R 325.10610b Disinfectant residuals, disinfection byproducts, and disinfection byproduct precursors; compliance requirements.

Rule 610b. (1) This rule, R 325.10610c, R 325.10719e, and R 325.10719f apply to community water supplies and nontransient noncommunity water supplies that add a chemical disinfectant to the water in any part of the drinking water treatment process and to transient noncommunity water supplies adding chlorine dioxide. These public water supplies are considered "water supplies" or "supplies" in this rule. Transient noncommunity water supplies are only required to comply with the chlorine dioxide requirements. Compliance with this rule is based on all of the following: (a) All samples taken under this rule, R 325.10610c, R 325.10719e, and R 325.10719f and analyzed under R 325.10605, shall be included in determining compliance with the maximum contaminant levels and maximum residual disinfectant levels of R 325.10610 and R 325.10610a. (b) If, during the first year of monitoring under R 325.10719e, any individual quarter's average will cause the running annual average of that water supply to exceed the MCL for total trihalomethanes, haloacetic acids (five), or bromate; or the MRDL for chlorine or chloramine, the supply is out of compliance at the end of that quarter. (c) A supply is in violation of the state drinking water standard if compliance is based on 4 consecutive quarters of monitoring and the average of samples, or quarterly averages, or running annual averages, whichever is applicable, exceeds the state drinking water standard, unless otherwise noted in this rule. (d) Where compliance is based on a running annual average of monthly or quarterly samples or averages and the supply fails to complete 4 consecutive quarters or 12 consecutive months of monitoring, whichever is applicable, compliance with the MCL for the last 4 quarter compliance period is based on an average of the available data unless otherwise stated in this rule. (2) Compliance with disinfection byproducts requirements is based on all of the following: (a) Compliance with TTHM and HAA5 requirements are based on R 325.10610d(4) and (5). (b) Compliance with the bromate requirements is based on a running annual average, computed quarterly, of monthly samples, or, for months in which the supply takes more than 1 sample, the average of all samples taken during the month, collected under R 325.10719e(2)(c). (c) Compliance with the chlorite requirements is based on an average of each 3 sample set taken in the distribution system under R 325.10719e(2)(b)(i)(B) and R 325.10719e(2)(b)(ii). If the average of any 3 sample set exceeds the MCL, the supply is in violation of the MCL. (3) Compliance with disinfectant residuals requirements is based on both of the following: (a) Compliance with the chlorine and chloramines requirements is based on a running annual average, computed quarterly, of monthly averages of all samples collected by the supply under R 325.10719e(3)(a). In cases where supplies switch between the use of chlorine and chloramines for residual disinfection during the year, compliance is determined by including together all monitoring results of both chlorine and chloramines in calculating compliance. Supplies shall clearly indicate which residual disinfectant was analyzed for each sample when submitting reports to the department under R 325.11502a. (b) Compliance with the chlorine dioxide requirements is based on consecutive daily samples collected by the supply under R 325.10719e(3)(b). (i) An acute violation occurs when a daily sample taken at the entrance to the distribution system exceeds the MRDL, and on the following day 1, or more, of the 3 samples taken in the distribution system exceed the MRDL. The supply shall take immediate corrective action to lower the level of chlorine dioxide below the MRDL. Failure to monitor in the distribution system the day following an exceedance of the chlorine dioxide MRDL at the entrance to the distribution system is also an MRDL violation and the supply shall notify the public of the violation under R 325.10402, Tier 1 public notice, and report to the department under R 325.10719f. (ii) A nonacute violation occurs when 2 consecutive daily samples taken at the entrance to the distribution system exceed the MRDL and all distribution system samples taken are below the MRDL. The supply shall take corrective action to lower the level of chlorine dioxide below the MRDL at the point of sampling. Failure to monitor at the entrance to the distribution system the day following an exceedance of the chlorine dioxide MRDL at the entrance to the distribution system is also an MRDL violation and the supply shall notify the public of the violation under R 325.10403, Tier 2 public notice, and report to the department under R 325.10719f. (c) Notwithstanding the MRDLs in R 325.10610b, supplies may increase residual disinfectant levels in the distribution system of chlorine or chloramines, but shall not increase the levels of chlorine dioxide, to a level and for a time necessary to protect public health to address specific microbiological contamination problems caused by circumstances such as distribution line breaks, storm run-off events, source water contamination events, or cross-connection events. (4) Compliance with the treatment technique for disinfection byproduct precursors (DBPP) is determined as specified by R 325.10610c(3). Supplies may begin monitoring to determine whether step 1 TOC removals can be met 12 months before the compliance date for the supply. This monitoring is not required and failure to monitor during this period is not a violation. However, a supply that does not monitor during this period, and then determines, in the first 12 months after the compliance date, that the supply is not able to meet the step 1 requirements in R 325.10610c(2)(b) and shall therefore apply for alternate minimum TOC removal (step 2) requirements, is not eligible for retroactive approval of alternate minimum TOC removal (step 2) requirements as allowed under R 325.10610c(2)(c) and is in violation. Supplies may apply for alternate minimum TOC removal (step 2) requirements any time after the compliance date. For supplies required to meet step 1 TOC removals, if the value calculated under R 325.10610c(3)(a)(iv) is less than 1.00 calculated as a running annual average of monthly samples, computed quarterly, the supply is in violation of the treatment technique requirements and shall notify the public.