Water Quality Standards
Water Quality Standards
The objective of the Clean Water Act of 1972 along with its amendments are to restore and maintain the chemical, physical, and biological integrity of the nation’s waters. The first national set of water quality standards were published in 1983 and codified in 40 CFR Part 131. These regulations allow individual states to construct their own water quality standards framework providing there is no reduction in protection compared to federal guidelines.
Missouri’s Water Quality Standards are reviewed and modified every three years. Termed the triennial review process, coordinators with the Missouri Department of Natural Resources meet with the U.S. Environmental Protection Agency, other state agencies, and concerned citizens to evaluate the effectiveness of our standards. Visit the Water Protection Program Rule Development page for up-to-date information on the status of 10 CSR 20-7.031-Water Quality Standards rule. Discussions of Water Quality Standards topics are being conducted through the Water Protection Forum, Water Quality Standards Workgroup.
Water quality standards provide a means by which attainment of water quality objectives can be measured. The objective is protection of designated uses through the application of narrative or numeric criteria. The level of protection given to a stream, lake, or river is dependent on the expected or "designated use(s)," of that water. Classified waters in Missouri have been assigned the designated uses that are listed in 10CSR 20-7.031(C) page 10. The antidegradation section requires actions to maintain existing uses. Attainment frequency of water quality standards are used in identifying and characterizing waters of the state for purposes of compiling the 303(d) list and 305(b) report. In addition, effluent limits contained in National Pollution Discharge Elimination System (NPDES) permits are frequently derived using water quality standards.
UPDATE: The EPA approved Missouri's Numeric Nutrient Criteria (NNC) for lakes and reservoirs on Dec. 14, 2018. The NNC approved by EPA address EPA's 2011 disapproval of NNC previously promulgated by the state. The EPA will continue to review the other components of the April 13, 2018 Water Quality Standards submittal and will act on those revisions at a later date. A link to the approval letter and decision document are provided below under EPA Actions on Water Quality Standards.
Evaluation of Environmental and Economic Impacts of Revised Water Quality Standards and Criteria on a Subbasin Basis
Section 644.058 of the Missouri Revised Statutes requires and evaluation of environmental and economic impacts be made when criteria are revised more than 25%.
Missouri Initiates Development of Nutrient Criteria For Water Quality
Water Quality Standards Map Viewer
Water Protection Rule Development
Recreational Use Attainability Analysis
Wetland Water Quality Standards
EPA Actions on Water Quality Standards
- April 6, 2021 EPA Disapproval Letter for Kirksville Variance and pH
- April 6, 2021 EPA Disapproval Rationale for Kirksville Variance and pH
- Dec. 26, 2019 EPA Decision Letter for Partial Approval of the 2018 WQS Submittal (includes MDV)
- Dec. 26, 2019 EPA Decision Document for Partial Approval of the 2018 WQS Submittal (includes MDV)
- July 30, 2019 EPA Decision Letter for the 2018 Water Quality Standards Submittal
- July 30, 2019 EPA Decision Document for the 2018 Water Quality Standards Submittal
- Dec. 14, 2018 EPA Letter of Approval for 10 CSR 20-7.031(5)(N) (including Tables L and M)
- Dec. 14, 2018 EPA Decision Document
- Nov. 17, 2015 EPA 3rd Action Letter on Mar. 19. 2014 Submittal
- May 14, 2015 EPA Action on Mar. 19, 2014 Submittal-Addresses Three Additional Elements in the State's Water Quality Submittal, All Bearing on the Development amd Application of Site-Specific Criteria for Protection and Propagation of Fish, Shellfish and Wildlife
- Jan. 6, 2015 EPA Action on Dec. 10, 2012 Submittal-Includes Proposed Chloride and Sulfate Criteria
- Oct. 22, 2014 EPA Action on New and Revised Unclassified Waters Rule
- Sept. 27, 2013 EPA Action on Phenol Criteria Provision of Missouri's 2012 Water Quality Standards
- Sept. 27, 2013 EPA Action on Recreational Use Attainability Analyses Determinations of Missouri's 2012 Water Quality Standards
- May 10, 2013 EPA Action on Site-Specific Dissolved Oxygen Criteria Provision of Missouri's 2012 Water Quality Standards
- Jan. 25, 2013 EPA Action on Schedule of Compliance Provision of Missouri's 2012 Water Quality Standards
- Jan. 18, 2012 EPA Comments on Missouri's 2012 Water Quality Standards
- Aug. 16, 2011 EPA Action on Missouri's 2009 Water Quality Standards
- Feb. 24, 2010 Comments to EPA on Proposed Update to Ammonia Criteria
- Nov. 12, 2008 Memo from EPA regarding Initial Zones of Dilution for Bacteria in Rivers and Streams Designated for Primary Contact Recreation
- Enclosure: EPA Region 7 Approval of Portions of the Missouri 2006 Water Quality Standards
- Feb. 20, 2007 EPA Letter regarding Review of Missouri Water Quality Standards
- Oct. 31, 2006 EPA Determination on Missouri Water Quality Standards for 141 Water Bodies
- Attachment: EPA’s Detailed Analysis of Whether New or Revised Water Quality Standards are Necessary for 141 Water Body Segments
- Dec. 27, 2004 Consent Decree between EPA and Missouri Coalition for the Environment
- Dec. 16, 2004 Settlement Agreement between EPA and Missouri Coalition for the Environment
- Sept. 8, 2000 EPA Program Review Letter