Office of Water (MS-140) EPA 815-F-15-002 October 2015 

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Revisions to the Unregulated Contaminant Monitoring Rule 

(UCMR 4) for Public Water Systems

Summary

The U.S. Environmental Protection Agency proposes the design for the fourth Unregulated Contaminant 

Monitoring Rule (UCMR 4). This revision establishes a new list of 30 chemical contaminants for public 

water system monitoring and applies to the period of 2017-2021. 

Environmental and Public Health Benefits

The UCMR 4 program provides the EPA and other interested parties with nationally representative data 

on the occurrence of targeted contaminants in drinking water, the number of people potentially being 

exposed and an estimate of the levels of that exposure. The UCMR information is a primary source of 

occurrence data for the Agency to determine whether or not to regulate these contaminants to protect 

public health.

Background 

As part of its responsibilities under the Safe Drinking Water Act, the EPA implements section 

1445(a)(2), Monitoring Program for Unregulated Contaminants. This section, as amended in 1996, 

requires that, once every five years, the EPA issue a list of no more than 30 unregulated contaminants to 

be monitored by public water systems. The data set collected through the UCMR informs the EPA on 

the occurrence and public exposure to support regulatory determinations of whether or not to establish

health based standards. The first UCMR was published on September 17, 1999, the second was 

published on January 4, 2007, and the third was published on May 2, 2012. The EPA anticipates that the 

fourth UCMR (final rule) will be published in late 2016. 
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About this Regulation

Proposed Contaminants

Assessment Monitoring: 30 Contaminants

10 Cyanotoxins

total microcystins microcystin-LA

microcystin-RR microcystin-LF

microcystin-YR microcystin-LR

nodularin microcystin-LY

cylindrospermopsin anatoxin-a

20 Additional Contaminants

germanium manganese

alpha-hexachlorocyclohexane profenofos

chlorpyrifos tebuconazole

dimethipin total permethrin (cis- & trans-)

ethoprop tribufos

oxyfluorfen HAA51,4

HAA6Br2,4 HAA93,4

1-butanol 2-propen-1-ol

2-methoxyethanol butylated hydroxyanisole

o-toluidine quinoline 1

Haloacetic Acids 5 (regulated): dibromoacetic acid, dichloroacetic acid, monobromoacetic acid, 

monochloroacetic acid, trichloroacetic acid

2

Brominated Haloacetic Acids 6: bromochloroacetic acid, bromodichloroacetic acid, dibromoacetic acid 

(regulated), dibromochloroacetic acid, monobromoacetic acid (regulated), tribromoacetic acid 3

Haloacetic Acids 9: bromochloroacetic acid, bromodichloroacetic acid, chlorodibromoacetic acid, 

dibromoacetic acid (regulated), dichloroacetic acid (regulated), monobromoacetic acid (regulated),

monochloroacetic acid (regulated), tribromoacetic acid, trichloroacetic acid (regulated)

4

Regulated HAAs are included in the proposed monitoring program to gain a better understanding of cooccurrence with currently unregulated disinfection byproducts.

As proposed, UCMR 4: 

• identifies a new list of contaminants to be monitored;

• lists the analytical methods to be used; 

• specifies the number of systems required to monitor and where they are required to monitor (e.g., 

entry point to the distribution system and, for some contaminants, at the source water intake or in 

the distribution system);

• modifies the sample collection time frame to March – November, excluding December –

February;

• updates the monitoring frequency such that, with the exception of cyanotoxins, monitoring 
Office of Water (MS-140) EPA 815-F-15-002 October 2015

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would occur every two months for surface water (SW) and ground water under the direct 

influence of surface water (GWUDI) systems (for a total of four sampling events) and every six 

months for ground water (GW) systems (for a total of two sampling events);

• establishes a cyanotoxin monitoring frequency of twice a month for four consecutive months (for 

a total of eight sampling events) for SW and GWUDI systems;

• specifies source water intake sampling locations for total microcystins, temperature, pH and 

indicators associated with haloacetic acid (HAA) monitoring; and,

• requires collection of quality control information related to sample analysis for large public 

water systems (the EPA collected the quality control information for small systems in previous 

UCMRs).

Costs of the Regulation

Nationwide, the agency estimates that the average annual cost of UCMR 4 is approximately $25.3 

million. The table below summarizes which entities will incur the costs (labor and non-labor). Over the 

UCMR 4 implementation period of 2017-2021, the agency assumes that one-third of the systems would 

monitor during each of the three monitoring years from January 2018 through December 2020. 

Respondent

Avg. Annual Cost 

All Respondents 

(2017-2021)1

Small Systems (25-10,000), labor only (non-labor costs paid for by the EPA) $0.16 m

Large Systems (10,001-100,000), including labor and non-labor costs $15.7 m

Very Large Systems (100,001 and greater), including labor and non-labor costs $4.3 m

States, including labor costs related to implementation coordination $0.50 m

The EPA, including labor for implementation, non-labor for small system testing $4.7 m

AVERAGE ANNUAL NATIONAL TOTAL $25.3 m

1 Totals may not equal the sum of components due to rounding.

Labor costs pertain to systems, states and the EPA. Costs include activities such as reading the rule, notifying systems 

selected to participate, sample collection, data review, reporting and record keeping.

Non-labor costs would be incurred primarily by the agency, large and very large public water systems. 

They include the cost of shipping samples to laboratories and the cost of laboratory analyses. The 

agency pays those costs for the small systems as required under the SDWA. Laboratory analysis and 

sample shipping account for approximately 80% of the total national cost for UCMR 4 implementation.

The agency expects that states would incur only labor costs associated with assistance with UCMR 4 

implementation. State participation is voluntary; thus the level of effort varies among states and depends 

on their individual agreements with the agency.

How to Get Additional Information

For general information on UCMR 4, please visit the UCMR 4 website at: http://www2.epa.gov/dwucmr

or contact the Safe Drinking Water Hotline at (800) 426-4791 (open Monday - Friday, excluding legal 

holidays, from 10:00 a.m. to 4:00 p.m., eastern time). The Safe Drinking Water Hotline may also be 

found on the Internet at: http://water.epa.gov/drink/hotline/index.cfm.