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Routine, Reduced & Increased Monitoring Requirements

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Routine Monitoring

Routine monitoring must be conducted according to the information in Table 2. All systems begin Stage 2 compliance monitoring on a routine monitoring schedule, except for:
  • Systems that were on Stage 1 DBPR reduced monitoring may start on Stage 2 DBPR reduced monitoring if they meet all of the following criteria:
    • The system received a VSS waiver or a 40/30 certification. To see if your system got a VSS or 40/30, check the IDSE Waiver Lists. The lists are alphabetical by water system name; there is one tab for 40/30 and one for VSS.
    • The system meets the reduced monitoring criteria for Stage 2 DBPR (see Reduced Monitoring, below).
    • The system will be monitoring at the same locations for Stage 2 DBPR as the Stage 1 DBPR. If the system had to add, subtract or change sample sites, they do not meet this portion of the criteria and cannot qualify initially for reduced monitoring.
  • Systems that were on Stage 1 DBPR increased monitoring must begin Stage 2 DBPR compliance monitoring on Stage 2 DBPR increased monitoring (see Increased Monitoring, below). Those systems must stay on increased monitoring until they meet the requirements for returning to routine monitoring.
Table 2. Stage 2 Routine Monitoring Requirements
Source Water TypePopulation Size CategoryRoutine Monitoring FrequencyRoutine Number of Samples or Dual Sample SetsDistribution System Monitoring Locations
Highest TTHM LocationsHighest HAA5 Locations
Notes:
  • A dual sample set is a set of two samples collected at the same time and same locations, with one sample analyzed for TTHM and the other sample analyzed for HAA5.
  • All systems must monitor during the month of the highest DBP concentration or warmest water temperature.
  • Surface water/GWUDI systems >3,300 and groundwater systems ≥ 500 must take dual sample sets at the locations and frequencies listed in the table above.
  • Surface water/GWUDI systems  3,300 and groundwater systems < 500 must take individual TTHM and HAA5 samples(instead of a dual sample set) at the locations with the highest TTHM and HAA5 concentrations, respectively. However, if the highest TTHM and HAA5 concentrations occur at the same location, you can collect a dual sample set at one locations per monitoring period.
Surface Water

or

Ground Water Under the Direct Influence
(GWUDI)
<500per year1 TTHM and 1 HAA5 sample11
500-3,300per quarter1 TTHM and 1 HAA5 sample11
3,301-9,9999per quarter2 dual sample sets11
10,000-49,999per quarter4 dual sample sets22
50,000-249,999per quarter8 dual sample sets44
250,000-999,999per quarter12 dual sample sets66
1,000,000-4,999,999per quarter16 dual sample sets88
=5,000,000per quarter20 dual sample sets1010
Ground Water<500per year1 TTHM and 1 HAA5 sample11
500-9,999per year2 dual sample sets11
10,000-99,999per quarter4 dual sample sets22
100,000-499,999per quarter6 dual sample sets33
=500,000per quarter8 dual sample sets44

Reduced Monitoring

To qualify for reduced monitoring in Table 3 below, a water system must have:
  • TTHM Locational Running Annual Averages (LRAAs) 0.040 mg/L at all locations
  • HAA5 Locational Running Annual Averages (LRAAs) 0.030 mg/L at all locations
  • Annual average source water TOCs at each treatment plant 4.0 mg/L for surface water systems
For groundwater systems on annual routine monitoring, the LRAA is equal to the annual results. For systems on quarterly routine monitoring, the LRAA is calculated after 4 quarters of data is obtained. If the water system exceeds the LRAA criteria above at any location, then the system does not meet the reduced monitoring requirements.

To remain on reduced monitoring:
  • Water systems that monitoring quarterly must maintain the TTHM and HAA5 LRAAs noted above
  • Surface water systems must continue to meet the source water TOCs at each treatment plant
  • Water systems that monitor annually or less frequently must meet the following LRAAs:
    • TTHM LRAA 0.060 mg/L at all locations
    • HAA5 LRAA 0.045 mg/L at all locations
  • Systems that do not meet the reduced monitoring requirements must return to routine monitoring in the next quarter after exceeding the above specified LRAAs.
Table 3. Stage 2 Reduced Monitoring Requirements
Source Water TypePopulation Size CategoryReduced Monitoring FrequencyReduced Number of Samples or Dual Sample SetsDistribution System Monitoring Locations
Highest
TTHM LRAAs
Locations
Highest
HAA5 LRAAs
Locations
* 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.
** One dual sample per year if the highest TTHM and HAA5 measurements occurred at the same location and quarter.
Surface Water

or

Ground Water Under the Direct Influence
(GWUDI)
<500Monitoring may not be reduced
500-3,300per year1 TTHM and 1 HAA5
sample
See * or ** below
3,301-9,9999per year2 dual sample setsSee * below
10,000-49,999per quarter2 dual sample sets11
50,000-249,999per quarter4 dual sample sets22
250,000-999,999per quarter6 dual sample sets33
1,000,000-4,999,999per quarter8 dual sample sets44
=5,000,000per quarter10 dual sample sets55
Ground Water<500every third year1 TTHM and 1 HAA5
sample
See * or ** below
500-9,999per year1 TTHM and 1 HAA5
sample
See * or ** below
10,000-99,999per year2 dual sample setsSee * below
100,000-499,999per quarter2 dual sample sets11
=500,000per quarter4 dual sample sets22

Increased Monitoring

Systems that monitor annually or less frequently (on either routine or reduced monitoring) must go to increased monitoring if any sample location exceeds the MCL for either TTHM or HAA5.

Note that increased monitoring is not based on an LRAA but rather on individual sample results. If any sample at any location is above either of the MCLs, then increased monitoring applies system-wide, not just at one location. Systems on increased monitoring can return to routine monitoring if, after four quarters of consecutive monitoring, each monitoring location's LRAA for TTHM is less than 0.060 mg/L and each monitoring location's LRAA for HAA5 is less than 0.045 mg/L.

Increased monitoring requirements do not apply to systems that monitor quarterly.