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PDFWAC 246-290-315

State action levels (SALs) and state maximum contaminant levels (MCLs).

(1) The department shall consider the following criteria to select a contaminant for developing a SAL:
(a) Drinking water contributes to human exposure to the contaminant.
(b) The contaminant is known or likely to occur in public water systems at levels of public health concern. Sources of occurrence information include, but are not limited to:
(i) Washington state department of agriculture;
(ii) Washington state department of ecology; and
(iii) Monitoring results reported in accordance with 40 C.F.R. 141.35.
(c) The contaminant has a possible adverse effect on the health of persons exposed based on peer-reviewed scientific literature or government publications, such as:
(i) An EPA health assessment such as an Integrated Risk Information System assessment;
(ii) Agency for Toxic Substances and Disease Registry toxicological profiles;
(iii) State government science assessment; and
(iv) EPA guidelines for exposure assessment such as the EPA exposure factors handbook.
(d) A certified drinking water lab can accurately and precisely measure the concentration of the contaminant in drinking water at and below the level of public health concern using EPA-approved analytical methods.
(2) After consideration of the criteria in subsection (1) of this section, the department may develop a SAL based on the following:
(a) Evaluation of available peer-reviewed scientific literature and government publications on fate, transport, exposure, toxicity and health impacts of the contaminant and relevant metabolites;
(b) An assessment based on the most sensitive adverse effect deemed relevant to humans and considering susceptibility and unique exposures of the most sensitive subgroup such as pregnant women, fetuses, young children, or overburdened and underserved communities; and
(c) Technical limitations to achieving the SAL such as insufficient analytical detection limit achievable at certified drinking water laboratories.
(3) The state board of health shall consider the department's findings under subsections (1) and (2) of this section when considering adopting a SAL under this chapter.
(4) Contaminants with a SAL.
(a) If a SAL under Table 9 of this section is exceeded, the purveyor shall take follow-up action as required under WAC 246-290-320. For contaminants where the SAL exceedance is determined based upon an RAA, the RAA will be calculated consistent with other organic contaminants per WAC 246-290-320(6) or other inorganic contaminants per WAC 246-290-320(3).
Contaminant or Group of Contaminants
SAL Exceedance Based On:
Per- and polyfluoroalkyl substances (PFAS)
10 ng/L
Confirmed detection
15 ng/L
Confirmed detection
65 ng/L
Confirmed detection
9 ng/L
Confirmed detection
345 ng/L
Confirmed detection
(b) If a system fails to collect and submit a confirmation sample to a certified lab within ten business days of notification of the sample results, or as required by the department, the results of the original sample will be used to determine compliance with the SAL.
(5) The department shall consider the following when developing a state MCL:
(a) The criteria in subsection (1) of this section;
(b) Whether regulating the contaminant presents a meaningful opportunity to reduce exposures of public health concern for persons served by public water systems;
(c) The need for an enforceable limit to achieve uniform public health protection in Group A public water systems; and
(d) The need for an enforceable limit to support source water investigation and clean-up of a contaminant in drinking water supplies by responsible parties.
(6) In addition to the requirements in subsection (5) of this section, the department shall:
(a) Meet the requirements of subsection (2) of this section;
(b) Comply with the requirements in RCW 70A.130.010 to establish standards for chemical contaminants in drinking water;
(c) Consider the best available treatment technologies and affordability taking into consideration the costs to small water systems; and
(d) Determine that the probable benefits of the rule are greater than its probable costs, taking into account both the qualitative and quantitative benefits and costs.
(7) The state board of health shall consider the department's findings under subsections (5) and (6) of this section and follow the requirements under chapters 34.05 and 19.85 RCW when adopting a state MCL under this chapter.
(8) Upon federal adoption of an MCL, the federal MCL will supersede a SAL or a less stringent state MCL, and the associated requirements, including for monitoring and public notice. If the federally adopted MCL is less stringent than a SAL or state MCL, the board may take one of the following actions:
(a) Adopt the federal MCL; or
(b) Adopt a state MCL, at least as stringent as the federal MCL, using the process in subsections (6) and (7) of this section.
[Statutory Authority: RCW 43.20.050, 70A.125.080, and 70A.130.010. WSR 21-23-097, ยง 246-290-315, filed 11/17/21, effective 1/1/22.]
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