Antidegradation

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:

• The department conducted a general analysis of wastewater treatment alternatives for small systems according to the July 2016 AIP, and concluded there are several available technologies capable of producing a high quality effluent.
• This optional approach allows applicants to forgo preparing a site-specific alternatives analysis.
• Applicants who wish to use this general analysis only need to complete three documents:
  1. Antidegradation Review/ Summary Request MO 780-2025
  2. Antidegradation Review Submittal: Voluntary Tier 2 - Significant Degradation for Domestic Wastewater Facilities with Design Flow Less Than 50,000 Gallons per Day MO 780-2804
  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
• Applicants using the general antidegradation approach agree to accept the effluent limits in Section 10 of the Antidegradation Review Submittal Voluntary Tier 2 - General Antidegradation for Domestic Wastewater Facilities with Design Flows Less than 50,000 gallons per day form
• This general antidegradation approach only is available to new or expanding domestic wastewater treatment systems that will discharge to Tier 2 waters (those waters that are not impaired and are not classified as Outstanding State or National Resource Waters)

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.

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:

• Document which federal effluent limit guideline(s) the facility or the production line is subject to;
• Provide details on the planned production and/or processing rates- average and peak numbers, days of operation;
• Provide sample results from Form C and Form D to document all pollutants of concern for the proposed discharge. If this is a new discharge, use sample results from similar industry or operation. Ensure the samples are tested using a test method that is sufficiently sensitive as discussed in the instructions for Form C and Standard Conditions Part I;
  • Form C – Application for Discharge Permit – Manufacturing, Commercial, Mining, Silviculture Operations, and Stormwater MO 780-1514
  • Form D – Application for Discharge Permit – Primary Industries MO 780-1516
  • Standard Conditions for NPDES Permits - Part I, Aug. 1, 2014
• Describe how the domestic wastewater generated at the facility is treated; and
• Describe how stormwater, especially impacted stormwater, at the site is dealt with.

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

• Antidegradation Implementation Procedure, July 13, 2016
• Geologic Evaluation Data Gateway Exchange (GeoEDGE)
• MAPiT
• Natural Heritage Review - Missouri Department of Conservation
• ​​​​Nutrient Criteria Implementation Plan, July 27, 2018
• StreamStats - U.S. Geological Survey
• Water Quality and Antidegradation Review: Department’s Alternatives Analysis for Domestic Wastewater Facilities with Design Flow Less Than 50,000 Gallons per Day
• Water Quality Data Search (MoCWIS)
• Water Quality Standards Search (MoCWIS)