Hard-copy editions of this work may be obtained by directly contacting Glenn Saums

Q: What exactly is a CAFO?
A: CAFOs are a subgroup of Animal Feeding Operations (AFO) that meet federal criteria primarily based upon the number of animals confined. An AFO is a lot or facility where animals have been, are, or will be stabled or confined and fed or maintained for a total of at least 45 days in any 12-month period, and the animal confinement area does not sustain crops, vegetation, forage growth, or post-harvest residues in the normal growing season. It is not necessary that the same animals are fed or maintained on the lot for the 45-day period nor do the 45 days need to be consecutive.

A Concentrated Animal Feeding Operation is an animal feeding operation that also has
• more than 1,000 animal units [40 CFR 122, Appendix B];
• between 301 and 1,000 animal units and that may or does discharge (to a surface water of the United States) by one of the methods covered by regulations at 40 CFR 122, Appendix B(b); or
• been designated a CAFO by the United States Environmental Protection Agency (USEPA) on a case-by-case basis after inspection (by USEPA) [40 CFR 122.23(c)].

The federal regulation also states:

. . . that no animal feeding operation is a concentrated animal feeding operation as defined above if such animal feeding operation discharges only in the event of a 25-year, 24-hour storm event. (40 CFR Appendix B) (Emphasis added.)

Q: What environmental permits are applicable to AFOs and CAFOs?
A: There are two different permits that may be required depending on the situation. The two permits are the federal National Pollutant Discharge Elimination System (NPDES) permit and the state Ground Water Discharge Permit (DP).

Q: Are these two permits the same, and if I comply with one will I automatically comply with the other?
A: No. The NPDES permit is a federal (United States Environmental Protection Agency) permit intended to protect surface water quality. The DP is a state (New Mexico Environment Department (NMED)) permit intended to primarily protect ground water quality. The NPDES permit is issued under the authority of the federal Clean Water Act (CWA) (1). The DP is issued under the authority of the New Mexico Water Quality Act (2) and the New Mexico Water Quality Control Commission (WQCC)Regulations (3). While there are many similarities between the two, compliance with one program will not assure compliance with the other (4). However, it is possible for operators to develop a single operational plan that will satisfy the discharge permit requirements of the Water Quality Control Commission Regulations and the pollution prevention plan requirements under the NPDES CAFO permit.

NPDES permits may be issued to facilities meeting the federal definition of "CAFO." A DP may be required for any facility where there is a discharge or activity that may affect ground water quality (i.e., either an AFO or a CAFO).

Q: What is a National Pollutant Discharge Elimination System (NPDES) permit?
A: NPDES permits are issued and enforced by the United States Environmental Protection Agency under the authority of the federal Clean Water Act. The NPDES program requires permits for "point source dischargesof "pollutants" to "waters of the United States" [ref. 40 CFR 122.1(b) and 122.2 (definitions)].

Q: Is a CAFO a "point source"?
A: When the Clean Water Act was passed in 1972, Congress was very clear in their intent that CAFOs be regulated as point sources. The statutory definition of a "point source" specifically includes CAFOs. CWA Section 502(14) states in part:

[t]he term "point source" means any discernible, confined and discrete conveyance, including but not limited to any pipe, ditch, channel, . . . concentrated animal feeding operation . . . from which pollutants are or may be discharged. (Emphasis added.)

Many discharges to surface water can be considered discharges to water of the United States. The discharge does not have to be directly to a large lake or major interstate river. Wetlands and tributaries (including small streams and dry arroyos) of interstate waters also are waters of the United States.

An actual or ongoing discharge is not required for a facility to be covered by the NPDES regulations because the definition of "point source" includes a CAFO "from which pollutants are or may be discharged."

Q: What does the NPDES permit require?
A: In general, the permit requires that "there shall be no discharge of process waste water pollutants to a water of the United States." There is one exception to this no discharge requirement for permitted facilities which is:

[p]rocess waste pollutants in the overflow may be discharged to water of the U.S. whenever rainfall events, either chronic or catastrophic, cause an overflow of process waste water from a facility designed, constructed and operated to contain all process generated waste water plus the runoff from a 25-year, 24-hour rainfall event for the location of the point source. There shall be no effluent limitations from detention structures constructed and maintained to contain the 25- year, 24- hour storm event if the discharge is the result of a rainfall event which exceeds the design capacity and proper maintenance (5). (ref.: NPDES permit Part II [58 F.R. 7628].)

Q: My Animal Feeding Operation (AFO) contains its runoff and waste water. If I don't intend to discharge to a surface water, what are the benefits of having an NPDES/CAFO permit?
A: Following are two reasons:

1. If a facility is permitted under the NPDES program, it may legally discharge (without effluent limitations) overflow from its retention structure whenever rainfall events, either chronic or catastrophic (6), cause an overflow of process waste water from a facility designed, constructed and operated to contain all process generated waste waters plus runoff from a >\=25-year, 24-hour storm event.

For example, in the summer of 1997, a New Mexico permittee experienced an excessive chronic rainfall event which caused their properly sized containment structure to overflow. In this case, the overflow was legal (provided the facility had been properly operated). If the same facility had not been permitted, the discharge would have been illegal.
2. The federal Clean Water Act's "Citizen Suit Provision (7) provides any concerned citizen the opportunity to sue a violator of the Clean Water Act. One reason the EPA developed the general NPDES permit in 1993 was to assure the industry had a mechanism to be easily permitted and thus prevent citizen suits which were being filed against CAFO's in other states for not having NPDES permit coverage.

Q: As a CAFO operator, if I don't have an NPDES/CAFO permit, what kind of discharge would be considered a violation of the federal Clean Water Act?
A: Discharges from an unpermitted facility, other than those from a 25-year, 24-hr storm, are in violation of the Clean Water Act regardless of retention capacity. These discharges include discharges due both to catastrophic events such as tornadoes, hurricanes, or other catastrophic conditions, and to a chronic rainfall event.

For example, the 25-year, 24-hour storm event for Somewhere, New Mexico is 2.59 inches of rain. An unpermitted facility here receives a 2" rainfall followed by a 1.75" rainfall 26 hours later. This is not a 25-year, 24-hour storm event because 2.59 or more inches of rain were not received in any single 24-hour period. A discharge from this unpermitted facility due to this chronic rainfall would be a violation of the CWA. If this same facility had been NPDES permitted and properly operated and maintained there would be no enforcement.

Subsurface discharges to a surface water through a hydrologic connection (8) would also be considered a violation.

Q: My CAFO is not permitted under the NPDES program but it is designed, built, and maintained to contain process wastewater and the runoff from a 25-year, 24-hour storm event. Does this protect me from liability under the federal Clean Water Act?
A: No. An unpermitted CAFO with a retention structure that is designed, built, and maintained to contain process wastewater and the runoff from a 25-year, 24-hour storm event is not protected from liability under the CWA in the event of a discharge due to smaller storm events. While design and equipment effectiveness may increase the confidence of the unpermitted discharger, capacity alone provides little protection from enforcement in the event of a discharge.

Q: As a CAFO operator what else should I know about how CWA compliance is determined at CAFO facilities?
A: A critical point in the determination of compliance, whether the facility is permitted or not, is the issue of proper operation and maintenance. Simply having an initial facility plan or design to contain 25-year, 24-hour storm events may not be sufficient to ensure compliance with federal requirements. Failure to properly operate and maintain even a properly designed (sized) facility could lead to violations because having the capacity to contain all runoff from a 25-year, 24-hour storm event protects unpermitted facilities from violating the CWA only if it actually functions to prevent discharges from smaller and chronic events. Examples of factors that could cause problems include: changes in the animal population or expansion of the facility after completion of design or construction; containment lagoons filling in thereby reducing their capacity; and not having adequate pumping schedules to reduce retention structure volume after minor storms in order to maintain capacity for subsequent storms. Having written operational/maintenance pollution prevention plans and "as-built" design specifications on-site can help operators prevent these types of problems. In fact, most of the performance and record keeping activities which are required for compliance with the NPDES/CAFO general permit are intended as guidance for the operator and are an indicator that the facility is being properly operated and maintained.

Q: Can you briefly summarize what is legal and what is not under the federal NPDES permit?
A: The following is a very simplified table for facilities which meet the definition of "CAFO" (the reader is cautioned to consult previous questions and answers, all NPDES regulations and permit requirements for full interpretation):
 

 

i)	Technically exempt from NPDES CAFO permit requirements if facility only discharges in the event of a greater than or equal to 25-yr, 24-hr storm event and the facility is properly designed, constructed, and operated
ii)	Regardless of facility design/construction/operation/maintenance
iii)	Provided facility is properly designed, constructed, operated and has complied with all other provisions of the NPDES permit (e.g., BMPs have been implemented).

Q: How is an NPDES permit obtained?
A: The easiest way to obtain an NPDES permit is to apply for coverage under the U.S. Environmental Protection Agency's general permit for CAFOs. A general permit is by nature a "blanket" permit for a category of dischargers (e.g., CAFOs). The permit was issued by the EPA in the February 8, 1993 Federal Register (58 F.R. 7626). A one page (no fee) application, called a "Notice of Intent" (NOI), for coverage under the permit must be filed with the Environmental Protection Agency with a copy to the New Mexico Environment Department Surface Water Quality Bureau. Facilities which meet USEPA's definition of "new source" will have to file an additional "Environmental Information Document" with their NOI. Instructions are provided in the Federal Register on how to file the NOI and what information is necessary for the Environmental Information Document. General permit coverage is effective upon submittal of the NOI to the USEPA and USEPA's issuance of an NPDES permit number. Facilities may elect to apply for individual permit coverage (i.e., not participate in the general "blanket" permit). However, the individual permit option is much more cumbersome and time consuming.

Q: Where can I get a copy of the NPDES permit and the application form?
A: There are several ways to obtain a copy. Since the permit and the application were published in the Federal Register, they may be obtained through public libraries directly or an inter-library loan. The permit and the application can be also be obtained on the Internet at NPDES Permit Program site.  You can also contact us directly, call or write the New Mexico Environment Department (NMED) at the address below and we will provide a copy free of charge.

Q: What is the New Mexico Environment Department's role in the implementation of the NPDES permit program?
A: The State of New Mexico does not administer or enforce the NPDES permit program. Before the final NPDES permit was issued, the State was required by federal law to review the USEPA's proposed permit. NMED performed this review to assure the permit was compatible with appropriate state law and protected state water quality standards. The USEPA has also requested that the NMED Surface Water Quality Bureau (SWQB) do some NPDES inspections as USEPA's representative. NMED SWQB personnel do not determine NPDES compliance. During an inspection, SWQB personnel discuss the permit and their preliminary findings with the responsible person on-site, and document conditions observed as they relate to the NPDES permit. The SWQB's written inspection report is transmitted to USEPA for their review and serves as a basis for their determinations regarding compliance. A copy of the inspection report is also sent to the facility. In addition to performing inspections, and because USEPA's nearest office is in Dallas Texas, the NMED Surface Water Quality Bureau provides a local contact for program information and assistance. Surface Water Quality Bureau routinely provides information to the public, permittees, and coordinates with other local, state, and federal programs.

Q: What is a State Ground Water Discharge Permit (DP)?
A: The New Mexico Water Quality Control Commission Regulations require a ground water Discharge Plan for any discharge of effluent or leachate which has the potential to move directly or indirectly into ground water (9). A Discharge Permit is a permit issued under the authority of the New Mexico Water Quality Act and is based upon the information submitted in the discharge plan. Discharge Permits are required for many kinds of industrial (e.g., mine) and domestic (e.g., municipal sanitary wastewater) discharges. Examples of regulated discharges from AFOs include dairy wastewater discharges to lagoons and land application areas. Discharge permits cover the operational components of a facility as well as mechanisms to address potential failure of the system (contingency plans), and closure of the facility. Discharge permits also include monitoring requirements such as sampling of ground water and effluent, flow measurements, and nutrient management record-keeping.

Q: Do State Ground Water Discharge Permits only address ground water issues?
A: No. While the primary purpose of the DP is to protect ground water quality, the New Mexico Water Quality Act (10) prohibits issuance of a DP if it will cause or contribute to a surface water quality standard (11) violation.

Q: Where can I get a copy of New Mexico Water Quality Control Commission's requirements and the application forms?
A: Please call or write the New Mexico Environment Department Ground Water Quality Bureau at the address below.

Q: Is there anything else, beyond the NPDES or DP regulations, that should be considered when applying for a permit?
A: Yes. Nationally, environmental regulatory agencies and regulated industries are realizing the benefits of pollution prevention. While "pollution prevention" often equates with "compliance assurance," it is actually much more. Pollution prevention involves evaluation and planning of activities with the objective to reduce, reuse and recycle. These three terms apply not only to the waste product, but also look at waste generation and often rely on minimized utilization of consumable resources (e.g., fresh water for washing). Pollution prevention planning can lead to significant economic as well as environmental benefits. Both the NPDES and DP programs rely heavily on pollution prevention planning and therefore present an opportunity for operators to benefit from a comprehensive evaluation of their process. The New Mexico Environment Department heartily endorses pollution prevention planning.

Q: Where can I get more information about CAFO requirements in New Mexico?
A: You can write to us at:

The Surface Water Quality Bureau can be contacted by phone at (505) 827-2933 and by fax at (505) 827-0160. The Ground Water Quality Bureau can be contacted by phone at (505) 827-2900 or by fax at (505) 827-2965. Some information, such as the WQCC Regulations are available on NMED's website. In the near future, additional CAFO information will also be available through NMED's home page. The USEPA maintains a public information telephone number which is (800) 887-6063. Region 6 USEPA also has on-line information available at the touch of a button. Furthermore, the USEPA has also published a document entitled Guide Manual On NPDES Regulations For Concentrated Animal Feeding Operations(EPA 833-B-95-001 -- December 1995). That manual was utilized in preparation of this document and is available to the public from the EPA. Another source of information is the USEPA's Agriculture Compliance Assistance Center. The Center can be contacted by regular mail at:

  On March 9, 1999, the USDA and USEPA issued the Unified National Strategy for Animal Feeding Operations. The Unified AFO Strategy discusses the relationships between AFOs and environmental and public health, is based on a national performance expectation for all AFO owners and operators, and presents a series of actions to minimize public health impacts and improve water quality while complementing the long-term sustainability of livestock production.   Please see the attached excerpts from the U.S. Code of Federal Regulations below for more information.

1. 33 U.S.C. 1253 et. seq.

2. Chapter 74, Article 6 NMSA 1978

3. 20 NMAC 6.2

4. This issue is also addressed in the NPDES permit's state specific language for the State of New Mexico (ref.: Feb. 8, 1993 Federal Register [58 f.r. 7636]).

5. The permit requirement is based upon EPA's effluent guidelines for best available technology as set forth in 40 CFR 412 for the "Feedlots Point Source Category" which have been in effect since publication in the Feb. 14, 1974 Federal Register [39 F.R. 5706].

6. A catastrophic event is equivalent to a 25- year, 24-hour storm event. Catastrophic events could also include tornadoes, hurricanes, or other catastrophic conditions that would cause an overflow from the required waste retention structure. A chronic rainfall is a series of wet weather conditions that preclude dewatering of properly maintained waste retention structures [58 F.R. 7620].

7. CWA Section 505.

8. Hydrologic connection is defined in the EPA's NPDES permit as "the interflow and exchange between surface impoundments and surface water through an underground corridor or groundwater...."

9. WQCC Regulations, Section 3104.

10. Section 74-6-5.E(3), NMSA 1978 (1993 Replacement Pamphlet).

11. 20.6.4 NMAC

Excerpts from the Code of Federal Regulations (Title 40)

For more extensive research, direct access to CFR Title 40 is available online.

In the following version, emphasis has been added by NMED in some sections to assist the reader interested in topics raised in the above Question and Answer sheet...

122.23 Concentrated animal feeding operations (applicable to State NPDES programs, see 123.25).

(a) Permit requirement.
Concentrated animal feeding operations are point sources subject to the NPDES permit program.
(b) Definitions. (1) Animal feeding operation means a lot or facility (other than an aquatic animal production facility) where the following conditions are met:
(I) Animals (other than aquatic animals) have been, are, or will be stabled or confined and fed or maintained for a total of 45 days or more in any 12-month period, and
(ii) Crops, vegetation forage growth, or post-harvest residues are not sustained in the normal growing season over any portion of the lot or facility.
(2) Two or more animal feeding operations under common ownership are considered, for the purposes of these regulations, to be a single animal feeding operation if they adjoin each other or if they use a common area or system for the disposal of wastes.
(3) Concentrated animal feeding operation means an "animal feeding operation" which meets the criteria in appendix B of this part, or which the Director designates under paragraph (c) of this section. (c) Case-by-case designation of concentrated animal feeding operations. (1) The Director may designate any animal feeding operation as a concentrated animal feeding operation upon determining that it is a significant contributor of pollution to the waters of the United States. In making this designation the Director shall consider the following factors:
(I) The size of the animal feeding operation and the amount of wastes reaching waters of the United States;
(ii) The location of the animal feeding operation relative to waters of the United States;
(iii) The means of conveyance of animal wastes and process waste waters into waters of the United States;
(iv) The slope, vegetation, rainfall, and other factors affecting the likelihood or frequency of discharge of animal wastes and process waste waters into waters of the United States; and
(v) Other relevant factors.
(2) No animal feeding operation with less than the numbers of animals set forth in appendix B of this part shall be designated as a concentrated animal feeding operation unless:
(I) Pollutants are discharged into waters of the United States through a manmade ditch, flushing system, or other similar manmade device; or
(ii) Pollutants are discharged directly into waters of the United States which originate outside of the facility and pass over, across, or through the facility or otherwise come into direct contact with the animals confined in the operation.
(3) A permit application shall not be required from a concentrated animal feeding operation designated under this paragraph until the Director has conducted an on-site inspection of the operation and determined that the operation should and could be regulated under the permit program.

Appendix B to Part 122 - Criteria for Determining a Concentrated Animal Feeding Operation (122.23)

An animal feeding operation is a concentrated animal feeding operation for purposes of 122.23 if either of the following criteria are met.
(a) More than the numbers of animals specified in any of the following categories are confined:
(1) 1,000 slaughter and feeder cattle,
(2) 700 mature dairy cattle (whether milked or dry cows),
(3) 2,500 swine each weighing over 25 kilograms (approximately 55 pounds),
(4) 500 horses,
(5) 10,000 sheep or lambs,
(6) 55,000 turkeys,
(7) 100,000 laying hens or broilers(if the facility has continuous overflow watering),
(8) 30,000 laying hens or broilers (if the facility has a liquid manure system),
(9) 5,000 ducks, or
(10) 1,000 animal units; or

(b) More than the following number and types of animals are confined:
(1) 300 slaughter or feeder cattle, (2) 200 mature dairy cattle (whethermilked or dry cows),
(3) 750 swine each weighing over 25 kilograms (approximately 55 pounds),
(4) 150 horses,
(5) 3,000 sheep or lambs,
(6) 16,500 turkeys,
(7) 30,000 laying hens or broilers (if the facility has continuous overflow watering),
(8) 9,000 laying hens or broilers (if the facility has a liquid manure handling system),
(9) 1,500 ducks, or
(10) 300 animal units;

and either one of the following conditions are met: pollutants are discharged into navigable waters through a manmade ditch, flushing system or other similar man-made device; or pollutants are discharged directly into waters of the United States which originate outside of and pass over, across, or through the facility or otherwise come into direct contact with the animals confined in the operation.

Provided, however, that no animal feeding operation is a concentrated animal feeding operation as defined above if such animal feeding operation discharges only in the event of a 25 year, 24-hour storm event.
The term animal unit means a unit of measurement for any animal feeding operation calculated by adding the following numbers: the number of slaughter and feeder cattle multiplied by 1.0, plus the number of mature dairy cattle multiplied by 1.4, plus the number of swine weighing over 25 kilograms (approximately 55 pounds) multiplied by 0.4, plus the number of sheep multiplied by 0.1, plus the number of horses multiplied by 2.0.
The term manmade means constructed by man and used for the purpose of transporting wastes.

122.1 Purpose and Scope

(b) Scope of the NPDES permit requirement.(1) The NPDES program requires permits for the discharge of "pollutants" from any "point source" into "waters of the United States."

(2) The following are point sources requiring NPDES permits for discharges:
(i) Concentrated animal feeding operations as defined in [CWA Section] 122.23 . . . .

122.2 Definitions.

Point source means any discernible, confined, and discrete conveyance, including but not limited to, any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, container, rolling stock, concentrated animal feeding operation, landfill leachate collection system, vessel or other floating craft from which pollutants are or may be discharged. This term does not include return flows from irrigated agriculture or agricultural storm water runoff. (See 122.3).

Pollutant means dredged spoil, solid waste, incinerator residue, filter backwash, sewage, garbage, sewage sludge, munitions, chemical wastes, biological materials, radioactive materials (except those regulated under the Atomic Energy Act of 1954, as amended (42 U.S.C. 2011 et seq.)), heat, wrecked or discarded equipment, rock, sand, cellar dirt and industrial, municipal, and agricultural waste discharged into water. It does not mean:....

Waters of the United States or waters of the U.S. means:

(a) All waters which are currently used, were used in the past, or may be susceptible to use in interstate or foreign commerce, including all waters which are subject to the ebb and flow of the tide;
(b) All interstate waters, including interstate "wetlands;"
(c) All other waters such as intrastate lakes, rivers, streams (including intermittent streams), mudflats, sandflats, "wetlands," sloughs, prairie potholes, wet meadows, playa lakes, or natural ponds the use, degradation, or destruction of which would affect or could affect interstate or foreign commerce including any such waters:
(1) Which are or could be used by interstate or foreign travelers for recreational or other purposes;
(2) From which fish or shellfish are or could be taken and sold in interstate or foreign commerce; or
(3) Which are used or could be used for industrial purposes by industries in interstate commerce;
(d) All impoundments of waters otherwise defined as waters of the United States under this definition;
(e) Tributaries of waters identified in paragraphs (a) through (d) of this definition;
(f) The territorial sea; and
(g) "Wetlands" adjacent to waters (other than waters that are themselves wetlands) identified in paragraphs (a) through (f) of this definition. Waste treatment systems, including treatment ponds or lagoons designed to meet the requirements of CWA (other than cooling ponds as defined in 40 CFR 423.11(m) which also meet the criteria of this definition) are not waters of the United States. This exclusion applies only to manmade bodies of water which neither were originally created in waters of the United States (such as disposal area in wetlands) nor resulted from the impoundment of waters of the United States. [See Note 1 of this section.] Waters of the United States do not include prior converted cropland. Notwithstanding the determination of an areas status as prior converted cropland by any other federal agency, for the purposes of the Clean Water Act, the final authority regarding Clean Water Act jurisdiction remains with EPA.

[CFR] PART 412 - FEEDLOTS POINT SOURCE CATEGORY
[NMED note: for brevity several sections are omitted from this summary, the reader is directed to the CFR for the full text of the CFR.]

Source: 39 FR 5706, Feb. 14, 1974, unless otherwise noted.
Subpart A - All Subcategories Except Ducks
412.10 Applicability; description of all subcategories except ducks.
The provisions of this subpart are applicable to discharges of pollutants resulting from feedlots in the following subcategories: Beef cattle - open lots; beef cattle - housed lots; dairy cattle - stall barn (with milk room); dairy - free stall barn (with milking center); dairy - cowyards (with milking center); swine - open dirt or pasture lots; swine - housed, slotted floor; swine - solid concrete floor, open or housed lot; sheep - open lots; sheep - housed lots; horses - stables (race tracks); chickens - broilers, housed; chickens - layers (egg production), housed; chickens - layer breeding or replacement stock; housed; turkeys - open lots; turkeys - housed; and for those feedlot operations within these subcategories as large or larger than the capacities given below:
1,000 slaughter steers and heifers; 700 mature dairy cattle (whether milkers or dry cows); 2,500 swine weighing over 55 pounds; 10,000 sheep; 55,000 turkeys; 100,000 laying hens or broilers when facility has unlimited continuous flow watering systems; 30,000 laying hens or broilers when facility has liquid manure handling system; 500 horses; and 1,000 animal units from a combination of slaughter steers and heifers, mature dairy cattle, swine over 55 pounds and sheep.

412.11 Specialized definitions.
For the purpose of this subpart:
(b) The term feedlot shall mean a concentrated, confined animal or poultry growing operation for meat, milk or egg production, or stabling, in pens or houses wherein the animals or poultry are fed at the place of confinement and crop or forage growth or production is not sustained in the area of confinement.
(c) The term process waste water shall mean any process generated waste water and any precipitation (rain or snow) which comes into contact with any manure, litter or bedding, or any other raw material or intermediate or final material or product used in or resulting from the production of animals or poultry or direct products (e.g. milk, eggs).
(d) The term process generated waste water shall mean water directly or indirectly used in the operation of a feedlot for any or all of the following:
Spillage or overflow from animal or poultry watering systems; washing, cleaning or flushing pens, barns, manure pits or other feedlot facilities; direct contact swimming, washing or spray cooling of animals; and dust control.
(e) The terms 10 year, 24 hour rainfall event and 25 year, 24 hour rainfall event shall mean a rainfall event with a probable recurrence interval of once in ten years or twenty-five years, respectively, as defined by the National Weather Service in Technical Paper Number 40, "Rainfall Frequency Atlas of the United States", May 1961, and subsequent amendments, or equivalent regional or state rainfall probability information developed therefrom.
(f) The term open lot shall mean pens or similar confinement areas with dirt, or concrete (or paved or hard) surfaces wherein animals or poultry are substantially or entirely exposed to the outside environment except for possible small portions affording some protection by windbreaks, small shed-type shade areas. For the purposes hereof the term "open lot" is synonymous with the terms "cowyard" (dairy cattle), "pasture lot" (swine), and "dirt lot" (swine, sheep or turkeys), "dry lot" (swine, cattle, sheep, or turkeys) which are terms widely used in the industry.
(g) The term housed lot shall mean totally roofed buildings which may be open or completely enclosed on the sides wherein animals or poultry are housed over solid concrete or dirt floors, slotted (partially open) floors over pits or manure collection areas in pens, stalls or cages, with or without bedding materials and mechanical ventilation. For the purposes hereof, the term "housed lot" is synonymous with the terms "slotted floor" buildings (swine, beef), "barn" (dairy cattle) or "stable" (horses), "houses" (turkeys, chickens), which are terms widely used in the industry.
(h) The term stall barn shall mean specialized facilities wherein producing cows and replacement cows are milked and fed in a fixed location.
(I) The term free stall barn shall mean specialized facilities wherein producing cows are permitted free movement between resting and feeding areas.
(j) The term milkroom shall mean milk storage and cooling rooms normally used for stall barn dairies.
(k) The term milking center shall mean a separate milking area with storage and cooling facilities adjacent to a free stall barn or cowyard dairy operation.

412.13 Effluent limitations guidelines representing the degree of effluent reduction attainable by the application of the best available technology economically achievable.
(a) Subject to the provisions of paragraph (b) of this section, the following limitations establish the quantity or quality of pollutants or pollutant properties which may be discharged by a point source subject to the provisions of this subpart after application of the best available technology economically achievable: There shall be no discharge of process waste water pollutants to navigable waters.
(b) Process waste pollutants in the overflow may be discharged to navigable waters whenever rainfall events, either chronic or catastrophic, cause an overflow of process waste water from a facility designed, constructed and operated to contain all process generated waste waters plus the runoff from a 25-year, 24-hour rainfall event for the location of the point source.

412.15 Standards of performance for new sources.
(a) Subject to the provisions of paragraph (b) of this section, the following standards of performance establish the quantity or quality of pollutants or pollutant properties which may be discharged by a source subject to the provisions of this subpart: There shall be no discharge of process waste water pollutants to navigable waters.
(b) Process waste pollutants in the overflow may be discharged to navigable waters whenever rainfall events, either chronic or catastrophic, cause an overflow of process waste water from a facility designed, constructed and operated to contain all process generated waste waters plus the runoff from a 25-year, 24-hour rainfall event for the location of the point source.