246-290-300  <<  246-290-310 >>   246-290-320

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 substance 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.
Note:
For the purposes of the public notification requirements in Part 7, Subpart A of this chapter, an E. coli MCL is a violation that requires Tier 1 public notification.
(3) Inorganic chemical and physical.
(a) The primary and secondary MCLs are listed in Table 5 and 6:
TABLE 5
INORGANIC CHEMICAL CHARACTERISTICS
 
Substance
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 (HCN)
 
0.2
 
Fluoride (F)
 
4.0
 
Lead (Pb)
 
**
 
Mercury (Hg)
 
0.002
 
Nickel (Ni)
 
0.1
 
Nitrate (as N)
 
10.0
 
Nitrite (as N)
 
1.0
 
Selenium (Se)
 
0.05
 
Sodium (Na)
 
**
 
Thallium (Tl)
 
0.002
 
Substance
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 (SO4)
 
250.0
 
Zinc (Zn)
 
5.0
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 ten percent of all samples collected from the distribution system. The EPA has also established a recommended level of twenty mg/L for sodium as a level of concern for those consumers that may be restricted for daily sodium intake in their diets.
TABLE 6
PHYSICAL CHARACTERISTICS
Substance
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:
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:
Disinfectant Residual
MRDL (mg/L)
Chlorine
 
4.0 (as C12)
Chloramines
 
4.0 (as C12)
Chlorine Dioxide
 
0.8 (as C1O2)
(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 shall be as listed in 40 C.F.R. 141.61(a).
(ii) The department shall determine compliance with this subsection based on compliance with 40 C.F.R. 141.24(f).
(c) SOCs.
(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).
(8) Other chemicals.
(a) The state board of health shall determine maximum contaminant levels for any additional substances.
(b) Purveyors may be directed by the department to comply with state advisory levels (SALs) for contaminants that do not have a MCL established in chapter 246-290 WAC. SALs shall be:
(i) MCLs that have been promulgated by the EPA, but which have not yet been adopted by the state board of health; or
(ii) State board of health adopted levels for substances recommended by the department and not having an EPA established MCL. A listing of these may be found in the department document titled Procedures and References for the Determination of State Advisory Levels for Drinking Water Contaminants dated June 1996, that has been approved by the state board of health and is available.
[Statutory Authority: RCW 43.20.050 and 70.119A.080. WSR 17-01-062, § 246-290-310, filed 12/14/16, effective 1/14/17. Statutory Authority: RCW 43.20.050. WSR 09-21-045, § 246-290-310, filed 10/13/09, effective 1/4/10. Statutory Authority: RCW 70.119A.180 and 43.20.050. WSR 08-03-061, § 246-290-310, filed 1/14/08, effective 2/14/08. Statutory Authority: RCW 43.20.050 and 70.119A.080. WSR 04-04-056, § 246-290-310, filed 1/30/04, effective 3/1/04. Statutory Authority: RCW 43.20.050 (2) and (3) and 70.119A.080. WSR 03-08-037, § 246-290-310, filed 3/27/03, effective 4/27/03. Statutory Authority: RCW 43.02.050 [43.20.050]. WSR 99-07-021, § 246-290-310, filed 3/9/99, effective 4/9/99. Statutory Authority: RCW 43.20.050. WSR 94-14-001, § 246-290-310, filed 6/22/94, effective 7/23/94; WSR 93-08-011 (Order 352B), § 246-290-310, filed 3/25/93, effective 4/25/93; WSR 92-04-070 (Order 241B), § 246-290-310, filed 2/4/92, effective 3/6/92. Statutory Authority: Chapter 43.20 RCW. WSR 91-07-031 (Order 150B), § 246-290-310, filed 3/15/91, effective 4/15/91. Statutory Authority: RCW 43.20.050. WSR 91-02-051 (Order 124B), recodified as § 246-290-310, filed 12/27/90, effective 1/31/91. Statutory Authority: P.L. 99-339. WSR 89-21-020 (Order 336), § 248-54-175, filed 10/10/89, effective 11/10/89. Statutory Authority: RCW 34.04.045. WSR 88-05-057 (Order 307), § 248-54-175, filed 2/17/88. Statutory Authority: RCW 43.20.050. WSR 83-19-002 (Order 266), § 248-54-175, filed 9/8/83.]
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