Monitoring Unregulated Drinking Water Contaminants

Fourth Unregulated Contaminant Monitoring Rule

The 1996 Safe Drinking Water Act (SDWA) amendments require that once every five years EPA issue a new list of no more than 30 unregulated contaminants to be monitored by public water systems (PWSs).

The fourth Unregulated Contaminant Monitoring Rule (UCMR 4) was published in the Federal Register on December 20, 2016. UCMR 4 requires monitoring for 30 chemical contaminants between 2018 and 2020 using analytical methods developed by EPA and consensus organizations. This monitoring provides a basis for future regulatory actions to protect public health.


UCMR 4 scope, analytical methods and contaminants

Assessment Monitoring (List 1 contaminants)

PWSs will monitor for 10 List 1 cyanotoxins during a 4-consecutive month period from March 2018 through November 2020. PWSs will monitor for 20 List 1 additional contaminants during a 12-month period from January 2018 through December 2020. See table below for the sampling design.

National Sample Assessment Monitoring Design

System Size (# of people served)

10 List 1 Cyanotoxins

20 Additional List 1 Chemicals

Small Systems (25 – 10,000)

800 randomly selected surface water (SW) or ground water under the direct influence of surface water (GWUDI) systems

A different group of 800 randomly selected SW, GWUDI and ground water (GW) systems

Large Systems (10,001 and over)

All SW or GWUDI systems

All SW, GWUDI and GW systems

  • EPA will pay for all analytical costs associated with monitoring at small systems.

Ten Cyanotoxin Chemical Contaminants

Contaminant

CAS Registry Number1

Minimum Reporting Level

Sampling Points2

Analytical Methods

total microcystin

N/A

0.3 µg/L

EPTDS

EPA 546
(ELISA)

microcystin-LA

96180-79-9

0.008 µg/L

EPTDS

EPA 544

microcystin-LF

154037-70-4

0.006 µg/L

EPTDS

EPA 544

microcystin-LR

101043-37-2

0.02 µg/L

EPTDS

EPA 544

microcystin-LY

123304-10-9

0.009 µg/L

EPTDS

EPA 544

microcystin-RR

111755-37-4

0.006 µg/L

EPTDS

EPA 544

microcystin-YR

101064-48-6

0.02 µg/L

EPTDS

EPA 544

nodularin

118399-22-7

0.005 µg/L

EPTDS

EPA 544

anatoxin-a

64285-06-9

0.03 µg/L

EPTDS

EPA 545

cylindrospermopsin

143545-90-8

0.09 µg/L

EPTDS

EPA 545

Two Metals

Contaminant

CAS Registry Number1

Minimum Reporting Level

Sampling Points2

Analytical MethodsThe following links exit the site Exit.Notice: fees are charged for ASTM and Standard Methods (SM) access.

germanium

7440-56-4

0.3 µg/L

EPTDS

EPA 200.8, ASTM D5673-10, SM 3125

manganese 7439-96-5 0.4 µg/L EPTDS EPA 200.8, ASTM D5673-10, SM 3125

Eight Pesticides and One Pesticide Manufacturing Byproduct

Contaminant

CAS Registry Number1

Minimum Reporting Level

Sampling Points2

Analytical Methods

alpha-hexachlorocyclohexane

319-84-6

0.01 µg/L

EPTDS

EPA 525.3

chlorpyrifos

2921-88-2

0.03 µg/L

EPTDS

EPA 525.3

dimethipin

55290-64-7

0.2 µg/L

EPTDS

EPA 525.3

ethoprop

13194-48-4

0.03 µg/L

EPTDS

EPA 525.3

oxyfluorfen

42874-03-3

0.05 µg/L

EPTDS

EPA 525.3

profenofos

41198-08-7

0.3 µg/L

EPTDS

EPA 525.3

tebuconazole 107534-96-3 0.2 µg/L EPTDS EPA 525.3

total permethrin (cis- & trans-)

52645-53-1 0.04 µg/L EPTDS EPA 525.3
tribufos 78-48-8 0.07 µg/L EPTDS EPA 525.3

Three Brominated Haloacetic Acid (HAA) Groups3,4

Contaminant

CAS Registry Number1

Minimum Reporting Level

Sampling Points2

Analytical Methods

HAA5

N/A

N/A

D/DBPR HAA location(s)

EPA 552.3 or EPA 557

HAA6Br

N/A

N/A

D/DBPR HAA location(s)

EPA 552.3 or EPA 557

HAA9

N/A

N/A

D/DBPR HAA location(s)

EPA 552.3 or EPA 557

Three Alcohols

Contaminant

CAS Registry Number1

Minimum Reporting Level

Sampling Points2

Analytical Methods

1-butanol

71-36-3

2.0 µg/L

EPTDS

EPA 541

2-methoxyethanol

109-86-4

0.4 µg/L

EPTDS

EPA 541

2-propen-1-ol

107-18-6

0.5 µg/L

EPTDS

EPA 541

Three Other Semivolatile Chemicals

Contaminant

CAS Registry Number1

Minimum Reporting Level

Sampling Points2

Analytical Methods

butylated hydroxyanisole

25013-16-5

0.03 µg/L

EPTDS

EPA 530

o-toluidine

95-53-4

0.007 µg/L

EPTDS

EPA 530

quinoline

91-22-5

0.02 µg/L

EPTDS

EPA 530

Indicators

Parameter

CAS Registry Number1

Minimum Reporting Level

Sampling Points2

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total organic carbon (TOC)

N/A

N/A

SR

SM 5310 B, SM 5310 C, SM 5310 D (21st edition), or SM 5310 B-00, SM 5310 C-00, SM 5310 D-00 (SM Online), EPA Method 415.3 (Rev. 1.1 or 1.2)

bromide

N/A

N/A

SR

EPA Methods 300.0 (Rev. 2.1), 300.1 (Rev. 1.0), 317.0 (Rev. 2.0), 326.0 (Rev. 1.0) or ASTM D 6581-12

Notes

  1. Chemical Abstract Service (CAS) Registry Number
  2. Sampling Locations
    1. Entry points to the distribution system (EPTDS)
    2. Source Water Intake Locations (SR)
    3. Stage 2 Disinfectants and Disinfection Byproducts Rule Sampling Locations (D/DBPR)
  3. TOC and bromide samples must be collected at the same time as HAA samples. These indicator samples must be collected at a single source water intake using methods already approved for compliance monitoring.
    1. TOC methods include: SM 5310 B, SM 5310 C, SM 5310 D (21st edition), or SM 5310 B-00, SM 5310 C-00, SM 5310 D-00 (SM Online), EPA Method 415.3 (Rev. 1.1 or 1.2).
    2. Bromide methods include: EPA Methods 300.0 (Rev. 2.1), 300.1 (Rev. 1.0), 317.0 (Rev. 2.0), 326.0 (Rev. 1.0) or ASTM D 6581-12.
  4. Regulated HAAs (HAA5) are included in the monitoring program to gain a better understanding of co-occurrence with currently unregulated disinfection byproducts.
    1. HAA5 includes: dibromoacetic acid, dichloroacetic acid, monobromoacetic acid, monochloroacetic acid, trichloroacetic acid.
    2. HAA6Br includes: bromochloroacetic acid, bromodichloroacetic acid, dibromoacetic acid, dibromochloroacetic acid, monobromoacetic acid, tribromoacetic acid.
    3. HAA9 includes: bromochloroacetic acid, bromodichloroacetic acid, chlorodibromoacetic acid, dibromoacetic acid, dichloroacetic acid, monobromoacetic acid, monochloroacetic acid, tribromoacetic acid, trichloroacetic acid. 

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Microcystin Phased Sample Analysis

PWSs that use surface water (SW) and ground water under the direct influence of surface water (GWUDI) must collect three samples at the entry point to the distribution system (EPTDS) for cyanotoxins. One sample will be collected for total microcystins analysis by EPA Method 546 (Adda ELISA), the second for potential microcystin analysis by EPA Method 544, and the third for cylindrospermopsin and anatoxin-a analysis by EPA Method 545.

  • If the Adda ELISA result is less than 0.3 micrograms per liter (µg/L) (i.e., the reporting limit for total microcystins), then the sample collected for Method 544 will not be analyzed for that sample event, and only the Adda ELISA result will be reported to EPA.
  • If the ELISA result is greater than or equal to 0.3 µg/L, the result will be reported to EPA and the EPA Method 544 sample will be analyzed to identify and quantify the six specific microcystin congeners and nodularin.
  • Cylindrospermopsin and anatoxin-a will be analyzed by EPA Method 545 for all sample events.

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