Section NR 810.38 - Monitoring requirements(1) MONITORING REQUIREMENTS FOR GROUNDWATER SYSTEMS UNDER THE DIRECT INFLUENCE OF SURFACE WATER THAT DO NOT PROVIDE FILTRATION. A public water system that uses a groundwater source under the direct influence of surface water and does not provide filtration treatment shall begin monitoring as specified in this subsection on December 31, 1990, or 6 months after the department determines that the groundwater source is under the direct influence of surface water, whichever is later. (a) Fecal coliform or total coliform density measurements as required by s. NR 810.30(1) (a) shall be performed on representative source water samples immediately prior to the first or only point of disinfectant application. The water supplier shall sample for fecal or total coliforms at the following minimum frequency each week the system serves water to the public: | System Size (persons served) | Samples/week |
| [LESS than]= 500 | 1 |
| 501 to 3,300 | 2 |
| 3,301 to 10,000 | 3 |
| 10,001 to 25,000 | 4 |
| [GREATER than] 25,000 | 5 |
(b) The samples in par. (a) shall be taken on separate days. In addition, one fecal or total coliform density measurement shall be performed every day the system serves water to the public and the turbidity of the source water exceeds one NTU. These samples count toward the weekly coliform sampling requirement. (c) Turbidity measurements as required by s. NR 810.30(1) (b) shall be performed on representative grab samples of source water immediately prior to the first or only point of disinfectant application every 4 hours, or more frequently, that the system serves water to the public. A public water system may substitute continuous turbidity monitoring for grab sample monitoring if it validates the continuous measurement for accuracy on a regular basis using a protocol approved by the department.(d) The total inactivation ratio for each day that the system is in operation shall be determined based on the CT values in ss. NR 810.47 to 810.62, as appropriate. The parameters necessary to determine the total inactivation ratio shall be monitored as follows: 1. Temperature of the disinfected water shall be measured at least once per day at each residual disinfectant concentration sampling point.2. If the system uses chlorine, the pH of the disinfected water shall be measured at least once per day at each chlorine residual disinfectant concentration sampling point.3. The disinfectant contact time ("T") shall be determined for each day during peak hourly flow.4. The residual disinfectant concentration ("C") of the water before or at the first customer shall be measured each day during peak hourly flow.5. If a system uses a disinfectant other than chlorine, the water supplier may demonstrate to the department, through the use of a department approved protocol for on-site disinfection challenge studies or other information satisfactory to the department, that CT values other than those specified in ss. NR 810.54 to 810.62, and other operational parameters, are adequate to demonstrate that the system is achieving the minimum inactivation rates specified in s. NR 810.31(1) (a).(e) For any given disinfectant, the total inactivation ratio shall be calculated as follows: 1. If the system uses only one point of disinfectant application, the water supplier may determine the total inactivation ratio based on either of the following 2 methods: a. One inactivation ratio (CTcalc/CT99.9) is determined before or at the first customer during peak hourly flow and if the (CTcalc/CT99.9) is greater than or equal to 1.0, the 99.9% Giardia lamblia inactivation requirement has been achieved.b. Successive (CTcalc/CT99.9) values, representing sequential inactivation ratios, are determined between the point of disinfectant application and a point before or at the first customer during peak hourly flow. Under this alternative, the following method shall be used to calculate the total inactivation ratio: Determine (CTcalc/CT99.9) for each sequence.
Add the (CTcalc/CT99.9) values together S(CTcalc/CT99.9).
If S (CTcalc/CT99.9) [GREATER than] or = 1.0, the 99.9% Giardia lamblia inactivation requirement has been achieved.
2. If the system uses more than one point of disinfectant application before or at the first customer, the water supplier shall determine the CT value of each disinfection sequence immediately prior to the next point of disinfectant application during peak flow. The (CTcalc/CT99.9) value of each sequence and S (CTcalc/CT99.9) shall be calculated using the method in subd. 1. b. to determine if the system is in compliance with s. NR 810.31. 3. Although not required, the total percent inactivation for a system with one or more points of residual disinfectant concentration monitoring may be calculated by solving the following equation: Percent inactivation = 100 - (100/10), where
z = 3 x summation of (CTcalc/CT99.9)
(f) The residual disinfectant concentration of the water entering the distribution system shall be monitored continuously, and the lowest value shall be recorded each day, except that if there is a failure in the continuous monitoring equipment, grab sampling every 4 hours may be conducted in lieu of continuous monitoring, but for no more than 5 working days following the failure of the equipment, and systems serving 3,300 or fewer persons may take grab samples in lieu of providing continuous monitoring on an ongoing basis at the following prescribed frequencies: | System Size by Population | Samples/day |
| [LESS than]= 500 | 1 |
| 501 to 1,000 | 2 |
| 1,001 to 2,500 | 3 |
| 2,501 to 3,300 | 4 |
(g) The day's samples to meet par. (f) cannot be taken at the same time. The sampling intervals are subject to department review and approval. If at any time the residual disinfectant concentration falls below 0.2 mg/l in a system using grab sampling in lieu of continuous monitoring, the water supplier for the system shall take a grab sample every 4 hours until the residual concentration is equal to or greater than 0.2 mg/l.(h) The residual disinfectant concentration of the water in the distribution system shall be measured as follows:1. The residual disinfectant concentration shall be measured at least at the same points in the distribution system and at the same time as total coliforms are sampled, except that the department may allow the water supplier for a public water system which uses a groundwater source, to take disinfectant residual samples at points other than the total coliform sampling points if the department determines that the points are more representative of treated (disinfected) water quality within the distribution system. Heterotrophic bacteria, measured as heterotrophic plate count (HPC) as specified in s. NR 809.311(1), Table F, may be measured in lieu of residual disinfectant concentration, when approved by the department.2. If the department determines, based on site specific considerations, that a system has no means for having a sample transported and analyzed for HPC by a certified laboratory under the requisite time and temperature conditions specified by s. NR 809.311, Table F, and that the system is providing adequate disinfection in the distribution system, the requirements of subd. 1. do not apply to that system. (2) MONITORING REQUIREMENTS FOR SYSTEMS USING FILTRATION TREATMENT. Water suppliers for a public water system that uses a surface water source or a groundwater source under the direct influence of surface water and provides filtration treatment shall monitor in accordance with all of the following:(a) Turbidity measurements as specified in s. NR 810.29 shall be performe don representative samples of the system's combined filter effluent water every 4 hours, or more frequently, that the system serves water to the public. A water supplier may substitute continuous turbidity monitoring for grab sample monitoring if it validates the continuous measurement for accuracy on a regular basis using a protocol approved by the department. For any systems using slow sand filtration or filtration treatment other than conventional filtration treatment, direct filtration or diatomaceous earth filtration, the department may reduce the sampling frequency to once per day if it determines that less frequent monitoring is sufficient to indicate effective filtration performance. For systems serving 500 or fewer persons, the department may reduce the turbidity sampling frequency to once per day, regardless of the type of filtration treatment used, if the department determines that less frequent monitoring is sufficient to indicate effective filtration performance.(b) Water suppliers for systems using conventional filtration treatment or direct filtration shall conduct continuous monitoring of turbidity for each individual filter using a method approved in s. NR 809.113(1), Tables A and B and shall calibrate turbidimeters using the procedure specified by the manufacturer. Water suppliers shall record the results of individual filter monitoring every 15 minutes. If there is a failure in the continuous monitoring equipment, the water supplier shall conduct grab sampling every 4 hours in lieu of continuous monitoring, until the turbidimeter is repaired and back on-line. The water supplier shall repair the equipment no later than 5 working days after the failure or the system is in violation.(c) The residual disinfectant concentration of the water entering the distribution system shall be monitored continuously, and the lowest value shall be recorded each day, except that if there is a failure in the continuous monitoring equipment, grab sampling every 4 hours may be conducted in lieu of continuous monitoring, but for no more than 5 working days following the failure of the equipment. Water suppliers for systems serving 3,300 or fewer persons may take grab samples in lieu of providing continuous monitoring on an ongoing basis at the frequencies each day prescribed as follows: | System Size by Population | Samples/day |
| [LESS than]= 500 | 1 |
| 501 to 1,000 | 2 |
| 1,001 to 2,500 | 3 |
| 2,501 to 3,300 | 4 |
1 The day's samples cannot be taken at the same time. The sampling intervals are subject to department review and approval.
If at any time the residual disinfectant concentration falls below 0.2 mg/l in a system using grab sampling in lieu of continuous monitoring, the water supplier shall take a grab sample every 4 hours until the residual disinfectant concentration is equal to or greater than 0.2 mg/l.
(d) The residual disinfectant concentration in the distribution system shall be measured as follows: 1. The residual disinfectant concentration shall be measured at least at the same points in the distribution system and at the same time as total coliforms are sampled. The department may allow a public water system which uses both a surface water source or a groundwater source under direct influence of surface water, and a groundwater source to take disinfectant residual samples at points other than the total coliform sampling points if the department determines that the points are more representative of treated or disinfected water quality within the distribution system. Heterotrophic bacteria, measured as heterotrophic plate count (HPC) as specified in s. NR 809.311(1), Table F, may be measured in lieu of residual disinfectant concentration, when approved by the department.2. If the department determines, based on site specific considerations, that a system has no means for having a sample transported and analyzed for HPC by a certified laboratory under the requisite time and temperature conditions specified in s. NR 809.311(1), Table F, and that the system is providing adequate disinfection in the distribution system, the requirements of subd. 1. do not apply to that system. Wis. Admin. Code Department of Natural Resources NR 810.38
CR 09-073: cr. Register November 2010 No. 659, eff. 12-1-10.