Topics
A to Z
Data &
 Statistics
Forms &
Publications
News &
Advisories
Licensing &
Certification
Rules &
Regulations
Public Health
Directory
Print this Article   Bookmark and Share
Routine, Reduced & Increased Monitoring Requirements
Quick Links:

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 (xls). 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 Type Population Size Category Routine Monitoring Frequency Routine Number of Samples or Dual Sample Sets Distribution System Monitoring Locations
Highest TTHM Locations Highest 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/GWUIDI systems >3,300 and groundwater systems ≥500 must take dual sample sets at the locations and frequencies listed in the table above.
  • Surface water/GWUIDI 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)
<500 per year 1 TTHM and 1 HAA5 sample 1 1
500-3,300 per quarter 1 TTHM and 1 HAA5 sample 1 1
3,301-9,9999 per quarter 2 dual sample sets 1 1
10,000-49,999 per quarter 4 dual sample sets 2 2
50,000-249,999 per quarter 8 dual sample sets 4 4
250,000-999,999 per quarter 12 dual sample sets 6 6
1,000,000-4,999,999 per quarter 16 dual sample sets 8 8
≥5,000,000 per quarter 20 dual sample sets 10 10
Ground Water <500 per year 1 TTHM and 1 HAA5 sample 1 1
500-9,999 per year 2 dual sample sets 1 1
10,000-99,999 per quarter 4 dual sample sets 2 2
100,000-499,999 per quarter 6 dual sample sets 3 3
≥500,000 per quarter 8 dual sample sets 4 4


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 TOCs at each treatment plant ≤ 4.0 mg/L for surface water systems

An 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 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 Type Population Size Category Reduced Monitoring Frequency Reduced Number of Samples or Dual Sample Sets Distribution 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)
<500 Monitoring may not be reduced
500-3,300 per year 1 TTHM and 1 HAA5
sample
See * or ** below
3,301-9,9999 per year 2 dual sample sets See * below
10,000-49,999 per quarter 2 dual sample sets 1 1
50,000-249,999 per quarter 4 dual sample sets 2 2
250,000-999,999 per quarter 6 dual sample sets 3 3
1,000,000-4,999,999 per quarter 8 dual sample sets 4 4
≥5,000,000 per quarter 10 dual sample sets 5 5
Ground Water <500 every third year 1 TTHM and 1 HAA5
sample
See * or ** below
500-9,999 per year 1 TTHM and 1 HAA5
sample
See * or ** below
10,000-99,999 per year 2 dual sample sets See * below
100,000-499,999 per quarter 2 dual sample sets 1 1
≥500,000 per quarter 4 dual sample sets 2 2


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.