Monitoring requirements for per- and polyfluoroalkyl substances

Monitoring requirements for per- and polyfluoroalkyl substances. (1) General monitoring requirements. A water supplier for a CWS or an NTCNWS must monitor for the PFAS listed under s. NR 809.221 (1) for the purposes of determining compliance with the MCLs as follows: (a) Groundwater sources must be sampled under normal operating conditions at every entry point to the distribution system that is representative of each well after treatment. Each sample must be taken at the same location unless, if approved by the department, conditions make another sampling location more representative of each source or treatment plant. (b) Surface water sources or combined surface water and groundwater sources must be sampled at each entry point to the distribution system after treatment, or at locations in the distribution system that are representative of each source after treatment under normal operating conditions. Each sample must be taken at the same entry point location unless, if approved by the department, conditions make another sampling location more representative of each source or treatment plant. (c) If the PWS draws water from more than one source and the sources are combined before distribution, the PWS must be sampled at an entry point to the distribution system during periods of normal operating conditions when water representative of all sources is being used. (d) A water supplier for a new PWS or for a PWS that uses a new source of water that begins operation after April 26, 2027, must demonstrate compliance with the MCLs specified under s. NR 809.221 (1) in accordance with the requirements in this section and s. NR 809.224 . The water supplier must also comply with the initial sampling frequencies specified by the department to ensure the PWS can demonstrate compliance with the MCLs. Compliance monitoring frequencies must be conducted in accordance with the requirements of this section. (e) A system must use only data collected under the requirements of this section for purposes of qualifying for reduced monitoring. (f) For purposes of this section, “trigger levels” are defined as the following concentrations for each contaminant shown in Table Dh. (g) Based on initial monitoring results, for each entry point at which a regulated PFAS listed under s. NR 809.221 (1) is detected at a level greater than or equal to the trigger level, the system must monitor quarterly for all regulated PFAS beginning April 26, 2027, in accordance with sub. (3) . (h) For purposes of this section, each water system must ensure that all results provided by a laboratory are reported to the department and used for determining the required sampling frequencies. This includes values below the practical quantitation levels defined under s. NR 809.224 (1) (f) 1. d. ; zero must not be used in place of reported values. (2) Initial monitoring for PFAS. A PWS must conduct initial monitoring to determine compliance with the MCLs for PFAS listed under s. NR 809.221 (1) using the following specified monitoring requirements and monitoring frequencies, as applicable: (a) Groundwater CWS and NTNCWS serving greater than 10,000 individuals and all surface water CWS and NTNCWS must take 4 consecutive quarterly samples 2 to 4 months apart within a 12-month period, for each regulated PFAS listed under s. NR 809.221 (1) . (b) Groundwater CWS and NTNCWS serving 10,000 or fewer individuals must take 2 samples 5 to 7 months apart within a 12-month period, for each regulated PFAS listed under s. NR 809.221 (1) . (c) Groundwater under the direct influence of surface water CWS and NTNCWS must follow the surface water CWS and NTNCWS monitoring schedule under par. (a) of this section. (d) A system that uses both surface water and groundwater must apply the requirements under pars. (a) to (c) depending on the source of water provided at a given entry point. If the entry point provides surface water, the requirements for a surface water CWS or NTNCWS apply. If the entry point provides groundwater, the requirements for a groundwater CWS or NTNCWS apply, based on system size. If an entry point provides a blend of surface water and groundwater, the requirements for a surface water system apply. For a system that changes the source water type at an entry point during the initial monitoring period, the sampling requirements for a surface water system apply. (e) A water supplier for a new CWS or for a CWS with a new source of water shall demonstrate compliance with the MCLs for PFAS listed under s. NR 809.221 (1) prior to initiating service. (f) A PWS must monitor at a frequency indicated in Table Di unless the department requires more frequent monitoring on a system-specific basis. (g) A new CWS, new NTNCWS, or system with a new source of water must monitor at the frequency indicated in Table Di beginning in the first quarter that a new system or a new source of water goes into service. (h) The department may accept data that has been previously acquired by a water system to count toward the initial monitoring requirements if the data meet the requirements of s. NR 809.222 (2) (a) , and samples were collected starting on or after January 1, 2019, and otherwise meet the timing requirements specified in Table Di. For the purposes of satisfying initial monitoring requirements, acceptable data may be reported to a concentration no greater than the MCLs. However, a system is only eligible for triennial monitoring under sub. (3) (a) at the start of the compliance monitoring period if the system demonstrates that concentrations in all samples it uses to satisfy the initial monitoring requirements are below the trigger levels as defined under sub. (1) (f) . (i) If a system has multiple years of data, the most recent data must be used. (j) A system using previously acquired data that has fewer than the number of samples required in a continuous 12-month period for initial monitoring as listed in Table Di must comply with the following, as applicable: 1. A surface water system, GWUDI system, or a groundwater system serving greater than 10,000 individuals must collect in a calendar year one sample in each quarter that was not represented, 2 to 4 months apart from the months with available data. 2. A groundwater system serving 10,000 or fewer individuals must collect one sample in a month that is 5 to 7 months apart from the month in which the previous sample was taken. (k) In determining the most recent data to report, a system must include all results provided by a laboratory, whether above or below the practical quantitation levels. These results must be used for the purposes of determining the frequency with which a system must monitor at that entry point at the start of the compliance monitoring period. (L) The department may delete results of obvious sampling errors. If the department deletes a result because of an obvious sampling error and the system fails to collect another sample, this is a monitoring violation as described under s. NR 809.226 (3) . (m) Initial monitoring requirements, including reporting results to the department, must be completed by April 26, 2027. (3) Compliance monitoring for PFAS. A system must complete compliance monitoring to determine compliance with the MCLs for PFAS listed under s. NR 809.221 (1) using the following specified monitoring conditions and monitoring frequencies: (a) Based on initial monitoring results, at the start of the monitoring period that begins on April 26, 2027, a system may reduce monitoring at each entry point at which all reported sample concentrations were below all trigger levels defined under sub. (1) (f) , unless otherwise provided for by the department. At eligible entry points, each water system must analyze one sample for all regulated PFAS during each 3-year monitoring period, at a time specified by the department, in the quarter in which the highest analytical result was detected during the most recent round of quarterly or semi-annual monitoring. If an entry point is not eligible for triennial monitoring, then the water system must monitor quarterly at the start of the compliance monitoring period. (b) If, during the compliance monitoring period, a system is monitoring triennially and a PFAS listed under s. NR 809.221 (1) is detected at a level equal to or exceeding the trigger levels defined under sub. (1) (f) in any sample, then the system must monitor quarterly for all regulated PFAS beginning in the next quarter at the entry point. The triggering sample must be used as the first quarter of monitoring for the running annual average calculation. (c) For all source water types, the department may determine that all regulated PFAS at an entry point are reliably and consistently below the MCL after considering, at a minimum, 4 consecutive quarterly samples collected during the compliance monitoring period. For an entry point that the department has determined to be reliably and consistently below the MCL, the water supplier is required to collect annual samples at that entry point for at least the first 3 years after that determination is made. Annual samples must be collected in the quarter in which detected concentrations were highest during the most recent year of quarterly monitoring. If, after 3 consecutive years, annual samples all contain results that are below the trigger levels defined under sub. (1) (f) , the department may allow a system to begin triennial monitoring at the entry point. The water system must collect triennial samples in the quarter with the highest concentrations during the most recent round of quarterly sampling. If an annual sample meets or exceeds an MCL or the department determines that the result is not reliably and consistently below the MCL for all regulated PFAS, then the system must monitor quarterly for all regulated PFAS beginning in the next quarter at the entry point. (d) The 3 different compliance monitoring schedules that may be assigned and the criteria for each are summarized in Table Dj. (e) The department may require a confirmation sample for any sampling result. If a confirmation sample is required by the department, the system must average the result with the first sampling result and the average must be used for the determination of compliance with MCLs as specified under s. NR 809.224 . The department may delete results of obvious sampling errors from the MCL compliance calculations described under s. NR 809.224 . If the department deletes a result because of an obvious sampling error and the system fails to collect another sample, this is a monitoring violation as described under s. NR 809.226 (3) . (f) The department may increase the required monitoring frequency, where necessary, to detect variations within the system, such as fluctuations in concentration due to seasonal use or changes in the water source. (g) Each PWS must monitor at the time designated by the department within each monitoring period. (h) When a system reduces its sampling frequency to annual or triennial sampling, the next compliance sample must be collected in the monitoring period that begins the calendar year following department approval of a reduction in monitoring frequency.