Antidegradation

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.

With more than 10 years 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 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.

Antidegradation Implementation Review

Since the earliest days of antidegradation implementation review, 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.

• Draft Antidegradation Considerations for Individual Pollutants - Nutrients

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.

General Antidegradation Review

The general antidegradation review has been revised. This voluntary review path is now available to domestic wastewater systems with design flows of up to 50,000 gallons per day. It also now 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 Missouri Antidegradation Implementation Procedure, and concluded there are several available technologies capable of producing a high quality effluent. Applicants who wish to use this general analysis only need to complete three documents:
  1. Antidegradation Review/ Summary Request MO 780-2025
     • Antidegradation Review Summary Path A: Tier 2 - Non-Degradation Mass Balance MO 780-2872
     • Antidegradation Review Summary Path B: Tier 2 - Minimal Degradation MO 780-2022
     • Antidegradation Review Summary Path C: Tier 2 - Significant Degradation MO 780-2021
     • Antidegradation Review Summary Path D: Tier 1 - Preliminary Review Request MO 780-2024
     • Antidegradation Review Summary Path E: Temporary Degradation MO 780-2023
  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. This optional approach would allow applicants to forgo preparing a site-specific alternatives analysis and eliminate the need to submit the "Path C” form.
• Section 10 Antidegradation Review Submittal Voluntary Tier 2 - Significant Degradation for Domestic Wastewater Facilities with Design Flows Less than 50,000 gallons per day provides a table of effluent limits that applicants will agree to accept using this approach.
• This approach would only be available to new or expanding domestic wastewater treatment systems that will discharge to Tier 2 waters (those waters that are not impaired or are classified as Outstanding State or National Resource Waters).
• The fee for this review will be $500.

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 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

Additional Information

• ​​​​Nutrient Criteria Implementation Plan, July 27, 2018
• Water Quality and Antidegradation Review: Department’s Alternatives Analysis for Domestic Wastewater Facilities with Design Flow Less Than 50,000 Gallons per Day