WAC 246-290-310. Maximum contaminant levels (MCLs) and maximum residual disinfectant levels (MRDLs)

(1) General. (a) The purveyor shall be responsible for complying with the standards of water quality identified in this section. If a contaminant exceeds its MCL or its maximum residual disinfectant level (MRDL), the purveyor shall take follow-up action under WAC 246-290-320 . (b) When enforcing the standards described under this section, the department shall enforce compliance with the primary standards as its first priority. (2) Bacteriological. (a) An E. coli MCL under this subsection is considered a primary standard. (b) E. coli MCL. An E. coli MCL violation occurs each month in which a system is required to monitor for total coliforms when there is: (i) E. coli presence in a repeat sample following a total coliform presence routine sample; (ii) Total coliform presence in any repeat samples collected as a follow-up to a sample with E. coli presence; (iii) The system fails to take all required repeat samples following an E. coli presence routine sample; or (iv) The system fails to test for E. coli when any repeat samples test positive for total coliform. (3) Inorganic chemical and physical. (a) The primary and secondary standards are listed in Tables 5 and 6 of this section: TABLE 5 INORGANIC CHEMICAL CHARACTERISTICS Contaminant Primary MCLs (mg/L) Antimony (Sb) 0.006 Arsenic (As) 0.010* Asbestos 7 million fibers/liter (longer than 10 microns) Barium (Ba) 2.0 Beryllium (Be) 0.004 Cadmium (Cd) 0.005 Chromium (Cr) 0.1 Copper (Cu) ** Cyanide (CN) 0.2 Fluoride (F) 4.0*** Lead (Pb) ** Mercury (Hg) 0.002 Nitrate (as N) 10.0 Nitrite (as N) 1.0 Selenium (Se) 0.05 Sodium (Na) ** Thallium (Tl) 0.002 Contaminant Secondary MCLs (mg/L) Chloride (Cl) 250.0 Fluoride (F) 2.0*** Iron (Fe) 0.3 Manganese (Mn) 0.05 Silver (Ag) 0.1 Sulfate (SO 4 ) 250.0 Zinc (Zn) 5.0 Contaminant Primary MCLs (mg/L) Antimony (Sb) 0.006 Arsenic (As) 0.010* Asbestos 7 million fibers/liter (longer than 10 microns) Barium (Ba) 2.0 Beryllium (Be) 0.004 Cadmium (Cd) 0.005 Chromium (Cr) 0.1 Copper (Cu) ** Cyanide (CN) 0.2 Fluoride (F) 4.0*** Lead (Pb) ** Mercury (Hg) 0.002 Nitrate (as N) 10.0 Nitrite (as N) 1.0 Selenium (Se) 0.05 Sodium (Na) ** Thallium (Tl) 0.002 Contaminant Secondary MCLs (mg/L) Chloride (Cl) 250.0 Fluoride (F) 2.0*** Iron (Fe) 0.3 Manganese (Mn) 0.05 Silver (Ag) 0.1 Sulfate (SO 4 ) 250.0 Zinc (Zn) 5.0 Note* Does not apply to TNC systems. Note* Does not apply to TNC systems. Note** Although the state board of health has not established MCLs for copper, lead, and sodium, there is sufficient public health significance connected with copper, lead, and sodium levels to require inclusion in inorganic chemical and physical source monitoring. For lead and copper, the EPA has established distribution system related levels at which a system is required to consider corrosion control. These levels, called "action levels," are 0.015 mg/L for lead and 1.3 mg/L for copper and are applied to the highest concentration in 10 percent of all samples collected from the distribution system. The EPA has also established a recommended level of 20 mg/L for sodium as a level of concern for those consumers that may be restricted for daily sodium intake in their diets. Note** Although the state board of health has not established MCLs for copper, lead, and sodium, there is sufficient public health significance connected with copper, lead, and sodium levels to require inclusion in inorganic chemical and physical source monitoring. For lead and copper, the EPA has established distribution system related levels at which a system is required to consider corrosion control. These levels, called "action levels," are 0.015 mg/L for lead and 1.3 mg/L for copper and are applied to the highest concentration in 10 percent of all samples collected from the distribution system. The EPA has also established a recommended level of 20 mg/L for sodium as a level of concern for those consumers that may be restricted for daily sodium intake in their diets. Note*** If a water system provides community fluoridation, the level of fluoride and associated requirements are set under WAC 246-290-460 . Note*** If a water system provides community fluoridation, the level of fluoride and associated requirements are set under WAC 246-290-460 . TABLE 6 PHYSICAL CHARACTERISTICS Contaminant Secondary MCLs Color 15 Color Units Specific Conductivity 700 umhos/cm Total Dissolved Solids (TDS) 500 mg/L Contaminant Secondary MCLs Color 15 Color Units Specific Conductivity 700 umhos/cm Total Dissolved Solids (TDS) 500 mg/L (b) Compliance with the MCLs, except for nitrate and nitrite, in this subsection is determined by a running annual average at each sampling point. The system will not be considered in violation of the MCL until it has completed one year of quarterly sampling and at least one sampling point is in violation of the MCL. If one sampling point is in violation of the MCL, the system is in violation of the MCL. (i) If any sample will cause the running annual average to exceed the MCL at any sampling point, the system is out of compliance with the MCL immediately. (ii) If a system fails to collect the required number of samples, compliance will be based on the total number of samples collected. (iii) If a sample result is less than the detection limit, zero will be used to calculate the running annual average. (c) Compliance with the MCLs for nitrate and nitrite is determined based on one sample if the levels of these contaminants are below the MCLs as determined under Table 5 of this section. If the levels of nitrate or nitrite exceed the MCLs in the initial sample, a confirmation sample is required under 40 C.F.R. 141.23 (f)(2), and compliance shall be determined based on the average of the initial and confirmation samples. (4) Disinfection byproducts. (a) The department shall consider standards under this subsection as primary standards. The MCLs in this subsection apply to monitoring required by WAC 246-290-300 (6) and 40 C.F.R. 141.620 - 629. (b) The MCLs for disinfection byproducts are as follows: TABLE 7 DISINFECTION BYPRODUCTS Disinfection Byproduct MCL (mg/L) Total Trihalomethanes (TTHMs) 0.080 Haloacetic acids (five) (HAA5) 0.060 Bromate 0.010 Chlorite 1.0 Disinfection Byproduct MCL (mg/L) Total Trihalomethanes (TTHMs) 0.080 Haloacetic acids (five) (HAA5) 0.060 Bromate 0.010 Chlorite 1.0 (c) Whether a system has exceeded the disinfection byproduct MCLs shall be determined in accordance with 40 C.F.R. 141.133. Beginning on the dates specified for compliance in 40 C.F.R. 141.620(c), compliance with the TTHMs and HAA5 MCLs shall be based on the LRAAs as required by 40 C.F.R. 141.64 (b)(2) and 40 C.F.R. 141.620(d). Compliance with the bromate and chlorite MCL will continue to be determined in accordance with 40 C.F.R. 141.133. (5) Disinfectant residuals. (a) The department shall consider standards under this subsection primary standards. The MRDLs in this subsection apply to monitoring required by WAC 246-290-300 (6). (b) The MRDL for disinfectants is as follows: TABLE 8 DISINFECTANT RESIDUAL MRDLs Disinfectant Residual MRDL (mg/L) Chlorine 4.0 (as C1 2 ) Chloramines 4.0 (as C1 2 ) Chlorine Dioxide 0.8 (as C1O 2 ) Disinfectant Residual MRDL (mg/L) Chlorine 4.0 (as C1 2 ) Chloramines 4.0 (as C1 2 ) Chlorine Dioxide 0.8 (as C1O 2 ) (c) Whether a system has exceeded MRDLs shall be determined in accordance with 40 C.F.R. 141.133. (6) Radionuclides. (a) The department shall consider standards under this subsection primary standards. (b) The MCLs for radium-226 and radium-228, gross alpha particle activity, beta particle and photon radioactivity, and uranium shall be as listed in 40 C.F.R. 141.66. (7) Organic chemicals. (a) The department shall consider standards under this subsection primary standards. (b) VOCs. (i) The MCLs for VOCs are as follows: Contaminant Chemical Abstract Service (CAS) Number MCL (ppb) Vinyl chloride 75-01-4 2 Benzene 71-43-2 5 Carbon tetrachloride 56-23-5 5 1,2-Dichloroethane 107-06-2 5 Trichloroethylene 79-01-6 5 para-Dichlorobenzene 106-46-7 75 1,1-Dichloroethylene 75-35-4 7 1,1,1-Trichloroethane 71-55-6 200 cis-1,2-Dichloroethylene 156-59-2 70 1,2-Dichloropropane 78-87-5 5 Ethylbenzene 100-41-4 700 Monochlorobenzene 108-90-7 100 o-Dichlorobenzene 95-50-1 600 Styrene 100-42-5 100 Trichloroethane 127-18-4 5 Toluene 108-88-3 1,000 trans-1,2-Dichloroethylene 156-60-5 100 Xylenes (total) 1330-20-7 10,000 Dichloromethane 75-09-2 5 1,2,4-Trichlorobenzene 120-82-1 70 1,1,2-Trichloroethane 79-00-5 5 Contaminant Chemical Abstract Service (CAS) Number MCL (ppb) Vinyl chloride 75-01-4 2 Benzene 71-43-2 5 Carbon tetrachloride 56-23-5 5 1,2-Dichloroethane 107-06-2 5 Trichloroethylene 79-01-6 5 para-Dichlorobenzene 106-46-7 75 1,1-Dichloroethylene 75-35-4 7 1,1,1-Trichloroethane 71-55-6 200 cis-1,2-Dichloroethylene 156-59-2 70 1,2-Dichloropropane 78-87-5 5 Ethylbenzene 100-41-4 700 Monochlorobenzene 108-90-7 100 o-Dichlorobenzene 95-50-1 600 Styrene 100-42-5 100 Trichloroethane 127-18-4 5 Toluene 108-88-3 1,000 trans-1,2-Dichloroethylene 156-60-5 100 Xylenes (total) 1330-20-7 10,000 Dichloromethane 75-09-2 5 1,2,4-Trichlorobenzene 120-82-1 70 1,1,2-Trichloroethane 79-00-5 5 (ii) The department shall determine compliance with this subsection based on compliance with 40 C.F.R. 141.24(f). (c) SOCs, except PFAS. (i) MCLs for SOCs shall be as listed in 40 C.F.R. 141.61(c). (ii) The department shall determine compliance with this subsection based on compliance with 40 C.F.R. 141.24(h). (d) PFAS. (i) The MCLs for PFAS, effective in accordance with 40 C.F.R. 141.6, are as follows: Contaminant Chemical Abstract Service (CAS) Number MCL (ppt or ng/L) HBWC (ppt or ng/L) for hazard index calculation PFOA 45285-51-6 4.0 Not applicable PFOS 45298-90-6 4.0 Not applicable PFHxS 108427-53-8 10 10 HFPO-DA 122499-17-6 10 10 PFNA 72007-68-2 10 10 PFBS 45187-15-3 No individual MCL 2,000 Hazard Index PFAS (HFPO-DA, PFBS, PFHxS, and PFNA) Not applicable 1 (unitless) 1 Not applicable Contaminant Chemical Abstract Service (CAS) Number MCL (ppt or ng/L) HBWC (ppt or ng/L) for hazard index calculation PFOA 45285-51-6 4.0 Not applicable PFOS 45298-90-6 4.0 Not applicable PFHxS 108427-53-8 10 10 HFPO-DA 122499-17-6 10 10 PFNA 72007-68-2 10 10 PFBS 45187-15-3 No individual MCL 2,000 Hazard Index PFAS (HFPO-DA, PFBS, PFHxS, and PFNA) Not applicable 1 (unitless) 1 Not applicable 1 The PFAS Mixture Hazard Index (HI) is the sum of component hazard quotients (HQs), which are calculated by dividing the measured component PFAS concentration in water by the relevant health-based water concentration when expressed in the same units (shown in ppt for simplification). The HBWC for PFHxS is 10 ng/l; the HBWC for HFPO-DA is 10 ng/l; the HBWC for PFNA is 10 ng/l; and the HBWC for PFBS is 2000 ng/l. (ii) The MCLs for PFAS will become effective according to the dates outlined in 40 C.F.R. 141.6. (8) Other contaminants. The state board of health shall determine state MCLs for any additional contaminants as described in WAC 246-290-315 (5) through (8).