EPA CAFO Wastewater Standards — Effluent Limits for Factory Farm Discharges

A Concentrated Animal Feeding Operation (CAFO) is a large-scale facility where animals are confined and fed rather than grazed, and where the density of animals and waste generates water pollution potential comparable to an industrial point source. The Clean Water Act treats large CAFOs as point sources — meaning they need NPDES permits and must meet effluent limitation guidelines set by EPA at 40 CFR Part 412. These guidelines establish the minimum technology-based standards for how CAFOs must manage the manure, litter, and wastewater generated in their production areas. For most large CAFOs, the standard is effectively zero discharge: process wastewater may not be discharged to U.S. waters except during rainfall events that exceed a 25-year, 24-hour storm.

Legal Authority

• 33 U.S.C. § 1311 — Clean Water Act § 301: prohibits discharge of pollutants from point sources into U.S. waters unless authorized by an NPDES permit; CAFOs are point sources subject to this prohibition
• 33 U.S.C. § 1342 — Clean Water Act § 402: establishes the NPDES permit program; large CAFOs require NPDES permits to discharge; effluent limitations in the permit must reflect EPA-established effluent limitation guidelines
• 40 CFR Part 412 — EPA effluent limitation guidelines and new source performance standards for the animal feeding operations point source category; sets technology-based discharge limits for beef, dairy, swine, poultry, and other CAFO sectors

Key Mechanics

Part 412 sets technology-based effluent limits for CAFOs through a sector-specific framework. The rule covers four livestock sectors (Beef Cattle Feedlots, Dairy Cows and Heifers, Swine and Poultry, Horses and Sheep) each with distinct production systems and waste management challenges. For most large CAFOs using liquid manure systems, the standard is "zero discharge" from production areas except during "process wastewater precipitation events" — discharge is only permitted when a storm exceeds the design storm (25-year, 24-hour). Dry litter operations (most broiler chicken and turkey facilities) must prevent dry litter from coming into contact with precipitation; if they discharge, they must meet specified effluent limits. CAFO operators must develop and implement a Nutrient Management Plan (NMP) to apply manure to agricultural land at agronomic rates, preventing over-application that would cause runoff to nearby waters.

Current Rule (2026)

What This Rule Does

The effluent limitation guidelines in Part 412 set the technology floor — the minimum treatment standard — that every regulated CAFO must achieve regardless of what any particular NPDES permit says. EPA establishes these standards by examining what the "best" technology can achieve across the industry and then requiring all facilities to meet that level. The Part 412 technology standards work alongside (and are distinct from) the NPDES permit requirements in 40 CFR Part 122, which govern who must get a permit and what site-specific conditions apply.

What is a CAFO?: a facility is a CAFO if it confines animals for more than 45 days per year, lacks crops, vegetation, or pasture in the confinement area, and meets a minimum size threshold. The thresholds vary by animal type — a facility with 1,000 or more beef cattle, 700 dairy cows, 2,500 swine over 55 lbs, 10,000 swine under 55 lbs, 30,000 laying hens (liquid waste), 125,000 chickens (other than layers), or 500 horses qualifies as a "large CAFO." Medium CAFOs (lower thresholds) may also be regulated if they discharge to U.S. waters.

The two pollution sources: Part 412 addresses two distinct waste streams:

1. Production area — the confinement pens, feedlots, animal houses, manure storage lagoons, and mortality composting areas; this is where the primary waste is generated and contained
2. Land application area — the fields where CAFOs spread manure as fertilizer; misapplication here creates runoff to streams

Technology Standards Framework

EPA uses four benchmarks to set CAFO effluent limits, each requiring more control than the last:

• BPT (Best Practicable Control Technology Currently Available): the baseline for existing sources; what the average well-controlled operation already does; for most CAFO categories, BPT requires no discharge of process wastewater except during storms exceeding a 25-year, 24-hour event
• BCT (Best Conventional Pollutant Control Technology): for conventional pollutants (BOD, TSS, fecal coliform, pH); generally the same as BPT for CAFOs
• BAT (Best Available Technology Economically Achievable): for toxic and non-conventional pollutants; the most stringent standard for existing sources; for most CAFO categories, BAT also requires zero discharge from production areas during normal conditions
• NSPS (New Source Performance Standards): for new facilities; may be more stringent than BAT; for new swine, poultry, and dairy CAFOs, zero discharge from production areas is absolute — no storm exceptions

Subparts and Animal Categories

Subpart A — Ducks (§§ 412.20–412.26):

• Applies to dry lot and wet lot duck CAFOs (5,000+ ducks)
• Dry lot ducks (barn-raised, solid litter): BPT/BAT require no discharge except during 25-year storm; NSPS require zero discharge
• Wet lot ducks (pond access): different discharge standards since wet lots have surface water contact; fecal coliform limits and pH requirements apply to discharges

Subpart B — Horses and Sheep (§§ 412.10–412.15):

• Applies to facilities with 500+ horses or 10,000+ sheep
• BPT/BAT: no discharge from production areas except during 25-year, 24-hour storm; best management practices for land application
• NSPS: zero discharge; new facilities must be designed with sufficient lagoon/pond capacity to contain all process wastewater with no storm-based exception

Subpart C — Cattle and Dairy (§§ 412.30–412.37):

• Applies to beef cattle (1,000+ head), dairy cattle (700+ milking or dry cows), and veal calves
• BPT: no discharge of manure, litter, or process wastewater from production areas except during 25-year, 24-hour storm events; feedlot areas must be designed to control runoff from less severe storms
• BAT: same as BPT for large CAFOs; additionally, each CAFO must implement a Nutrient Management Plan (NMP) for land application — setting limits on phosphorus and nitrogen application rates based on soil testing and crop uptake
• § 412.37 — Additional measures: routine visual inspections (weekly minimum) of all storm water control structures, manure and litter storage areas, and process water storage ponds; dead animal disposal must comply with applicable federal, state, and local requirements; record-keeping for at least 5 years covering land application records, inspection logs, and mortality records
• NSPS (§ 412.35): new sources must meet same zero-discharge standard as BAT with no storm exception

Subpart D — Swine, Poultry, and Veal Calves (§§ 412.40–412.47):

• Applies to swine (2,500+ over 55 lbs; 10,000+ under 55 lbs), chickens/turkeys (125,000+ broilers; 30,000+ layers using liquid systems), and veal calves (1,000+)
• BPT/BAT: no discharge from production areas except 25-year storm; land application NMP required
• § 412.47 — Additional measures: same weekly inspections and mortality records as Subpart C; must also implement the BMP requirements of § 412.4 for land application
• NSPS: zero discharge from production areas (§ 412.46)

Land Application BMPs (§ 412.4)

For cattle (Subpart C) and swine/poultry/veal calves (Subpart D), land application of manure must follow Best Management Practices:

• CAFO must have a site-specific Nutrient Management Plan incorporating soil testing, field-specific nutrient application rates, and setbacks from water bodies
• Application rates must be consistent with agronomic nutrient uptake — applying more nitrogen or phosphorus than crops can absorb is prohibited
• Minimum 100-foot setback from surface water bodies before applying manure; setback from water bodies and tile drains required
• Application is prohibited when land is frozen, snow-covered, or saturated; when rain is forecast within 24 hours
• Records of all land application activities (date, field, acreage, volume, nutrient content) must be maintained for 5 years

How It Affects You

If you operate a CAFO: Part 412 is the technology floor — your NPDES permit will incorporate these standards, but states and EPA regions may impose stricter permit conditions. The "no discharge" standard means you must design your lagoon and pond system to contain all process wastewater from your production area during a 25-year, 24-hour precipitation event, plus any additional volume generated during that storm from the production area. Have a qualified engineer calculate your storage needs. Routine visual inspections are mandatory and records must be kept for 5 years — these are the most common compliance deficiency in CAFO enforcement actions.

If you are a state NPDES permitting authority: Part 412 sets the floor; you cannot issue NPDES permits that allow CAFOs to discharge more than these standards allow. You may impose more stringent limits based on receiving water quality standards. The 2003 CAFO rule (68 FR 7176) required states to issue NPDES permits to large CAFOs that discharge or propose to discharge — enforcement of permit coverage has been uneven across states, and EPA periodically reviews state programs.

If you are a neighbor, environmental group, or downstream water user: the CWA prohibits CAFOs from discharging without an NPDES permit and from exceeding effluent limits. Citizen suits under CWA § 505 (33 U.S.C. § 1365) allow private parties to sue permit holders for permit violations; EPA and state regulators also enforce through administrative orders and civil penalties. The 2005 Second Circuit decision (Waterkeeper Alliance v. EPA) struck down EPA's exemption for CAFOs that "propose to discharge" but do not actually discharge — meaning CAFOs can no longer avoid permit requirements simply by planning not to discharge; they may still need permits based on design and location.

Statutory Authority

This rule implements:

• 33 U.S.C. § 1311 (CWA § 301) — prohibits discharge of pollutants from point sources to U.S. waters without an NPDES permit; authorizes EPA to set effluent limitation guidelines applying technology-based standards
• 33 U.S.C. § 1342 (CWA § 402) — NPDES permit program; permits must require compliance with EPA's effluent limitation guidelines; authorizes states to administer state NPDES programs subject to EPA oversight

Recent Rulemakings

2008 Amendment (73 FR 70418, November 2008): EPA revised Part 412 in response to the Waterkeeper Alliance v. EPA decision. The 2d Circuit vacated portions of the 2003 rule — specifically the "duty to apply" approach that required only CAFOs that discharge to get permits. The 2008 revision removed the blanket permit exemption for CAFOs not actually discharging and required all large CAFOs to seek NPDES permit coverage unless they demonstrate they have no potential to discharge. The 2008 rule also added the land application record-keeping requirements and strengthened the Nutrient Management Plan provisions.

2012 proposed rule: EPA proposed to strengthen the land application standards, including mandatory phosphorus-based application rates for phosphorus-saturated soils. The proposal was withdrawn in 2012 under agricultural industry pressure. Land application standards remain the major gap in CAFO water quality protection — nitrogen and phosphorus runoff from manure-applied fields is a significant contributor to downstream hypoxia (including the Gulf of Mexico dead zone).

Pending Action