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National Pollutant Discharge Elimination System (NPDES)

National Pretreatment Program Regulatory History

EPA originally published the general pretreatment regulations in 1978. These regulations have been updated many times since then, with substantial amendments in 2005 as the “Streamlining Rule” and minor edits with the NPDES Electronic Reporting Rule. The timeline below highlights key pretreatment regulatory changes and the significant events or publications that brought about those changes. Related documents and materials are also provided.

Current Regulatory Activities

EPA develops and publishes new regulations and periodically updates existing regulations. There are current rulemaking activities expected to result in changes to the general pretreatment regulations at 40 CFR Part 403. The following will affect the implementation of the national pretreatment program:

Regulatory Timeline

Regulatory Activity

Related Materials




Availability of and Procedures for

Removal Credits

70 FR 60199 – 60202(4 pp, 173 K, About PDF)


EPA sought comment on two issues concerning the removal credits provisions in the General Pretreatment Regulations

  • Requested comments on whether to amend the list of pollutants for which removal credits are available to add certain pollutants
  • Comments were closed on December 13, 2005 and no rulemaking activities were initiated for these issues

Streamlining the General Pretreatment

Regulations for Existing and New Sources of Pollution (Streamlining Rule)

Streamlining Rule Fact Sheets

2006 - 2009

Fact sheet series outlining the changes made to the pretreatment program at 40 CFR Part 403 under the Pretreatment Streamlining Rule

  • 1: Summary of Changes Made Under the Streamlining Rule
  • 2: Required Changes
  • 3: Equivalent Mass Limits for Concentration Limits
  • 4: Equivalent Concentration-Based Limits for Flow-Based Standards
  • 5: New Classifications for Categorical Industrial Users
  • 6: Optional Sampling Waiver for Pollutants Not Present
  • 7: Best Management Practices
  • 8: Slug Control Plans
  • 9: General Control Mechanisms Option

70 FR 60134-60198(65 pp, 463 K, About PDF)


Changes to the General Pretreatment Regulations that address restrictions on and oversight of industrial users who introduce pollutants into publicly owned treatment works (POTWs) and modified certain program requirements to be consistent with National Pollutant Discharge Elimination System (NPDES) requirements

  • Authorized representative/duly-authorized employee
  • Best management practices
  • Concentration-based categorical pretreatment standards expressed as equivalent mass limits
  • Equivalent concentration limits in lieu of mass limits for certain categories of categorical industrial users (CIUs)
  • Flexibility in the use of certain sampling techniques
  • General control mechanisms
  • Middle-tier CIUs
  • Non-significant CIUs
  • Notification requirements
  • Reduced sampling for categorically regulated pollutants neither present nor expected to be present
  • Removal credits reference update
  • Representative samples
  • Significant noncompliance (SNC) criteria
  • Slug control requirements

64 FR 39564 - 39605(42 pp, 457 K, About PDF)


Project eXcellence and Leadership for Communities (Project XL)

63 FR 34170 - 34176(7 pp, 177 K, About PDF)


Solicitation of local pilot pretreatment program proposals under Project XL

  • Invited POTWs to propose alternative environmental performance-based pretreatment programs
  • Four POTWs conducted five experimental water regulatory projects
  • None of the pilot projects demonstrated pretreatment program alternatives that could be implemented at the national level

Streamlined Procedures for Modifying

Approved Publicly Owned Treatment

Works Pretreatment Programs

62 FR 38406-38415(10 pp, 155 K, About PDF)


  • Revised the procedures for modifying approved POTW Pretreatment Programs incorporated into NPDES permits issued to POTWs
  • Revisions designed to reduce the administrative burden and cost associated with maintaining approved pretreatment programs without affecting environmental protection

61 FR 39804-39810(7 pp, 137 K, About PDF)



Standards for the Disposal of Sewage Sludge

60 FR 54764-54770(7 pp, 215 K, About PDF)


EPA reconsidered issues remanded by the U.S. Court of Appeals for additional justification or modification

  • EPA amended 40 CFR Part 503 to delete the land application pollutant limits for chromium and to change the land application pollutant concentration limit for selenium
  • EPA also amended the list of pollutants (in Appendix G of 40 CFR Part 403) for which a removal credit may be available

58 FR 9248 – 9404


  • Leather Industries of America, Inc., (3/5/1993) and City of Pueblo, CO (6/17/1993) file petitions challenging the proposed rule, which are consolidated as the court case Leather Industries of America, Inc. v. Environmental Protection Agency, 40 F.3d 392, D.C. Cir., 1994 (11/15/1994)
  • Adds Appendix G to the Part 403 general pretreatment regulations
  • Appendix G—Section I lists the pollutants regulated in Part 503 and eligible for removal credit authorization
  • Appendix G–Section II lists additional pollutants that are eligible for a removal credit if the concentration of the pollutant in sewage sludge does not exceed a prescribed concentration
  • Appendix G—Section II lists the pollutants that EPA evaluated and opted not to regulate during development of the Part 503 regulation
  • Establishes 40 CFR Part 503
  • EPA promulgated regulation to protect public health and the environment from the reasonably anticipated adverse effects of certain pollutants in sewage sludge
  • Established requirements for the following final uses or disposal of sewage sludge: 1) land application either to condition the soil or to fertilize crops grown in the soil; 2) final disposal on the land; and 3) incineration

54 FR 5746 – 5902



Pretreatment Program and Domestic Sewage Exclusion Rulemaking (“Hazardous Solid Waste Amendments” [HSWA])

55 FR 30082 – 31033 Final Rule


Regulations to enhance control of toxic pollutants and hazardous waste discharges to POTWs

  • Expanded specific prohibitions on discharges into POTWs; established requirements regarding significant industrial user slug discharge control plans and POTW enforcement response plans; and strengthened and revised program implementation definitions and procedures

53 FR 47632 – 45656


Proposal to Implement the Recommendations of the Domestic Sewage Study (DSS)

52 FR 23477 – 23485


Response to comments on the Advanced Notice of Proposed Rulemaking

  • Agency summarized the comments received during three public meetings on DSS recommendations ANPR
  • Response to comments

51 FR 30166 – 30175


Preliminary Approaches to Implementing the Recommendations of the DSS

  • Based on DSS findings
  • Proposal to improve methods for controlling hazardous waste discharges to POTWs under the NPDES and general pretreatment programs.

Report to Congress on the Discharge of Hazardous Wastes to Publicly Owned Treatment Works (Domestic Sewage Study)


Response to the HSWA requirements to prepare a report to Congress

  • Contained information on 160,000 waste dischargers from 47 industrial categories and the residential sector
  • Provided information on the effectiveness of existing government controls for wastewater discharges, especially federal and local pretreatment programs and categorical pretreatment standards

Solid Waste Disposal Act(163 pp, 420 K, About PDF)


Congress enacts the Solid Waste Disposal Act

  • Section 3018(a)
  • Excluded coverage of solid and dissolved wastes in domestic sewage, meaning such wastes did not have to meet RCRA standards for hazardous waste treatment, storage, or disposal
  • Required EPA to prepare a report to Congress on the extent to which excluded wastes pass through POTWs

Pretreatment Implementation Review Task Force (PIRT)

53 FR 40561 – 40616


General Pretreatment Regulations for Existing and New Sources (PIRT Proposed and Final Rules)

  • Changes to 40 CFR Parts 122 and 403
  • Response to PIRT recommendations
  • Revisions included changes to local limits requirements, enforcement remedies, control authority and state program approvals, as well as industrial user and control authority monitoring and reporting requirements

51 FR 21454 – 21482


Pretreatment Review Task Force: Final Report to the Administrator


Task Force studied programs and recommended program improvements

  • Recommended ways to address day-to-day problems faced by POTWs, states, and industries in implementing the National Pretreatment Program
  • Included suggestions for simplifying and clarifying aspects of the program, on enforcement procedures, on the need for program resources, on the roles and relationships between program oversight authorities, and for regulatory updates

Amendments to the General Pretreatment Regulations

47 FR 42688 – 42689


EPA reinstated the January 1981 amendments

  • After Natural Resources Defense Council (NRDC) v. EPA (No. 81-2068) (7/8/1982) in which NRDC challenged EPA over the Agency’s deferral of the amendments to the General Pretreatment Regulations without having first given public notice
  • Court held that EPA’s suspension violated the Administrative Procedure Act
  • Court ordered EPA to reinstate all pretreatment amendments retroactive to March 30, 1981

46 FR 19936


EPA indefinitely postponed the 1981 Amendments' effective date

46 FR 11972


Deferral of Amendments to the General Pretreatment Regulations

  • Presidential memorandum temporarily deferring amendment to March 30, 1981

46 FR 9404 – 9460


  • Proposed changes to definitions, general prohibitions, determination of industrial subcategories, removal allowances, and implementation issues for local pretreatment programs
  • Scheduled to take effect on March 13, 1981

44 FR 62260 – 62275



Part 403 General Pretreatment Regulations for Existing and New Sources of Pollution

43 FR 27736 - 27773


EPA response to environmental groups (NRDC, Environmental Defense Fund (EDF), and Citizens For A Better Environment) bringing suit against EPA and the resulting consent decree

  • In the 1976, NRDC vs. Train Consent Decree (8ERC 2120, D.D.C. 1976), 21 industries are under consideration by EPA for national pretreatment standards pursuant to a settlement agreement between EPA and environmental groups filed in the U.S. District Court for the District of Columbia
  • Promulgation of General Pretreatment Regulations at 40 CFR Part 403, replacing the 40 CFR Part 128 requirements
  • EPA agreed to regulate the discharge of 65 categories of pollutants comprising the 126 priority pollutants from 21 industrial categories

42 FR 6476 – 6502


Pollutants in Publicly Owned Treatment Works Pretreatment Standards; 40 CFR Part 128 Pretreatment Standards

38 FR 30982 Final Rule


Original pretreatment regulations

  • Established 40 CFR Part 128
  • Defined: joint treatment works, major contributing industry; pretreatment
  • First proposal of pretreatment standards, prohibited discharges, pretreatment of compatible and incompatible pollutants, and timeline for compliance with pretreatment standards
38 FR 19236 -19237 Proposed Rule 7/19/1973

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