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The January 21st edition of the publication Ozarks Water Watch noted that the United States Environmental Protection Agency (“EPA”) in a December 14, 2018, letter approved Clean Water Act Numeric Nutrient Criteria for Missouri Lakes.
The Missouri Department of Natural Resources (“DNR”) included these provisions in a Water Quality Standards package submitted to EPA for review in a letter dated April 13, 2018.
Section 303 of the Clean Water Act requires that each state develop water quality standards (‘WQS”) for jurisdictional waters of the United States within their borders. WQS serve a dual purpose. They establish the water quality goals for a specific body of water and also serve as the regulatory basis for the development of water-quality based effluent limits and strategies for individual point source discharges.
A WQS consists of three parts:
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The designated uses of a waterbody;
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The water quality criteria (“WQC”) that are necessary to protect existing uses and to attain the beneficial uses designated by the state; and
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An anti-degradation statement or policy to protect existing uses in high quality water
WQS may be expressed either as a numeric concentration level or a narrative standard.
WQC are ambient water quality conditions that are deemed protective of the uses established for a waterbody. States are required to adopt WQC protective of the designated uses. The WQC must specify the maximum concentration of pollutants that may be present in the water without impairing its suitability for certain uses. The WQC represent a judgment as to what levels, concentrations, or conditions can support a desired use.
The Missouri DNR Lake Numeric Nutrient Criteria approved by EPA include:
MO’s Approved Plan
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Ecoregion
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Chlorophyll Criteria (μg/L)
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Plains
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30.0
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Ozark Border
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22.0
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Ozark Highlands
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15.0
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The Ozarks Water Watch article notes that the approved plan identifies about 35 percent of monitored Missouri Lakes (34 lakes total) as impaired with approximately 33 percent requiring additional evaluation to determine if there is an impairment.
A copy of the Ozarks Water Watch article can be found here and the December 14, 2018, EPA letter here.
