Wisconsin Administrative Code › Department of Natural Resources › NR 800 - Environmental Protection - Water Supply › Chapter NR 810 - Requirements for the operation and maintenance of public water systems › Subchapter II - Surface Water Treatment and Groundwater Under the Direct Influence of Surface Water Treatment Operations › Section NR 810.38 - Monitoring requirements

Current through June 24, 2024
(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.