11 Miss. Code. R. 6-2.2 - Minimum Conditions Applicable to All Surface Waters of the State | State Regulations | US Law

A. Narrative Standards:

(1) Waters shall be free from substances attributable to municipal, industrial, agricultural, or other discharges that will settle to form putrescent or otherwise objectionable sludge deposits.

(2) Waters shall be free from floating debris, oil, scum, and other floating materials attributable to municipal, industrial, agricultural, or other discharges in amounts sufficient to be unsightly or deleterious.

(3) Waters shall be free from materials attributable to municipal, industrial, agricultural, or other discharges producing color, odor, taste, total suspended or dissolved solids, sediment, turbidity, or other conditions in such degree as to create a nuisance, render the waters injurious to public health, recreation, or to aquatic life and wildlife, or adversely affect the palatability of fish, aesthetic quality, or impair the waters for any designated use. Except as prohibited in Rule 2.5.C., the turbidity outside the limits of a 750-foot mixing zone shall not exceed the background turbidity at the time of discharge by more than 50 Nephelometric Turbidity Units (NTU). Exemptions to the turbidity standard may be granted under the following circumstances:

(a) in cases of emergency to protect the public health and welfare

(b) for environmental restoration projects which will result in reasonable and temporary deviations and which have been reviewed and approved by the Department of Environmental Quality.

(4) Waters shall be free from substances attributable to municipal, industrial, agricultural, or other discharges in concentrations or combinations that are toxic or harmful to humans, animals, or aquatic life. Specific requirements for toxicity are found in Rule 2.2.F.

(5) Municipal wastes, industrial wastes, or other wastes shall receive effective treatment or control in accordance with Section 301, 306, and 307 of the Clean Water Act. A degree of treatment greater than defined in these sections may be required when necessary to protect designated uses.

B. Waterbody Classifications and Designated Uses: The State of Mississippi assigns one or more waterbody classifications to all Surface Waters of the State. Each waterbody classification has one or more corresponding designated uses. The waterbody classifications and corresponding designated uses are provided in Table 1. All Surface Waters of the State default to the Fish and Wildlife Classification. Any waterbody classified as Public Water Supply, Recreation, or Shellfish Harvesting shall meet not only the criteria to support its respective classification, but also shall meet the criteria to support the Fish and Wildlife Classification.

Table 1. Mississippi Waterbody Classifications and Designated Uses

MS Waterbody Classifications	U.S. EPA Associated Designated Uses
Fish and Wildlife	Aquatic Life Use* Fish Consumption* Secondary Contact Recreation
Recreation	Primary Contact Recreation*
Public Water Supply	Drinking Water Supply*
Shellfish Harvesting	Shellfish Consumption*
Modified Fish and Wildlife	Aquatic Life Use-Modified Fish Consumption* Secondary Contact Recreation
Drainage Waters	Aquatic Life Use-Drainage Waters Fish Consumption* Secondary Contact Recreation
Outstanding Mississippi Water**	Aquatic Life Use* Fish Consumption* Secondary Contact Recreation

* Denotes designated uses as outlined in the Clean Water Act

** All existing designated uses will remain in place for any waterbody or waterbody segment assigned the classification of Outstanding Mississippi Water

C. Dissolved Oxygen: Dissolved oxygen concentrations shall be maintained at a daily average of not less than 5.0 mg/l with an instantaneous minimum of not less than 4.0 mg/l.

When possible, samples should be taken from ambient sites according to the following guidelines:

For water bodies that are not stratified, samples should be taken:

At mid-depth if the total water column depth is 10 feet or less.

At 5 feet from the water surface if the total water column depth is greater than 10 feet.

For waters that are stratified, samples should be taken:

At mid-depth of the epilimnion if the epilimnion depth is 10 feet or less. At 5 feet from the water surface if the epilimnion depth is greater than 10 feet.

D. pH: The normal pH of the waters shall be 6.0 to 9.0. The discharge of waters or wastewaters shall not cause the pH to vary more than 1.0 unit within this range, nor be less than 6.0, nor be greater than 9.0. Variations may be allowed on a case-by-case basis if the Commission determines that there will be no detrimental effect on attainment of the waterbody's designated use(s) as a result of the larger pH change. In black water streams and in those watersheds with highly acidic soils, the pH may be lower than 6.0 due to natural conditions.

E. Temperature: The maximum water temperature increase above natural temperatures shall not exceed 5°F (2.8°C) in streams, lakes, and reservoirs, nor shall the maximum water temperature exceed 90°F (32.2°C), except that in the Tennessee River, the temperature shall not exceed 86°F (30° C). In lakes and reservoirs, there shall be no withdrawals from or discharge of heated waters to the hypolimnion unless it can be shown that such discharge will be beneficial to water quality.

In all waters, the normal daily and seasonal temperature variations that were present before the addition of artificial heat shall be maintained. The maximum water temperature shall not exceed 90°F (32.2°C) in coastal or estuarine waters. The discharge of any heated waste into any coastal or estuarine waters shall not raise temperatures more than 4°F (2.2°C) above natural background temperatures during the months of October through May nor more than 1.5°F (0.8° C) above natural background temperature during the months of June through September.

There shall be no thermal block to the migration of aquatic organisms. Requirements for zones of passage as referenced in Rule 2.5.C. shall apply. The general requirements of Rule 2.1.B. state that samples should be taken from points so distributed over the seasons of the year, time of day, and area and depth of the waters being studied as to permit a realistic assessment of water quality. Therefore, the temperature shall be measured during the environmentally critical period. In addition, temperature shall be measured at a depth of 5 feet in waters 10 feet or greater in depth; and for those waters less than 10 feet in depth, temperature criteria will be applied at mid-depth.

In those specific cases where natural conditions elevate the temperatures in excess of the limits expressed herein, Rule 2.2.E. shall apply on a case-by-case basis. The discharge of any heated waters into a stream, lake, or reservoir shall not raise temperatures more than 5°F(2.8°C) above natural condition temperatures. The discharge of any heated waste into any coastal or estuarine waters shall not raise temperatures more than 4°F (2.2 °C) above natural condition temperatures during the months of October through May nor more than 1.5°F (0.8° C) above natural condition temperatures during the months of June through September. This will also be considered on a case-by-case basis requiring evidence that the aquatic life of the waterbody will not be adversely impacted by the elevated temperatures.

F. Toxic Substances:

(1) Aquatic Life and Human Health Standards

(a) Aquatic Life - The concentration of toxic substances in Surface Waters of the State shall not result in chronic or acute toxicity or impairment of the uses of aquatic life. Toxicity concentrations in Surface Waters of the State in excess of these values shown in Table 2 will be assessed to determine chronic or acute toxicity, and/or the impairment of the uses of aquatic life. Chronic and/or acute toxicity will be determined in accordance with the most recent version of the U.S. EPA's Water Quality Standards Handbook and Technical Support Document for Water Quality-Based Toxics Control (U.S. EPA-505/2-90-001, March 1991). Regardless of the results of chronic or acute toxicity bioassay surveys, the concentrations of toxic substances shall not exceed the chronic or acute values, except as provided for in Rules 2.2.F.5(a) and 2.2.F.5(b).

(b) Human Health - The concentration of toxic substances shall not exceed the level necessary to protect human health through exposure routes of fish (and shellfish) tissue consumption, water consumption, or other routes identified as appropriate for the waterbody.

(2) Numeric criteria for all Surface Waters of the State are established herein for certain toxic pollutants for which the U.S. EPA has published national criteria recommendations for the protection of aquatic life and human health pursuant to Section 304(a) of the Clean Water Act in addition to chlorine and ammonia. The pollutants are listed in Table 2 and are expressed as the dissolved phase of the parameter.

(3) Ammonia toxicity shall be evaluated according to U.S. EPA guidelines published in Aquatic Life Ambient Water Quality Criteria for Ammonia (Freshwater)-2013 (U.S. EPA-822-R-18-002) or Ambient Water Quality Criteria for Ammonia (Saltwater)-1989 (U.S. EPA-440/5-88-004).

(4) Application of Numerical Criteria:

(a) When evaluating human health effects all waters must comply with the Organisms Only criteria except for waters classified as Public Water Supply and all stream segments within 50 stream miles upstream of a drinking water intake. Stream segments that are classified as Public Water Supply or are within 50 miles upstream of a drinking water intake shall comply with the Water and Organisms criteria.

(b) When applying acute or chronic toxicity or human health criteria the following stream flows shall be used:

Acute Toxicity - 7Q10

Chronic Toxicity - 7Q10

Human Health - Mean Annual Flow

(c) Criteria for certain metals may be modified on a site-specific basis when a water effect ratio (WER) study is conducted in accordance with Mississippi's Wastewater Regulations for National Pollutant Discharge Elimination System (NPDES) Permits, Underground Injection Control (UIC) Permits, State Permits, Water Quality Based Effluent Limitations and Water Quality Certification, Title 11, Part 6, Chapter 1. In these instances, the criterion for the specific metal in the affected waterbody shall be equal to the criterion concentrations calculated using the following equations:

CMC = WER * Acute

CCC = WER * Chronic

Where: CCC = Criteria Continuous Concentration

CMC = Criteria Maximum Concentration

WER = Water Effects Ratio for a Specific Pollutant

Acute = Acute Criterion from Table 2

Chronic = Chronic Criterion from Table 2

When a WER study has not been conducted, the criterion listed in Table 2 of this regulation shall apply. The value of the WER is presumed to equal one in the absence of data to indicate otherwise.

(5) Discharger-Specific Modified Criteria:

(a) Existing Discharges

(1) The Commission may establish discharger-specific modified criteria for existing discharges if all of the following conditions are satisfied:

(i) Discharge existed prior to December 1, 1988.

(ii) Discharger performs acute and/or chronic bioassays, in-stream biological assessments, and other evaluations as deemed appropriate by the Commission.

(iii) The designated uses of the waters are maintained.

(2) All discharger-specific modified criteria will be subject to Mississippi public participation requirements for revisions to water quality standards and will be subject to review by the U.S. EPA.

(b) New Source Discharges

(1) The Commission may establish discharger-specific modified criteria for new source discharges if the discharger can demonstrate that established State water quality criteria are based on conditions not applicable to Mississippi such as, but not limited to, water quality criteria established based on the use of species not indigenous to Mississippi. The Revised Deletion Process for the Site-Specific Recalculation Procedure for Aquatic Life Criteria (U.S. EPA-823-R-13-001) should be applied for any revisions to the composition of the sensitive species distribution to better reflect the taxonomy of species within a specific waterbody or location.

(2) All discharger-specific modified criteria will be subject to Mississippi public participation requirements for revisions to water quality standards and will be subject to review by the U.S. EPA if the discharge is to a Water of the United States. Discharges to Surface Waters of the State which are not within federal jurisdiction will not be subject to U.S. EPA review.

(6) Toxic and Human Health Parameters for which No State Numeric Criteria have been Established:

(a) For those toxic and human health parameters for which no State numeric criteria have been established, the Commission shall determine criteria using available references which shall include, but not be limited to, the latest version of U.S. EPA Quality Criteria for Water (Section 304(a)), Federal regulations under Section 307 of the Clean Water Act, and Federal regulations under Title XIV of the Federal Public Health Services Act: Safety of Public Water Systems (Safe Drinking Water Act).

(b) The not to be exceeded value for criteria published in 1980 or the one hour average value for criteria published in 1985 or later shall be used as an acute toxicity number for calculating effluent limitations, establishing Total Maximum Daily Loads (TMDLs), or reviewing ambient water quality data.

(c) The 24-hour average for criteria published in 1980 or the 4-day average for criteria published in 1985 or later shall be used as a chronic toxicity number for calculating effluent limitations, establishing TMDLs, or reviewing ambient water quality data.

(d) If metals concentrations for criteria are hardness-dependent, the chronic and acute concentrations shall be based on the actual mixed in-stream hardness.

(e) If separate criteria are given for freshwater and saltwater, they shall be applied as appropriate.

(f) For non-carcinogens, these concentrations will be determined using a Reference Dose (RfD) as published by the U.S. EPA pursuant to Section 304(a) of the Federal Water Pollution Act as amended unless a more recent RfD is issued by the U.S. EPA as listed in the Integrated Risk Information System file, in which case the more recent value will be used.

Water quality standards or criteria used to calculate water quality-based effluent limitations (and for all other purposes of water quality criteria under Section 303(c) of the Clean Water Act) to protect human health through the different exposure routes are determined as follows:

(1) Fish tissue consumption:

WQC = (RfD) x [(Body Weight) / (FCR x BCF)]

where: WQC = water quality criterion

RfD = reference dose

FCR = fish consumption rate (17.5 gm/person-day)

BCF = bioconcentration factor

BCF values are based on U.S. EPA publications pursuant to Section 304(a) of the Clean Water Act. FCR values are average consumption rates for a 70 kg adult for a lifetime of the population; alternative FCR values may be used when it is considered necessary to protect localized populations which may be consuming fish at a higher rate.

(2) Water consumption and fish tissue consumption:

WQC = (RfD) x [(Body Weight) / (WCR + (FCR x BCF))]

where: WQC = water quality criterion

RfD = reference dose

FCR = fish consumption rate (17.5 gm/person-day)

BCF = bioconcentration factor

WCR = water consumption rate (2 liters/day for adults)

The equations listed in this subparagraph will be used to develop water quality criteria or standards on a case-by-case basis for toxic substances that are not presently included in the water quality standards. Alternative FCR values may be used when it is considered necessary to protect localized populations that may be consuming fish at a higher rate.

(g) For carcinogens, the concentrations of toxic substances will not result in unacceptable health risk and will be based on a Cancer Potency Factor (CPF). An unacceptable health risk for cancer will be considered to be more than one additional case of cancer per one million people exposed (10^-6 risk level).

Water quality standards or criteria used to calculate water quality-based effluent limitations (and for all other purposes of water quality criteria under Section 303(c) of the Clean Water Act) to protect human health through the different exposure routes are determined as follows:

(1) Fish tissue consumption:

WQC = (Risk) x [(Body Weight) / (CPF x (FCR x BCF))]

where: WQC = water quality criterion

Risk = risk factor (10)

CPF = cancer potency factor

FCR = fish consumption rate (17.5 gm/person-day)

BCF = bioconcentration factor

BCF values are based on U.S. EPA publications pursuant to Section 304(a) of the Clean Water Act. FCR values are average consumption rates for a 70 kg adult for a lifetime of the population; alternative FCR values may be used when it is considered necessary to protect localized populations which may be consuming fish at a higher rate.

(2) Water consumption (including a correction for fish consumption):

WQC = (Risk) x [(Body Weight) / (CPF x (WCR + (FCR x BCF)))]

where: WQC = water quality criterion

Risk = risk factor (10)

CPF = cancer potency factor

FCR = fish consumption rate (17.5 gm/person-day)

BCF = bioconcentration factor

WCR = water consumption rate (2 liters/day for adults)

The equations listed in this subparagraph will be used to develop water criteria or standards on a case-by-case basis for toxic substances that are not presently included in the water quality standards. Alternative FCR values may be used when it is considered necessary to protect localized populations that may be consuming fish at a higher rate.

G. Numeric Criteria: Numeric water quality criteria for the protection of human health and aquatic life within Surface Waters of the State are provided in Table 2. These criteria shall be applied as described in above in Rule 2.2.F. Additional details regarding the information provided in Table 2 are provided below.

Notes for Table 2. Numeric Criteria for All Surface Waters of the State

a The CMC = 1/[(f₁/CMC₁) + (f₂/CMC₂)] where f₁ and f₂ are the fractions of total selenium that are treated as selenite and selenate, respectively, and CMC₁ and CMC₂ are 185.9 µg/l and 12.83 µg/l. The value in the table is calculated assuming a worst case scenario in which all selenium is present as selenate.

b Hardness dependent parameter. Criteria values provided in Table 2 are based on an instream hardness of 50 mg/l as CaCO₃. For hardness dependent parameters, chronic and acute criteria values should be based on the actual mixed in-stream hardness. Equations for calculating criteria values for hardness dependent parameters can be found in Quality Criteria for Water

c Criteria for pentachlorophenol are based on a pH dependent equation as found in Quality Criteria for Water. Values listed are for a pH of 7.0 s.u.

e Parameter subject to water effects ratio equations where:

CMC = WER * Acute

CCC = WER * Chronic

f Ammonia criteria are dependent on pH, temperature, and salinity. See Rule 2.2.F.3. for more detail.

g Expressed as µg free cyanide (as CN)/L.

h Refers to the inorganic form only.

i Applies to the sum of a and b isomers.

j Chemical Abstracts Service (CAS) registry numbers, which provide a unique identification for each chemical.

k This criterion applies to total PCBs (e.g., the sum of all congener or all isomer or homolog or Aroclor analyses).

TABLE 2

Numeric Criteria for All Surface Waters of the State (µg/l)

CAS ^j	Parameter	Freshwater		Saltwater		Human Health
CAS ^j	Parameter	Acute	Chronic	Acute	Chronic	Organisms Only	Water & Organisms
107028	Acrolein	3	3
309002	Aldrin	3.0	1.3	0.000050	0.000049
959988	alpha-Endosulfan	0.22 ⁱ	0.056 ⁱ	0.034 ⁱ	0.0087 ⁱ	89	62^j
7664417	Ammonia	^f	^f	^f	^f
7440382	Arsenic (III), Total Dissolved	340 ^e	150 ^e	69	36
7440382	Arsenic, Total Dissolved	24 ^h	0.078 ^h
33213659	beta-Endosulfan	0.22 ⁱ	0.056 ⁱ	0.034 ⁱ	0.0087 ⁱ	89^j	62
7440439	Cadmium, Total Dissolved	1.03 ^b,e	0.15 ^b,e	33	7.9	168	5
63252	Carbaryl	2.1	2.1	1.6
57749	Chlordane	2.4	0.0043	0.09	0.004	0.00081	0.00080
16887006	Chloride	860000	230000
7782505	Chlorine	19	11	13	7.5
2921882	Chlorpyrifos	0.083	0.041	0.011	0.0056
16065831	Chromium (III), Total Dissolved	323^b,e	42^b,e	140468	100
18540299	Chromium (Hex), Total Dissolved	16 ^e	11 ^e	1100	50	1470	98
7440508	Copper, Total Dissolved	7.0 ^b,e	5.0 ^b,e	4.8	3.1	1000	1300
57125	Cyanide	22.0 ^g	5.2 ^g	1.0 ^g	1.0 ^g	140	140
8065483	Demeton	0.1	0.1
333415	Diazinon	0.17	0.17	0.82	0.82
60571	Dieldrin	0.24	0.056	0.71	0.0019	0.000054	0.000052
1031078	Endosulfan Sulfate	89 ^j	62 ^j
72208	Endrin	0.086	0.036	0.037	0.0023	0.060	0.059
58899	gamma-BHC (Lindane)	0.95	0.08	0.16	1.8	0.98
86500	Guthion	0.01	0.01
76448	Heptachlor	0.52	0.0038	0.053	0.0036	0.000079	00.00079
1024573	Heptachlor Epoxide	0.52	0.0038	0.053	0.0036
7439896	Iron	1000
7439921	Lead, Total Dissolved	30^b,e	1.18 ^b,e	210	8.1	15
121755	Malathion	0.1	0.1
7439976	Mercury (II), Total Dissolved	2.1^e	0.012	1.8	0.025
7439976	Mercury	0.153	0.151
72435	Methoxychlor	0.03	0.03
2385855	Mirex	0.001	0.001
7440020	Nickel, Total Dissolved	260^b,e	29^b,e	75	8.3	4600	610
84852153	Nonylphenol	28	6.6	7	1.7
56382	Parathion	0.065	0.013
87865	Pentachlorophenol	8.7 ^c	6.7 ^c	13 ^c	7.9 ^c	3.0	0.27
108952	Phenol	300	102	300	58	860000	10000
Polychlorinated Biphenyls (Total PCBs)	0.02 ^k	0.014 ^k	1.0 ^k	0.03 ^k	0.000064 ^k	0.000064 ^k
7782492	Selenium, Total Dissolved	11.8_a,e	4.6 ^e	290 ^e	71 ^e	4200	170
7440224	Silver, Total Dissolved	0.98 ^b,f	1.9	100
7783064	Sulfide-Hydrogen Sulfide	2.0	2.0
8001352	Toxaphene	0.73	0.0002	0.21	0.0002	0.00028	0.00028
Tributyltin (TBT)	0.46	0.072	0.42	0.0074
7440666	Zinc, Total Dissolved	65^b,e	65^b,e	90	81	26,000	7,400
1746016	2,3,7,8 TCDD (Dioxin)	51 x 10^-9	50 x 10 ^-9
50293	4,4 DDT	1.1	0.001	0.13	0.001	0.00022	0.00022