S.C. Code Regs. § § 61-68.E

Current through Register Vol. 48, No. 9, September 27, 2024

Section 61-68.E - GENERAL RULES AND STANDARDS APPLICABLE TO ALL WATERS

1. The General Assembly of South Carolina in the Act has declared the following policy: "It is declared to be the public policy of the State to maintain reasonable standards of purity of the air and water resources of the State, consistent with the public health, safety and welfare of its citizens, maximum employment, the industrial development of the State, the propagation and protection of terrestrial and marine fauna and flora, and the protection of physical property and other resources. It is further declared that to secure these purposes and the enforcement of the provisions of this Act, the Department of Health and Environmental Control shall have authority to abate, control and prevent pollution."

2. The classes and standards described in Sections G and H of this regulation implement the above State policy by protecting the waters of South Carolina. Consistent with the above policy, the Department adopts the following general standards in items 3-19 for all waters of South Carolina.

3. No waters of the State shall be used for the sole or principal purpose of transporting or treating wastes.

Any discharge into waters of the State must be permitted by the Department and receive a degree of treatment and/or control which shall produce an effluent which is consistent with the Act, the Clean Water Act (P.L. 92-500, 95-217, 97-117, 100-4), this regulation, and related regulations. No permit issued by the Department shall be interpreted as creating any vested right in any person. Additionally, any discharge into waters of the State containing sanitary wastes shall be effectively disinfected as necessary to meet the appropriate standards of this regulation. The Department may require best management practices (BMPs) for control of stormwater runoff as part of the requirements of an NPDES permit, a State construction permit, or a State 401 Water Quality Certification.

b. When not specifically covered by permit reporting requirements, any unauthorized discharge into waters of the State which may cause or contribute to an excursion of a water quality standard must be reported by the responsible party to the Department orally within twenty-four (24) hours of becoming aware of such conditions. Further, written notification must be provided to the Department (Bureau of Water) within five (5) calendar days of becoming aware of such conditions and the written notice must include the following:

(1) A description of the discharge and cause;

(2) The duration of the discharge, including exact dates and times, and if not corrected, the time that the unauthorized discharge is expected to cease, and what steps are being taken to eliminate, minimize, and prevent recurrence of the discharge.

5. All ground waters and surface waters of the State shall at all times, regardless of flow, be free from:

a. Sewage, industrial waste, or other waste that will settle to form sludge deposits that are unsightly, putrescent, or odorous to such a degree as to create a nuisance, or interfere with classified water uses or existing water uses;

b. Floating debris, oil, grease, scum, and other floating material attributable to sewage, industrial waste, or other waste in amounts sufficient to be unsightly to such a degree as to create a nuisance or interfere with classified water uses or existing water uses;

c. Sewage, industrial, or other waste which produce taste or odor or change the existing color or physical, chemical, or biological conditions in the receiving waters or aquifers to such a degree as to create a nuisance, or interfere with classified water uses (except classified uses within mixing zones as described in this regulation) or existing water uses; and d. High temperature, toxic, corrosive, or deleterious substances attributable to sewage, industrial waste, or other waste in concentrations or combinations which interfere with classified water uses (except classified uses within mixing zones as described in this regulation), existing water uses, or which are harmful to human, animal, plant or aquatic life.

6. Waters where classified uses are not being attained can be reclassified for protection of an attainable use and standards designated for that use where:

a. Natural conditions prevent the attainment of the use; or

b. Natural, ephemeral, intermittent, low flow conditions, or water levels prevent the attainment of the use; or

c. Human caused conditions or sources prevent the attainment of the use and cannot be remedied or would cause more environmental damage to correct than to leave in place; or

d. Dams, diversions, or other types of hydrologic modifications preclude the attainment of the use, and it is not feasible to restore the waterbody to its original condition or to operate such modification in a way that would result in the attainment of the use; or

e. Physical conditions related to the natural features of the water body, such as the lack of a proper substrate, cover, flow, depth, pools, riffles, and the like, preclude attainment of aquatic life protection uses; or

f. Controls more stringent than those required by Sections 301(b) and 306 of the Clean Water Act would result in substantial and widespread economic and social impact.

7. Before the Department may grant a variance for any water of the State, there must be a demonstration that one of the following factors for reclassifying uses has been satisfied:

a. Natural conditions prevent the attainment of the use; or

b. Natural, ephemeral, intermittent, low flow conditions, or water levels prevent the attainment of the use; or

c. Human caused conditions or sources prevent the attainment of the use and cannot be remedied or would cause more environmental damage to correct than to leave in place; or

f. Controls more stringent than those required by Sections 301(b) and 306 of the Clean Water Act would result in adverse social and economic impact, disproportionate to the benefits to the public health, safety, or welfare as a result of maintaining the standard.

8. If the demonstration necessary under Section E.7 above has been satisfied, the Department may then grant a variance provided the following apply:

a. The variance is granted to an individual discharger for a specific pollutant(s) or parameter(s) and does not otherwise modify water quality standards; and

b. The variance identifies and justifies the criterion that shall apply during the existence of the variance; and

c. The variance is established as close to the underlying criterion as is possible and, upon expiration of the variance, the underlying criterion shall become the effective water quality standard for the waterbody; and

d. The variance is reviewed every three (3) years, at a minimum, and extended only where the conditions for granting the variance still apply; and

e. The variance does not exempt the discharger from compliance with any applicable technology or other water quality-based permit effluent limitations; and

f. The variance does not affect permit effluent limitations for other dischargers.

9. Prior to removing any uses or granting a variance, notice and an opportunity for a public hearing shall be provided.

10. Discharge of fill into waters of the State is not allowed unless the activity is consistent with Department regulations and will result in enhancement of classified uses with no significant degradation to the aquatic ecosystem or water quality.

11. In order to protect and maintain lakes and other waters of the State, consideration needs to be given to the control of nutrients reaching the waters of the State. Therefore, the Department shall control nutrients as prescribed below.

a. Discharges of nutrients from all sources, including point and nonpoint, to waters of the State shall be prohibited or limited if the discharge would result in, or if the waters experience growths of, microscopic or macroscopic vegetation such that the water quality standards would be violated or the existing or classified uses of the waters would be impaired. Loading of nutrients shall be addressed on an individual basis as necessary to ensure compliance with the narrative and numeric criteria.

b. Numeric nutrient criteria for lakes are based on an ecoregional approach which takes into account the geographic location of the lakes within the State and are listed below. These numeric criteria are applicable to lakes of forty (40) acres or more. Lakes of less than forty (40) acres will continue to be protected by the narrative criteria.

(1) For the Blue Ridge Mountains ecoregion of the State, total phosphorus shall not exceed 0.02 mg/L, chlorophyll a shall not exceed 10 µg/L, and total nitrogen shall not exceed 0.35 mg/L.

(2) For the Piedmont and Southeastern Plains ecoregions of the State, total phosphorus shall not exceed 0.06 mg/L, chlorophyll a shall not exceed 40 µg/L, and total nitrogen shall not exceed 1.50 mg/L.

(3) For the Middle Atlantic Coastal Plains ecoregion of the State, total phosphorus shall not exceed 0.09 mg/L, chlorophyll a shall not exceed 40 µg/L, and total nitrogen shall not exceed 1.50 mg/L.

c. In evaluating the effects of nutrients upon the quality of lakes and other waters of the State, the Department may consider, but not be limited to, such factors as the hydrology and morphometry of the waterbody, the existing and projected trophic state, characteristics of the loadings, and other control mechanisms in order to protect the existing and classified uses of the waters.

d. The Department shall take appropriate action, to include, but not be limited to: establishing numeric effluent limitations in permits, establishing Total Maximum Daily Loads, establishing waste load allocations, and establishing load allocations for nutrients to ensure that the lakes attain and maintain the above narrative and numeric criteria and other applicable water quality standards.

e. The criteria specific to lakes shall be applicable to all portions of the lake. For this purpose, the Department shall define the applicable area to be that area covered when measured at full pool elevation.

12.

The water temperature of all Freshwaters which are free flowing shall not be increased more than 5°F (2.8°C) above natural temperature conditions and shall not exceed a maximum of 90°F (32.2°C) as a result of the discharge of heated liquids unless a different site-specific temperature standard as provided for in C.12. has been established, a mixing zone as provided in C.10. has been established, or a Section 316(a) determination under the Federal Clean Water Act has been completed.

b. The weekly average water temperature of all Shellfish Harvesting, Class SA and Class SB waters shall not exceed 4°F (2.2°C) above natural conditions during the fall, winter or spring, and shall not exceed 1.5°F (0.8°C) above natural conditions during the summer as a result of the discharge of heated liquids unless a different site-specific temperature standard as provided for in C.12. has been established, a mixing zone as provided for in C.10 has been established, or a Section 316(a) determination under the Federal Clean Water Act has been completed.

c. The weekly average water temperature of all Freshwaters which are lakes shall not be increased more than 5°F (2.8°C) above natural conditions and shall not exceed 90°F (32.2°C) as a result of the discharge of heated liquids unless a different site-specific temperature standard as provided for in C.12. has been established, a mixing zone as provided in C.10. has been established, or a Section 316(a) determination under the Federal Clean Water Act has been completed.

13. Numeric criteria based on organoleptic data (prevention of undesirable taste and odor) are adopted herein. Those substances and their criteria are listed in the appendix. For those substances which have aquatic life and/or human health numeric criteria and organoleptic numeric criteria, the most stringent of the three (3) shall be used for derivation of permit effluent limitations.

14. Numeric criteria for the protection and maintenance of all classes of surface waters are adopted herein and are listed in Sections E, G, and the appendix. Footnotes that further describe the application of these numeric criteria are included in the appendix.

a. Application of numeric criteria to protect aquatic life.

(1) The stated CMC value shall be used as an acute toxicity number for calculating permit effluent limitations.

(2) The stated CCC value shall be used as a chronic toxicity number for calculating permit effluent limitations.

(3) If metals concentrations for numeric criteria are hardness-dependent, the CMC and CCC concentrations shall be based on 25 mg/L hardness (as expressed as CaCO₃) if the ambient hardness is less than 25 mg/L. Concentrations of hardness less than 400 mg/L maybe based on the actual mixed stream hardness if it is greater than 25 mg/L and less than 400 mg/L and 400 mg/L if the ambient hardness is greater than 400 mg/L.

(4) If separate numeric criteria are given for fresh and salt waters, they shall be applied as appropriate. In transitional tidal and estuarine areas, the Department shall apply the more stringent of the criteria to protect the existing and classified uses of the waters of the State.

(5) The Department shall review new or revised EPA criteria for adoption by South Carolina when published in final form.

(6) If the State develops site-specific criteria for any substances for which EPA has developed national criteria, the site-specific criteria shall supersede the national criteria.

b. Application of numeric criteria to protect human health.

(1) If separate numeric criteria are given for organism consumption, water and organism consumption (W/O), and drinking water Maximum Contaminant Levels (MCLs), they shall be applied as appropriate. The most stringent of the criteria shall be applied to protect the existing and classified uses of the waters of the State.

(2) The Department shall review new or revised EPA criteria for adoption by South Carolina when published in final form by EPA.

(3) If the State develops site-specific criteria for any substances for which EPA has developed national criteria, the site-specific criteria shall supersede the national criteria.

(4) Adoption of EPA human health criteria does not preclude the Department from considering health effects of other pollutants or from considering new or revised EPA criteria when developing effluent permit conditions.

c. Application of criteria for the derivation of permit effluent limitations.

(1) Numeric criteria for substances listed in Sections E, G, and the appendix shall be used by the Department to derive NPDES permit effluent limitations at the applicable critical flow conditions as determined by the Department unless an exception is provided below.

(2) When the derived permit effluent limitation based on aquatic life numeric criteria is below the practical quantitation limit for a substance, the derived permit effluent limitation shall include an accompanying statement in the permit that the practical quantitation limit using approved analytical methods shall be considered as being in compliance with the limit. Appropriate biological monitoring requirements shall be incorporated into the permit to determine compliance with appropriate water quality standards. Additionally, if naturally occurring instream concentration for a substance is higher than the derived permit effluent limitation, the Department may establish permit effluent limitations at a level higher than the derived limit, but no higher than the natural background concentration. In such cases, the Department may require biological instream monitoring and/or WET testing.

(3) When the derived permit effluent limitation based on human health numeric criteria is below the practical quantitation limit for a substance, the derived permit effluent limitation shall include an accompanying statement in the permit that the practical quantitation limit using approved analytical methods shall be considered as being in compliance with the limit. Additionally, if naturally occurring instream concentration for a substance is higher than the derived permit effluent limitation, the Department may establish permit effluent limitations at a level higher than the derived limit, but no higher than the natural background concentration.

(4) NPDES permit effluent limitations for metals shall normally be expressed on the permits as total recoverable metals, but the Department may utilize a federally-approved methodology to predict the dissolved fraction, partitioning coefficient, or the bioavailable portion of metals in calculating these limits.

(5) Except as provided herein, where application of MCLs or W/O numeric criteria using annual average flow for carcinogens, 7Q10 (or 30Q5 if provided by the applicant) for noncarcinogens, or comparable tidal conditions as determined by the Department results in permit effluent limitations more stringent than limitations derived from other applicable human health criteria (organism consumption only), aquatic life criteria, or organoleptic numeric values, MCLs or W/O shall be used in establishing permit effluent limitations for human health protection. The Department may, after Notice of Intent included in a notice of a proposed NPDES permit in accordance with R.61-9.124.10, Procedures for Decision Making, determine that drinking water MCLs or W/O shall not apply to discharges to those waterbodies where there is: no potential to affect an existing or proposed drinking water source and no state-approved source water protection area. For purposes of this section, a proposed drinking water source is one for which a complete permit application, including plans and specifications for the intake, is on file with the Department at the time of consideration of an NPDES permit application for a discharge that will affect or has the potential to affect the drinking water source.

(6) Except as provided herein, the Department may determine that an NPDES permitted discharge will not cause, have reasonable potential to cause, or contribute to an exceedance of the numeric criterion for turbidity under the following conditions:

i. The facility withdraws its surface intake water containing turbidity from the same body of water into which the discharge is made;

ii. The facility does not significantly concentrate or contribute additional turbidity to the discharged water; or iii. The facility does not alter the turbidity through chemical or physical means that would cause adverse water quality impacts to occur.

(7) Site-specific permit effluent limitations and alternate criteria less stringent than those derived in accordance with the above requirements may be derived where it is demonstrated that such limits and criteria shall maintain the existing and classified uses, adequate opportunity for public participation in such derivation process has occurred, and the effluent shall not cause human health criteria to be exceeded. Where a site-specific permit effluent limitation and alternate criterion has been derived, such derivation shall be subject to EPA review as appropriate. Also, at a minimum, opportunity for input in derivation of a site-specific permit effluent limitation and alternate criterion shall be provided via public notice in NPDES permit notices.

(8) In order to protect recreational uses in freshwaters (including FW, and all types of Trout Waters) of the State, NPDES permit effluent limitations shall be specified as indicated below:

i. Monthly Average (E. coli)	126 MPN per 100 mL
ii. Daily Maximum (E. coli)	349 MPN per 100 mL (see c(12) below)
iii. Shellfish protection	Class SFH requirements for fecal coliform (see c(11)i. and c(11)ii. below) may be specified (in addition to the limits above) for the protection of downstream waters (regardless of their individual classification) with shellfish uses.
iv. Municipal separate storm sewer systems	For municipal separate storm sewer systems (as described in R.61-9.122.26.a.), compliance with the bacterial standards shall be determined in accordance with c(13) below.
v. Protection of upstream and/or downstream waters	Permit limitations may include (in addition to the requirements listed in c(8)i. and c(8)ii. above) one or more bacterial limitations for fecal coliform, E. coli, and/or enterococci to protect both uses in the specific receiving waterbody and also to protect any upstream and/or downstream uses that may be required. If more than one bacterial limit is required, the conditions associated with each section below shall apply independently regardless of the water classification at the point of discharge.
vi. Class ORW or ONRW protection	For Class ORW or ONRW waters, the bacterial requirements shall be those applicable to the classification of the waterbody immediately prior to reclassification to either ORW or ONRW, including consideration of natural conditions. See G.5 and G.7 for prohibitions.

(9) In order to protect recreational uses in Class SA saltwaters of the State, NPDES permit effluent limitations shall be specified as indicated below:

i. Monthly Average (enterococci)	35 MPN per 100 mL
ii. Daily Maximum (enterococci)	104 MPN per 100 mL (see c(12) below)
iii. Shellfish protection	Class SFH requirements for fecal coliform (see c(11)i. and c(11)ii. below) may be specified (in addition to the limits above) for the protection of upstream and/or downstream waters (regardless of their individual classification) with shellfish uses.
iv. Municipal separate storm sewer systems	For municipal separate storm sewer systems (as described in R.61-9.122.26.a.), compliance with the bacterial standards shall be determined in accordance with c(13) below.
v. Protection of upstream downstream waters	and/or Permit limitations may include (in addition to the requirements listed in c(9)i. and c(9)ii. above) one or more bacterial limitations for fecal coliform, E. coli, and /or enterococci to protect both uses in the specific receiving waterbody and also to protect any upstream or downstream uses that may be required. If more than one bacterial limit is required, the conditions associated with each section above
or below shall apply independently regardless of the water classification at the point of discharge.
vi. Class ORW or ONRW protection	For Class ORW or ONRW waters, the bacterial requirements shall be those applicable to the classification of the waterbody immediately prior to reclassification to either ORW or ONRW, including consideration of natural conditions. See G.5 and G.7 for prohibitions.

(10) In order to protect recreational uses in Class SB saltwaters of the State, NPDES permit effluent limitations shall be specified as indicated below:

i. Monthly Average (enterococci)	35MPNper lOOmL
ii. Daily Maximum (enterococci)	104 MPN per 100 mL (see c(12) below)
iii. Class SA recreational daily maximum and/or shellfish protection	Class SA daily maximum (see c(9)ii. above) recreational use requirements for enterococci and/or Class SFH requirements (see c(ll)i. and c(ll)ii. below) for fecal coliform may be specified (in addition to the limits above) for the protection of upstream and/or downstream waters (regardless of their individual classification).
iv. Municipal separate storm sewer systems	For municipal separate storm sewer systems (as described in R.61-9.122.26.a.), compliance with the bacterial standards shall be determined in accordance with c(13) below.
V. Protection of upstream and/or downstream waters	Permit limitations may include (in addition to the requirements hsted in c(10)i. and c(10)ii. above) one or more bacterial limitations for fecal coliform, E. coli and /or enterococci to protect both uses in the specific receiving waterbody and also to protect any upstream or downstream uses that may be required. If more than one bacterial limit is required, the conditions associated with each section above or below shall apply independently regardless of the water classification at the point of discharge.
vi. Class ORW or ONRW protection	For Class ORW or ONRW waters, the bacterial requirements shall be those applicable to the classification of the waterbody immediately prior to reclassification to either ORW or ONRW, including consideration of natural conditions. See G.5 and G.7 for prohibitions.

(11) In order to protect for the consumption of shellfish, for any discharge either directly or indirectly in Class SFH waters or in Class SA, Class SB, ORW, or ONRW waters with existing and/or approved shellfish harvesting uses as described in Section C.7, including protection of shellfish upstream and/or downstream uses in all waters regardless of their classification, NPDES permit effluent limitations shall be specified as indicated below:

i. For protection of shellfish uses-Monthly Average (Fecal coliform)	14 MPN per 100 mL
ii. For protection of shellfish uses- Daily Maximum (Fecal coliform)	43 MPN per 100 mL (see c(12) below)
iii. For protection of recreational uses - Monthly Average (enterococci)	35 MPN per 100 mL
iv. For protection of recreational uses-Daily Maximum (enterococci)	104 MPN per 100 mL (see c(12) below)
v. Protection of upstream and/or downstream waters	Permit limitations may include (in addition to the requirements listed in c(11)i. through c(11)iv. above) one or more bacterial limitations for fecal coliform, E. coli and /or enterococci to protect both uses in the specific receiving waterbody and also to protect any upstream or downstream uses that may be required. If more than one bacterial limit is required, the conditions associated with each section above shall apply independently regardless of the water classification at the point of discharge.
vi. Municipal separate storm sewer systems	For municipal separate storm sewer systems (as described in R.61-9.122.26.a.), compliance with the bacterial standards shall be determined in accordance with c(13) below.

(12) Provided the permittee verifies in writing to the Department that conditions (12)i. through (12)iv. below have been met, the permittee would be in compliance with the daily maximum bacterial requirement. However, nothing in this regulation precludes the Department from taking action, depending on the individual circumstances, to protect public health and/or the environment.

i. If the facility exceeds the permitted Daily Maximum bacterial limitation listed above (for E. coli, enterococci, or fecal coliform) but two (2) additional samples collected within forty-eight (48) hours of the original sample result do NOT exceed the required Daily Maximum limit; and

(A) For all waters not involving shellfish protection (regardless of the specific water classification), the individual bacterial sample result has not exceeded 800 MPN per 100 mL, and for those waters involving shellfish protection, the individual bacterial sample result for fecal coliform has not exceeded 200 MPN per 100 mL; and

(B) There is neither an existing Consent Order nor Administrative Order associated with the facilities operation of their disinfection system; and

(C) Either:

1. For facilities that routinely collect ten (10) bacterial samples per month (or one hundred twenty (120) or more samples per calendar year), there were no more than four (4) total bacteria samples exceeding the daily maximum limit in the previous twelve (12) months; or

2. For facilities other than those listed in (C)1. above (e.g., smaller facilities or those that do not routinely collect ten (10) samples or more per month), there was no more than one (1) bacterial sample exceeding the daily maximum limit in the previous twelve (12) months; and ii. The permittee verifies that all disinfection equipment was fully functional, and the solids handling system was fully functional during that monitoring period; and iii. Any additional bacterial sampling collected during the monthly monitoring period when the daily maximum exceedance occurred was reasonably distributed in time while maintaining representative sampling; and iv. The permittee must provide sufficient laboratory data sensitivity (e.g., dilutions) to accurately represent the effluent bacterial concentration to utilize this procedure. Effluent bacterial results reported as greater than (>) do not meet this criteria, since the actual results are unknown.

(13) For waters of the State, where a permit has been issued pursuant to R.61-9.122.26 and R.61-9.122.34, the Department shall consider the permittee in compliance with the established bacterial (i.e., E. coli, enterococci, fecal coliform) criteria for recreational uses of the waterbody if the permittee is in compliance with their permit.

(14) TMDL(s), WLA(s), and LA(s) included in currently approved freshwater fecal coliform TMDL documents shall be converted to E. coli utilizing a translator equation established by the Department and shall be based upon existing targets included in approved freshwater fecal coliform bacteria TMDL documents.

(15) All effluent permit limitations which include WET shall require that the WET tests be conducted using Ceriodaphnia dubia (C. dubia), except as stated. If the salinity of a discharge to a saline waterbody is high enough to be toxic to C. dubia, Mysidopsis bahia (M. bahia) shall be used. If the hardness of a waterbody is low enough to be toxic to C. dubia, then Daphnia ambigua (D. ambigua) may be used. Low salinity discharges to saltwater may be tested using either C. dubia or M. bahia with salinity adjustment, as determined by the Department. The Department may consider an alternative species if it can be demonstrated that the proposed species meets the requirements of 40 CFR 136.4 and 5, as approved by EPA. EPA test methods (40 CFR 136) for acute and chronic toxicity testing with freshwater organisms or marine and estuarine organisms must be followed. The Department may consider an alternative method if it can be demonstrated that the proposed method meets the requirements of 40 CFR 136 and is approved by EPA.

d. Evaluation of ambient water quality.

(1) If the numeric criterion for toxic pollutants is lower than the analytical detection limit, the criterion is not considered violated if the ambient concentration is below the detection limit and the instream indigenous biological community is not adversely impacted.

(2) If the ambient concentration is higher than the numeric criterion for toxic pollutants, the criterion is not considered violated if biological monitoring has demonstrated that the instream indigenous biological community is not adversely impacted.

(3) In order to appropriately evaluate the ambient water quality for the bioavailability of the dissolved portion of hardness dependent metals, the Department may utilize a federally-approved methodology to predict the dissolved fraction or partitioning coefficient in determining compliance with water quality standards established in this regulation.

(4) The assessment of fecal coliform for purposes of evaluating the shellfish harvesting use for South Carolina's Shellfish Management Units is conducted in accordance with provisions of R.61-47, Shellfish. R.61-47 also includes specific language describing the use of the allowable ten percent (10%) exceedance value in the shellfish program.

(5) The assessment of enterococci for purposes of issuing swimming advisories for ocean beaches for recreational use will be based on the single sample maximum of 104/100 mL.

(6) The assessment of enterococci and E. coli for purposes of Section 303(d) listing determinations for recreational uses shall be based on either the geometric mean with an allowable ten percent (10%) exceedance,where sufficient data exists to calculate a geometric mean, or the single sample maximum with an allowable ten percent (10%) exceedance.

(7) The assessment of total microcystins for purposes of issuing a swimming advisory for freshwater recreational use will be based on the single sample maximum of 8 µg/L. Once issued, the swimming advisory will remain in effect until resample results indicate the toxin concentration falls below 8 µg/L.

(8) The assessment of total microcystins for purposes of Section 303(d) listing determinations for recreational uses shall be based on no more than three (3) swimming advisories in a three (3)-year assessment period.

(9) The assessment of cylindrospermopsin for purposes of issuing a swimming advisory for freshwater recreational use will be based on the single sample maximum of 15 µg/L. Once issued, the swimming advisory will remain in effect until resample results indicate the toxin concentration falls below 15 µg/L.

(10) The assessment of cylindrospermopsin for purposes of Section 303(d) listing determinations for recreational uses shall be based on no more than three (3) swimming advisories in a three (3)-year assessment period.

15. The Department may require biological or other monitoring in NPDES permits to further ascertain any bioaccumulative effects of pollutants. Such monitoring may include analyses of fish and shellfish, macroinvertebrates, macrophytes, and/or sediments in order to assess the accumulation of pollutants in tissues or sediments that:

a. May cause or have the potential to cause adverse impacts to the balanced indigenous aquatic community; and

b. May cause or have the potential to cause adverse impacts to human health and/or terrestrial flora and fauna.

16. The Department may consider other scientifically-defensible published data which are appropriate for use in developing permit limits and evaluating water quality for constituents for which EPA has not developed national criteria or South Carolina has no standards.

a. The Department shall apply a sensitivity factor to aquatic toxicity data unless, in the Department's judgment, the data represent a minimum of three (3) appropriately sensitive species representing three (3) taxonomic groups (plant, macroinvertebrate, and fish).

(1) If only an acute toxicity effect concentration for a number of species for a particular pollutant is given as an LC₅₀, the lowest concentration should be divided by an acute-to-chronic ratio (ACR) of ten (10) and a sensitivity factor of 3.3, for an acceptable instream concentration in order to protect against chronic toxicity effects.

(2) If a chronic toxicity effect concentration for a number of species for a particular pollutant is given as a no observed effect concentration (NOEC), the lowest concentration should be divided by a sensitivity factor of 3.3 in order to protect against chronic toxicity to the most sensitive species.

b. The Department must notify the permittee that other such data were used in developing permit limits and provide justification for their use.

17. Tests or analytical methods to determine compliance or non-compliance with standards shall be made in accordance with methods and procedures approved by the Department and the EPA. In making any tests or applying analytical methods to determine compliance or non-compliance with water quality standards,representative samples shall be collected in accordance with methods and procedures approved by the Department and the EPA. Consideration of representative sample methods shall include the following:

a. Surface water and ground water samples shall be collected so as to permit a realistic appraisal of quality and actual or potential damage to existing or classified water uses. For ground waters, consideration shall be given to, but shall not be limited to, depth to water table, flow direction, and velocity. For surface waters, time of day, flow, surface area, and depth shall be considered.

b. Biological assessment methods may be employed in appropriate situations to determine abnormal nutrient enrichment, trophic condition, LC₅₀, concentration of toxic substances, acceptable instream concentrations, or acceptable effluent concentrations for maintenance of a balanced indigenous aquatic community.

c. Temporal distribution of samples in tidally influenced waters shall cover the full range of tidal conditions.

d. Ambient toxicity tests used for screening purposes shall be conducted using Ceriodaphnia dubia (C. dubia), except as stated. If salinity of a waterbody is high enough to be toxic to C. dubia, Mysidopsis bahia (M. bahia) will be used. If the hardness of a waterbody is low enough to be toxic to C. dubia, then Daphnia ambigua (D. ambigua) may be used. The Department may consider an alternative species if it can be demonstrated that the proposed species meets the requirements of 40 CFR Part 136 .4 and 5 , as approved by EPA. EPA test methods (40 CFR Part 136) for acute and chronic toxicity testing with freshwater organisms or marine and estuarine organisms must be followed. The Department may consider an alternative method if it can be demonstrated that the proposed method meets the requirements of 40 CFR Part 136, and is approved by EPA.

18. For the protection of human health, methylmercury concentration in fish or shellfish shall not exceed 0.3 mg/kg in wet weight of edible tissue.

a. NPDES permit implementation for methylmercury will require mercury monitoring, assessment and minimization for discharges that meet the following conditions;

(1) The receiving stream is impaired for methylmercury in fish or shellfish tissue; and

(2) The discharge or proposed discharge has consistently quantifiable levels of mercury.

b. The need for a total mercury effluent limit, for the protection of aquatic life and/or human health, pursuant to R.61-9.122.44(d), shall be based on a reasonable potential analysis of the discharge compared to the mercury standards for ambient waters.

19. The assessment of methylmercury in fish or shellfish for purposes of Section 303(d) listing determinations shall be based on the Department's Fish Consumption Advisories.

S.C. Code Regs. § 61-68.E

Added by State Register Volume 38, Issue No. 6, eff 6/27/2014; State Register Volume 44, Issue No. 06, eff. 6/26/2020; State Register Volume 47, Issue No. 05, eff. 5/26/2023.