NR 809.542(2)(c)1. 1. The department may deem that public water systems whose highest source water lead level is below method detection limit have optimized corrosion control under this subsection if the 90th percentile tap water lead level is less than or equal to the practical quantitation level for 2 consecutive 6-month monitoring periods.

NR 809.542(2)(c)2. 2. Any public water system deemed to have optimized corrosion control in accordance with this subsection shall continue monitoring for lead and copper at the tap no less frequently than once every 3 calendar years using the reduced number of sites specified in s. NR 809.547 (3) and collecting the samples at times and locations specified in s. NR 809.547 (4) (d) 4. Any water supplier for a public water system that has not conducted a round of monitoring pursuant to s. NR 809.547 (4) (d) since September 30, 1997, shall complete a round of monitoring pursuant to this subsection as specified by the department.

NR 809.542(2)(c)3. 3. Any water suppliers for a public water system deemed to have optimized corrosion control pursuant to this paragraph shall notify the department in writing pursuant to s. NR 809.55 (1) (c) 3. of any upcoming long-term change in treatment or addition of a new source as described in that section. The department shall review and approve the addition of a new source or long-term change in water treatment before it is implemented by the water supplier. The department may require any water supplier to conduct additional monitoring or to take other action the department deems appropriate to ensure that the water supplier maintains minimal levels of corrosion in the distribution system.

NR 809.542(2)(c)4. 4. As of December 1, 2002, a public water system is not deemed to have optimized corrosion control under this subsection, and the water supplier shall implement corrosion control treatment pursuant to subd. 5. unless the public water system meets the copper action level.

NR 809.542(2)(c)5. 5. Any public water system triggered into corrosion control because it is no longer deemed to have optimized corrosion control under this subsection shall implement corrosion control treatment in accordance with the deadlines in sub. (5). Any large system shall adhere to the schedule specified in that paragraph for medium-size systems, with the time periods for completing each step being triggered by the date the public water system is no longer deemed to have optimized corrosion control under this subsection.

NR 809.542(3) (3) Criteria for completing corrosion control treatment studies for small and medium-size systems. Any water supplier for a small or medium-size water system that is required to complete the corrosion control steps due to the exceedance of the lead or copper action level may cease completing the treatment steps whenever the public water system meets both action levels during each of 2 consecutive monitoring periods conducted pursuant to s. NR 809.547 and the results are submitted to the department. If any such public water system thereafter exceeds the lead or copper action level during any monitoring period, the water supplier shall recommence completion of the applicable treatment steps, beginning with the first treatment step which was not previously completed in its entirety. The department may require a water supplier to repeat treatment steps previously completed by the water supplier if the department determines that this is necessary to properly implement the treatment requirements. The department shall notify the water supplier in writing of such a determination and explain the basis for its decision. The water supplier for a small or medium-size water system shall implement corrosion control treatment steps in accordance with sub. (5), including a public water system deemed to have optimized corrosion control under sub. (2) (a), whenever it exceeds the lead or copper action level.

NR 809.542(4) (4) Treatment steps and deadlines for large systems. Except as provided in sub. (2) (b) and (c), water suppliers for large systems shall complete the following corrosion control treatment steps by the indicated dates:

NR 809.542(4)(a) (a) Step 1: The water supplier shall conduct initial monitoring during 2 consecutive 6-month monitoring periods by January 1, 1993.

NR 809.542(4)(b) (b) Step 2: The water supplier shall complete corrosion control studies and submit option for optimal corrosion control treatment to the department by July 1, 1994.

NR 809.542(4)(c) (c) Step 3: The department shall approve optimal corrosion control treatment by January 1, 1995.

NR 809.542(4)(d) (d) Step 4: The water supplier shall install optimal corrosion control treatment by January 1, 1997.

NR 809.542(4)(e) (e) Step 5: The water supplier shall complete follow-up sampling by January 1, 1998.

NR 809.542(4)(f) (f) Step 6: The department shall review installation of treatment and approve optimal water quality control parameters by July 1, 1998.

NR 809.542(4)(g) (g) Step 7: The water supplier shall operate in compliance with the department-approved optimal water quality control parameters and continue to conduct tap sampling.

NR 809.542(5) (5) Treatment steps and deadlines for small and medium-size systems. Except as provided in sub. (2), water suppliers for small and medium-size systems shall complete the following corrosion control treatment steps by the indicated time periods:

NR 809.542(5)(a) (a) Step 1: The water supplier shall conduct initial tap sampling until the public water system either exceeds the lead or copper action level or becomes eligible for reduced monitoring under s. NR 809.547 (4) (d). A water supplier exceeding the lead or copper action level shall recommend optimal corrosion control treatment, under s. NR 809.543 (1), within six months after the end of the monitoring period during which the public water system exceeds one of the action levels.

NR 809.542(5)(b) (b) Step 2: Within 12 months after the end of the monitoring period during which a public water system exceeds the lead or copper action level, the department may require the water supplier to perform corrosion control studies, under s. NR 809.543 (2). If the department does not require the water supplier to perform such studies, the department shall specify optimal corrosion control treatment, under s. NR 809.543 (4) within the following timeframes:

NR 809.542(5)(b)1. 1. For medium-size systems, within 18 months after the end of the monitoring period during which such public water system exceeds the lead or copper action level.

NR 809.542(5)(b)2. 2. For small systems, within 24 months after the end of the monitoring period during which such public water system exceeds the lead or copper action level.

NR 809.542(5)(c) (c) Step 3: If the department requires a water supplier to perform corrosion control studies under step 2, the water supplier shall complete the studies within 18 months after the department requires the studies be conducted.

NR 809.542(5)(d) (d) Step 4: If the water supplier has performed corrosion control studies under step 2, the department shall review and determine adequacy of public water system’s optimal corrosion control treatment within 6 months after completion of step 3.

NR 809.542(5)(e) (e) Step 5: The water supplier shall install optimal corrosion control treatment within 24 months after the department approves the treatment.

NR 809.542(5)(f) (f) Step 6: The water supplier shall complete follow-up sampling within 36 months after the department approves optimal corrosion control treatment.

NR 809.542(5)(g) (g) Step 7: The department shall review the installation of treatment and approve optimal water quality control parameters within 6 months after completion of step 6.

NR 809.542(5)(h) (h) Step 8: The water supplier shall operate in compliance with the department-approved optimal water quality control parameters and continue to conduct tap sampling.

NR 809.542 History History: CR 09-073: cr. Register November 2010 No. 659, eff. 12-1-10; correction in (2) (c) made under s. 13.92 (4) (b) 7., Stats., Register November 2010 No. 659; CR 15-049: am. (2) (c) 3. Register March 2016 No. 723, eff. 4-1-16; correction in (5) (b) made under s. 13.92 (4) (b) 7., Stats., Register July 2022 No. 799.

NR 809.543 NR 809.543 Description of corrosion control treatment requirements. Each water supplier shall complete the following corrosion control treatment requirements which are applicable to their public water system under s. NR 809.542.

NR 809.543(1) (1) Water supplier recommendation regarding corrosion control treatment. Based upon the results of lead and copper tap monitoring and water quality parameter monitoring, water supplier for a small and medium-size water systems exceeding the lead or copper action level shall recommend installation of one or more of the corrosion control treatments listed in sub. (3) (a) which the water supplier believes constitutes optimal corrosion control for that public water system. The department may require the water supplier to conduct additional water quality parameter monitoring in accordance with s. NR 809.548 (2) to assist the department in reviewing the water supplier’s recommendation. In no case may the time period for installation of optimal corrosion control treatment on a small or medium-size system exceed the schedule as listed in s. NR 809.542 (5) (a) to (h).

NR 809.543(2) (2) Department decision to require studies of corrosion control treatment by small and medium-size systems. The department may require the water supplier of any small or medium-size system that exceeds the lead or copper action level to perform corrosion control studies under sub. (3) to identify optimal corrosion control treatment for the public water system.