Mixing Zone Appendices

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Table of Contents

• Technical and Policy Guidance
• Modeling Documents
• Great Lakes Rule
• Appendices
  • A: EPA Regional Documents
  • B: State Documents
  • C: Other Documents
• Search Compilation by Major Topics

Appendix A: EPA Regional Documents*

* Note: No guidance has been developed specifically for Regions 1, 2, 3, 5, 6, 7, 9, and 10.

USEPA. 1995. "EPA Region VIII Mixing Zones and Dilution Policy. (PDF)" U.S. Environmental Protection Agency, Region 8, Water Management Division, Denver, CO. (3.2 MB, 111 pp.)

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The objective of "Region VIII Mixing Zones and Dilution Policy" is to help states and Indian tribes upgrade methods for deriving water quality-based permit limits, improve the technical defensibility of National Pollutant Discharge Elimination System (NPDES) permits, and reduce risks associated with mixing zone and dilution practices. The basis for the policy was the desire of the region to clarify the approaches for using mixing zones in NPDES permits. Prior to the policy, some applications of mixing zones presumptively provided the entire stream flow for dilution, which often resulted in effluent plumes (with elevated pollutant concentrations) extending far downstream of the discharge. The clarifications sought to prevent applications of mixing zones that did not adequately control effluent plume size or quality, possibly posing considerable risk to sensitive downstream uses.

USEPA. 1993. "EPA Region VIII Interim Guidance: Water Quality Standards for Indian Tribes. (PDF)" U.S. Environmental Protection Agency, Region 8, Water Management Division, Denver, CO. (188 K, 42 pp)

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"EPA Region VIII Interim Guidance: Water Quality Standards for Indian Tribes" is intended to assist the Indian tribes in EPA Region 8 to qualify to administer water quality standards programs and to develop water quality standards pursuant to Clean Water Act (CWA) sections 518 and 303(c). The guidance includes recommendations on mixing zone policy development.

USEPA. 1980. "EPA Region IV Guidance on Mixing Zones. (PDF)" U.S. Environmental Protection Agency, Region 4, Atlanta, GA. (198 K, 6 pp.)

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"EPA Region IV Guidance on Mixing Zones" provides a basis for Region 4 review and approval of state use of mixing zones in the development of effluent limitations. The guidance provides detailed descriptions of (1) appropriateness of assigning a mixing zone to a discharger, (2) the level of water quality that should be maintained in a mixing zone and surrounding waters, and (3) the factors governing the size and shape of a mixing zone.

"EPA Region IV Guidance on Mixing Zones" provides a basis for Region 4 review and approval of state use of mixing zones in the development of effluent limitations. The guidance provides detailed descriptions of (1) appropriateness of assigning a mixing zone to a discharger, (2) the level of water quality that should be maintained in a mixing zone and surrounding waters, and (3) the factors governing the size and shape of a mixing zone.

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Appendix B: State Documents

• California Environmental Protection Agency. 2005. "Policy for Implementation of Toxics Standards for Inland Surface Waters, Enclosed Bays, and Estuaries of California. (PDF)" California Environmental Protection Agency, State Water Resources Control Board. (1.5 MB, 64 pp.)
• Colorado Department of Public Health and Environment. 2002. "Colorado Mixing Zone Implementation Guidance. (PDF)" Colorado Department of Public Health and Environment, Water Quality Control Division. (246 K, 64 pp.)
• Massachusetts Department of Environmental Protection. 1993. "Massachusetts Surface Water Quality Standards Implementation Policy for Mixing Zones. (PDF)" Massachusetts Department of Environmental Protection, Boston, MA. (37 K, 10 pp.)
• New York State Department of Environmental Conservation. 1996. "Total Maximum Daily Loads and Water Quality Based Effluent Limits. (PDF)" Memo dated July 8, 1996. (60 K, 16 pp.)
• North Carolina Department of the Environment and Natural Resources. 1999. "Mixing Zones in North Carolina. (PDF)" North Carolina Department of the Environment and Natural Resources, Division of Water Quality. (28 K, 5 pp.)
• Oregon Department of Environmental Quality. 2000. "A Mixing Zone Guidance Document Prepared for the Oregon Department of Environmental Quality. (PDF)" S. Schnurbusch, Portland State University. (1.3 MB, 70 pp.)
• South Carolina Department of Health and Environmental Control. 1997. "Groundwater Mixing Zone Application Guidance. (PDF)" South Carolina Department of Health and Environmental Control, Columbia, SC. (531 K, 8 pp.)
• South Dakota Department of Environmental and Natural Resources. 1998. "Mixing Zone and Dilution Implementation Procedures. (PDF)" South Dakota Department of Environmental and Natural Resources. (1 MB, 12 pp.)
• Utah Division of Water Quality. 2000. "Mixing Zone Implementation Procedure. (PDF)" Utah Division of Water Quality. (730 K, 11 pp.)
• Virginia Department of Environmental Quality. 2000. Guidance Memo No. 00-2011; "Guidance on Preparing VPDES Permit Limits. (PDF)" Memo from Larry G. Lawson to Regional Directors, dated August 24, 2000. Virginia Department of Environmental Quality, Richmond, VA. (311 K, 118 pp.)
• Virginia Department of Environmental Quality. 2004. Guidance Memorandum No. 04-2021; "Guidance for Exceptional State Waters Designations in Antidegradation Policy Section of Virginia Water Quality Standards Regulation (9 VAC 25-260-30.A.3). (PDF)" Memo from Ellen Gilinsky to Regional Directors, dated November 15, 2004. Virginia Department of Environmental Quality, Richmond, VA. (52 K, 11 pp.)
• Washington Department of Ecology. No date. "Guidance for Conducting Mixing Zone Analyses. (PDF)" Washington Department of Ecology, Olympia, WA. (302 K, 48 pp.)
• Washington Department of Ecology. 2005. "Permit Writer's Manual.(PDF)" Washington Department of Ecology, Olympia, WA. (4.9 MB, 783 pp.)
• West Virginia Division of Environmental Protection. 1997. "Water Quality Standards/Mixing Zones Implementation Guidance. (PDF)" West Virginia Division of Environmental Protection Office of Water Resources. (40 K, 16 pp.)
• Wisconsin Department of Natural Resources. 1992. "Mixing Zone Guidance for Chronic Toxicity and Zones of Initial Dilution. (PDF)" Wisconsin Department of Natural Resources, Modeling and Analysis Unit, Bureau of Water Resources Management. (1.9 MB, 27 pp.)
• Wyoming Department of Environmental Quality. 2001. "Wyoming Surface Water Quality Standards, Implementation Policies for Antidegradation, Mixing Zones, Turbidity, and Use Attainability Analysis. (PDF)" Wyoming Department of Environmental Quality. (2.2 MB, 39 pp.)

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Appendix C: Other Documents to Consider When Establishing Mixing Zones^†

^† Note: these documents are often referred to in mixing zone guidance, but they have been updated or superseded by newer guidance documents and rules.

• FWPCA. 1968. "Water Quality Criteria" (Green Book). Federal Water Pollution Control Administration. Report of the National Technical Advisory Committee to the Secretary of the Interior. U.S. Department of Interior, Washington DC. [Superseded by Water Quality Standards Handbook, Second Edition (USEPA, 1994)]
• NAS/NAE. 1973. "Water Quality Criteria 1972" (Blue Book). A Report of the Committee on Water Quality Criteria. National Academy of Science and National Academy of Engineers, Washington, DC. NTIS-PB 236199. USGPO #5501-00520. [Superseded by Water Quality Standards Handbook, Second Edition (USEPA, 1994)]
• USEPA. 1976. "Quality Criteria for Water" (Red Book). U.S. Environmental Protection Agency, Washington, DC.
• USEPA. 1986. "Quality Criteria for Water" (Gold Book). EPA 440586001. U.S. Environmental Protection Agency, Office of Regulations and Standards, Washington, DC.
• USEPA. 1987. "Permit Writers Guide to Water Quality-based Permitting for Toxic Pollutants". EPA 440487005. U.S. Environmental Protection Agency, Office of Water, Washington, DC. (Rescinded)
• USEPA. 1995. Final Water Quality Guidance for the Great Lakes System; Final Rule. U.S. Environmental Protection Agency. "Federal Register," March 23, 1995, 60:15366. (Superseded by the 2000 Final Rule)

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