R 325.10604g MCLs for per- and polyfluoroalkyl substances.

Rule 604g. (1) The maximum contaminant levels and effective dates for per- and polyfluoroalkyl substances in table 1 of this rule apply to community and nontransient noncommunity water supplies. Table 1 MCLs for per and polyfluoroalkyl substances Contaminant Maximum Contaminant Level in ng/l Effective Date Hexafluoropropylene oxide dimer acid (HFPO-DA) 370 [effective date of this rule] Perfluorobutane sulfonic acid (PFBS) 420 [effective date of this rule] Perfluorohexane sulfonic acid (PFHxS) 51 [effective date of this rule] Perfluorohexanoic acid (PFHxA) 400,000 [effective date of this rule] Perfluorononanoic acid (PFNA) 6 [effective date of this rule] Perfluorooctane sulfonic acid (PFOS) 16 [effective date of this rule] Perfluorooctanoic acid (PFOA) 8 [effective date of this rule] (2) Compliance with the MCLs in table 1 of this rule must be determined based on the analytical results obtained at each sampling point. If 1 sampling point is in violation of an MCL, then the supply is in violation of the MCL. All of the following provisions apply: (a) For supplies monitoring more than once per year, compliance with the MCL is determined by a running annual average at each sampling point. (b) Supplies monitoring annually whose sample result exceeds an MCL in table 1 of this rule shall begin quarterly sampling. Compliance with the MCL must be based on the running annual average. For the purpose of calculating the running annual average, the initial exceedance must be the result for the first quarter. If the department requires a confirmation sample under R 325.10717d(12), then the average of the initial exceedance and the confirmation sample must be the result for the first quarter, unless the department determines a sample should be excluded per R 325.10717d(12). The supply shall not be in violation of the MCL until it has completed 1 year of quarterly sampling. (c) If any sample result causes the running annual average to exceed the MCL at any sampling point, then the supply is out of compliance with the MCL immediately. (d) If a supply fails to collect the required number of samples, then compliance must be based on the total number of samples collected. (e) If a sample result is less than the reporting limit, then zero must be used to calculate the annual average.