A.Antidegradation: The policy inherent in the standards shall be to protect water quality existing at the time these water quality standards were adopted and to upgrade or enhance water quality within the State of Mississippi. Waters whose existing quality is better than the established standards will be maintained at high quality unless the Commission finds, after full satisfaction of the intergovernmental coordination and public participation provisions of the State's continuing planning process, that allowing lower water quality is necessary to accommodate important economic or social development in the area in which the waters are located. In no event, however, may degradation of water quality interfere with, or become injurious to, existing in-stream water uses. Further, in no case will water quality be degraded below (or above) the base levels set forth in these standards for the protection of the beneficial uses described herein. In addition, the State will assure that there shall be achieved the highest statutory and regulatory requirements for all new and existing point sources and all cost-effective and reasonable best management practices for nonpoint source control.
Where the Commission determines that high quality waters constitute an outstanding national resource, such as waters of National State Parks, Wildlife Refuges, and waters of exceptional recreational or ecological significance, that water quality shall be maintained and protected. For the purposes of this rule, existing uses are defined as those uses actually attained in the waterbody on or after November 28, 1975, whether or not they are included in the Water Quality Criteria.
B.Sampling and Assessment: The limiting values of water quality herein described shall be measured by the Commission in surface waters under consideration as determined by good environmental engineering and scientific practice and after consultation with affected parties. Samples shall be taken from points so distributed over the seasons of the year, time of day, and area and depth of the waters being studied to provide a realistic assessment of water quality. All sampling must be conducted in accordance with the appropriate MDEQ-approved Quality Management Plan (QMP), Quality Assurance Project Plan (QAPP), or its equivalent. Water quality assessments are technical reviews of physical, chemical, bacteriological, biological, and/or toxicological data and information to determine the quality of the State's surface water resources. Monitoring data are evaluated against both narrative and numeric water quality criteria to determine if a waterbody is supporting or not supporting its classification(s)/designated use(s). Water quality assessments regarding designated use attainment are conducted in accordance with the most recent version of Mississippi's Consolidated Listing and Assessment Methodology (CALM). All samples shall be collected and analyzed in accordance with the appropriate methodology specified in 40 CFR 136 and with the latest edition of Standard Methods for the Examination of Water and Wastewater or other methods acceptable to the Commission.
C. Waterbody Classifications, Designated Uses, and Attainment: Water quality standards define the water quality goals of each waterbody or portion thereof, in part, by designating the use or uses to be made of the water. States adopt water quality standards to protect public health or welfare, to enhance water quality, and to serve the purposes of the Clean Water Act: (1) provide, wherever attainable, water quality for the protection and propagation of fish, shellfish, and wildlife, as well as, recreation in and on the water and (2) consider the use and value of State waters for public water supplies, protection and propagation of fish, shellfish and wildlife, recreation in and on the water, agriculture and industrial purposes, and navigation. 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. A waterbody, or a specific waterbody segment, may be assigned multiple waterbody classifications. When multiple classifications are assigned to a waterbody, the State must ensure protection of the most sensitive use. The State must also consider the water quality standards of downstream waters and ensure that its water quality standards provide for the attainment and maintenance of the water quality standards of downstream waters. In no case shall it be permissible to deposit or introduce materials into Surface Waters of the State that will cause impairment of the designated use(s) of said waters.
Certain Surface Waters of the State may not fall within desired or prescribed limitations as outlined within these water quality standards. In such instances, the Commission may authorize exceptions or alternatives to these criteria as described in more detail within Rule 2.5 Implementation of Water Quality Standards.
D.Natural Conditions: Natural conditions are defined as background water quality conditions due only to non-anthropogenic sources. The criteria herein apply specifically with regard to substances attributed to sources (permitted discharges, nonpoint sources, or in-stream activities) as opposed to natural phenomena. Some water bodies may have characteristics that are naturally outside the criteria established herein. Therefore, naturally occurring conditions that preclude attainment of these criteria should not be interpreted as violations of the criteria.E.Site-Specific Modified Criteria: In some instances, the statewide aquatic life criteria for one or more parameters may not be appropriate for a particular waterbody or waterbody segment. In such circumstances, the Commission may establish site-specific modified aquatic life criteria for one or more parameters applicable to a specific waterbody or waterbody segment. Site-specific modified aquatic life criteria must be based on natural conditions, the recalculation procedure outlined in Revised Deletion Process for the Site Specific Recalculation Procedure for Aquatic Life Criteria - 2013 (U.S. EPA-823-R-13-001), or other scientifically defensible methods. Site-specific modified aquatic life criteria must be based on sound scientific rationale and supported by adequate scientific evidence to validate that the modified criteria are more appropriate for the identified waterbody or waterbody segment. All site-specific modified aquatic life criteria must fully maintain and protect the designated use(s) within the identified waterbody or waterbody segment. All site-specific modified aquatic life criteria must also protect the attainment of water quality standards within downstream waters. Site-specific modified aquatic life criteria are subject to Mississippi public participation requirements for revisions to water quality standards and will be subject to review by the U.S. EPA.
F.Criteria for New Materials: Industries continue to produce new materials whose characteristics and effects are unknown at this time or for which national water quality criteria recommendations have not been established. For the purposes of setting water quality standards or permit limits on a case-by-case basis, these new materials shall be evaluated on their merits as information becomes available to the Commission. Sources of information shall include, but not be limited to, the latest edition of Quality Criteria for Water, prepared by the U.S. Environmental Protection Agency (U.S. EPA) pursuant to Section 304(a) of the Clean Water Act and Title XIV of the Federal Public Health Services Act: Safety of Public Water Systems (Safe Drinking Water Act). G. Water Contact Advisories: Bacteria: According to 40 CFR 131.41(b), Coastal Recreational Waters are defined as marine coastal waters (including coastal estuaries) that are suitable for recreational purposes, including but not limited to, such water contact activities as swimming, wading, and water skiing. Coastal recreational waters do not include inland waters or waters upstream from the mouth of a river or a stream having a natural connection to the open sea. Water quality monitoring for bacteria is conducted by MDEQ within Coastal Recreational Waters to protect the health of bathers. Water contact is discouraged on Mississippi's public access bathing beaches along the shoreline of Jackson, Harrison, and Hancock Counties when enterococci exceed 104 colonies per 100 ml. When enterococci counts exceed 104 per 100 ml at the public access beaches, water contact advisories are issued by Mississippi's Beach Monitoring Task Force.
H.Definitions:(1)Acute criterion or Criteria Maximum Concentration (CMC) is the highest concentration of a pollutant to which aquatic life can be exposed for a short period of time (1-hour average) without deleterious effects. ( 40 CFR 131.36 )(2)Best management practice (BMP) means a structural or non-structural management-based practice used singularly or in combination to reduce nonpoint source inputs to receiving waters in order to achieve water quality protection goals.(3) Bioconcentration factor (BCF) is defined as the ratio (in L/kg-tissue) of the concentration of a substance in tissue of an aquatic organism to its concentration in the ambient water, in situations where the organism is exposed through the water only and the ratio does not change substantially over time. (U.S. EPA-822-B-00-004)(4)Biological integrity is defined as the ability of a system to support and maintain a balanced, integrated, and adaptive community of organisms having a composition, diversity, and functional organization comparable to that of natural habitats of the region.(5)Cancer Potency Factor (CPF) is a measure of the cancer-causing potency of a substance estimated by the upper 95 percent confidence limit of the slope of a straight line calculated by the Linearized Multistage Model according to the U.S. EPA Guidelines (FR 51(185): 339992-34003, and FR 45(231 Part V); 7931879379).(6)Chronic criterion or Criteria Continuous Concentration (CCC) is the highest concentration of a pollutant to which aquatic life can be exposed for an extended period of time (4 days) without deleterious effects. ( 40 CFR 131.36 )(7)Clean techniques refers to an integrated system of sample collection and laboratory analytical procedures designed to detect concentrations of trace metals below criteria levels and eliminate or minimize inadvertent sample contamination that can occur during traditional sampling practices.(8)Composite sampling is a technique whereby multiple temporally or spatially discrete media or tissue samples are combined, thoroughly homogenized, and treated as a single sample.(9)E. coli (Escherichia coli) is a common inhabitant of the intestinal tract of warmblooded animals, and its presence in water samples is an indication of fecal pollution and the possible presence of enteric pathogens. (10)Enteric pathogens are a species of bacteria can be highly pathogenic when they enter and colonize the human digestive tract.(11)Existing uses are those uses actually attained in the waterbody on or after November 28, 1975, whether or not they are included in the water quality standards.(12)Grab samples are samples where the entire sample is collected in one uninterrupted interval.(13) Highest attainable use is the modified aquatic life, wildlife, or recreation use that is both closest to the uses specified in section 101(a)(2) of the Clean Water Act and attainable, based on the evaluation of the factor(s) in § 131.10(g) that preclude(s) attainment of the use and any other information or analyses that were used to evaluate attainability. There is no required highest attainable use where the State demonstrates the relevant use specified in section 101(a)(2) of the Clean Water Act and sub-categories of such a use are not attainable.(14)Mean Annual Flow is the total of daily mean flows for the full period of record divided by the total days for the full period of record.(15)Membrane Filtration (MF) is a method of quantitative or qualitative analysis of bacterial or particulate matter in a water sample filtered through a membrane capable of retaining bacteria.(16) Modified criterion is a waterbody-specific criterion adopted to protect either the Modified Fish and Wildlife or Drainage Waters classifications. The criterion should be supported by the findings of the respective waterbody's use attainability analysis in support of the designated use change and reflect the use of scientifically defensible methods. Following adoption of modified criteria into Rule 2.4, the state will submit the modified criteria for review and require action by the U.S. EPA before the modified criteria supersede the previously applicable criterion.(17)Most probable number (MPN) is the most probable number of coliform-group organisms per unit volume of sample water.(18)Pollutant minimization program in the context of40 CFR 131.14, is a structured set of activities to improve processes and pollutant controls that will prevent and reduce pollutant loadings.(19)Point source is a stationary location or fixed facility from which pollutants are discharged or emitted. Also, any single identifiable source of pollution, e.g., a pipe, ditch, or ship.(20)7Q10 is the average streamflow rate over seven consecutive days that may be expected to be reached as an annual minimum no more frequently than one year in ten years.(21)7Q2 is the average streamflow rate over seven consecutive days that may be expected to be reached as an annual minimum no more frequently than one year in two years.(22)Stratification is the formation of layers of water within a waterbody that are of different densities. The density difference may be caused by variations of temperature, salinity, or concentrations of other dissolved substances within the water at different depths.(23) Surface Waters of the State means all waters within the jurisdiction of this state, including all streams, lakes, ponds, impounding reservoirs, marshes, watercourses, waterways, wells, springs, irrigation systems, drainage systems, and all other bodies or accumulations of water, natural or artificial, situated wholly or partly within or bordering upon the state, and such coastal waters as are within the jurisdiction of the state, except lakes, ponds or other surface waters which are wholly landlocked and privately owned, and which are not regulated under the Clean Water Act ( 33 U.S.C. 1251 et seq).(24)Threshold odor number is the number of times a sample needs to be diluted with clean water in order to reach the level that smell is not detectable.(25)Toxic substance means any substance or combination of substances (including disease-causing agents), which after discharge and upon exposure, ingestion, inhalation, or assimilation into any organism, whether directly from the environment or indirectly by ingestion through food chains, has the potential to cause death, disease, behavioral abnormalities, cancer, genetic mutations, physiological malfunctions (including malfunctions or suppression in reproduction or growth) or physical deformities in such organisms or their offspring.(26) Use attainability analysis is a structured scientific assessment of the factors affecting the attainment of a designated use. This assessment may include physical, chemical, biological, and economic factors as described in 40 CFR 131.10(g).(27)Toxic substance means any substance or combination of substances (including disease-causing agents), which after discharge and upon exposure, ingestion, inhalation, or assimilation into any organism, whether directly from the environment or indirectly by ingestion through food chains, has the potential to cause death, disease, behavioral abnormalities, cancer, genetic mutations, physiological malfunctions (including malfunctions or suppression in reproduction or growth) or physical deformities in such organisms or their offspring.(28) Waters of the State means all waters within the jurisdiction of this state, including all streams, lakes, ponds, impounding reservoirs, marshes, watercourses, waterways, wells, springs, irrigation systems, drainage systems, and all other bodies or accumulations of water, surface and underground, natural or artificial, situated wholly or partly within or bordering upon the state, and such coastal waters as are within the jurisdiction of the state, except lakes, ponds or other surface waters which are wholly landlocked and privately owned, and which are not regulated under the Clean Water Act ( 33 U.S.C. 1251 et seq). Source: Miss. Code Ann. § 49-17-5(1)(f)(29) Water quality standards variance is a time-limited designated use and criterion for a specific pollutant(s) or water quality parameter(s) that reflect the highest attainable condition during the term of the water quality standards variance. Miss. Code Ann. §§ 49-2-1, et seq. and 49-17-1, et seq