapable of meeting percent removal requirements during storm events when dilute stormwater overwhelms the plant; EPA allows these systems to apply for modified secondary treatment standards during wet weather; lag ponds and stabilization ponds used in rural and small-community systems may qualify as "equivalent treatment" under § 133.105 if they achieve the same effluent quality even though the process differs from conventional activated sludge treatment
  • § 133.105 — Equivalent secondary treatment: treatment facilities using processes other than conventional activated sludge (trickling filters, oxidation ditches, rotating biological contactors, constructed wetlands) qualify as meeting secondary treatment if their effluent quality equals the numerical standards in § 133.102; this technology-neutral approach allows smaller communities to use lower-cost treatment processes without sacrificing compliance status

The secondary treatment standards in Part 133 were established at the time of CWA's enactment in 1972 and have been essentially unchanged for 50 years — they represent the minimum floor that every municipal sewage plant in the country must achieve to receive an NPDES permit. A POTW that fails to consistently achieve 30/30 BOD5/SS on a monthly average basis is in permit violation; repeated violations can trigger formal enforcement, compliance schedules, consent decrees, and significant civil penalties. The standards have driven an enormous infrastructure investment: the CWA's § 202 construction grants and the Clean Water State Revolving Fund (CWSRF) have directed billions in federal and state dollars to POTWs specifically to enable them to reach and maintain secondary treatment compliance. Despite 50 years of the standard, roughly 15-20% of smaller POTWs still report treatment performance issues during high-flow events, storm events, or aging infrastructure failures.

• 33 CFR Part 323 — Permits for Discharges of Dredged or Fill Material into Waters of the United States: the Army Corps of Engineers' procedural regulations implementing CWA § 404 (33 U.S.C. § 1344). While 40 CFR Part 230 establishes the EPA's substantive environmental criteria, Part 323 sets out the Corps' own permit jurisdiction and procedures. Key provisions:

  • § 323.3 — Discharges requiring permits: any discharge of dredged or fill material into waters of the United States requires a Department of the Army (DA) permit; "dredged material" means material excavated or dredged from waters; "fill material" means any material used to replace an aquatic area with dry land or to change the bottom elevation — includes dirt, rock, concrete, sand, clay, plastic, and construction debris; building pads, road fills, and bank stabilization structures all require Section 404 authorization when placed in jurisdictional waters
  • § 323.4 — Exemptions: several activities are categorically exempt: normal farming, silviculture, and ranching activities (plowing, seeding, cultivating, minor drainage); maintenance of currently serviceable structures (dikes, dams, levees, bridges); construction of temporary sediment basins at construction sites; construction of farm or forest roads built in accordance with best management practices; and emergency flood control operations — the farming exemption is broad and has been actively contested in litigation over what constitutes "normal" agricultural activity
  • § 323.5 — State program assumption: CWA § 404(h) authorizes EPA to transfer Section 404 administration to states for discharges into certain non-navigable waters; Michigan and New Jersey have assumed the Section 404 program; in assumed states, the state agency (not the Corps) issues permits for non-navigable waters; the Corps retains jurisdiction over traditionally navigable waters in assumed states regardless of state program assumption
  • § 323.6 — Permit authority: the Secretary of the Army has delegated Section 404 permit authority to the Chief of Engineers, who has re-delegated to district engineers; district engineers (there are 41 Corps districts nationwide) are the front-line permit decision-makers; the district engineer may issue permits with or without conditions, deny permits, or refer to higher authority on matters of significant public importance

• 33 CFR Part 330 — Nationwide Permit Program: the Army Corps' "general permit" program under CWA § 404(e), which pre-authorizes categories of low-impact activities that individually and cumulatively have minimal adverse effects on aquatic resources. Nationwide Permits (NWPs) eliminate the need for individual permits for covered activities meeting their terms:

  • § 330.1 — Purpose and policy: NWPs are general permits issued by the Chief of Engineers on a nationwide basis for specific categories of activities; they authorize work without requiring a full individual permit application if the prospective permittee complies with all NWP terms and conditions; the goal is to reduce regulatory burden for minor, routine activities while protecting aquatic resources through categorical conditions
  • § 330.4 — Conditions and thresholds: each NWP has activity-specific conditions (typically a 0.1-acre or 0.5-acre fill threshold depending on the NWP, combined with limits on linear feet of stream impact); NWPs also have general nationwide conditions that apply to all NWPs — including requirements for pre-construction notification (PCN) for impacts above certain thresholds, endangered species consultation, and historic property avoidance; the prospective permittee must satisfy every condition for NWP authorization to be valid
  • § 330.5 — Reissuance cycle: the Corps reissues the full suite of NWPs every 5 years; the 2021 NWP reissuance created 12 new NWPs and modified existing ones; NWP 12 (oil and gas pipeline activities) was the subject of major litigation in Army Corps of Engineers v. Yankton Sioux Tribe (2021) context; district engineers may add regional conditions or suspend individual NWP authorizations in their districts when necessary to protect specific aquatic resources
  • § 330.6 — Verification: for activities requiring pre-construction notification (PCN), the district engineer must review and verify that the NWP applies within 45 days of receiving a complete PCN; activities not requiring PCN are self-executing — the permittee may proceed if all conditions are met without any Corps response; verification letters are not required but common for activities that may trigger jurisdictional questions

NWPs cover the vast majority of Section 404 authorizations by number — the Corps processes approximately 50,000–60,000 Section 404 actions per year, of which roughly 85% are NWPs. Only 5-10% of Section 404 cases reach full individual permit review. The NWP program has been repeatedly challenged by environmental groups who argue that categorical pre-authorization fails to evaluate cumulative impacts adequately; the Corps responds that the thresholds, conditions, and 5-year reissuance cycle adequately protect aquatic resources for low-impact activities. NWP 12 (pipelines) and NWP 14 (linear transportation) are the most frequently used and most frequently litigated nationwide permits.

• 33 CFR Part 328 — Definition of Waters of the United States (WOTUS): the Army Corps of Engineers' regulatory definition of the term "navigable waters" — called "waters of the United States" in the regulations — that determines the geographic scope of CWA § 404 permit jurisdiction. No provision in environmental law has generated more sustained litigation; the definition determines whether a wetland, creek, pond, or drainage ditch on private land falls under federal permitting authority. Key sections:

  • § 328.1 — Purpose: Part 328 defines "waters of the United States" for the Army Corps' Section 404 (dredge-and-fill) program; the CWA's term "navigable waters" is defined in the statute to mean "waters of the United States, including the territorial seas" — this regulation gives that statutory term its practical content
  • § 328.2 — Geographic and jurisdictional scope: three main categories of waters are addressed — territorial seas (to 3 nautical miles from baseline), tidal waters (where salinity or tidal action is present), and non-tidal waters; each category has different lateral extent rules
  • § 328.3 — WOTUS definition: "waters of the United States" means (1) waters that are currently used, or were used in the past, or may be susceptible to use in interstate or foreign commerce, including all waters subject to the ebb and flow of the tide; (2) territorial seas; (3) interstate waters, including interstate wetlands; (4) impoundments of jurisdictional waters; (5) tributaries of paragraphs (1)–(4) waters; and (6) adjacent wetlands — wetlands adjacent to any of the above categories; the "adjacent wetlands" category is the most contested provision and the one most affected by Sackett v. EPA (2023)
  • § 328.4 — Lateral limits: territorial seas extend to 3 nautical miles; tidal waters' lateral limit is the high tide line (mean high water); non-tidal waters' lateral limit is the ordinary high water mark (OHWM) — defined in § 328.3(e) as the line on the shore established by the fluctuations and actions of water, evidenced by physical characteristics such as clear, natural lines impressed on the bank, shelving, destruction of terrestrial vegetation, or changes in the character of soil
  • § 328.5 — Effect of alterations: gradual natural changes (erosion, accretion, avulsion) modify WOTUS boundaries in real time; artificially constructed drains, ditches, or channels that connect to jurisdictional waters may or may not qualify depending on whether they have a continuous surface connection

  33 CFR Part 328 has been the regulatory battleground for three Supreme Court cases: Solid Waste Agency of Northern Cook County v. Army Corps (SWANCC, 2001) struck down Corps jurisdiction over isolated non-navigable waters used by migratory birds; Rapanos v. United States (2006) produced a fractured Court with Justice Scalia's plurality requiring a continuous surface connection between a wetland and a navigable-in-fact water, and Justice Kennedy's solo concurrence requiring only a "significant nexus"; Sackett v. EPA (2023) resolved the Rapanos split in favor of the Scalia plurality standard — wetlands must have a continuous surface connection to a navigable-in-fact water to fall within WOTUS jurisdiction. The Sackett decision eliminated federal jurisdiction over many "adjacent" wetlands that lack a direct surface water connection to a navigable body, significantly narrowing the § 404 program's geographic reach. The Biden administration's 2023 WOTUS rule (88 FR 3004) was substantially revised in a 2023 interim final rule following Sackett to conform to the new standard; the Trump administration has proposed further revisions. No rulemakings since the post-Sackett conforming amendment — the regulatory definition is under active review.

• 40 CFR Part 233 — 404 State Program Regulations (EPA, 37 sections across 8 subparts — the federal regulatory framework under which states may assume administration of the Section 404 dredge-and-fill permit program for certain waters within their boundaries; authority: 33 U.S.C. § 1344(g)–(h)): CWA § 404(g) authorizes the EPA Administrator to transfer Section 404 permit authority to a state for discharges into non-navigable waters within the state; traditionally navigable waters (waters currently or historically used in interstate commerce) always remain under Army Corps jurisdiction regardless of state program assumption:

  • Subpart A — General (§§ 233.1–233.2): Part 233 governs the process for evaluating state applications, the requirements for state permit programs, ongoing oversight, and grounds for program withdrawal; as of 2026, only two states — Michigan (assumed 1984) and New Jersey (assumed 1994) — have assumed the Section 404 program; Florida assumed the program in December 2020, but EPA withdrew that assumption in January 2025 following a Biden-era finding that Florida had inadequate safeguards; the low uptake reflects the administrative burden states face in running parallel permitting systems and the political resistance from state industries that prefer the Corps' programmatic approach
  • Subpart B — Program Approval (§§ 233.10–233.16): a state seeking program assumption must submit a complete program package to the EPA Regional Administrator including: a program description (§ 233.11) explaining how the state permit program will operate; a statement from the state attorney general confirming the state has sufficient legal authority (§ 233.12); a Memorandum of Agreement (MOA) with the Regional Administrator (§ 233.13) specifying how the state and EPA will coordinate on permit review, waiver of federal review for specified permit categories, and annual program reporting; a Memorandum of Agreement with the Secretary of the Army (§ 233.14) establishing how the state and Corps will coordinate on the boundary between assumed and non-assumed waters; EPA has 120 days to approve or deny after receiving a complete submission (§ 233.15)
  • Subpart C — Permit Requirements (§§ 233.20–233.25): state permits under an assumed program must prohibit the same discharges that the Corps would deny under Part 230's guidelines (§ 233.20); states may issue general permits (categorical pre-authorizations for low-impact categories) mirroring the Corps' Nationwide Permit program (§ 233.21); emergency permits may be issued for imminent hazards without full public notice, subject to retroactive review (§ 233.22); all state permits must ensure that discharges comply with water quality standards and the substantive criteria in EPA's Part 230 guidelines — states may not issue permits that EPA could veto under § 1344(c)
  • Subpart D — Program Operation (§§ 233.30–233.41 — largest subpart): the operational requirements that assumed state programs must maintain on an ongoing basis: public notice (§ 233.32) — each permit application must receive public notice providing at least 30 days for public comment; EPA review (§ 233.33) — the state must transmit all public notices to the Regional Administrator, who may object to proposed permits that violate Part 230 criteria or water quality standards; permit content standards (§ 233.35) — state permits must specify the location of the discharge, the type and quantity of material, and conditions necessary to ensure compliance; records (§ 233.36) — states must maintain permit files for at least 5 years; reporting (§ 233.38) — states must report permit statistics to EPA annually including number of permits issued, denied, and pending, and acres of wetlands affected
  • Subpart F — Federal Oversight (§§ 233.50–233.53): EPA retains authority over assumed state programs: § 233.50 — the Regional Administrator reviews state permit applications upon receipt and may object within 15 days of the close of the comment period; if EPA objects, the state may not issue the permit until EPA's concerns are resolved or EPA withdraws its objection; § 233.51 — EPA and the state may agree to waive federal review for specified categories of permits (routine, low-impact discharges) to reduce administrative burden; § 233.53 — EPA may withdraw a state's program approval if the state fails to administer the program in conformance with CWA requirements; the withdrawal process includes notice, an opportunity to comply, and a public hearing before approval is revoked
  • Subpart G — Eligible Indian Tribes (§§ 233.60–233.62): CWA § 518 authorizes EPA to treat Indian tribes as states for purposes of § 404 program assumption; an eligible tribe may assume the Section 404 program for waters within its reservation; only tribes that meet the § 518 eligibility criteria (governmental authority over the tribe's territory, adequate legal mechanisms, adequate administrative capacity) may apply; no tribe had assumed the § 404 program as of 2026; tribal § 401 water quality certification authority (a precursor step to § 404 jurisdiction) has seen increasing tribal activity following the Biden administration's 2022 WQC regulations

  The practical significance of § 404 state assumption is limited by the boundary between assumed waters (non-navigable) and retained Corps jurisdiction (navigable and tidal). Even in Michigan and New Jersey, the Corps retains jurisdiction over the most environmentally sensitive wetlands — the coastal and tidal waters and wetlands adjacent to traditionally navigable rivers — while the state handles permit activity further inland. The Sackett v. EPA (2023) decision's narrowing of WOTUS paradoxically may reduce the value of state assumption programs, since many formerly federal "adjacent wetlands" no longer fall under CWA jurisdiction at all after Sackett. Florida's 2025 loss of program approval demonstrates that EPA retains meaningful oversight authority and can reverse assumption decisions when state programs fail to maintain adequate protective standards.

• 40 CFR Part 123 — State NPDES Program Approval Requirements (EPA, 29 sections across 7 subparts — the federal framework under which states may assume administration of the NPDES permit program for point source discharges under CWA §§ 318, 402, and 405(a); authority: 33 U.S.C. §§ 1251, 1318, 1342, 1345; as of 2026, 47 states and the U.S. Virgin Islands administer their own NPDES programs, making state-administered permits the dominant permitting mechanism for most industrial and municipal dischargers in the United States):

  • § 123.1 — Purpose: Part 123 governs EPA review of state applications to assume NPDES permitting authority for point source discharges into navigable waters; it covers three distinct CWA programs: the §402 NPDES permit program (the primary discharge permit program), the §318 aquaculture discharge program, and §405(a) sewage sludge management permits; EPA retains direct permitting authority in states that have not received program approval (currently: Alaska, Idaho, Massachusetts, New Hampshire, New Mexico, District of Columbia, Puerto Rico, and federal territories other than U.S.V.I.)
  • §§ 123.21–123.24 — Program submission requirements: a state seeking NPDES authorization must submit four core documents: (1) a Governor's letter certifying the state's intent to operate the program and designating the agency responsible; (2) a program description (§ 123.22) including a narrative of how the program will be structured, an organizational chart, a staffing plan, a proposed Memorandum of Agreement with the Regional Administrator, and a description of state permit and enforcement procedures; (3) an Attorney General's statement (§ 123.23) certifying that state law provides adequate legal authority to administer each program element — including permit issuance, enforcement, and civil penalty authority; and (4) a Memorandum of Agreement (MOA) with the EPA Regional Administrator (§ 123.24) establishing how EPA and the state will coordinate permit review, enforcement referrals, and transfer of existing EPA permits to the state program; EPA has 120 days to approve or deny after receiving a complete submission
  • § 123.25 — Permitting requirements: the state's permit program must require permits equivalent to federal NPDES permits in substance — including technology-based effluent limits (BAT/BPT/BCT), water quality-based effluent limits, monitoring, reporting, and compliance schedule provisions; states may not issue permits less stringent than federal CWA requirements; states may impose stricter conditions under state law; permits must include a fact sheet for significant permits (those discharging toxic pollutants or discharging at volumes above thresholds) explaining the basis for permit limits
  • § 123.26 — Compliance evaluation program: the state must implement a compliance monitoring program that tracks permit compliance for all NPDES permittees, conducts periodic facility inspections, reviews discharge monitoring reports (DMRs), and identifies violations; states must enter compliance data into EPA's ICIS-NPDES national database to support EPA oversight and the public ECHO portal; the compliance evaluation requirement is the mechanism for ensuring that state-administered permits produce the same real-world discharge control as federal permits
  • § 123.27 — Enforcement authority requirements: the state must have legal authority to: seek civil penalties of at least $10,000 per day of violation; seek injunctive relief requiring immediate compliance; require and inspect records and monitoring equipment; enter any permitted facility for inspection purposes; and revoke or modify permits for noncompliance; states without adequate civil penalty authority cannot receive program approval — the enforcement authority requirement is the most common deficiency cited when states' program applications are found incomplete
  • § 123.28 — Disposal and use of sewage sludge (§ 405 programs): states seeking to assume the sewage sludge use and disposal permit program must demonstrate authority over biosolids management at POTWs — including application of biosolids to land (the primary disposal pathway for treated sludge), incineration, and surface disposal; sludge program authority is often assumed separately from the §402 NPDES authority

  The NPDES state authorization framework is what makes "47 states run their own NPDES program" operationally meaningful. Once authorized, the state agency — not EPA — is the permitting authority for most dischargers within the state. EPA reviews state permits for significant dischargers and retains authority to object (within 30 days of receiving the permit) and to veto permits that violate CWA requirements. EPA may also withdraw state program approval if the state fails to maintain adequate program performance — a power rarely exercised but held in reserve as ultimate oversight authority. The MOA is the key operational document governing how EPA and state programs interface: it specifies which permits EPA reviews, how enforcement referrals work, and how EPA handles permits for federally-owned facilities within the state that the state may lack jurisdiction over. No major Part 123 amendments in recent years — the state authorization framework has been stable since the 1980s, though EPA has periodically updated guidance on the minimum enforcement authorities required.

How It Works

The Clean Water Act is the primary federal law governing water pollution in the United States, complementing the Clean Air Act on the atmospheric side. Its central innovation is the NPDES permit system — making it illegal to discharge pollutants without a permit, and using permits to impose technology-based and water quality-based limits on every discharger.

The CWA's core mechanism is the prohibition in § 1311: discharging pollutants is unlawful except in compliance with the Act. Every point source — any discernible, confined conveyance such as a pipe, ditch, channel, or tunnel — that discharges pollutants into "navigable waters" must obtain an NPDES permit containing specific effluent limits, monitoring requirements, and reporting obligations. Forty-seven states administer their own NPDES programs under EPA oversight. Industrial dischargers must meet technology-based effluent limits regardless of receiving water conditions: "Best Available Technology Economically Achievable" (BAT) for toxic and non-conventional pollutants; "Best Conventional Pollutant Control Technology" (BCT) for conventional pollutants; "secondary treatment" for publicly owned sewage plants. Technology-based limits are the floor: when they're insufficient to meet water quality standards, states must impose stricter water quality-based limits. States designate uses for each water body (drinking water, recreation, aquatic life support) and set numeric criteria; when a body is "impaired," the state must establish a Total Maximum Daily Load (TMDL) allocating the total allowable pollutant load among all sources to restore it.

Section 404 gives the Army Corps of Engineers permit authority over the discharge of dredged or fill material into "waters of the United States" — which includes wetlands — effectively giving the federal government authority over development activities affecting wetlands (construction, land clearing, mining, road building). EPA holds veto authority over Corps permit decisions under § 1344(c). The scope of "waters of the United States" (WOTUS) has been the subject of decades of litigation and regulatory changes, with the Supreme Court most recently narrowing the definition in Sackett v. EPA (2023). The CWA's permit system primarily covers point sources — nonpoint source pollution (agricultural and urban runoff, the largest remaining source of water pollution) is not directly regulated through NPDES; agricultural runoff is explicitly exempted from the point source definition. The CWA's enforcement framework is among the strongest in environmental law: criminal penalties for knowing violations reach $50,000/day and 3 years imprisonment; "knowing endangerment" carries up to 15 years. Citizen suits under § 1365 allow any person to sue violators directly in federal court.

How It Affects You

State Variations

Pending Legislation

• HR 6668 — Clean Water Standards for PFAS Act of 2025: creates an EPA-led PFAS regulatory program under the Clean Water Act with deadlines, testing standards, monitoring, and grants to control PFAS discharges. Status: In Committee.
• S 3457 — Clean Water Standards for PFAS Act of 2025 (Senate companion): forces EPA to set PFAS water-quality rules, expand monitoring, and authorize grants for treatment plants. Status: Introduced.
• HR 6616 — Clean Water Justice Act: raises criminal fines for Clean Water Act violations and requires annual CPI-based inflation adjustments. Status: In Committee.
• HR 6626 — PFAS Accountability Act of 2025: allows citizens to sue PFAS producers and obtain court-ordered medical monitoring. Status: Introduced.
• S 3460 — PFAS Accountability Act of 2025 (Senate companion): creates federal right to sue for PFAS exposure with cost-shifting to responsible manufacturers. Status: Introduced.
• S 3445 — Requires DoD to provide alternative drinking water to households with private wells contaminated by PFOS/PFOA from military sites. Status: Introduced.
• HR 6669 — No Taxation on PFAS Remediation Act: creates tax exclusion for PFAS cleanup reimbursements. Status: Introduced.
• HR 6464 — Affordable Clean Water Infrastructure Act. Status: In Committee.
• HR 2421 — CLEAR Waters Act: would narrow Clean Water Act's "navigable waters" definition to exclude treatment-system parts, ephemeral flows, and groundwater. Status: Introduced.
• HR 2415 — Columbia River Clean-Up Act: extends Columbia River Basin Restoration program authorization through 2026-2030. Status: Introduced.
• HR 2388 — Water Infrastructure Modernization Act: would fund 'intelligent water infrastructure' technologies and expand grant uses. Status: Introduced.
• HR 1730 — Water Affordability, Transparency, Equity, and Reliability Act: allocates ~$35 billion in mandatory water/sewer transfers with lead/PFAS remediation. Status: Introduced.

Recent Developments

• The Supreme Court's Sackett v. EPA (2023) decision significantly narrowed the scope of "waters of the United States," limiting CWA jurisdiction to waters with a continuous surface connection to traditionally navigable waters — potentially removing protections from millions of acres of wetlands
• EPA finalized a revised WOTUS rule in response to Sackett, adapting its regulatory framework to the narrower jurisdictional scope
• PFAS contamination in drinking water and surface water has driven new EPA water quality criteria under both the CWA and the Safe Drinking Water Act and enforcement actions, though comprehensive PFAS regulation under the CWA is still evolving
• EPA withdraws meat/poultry effluent guidelines (September 2025): EPA withdrew its proposed effluent limitations guidelines for Meat and Poultry Products point sources under the Trump administration's deregulatory agenda, removing proposed discharge standards that would have required upgraded wastewater treatment at slaughterhouses and food processing facilities. The withdrawal signals a broader rollback of CWA effluent guidelines rulemaking initiated under Biden. EPA also initiated reconsidering the CWA Hazardous Substance Facility Response Plans rule (February 2026), signaling potential rollback of Biden-era chemical discharge preparedness requirements.