(a) Summary table purpose. The maximum contaminant levels (MCLs), maximum residual disinfectant levels (MRDLs), treatment techniques, and action levels are presented in this section as a reference source. Only the regulatory concentrations are shown in these tables. Compliance requirements are given in the specific section for each chemical.
(b) MCLs for inorganic compounds. The MCLs for inorganic contaminants listed in this subsection apply to public water systems as provided in §290.106 of this title (relating to Inorganic Contaminants).
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(c) MCLs for organic compounds. The following MCLs for synthetic organic contaminants and volatile organic contaminants apply to public water systems as provided in §290.107 of this title (relating to Organic Contaminants).
  (1) The following are the MCLs for synthetic organic contaminants.
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  (2) The following are the MCLs for volatile organic contaminants.
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(d) MCLs for radionuclide contaminants. MCLs for radionuclide contaminants apply to public water systems as provided in §290.108 of this title (relating to Radionuclides Other than Radon).
(e) Microbial contaminants. The MCL for microbial or bacteriological contaminants applies to public water systems as provided in §290.109 of this title (relating to Microbial Contaminants). The MCL for microbiological contaminants is based on the presence or absence of Escherichia coli (E. coli).
(f) Minimum residual disinfectant concentrations and MRDLs. Minimum residual disinfectant concentrations and MRDLs apply to public water systems as provided in §290.110 of this title (relating to Disinfectant Residuals).
  (1) The minimum residual disinfectant concentration in the water entering the distribution system is 0.2 milligrams per liter (mg/L) free chlorine or 0.5 mg/L chloramine.
  (2) The minimum residual disinfectant concentration in the water within the distribution system is 0.2 mg/L free chlorine or 0.5 mg/L chloramine.
  (3) The MRDL of chlorine dioxide in the water entering the distribution system is 0.8 mg/L.
  (4) The MRDL of free chlorine or chloramine in the water within the distribution system is 4.0 mg/L based on a running annual average.
(g) Surface water treatment. Systems treating surface water or groundwater under the direct influence of surface water must meet the turbidity treatment technique requirements as provided in §290.111 of this title (relating to Surface Water Treatment).
  (1) The turbidity level of the combined filter effluent must never exceed 1.0 nephelometric turbidity unit (NTU) and the turbidity level of the combined filter effluent must be 0.3 NTU or less in at least 95% of the samples tested each month.
  (2) Systems are subject to the raw water monitoring, pathogen removal and inactivation and individual filter turbidity provisions of §290.111 of this title.
(h) Disinfection by-product precursors. The treatment technique requirements for disinfection by-product precursors apply to water systems as provided in §290.112 of this title (relating to Total Organic Carbon (TOC)).
(i) Disinfection by-products (total trihalomethanes (TTHM) and haloacetic acids (HAA5)). The MCLs for TTHM and HAA5 apply to water systems as provided in §290.113 of this title (relating to Stage 1 Disinfection By-products (TTHM and HAA5)) and in §290.115 of this title (relating to Stage 2 Disinfection By-products (TTHM and HAA5)). The MCLs for TTHM and HAA5 are:
  (1) 0.080 mg/L for TTHM; and
  (2) 0.060 mg/L for HAA5.
(j) Disinfection by-products other than TTHM and HAA5. The MCLs for chlorite and bromate apply to water systems as provided in §290.114 of this title (relating to Other Disinfection By-products (Chlorite and Bromate)). The MCLs for chlorite and bromate are as follows:
  (1) 1.0 mg/L for chlorite; and
  (2) 0.010 mg/L for bromate.
(k) Lead and copper action levels. The action levels for lead and copper apply to water systems as provided in §290.117 of this title (relating to Regulation of Lead and Copper). Action levels for lead and copper are as follows:
  (1) 0.015 mg/L for lead; and
  (2) 1.3 mg/L for copper.
(l) Recycle streams. The treatment technique requirements for recycle streams are specified in §290.42(c)(6) and (d)(3) of this title (relating to Water Treatment).

Source Note: The provisions of this §290.104 adopted to be effective September 13, 2000, 25 TexReg 8880; amended to be effective May 16, 2002, 27 TexReg 4127; amended to be effective February 19, 2004, 29 TexReg 1373; amended to be effective December 23, 2004, 29 TexReg 11729; amended to be effective January 9, 2008, 33 TexReg 198; amended to be effective March 30, 2017, 42 TexReg 1466