Rules of Department of Natural Resourcessos.mo.gov/adrules/csr/current/10csr/10c20-7A.pdf · Rules of Department of Natural Resources Division 20—Clean Water Commission ... CFR

CODE OF STATE REGULATIONS 1JOHN R. ASHCROFT (1/29/19)Secretary of State

Rules of

Department of Natural ResourcesDivision 20—Clean Water Commission

Chapter 7—Water Quality

Title Page

10 CSR 20-7.010 Prevention of Pollution from Wells to Subsurface Waters of the State (Rescinded July 10, 1980) ...................................................................3

10 CSR 20-7.015 Effluent Regulations............................................................................3

10 CSR 20-7.020 Effluent Regulations (Rescinded July 10, 1980) .........................................11

10 CSR 20-7.030 Water Quality Standards (Rescinded December 11, 1977).............................11

10 CSR 20-7.031 Water Quality Standards .....................................................................11

10 CSR 20-7.050 Methodology for Development of Impaired Waters List ..............................130


Chapter 7—Water Quality 10 CSR 20-7

Title 10—DEPARTMENT OFNATURAL RESOURCES

Division 20—Clean Water CommissionChapter 7—Water Quality

10 CSR 20-7.010 Prevention of Pollutionfrom Wells to Subsurface Waters of theState(Rescinded July 10, 1980)

AUTHORITY: section 204.026, RSMo 1978.Original rule filed June 19, 1974, effectiveJune 29, 1974. Amended: Filed April 1,1975, effective April 11, 1975. Rescinded:Filed Oct. 12, 1979, effective July 10, 1980.

10 CSR 20-7.015 Effluent Regulations

PURPOSE: This rule sets forth the limits forvarious pollutants which are discharged tothe various waters of the state. The two pre-vious rules 10 CSR 20-6.050 and 10 CSR 20-7.010 have been rescinded and this rule com-bines certain aspects of both rules andmodifies the format of the effluent regula-tions. This rule also complies with the latestchanges to the Federal Clean Water Act, P.L.97-117 (1981).

PUBLISHER’S NOTE: The secretary of statehas determined that the publication of theentire text of the material which is incorpo-rated by reference as a portion of this rulewould be unduly cumbersome orexpensive. This material as incorporated byreference in this rule shall be maintained bythe agency at its headquarters and shall bemade available to the public for inspectionand copying at no more than the actual costof reproduction. This note applies only to thereference material. The entire text of the ruleis printed here.

(1) Designations of Waters of the State.(A) Definitions.

1. Acute Toxicity Test—a test used todetermine the concentration of an effluentthat causes an adverse effect (usually death)in a group of test organisms during a short-term exposure.

2. Allowable Effluent Concentration—the concentration of a toxicant or the param-eter toxicity in the receiving water after mix-ing, sometimes referred to as the receivingwater concentration or the in-stream wasteconcentration.

3. Chronic Toxicity Test—A short-termtest, usually ninety-six (96) hours or longerin duration, in which sub-lethal effects suchas reduced growth or reproduction rates aremeasured in addition to lethality.

4. Representative sample— a small quan-tity whose characteristics represent the natureand volume of the whole as described in 40CFR Part 122.48 September 26, 1984, as pub-lished by the Office of the Federal Resister,National Archives and Records Administra-tion, 700 Pennsylvania Avenue, Washington,DC 20408 which is hereby incorporated byreference and does not include later amend-ments or additions.

5. Toxic Unit—a measure of effluenttoxicity generally expressed as acute toxicityunit or chronic toxicity unit. The larger thetoxicity unit, the greater the toxicity.

6. Toxic Unit–Acute—one-hundred(100) times the reciprocal of the effluent con-centration that causes fifty percent (50%) ofthe organisms to die in an acute toxicity test.

7. Toxic Unit-Chronic—one-hundred(100) divided by either the highest effluentconcentration that causes no observable effecton the test organisms or the inhibition con-centration (IC25) causing a twenty-five per-cent (25%) or more reduction in the repro-duction or growth of the test organisms in achronic toxicity test.

(B) For the purpose of this rule, the watersof the state are divided into the following cat-egories:

1. The Missouri and Mississippi Rivers(section (2) of this rule);

2. Lakes and reservoirs, including natu-ral lakes and any impoundments created bythe construction of a dam across any water-way or watershed. An impoundment designedfor or used as a disposal site for tailings orsediment from a mine or mill shall be consid-ered a wastewater treatment device and not alake or reservoir. Releases to lakes and reser-voirs include discharges into streams one-half(1/2) stream mile (.80 km) before the streamenters the lake as measured to its conserva-tion pool (section (3) of this rule);

3. A losing stream is a stream which dis-tributes thirty percent (30%) or more of itsflow through natural processes such asthrough permeable geologic materials into abedrock aquifer within two (2) miles flow dis-tance downstream of an existing or proposeddischarge. Flow measurements to determinepercentage of water loss must be corrected toapproximate the seven (7)-day Q10 streamflow. If a stream bed or drainage way has anintermittent flow or a flow insufficient to mea-sure in accordance with this rule, it may bedetermined to be a losing stream on the basisof channel development, valley configuration,vegetation development, dye tracing studies,bedrock characteristics, geographical data,and other geological factors. Only dischargeswhich in the opinion of the Missouri Depart-ment of Natural Resources (department) reach

the losing section and which occur within two(2) miles upstream of the losing section of thestream shall be considered releases to a losingstream. A list of known losing streams is avail-able in the Water Quality Standards, 10 CSR20-7.031 Table J—Losing Streams. Otherstreams may be determined to be losing by thedepartment (section (4) of this rule);

4. Metropolitan no-discharge streams.These streams and the limitations on dis-charging to them are listed in Table F of 10CSR 20-7.031 Water Quality Standards;

5. Special streams—Outstanding Nation-al Resource Waters and Outstanding StateResource Waters, as listed in Tables D and Eof 10 CSR 20-7.031 (section (6) of this rule);

6. Subsurface waters in aquifers (section(7) of this rule); and

7. All other waters except as noted inparagraphs (1)(B)1.–6. of this rule (section(8) of this rule).

(C) Sections (2) though (8) of this ruleestablish requirements for discharges to thewaters specified in these sections, and therequirements of section (9) of this rule applyto all discharges. The requirements of thisrule do not apply to stormwater discharges;effluent limits for stormwater discharges areprescribed in 10 CSR 20-6.200 Storm WaterRegulations.

(2) Effluent Limitations for the Missouri andMississippi Rivers. In addition to the require-ments of section (9) of this rule, the followinglimitations represent the maximum amount ofpollutants which may be discharged from anypoint source, water contaminant source, orwastewater treatment facility.

(A) Discharges from wastewater treatmentfacilities which receive primarily domesticwaste or from publicly-owned treatmentworks (POTWs) shall undergo treatment suf-ficient to conform to the following limita-tions:

1. Biochemical Oxygen Demand5 (BOD5)and Total Suspended Solids (TSS) equal to orless than a monthly average of thirty mil-ligrams per liter (30 mg/L) and a weekly aver-age of forty-five milligrams per liter (45mg/L);

2. pH shall be maintained in the rangefrom six to nine (6–9) standard units in accor-dance with 40 CFR 133.102 “SecondaryTreatment Regulation” October 16, 1984, aspublished by the Office of the FederalResister, National Archives and RecordsAdministration, 700 Pennsylvania Avenue,Washington, DC 20408 which is hereby incor-porated by reference and does not includelater amendments or additions;

3. Exceptions to paragraphs (2)(A)1.and 2. of this rule are as follows:

A. If the facility is a wastewaterlagoon, the TSS shall be equal to or less thana monthly average of eighty milligrams perliter (80 mg/L) and a weekly average of onehundred twenty milligrams per liter (120mg/L) and the pH shall be maintained abovesix 6.0, and the BOD5 shall be equal to orless than a monthly average of forty-five mil-ligrams per liter (45 mg/L) and a weeklyaverage of sixty-five milligrams per liter (65mg/L);

B. If the facility is a trickling filterplant the BOD5 and TSS shall be equal to orless than a monthly average of forty-five mil-ligrams per liter (45 mg/L) and a weeklyaverage of sixty-five milligrams per liter (65mg/L);

C. Where the use of effluent limita-tions set forth in this section is known orexpected to produce an effluent that willendanger or violate water quality, the depart-ment will set specific effluent limitations forindividual dischargers to protect the waterquality of the receiving streams;

D. The department may require morestringent limitations than authorized in para-graphs (2)(A)1. and 2. and subparagraphs(2)(A)3.A., B., and C. of this rule under thefollowing conditions:

(I) If the facility is an existing facil-ity, the department may set the BOD5 andTSS limits based upon an analysis of the pastperformance, rounded up to the next five mil-ligrams per liter (5 mg/L) range; and

(II) If the facility is a new facility,the department may set the BOD5 and TSSlimits based upon the design capabilities ofthe plant considering geographical and cli-matic conditions;

(a) A design capability study hasbeen conducted for new lagoon systems. Thestudy reflects that the effluent limitationsshould be BOD5 equal to or less than amonthly average of forty-five milligrams perliter (45 mg/L) and a weekly average of sixty-five milligrams per liter (65 mg/L) and TSSequal to or less than a monthly average ofseventy milligrams per liter (70 mg/L) and aweekly average of one hundred ten mil-ligrams per liter (110 mg/L).

(b) A design capability study hasbeen conducted for new trickling filter sys-tems and the study reflects that the effluentlimitations should be BOD5 and TSS equal toor less than a monthly average of forty mil-ligrams per liter (40 mg/L) and a weeklyaverage of sixty milligrams per liter (60mg/L); and

4. When the wastewater treatment pro-cess causes nitrification which affects theBOD5 reading, the permittee can petition thedepartment to substitute carbonaceous BOD5

in lieu of regular BOD5 testing. If the depart-ment concurs that nitrification is occurring,the department will set a carbonaceous BOD5at five milligrams per liter (5 mg/L) less thanthe regular BOD5 in the operating permit.

(B) The suspended solids which are pre-sent in stream water and which are removedduring treatment may be returned to the samebody of water from which they were taken,along with any additional suspended solidsresulting from the treatment of water to beused as public potable water or industrialpurposes using essentially the same processas a public water treatment process. Thisincludes the solids that are removed frompotable waters that are withdrawn from wellslocated in the alluvial valley of the Missouriand Mississippi Rivers.

(C) Monitoring Requirements.1. The department will develop a

wastewater and sludge sampling programbased on design flow and other site-specificfactors. Sampling frequency shall not exceedonce per day.

A. The department may establish lessfrequent sampling requirements for pointsources that produce an effluent that does notexhibit high variability and consistently com-plies with the applicable effluent limit; and

B. Sludge sampling will be estab-lished in the permit.

2. Unless otherwise specified in theoperating permit, sample types shall be:

A. Grab samples for lagoons andrecirculating media beds;

B. Twenty-four- (24-) hour compositesamples for mechanical plants; and

C. Sludge samples will be grab sam-ples unless otherwise specified in the operat-ing permit.

3. The monitoring frequency and sampletypes stated in subsection (2)(C) of this ruleare minimum requirements.

(3) Effluent Limitations for the Lakes andReservoirs.

(A) In addition to the requirements of sec-tion (9) of this rule, the following limitationsrepresent the maximum amount of pollutantswhich may be discharged from any pointsource, water contaminant source, or wastew-ater treatment facility to a lake or reservoirdesignated in 10 CSR 20-7.031 as L2 and L3which is publicly owned. Releases to lakesand reservoirs include discharges into streamsone-half (1/2) stream mile (.80 km) beforethe stream enters the lake as measured to itsconservation pool.

1. Discharges from wastewater treat-ment facilities which receive primarilydomestic waste or from POTWs shall under-go treatment sufficient to conform to the fol-

lowing limitations:A. BOD5 and TSS equal to or less

than a monthly average of twenty milligramsper liter (20 mg/L) and a weekly average ofthirty milligrams per liter (30 mg/L);

B. pH shall be maintained in the rangefrom six to nine (6–9) standard units inaccordance with 40 CFR 133.102 “Sec-ondary Treatment Regulation” October 16,1984, as published by the Office of the Fed-eral Resister, National Archives and RecordsAdministration, 700 Pennsylvania Avenue,Washington, DC 20408 which is herebyincorporated by reference and does notinclude later amendments or additions;

C. Where the use of effluent limita-tions set forth in section (3) of this rule arereasonably expected to exceed applicablewater quality standards, the department mayeither—conduct waste load allocation studiesin order to arrive at a limitation which pro-tects the water quality of the state or set spe-cific effluent limitations for individual dis-chargers to protect the water quality of thereceiving streams; and

D. When the wastewater treatmentprocess causes nitrification which affects theBOD5 reading, the permittee can petition thedepartment to substitute carbonaceous BOD5in lieu of regular BOD5 testing. If the depart-ment concurs that nitrification is occurring,the department will set a carbonaceous BOD5at five milligrams per liter (5 mg/L) less thanthe regular BOD5 in the operating permit.

(B) Monitoring Requirements.1. The department will develop a







C. Sludge samples shall be grab sam-ples unless otherwise specified in the operat-ing permit.

3. The monitoring frequency and sampletypes stated in paragraphs (3)(B)1. through 2.of this rule are minimum requirements.

(C) For lakes designated in 10 CSR 20-7.031 as L1, which are primarily used forpublic drinking water supplies, there will be

4 CODE OF STATE REGULATIONS (1/29/19) JOHN R. ASHCROFT

Secretary of State

10 CSR 20-7—DEPARTMENT OF NATURAL RESOURCES Division 20—Clean Water Commission

no discharge into the watersheds above theselakes from domestic or industrial wastewatersources regulated by these rules. Dischargesfrom potable water treatment plants, such asfilter wash, may be permitted. Separate stormsewers will be permitted, but only for thetransmission of storm water. Discharges per-mitted prior to the effective date of thisrequirement may continue to discharge solong as the discharge remains in compliancewith its operating permit.

(D) For lakes designated in 10 CSR 20-7.031 as L3 which are not publicly owned,the discharge limitations shall be those con-tained in section (8) of this rule.

(E) In addition to other requirements inthis section, discharges to Lake Taneycomoand its tributaries between Table Rock Damand Power Site Dam (and excluding the dis-charges from the dams) shall not exceed fivetenths milligrams per liter (0.5 mg/L) ofphosphorus as a monthly average. Dischargesmeeting both the following conditions shallbe exempt from this requirement:

1. Those permitted prior to May 9,1994; and

2. Those with design flows of less thantwenty-two thousand five hundred (22,500)gpd. The department may allow the construc-tion and operation of interim facilities with-out phosphorus control provided their dis-charges are connected to regional treatmentfacilities with phosphorus control not laterthan three (3) years after authorization.

(F) In addition to other requirements inthis section, discharges to Table Rock Lakewatershed, defined as hydrologic units num-bered 11010001 and 11010002, shall notexceed five-tenths milligrams per liter (0.5mg/L) of phosphorus as a monthly average.Discharges meeting both of the followingconditions are exempt from this requirement.

1. Those permitted prior to November30, 1999; and

2. Those with design flows less thantwenty-two thousand five hundred (22,500)gpd.

(G) Discharges in the White River basinand outside of the areas identified in (3)(E)and (F) of this section for phosphorus limita-tions shall be monitored for phosphorus dis-charges, and the frequency of monitoringshall be the same as that for BOD5 and TSS,but not less than annually. The departmentmay reduce the frequency of monitoring if themonitoring data is sufficient for water qualityplanning purposes.

(4) Effluent Limitations for Losing Streams.(A) Prior to discharging to a losing stream,

alternatives such as relocating the dischargeto a gaining stream, and connection to a

regional wastewater treatment facility must beevaluated and determined to be unacceptablefor environmental and/or economic reasons.

(B) In addition to the requirements of sec-tion (9) of this rule, each permit for a dis-charge from a wastewater treatment facility toa losing stream, shall be written using thelimitations contained in subsections (4)(B)and (C) of this rule in accordance with anyapplicable compliance schedule. Dischargesfrom private wastewater treatment facilitieswhich receive primarily domestic waste,industrial sources that treat influents contain-ing significant amounts of organic loading, orPOTWs permitted under this section shallundergo treatment sufficient to conform tothe following limitations:

1. BOD5 equal to or less than a monthlyaverage of ten milligrams per liter (10 mg/L)and a weekly average of fifteen milligramsper liter (15 mg/L);

2. TSS equal to or less than a monthlyaverage of fifteen milligrams per liter (15mg/L) and a weekly average of twenty mil-ligrams per liter (20 mg/L);

3. pH shall be maintained in the rangefrom six to nine (6–9) standard units inaccordance with 40 CFR 133.102 “Sec-ondary Treatment Regulation” October 16,1984, as published by the Office of the Fed-eral Resister, National Archives and RecordsAdministration, 700 Pennsylvania Avenue,Washington, DC 20408 which is herebyincorporated by reference and does notinclude later amendments or additions;

4. All chlorinated effluent discharges tolosing streams or within two (2) stream milesflow distance upstream of a losing streamshall also be dechlorinated prior to discharge;

5. When the wastewater treatment pro-cess causes nitrification which affects theBOD5 reading, the permittee can petition thedepartment to substitute carbonaceous BOD5in lieu of regular BOD5 testing. If the depart-ment concurs that nitrification is occurring,the department will set a carbonaceous BOD5at five milligrams per liter (5 mg/L) less thanthe regular BOD5 in the operating permit;and

6. For situations in which nitrates in adischarge can be reasonably expected toimpact specific drinking water wells, the con-centration of nitrates in the discharge shall belimited to an average monthly limit of tenmilligrams per liter (10 mg/L) as nitrogenand a maximum daily limit of twenty mil-ligrams per liter (20 mg/L). Applicants mayconduct a study in the same manner as theMissouri Risk-Based Corrective Action Tech-nical Guidance published in 2006 to deter-mine if nitrate limits are necessary to protectgroundwater. In such cases, applicants shall

submit a study plan for approval prior to thestudy, and submit all findings as part of theirpermit application.

(C) Monitoring Requirements.1. The department will develop a



B. Sludge samples will be establishedin the permit.





3. The monitoring frequency and sampletypes stated in paragraphs (4)(C)1. through2. of this rule are minimum requirements.

(5) Effluent Limitations for Metropolitan No-Discharge Streams.

(A) Discharge to metropolitan no-dischargestreams is prohibited, except as specificallypermitted under the Water Quality Standards10 CSR 20-7.031 and noncontaminated stormwater flows.





2. Unless otherwise specified in theoperating permits, sample types shall be:







(6) Effluent Limitations for Special Streams.(A) Limits for Outstanding National

Resource Waters as listed in Table D of 10CSR 20-7.031 and Drainages Thereto.

1. In addition to the requirements of sec-tion (9) of this rule, the following limitationsrepresent the maximum amount of pollutantswhich may be discharged from any pointsource, water contaminant source, or wastew-ater treatment facility to waters included inthis section.

2. Discharges from wastewater treat-ment facilities, which receive primarilydomestic waste, or from POTWs are limitedas follows:

A. New releases from any source areprohibited;

B. Discharges from sources that exist-ed before June 29, 1974, or if additionalstream segments are placed in this section,discharges that were permitted at the time ofthe designation will be allowed.

3. Industrial, agricultural, and othernon-domestic contaminant sources, pointsources, or wastewater treatment facilitieswhich are not included under subparagraph(6)(A)2.B. of this rule shall not be allowed todischarge. All precipitation collected in theoperational containment area or secondarycontainment area as well as process generatedwastewater shall be stored and disposed of ina no-discharge manner.

4. Monitoring requirements.A. The department will develop a


(I) The department may establishless frequent sampling requirements for pointsources that produce an effluent that does notexhibit high variability and consistently com-plies with the applicable effluent limit;

(II) Sludge sampling will be estab-lished in the permit.

B. Unless otherwise specified in theoperating permit, sample types shall be:

(I) Grab samples for lagoons andrecirculating media beds;

(II) Twenty-four- (24-) hour com-posite samples for mechanical plants; and

(III) Sludge samples shall be grabsamples unless otherwise specified in theoperating permit.

C. The monitoring frequency andsample types stated in subparagraphs(6)(A)4.A. through B. of this rule are mini-mum requirements.

(B) Limits for Outstanding State ResourceWaters as listed in Table E of 10 CSR 20-7.031.

1. Discharges shall not cause the current

water quality in the streams to be lowered.2. Discharges will be permitted as long

as the requirements of paragraph (6)(B)1. ofthis rule are met and the limitations in section(8) of this rule are not exceeded.

(7) Effluent Limitations for SubsurfaceWaters.

(A) No person shall release any water intoaquifers, store or dispose of water in a waywhich causes or permits it to enter aquiferseither directly or indirectly unless it meetsthe requirements of section (9) of this ruleand it meets the appropriate groundwater pro-tection criteria set in 10 CSR 20-7.031, TableA at a point ten feet (10’) under the releasepoint, or other compliance point based on sitespecific considerations, except as provided insubsection (7)(D) of this rule. The permitwriter shall review the complete applicationand other data to determine which parameterto include in the permit.

(B) No wastewater shall be introduced intosinkholes, caves, fissures, or other openingsin the ground which do or are reasonably cer-tain to drain into aquifers except as providedin section (4) of this rule.

(C) All abandoned wells and test holesshall be properly plugged or sealed to preventpollution of subsurface waters, as per therequirements of the department.

(D) The effluent limitations specified insubsection (7)(A) of this rule shall not applyto facilities designed and constructed to meetdepartment design criteria provided thesedesigns have been reviewed and approved bythe department. The department has the rightto require monitoring, reporting, publicnotice, and other information as deemedappropriate. This exemption may be revokedby the department should any monitoringindicate an adverse effect on a beneficialwater use or if the numeric criteria in theWater Quality Standards are being exceeded.

(E) Any person not included in subsection(7)(D) of this rule who releases, stores, ordisposes of water in a manner which resultsin releases of water to an aquifer having con-centrations in excess of one (1) or moreparameter limitations provided in subsection(7)(A) of this rule may be allowed to resam-ple for purposes of verification of the excess.At their discretion, persons may demonstrate,at the direction of the department, that theimpact on the water quality in the aquifer isnegligible on the beneficial uses. The demon-stration shall consider, at a minimum, the fol-lowing factors:

1. Site geology;2. Site geohydrology;3. Existing and potential water uses;4. Existing surface water and groundwa-

ter quality;5. Characteristics of wastes or wastewa-

ter contained in facilities; and6. Other items as may be required by the

department to assess the proposal.A. Demonstrations conducted under

10 CSR 25-18.010 shall be reviewed by thedepartment in accordance with such rules. Ifthe demonstrations show that the impact ongroundwater quality will not result in anunreasonable risk to human health or theenvironment, alternate effluent limitationswill be established by the department.

B. All other demonstrations shall bereviewed by the department. If the demon-strations show that the impact on groundwa-ter quality will not result in an unreasonablerisk to human health or the environment,alternate effluent limitation(s) will be pro-posed by the department and presented to theClean Water Commission for approval. TheClean Water Commission has the right torequire monitoring, reporting, public notice,and other information as deemed appropriatein the approval of the alternate limitation forone (1) or more parameters from subsection(7)(A) of this rule. The Clean Water Com-mission may hold a public hearing to securepublic comment prior to final action on analternate limitation.

C. No alternate limitations will begranted which would impair beneficial usesof the aquifer or threaten human health or theenvironment.

D. Alternate limitations may berevoked by the department should any moni-toring indicate an adverse effect on a benefi-cial water use or violations of the alternatelimitation.

(8) Effluent Limitations for All Waters,Except Those in Paragraphs (1)(B)1.–6. ofThis Rule. In addition to the requirements ofsection (9) of this rule, the following limita-tions represent the maximum amount of pol-lutants which may be discharged from anypoint source, water contaminant source, orwastewater treatment facility.

(A) Discharges from wastewater treatmentfacilities which receive primarily domesticwaste or POTWs shall undergo treatment suf-ficient to conform to the following limita-tions:

1. BOD5 and TSS equal to or less than amonthly average of thirty milligrams per liter(30 mg/L) and a weekly average of forty-fivemilligrams per liter (45 mg/L);

2. pH shall be maintained in the rangefrom six to nine (6–9) standard units in accor-dance with 40 CFR 133.102 “SecondaryTreatment Regulation” October 16, 1984, aspublished by the Office of the Federal


Secretary of State


Resister, National Archives and RecordsAdministration, 700 Pennsylvania Avenue,Washington, DC 20408 which is herebyincorporated by reference and does notinclude later amendments or additions;

3. The limitations of paragraphs(8)(A)1. and 2. of this rule will be effectiveunless an alternate limitation will not causeviolations of the Water Quality Standards orimpairment of the uses in the standards.When an Antidegradation Review has beencompleted for new or expanded discharges,the following alternate limitation may also beallowed:

A. If the facility is a wastewaterlagoon, the TSS shall be equal to or less thana monthly average of eighty milligrams perliter (80 mg/L) and a weekly average of onehundred twenty milligrams per liter (120mg/L) and the pH shall be maintained abovesix (6.0) and the BOD5 shall be equal to orless than a monthly average of forty-five mil-ligrams per liter (45 mg/L) and a weeklyaverage of sixty-five milligrams per liter (65mg/L);

B. If the facility is a trickling filterplant, the BOD5 and TSS shall be equal to orless than a monthly average of forty-five mil-ligrams per liter (45 mg/L) and a weeklyaverage of sixty-five milligrams per liter (65mg/L);

C. Where the use of effluent limita-tions set forth in section (8) of this rule isknown or expected to produce an effluent thatwill endanger water quality, the departmentwill set specific effluent limitations for indi-vidual dischargers to protect the water qualityof the receiving streams; and

D. The department may require morestringent limitations than authorized in para-graphs (8)(A)1. and 2. and subparagraphs(8)(A)3.A., B., and C. of this rule under thefollowing conditions:

(I) If the facility is an existing facil-ity, the department may set the BOD5 andTSS limits based upon an analysis of the pastperformance, rounded up to the next five mil-ligrams per liter (5 mg/L) range; and

(II) If the facility is a new facilitythe department may set the BOD5 and TSSlimits based upon the design capabilities ofthe plant considering geographical and cli-matic conditions:

(a) A design capability study hasbeen conducted for new lagoon systems. Thestudy reflects that the effluent limitationsshould be BOD5 equal to or less than amonthly average of forty-five milligrams perliter (45 mg/L) and a weekly average of sixty-five milligrams per liter (65 mg/L) and TSSequal to or less than a monthly average ofseventy milligrams per liter (70 mg/L) and a

weekly average of one hundred ten mil-ligrams per liter (110 mg/L); or

(b) A design capability study hasbeen conducted for new trickling filter sys-tems and the study reflects that the effluentlimitations should be BOD5 and TSS equal toor less than a monthly average of forty mil-ligrams per liter (40 mg/L) and a weeklyaverage of sixty milligrams per liter (60mg/L); and

4. When the wastewater treatment pro-cess causes nitrification which affects theBOD5 reading, the permittee can petition thedepartment to substitute carbonaceous BOD5in lieu of regular BOD5 testing. If the depart-ment concurs that nitrification is occurring,the department will set a carbonaceous BOD5at five milligrams per liter (5 mg/L) less thanthe regular BOD5 in the operating permit.










(9) General Conditions.(A) Establishing Effluent Limitations.

Unless a formal variance from water qualitystandards have been approved by the CleanWater Commission and the U.S. Environ-mental Protection Agency, operating permitsissued under 10 CSR 20-6.010(7) shallinclude, if applicable, the most protectivelimits set forth as follows:

1. Technology-based effluent limits andstandards based on specific requirementsunder sections (2) through (8) of this rule;

2. Water quality-based effluent limitsbased on a waste load allocation in accor-dance with federal regulations (40 CFR122.44(d)(1)), which would address pollu-tants that have a reasonable potential to cause

or contribute to an excursion above WaterQuality Standards established in 10 CSR 20-7.031.

A. Local effluent and receiving waterdata may be used to develop site specificeffluent limits provided the department deter-mines that this data is representative and 10CSR 7.031 provides for their development;

B. Water quality-based effluent limi-tations incorporating mixing zones and zonesof initial dilution as provided for in 10 CSR20-7.031(5)(A)4.B. may be based on streamflows other than critical low-flow conditions,if the following conditions are met:

(I) The limits are protective of crit-ical low-flow conditions, as well as higherflow conditions; and

(II) The permit shall require in-stream flow measurements and methods todetermine compliance;

3. Effluent limit guidelines or standardsthat have been federally promulgated underSections 301, 304, 306, 307, 318, and 405 ofthe Clean Water Act and case-by-case deter-minations of technology-based effluent limi-tations under section 402(a)(1) of the CleanWater Act;

4. Effluent limits for discharges subjectto a TMDL necessary to achieve water qualitystandards, including permit limits in lieu of aTMDL. Permit limitations consistent with therequirements and assumptions of an approvedwaste load allocation within a TMDL shall beplaced in permits as needed. Permits mayinclude schedules of compliance and, if devel-oped, follow TMDL implementation plans,adaptive management approaches or otherflexibilities so long as they are allowed by fed-eral regulation. The department may reopenexisting permits to implement TMDL require-ments;

5. Effluent limits that are developedthrough the antidegradation review process,provided there is reasonable potential toexceed these limits; and

6. Effluent Limits that are required as aresult of legal agreements between discharg-ers and the department or the Clean WaterCommission, or as otherwise required orallowed by law.

(B) Bacteria and Statewide Nutrient Lim-its. Operating Permits as required under 10CSR 20-6.010(7) shall include, if applicable,the following bacteria and nutrient limits:

1. Bacteria. The following water qualityEscherichia coli (E. coli) discharge limitsapply:

A. Discharges to stream segments des-ignated in Table H of 10 CSR 20-7.031 forwhole body contact recreation and secondarycontact recreation shall not exceed the waterquality E. coli counts established in subsection



(5)(C) of 10 CSR 20-7.031;B. Discharges to lakes designated as

whole body contact recreational or secondarycontact recreational in Table G of 10 CSR 20-7.031 shall not exceed the water quality E.coli counts established in subsection (5)(C) of10 CSR 20-7.031;

C. Discharges located within two (2)miles upstream of stream segments or lakesdesignated for whole body contact recreation-al or secondary contact recreational in TablesH and G of 10 CSR 20-7.031 shall not exceedthe water quality E. coli counts established insubsection (5)(C) of 10 CSR 20-7.031 for thereceiving stream segment or lake designatedfor those uses;

D. E. coli limits. During the recre-ation season, discharges to waters designatedfor whole body contact “A” as defined in part(1)(C)2.A.(I) of 10 CSR 20-7.031 shall belimited to one hundred twenty-six (126)colony forming units per one hundred (100)milliliters (ml) expressed as a monthly geo-metric mean for POTWs and non-POTWs.During the recreation season, discharges towaters designated for whole body contact“B” as defined in part (1)(C)2.A.(II) of 10CSR 20-7.031 shall be limited to two hun-dred six (206) colony forming units per onehundred (100) ml expressed as a monthlygeometric mean for POTWs and non-POTWs. During the recreation season, dis-charges to waters designated for secondarycontact recreational as defined in subpara-graph (1)(C)2.B. of 10 CSR 20-7.031 shall belimited to one thousand one hundred thirty-four (1,134) colony forming units per onehundred (100) ml expressed as a monthlygeometric mean for POTWs and non-POTWs. For the entire calendar year, dis-charges to waters that are defined by para-graph (1)(B)3. of this rule as losing streamsshall be limited to one hundred twenty-six(126) colony forming units per one hundred(100) ml expressed as a daily maximum;

E. Short-term E. coli limits. Short-term effluent limitations shall be expressed asa daily maximum for non-POTWs and as aweekly geometric mean for POTWs. Short-term effluent limitations for discharges towaters designated for whole body contact “A”and “B” as well as those designated for sec-ondary contact recreation shall be derived bymultiplying the monthly geometric meaneffluent limitations identified in (9)(B)D. ofthis rule by a factor of five (5), except thatalternative multipliers may be utilized to cal-culate short-term E. coli limitations whenproposed and incorporated into permits. Atno time shall using alternative multipliers inshort-term effluent limitations cause or con-tribute to an excursion of the in-stream water

quality criteria.F. As an alternative to the limits pre-

scribed in subparagraphs (9)(B)1.A. throughE. of this rule, the department may allow per-mit applicants to conduct a study to developE. coli limits that reflect pathogen decay.Prior to conducting this study applicants shallsubmit a quality assurance project plan forapproval prior to the study, and submit allfindings as part of their permit application;and

G. Notwithstanding the bacteria lim-its prescribed in paragraphs (9)(1)A. throughF. of this rule, discharges to losing streamsshall be considered in compliance so long asno more than ten (10) percent of samplesexceed one hundred twenty-six (126) colonyforming units per one hundred (100) ml dailymaximum;

2. Nutrients. Reserved for StatewideNutrient Effluent Limits.

(C) Schedules of Compliance.1. Compliance with new or revised

National Pollutant Discharge EliminationSystem (NPDES) or Missouri operating per-mit limitations shall be achieved and inaccordance with the federal regulation 40CFR Part 122.47, “Schedules of Compli-ance,” May 15, 2000, as published by theOffice of the Federal Register, NationalArchives and Records Administration, Super-intendent of Documents, Pittsburgh, PA15250-7954, which is hereby incorporated byreference and does not include later amend-ments or additions.

2. A compliance schedule may be modi-fied in accordance with the federal regulation40 CFR 122.62 “Modification or revocationand reissuance of permits,” November 20,2008, as published by the Office of the FederalResister, National Archives and RecordsAdministration, 700 Pennsylvania Avenue,Washington, DC 20408 which is hereby incor-porated by reference and does not includelater amendments or additions.

(D) Monitoring, Analysis, and Reporting.1. All construction and operating permit

holders shall submit reports at intervalsestablished by the permit or at any other rea-sonable intervals required by the department.The monitoring and analytical schedule shallbe as established by the department in theoperating permit.

2. The analytical and sampling methodsused must conform to federal regulation 40CFR Part 136.3 “Identification of test proce-dures,” August 28, 2017, as published by theOffice of the Federal Register, NationalArchives and Records Administration, 700Pennsylvania Avenue, Washington, DC 20408which is hereby incorporated by reference anddoes not include later amendments or addi-

tions.3. Approval of alternative test proce-

dures shall follow the criteria set forth in fed-eral regulation 40 CFR 136.4 “Applicationfor and approval of alternate test proceduresfor nationwide use,” August 28, 2017, aspublished by the Office of the Federal Regis-ter, National Archives and Records Adminis-tration, Washington, DC 20408 or federalregulation 40 CFR 136.5 “Approval of alter-nate test procedures for limited use,” August28, 2017, as published by the Office of theFederal Register, National Archives andRecords Administration, 700 PennsylvaniaAvenue, Washington, DC 20408, which areincorporated by reference and do not includelater amendments or additions.

4. Sampling and analysis by the depart-ment to determine violations of this regula-tion will be conducted in accordance with themethods listed in paragraph (9)(D)2. of thisrule or any other approved by the department.Violations may be also determined by reviewof the permittee’s self-monitoring reports.

5. If, for any reason, the permittee doesnot comply with or will be unable to complywith any discharge limitations or standardsspecified in the permit, the permittee shallprovide the department with the followinginformation, with the next discharge monitor-ing report as required under subsection(9)(D) of this rule:

A. A description of the discharge andcause of noncompliance;

B. The period of noncompliance,including exact dates and times and/or theanticipated time when the discharge willreturn to compliance; and

C. The steps being taken to reduce,eliminate, and prevent recurrence of the non-compliance.

6. In the case of any discharge subject toany applicable toxic pollutant effluent stan-dard under Section 307(a) of the federalClean Water Act, the information required byparagraph (9)(D)5. of this rule regarding aviolation of this standard shall be providedwithin twenty-four (24) hours from the timethe owner or operator of the water contami-nant source, point source, or wastewatertreatment facility becomes aware of the viola-tion or potential violation. This informationmay be provided via an electronic web-basedsystem developed by the department, provid-ed it is available. If this information is provid-ed orally, a written submission covering thesepoints shall be provided within five (5) work-ing days of the time the owner or operator ofthe water contaminant source, point source,or wastewater treatment facility becomesaware of the violation.

7. Bacteria Monitoring for Disinfection.


Secretary of State


A. For systems that have a designcapacity of greater than one hundred thou-sand (100,000) gpd, a minimum of one (1)sample shall be collected for E. coli analysiseach calendar week during the recreationalseason from April 1 through October 31.Compliance with the E. coli water qualitystandard established in subsection (5)(C) of10 CSR 20-7.031 shall be determined eachcalendar month by calculating the geometricmean of all of the samples collected each cal-endar month. Compliance with the short-term E. coli limits established in subpara-graph (9)(B)1.E. of this rule shall also bedetermined.

B. For systems that discharge tostream segments that are defined by para-graph (1)(B)3. as losing streams and have adesign capacity of greater than one hundredthousand (100,000) gpd, a minimum of one(1) sample shall be collected for E. coli anal-ysis each calendar week all year. Compliancewith the E. coli water quality standard estab-lished in subsection (5)(C) of 10 CSR 20-7.031 and with the short term E. coli limitsestablished in subparagraph (9)(B)1.E. of thisrule shall also be determined.

C. For systems that have a designcapacity of one hundred thousand (100,000)gpd or less, the sampling frequency for E.coli analysis shall be in accordance with thewastewater and sludge sampling programbased on the design flow which is dependentupon the receiving water category as listed insubsection (1)(B) of this rule. Compliancewith the E. coli water quality standard estab-lished in subsection (5)(C) of 10 CSR 20-7.031 shall be determined each calendarmonth by calculating the geometric mean ofall of the samples collected each calendarmonth. Compliance with the short-term E.coli limits established in subparagraph(9)(B)1.E. of this rule shall also be deter-mined.

8. Statewide Monitoring for Nutrients.Point sources that have the design capacity ofgreater than one hundred thousand (100,000)gpd that typically discharge nitrogen andphosphorus shall collect and analyze influentand effluent samples for total phosphorus,ammonia, total kjeldahl nitrogen and nitrateplus nitrite utilizing methods outlined in(D)2. of this section using the following fre-quencies:

A. Quarterly for facilities with designcapacities greater than one hundred thousand(100,000) gpd and less than one million(1,000,000) gpd per day for a period up tofive (5) years. The department may requireadditional monitoring to ascertain a dis-charge’s nutrient contribution and the effica-cy of the treatment technology as it pertains

to nutrient removal.B. Monthly for facilities with design

capacities greater than or equal to one million(1,000,000) gpd for a period up to five (5)years. The department may require additionalmonitoring to ascertain a discharge’s nutrientcontribution and the efficacy of the treatmenttechnology as it pertains to nutrient removal.

C. The department may impose ongo-ing or more frequent monitoring in permitsthat impose effluent limits for total nitrogenor total phosphorus or in situations in whichmonitoring is appropriate to ensure compli-ance with water quality standards or specificlake limits specified under subsection (3)(E)and (F) of this rule.

(E) Dilution Water. Dilution of treatedwastewater with cooling water or other lesscontaminated water to lower the effluent con-centration to limits required by an effluentregulation of the Clean Water Law shall notbe an acceptable means of treatment.

(F) Compliance with New Source Perfor-mance Standards.

1. Except as provided in paragraph(9)(F)2. of this rule, any new water contami-nant source, point source, or wastewater treat-ment facility on which construction com-menced after October 18, 1972, or any newsource, which meets the applicable promulgat-ed new source performance standards beforethe commencement of discharge, shall not besubject to any more stringent new source per-formance standards or to any more stringenttechnology-based standards under subsection301(b)(2) of the federal Clean Water Act forthe shortest of the following periods:

A. Ten (10) years from the date thatconstruction is completed;

B. Ten (10) years from the date thesource begins to discharge process or othernonconstruction related wastewater; or

C. The period of depreciation oramortization of the facility for the purposes ofsection 167 or 169 (or both) of the InternalRevenue Code of 1954.

2. The protection from more stringentstandards of performance afforded by para-graph (9)(F)1. of this rule does not apply to—

A. Additional or more stringent per-mit conditions which are not technologybased, for example, conditions based onwater quality standards or effluent standardsor prohibitions under Section 307(a) of thefederal Clean Water Act; and

B. Additional permit conditions con-trolling pollutants listed as toxic under Sec-tion 307(a) of the federal Clean Water Act oras hazardous substances under Section 311 ofthe federal Clean Water Act and which arenot controlled by new source performancestandards. This exclusion includes permit

conditions controlling pollutants other thanthose identified as hazardous where controlof those other pollutants has been specificallyidentified as the method to control the haz-ardous pollutant.

(G) Bypass. Bypass means the intentionaldiversion of waste streams from any portionof a treatment facility, except in the case ofblending. Severe property damage meanssubstantial physical damage to property, dam-age to the treatment facilities which causesthem to become inoperable, or substantialand permanent loss of natural resourceswhich can reasonably be expected to occur inthe absence of a bypass. Severe propertydamage does not mean economic loss causedby delays in production. Blending is the prac-tice of diverting wet-weather flows aroundany treatment unit and recombining thoseflows within the treatment facility, while pro-viding primary and secondary or biologicaltreatment up to the available capacity, consis-tent with all applicable effluent limits andconditions. Stipulations regarding bypassallowances, prohibitions and reportingrequirements shall comply with federal regu-lation 40 CFR 122.41 “Conditions applicableto all permits (applicable to state programs,See section 123.25), October 22, 2015, aspublished by the Office of the Federal Regis-ter, National Archives and Records Adminis-tration, 700 Pennsylvania Avenue, Washing-ton, DC 20408, which are incorporated byreference and do not include later amend-ments or additions.

(H) Sludge facilities shall meet the applica-ble control technology for sewage sludgetreatment, use, and disposal as published bythe EPA in 40 CFR 503 and applicable statestandards and limitations published in 10CSR 20 and 10 CSR 80. Where there are nostandards available or applicable, or whenmore stringent standards are appropriate toprotect human health and the environment,the department shall set specific limitations inpermits on a case-by-case basis using bestprofessional judgment.

(I) Industrial, agricultural, and other non-domestic water contaminant sources, pointsources, or wastewater treatment facilitieswhich are not included under subsections(2)(A) or (8)(A) of this rule—

1. These facilities shall meet the applica-ble control technology currently effective aspublished by the EPA in 40 CFR 405–471.Where there are no standards available orapplicable, the department shall set specificparameter limitations using best professionaljudgment. The pH shall be maintained in therange from six to nine (6–9) standard units,except that discharges of uncontaminated cool-ing water and water treatment plant effluent



may exceed nine (9) standard units, but maynot exceed ten and one-half (10.5) standardunits, if it can be demonstrated that the pHwill not exceed nine (9) standard units beyondthe regulatory mixing zone; and

2. All precipitation collected in theoperational containment area or secondarycontainment area as well as process generatedwastewater shall be stored and disposed of ina no-discharge manner or treated to meet theapplicable control technology referenced inparagraph (9)(I)1. of this rule.

(J) Implementation Schedule for Protectionof Whole Body Contact and Secondary Con-tact Recreation.

1. For discharges to water bodies desig-nated for whole body contact and secondarycontact recreational use prior to July 1, 2012,in 10 CSR 20-7.031, permits shall insurecompliance with effluent limits to protectwhole body contact and secondary contactrecreation by no later than December 31,2013, unless the permittee presents an evalu-ation sufficient to show that disinfection isnot required to protect one (1) or both desig-nated recreational uses, or a UAA demon-strates that one (1) or both designated recre-ational uses are not attainable in the classifiedwaters receiving the effluent.

2. For discharges to water bodies desig-nated for whole body contact and secondarycontact recreational use after June 30, 2012,in 10 CSR 20-7.031, permits shall includeschedules of compliance to meet bacteria lim-its in accordance with subsection (9)(C) ofthis rule.

(K) Temporary Suspension of Accountabil-ity for Bacteria Standards during Wet Weath-er. The accountability for bacteria standardsmay be temporarily suspended for specificdischarges when conditions contained inparagraphs (9)(K)1. through 3. of this ruleare met.

1. No existing recreational uses down-stream of the discharge will be impacted dur-ing the period of suspension as confirmedthrough a water quality review for reasonablepotential for downstream impacts and a UAAperformed in accordance with the MissouriRecreational Use Attainability Analysis Pro-tocol approved by the Missouri Clean WaterCommission.

2. The period of suspension must berestricted to the defined wet weather eventthat corresponds to the period when recre-ational uses are unattainable. The periodmust be determinable at any time by the dis-charger and the general public (such as fromstream depth or flow readings or other streamconditions on which publicly accessiblerecords are kept).

3. The suspension shall be subject to

public review and comment, Missouri CleanWater Commission approval, and EPAapproval before becoming effective and shallbe contained as a condition in a dischargepermit or other written document developedthrough public participation.

(L) Whole Effluent Toxicity (WET) Test.The following are permit requirements foracute and chronic WET tests:

1. WET tests are to be conductedaccording to the methods prescribed in 40CFR 136.3;

2. Test Types.A. Acute WET tests shall be a multi-

ple dilution series, static, non-renewal test todetermine the degree at which acute forty-eight to ninety-six hour (48–96 hour) expo-sure to the effluent is acutely toxic to aquaticlife expressed in species survival.

B. Chronic WET test shall be a mul-tiple dilution series, static, renewal test todetermine the degree at which chronic (sublethal) exposure to the effluent is toxic toaquatic life or affects an alternative endpointsuch as species reproduction and/or growth.Duration of chronic WET tests shall be estab-lished according to 40 CFR 136.3 Identifica-tion of test procedures, promulgated as ofJuly 1, 2011, is hereby incorporated by refer-ence in this rule, as published by the Officeof the Federal Register, U.S. NationalArchives and Records, 700 PennsylvaniaAvenue NW, Washington, DC 20408. Thisrule does not incorporate any subsequentamendments or additions;

3. Applicability. WET test type and fre-quency shall be determined and expressed inpermits by the department. At permitissuance or reissuance, the department willuse valid and representative data to establishon a case-by-case basis, whether an existingdischarge causes, has the reasonable potentialto cause, or contributes to an excursion fromthe narrative water quality criteria. Where thedepartment concludes that a discharge has thereasonable potential to contribute to an excur-sion from the narrative water quality criteria,as established in 10 CSR 20- 7.031 the per-mit will include WET limits. If the depart-ment determines the facility has no reason-able potential to violate water qualitystandards, WET testing may be removed, orif more information is required, WET testingmay be retained at a reduced frequency. WETtest applicability for NPDES permits shall befully addressed in the permit factsheet; and

4. Specifications.A. A dilution series shall be estab-

lished in the permit for WET test. The dilu-tion series shall be a set of proportional efflu-ent dilutions based on an Allowable EffluentConcentration (AEC).

B. All WET tests shall be performedwith Pimephales promelas (a fathead min-now) and Ceriodaphnia dubia (a water flea),except facilities which discharge to receivingstreams designated as cold-water fisheries.Facilities which discharge to receivingstreams designated as cold-water fisheriesmay be required to perform WET tests usingOncorhynchus mykiss (rainbow trout) insteadof the fathead minnow. Other test species forwhich test methods are provided in 40 CFR136.3 may be approved by the department ona case-by-case basis provided the species areappropriately sensitive and representative.Alternative species (not included in 40 CFR136.3) shall be approved in accordance withthe procedures in 40 CFR 136.4. Applicationfor alternate test procedures, promulgated asof August 28, 2017, is hereby incorporatedby reference in this rule, as published by theOffice of the Federal Register, U.S. NationalArchives and Records, 700 PennsylvaniaAvenue NW, Washington, DC 20408. Thisrule does not incorporate any subsequentamendments or additions.

C. A Toxic Unit (TU) water qualitybased limit shall be established in the permitfor WET test where the department con-cludes that a discharge has the reasonablepotential to cause or contribute to an excur-sion from the narrative water quality criteriaas established in 10 CSR 20-7.031(4)(D).The TU limit shall be determined in accor-dance with 40 CFR 122.44(d)(1)(v) and uti-lizing the methods established in TechnicalSupport Document For Water Quality-basedToxics Control (March 1991, EPA,EPA/505/2-90-001) and documented in thefactsheet. Exceedance of a TU limit shall bea WET test failure.

D. Upon completion of a WET testthe lab report and department form as refer-enced in the permit shall be submitted by thepermittee to the department within the time-frame established by the permit.

(10) Control of Combined Sewer Overflows(CSOs). The permitting and control of CSOsshall conform to EPA’s CSO Control Policy,EPA Number 830/B-94-001 (published byEPA April 19, 1994, at 59 Fed. Reg. 18688)as referenced by Section 402 (q) of the CleanWater Act, 33 USC 1342(q). The CSO Con-trol Policy is hereby incorporated by refer-ence, without any later amendments or addi-tions. This document is available by writingto U.S. Environmental Protection Agency,Office of Water Resource Center, Mail CodeRC-4100T, 1200 Pennsylvania Avenue NW,Washington, DC 20460 or upon request fromthe Department of Natural Resources, WaterProtection Program, Water Pollution Control


Secretary of State


Branch, PO Box 176, Jefferson City, MO65102-0176. Effluent monitoring commit-ments for CSOs shall be addressed in thelong term control plans required under EPA’sCSO Control Policy.

AUTHORITY: section 644.026, RSMo 2016.*Original rule filed June 6, 1974, effectiveJune 16, 1974. Amended: Filed April 1,1975, effective April 11, 1975. Rescinded:Filed Oct. 16, 1979, effective July 11, 1980.Readopted: Filed Feb. 4, 1980, effective July11, 1980. Rescinded and readopted: FiledNov. 10, 1982, effective May 12, 1983.Amended: Filed Sept. 11, 1984, effectiveMarch 12, 1985. Amended: Filed July 25,1985, effective Dec. 26, 1985. Amended:Filed Feb. 1, 1988, effective June 13, 1988.Amended: Filed Sept. 13, 1988, effective Feb.14, 1989. Amended: Filed July 15, 1991,effective Jan. 13, 1992. Amended: Filed Sept.2, 1993, effective May 9, 1994. Amended:Filed March 1, 1999, effective Nov. 30, 1999.Amended: Filed Dec. 30, 1999, effectiveSept. 30, 2000. Amended: Filed March 31,2005, effective Dec. 31, 2005. Amended:Filed Sept. 28, 2009, effective June 30, 2010.Amended: Filed May 15, 2013, effective Feb.28, 2014. Amended: Filed June 15, 2018,effective Feb. 28, 2019.

*Original authority: 644.026, RSMo 1972, amended1973, 1987, 1993, 1995, 2000, 2012, 2014.

10 CSR 20-7.020 Effluent Regulations(Rescinded July 10, 1980)

AUTHORITY: section 204.026, RSMo 1978.Original rule filed June 6, 1974, effectiveJune 16, 1974. Amended: Filed April 1,1975, effective April 11, 1975. Rescinded:Filed Oct. 12, 1979, effective July 10, 1980.

10 CSR 20-7.030 Water Quality Standards(Rescinded December 11, 1977)

AUTHORITY: sections 204.021 and 204.026,RSMo Supp. 1973. Rescinded: effective Dec.11, 1977.

10 CSR 20-7.031 Water Quality Standards

PURPOSE: This rule identifies uses of watersof the state, criteria to protect those uses, anddefines the antidegradation policy. It is devel-oped in response to the Missouri Clean WaterLaw and the federal Clean Water Act, Section303(c)(1) and (2), which requires that statewater quality standards be reviewed at leastonce every three (3) years. These revisions

are pursuant to the national goal of protec-tion of fish, shellfish, and wildlife and recre-ation in and on the water as outlined in Sec-tion 101(a)(2) of the Act.

PUBLISHER’S NOTE: The secretary of statehas determined that the publication of theentire text of the material which is incorpo-rated by reference as a portion of this rulewould be unduly cumbersome or expensive.This material as incorporated by reference inthis rule shall be maintained by the agency atits headquarters and shall be made availableto the public for inspection and copying at nomore than the actual cost of reproduction.This note applies only to the reference mate-rial. The entire text of the rule is printedhere.

(1) Definitions.(A) Acute toxicity—Conditions producing

adverse effects or lethality on aquatic life fol-lowing short-term exposure. The acute crite-ria in Tables A1, A2, and B1 are maximumconcentrations which protect against acutelytoxic conditions. Acute toxicity is also indi-cated by exceedence of whole-effluent toxici-ty (WET) test conditions of paragraph(4)(I)2. For substances not listed in TablesA1, A2, and B1, three-tenths (0.3) of themedian lethal concentration, or the noobserved acute effect concentration for repre-sentative species, may be used to determineabsence of acute toxicity.

(B) Aquifer—A subsurface water-bearingbed or stratum which stores or transmitswater in recoverable quantities that is current-ly being used or could be used as a watersource for private or public use. It does notinclude water in the vadose zone.

(C) Designated uses—Uses specified foreach water body whether or not they arebeing attained. Uses are designated accordingto section (2) of this rule and include, but arenot limited to—

1. Protection and propagation of fish,shellfish, and wildlife. Streams will be desig-nated to one (1) of the following aquatic habi-tat protection uses based on watershed size,scale within the stream network, and otherhydrological and physical data. Lakes andreservoirs will be designated to one (1) of thefollowing aquatic habitat protection usesbased on limnological characteristics (such astemperature) and biological assemblages.

A. Warm Water Habitat (WWH)—Waters in which naturally-occurring waterquality and habitat conditions allow the main-tenance of a wide variety of warm-water biota.

(I) Great River(II) Large River(III) Small River

(IV) Creek(V) Headwater(VI) Lake or reservoir

B. Cool Water Habitat (CLH)—Waters in which naturally-occurring waterquality and habitat conditions allow the main-tenance of a wide variety of cool-water biota.These waters can support a sensitive, high-quality sport fishery (i.e., smallmouth bassand rock bass).

(I) Large River(II) Small River(III) Creek(IV) Headwater(V) Lake or reservoir

C. Cold Water Habitat (CDH)—Waters in which naturally-occurring waterquality and habitat conditions allow the main-tenance of a wide variety of cold-water biota.These waters can support a naturally repro-ducing or stocked trout fishery and popula-tions of other cold-water species.

(I) Large River(II) Small River(III) Creek(IV) Headwater(V) Lake or reservoir

D. Ephemeral Aquatic Habitat(EAH)—Waters having surface flow or poolsin response to precipitation events or snowmelt, but without permanent surface flow orpermanent pools; naturally-occurring waterquality and habitat conditions may allow themaintenance of a limited or transient commu-nity of aquatic biota.

E. Modified Aquatic Habitat(MAH)—Waters in which natural habitat con-ditions have been physically, chemically, orbiologically modified; habitat and resultingwater quality conditions may prevent themaintenance of a wide variety or diversity ofaquatic biota.

F. Limited Aquatic Habitat (LAH)—Waters in which natural habitat conditionshave been substantially and irretrievablyaltered; habitat and resulting water qualityconditions do not allow maintenance ofaquatic biota, or if present, the community isof poor variety or diversity;

2. Recreation in and on the water.Assignment of these uses does not grant anindividual the right to trespass.

A. Whole body contact recreation(WBC)—Activities involving direct humancontact with waters of the state to the point ofcomplete body submergence. The water maybe ingested accidentally and certain sensitivebody organs, such as the eyes, ears, and thenose, will be exposed to the water. Althoughthe water may be ingested accidentally, it isnot intended to be used as a potable supplyunless acceptable treatment is applied. Waters



so designated are intended to be used forswimming, water skiing, or skin diving.

(I) Category A (WBC-A)—Thiscategory applies to waters that have beenestablished by the property owner as publicswimming areas welcoming access by thepublic for swimming purposes and waterswith documented existing whole body contactrecreational use(s) by the public. Examples ofthis category include, but are not limited to:public swimming beaches and propertywhere whole body contact recreational activ-ity is open to and accessible by the publicthrough law or written permission of thelandowner.

(II) Category B (WBC-B)—Thiscategory applies to waters designated forwhole body contact recreation not containedwithin category A.

B. Secondary contact recreation(SCR)—Uses include fishing, wading, com-mercial and recreational boating, any limitedcontact incidental to shoreline activities, andactivities in which users do not swim or floatin the water. These recreational activities mayresult in contact with the water that is eitherincidental or accidental and the probability ofingesting appreciable quantities of water isminimal;

3. Human health protection (HHP)—Criteria to protect this use are based on theassumption of an average amount of fish con-sumed on a long-term basis. Protection ofthis use includes compliance with Food andDrug Administration (FDA) limits for fishtissue, maximum water concentrations corre-sponding to the 10-6 cancer risk level, andother human health fish consumption criteria;

4. Irrigation (IRR)—Application of waterto cropland or directly to cultivated plants thatmay be used for human or livestock consump-tion. Occasional supplemental irrigation,rather than continuous irrigation, is assumed;

5. Livestock and wildlife protection(LWP)—Maintenance of conditions in watersto support health in livestock and wildlife;

6. Drinking water supply (DWS)—Main-tenance of a raw water supply which will yieldpotable water after treatment by public watertreatment facilities;

7. Industrial water supply (IND)—Waterto support various industrial uses; since qual-ity needs will vary by industry, no specificcriteria are set in these standards;

8. Storm- and flood-water storage andattenuation (WSA)—Wetlands and otherwaters which serve as overflow and storageareas during flood or storm events slowlyrelease water to downstream areas, thus low-ering flood peaks and associated damage tolife and property;

9. Habitat for resident and migratory

wildlife species, including rare and endan-gered species (WHP)—Wetlands and otherwaters that provide essential breeding, nest-ing, feeding, and predator escape habitats forwildlife including waterfowl, birds, mam-mals, fish, amphibians, and reptiles;

10. Recreational, cultural, educational,scientific, and natural aesthetic values anduses (WRC)—Wetlands and other waters thatserve as recreational sites for fishing, hunting,and observing wildlife; waters of historic orarchaeological significance; waters which pro-vide great diversity for nature observation,educational opportunities, and scientificstudy; and

11. Hydrologic cycle maintenance(WHC)—Wetlands and other waters hydro-logically connected to rivers and streamsserve to maintain flow conditions during peri-ods of drought. Waters that are connectedhydrologically to the groundwater systemrecharge groundwater supplies and assume animportant local or regional role in maintain-ing groundwater levels.

(D) Biocriteria—Numeric values or narra-tive expressions that describe the referencebiological integrity of aquatic communitiesinhabiting waters that have been designatedfor aquatic-life protection.

(E) Chronic toxicity—Conditions produc-ing adverse effects on aquatic life or wildlifefollowing long-term exposure but having noreadily observable effect over a short timeperiod. Chronic numeric criteria in TablesA1, A2, B2, and B3 are maximum concentra-tions which protect against chronic toxicity;these values shall be considered four- (4-) dayaverages, with the exception of total ammoniaas nitrogen which shall be considered a thir-ty- (30-) day average. Chronic toxicity is alsoindicated by exceedence of WET test condi-tions of subsection (5)(Q). For substances notlisted in Tables A1, A2, B2, and B3, com-monly used endpoints such as the no-observed effect concentration or inhibitionconcentration of representative species maybe used to demonstrate absence of toxicity.

(F) Class—All waters listed in the Mis-souri Use Designation Dataset and in Table Gand Table H of this rule shall have a hydro-logic class. During normal flow periods,some rivers back water into tributaries whichdo not otherwise have a hydrologic class.These permanent backwater areas are consid-ered to have the same hydrologic class as thewater body into which the tributary flows.

1. Class L1—Lakes used primarily forpublic drinking water supply.

2. Class L2—Major reservoirs.3. Class L3—Other lakes which are

waters of the state. These include both publicand private lakes. For effluent regulation pur-

poses, publicly-owned L3 lakes are those forwhich a substantial portion of the surround-ing lands are publicly owned or managed.

4. Class P—Streams that maintain per-manent flow even in drought periods.

5. Class P1—Standing-water reaches ofClass P streams.

6. Class C—Streams that may ceaseflow in dry periods but maintain permanentpools which support aquatic life.

7. Class E—Streams that do not main-tain permanent surface flow or permanentpools, but have ephemeral surface flow orpools in response to precipitation events.

8. Class W—Wetlands that are waters ofthe state that meet the criteria in the Corps ofEngineers Wetlands Delineation Manual(January 1987), and subsequent federal revi-sions and supplements. Class W waters donot include wetlands that are artificially cre-ated on dry land and maintained for the treat-ment of mine drainage, stormwater control,drainage associated with road construction,or industrial, municipal, or agriculturalwaste.

(G) Early life stages of fish—The pre-hatchembryonic period, the post-hatch free embryoor yolk-sac fry, and the larval period duringwhich the organism feeds. Juvenile fish,which are anatomically rather similar toadults, are not considered an early life stage.

(H) Ecoregion—Ecoregions denote areasof general similarity in ecosystems and in thetype, quality, and quantity of environmentalresources. They are designed to serve as aspatial framework for the research, assess-ment, management, and monitoring ofecosystems and ecosystem components. Byrecognizing the spatial differences in thecapacities and potentials of ecosystems,ecoregions stratify the environment by itsprobable response to disturbance (Bryce,Omernik, and Larsen, 1999).

(I) Epilimnion—Zone of atmospheric mix-ing in a thermostratified lake.

(J) Escherichia coli (E. coli)—A type offecal coliform bacteria found in the intestinesof animals and humans. The presence of E.coli in water is a strong indication of recentsewage or animal waste contamination.Sewage may contain many types of disease-causing organisms (pathogens).

(K) Eutrophication—The process by whicha body of water becomes enriched in dis-solved nutrients, such as nitrogen and phos-phorus, that stimulate the excessive growth ofalgae and other plants. Eutrophication may beaccelerated by human activities.

(L) Existing uses—Those uses actuallyattained in the water body on or after Novem-ber 28, 1975, whether or not they are identi-fied in the water quality standards.


Secretary of State


(M) Hypolimnion—Zone beneath the zoneof atmospheric mixing in a thermostratifiedlake.

(N) Lethal concentration50 (LC50)—Con-centration of a toxicant which would beexpected to kill fifty percent (50%) of theindividuals of the test species organisms in atest of specified length of time.

(O) Losing stream—A stream which dis-tributes thirty percent (30%) or more of itsflow during low flow conditions through nat-ural processes, such as through permeablegeologic materials into a bedrock aquiferwithin two (2) miles flow distance down-stream of an existing or proposed discharge.Flow measurements to determine percentageof water loss must be corrected to approxi-mate the 7Q10 stream flow. If a stream bed ordrainage way has an intermittent flow or aflow insufficient to measure in accordancewith this rule, it may be determined to be alosing stream on the basis of channel devel-opment, valley configuration, vegetationdevelopment, dye tracing studies, bedrockcharacteristics, geographical data, and othergeological factors. Losing streams are identi-fied in the digital geospatial dataset ‘LOS-ING_STREAM’ developed by the MissouriDepartment of Natural Resources, MissouriGeological Survey; additional streams may bedetermined to be losing by the MissouriDepartment of Natural Resources.

(P) Low-flow conditions—Where used inthis regulation in the context of mixing zones,the low-flow conditions shall refer to the min-imum amount of stream flow occurringimmediately upstream of a wastewater dis-charge and available, in whole or in part, forattenuation of wastewater pollutants.

1. Seven- (7-) day, one- (1-) in-ten- (10-)year low flow (7Q10)—The lowest averageflow for seven (7) consecutive days that has aprobable recurrence interval of once-in-ten(10) years.

2. Sixty- (60-) day, one- (1-) in-two- (2-)year low flow (60Q2)—The lowest averageflow for sixty (60) consecutive days that hasa probable recurrence interval of once-in-two(2) years.

3. Thirty- (30-) day, one- (1-) in-ten-(10-) year low flow (30Q10)—The lowestaverage flow for thirty (30) consecutive daysthat has a probable recurrence interval ofonce-in-ten (10) years.

4. One- (1-) day, one- (1-) in-ten- (10-)year low flow (1Q10)—The lowest averageflow for one (1) day that has a probablerecurrence interval of once-in-ten (10) years.

(Q) Missouri Use Designation Dataset—Adigital geospatial dataset used in conjunctionwith geographic information systems andmaintained by the department. This dataset

documents the names and locations of thestate’s rivers, streams, lakes, and reservoirswhich have been assigned designated uses.The initial version of this dataset, as adoptedon November 6, 2013, reflects Tables G andH plus any additional presumptive usesdescribed in section (2). The dataset will alsoinclude information regarding both pendingand approved determinations, variances, useattainability analyses, and water quality stan-dards revisions. The dataset uses the geospa-tial framework provided by the NationalHydrography Dataset and is enhanced andsupported by hydrological and physical infor-mation obtained through the MissouriResource Assessment Partnership (MoRAP)and other scientific sources. The dataset islimited in geographic extent to the state ofMissouri.

(R) Mixing zone—An area of dilution ofeffluent in the receiving water beyond whichchronic toxicity criteria must be met.

(S) National Hydrography Dataset(NHD)—A digital vector dataset used in con-junction with geographic information systemsto describe the location of rivers, streams,lakes, reservoirs, and other surface water fea-tures. As applied in this rule, the term refersto the 1:100,000 scale dataset generated bythe United States Geological Survey. Thisdataset provides the geospatial framework forthe Missouri Use Designation Dataset.

(T) Outstanding national resource waters—Waters which have outstanding nationalrecreational and ecological significance.These waters shall receive special protectionagainst any degradation in quality. Congres-sionally-designated rivers, including those inthe Ozark national scenic riverways and thewild and scenic rivers system, are so desig-nated (see Table D).

(U) Outstanding state resource waters—High quality waters with a significant aesthet-ic, recreational, or scientific value which arespecifically designated as such by the CleanWater Commission (see Table E).

(V) Ozark streams—Streams lying withinthe Ozark faunal region as described in theAquatic Community Classification System forMissouri, 1989, Aquatic Series No. 19, Mis-souri Department of Conservation, JeffersonCity, MO 65109, which is hereby incorporat-ed by reference and does not include any lateramendments or additions. The departmentshall maintain a copy of the referenced docu-ments and shall make them available to thepublic for inspection and copying at no morethan the actual cost of reproduction.

(W) Reference lakes or reservoirs—Lakesor reservoirs determined by Missouri Depart-ment of Natural Resources to be the bestavailable representatives of ecoregion waters

in a natural condition with respect to habitat,water quality, biological integrity and diversity,watershed land use, and riparian conditions.

(X) Reference stream reaches—Streamreaches determined by the department to bethe best available representatives of ecoregionwaters in a natural condition, with respect tohabitat, water quality, biological integrity anddiversity, watershed land use, and riparianconditions.

(Y) Regulated-flow streams—A stream thatderives a majority of its flow from animpounded area with a flow-regulatingdevice.

(Z) Use Attainability Analysis (UAA)—Astructured scientific assessment of the factorsaffecting the attainment of the use which mayinclude physical, chemical, biological, andeconomic factors as described in 40 CFR131.10(g).

(AA) Variance—A temporary modificationto 10 CSR 20-7.031 that is deemed necessaryin accordance with section (12) of this rule.

(BB) Water effect ratio—Appropriate mea-sure of the toxicity of a material obtained ina site water divided by the same measure ofthe toxicity of the same material obtainedsimultaneously in a laboratory dilution water.

(CC) Water hardness—The total concentra-tion of calcium and magnesium ionsexpressed as calcium carbonate. For purposesof this rule, hardness will be the median valueof a representative number of samples fromthe water in question or from similar watersat the appropriate stream flow conditionswithin the same ecoregion.

(DD) Water quality criteria—Chemical,physical, and biological properties of waterthat are necessary to protect beneficial wateruses.

(EE) Waters of the state—As defined insection 644.016, RSMo.

(FF) Wetlands—Those areas that are inun-dated or saturated by surface or groundwaterat a frequency and duration sufficient to sup-port, and that under normal circumstances dosupport, a prevalence of vegetation typicallyadapted for life in saturated soil conditions.Wetlands generally include swamps, marshes,bogs, and similar areas. This definition isconsistent with both the United States ArmyCorps of Engineers wetlands definition at 33CFR 328.3(b) and the United States Environ-mental Protection Agency wetlands definitionat 40 CFR 232.2(r).

(GG) Whole effluent toxicity tests—A toxi-city test conducted under specified laboratoryconditions on specific indicator organisms. Toestimate chronic and acute toxicity of theeffluent in its receiving stream, the effluentmay be diluted to simulate the computed per-cent effluent at the edge of the mixing zone or



zone of initial dilution.(HH) Zone of initial dilution—A small area

of initial mixing below an effluent outfallbeyond which acute toxicity criteria must bemet.

(II) Zone of passage—A continuous waterroute necessary to allow passage of organismswith no acutely toxic effects produced ontheir populations.

(JJ) Other definitions as set forth in theMissouri Clean Water Law and 10 CSR 20-2.010 shall apply to terms used in this rule.

(2) Designation of Uses.(A) Rebuttable presumption. Consistent

with the presumptive beneficial use protec-tions described by 40 CFR Part 131 and sec-tion 101(a)(2) of the federal Clean WaterAct—

1. All perennial rivers and streams;2. All streams with permanent pools;3. All rivers and streams included with-

in the 1:100,000 scale National HydrographyDataset (NHD) described in subsection(1)(R) of this rule; and

4. All lakes and reservoirs that intersectthe flow lines of rivers and streams identifiedin paragraph (2)(A)3. of this rule, shall bepresumed to support the following designateduses: Aquatic habitat protection; Humanhealth protection; Whole body contact recre-ation – Category B; and Secondary contactrecreation, as defined in this rule. This pre-sumption is rebuttable subject to demonstra-tion based on use attainability analyses asdescribed in subsection (2)(F) of this rule.

(B) Presumed Uses. All waters describedin subsection (2)(A) shall also be assignedLivestock and wildlife protection and Irriga-tion designated uses, as defined in this rule.

(C) Other Uses. Use designations otherthan those mentioned in subsections (2)(A)and (2)(B) of this rule may be applied towaters identified in subsection (2)(A), TableG and Table H of this rule on a site-specific,case-by-case basis following approval by theClean Water Commission and U.S. Environ-mental Protection Agency.

(D) Use Designation. Uses of waters shallbe designated as follows—

1. Designated uses applied to individualwater bodies or stream segments pursuant tosubsections (2)(A) through (2)(C) of this ruleshall include those identified in Tables G andH and in the Missouri Use DesignationDataset maintained by the department, exceptas described in paragraph (2)(D)3. of thisrule.

2. Designated uses may be assigned on acase-by-case basis to water bodies or streamsegments not otherwise represented in TablesG and H or in the Missouri Use Designation

Dataset but falling within the jurisdiction ofthe Missouri Clean Water Law.

3. Assuming reasonable evidence, pre-sumptive beneficial use protections describedabove shall not apply to water bodies withoutdesignated uses pursuant to Tables G or Hprior to November 6, 2013 that meet one ofthe following criteria:

A. Waste treatment systems, or priorconverted cropland, which are excluded fromthe federal definition of “waters of the UnitedStates” under 40 CFR 122.2; or

B. Man-made structures which wereconstructed solely to treat or convey wastew-ater; or

C. Man-made bodies of water or struc-tures which lack perennial flow and were con-structed to treat, convey, or temporarily holdor slow stormwater following precipitationevents (this may include certain structuresassociated with Best Management Practicessuch as sediment basins, wet and dry detentionbasins, bioretention basins, rain gardens,bioswales, etc.); or

D. Water bodies that lack jurisdictionunder either the federal Clean Water Act orMissouri Clean Water Law.After receiving such evidence, the departmentshall make a written determination regardingthe applicability of the above-described pre-sumptions, and such determination shall besubject to appeal pursuant to section 621.250,RSMo.

(E) Missouri Use Designation Dataset.The department shall maintain the geospatialdataset described in subsection (1)(P) of thisrule. Future revisions to water quality stan-dards in the State of Missouri shall be reflect-ed in the Missouri Use Designation Datasetand shall take effect upon approval by theClean Water Commission and U.S. Environ-mental Protection Agency.

(F) Use Attainability. Demonstrations ofuse attainability for the protection of fish,shellfish and wildlife, recreation in and onthe water, or human health protection shallassess the physical, chemical, biological,economic or other factors affecting the attain-ment of a use pursuant to 40 CFR 131.10(g).Use attainability analyses intended for otherdesignated uses shall be designed and imple-mented on a case-by-case basis. In accor-dance with 40 CFR 131.10(j), the followingpotential actions must be preceded and sup-ported by a use attainability analysis:

1. Designation of a water body for usesthat do not include the protection of fish,shellfish and wildlife, recreation in and onthe water, and human health protection;

2. Removal of one (1) or more of the usesidentified in paragraph 1. of this section; or

3. Application of any use sub-categories

for the protection of fish, shellfish andwildlife, recreation in and on the water, orhuman health protection which require lessstringent criteria.After receiving such demonstration, thedepartment shall make a written determinationregarding the use attainability analysis, andsuch determination shall be subject to appealpursuant to section 621.250, RSMo.

(3) Antidegradation. The antidegradationpolicy shall provide three (3) levels of protec-tion.

(A) Tier One. Public health, existing in-stream water uses, and a level of water qual-ity necessary to protect existing uses shall bemaintained and protected.

(B) Tier Two. For all waters of the state, ifexisting water quality is better than applicablewater quality criteria established in theserules, that existing quality shall be fullymaintained and protected. Water quality maybe lowered only if the state finds, after fullsatisfaction of the intergovernmental coordi-nation and public participation requirements,that the lowered water quality is necessary toallow important economic and social develop-ment in the geographical area in which thewaters are located. In allowing the loweringof water quality, the state shall assure thatthere shall be achieved the highest statutoryand regulatory requirements for all new andexisting point sources and all cost-effectiveand reasonable best management practices fornonpoint source control before allowing anylowering of water quality. This provisionallows a proposed new or modified point ornonpoint source of pollution to result in lim-ited lowering of water quality provided that—

1. The source does not violate any of thegeneral criteria set forth in section (4) of thisrule, or any of the criteria for protection ofbeneficial uses set forth in section (5) of thisrule;

2. The source meets all applicable tech-nological effluent limitations and minimumstandards of design for point sources or min-imum pollution control practices for nonpointsources; and

3. The lowering of water quality, in thejudgment of the department, is necessary forthe accommodation of important economicand social development in the geographicalvicinity of the discharge. In making a prelim-inary determination based on socioeconomicdevelopment considerations, the departmentmay consider the potential for regionalincreases in utility rates, taxation levels, orrecoverable costs associated with the produc-tion of goods or services that may result fromthe imposition of a strict no-degradation poli-cy. Consideration may also be given to the


Secretary of State


possible indirect effects of a policy on percapita income and the level of employment inthe geographical vicinity of the proposed pol-lution source. Any preliminary decision bythe department to allow a limited lowering ofwater quality will be stated as such in a publicnotice issued pursuant to 10 CSR 20-6.010.Pursuant to that provision, a public hearingwill be held in the geographical vicinity ofthe proposed pollution source, if the depart-ment determines there is significant publicinterest in and need for a hearing.

(C) Tier Three. There shall be no loweredwater quality in outstanding national resourcewaters or outstanding state resource waters,as designated in Tables D and E.

(D) The three (3) levels of protection pro-vided by the antidegradation policy in subsec-tions (A) through (C) of this section shall beimplemented according to procedures herebyincorporated by reference and known as the“Missouri Antidegradation Rule and Imple-mentation Procedure, July 13, 2016.” Nolater amendments or additions are included.This document shall be made available toanyone upon written request to the Depart-ment of Natural Resources, Water ProtectionProgram, Water Pollution Control Branch,PO Box 176, Jefferson City, MO 65102-0176.

(4) General Criteria. The following waterquality criteria shall be applicable to allwaters of the state at all times including mix-ing zones. No water contaminant, by itself orin combination with other substances, shallprevent the waters of the state from meetingthe following conditions:

(A) Waters shall be free from substances insufficient amounts to cause the formation ofputrescent, unsightly, or harmful bottomdeposits or prevent full maintenance of bene-ficial uses;

(B) Waters shall be free from oil, scum,and floating debris in sufficient amounts to beunsightly or prevent full maintenance of ben-eficial uses;

(C) Waters shall be free from substances insufficient amounts to cause unsightly color orturbidity, offensive odor, or prevent fullmaintenance of beneficial uses;

(D) Waters shall be free from substances orconditions in sufficient amounts to result intoxicity to human, animal, or aquatic life.However, acute toxicity criteria may beexceeded by permit in zones of initial dilu-tion, and chronic toxicity criteria may beexceeded by permit in mixing zones;

(E) Waters shall maintain a level of waterquality at their confluences to downstreamwaters that provides for the attainment andmaintenance of the water quality standards of

those downstream waters, including waters ofanother state;

(F) There shall be no significant humanhealth hazard from incidental contact with thewater;

(G) There shall be no acute toxicity to live-stock or wildlife watering;

(H) Waters shall be free from physical,chemical, or hydrologic changes that wouldimpair the natural biological community;

(I) Waters shall be free from used tires, carbodies, appliances, demolition debris, usedvehicles or equipment, and solid waste asdefined in Missouri’s Solid Waste Law, sec-tion 260.200, RSMo, except as the use ofsuch materials is specifically permitted pur-suant to sections 260.200–260.247, RSMo;

(J) Waters in mixing zones, ephemeralaquatic habitat and waters of the state lackingdesignated uses shall be subject to the follow-ing requirements:

1. The acute toxicity criteria of TablesA1, A2, and B1 and the requirements of sub-section (5)(B); and

2. The following whole effluent toxicityconditions must be satisfied:

A. Single dilution method. The per-cent effluent at the edge of the zone of initialdilution will be computed and toxicity testsperformed at this percent effluent. Thesetests must show statistically-insignificantmortality on the most sensitive of at least two(2) representative, diverse species; and

B. Multiple dilution method. An LC50will be derived from a series of test dilutions.The computed percent effluent at the edge ofthe zone of initial dilution must be less thanthree-tenths (0.3) of the LC50 for the mostsensitive of at least two (2) representative,diverse species.

(5) Specific Criteria. The specific criteriashall apply to waters contained in Tables Gand H of this rule and the Missouri Use Des-ignation Dataset. Protection of drinking watersupply is limited to surface waters designatedfor raw drinking water supply and aquifers.Protection of whole body contact recreationis limited to waters designated for that use.

(A) The maximum chronic toxicity criteriain Tables A1, A2, B2, and B3 shall apply towaters designated for the indicated uses givenin the Missouri Use Designation Dataset andTables G and H. All Table A1, A2, B2, andB3 criteria are chronic toxicity criteria,except those specifically identified as acutecriteria. Water contaminants shall not causeor contribute to concentrations in excess ofthese values. Table A1 values listed as healthadvisory levels shall be used in establishingdischarge permit limits and managementstrategies until additional data becomes avail-

able to support alternative criteria, or otherstandards are established. However, excep-tions may be granted in the following cases:

1. Permanent flow streams when thestream flow is less than 7Q10;

2. Regulated flow streams if the flow isless than the minimum release flow agreedupon by the regulating agencies;

3. For the natural and unavoidablechemical and physical changes that occur inthe hypolimnion of lakes. Streams belowimpoundments shall meet applicable specificcriteria;

4. For mixing zones.A. The mixing zone shall be exempt-

ed from the chronic criteria requirements ofthis section for those components of wastethat are rendered nontoxic by dilution, dissi-pation, or rapid chemical transformation.Acute numeric criteria of Tables A1, A2, andB1 and whole effluent acute toxicity require-ments of subsection (4)(I) must be met at alltimes within the mixing zone, except withinthe zone of initial dilution. The following cri-teria do not apply to thermal mixing zones.Criteria for thermal mixing zones are listed inparagraph (5)(D)6.

B. The maximum size of mixingzones and zones of initial dilution will bedetermined as follows (the size may berefined by the use of mixing zone models,e.g. CORMIX, as appropriate):

(I) Streams with 7Q10 low flows ofless than one-tenth cubic foot per second (0.1cfs)—

(a) Mixing zone—not allowed;and

(b) Zone of initial dilution—notallowed;

(II) Streams with 7Q10 low flow ofone-tenth to twenty cubic feet per second(0.1–20 cfs)—

(a) Mixing zone—one-quarter(1/4) of the stream width, cross-sectionalarea, or volume of flow; length one-quarter(1/4) mile. If the discharger can documentthat rapid and complete mixing of the effluentoccurs in the receiving stream, the mixingzone may be up to one-half (1/2) of thestream width, cross-sectional area, or volumeof flow; and

(b) Zone of initial dilution—one-tenth (0.1) of the mixing zone width, cross-sectional area, or volume of flow;

(III) Streams with 7Q10 low flowof greater than twenty cubic feet per second(20 cfs)—

(a) Mixing zone—one-quarter(1/4) of stream width, cross-sectional area, orvolume of flow; length of one-quarter (1/4)mile. If the discharger can document that rapidand complete mixing of the effluent occurs in



the receiving stream, the mixing zone may beup to one-half (1/2) of the stream width,cross-sectional area, or volume of flow; and

(b) Zone of initial dilution—one-tenth (0.1) of the mixing zone width, cross-sectional area, or volume of flow and nomore than ten (10) times the effluent designflow volume unless the use of diffusers orspecific mixing zone studies can justify moredilution; and

(IV) Lakes—(a) Mixing zone—not to exceed

one-quarter (1/4) of the lake width at the dis-charge point or one hundred feet (100') fromthe discharge point, whichever is less; and

(b) Zone of initial dilution—notallowed.

C. A mixing zone shall not overlapanother mixing zone in a manner that themaintenance of aquatic life in the body ofwater in the overlapping area would be fur-ther adversely affected.

D. Other factors that may prohibit orfurther limit the size and location of mixingzones are the size of the river, the volume ofdischarge, the stream bank configuration, themixing velocities, other hydrologic or physio-graphic characteristics, and the designateduses of the water, including type of aquaticlife supported, potential effects on mouths oftributary streams, and proximity to watersupply intakes.

E. Zones of passage must be providedwherever mixing zones are allowed.

F. Mixing zone and zone of initialdilution size limits will normally be based onstreams at the 7Q10 low flow. However, thispercent of stream size limits also applies athigher stream flows and discharge limitationsmay be based on higher stream flows if dis-charge volume or quality may be adjusted tocorrelate with stream flow; and

5. For wetlands. Water quality needswill vary depending on the individual charac-teristics of the wetland. Application ofnumeric criteria will depend on the specificaquatic life, wildlife, and vegetation require-ments.

A. Specific criteria for wetlands shallbe developed using scientific proceduresincluding, but not limited to, those proce-dures described in the U.S. EnvironmentalProtection Agency’s Water Quality StandardsHandbook, Second Edition, August 1994 aspublished by the Office of Science and Tech-nology, Office of Water, U.S. EnvironmentalProtection Agency, Washington, DC 20460,which are hereby incorporated by referenceand do not include any later amendments oradditions. The department shall maintain acopy of the referenced documents and shallmake them available to the public for inspec-

tion and copying at no more than the actualcost of reproduction.

B. Specific criteria shall protect alllife stages of species associated with wetlandsand prevent acute and chronic toxicity in allparts of the wetland.

C. Specific criteria shall include bothchronic and acute concentrations to betterreflect the different tolerances to the inherentvariability between concentrations and toxi-cological characteristics of a condition.

D. Specific criteria shall be clearlyidentified as maximum “not to be exceeded”or average values, and if an average, the aver-aging period and the minimum number ofsamples. The conditions, if any, when the cri-teria apply shall be clearly stated (e.g., spe-cific levels of hardness, pH, or water temper-ature). Specific sampling requirements (e.g.,location, frequency), if any, shall also beidentified.

E. The data, testing procedures, andapplication (safety) factors used to developspecific criteria shall reflect the nature of thecondition (e.g., persistency, bioaccumulationpotential) and the most sensitive species asso-ciated with the wetland.

F. Each specific criterion shall be pro-mulgated in rule 10 CSR 20-7.031. The pub-lic notice shall include a description of theaffected wetland and the reasons for applyingthe proposed criterion. A public hearing maybe held in the geographical vicinity of theaffected wetland. Any specific criterion pro-mulgated under these provisions is subject toU.S. Environmental Protection Agencyapproval prior to becoming effective.

(B) Toxic Substances.1. Water contaminants shall not cause

the criteria in Tables A1, A2, B1, B2, and B3to be exceeded. Concentrations of these sub-stances in bottom sediments or waters shallnot harm benthic organisms and shall notaccumulate through the food chain in harmfulconcentrations, nor shall state and federalmaximum fish tissue levels for fish consump-tion be exceeded. More stringent criteria maybe imposed if there is evidence of additive orsynergistic effects.

2. For compliance with this rule, metalsshall be analyzed by the following methods:

A. Aquatic life protection and humanhealth protection—

(I) Mercury—total recoverable met-als; and

(II) All other metals—dissolvedmetals;

B. Drinking water supply—total recov-erable metals; and

C. All other beneficial uses—totalrecoverable metals.

3. Other potentially toxic substances for

which sufficient toxicity data are not availablemay not be released to waters of the stateuntil safe levels are demonstrated throughadequate bioassay studies.

4. Drinking water criteria, for sub-stances which are rendered nontoxic by trans-formation processes in the surface waterbody, shall apply at water supply withdrawalpoints.

5. Site-specific alternative criteria forhuman health protection may be allowed.Designation of these site-specific criteriamust follow procedures set forth in U.S.Environmental Protection Agency’s Method-ology for Deriving Ambient Water QualityCriteria for the Protection of Human Health,October 2000 (EPA-822-B-00-004), as pub-lished by the Office of Science and Technol-ogy, Office of Water, U.S. EnvironmentalProtection Agency, Washington, DC 20460,which is hereby incorporated by referenceand does not include any later amendments oradditions. The department shall maintain acopy of the referenced document and shallmake it available to the public for inspectionand copying at no more than the actual costof reproduction.

6. Metals criteria for which toxicity ishardness dependent are in equation format inTable A2.

7. Total ammonia nitrogen. For anygiven sample, the total ammonia nitrogen cri-teria shall be based on the pH and tempera-ture of the water body measured at the timeof each sample at the point of compliance.

A. The acute criteria shall not beexceeded at any time except in those watersfor which the department has allowed a zoneof initial dilution (ZID). The one- (1-) dayQ10 low flow condition will be used in deter-mining acute total ammonia nitrogen criteria.

B. The chronic criteria shall not beexceeded except in water segments for whichthe department has allowed a mixing zone(MZ). The chronic criteria shall be based ona thirty- (30-) day exposure period. There-fore, the thirty- (30-) day Q10 low flow condi-tion of the receiving water body will be usedin determining chronic total ammonia nitro-gen criteria.

C. Without sufficient and reliabledata, it is assumed that early life stages arepresent and must be protected at all times ofthe year.

(I) Sufficient and reliable data shallinclude, but are not limited to, seasonal stud-ies on the fish species distributions, spawningperiods, nursery periods, duration of sensitivelife stages, and water body temperature. Bestprofessional judgment from fishery biologistsand other scientists will be considered asappropriate.


Secretary of State


(II) The time frames during theyear when early life stages are considered tobe absent are those time periods when earlylife stages are present in numbers that, ifchronic toxicity did occur, would not affectthe long-term success of the populations.

(III) A source of information fordetermining the duration of early life stages isThe American Society for Testing and Mate-rials (ASTM) Standard E-1241, “StandardGuide for Conducting Early Life-Stage Toxi-city Tests with Fishes.”

(IV) Protection of early life stagesshould include the most sensitive species thathave used a water body for spawning andrearing since November 28, 1975.

(C) Bacteria. The protection of whole bodycontact recreation is limited to waters desig-nated for that use. The recreational season isfrom April 1 to October 31. The E. colicount shall not exceed the criterion listed inTable A1 as a geometric mean during therecreational season in waters designated forwhole body contact recreation. The E. colicount shall not exceed one hundred twenty-six (126) per one hundred milliliters (100mL) at any time in losing streams. For watersdesignated for secondary contact recreation,the E. coli count shall not exceed one thou-sand one hundred thirty-four (1,134) per onehundred milliliters (100 mL) as a geometricmean during the recreational season.

(D) Temperature.1. For warm water habitats beyond the

mixing zone, water contaminant sources andphysical alteration of the water course shallnot raise or lower the temperature of a streammore than five degrees Fahrenheit (5 °F) ortwo and seven-ninths degrees Celsius (2 7/9°C). Water contaminant sources shall notcause or contribute to stream temperature inexcess of ninety degrees Fahrenheit (90 °F)or thirty-two and two-ninths degrees Celsius(32 2/9 °C). However, site-specific ambienttemperature data and requirements of sensi-tive resident aquatic species will be consid-ered, when data are available, to establishalternative maxima or deviations from ambi-ent temperatures.

2. For cool water habitats beyond themixing zone, water contaminant sources andphysical alteration of the water course shallnot raise or lower the temperature of a streammore than five degrees Fahrenheit (5 °F) ortwo and seven-ninths degrees Celsius (2 7/9°C). Water contaminant sources shall notcause or contribute to stream temperature inexcess of eighty-four degrees Fahrenheit (84°F) or twenty-eight and eight-ninths degreesCelsius (28 8/9 °C).

3. For cold water habitats beyond themixing zone, water contaminant sources and

physical alteration of the water course shallnot raise or lower the temperature of thewater body more than two degrees Fahrenheit(2 °F) or one and one-ninth degrees Celsius(1 1/9 °C). Water contaminant sources shallnot cause or contribute to temperatures abovesixty-eight degrees Fahrenheit (68 °F) ortwenty degrees Celsius (20 °C).

4. Water contaminant sources shall notcause any measurable rise in the temperatureof lakes. An increase is allowable for LakeSpringfield, Thomas Hill Reservoir, andMontrose Lake; however, discharges fromthese lakes must comply with temperaturelimits for streams.

5. For the Mississippi River Zones 1Aand 2, the water temperature outside the mix-ing zone shall not exceed the maximum limitsindicated in the following list during morethan one percent (1%) of the time in any cal-endar year. In Zone 1B, limits may not beexceeded more than five percent (5%) of thetime in a calendar year. At no time shall theriver water temperature outside of the ther-mal mixing zone exceed the listed limits bymore than three degrees Fahrenheit (3 °F) orone and six-ninths degrees Celsius (1 6/9°C).

A and B C (°F) (°C) (°F) (°C)January 45 7 2/9 50 10February 45 7 2/9 50 10March 57 13 8/9 60 15 5/9April 68 20 70 21 1/9May 78 25 5/9 80 26 6/9June 86 30 87 30 5/9July 88 31 1/9 89 31 6/9August 88 31 1/9 89 31 6/9September 86 30 87 30 5/9October 75 23 8/9 78 25 5/9November 65 18 3/9 70 21 1/9December 52 11 1/9 57 13 8/9

A = Zone 1A—Des Moines River to Lockand Dam No. 25.B = Zone 1B—Lock and Dam No. 25 toLock and Dam No. 26. C = Zone 2—Lock and Dam No. 26 to theMissouri-Arkansas state line.

6. Thermal mixing zones shall be limit-ed to twenty-five percent (25%) of the cross-sectional area or volume of a river, unlessbiological surveys performed in response tosection 316(a) of the federal Clean Water Act(or equivalent) indicate no significant adverseimpact on aquatic life. Thermal plumelengths and widths within rivers, and allplume dimensions within lakes, shall bedetermined on a case-by-case basis and shallbe based on physical and biological surveys

when appropriate.(E) pH. Water contaminants shall not

cause the four- (4-) day average pH concen-tration of representative samples to be outsideof the range of 6.5 to 9.0 standard pH units(chronic toxicity).

(F) Taste- and Odor-Producing Substances.Taste- and odor-producing substances shallbe limited to concentrations in the streams orlakes that will not interfere with beneficialuses of the water. For those streams and lakesdesignated for drinking water supply use, thetaste- and odor-producing substances shall belimited to concentrations that will not inter-fere with the production of potable water byreasonable water treatment processes.

(G) Turbidity and Color. Water contami-nants shall not cause or contribute to turbidi-ty or color that will cause substantial visiblecontrast with the natural appearance of thestream or lake or interfere with beneficialuses.

(H) Solids. Water contaminants shall notcause or contribute to solids in excess of alevel that will interfere with beneficial uses.The stream or lake bottom shall be free ofmaterials which will adversely alter the com-position of the benthos, interfere with thespawning of fish or development of theireggs, or adversely change the physical orchemical nature of the bottom.

(I) Radioactive Materials. All streams andlakes shall conform to state and federal limitsfor radionuclides established for drinkingwater supply.

(J) Dissolved Oxygen. Water contaminantsshall not cause the dissolved oxygen to belower than the levels described in Table A1.

(K) Total Dissolved Gases. Operation ofimpoundments shall not cause the total dis-solved gas concentrations to exceed one hun-dred ten percent (110%) of the saturationvalue for gases at the existing atmosphericand hydrostatic pressures.

(L) Sulfate and Chloride Limit for Protec-tion of Aquatic Life.

1. Streams with 7Q10 low flow of lessthan one cubic foot per second (1 cfs). Theconcentration of chloride plus sulfate shallnot exceed one thousand milligrams per liter(1,000 mg/L). Table A1 includes additionalchloride criteria.

2. Streams with 7Q10 low flow of morethan one cubic foot per second (1 cfs) andClass P1, L1, L2, and L3 waters. The totalchloride plus sulfate concentration shall notexceed the estimated natural background con-centration by more than twenty percent(20%) at the 60Q10 low flow.

(M) Carcinogenic Substances. Carcino-genic substances shall not exceed concentra-tions in water which correspond to the 10-6



cancer risk rate. This risk rate equates to one(1) additional cancer case in a population ofone (1) million with lifetime exposure.Derivation of this concentration assumesaverage water and fish consumption amounts.Assumptions are two (2) liters of water andsix and one-half (6.5) grams of fish con-sumed per day. Federally established finalmaximum contaminant levels for drinkingwater supply shall supersede drinking watersupply criteria developed in this manner.

(N) Nutrients and Chlorophyll.1. Definitions.

A. For the purposes of these criteria,all lakes and reservoirs shall be referred to as“lakes.”

B. Lake ecoregions—Due to differ-ences in watershed topography, soils, andgeology, nutrient criteria for lakes and reser-voirs will be determined by the use of four (4)major ecoregions based upon dominantwatershed ecoregion. These regions weredelineated by grouping the ecological subsec-tions described in Nigh and Schroeder, 2002,Atlas of Missouri Ecoregions, as follows:

(I) Plains: OP1 – Scarped OsagePlains; OP2 – Cherokee Plains; TP2—DeepLoess Hills; TP3—Loess Hills; TP4— GrandRiver Hills; TP5—Chariton River Hills;TP6—Claypan Till Plains; TP7—WyacondaRiver Dissected Till Plains; TP8— Mississip-pi River Hills;

(II) Ozark Border: MB2a—Crow-ley’s Ridge Loess Woodland/Forest Hills;OZ11—Prairie Ozark Border; OZ12— OuterOzark Border; OZ13—Inner Ozark Border;

(III) Ozark Highland: OZ1—Spring-field Plain; OZ2—Springfield Plateau; OZ3—Elk River Hills; OZ4—White River Hills;OZ5—Central Plateau; OZ6—Osage RiverHills; OZ7—Gasconade River Hills; OZ8—Meramec River Hills; OZ9—Current RiverHills; OZ10—St. Francois Knobs and Basins;OZ14—Black River Ozark Border; and

(IV) Big River Floodplain: MB1—Black River Alluvial Plain; MB2b—Crow-ley’s Ridge Footslopes and Alluvial Plains;MB3—St. Francis River Alluvial Plain;MB4, OZ16, TP9—Mississippi River Allu-vial Plain; OZ15, TP1—Missouri River Allu-vial Plain.

C. Nutrient Criteria—Nutrient crite-ria represent the desired condition for a waterbody necessary to protect the designated usesassigned in rule.

(I) Lake Ecoregion Criteria—Adecision framework that integrates causal andresponse parameters into one water qualitystandard that accounts for uncertainty in link-ages between causal and response parameters.

(a) Response Impairment Thresh-olds—Maximum ambient concentrations of

chlorophyll-a (Chl-a) that are based on annualgeometric means of samples collected Maythrough September with an allowableexceedance frequency of one in three (1-in-3)years for lakes that have not been assignedsite-specific criteria.

(b) Nutrient Screening Thresh-olds—Maximum ambient concentrations oftotal phosphorus (TP), total nitrogen (TN),and Chl-a that are based on the annual geo-metric mean of samples collected Maythrough September. Nutrient screening thresh-olds represent causal and response parameterconcentrations, above which an exceedance inany one year warrants further evaluation ofResponse Assessment Endpoints.

(c) Response Assessment End-points—Narrative and numeric biologicalresponse endpoints that link directly to desig-nated use impairment.

(II) Lake Site-Specific Criteria—Maximum Ambient Concentrations of TP,TN, or Chl-a that are based on the geometricmean of a minimum of three (3) years of dataand the characteristics of the waterbody.

2. This rule applies to all lakes that arewaters of the state and have an area of at leastten (10) acres during normal pool condition.Big River Floodplain lakes shall not be sub-ject to these criteria.

3. Response Impairment Thresholds arelisted in Table L. Nutrient Screening Thresh-olds are listed in Table M. Lake Site-SpecificCriteria for TP, TN, and Chl-a are listed inTable N. Additional lake site-specific criteriamay be developed in accordance with subsec-tion (5)(S) to account for the unique charac-teristics of the waterbody that affect trophicstatus, such as lake morphology, hydraulicresidence time, temperature, internal nutrientcycling, or watershed contribution from mul-tiple ecoregions.

4. All TP, TN, and Chl-a concentrationsmust be calculated as the geometric mean ofa minimum of four (4) representative samplesper year for one (1) year for purposes of com-parison to lake ecoregion criteria thresholds.All samples must be collected from the lakesurface, near the outflow of the lake, and dur-ing the period May 1 – September 30.

5. Lakes with water quality that exceedResponse Impairment Thresholds or LakeSite-Specific Criteria identified in Tables Land N are to be deemed impaired for excessnutrients.

6. Lakes are to be deemed impaired forexcess nutrients if any of the followingResponse Assessment Endpoints are docu-mented to occur within the same year as anexceedances of Nutrient Screening Thresholdsin Table M. The department shall collectinformation on Response Assessment End-

points concurrently with collection of NutrientScreening Threshold parameters. The depart-ment shall determine attainment of NutrientCriteria during the biennial assessment ofMissouri waters.

A. Occurrence of eutrophication-related mortality or morbidity events for fishand other aquatic organisms;

B. Epilimnetic excursions from dis-solved oxygen or pH criteria;

C. Cyanobacteria counts in excess ofone hundred thousand (100,000) cells permilliliter (cells/mL);

D. Observed shifts in aquatic diversi-ty attributed to eutrophication; and

E. Excessive levels of mineral turbid-ity that consistently limit algal productivityduring the period May 1 – September 30.

(O) All methods of sample collection,preservation, and analysis used in applyingcriteria in these standards shall be in accordwith those prescribed in the latest edition ofStandard Methods for the Examination ofWater and Wastewater or other proceduresapproved by the Environmental ProtectionAgency and the Missouri Department of Nat-ural Resources.

(P) Criteria to protect designated uses arebased on current technical literature, espe-cially the Environmental Protection Agency’spublication, Quality Criteria for Water,1986. Criteria may be modified or expandedas additional information is developed or asneeded to define narrative criteria for partic-ular situations or locations.

(Q) WET Chronic Tests. Chronic WETtests performed at the percent effluent at theedge of the mixing zone shall not be toxic tothe more sensitive of at least two (2) repre-sentative, diverse species. Pollutant attenua-tion processes such as volatilization andbiodegradation which may occur within theallowable mixing zone will be considered ininterpreting results.

(R) Biocriteria. The biological integrity ofwaters, as measured by lists or numericindices of benthic invertebrates, fish, algae, orother appropriate biological indicators, shallnot be significantly different from referencewaters. Waters targeted for numeric biologicalcriteria assessment must be contained withinthe Missouri Use Designation Dataset andshall be compared to reference waters of sim-ilar size, scale within the stream network,habitat type, and aquatic ecoregion type. Ref-erence water locations for some aquatic habi-tat types are listed in Table I.

(S) Site-Specific Criteria Development forthe Protection and Propagation of Fish, Shell-fish, and Wildlife. When water quality crite-ria in this regulation are either underprotec-tive or overprotective of water quality due to


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factors influencing bioavailability, or nonan-thropogenic conditions for a given waterbody segment, a petitioner may request site-specific criteria. The petitioner must providethe department with sufficient documentationto show that the current criteria are not ade-quate and that the proposed site-specific cri-teria will protect all existing and/or potentialuses of the water body.

1. Site-specific criteria may be appropri-ate where, but is not limited to, the examplesgiven in subparagraphs A. or B. of this para-graph.

A. The resident aquatic species of theselected water body have a different degree ofsensitivity to a specific pollutant as comparedto those species in the data set used to calcu-late the national or state criteria as describedin either of the following parts:

(I) Natural adaptive processes haveenabled a viable, balanced aquatic communi-ty to exist in waters where natural (non-anthropogenic) background conditions exceedthe criterion (e.g., resident species haveevolved a genetically-based greater toleranceto high concentrations of a chemical); or

(II) The composition of aquaticspecies in a water body is different from thoseused in deriving a criterion (e.g., most of thespecies considered among the most sensitive,such as salmonids or the cladoceran, Cerio-daphinia dubia, which were used in develop-ing a criterion, are absent from a water body).

B. The physical and/or chemical char-acteristics of the water body alter the biologi-cal availability and/or toxicity of the pollutant(e.g., pH, alkalinity, salinity, water tempera-ture, hardness). Such an example is the WaterEffect Ratio (WER) defined at (1)(BB) of thisrule.

2. All petitioners seeking to develop site-specific criteria shall coordinate with thedepartment early in the process. This coordi-nation will ensure the use of adequate, rele-vant, and quality data; proper analysis andtesting; and defendable procedures.

A. The department will provide guid-ance for establishing site-specific water qual-ity criteria using scientific procedures includ-ing, but not limited to, those proceduresdescribed in:

(I) U.S. Environmental ProtectionAgency’s Water Quality Standards Hand-book, Second Edition, August 1994;

(II) U.S. Environmental ProtectionAgency’s Interim Guidance on Determinationand Use of Water-Effect Ratios for Metals(EPA-823-B-94-001) and subsequent 1997modifications;

(III) U.S. Environmental Protec-tion Agency’s Streamlined Water-Effect RatioProcedure for Discharges of Copper (EPA-

822-R-01-005); and(IV) U.S. Environmental Protec-

tion Agency’s Aquatic Life Ambient Freshwa-ter Quality Criteria – Copper 2007 Revision(EPA-822-R-07-001).

B. Site-specific criteria developmentfor the Protection and Propagation of Fish,Shellfish, and Wildlife shall be performedusing the guidance documents listed in parts(5)(S)2.A.(I)–(IV) as published by the Officeof Science and Technology, Office of Water,U.S. Environmental Protection Agency, Wash-ington, DC 20460, which are hereby incorpo-rated by reference and do not include any lateramendments or additions. The departmentshall maintain a copy of the referenced docu-ments and shall make them available to thepublic for inspection and copying at no morethan the actual cost of reproduction.

3. Site-specific criteria shall protect alllife stages of resident species and preventacute and chronic toxicity in all parts of awater body.

4. Site-specific criteria shall include bothchronic and acute concentrations to betterreflect the different tolerances of residentspecies to the inherent variability betweenconcentrations and toxicological characteris-tics of a chemical.

5. Site-specific criteria shall be clearlyidentified as maximum “not to be exceeded”or average values, and if an average, the aver-aging period and the minimum number ofsamples. The conditions, if any, when the cri-teria apply shall be clearly stated (e.g., spe-cific levels of hardness, pH, or water temper-ature). Specific sampling requirements (e.g.,location, frequency), if any, shall also beidentified.

6. The data, testing procedures, andapplication (safety) factors used to developsite-specific criteria shall reflect the nature ofthe chemical (e.g., persistency, bioaccumula-tion potential, and avoidance or attractionresponses in fish) and the most sensitive resi-dent species of a water body.

7. The size of a site may be limited to asingle water segment, single water subseg-ment, or may cover a whole watersheddepending on the particular situation forwhich the specific criterion is developed. Agroup of water bodies may be considered one(1) site if their respective aquatic communitiesare similar in composition and have compara-ble water quality.

8. The department shall determine if asite-specific criterion is adequate and justifi-able. The public notice shall include a descrip-tion of the affected water body or water bodysegment and the reasons for applying the pro-posed criterion. If the department determinesthat there is significant public interest, a pub-

lic hearing may be held in the geographicalvicinity of the affected water body or waterbody segment. Any site-specific criterion pro-mulgated under these provisions is subject toU.S. Environmental Protection Agencyapproval prior to becoming effective for CleanWater Act purposes.

(6) Groundwater.(A) Water contaminants shall not cause or

contribute to exceedence of Table A1,groundwater limits in aquifers and caves.Table A1 values listed as health advisory lev-els shall be used in establishing managementstrategies and groundwater cleanup criteria,until additional data becomes available tosupport alternative criteria or other standardsare established. Substances not listed in TableA1 shall be limited so that drinking water,livestock watering, and irrigation uses areprotected.

(B) When criteria for the protection ofaquatic life or human health protection inTable A1 are more stringent than groundwa-ter criteria, appropriate criteria for the pro-tection of aquatic life or human health shallapply to waters in caves and to aquifers whichcontribute an important part of base flow ofsurface waters designated for aquatic life pro-tection. Other substances not listed in TableA1 shall be limited in these aquifers andcaves so that the aquatic life use is protected.

(C) Groundwater and other criteria shallapply in any part of the aquifer, including thepoint at which the pollutant enters theaquifer. A specific monitoring depth require-ment for releases to aquifers is included in 10CSR 20-7.015(7)(A).

(D) For aquifers in which contaminantconcentrations exceed groundwater criteria orother protection criteria, and existing andpotential uses are not impaired, alternativesite-specific criteria may be allowed. To allowalternative criteria, the management authoritymust demonstrate that alternative criteria willnot impair existing and potential uses. Thedemonstration must consider the factors andbe subject to the review requirements of 10CSR 20-7.015(7)(F).

(7) Metropolitan No-Discharge Streams. Nowater contaminant except uncontaminatedcooling water, permitted stormwater dis-charges in compliance with permit condi-tions, and excess wet-weather bypass dis-charges not interfering with beneficial usesshall be discharged to the watersheds ofstreams listed in Table F. Existing interimdischarges may be allowed until interceptorsare available within two thousand feet(2,000') or a distance deemed feasible by thedepartment, or unless construction of outfalls



to alternative receiving waters not listed inTable F is deemed feasible by the department.Existing discharges include wastewater vol-umes up to the design capacity of existingpermitted treatment facilities, includingphased increases in design capacity approvedby the department prior to the effective dateof this rule. Additional facilities may be con-structed to discharge to these waters only ifthey are intended to be interim facilities inaccordance with a regional wastewater treat-ment plan approved by the department.

(8) Outstanding National Resource Waters.Under section (3), antidegradation section ofthis rule, new releases to outstanding nationalresource waters from any source are prohibit-ed, and releases from allowed facilities aresubject to special effluent limitations asrequired in 10 CSR 20-7.015(6). Table Dcontains a list of the outstanding nationalresource waters in Missouri.

(9) Outstanding State Resources Waters. Thecommission wishes to recognize certain high-quality waters that may require exceptionallystringent water-quality management require-ments to assure conformance with theantidegradation policy. The degree of man-agement requirements will be decided on anindividual basis. To qualify for inclusion, allof the following criteria must be met. Thewaters listed in Table E must—

(A) Have a high level of aesthetic or scien-tific value;

(B) Have an undeveloped watershed; and(C) Be located on or pass through lands

which are state or federally owned, or whichare leased or held in perpetual easement forconservation purposes by a state, federal, orprivate conservation agency or organization.

(10) Lake Taneycomo. The commission wish-es to recognize the uniqueness of Lake Taney-como with respect to its high water clarity, itsimportance as a trout fishery, and as the cen-tral natural resource in the rapidly developingBranson area and threats to the lake’s waterquality imposed by development. An espe-cially stringent antidegradation policy will beobserved in the development of effluent rules,discharge permits, and nonpoint-source man-agement plans and permits to assure that thehigh visual quality and aquatic resources aremaintained. The use of the best treatmenttechnology for point- and nonpoint-sourcedischarges in the lake’s watershed betweenTable Rock Lake and Power Site Dam will bethe guiding principle in establishing limita-tions.

(11) Compliance with Water Quality Based

Limitations. Compliance with new or revisedNational Pollutant Discharge EliminationSystem (NPDES) or Missouri operating per-mit limitations based on criteria in this ruleshall be achieved in accordance with federalregulation at 40 CFR Part 122.47, “Sched-ules of Compliance,” May 15, 2000, as pub-lished by the Office of the Federal Register,National Archives and Records Administra-tion, Superintendent of Documents, Pitts-burgh, PA 15250-7954, which is herebyincorporated by reference and does notinclude any later amendments or additions.The department shall maintain a copy of thereferenced document and shall make it avail-able to the public for inspection and copyingat no more than the actual cost of reproduc-tion.

(12) Water Quality Standards Variances. Apermittee or an applicant for a National Pol-lutant Discharge Elimination System(NPDES) or Missouri state operating permitmay pursue a temporary variance pursuant toeither section 644.061 or section 644.062,RSMo. A variance from water quality stan-dards shall comply with 40 CFR 131.14.

(A) Each variance shall be granted onlyafter public notification and opportunity forpublic comment. Once any variance to waterquality standards is granted, the departmentshall submit the variance, with an AttorneyGeneral Certification that the Clean WaterCommission adopted the variance in accor-dance with state law, to the U.S. Environ-mental Protection Agency for approval.

(B) Individual variances may be grantedusing the terms, conditions, and proceduresfound in the “Missouri Multiple DischargerVariance Framework from the Water QualityStandards of Total Ammonia Nitrogen,CWC-MDV-1-17,” finalized by the depart-ment on September 15, 2017, which is incor-porated by reference and does not include anylater amendments or additions. The depart-ment shall maintain a copy of the referenceddocuments and shall make them available tothe public for inspection and copying at nomore than the actual cost of reproduction.

(C) Variance terms and conditions, includ-ing facility name, permit number, receivingstream name, first classified water body ID,discharge location, highest attainable condi-tion, effective permit date, and the varianceexpiration date will be incorporated into theMissouri Use Designation Dataset and TableJ.

(13) Losing Streams.(A) Losing stream determinations will usu-

ally be made upon the first application fordischarge to a specific water or location with-

in a watershed for a wastewater treatmentfacility, subdivision development, or animalwaste management facility.

(B) Permits or other approvals for thoseapplications will be processed in accordancewith the determinations. Additional permitsor approvals will be processed in accordancewith the latest determination.

(C) For application purposes, any pro-posed facility within five (5) miles of aknown losing stream segment should presumethat facility’s receiving stream segment isalso losing until and unless a specific geolog-ic evaluation is made of that stream and con-cludes the stream segment is gaining.

(D) Existing facilities operating under astate operating permit and new facilitiesbeing constructed under a construction per-mit in proximity to stream segments subse-quently determined to be losing will beallowed to continue in operation at permittedor approved effluent limits for a period oftime lasting the design life of the facility(usually twenty (20) years from the originalconstruction completion), provided the facili-ty is in compliance with its effluent limits andremains in compliance with those limits, andif neither of the following conditions is pre-sent:

1. If the discharge from such a facilitycan be eliminated by connection to a locallyavailable facility, the facility shall be connect-ed within three (3) years of the losing streamdetermination. A local facility shall be con-sidered available if that facility or an inter-ceptor is within two thousand feet (2000') ora distance deemed feasible by the depart-ment; and

2. If the discharge from such a facility isshown to cause pollution of groundwater, thefacility shall be upgraded to appropriate efflu-ent standards within three (3) years. Thedepartment shall include appropriate ground-water monitoring requirements in permits forany such facilities so that pollution, should itoccur, would be detected.

(E) Any additional permits or approvals forincreased treatment plant design capacity willbe processed in accordance with the newestlosing stream determination. No additionalpermits or approvals for any facilities shall beconstrued as lengthening the time for compli-ance with losing stream effluent limitationsas established in subsection (13)(D).

(14) Severance. If a section, subsection, para-graph, sentence, clause, phrase, or any partof this rule be declared unconstitutional orinvalid for any reason, the remainder of thisrule shall not be affected and shall remain infull force and effect.


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(15) Effective Date. This rule becomes effec-tive immediately upon adoption and compli-ance with the requirements of subsection644.036.3., RSMo, of the Missouri CleanWater Law and Chapter 536, RSMo.


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