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Research for New Regulation: UCMR4
Massachusetts Water Resources Authority

The US Environmental Protection Agency (EPA) periodically requires water systems across the country to conduct monitoring for substances that may be present in drinking water to help understand their national occurrence as part of the process of deciding whether to regulate them.  Under the Safe Drinking Water Act Amendments, EPA established the Unregulated Contaminant Monitoring Rule and is required once every five years to develop a list of up to 30 new contaminants that must be monitored during a three year period by public water systems that meet the criteria for sampling.  This monitoring is used by EPA to understand the frequency and level of occurrence of unregulated contaminants in the nation’s public water systems (PWSs).

EPA will collect and analyze data for all three years and from systems all across the country to develop an understanding of the occurrence, level and distribution of these substances in drinking water. That data, along with information on potential halth effects and water treatment effectiveness will be used by EPA to determine if any new regulations are needed.

Return to UCMR Main Page

UCMR 4 (2018-2020)

In December 2016, EPA issued a final rule establishing the fourth round of the Unregulated Contaminant Monitoring Rule (UCMR4).  UCMR 4 requires monitoring for 30 chemicals between 2018 and 2020. MWRA collected samples for 20 of the contaminants during 2018, 2019 and 2020 at community locations which are fully supplied by MWRA.  Cyanotoxin monitoring includes an additional 10 contaminants and took place primarily in 2020.  Some of the MWRA partially-supplied communities were also required to do UCMR sampling during this three year period.

Even with the extremely sensitive test methods used at EPA-approved laboratories, capable of detecting some substances at parts per trillion levels – which is 1000 times more sensitive than parts per billion, we expected to find very few of the substances due to MWRA’s highly protected watershed and reservoirs. Only 4 of the 30 tested for were detected in fully supplied communities, and all were at extremely low levels.  The results for those are reported below and you can click the links for data from partially supplied communities.

Here is a list of the UCMR 4 contaminants:

Contaminants (20)
germanium  total permethrin (cis- & trans-) 
tebuconazole butylated hydroxyanisole
oxyfluorfen profenofos
2-methoxyethanol ethoprop
manganese 1-butanol
dimethipin o-toluidine
HAA5 chlorpyrifos
HAA6Br tribufos
HAA9    2-propen-1-ol
alpha-hexachlorocyclohexane quinoline


Cyanotoxins (10)
total microcystins anatoxin-a
microcystin-YR microcystin-RR
cylindrospermopsin microcystin-LY
microcystin-LA microcystin-LF
microcystin-LR nodularin

More information on these substances and UCMR4 can be found on the US EPA web site here.

UCMR 4 Test Results

UCMR 4 monitoring occurred between 2018 and 2020 - these are now complete results.

MWRA UCMR 4 Test Results (2018-2020)
Fully Supplied Communities Partially Supplied Communities Chicopee Valley Aqueduct (CVA)
Results below Bedford Chicopee
  Canton South Hadley FD #1

Results for Fully Supplied Communities

Only the substances discussed below were detected.  All other substances listed in the UCMR4 were not detected.  Note:  ppb = parts per billion = ug/L.    

Substance Measurement Units Average Range
Manganese  parts per billion (ppb)   9.9 5.1 – 61.7

Manganese is a common mineral that naturally occurs in rocks and soil, and is commonly found in ground and surface waters in New England. It may also be present due to underground pollution sources.  Manganese is an essential mineral for proper digestion, bone development, and immune function.  Primary sources in the diet include grains, beans, nuts and teas. At excessively high levels, however, manganese can have adverse neurological effects.  EPA has a secondary, aesthetic standard of 50 ppb.  Above the 50 ppb level, consumers may notice a gray or black coloring in their water and/or fixture staining. To be protective of public health MA DEP has a health guideline value of 300 ppb, and Consumer Confidence Report Notification Limit of 50 ppb. MWRA routinely samples for manganese in the source and finished water with results posted to MWRA’s web site on a monthly basis.  UCMR4 results are typical for results found through routine monitoring, and are well below the state and EPA health guidelines. Only two of 88 results were over the aesthetic standard of 50 ppb, likely due to local flushing or hydrant use.

Substance Measurement Units Average Range
1-Butanol parts per billion (ppb)   0.18 0 –10

1-Butanol is a naturally occurring alcohol, and also widely used in industry.  1-Butanol is not currently regulated by EPA, or by Massachusetts.  New York has a guidance value of 50 ppb.  There is an EPA Health Reference concentration of 700 ppb.  Only five of 185 samples had detectable concentrations, and all were well below the New York guidance and EPA Health Reference Levels.

Substance Measurement Units Average Range
Haloacetic acids 5 (HAA5) parts per billion (ppb)   12.9   4.9 – 18.7
Haloacetic acids 6 Br (HAA6Br) parts per billion (ppb)   1.27   0 - 2.43
Haloacetic acids 9 (HAA9) parts per billion (ppb)   14.5   5.6 - 20.4
Bromochloroacetic Acid parts per billion (ppb)   1.1 0.4 - 1.7
Bromodichloroacetic Acid parts per billion (ppb)   0.26 0 – 0.9
Chlorodibromoacetic Acid parts per billion (ppb)   0.04 0 - 0.3

Haloacetic acids (HAA) are a group of disinfection byproducts that form when chlorine compounds that are used to disinfect water react with other naturally occurring material in the water.  There are five significant HAAs potentially found in disinfected drinking water and their combined concentration is referred to as HAA5.  HAA5's are already regulated by the EPA and MassDEP and have a Maximum Contaminant Level (MCL) standard of 60 ppb as a locational running annual average.  MWRA’s HAA5 levels are always well below this 60 ppb standard with an average of about 10-15 ppb. HAA9 and HAA6Br include 4 more HAA compounds that are not currently regulated by EPA or MassDEP.  We detected 3 of the 4 new compounds, all at very low levels.  We did not detect tribromoacetic acid.  If you combined all 9 species in the HAA9 group, MWRA would still be well below the current HAA5 MCL of 60 ppb, with average of around 15 ppb.  

Substance Measurement Units Average Range
Quinoline parts per billion (ppb) 0.001 0 to 0.03

Only 6 of 185 samples taken at the required UCMR4 sample locations had any detections. The health effects of quinoline are uncertain, and thus EPA only provides a wide range for its health reference level (HRL), from 0.01 to 1 ppb. The average level detected is 10 to 1000 times lower than EPA HRLs.

Given the extremely sensitive test methods required and lack of published information on quinoline, MWRA conducted additional sampling beyond that required by UCMR4. This included field blanks to rule out any potential environmental contamination at the sample location, and samples before and after treatment and at other key locations. One of these 15 additional samples was positive with a value of 0.071 ppb.

Updated May 5, 2022

Historic Withdrawls Reservoir Levels