1. (1) Finished drinking water from chemical contaminant treatment facilities must comply with the minimum water quality standards established in WAC 246-290-310. This section does not apply to facilities used only for corrosion control treatment purposes.

   1. (a) The purveyor shall collect finished drinking water samples at a point directly downstream of the treatment system prior to the first consumer on a monthly basis.

      1. (i) Finished drinking water samples from treatment systems utilized for removal of contaminants with established primary MCLs shall be submitted to a certified laboratory for analysis of the specific contaminant(s) of concern.
      2. (ii) Finished drinking water samples from treatment systems utilized for removal of contaminants with established secondary MCLs shall be submitted to a certified laboratory for analysis or analyzed for the specific contaminant(s) of concern by the purveyor through department-approved on-site methods.
      3. (iii) Additional finished drinking water monitoring may be required by the department based on the complexity or size of the water system.
   2. (b) If primary MCLs following treatment are exceeded in four or more months of a consecutive twelve-month compliance period, the purveyor shall submit a project report to the department that addresses the failure to maintain compliance. The project report shall include methods and schedules to correct the treatment deficiency and/or indicate schedules for implementing an alternate source of supply or an effective treatment technology.
   3. (c) If secondary MCLs following treatment are exceeded in four or more months of a consecutive twelve-month compliance period, the purveyor shall take action per WAC 246-290-320 (3)(d).

2. (2) Purveyors that treat to remove or blend to reduce a contaminant that exceeds the SAL shall:

   1. (a) Collect finished drinking water samples at a point downstream of the treatment system prior to the first consumer on a quarterly basis; and
   2. (b) Submit the samples to a certified lab for analysis or analyze the samples using department-approved on-site methods.

[Statutory Authority: RCW 43.20.050, 70A.125.080, and 70A.130.010. WSR 21-23-097, § 246-290-455, filed 11/17/21, effective 1/1/22. Statutory Authority: RCW 43.02.050 [43.20.050]. WSR 99-07-021, § 246-290-455, filed 3/9/99, effective 4/9/99.]