&EPA
United States
Environmental Protection
Agency
The Third Unregulated Contaminant Monitoring Rule (UCMR 3):
Data Summary
June 2015
EPA uses the Unregulated Contaminant Monitoring Rule (UCMR) program to collect data for contaminants
suspected to be present in drinking water, but that do not have health-based standards set under the Safe
Drinking Water Act (SDWA). Every five years EPA develops a new list of UCMR contaminants, largely based
on the Contaminant Candidate List (CCL). The SDWA Amendments of 1996 provide for:
• Monitoring no more than 30 contaminants per 5-year cycle
• Monitoring only a representative sample of public water systems serving less than or equal to 10,000 people
• Storing analytical results in a National Contaminant Occurrence Database (NCOD)
This dataset represents the seventh NCOD release of analytical results for UCMR 3. Updates will occur
approximately quarterly and EPA anticipates that additional reference material will be made available to assist
with the assessment of the UCMR 3 data. For more information about UCMR 3, please visit our website:
http://water.epa.gov/lawsregs/rulesregs/sdwa/ucmr/ucmr3/index.cfm. Information regarding many of the UCMR
3 contaminants (including a description of their use) may also be found at the CCL website:
http://water.epa.gov/scitech/drinkingwater/dws/ccl/ccl3.cfmtfchemical.
UCMR 3 Data Considerations
• This dataset is not complete. UCMR 3 monitoring occurs through December 2015, and data are
expected to be reported to EPA through the summer of 2016.
• Data are added and possibly removed or updated over the course of this reporting cycle. These results
are subject to change following further review by the analytical laboratory, the public water system, the
State and EPA.
• Data are presented as method-specific text files (UCMR3_200_8.txt, UCMR3_218_7.txt,
UCMR3_300_1.txt, UCMR3_522.txt, UCMR3_524_3.txt, UCMR3_537.txt, UCMR3_539.txt,
EPA_1615A, EPA_1615B, EPA_1615C, EPA_1615D, EPA_1615E, SM_9223B, ASTM_D6503_99,
SM_9218, EPA_1602), one text file containing disinfectant residual type (UCMR3_DRT.txt), one text
file containing the U.S. Postal Service Zip Code(s) for all areas served by a PWS
(UCMR3_ZipCodes.txt) and one text file containing all UCMR 3 data to date (UCMR3_All.txt).
• These text files are tab delimited and have no text qualifier. Field names are included in the first row of
each file.
• If you wish to perform additional data analyses, EPA suggests you import each field into your choice of
software as text. Some of the IDs can be misinterpreted as long integer field types when they actually
contain alpha characters.
• Samples collected at the maximum residence time in the distribution system (MR) are required to be
analyzed for metals (including chromium-6) and chlorate.
• Water systems monitoring for Method 300.1 (chlorate) report disinfectant types.
• Population categories are based on retail population as indicated by the Safe Drinking Water
Information System (Federal) (SDWIS/FED) as of December 31, 2010.
• In addition to reporting occurrence data for UCMR 3 target analytes, EPA tasked its small-system
contract-support laboratories with reporting results for sec-butylbenzene, n-propylbenzene, tellurium,
germanium and manganese. These additional unregulated analytes are within the scope of the
methods already being performed for the UCMR analytes.
Office of Water (MS-140)
EPA 815-S-15-002
June 2015
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UCMR 3 Data Field Names and Definitions
Field Name
PWSID
PWSName
Size
FacilitylD
FacilityName
FacilityWaterType
SamplePointID
SamplePointName
SamplePointType
AssociatedFacilitylD
AssociatedSamplePointID
Definition
Public Water System Identification Code, 9-character identification code (Begins with the standard 2-character postal State abbreviation or Region
code, and the remaining seven numbers are unique to each PWS in the state)
Name of the Public Water System (PWS)
Size category of the PWS for UCMR, based on retail population as of December 31 , 201 0
S: < 10,000
L: > 10,000
Public Water System Facility Identification Code, 5-digit identification code
Name of the facility at the PWS
Source of water at the facility
SW: Surface water
GW: Ground water
GU: Ground water under the direct influence of surface water
MX: Any combination of SW, GW and GU
Identification code for each sample point location in the PWS
Name of the sample point for every sample point ID at a PWS
Sampling Point Type Code
EP: Entry point to the distribution system
MR: Distribution system at maximum residence time
The facility ID of the associated DS/MRT
The sample point ID of the associated DS/MRT
UCMR 3, June 2015
Page 2 of 12
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Field Name Definition
Disinfectant Type
CollectionDate
SamplelD
Contaminant
MRL
MethodID
AnalyticalResultsSign
AnalyticalResultValue
SampleEventCode
CLGA: Gaseous Chlorine
CLOF: Offsite Generated Hypochlorite (stored as liquid)
CLON: Onsite Generated Hypochlorite (no storage)
CAGC: Chloramine (formed from gaseous chlorine)
CAOF: Chloramine (formed from offsite hypochlorite)
CAON: Chloramine (formed from onsite hypochlorite)
CLDO: Chlorine Dioxide
OZON: Ozone
ULVL: Ultraviolet Light
OTHD: All other types of disinfectant
NODU: No Disinfectant Used
Date of sample collection (month, day, year)
Identification code for each sample, as defined by the laboratory
Unregulated contaminant being analyzed in UCMR 3
Minimum Reporting Level defined by UCMR 3
Identification code of the analytical method
Less than (<) the minimum reporting level (MRL) or equal to (=) a numeric value at or above the MRL
Numeric value of the analytical result, null values represent less than MRL
Identification code for each sample event. Includes sample event one (SE1 ), sample event two (SE2), sample event three (SE3), and sample event four
(SE4).
UCMR 3, June 2015
Page 3 of 12
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Field Name Definition
MonitoringRequirement
Region
State
ZipCode
AM: Assessment Monitoring (List 1)
SS: Screening Survey (List 2)
PST: Pre-Screen Testing (List 3)
EPA Region: States
1: CT, ME, MA, NH, Rl, VT
2: NJ, NY, PR (Puerto Rico), VI (Virgin Islands)
3: DE, DC, MD, PA, VA, WV
4: AL, FL, GA, KY, MS, NC, SC, TN
5: IL, IN, Ml, MN, OH, Wl
6: AR, LA, NM, OK, TX
7: IA, KS, MO, NE
8: CO, MT, ND, SD, UT, WY
9: AZ, CA, HI, NV, AS (American Samoa), GU (Guam), MP (Northern Marianas Islands), NN (Navajo Nation)
10: AK, ID, OR, WA
State abbreviation
U.S. Postal Service zip code(s) for all areas being served water by a PWS
UCMR3, June 2015
Page 4 of 12
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UCMR3 Chemical Contaminants and Methods
Contaminant Contaminant Full Name
1 ,2,3-trichloropropane
1,3-butadiene
Chloromethane
1,1-dichloroethane
Bromomethane
HCFC-22
Halon 1011
1 ,4-dioxane
Vanadium
Molybdenum
Cobalt
Strontium
Chromium
Chromium-6
Chlorate
PFOS
PFOA
PFNA
PFHxS
PFHpA
PFBS
17p-estradiol
17a-ethynylestradiol
Estriol
Equilin
Estrone
Testosterone
4-androstene-3,17-dione
1 ,2,3-trichloropropane
1,3-butadiene
methyl chloride
1,1-dichloroethane
methyl bromide
chlorodifluoromethane
bromochloromethane
1,4-dioxane
vanadium
molybdenum
Cobalt
Strontium
total chromium
chromium-6
Chlorate
perfluorooctanesulfonic acid
perfluorooctanoic acid
perfluorononanoic acid
perfluorohexanesulfonic acid
perfluoroheptanoic acid
perfluorobutanesulfonic acid
estradiol
ethinyl estradiol
16-a-hydroxyestradiol
Equilin
Estrone
testosterone
4-androstene-3,17-dione
«->MO
Number
96-18-4
106-99-0
74-87-3
75-34-3
74-83-9
75-45-6
74-97-5
123-91-1
7440-62-2
7439-98-7
7440-48-4
7440-24-6
N/A
18540-29-9
14866-68-3
1763-23-1
335-67-1
375-95-1
355-46-4
375-85-9
375-73-5
50-28-2
57-63-6
50-27-1
474-86-2
53-16-7
58-22-0
63-05-8
Method ID
524.3
524.3
524.3
524.3
524.3
524.3
524.3
522
200.8
200.8
200.8
200.8
200.8
218.7
300.1
537
537
537
537
537
537
539
539
539
539
539
539
539
Method Name Requirement
Volatile Organic Compounds
Volatile Organic Compounds
Volatile Organic Compounds
Volatile Organic Compounds
Volatile Organic Compounds
Volatile Organic Compounds
Volatile Organic Compounds
Synthetic Organic Compound
Metals
Metals
Metals
Metals
Metals
Chromium-6
Oxyhalide Anion
Perfluorinated Compounds
Perfluorinated Compounds
Perfluorinated Compounds
Perfluorinated Compounds
Perfluorinated Compounds
Perfluorinated Compounds
Hormones
Hormones
Hormones
Hormones
Hormones
Hormones
Hormones
QH^^^^^I
AM
AM
AM
AM
AM
AM
AM
AM
AM
AM
AM
AM
AM
AM
AM
AM
AM
AM
AM
AM
SS
SS
SS
SS
SS
SS
SS
1Chemical Abstract Service
UCMR3, June 2015
Page 5 of 12
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UCMR3 Microbiological Contaminants and Methods
Contaminant
Enteroviruses
Enteroviruses
Noroviruses
Noroviruses
Noroviruses
Total conforms
E.coli
Enterococci
Aerobic spores
Somatic phage
Male specific phage
Method ID
EPA1615A
EPA1615B
EPA1615C
EPA1615D
EPA1615E
SM 9223B
SM 9223B
ASTM D6503-99
SM9218
EPA 1602
EPA 1602
Method Name
Enterovirus cell culture
Enterovirus RT-qPCR
Norovirus genogroup I with RT-qPCR primer set A
Norovirus genogroup I with RT-qPCR primer set B
Noroviruses genogroup II
Colilert®
Colilert®
Enterolert®
Aerobic endospores
Bacteriophage
Bacteriophage
Monitoring Requirement
PST
PST
PST
PST
PST
PST
PST
PST
PST
PST
PST
UCMR3, June 2015
Page 6 of 12
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UCMR 3 Reference Concentrations for Chemical Contaminants
Under the current cycle of the Unregulated Contaminant Monitoring Rule (UCMR 3) chemicals are being
studied at levels that are often significantly below those in prior UCMR cycles. Importantly, UCMR 3
minimum reporting levels (MRLs) were established based on the capability of the analytical method, not
based on a level established as "significant" or "harmful." In fact, the UCMR 3 MRLs are often below
current "health reference levels" (to the extent that HRLs have been established).
Results of UCMR 3 measurements should be interpreted accordingly. The detection of a UCMR 3
contaminant above the MRL does not represent cause for concern, in and of itself. Rather, the
implications of the detection should be judged considering health effects information (which is often still
under development or being refined for unregulated contaminants).
The intent of the following table is to identify draft UCMR reference concentrations, where possible, to
provide context around the detection of a particular UCMR contaminant above the MRL. The draft
reference concentration does not represent an "action level" (EPA requires no particular action1'2 based
simply on the fact that UCMR monitoring results exceed draft reference concentrations), nor should the
draft reference concentration be interpreted as any indication of an Agency intent to establish a future
drinking water regulation for the contaminant at this or any other level. Decisions as to whether or not to
regulate the contaminant in drinking water will continue to be made following the Agency's Regulatory
Determination process: [http://water.epa.qov/scitech/drinkinqwater/dws/ccl/index.cfml.
The following key principles guided the development of the table:
(1) The reference concentrations are based on publically-available health information found in the
following EPA resources: 2012 Drinking Water Standards and Health Advisories, the CCL 3
Contaminant Information Sheets, the Human Health Benchmark for Pesticides (HHBPs), the
Integrated Information Risk System (IRIS), or the 2014 Preliminary Regulatory Determinations for
Contaminants on CCL 3. The primary/secondary sources of health information vary with respect to
scientific rigor from health assessment to single studies and are cited in the table.
(2) If health information was available from more than one of the EPA resources listed above, the most
recent health information was used for the draft reference concentrations.
(3) Where both cancer and non-cancer draft reference concentrations existed, the lower (more
conservative) of the two concentrations was used. For chemicals with reference concentrations
based on a cancer endpoint, the table presents a range of values associated with 10~6 to 10~4
cancer risk. For chemicals with reference concentrations based on a non-cancer endpoint, the
duration of exposure (short-term, intermediate/long-term, chronic) of the toxicity factor (e.g.
Reference Dose) used as the basis for the reference concentration is shown.
Recognizing that additional health effects information will become available over time, EPA will
periodically update the following table. Those attempting to assess UCMR occurrence data are
encouraged to visit EPA's website for the most recent information.
1 Consumer Confidence Report (CCR) and Public Notification (PN) reporting requirements (see 40 CFR 141.153(d) and 141.207,
respectively) apply to public water systems; CCR requires particular reporting based on measurements relative to the UCMR method
reporting limits (MRLs) defined in 40 CFR 141.40.
2States may establish requirements for drinking water contaminants not yet regulated by EPA, and those requirements may be based
on State-established levels that differ from EPA's reference concentrations. Public Water Systems are responsible for being aware of
and complying with their State's requirements, if any.
UCMR 3, June 2015 Page 7 of 12
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Contaminant
Cobalt1
Molybdenum2
Strontium3
Vanadium1'4
Chromium (Total)
Chromium-61
Chlorate
1,4-dioxane5
1,1-dichloroethane5
1 ,2,3-trichloropropane5'6'7
1,3-butadiene5'6
MRL
(V9/L)
1
1
0.3
0.2
0.2
0.03
20
0.07
0.03
0.03
0.1
Reference
Concentration
(V9/L)
70
40
1,500
21
100
N/A
210
0.35 to 35
6.14 to 614
0.0004 to 0.04
0.0103 to 1.03
Reference Concentration
based on a Cancer
Endpoint
(Y/N)
N
(intermediate exposure)
N
(chronic exposure)
N
(chronic exposure)
N
(intermediate exposure)
N
(chronic exposure)
N
(chronic exposure)
Y
Y
Y
Y
EPA Referencefs)
CCL 3 Contaminant Information Sheets
2012 Edition of the Health Advisories Table
Federal Register Notice for the Preliminary
Regulatory Determinations for Contaminants on
CCL 3
CCL 3 Contaminant Information Sheets
The MCL for the National Primary Drinking Water
Regulation
CCL 3 Contaminant Information Sheets
2012 Edition of the Health Advisories Table
CCL 3 Contaminant Information Sheets
2009 IRIS Assessment
CCL 3 Contaminant Information Sheets
1 The contaminant is on the IRIS 2012 Agenda for either a new assessment or an updated assessment (Federal Register Notice May 7, 2012).
2 The 2012 Edition of the Health Advisories Table and the CCL 3 Contaminant Information Sheets (35 u.g/L) have slightly different numbers due to rounding.
3 The reference concentration has been updated based on the HRL cited in the preliminary regulatory determination for strontium [Docket No. EPA-HQ-OW-2012-0155].
4 The ATSDR, 1992 used for the CCL 3 Contaminant Information Sheets is no longer publically available and has been replaced by a new assessment (ATSDR, 2013).
The minimum risk level (RfD equivalent) was 0.003 mg/kg/day for minor renal effects in an animal study (ATSDR, 1992) compared to 0.01 mg/kg/day for lack of minor effects in
blood pressure, body weight, and hematological parameters in a human study with a 12 weeks exposure (ATSDR, 2013).
5 Reference Concentration range based on cancer risk of 10"6 to 10"4.
610'6 cancer risk < MRL < 10'4 cancer risk.
7 To derive the reference concentration, age dependent adjustment factors were applied to the IRIS oral slope factor of 30 per mg/kg-day (calculated using adult exposure data)
to address presumed early-life susceptibility for this chemical (per www.epa.gov/cancerguidelines/).
UCMR3, June 2015
Page 8 of 12
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Contaminant
HCFC-22
(chlorodifluoromethane) 8
Chloromethane
(methyl chloride)5
Halon 1011
(bromochloromethane)9
Bromomethane
(methyl bromide)
PFBS
PFHpA
PFHxS
PFNA
PFOS
PFOA
1 7a-ethynylestradiol
(ethinyl estradiol)10
17(3-estradiol
(estradiol)5
Equilin
Estriol
(16-a-hydroxyestradiol)
Estrone
4-androstene-3, 1 7-dione
Testosterone
MRL
(V9/L)
0.08
0.2
0.06
0.2
0.09
0.01
0.03
0.02
0.04
0.02
0.0009
0.0004
0.004
0.0008
0.002
0.0003
0.0001
Reference
Concentration
(V9/L)
N/A
2.69 to 269
90
140
N/A
N/A
N/A
N/A
0.2
0.4
0.035
0.0009 to 0.09
0.35
0.35
0.35
N/A
N/A
Reference Concentration
based on a Cancer
Endpoint
(Y/N)
Y
N
(chronic exposure)
N
(chronic exposure)
N
(short-term exposure)
N
(short-term exposure)
N
(chronic exposure)
Y
N
(chronic exposure)
N
(chronic exposure)
N
(chronic exposure)
EPA Referencefs)
CCL 3 Contaminant Information Sheets
2012 Edition of the Health Advisories Table
Human Health Benchmark for Pesticides (HHBPs)
2012 Edition of the Health Advisories Table
2012 Edition of the Health Advisories Table
CCL 3 Contaminant Information Sheets
CCL 3 Contaminant Information Sheets
CCL 3 Contaminant Information Sheets
CCL 3 Contaminant Information Sheets
CCL 3 Contaminant Information Sheets
8 The CCL 3 Contaminant Information Sheets provide a reference level of 31.5 u.g/L; the number is based on a single LOAEL from a 1983 study.
9 The 2012 Edition of the Health Advisories Table and the CCL 3 Contaminant Information Sheets (70 u.g/L) have slightly different numbers due to rounding.
10 This corrects the CCL 3 Contaminant Information Sheets reference level (originally listed as 0.28 u.g/L).
UCMR3, June 2015 Page 9 of 12
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Terms
a) UCMR Draft Reference Concentration = The reference concentrations are based on publically-available health information found in the
following EPA resources: 2012 Drinking Water Standards and Health Advisories, the CCL 3 Contaminant Information Sheets, the Human
Health Benchmark for Pesticides (HHBPs), or the 2014 Preliminary Regulatory Determinations for Contaminants on CCL 3. The
primary/secondary sources of health information vary with respect to scientific rigor from health assessment to single studies. Many of the
contaminants are currently under regulatory review or development and are subject to change as new health assessments are completed.
b) MRL = UCMR Minimum Reporting Level. [Note that the Agency for Toxic Substances & Disease Registry (ATSDR) uses the term "MRL'for
a different purpose (i.e., to describe "Minimal Risk Levels"). The UCMR term and the ATSDR term have no relationship to each other.]
c) HRLs = Health Reference Levels. HRLs are not final determinations about the level of a contaminant in drinking water that is necessary to
protect any particular population and are derived prior to development of a complete exposure assessment. HRLs are risk derived
concentrations against which to evaluate the occurrence data to determine if contaminants occur at levels of potential public health concern.
d) MCL = Maximum Contaminant Level. The highest level of a contaminant allowed in drinking water. MCLs are enforceable standards.
e) Cancer Risk of 10'6 to 10'4 = the concentration of a contaminant in drinking water corresponding to an excess estimated lifetime cancer risk
of one-in-a-million (1x 10~6) to one-in-ten-thousand (1 x 10~4). The 2012 Drinking Water Standards and Health Advisories provide the cancer
risk at 1 x 10'4. The CCL 3 Contaminant Information Sheets provide the cancer risk at 1x 10'6.
f) LOAEL = Lowest Observed Adverse Effect Level
g) N/A = Not Available
h) Short-term = Typically refers to animal toxicological studies with an exposure duration of days to weeks.
i) Intermediate/Longer-term = Typically refers to animal toxicological studies with an exposure duration of weeks to months.
j) Chronic = Typically refers to animal toxicological studies with an exposure duration of months to years; representing a lifetime exposure in
humans.
References
k) 2012 Drinking Water Standards and Health Advisories
I) CCL 3 Contaminant Information Sheets
m) Human Health Benchmark for Pesticides (HHBPs)
n) Announcement of Preliminary Regulatory Determinations for Contaminants on the Third Drinking Water Contaminant Candidate List
o) Integrated Risk Information System (IRIS)
UCMR 3, June 2015 Page 10 of 12
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June 2015 UCMR 3 Data Summary for Chemical Contaminants
1,2,3-trichloropropane
0.03
number
of results
of results
0.0004 / 0.042
28,901
217
results results
> Reference >Refereni
oncentration Concentration
217/1682
0.8% / 0.6%2
4,398
1,3-butadiene
0.1
0.0103/1.032
28,901
1 /O2
0.003% / 0%2
4,398
1 /O2
0.02% / 0%2
Chloromethane
0.2
2.69/2692
28,899
209
18/O2
0.06% / 0%2
4,398
108
7/02
0.2% / 0%2
1,1-dichloroethane
0.03
6.14/6142
28,900
686
1 /O2
0.003% / 0%2
4,398
209
1 /O2
0.02% / 0%2
Bromomethane
0.2
140
28,900
0%
4,398
45
0%
HCFC-22
0.08
N/A
28,901
661
4,398
245
Halon1011
0.06
90
28,901
539
0%
4,398
260
0%
1,4-dioxane
0.07
0.35 / 352
28,702
3,350
882 / O2
3.1%/0%2
4,394
943
294/ O2
6.7% / 0%2
Vanadium
0.2
21
49,219
29,617
1,402
2.8%
4,413
3,185
145
3.3%
Molybdenum
40
49,230
20,473
121
0.2%
4,413
2,261
31
0.7%
Cobalt
70
49,216
722
0.006%
4,413
215
0.07%
Strontium
0.3
1,500
49,157
48,982
1,312
2.7%
4,413
4,412
247
5.6%
Chromium
0.2
100
49,094
24,791
1
0.002%
4,413
3,220
0.02%
Chromium-6
0.03
N/A
49,159
36,992
4,425
3,899
Chlorate
20
210
49,172
27,459
7,574
15.4%
4,412
2,994
1,590
36%
PFOS
0.04
0.2
29,076
234
31
0.1%
4,418
87
17
0.4%
PFOA
0.02
0.4
29,075
287
0%
4,418
94
0%
PFNA
0.02
N/A
29,076
17
4,418
13
PFHxS
0.03
N/A
29,076
176
4,418
52
PFHpA
0.01
N/A
29,076
193
4,418
70
PFBS
0.09
N/A
29,076
4,418
17|3-estradiol
0.0004
0.0009 / 0.092
9,027
1 /O2
0.01 %/0%2
961
1 /O2
0.1%/0%2
17a-ethynylestradiol
0.0009
0.035
9,028
0%
961
0%
Estriol
0.0008
0.35
9,027
0%
961
0%
Equilin
0.004
0.35
9,028
0%
961
0%
Estrone
0.002
0.35
9,028
0%
961
0%
Testosterone
0.0001
N/A
9,027
51
961
45
4-androstene-3,17-dione
0.0003
N/A
9,028
73
961
55
Measured in ug/L (ppb)
2Where two reference concentrations are listed, the
Where two results are presented the first number
UCMR 3, June 2015
! first number is associated with a 10~6 cancer risk; the second number a 10^ cancer risk.
is associated with the first reference concentration; the second number is associated with the second reference concentration.
Page 11 of 12
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June 2015 UCMR 3 Data Summary for Microbiological Contaminants
Aerobic spores
E. coli
Enterococci
Enteroviruses (cell culture)
Enteroviruses (RT-qPCR)
Male specific phage
Noroviruses GIA
Noroviruses GIB
Noroviruses Gil
Somatic phage
Total coliforms
1
1
1
0.002
0.398
1
0.398
0.398
0.398
1
1
SFO/100ml_
MPN/100ml_
MPN/100ml_
MPN/L
GC/L
PFU/100ml_
GC/L
GC/L
GC/L
PFU/100mL
MPN/100mL
Total Number of Total number Number of
number of results ofPWSswith PWSswith
511
511
513
507
507
515
507
507
507
515
511
^C^FT^^^^^B
155
3
33
2
6
9
0
1
4
3
29
•vS^T^ff^M
492
492
494
488
488
496
488
488
488
496
492
results >MRL
153
3
33
2
6
9
0
1
4
3
28
UCMR 3 Minimum Reporting Levels for Microbiological Contaminants
Under UCMR 3 microbe analytical results are reported as "below", "at" or "above" MRL. UCMR 3 MRLs were established based on
the capability of the analytical method.
It is important to note that microbial contamination can be transient in nature and microbial detections under UCMR 3 should be
interpreted in the context of the time samples were collected. However, the presence of any UCMR 3 microbe indicates a potential
vulnerability of the PWS to contamination.
UCMR 3, June 2015
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