Antidegradation means that no pollutant discharges or activities will be permitted if these may cause surface waters already meeting water quality standards to drop below those standards. According to Code of Federal Regulations 40 CFR 131.12, Missouri is required to develop and adopt a statewide antidegradation policy and identify methods for implementing such policy.

Missouri Antidegradation Implementation Procedure

With more than 10 years of experience, Missouri’s antidegradation processes are well-developed. All construction permits for new or expanded discharges are required to follow the Missouri Antidegradation Rule and Missouri Antidegradation Implementation Procedure (AIP). The most recent version was approved by the Missouri Clean Water Commission on July 13, 2016, and approved by EPA on July 30, 2018. The AIP is intended to satisfy the federal requirements and has provided reasonable wastewater treatment technology determinations that have helped maintain the quality of Missouri waters.

Since the earliest days of the antidegradation implementation procedure, engineers identified a number of areas in which the AIP is unclear, situations that were not addressed or elements that needed additional clarification. The goal of this current revision is to address many of these elements and incorporate ideas that improve and streamline the process, while maintaining the fundamental goal of antidegradation. The department organized a stakeholder workgroup to help revise the AIP. For more information about the workgroup or meeting information, visit the Antidegradation Implementation Procedure Workgroup webpage.

The below information describes submittal requirements for the different pathways for completing an antidegradation review, as discussed in the AIP. The Antidegradation Review Pathways Flow Chart may also be referenced to aid in determining the appropriate pathway.

General Review

The voluntary general antidegradation review path is available to domestic wastewater systems with design flows of up to 50,000 gallons per day. It also incorporates less-degrading effluent limits for total phosphorus when the proposed discharge to a Tier 2 water is located in the watershed of a lake greater than 10 acres. Please note the following elements regarding this voluntary path:

Site-Specific Review

Applicants who do not wish to apply, or do not qualify, for a general antidegradation review need to complete and submit an antidegradation review request submittal that includes:

  1. An Antidegradation Review Report detailing the proposed project in addition to all supporting documentation. The forms below are only a summary.
  2. Antidegradation Review/ Summary Request MO 780-2025 - As noted on the form, you also must submit:
    • Geohydrologic Evaluation - Requested through the Missouri Geological Survey website 
    • Missouri Natural Heritage Review from the Missouri Department of Conservation website
  3. Antidegradation: Regionalization and No-Discharge Evaluation MO 780-2805 - Used to demonstrate that regionalization is not feasible nor is land application or subsurface wastewater disposal
  4. One or more of the following forms, as applicable, on a pollutant-by-pollutant basis. Review the AIP for more information.
    • Antidegradation Review Summary Path A: Tier 2 - Non-Degradation Mass Balance MO 780-2872
      • This form is applicable when making a demonstration of no increase in pollutant loading
      • Events or activities that are non-degrading are not generally required to undergo a Tier 2 alternatives analysis review
    • Antidegradation Review Summary Path B: Tier 2 - Minimal Degradation MO 780-2022
      • A demonstration of reducing a water body’s assimilative capacity (ability to naturally attenuate a discharged substance without impairing beneficial uses) by less than 10% for any pollutant as a result of any single discharge, or combination of discharges, after existing water quality has been determined 
      • Events or activities causing minimal degradation are not generally required to undergo a Tier 2 alternatives analysis review
    • Antidegradation Review Summary Path C: Tier 2 - Significant Degradation MO 780-2021
      • A reduction, or assumed reduction, by 10% or more of a water body’s assimilative capacity (ability to naturally attenuate a discharged substance without impairing beneficial uses) as a result of any single discharge; or any new or expanded discharge that the department determines will likely result in the increased accumulation of pollutants or their degradation products in sediment or fish tissue
      • Events or activities in this category are required to undergo a Tier 2 alternatives analysis review where the applicant must evaluate a range of alternatives including regionalization, land application and less-degrading discharging treatment alternatives, and explain the social and economic importance of the project
      • This is the most common review path
    • Antidegradation Review Summary Path D: Tier 1 - Preliminary Review Request MO 780-2024
      • A Tier 1 Review is designed to prohibit degradation that may cause or contribute to the impairment of a beneficial use, or violation of water quality criteria and to prohibit further degradation of existing water quality where pollutants of concern have resulted in the water being included on the 303(d) list of impaired waters or having an established Total Maximum Daily Load (TMDL)
    • Antidegradation Review Summary Path E: Temporary Degradation MO 780-2023
      • A time-limited discharge required to meet all water quality standards. The project at a minimum must not cause or contribute to the impairment of a beneficial use or violate water quality criteria. The temporary degradation applicant must provide justification for why the discharge is necessary and discuss the problem it resolves. It is recommended that the request include information on the socioeconomic impacts to the community with this project. 
      • If the discharge is for pollutants that bioaccumulate, such as metals, the facility should include a discussion of what alternatives were considered.

Industrial Facilities

It is recommended that industrial facilities considering expanding or adding a new discharge, or with the potential for new pollutants of concern in the discharge, contact the Engineering and Permitting Sections to set up a pre-submittal meeting to help identify items that will need to be addressed as part of the Antidegradation Review. At a minimum, in addition to the Antidegradation Report, the Geohydrologic Evaluation, and the Natural Heritage Review, please submit the following information within your report:

Fees

For a review in which the existing wastewater treatment train is being retained as part of an upgrade or for a water quality review analysis the fee is $250.

For a new or previously unpermitted wastewater treatment plant, the fee is determined by design flow:

  • $500 - design flow is less than 100,000 gallons per day
  • $1000 - design flow is equal to or more than 100,000 gallons per day

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