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 proposed on December 11, 2015. The proposal outlines 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 determinations and, as warranted, actions to protect public health.


Proposed UCMR 4 analytical methods and contaminants

Assessment Monitoring (List 1 contaminants)

The proposed Assessment Monitoring sampling time frame addresses the period of March 2018 through November 2020. See table below for the proposed 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

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

  • Total for small systems is additive because these systems would only be selected for one component of UCMR 4 sampling (10 cyanotoxins or 20 additional chemicals). EPA would pay for all analytical costs associated with monitoring at small systems.
  • The number of large systems is not additive. All SW and GWUDI systems would monitor for cyanotoxins; those same systems would also monitor for the 20 additional List 1 chemicals, as would the large GW systems.

Ten Cyanotoxin Chemical Contaminants3,4

Contaminant

CAS Registry Number1

Minimum Reporting Level

Sampling Points2

Analytical Methods

total microcystin

N/A

0.3 µg/L

EPTDS and SR

ELISAExit

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

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) Groups4,5

Contaminant

CAS Registry Number1

Minimum Reporting Level

Sampling Points2

Analytical Methods

HAA5

N/A

N/A

Stage 2 DBPR and/or DSMRT

EPA 552.3 or EPA 557

HAA6Br

N/A

N/A

Stage 2 DBPR and/or DSMRT

EPA 552.3 or EPA 557

HAA9

N/A

N/A

Stage 2 DBPR and/or DSMRT

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

Analytical MethodsThe following links exit the site Exit

Total Organic Carbon (TOC)

N/A

N/A

EPTDS

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

EPTDS

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

Temperature N/A N/A EPTDS SM 2550 (21st edition), or SM 2550-10 (SM Online)
pH N/A N/A EPTDS EPA Method 150.1 and 150.2, ASTM D1293-12, SM 4500-H+ B (21st edition) or SM 4500-H+ B-00 (SM Online)

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 Byproduct Rule Sampling Locations (Stage 2 DBPR)
    4. Distribution system maximum residence time (DSMRT)
  3. Temperature and pH must be measured at the same time as cyanotoxin sample collection at the source water intake.
    1. pH methods include: EPA Method 150.1 and 150.2, ASTM D1293-12, SM 4500-H+ B (21st edition) or SM 4500-H+ B-00 (SM Online).
    2. Temperature methods include: SM 2550 (21st edition), or SM 2550-10 (SM Online).
  4. 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.
  5. Regulated HAAs (HAA5) are included in the proposed 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. 

Top of Page


Proposed Microcystin Phased Sample Analysis

As proposed, PWSs that use surface water (SW) and ground water under the direct influence of surface water (GWUDI) must collect all required samples for each sampling event but not all samples may need to be analyzed. The following figure outlines the proposed analytical approach.

EPA is proposing a phased sample analysis approach for microcystins to reduce analytical costs (i.e., PWSs must collect all required samples for each sampling event but not all samples may need to be analyzed).

Top of Page