United States
Environmental Protection
Agency
The Analysis of Occurrence Data
from the Unregulated Contaminant
Monitoring Program (UCM) and
National Inorganics and
Radionuclides Survey (NIRS) in
Support of Regulatory
Determinations for the Second
Drinking Water Contaminant
Candidate List (CCL 2)
Office of Water (4607M) EPA 815-R-08-014 June 2008 www.epa.gov/safewater
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EPA - OGWDW Analysis of Occurrence Data from the UCM and MRS for CCL 2 June 2008
Disclaimer
This document is designed to provide technical background information for the
regulatory determinations being made on the second drinking water Contaminant Candidate List
(CCL 2).
This document is not a regulation itself, and it does not substitute for the Safe Drinking
Water Act (SDWA) or the Environmental Protection Agency's (EPA's) regulations. Mention of
trade names or commercial products does not constitute endorsement or recommendation for use.
in
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EPA - OGWDW Analysis of Occurrence Data from the UCM and MRS for CCL 2 June 2008
Acknowledgments
The compilation and analysis of data presented in this report were undertaken by EPA's
Office of Ground Water and Drinking Water (OGWDW) in support of the regulatory
determinations for specific contaminants listed on CCL 2. This effort was directed by Mr.
Clifton Townsend and Ms. Yvette Selby-Mohamadu of OGWDW's Standards and Risk
Management Division (SRMD) Targeting and Analysis Branch (TAB). Yvette Selby-
Mohamadu served as the Team Lead for the CCL 2 final regulatory determinations under the
guidance of Wynne Miller (TAB Associate Branch Chief), Eric Burneson (TAB Branch Chief),
Phil Oshida (SRMD Deputy Division Director), Pamela Barr (SRMD Division Director) and
Cynthia Dougherty (OGWDW Office Director).
We would like to thank the many States, as well as the American Water Works Service
Company, that contributed data sets and valuable advice. Thanks also to the many public water
systems that conducted the monitoring that provided the contaminant occurrence data used in
this report.
The Cadmus Group, Inc., served as the prime contractor for this project, supporting the
data management, analysis, and report development under Contract # 68-C-02-026. The major
contributions of Morgan Tingley, Erin Mateo, Alison Cullity, Brent Ranalli, and Dr. George
Hallberg are gratefully acknowledged. Dr. Jonathan Koplos served as the Cadmus Project
Manager.
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EPA - OGWDW Analysis of Occurrence Data from the UCM and MRS for CCL 2 June 2008
Executive Summary
The Unregulated Contaminant Monitoring (UCM) program (Rounds 1 and 2) and the
National Inorganics and Radionuclides Survey (NIRS) were important sources of data
considered by the United States Environmental Protection Agency (EPA) when evaluating the
occurrence of unregulated contaminants on the second Contaminant Candidate List (CCL 2).
This report presents EPA's analysis of national occurrence of CCL 2 contaminants with data
from those sources. Detailed occurrence analyses are presented in this report to support the EPA
regulatory determinations for the four CCL 2 contaminants with Round 1, Round 2 and NIRS
data: boron, metolachlor, 1,3-dichloropropene, and 1,1,2,2-tetrachloroethane. Detailed
descriptions are presented of the data sources, data editing and management, development of
national cross-sections using UCM Round 1 and Round 2 data from States, and the analytical
approaches used to assess the occurrence data.
The UCM Round 1 monitoring data represent public water system (PWS) monitoring
results from 1988 to 1992 for unregulated contaminants collected under the authority of Safe
Drinking Water Act (SDWA). Forty States/primacy entities have submitted PWS monitoring
data for Round 1. Subsequent UCM Round 2 monitoring data collected from 1993 to 1997 were
reported by 35 States/entities. The raw data from these two databases were reviewed and edited
for data quality considerations to ensure consistency and repeatability in the analyses. A data
management approach was developed to construct representative national cross-sections using
the State data sets determined to be of the highest quality and most complete.
The development of the UCM Round 1 and Round 2 national cross-sections enabled
occurrence analyses that were indicative of national occurrence using data from these two large
databases. All States with monitoring data were first evaluated by their distribution across a
range of pollution potential indicators and spatial/hydrogeologic diversity. A select group of
States, representing a balanced distribution across these pollution potential measures and across
the nation geographically, was then used to construct national cross-sections (one using Round 1
data, the other Round 2 data) that would provide reasonable representations of national
occurrence. While the Round 1 and Round 2 national cross-sections cannot be presented as
"statistically representative," they comprise very large samples (24 and 20 States, respectively),
provide analytical occurrence results that are clear indications of central tendency of the
occurrence data, and are generally indicative of national contaminant occurrence.
The NIRS provides contaminant occurrence data from 1984 through 1986 from a group
of statistically selected, nationally representative PWSs served by ground water. These data are
from 49 States (there are no data from Hawaii), as well as Puerto Rico. Given the statistical
design of NIRS, the resulting contaminant occurrence analyses can be considered representative
of national occurrence in PWSs served by ground water.
Occurrence analyses of the UCM Rounds 1 and 2 and the NIRS data are conducted using
a two-stage analytical approach. In Stage 1, the data are first reviewed, quality-checked and
characterized, and then analyzed to generate simple, clear non-parametric estimates of
contaminant occurrence. The Stage 1 analysis, based on maximum sample analytical values, is
inherently conservative; it is careful not to underestimate occurrence toward the goal of
protecting public health. Simple counts are made of the number of systems, and populations-
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served by those systems, with at least one analytical result above a specified concentration
threshold. Any contaminant found to have significant occurrence at or near health reference
level (HRL) concentrations based on the Stage 1 analysis can additionally be analyzed using the
Stage 2 analysis. In Stage 2, statistical modeling is used to generate national probability
estimates of contaminant occurrence based on estimated annual mean concentrations of
contaminants while providing statistical measures of uncertainty and error. Because no
contaminants in this report were found with significant levels of contaminant occurrence at or
near the HRLs of concern based on the Stage 1 analyses, the Stage 2 analyses were not warranted
for any of the contaminants.
Stage 1 assessments of occurrence are presented in several ways for each contaminant to
characterize different aspects of occurrence. For each contaminant, occurrence statistics
presented include the number and percent of samples with laboratory analytical detections,
which are quantified analytical values above the laboratory method reporting limit or minimum
reporting level (MRL). All analytical detections are summarized by calculating and presenting
the minimum, median, and 99th percentile values of detections for each contaminant. At the
system level, the number and percent of systems with at least one detection at or above the MRL,
and the number and percent of systems with at least two detections at or above the MRL, are
presented. For contaminants with HRLs, similar types of occurrence assessments are presented
relative to the concentration values of the HRL. The occurrence of the four contaminants
described in this report is summarized as follows:
• For boron, 989 total samples (1 sample per system) were collected by the NIRS. Boron
was detected at or above the MRL of 0.005 mg/L in 810 (81.9% of) systems. The
maximum detection was 3.95 mg/L and the median detection was 0.047 mg/L.
Detections were found in PWSs in all States that conducted sampling, with the exception
of Rhode Island. Seventeen PWSs had detections greater than the boron HRL of 1.4
mg/L, and 43 PWSs detected concentrations greater than 1A HRL (0.7 mg/L). A national
extrapolation from the statistical sample of PWSs finds that 48,682 ground water
systems, serving more than 75.5 million people, are estimated to have at least one sample
detection of boron. Approximately 2,584 ground water systems, serving nearly 2.5
million people are estimated to have at least one sample detection of boron above the 1A
HRL and approximately 1,022 ground water systems, serving approximately 372,000
people are estimated to have at least one sample detection of boron above the HRL of 1.4
mg/L.
For metolachlor, a total of 33,930 samples were collected by the Round 2 cross-section.
Metolachlor was detected at or above the MRL in 108 (0.83% of) systems. (MRLs
varied from system to system. They ranged from 0.01 to 52 |ig/L. The modal MRL
value was 0.2 |ig/L.) Although occurrence was relatively widespread, the metolachlor
concentrations found were consistently low. In the Round 2 cross-section, the maximum
detection was 13.8 |ig/L, the 99th percentile of detections was 7.1 |ig/L, and the median
detection was 0.61 |ig/L. Detections were found in PWSs in 12 of the 19 Round 2 cross-
section States. The proportion of surface water systems with metolachlor detections
(6.55%) was much greater than that for ground water systems (0.11%). A national
extrapolation from the Round 2 cross-section results estimates that 542 systems, serving
approximately 24.7 million people, have at least one sample detection of metolachlor.
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No analytical results in the Round 2 database were greater than the metolachlor HRL of
70 |ig/L. Metolachlor was not monitored under the UCM Round 1.
For 1,3-dicloropropene, in the Round 1 national cross-section, a total of 31,104 samples
were collected from 9,164 PWSs. 1,3-Dichloropropene was detected at or above the
MRL in 15 (0.16% of) systems. (MRLs varied from system to system. They ranged
from 0.02 to 10 |ig/L. The modal MRL value was 0.5 |ig/L.) The maximum detection in
the Round 1 cross-section was 2.0 jig/L and the median detection was 1.0 |ig/L.
Detections were found in PWSs in 5 of the Round 1 cross-section States. A national
extrapolation from the Round 1 cross-section results estimates 106 systems, serving
approximately 1.8 million people, have at least one sample detection of 1,3-
dichloropropene. All PWSs with detections of 1,3-dichlorpropane in Round 1 also had
detections greater than the 1A HRL (0.2 |ig/L) and HRL (0.4 |ig/L).
For 1,3-dicloropropene, in the Round 2 national cross-section, a total of 70,631 samples
were collected from 16,787 PWSs. 1,3-Dichloropropene was detected at or above the
MRL in 58 (0.35% of) systems. (MRLs varied from system to system. They ranged
from 0.08 to 1 |ig/L. The modal MRL value was 0.5 |ig/L.) The maximum detection in
the Round 2 cross-section was 39 |ig/L and the median detection was 0.5 |ig/L.
Detections were found in PWSs in 7 of the Round 2 cross-section States. Fifty PWSs had
detections of 1,3-dichloropropene greater than 1A HRL (0.2 |ig/L) and 38 PWSs had
detections greater than HRL of 0.4 |ig/L. All 7 Round 2 States had at least one PWS with
a detection greater than the HRL. A national extrapolation from the Round 2 cross-
section results estimates 225 systems, serving approximately 1.2 million people, have at
least one sample detection of 1,3-dichloropropene. Approximately 194 systems, serving
approximately 894,000 people are estimated to have at least one sample detection of 1,3-
dichloropropene greater than the /^ HRL and approximately 147 systems, serving
approximately 703,000 people are estimated to have at least one sample detection greater
than the HRL.
For 1,1,2,2-tetrachloroethane, in the Round 1 national cross-section, a total of 67,688
samples were collected from 20,407 PWSs. 1,1,2,2-Tetrachloroethane was detected at or
above the MRL in 91 (0.45% of) systems. (MRLs varied from system to system. They
ranged from 0.01 to 10 |ig/L. The modal MRL value was 0.5 |ig/L.) The maximum
detection in the Round 1 cross-section was 200 |ig/L and the median detection was 0.5
|ig/L. Detections were found in PWSs in 13 of the Round 1 cross-section States. Forty-
one PWSs had detections of 1,1,2,2-tetrachloroethane greater than the HRL of 0.4 jig/L
and 44 PWSs had detections greater than the V2 HRL (0.2 |ig/L.). 1,1,2,2-
Tetrachloroethane detections greater than the HRL were found in PWSs in 9 of the
Round 1 cross-section States. A national extrapolation from the Round 1 cross-section
results estimates 290 systems, serving approximately 4.0 million people, have at least one
sample detection of 1,1,2,2-tetrachloroethane. Approximately 140 systems, serving
approximately 3.6 million people are estimated to have at least one sample detection of
1,1,2,2-tetrachloroethane greater than the 1A HRL and approximately 131 systems,
serving approximately 3.5 million people are estimated to have at least one sample
detection greater than the HRL.
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For 1,1,2,2-tetrachloroethane, in the Round 2 national cross-section, a total of 98,911
samples were collected from 24,800 PWSs. 1,1,2,2-Tetrachloroethane was detected at or
above the MRL in 19 (0.08% of) systems. (MRLs varied from system to system. They
ranged from 0.1 to 2.5 |ig/L. The modal MRL value was 0.5 |ig/L.) The maximum
detection in the Round 2 cross-section was 2 jig/L and the median detection was 0.5
|ig/L. Detections were found in PWSs in 9 of the Round 2 cross-section States. Eighteen
PWSs had detections of 1,1,2,2-tetrachloroethane greater than V2 HRL (0.2 |ig/L) and 17
PWSs had detections of 1,1,2,2-tetrachloroethane greater than HRL of 0.4 |ig/L. 1,1,2,2-
Tetrachloroethane detections greater than the HRL were found in PWSs in 7 of the
Round 2 cross-section States. A national extrapolation from the Round 2 cross-section
results estimates 50 systems, serving approximately 5.6 million people, have at least one
sample detection of 1,1,2,2-tetrachloroethane. Approximately 47 systems, serving
approximately 1.1 million people are estimated to have at least one sample detection of
1,1,2,2-tetrachloroethane greater than V2 the HRL and approximately 45 systems, serving
approximately 168,000 people are estimated to have at least one sample detection greater
than the HRL.
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EPA - OGWDW Analysis of Occurrence Data from the UCM and MRS for CCL 2 June 2008
Contents
Disclaimer iii
Acknowledgments v
Executive Summary vii
Exhibits xiii
Appendices xv
Acronyms xvii
1. Introduction 1
1.1 Regulatory Background 1
1.2 Sources of Data Used for Analysis 2
1.3 Threshold Evaluations 5
1.4 General Description of the Two-Stage Analytical Approach 6
1.5 Detailed Description of the Stage 1 Analytical Methodology 7
1.6 Analytical Tools 8
2. UCM Round 1 Data Overview 9
2.1 Description of Data 9
2.2 Data Management and Data Quality 10
2.3 Round 1 Data Bias and Representativeness: Further Data Quality Review and Editing
11
2.4 Data Characteristics Overview 14
3. UCM Round 2 Data Overview 19
3.1 Description of Data 19
3.2 Data Management and Data Quality 19
3.3 Round 2 Data Bias and Representativeness: Further Data Quality Review and Editing
20
3.4 Data Characteristics Overview 23
4. National Inorganics And Radionuclides Survey (NIRS) Data 27
4.1 Description of Data 27
4.2 Representativeness 27
4.3 Data Characteristics Overview 28
4.4 Supplemental IOC Data 29
5. Developing aNationally Representative Perspective 31
6. Analysis of National Occurrence 35
6.1 Round 1 Contaminant Occurrence 35
6.2 Round 2 Contaminant Occurrence 36
6.3 NIRS Contaminant Occurrence 38
6.4 National Extrapolation of Stage 1 Occurrence Measures 39
6.5 Comparing Data Coverage of Round 1 and Round 2 40
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7. Graphical and Spatial Assessments of the Contaminants Considered During CCL 2 Regulatory
Determinations 43
7.1 Metolachlor 44
7.2 1,3-Dichloropropene 47
7.3 1,1,2,2-Tetrachloroethane 52
8. References 59
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Exhibits
Exhibit 1.2. a. Diagram of the Inter-Relationship of the Databases, Monitoring Rounds and
Contaminant Lists Discussed in the Report 3
Exhibit 1.2.b. List and Description of Contaminants with Round 1 and Round 2 Data
Considered During CCL 2 Regulatory Determinations 4
Exhibit 1.2.c. Description of the Inorganic Chemical with data in NIRS Considered During
CCL 2 Regulatory Determinations 5
Exhibit 1.5.a. Total Number Systems and Population Served Systems Used in All National
Extrapolations 8
Exhibit 2.3.a. Summary of Round 1 Data Quantity and Quality for the States, Tribes and
Territories 13
Exhibit 2.3.b. Summary of Round 1 Data Quantity and Quality for the States, Tribes and
Territories 14
Exhibit 2.4.a. Round 1 Data - Number of Records and Systems by Source Water Type 15
Exhibit 2.4.b. Round 1 Data-Number of Records and Systems by System Type 16
Exhibit 2.4.c. Round 1 Data-Number of Records by Year and Source Water Type 17
Exhibit 2.4.d. Round 1 Data -Number of Records by Month and Source Water Type 17
Exhibit 3.3.a. Summary of Round 2 Data Quantity and Quality for the States, Tribes and
Territories 22
Exhibit 3.3.b. Summary of Round 2 Data Quantity and Quality for the States, Tribes and
Territories 22
Exhibit 3.4.a. Round 2 Data - Number of Records and Systems by Source Water Type 24
Exhibit 3.4.b. Round 2 Data-Number of Records and Systems by System Type 24
Exhibit 3.4.c. Round 2 Data-Number of Records by Year and Source Water Type 25
Exhibit 3.4.d. Round 2 Data -Number of Records by Month and Source Water Type 25
Exhibit 4.3.a. NIRS Data-Number of Records by Year 28
Exhibit 4.3.b. NIRS Data-Number of Records by Month 28
Exhibit 5.a. 24 Round 1 Cross-Section States and States Not Included in the Cross-Section. 33
Exhibit 5.b. 20 Round 2 Cross-Section States and States Not Included in the Cross-Section. 33
Exhibit 6.1 .a. Round 1 Data - 24-State Cross-Section Summary of System-Level Occurrence
for Contaminants Considered During CCL 2 Regulatory Determinations 36
Exhibit 6.1.b. Round 1 Data - 24-State Cross-Section Summary of Population Served-Level
Occurrence for Contaminants Considered During CCL 2 Regulatory
Determinations 36
Exhibit 6.2.a. Round 2 Data - 20-State Cross-Section Summary of System-Level Occurrence
for Contaminants Considered During CCL 2 Regulatory Determinations 37
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Exhibit 6.2.b. Round 2 Data - 20-State Cross-Section Summary of Population Served-Level
Occurrence for Contaminants Considered During CCL 2 Regulatory
Determinations 38
Exhibit 6.3.a. NIRS Data - Summary of Boron Occurrence in Surveyed Ground Water Systems
- Based on the System Level 39
Exhibit 6.3.b. NIRS Data - Summary of Boron Occurrence in Surveyed Ground Water Systems
- Based on Population Served 39
Exhibit 6.4. National Extrapolation of Stage 1 Occurrence Measures 40
Exhibit 6.5. States Common to Both Round 1 and Round 2, and Respective Cross-Sections. 41
Exhibit 7.1 .a. Geographic Distribution of Metolachlor Detections in Both Cross-Section and
Non-Cross-Section States (Round 2 Data) 45
Exhibit 7.1 .b. Geographic Distribution of Metolachlor Detection Frequencies in Cross-Section
States (Round 2 Data) 45
Exhibit 7. I.e. Annual Frequency of Metolachlor Detections By Year (1992-1997) from the
19-State Round 2 Cross-Section 46
Exhibit 7.2.a. Geographic Distribution of 1,3-Dichloropropene Detections in Both Cross-
Section and Non-Cross-Section States (Combined Rounds 1 and 2) 47
Exhibit 7.2.b. Geographic Distribution of 1,3-Dichloropropene Detection Frequencies in Cross-
Section States (Upper Map: Round 1; Lower Map: Round 2) 48
Exhibit 7.2.c. Geographic Distribution of 1,3-Dichloropropene Detection Frequencies
(upper map) and HRL Exceedance Frequencies (lower map) for All Round 1
and Round 2 Cross-Section States 50
Exhibit 7.2.d. Annual Frequency of 1,3-Dichloropropene Detections (left) and FtRL
Exceedances (right), 1985 - 1997, in Select Cross-Section States 51
Exhibit 7.2.e. Distribution of 1,3-Dichloropropene Detections (left) and HRL Exceedances
(right) Among Select Cross-Section States 51
Exhibit 7.3.a. Geographic Distribution of 1,1,2,2-Tetrachloroethane Detections in Both
Cross-Section and Non-Cross-Section States (Combined Rounds 1 and 2) 52
Exhibit 7.3.b. Geographic Distribution of 1,1,2,2-Tetrachloroethane Detection Frequencies in
Cross-Section States (Upper Map: Round 1; Lower Map: Round 2) 53
Exhibit 7.3.c. Geographic Distribution of 1,1,2,2-Tetrachloroethane Detection Frequencies
(upper map) and FtRL Exceedance Frequencies (lower map) for All Round 1 and
Round 2 Cross-Section States 55
Exhibit 7.3.d. Annual Frequency of 1,1,2,2-Tetrachloroethane Detections (left) and FtRL
Exceedances (right), 1985 - 1997, in Select Cross-Section States 56
Exhibit 7.3.e. Distribution of 1,1,2,2-Tetrachloroethane Detections (left) and FtRL Exceedances
(right) Among Select Cross-Section States 57
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Analysis of Occurrence Data from the UCM and MRS for CCL 2
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Appendices
APPENDIX A.
APPENDIX B.
APPENDIX C.
APPENDIX D.
APPENDIX E.
Development of Health Reference Levels
Detailed Round 1 Data Summary for 1,3-Dichloropropene, and 1,1,2,2-
Tetrachloroethane
Detailed Round 2 Data Summary for Metolachlor, 1,3-Dichloropropene,
and 1,1,2,2-Tetrachloroethane
Detailed NIRS Data Summary for Boron
Data Summaries of Occurrence and Population Served for Four
Contaminants Considered During CCL 2 Regulatory Determinations
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June 2008
Acronyms
AWWARF American Water Works Association Research Foundation
CAS Chemical Abstract Services
CCL Contaminant Candidate List
CCL 1 EPA's First Contaminant Candidate List
CCL 2 EPA's Second Contaminant Candidate List
CMR Chemical Monitoring Reform
CWS Community Water System
DCPA Dimethyl Tetrachloroterephthalate (Dacthal)
DDE 1, l-Dichloro-2,2-bis(p-chlorophenyl)ethylene
EPA Environmental Protection Agency
EPIC s-Ethyl Dipropylthiocarbamate
GWUDI Ground Water under Direct Influence
GW Ground Water
FIRL Health Reference Level
IOC Inorganic Compound
MRL Minimum Reporting Level or Method Reporting Limit
MTBE Methyl Tertiary Butyl Ether
NCWS Non-Community (or Transient) Water System
NCFAP National Center for Food and Agricultural Policy
NIRS National Inorganic and Radionuclides Survey
NPDWR National Primary Drinking Water Regulation
NTNCWS Non-Transient Non-Community Water System
OGWDW Office of Ground Water and Drinking Water
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PWS Public Water System
PWSID Public Water System Identifier
SDWA Safe Drinking Water Act
SDWIS Safe Drinking Water Information System
SDWIS/FED Safe Drinking Water Information System/Federal Version
SOC Synthetic Organic Compound
SRMD Standards and Risk Management Division
SW Surface Water
TAB Targeting and Analysis Branch
UCM Unregulated Contaminant Monitoring
UCMR Unregulated Contaminant Monitoring Regulation
URCIS Unregulated Contaminant Monitoring Information System
VOC Volatile Organic Compound
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1. Introduction
This report presents an analysis of national occurrence in public drinking water systems
of four unregulated contaminants: one inorganic compound (IOC), boron; one synthetic organic
compound (SOC), metolachlor, and two volatile organic compounds (VOCs), 1,3-
dichloropropene and 1,1,2,2-tetrachloroethane. These four contaminants are on the second
Contaminant Candidate List (CCL 2) for which the United States Environmental Protection
Agency (EPA) is currently considering during the CCL 2 regulatory determination process.
Drinking water contaminant occurrence findings developed in this report are based on
three different data sets. The Unregulated Contaminant Monitoring (UCM) program Round 1
and Round 2 monitoring data sets were collected under provisions of the Safe Drinking Water
Act (SDWA). These data sets provide occurrence data for 1,1,2,2-tetrachloroethane, 1,3-
dichloropropene, and metolachlor. The occurrence data for boron were collected through the
National Inorganics and Radionuclides Survey (MRS). Reviews of these unregulated
contaminant occurrence data sets, as well as detailed occurrence findings for 1,1,2,2-
tetrachlroethane, 1,3-dichloropropene, metolachlor and boron, are presented in this report.
Additionally, the CCL 2 includes several contaminants monitored under the first Unregulated
Contaminant Monitoring Regulation (UCMR 1). EPA presents the occurrence findings for ten
UCMR 1 contaminants (l,l-dichloro-2,2-bis(p-chlorophenyl)ethylene, also known as DDE; the
mono- and di-acid degradates of dimethyl tetrachloroterephthalate, also known as DCPA or
dacthal; 1,3-dichloropropene; 2,4-dinitrotoluene; 2,6-dinitrotoluene; s-ethyl
dipropylthiocarbamate, also known as EPTC; fonofos; methyl tertiary butyl ether, also known as
MTBE; and terbacil) in a separate report entitled The Analysis of Occurrence Data from the First
Unregulated Contaminant Monitoring Regulation (UCMR 1) in Support of Regulatory
Determinations for the Second Drinking Water Contaminant Candidate List (USEPA, 2008a).
For those contaminants considered as part of the CCL 2 regulatory determinations, a
Regulatory Determinations Support Document (USEPA, 2008b) provides contaminant-specific
information regarding chemical and physical properties, use and release, and supplemental
occurrence data and analyses. Based on contaminant occurrence, exposure, and other risk
considerations, EPA must determine if regulating these contaminants will present a meaningful
opportunity to reduce public health risk.
1.1 Regulatory Background
Under §1412(b)(l) of the SDWA Amendments, EPA was required to publish a list of
contaminants (the CCL) to assist in priority-setting efforts. The contaminants included on a CCL
are not subject to any current or proposed National Primary Drinking Water Regulation
(NPDWR). CCL contaminants may pose risks for drinking water, and therefore may require
regulation under SDWA.
The first CCL (CCL 1) contained 60 contaminants, including 50 chemicals or chemical
groups and 10 microbiological contaminants or microbial groups. In 2003, EPA released final
regulatory decisions on nine of these contaminants (68 FR 42898). The second and current CCL
(CCL 2: 70 FR 9071) contains 51 contaminants, consisting of all the contaminants from CCL 1
that did not progress to regulatory determination. The 1996 SDWA Amendments require EPA to
make determinations on whether or not to regulate at least five contaminants on a five-year
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cycle, or three and a half years after each CCL. This report presents contaminant occurrence
findings that serve to support the second round of regulatory determinations.
1.2 Sources of Data Used for Analysis
Brief descriptions of the occurrence data sources used in this report are provided in this
section (see Sections 2, 3, 4, and 5 for more details on data management). Occurrence data for
three of the contaminants evaluated in this report (metolachlor, 1,3-dichloropropene, and 1,1,2,2-
tetrachloroethane) were collected as part of the UCM program. The SDWA, Amendments of
1986 required public water systems (PWSs) to monitor for specified unregulated contaminants
on a five-year cycle, and to report the monitoring results to the States. Data from the first round
of monitoring starting in 1988 were stored in the Unregulated Contaminant Monitoring
Information System (URCIS) database, referred to in this report as the UCM "Round 1
database." In 1993, Congress amended SDWA to add new unregulated contaminants for
monitoring. Data from this second round of monitoring, starting in 1993, were stored in the Safe
Drinking Water Information System/Federal version (SDWIS/FED1) database, referred to in this
report as the UCM "Round 2 database." Occurrence data for the fourth contaminant evaluated in
this report, boron, is derived from the occurrence data collected under the National Inorganic and
Radionuclides Survey.
Unregulated contaminants are contaminants that do not have an established or proposed
NPDWR, but they may be formally listed and scheduled for monitoring under Federal
regulations. The intent of the monitoring is to gather scientific information on the occurrence of
these contaminants, to enable a decision regarding whether regulations were needed. EPA
required all non-purchased community water systems (CWSs) and non-purchased non-transient
non-community water systems (NTNCWSs) with more than 150 service connections to
participate in this UCM. Smaller systems were not universally required to participate in the
monitoring, but they were required to be available for monitoring if the State decided such
monitoring was necessary. (As evident in the data, many States did collect data from small
systems as well.)
The 1993 SDWA Amendments added other contaminants to the unregulated contaminant
list for required monitoring, and the 1996 SDWA Amendments directed EPA to develop a
revised program for such monitoring. This new program was formally published in the Federal
Register on September 17, 1999 (64 FR 50556), as the UCMR 1. The UCMR 1, and related
rules, replaced the older (UCM) requirements, putting forth a new list of contaminants, a new set
of rules about which systems must monitor, a new structure to the monitoring program, and a
new framework to ensure that all the monitoring results are reported to EPA. Monitoring under
UCMR 1 began in 2001. Every five years EPA must develop a new list of unregulated
contaminants for UCMR monitoring.
Exhibit 1.2.a diagrams the inter-relationship of the various databases, monitoring rounds
and contaminant lists related to the UCM Round 1 and Round 2 data. The Round 1 and Round 2
databases contain occurrence data from other contaminants besides those required as part of the
UCM in 1987 (referred to as UCM [1987]) or as amended in 1993 (referred to as UCM [1993]).
1 SDWIS/FED is the official database repository of data provided by public drinking water systems, and includes
data from earlier EPA public water system databases.
2
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Also, although each database primarily contains data collected during the years of the two formal
monitoring periods (1988-1992 and 1993-1997), there are some earlier "grandfathered" data
from years that pre-date the beginning of each of the respective monitoring periods.
Exhibit 1.2.a. Diagram of the Inter-Relationship of the Databases, Monitoring
Rounds and Contaminant Lists Discussed in the Report
Monitoring Period:
1988-1992
Round 1
(62
"-UCM (1987)
Chemicals
-28 Additional
Chemicals
• 20 Mandatory VOCs
• 14 Discretionary VOCs
• 21 Phase I VOCs
• 2 Regulated SOCs
• 5 Miscellaneous Contaminants
Monitoring Period:
1993-1997
Round?
(48
JUCM (1993)
[Chemicals
T-34 Chemicals
I from UCM (1987)
| -14 Additional
I^Chemicals
• 20 Mandatory VOCs
(Group 3)
• 14 Discretionary VOCs
(Group 4)
• 13 SOCs (Group 1)
• 1 IOC (Group 2)
The UCM (1987) contaminants included 34 VOCs, divided into two groups: one with 20
VOCs for mandatory monitoring, and the other with 14 VOCs for discretionary monitoring. The
UCM (1987) contaminants were first monitored coincident with the Phase I regulated
contaminants, during the 1988-1992 period. This period is referred to as the "Round 1"
monitoring period. The monitoring data collected by the PWSs were reported to the States (as
primacy agents), but there was no protocol in place that defined reporting of these data to EPA.
The Round 1 data were stored in the URCIS (or "Round 1") database. Most of the Phase
1 regulated contaminants were also VOCs. Both the unregulated and regulated VOCs are
analyzed using the same sample and the same laboratory methods. Hence, the Round 1 database
included data on all of these 62 Round 1 contaminants: the 34 UCM (1987) VOCs; the 21
regulated Phase I VOCs; 2 regulated SOCs; and 5 miscellaneous contaminants that were
voluntarily reported by some States (e.g., isomers of other organic contaminants). Details of the
Round 1 database, its contained data, data quantity and quality, etc., are discussed in Section 2 of
this report.
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Monitoring for the UCM (1993) contaminants began coincident with the Phase II-V
regulated contaminants in 1993 through 1998. This is often referred to as "Round 2" monitoring.
The UCM (1987) contaminants were also included in the Round 2 monitoring. In the updated
listing for the unregulated contaminants required for the monitoring, the UCM (1993)
contaminants were listed as: Group 1 (13 SOCs); Group 2 (1 IOC); Group 3 (the 20 mandatory
VOCs in UCM (1987)); and Group 4 (the 14 discretionary VOCs in UCM (1987)). The group
numbering is somewhat reversed, with the first unregulated contaminants, from UCM (1987), in
the last two groups. Data from Round 2 monitoring were stored in the SDWIS/FED (or "Round
2") database. Further details of the Round 2 database, its data and management, are discussed in
Section 3 of this report.
Exhibit 1.2.b presents the list of three contaminants evaluated during CCL 2 regulatory
determinations contained in the Round 1 and Round 2 databases. This table includes Chemical
Abstract Services (CAS) number and Safe Drinking Water Information System (SDWIS)
contaminant code, and indicates the monitoring Rounds and Group reference numbers for the
contaminants. Note that the minimum reporting levels (MRLs) were not uniform for
metolachlor, 1,3-dichloropropene, or 1,1,2,2-tetrachloroethane, as several analytical methods
were used in analyzing these data. MRLs for metolachlor varied from 0.01 to 52 |ig/L with a
modal value of 0.2 |ig/L. MRLs for 1,3-dichloropropene varied from 0.02 to 10 |ig/L in Round 1
and from 0.08 to 1 |ig/L in Round 2. The modal MRL in both rounds was 0.5 |ig/L. MRLs for
1,1,2,2-tetrachloroethane varied from 0.01 ug/L to 10 |ig/L in Round 1 and from 0.01 |ig/L to 2.5
|ig/L in Round 2. The modal MRL in both rounds was 0.5 |ig/L.
Exhibit 1.2.b. List and Description of Contaminants with Round 1 and Round 2
Data Considered During CCL 2 Regulatory Determinations
Contaminant
CAS
Number
SDWIS
ID
Modal
MRL
(^9/L)
HRL
(^g/L)
UCM
Round
Common Sources of
Contaminant
Synthetic Organic Chemicals
Metolachlor
51218-45-2
2045
0.2
70
-
2
Herbicide for corn, soybeans,
peanuts, cotton, pod crops
Volatile Organic Chemicals
1,3-Dichloropropene
1,1,2,2-
Tetrachloroethane
542-75-6
79-34-5
2413
2988
0.5
0.5
0.4
0.4
1
1
2
2
Solvent, used as fungicide
Used in paint manufacturing;
cement; paint removers; moth-
proofing
Modal MRL = Because different laboratory analytical methods were used during the approximately ten years of Round 1 and 2
monitoring, the resulting sample concentration data reflect a range of MRLs; the modal value is the most common MRL.
HRL = Health Reference Level (concentration values used only as reference levels for analyses in this report)
UCM Round = data included in Round 1 and/or Round 2 monitoring and database.
The third and final database used in this report is the MRS database. Data used for
analysis of the remaining IOC (boron) comes from this database. The MRS data, collected for a
statistically designed, nationally representative survey, can be used directly for national
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contaminant occurrence analyses with very few, if any, data quality or use issues. One
limitation, however, is that the NIRS data are from groundwater systems only. The NIRS data,
and assessments of supplemental IOC data, are discussed in detail in Section 4.
The NIRS survey was designed and conducted by EPA specifically to provide data on the
occurrence of a select set of radionuclides and lOCs being considered for NPDWRs. The NIRS
provides contaminant occurrence data from approximately 989 nationally representative
community PWSs served by ground water. Each of these statistically randomly selected PWSs
was sampled a single time between 1984 and 1986. Exhibit 1.2.c describes the single IOC for
which occurrence was assessed in this report. The MRL for boron in the NIRS was always 0.005
mg/L.
Exhibit 1.2.c. Description of the Inorganic Chemical with Data in NIRS Considered
During CCL 2 Regulatory Determinations
Contaminant
CAS
Number
MRL
(mg/L)
HRL
(mg/L)
Common Sources of Contaminant
Inorganic Chemicals
Boron
7440-42-8
0.005
1.4
Naturally occurring in environment as borates, widely
used in production of industrial and household goods
1.3 Threshold Evaluations
Assessments of contaminant occurrence included in this report are conducted relative to
the MRL. Analytical detections are samples with contaminants detected at concentrations equal
to or greater than the MRL. An analytical non-detection is a sample that either had no
contaminant present and therefore detected no contaminant or had the contaminant present at a
concentration less than the MRL (and therefore was undetected). Evaluations of occurrence
relative to the MRL provide the baseline measure of occurrence.
Detections of the contaminants are also evaluated relative to at least two other
concentration thresholds: the health reference level (HRL) and one-half the HRL (l/2 HRL). The
HRL is an EPA-defined benchmark for evaluating contaminant occurrence based on health
effects information. By conducting occurrence assessments relative to several thresholds (such
as the MRL, l/2 HRL, and HRL), additional information is provided on the degree as well as the
frequency of contaminant occurrence. This serves to better characterize the distribution of
occurrence.
EPA evaluated the best available, peer-reviewed assessments and studies to characterize
the human health effects that may result from exposure to individual contaminants when found in
drinking water. Based on this characterization, the Agency estimated an HRL for each
contaminant. For more details regarding the development of the HRLs, see Appendix A in this
report.
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It is important to note that HRL values have been derived by EPA as a means to provide
additional information regarding the distribution of occurrence and occurrence relative to
concentrations of potential health effects.
Some contaminants with analytical detects may not have been detected at concentrations
greater than their respective HRL or 1A HRL. Although many of the 1,3-dichloropropene and
1,1,2,2-tetrachloroethane occurrence data in the cross-section were generated using analytical
methods with MRLs that were higher than the HRL, all MRLs did fall within (or below) the risk
range of 10"6 to 10"4 used by EPA to evaluate carcinogens. It is possible, though, that monitoring
failed to identify some HRL exceedances at the participating systems. Using the Stage 1
analytical approach, direct occurrence measures cannot be made relative to concentration
thresholds below (less than) the MRL. Thus, the HRL analyses might reflect underestimates of
actual occurrence at concentrations above the 1A HRL and below the MRL. If warranted, the
Stage 2 analytical approach (probabilistic modeling) can estimate system mean concentrations at
any level above or below the MRL.2
1.4 General Description of the Two-Stage Analytical Approach
A two-stage analytical approach is used to evaluate the UCM Round 1 and 2 and NIRS
contaminant occurrence data. The first stage of analysis provides a straightforward evaluation of
occurrence of all contaminants under consideration. This "Stage 1 analysis" of occurrence
assesses the data sources, quality, and characteristics, and then uses the data to conduct simple,
non-parametric, and conservative assessments for a broad evaluation of contaminant
occurrence.3 Occurrence analyses for each contaminant are assessed for samples, systems, and
population served by systems. A typical Stage 1 analysis is a simple count of the number (or
percentage) of systems with at least one analytical detection of a specific contaminant, or at least
one analytical detection with a concentration greater than an HRL.
Any contaminant found to have significant occurrence at or near HRL concentrations
based on the Stage 1 analysis can additionally be analyzed using the "Stage 2 analysis." The
Stage 2 analysis generates an estimated number of systems with a mean contaminant
concentration exceeding a specified threshold and includes measures of uncertainty
(corresponding confidence intervals based on calculated standard errors). The Stage 2 analysis
uses statistical modeling to generate national probability estimates of contaminant occurrence by
generating estimated annual mean concentrations of contaminants at PWSs. This provides an
occurrence analysis that is less conservative since it is based on estimated annual mean
concentrations rather than maximum sample concentration results as in the Stage 1 analysis. The
Stage 2 analysis also provides more direct estimates of potential chronic exposure since it is
based on estimated annual (long-term) mean concentrations of contaminant occurrence. In a
general sense, the Stage 1 analysis reflects an approximation of peak analytical results while the
Stage 2 analysis estimates long-term, average occurrence.
2 Stage 2 analysis allows an assessment of systems with mean, rather than peak, concentrations estimated to exceed
the HRL and l/i the HRL. Because the Stage 2 mean concentration estimates are based on annual, or longer-term,
occurrence data, the Stage 2 analyses may be more appropriate for contaminants with chronic health effects.
These analyses are conservative in the sense that they are protective of human health (i.e., they are more likely to
overestimate risks to human health than underestimate them).
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Because none of the contaminants discussed in this report were found with significant
levels of contaminant occurrence at or near the HRLs of concern based on the Stage 1 analyses,
Stage 2 analyses were not warranted for any of the contaminants.4 The two-stage analytical
approach was previously developed for other EPA Office of Ground Water and Drinking Water
(OGWDW) national occurrence studies, including the first Six-Year Review of NPDWRs (see
USEPA, 2003a). This data management and occurrence analytical approach was previously
peer-reviewed for use under the Six-Year Review and, partly for consistency across OGWDW
projects, has been adapted for the analyses of the CCL 2 regulatory determination occurrence
data. A detailed description of the Stage 1 analytical approach is included in Section 1.5 below.
For more details on the Stage 2 analytical approach, see Section 5 and Appendix B of The
Analysis of Occurrence Data from the First Unregulated Contaminant Monitoring Regulation
(UCMR 1) In Support of Regulatory Determinations for the Second Drinking Water Contaminant
Candidate List (USEPA, 2008a).
1.5 Detailed Description of the Stage 1 Analytical Methodology
Stage 1 analysis provides a conservative assessment of occurrence for each contaminant
by counting the number of PWSs with at least one analytical result that equals or exceeds the
MRL, or exceeds the !/2 HRL or the HRL. Hence, these Stage 1 analyses are essentially based on
the single maximum analytical value recorded at each PWS. The Stage 1 analyses are
conservative - cautious regarding public health concerns - in the sense that they are descriptive
statistics based on peak, rather than long-term mean, concentrations of contaminants. The Stage
1 analyses are conducted at both the system level and the population-served level, allowing
exposure to be characterized both in terms of the number and percent of systems with detections,
and the number and percent of population-served by systems with detections. Estimates based
on the population served by PWSs provide a rudimentary characteristic of exposure potential.
By conducting the Stage 1 analyses at the system level and not the sample level, several
biases of the Round 1 and Round 2 sampling methodology are avoided. During Round 1 and
Round 2 monitoring, when detects were found in a system, sampling frequency increased for that
system. Conducting Stage 1 analyses at the sample level, consequently, would bias the results
toward increased detection frequencies. As such, the detection frequency portion of Stage 1
analyses was conducted only on systems and the population-served. The only sample-level
analyses that were conducted were calculations of the minimum, median, maximum, and 99th
percentile values. Note that due to the inherent vulnerability, occurrence pattern, and some
regulatory differences between surface water-supplied and ground water-supplied PWSs,
separate analyses were generated for surface water (SW) systems and ground water (GW)
systems. All Stage 1 analytical findings are presented in Appendix B (for Round 1), Appendix C
(for Round 2), and Appendix D (for the NIRS). At the beginning of the Appendices section, the
"List of Appendix Tables" identifies all tables included in each of the three appendices.
4 It is important to note that Stage 2 analysis would not have been appropriate for the NIRS data. Stage 2 uses
multiple records for a specific contaminant per system to model a system's long-term mean concentration. As the
NIRS only contains one record per contaminant per system, Stage 2 analyses were therefore not appropriate for the
NIRS data set.
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1.5.1 Extrapolation of National Cross-Section Results
The development of the UCM Round 1 and Round 2 national cross-sections enables
occurrence analyses that are indicative of national occurrence. In addition, the MRS data were
collected for a statistically designed, nationally representative survey. Extrapolations provide the
best available estimate of contaminant occurrence on a nationwide scale. To calculate the
extrapolations, the total national number of systems (or population served by systems) estimated
to exceed a specified threshold is generated by multiplying the representative cross-section (or
MRS) percentage of systems with a threshold exceedance (e.g., % systems > !/2 HRL) by the
national numbers for systems (and population served by systems) documented in the Water
Industry Baseline Handbook, Second Edition - 2000 (USEPA, 2000).
Exhibit 1.5.a. Total Number Systems and Population Served Systems
Used in All National Extrapolations
Source Water
Type
Ground Water
Surface Water
Total
National Inventory of
CWSs plus NTNCWSs
Systems
59,440
5,590
65,030
Population
85,681,696
127,326,486
213,008,182
Source: USEPA, 2000.
To estimate the national number of ground water systems with a detection of metolachlor,
for example, the percentage of ground water systems from the Round 2 cross-section with
detections of metolachlor (0.113%) is multiplied by the total number of ground water systems
nationally (59,440 systems). The resulting estimate equals 67 systems (59,440*0.00113=67).
The national estimate of population exposed to a given contaminant is extrapolated in a similar
fashion (i.e., the proportion of population served by a system with a threshold exceedance is
multiplied by the total population served nationally). Extrapolated results are presented in
Section 6.4 and Appendix E.
1.6 Analytical Tools
All statistical analyses, and most management efforts, were conducted with SAS®
statistical software. Some data formatting problems were corrected in Microsoft® Excel with the
aid of specialized programs written in Visual Basic® or were corrected directly in SAS before the
analysis began.5 After analysis, results were typically exported into Excel for secondary
analysis, sorting, or the development of report tables.
5 SAS is a registered trademark of the SAS Institute, Inc. Excel and Visual Basic are trademarks of the Microsoft
Corporation.
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2. UCM Round 1 Data Overview
In this section of the report, the monitoring results for the UCM program Round 1 data
(from approximately 1988-1992) are reviewed. The data were derived from EPA's Unregulated
Contaminant Information System database. As described previously, this report refers to URCIS
as the Round 1 database.
2.1 Description of Data
The Round 1 database is a compilation of PWS monitoring results for unregulated
contaminants, collected under the authority of SDWA, and reported to the States (as the primacy
agents for SDWA). EPA requested that the States submit these data to EPA in the early 1990s,
but no formal protocol or format had been established for reporting. Given the evolving nature
of data management during this era various problems were encountered. The data were supplied
by States on a variety of media, ranging from photocopies of hand-written files to electronic files
on magnetic tape or diskettes of various kinds, and in many different formats and software
configurations. Some data were electronically transferable, other data had to be manually
entered or re-entered. EPA worked on the entry, cleanup, and analysis of these data during the
1990s. Through this long effort, many critical data quality problems were resolved (such as
getting the data into consistent, standard units of measure).6
Data from Round 1 were reviewed, edited, and analyzed by the EPA in several other
studies. Some initial analyses of the Round 1 data were presented in the occurrence data report
produced for EPA's OGWDW Chemical Monitoring Reform (CMR) project. That report, A
Review of Contaminant Occurrence in Public Water Systems (USEPA, 1999), is referred to as
the "CMR Report." Additionally, an occurrence review of select unregulated contaminants
based on the Round 1 and Round 2 data is presented within the EPA report Analysis of National
Occurrence of the 1998 Contaminant Candidate List (CCL) Regulatory Determination Priority
Contaminants in Public Water Systems (USEPA, 2002), referred to as the "Priority
Contaminants Report." The Priority Contaminants Report presents a comprehensive overview
of national occurrence data for eight contaminants on the 1998 CCL. It was followed by the
Analysis of National Occurrence of 14 Contaminants from the 1998 Contaminants Candidate
List (CCL) (USEPA, 2003), referred to as the "Occurrence of 14 Report" The Occurrence of 14
Report contains Round 1 analyses for two of the contaminants discussed in this current report
(1,3-dichloropropene and 1,1,2,2-tetrachloroethane). As descriptions of occurrence based on the
Round 1 database have been covered thoroughly elsewhere, this current report presents only the
information related to understanding occurrence findings for the contaminants evaluated for CCL
2 regulatory determinations. For the most comprehensive description of the creation and
management of the Round 1 database, refer to Section II of the Priority Contaminants Report.
The version of the Round 1 database used as the basis for this current analysis was the
same final edited version developed and used for the regulatory determinations made on the 1998
6 For examples of data problem resolution, see Fallen, Fran, 1994 (November), "Unregulated Contaminants
Information System (URCIS) System Inventory;" Computer Sciences Corp, 1993 (March), "Unregulated
Contaminants Maintenance Manual;" Fallen, Fran, 1993 (December), "Unregulated Contaminants Maintenance
Manual Supplement;" and, Computer Sciences Corp, 1992 (July), "A Statistical Survey of the Unregulated
Contaminant Data." (All of these internal reports contain many pages of text, sometimes unnumbered, and typically
many pages of unnumbered tabulated data and/or computer code.)
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CCL 1 contaminants. Some of the actual analytical findings developed and presented in the
Occurrence of 14 Report (USEPA, 2003) are used in the current report. Other analyses,
including new analyses using updated URLs, have been conducted for and are presented for the
first time in this current report.
The Round 1 database (as noted in Section 1) includes information on 62 contaminants,
including: 34 unregulated VOCs; 2 regulated SOCs and 21 regulated VOCs; and 5 miscellaneous
contaminants reported by the States. The data were reported from 38 States, Washington, D.C.,
and the Virgin Islands. The data are from the first round of required UCM initiated in 1987 (i.e.,
UCM (1987)), but also include older data that are comparable to, but predate, the formal
beginning of first round monitoring.
2.2 Data Management and Data Quality
During 1997-1998, the Round 1 database was reviewed for various data quality problems
and subsequently edited to remove problematic data to ensure the quality of the data used in the
analysis. In the process of initial database download and translation, unreadable lines of text and
characters were apparently introduced into the data set and were subsequently deleted. (These
lines did not appear to be actual data, but were artifacts related to the download, translation, and
merger of various data sets.) Additionally, data from 946 systems of unknown source water type
were eliminated. (Other systems had no source type specified, but this missing inventory
information was supplemented with SDWIS inventory data.) Five observations with
contaminant concentrations greater than 9,000 |ig/L were excluded from the analysis (as
presumed errors; this outlier editing was consistent with other processing that EPA has
completed, see USEPA, 1999). Another 1,503 observations with erroneous sampling dates (e.g.,
years indicated as 00, 01, 39, etc.) were eliminated. In addition to these, a variety of other post-
download editing procedures were conducted to fill in data gaps, eliminate inconsistencies, and
reduce potential sources of error. A more detailed description of these procedures is discussed in
Section II.B of the Priority Contaminants Report (USEPA, 2002). After these data management
and editing efforts, the Round 1 database contained 3,452,530 analytical records for 62
contaminants.
Even with these management endeavors, there are still potential data quality problems
given the diverse sources of the data and the sheer size of the database (i.e., 3.5 million records).
Sources of problems may include some data recorded in incorrect units, (e.g., the results are
actually in mg/L, but are recorded as |ig/L) or data units mistakenly converted in the original
compilation of the data (e.g., the data units were actually in |ig/L, were incorrectly assumed to be
in mg/L, and were then mistakenly 'converted' to |ig/L as if they were mg/L). Reviews of the
original database found that this did not affect many data. There are a few apparently high
analytical results (outliers) that may be caused by this units problem. While outliers affect a
review of the maximum concentration values of a contaminant, there are few such data and they
will have limited impact on other occurrence statistics reviewed in this report. (For most
analytical summaries included in this report, the value of the 99th percentile is presented to avoid
this problem.)
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2.3 Round 1 Data Bias and Representativeness: Further Data Quality Review
and Editing
Subsequent to the major editing efforts on this database, a basic analysis of the 3.5
million records was undertaken. As a first step, various descriptive statistics were compiled by
State to enable a further data review for bias and representativeness. Some State data, as will be
described, are so incomplete that their use would introduce bias into the analyses. These data are
used in certain parts of this report to provide context or reference, but not to make determinations
based on their occurrence analyses.
Exhibits 2.3.a. and 2.3.b summarize some key results from this next stage of data review.
Together, they summarize the data availability for 57 primacy entities considered under SDWA:
the 50 States, 5 territories, the District of Columbia, and an aggregate entry for the Native
American Tribes. Within the Round 1 database there are data for 38 States, the Virgin Islands,
and Washington, D.C., and no data for 17 primacy entities. Some States only reported data for
detections. For eight States (identified in Exhibit 2.3.b as "Entities with Data sets with 100%
Detects"), the percent of samples with analytical detections (i.e., analytical results equal to or
greater than the MRL) ranged from 80-100%. These States only reported data for detections
and, hence, are highly biased (they did not report the majority of the monitoring sample results
for which there were no detections above the MRL). As presented in Exhibit 2.3.a, the percent
of samples with detections (aggregating all the data), typically ranged from 1-5% for States with
complete data reporting.
The number of unique PWSs included in each State's data record is shown in Exhibit
2.3.a. The number of PWSs included were compared to the total number of non-purchased
CWSs and NTNCWSs in the current State inventory, and to the number of non-purchased CWSs
and NTNCWSs serving more than 500 people (since not all small systems may have had to
conduct this monitoring). The States identified as "Most Complete Data Sets" in Exhibit 2.3.b
all approximated or exceeded 100% of one of these numbers (i.e., New Mexico's Round 1 PWS
numbers were only 70% of their current total inventory, but equaled 300% of the number of
systems serving more than 500 persons). The States identified as "Significantly Too Few
Systems" had far less representativeness. For example, Colorado only has Round 1 data for 60
PWSs. This represents only 24% of the reported number of systems in their inventory lists.
Also, Colorado data show 34% of all sample data are detections. Further review suggests that
their data mainly include records for systems that had detections, but that analytical records were
provided for all samples for these systems. This partial, selective reporting lowers the percent of
sample records that represent detections (to less than 100% detection), but still reflects biased
reporting and creates a biased analytical record, since not all non-detection records have been
reported (such as records from the likely large number of systems with non-detections). In other
cases, it is not clear what the data represent. Nevada's reported percent samples with detections
suggests the data may be complete, but there is only data for 10 systems - about 3% of systems
as based on State inventory records. Another five States are identified as having too few
systems.
Exhibit 2.3.a also presents the number of samples per PWS in each State's data. This
summary statistic provides a perspective on the relative completeness of reporting. For example,
the States reporting only samples with detections typically reported 2 to 10 samples per PWS.
For most States, approximately 100 to 300 samples were collected and reported per PWS.
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The last category in Exhibit 2.3.b identifies States with data records that are not complete
(i.e., less than 100% of systems reported as based on inventory listings), but that have other
parameters (e.g., "Percent Sample Detections," "Samples per PWS," etc.) that suggest that the
data are balanced and perhaps complete for the systems that did report. The relatively low
system numbers may simply relate to how the State implemented the program (e.g.,
implementation related to system size or other waivers, etc.). For example, Florida reported data
for 855 PWSs, a substantive number, but it's only a small share of their relatively large
inventory. Nevertheless, the whole data picture for Florida (e.g., the total detection rate) appears
balanced.
In summary, of the 40 States/territories with Round 1 data, 21 States had records that
appear relatively complete and balanced, and another 6 had records that likely are balanced and
with a substantial (though not complete) number of systems. The data from these 27 States
should provide the most complete and unbiased summary of the occurrence data; the remaining
13 States are clearly biased since results were reported only (or primarily) for detections. To
present a national summary of the data, the 27 primacy entities with most complete records were
evaluated for their national representativeness (to be discussed in Section 4) and considered for
inclusion in the subsequent analyses.
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Exhibit 2.3.a. Summary of Round 1 Data Quantity and Quality for the States,
Tribes and Territories
States/ Tribes/
Territories
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
Alabama
Alaska
American Samoa
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Guam
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Mariana Is.
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Total
Unique
PWSs
152
748
-
973
6
4,167
60
-
13
855
1,165
-
127
-
1,307
415
1,002
-
525
13
-
-
998
220
139
1,565
206
85
565
Percent
Sample
Detections
5%
2%
1%
100%
7%
34%
6%
20%
2%
1%
5%
4%
5%
3%
3%
2%
91%
100%
1%
100%
1%
2%
Samples
per PWS
136
132
151
5
111
38
1,207
14
120
370
147
292
62
273
95
105
14
16
100
6
215
94
States/ Tribes/
Territories
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Puerto Rico
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Tribes
Utah
Vermont
Virgin Islands
Virginia
Washington
Washington, D.C.
West Virginia
Wisconsin
Wyoming
TOTAL
Total
Unique
PWSs
214
10
201
1,551
617
357
298
-
2,657
-
-
-
-
-
-
335
306
124
-
430
133
3
-
992
1
139
-
145
23,819
Percent
Sample
Detections
100%
2%
100%
2%
0%
1%
2%
1%
4%
4%
98%
1%
82%
9%
1%
5%
6%
3%
2.9%
Samples
per PWS
6
860
5
94
151
348
134
313
52
197
2
150
10
186
229
3,432
157
125
146
13
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EPA - OGWDW
Analysis of Occurrence Data from the UCM and MRS for CCL 2
June 2008
Exhibit 2.3.b. Summary of Round 1 Data Quantity and Quality for the States,
Tribes and Territories
Guam|
Virgin Is.
Tribes
Mariana Is. \_
Puerto Rico |
Am. Samoa [__
Entities with No Round I '.
Entities with Data Sets with 100% Detects
Entities with Significantly Too l-'ew Systems
Entities Usable for Cross-section
J O -Most Complete Data Sets
I (A Incomplete hut Adequate Data Sets
From the 27 States with reasonably complete data, three primacy entities were removed.
Washington, D.C. and the Virgin Islands were removed because they are not States, and the New
York State data were excluded because there were various and numerous problems associated
with the data and metadata. For example, New York did not use standard PWS identifiers
(PWSIDs) that could be associated with SDWIS records, and the total number of reporting PWSs
in the New York data set represented only 12 to 40% of the expected number of PWSs as based
on the State's inventory numbers. Also, there were some embedded errors in the data that
sometimes caused data processing problems. Therefore, as summarized in Section 6, data are
aggregated for a representative cross-section of 24 States (the 27 entities less Washington, D.C.,
the Virgin Islands, and New York), as well as for all 40 entities (which includes all entities; those
with complete and balanced records, as well as the entities with biased records).
2.4 Data Characteristics Overview
After data management and editing, 3.45 million records were available for analysis
representing more than 24,000 PWSs from the 40 States/entities. For the 24 States comprising
the Round 1 representative cross-section (see Section 6 for a discussion regarding cross-section),
the analytical results total 3.27 million records, from 22,034 PWSs.
14
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EPA - OGWDW
Analysis of Occurrence Data from the UCM and MRS for CCL 2
June 2008
For both all states and the 24-state cross-section, Exhibit 2.4.a reports the number and
percentage of sample records and systems related to source water type: 87% of the systems are
classified as ground water and 13% as using surface water. The Round 1 data were collected
before "ground water under the direct influence of surface water" (GWUDI) was introduced as a
source definition. The classification used follows the regulatory guidelines: if a system uses any
surface water, the system is classified, and is required to monitor, as a surface water system.
Exhibit 2.4.a. Round 1 Data - Number of Records and Systems by Source Water
Type
SOURCE TYPE
All States - Ground Water
All States - Surface Water
All States - Total
24 States - Ground Water
24 States - Surface Water
24 States - Total
RECORDS
NUMBER
2,950,618
501,912
3,452,530
2,814,472
453,173
3,267,645
PERCENT
85.5%
14.5%
100.0%
86.1%
13.9%
100.0%
SYSTEMS
NUMBER
21,046
3,130
23,81 9 1
19,637
2,695
22,034 1
PERCENT
87.1%
12.9%
100.0%
87.9%
12.1%
100.0%
1. Because some water systems have more than one source water type, the total number of systems does not equal the
sum of the ground water systems plus surface water systems.
For both all states and the 24-state cross-section, Exhibit 2.4.b shows the number and
percent of records and systems by system type. About 7% of systems were coded as "NCWS," a
SDWIS code typically used for non-community water systems, or transient systems. Transient
PWSs were not required by Federal rule to monitor, but may have been required to by some
States. Also, about 7% of the systems did not indicate a system type (and the type could not be
determined by SDWIS inventory records). These data remained in the database for the first
stages of analysis, because other data elements were complete.
15
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EPA - OGWDW
Analysis of Occurrence Data from the UCM and MRS for CCL 2
June 2008
Exhibit 2.4.b. Round 1 Data - Number of Records and Systems by System Type
SYSTEM TYPE
All States - CWS 1
All States - NCWS 2
All States - NTNCWS 3
All States - UNKNOWN
All States - Total
24 States - CWS 1
24 States - NCWS 2
24 States - NTNCWS 3
24 States - UNKNOWN
24 States - Total
RECORDS
NUMBER
2,608,840
89,707
516,047
237,936
3,452,530
2,546,144
89,533
515,807
116,161
3,267,645
PERCENT
75.6%
2.6%
14.9%
6.9%
100.0%
77.9%
2.7%
15.8%
3.6%
100.0%
SYSTEMS
NUMBER
15,562
1,771
4,872
1,614
23,819
14,260
1,746
4,774
1,254
22,034
PERCENT
65.3%
7.4%
20.5%
6.8%
100.0%
64.7%
7.9%
21 .7%
5.7%
100.0%
1. CWS = Community Water System
2. NCWS = Non-Community (Transient) Water System
3. NTNCWS = Non-Transient Non-Community Water System
Exhibits 2.4.c and 2.4.d show the distribution of data by year and by month for States in
the 24-State cross-section for the years 1983-1992. This period includes the compliance cycle
(1988-1992) when the majority of data were collected, with a peak of data collection in 1991.
Records prior to 1988 predate the formal beginning of first round monitoring, but represent
comparable data, and are therefore included to expand the coverage of these analyses. Exhibit
2.4.c shows the distribution of records for the years 1983-19927, while Exhibit 2.4.d shows the
monthly distribution of all the records used in the Round 1 analyses for the same time period.
Records were well distributed throughout the year, with an average of 272,304 records
per month for the 24-State cross-section. Although in the month of March there is a slightly
greater monthly percentage of data, there is no significant difference, suggesting that there
should be no seasonal bias due to monthly differences in reporting. For Round 1 data from the
24-State cross-section, the total number of records during the compliance period of 1988 to 1992
ranged between a minimum of 321,618 records in 1988 and a maximum of 1,280,797 records in
1991, with an average of 573,945 records per year. By month for the 24-State cross-section, the
total number of records ranged between 221,314 (July) and 371,492 (March), with an average of
272,304 records per month. For a more detailed coverage of these numbers and other Round 1
data statistics, refer to Section II.D of the Priority Contaminants Report (USEPA, 2002).
7 Some data contained in the Round 1 data set are older, "grandfathered" data that predate the formal beginning of
the 1988-1992 Round 1 monitoring period.
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EPA - OGWDW
Analysis of Occurrence Data from the UCM and MRS for CCL 2
June 2008
Exhibit 2.4.c. Round 1 Data - Number of Records by Year and Source Water Type
YEAR
24 States -1983
24 States -1984
24 States - 1 985
24 States -1986
24 States -1987
24 States -1988
24 States -1989
24 States -1990
24 States -1991
24 States - 1 992
24 States - Total
# SURFACE
WATER
RECORDS
0
30
175
1,852
12,867
107,428
111,979
87,273
106,338
25,222
453,164
# GROUND
WATER
RECORDS
5
43,837
78,696
140,155
120,292
214,190
337,068
509,889
1,174,459
195,881
2,814,472
TOTAL #
RECORDS
5
43,867
78,871
142,007
133,168
321,618
449,047
597,162
1,280,797
221,103
3,267,645
% OF TOTAL
RECORDS
0.0%
1 .3%
2.4%
4.3%
4.1%
9.8%
13.7%
18.3%
39.2%
6.8%
100.0%
Exhibit 2.4.d. Round 1 Data - Number of Records by Month and Source Water
Type
MONTH
24 States - January
24 States - February
24 States - March
24 States - April
24 States - May
24 States - June
24 States - July
24 States - August
24 States - September
24 States - October
24 States - November
24 States - December
24 States - Total
# SURFACE
WATER
RECORDS
33,315
42,774
42,903
33,625
45,221
38,140
31,060
40,967
33,214
35,756
39,480
36,718
453,173
# GROUND
WATER
RECORDS
266,685
259,528
328,589
262,270
254,900
190,791
190,254
185,958
209,679
222,984
215,372
227,462
2,814,472
TOTAL # OF
RECORDS
300,000
302,302
371,492
295,895
300,121
228,931
221,314
226,925
242,893
258,740
254,852
264,180
3,267,645
% OF TOTAL
RECORDS
9.2%
9.3%
1 1 .4%
9.1%
9.2%
7.0%
6.8%
6.9%
7.4%
7.9%
7.8%
8.1%
100.0%
The analytical findings of the 24-State Round 1 cross-section occurrence data for 1,3-
dichloropropene and 1,1,2,2-tetrachloroethane are developed and summarized in Section 6 of this
report.
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EPA - OGWDW Analysis of Occurrence Data from the UCM and MRS for CCL 2 June 2008
18
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EPA - OGWDW Analysis of Occurrence Data from the UCM and MRS for CCL 2 June 2008
3. UCM Round 2 Data Overview
In this section of the report, the monitoring results for the UCM (1993) list of unregulated
contaminants, from Round 2 (approximately 1992-1997), are analyzed and reviewed. These
Round 2 data (as discussed in Section 1) were derived from the SDWIS/FED (or "Round 2")
database. Significant data review, formatting, and data quality checking and editing were
required of these Round 2 data to enable the evaluations and analyses conducted.
3.1 Description of Data
The analyses in this section of the report are based on Round 2 data derived from the
monitoring data collected between 1992 and 1997 and subsequently submitted to EPA.
(Although the Round 2 monitoring period was formally initiated in 1993, data in the Round 2
data set include some older, "grandfathered" data from 1992.) The Round 2 database includes
information on 48 contaminants, including: 1 IOC, 13 SOCs, 20 mandatory VOCs and 14
discretionary VOCs. These data are from 35 States/primacy entities.
Like the Round 1 data, much of the Round 2 data analyses and all of the data
management and editing was conducted and described previously in several EPA reports. The
two most relevant of these reports are the Analysis of National Occurrence of the 1998
Contaminant Candidate List (CCL) Regulatory Determination Priority Contaminants in Public
Water Systems (the "Priority Contaminants Report;" USEPA, 2002), which contains more
detailed information on data management and analysis of the Round 2 database, and the Analysis
of National Occurrence of 14 Contaminants from the 1998 Contaminant Candidate List (CCL)
(the "Occurrence of 14 Report;" USEPA, 2003), which contains Round 2 analyses for 3 of the
contaminants discussed in this report (1,3-dichloropropene, 1,1,2,2-tetrachlorethane, and
metolachlor). For the most comprehensive description of the creation, management, and
maintenance of the Round 2 database, refer to Section III of the Priority Contaminants Report
(USEPA, 2002). Some of the actual analytical findings developed and presented in USEPA
(2003) are used in this current report. Other analyses, including those based on updated HRLs,
have been conducted for, and are presented in, this current report.
3.2 Data Management and Data Quality
The raw Round 2 data from the 35 States/primacy entities contained a total of 4,350,874
records. An important and substantial component of the Priority Contaminants Report (USEPA,
2002) consisted of the detailed and extensive review of these data records for numerous data
quality considerations including reporting consistencies, uniform and valid coding, data
completeness, correct and consistent use of analytical units, and any inherent bias in the raw
records. To ensure data quality for sound and dependable occurrence analysis, extensive data
review, checking, and editing were required. This data management and quality review process
identified and addressed problematic data or data that could not be uniquely categorized. For
more information on the types of problematic data encountered and how they were managed,
refer to Section III.B of the Priority Contaminants Report (USEPA, 2002). With these data
quality improvements, the initial 4,350,874 analytical records from the 35 States/primacy entities
for the 48 contaminants decreased to 4,211,446 analytical records for this Round 2 analysis.
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EPA - OGWDW Analysis of Occurrence Data from the UCM and MRS for CCL 2 June 2008
3.3 Round 2 Data Bias and Representativeness: Further Data Quality Review
and Editing
Subsequent to this initial editing and filtering of the data, a basic analysis of the 4.21
million records was undertaken. Similar to the Round 1 data, various descriptive statistics were
compiled by State to enable a further more detailed data review to assess data bias and
representativeness. Some State data, as described below, are seriously biased because they are
so incomplete, and should only be used with caution for any statistical summary of occurrence.
Exhibits 3.3.a and 3.3.b summarize some key results from this next stage of Round 2 data
review. Together, they summarize the data availability and data quality for 57 primacy entities
considered under SDWA (the 50 States, 5 territories and the District of Columbia, and an
aggregate entry for the Native American Tribes). Of the 57 primacy entities in Round 2, 35 have
reported Round 2 data and 22 have not. Exhibit 3.3.a also provides an overview of data quality,
while Exhibit 3.3.b presents the 20 States (the States identified with data sets of adequate quality
and completeness) that comprise the 20-State cross-section for Round 2 data.
Of the 35 States with Round 2 data, 15 States have incomplete data and/or data of
inadequate quality. For two States (Alabama and Mississippi), the percent of samples with
detections (with analytical results equal to or greater than the MRL; "Percent Sample
Detections") ranged from 70-100%. These States are identified in Exhibit 3.3.b as "Entities with
Data Sets with 100% Detects." These States reported only (or mainly) analytical records for
detections and, hence, their data sets are highly biased (over-representing occurrence) and are
therefore excluded from additional analysis. As shown in Exhibit 3.3.a, the percent samples with
detections typically range from 1% to 8% for States with almost complete data reporting. An
additional secondary check on these two States reporting only analytical detections is the
measure of the number of samples per PWS. The numbers of samples per PWS for Alabama (2
samples/PWS) and Mississippi (4 samples/PWS) are significantly below the common range of
50 to 250 samples per PWS in most States.
The number of unique PWSs included in each State's data sets, and the number of
samples per PWS, are also included in Exhibit 3.3.a. These summary statistics provide a
perspective on the relative completeness of reporting. The number of PWSs included were
compared to the total number of non-purchased CWSs and NTNCWSs in the current State
inventory, and to the number of non-purchased CWSs and NTNCWSs serving more than 500
people (since not all small systems may have had to conduct this monitoring). Most States
approximated or exceeded 100% of one of these comparative inventory numbers. The States
(entities) identified with "Significantly Too Few Systems" in Exhibit 3.3.b have data reported
from far fewer systems than listed in the current State inventory. For example, New Jersey (17
PWSs) and California (67 PWSs) have far too few systems with Round 2 data based on this
comparison. Therefore, to reduce potential analytical results bias, New Jersey, California, and
seven other States were excluded from the analyses since a significant portion of PWSs in these
States do not have contaminant occurrence data for Round 2.
Exhibit 3.3.b also indicates States with data quality problems. The data from Louisiana,
Pennsylvania, South Carolina, and Vermont were very problematic. For instance, 100% of the
data reported by Louisiana (for a very large number of systems and samples) were non-
detections. There were no positive analytical findings of contaminant occurrence in the 164,492
20
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EPA - OGWDW Analysis of Occurrence Data from the UCM and MRS for CCL 2 June 2008
sample results reported. Data from the other three States were very inconsistent (e.g., data for
VOCs within a single State appeared to be reported in mixed units). The data from these four
States were excluded from the analysis and are identified as "Data Quality Problems". The last
category in Exhibit 3.3.b, "Entities Usable for Cross-section," identifies States with data records
that are reasonably balanced and perhaps complete for the systems that did report. These 20
Round 2 primacy entities with adequate and unbiased data were further considered for
occurrence analyses.
The next level of data evaluation assessed the analytical results for each State in even
more detail. For example, the minimum, median, 99th percentile, and maximum analytical
values were determined for every contaminant in each State. With this more in-depth level of
analysis, some additional data quality problems were identified within the data sets of the 20
Round 2 cross-section States. Most of these problems were determined to be specific to certain
contaminants (or contaminant groups). With additional data editing efforts, these problems have
either been resolved or the problematic portion of data omitted from further analysis. For
additional discussion of specific problems, refer to Section III.C of the Priority Contaminants
Report (USEPA, 2002).
21
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EPA - OGWDW
Analysis of Occurrence Data from the UCM and MRS for CCL 2
June 2008
Exhibit 3.3.a. Summary of Round 2 Data Quantity and Quality for the States,
Tribes and Territories
State/ Tribes/
Territories
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
Alabama
Alaska
American Samoa
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Guam
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Mariana Is.
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Total
Unique
PWSs
314
625
_
123
577
67
833
87
_
_
_
_
_
_
_
120
_
_
445
1,394
745
_
1,015
506
3,209
1,581
1,155
1,434
-
Percent
Sample
Detections
94.08%
3.10%
2.75%
7.29%
6.75%
3.72%
4.53%
2.26%
7.50%
0.00%
0.89%
0.62%
3.12%
7.26%
1 .66%
71 .27%
6.08%
Samples
per PWS
2
194
55
118
44
143
921
58
125
118
163
140
125
97
198
4
109
State/ Tribes/
Territories
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Puerto Rico
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Tribes
Utah
Vermont
Virgin Islands
Virginia
Washington
Washington, D.C.
West Virginia
Wisconsin
Wyoming
TOTAL
Total
Unique
PWSs
_
_
849
17
755
_
2,263
296
2,259
888
1,168
1,424
_
117
1,047
27
78
4,863
26
_
636
_
_
2,680
_
_
225
-
33,848
Percent
Sample
Detections
5.45%
2.32%
0.75%
2.05%
7.73%
3.45%
3.99%
1 .66%
10.32%
0.30%
0.33%
2.34%
9.31%
1 .23%
1 .22%
2.65%
2.23%
1.41%
2.95%
Samples
per PWS
23
28
277
55
59
291
180
75
16
136
147
40
147
124
57
74
123
51
124
22
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EPA - OGWDW
Analysis of Occurrence Data from the UCM and MRS for CCL 2
June 2008
Exhibit 3.3.b. Summary of Round 2 Data Quantity and Quality for the States,
Tribes and Territories
Virgin Is. \
Tribes
Mariana Is.
Puerto Rico £_
Am. Samoa [ ]
__l Entities with No Round 2 Data
Entities with Data Sets with 100% Detects
ifj Entities with Significantly Too Few Systems
I bntilics with Data Quality Problems
I Entities Usable for Cross-section
3.4 Data Characteristics Overview
A descriptive overview of the Round 2 data is presented in Exhibits 3.4.a through 3 Ad to
provide additional insight and perspective on the results. As noted, after the initial data
management and editing, 4.21 million records were available for analysis from more than 33,000
PWSs in the 35 States/entities. The Round 2 cross-section States total 3.69 million records from
slightly more than 27,000 PWSs. These 20 States, therefore, contain nearly 88% of all available
Round 2 State contaminant occurrence data.
Exhibit 3.4.a shows the number and percentage of sample records and systems according
to source water type: approximately 89% of the systems in the 20-State cross-section are
classified as ground water and 11% as surface water. These source water percentages are
essentially the same for the entire data set using all 35 States/entities. The Round 2 data contains
systems using GWUDI as a source definition. The classification used follows the regulatory
guidelines: if a system uses any surface water (such as a GWUDI), it is classified as a surface
water system.
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EPA - OGWDW
Analysis of Occurrence Data from the UCM and MRS for CCL 2
June 2008
Exhibit 3.4.a. Round 2 Data - Number of Records and Systems by Source Water
Type
SOURCE TYPE
All States - Ground Water
All States - Surface Water
All States - Total
20 States - Ground Water
20 States - Surface Water
20 States - Total
RECORDS
NUMBER
3,479,102
732,344
4,211,446
3,085,266
609,619
3,694,885
PERCENT
82.6%
17.4%
100.0%
83.5%
16.5%
100.0%
SYSTEMS
NUMBER
30,085
3,763
33,848
24,199
2,909
27,108
PERCENT
88.9%
11.1%
100.0%
89.3%
10.7%
100.0%
Exhibit 3.4.b shows the number and percentage of records and systems by system type.
Approximately 70% of systems in the 20-State cross-section were CWSs and 30% were
NTNCWSs. The CWS percentage was slightly higher for the entire 35 States/entities data set,
and the percentage for NTNCWS correspondingly lower. Systems coded as NCWSs (or
transients) were excluded from these analyses.
Exhibit 3.4.b. Round 2 Data - Number of Records and Systems by System Type
SYSTEM TYPE
All States - CWS 1
All States -NTNCWS2
All States - Total
20 States - CWS 1
20 States -NTNCWS2
20 States - Total
RECORDS
NUMBER
3,255,222
956,224
4,211,446
2,808,341
886,544
3,694,885
PERCENT
77.3%
22.7%
100.0%
76.0%
24.0%
100.0%
SYSTEMS
NUMBER
24,357
9,491
33,848
19,055
8,053
27,108
PERCENT
72.0%
28.0%
100.0%
70.3%
29.7%
100.0%
1. CWS = Community Water System
2. NTNCWS = Non-Transient Non-Community Water System
Exhibits 3.4.c and 3.4.d show the distribution of data by years and by month (based on
actual sample collection or analysis date). These tables only present the 20-State cross-section
data. Exhibit 3 Ac indicates the amount of data annually collected during the 1993-1997
compliance cycle (including some 1992 "grandfathered" data). For Round 2 data from the 20-
State cross-section, the total number of records ranged between 220,745 in 1992 and 823,587 in
1995, with an average of 615,814 records per year. In Exhibit 3.4.d, a fairly uniform distribution
of occurrence data by month is shown, suggesting that there should be no inherent seasonal bias
in the data. For the 20-State cross-section, the total number of records ranged between 259,787
(November) and 371,122 (March), with an average of 307,907 records per month. Trends were
similar for the entire 35 States/entities data set as for the 20-State cross-section. For a more
24
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detailed summary of these numbers, refer to Section HID of the Priority Contaminants Report
(USEPA, 2002).
Exhibit 3.4.c. Round 2 Data - Number of Records by Year and Source Water Type
YEAR
20 States- 1992
20 States- 1993
20 States- 1994
20 States - 1 995
20 States - 1 996
20 States- 1997
20 States - Total
# SURFACE
WATER
RECORDS
33,187
115,859
105,673
112,144
136,182
106,574
609,619
# GROUND
WATER
RECORDS
187,558
592,555
504,410
711,443
589,788
499,512
3,085,266
TOTAL # OF
RECORDS
220,745
708,414
610,083
823,587
725,970
606,086
3,694,885
% OF TOTAL
RECORDS
6.0%
19.2%
16.5%
22.3%
19.6%
16.4%
100.0%
Exhibit 3.4.d. Round 2 Data - Number of Records by Month and Source Water
Type
MONTH
20 States - January
20 States - February
20 States - March
20 States - April
20 States - May
20 States - June
20 States - July
20 States - August
20 States - September
20 States - October
20 States - November
20 States - December
20 States - Total
# SURFACE
WATER
RECORDS
40,939
49,405
65,525
41,692
44,374
55,612
44,174
52,087
65,814
46,113
46,492
57,392
609,619
# GROUND
WATER
RECORDS
221,420
211,499
305,597
257,085
245,051
285,159
262,611
266,475
293,692
254,688
213,295
268,694
3,085,266
TOTAL # OF
RECORDS
262,359
260,904
371,122
298,777
289,425
340,771
306,785
318,562
359,506
300,801
259,787
326,086
3,694,885
% OF TOTAL
RECORDS
7.1%
7.1%
10.0%
8.1%
7.8%
9.2%
8.3%
8.6%
9.7%
8.1%
7.0%
8.8%
100.0%
The analytical findings of the 20-State Round 2 cross-section occurrence data for 1,3-
dichloropropene, 1,1,2,2-tetrachlorethane, metolachlor are developed and summarized in Section
6 of this report.
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4. National Inorganics And Radionuclides Survey (NIRS) Data
The EPA's NIRS occurrence data are assessed for one contaminant considered during
CCL 2 regulatory determinations, boron, and are only applicable for PWSs served by ground
water.
4.1 Description of Data
The NIRS survey was conducted by EPA specifically to provide data on the occurrence
of a select set of radionuclides and lOCs being considered for NPDWRs. The NIRS provides
contaminant occurrence data from 989 CWSs served by ground water sources. Each of these
randomly selected PWSs was sampled a single time between 1984 and 1986. The selection of
this group of PWSs was designed so that the contaminant occurrence results from these PWSs
are representative of national occurrence of contaminants in ground water systems. Further
description of the NIRS survey can be found in Longtin (1988).
The NIRS sample design included random selection of a number of systems from each
size category in proportion to the number of PWSs in those size categories nationally. NIRS was
structured as a stratified, random sampling of the nation's community ground water supplies as
they existed in the mid-1980s. The stratification for sample selection was based on system size.
However, the sampling frame used in NIRS was not specifically designed to be representative of
ground water supplies on a State-by-State, regional, or other geographic basis. The resulting
sample of systems represents approximately 2% of the nation's community ground water supply
in each system size category. Therefore, since there are many more small than large PWSs in the
US, most of the NIRS data are from smaller systems. In aggregate, approximately 95% of the
analytical sample results in the entire NIRS database indicate no detections of the contaminants
sampled and analyzed. The NIRS database includes information on 42 contaminants, including:
36 lOCs (including 10 regulated lOCs), 2 regulated radionuclides, and 4 unregulated
radionuclides. The data are from 49 States (there are no data from Hawaii), as well as Puerto
Rico. One contaminant from the NIRS is evaluated in this report: boron. Concentration values
for boron are presented in milligrams per liter (mg/L), not micrograms per liter (|ig/L).
4.2 Representativeness
By design, the data collected and contained in the NIRS database are nationally
representative of ground water systems, and furthermore, can be divided into strata based on
system size for additional statistical resolution. Especially when compared to the Round 1 and 2
databases, there are few contaminant occurrence data quality or completeness issues with the
NIRS data set. The NIRS contains analytical results that were specifically collected to establish
a nationally representative sample, so the sample is "complete and adequate" simply by correct
implementation of the sample selection design. Also, there are often computational (statistical)
problems resulting from multiple laboratory analytical detection limits that must be addressed in
the analysis of occurrence data. In the case of NIRS (for the IOC being evaluated in this report)
analytical methods with uniform detection limits were employed. Therefore, the extensive
concerns and problems with data quality, completeness, and representativeness encountered in
the use of Round 1 or 2 data are not issues when considering the use of the NIRS data.
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4.3 Data Characteristics Overview
A descriptive overview of the data is presented in two tables to provide additional insight
and perspective on the results. Summary results for all States are included in the following
results tables. For more descriptive information on the NIRS data characteristics, refer to
Section IV.C of the Priority Contaminants Report (USEPA, 2002).
Exhibits 4.3.a and 4.3.b show the distribution of data by years and by month across all
years. The data were collected between 1984 and 1986, with a peak of data collection in 1985.
Somewhat more samples were collected in 1985, and a somewhat larger proportion of samples
was collected in the fall months of September, October, and November (though seasonal effects
for the occurrence of lOCs in groundwater is likely not high). The analytical findings of the
occurrence data for boron are developed and summarized in Section 6.3 of this report.
Exhibit 4.3.a. NIRS Data - Number of Records by Year
YEAR
1984
1985
1986
Total
# OF RECORDS
268
466
255
989
% OF TOTAL
RECORDS
27.1%
47.1%
25.8%
100.0%
Exhibit 4.3.b. NIRS Data - Number of Records by Month
MONTH
January
February
March
April
May
June
July
August
September
October
November
December
Total
#OF
RECORDS
19
29
63
92
70
68
92
94
118
153
132
59
989
% OF TOTAL
RECORDS
1 .9%
2.9%
6.4%
9.3%
7.1%
6.9%
9.3%
9.5%
1 1 .9%
15.5%
13.3%
6.0%
100.0%
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4.4 Supplemental IOC Data
Efforts were made to identify data sources from surface water systems to supplement the
ground water data in the NIRS data. Boron was not monitored in either the UCM or UCMR. To
gain a better understanding of the potential occurrence of boron in surface water systems, EPA
evaluated a report funded by the American Water Works Association Research Foundation
(AWWARF; Frey et a/., 2004). The AWWARF study recruited 189 PWSs representing 407
source waters that covered 41 states. Of these 407 PWS source water samples, 342 were
returned and 341 were analyzed for boron. Of these 341 samples, approximately 67% (or 228)
represented ground water sources and 33% (or 113) represented surface water sources. None of
the 113 surface water sources exceeded the boron FtRL of 1.4 mg/L and the maximum
concentration observed in surface water was 0.345 mg/L. Extrapolation of the data indicates that
95% of the ground water detections had boron levels less than 1.054 mg/L; the maximum
observed concentration in ground water was approximately 3.3 mg/L. Seven of the 228 ground
water sources (from 5 systems) had boron concentrations greater than 1.4 mg/L (Seidel, 2006).
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5. Developing a Nationally Representative Perspective
As discussed in previous sections of this report, the Round 1 and Round 2 databases
contain contaminant occurrence data from a total of 40 and 35 States/entities, respectively.
However, data from many of these States are incomplete, problematic, and/or biased. An
evaluation of these data suggested that data from certain States were most complete and might,
therefore, be used to generate summary statistics indicative of national contaminant occurrence.
The representativeness of the State data was evaluated across a range of potential contaminant
occurrence and across the spatial/hydrologic diversity of the nation. Based on these assessments,
a cross-section of States was developed for each database to provide a reasonable indication of
national occurrence.
The approach used for the construction of the cross-sections in this analysis was
originally developed for the CMR report (USEPA, 1999). The approach to establish national
cross-sections from State SDWA contaminant databases was supported by peer reviewers and by
stakeholders as providing a clear, replicable, and understandable approach. Although this
approach cannot provide a statistically representative sample (since the data could not be
selected in a statistically random manner), the resultant data provide a clear indication of the
central tendency of national occurrence. The methods by which the national cross-section was
developed and tested for representativeness will be summarized in this report in a condensed
form. For a detailed description of the methods used to develop the nationally-representative
cross-sections, see Section V of the Priority Contaminants Report (USEPA, 2002).
States selected for the national cross-section were evaluated along two main criteria.
First, the States had to provide the best data quality and completeness. Evaluation of this
criterion has been discussed previously in this report. Second, the States had to provide a
balanced national cross-section of occurrence data, requiring them to be representative of other
characteristics as well. Determination of cross-sectional balance was based on evaluating the
States' pollution potential and geographic coverage in relation to all States. Pollution potential
was included to ensure the selection of states that represent the range of likely contaminant
occurrence and a balance with regard to likely high and low occurrence. Geographic
consideration was included so that the wide range of climatic and hydrogeologic conditions
across the United States would be represented, again balancing the varied conditions that affect
transport and fate of contaminants. Two primary indicators were chosen to represent pollution
potential in each State: the number of manufacturing establishments per square mile, and the
total farm agricultural chemical expenses. Sources of information for the first indicator were the
1995 Annual Survey of Manufactures (USDOC, 1997) and the 1992 Census of Manufactures
(USDOC, 1996), while data for the second indicator was taken from the 1992 Census of
Agriculture (USDOC, 1994).
The states were divided into quartiles based on their pollution potential rankings for the
two indicators, and the cross-section states were chosen to ensure equitable representation from
each quartile. In addition, some secondary pollution potential indicators were considered to
further ensure that the cross-section states included the spectrum of pollution potential conditions
(high to low). At the same time, care was taken to ensure that the cross-section provided
representative coverage across all geographic regions of the United States.
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The product of the data quality screening, pollution potential rankings, and geographic
coverage analysis was a national cross-section of 24 Round 1 states and a national cross-section
of 20 Round 2 states (see Exhibit 5.a-b). The Round 1 24-State cross-section includes about
49% of the PWSs nationally and about 56% of the population served by PWSs. By comparison,
the Round 2 20-State cross-section includes more than 41% of the PWSs nationally and about
34% of the population served by PWSs. In each case, the cross-section states provide good
representation of the nation's varied climatic and hydrogeologic regimes and the breadth of
pollution potential for the contaminant groups.
To assess the representativeness of the Round 1 24-State cross-section, and the cross-
section methodology in general, cross-sections of 4, 8, and 13 States were developed and
contaminant statistics for each cross-section were compared to the 24-State cross section. These
statistics were also compared to contaminant statistics derived from cross-sections including
biased data. Following this comparison, the 24-State cross-section appeared to be a successful
balance between the problems associated with too little data (unrepresentative sampling) and
those associated with too much data (including "bad" or biased data). Consequently, although
they are not "statistically representative," both the 20- and 24-State cross-sections were used for
further analyses of occurrence data. For more information on the construction and validation of
both the Round 1 and Round 2 cross-sections, see Section V of the Priority Contaminants Report
(USEPA, 2002).
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Exhibit 5.a. 24 Round 1 Cross-Section States and States Not Included in the
Cross-Section
Slates Not in Round I Cross-Section (no data)
Slates wilh Biased Data
24 Cross-Section States (data used in report)
Exhibit 5.b. 20 Round 2 Cross-Section States and States Not Included in the
Cross-Section
States Not in Round 2 Cross-Section (no data)
States with Biased Data
20 Cross-Section States (data used in report)
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6. Analysis of National Occurrence
This section of the report contains detailed occurrence assessments of four contaminants
considered during CCL 2 regulatory determinations: data for 1,3-dichloropropene and 1,1,2,2-
tetrachloroethane are found in the Round 1 and Round 2 databases, data for metolachlor are
found in the Round 2 database, and data for boron are found in the NIRS database. In the
following section (Section 7), a series of graphs and maps are presented as a complimentary
graphical evaluation of the occurrence of these four contaminants.
The summary data developed for the occurrence assessments are presented in detail in
Appendices B through E. Appendix B contains analyses of the two Round 1 contaminants.
Appendix C contains analyses of the three Round 2 contaminants. Appendix D presents an
analysis of the NIRS data for boron. Detailed summaries of all four contaminants are presented
in Appendix E. At the beginning of the Appendices section, a complete "List of Appendix
Tables" identifies all tables included in the four appendices. Also included are "Notes to
Accompany Unregulated Contaminant Occurrence Data Tables" which presents definitions of
terms and phrases commonly used in the many tables, graphs, and maps included in this report
and its appendices.
6.1 Round 1 Contaminant Occurrence
Exhibits 6.1.a and 6.1.b summarize the Round 1 24-State cross-section occurrence data
for 1,3-dichloropropene and 1,1,2,2-tetrachloroethane. For both 1,3-dichloropropene and
1,1,2,2-tetrachloroethane, less than 1% of PWSs in the cross-section States have analytical
detections in the Round 1 database. Approximately 2% of the population served by PWSs had
analytical detections of 1,1,2,2-tetrachloroethane while less than 1% of the population served by
PWSs had detections of 1,3-dichloropropene. While detection frequencies of both contaminants
suggest very low levels of national occurrence, both contaminants also were found more
frequently in surface water PWSs than ground water PWSs. This pattern is found at both the
detection (> MRL) and threshold (> HRL) level.
Nevertheless, the low percentage of systems with at least one sample analytical result
exceeding the HRL (< 0.6% for both contaminants in surface water) suggests that both
contaminants are only very rarely found in concentrations surpassing the defined health-based
thresholds. Because much of the 1,1,2,2-tetrachloroethane and 1,3-dichloropropene occurrence
data were generated using laboratory methods with MRLs higher than the respective HRLs and
!/2 HRLs, it is likely that occurrence analyses did not identify some HRL and !/2 HRL
exceedances at the participating systems. Given this, the analyses may potentially underestimate
actual 1,1,2,2-tetrachloroethane and 1,3-dichloropropene occurrence relative to their respective
HRLs and l/2 HRLs. Although many of the MRLs used in the cross-section for 1,3-
dichloropropene and 1,1,2,2-tetrachloroethane were higher than the HRL, all MRLs did fall
within (or below) the risk range of 10"6 to 10"4 used by EPA to evaluate carcinogens. A complete
presentation of the occurrence data for the two contaminants considered during CCL 2 regulatory
determinations in Round 1 is provided in Appendix B.
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Exhibit 6.1.a. Round 1 Data - 24-State Cross-Section Summary of System-Level
Occurrence for Contaminants Considered During CCL 2 Regulatory
Determinations
CHEMICAL NAME
(HRL in ng/L)
# of PWSs
Total
GW
SW
% PWSs > MRL
Total
GW
SW
% PWSs > HRL
Total
GW
SW
99th
Percent! le
Value
(H9/L)
VOCs
1 ,3-Dichloropropene
(HRL=0.4)
1,1,2,2-
Tetrachloroethane
(HRL=0.4)
9,164
20,407
8,303
18,693
898
1,867
0.16%
0.45%
0.12%
0.39%
0.56%
1.02%
0.16%
0.20%
0.12%
0.17%
0.56%
0.48%
HRL"
indicates the proportion of systems with any analytical results exceeding the concentration value of the HRL. 99th Percentile Value
= the 99th percentile of all samples, not just detects.
Exhibit 6.1.b. Round 1 Data - 24-State Cross-Section Summary of Population
Served-Level Occurrence for Contaminants Considered During CCL 2 Regulatory
Determinations
CHEMICAL NAME
(HRL in ng/L)
Total Population Served by PWSs
Total
GW
SW
% Population Served by
PWSs > MRL
Total
GW
SW
% Population Served by
PWSs > HRL
Total
GW
SW
VOCs
1,3-
Dichloropropene
(HRL=0.4)
1,1,2,2-
Tetrachloroethane
(HRL=0.4)
50,917,006
94,710,065
24,660,968
55,763,644
29,271,833
43,763,942
0.86%
1.86%
0.59%
1.82%
0.99%
1.70%
0.86%
1 .63%
0.59%
1.53%
0.99%
1.58%
PWS = Public Water System; GW = Ground Water; SW = Surface Water; MRL = Minimum Reporting Limit (for laboratory analyses);
HRL = Health Reference Level (concentration values used only as reference levels for analyses in this report). "% Population
Served by PWSs > HRL" indicates the proportion of population served by systems with any analytical results exceeding the
concentration value of the HRL.
6.2 Round 2 Contaminant Occurrence
The Round 2 20-state cross-section data are discussed in Section 5 of this report, and are
identified in Exhibit 5.b. Exhibit 6.2.a summarizes the Round 2 20-state cross-section
occurrence data for metolachlor, 1,3-dichloropropene, and 1,1,2,2-tetrachloroethane. For all
three contaminants, less than 1% of PWSs in the cross-section States have analytical detections.
Analytical detections of 1,1,2,2-tetrachloroethane are found in less than 0.1% of PWSs,
suggesting very low levels of national occurrence for this contaminant. However, based on the
percentage of population served by systems, almost 12% of the population served by PWSs had
detections of metolachlor, less than 1% of the population served by PWSs had detections of 1,3-
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dichloropropene, and slightly more than 2.5% of the population served by PWSs had detections
of 1,1,2,2-tetrachloroethane. The percent of systems with at least one sample analytical result
greater than the HRL for 1,3-dichloropropene and 1,1,2,2-tetrachloroethane is less than 0.25%,
suggesting that these contaminants are only very rarely found in concentrations surpassing the
defined HRL. No PWSs had any analytical results of metolachlor greater than the HRL of 70
|ig/L. Appendix C contains complete occurrence summaries for these three contaminants
contained in Round 2 data.
Exhibit 6.2.a. Round 2 Data - 20-State Cross-Section Summary of System-Level
Occurrence for Contaminants Considered During CCL 2 Regulatory
Determinations
CHEMICAL
NAME
(HRL in ng/L)
# of PWSs
Total
GW
SW
% PWSs > MRL
Total
GW
SW
% PWSs > HRL
Total
GW
SW
99th
Percent! le
Value
(H9/L)
SOCs
Metolachlor1
(HRL=70)
12,953
11,503
1,450
0.83%
0.11%
6.55%
0.00%
0.00%
0.00%
HRL"
indicates the proportion of systems with any analytical results exceeding the concentration value of the HRL. 99th Percentile Value =
the 99th percentile of all samples, not just those with detections.
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Exhibit 6.2.b. Round 2 Data - 20-State Cross-Section Summary of Population
Served-Level Occurrence for Contaminants Considered During CCL 2 Regulatory
Determinations
CHEMICAL
NAME
(HRL in ng/L)
Total Population Served by PWSs
Total
GW
SW
% Population Served by
PWSs > MRL
Total
GW
SW
% Population Served by
PWSs > HRL
Total
GW
SW
SOCs
Metolachlor1
(HRL=70)
47,098,573
14,279,627
32,818,946
11.58%
0.70%
16.31%
0.00%
0.00%
0.00%
VOCs
1,3-
Dichloropropene
(HRL=0.4)
1,1,2,2-
Tetrachloroethane
(HRL=0.4)
45,951,052
71,294,263
17,423,030
25,978,359
28,528,022
45,315,904
0.55%
2.61%
1.13%
0.09%
0.19%
4.06%
0.33%
0.08%
0.57%
0.09%
0.18%
0.07%
1. Massachusetts data not included in summary statistics for this contaminant.
PWS = Public Water System; GW = Ground Water; SW = Surface Water; MRL = Minimum Reporting Limit (for laboratory analyses);
HRL = Health Reference Level (concentration values used only as reference levels for analyses in this report). "% Population
Served by PWSs > HRL" indicates the proportion of systems with any analytical results exceeding the concentration value of the
HRL.
6.3 NIRS Contaminant Occurrence
The NIRS data are discussed in Section 4 of this report. Exhibit 63.a summarizes the
occurrence data of the NIRS (for ground water systems only) for boron. Nearly 82% of PWSs,
serving 88% of the population served, had analytical detections of boron. This is consistent with
the known widespread natural occurrence of boron in soil and minerals. The percentage of
systems with at least one sample analytical result greater than the HRL (1.7%) is higher than the
other contaminants analyzed, again indicating boron's widespread nature. (Note that these
results are for ground water systems only, and that the NIRS survey was designed to provide
statistically valid results for ground water systems nationally.) Appendix D summarizes the
NIRS data coverage for boron.
Since the NIRS data were collected from a select group of nationally representative
PWSs (served by ground water), the percentage of samples (or systems) exceeding various
thresholds are also estimates of national occurrence. For example, since 1.7% of NIRS systems
sampled for boron have detections greater than the HRL (of 1.4 mg/L), it can be concluded that
approximately 1.7% of ground water systems sampled nationally for boron will also have
detections greater than the specified HRL. Furthermore, it can be concluded that approximately
0.4% of the population served by ground water systems sampled nationally for boron will also
have detections greater than the specified HRL.
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Exhibit 6.3.a. NIRS Data - Summary of Boron Occurrence in Surveyed Ground
Water Systems - Based on the System Level
CHEMICAL NAME
(HRL in mg/L)
Total No.
PWS
Percent PWS
>MRL
Percent PWS
> 1/2 HRL
Percent PWS
>HRL
99th Percentile
Value (mg/L)
Inorganic Chemicals
Boron
(HRL=1.4)
989
81.90%
4.32%
1.72%
2.44
PWS = Public Water System; MRL = Minimum Reporting Limit (for laboratory analyses); HRL = Health Reference Level
(concentration values used only as reference levels for analyses in this report). 99th Percentile Value = the 99th percentile of all
samples, not just those with detections.
Exhibit 6.3.b. NIRS Data - Summary of Boron Occurrence in Surveyed Ground
Water Systems - Based on Population Served
CHEMICAL
NAME
(HRL in mg/L)
Total Population
Served by PWSs
% Population
Served by PWSs
>MRL
% Population
Served by PWS
> 1/2 HRL
% Population
Served by PWS
>HRL
Inorganic Chemicals
Boron
(HRL=1.4)
1,482,153
88.10%
2.90%
0.40%
PWS = Public Water System; MRL = Minimum Reporting Limit (for laboratory analyses); HRL = Health Reference Level
(concentration values used only as reference levels for analyses in this report).
6.4 National Extrapolation of Stage 1 Occurrence Measures
As stated earlier, both the Round 1 and Round 2 cross-sections, as well as the NIRS
database, were developed to be nationally representative. National estimates of the contaminant
occurrence data can be generated via extrapolations. Exhibit 6.4 presents the national
extrapolations of the Stage 1 occurrence measures from the UCM Rounds 1 and 2 cross-sections
and the NIRS data. These national extrapolations were calculated by multiplying the percentages
of systems (or population served by systems) with threshold exceedances (presented in Exhibits
6.1.a through 6.3.b) by the number of systems and population served by systems nationally
(presented in Exhibit 1.51).
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Exhibit 6.4. National Extrapolation of Stage 1 Occurrence Measures
Chemical Name
(HRL)
Source
Water Type
Detections (> MRL)
Systems
Population
Served
Detections > 1/2 HRL
Systems
Population
Served
Detections > HRL
Systems
Population
Served
National Extrapolation of Round 1 24-State Cross-Section Data
1,3-
Dichloropropene
(0.4 ng/L)
1,1,2,2-
Tetrachloroethane
(0.4 ng/L)
GW
SW
Total
GW
SW
Total
72
31
106
229
57
290
508,000
1 ,262,000
1 ,825,000
1 ,564,000
2,166,000
3,963,000
72
31
106
105
33
140
508,000
1 ,262,000
1 ,825,000
1 ,329,000
2,131,000
3,592,000
72
31
106
102
27
131
508,000
1 ,262,000
1 ,825,000
1 ,309,000
2,013,000
3,472,000
National Extrapolation of Round 2 20 -State Cross-Section Data
Metolachlor
(70 ng/L)
1,3-
Dichloropropene
(0.4 ng/L)
1,1,2,2-
Tetrachloroethane
(0.4 ng/L)
GW
SW
Total
GW
SW
Total
GW
SW
Total
67
366
542
188
35
225
30
17
50
596,000
20,769,000
24,660,000
969,000
248,000
1,171,000
80,000
5,164,000
5,563,000
0.00%
0.00%
0.00%
161
31
194
30
15
47
0.00%
0.00%
0.00%
695,000
230,000
894,000
80,000
950,000
1 ,082,000
0.00%
0.00%
0.00%
114
31
147
30
12
45
0.00%
0.00%
0.00%
492,000
230,000
703,000
80,000
90,000
168,000
National Extrapolation of NIRS Data
Boron
(1 .4 mg/L)
GW (only)
48,682
75,501 ,000
2,584
2,469,000
1,022
372,000
6.5 Comparing Data Coverage of Round 1 and Round 2
The Round 1 and Round 2 data were evaluated to determine if comparable States, PWSs,
and contaminants are contained in both databases. As previously noted, Round 1 consisted of
data from 40 States/territories and Round 2 consisted of data from 35 States/territories.
Exhibit 6.4 illustrates the States in Round 1 and 2, identifying the States common to both.
Although 25 States are common to both Rounds 1 and 2, most of these States could not be
considered for this analysis because of data quality issues (see Exhibit 2.3.a and Exhibit 3.3.a).
Many States reported analytical results from a very low proportion of systems, reported results in
mixed units, and/or reported only analytical detections (highly censored reporting) in Round 1
and/or Round 2.
40
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Analysis of Occurrence Data from the UCM and MRS for CCL 2
June 2008
Of the 25 States in both Round 1 and 2 (identified in Exhibit 6.4), only eight were
determined to be sufficiently complete for use in this comparison analysis. Alaska, Kentucky,
Maryland, Minnesota, North Carolina, New Mexico, Ohio, and Washington were contained in
both databases and have data of adequate quality for analyses and comparisons.
Exhibit 6.5. States Common to Both Round 1 and Round 2, and Respective Cross-
Sections
Guam | Mariana is. [
Virgin Is. | ] /\ Puerto Rico [
Tribes Q (_) Am. Samoa [
States Not in Round 1 or 2 ^ In Rnd 1 x-section
States only in Round 1 ,/\ Not in Rnd 1 x-section
States only in Round 2 £ In Rnd 2 x-section
States in both Round 1 and 2 Q Not in Rnd 2 x-section
In addition to the States that have data in both the Round 1 and Round 2 databases, a
determination was made regarding actual PWSs that are common to both databases. Thirty-one
percent of all PWSs in Round 1 are also in Round 2, while only 22% of all Round 2 PWSs are
common to both rounds. This is, in part, because there are many more systems reporting
analytical results in Round 2 than in Round 1.
Michigan, for example, has only 139 systems in Round 1, and 123 of those systems
(88%) are also in Round 2. In Round 2, Michigan has a total of 3,209 systems. Of these Round
2 systems, 123 (approximately 4%) are in Round 1. The number of PWSs in Alaska is
problematic because the PWSIDs from Round 1 do not match the PWSIDs in Round 2. A few
States do have a higher percentage of systems common to both rounds. Kentucky, Maryland,
Minnesota, New Mexico, and Ohio each have over 70% of their total number of systems
common to both Round 1 and Round 2. Coincidently, these are five of the States used for the
comparison of occurrence data in States common in Round 1 and Round 2, which makes this
41
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EPA - OGWDW Analysis of Occurrence Data from the UCM and MRS for CCL 2 June 2008
analysis more representative for comparison of the States for each contaminant. For specific
numbers associated with each State, refer to Section IV.D of the Priority Contaminants Report
(USEPA, 2002).
Comparisons of contaminants in Round 1 and Round 2 indicated that there were no
common lOCs (Group 1) or SOCs (Regulated or Group 2) reported in both databases. In
contrast, all of the unregulated Group 3 and Group 4 VOCs reported in Round 2 were also
reported in Round 1. None of the regulated VOCs reported in Round 1, however, were reported
in Round 2. Summary data for the two VOCs considered during CCL 2 regulatory
determinations (1,3-dichloropropene and 1,1,2,2-tetrachloroethane) common to both Round 1
and Round 2 are presented in Appendix E (Tables E.3 and E.4) and comparisons between the
rounds can be made. Further comparisons, in graphical form, are presented in Sections 7.2 and
7.3 of this report.
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EPA - OGWDW Analysis of Occurrence Data from the UCM and MRS for CCL 2 June 2008
7. Graphical and Spatial Assessments of the Contaminants Considered During
CCL 2 Regulatory Determinations
This section presents graphical assessments of the contaminants considered during CCL 2
regulatory determinations with data in the Round 1 and Round 2 cross-section States. Most of
the Section 7 exhibits (maps and graphs) present analytical results based on these cross-section
States. Some exhibits (discussed below) use additional State data to increase spatial coverage.
The occurrence data used for all of the following maps and graphs are found in the occurrence
summary tables in Appendix B and Appendix C of this report.
The development of the nationally representative cross-sections is an important aspect of
the Round 1 and Round 2 data that must be considered as part of any conclusions drawn from the
maps and graphs in this report. This development was discussed for Round 1 and Round 2 data
in Section 5. The national cross-sections are developed from PWSs' contaminant monitoring
data with the intent that, in aggregate, the cross-section States' occurrence findings are indicative
of national occurrence. (Various occurrence comparisons between the Round 1 and Round 2
data, as well as comparisons to other State data sets, indicate that these cross-section States do
provide contaminant occurrence data that are reasonable indications of national occurrence.)
Although sub-national occurrence findings, such as regional or multi-State occurrence
patterns, can be useful for these initial assessments, any regional occurrence patterns (or absence
of patterns) should be considered in the context of the source and coverage of the State cross-
section data. With half (or more) of the States excluded from the cross-sections because they
lack adequate data, regional patterns may be difficult to characterize and must be interpreted
with caution. Supplemental information should be collected and used, whenever possible, to
assist in evaluating the significance of any apparent regional patterns. For example, when
assessing a particular pesticide occurrence pattern in this report, supplemental State or regional
pesticide-use information could be reviewed to determine how the possible absence of a
pesticide high-use State might affect interpretation of any occurrence pattern in the cross-section
State maps.
The MRS, designed to provide a single national occurrence assessment, is based on
significantly less data than that provided by the Round 1 or Round 2 databases. Also, the NIRS
data reflect a single sample per system (in contrast to 5 or 6 years of monitoring data from
systems in the Round 1 and Round 2 databases). The NIRS survey results should only be
reviewed in aggregate (i.e., at the national level and not at any regional or State level); therefore,
no maps or graphs using the NIRS data for boron are included.
Most of the exhibits below that illustrate distribution of occurrence are based on non-
biased data; for these exhibits only the cross-section State data are used to develop the maps and
graphs. However, to increase the spatial coverage of the exhibits that broadly identify
contaminant occurrence (Exhibits 7.1 .a, 7.2.a, and 7.3 .a), all data from all States with data in
Round 1 and Round 2 are used. Therefore, in these exhibits the data from non-cross-section
States (i.e., States with limited or biased data) are included, in addition to data from the cross-
section States. This more extensive use of the data in the databases can be appropriate when a
simple 'yes or no' identification of States with any PWS contaminant detection is of interest.
43
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EPA - OGWDW Analysis of Occurrence Data from the UCM and MRS for CCL 2 June 2008
7.1 Metolachlor
There are only Round 2 occurrence data for metolachlor. Based on these data,
metolachlor appears to occur throughout the United States, especially in the eastern half of the
country. Fifteen of the 24 States with metolachlor data in Round 2 had at least one PWS with at
least one analytical detection of this contaminant (see Exhibit 7.1. a, which includes all States,
both cross-section and non-cross-section States, from the Round 2 database). In Exhibit 7.1 .b,
occurrence relative to the MRL is presented for only the Round 2 cross-section States. (MRLs
varied from system to system. They ranged from 0.01 to 52 |ig/L. The modal MRL value was
0.2 ng/L.) There is no apparent geographic trend among the States with the highest proportion
of analytical detections of metolachlor. The States with the highest percentage (between 10.1%
and 20%) of metolachlor analytical detections are Kentucky and Rhode Island. No States had
any analytical results of metolachlor greater than the HRL of 70 |ig/L. Although occurrence is
relatively widespread, the degree of occurrence (as measured by concentration) appears low.
44
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Analysis of Occurrence Data from the UCM and MRS for CCL 2
June 2008
Exhibit 7.1.a. Geographic Distribution of Metolachlor Detections in Both Cross-
Section and Non-Cross-Section States (Round 2 Data)
states Not in Round 2
stoles wuh No Data for Contaminant
states with No Detections
States wilh Detections
Exhibit 7.1.b. Geographic Distribution of Metolachlor Detection Frequencies in
Cross-Section States (Round 2 Data)
n States Not in Round 2 Cross-scction g States with Detections at 0.01 - 1.00% of PWSs
O Slates wilh No Data tor Contaminant | states with Detections at 1.01 - 10.0!(, of PWSs
O Slates with No Detections | States wilh Detections al 10.1 - 20.0% of PWSs
45
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Analysis of Occurrence Data from the UCM and MRS for CCL 2
June 2008
Metolachlor occurrence over time, relative to the MRL, is presented in Exhibit 7.I.e.
Based on these data, the highest percentage of PWSs had analytical detections of metolachlor
equal to or greater than the MRL in 1992 and 1997. Note: Significantly fewer PWSs collected
metolachlor data in 1992, as compared to subsequent years; however, there were about the same
number of PWSs with detections in 1992 as in other years, causing an elevated percentage of
PWSs with metolachlor detections for 1992. A much smaller percentage of PWSs had analytical
detections of metolachlor in 1993 through 1996. The increased percentage of PWSs with
metolachlor detections in 1997 could be due to the increased use of metolachlor between 1992
and 1997. According to the National Center for Food and Agricultural Policy (NCFAP), around
1992 approximately 59.4 million pounds of metolachlor active ingredient (a.i.) were applied
annually to 16 types of crops on 32.4 million acres, and around 1997 approximately 67.3 million
pounds of metolachlor a.i. were applied annually to 21 types of crops on 36.7 million acres
(NCFAP, 2004 as cited in Chapter 12 of USEPA, 2008b).
Exhibit 7.1.c. Annual Frequency of Metolachlor Detections By Year (1992-1997)
from the 19-State Round 2 Cross-Section
Percent PWSs > MRL
1992
1993
1994
1995
1996
1997
46
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Analysis of Occurrence Data from the UCM and MRS for CCL 2
June 2008
7.2 1,3-Dichloropropene
There are 1,3-dichloropropene occurrence data in both Round 1 and Round 2. Based on
these data, the States with detections of 1,3-dichloropropene are widely distributed across the
United States (see Exhibit 7.2.a, which includes all States, both cross-section and non-cross-
section States, from both the Round 1 and 2 databases). Fourteen of the 37 States with 1,3-
dichloropropene data in Round 1 and Round 2 had at least one PWS with at least one analytical
detection. In Exhibit 7.2.b, occurrence relative to the MRL is presented for the Round 1 cross-
section States in the left map and the Round 2 cross-section States in the right map. (MRLs
varied from system to system. They ranged from 0.02 to 10 |ig/L in the Round 1 cross-section
and from 0.08 to 1 |ig/L in the Round 2 cross-section. The modal MRL value was 0.5 |ig/L in
both cross-sections.) Utah and Minnesota have a higher percentage of 1,3-dichloropropene
detections (between 1% and 3%) relative to other States.
Exhibit 7.2.a. Geographic Distribution of 1,3-Dichloropropene Detections in Both
Cross-Section and Non-Cross-Section States (Combined Rounds 1 and 2)
States Not in Round I or 2
States with No Data for Contaminant
States with No Detections
States with Detections
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Analysis of Occurrence Data from the UCM and MRS for CCL 2
June 2008
Exhibit 7.2.b. Geographic Distribution of 1,3-Dichloropropene Detection
Frequencies in Cross-Section States (Upper Map: Round 1; Lower Map: Round 2)
**
Slates Not in Round I Cross-section
I I Stales with No Dala for Contaminant
I I Slales with No Detections
I Slates with Detections at 0.01 - LOOT* of PVVSs
I Slates with Detection* at 1.01 - 3.00% of PVVSs
Q] Sutes Not in Round 2 Cross-section
t] Slates with No Data for Contaminant
I I Slates with No Detections
I States with Detections at 0.01-1.00% of PWSs
• Slales wilh Detections 311 01 - 3.
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EPA - OGWDW Analysis of Occurrence Data from the UCM and MRS for CCL 2 June 2008
Exhibit 7.2.c presents the combined Round 1 and Round 2 Cross-Section States with
analytical detections of 1,3-dichloropropene equal to or greater than the MRL (upper map) and
greater than the HRL (lower map). Each State shows the highest percentage of detections for
either Round 1 or Round 2 - State detection frequencies for the maps below are not averages of
Round 1 and Round 2 data. The States with the highest percentage (between 1% and 3%) of 1,3-
dichloropropene analytical detections are Minnesota and Utah. PWSs in several States detected
concentrations above the HRL of 0.4 |ig/L. The States with the highest percentage (between
0.51% and 1.75%) of 1,3-dichloropropene concentrations greater than the HRL are Minnesota,
Utah, Illinois, Alabama, and North Carolina. Minnesota and Utah, consequently, exhibit both
elevated numbers of detections for 1,3-dichloropropene, and elevated concentrations, relative to
the other States in the cross-sections.
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Analysis of Occurrence Data from the UCM and MRS for CCL 2
June 2008
Exhibit 7.2.c. Geographic Distribution of 1,3-Dichloropropene Detection
Frequencies (upper map) and HRL Exceedance Frequencies (lower map) for All
Round 1 and Round 2 Cross-Section States
DEL.D
MD
Stales Not in Round 1 & 1 Cross-sections
| | Stales with No Data for Conlammanl
CH Stales with N'o Detections
I Stales with Detections at 0.01 - 1.00% of PWSs
I Stales with Detectionsal 1.01 - 3.00% ofPWSs
I I Stales Not in Round }& 2 Cross-sections
I I Stales wilh No Data for Contaminant
[~] Stales wilh No HRL Eweedances
B Stales wilh HRL Excccdances al 0.0] - O.SO0'. ol'PWSs
• Stales wilh flRI. liMeedances al 0,5! - 1.75% of PWSs
1,3-Dichloropropene occurrence over time is presented in Exhibits 7.2.d and 7.2.e. The
data used in these two exhibits were from the eight States that had 1,3-Dichloropropene
50
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EPA - OGWDW
Analysis of Occurrence Data from the UCM and MRS for CCL 2
June 2008
occurrence data in both the Round 1 and Round 2 databases (Alaska, Kentucky, Maryland,
Minnesota, North Carolina, New Mexico, Ohio and Washington). In both exhibits, occurrence is
measured relative to the MRL in the left graph and relative to the HRL in the right graph. In
Exhibit 7.2.d, the graphs suggest annual variability in occurrence between 1991 and 1997, with
an increase in concentrations starting in 1992. Note: Significantly fewer PWSs collected 1,3-
dichloropropene data in 1992, as compared to subsequent years so the single detection of 1,3-
dichloropropene in 1992 caused the overall percentage of PWSs with detections in that year to
appear high. However, it is unclear why there is an increase in occurrence between 1992 and
1994; the use and release of 1,3-dichloropropene decreased throughout the 1990s (Chapter 6 of
USEPA, 2008b). Exhibit 7.2.e presents the occurrence of 1,3-dichloropropene by State. With
the exception of Ohio, none of the eight States had any detections in the Round 1 data.
Exhibit 7.2.d. Annual Frequency of 1,3-Dichloropropene Detections (left) and HRL
Exceedances (right), 1985 -1997, in Select Cross-Section States
0.80% -
Percent PWSs >
I — i
r-i
1985 1986 1987 1988 1989 1990 1991 1992
D Round 1 • Round
2
MRL
.
1992 1993 1994 1995 1996 1997
0.80%
Percent PWSs >
1985 1986 1987
i-.
1988 1989 1990 1991 1992
D Round 1 • Round 2
HRL
J_
I.I
• 1
1992 1993 1994 1995 1996 1997
Summary statistics by year are from 8 States: AK, KY, MD, MN, NC, NM, OH and WA. These are the only Cross-Section States
with PWS 1,3-dichloropropene data in both Round 1 and Round 2. There are data for 1992 in both the Round 1 and Round 2
databases. The HRL used for 1,3-dichloropropene is 0.4 jig/L.
Exhibit 7.2.e. Distribution of 1,3-Dichloropropene Detections (left) and HRL
Exceedances (right) Among Select Cross-Section States
3.0% -
20% -
05% -
Percent PWSs > MRL
B
AK KY MD
MN NC
D Round 1 • Round 2
NM OH WA
3.0%-
• °
0.0% -1
Percent PWSs > HRL
i
_
• _
AK KY MD MN NC NM OH WA
Q Round 1 B Round 2
These are the only Cross-Section States with PWS 1,3-dichloropropene data in both Round 1 and Round 2. The Health Reference
Level (HRL) used for 1,3-dichloropropene is 0.4 ng/L.
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Analysis of Occurrence Data from the UCM and MRS for CCL 2
June 2008
7.3 1,1,2,2-Tetrachloroethane
Both Round 1 and Round 2 contain occurrence data for 1,1,2,2-tetrachloroethane. Based
on these data, 1,1,2,2-tetrachloroethane appears to occur throughout the United States. However,
its occurrence does not appear to have a distinct geographic pattern (see Exhibit 7.3.a, which
includes all States, both cross-section and non-cross-section States, from both Round 1 and 2
databases). Twenty-five of 46 States with 1,1,2,2-tetrachloroethane data in Round 1 and Round
2 had at least one PWS with at least one analytical detection of the contaminant. In Exhibit
7.3.b, occurrence relative to the MRL is presented for the Round 1 cross-section States in the left
map and the Round 2 cross-section States in the right map. (MRLs varied from system to
system. They ranged from 0.01 to 10 |ig/L in the Round 1 cross-section and ranged from 0.1 to
2.5 |ig/L in the Round 2 cross-section. The modal MRL value was 0.5 |ig/L in both cross-
sections.) Generally, the maps reflect 1,1,2,2-tetrachloroethane's broad occurrence. There is no
apparent geographic trend among the States with the highest proportion of analytical detections.
South Dakota has an especially high percentage of detections with 11.64%. Florida is the second
highest with 4.15%.
Exhibit 7.3.a. Geographic Distribution of 1,1,2,2-Tetrachloroethane Detections in
Both Cross-Section and Non-Cross-Section States (Combined Rounds 1 and 2)
| | Stales Not in Round 1 or 2
I I Stoles with No Data for Contaminant
Q Stales with No Detections
I States with Detections
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Analysis of Occurrence Data from the UCM and MRS for CCL 2
June 2008
Exhibit 7.3.b. Geographic Distribution of 1,1,2,2-Tetrachloroethane Detection
Frequencies in Cross-Section States (Upper Map: Round 1; Lower Map: Round 2)
I I Slates Not in Round I Cross-section
I I States with Nn Detections
• States with (Elections at 0.01 - 0.49% of PWSs
I Suites with Detections at 0.50 - 4.14°b of PWSs
• Stales with Detections at 4 15 - 11.64% of PWSs
M
States Not in Round 2 Cross-section
J States with No Detect ions
H Slates with Delect mm at d III 11 49% of PWSs
• Slates with Detections alO.SO- 4. Wbof PWSs
• States with Detections at 4 15 - \ I 64'oof PWSs
53
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EPA - OGWDW Analysis of Occurrence Data from the UCM and MRS for CCL 2 June 2008
Exhibit 7.3.c presents the combined Round 1 and Round 2 States with analytical
detections of 1,1,2,2-tetrachloroethane equal to or greater than the MRL (upper map) and greater
than the HRL (lower map). Each State shows the highest percentage of system detections for
either Round 1 or Round 2 - State detection frequencies for the maps below are not averages of
Round 1 and Round 2 data. As presented previously, the two States with the highest percentage
(between 4.15% and 11.6%) of 1,1,2,2-tetrachloroethane analytical detections are South Dakota
and Florida. PWSs in several States detected concentrations above the HRL of 0.4 |ig/L. The
States with the highest percentage (between 0.65% and 2.76%) of 1,1,2,2-tetrachloroethane
concentrations greater than the HRL are Utah, Alabama, and Florida. In Round 2, North
Carolina is the only State to have more than 0.50% system detections greater than the HRL.
54
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Analysis of Occurrence Data from the UCM and MRS for CCL 2
June 2008
Exhibit 7.3.c. Geographic Distribution of 1,1,2,2-Tetrachloroethane Detection
Frequencies (upper map) and HRL Exceedance Frequencies (lower map) for All
Round 1 and Round 2 Cross-Section States
[ ] Stales Nol in Round I £ 2 Cross-sections
I I States u-tlh No Detect ions
• States wilh Detections at 0 Gl - 0.49% of PWSs
| States wvlh Detections at 0.50 - 4.14% of PWSs
• .Slates wilh Detect ions at 4.15- 11.54% ofPWSs
Stales N7ot in Round 1 & 2 Cures-sections
Stales with Xo 11RJ. Bxcetdances
Slates wilh HRL Excecdanccs at 0.01 - 0.64% ofPWSs
Stales with HRL Excccdanccs at 0.65 - 2 76% ol'PWSs
55
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EPA - OGWDW
Analysis of Occurrence Data from the UCM and MRS for CCL 2
June 2008
1,1,2,2-Tetrachloroethane occurrence over time is presented in Exhibits 7.3.d and 7.3.e
for the cross-section States. The data used in these two exhibits are from the eight States that
had 1,1,2,2-tetrachloroethane occurrence data in both the Round 1 and Round 2 databases
(Alaska, Kentucky, Maryland, Minnesota, North Carolina, New Mexico, Ohio and Washington).
In both exhibits, occurrence is measured relative to the MRL in the left graph and relative to the
HRL in the right graph. In Exhibit 7.3.d, the graphs suggest annual variability in occurrence
between 1988 and 1997, with a spike in concentrations in 1994. Detections greater than the HRL
were disproportionately observed in 1988 (Round 1) and 1994 (Round 2). Many fewer PWSs
collected 1,1,2,2-tetrachloroethane samples in Round 1 compared to Round 2; thus, any
detections that occurred in the Round 1 data caused the overall percentage of PWSs with 1,1,2,2-
tetrachloroethane detections to appear elevated. It is unclear why there were more detections of
1,1,2,2-tetrachloroethane in 1994 compared to other years. Production for commercial uses in
the United States ceased by the late 1980's and releases of the contaminant steadily declined
from 1989 to 2003 (Chapter 11 of USEPA, 2008b). Exhibit 7.3.e presents the occurrence of
1,1,2,2-tetrachloroethane by State. No trend is evident between 1,1,2,2-tetrachloroethane
occurrence in Round 1 and Round 2, based on these graphs.
Exhibit 7.3.d. Annual Frequency of 1,1,2,2-Tetrachloroethane Detections (left) and
HRL Exceedances (right), 1985 -1997, in Select Cross-Section States
Percent PWSs > MRL
n
1985 1986 1987 1988 1989 1990 1991 1992 1992 1993 1994 1995 1996 1997
Percent PWSs > HRL
n
1985 1986 1987 1988 1989 1990 1991 1992 1992 1993 1994 1995 1996 1997
Summary statistics by year are from 8 States: AK, KY, MD, MN, NC, NM, OH and WA. These are the only Cross-Section States
with PWS 1,1,2,2-tetrachloroethane data in both Round 1 and Round 2. There are data for 1992 in both the Round 1 and Round 2
databases. The HRL used for 1,1,2,2-tetrachloroethane is 0.4
56
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Analysis of Occurrence Data from the UCM and MRS for CCL 2
June 2008
Exhibit 7.3.e. Distribution of 1,1,2,2-Tetrachloroethane Detections (left) and HRL
Exceedances (right) Among Select Cross-Section States
Percent PWSs > MRL
AK KY MD MN NC NM OH WA
Percent PWSs > HRL
AK KY MD MN NC NM OH WA
These are the only Cross-Section States with PWS 1,1,2,2-tetrachloroethane data in both Round 1 and Round 2. The Health
Reference Level (HRL) used for 1,1,2,2-tetrachloroethane is 0.4 jig/L.
57
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EPA - OGWDW Analysis of Occurrence Data from the UCM and MRS for CCL 2 June 2008
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EPA - OGWDW Analysis of Occurrence Data from the UCM and MRS for CCL 2 June 2008
8. References
Frey, M.M., C. Seidel, M. Edwards, J. Parks, and L. McNeill. 2004. Occurrence Survey for
Boron and Hexavalent Chromium. AwwaRF Report 91044F.
Longtin, J. P. 1988. Occurrence of Radon, Radium, and Uranium in Groundwater. Journal of
the American Water Works Association. 80(7): 84-93.
National Center for Food and Agricultural Policy (NCFAP). 2004. National Pesticide Use
Database. Available on the Internet at: http://www.ncfap.org/database/default.htm.
Seidel, C. 2006. Email Communication to Brent Ranalli at The Cadmus Group, Inc.
[concerning boron data from an AwwaRF-sponsored study, with data in an attached
spreadsheet]. Denver, CO: McGuire Malcolm Pirnie; May 19, 2006.
U.S. Department of Commerce (USDOC), Bureau of the Census. 1994. 1992 Census of
Agriculture. Washington, D.C.: U.S. Government Printing Office.
USDOC, Bureau of the Census. 1996. 1992 Census of Manufactures. Washington, D.C.: U.S.
Government Printing Office.
USDOC, Bureau of the Census. 1997. 1995 Annual Survey of Manufactures. Washington,
D.C.: U.S. Government Printing Office.
U.S. Environmental Protection Agency (USEPA). 1999. A Review of Contaminant Occurrence
in Public Water Systems. EPA 816-R-99-006. Office of Water. 78 pp.
USEPA. 2000. Water Industry Baseline Handbook, Second Edition (Draft).
USEPA. 2002. Analysis of National Occurrence of the 1998 Contaminant Candidate List (CCL)
Regulatory Determination Priority Contaminants in Public Water Systems. EPA 815-D-
01-002. Office of Water. 77 pp.
USEPA. 2003. Analysis of National Occurrence of 14 Contaminants from the 1998
Contaminant Candidate List (CCL). Office of Water. 58 pp.
USEPA. 2008a. The Analysis of Occurrence Data from the First Unregulated Contaminant
Monitoring Regulation (UCMR 1) in Support of Regulatory Determinations for the
Second Drinking Water Contaminant Candidate List. EPA 815-R-08-013. June 2008.
USEPA. 2008b. Regulatory Determinations Support Document for Selected Contaminants from
the Second Drinking Water Contaminant Candidate List (CCL 2). EPA 815-R-08-012.
June 2008.
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APPENDICES
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APPENDICES
APPENDIX A. Development of Health Reference Levels (HRLs)
APPENDIX B. Detailed Round 1 Data Summary for
1,3-Dichloropropene, and 1,1,2,2-Tetrachloroethane
APPENDIX C. Detailed Round 2 Data Summary for Metolachlor,
1,3-Dichloropropene, and 1,1,2,2-Tetrachloroethane
APPENDIX D.
APPENDIX E.
Detailed MRS Data Summary for Boron
Data Summaries of Occurrence and Population Served for
Four Contaminants Considered During CCL 2 Regulatory
Determinations
-------
-------
Notes to Accompany Appendix Tables
The following tables present a summary of the analytical results and occurrence for the listed
contaminants. The various measures and descriptive statistics shown on the tables include:
Total # Samples = the total number of analytical records for the contaminant in the state (or in the
portion of the data indicated).
Total Unique PWS = the total number of public water systems with records for the contaminant in
the state (or in the portion of the data indicated).
Total Pop Served = the total summation of population served-by values for all public water systems
with records for the contaminant in the state (or in the portion of the data indicated).
Minimum Value = the minimum analytical value of all analytical results for the contaminant in the
state data set (or in the portion of the data indicated).
99th Value = the concentration value of the 99th percentile of all analytical results for the
contaminant in the state data set (or in the portion of the data indicated).
Maximum Value = the maximum analytical value of all analytical results for the contaminant in the
state data set (or in the portion of the data indicated).
Minimum Detects = the minimum analytical value of all the detections (analytical results greater
than the Minimum Reporting Level) for the contaminant in the state dataset (or in the portion
of the data indicated).
Median Detects = the median analytical value of all the detections (analytical results greater than the
Minimum Reporting Level) for the contaminant in the state dataset (or in the portion of the
data indicated).
% PWS (or POP) > MRL = percent of the total number of (or population served-by) public water
systems with at least one analytical result equal to or greater than the Minimum Reporting
Level.
% PWS (or POP) > 1A HRL = percent of the total number of (or population served-by) public water
systems with at least one analytical result that exceeded half the Health Reference Level.
% PWS (or POP) > HRL = percent of the total number of (or population served-by) public water
systems with at least one analytical result that exceeded the Health Reference Level.
-------
Total = the total number of samples, unique PWSs, and percent PWSs exceeding the MRL, 1A HRL,
or HRL are the summation of all values for all the states for the contaminant; i.e. Total = all
data from 40 states/territories; 24 States = all data from cross-section of 24 states. The values
indicated as "totals" for the analytical results, e.g. minimum value, 99th percentile value, etc.,
are similarly the value derived from the data from all states, or 24 states respectively.
Concentration values for Round 1 and Round 2 data are measured in micrograms per liter (j^g/L).
Concentration values for MRS data are measured in milligrams per liter (mg/L).
-------
Appendix A. Development of Health Reference Levels (HRLs)
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-------
Appendix A. Development of Health Reference Levels
Appendix A. Development of Health Reference Levels
Section 1412(b)(l)(A)(i) of SDWA requires EPA to determine whether each candidate
contaminant may have an adverse effect on public health. This appendix describes the overall
process the Agency used to evaluate health effects information, the approach used to estimate a
contaminant health reference level or HRL (a benchmark against which to conduct the initial
evaluation of the occurrence data), and the approach used to identify and evaluate information on
hazard and dose-response for the contaminants under consideration.
There are two different approaches to the derivation of an HRL. One approach is used for
chemicals that cause cancer and exhibit a linear response to dose and the other applies to non-
carcinogens and carcinogens evaluated using a non-linear approach.
Use of Carcinogenicity Data for the Derivation of a Health Reference Level
Two of the contaminants discussed in this report had data available to classify them as
likely or probable human carcinogens. These two contaminants (1,3-dichloropropene and
1,1,2,2-tetrachloroethane) are also the only contaminants for which low dose linear
extrapolations were performed. For these contaminants, EPA evaluated data on the mode of
action of the chemical to determine the method of low dose extrapolation. When this analysis
indicates that a linear low dose extrapolation is appropriate or when data on the mode of action
are lacking, EPA uses a low dose linear extrapolation to calculate risk-specific doses. The risk-
specific doses are the estimated oral exposures associated with lifetime excess risk levels that
range from one cancer in ten thousand (10"4) to one cancer in a million (10"6). The risk-specific
doses (expressed as mg/kg of body weight per day) are combined with adult body weight and
drinking water consumption data to estimate drinking water concentrations corresponding to this
risk range. EPA generally used the one-in-a-million (10"6) cancer risk in the initial screening of
the occurrence data for carcinogens evaluated using linear low dose extrapolation.
Use of Non-carcinogenic Health Effects Data for Derivation of a Health Reference Level
The remaining contaminant (metolachlor) has not been identified as known, likely or
probable carcinogens. For this contaminant, EPA calculated a reference dose (RfD). An RfD is
an estimate of a daily oral exposure to the human population (including sensitive subgroups) that
is likely to be without an appreciable risk of deleterious effects during a lifetime. It can be
derived from either a "no-observed-adverse-effect level" (NOAEL), a "lowest-observed-adverse-
effect level" (LOAEL), or a benchmark dose, with uncertainty factors applied to reflect
limitations of the data used.
EPA used uncertainty factors (UFs) to address uncertainty resulting from incompleteness
of the toxicological database. The individual UFs (usually applied as integers of 1, 3, or 10) were
multiplied together and used to derive the RfD from experimental data. Individual UFs are
intended to account for:
(1) the variation in sensitivity among the members of the human population (i.e.,
intraspecies variability);
A-l
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Appendix A. Development of Health Reference Levels
(2) the uncertainty in extrapolating animal data to humans (i.e., interspecies variability);
(3) the uncertainty in extrapolating from data obtained in a study with less-than-lifetime
exposure to lifetime exposure (i.e., extrapolating from subchronic to chronic exposure);
(4) the uncertainty in extrapolating from a LOAEL rather than from a NOAEL; and/or
(5) the uncertainty associated with an incomplete database.
EPA derived the HRLs using the RfD approach as follows:
HRL = [(RfD x BW)/DWI] x RSC
Where:
RfD = Reference Dose
BW = Body Weight for an adult, assumed to be 70 kilograms (kg)
DWI = Drinking Water Intake, assumed to be 2 L/day (90th percentile)
RSC = Relative Source Contribution, or the level of exposure believed to result from drinking
water when compared to other sources (e.g., food, ambient air). A 20 percent RSC is being used
to estimate the HRL and screen the occurrence data because it is the lowest and most
conservative RSC used in the derivation of a maximum contaminant level goal (MCLG) for
drinking water.
For metolachlor, EPA used the RfD in conjunction with a 20 percent RSC to derive a
conservative HRL estimate and perform an initial screening of the drinking water occurrence
data. Since the initial screening of the occurrence data at this conservative HRL value resulted in
negligible occurrence findings for metolachlor, EPA recognized that it was not necessary to
further evaluate the RSC in making the regulatory determination.
A-2
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Appendix B. Detailed Round 1 Data Summary for
1,3-Dichloropropene and l,l>2,2-Tetrachloroethane
Table B La Round 1 Data - 1,3-Dichloropropene Occurrence in Public Water Systems
Based on Number of Samples
Table B.l.b Round 1 Data - 1,3-Dichloropropene Occurrence in Public Water Systems
Based on Number of Systems
Table B.l.c Round 1 Data - 1,3-Dichloropropene Occurrence in Public Water Systems
Based on Population Served
Table B.2.a Round 1 Data - 1,1,2,2-Tetrachloroethane Occurrence in Public Water
Systems - Based on Number of Samples
Table B.2.b Round 1 Data - 1,1,2,2-Tetrachloroethane Occurrence in Public Water
Systems - Based on Number of Systems
Table B.2.c Round 1 Data - 1,1,2,2-Tetrachloroethane Occurrence in Public Water
Systems - Based on Population Served
-------
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Appendix B. Detailed Round 1 Data Summary
Table B.1.a. Round 1 Data- 1,3-Dichloropropene Occurrence in Public Water Systems - Based on Number of Samples
STATE
AK
AL
AR
AZ
CA
CO
DC
DE
FL
GA
HI
IA
IL
IN
KY
LA
MA
MD
Ml
MN
MO
MS
MT
NC
NE
NH
NJ
NM
NV
NY
OH
SD
TN
TX
UT
VI
VT
WA
WV
WY
TOTAL
24 STATES
TOTAL
UNIQUE
PWSs
656
131
259
5
9
745
258
146
1
2
978
85
20
297
1,455
590
7
29
2,532
335
303
2
400
3
58
1
9,307
9,164
TOTAL #
SAMPLES
1,568
351
1,994
15
280
1,055
938
819
1
8
1,582
324
35
644
3,067
1,595
125
104
14,328
444
1,220
2
1,259
10
204
1
31,973
31,104
#GW
SAMPLES
1,283
244
1,862
14
145
952
624
618
1
5
1,275
298
16
569
2,706
1,475
115
28
13,659
363
433
2
1,154
0
61
1
27,903
27,295
#SW
SAMPLES
285
107
132
1
135
103
314
201
0
3
307
26
19
75
361
120
10
76
669
81
787
0
105
10
143
0
4,070
3,809
% TOTAL
SAMPLES
>MRL
0.00%
0.28%
0.00%
0.00%
0.00%
0.00%
0.21%
0.00%
0.00%
75.00%
0.00%
0.31%
0.00%
0.00%
0.10%
0.00%
0.00%
0.00%
0.01%
0.00%
0.00%
100.00%
0.95%
0.00%
0.00%
0.00%
0.09%
0.06%
%GW
SAMPLES
>MRL
0.00%
0.41%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
60.00%
0.00%
0.34%
0.00%
0.00%
0.07%
0.00%
0.00%
0.00%
0.01%
0.00%
0.00%
100.00%
0.78%
0.00%
0.00%
0.00%
0.07%
0.05%
%sw
SAMPLES
>MRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.64%
0.00%
0.00%
100.00%
0.00%
0.00%
0.00%
0.00%
0.28%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
2.86%
0.00%
0.00%
0.00%
0.22%
0.16%
MIN
VALUE
(M9/L)
< 0.00
< 0.50
< 0.00
< 0.08
< 0.50
< 0.20
< 0.02
< 0.02
< 0.50
< 0.00
< 0.50
< 0.20
< 0.50
< 0.50
< 0.00
< 0.00
< 0.20
< 0.20
< 0.00
< 0.50
< 0.02
2.00
< 0.00
< 1.00
< 0.20
< 0.00
< 0.00
< 0.00
99%
VALUE
(M9/L)
< 0.00
< 0.50
< 0.50
< 5.00
< 0.80
< 1.00
< 2.00
< 1.00
< 0.50
17.00
< 0.50
< 2.00
< 2.00
< 0.50
< 1.00
< 1.00
< 0.20
< 0.50
< 1.00
< 0.50
< 0.50
12.00
< 10.00
< 1.00
< 4.00
< 0.00
< 1.00
< 1.00
MAX
VALUE
(M9/L)
< 0.00
1.60
< 2.00
< 5.00
< 0.80
< 1.00
2.00
< 1.00
< 0.50
17.00
< 0.50
0.20
< 2.00
< 0.50
1.40
< 5.00
< 0.20
< 1.00
1.00
< 0.50
< 0.50
12.00
1.90
< 1.00
< 4.00
< 0.00
17.00
2.00
MIN
DETECTS
(M9/L)
1.60
1.20
0.50
0.20
1.00
1.00
2.00
0.50
0.20
0.50
MEDIAN
DETECTS
(M9/L)
1.60
1.60
1.85
0.20
1.30
1.00
7.00
0.50
1.00
1.00
PWS = Public Water System; GW= Ground Water; SW= Surface Water; MRL= Minimum Reporting Limit; Min, 99%, and Max Value = the minimum, the 99th
percentile value, and the maximum value of all samples; Min and Median Detects = the minimum and median of all sample detects.
- The highlighted States are part of the 24-State Round 1 Cross-Section.
- Less-than (<) values indicate MRL values. Some systems did not report MRL values. In the data, these MRL values are represented by zeros (e.g "< 0.00").
B-1
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Appendix B. Detailed Round 1 Data Summary
Table B.1.b. Round 1 Data- 1,3-Dichloropropene Occurrence in Public Water Systems - Based on Number of Systems
STATE
AK
AL
AR
AZ
CA
CO
DC
DE
FL
GA
HI
IA
IL
IN
KY
LA
MA
MD
Ml
MN
MO
MS
MT
NC
NE
NH
NJ
NM
NV
NY
OH
SD
TN
TX
UT
VI
VT
WA
WV
WY
TOTAL
24 STATES
TOTAL #
SAMPLES
1,568
351
1,994
15
280
1,055
938
819
1
8
1,582
324
35
644
3,067
1,595
125
104
14,328
444
1,220
2
1,259
10
204
1
31,973
31,104
TOTAL
UNIQUE
PWS
656
131
259
5
9
745
258
146
1
2
978
85
20
297
1,455
590
7
29
2,532
335
303
2
400
3
58
1
9,307
9,164
#GW
PWS
527
93
227
4
7
716
185
121
1
2
935
71
11
254
1,430
555
6
5
2,384
306
156
2
382
0
20
1
8,401
8,303
#SW
PWS
134
42
46
1
2
29
73
25
0
1
43
14
9
44
25
35
2
26
150
29
147
0
29
3
38
0
947
898
% PWS
>MRL
0.00%
0.76%
0.00%
0.00%
0.00%
0.00%
0.78%
0.00%
0.00%
50.00%
0.00%
1.18%
0.00%
0.00%
0.21%
0.00%
0.00%
0.00%
0.08%
0.00%
0.00%
100.00%
1.75%
0.00%
0.00%
0.00%
0.20%
0.16%
%GW
PWS
>MRL
0.00%
1 .08%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
50.00%
0.00%
1.41%
0.00%
0.00%
0.14%
0.00%
0.00%
0.00%
0.08%
0.00%
0.00%
100.00%
1.31%
0.00%
0.00%
0.00%
0.17%
0.12%
%sw
PWS
>MRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
2.74%
0.00%
0.00%
100.00%
0.00%
0.00%
0.00%
0.00%
4.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
6.90%
0.00%
0.00%
0.00%
0.63%
0.56%
% PWS
> 1/2 HRL
0.00%
0.76%
0.00%
0.00%
0.00%
0.00%
0.78%
0.00%
0.00%
50.00%
0.00%
0.00%
0.00%
0.00%
0.21%
0.00%
0.00%
0.00%
0.08%
0.00%
0.00%
100.00%
1.75%
0.00%
0.00%
0.00%
0.19%
0.16%
%GW
PWS
> 1/2 HRL
0.00%
1 .08%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
50.00%
0.00%
0.00%
0.00%
0.00%
0.14%
0.00%
0.00%
0.00%
0.08%
0.00%
0.00%
100.00%
1.31%
0.00%
0.00%
0.00%
0.15%
0.12%
%sw
PWS
> 1/2 HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
2.74%
0.00%
0.00%
100.00%
0.00%
0.00%
0.00%
0.00%
4.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
6.90%
0.00%
0.00%
0.00%
0.63%
0.56%
% PWS
>HRL
0.00%
0.76%
0.00%
0.00%
0.00%
0.00%
0.78%
0.00%
0.00%
50.00%
0.00%
0.00%
0.00%
0.00%
0.21%
0.00%
0.00%
0.00%
0.08%
0.00%
0.00%
100.00%
1 .75%
0.00%
0.00%
0.00%
0.19%
0.16%
%GW
PWS
>HRL
0.00%
1 .08%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
50.00%
0.00%
0.00%
0.00%
0.00%
0.14%
0.00%
0.00%
0.00%
0.08%
0.00%
0.00%
100.00%
1.31%
0.00%
0.00%
0.00%
0.15%
0.12%
%sw
PWS
>HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
2.74%
0.00%
0.00%
100.00%
0.00%
0.00%
0.00%
0.00%
4.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
6.90%
0.00%
0.00%
0.00%
0.63%
0.56%
PWS = Public Water System; GW = Ground Water; SW = Surface Water;"% PWS > MRL", "> 1/2 HRL", and "> HRL" are the proportion of systems with at least
one analytic result equal to or greater than the MRL, exceeding the 1/2 HRL benchmark, and exceeding the HRL benchmark, respectively.
- The highlighted States are part of the 24-State Round 1 Cross-Section.
- The HRL used for 1,3-Dichloropropene is 0.4 pg/L.
B-2
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Appendix B. Detailed Round 1 Data Summary
Table B.1 .c. Round 1 Data -1,3-Dichloropropene Occurrence in Public Water Systems - Based on Population Served
STATE
:
AR
AZ
CA
CO
DC
DE
FL
GA
HI
IA
IL
IN
KY
LA
MA
MD
Ml
MN
MO
MS
MT
NC
NE
NH
NJ
NM
NV
NY
OH
SD
TN
TX
UT
VI
VT
WA
WV
WY
TOTAL
24 STATES
TOTAL
POP
SERVED
1,086
2,417,639
9,972,097
386,658
479,534
1,086,985
6,257,995
2,251,503
400
66,550
4,811,057
890,030
190,933
1,109,397
5,309,506
1,361,172
63,910
8,083,502
510,708
3,915,111
8,973
3,098,407
66,000
539,758
150
52,879,061
50,917,006
GWPOP
SERVED
1,086
1,195,423
9,331,228
349,700
246,534
804,288
1,529,195
567,606
400
66,550
761,204
717,341
9,861
452,814
1,738,792
1 162879
56,410
3,300,218
230,535
1,240,820
8,973
2,276,635
0
58,234
150
26,106,876
24,660,968
SWPOP
SERVED
0
1,514,944
2,422,363
36,958
233,000
282,697
4,728,800
1,683,897
0
52,050
4,049,853
172,689
181,072
656,833
3,570,714
198,293
34,560
4,810,984
280,173
2,674,291
0
1,735,395
66,000
481,524
0
29,867,090
29,271,833
% POP
>MRL
0.00%
0.22%
0.00%
0.00%
0.00%
0.00%
0.24%
0.00%
0.00%
78.21%
0.00%
0.36%
0.00%
0.00%
4.25%
0.00%
0.00%
0.01%
0.00%
0.00%
100.00%
6.12%
0.00%
0.00%
0.00%
0.95%
0.86%
%GW
POP
>MRL
0.00%
0.44%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
78.21%
0.00%
0.45%
0.00%
0.00%
0.04%
0.00%
0.00%
0.02%
0.00%
0.00%
100.00%
6.13%
0.00%
0.00%
0.00%
0.81%
0.59%
%sw
POP
>MRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.32%
0.00%
0.00%
100.00%
0.00%
0.00%
0.00%
0.00%
6.30%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
2.88%
0.00%
0.00%
0.00%
1.15%
0.99%
% POP
> 1/2 HRL
0.00%
0.22%
0.00%
0.00%
0.00%
0.00%
0.24%
0.00%
0.00%
78.21%
0.00%
0.00%
0.00%
0.00%
4.25%
0.00%
0.00%
0.01%
0.00%
0.00%
100.00%
6.12%
0.00%
0.00%
0.00%
0.94%
0.86%
%GW
POP
> 1/2 HRL
0.00%
0.44%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
78.21%
0.00%
0.00%
0.00%
0.00%
0.04%
0.00%
0.00%
0.02%
0.00%
0.00%
100.00%
6.13%
0.00%
0.00%
0.00%
0.79%
0.59%
%sw
POP
> 1/2 HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.32%
0.00%
0.00%
100.00%
0.00%
0.00%
0.00%
0.00%
6.30%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
2.88%
0.00%
0.00%
0.00%
1.15%
0.99%
% POP
>HRL
0.00%
0.22%
0.00%
0.00%
0.00%
0.00%
0.24%
0.00%
0.00%
78.21%
0.00%
0.00%
0.00%
0.00%
4.25%
0.00%
0.00%
0.01%
0.00%
0.00%
100.00%
6.12%
0.00%
0.00%
0.00%
0.94%
0.86%
%GW
POP
>HRL
0.00%
0.44%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
78.21%
0.00%
0.00%
0.00%
0.00%
0.04%
0.00%
0.00%
0.02%
0.00%
0.00%
100.00%
6.13%
0.00%
0.00%
0.00%
0.79%
0.59%
%sw
POP
>HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.32%
0.00%
0.00%
100.00%
0.00%
0.00%
0.00%
0.00%
6.30%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
2.88%
0.00%
0.00%
0.00%
1.15%
0.99%
PWS = Public Water System; GW= Ground Water; SW = Surface Water;"% POP > MRL", "> Vi HRL", and "> HRL" are the proportion of the total population
served by systems with at least one analytic result equal to or greater than the MRL, exceeding the Vi HRL benchmark, and exceeding the HRL benchmark,
respectively.
- The highlighted States are part of the 24-State Round 1 Cross-Section.
- The HRL used for 1,3-Dichloropropene is 0.4 |jg/L.
B-3
-------
Appendix B. Detailed Round 1 Data Summary
Table B.2.a. Round 1 Data - 1,1,2,2-Tetrachloroethane Occurrence in Public Water Systems - Based on Number of Samples
STATE
AK
AL
AR
AZ
CA
CO
DC
DE
FL
GA
HI
IA
IL
IN
KY
LA
MA
MD
Ml
MN
MO
MS
MT
NC
NE
NH
NJ
NM
NV
NY
OH
SD
TN
TX
UT
VI
VT
WA
WV
WY
TOTAL
24 States
TOTAL
UNIQUE
PWS
661
131
944
3,522
9
1
13
217
1,161
127
1,002
1,302
311
524
13
2
986
1
1,565
85
565
297
1
1,511
590
8
355
2,656
335
303
423
3
1
992
137
145
20,899
20,407
TOTAL #
SAMPLES
1,610
351
2,932
1 1 ,667
33
62
333
315
2,460
1,221
1,908
6,002
1,724
2,076
22
2
1,909
1
2,756
323
1,624
644
1
3,130
1,595
148
2,160
16,084
444
1,220
1,328
10
1
3,987
388
313
70,784
67,688
#GW
SAMPLES
1,323
244
2,272
11,564
30
0
189
70
1,861
1,081
1,697
5,035
1,338
1,119
18
1
1,441
1
2,677
297
1,376
569
1
2,775
1,475
136
1,618
15,166
363
433
1,215
0
1
3,656
164
259
61 ,465
59,173
#SW
SAMPLES
287
107
660
103
3
62
144
245
599
140
211
967
386
957
4
1
468
0
79
26
248
75
0
355
120
12
542
918
81
787
113
10
0
331
224
54
9,319
8,515
% TOTAL
SAMPLES
>MRL
0.12%
0.85%
0.00%
0.12%
0.00%
0.00%
0.60%
3.17%
0.00%
0.00%
0.00%
0.10%
0.17%
0.00%
0.00%
100.00%
0.05%
100.00%
0.11%
0.00%
0.00%
0.16%
100.00%
0.35%
0.00%
0.68%
0.09%
0.01%
8.78%
0.00%
0.83%
0.00%
100.00%
0.00%
0.00%
0.00%
0.16%
0.16%
%GW
SAMPLES
>MRL
0.08%
0.82%
0.00%
0.12%
0.00%
0.00%
1.06%
4.29%
0.00%
0.00%
0.00%
0.06%
0.22%
0.00%
0.00%
100.00%
0.00%
100.00%
0.11%
0.00%
0.00%
0.18%
100.00%
0.40%
0.00%
0.74%
0.06%
0.01%
9.37%
0.00%
0.82%
0.00%
100.00%
0.00%
0.00%
0.00%
0.15%
0.15%
%sw
SAMPLES
>MRL
0.35%
0.93%
0.00%
0.00%
0.00%
0.00%
0.00%
2.86%
0.00%
0.00%
0.00%
0.31%
0.00%
0.00%
0.00%
100.00%
0.21%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.18%
0.00%
6.17%
0.00%
0.88%
0.00%
0.00%
0.00%
0.00%
0.00%
0.23%
0.22%
MIN
VALUE
(M9/L)
< 0.00
< 0.50
< 0.05
< 0.00
< 0.04
< 0.50
< 0.20
< 0.00
< 0.50
< 0.00
< 0.40
< 0.02
< 0.10
< 0.50
< 0.50
0.63
< 0.10
13.00
< 0.20
< 0.20
< 0.50
< 0.07
1.20
< 0.00
< 0.00
< 0.00
< 0.04
< 0.00
< 0.15
< 0.01
< 0.00
< 1.00
1.10
< 0.50
< 0.03
< 0.20
< 0.00
< 0.00
99%
VALUE
(M9/L)
< 0.00
< 0.50
< 2.00
< 0.50
< 5.00
< 0.50
< 0.50
1.00
< 0.50
< 0.30
< 1.00
< 1.00
< 2.00
< 1.00
< 0.50
2.20
< 0.50
13.00
< 1.00
< 2.00
< 1.00
< 0.50
1.20
< 1.00
< 1.00
< 0.20
< 1.00
< 1.00
0.15
< 0.50
5.00
< 1.00
1.10
< 0.50
< 4.00
< 0.40
< 1.00
< 1.00
MAX
VALUE
(M9/L)
200.00
0.90
< 10.00
5.80
< 5.00
< 0.50
9.00
1.00
< 0.50
< 0.30
< 1.00
2.50
2.74
< 1.00
< 0.50
2.20
0.20
13.00
0.20
< 2.00
< 1.00
0.07
1.20
112.00
< 5.00
1.00
3.00
2.00
0.22
< 0.50
1.00
< 1.00
1.10
< 4.00
< 1.00
200.00
200.00
MIN
DETECTS
(M9/L)
49.00
0.50
0.50
0.40
0.05
0.11
0.49
0.63
0.20
13.00
0.20
0.07
1.20
0.52
1.00
2.00
2.00
0.15
0.30
1.10
0.05
0.05
MEDIAN
DETECTS
(M9/L)
124.50
0.80
1.55
4.70
0.80
0.50
0.88
1.42
0.20
13.00
0.20
0.07
1.20
2.80
1.00
2.50
2.00
0.15
0.50
1.10
0.50
0.50
PWS = Public Water System; GW= Ground Water; SW= Surface Water; MRL= Minimum Reporting Limit; Min, 99%, and Max Value = the minimum, the 99th
percentile value, and the maximum value of all samples; Min and Median Detects = the minimum and median of all sample detects.
- The highlighted States are part of the 24-State Round 1 Cross-Section.
- Less-than (<) values indicate MRL values. Some systems did not report MRL values. In the data, these MRL values are represented by zeros (e.g "< 0.00").
B-4
-------
Appendix B. Detailed Round 1 Data Summary
Table B.2.b. Round 1 Data- 1,1,2,2-Tetrachloroethane Occurrence in Public Water Systems - Based on Number of Systems
STATE
AK
AL
AR
AZ
CA
CO
DC
DE
FL
GA
HI
A
IL
IN
KY
LA
MA
MD
Ml
MN
MO
MS
MT
NC
NE
NH
NJ
NM
NV
NY
OH
SD
TN
TX
UT
VI
VT
WA
WV
WY
TOTAL
24 States
TOTAL #
SAMPLES
1,610
351
2,932
1 1 ,667
33
62
333
315
2,460
1,221
1,908
6,002
1,724
2,076
22
2
1,909
1
2,756
323
1,624
644
1
3,130
1,595
148
2,160
16,084
444
1,220
1,328
10
1
3,987
388
313
70,784
67,688
TOTAL
UNIQUE
PWS
661
131
944
3,522
9
1
13
217
1,161
127
1,002
1,302
311
524
13
2
986
1
1,565
85
565
297
1
1,511
590
8
355
2,656
335
303
423
3
1
992
137
145
20,899
20,407
#GW
PWS
532
93
874
3,495
7
11
42
1,052
112
963
1,187
280
291
9
1
940
1
1,540
71
523
254
1
1,486
555
7
252
2,493
306
156
403
0
1
937
63
116
19,054
18,693
#SW
PWS
134
42
106
37
3
1
2
196
109
16
39
115
32
233
4
1
51
0
29
14
57
44
0
25
35
2
122
167
29
147
34
3
0
77
75
38
2,019
1,867
% PWS
>MRL
0.30%
2.29%
0.00%
0.31%
0.00%
0.00%
15.38%
4.15%
0.00%
0.00%
0.00%
0.46%
0.64%
0.00%
0.00%
100.00%
0.10%
100.00%
0.19%
0.00%
0.00%
0.34%
100.00%
0.40%
0.00%
12.50%
0.56%
0.04%
1 1 .64%
0.00%
1 .65%
0.00%
100.00%
0.00%
0.00%
0.00%
0.48%
0.45%
%GW
PWS
>MRL
0.19%
2.15%
0.00%
0.31%
0.00%
0.00%
18.18%
4.76%
0.00%
0.00%
0.00%
0.25%
0.71%
0.00%
0.00%
100.00%
0.00%
100.00%
0.19%
0.00%
0.00%
0.39%
100.00%
0.40%
0.00%
14.29%
0.40%
0.04%
11.11%
0.00%
1 .49%
0.00%
100.00%
0.00%
0.00%
0.00%
0.42%
0.39%
%SW
PWS
>MRL
0.75%
2.38%
0.00%
0.00%
0.00%
0.00%
0.00%
3.57%
0.00%
0.00%
0.00%
2.61%
0.00%
0.00%
0.00%
100.00%
1 .96%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.82%
0.00%
17.24%
0.00%
2.94%
0.00%
0.00%
0.00%
0.00%
0.00%
1 .04%
1 .02%
% PWS
> 1/2 HRL
0.30%
2.29%
0.00%
0.31%
0.00%
0.00%
15.38%
2.76%
0.00%
0.00%
0.00%
0.38%
0.64%
0.00%
0.00%
100.00%
0.00%
100.00%
0.00%
0.00%
0.00%
0.00%
100.00%
0.40%
0.00%
12.50%
0.56%
0.04%
0.30%
0.00%
1 .65%
0.00%
100.00%
0.00%
0.00%
0.00%
0.26%
0.22%
%GW
PWS
> 1/2 HRL
0.19%
2.15%
0.00%
0.31%
0.00%
0.00%
18.18%
4.76%
0.00%
0.00%
0.00%
0.17%
0.71%
0.00%
0.00%
100.00%
0.00%
100.00%
0.00%
0.00%
0.00%
0.00%
100.00%
0.40%
0.00%
14.29%
0.40%
0.04%
0.00%
0.00%
1 .49%
0.00%
100.00%
0.00%
0.00%
0.00%
0.22%
0.18%
%SW
PWS
> 1/2 HRL
0.75%
2.38%
0.00%
0.00%
0.00%
0.00%
0.00%
2.04%
0.00%
0.00%
0.00%
2.61%
0.00%
0.00%
0.00%
100.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.82%
0.00%
3.45%
0.00%
2.94%
0.00%
0.00%
0.00%
0.00%
0.00%
0.64%
0.59%
% PWS
>HRL
0.30%
2.29%
0.00%
0.31%
0.00%
0.00%
7.69%
2.76%
0.00%
0.00%
0.00%
0.31%
0.64%
0.00%
0.00%
100.00%
0.00%
100.00%
0.00%
0.00%
0.00%
0.00%
100.00%
0.40%
0.00%
12.50%
0.56%
0.04%
0.00%
0.00%
1 .42%
0.00%
100.00%
0.00%
0.00%
0.00%
0.24%
0.20%
%GW
PWS
>HRL
0.19%
2.15%
0.00%
0.31%
0.00%
0.00%
9.09%
4.76%
0.00%
0.00%
0.00%
0.17%
0.71%
0.00%
0.00%
100.00%
0.00%
100.00%
0.00%
0.00%
0.00%
0.00%
100.00%
0.40%
0.00%
14.29%
0.40%
0.04%
0.00%
0.00%
1 .24%
0.00%
100.00%
0.00%
0.00%
0.00%
0.20%
0.17%
%sw
PWS
>HRL
0.75%
2.38%
0.00%
0.00%
0.00%
0.00%
0.00%
2.04%
0.00%
0.00%
0.00%
1 .74%
0.00%
0.00%
0.00%
100.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.82%
0.00%
0.00%
0.00%
2.94%
0.00%
0.00%
0.00%
0.00%
0.00%
0.54%
0.48%
PWS = Public Water System; GW = Ground Water; SW= Surface Water;"% PWS > MRL", "> 1/2 HRL", and "> HRL" are the proportion of systems with at least
one analytic result equal to or greater than the MRL, exceeding the Vi HRL benchmark, and exceeding the HRL benchmark, respectively.
- The highlighted States are part of the 24-State Round 1 Cross-Section.
-The HRL used for 1,1,2,2-Tetrachloroethane is 0.4 pg/L.
B-5
-------
Appendix B. Detailed Round 1 Data Summary
Table B.2.C. Round 1 Data -1,1,2,2-Tetrachloroethane Occurrence in Public Water Systems - Based on Population Served
STATE
AK
AL
AR
AZ
CA
CO
DC
DE
FL
GA
HI
IA
IL
IN
KY
LA
MA
MD
Ml
MN
MO
MS
MT
NC
NE
NH
NJ
NM
NV
NY
OH
SD
TN
TX
UT
VI
VT
WA
WV
WY
TOTAL
24 States
TOTAL POP
SERVED
1,126
2,417,639
4,001,762
26,356,783
1,681,658
499,732
4,315,466
4,919,208
1,260,603
2,128,421
7,228,378
2,287,534
3,134,692
240,115
15,725
4,849,911
131,546
2,303,765
890,030
549,172
1,109,397
985
5,246,072
1,361,172
70,910
27,880
8,745,892
510,708
3,915,111
3,116,052
66,000
40
3,801,040
777,629
372,532
98,334,686
94,710,065
GWPOP
SERVED
1,126
1,195,423
1,323,094
26,085,197
644,700
266,732
1,745,246
1,373,936
1,215,122
1,499,541
2,442,436
820,099
241,389
58,905
6,425
864,423
131,546
2,158,522
717,341
276,682
452,814
985
1,675,358
1,162,879
63,410
9,880
3,554,348
230,535
1,240,820
2,289,457
0
40
3,462,027
187,714
265,456
57,663,608
55,763,644
SWPOP
SERVED
0
1,514,944
2,909,062
841,643
1,290,958
233,000
3,704,774
3,545,272
81,837
628,880
4,785,942
1,484,247
2,893,303
181,210
9,300
4,068,878
0
175,509
172,689
334,304
656,833
0
3,570,714
198,293
34,560
24,500
5,262,754
280,173
2,674,291
1,746,978
66,000
0
1,547,480
594,025
263,806
45,776,159
43,763,942
% POP
>MRL
0.00%
25.48%
0.00%
1.92%
0.00%
40.94%
0.64%
0.00%
0.00%
0.00%
3.11%
4.95%
0.00%
0.00%
100.00%
0.23%
100.00%
0.01%
0.00%
0.00%
0.07%
100.00%
0.85%
0.00%
6.70%
0.00%
0.001%
4.87%
0.00%
6.19%
0.00%
100.00%
0.00%
0.00%
0.00%
2.16%
1.86%
%GW
POP
>MRL
0.00%
1.34%
0.00%
1.94%
0.00%
76.71%
1.54%
0.00%
0.00%
0.00%
6.02%
13.80%
0.00%
0.00%
100.00%
0.00%
100.00%
0.01%
0.00%
0.00%
0.18%
100.00%
2.65%
0.00%
7.49%
0.00%
0.002%
4.28%
0.00%
6.67%
0.00%
100.00%
0.00%
0.00%
0.00%
2.37%
1.82%
%sw
POP
>MRL
0.00%
39.61%
0.00%
0.00%
0.00%
0.00%
0.01%
0.00%
0.00%
0.00%
1.63%
0.00%
0.00%
0.00%
100.00%
0.27%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
5.36%
0.00%
2.30%
0.00%
0.00%
0.00%
0.00%
0.00%
1.65%
1.70%
% POP
> 1/2 HRL
0.00%
25.48%
0.00%
1.92%
0.00%
40.94%
0.63%
0.00%
0.00%
0.00%
1.15%
4.95%
0.00%
0.00%
100.00%
0.00%
100.00%
0.00%
0.00%
0.00%
0.00%
100.00%
0.85%
0.00%
6.70%
0.00%
0.001%
2.73%
0.00%
6.19%
0.00%
100.00%
0.00%
0.00%
0.00%
1.99%
1.69%
%GW
POP
> 1/2 HRL
0.00%
1.34%
0.00%
1.94%
0.00%
76.71%
1.54%
0.00%
0.00%
0.00%
0.21%
13.80%
0.00%
0.00%
100.00%
0.00%
100.00%
0.00%
0.00%
0.00%
0.00%
100.00%
2.65%
0.00%
7.49%
0.00%
0.002%
0.00%
0.00%
6.67%
0.00%
100.00%
0.00%
0.00%
0.00%
2.10%
1.55%
%sw
POP
> 1/2 HRL
0.00%
39.61%
0.00%
0.00%
0.00%
0.00%
0.01%
0.00%
0.00%
0.00%
1.63%
0.00%
0.00%
0.00%
100.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
4.98%
0.00%
2.30%
0.00%
0.00%
0.00%
0.00%
0.00%
1.62%
1.67%
% POP
>HRL
0.00%
25.48%
0.00%
1.92%
0.00%
34.38%
0.63%
0.00%
0.00%
0.00%
0.78%
4.95%
0.00%
0.00%
100.00%
0.00%
100.00%
0.00%
0.00%
0.00%
0.00%
100.00%
0.85%
0.00%
6.70%
0.00%
0.00%
0.00%
0.00%
5.77%
0.00%
100.00%
0.00%
0.00%
0.00%
1.90%
1.63%
%GW
POP
>HRL
0.00%
1.34%
0.00%
1.94%
0.00%
64.41%
1.54%
0.00%
0.00%
0.00%
0.21%
13.80%
0.00%
0.00%
100.00%
0.00%
100.00%
0.00%
0.00%
0.00%
0.00%
100.00%
2.65%
0.00%
7.49%
0.00%
0.00%
0.00%
0.00%
6.10%
0.00%
100.00%
0.00%
0.00%
0.00%
2.02%
1.53%
%sw
POP
>HRL
0.00%
39.61%
0.00%
0.00%
0.00%
0.00%
0.01%
0.00%
0.00%
0.00%
1.07%
0.00%
0.00%
0.00%
100.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
2.30%
0.00%
0.00%
0.00%
0.00%
0.00%
1.53%
1.58%
PWS = Public Water System; GW= Ground Water; SW= Surface Water;"% POP > MRL", "> 1/2 HRL", and "> HRL" are the proportion of the total population
served by systems with at least one analytic result equal to or greater than the MRL, exceeding the Vi HRL benchmark, and exceeding the HRL benchmark,
respectively.
- The highlighted States are part of the 24-State Round 1 Cross-Section.
- The HRL used for 1,1,2,2-Tetrachloroethane is 0.4 |jg/L.
B-6
-------
Appendix C. Detailed Round 2 Data Summary for
Metolachlor, 1,3-Dichloropropene and l,l>2,2-Tetrachloroethane
Table C. 1 .a Round 2 Data - Metolachlor Occurrence in Public Water Systems -
Based on Number of Samples
Table C. 1 .b Round 2 Data - Metolachlor Occurrence in Public Water Systems -
Based on Number of Systems
Table C. 1 .c Round 2 Data - Metolachlor Occurrence in Public Water Systems -
Based on Population Served
Table C.2.a Round 2 Data - 1,3-Dichloropropene Occurrence in Public Water Systems -
Based on Number of Samples
Table C 2.b Round 2 Data - 1,3-Dichloropropene Occurrence in Public Water Systems -
Based on Number of Systems
Table C 2.c Round 2 Data - 1,3-Dichloropropene Occurrence in Public Water Systems -
Based on Population Served
Table C.3.a Round 2 Data - 1,1,2,2-Tetrachloroethane Occurrence in Public Water
Systems - Based on Number of Samples
Table C.3.b Round 2 Data - 1,1,2,2-Tetrachloroethane Occurrence in Public Water
Systems - Based on Number of Systems
Table C.3.c Round 2 Data - 1,1,2,2-Tetrachloroethane Occurrence in Public Water
Systems - Based on Population Served
-------
-------
Appendix C. Detailed Round 2 Data Summary
Table C.1 .a. Round 2 Data - Metolachlor Occurrence in Public Water Systems - Based on Number of Samples
STATE
Tribes (06)
AK
AL
AR
AZ
CA
CO
CT
IN
KY
LA
MA
MD
ME
Ml
MN
MO
MS
NC
ND
NH
NJ
NM
OH
OK
OR
PA
Rl
SC
SD
TN
TX
VT
WA
Wl
TOTAL
20 STATES
19 STATES1
TOTAL
UNIQUE
PWS
1
17
536
750
70
38
54
683
2,650
1,264
538
495
296
592
716
2,202
1
1,135
459
15
940
10
426
391
599
14,878
13,007
12,953
TOTAL #
SAMPLES
3
23
1,610
2,230
317
156
182
1,135
4,162
5,985
1,798
730
384
612
4,288
5,386
1
2,528
2,012
188
5,692
50
1,545
612
1,169
42,798
34,112
33,930
#GW
SAMPLES
3
19
1,225
1,365
116
65
72
913
3,780
5,706
780
694
317
577
4,094
4,901
0
1,972
1,157
82
4,699
16
194
483
967
34,197
27,723
27,651
#SW
SAMPLES
0
4
385
865
201
91
110
222
382
279
1,018
36
67
35
194
485
1
556
855
106
993
34
1,351
129
202
8,601
6,389
6,279
% TOTAL
SAMPLES
>MRL
0.00%
0.00%
0.00%
0.04%
0.63%
7.69%
8.79%
0.18%
0.17%
0.37%
2.34%
0.14%
0.00%
0.00%
0.00%
0.48%
0.00%
0.04%
7.55%
3.72%
0.00%
0.00%
4.79%
0.16%
0.00%
0.86%
0.62%
0.57%
%GW
SAMPLES
>MRL
0.00%
0.00%
0.00%
0.00%
1 .72%
0.00%
15.28%
0.11%
0.00%
0.33%
0.00%
0.14%
0.00%
0.00%
0.00%
0.02%
0.00%
0.05%
6.57%
8.54%
0.00%
0.00%
0.21%
0.00%
0.37%
0.17%
0.13%
%sw
SAMPLES
>MRL
0.00%
0.00%
0.00%
0.12%
0.00%
13.19%
4.55%
0.45%
1 .83%
1 .08%
4.13%
0.00%
0.00%
0.00%
0.00%
5.15%
0.00%
0.00%
8.89%
0.00%
0.00%
0.00%
5.11%
0.00%
0.00%
2.80%
2.58%
2.55%
MIN
VALUE
(H9/L)
< 0.07
< 0.00
< 0.00
< 0.00
< 0.00
< 0.01
< 0.20
< 0.05
< 0.00
< 0.00
< 0.50
< 0.00
< 0.00
< 0.00
< 0.03
< 0.01
< 0.00
< 0.00
< 0.00
< 0.00
< 0.00
< 0.00
< 0.10
< 0.00
< 0.00
< 0.00
< 0.00
< 0.00
99%
VALUE
(H9/L)
< 0.07
< 0.00
< 0.00
< 0.00
< 0.00
0.33
0.33
< 2.00
< 0.00
< 0.00
0.91
< 0.00
< 0.07
< 0.00
< 0.20
< 5.00
< 0.00
< 0.00
3.00
0.61
< 0.00
< 0.00
0.67
< 0.00
< 0.00
< 5.00
< 5.00
< 5.00
MAX
VALUE
(H9/L)
< 0.07
< 0.00
< 0.00
0.60
4.40
0.70
0.33
1.58
6.00
2.00
13.80
0.70
< 0.07
< 0.00
< 0.20
10.10
< 0.00
1.00
3.00
0.75
< 0.00
< 0.00
7.10
0.10
< 0.00
13.80
13.80
13.80
MIN
DETECTS
(M9/L)
0.60
0.59
0.01
0.33
1.07
1.00
0.50
0.50
0.70
0.20
1.00
0.03
0.17
0.10
0.10
0.01
0.01
0.01
MEDIAN
DETECTS
(M9/L)
0.60
2.50
0.15
0.33
1.33
2.00
0.80
0.84
0.70
1.20
1.00
1.00
0.33
0.30
0.10
1.00
0.57
0.61
PWS = Public Water System; GW= Ground Water; SW= Surface Water; MRL= Minimum Reporting Limit; Min, 99%, and Max Value = the minimum, the 99th percentile value, and
the maximum value of all samples; Min and Median Detects = the minimum and median of all sample detects.
- Massachusetts data not included in "19 States" summary statistics for Metolachlor. See text for details.
- The highlighted States are part of the 20-State Round 2 Cross-Section.
- Less-than (<) values indicate MRL values. Some systems did not report MRL values. In the data, these MRL values are represented by zeros (e.g "< 0.00").
C-1
-------
Appendix C. Detailed Round 2 Data Summary
Table C.1.b. Round 2 Data - Metolachlor Occurrence in Public Water Systems - Based on Number of Systems
STATE
Tribes (06)
AK
AL
AR
AZ
CA
CO
CT
IN
KY
LA
MA
MD
ME
Ml
MN
MO
MS
NC
ND
NH
NJ
NM
OH
OK
OR
PA
Rl
SC
SD
TN
TX
VT
WA
Wl
TOTAL
20 STATES
19 STATES1
TOTAL #
SAMPLES
3
23
1,610
2,230
317
156
182
1,135
4,162
5,985
1,798
730
384
612
4,288
5,386
1
2,528
2,012
188
5,692
50
1,545
612
1,169
42,798
34,112
33,930
TOTAL
UNIQUE
PWS
1
17
536
750
70
38
54
683
2,650
1,264
538
495
296
592
716
2,202
1
1,135
459
15
940
10
426
391
599
14,878
13,007
12,953
#GW
PWS
1
14
431
538
35
18
27
626
2,570
1,234
437
470
258
559
687
2,021
0
984
313
6
842
2
121
339
529
13,062
11,530
11,503
#SW
PWS
0
3
105
212
35
20
27
57
80
30
101
25
38
33
29
181
1
151
146
9
98
8
305
52
70
1,816
1,477
1,450
% PWS
>MRL
0.00%
0.00%
0.00%
0.13%
1 .43%
13.16%
14.81%
0.29%
0.19%
0.40%
4.28%
0.20%
0.00%
0.00%
0.00%
1 .00%
0.00%
0.09%
13.07%
20.00%
0.00%
0.00%
9.39%
0.26%
0.00%
1 .20%
0.89%
0.83%
%GW
PWS
>MRL
0.00%
0.00%
0.00%
0.00%
2.86%
0.00%
14.81%
0.16%
0.00%
0.32%
0.00%
0.21%
0.00%
0.00%
0.00%
0.05%
0.00%
0.10%
8.95%
50.00%
0.00%
0.00%
1 .65%
0.29%
0.00%
0.36%
0.15%
0.11%
%SW
PWS
>MRL
0.00%
0.00%
0.00%
0.47%
0.00%
25.00%
14.81%
1.75%
6.25%
3.33%
22.77%
0.00%
0.00%
0.00%
0.00%
11.60%
0.00%
0.00%
21 .92%
0.00%
0.00%
0.00%
12.46%
0.00%
0.00%
7.21%
6.70%
6.55%
% PWS
> 1/2 HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
%GW
PWS
> 1/2 HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
%sw
PWS
> 1/2 HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
% PWS
>HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
%GW
PWS
>HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
%sw
PWS
>HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
PWS = Public Water System; GW = Ground Water; SW = Surface Water;"% PWS > MRL" is the proportion of systems with at least one analytic result equal to
or greater than the MRL.
- Massachusetts data not included in "19 States" summary statistics for Metolachlor.
- The highlighted States are part of the 20-State Round 2 Cross-Section.
- The HRL used for metolachlor is 70 ug/L.
C-2
-------
Appendix C. Detailed Round 2 Data Summary
Table C.1.C. Round 2 Data - Metolachlor Occurrence in Public Water Systems - Based on Population Served
STATE
Tribes (06)
AL
AR
AZ
CA
CO
CT
IN
KY
LA
MA
MD
ME
Ml
MN
MO
MS
NC
ND
NH
NJ
NM
OH
OK
OR
PA
Rl
SC
SD
TN
TX
VT
WA
Wl
TOTAL
20 STATES
19 STATES1
TOTAL
POP
SERVED
9,500
1,549,257
3,530,819
1,802,411
184,262
885,780
4,350,399
4,154,030
3,399,893
1,732,871
651,824
478,189
441,328
1,352,305
8,917,037
2,989
2,287,248
6,104,554
722,671
2,570,542
260,764
10,304,341
369,364
3,012,463
59,101,488
47,984,353
47,098,573
GWPOP
SERVED
9,500
25,947
791,316
404,353
160,372
5,795
107,685
487,444
1 ,879,382
2,139,231
590,275
485,104
227,270
138,778
1,211,125
3,102,837
0
698,065
345,376
101,600
735,470
3,014
561,815
108,156
1,429,290
15,749,200
14,387,312
14,279,627
SWPOP
SERVED
0
700
757,941
3,126,466
1,642,039
178,467
778,095
3,862,955
2,274,648
1 ,260,662
1,142,596
166,720
250,919
302,550
141,180
5,814,200
2,989
1,589,183
5,759,178
621,071
1 ,835,072
257,750
9,742,526
261,208
1,583,173
43,352,288
33,597,041
32,818,946
% POP
>MRL
0.00%
0.00%
0.00%
0.04%
0.73%
30.10%
13.47%
0.13%
1 .23%
0.38%
9.94%
2.74%
0.00%
0.00%
0.00%
5.50%
0.00%
0.00%
48.02%
9.62%
0.00%
0.00%
44.41%
0.07%
0.00%
14.41%
11.61%
1 1 .58%
% GW POP
>MRL
0.00%
0.00%
0.00%
0.00%
8.19%
0.00%
16.00%
0.12%
0.00%
0.07%
0.00%
3.68%
0.00%
0.00%
0.00%
0.00%
0.00%
0.01%
12.41%
68.41%
0.00%
0.00%
1 .76%
0.24%
0.00%
1.10%
0.81%
0.70%
% SW POP
>MRL
0.00%
0.00%
0.00%
0.05%
0.00%
31.08%
13.12%
0.13%
2.25%
0.91%
15.08%
0.00%
0.00%
0.00%
0.00%
8.43%
0.00%
0.00%
50.15%
0.00%
0.00%
0.00%
46.86%
0.00%
0.00%
19.25%
16.24%
16.31%
% POP
> 1/2 HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
%GW
POP
> 1/2 HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
%sw
POP
> 1/2 HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
% POP
>HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
%GW
POP
>HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
%sw
POP
>HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
PWS = Public Water System; GW= Ground Water; SW= Surface Water;"% POP >MRL" is the proportion of the total population served by systems with at
least one analytic result equal to or greater than the MRL.
- Massachusetts data not included in "19 States" summary statistics for Metolachlor.
- The highlighted States are part of the 20-State Round 2 Cross-Section.
- The HRL used for metolachlor is 70 pg/L.
C-3
-------
Appendix C. Detailed Round 2 Data Summary
Table C.2.a. Round 2 Data - 1,3-Dichloropropene Occurrence in Public Water Systems - Based on Number of Samples
STATE
Tribes (06)
AK
AL
AR
AZ
CA
CO
CT
IN
KY
LA
MA
MD
ME
Ml
MN
MO
MS
NC
ND
NH
NJ
NM
OH
OK
OR
PA
Rl
SC
SD
TN
TX
VT
WA
Wl
TOTAL
20 STATES
TOTAL
UNIQUE
PWS
21
625
407
16
831
86
86
181
1,310
419
976
744
2,735
1,480
1,053
1,505
296
687
12
718
2,232
1,081
102
23
77
526
715
18,944
16,787
TOTAL #
SAMPLES
30
3,535
1,352
81
2,643
2,265
153
354
4,055
1,822
4,871
3,540
13,929
6,381
1,071
2,854
382
944
15
4,830
17,788
2,617
291
28
533
1,597
1,427
79,388
70,631
#GW
SAMPLES
29
2,596
1,078
61
1,693
934
147
128
3,451
1,371
4,320
3,138
12,281
6,205
980
2,455
316
898
12
4,613
16,432
2,071
241
22
191
1,405
1,279
68,347
62,095
#SW
SAMPLES
1
939
274
20
950
1,331
6
226
604
451
551
402
1,648
176
91
399
66
46
3
217
1,356
546
50
6
342
192
148
1 1 ,041
8,536
% TOTAL
SAMPLES
>MRL
0.00%
0.03%
0.00%
0.00%
0.00%
0.04%
0.00%
0.00%
0.00%
0.05%
0.02%
0.00%
0.00%
1 .00%
0.00%
0.32%
0.00%
0.00%
0.00%
0.00%
0.02%
0.04%
0.00%
0.00%
0.00%
0.00%
0.00%
0.10%
0.11%
%GW
SAMPLES
>MRL
0.00%
0.04%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.07%
0.02%
0.00%
0.00%
0.81%
0.00%
0.29%
0.00%
0.00%
0.00%
0.00%
0.02%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.09%
0.10%
%sw
SAMPLES
>MRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.08%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
7.95%
0.00%
0.50%
0.00%
0.00%
0.00%
0.00%
0.00%
0.18%
0.00%
0.00%
0.00%
0.00%
0.00%
0.16%
0.20%
MIN
VALUE
(M9/L)
< 0.50
< 0.00
< 0.00
< 0.20
< 0.00
< 0.00
< 0.10
< 0.10
< 0.50
< 0.00
< 0.50
< 0.00
< 0.00
< 0.00
< 0.00
< 0.00
< 0.00
< 0.00
< 0.14
< 0.50
< 0.50
< 0.00
< 0.00
< 0.50
< 0.00
< 0.00
< 0.00
< 0.00
< 0.00
99%
VALUE
(M9/L)
< 1.00
< 0.00
< 0.08
< 0.50
< 0.00
< 0.00
< 1.00
< 1.00
< 0.50
< 0.50
< 0.50
< 0.00
< 0.00
0.20
< 0.00
< 0.00
< 1.00
< 0.00
< 1.61
< 1.00
< 0.50
< 0.00
< 1.00
< 0.50
< 0.00
< 0.00
< 0.00
< 0.50
< 0.50
MAX
VALUE
(M9/L)
< 1.00
39.00
< 0.08
< 0.50
< 0.00
0.35
< 1.00
< 1.00
< 0.50
0.99
0.60
< 0.00
< 0.00
22.00
< 0.00
0.50
< 1.00
< 0.00
< 1.61
< 1.00
1.60
0.50
< 1.00
< 0.50
< 0.00
< 0.00
< 0.00
39.00
39.00
MIN
DETECTS
(M9/L)
39.00
0.35
0.99
0.60
0.20
0.50
0.62
0.50
0.20
0.20
MEDIAN
DETECTS
(M9/L)
39.00
0.35
0.99
0.60
0.40
0.50
1.15
0.50
0.50
0.50
PWS = Public Water System; GW= Ground Water; SW= Surface Water; MRL= Minimum Reporting Limit; Min, 99%, and Max Value = the minimum, the 99th
percentile value, and the maximum value of all samples; Min and Median Detects = the minimum and median of all sample detects.
- The highlighted States are part of the 20-State Round 2 Cross-Section.
- Less-than (<) values indicate MRL values. Some systems did not report MRL values. In the data, these MRL values are represented by zeros (e.g "< 0.00").
C-4
-------
Appendix C. Detailed Round 2 Data Summary
Table C.2.b. Round 2 Data -1,3-Dichloropropene Occurrence in Public Water Systems - Based on Number of Systems
STATE
Tribes (06)
AK
AL
AR
AZ
CA
CO
CT
IN
KY
LA
MA
MD
ME
Ml
MN
MO
MS
NC
ND
NH
NJ
NM
OH
OK
OR
PA
Rl
SC
SD
TN
TX
VT
WA
Wl
TOTAL
20 STATES
TOTAL #
SAMPLES
30
3,535
1,352
81
2,643
2,265
153
354
4,055
1,822
4,871
3,540
13,929
6,381
1,071
2,854
382
944
15
4,830
17,788
2,617
291
28
533
1,597
1,427
79,388
70,631
TOTAL
UNIQUE
PWS
21
625
407
16
831
86
86
181
1,310
419
976
744
2,735
1,480
1,053
1,505
296
687
12
718
2,232
1,081
102
23
77
526
715
18,944
16,787
#GW
PWS
20
481
319
12
619
44
80
84
1,241
345
920
676
2,644
1,450
964
1,329
258
656
10
692
2,050
931
92
17
30
466
668
17,098
15,178
#SW
PWS
1
144
88
4
212
42
6
97
69
74
56
68
91
30
89
176
38
31
2
26
182
150
10
6
47
60
47
1,846
1,609
% PWS
>MRL
0.00%
0.16%
0.00%
0.00%
0.00%
1.16%
0.00%
0.00%
0.00%
0.24%
0.10%
0.00%
0.00%
2.91%
0.00%
0.53%
0.00%
0.00%
0.00%
0.00%
0.13%
0.09%
0.00%
0.00%
0.00%
0.00%
0.00%
0.31%
0.35%
%GW
PWS
>MRL
0.00%
0.21%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.29%
0.11%
0.00%
0.00%
2.48%
0.00%
0.45%
0.00%
0.00%
0.00%
0.00%
0.15%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.28%
0.32%
%sw
PWS
>MRL
0.00%
0.00%
0.00%
0.00%
0.00%
2.38%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
23.33%
0.00%
1.14%
0.00%
0.00%
0.00%
0.00%
0.00%
0.67%
0.00%
0.00%
0.00%
0.00%
0.00%
0.60%
0.62%
% PWS
> 1/2 HRL
0.00%
0.16%
0.00%
0.00%
0.00%
1.16%
0.00%
0.00%
0.00%
0.24%
0.10%
0.00%
0.00%
2.36%
0.00%
0.53%
0.00%
0.00%
0.00%
0.00%
0.13%
0.09%
0.00%
0.00%
0.00%
0.00%
0.00%
0.27%
0.30%
%GW
PWS
> 1/2 HRL
0.00%
0.21%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.29%
0.11%
0.00%
0.00%
2.00%
0.00%
0.45%
0.00%
0.00%
0.00%
0.00%
0.15%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.24%
0.27%
%sw
PWS
> 1/2 HRL
0.00%
0.00%
0.00%
0.00%
0.00%
2.38%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
20.00%
0.00%
1.14%
0.00%
0.00%
0.00%
0.00%
0.00%
0.67%
0.00%
0.00%
0.00%
0.00%
0.00%
0.54%
0.56%
% PWS
>HRL
0.00%
0.16%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.24%
0.10%
0.00%
0.00%
1 .55%
0.00%
0.53%
0.00%
0.00%
0.00%
0.00%
0.13%
0.09%
0.00%
0.00%
0.00%
0.00%
0.00%
0.20%
0.23%
%GW
PWS
>HRL
0.00%
0.21%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.29%
0.11%
0.00%
0.00%
1.17%
0.00%
0.45%
0.00%
0.00%
0.00%
0.00%
0.15%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.17%
0.19%
%sw
PWS
>HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
20.00%
0.00%
1.14%
0.00%
0.00%
0.00%
0.00%
0.00%
0.67%
0.00%
0.00%
0.00%
0.00%
0.00%
0.49%
0.56%
PWS = Public Water System; GW = Ground Water; SW = Surface Water;"% PWS > MRL", "> Yz HRL", and "> HRL" are the proportion of systems with at least
one analytic result equal to or greater than the MRL, exceeding the 1/2 HRL benchmark, and exceeding the HRL benchmark, respectively.
- The highlighted States are part of the 20-State Round 2 Cross-Section.
- The HRL used for 1,3-Dichloropropene is 0.4 [ig/L.
C-5
-------
Appendix C. Detailed Round 2 Data Summary
Table C.2.C. Round 2 Data -1,3-Dichloropropene Occurrence in Public Water Systems - Based on Population Served
STATE
Tribes (06)
AK
AL
AR
AZ
CA
CO
CT
IN
KY
LA
MA
MD
ME
Ml
MN
MO
MS
NC
ND
NH
NJ
NM
OH
OK
OR
PA
Rl
SC
SD
TN
TX
VT
WA
Wl
TOTAL
20 STATES
TOTAL POP
SERVED
49,986
480,068
1 ,301 ,907
1,171,659
3,576,561
2,330,321
392,657
2,212,474
4,535,907
3,402,403
5,012,575
675,407
3,237,068
3,622,825
1 ,554,953
4,690,803
478,189
476,008
27,774
1 ,351 ,088
9,095,427
1 ,820,043
689,332
44,854
792,356
417,057
2,273,921
55,713,623
45,951 ,052
GWPOP
SERVED
41,486
204,976
612,648
529,897
440,514
211,367
349,013
179,998
2,598,561
1 ,326,669
671,808
244,096
1,920,249
2,362,163
1,131,780
1,186,827
227,270
169,280
5,374
1,212,253
3,311,171
690,965
112,386
21,240
105,819
160,828
1,417,977
21,446,615
17,423,030
SWPOP
SERVED
8,500
275,092
689,259
641 ,762
3,136,047
2,118,954
43,644
2,032,476
1 ,937,346
2,075,734
4,340,767
431,311
1,316,819
1 ,260,662
423,173
3,503,976
250,919
306,728
22,400
138,835
5,784,256
1,129,078
576,946
23,614
686,537
256,229
855,944
34,267,008
28,528,022
% POP
>MRL
0.00%
0.83%
0.00%
0.00%
0.00%
0.32%
0.00%
0.00%
0.01%
0.004%
0.00%
0.00%
5.78%
0.00%
0.55%
0.00%
0.00%
0.00%
0.00%
0.11%
0.16%
0.00%
0.00%
0.00%
0.00%
0.00%
0.47%
0.55%
%GW
POP
>MRL
0.00%
1 .95%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.03%
0.03%
0.00%
0.00%
7.43%
0.00%
0.59%
0.00%
0.00%
0.00%
0.00%
0.30%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.92%
1.13%
%sw
POP
>MRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.35%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
2.69%
0.00%
0.54%
0.00%
0.00%
0.00%
0.00%
0.00%
0.26%
0.00%
0.00%
0.00%
0.00%
0.00%
0.18%
0.19%
% POP
> 1/2 HRL
0.00%
0.83%
0.00%
0.00%
0.00%
0.32%
0.00%
0.00%
0.01%
0.004%
0.00%
0.00%
4.13%
0.00%
0.55%
0.00%
0.00%
0.00%
0.00%
0.11%
0.16%
0.00%
0.00%
0.00%
0.00%
0.00%
0.36%
0.42%
%GW
POP
> 1/2 HRL
0.00%
1 .95%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.03%
0.03%
0.00%
0.00%
5.06%
0.00%
0.59%
0.00%
0.00%
0.00%
0.00%
0.30%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.66%
0.81%
% SW POP
> 1/2 HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.35%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
2.37%
0.00%
0.54%
0.00%
0.00%
0.00%
0.00%
0.00%
0.26%
0.00%
0.00%
0.00%
0.00%
0.00%
0.17%
0.18%
% POP
>HRL
0.00%
0.83%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.01%
0.004%
0.00%
0.00%
2.99%
0.00%
0.55%
0.00%
0.00%
0.00%
0.00%
0.11%
0.16%
0.00%
0.00%
0.00%
0.00%
0.00%
0.27%
0.33%
%GW
POP
>HRL
0.00%
1 .95%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.03%
0.03%
0.00%
0.00%
3.31%
0.00%
0.59%
0.00%
0.00%
0.00%
0.00%
0.30%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.47%
0.57%
% SW POP
>HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
2.37%
0.00%
0.54%
0.00%
0.00%
0.00%
0.00%
0.00%
0.26%
0.00%
0.00%
0.00%
0.00%
0.00%
0.15%
0.18%
PWS = Public Water System; GW= Ground Water; SW= Surface Water;"% POP >MRL", "> Vi HRL", and "> HRL" are the proportion of the total population
served by systems with at least one analytic result equal to or greater than the MRL, exceeding the Vi HRL benchmark, and exceeding the HRL benchmark,
respectively.
- The highlighted States are part of the 20-State Round 2 Cross-Section.
- The HRL used for 1,3-Dichloropropene is 0.4 pg/L.
C-6
-------
Appendix C. Detailed Round 2 Data Summary
Table C.3.a. Round 2 Data -1,1,2,2-Tetrachloroethane Occurrence in Public Water Systems - Based on Number of Samples
STATE
Tribes (06)
TOTAL
UNIQUE
PWS
22
625
TOTAL #
SAMPLES
32
3,548
#GW
SAMPLES
31
2,604
#SW
SAMPLES
1
944
% TOTAL
SAMPLES
>MRL
0.00%
0.00%
%GW
SAMPLES
>MRL
0.00%
0.00%
%sw
SAMPLES
>MRL
0.00%
0.00%
MIN
VALUE
(H9/L)
< 0.50
< 0.00
99%
VALUE
(H9/L)
< 1.00
< 0.00
MAX
VALUE
(H9/L)
< 1.00
< 0.00
MIN
DETECTS
(M9/L)
MEDIAN
DETECTS
(M9/L)
AL
AR
AZ
CA
CO
CT
IN
KY
LA
MA
MD
ME
Ml
MN
MO
MS
NC
ND
NH
NJ
NM
OH
OK
OR
PA
Rl
SC
SD
TN
TX
VT
WA
Wl
TOTAL
20 STATES
407
121
16
831
86
69
433
1,310
418
976
744
2,735
1,558
1,413
1,785
296
681
16
716
2,232
792
1,085
114
907
27
77
4,412
558
2,547
200
28,209
24,800
1,352
244
81
2,643
2,280
142
1,972
4,055
1,823
4,869
3,559
6,965
6,864
3,773
3,393
382
935
19
4,820
17,788
4,746
2,658
423
3,984
35
531
16,849
1,806
9,549
360
112,480
98,911
1,078
172
61
1,693
918
129
899
3,451
1,372
4,319
3,154
6,141
6,678
3,275
2,906
316
892
16
4,602
16,432
3,492
2,096
338
3,424
26
191
12,190
1,600
8,665
356
93,517
83,142
274
72
20
950
1,362
13
1,073
604
451
550
405
824
186
498
487
66
43
3
218
1,356
1,254
562
85
560
9
340
4,659
206
884
4
18,963
15,769
0.00%
0.00%
0.00%
0.00%
0.53%
0.00%
0.00%
0.00%
0.05%
0.02%
0.03%
0.01%
0.00%
0.00%
0.32%
0.00%
0.00%
0.00%
0.00%
0.01%
0.02%
0.00%
0.00%
0.00%
0.00%
0.00%
0.01%
0.00%
0.01%
0.00%
0.03%
0.02%
0.00%
0.00%
0.00%
0.00%
0.22%
0.00%
0.00%
0.00%
0.07%
0.00%
0.00%
0.02%
0.00%
0.00%
0.31%
0.00%
0.00%
0.00%
0.00%
0.01%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.02%
0.02%
0.00%
0.00%
0.00%
0.00%
0.73%
0.00%
0.00%
0.00%
0.00%
0.18%
0.25%
0.00%
0.00%
0.00%
0.41%
0.00%
0.00%
0.00%
0.00%
0.00%
0.08%
0.00%
0.00%
0.00%
0.00%
0.00%
0.04%
0.00%
0.11%
0.00%
0.09%
0.05%
< 0.00
< 0.20
< 0.20
< 0.00
< 0.00
< 0.50
< 0.10
< 0.50
< 0.00
< 0.10
< 0.00
< 0.00
< 0.00
< 0.00
< 0.00
< 0.00
< 0.00
< 0.23
< 0.50
< 0.50
< 0.00
< 0.00
< 0.00
< 0.00
< 0.50
< 0.00
< 1.00
< 0.00
< 0.00
< 0.00
< 0.00
< 0.00
< 0.10
< 2.00
< 0.50
< 0.00
< 0.00
< 2.00
< 2.50
< 0.50
< 0.50
< 0.50
< 0.00
< 0.00
< 0.20
< 1.00
< 0.00
< 0.50
< 0.00
< 1.32
< 1.00
< 0.50
< 0.00
< 0.00
< 1.00
< 0.50
< 0.50
< 0.00
< 1.00
< 0.00
< 0.00
< 3.00
< 1.00
< 1.00
< 0.10
< 2.00
< 0.50
< 0.00
3.90
< 2.00
< 2.50
< 0.50
1.40
0.50
2.00
0.50
< 0.40
< 1.00
0.50
< 0.50
< 0.00
< 1.32
< 1.00
0.56
0.80
< 0.00
< 1.00
< 0.50
< 0.50
< 0.00
1.60
< 0.50
0.30
< 3.00
3.90
2.00
0.06
1.40
0.10
2.00
0.50
0.50
0.50
0.80
1.50
0.30
0.06
0.10
0.12
1.40
0.10
2.00
0.50
0.50
0.53
0.80
1.55
0.30
0.50
0.50
PWS = Public Water System; GW = Ground Water; SW= Surface Water; MRL= Minimum Reporting Limit; Min, 99%, and Max Value = the minimum, the 99th percentile
value, and the maximum value of all samples; Min and Median Detects = the minimum and median of all sample detects.
- The highlighted States are part of the 20-State Round 2 Cross-Section.
- Less-than (<) values indicate MRL values. Some systems did not report MRL values. In the data, these MRL values are represented by zeros (e.g "< 0.00").
C-7
-------
Appendix C. Detailed Round 2 Data Summary
Table C.3.b. Round 2 Data - 1,1,2,2-Tetrachloroethane Occurrence in Public Water Systems - Based on Number of Systems
STATE
Tribes (06)
AK
AL
AR
AZ
CA
CO
CT
IN
KY
LA
MA
MD
ME
Ml
MN
MO
MS
NC
ND
NH
NJ
NM
OH
OK
OR
PA
Rl
SC
SD
TN
TX
VT
WA
Wl
TOTAL
20 STATES
TOTAL #
SAMPLES
32
3,548
1,352
244
81
2,643
2,280
142
1,972
4,055
1,823
4,869
3,559
6,965
6,864
3,773
3,393
382
935
19
4,820
17,788
4,746
2,658
423
3,984
35
531
16,849
1,806
9,549
360
112,480
98,911
TOTAL
UNIQUE
PWS
22
625
407
121
16
831
86
69
433
1,310
418
976
744
2,735
1,558
1,413
1,785
296
681
16
716
2,232
792
1,085
114
907
27
77
4,412
558
2,547
200
28,209
24,800
#GW
PWS
21
481
319
106
12
619
44
62
208
1,241
344
920
676
2,644
1,528
1,297
1,592
258
651
14
689
2,050
541
934
102
806
19
30
3,825
494
2,428
197
25,152
22,106
#SW
PWS
1
144
88
15
4
212
42
7
225
69
74
56
68
91
30
116
193
38
30
2
27
182
251
151
12
101
8
47
587
64
119
3
3,057
2,694
% PWS
>MRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
3.49%
0.00%
0.00%
0.00%
0.24%
0.10%
0.13%
0.04%
0.00%
0.00%
0.50%
0.00%
0.00%
0.00%
0.00%
0.09%
0.13%
0.00%
0.00%
0.00%
0.00%
0.00%
0.05%
0.00%
0.04%
0.00%
0.08%
0.08%
%GW
PWS
>MRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
4.55%
0.00%
0.00%
0.00%
0.29%
0.00%
0.00%
0.04%
0.00%
0.00%
0.44%
0.00%
0.00%
0.00%
0.00%
0.10%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.05%
0.05%
%sw
PWS
>MRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
2.38%
0.00%
0.00%
0.00%
0.00%
1 .79%
1 .47%
0.00%
0.00%
0.00%
1 .04%
0.00%
0.00%
0.00%
0.00%
0.00%
0.40%
0.00%
0.00%
0.00%
0.00%
0.00%
0.34%
0.00%
0.84%
0.00%
0.29%
0.30%
% PWS
> 1/2 HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
1.16%
0.00%
0.00%
0.00%
0.24%
0.00%
0.13%
0.04%
0.00%
0.00%
0.50%
0.00%
0.00%
0.00%
0.00%
0.09%
0.13%
0.00%
0.00%
0.00%
0.00%
0.00%
0.05%
0.00%
0.04%
0.00%
0.07%
0.07%
%GW
PWS
> 1/2 HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
2.27%
0.00%
0.00%
0.00%
0.29%
0.00%
0.00%
0.04%
0.00%
0.00%
0.44%
0.00%
0.00%
0.00%
0.00%
0.10%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.05%
0.05%
%sw
PWS
> 1/2 HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
1 .47%
0.00%
0.00%
0.00%
1 .04%
0.00%
0.00%
0.00%
0.00%
0.00%
0.40%
0.00%
0.00%
0.00%
0.00%
0.00%
0.34%
0.00%
0.84%
0.00%
0.23%
0.26%
% PWS
>HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
1.16%
0.00%
0.00%
0.00%
0.24%
0.00%
0.13%
0.04%
0.00%
0.00%
0.50%
0.00%
0.00%
0.00%
0.00%
0.09%
0.13%
0.00%
0.00%
0.00%
0.00%
0.00%
0.05%
0.00%
0.00%
0.00%
0.06%
0.07%
%GW
PWS
>HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
2.27%
0.00%
0.00%
0.00%
0.29%
0.00%
0.00%
0.04%
0.00%
0.00%
0.44%
0.00%
0.00%
0.00%
0.00%
0.10%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.05%
0.05%
%sw
PWS
>HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
1 .47%
0.00%
0.00%
0.00%
1 .04%
0.00%
0.00%
0.00%
0.00%
0.00%
0.40%
0.00%
0.00%
0.00%
0.00%
0.00%
0.34%
0.00%
0.00%
0.00%
0.20%
0.22%
PWS = Public Water System; GW = Ground Water; SW = Surface Water;"% PWS > MRL", "> Vi HRL", and "> HRL" are the proportion of systems with at least
one analytic result equal to or greater than the MRL, exceeding the Vi HRL benchmark, and exceeding the HRL benchmark, respectively.
- The highlighted States are part of the 20-State Round 2 Cross-Section.
- The HRL used for 1,1,2,2-Tetrachloroethane is 0.4 pg/L.
Co
-O
-------
Appendix C. Detailed Round 2 Data Summary
Table C.3.C. Round 2 Data - 1,1,2,2-Tetrachloroethane Occurrence in Public Water Systems - Based on Population Served
STATE
Tribes (06)
AK
AL
AR
AZ
CA
CO
CT
IN
KY
LA
MA
MD
ME
Ml
MN
MO
MS
NC
ND
NH
NJ
NM
OH
OK
OR
PA
Rl
SC
SD
TN
TX
VT
WA
Wl
TOTAL
20 STATES
TOTAL POP
SERVED
51 ,486
480,068
1 ,301 ,907
862,408
1,171,659
3,576,561
2,330,321
250,248
3,047,973
4,535,907
3,401,953
5,012,575
675,407
3,237,068
3,648,944
2,297,960
4,927,499
478,189
466,045
28,130
1,352,001
9,095,427
3,012,419
2,280,323
759,625
2,556,069
57,723
792,356
17,945,854
419,236
4,296,465
342,561
84,692,367
71,294,263
GWPOP
SERVED
42,986
204,976
612,648
181,619
529,897
440,514
211,367
214,333
296,772
2,598,561
1,326,219
671 ,808
244,096
1,920,249
2,388,282
1,477,191
1,254,514
227,270
168,817
5,730
1,211,338
3,311,171
639,513
691,245
132,623
708,949
25,359
105,819
6,369,774
161,487
2,389,339
305,110
31,069,576
25,978,359
SWPOP
SERVED
8,500
275,092
689,259
680,789
641 ,762
3,136,047
2,118,954
35,915
2,751,201
1 ,937,346
2,075,734
4,340,767
431,311
1,316,819
1 ,260,662
820,769
3,672,985
250,919
297,228
22,400
140,663
5,784,256
2,372,906
1 ,589,078
627,002
1,847,120
32,364
686,537
1 1 ,576,080
257,749
1,907,126
37,451
53,622,791
45,315,904
% POP
>MRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
1 .32%
0.00%
0.00%
0.03%
29.92%
0.32%
0.002%
0.00%
0.00%
0.54%
0.00%
0.00%
0.00%
0.00%
0.17%
0.02%
0.00%
0.00%
0.00%
0.00%
0.00%
0.06%
0.00%
7.12%
0.00%
2.23%
2.61%
%GW
POP
>MRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
12.98%
0.00%
0.00%
0.07%
0.00%
0.00%
0.003%
0.00%
0.00%
0.62%
0.00%
0.00%
0.00%
0.00%
0.47%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.17%
0.09%
%sw
POP
>MRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.16%
0.00%
0.00%
0.00%
34.56%
0.50%
0.00%
0.00%
0.00%
0.51%
0.00%
0.00%
0.00%
0.00%
0.00%
0.03%
0.00%
0.00%
0.00%
0.00%
0.00%
0.09%
0.00%
16.05%
0.00%
3.43%
4.06%
% POP
> 1/2 HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.42%
0.00%
0.00%
0.03%
0.00%
0.32%
0.002%
0.00%
0.00%
0.54%
0.00%
0.00%
0.00%
0.00%
0.17%
0.02%
0.00%
0.00%
0.00%
0.00%
0.00%
0.06%
0.00%
7.12%
0.00%
0.44%
0.51%
%GW
POP
> 1/2 HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
4.67%
0.00%
0.00%
0.07%
0.00%
0.00%
0.003%
0.00%
0.00%
0.62%
0.00%
0.00%
0.00%
0.00%
0.47%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.11%
0.09%
% SW POP
> 1/2 HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.50%
0.00%
0.00%
0.00%
0.51%
0.00%
0.00%
0.00%
0.00%
0.00%
0.03%
0.00%
0.00%
0.00%
0.00%
0.00%
0.09%
0.00%
16.05%
0.00%
0.63%
0.75%
% POP
>HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.42%
0.00%
0.00%
0.03%
0.00%
0.32%
0.002%
0.00%
0.00%
0.54%
0.00%
0.00%
0.00%
0.00%
0.17%
0.02%
0.00%
0.00%
0.00%
0.00%
0.00%
0.06%
0.00%
0.00%
0.00%
0.08%
0.08%
%GW
POP
>HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
4.67%
0.00%
0.00%
0.07%
0.00%
0.00%
0.003%
0.00%
0.00%
0.62%
0.00%
0.00%
0.00%
0.00%
0.47%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.11%
0.09%
%sw
POP
>HRL
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.50%
0.00%
0.00%
0.00%
0.51%
0.00%
0.00%
0.00%
0.00%
0.00%
0.03%
0.00%
0.00%
0.00%
0.00%
0.00%
0.09%
0.00%
0.00%
0.00%
0.06%
0.07%
PWS = Public Water System; GW = Ground Water; SW = Surface Water;"% POP > MRL", "> Vi HRL", and "> HRL" are the proportion of the total population
served by systems with at least one analytic result equal to or greater than the MRL, exceeding the Vi HRL benchmark, and exceeding the HRL benchmark,
respectively.
- The highlighted States are part of the 20-State Round 2 Cross-Section.
-The HRL used for 1,1,2,2-Tetrachloroethane is0.4 pg/L.
C-9
-------
-------
Appendix D. Detailed NIRS Data Summary
for Boron
Table D. 1 .a NIRS Data - Boron Occurrence in Public Water Systems
-------
-------
Appendix D. Detailed NIRS Data Summary
Table D.1. NIRS Data - Boron Occurrence in Public Water Systems
State
AK
AL
AR
AZ
CA
CO
CT
DE
FL
GA
IA
ID
IL
IN
KS
KY
LA
MA
MD
ME
Ml
MN
MO
MS
MT
NC
ND
NE
NH
NJ
NM
NV
NY
OH
OK
OR
PA
PR
Rl
SC
SD
TN
TX
UT
VA
VT
WA
Wl
WV
WY
Total
# Samples
8
8
9
14
60
10
23
10
56
23
28
12
46
19
6
8
26
7
6
7
25
19
21
26
11
44
19
19
10
6
7
2
57
25
12
8
36
1
1
18
8
9
74
10
30
12
52
30
8
3
989
# Samples
>MRL
7
3
9
13
56
9
19
8
55
14
28
8
45
19
6
7
25
4
5
3
25
18
15
19
11
17
19
19
3
1
7
2
43
25
12
7
29
1
10
8
5
74
9
14
3
37
25
6
3
810
%
Samples
>MRL
87.50%
37.50%
100.00%
92.86%
93.33%
90.00%
82.61%
80.00%
98.21%
60.87%
100.00%
66.67%
97.83%
100.00%
100.00%
87.50%
96.15%
57.14%
83.33%
42.86%
100.00%
94.74%
71 .43%
73.08%
100.00%
38.64%
100.00%
100.00%
30.00%
16.67%
100.00%
100.00%
75.44%
100.00%
100.00%
87.50%
80.56%
100.00%
0.00%
55.56%
100.00%
55.56%
100.00%
90.00%
46.67%
25.00%
71.15%
83.33%
75.00%
100.00%
81.90%
# Detects
> 1/2 HRL
1
5
1
1
7
3
1
1
1
7
1
1
2
8
2
1
43
% Detects
> 1/2 HRL
0.00%
0.00%
0.00%
7.14%
8.33%
0.00%
0.00%
10.00%
0.00%
0.00%
3.57%
0.00%
15.22%
0.00%
0.00%
0.00%
1 1 .54%
0.00%
0.00%
0.00%
4.00%
5.26%
0.00%
0.00%
9.09%
0.00%
36.84%
0.00%
0.00%
0.00%
0.00%
0.00%
1 .75%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
5.56%
25.00%
0.00%
10.81%
0.00%
6.67%
0.00%
1.92%
0.00%
0.00%
0.00%
4.35%
# Detects
>HRL
2
1
1
1
5
1
1
3
2
17
%
Detects
>HRL
0.00%
0.00%
0.00%
0.00%
3.33%
0.00%
0.00%
0.00%
0.00%
0.00%
3.57%
0.00%
2.17%
0.00%
0.00%
0.00%
3.85%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
26.32%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
5.56%
12.50%
0.00%
4.05%
0.00%
6.67%
0.00%
0.00%
0.00%
0.00%
0.00%
1.72%
Min Value
(mg/L)
< 0.01
< 0.01
0.01
< 0.01
< 0.01
< 0.01
< 0.01
< 0.01
< 0.01
< 0.01
0.01
< 0.01
< 0.01
0.01
0.02
< 0.01
< 0.01
< 0.01
< 0.01
< 0.01
0.01
< 0.01
< 0.01
< 0.01
0.01
< 0.01
0.02
0.01
< 0.01
< 0.01
0.02
0.01
< 0.01
0.01
0.01
< 0.01
< 0.01
0.04
< 0.01
< 0.01
0.06
< 0.01
0.01
< 0.01
< 0.01
< 0.01
< 0.01
< 0.01
< 0.01
0.03
< 0.01
99%
Value
(mg/L)
0.12
0.41
0.60
1.00
3.89
0.22
0.14
0.89
0.24
0.06
1.44
0.13
1.63
0.22
0.27
0.12
2.82
0.02
0.68
0.03
0.79
1.11
0.63
0.50
1.21
0.64
3.95
0.22
0.06
0.10
0.20
0.34
0.83
0.61
0.51
0.25
0.41
0.04
< 0.01
2.44
2.87
0.04
3.15
0.16
2.12
0.02
0.93
0.59
0.12
0.39
2.44
Max
Value
(mg/L)
0.12
0.41
0.60
1.00
3.89
0.22
0.14
0.89
0.24
0.06
1.44
0.13
1.63
0.22
0.27
0.12
2.82
0.02
0.68
0.03
0.79
1.11
0.63
0.50
1.21
0.64
3.95
0.22
0.06
0.10
0.20
0.34
0.83
0.61
0.51
0.25
0.41
0.04
< 0.01
2.44
2.87
0.04
3.15
0.16
2.12
0.02
0.93
0.59
0.12
0.39
3.95
Min
Detects
(mg/L)
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.02
0.01
0.01
0.01
0.08
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.02
0.01
0.01
0.10
0.02
0.01
0.01
0.01
0.01
0.01
0.01
0.04
0.01
0.06
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.03
0.01
Median
Detects
(mg/L)
0.04
0.01
0.09
0.04
0.07
0.04
0.02
0.01
0.02
0.01
0.06
0.04
0.32
0.08
0.07
0.02
0.05
0.01
0.13
0.01
0.04
0.18
0.04
0.13
0.12
0.02
0.49
0.05
0.02
0.10
0.07
0.18
0.04
0.05
0.07
0.01
0.05
0.04
0.01
0.25
0.01
0.17
0.03
0.14
0.01
0.02
0.02
0.03
0.06
0.05
PWS = Public Water System; GW = Ground Water; SW = Surface Water; MRL= Minimum Reporting Limit; "# (or %) PWS > MRL", "> 1/2 HRL", and
"> HRL" are the number (or proportion) of systems with at least one analytic result equal to or greater than the MRL, exceeding the % HRL
benchmark, and exceeding the HRL benchmark, respectively; Min, 99%, and Max Value = the minimum, the 99th percentile value, and the maximum
value of all samples; Min and Median Detects = the minimum and median of all sample detects.
- Only one sample was taken per system, so # samples = # systems.
- Less-than (<) values indicate MRL values.
- The HRL used for boron is 1.4 mg/L.
D-1
-------
-------
Appendix E. Data Summaries of Occurrence and Population Served
for Four Contaminants Considered During CCL 2 Regulatory Determinations
Table E.I Boron Occurrence Summary Statistics in Ground Water Surveys (MRS)
Table E.2 Metolachlor Occurrence Summary Statistics (Round 2)
Table E.3.a 1,3-Dichloropropene Occurrence Summary Statistics (Round 1)
Table E.3.b 1,3-Dichloropropene Occurrence Summary Statistics (Round 2)
Table E.4.a 1,1,2,2-Tetrachloroethane Occurrence Summary Statistics (Round 1)
Table E.4.b 1,1,2,2-Tetrachloroethane Occurrence Summary Statistics (Round 2)
-------
-------
Determinations
Table E.1. Boron Occurrence Summary Statistics in Ground Water Surveys (NIRS)
Frequency Factors
Total Number of Samples/Systems
99th Percentile Concentration (all samples)
Health Reference Level (HRL)
Minimum Reporting Level (MRL)
Maximum Concentration of Detections
99l Percentile Concentration of Detections
Median Concentration of Detections
Total Population Served
Occurrence by Sample/System
Ground Water PWSs with Detections (> MRL)
Range of NIRS States
Ground Water PWSs > '/2 HRL
Range of NIRS States
Ground Water PWSs > HRL
Range of NIRS States
Occurrence by Population Served
Population Served by GW PWSs with Detections
Range of NIRS States
Population Served by GW PWSs > '/2 HRL
Range of NIRS States
Population Served by GW PWSs > HRL
Range of NIRS States
NIRS Data on Boron
989
2.44 mg/L
1.4mg/L
0.005 mg/L
3.95 mg/L
2.6 mg/L
0.047 mg/L
1,482,153
Number
810
0-74
43
0-8
17
0-5
1,306,048
0 - 343,465
42,702
0 - 20,465
6,443
0 - 2,500
Percentage
81.9%
0 - 100%
4.3%
0 - 37%
1.7%
0 - 26%
88.1%
0 - 100%
2.9%
0 - 34%
0.4%
0 - 34%
National System
& Population Numbers1
59,440
~
~
~
~
~
85,681,696
National Extrapolation
48,682
N/A
2,584
N/A
1,022
N/A
75,501,000
N/A
2,469,000
N/A
372,000
N/A
1. Total PWS and population numbers are from EPA's March 2000 Water Industry Baseline Handbook, 2nd Edition. National extrapolations are generated by multiplying
the system/population percentages and the national Baseline Handbook system/population numbers.
Abbreviations:
PWS = Public Water Systems; GW = Ground Water; N/A = Not Applicable; Total Number of Samples/Systems = total number of samples/systems on record for the
contaminant; 99th Percentile Concentration = the concentration in the 99th percentile sample (out of either all samples or just samples with detections); Median
Concentration of Detections = the concentration in the median sample (out of samples with detections); Total Population Served = the total population served by PWSs for
which sampling results are available; Ground Water PWSs with Detections, PWSs >V2HRL, or PWSs >HRL = GW PWSs with at least one sampling result greater than or
equal to the MRL, exceeding the VzHRL benchmark, or exceeding the HRL benchmark, respectively; Population Served by GW PWSs with Detections, by PWSs >1/2HRL,
or by PWSs >HRL = population served by GW PWSs with at least one sampling result greater than or equal to the MRL, exceeding the VzHRL benchmark, or exceeding the
HRL benchmark, respectively.
Notes:
- Only results at or above the MRL were reported as detections. Concentrations below the MRL are considered non-detects.
E-1
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Appendix E. Data Summaries of Occurrence Population Served for Four Contaminants Considered During CCL 2 Regulatory Determinations
Table E.2. Metolachlor Occurrence Summary Statistics (Round 2)
Frequency Factors
Total Number of Samples
Percent of Samples with Detections
99 Percentile Concentration (all samples)
Health Reference Level (HRLJ
Minimum Reporting Level (MRL) - Range
- (modal value)
Maximum Concentration of Detections
99"1 Percentile Concentration of Detections
Median Concentration of Detections
Total Number of PWSs
Number of GWPWSs
Number of SW PWSs
Total Population
Population of GW PWSs
Population of SW PWSs
Occurrence by System
PWSs with detections (> MRL)
Range across States
GW PWSs with detections
SW PWSs with detections
PWSs > Vz HRL
Range across States
GW PWSs > y2 HRL
SW PWSs > !/2 HRL
PWSs > HRL
Range across States
GW PWSs > HRL
SW PWSs > HRL
Occurrence by Population Served
Population served by PWSs with detections
Range across States
Pop. Served by GW PWSs with detections
Pop. Served by SW PWSs with detections
Population served by PWSs > Vz HRL
Range across States
Pop. Served by GW PWSs > Vi HRL
Pop. Served by SW PWSs > Vi HRL
Population served by PWSs > HRL
Range across States
Pop. Served by GW PWSs > HRL
Pop. Served by SW PWSs > HRL
19 State
Cross-Section
33,930
0.57%
1/2HRL, or PWSs >HRL = PWSs with at least one sampling result greater than or equal to
the MRL, exceeding the 1/?HRL benchmark, or exceeding the HRL benchmark, respectively; Population Served by PWSs with Detections, by PWSs >1/?HRL, or by PWSs >HRL = population
served by PWSs with at least one sampling result greater than or equal to the MRL, exceeding the V^HRL benchmark, or exceeding the HRL benchmark, respectively.
Notes:
- Only results at or above the MRL were reported as detections. Concentrations below the MRL are considered non-detects.
- Because some systems were counted as both ground water and surface water systems and others could not be classified, GW and SW figures might not add up to totals.
- Due to differences between the ratios of GW and SW systems with monitoring results and the national ratio, extrapolated GW and SW figures might not add up to extrapolated totals.
E-2
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Appendix. E. Data Summaries of Occurrence Population Served for Four Contaminants Considered During CCL 2 Regulatory Determinations
Table E.3.a. 1,3-Dichloropropene Occurrence Summary Statistics (Round 1)
Frequency Factors
Total Number of Samples
Percent of Samples with Detections
99 Percentile Concentration (all samples)
Health Reference Level (HRL)
Minimum Reporting Level (MRL) - Range
- (modal value)
Maximum Concentration of Detections
99 Percentile Concentration of Detections
Median Concentration of Detections
Total Number of PWSs
Number of GWPWSs
Number of SW PWSs
Total Population
Population of GW PWSs
Population of SW PWSs
Occurrence by System
PWSs with detections (> MRL)
Range across States
GW PWSs with detections
SW PWSs with detections
PWSs > !/2 HRL
Range across States
GW PWSs >!/2 HRL
SW PWSs >!/2 HRL
PWSs > HRL
Range across States
GW PWSs > HRL
SW PWSs > HRL
Occurrence by Population Served
Population served by PWSs with detections
Range across States
Pop. Served by GW PWSs with detections
Pop. Served by SW PWSs with detections
Population served by PWSs > Vi HRL
Range across States
Pop. Served by GW PWSs > Vi HRL
Pop. Served by SW PWSs > V2 HRL
Population served by PWSs > HRL
Range across States
Pop. Served by GW PWSs > HRL
Pop. Served by SW PWSs > HRL
24 State
Cross-Section1
31,104
0.06%
1/2HRL, orPWSs>HRL = PWSs with at least one sampling result greater than or equal to the MRL,
exceeding the 1/^HRL benchmark, or exceeding the HRL benchmark, respectively; Population Served by PWSs with Detections, by PWSs >1/3HRL, or by PWSs >HRL = population served by
PWSs with at least one sampling result greater than or equal to the MRL, exceeding the 1/^HRL benchmark, or exceeding the HRL benchmark, respectively.
Notes:
- Only results at or above the MRL were reported as detections. Concentrations below the MRL are considered non-detects.
- Because some systems were counted as both ground water and surface water systems and others could not be classified, GW and SW figures might not add up to totals.
- Due to differences between the ratios of GWand SW systems with monitoring results and the national ratio, extrapolated GWand SW figures might not add up to extrapolated totals.
- Due to MRL variability, it is likely that the sampling failed to capture some Y* HRL and HRL exceedances at participating systems, and the Y* HRL and HRL analyses underestimate actual
contaminant occurrence.
E-3
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Appendix E. Data Summaries of Occurrence Population Served for Four Contaminants Considered During CCL 2 Regulatory Determinations
Table E.3.b. 1,3-Dichloropropene Occurrence Summary Statistics (Round 2)
Frequency Factors
Total Number of Samples
Percent of Samples with Detections
99 Percentile Concentration (all samples)
Health Reference Level (HRL)
Minimum Reporting Level (MRL) - Range
- (modal value)
Maximum Concentration of Detections
99 Percentile Concentration of Detections
Median Concentration of Detections
Total Number of PWSs
Number of GWPWSs
Number of SW PWSs
Total Population
Population of GW PWSs
Population of SW PWSs
Occurrence by System
PWSs with detections (> MRL)
Range across States
GW PWSs with detections
SW PWSs with detections
PWSs > H HRL
Range across States
GW PWSs > H HRL
SW PWSs > '/2 HRL
PWSs > HRL
Range across States
GW PWSs > HRL
SW PWSs > HRL
Occurrence by Population Served
Population served by PWSs with detections
Range across States
Pop. Served by GW PWSs with detections
Pop. Served by SW PWSs with detections
Population served by PWSs > '/2 HRL
Range across States
Pop. Served by GW PWSs > '/2 HRL
Pop. Served by SW PWSs > '/2 HRL
Population served by PWSs > HRL
Range across States
Pop. Served by GW PWSs > HRL
Pop. Served by SW PWSs > HRL
20 State
Cross-Section1
70,631
0.11%
1/2HRL, or PWSs >HRL = PWSs with at least one sampling result greater than or equal to the MRL, exceeding
the 1/?HRL benchmark, or exceeding the HRL benchmark, respectively; Population Served by PWSs with Detections, by PWSs >1/2HRL, or by PWSs >HRL = population served by PWSs with at
least one sampling result greater than or equal to the MRL, exceeding the V^HRL benchmark, or exceeding the HRL benchmark, respectively.
Notes:
- Only results at or above the MRL were reported as detections. Concentrations below the MRL are considered non-detects.
- Due to differences between the ratios of GW and SW systems with monitoring results and the national ratio, extrapolated GW and SW figures might not add up to extrapolated totals.
- Due to MRL variability, it is likely that the sampling failed to capture some Y-i HRL and HRL exceedances at participating systems, and the Y-i HRL and HRL analyses underestimate actual
contaminant occurrence.
E-4
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Appendix E. Data Summaries of Occurrence Population Served for Four Contaminants Considered During CCL 2 Regulatory Determinations
Table E.4.a. 1,1,2,2-Tetrachloroethane Occurrence Summary Statistics (Round 1)
Frequency Factors
Total Number of Samples
Percent of Samples with Detections
99 Percentile Concentration (all samples)
Health Reference Level (HRL;
Minimum Reporting Level (MRL) - Range
- (modal value)
Maximum Concentration of Detections
99"1 Percentile Concentration of Detections
Median Concentration of Detections
Total Number of PWSs
Number of GW PWSs
Number of SW PWSs
Total Population
Population of GW PWSs
Population of SW PWSs
Occurrence by System
PWSs with detections (> MRL)
Range across States
GW PWSs with detections
SW PWSs with detections
PWSs > Vz HRL
Range across States
GW PWSs > y2 HRL
SW PWSs > !/2 HRL
PWSs > HRL
Range across States
GW PWSs > HRL
SW PWSs > HRL
Occurrence by Population Served
Population served by PWSs with detections
Range across States
Pop. Served by GW PWSs with detections
Pop. Served by SW PWSs with detections
Population served by PWSs > Vz HRL
Range across States
Pop. Served by GW PWSs > Vi HRL
Pop. Served by SW PWSs > '/2 HRL
Population served by PWSs > HRL
Range across States
Pop. Served by GW PWSs > HRL
Pop. Served by SW PWSs > HRL
24 State
Cross-Section
67,688
0.16%
1/?HRL, or PWSs >HRL = PWSs with at least one sampling result greater than or equal
to the MRL, exceeding the 1/?HRL benchmark, or exceeding the HRL benchmark, respectively; Population Served by PWSs with Detections, by PWSs >1/?HRL, or by PWSs>HRL =
population served by PWSs with at least one sampling result greater than or equal to the MRL, exceeding the V^HRL benchmark, or exceeding the HRL benchmark, respectively.
Notes:
- Only results at or above the MRL were reported as detections. Concentrations below the MRL are considered non-detects.
- Because some systems were counted as both ground water and surface water systems and others could not be classified, GW and SW figures might not add up to totals.
- Due to differences between the ratios of GW and SW systems with monitoring results and the national ratio, extrapolated GW and SW figures might not add up to extrapolated totals.
- Due to MRL variability, it is likely that the sampling failed to capture some 1/2 HRL and HRL exceedances at participating systems, and the 1/2 HRL and HRL analyses underestimate actual
contaminant occurrence.
E-5
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Appendix E. Data Summaries of Occurrence Population Served for Four Contaminants Considered During CCL 2 Regulatory Determinations
Table E.4.b. 1,1,2,2-Tetrachloroethane Occurrence Summary Statistics (Round 2)
Frequency Factors
Total Number of Samples
Percent of Samples with Detections
99 Percentile Concentration (all samples)
Health Reference Level (HRLJ
Minimum Reporting Level (MRL) - Range
- (modal value)
Maximum Concentration of Detections
99"1 Percentile Concentration of Detections
Median Concentration of Detections
Total Number of PWSs
Number of GWPWSs
Number of SW PWSs
Total Population
Population of GW PWSs
Population of SW PWSs
Occurrence by System
PWSs with detections (> MRL)
Range across States
GW PWSs with detections
SW PWSs with detections
PWSs > !/2 HRL
Range across States
GW PWSs > y2 HRL
SW PWSs > Vi HRL
PWSs > HRL
Range across States
GW PWSs > HRL
SW PWSs > HRL
Occurrence by Population Served
Population served by PWSs with detections
Range across States
Pop. Served by GW PWSs with detections
Pop. Served by SW PWSs with detections
Population served by PWSs > Vi HRL
Range across States
Pop. Served by GW PWSs > V2 HRL
Pop. Served by SW PWSs > Vi HRL
Population served by PWSs > HRL
Range across States
Pop. Served by GW PWSs > HRL
Pop. Served by SW PWSs > HRL
20 State
Cross-Section
98,911
0.02%
1/2HRL, or PWSs >HRL = PWSs with at least one sampling result greater than or equal to
the MRL, exceeding the 1/?HRL benchmark, or exceeding the HRL benchmark, respectively; Population Served by PWSs with Detections, by PWSs >1/?HRL, or by PWSs >HRL = population
served by PWSs with at least one sampling result greater than or equal to the MRL, exceeding the V^HRL benchmark, or exceeding the HRL benchmark, respectively.
Notes:
- Only results at or above the MRL were reported as detections. Concentrations below the MRL are considered non-detects.
- Due to differences between the ratios of GW and SW systems with monitoring results and the national ratio, extrapolated GW and SW figures might not add up to extrapolated totals.
- Due to MRL variability, it is likely that the sampling failed to capture some 1/2 HRL and HRL exceedances at participating systems, and the 1/2 HRL and HRL analyses underestimate actual
contaminant occurrence.
E-6
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