State-Wide Disinfection Byproduct Data
(Total Trihalomethanes and Haloacetic Acids)

About the Drinking Water Quality Data

Tables on this page:

As shown in the "Key Dates" section below, the Community Water System (CWS) size and type of source water are factors that determine when a system is first required to comply with Disinfection Byproduct (DBP) regulations. The fact that the majority of CWS in Minnesota rely on groundwater and are small in size means that many CWS were not required to monitor for DBPs until 2004. Furthermore, not all CWS in Minnesota disinfect, and the majority of systems that do not disinfect do not conduct any DBP sampling. These factors impact the number of systems with available DBP monitoring data in Minnesota.

Key dates in DBP monitoring requirements for water supply systems using disinfectants

  • 1981 to present: THMs for water systems serving 10,000 or more people
  • 2002 to present: THMs and HAAs for surface water systems and ground water systems under direct influence of surface water serving more than 10,000 people
  • 2004 to present: THMs and HAAs for all other community water systems

Total Trihalomethanes (TTHM)

Table 1 below shows the number of Community Water Systems by TTHM annual mean concentration category. The number of systems in actual violation of the >80 µg/L Maximum Contaniment Level (MCL) standard is not equivalent to the number of systems listed in the table with concentrations ≥80 µg/L, mainly because the MCL is currently based on a "locational" running annual average (i.e., monthly averages of each sample collected at the specified location collected in the previous 12 months), rather than a system-wide calendar year average. According to MDH Drinking Water Protection, the last year in which the MCL for TTHM was exceeded was 2009, when three community water systems, including two municipal systems, violated the standard.

Annual mean total trihalomethanes concentrations in Minnesota Community Water Systems, 1999-2009

Year Cumulative Number of Community Water Systems Sampled, 1999-2009 Number of Community Water Systems by Concentration Category (µg/L)
<20 20 to <40 40 to <60 60 to <80 80 to <100 100 to <120 120+
1999 0 (0%) 0 0 0 0 0 0 0
2000 0 (0%) 0 0 0 0 0 0 0
2001 0 (0%) 0 0 0 0 0 0 0
2002 0 (0%) 0 0 0 0 0 0 0
2003 377 (39%) 294 53 22 3 3 1 1
2004 664 (69%) 527 88 33 14 2 0 0
2005 680 (71%) 561 79 30 8 1 1 0
2006 686 (72%) 561 90 30 3 2 0 0
2007 702 (73%) 547 101 40 12 1 0 1
2008 720 (75%) 558 105 37 16 2 2 0
2009 728 (76%) 582 108 31 5 2 0 0

*µg/L means micrograms per liter of water.


Table 2 below shows the number of Community Water Systems by annual maximum concentration category during years 1999-2009. A Community Water System may have a number of different locations in the distribution system with differing levels of trihalomethanes. In this table, the maximum value reflects the sample with the highest concentration at a single location. The level of TTHM in water that ultimately reaches the consumer's tap may be different.

Annual maximum total trihalomethanes concentrations in Minnesota Community Water Systems, 1999-2009

Year Cumulative Number of Community Water Systems Sampled, 1999-2009 Number of Community Water Systems by Concentration Category (µg/L)
<20 20 to <40 40 to <60 60 to <80 80 to <100 100 to <120 120+
1999 0 (0%) 0 0 0 0 0 0 0
2000 0 (0%) 0 0 0 0 0 0 0
2001 0 (0%) 0 0 0 0 0 0 0
2002 0 (0%) 0 0 0 0 0 0 0
2003 377 (39%) 279 53 30 7 4 3 1
2004 664 (69%) 511 88 43 17 2 2 1
2005 680 (71%) 556 73 32 12 3 2 2
2006 686 (72%) 559 84 30 8 3 2 0
2007 702 (73%) 547 90 40 17 5 2 1
2008 720 (75%) 555 92 37 23 7 3 3
2009 728 (76%) 577 96 31 16 4 2 2

*µg/L means micrograms per liter of water.


Table 3 below shows the number of people served by Community Water Systems within each TTHM mean concentration category. A total of 4,234,479 people were estimated to be served by community water systems in Minnesota as of April 2010. TTHM monitoring data are available for 97% of these people. Note that the estimates of number of people served by each system are rough calculations periodically updated by water purveyors. Estimates are not available for years past. 

Number of people served by Community Water Systems by mean total trihalomethanes concentration, Minnesota 2009

Year Number of People Served with Available Monitoring Data Number of People Served by Community Water Systems by Concentration Category (µg/L)
<20 20 to <40 40 to <60 60 to <80 80 to <100 100+
2009 4,094,709
(97%)
2,478,319
(61%)
1,368,970
(33%)
222,094
(5%)
24,254
(1%)
1,072
(0%)
0
(0)

*µg/L means micrograms per liter of water.


Haloacetic Acids

Table 4 below shows the number of Community Water Systems by HAA5 annual mean concentration category. The number of systems in actual violation of the >60 µg/L MCL standard is not equivalent to the number of systems listed in the table with concentrations ≥60 µg/L, mainly because the MCL is currently based on a "locational" running annual average (i.e., monthly averages of each sample collected at the specified location collected in the previous 12 months), rather than a system-wide calendar year average. According to the MDH Drinking Water Protection Program, the last year in which the MCL for HAA5 was exceeded was 2006, when one Community Water Systems violated the standard.

Annual mean haloacetic acids concentrations in Minnesota Community Water Systems, 1999-2009

Year Cumulative Number of Community Water Systems Sampled, 1999-2009 Number of Community Water Systems by Concentration Category (µg/L)
<15 15 to <30 30 to <45 45 to <60 60 to <80 80 to <100 100+
1999 0 (0%) 0 0 0 0 0 0 0
2000 0 (0%) 0 0 0 0 0 0 0
2001 0 (0%) 0 0 0 0 0 0 0
2002 0 (0%) 0 0 0 0 0 0 0
2003 377 (39%) 323 33 12 7 1 0 1
2004 664 (69%) 589 57 14 3 0 1 0
2005 680 (71%) 618 35 20 6 1 0 0
2006 687 (72%) 632 39 13 1 2 0 0
2007 701 (73%) 632 49 14 5 1 0 0
2008 720 (75%) 631 61 22 5 1 0 0
2009 728 (76%) 658 55 14 1 0 0 0

*µg/L means micrograms per liter of water.


Table 5 below shows the number of Community Water Systems by annual maximum HAA5 concentration category during years 1999-2009. A community water system may have a number of different locations in the distribution system with differing levels of haloacetic acids. In this table, the maximum value reflects the sample with the highest concentration at a single location. The level of HAA5 in water that ultimately reaches the consumer's tap may be different.

Annual maximum haloacetic acids concentrations in Minnesota Community Water Systems, 1999-2009

Year Cumulative Number of Community Water Systems Sampled, 1999-2009 Number of Community Water Systems by Concentration Category (µg/L)
<15 15 to <30 30 to <45 45 to <60 60 to <80 80 to <100 100+
1999 0 (0%) 0 0 0 0 0 0 0
2000 0 (0%) 0 0 0 0 0 0 0
2001 0 (0%) 0 0 0 0 0 0 0
2002 0 (0%) 0 0 0 0 0 0 0
2003 377 (39%) 314 28 24 8 1 1 1
2004 664 (69%) 578 57 17 8 3 0 1
2005 680 (71%) 614 25 27 11 2 0 1
2006 686 (72%) 627 33 22 2 2 1 0
2007 701 (73%) 624 43 19 12 2 1 0
2008 720 (75%) 626 55 21 14 3 0 1
2009 728 (76%) 651 47 18 10 1 0 1

*µg/L means micrograms per liter of water.


Table 6 below shows the number of people served by Community Water Systems within each HAA5 mean concentration category. A total of 4,234,479 people were estimated to be served by community water systems in Minnesota as of April 2010. HAA5 monitoring data are available for 97% of these people. Note that the estimates of number of people served by each system are rough calculations periodically updated by water purveyors. Estimates are not available for years past.

Number of people served by Community Water Systems by mean haloacetic acids concentration, Minnesota 2009

Year Number of People Served with Available Monitoring Data Number of People Served by Community Water Systems by Concentration Category (µg/L)
<15 15 to <30 30 to <45 45 to <60 60+
2009 4,094,709
(97%)
2,915,972
(71%)
1,123,806
(28%)
51,315
(1%)
3,616
(0%)
0
(0)

*µg/L means micrograms per liter of water.