Water Quality Standards Regulations: Missouri

Presented are water quality standards in effect for Clean Water Act (CWA) purposes for this state.

EPA is posting these standards as a convenience to users and has made a reasonable effort to assure their accuracy. For each document listed under "State Standards in Effect for CWA Purposes", EPA has made a reasonable effort to identify parts of the standards that are disapproved or are otherwise not in effect for CWA purposes. Additionally, please note the documents may also contain provisions that EPA does not have the authority and duty to act on under the Clean Water Act because the provisions are not water quality standards.

• State Standards in Effect for CWA Purposes
• Federally Proposed or Promulgated Standards

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State Standards in Effect for CWA Purposes

• Rules of Department of Natural Resources: Division 20 - Chapter 7 - 10 CSR 20-7.010 - 10 CSR 20-7.050 (2023) (pdf) (2.44 MB)
  (Effective March 8, 2023) Water quality standards for waters of the state. Please note that some provisions in this document have not been approved by EPA and are therefore not in effect for CWA purposes.  Refer to the cover page for more information.
• Variances to Missouri Surface Water Quality Standards (pdf) (226.31 KB)
  (Effective February 25, 2015) Information detailing EPA-approved variances from water quality standards for dischargers to Missouri surface waters.

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Federally Proposed or Promulgated Standards

• Proposed Nutrient Criteria for Missouri Lakes and Reservoirs (December 2017)

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Federal Clean Water Act Determinations that New or Revised Standards Are Necessary

EPA has issued the following determinations under Clean Water Act section 303(c)(4)(B) that new or revised standards are necessary. EPA may propose federal replacement standards in these cases if the state does not adopt standards consistent with the Act.

• Determinations that New Water Quality Standards are Necessary to Protect the Mississippi River for Recreation
  • For segments upstream and downstream of St. Louis
    • Determination that WQS are needed for Mississippi River segments upstream and downstream of St. Louis (pdf) (265.79 KB, December 12, 2008)
  • For the segment near St. Louis
    • Determination that WQS are needed for the Mississippi River segment near St. Louis (pdf) (177.61 KB, October 29, 2009)
• Determination that New Water Quality Standards are Necessary to Protect Water Body Segments in the State of Missouri
  • Determination that WQS are needed for 141 Water Body Segments in the State of Missouri (pdf) (539.55 KB, October 31, 2006)
  • EPA’s Detailed Analysis of Whether New or Revised Water Quality Standards are Necessary for 141 Water Body Segments (pdf) (134.18 KB, October 31, 2006)