Third Unregulated Contaminant Monitoring Rule

The Safe Drinking Water Act (SDWA) requires that once every five years the EPA issue a list of unregulated contaminants to be monitored by public water systems (PWSs).

The third Unregulated Contaminant Monitoring Rule (UCMR 3) was published on May 2, 2012. UCMR 3 required monitoring for 30 contaminants (28 chemicals and two viruses) between 2013 and 2015 using analytical methods developed by the EPA and consensus organizations. This monitoring provides a basis for future actions to protect public health.

• Federal Register Notice: Final Revisions to the UCMR 3 for Public Water Systems, May 2, 2012
• UCMR 3 Basic Information Fact Sheet

UCMR 3 Scope, Analytical Methods, and Contaminants

Assessment Monitoring (AM)

All PWSs serving more than 10,000 people and 800 representative PWSs serving 10,000 or fewer people monitored for 21 contaminants during a 12-month period from January 2013 through December 2015.

• UCMR 3: Fact Sheet for Assessment Monitoring

Screening Survey (SS)

All PWSs serving more than 100,000 people, 320 representative PWSs serving 10,001 to 100,000 people, and 480 representative PWSs serving 10,000 or fewer people monitored for seven contaminants during a 12-month period from January 2013 through December 2015.

• UCMR 3: Fact Sheet for Screening Survey

Pre-Screen Testing (PST)

The EPA selected 800 representative PWSs that serve 1,000 or fewer people, do not disinfect, and have wells located in areas of karst or fractured bedrock to monitor for two viruses during a 12-month period from January 2013 through December 2015.

• UCMR 3: Fact Sheet for Pre-Screen Testing

The EPA paid all analytical costs associated with monitoring at PWSs serving 10,000 or fewer people.

Table 1. Chemical Contaminants, Minimum Reporting Levels, Sampling Locations, and Analytical Methods

Table 2. Microbiological Contaminants, Indicators, Sampling Locations, and Analytical Methods

Notes

1. Chemical Abstracts Service Registry Number (CASRN)
2. The EPA-established UCMR Minimum Reporting Level (MRL) is the lowest concentration that laboratories may report to the EPA during UCMR monitoring. UCMR MRLs are determined using data from multiple laboratories that participate in the EPA’s MRL-setting studies and are not associated with contaminant health effects information. More specifically, an MRL is the quantitation limit for a contaminant that is considered achievable, with 95% confidence, by at least 75% of laboratories nationwide using a specified analytical method (recognizing that individual laboratories may be able to measure at lower levels).
3. Sample Point Locations
   1. Entry point to the distribution system (EP)
   2. Distribution system maximum residence time (MR)
4. Samples for microbial indicators, including total coliforms, E. coli, Enterococci, aerobic spores, and bacteriophage, were required to be collected at the same time as samples for enteroviruses and noroviruses.