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 809.63 - Requirements for reduced and increased monitoring for Stage 2 DBP

Current through June 24, 2024
(1) REDUCED
				  MONITORING. The department may reduce the monitoring frequency when the LRAA is
				  less than or equal to 0.040 mg/L for TTHM and less than or equal to 0.030 mg/L
				  for HAA5 at all compliance monitoring locations. Systems may only use data
				  collected in compliance with s.
				  NR
				  809.565 and under this section to qualify for reduced
				  monitoring. In addition, the source water annual average TOC level, before any
				  treatment, must be d4.0 mg/L at each treatment plant treating surface water or
				  GWUDI, based on monitoring conducted under s.
				  NR
				  809.565(2) (c) 2m. The reduced
				  sampling frequency and number of sample sites are given in Table Z:
Table Z
Reduced Stage 2 Monitoring Frequency and Number of
					 Sites
Source Water Type
Population Size Category
Monitoring Frequency
Distribution System Monitoring Location
								  Total per Monitoring Period
Surface Water or GWUDI
less than 500
Annual
Monitoring may not be reduced.
500 to 3,300
Annual
1 TTHM and 1 HAA5 at the respective locations
									 and quarters with the highest individual DBP; 1 dual sample set per year if the
									 highest TTHM and HAA5 measurements occurred at the same location and
									 quarter.
3,301 to 9,999
Annual
2 dual sample sets: one at the location and
									 during the quarter with the highest TTHM single measurement, one at the
									 location and during the quarter with the highest HAA5 single
									 measurement.
10,000 to 49,999
quarterly
2 dual sample sets at the locations with the
									 highest TTHM and highest HAA5 LRAAs
50,000 to 249,999
quarterly
4 dual sample sets at the locations with the
									 two highest TTHM and two highest HAA5 LRAAs
250,000 to 999,999
quarterly
6 dual sample sets at the locations with the
									 three highest TTHM and three highest HAA5 LRAAs
1,000,000 to 4,999,999
quarterly
8 dual sample sets at the locations with the
									 four highest TTHM and four highest HAA5 LRAAs
5,000,000 or more
quarterly
10 dual sample sets at the locations with the
									 five highest TTHM and five highest HAA5 LRAAs
Groundwater
less than 500
every third year (triennial)
1 TTHM and 1 HAA5 at the respective locations and
								  quarters with the highest individual DBP; 1 dual sample set per year if the
								  highest TTHM and HAA5 measurements occurred at the same location and
								  quarter.
500 to 9,999
Annual
1 TTHM and 1 HAA5 at the respective locations
									 and quarters with the highest individual DBP; 1 dual sample set per year if the
									 highest TTHM and HAA5 measurements occurred at the same location and
									 quarter.
10,000 to 99,999
Annual
2 dual sample sets: one at the location and
									 during the quarter with the highest TTHM single measurement, one at the
									 location and during the quarter with the highest HAA5 single measurement
100,000 to 499,999
quarterly
2 dual sample sets at the locations with the
									 highest TTHM and highest HAA5 LRAAs
500,000 or more
quarterly
4 dual sample sets at the locations with the
									 two highest TTHM and two highest HAA5 LRAAs
(a) Water
				  suppliers for public water systems on quarterly monitoring shall take dual
				  sample sets every 90 days.
(b)
				  Public water systems on annual monitoring and surface water or GWUDI systems
				  serving 500 to 3,300 people may use a single site if the highest TTHM and HAA5
				  concentrations occur at the same time and place. Any such public water system
				  may be required to take individual TTHM and HAA5 samples, instead of a dual
				  sample set, at sites identified as the highest TTHM and HAA5 sites,
				  respectively. If separate sites for individual TTHM and HAA5 samples are used,
				  then the TTHM sample shall be collected during the quarter with highest
				  historical TTHM levels and the HAA5 sample shall be collected during the
				  quarter with the highest historical HAA5 level.
(c) Only data collected under the provisions
				  of s.
				  NR
				  809.565 and under this section may be used to qualify
				  for reduced monitoring.
(d) To
				  remain on reduced monitoring, a public water system shall meet the following
				  conditions:
1. Public water systems on a
				  quarterly reduced monitoring schedule may remain on that reduced schedule as
				  long as the TTHM LRAA <= 0.040 mg/L and the HAA5 LRAA <= 0.030 mg/L at
				  each monitoring location.
2. Public
				  water systems on an annual or less frequent reduced monitoring schedule may
				  remain on that reduced schedule as long as each TTHM sample <= 0.060 mg/L
				  and each HAA5 sample <= 0.045 mg/L.
3. In addition to subds. 1. and 2., for a
				  surface water or GWUDI system, the source water annual average TOC level,
				  before any treatment, shall be <= 4.0 mg/L, based on monitoring conducted
				  under s.
				  NR
				  809.565(2) (c) 2m.
(e) If the LRAA based on quarterly
				  monitoring at any monitoring location exceeds either 0.040 mg/L for TTHM or
				  0.030 mg/L for HAA5 or if the annual (or less frequent) sample at any location
				  exceeds either 0.060 mg/L for TTHM or 0.045 mg/L for HAA5, or if the source
				  water annual average TOC level, before any treatment, is >4.0 mg/L at any
				  treatment plant treating surface water or groundwater under the direct
				  influence of surface water, the water supplier shall resume routine monitoring
				  under s.
				  NR
				  809.61 or begin increased monitoring under sub.
				  (2).
(f) The department may return
				  a public water system to routine monitoring, at any time, at the department's
				  discretion.