Rule 391-3-5-.18. Primary Maximum Contaminant Levels for Drinking Water

1. (1) Primary MCLs for Inorganics. INORGANICS - The maximum contaminant levels (MCLs) for antimony, arsenic, asbestos, barium, beryllium, cadmium, chromium, mercury, nickel, selenium and thallium of this Rule apply to community water systems and non-transient, non-community water systems. The MCLs for fluoride in this Rule apply to community water systems. The MCLs for nitrate, nitrite, and total nitrate-nitrite of this Rule apply to all (CWS, NTNCWS, TNCWS) public water systems.

   1. (a) The following are the maximum contaminant levels for inorganic chemicals:

      Contaminant Maximum Contaminant Level (mg/L) Applicable Systems Antimony 0.006 CWS, NTNCWS Arsenic 0.010 CWS, NTNCWS Asbestos 7 Million Fibers/Liter Longer than 10 µm CWS, NTNCWS Barium 2 CWS, NTNCWS Beryllium 0.004 CWS, NTNCWS Cadmium 0.005 CWS, NTNCWS Chromium 0.1 CWS, NTNCWS Cyanide 0.2 CWS, NTNCWS Fluoride^1,2 4.0 CWS Lead see 391-3-5-.25 Treatment Technique CWS, NTNCWS Mercury 0.002 CWS, NTNCWS Nickel 0.1 CWS, NTNCWS Nitrate 10 (as N) CWS, NTNCWS, TNCWS Nitrite 1 (as N) CWS, NTNCWS, TNCWS Total Nitrate + Nitrite 10 (as N) CWS, NTNCWS, TNCWS Selenium 0.05 CWS, NTNCWS Thallium 0.002 CWS, NTNCWS

      NOTES:

      1. 1. Effective date for fluoride was October 2, 1987.
      2. 2. Fluoride also has a secondary MCL (Rule 391-3-5-.19(2)).

   2. (b) At the discretion of the Director, nitrate levels not to exceed 20 mg/L may be allowed in a non-community water system if the supplier of water demonstrates to the satisfaction of the Director that:

      1. 1. such water will not be available to children under 6 months of age;
      2. 2. the water system is meeting the public notification requirements under Rule 391-3-5-.32, including continuous posting of the fact that nitrate levels exceed 10 mg/L and the potential health effects of exposure;
      3. 3. local and State public health authorities will be notified annually of nitrate levels that exceed 10 mg/L; and
      4. 4. no adverse health effects shall result.

(2) Primary MCLs for Organics. ORGANIC CHEMICALS - The following maximum contaminant levels for organic contaminants apply to community water systems and non-transient, non-community water systems. Compliance with maximum contaminant levels for the following organics is to be calculated pursuant to Rule 391-3-5-.22. (a) Synthetic Organic Chemicals, Pesticides and Polychlorinated biphenyls Contaminant Maximum Contaminant Level (mg/L) Alachlor 0.002 Aldicarb Deferred Aldicarb sulfone Deferred Aldicarb sulfoxide Deferred Atrazine 0.003 Benzo(a)Pyrene 0.0002 Carbofuran 0.04 Chlordane 0.002 Dalapon 0.2 Di(2-ethylhexyl) adipate 0.4 Di(2-ethylhexyl) phthalate 0.006 Dibromochloropropane (DBCP) 0.0002 Dinoseb 0.007 Diquat 0.02 2,4-D 0.07 Endothall 0.1 Endrin 0.002 Ethylene dibromide (EDB) 0.00005 Glyphosate 0.7 Heptachlor 0.0004 Heptachlor Epoxide 0.0002 Hexachlorobenzene 0.001 Hexachlorocyclopentadiene 0.05 Lindane 0.0002 Methoxychlor 0.04 Oxamyl (Vydate) 0.2 Pentachlorophenol 0.001 Picloram 0.5 Polychlorinated biphenyls (PCBs) 0.0005 Simazine 0.004 Toxaphene 0.003 2,4,5-TP (Silvex) 0.05 2,3,7,8-TCDD (Dioxin) 3 x 10 ^-8 (b) Volatile Organic Contaminants (VOCs) Contaminant Maximum Contaminant Level (mg/L) Vinyl chloride 0.002 Benzene 0.005 Carbon tetrachloride 0.005 1,2-Dichloroethane 0.005 Trichloroethylene 0.005 para-Dichlorobenzene 0.075 1,1-Dichloroethylene 0.007 1,1,1-Trichloroethane 0.2 cis-1,2-Dichloroethylene 0.07 1,2-Dichloropropane 0.005 Ethylbenzene 0.7 Monochlorobenzene 0.1 o-Dichlorobenzene 0.6 Styrene 0.1 Tetrachloroethylene 0.005 Toluene 1 trans-1,2-Dichloroethylene 0.1 Xylenes (total) 10 Dichloromethane 0.005 1,2,4-Trichlorobenzene 0.07 1,1,2-Trichloroethane 0.005

1. (3) Primary MCLs for Turbidity. Turbidity - Treatment Technique Requirements:

   1. (a) The maximum contaminant level for turbidity is determined by a treatment technique requirement as set forth in this Rule.

   2. (b) The treatment technique requirement for turbidity is applicable to both community water systems and non-community water systems using surface water sources or ground water sources under the direct influence of surface water in whole or in part. The treatment technique requirement for turbidity in drinking water, measured at a representative point(s) in the filtered water is:

      1. 1. Less than or equal to 0.3 turbidity unit in at least 95 percent of the monthly measurements. One turbidity unit is the maximum allowable level and must not be exceeded at any time.
      2. 2. Five turbidity units is the maximum allowable level and must not be exceeded at any time.
      3. 3. In accordance with 40 CFR § 141.73, the Division may allow higher turbidity levels for slow sand filtration, diatomaceous earth filtration, or other filtration technologies.
      4. 4. Beginning January 1, 2002, public water systems that use surface water or ground water under the direct influence of surface water and serve at least 10,000 people must meet the filtration requirements specified in 40 CFR § 141.173 (see Rule 391-3-5-.20(5)).
      5. 5. The Enhanced Filtration and Disinfection requirements specified in 40 CFR Part 141, Subpart P are applicable to Subpart H systems serving at least 10,000 people (see Rule 391-3-5-.20(8)).
      6. 6. Beginning January 14, 2005, public water systems that use surface water or ground water under the direct influence of surface water as a source and serve fewer than 10,000 people must meet the filtration and disinfection requirements in 40 CFR Part 141, Subpart T. This requirement is in addition to complying with requirements in Subpart H of 40 CFR Part 141 [see Rule 391-3-5-.20(8)].

2. (4) Primary MCLs for Microbiologicals. Microbiological - Maximum contaminant levels (MCLs) for microbiological contaminants.

   1. (a) Until March 31, 2016, the total coliform MCL is based on the presence or absence of total coliforms in a sample, rather than coliform density.

      1. 1. For a system that collects at least 40 samples per month, if no more than 5.0 percent of the samples collected during a month are total coliform-positive, the system is in compliance with the MCL for total coliforms.
      2. 2. For a system that collects fewer than 40 samples per month, if no more than one sample collected during a month is total coliform-positive, the system is in compliance with the MCL for total coliforms.
   2. (b) Until March 31, 2016, any fecal coliform-positive repeat sample or E. coli-positive repeat sample, or any total coliform-positive repeat sample following a fecal coliform-positive or E. coli­-positive routine sample, constitutes a violation of the MCL for total coliforms. For purposes of the public notification requirements in Rule 391-3-5-.32, this is a violation that may pose an acute risk to health.

   3. (c) Beginning April 1, 2016, a system is in compliance with the MCL for E. coli for samples taken under the provisions of Rule 391-3-5-.55 unless any of the conditions identified in paragraphs (4)(c)1. through (4)(c)4. occur. For purposes of the public notification requirements in Rule 391-3-5-.32, violation of the MCL may pose an acute risk to health.

      1. 1. The system has an E. coli-positive repeat sample following a total coliform-positive routine sample.
      2. 2. The system has a total coliform-positive repeat sample following an E. coli-positive routine sample.
      3. 3. The system fails to take all required repeat samples following an E. coli-positive routine sample.
      4. 4. The system fails to test for E. coli when any repeat sample tests positive for total coliform.
   4. (d) Until March 31, 2016, a public water system must determine compliance with the MCL for total coliforms in paragraphs (4)(a) and (4)(b) for each month in which it is required to monitor for total coliforms. Beginning April 1, 2016, a public water system must determine compliance with the MCL for E. coli in paragraph (4)(c) for each month in which it is required to monitor for total coliforms.

   5. (e) The EPA Administrator, pursuant to section 1412 of the federal Safe Drinking Water Act, identifies the following as the best technology, treatment techniques, or other means available for achieving compliance with the maximum contaminant level for total coliforms in paragraphs (4)(a) and (4)(b) and for achieving compliance with the maximum contaminant level for E. coli in paragraph (4)(c):

      1. 1. Protection of wells from fecal contamination by appropriate placement and construction;
      2. 2. Maintenance of a disinfectant residual throughout the distribution system;
      3. 3. Proper maintenance of the distribution system including appropriate pipe replacement and repair procedures, main flushing programs, proper operation and maintenance of storage tanks and reservoirs, cross connection control, and continual maintenance of positive water pressure in all parts of the distribution system;
      4. 4. Filtration and/or disinfection of surface water, as described in 40 CFR Part 141 Subparts H, P, T, and W, or disinfection of ground water, as described in 40 CFR Part 141 Subpart S, using strong oxidants such as chlorine, chlorine dioxide, or ozone; and
      5. 5. For systems using ground water, compliance with the requirements of an EPA-approved Division Wellhead Protection Program developed and implemented under section 1428 of the federal Safe Drinking Water Act.
   6. (f) The EPA Administrator, pursuant to section 1412 of the federal Safe Drinking Water Act, identifies the technology, treatment techniques, or other means available identified in paragraph (4)(e) as affordable technology, treatment techniques, or other means available to systems serving 10,000 or fewer people for achieving compliance with the maximum contaminant level for total coliforms in paragraphs (4)(a) and (4)(b) and for achieving compliance with the maximum contaminant level for E. coli in paragraph (4)(c).

(5) Primary MCLs for Radioactivity and Radionuclides. Radioactivity - Maximum contaminant levels for Radium-226, Radium-228, gross alpha particle radioactivity, beta particle and photon radioactivity from man-made radionuclides in community water systems. (a) The following are the maximum contaminant levels for Radium-226, Radium-228, gross alpha radioactivity, and Uranium: Radionuclides / Radioactivity Maximum Contaminant Level Combined Radium-226 and Radium-228 (²²⁶ Ra, ²²⁸ Ra) 5 pCi/L Gross alpha particle activity (including Radium-226 but excluding Radon and Uranium) 15 pCi/L Uranium 30 µg/L (b) The average annual concentration of beta particle and photon radioactivity from man­made radionuclides in drinking water shall not produce an annual dose equivalent to the total body or any internal organ greater than 4 millirem per year. (c) Except for the radionuclides listed in Table A, the concentration of man-made radionuclides causing 4 mrem total body or organ dose equivalents shall be calculated on the basis of a 2 liter per day drinking water intake using the 168 hour data listed in "Maximum Permissible Body Burdens and Maximum Permissible Concentrations of Radionuclides in Air or Water for Occupational Exposure", NBS Handbook 69 as amended August, 1963, U.S. Department of Commerce. If two or more radionuclides are present, the sum of their annual dose equivalent to the total body or to any organ shall not exceed 4 millirem per year. TABLE A. - Average annual concentrations assumed for the purpose of this rule to produce a total body or organ dose of 4 millirem per year. Radionuclide Critical Organ Average Annal Concentration Tritium (³H) Total Body 20,000 pCi/L Strontium-90 (⁹⁰ Sr) Bone Marrow 8 pCi/L

1. (6) Primary MCLs for Trihalomethanes. TRIHALOMETHANES - Maximum contaminant level for trihalomethanes: see paragraph (7), DISINFECTANTS and DISINFECTION BYPRODUCTS, below.

(7) Primary MCLs for Disinfectants and Disinfection Byproducts. DISINFECTANTS and DISINFECTION BYPRODUCTS (D/DBPs). Beginning January 1, 2002, this paragraph shall be applicable as specified below: (a) The maximum contaminant levels (MCLs) for disinfection byproducts (DBPs) are as specified in 40 CFR § 141.64 and the maximum residual disinfectant levels (MRDLs) are as specified in 40 CFR § 141.65. Disinfection Byproduct Maximum Contaminant Level (mg/L) Total trihalomethanes 0.080 Haloacetic acids (five) 0.060 Bromate 0.010 Chlorite 1.0 Disinfectant Residuals Maximum Residual Disinfectant Level (mg/L) Chlorine 4.0 (as Cl₂) Chloramines 4.0 (as Cl₂) Chlorine Dioxide 0.8 (as ClO₂) (b) Beginning January 1, 2002, community and non-transient, non-community Subpart H water systems which serve a population of 10,000 people or more must comply with paragraph (7). All systems must comply with these MCLs until the date specified for Subpart V compliance in 40 CFR § 141.620(c). (c) Beginning January 1, 2004, community and non-transient, non-community Subpart H water systems serving fewer than 10,000 people and systems using only ground water not under the direct influence of surface water must comply with paragraph (7). All systems must comply with these MCLs until the date specified for Subpart V compliance in 40 CFR § 141.620(c). (d) The Subpart V MCLs for TTHM and HAA5 must be complied with as a locational running annual average at each monitoring location beginning the date specified for Subpart V compliance in 40 CFR § 141.620(c). (e) A system that is installing granular activated carbon (GAC) or membrane technology to comply with paragraph (7) may apply to the Division for an extension of up to 24 months past the dates in paragraphs (7)(b) and (7)(c), but not beyond December 31, 2003. (f) Transient non-community Subpart H water systems serving 10,000 or more persons and using chlorine dioxide as a disinfectant or oxidant must comply with the chlorine dioxide MRDL beginning January 1, 2002. (g) Transient non-community Subpart H water systems serving fewer than 10,000 persons and using chlorine dioxide as a disinfectant or oxidant and systems using only ground water not under the direct influence of surface water and using chlorine dioxide as a disinfectant or oxidant must comply with the chlorine dioxide MRDL beginning January 1, 2004. (h) The best technology, treatment technique, or other means available for achieving compliance with the maximum contaminant levels for disinfection byproducts identified in paragraph (7)(a) shall be in accordance with 40 CFR §§ 141.64(a)(2) and (b)(2).

1. (8) Maximum Contamination Level Goals (MCLG). The maximum contaminant level goals for organic contaminants, inorganic contaminants, and microbiological contaminants shall be in accordance with 40 CFR §§ 141.50, 141.51, 141.52, 141.53, and 141.54.

Authority: O.C.G.A. § 12-5-170et seq.

History. Original Rule entitled - Operating Records" adopted. F. Sept. 6, 1973; eff. Sept. 26, 1973.

Repealed: New Rule entitled - Primary Maximum Contaminant Levels for Drinking Water" adopted. F. July 5, 1977; eff. July 26, 1977, as specified by Rule 391-3-5-.47.

Amended: F. July 15, 1983; eff. August 4, 1983.

Repealed: New Rule of same title adopted. F. May 12, 1989; eff. June 1, 1989.

Amended: F. Dec. 4, 1990; eff. Dec. 24, 1990.

Repealed: New Rule, same title adopted. F. June 25, 1992; eff. July 15, 1992.

Repealed: New Rule of same title adopted. F. Mar. 10, 1994; eff. Mar. 30, 1994.

Amended: F. Sept. 26, 1997; eff. Oct. 16, 1997.

Amended: F. Sept. 29, 2000; eff. Oct. 19, 2000.

Amended: F. June 8, 2001; eff. June 28, 2001.

Amended: F. Dec. 10, 2002; eff. Dec. 30, 2002.

Amended: F. Dec. 21, 2004; eff. Jan. 10, 2005.

Amended: F. May 27, 2009; eff. June 16, 2009.

Amended: New title "Primary Maximum Contaminant Levels for Drinking Water. Amended." F. Jan. 8, 2014; eff. Jan. 28, 2014.

Amended: New title "Primary Maximum Contaminant Levels for Drinking Water." F. Feb. 29, 2016; eff. Mar. 20, 2016.

Amended: F. Apr. 22, 2021; eff. May 12, 2021.