Wisconsin Administrative Code
Department of Natural Resources
NR 800 - Environmental Protection - Water Supply
Chapter NR 809 - Safe Drinking Water
Subchapter III - Maximum Contaminant Levels, Maximum Residual Disinfectant Levels, Monitoring, Analytical Requirements and Control of Disinfection Byproducts, Disinfection Residuals and Stage 1 and Stage 2 DBP
Section NR 809.565 - Monitoring requirements for disinfection byproducts and disinfection residuals Stage 1 DBP

Universal Citation: WI Admin Code § NR 809.565

Current through August 26, 2024

(1) GENERAL REQUIREMENTS. General requirements under this subchapter for analytical requirements, determining maximum contaminant levels, conducting monitoring and control of disinfection byproducts are as follows:

(a) Water suppliers shall take all samples during normal operating conditions.

(b) Water suppliers may consider multiple wells drawing water from a single aquifer as one treatment plant for determining the minimum number of TTHM and HAA5 samples required, on a case-by-case basis with department approval.

(d) Failure to monitor shall be treated as a violation for the entire period covered by the annual average where compliance is based on a running annual average of monthly or quarterly samples or averages and the water supplier's failure to monitor makes it impossible to determine compliance with MCLs or MRDLs.

(e) Water suppliers may use only data collected under the provisions of this subchapter

(2) MONITORING FREQUENCY AND LOCATION FOR TTHMS AND HAA5S. Water suppliers shall monitor at the following frequency and locations for TTHMs and HAA5 disinfection byproducts:

(a) Routine monitoring.

1. Water suppliers for public water systems serving at least 10,000 persons which are supplied by a surface water source or by a groundwater source under the direct influence of surface water shall collect and have analyzed 4 water samples per quarter per treatment plant.

a. At least 25% of all samples collected each quarter at each treatment plant shall be at locations representing the maximum residence time in the public water system.

b. The remaining samples shall be taken in the distribution system at locations representing at least average residence time in the public water system and representative of the entire distribution system, taking into account the number of people served, different sources of water and different treatment methods.

2. Water suppliers for public water systems serving from 500 to 9,999 persons which are supplied by a surface water source or by a groundwater source under the direct influence of surface water shall collect and have analyzed one water sample per quarter per treatment plant. The samples shall be collected at locations representing the maximum residence time of water in the public water system.

3. Water suppliers for public water systems serving fewer than 500 people which are supplied by a surface water source or by a groundwater source under the direct influence of surface water shall collect one sample per treatment plant annually. The samples shall be collected during the month with the warmest water temperature at locations representing the maximum residence time in the public water system.

4. Water suppliers for public water systems using chemical disinfection, using only groundwater not under the direct influence of surface water, and serving at least 10,000 people shall collect one sample per treatment plant per quarter. The sample or samples shall be collected at the location representing the maximum residence time in the public water system.

5. Water suppliers for public water systems using chemical disinfection, using only groundwater not under the direct influence of surface water, and serving fewer than 10,000 people shall collect one sample per treatment plant annually. The sample shall be collected during the month with the warmest water temperature, at locations representing the maximum residence time, in the public water system.

(b) Monitoring after exceeding an MCL. If a sample or the average of samples, if more than one sample is taken, exceeds the MCL for TTHMs or HAA5 disinfection byproducts, the water supplier shall collect quarterly samples until the public water system meets the requirements of reduced monitoring in par. (c).

1. Water suppliers for surface water systems or groundwater systems under the direct influence of surface water with an annual average of TTHM of <= 0.040 mg/L and HAA5 = 0.030 mg/L with an annual average TOC concentration of <= 4.0 mg/L, before any treatment may reduce monitoring to the following:

a. Water suppliers for a public water system serving at least 10,000 people may reduce monitoring to one sample per quarter per treatment plant so long as the sample is taken at a location representing maximum residence time in the public water system.

b. Water suppliers for a public water system serving from 500 to 9,999 people may reduce monitoring to one sample per year per treatment plant so long as the sample is taken at a location representing maximum residence time in the public water system during the month of warmest water temperature.

c. A water supplier for a public water system serving less than 500 people may not reduce monitoring to less than one sample during the month of warmest water temperature per treatment plant per year.

2. A water supplier for a public water system using only groundwater not under the direct influence of surface water using chemical disinfection with an annual average of TTHM of <= 0.040 mg/L and HAA5 <= 0.030 mg/L may reduce sampling to the following:

a. A water supplier for a public water system serving at least 10,000 people may reduce monitoring to one sample per year per treatment plant during the month of warmest water temperature at a location representing maximum residence time in the public water system.

b. A water supplier for a public water system serving fewer than 10,000 people may reduce monitoring to one sample per treatment plant per 3 year monitoring cycle during the month of warmest water temperature at a location representing maximum residence time in the public water system. The reduced monitoring will begin on January 1 following the quarter in which the public water system first qualifies for reduced monitoring.

2m. To qualify for reduced monitoring for TTHM and HAA5 under this paragraph, water suppliers for surface water systems or groundwater systems under the direct influence of surface water not monitoring under the provisions of sub. (5) shall take monthly TOC samples every 30 days at a location prior to any treatment, beginning April 1, 2008, or earlier, if specified by the department. In addition to meeting other criteria for reduced monitoring in this paragraph, the source water TOC running annual average shall be = 4.0 mg/L, based on the most recent four quarters of monitoring, on a continuing basis at each treatment plant to reduce or remain on reduced monitoring for TTHM and HAA5. Once qualified for reduced monitoring for TTHM and HAA5 under this paragraph, a system may reduce source water TOC monitoring to quarterly TOC samples taken every 90 days at a location prior to any treatment.

3. Public water systems on a reduced monitoring schedule may remain on that reduced schedule as long as the average of all samples taken in the year, for public water systems which shall monitor quarterly, or the result of the sample, for public water systems which shall monitor no more frequently than annually, is no more than 0.060 mg/L and 0.045 mg/L for TTHMs and HAA5, respectively. A water supplier for a public water systems that do not meet these levels shall resume monitoring at the frequency identified in par. (a) in the quarter immediately following the quarter in which the public water system exceeds 0.060 mg/L and 0.045 mg/L for TTHMs and HAA5, respectively.

(d) Return to routine monitoring. The department may return a public water system to routine monitoring at the department's discretion.

(3) MONITORING FREQUENCY AND LOCATION FOR CHLORITE AND BROMATE. Water suppliers for public water systems shall monitor at the following frequency and locations for chlorite and bromate disinfection byproducts:

(a) Chlorite. Water supplier for community and nontransient noncommunity water systems using chlorine dioxide, for disinfection or oxidation, shall conduct monitoring for chlorite as follows:

1. `Routine daily monitoring.' A water supplier for a public water system shall take daily samples at the entrance to the distribution system. For any daily sample that exceeds the chlorite MCL, the water supplier shall take additional samples in the distribution system the following day at the locations required by subd. 3. in addition to the sample required at the entrance to the distribution system.

2. `Routine monthly monitoring.' A water supplier shall take a 3-sample set each month in the distribution system. The water supplier shall take one sample at each of the following locations: near the first customer, at a location representative of average residence time, and at a location reflecting maximum residence time in the distribution system. Any additional routine sampling shall be conducted in the same manner, as 3-sample sets, at the specified locations. The water supplier may use the results of additional monitoring conducted under subd. 3. to meet the requirement for monitoring in this subdivision.

3. `Additional monitoring.' On each day following a routine sample monitoring result that exceeds the chlorite MCL at the entrance to the distribution system, the water supplier shall take 3 chlorite distribution system samples at the following locations: as close to the first customer as possible, in a location representative of average residence time, and as close to the end of the distribution system as possible, reflecting maximum residence time in the distribution system.

4. `Reduced monitoring.' Chlorite monitoring at the entrance to the distribution system required under subd. 1. may not be reduced. Chlorite monitoring in the distribution system required under subd. 2 may be reduced to one 3-sample set per quarter after one year of monitoring where no individual chlorite sample taken in the distribution system under subd. 2. has exceeded the chlorite MCL and the public water system has not been required to conduct monitoring under subd. 3. The public water system may remain on the reduced monitoring schedule until either any of the 3 individual chlorite samples taken quarterly in the distribution system under subd. 2. exceeds the chlorite MCL or the water supplier is required to conduct monitoring under subd. 3., at which time the public water system shall revert to routine monitoring.

(b) Bromate.

1. `Routine monitoring.' Water suppliers for community and nontransient noncommunity systems using ozone, for disinfection or oxidation, shall take one sample per month for each treatment plant in the public water system using ozone. Water suppliers shall take samples monthly at the entrance to the distribution system while the ozonation treatment system is operating under normal conditions.

2. `Reduced monitoring.' Water suppliers for public water systems may reduce monitoring for bromate from monthly to once per quarter, if the water supplier demonstrates that the public water system's running annual average concentration for bromate is =0.0025 mg/L based on monthly bromate measurements under par. (b) for the most recent four quarters. Samples shall be analyzed using Method 317.0 Revision 2.0, 326.0 or 321.8. If the running annual average bromate concentration is >0.0025 mg/L, the system must resume routine monitoring required by par. (b).

(4) MONITORING FREQUENCY AND LOCATION FOR DISINFECTANT RESIDUALS. Water suppliers for systems shall monitor at the following frequency and locations for disinfectant residuals:

(a) Chlorine and chloramines. Water suppliers for public water systems shall perform routine monitoring by measuring the residual disinfectant level at the same points in the distribution system and at the same time as total coliforms are sampled, as specified in s. NR 809.31. The department may allow suppliers for surface water systems to take disinfectant residual samples at points other than the total coliform sampling points if the department determines that such points are more representative of disinfected water quality within the distribution system. Water suppliers for surface water systems may use the results of residual disinfectant concentration sampling conducted under s. NR 810.38(1) (h) for unfiltered systems or s. NR 810.38(2) (d) for public water systems that filter, in lieu of taking separate samples. Monitoring may not be reduced.

(b) Chlorine dioxide.

1. `Routine monitoring.' Water suppliers for community, nontransient noncommunity, and transient noncommunity water systems that use chlorine dioxide for disinfection or oxidation shall take daily samples at the entrance to the distribution system. For any daily sample that exceeds the MRDL, the water supplier shall take samples in the distribution system the following day at the locations required by subd. 2., in addition to the sample required at the entrance to the distribution system.

2. `Additional monitoring.' On each day following a routine sample monitoring result that exceeds the MRDL, the water supplier shall take 3 chlorine dioxide distribution system samples. If chlorine dioxide or chloramines are used to maintain a disinfectant residual in the distribution system, or if chlorine is used to maintain a disinfectant residual in the distribution system and there are no disinfection addition points after the entrance to the distribution system, i.e., no booster chlorination, the water supplier shall take 3 samples as close to the first customer as possible, at intervals of at least 6 hours. If chlorine is used to maintain a disinfectant residual in the distribution system and there are one or more disinfection addition points after the entrance to the distribution system, i.e., booster chlorination, the water supplier shall take one sample at each of the following locations: as close to the first customer as possible, in a location representative of average residence time, and as close to the end of the distribution system as possible, reflecting maximum residence time in the distribution system.

3. `Reduced monitoring.' Chlorine dioxide monitoring may not be reduced.

(5) MONITORING FREQUENCY AND LOCATION FOR DISINFECTANT BYPRODUCT PRECURSORS. Water suppliers for public water systems shall monitor at the following frequency and locations for disinfection byproduct precursors (DBPP):

(a) Routine monitoring.

1. Water suppliers for public water systems which use conventional filtration treatment and are supplied by a surface water source or by a groundwater source under the direct influence of surface water shall monitor each treatment plant monthly for TOC no later than the point of combined filter effluent turbidity monitoring and representative of the treated water.

2. All water suppliers for public water systems required to monitor under subd. 1. shall also monitor for TOC in the source water prior to any treatment at the same time as monitoring for TOC in the treated water.

Note: These samples, source water and treated water, are referred to as paired samples.

3. At the same time as the source water sample is taken, all water suppliers shall monitor for alkalinity in the source water prior to any treatment. Water suppliers shall take one paired sample and one source water alkalinity sample per month per plant at a time representative of normal operating conditions and influent water quality.

(b) Reduced monitoring. Water suppliers for public water systems which use conventional filtration treatment and are supplied by a surface water source or by a groundwater source under the direct influence of surface water and which have an average treated water TOC of less than 2.0 mg/L for 2 consecutive years, or less than 1.0 mg/L for one year, may reduce monitoring for both TOC and alkalinity to one paired sample and one source water alkalinity sample per plant per quarter. The water supplier shall revert to routine monitoring in the month following the quarter when the annual average treated water TOC >= 2.0 mg/L for the public water system.

(6) MONITORING PLANS. Each water supplier for a public water system required to monitor under this subchapter shall develop and implement a monitoring plan, and shall maintain the plan and make it available for inspection by the department and the general public no later than 30 days following the applicable compliance dates in s. NR 809.562(2).

(a) Water suppliers for public water systems which are supplied by a surface water source or by a groundwater source under the direct influence of surface water and which serve more than 3,300 people shall submit a copy of the monitoring plan to the department no later than the date of the first report required under s. NR 809.567. The department may also require water suppliers for any other public water system to submit a monitoring plan. After review, the department may require changes in any plan elements.

(b) The plan shall include at least the following elements:

1. Specific locations and schedules for collecting samples for any parameters included in this subchapter.

2. How the water supplier will calculate compliance with MCLs, MRDLs and treatment techniques.

3. If approved for monitoring as a consecutive system, or if providing water to a consecutive system, under s. NR 809.77, the sampling plan shall reflect the entire distribution system.

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