Water Quality Division: Permits: Anti-degradation Implementation Checklist

Applicants for new Arizona Pollutant Discharge Elimination System (AZPDES) permits, permittees modifying or expanding their facilities (greater than 10 percent), or permittees renewing permits where anti-degradation has not been previously evaluated, are required to submit information necessary for the state to conduct an "anti-degradation review." The anti-degradation rule requires that existing instream uses and the level of water quality necessary to protect those uses be maintained and protected. The review involves determining whether pollutants in the discharge will degrade the receiving water body. Arizona's approach to anti-degradation is on a pollutant-by-pollutant basis and is categorized by tiers.

  • Tier 1: Current water quality is below standards and no degradation can be tolerated.
  • Tier 2: Current water quality is above standards and must be maintained and protected.
  • Tier 3: Current water quality is classified as "unique" and no degradation can be tolerated.

The policy requires that where the quality of a river or stream exceeds levels necessary to support propagation of fish, shellfish and wildlife and recreation in or on the water, that high quality be maintained and protected except under very limited conditions. In order to determine whether a proposed discharge will degrade a water, the individual water body must be analyzed to determine its tier and assimilative capacity based on the information submitted for the review.

Anti-degradation Checklist

  1. Information required to be supplied by all applicants.
    • Discharge location(s) (latitude and longitude)
    • USGS quad with discharges identified
    • Scale map of facility showing equipment, storage impoundments, discharge locations, etc.
  2. If discharge is to a perennial, intermittent or effluent dependent waterbody, the applicant shall provide ambient water quality data for the receiving water. Possible sources include:
    • STORET, USGS or other available data for the segment where the proposed discharge will take place, for a period of two to five years prior to application. NOTE: Data should be from stations within five stream miles upstream or downstream of the discharge point.
    • Data from an integrated surface water sample. Samples will be taken according to the "Handbook for the Sampling and Sample Preservation of Water and Wastewater," U.S. EPA 600/4-82-029, for the following parameters (list may be modified on a case-by-case basis):
      • Field Measurements:
        • pH
        • specific conductivity
        • dissolved oxygen
        • temperature
        • turbidity
        • flow
      • Lab Analytes (if reasonable potential exists):
        • alkalinity
        • hardness
        • total dissolved solids/EL
        • ammonia (as N)
        • nitrogen species (nitrate (NO3-N), nitrite (NO2 - N), total Kjehldahl nitrogen (TKN-N)
        • phosphorus
        • priority pollutant scan, priority pollutant metals, organochlorine pesticides and PCBs
      • Long term flow data from the segment where the proposed discharge will take place showing average annual peak and minimum discharges. If long term data does not exist, models, short term data and/or anecdotal information should be presented.
  3. All applicants shall provide information on the effluent quality (actual or anticipated):
    • Physical/chemical characteristics of the proposed effluent including:
      • temperature (oC)
      • pH
      • alkalinity
      • hardness
      • dissolved oxygen
      • redox potential (for discharges to lakes)
      • total dissolved solids/conductivity
      • major cations and anions
      • average and maximum pollutant loading
  4. All applicants shall provide information on the following as applicable:
    • Location of any unique waters within the segment or downstream of where the proposed discharge will take place (A.A.C. R18-11-122 ).
    • Any threatened or endangered species habitat located within the segment or downstream of where the proposed discharge will take place. (Contact USFWS or AGFD for information)
    • A land use map for the segment where the proposed discharge will take place. USGS topographic map series is preferred, otherwise a map showing land uses within 3 miles of perimeter of facility boundaries.
    • A description of the natural features for the segment and adjacent land areas where the discharge will take place (describe riparian vegetation, general terrain, bank condition, human impacts on the water body and wildlife in the area).
    • A description of the socio-economic activities for the segment where the discharge will take place and adjacent land areas.
    • A description of the proposed facility, including purpose, service area, principal/equipment/activities/structure.
    • A description of the treatment process.
    • A description of any discharges and other residues/wastes that will be produced by the proposed facility.
    • A description of all best management practices that will be in place.
    • Photographs of the segment which will be affected by the discharge.
    • Summary of discharge monitoring report (DMR) data for the previous two years. Copies of the DMRs can be provided in lieu of the summary.

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