Section 246-291-170 - Water quality requirements for groundwater source approval(1) All water quality samples collected under this section must be: (a) Collected without chlorine, ultraviolet light, ozone, or other disinfectant in use to treat the source;(b) Collected after the well has been pumped long enough to allow for collection of a representative sample of the aquifer, as described in the Group B Water System Design Guidelines (2012); and(c) Analyzed by a certified lab.(2) To meet the requirements for design approval under WAC 246-291-120, a purveyor shall obtain, at a minimum:(a) Satisfactory results from two raw source water samples analyzed for coliform bacteria;(b) Results from one raw source water sample that has been analyzed for, and does not exceed, any primary MCL in Table 2 of this section; and(c) In areas known or suspected to have contaminants of public health concern, one raw source water sample analyzed for the contaminant(s) as directed by the department or health officer.(3) When analytical results indicate a presence of coliform bacteria, a purveyor shall do the following: (a) Disinfect the source using procedures under WAC 246-291-220; and(b) Collect two repeat samples and analyze for coliform bacteria by a certified lab.(4) A purveyor shall collect a confirmation raw source water sample and have the sample analyzed for each parameter that exceeded the MCL in the initial sample, if: (a) An analysis exceeds a primary MCL in Table 2 of this section; or(b) A contaminant of public health concern under subsection (2)(c) of this section exceeds the primary MCL under WAC 246-290-310.(5) The department or health officer shall not approve the proposed source if: (a) The average concentration from all samples for each substance taken under this section exceeds a primary MCL in Table 2 of this section;(b) The repeat sample results collected under subsection (3) of this section indicate a presence of coliform bacteria; or(c) A contaminant of public health concern collected under this section exceeds the primary MCL under WAC 246-290-310.(6) When an analysis exceeds a secondary MCL in Table 3 or 4 of this section, a purveyor shall include treatment in the Group B system design under WAC 246-291-200 so that drinking water delivered to consumers does not exceed a secondary MCL. Table 2 Primary Inorganic Chemical Contaminants
Substance | MCLs (mg/L) |
Antimony (Sb) | 0.006 | |
Arsenic (As) | 0.010* | |
Barium (Ba) | 2.0 | |
Beryllium (Be) | 0.004 | |
Cadmium (Cd) | 0.005 | |
Chromium (Cr) | 0.1 | |
Cyanide (HCN) | 0.2 | |
Fluoride (F) | 4.0 | |
Mercury (Hg) | 0.002 | |
Nitrate (as N) | 10.0 | |
Nitrite (as N) | 1.0 | |
Selenium (Se) | 0.05 | |
Thallium (Tl) | 0.002 | |
Note: | *The arsenic MCL in Table 2 applies to new and expanding Group B systems. For Group B systems constructed prior to January 1, 2014, the arsenic MCL is 0.05 mg/L. WAC 246-291-360(3) and (4) establish public notification requirements for Group B systems constructed prior to January 1, 2014, with an arsenic concentration exceeding 0.010 mg/L. |
Table 3 Secondary Inorganic Chemical Contaminants
Substance | 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 | |
Table 4 Secondary Physical Characteristics
Substance | MCLs |
Color | 15 color units | |
Specific conductivity | 700 umhos/cm | |
Total dissolved solids (TDS) | 500 mg/L | |
Wash. Admin. Code § 246-291-170
Statutory Authority: RCW 43.20.050 and chapter 70.119A RCW. 12-24-070, § 246-291-170, filed 12/4/12, effective 1/1/14.