The proposed changes to state water quality standards could have a long-term impact on wastewater discharge permitting around Missouri lakes, though permittees might not be affected for several years.

Revised water quality criteria that could impact Lake of the Ozarks and Harry S Truman Lake will be the subject of an upcoming public hearing hosted by the Missouri Department of Natural Resources.

MDNR is seeking comments on proposed changes to 10 CSR 20-7.031 Water Quality Standards including revised nutrient criteria for lakes and an amended Regulatory Impact Report on the proposed changes.

The proposed changes to state water quality standards could have a long-term impact on wastewater discharge permitting around Missouri lakes, though permittees might not be affected for several years. For that reason, the most significant component of the proposed water quality rules is the revision of lake nutrient criteria, according to MDNR.

The mission of the standards is to maintain healthy ecosystems of lakes and reservoirs and aquatic life. The immediate impetus, however, is to implement criteria before falling under standards from the EPA due to a lawsuit.

MDNR estimates the cost to implement its proposed changes to these standards could range from $47.8 million to $83.1 million, compared to the $2.4 billion price tag that is believed would be attached to complying with a federal rule. 

What to know

MDNR is proposing revised numeric nutrient criteria for lakes and providing improved scientific rationale for criteria development while strengthening the link between the criteria and the designated uses of lake waters, according to the department, after its previous proposal was rejected by the EPA in 2011.

The amended version of the Regulatory Impact Report on the proposed standards has had lake numeric nutrient criteria for recreational uses and the protection of the drinking water supply removed, focusing now on aquatic habitat protection and location.

Numeric nutrient criteria for recreational uses will be pursued during a future rulemaking, likely within a 5-10 year timeframe, as studies and science for recreational uses become better established, according to the MDNR report.

The proposed water quality standards rule includes numeric Chlorophyll A criteria for lakes based on location. These criteria will apply to all lakes at least 10 acres in size during normal conditions assigned with the exception of lakes located in the big river floodplains.

Numeric nutrient criteria for lakes, water quality criteria for pH and other pollutants and sections describing mixing zones, general criteria and existing definitions are all being revised under the proposal. This set of rules relates to levels of nutrients such as nitrogen, phosphorus and chlorophyll in water, not bacteria.

While nutrients are an important part of a healthy lake system, excess nutrients cause harmful algal blooms, which can be toxic to fish and other wildlife. Chlorophyll A is a measure of the amount of algae growing in a body of water, used to classify the waterbody’s “trophic” condition.

Nutrient levels in a body of water are a balancing act, a certain level is needed to maintain aquatic life but too much can produce conditions that create dead zones. Eutrophic or hypereutrophic conditions can lead to algal blooms and fish death due to algae and bacteria sucking up too much oxygen in the water that is necessary to aquatic creatures.

Chlorophyll A is the main indicator test. If the changes are approved, the allowable levels of Chlorophyll A in Missouri lakes would vary from region to region within the state.

Since the proposed changes were first opened for public comment, Harry S Truman Lake has been reassigned from the Ozark Highlands region to the Plains region. The Ozark Highlands region has stricter nutrient standards.

Under the Ozark Highlands category, Truman would have been considered impaired.

“The department has re-evaluated Harry S Truman Lake and determined that although the Lake is in the Ozark Highlands ecoregion, its watershed is mostly in the Plains ecoregion. Reclassifying the lake to the Plains ecoregion in the draft Water Quality Standards Rule more accurately reflects the watershed’s contribution to water quality in the lake,” explains a press release from MDNR.

Essentially, due to its location at the edge of the Ozarks, Truman’s main tributary streams drain lands to the west as far away as Kansas. Streams traveling through this region typically have higher nutrient levels because of the runoff from the agricultural land they drain. These nutrients are flushed downstream, accumulating more along the way.

The reassessment of Truman into the Plains region will reduce regulations for the more than 130 wastewater treatment plants around the reservoir, saving the systems and their customers millions of dollars in upgrades to reduce nutrient output.

Lake of the Ozarks will remain in the Ozarks Highlands region, and it is believed it will be able to meet nutrient standards under the proposed rule.

Lake of the Ozarks has approximately 475 permittees discharging into it, according to information provided by MDNR Communications. This includes the Lake of the Ozarks and Niangua River watersheds, but not facilities in the Truman watershed upstream of Truman Dam.

Table L of the 79-page rule shows Chlorophyll A criteria for the protection of aquatic life of the Ozark Highlands region at 15 μg/L. Screening values for phosphorous and nitrogen would be 16 and 401 μg/L respectively. The screening value for Chlorophyll A is 6.

Site-specific criteria for Lake of the Ozarks includes Chlorophyll A standards of 26 μg/L for the Grand Glaze, Gravois and Niangua arms.

Levels are based on nutrient concentrations using a geometric mean of a minimum of three years of data and the unique characteristics of the body of water, according to the proposed rule.


According to MDNR Director of the Division of Environmental Quality Ed Galbraith, Missouri first passed lake nutrient standards in 2009-10, but those standards were “disapproved” by EPA in 2011. Since then the state and stakeholders have been working on different standards including expertise from the University of Missouri, though the effort really began in earnest only in 2015.

The goal, he says, is to develop a set of standards that is right for Missouri based on Missouri data.

As MDNR has worked towards its goal of developing its own nutrient standards, the Missouri Coalition for the Environment filed a lawsuit against the EPA in 2016 seeking a ruling to get standards implemented. Without standards from the state after the disapproval from EPA, the lawsuit pushed for implementation of EPA standards for Missouri lakes, according to Galbraith.

A consent judgement was reached, requiring the EPA to propose rules by Dec. 15, 2017 if Missouri does not submit its own proposed rule before that date.

“That’s the reason why it’s moving at this time, but the rule has been in development for a couple of years,” commented Galbraith. “We want want to make sure the standards set for lake in Missouri are applicable to lakes in Missouri, not California.”

To comment

The public hearing will be held at 9 a.m., Nov. 21, at the Lewis and Clark State Office Building, 1101 Riverside Dr., in Jefferson City. The comment period for the Regulatory Impact Report ends Nov. 24. The comment period for the proposed changes to the Water Quality Standards runs from Oct. 16 to Nov. 28.

The revised Regulatory Impact Report can be accessed online at Under “Program” select “Water Protection” then “Search.” The draft Regulatory Impact Report, 10 CSR 20-7.031, is at the bottom of the list.

To submit comments electronically, go to and, under “Program” select “Water Protection” then click on the green plus sign next to 10 CSR 20-7.031. This will take you to a screen that allows you to submit your comments electronically.

Comments may also be submitted by mail to the Missouri Department of Natural Resources, Water Protection Program, PO Box 176, Jefferson City, MO 65102-0176, Attn: WQS Coordinator. Contact information in all comments should include name, email address and phone number.