Occurrence Estimation
       Methodology and
  Occurrence Findings Report
    for the Six-Year Review of
Existing National Primary Drinking
       Water Regulations

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Office of Water (4606)
EPA-815-R-03-006
www.epa.gov
June 2003
                   Printed on Recycled Paper

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                                   ACKNOWLEDGMENTS


The compilation and analysis of the data summarized in this report were undertaken by EPA's Office of
Ground Water and Drinking Water (OGWDW) in support of the Six-Year Review of National Primary
Drinking Water Regulations.  This effort was directed by Mr. Peter Lassovszky and Dr. Andrew Shulman
of OGWDW.

We would like to thank the many States and State staff who contributed data sets and valuable advice.
Thank you also to the many public water systems and their staffs who conducted the compliance
monitoring that provided the extensive amount of contaminant occurrence data used in this report.
External expert reviewers also provided constructive comments on earlier drafts of the statistical
methodology used for the contaminant occurrence estimations.

EPA also appreciates the technical support provided by The Cadmus Group, Inc., the prime contractor for
this project.  Dr. Jonathan Koplos  and Dr. George Hallberg served as Cadmus Project Managers in the
provision of support for data management, data quality assurance and quality control, statistical model
development and validation, contaminant occurrence  analysis, and report development. The major
contributions of Dr. Song Qian (in statistical model development and validation), Alison Kotros, and Erin
Hartigan are gratefully acknowledged.
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                                      CONTENTS


ACKNOWLEDGMENTS	iii

TABLES AND FIGURES 	 vii

APPENDICES	ix

ABBREVIATIONS  	xi

EXECUTIVE SUMMARY 	xiii

I.  INTRODUCTION	 1
       LA.      Purpose and Scope	 1
       I.E.      Sources of Data Used for Analysis  	 1
       I.C.      Data Analysis	 2

II.  DEVELOPING A NATIONAL CROSS-SECTION OF STATES	 2
       II.A.  Pollution Potential Indicators 	 3
              II.A. 1.  Manufacturing Indicators  	 3
              II.A.2.  Agricultural Indicators  	 4
              II.A.3.  Summary	 4
       II.B.  Representativeness of the Selected State Data Sets	 4

III.   INITIAL EIGHT STATE DATA SETS	 7
       III.A.   Data Management 	 8
       III.B.   Data Quality Issues	 9
              III.B.l. Data Quality Assessment and Control 	 9

IV   STAGE 1 ANALYSIS	 10
       IVA.   Summary of Contaminant Occurrence Ranking Findings 	 11
       IVB.  Comparison of State Data and URCIS Stage 1 Findings 	 14

V  FULL SIXTEEN STATE DATA SETS AND CROSS-SECTION	 15
       V.A.  Data Use and Editing	 20
       V.B.  Comparison of 8-State vs. 16-State National Cross-Sections  	 21

VI.   STAGE 2 ANALYSIS	 26
       VI.A.   Preparation of State Data for the Stage 2 Analysis 	 26
       VLB.   Previous Occurrence Estimation Methods	 29
       VI.C.   General Description of Bayesian Statistics  	 31
       VI.D.   Estimating System Mean Concentrations  	 31
       VI.E.   Estimation of Probabilities of Threshold Exceedance	 32
       VI.F.   Credible Intervals	 33
       VI.G.   Using the Occurrence Probability Estimates to Obtain National Occurrence
               Estimates	 33
       VI.H.   Summary of Occurrence Estimations	 34
       VI.I.   Stage 2 Model Verification  	 42
       VI.J.   Stage 2 Model Validation	 44
              VI.J.I. Centers for Disease Control and Prevention Fluoridation Census	 44
              VI.J.2. SDWIS/Fed Comparison	 48
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VII. CONCLUSION	  49




REFERENCES	  51




DEFINITIONS	  53
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                                   TABLES AND FIGURES


Table II.B.I. Initial Eight Cross-Section States with Ranking of Pollution Potential Indicators 	  5

Figure II.B.2. Distribution of State Rankings of Manufacturing Establishments/ Sq. Mile vs.
       Farm Ag. Chemical Expenses (Cross-Section States Represented by Solid Circles)  	  6

Figure II.B.3. Map of the Initial 8 Cross-Section States	  7

Table III.A.l. Initial 8 State Data Sets Used for Analyses  	  7

Table IV.A.I. Stage 1 Analysis - High Occurrence Contaminants Ranked by MCL for
       All Systems in the Eight Cross-Section States  	  11

Table IV.A.2. Stage 1 Analysis - Low Occurrence Contaminants Ranked by MRL for
       All Systems in the Eight Cross-Section States  	  12

Table IV.B.l. Stage 1 Analysis Comparison of Tetrachloroethylene Occurrence in Different
       Cross-Sections	  15

Table V. 1. Additional State Data Sets Used for Analyses	  17

Table V.2. National Cross-Section States with Ranking of Pollution Potential Indicators	  18

Figure V.2. Distribution of State Ranking for Manufacturing Establishments/ Sq.  Mile vs.
       Farm Ag. Chemical Expenses (Highlighting Initial 8 & Additional 8 Cross-Section States) . .  19

Figure V.3. Map of the  16 Cross-Section States	  20

Table V.B.I. Comparison of Stage  1 Analyses for 8-State vs. 16-State National Cross-Sections
       Based on the Percent of Systems  	  21

Table V.B.2. Comparison of Stage  1 Analyses for 8-State vs. 16-State National Cross-Sections
       Based on the Percent of Population Served by Systems	  24

Table VI.A. 1. Contaminant Occurrence Data From the 16-State Cross-Section Used in
       Stage 2 Analysis	  27

Table VI.G.l. Calculating National Estimates of Exceedance 	  34

Table VI.H.l. Comparison of Aggregate Stage 1 and Stage 2 Analytical Results Based on the
       16-State National Cross-Section - Percent of Systems and Population Served by Systems
       Greater than the MCL	  35

Table VI.H.2. Best Estimate and Range of the Number of Systems Exceeding the MCL in the
       16 Cross-Section States and Nationally  	  38

Table VI.H.3. Best Estimate and Range of the Population-Served by Systems Exceeding the
       MCL in the 16 Cross-Section States and Nationally  	  40

Table VI.I.l. Stage 2 Comparison of Top Quartile and  Bottom Quartile States' Mean
       Concentration Values  	  43

Table Vl.J.l.a.   Comparison of the National Extrapolations of the Stage 2 Modeled Estimates
       with the CDC Fluoridation Census Findings 	  45


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Table Vl.J.l.b.  Size Distribution of Fluoridating Systems in the 16 Cross-Section States and
       the CDC Fluoridation Census 1992  	  46

Table VI.J.2.a.  Preliminary Comparison of Stage 2 Analytical Findings and SDWIS/Fed
       MCL Violation Information  	  49
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                                      APPENDICES
APPENDIX A.

APPENDIX Bl.


APPENDIX B2.


APPENDIX C.

APPENDIX D.

APPENDIX E.
Stage 1 Analytical Findings

Detailed Description of Bayesian-Based Hierarchical Model
(Stage 2 Analytical Approach)

Tabulated Description of National Cross-Section Data
(used for Stage 2 analyses)

Stage 2 Analytical Findings

Model Bounding Analysis

Summary of Stage 2 Analytical Findings
Occurrence Estimation Methodology
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                                    ABBREVIATIONS






CB           Credible Bound




CI            Credible Interval



CMR         Chemical Monitoring Reform




CWS         Community Water System




DBCP         l,2-Dibromo-3-chloropropane




EDB          Ethylene Dibromide




EPA          Environmental Protection Agency




FTP          File Transfer Protocol




GW          Ground Water




IOC          Inorganic Chemical




MCL         Maximum Contaminant Level



mg/L         milligrams per liter




MLE         Maximum Likelihood Estimation




MRL         Minimum Reporting Level




NAWQA      National Water Quality Assessment Program




NTNCWS     Non-Transient Non-Community Water System



NPDWR      National Primary Drinking Water Regulation




OGWDW     Office of Ground Water and Drinking Water



PWS          Public Water System




PWSID        Public Water System Identifier




ROS          Regression on Ordered Statistics



SDWA        Safe Drinking Water Act




SDWIS/Fed    Safe Drinking Water Information System/Federal Version




SOC          Synthetic Organic Chemical




SW           Surface Water
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                               ABBREVIATIONS (Continued)




TNCWS       Transient Non-Community Water System




TRI           Toxics Release Inventory




• g/L          micrograms per liter




URCIS        Unregulated Contaminant Information System




USGS         United States Geological Survey




VOC          Volatile Organic Chemical
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                                   EXECUTIVE SUMMARY


The 1996 Amendments to the Safe Drinking Water Act (SDWA) require that the Environmental
Protection Agency (EPA) shall, not less often than every six years, review and revise, as appropriate, each
national primary drinking water regulation promulgated by the Agency. This report presents an overview
of the regulated contaminant occurrence data, data management, and statistical methods used to develop
national contaminant occurrence estimations generated in support of EPA's Six-Year Review of National
Primary Drinking Water Regulations. Using the data and methods described, estimations of national
occurrence and preliminary assessments of exposure are derived, evaluated, and presented.

The contaminant occurrence  data used are public water system compliance monitoring results originally
reported to and contained in State data sets. A data management approach, consisting of the development
of a 16-State national cross-section, enables statistical estimations that are indicative of national
occurrence of contaminants in public drinking water systems.  The Safe Drinking Water Act compliance
monitoring data in the 16-State national cross-section represent more than 13  million analytical results
from approximately 41,000 public water systems. The national cross-section data are used to develop
contaminant occurrence estimates that are indicative of national occurrence.  For individual contaminants,
the amount of compliance monitoring data used in occurrence analyses range from almost 27,700
analytical records for Cyanide (from 9,559 public water systems) to slightly more than 201,000 analytical
records for trichloroethylene  (from 23,035 public water systems).

The primary objective regarding the  data used in these contaminant occurrence analyses was development
of a consistent and repeatable data management approach that would allow valid comparisons between
and among the various data sets, and allow the data to be jointly evaluated to provide an overview of
occurrence patterns at the national level.  As part of the data management process, an extensive data
quality assurance assessment was conducted to ensure  adequate quality of the data used.

A two-stage analytical approach was developed to evaluate the national occurrence of regulated
contaminants using the national cross-section of compliance monitoring data. The first stage of analysis,
referred to as the "Stage 1 analysis," provides a straightforward evaluation of occurrence for all regulated
contaminants. In this  Stage 1 analysis, the data sources, data quality, and data characteristics were
assessed, and the data were used to conduct simple, clear, and conservative non-parametric assessments
for a broad evaluation of contaminant occurrence.

The subsequent "Stage 2 analysis" is a more rigorous parametric statistical estimation based on
probabilistic modeling. The  Stage 2 analysis enables estimation of the national number of public drinking
water systems, and the population served by those systems, that have an estimated long-term mean
concentration of a particular contaminant that exceeds  a specified threshold concentration of interest. The
stage 2 analyses yield detailed, stratified (assessed according to source water type and system size)
occurrence estimations using a Bayesian-based hierarchical model estimation method.  This method
provides  estimates of numbers of systems, and population served by those systems, with system mean
concentrations exceeding specified contaminant threshold concentrations, and includes quantified error
for the estimation procedures.

In the process of developing this two-stage analytical approach for the Six-Year Review, the national
cross-section development and analytical approach were peer-reviewed, assessed relative to another
significant drinking water contaminant occurrence estimation method, and evaluated with simulated data
sets designed to assess the log-normal and constant variance assumptions made at the system level
regarding the national distribution of system means. Assessments indicated the Bayesian-based
hierarchical model and the 16-State national cross-section of compliance monitoring data are appropriate
for use for the Six-Year Review occurrence estimations.

The occurrence of 60 regulated contaminants was evaluated with both Stage 1 and Stage 2 analytical
approaches using the 16-State national cross-section data. The Stage  1 and Stage 2 analyses yielded
similar occurrence findings.  Based on the Stage 1 estimates, the highest occurrence IOC was fluoride, the


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highest occurrence SOC was bis(2-ethylhexyl)phthalate and the highest occurrence VOC was
tetrachloroethylene. Based on the Stage 2 estimates, the highest occurrence IOC was fluoride, the highest
occurrence SOC was l,2-dibromo-3-chloropropane (bis[2-ethylhexyl]phthalate was the second highest
occurrence SOC) and the highest occurrence VOC was trichloroethylene (tetrachloroethylene was the
second highest occurrence VOC).

The summary of Stage 1 analytical findings is presented in report Section IVA., and complete detailed
Stage 1 findings for all 60 contaminants are included in Appendix A. The summary of Stage 2 analytical
findings is presented in report Section VI .H., and complete detailed Stage 2 findings for all 60
contaminants are included in Appendix C.
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I.   INTRODUCTION

This report presents a detailed review of the contaminant occurrence data used and the statistical methods
developed to estimate regulated contaminant occurrence in public drinking water systems.  These
regulated contaminant occurrence estimates are generated in support of the Environmental Protection
Agency's Six-Year Review of National Primary Drinking Water Regulations (NPDWRs). This "Six-
Year Review" assesses the potential revision of regulations for regulated contaminants. The contaminant
occurrence data used for the Six-Year Review's statistical estimations are Safe Drinking Water Act
(SDWA) compliance monitoring data. Using the data and statistical methods described, estimations of
national occurrence and preliminary assessments of exposure are derived, evaluated, described, and
presented.

The contaminant occurrence estimations conducted for the Six-Year Review represent a long-term,
detailed, and comprehensive undertaking of data acquisition, quality analysis, editing and formatting.
This extensive data management work was conducted concurrently with the development of a two-stage
contaminant occurrence estimation approach. The first stage of analysis comprises a simple,
straightforward assessment that provides a broad overview of contaminant occurrence.  The second stage
of analysis is a more rigorous, statistical approach that provides detailed estimates of occurrence with
quantified error of estimation to enable measures of the certainty of the estimates. The detailed
descriptions of these data and estimation methods are presented in the following sections and appendices
of this report.

LA.      Purpose and Scope

The United States Environmental Protection Agency (EPA) Office of Ground Water and Drinking Water
(OGWDW) is responsible for implementing the provisions of SDWA. Under SDWA, OGWDW
develops regulations to address the public health risks from contaminated drinking water and develops
related programs to protect ground water and surface water supplies. The  1996 Amendments to SDWA
require that EPA shall, at least once every  six years, review and revise, as appropriate, each NPDWR
promulgated by the Agency. SDWA specifies that revision of a national primary drinking water
regulation shall maintain or provide for greater protection of public health. Any revision of the
regulations will be partially dependent on  contaminant occurrence findings, and on the reevaluation of the
public's exposure to the contaminants and the potential adverse health effects from that exposure. The
purpose of this report is to describe the contaminant occurrence data, data management, and statistical
methods used to develop national contaminant occurrence estimations. Estimations of national
occurrence and preliminary assessments of exposure are derived and evaluated using the data and
methods described.

I.E.      Sources of Data Used for Analysis

State data sets, comprising SDWA compliance monitoring data from public water systems (PWSs), were
the  primary data sources for this analysis.  An approach was developed to construct a national cross-
section of State data sets that contain contaminant occurrence data that would be indicative (or as
representative as possible) of national contaminant occurrence.  Data from 16 States were selected and
used in the national cross-section of State data sets. The States were selected to represent the national
range of pollution potential, and hydrologic and geographic diversity. The SDWA compliance
monitoring data in the 16-State national cross-section represent more than 13 million analytical results
from approximately 41,000 PWSs. Analytical results based on the cross-section are therefore indicative
(though not strictly statistically representative) of national occurrence.  In other terms, the analyses based
on the cross-section data should indicate a central tendency of occurrence in part based on the very large
size of the cross-section data set and how the cross-section was constructed.  The 16-State national cross-
section data set is the largest compliance monitoring data set compiled by EPA to date.  Construction of
the  cross-section is discussed in Section II.
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I.C.      Data Analysis

A two-stage analytical approach was developed for this evaluation of the national occurrence of regulated
contaminants.  The first stage of analysis, referred to as "Stage 1," provides a straightforward evaluation
of occurrence for all regulated contaminants.  In the Stage 1 analysis, the compliance monitoring
analytical results data for all regulated contaminants for the cross-section States were compiled in
contaminant-specific data sets and the data were used to simply count the percent of PWSs that recorded
at least one analytical result exceeding the Minimum Reporting Level (MRL) and Maximum Contaminant
Level (MCL) for each contaminant.1 With these results, general assessments such as relative rankings of
the  contaminants' occurrence provide a broad characterization of contaminant occurrence.  The Stage 1
analyses generate occurrence estimates that are clear and easy to understand.  They were developed as a
rudimentary analytical technique, and they provide conservative estimates of occurrence. Stage 1
analysis methods are described in more detail below in Section IV.

In part based on the findings of the Stage 1 analysis, EPA selected a set of contaminants for which more
rigorous parametric statistical estimations, the  Stage 2 analyses, were warranted as a next step.  Using the
Stage 2  approach, estimates were made for the number of public drinking water systems nationally, and
the  population served by those  systems, that are expected to have a particular mean contaminant
concentration present at levels exceeding any specified threshold(s) of concern to EPA. The Stage 2
analyses employ a Bayesian-based hierarchical model estimation method which yield detailed, stratified
occurrence estimates and include quantified error for those estimates. The Stage 2 analysis is described in
more detail below in Section VI.
II.   DEVELOPING A NATIONAL CROSS-SECTION OF STATES

Currently, there is no complete analytical record of contaminants in drinking water from public water
systems collected under SDWA that can be processed for a comprehensive national overview of
occurrence and exposure. EPA's Safe Drinking Water Information System (SDWIS/Fed) maintains a
variety of water system inventory and operation information, as well as compliance program information.
For most contaminants, however, the only analytical results filed in SDWIS/Fed are those related to
violations of the MCL.  The analytical results from monitoring of the Phase II/V rule chemicals, and most
other contaminants, are stored in individual State databases. Until the data management effort for this
report, there had been no feasible way to access these data to construct a national sample except through
analyzing data sets from the individual States.

EPA previously completed a study reviewing the occurrence of regulated contaminants in public drinking
water systems using data sets voluntarily provided by eight States. These data were used in the
development of an initial analysis of a national cross-section of contaminant occurrence. The results of
this prior work in support of the Chemical Monitoring Reform (CMR), and the report generated (referred
to as the "CMR Report," U.S. EPA 1999) have generated wide and very positive support by stakeholders
and peer-reviewers alike.

The data sets received from the eight States were used for a detailed national cross-section analysis in the
CMR Report. The data sets from these same eight States provide the basis for analyses conducted for this
current report. Described in the following sections are the evaluations and procedures used in identifying
the eight initial cross-section States. These eight States, in aggregate, provide contaminant occurrence
data compiled to be indicative of contaminant occurrence nationally.
1  The MRL is the lowest level that can be reliably achieved within specified limits of precision and accuracy under
routine laboratory operating conditions. The MCL is maximum permissible level of a contaminant in water which
is delivered to any user of a public water system.

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II.A.  Pollution Potential Indicators

Many past EPA and United States Geological Survey (USGS) studies have shown that some simple
measures, such as population (or population density) are closely associated with pollution.2 This is both
intuitively and empirically apparent, since it is human activity and its related land use -be it
manufacturing or agriculture- that is the source of most pollutants, particularly the organic chemicals.  In
the CMR Report, various demographic and other factors were evaluated as independent measures or
indicators of pollution potential.

More than thirty-five different factors that are potentially useful as indicators of each State's3 pollution
potential were considered for the CMR analyses. The factors ranged from Census data on manufacturing,
agriculture, and population density, to indices such as EPA's Section 106 allocation factors or the 7997-
7992 Green Index: A State by State Guide to  the Nation's Environmental Health (prepared by the
Institute for Southern Studies) (Hall and Kerr 1993). Two methods were considered for evaluating the
States' comparable pollution potential.  The first was the development of a singular numerical index,
incorporating factors such as manufacturing in the State, total pounds of chemicals released, and
pesticides used, into a comprehensive ranking for each State. However, such a ranking for all sources
requires various factors to be weighted, and the meaning of the  resultant number can be difficult to
understand, as well as arguable.

A second, simpler method, evaluating the pollution potential of the States, was adopted for the CMR
analyses.  The primary factors used indicated the potential pollution from manufacturing and agriculture
in each State.  States were then ranked from 1 to 50 for each factor.  This method does not, of course,
avoid all of the problems discussed above, but it does provide a simple, practical evaluation of the range
of pollution potential conditions represented by the States.

In general, manufacturing/industrial activities are considered the major sources of many volatile organic
contaminants (VOCs) (degreasers, solvents, petroleum compounds).  Most synthetic organic
contaminants (SOCs) are pesticides, and agriculture is the largest user of these compounds.  While
inorganic contaminants (lOCs) can have various uses in manufacturing, they also occur naturally. Natural
geologic sources of lOCs were not directly considered in the assessment for representativeness, in part
because whole States needed to be evaluated and such sources are often localized. However, by including
geographic or spatial coverage across the United States as a factor (e.g., from New Jersey to Montana), a
range of geologic, hydrogeologic, and climatic variability were  inherently included in this cross-section
development.

II.A.1.   Manufacturing Indicators

Numerous factors were considered as potential indicators of manufacturing-related pollution, including
EPA's  Toxics Release Inventory (TRI) (including total releases, releases per square mile, and releases
excluding air releases), the number of manufacturing establishments per square mile, the number of
manufacturing employees, the value added by manufacturers, and the value added per capita. This
information was taken directly from the 7995 Annual Survey of Manufactures (U.S. DOC 1997), the 7992
Census of Manufactures (U.S. DOC 1996), and the 7995 Toxics Release Inventory (U.S. EPA 2001).  All
factors were considered in terms of their inherent value as pollution potential indicators, their range and
variance in providing a relative ranking of the States, and their interrelationships.

The total TRI releases per square mile and the number of manufacturing establishments per square mile
were considered the two most useful indicators.  While there are problems with the TRI (e.g., some
2 For example, the most recent report is Squillace et al. 1999.

3 Data were analyzed on a Statewide basis so any determination of representativeness was based on whether the
States, for which information was available, were representative of the nation as a whole.  There are problems, of
course, with using large, diverse entities such as States to determine representativeness; however, it was not
practical to break the data down any further.

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inconsistent release estimation techniques; omission of many small establishments, or those with releases
below specified thresholds), the TRI was considered useful because it is a measure of how many pounds
of toxic chemicals are released within the State.  The number of manufacturing establishments takes into
account how many factories are actually engaged in manufacturing and thus how many establishments
potentially contribute to pollution. By breaking down the number of manufacturing establishments per
square mile, the size of the State is also taken into account.

The data clearly showed a close correlation between the number of manufacturing establishments per
square mile and the population density in each State,  as well as a clear linear association with the total
TRI pounds released/square mile. Hence, the number of manufacturing establishments per square mile
was used as the primary indicator because it is a simple measure of how many establishments are actually
engaged in manufacturing and thus is potentially polluting sources of drinking water. The TRI total
pounds released per square mile was used as a secondary  factor in determining representativeness.
Squillace et al. (1999) found a significant correlation between VOC occurrence in ambient ground water
and population density in a USGS national NAWQA study. As noted,  population density and
manufacturing density are highly correlated. Manufacturing density and TRI data were used in this
ranking because they were considered more direct measures of pollution potential for this study.

II.A.2.   Agricultural Indicators

There is no complete measure of pesticide usage by States that is readily available. Thus, a variety of
factors were considered to assess potential organic chemical pollution from agriculture  in each State.
These included the percent of the State's population that is classified as rural, the percent of land in the
State that is crop land, the percent of land that is grassland pasture and rangeland (a possible inverse
indicator), and total farm agricultural chemical expenses.  Like the manufacturing factors, these
agricultural variables were considered in terms of their value in indicating potential sources of pollution
and were plotted against one another to determine how closely they are correlated.

Of these factors, total farm agricultural chemical expenses was considered to be the best indicator of
potential pollution. The percent of the State's population that lives in rural areas does not necessarily
relate to agricultural chemical use or crop land. There is, of course, a correlation between crop land and
agricultural chemical use. However, there are  notable exceptions such as Florida and California which
use a large amount of agricultural chemicals despite having more limited crop land area. While there are
some incomplete surveys of pesticide use, the 7992 Census of Agriculture (U.S. DOC 1994) measure of
dollars spent on agricultural chemicals was a more consistent and complete measure.

II.A.3.   Summary

The following three measures were selected as reasonable indicators of pollution potential of the States:
the number of manufacturing facilities per square mile (to reflect the range of potential  VOC occurrence),
total expenditures on farm agricultural chemicals (to reflect the range of potential SOC  occurrence), and
TRI releases (in total pounds) per square mile (to reflect the releases of any type of chemical into the
environment). Additionally, in the development of a nationally representative group of States, a
geographic distribution of States is also considered (to reflect the range of hydrologic and climatic
conditions, and geologically-influenced, potential IOC occurrence).

II.B.   Representativeness of the Selected State Data Sets

Most of the data used in this  review were provided voluntarily by States. In all,  14 States originally
provided data in support of the CMR analyses. While 14 of 50 States is a substantial sample,  it is not
necessarily representative of national occurrence. Six of the 14 States  available for use in the analysis
were from the Midwestern "Cornbelt" States.  The inclusion of all six Cornbelt States would have
resulted in an over-representation of the "pollution potential'Tor agricultural chemicals. Hence, various
means were evaluated to enable the construction of a grouping of the available State data sets that would
provide a reasonable  first view of national occurrence based on a representative cross-section  of States.
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As described in the previous section, two broad factors were considered in the assessment of a nationally
representative compilation of State data sets: geographic or spatial diversity, and pollution potential.
Consideration of States that collectively provide a geographic diversity was one means by which to
include contaminant occurrence data from the wide, and national, range of climatic and hydrologic
conditions across the United States. The representative group of State data sets was also selected to
represent the range of pollution potential across the various regions and States of the United States. The
50 States' pollution potential indicators were ranked from 1 to 50 (1 being the highest and 50 being the
lowest). These ranked lists of States were then divided into four quartiles. The rankings were reviewed
to assess if States could be selected in approximate balance from each quartile. The primary ranking
indicator was the number of manufacturing establishments per square mile, but total farm agricultural
chemical expenditures and TRI releases were also considered to contribute further to insuring that the
occurrence data from the selected States were, collectively, representative or indicative of national
occurrence. This cross-section selection process was used to select the initial 8 State cross-section, and
the compliance monitoring data from these initial 8 cross-section States provides a broad distribution
geographically and across the pollution potential rankings.

The quartile division of the States selected to approximate the national cross-section are summarized in
Table II.B. 1.  The compliance monitoring contaminant occurrence data from these eight States
collectively provide a balanced cross-section, based on relative rankings for pollution potential (reflecting
a range of high, medium, and low contaminant occurrence) and geographic coverage (reflecting a range
of climatic and hydrologic conditions across the United States).  The eight initial cross-section States
represent over 25 percent of the United States population using PWSs, and over 20 percent of the PWSs
nationally.
Table II.B.l.  Initial Eight Cross-Section States with Ranking of Pollution Potential Indicators
Quartiles
for Rank-Order of
All States Based on
Manufacturing Ranking
1
2
3
4
Initial Eight
States in
National Cross-
Section
NJ
IL
CA
MI
AL
OR
NM
MT
National Ranking of
Pollution Potential Indicators
Manufacturing1
2
10
11
13
25
34
44
48
Agriculture2
37
2
1
18
26
22
40
34
TRI Releases3
8
11
38
16
7
39
40
34
1) "Manufacturing" = the number of manufacturing facilities per square mile
2) "Agriculture" = total expenditures on farm agricultural chemicals
3) "TRI" = TRI releases (in total pounds) per square mile
The States were also plotted on a two-dimensional scatter plot (see Figure II.B.2), with the x- and y-axes
representing the manufacturing and agricultural ranking, respectively, of each State. The amount spent on
agricultural chemicals per State increases along the y-axis from bottom to top. The number of
manufacturing establishments per square mile per State increases along the x-axis from left to right.
Figure II.B.2 illustrates the balanced distribution of the 8 cross-section States across the four quartiles of
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both of those indicators. An ideal balanced distribution of the 8 States across the range of low to high
pollution potential would be achieved by selecting two States in each of the four quartiles (rows)
representing the low to high range agricultural pollution potential indicators, while also having two States
in each of the four quartiles (columns) representing the low to high range of manufacturing pollution
potential indicators. The map presented in Figure II.B.3 shows the geographic distribution  of the cross-
section States across the United States, to ideally provide a broad representation across the low to high
range of often geographically-influence occurrence of inorganic contaminants.


Figure II.B.2.  Distribution of State Rankings of Manufacturing Establishments/ Sq. Mile vs. Farm
Ag.  Chemical  Expenses (Cross-Section States Represented by Solid Circles)
                        Ranking of the No. of Manufacturing Establishments/ Sq. Mile
         CA
         IL
         MI


         OR


         AL




         MX

         NJ

         NM
      w
      1
       0>
      6
TO    <
                    MT  NM
                                                            MI CA IL       NJ
•
o
Cross-Section States
All Other Stales
Occurrence Estimation Methodology
            June 2003

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Figure II.B.3. Map of the Initial 8 Cross-Section States
                                                        |  | Initial 8-State Cross-Section
                                                        |  | States not included in Cross-Section
III.   INITIAL EIGHT STATE DATA SETS

The initial eight State data sets are comprised of SDWA compliance monitoring data from public drinking
water systems as provided by the States. These data represent the analytical results for Non-Purchased
Community Water Systems (CWSs) and Non-Purchased Non-Transient Non-Community Water Systems
(NTNCWSs) that are required to monitor for the Phase II/V chemicals. Some States included data from
Transient Non-Community Water Systems (TNCWSs), but these systems are not required to monitor for
the Phase II/V contaminants. As summarized in Table III.A.l, these data represent approximately 10
million analytical results from nearly 22,000 public water systems.  In most cases, the initial State data
sets contained additional data that were not included in these analyses either because they were not
appropriate (e.g., data for non-Phase II/V contaminants) or because they posed various data quality
problems (e.g., missing significant data elements such as source water type) that prevented analysis of
adequate quality, specificity, or accuracy. Additional information describing the overall quality of the
data is discussed in Sections III .A and III.B.
Table III.A.1. Initial 8 State Data Sets Used for Analyses
State
Alabama
California
Illinois
Michigan 2
Montana
New Jersey
Contaminant Groups
Represented '
lOCs, SOCs, VOCs, O
IOCs, SOCs, VOCs, 0
lOCs, SOCs, VOCs, O
SOCs, VOCs, 0
IOCs, SOCs, VOCs, O
IOCs, SOCs, VOCs, 0
Number of
Analytical Results
708,569
3,897,362
2,967,946
685,721
276,675
980,915
Number of PWSs
Represented
731
6,414
1,392
3,252
1,786
4,503
Time Period
1985-1998
1984-1998
1987-1997
1993-1997
1993-1998
1993-1998
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June 2003

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State
New Mexico
Oregon
Initial Eight
Cross-Section State
TOTAL
Contaminant Groups
Represented '
lOCs, SOCs, VOCs, O
IOCs, SOCs, VOCs, 0
lOCs, SOCs, VOCs, 0
Number of
Analytical Results
266,262
169,521
9,952,971
Number of PWSs
Represented
1,299
2,345
21,722
Time Period
1992-1996
1990-1998
1984-1998
These State data sets were initially developed for the analyses conducted in the CMR Report and were used for the analyses in this current report.

1) IOCs = the 13 regulated inorganic chemicals; SOCs = the 30 regulated synthetic organic chemicals; VOCs = the 21 regulated volatile organic
chemicals; O = Other regulated or unregulated chemicals.

2) No IOC data were originally available from the State of Michigan, and therefore no Michigan data were used in Stage 1 analyses for IOCs.
However, subsequently, Michigan compliance monitoring data were acquired for the IOCs fluoride, beryllium, chromium, mercury, and thallium.
These data were checked and edited for quality, added to the cross-section data set, and included in the later Stage 2 analyses.


III.A.   Data Management

There are many issues regarding the management of very large data sets for a project such as this.
Selection of appropriate State data sets and significant management of the data (i.e., handling, editing,
formatting, etc.) was necessary before any analysis could be conducted. The primary objective regarding
the data used in these contaminant occurrence analyses was development of a consistent and repeatable
data management approach that would allow valid comparisons between and among the various data sets,
and allow the data to be jointly evaluated to provide an overview of occurrence patterns at the national
level.

For the most part, the States that provided data did not reorganize or reformat data, but simply transmitted
the data in whatever manner was easiest.  Data were transferred using three main media: file transfer
protocol (FTP), e-mail, and diskettes.  The data were received in a number of file types, including
spreadsheet, database, and image files. Many of the data sets were received "as is" and had not been
formatted by the State in any way. For example, while the Phase II/V compliance data from 1993-1997
were of greatest interest, in many  cases it was easier for the State to simply transmit their entire data set,
which  generally contained information on all chemical contaminants (in addition to the Phase II/V) over a
greater span of years.

After receipt, an initial review of the information in each data set was performed. Each data set was
unique in format, layout, custom codes, and data element usage. In most cases, the data were not
accompanied by a protocol outlining each variable.  In every instance, follow-up with a State contact was
necessary to decipher variable headings or contaminant codes. When all variables were understood, a
formatting plan was developed for the data.  Nearly all of the data sets required some type of formatting
to facilitate analysis. Data formatting problems varied from one data set to another.

All statistical analyses were conducted in SAS® statistical software. 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.4 Data management and formatting was the most
time consuming and labor intensive part of the data analysis.  While analysis of the data was consistent
from one data set to another, each data set required some unique editing and filtering because of
differences among basic data elements.
4 SAS is a registered trademark of the SAS Institute, Inc. Excel and Visual Basic are trademarks of the Microsoft
Corporation.
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III.B.   Data Quality Issues

There are numerous data quality issues inherent to a study where very large data sets of differing format
and quality are assembled from many States to be used to characterize contaminant occurrence in the
nation's public water systems. The quality and dependability of the data used in the contaminant
occurrence analyses directly affect the quality and dependability of the results of the analyses conducted.
Therefore, many of the data quality issues, as well as the processes required before the analytical results
could be generated, are reviewed below as a preface to understanding the analytical results. For a
complete summary of data editing, please refer to the First Stage Occurrence and Exposure Report for
Six-Year Review (Cadmus 2000).

This study only used data from State primacy agencies; i.e., official data from the regulated drinking
water program.  All such analytical results are generated by laboratories that are certified for drinking
water programs, which assumes the use of various quality assurance and quality control procedures.  Only
standard SDWA compliance samples were used; "special" samples, or "investigation" samples
(investigating a contaminant problem that would bias results), or samples of unknown type were not used
in the analysis.  Certainly data problems exist, but efforts have been taken to reduce the problems and
increase the dependability and quality of the State occurrence data used in these analyses.

Many of the State data sets included data from different time periods (see Table III.A.l). However, the
majority of data are from 1993 and later (which coincides with the beginning of Phase II/V monitoring).
Initial screening of the data showed that most data quality problems were in pre-1993 data. Therefore, in
some of the data sets, results gathered before 1993 were eliminated from these analyses. More than 80
percent of all data utilized in this report are from 1993 or later; this proportion is even greater for most
SOCs. More than 92 percent of all data used for this analysis are from 1990 or  later.  Beyond these
generalities, though, the amount of problematic data was quite small in the State data sets selected for use
in the cross-section, and there was no apparent or particular systematic data problem. Therefore, all data
collected prior to 1993  used for this analysis that met the necessary data quality conditions for this
analysis were retained.

III.B.l. Data Quality Assessment and Control

Every State data set reviewed for this study contained unique data elements or unique treatment of
common elements. Even after initial screening and conversion to uniform formats and data set structure,
unique factors were always uncovered during data analysis.  Many of the potentially confounding factors
were resolved only through direct consultation with the States.  As a general rule, when errors or
ambiguities in various data elements could not be resolved, those particular data elements were not
included in the analyses to avoid problematic results or results based on data of questionable quality.
This data quality measure eliminated relatively very few observations as compared to the thousands of
analytical results included in the data sets. Many of the most problematic data quality problems
encountered occurred with older data (especially, pre-1990 or 1993).

System and sample data elements also required some time-consuming editing. Many States' data sets
contained no, or only incomplete, source water type and population records (both of which are essential
for these analyses).  When these data elements were not reported, the data set was linked (by common
PWSID) with the Needs Survey sample frame which provided the  source water type and population
information for many PWSs. However, information for all systems could not always be determined from
the Needs Survey.  Observations whose source water type could not be determined were not included in
the analysis.

Any issues within the analytical results data elements affect fundamental data processing procedures
before any statistical processing can even begin.  Very few databases contained  a field for the MRL for a
contaminant/method combination. (The Minimum Reporting Level is the lowest level that can be reliably
achieved within specified limits of precision and accuracy under routine laboratory operating conditions.)
The actual analytical results generally comprise multiple fields, and one critical component in such
databases is how analytical results with values that are less than  the MRL are recorded. The State data
sets vary widely in how these "less than the MRL" values (also referred to as "non-detections") are


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recorded.  Some record a "<" symbol in one field and then the actual MRL concentration value in a
corresponding field while others simply enter zero in the results field.  Other States record an "ND" or
some other code for non-detections while many States indicate a mixed usage that required careful editing
and attention to detail to correctly resolve.

The actual value of the MRL can have important consequences when computing basic occurrence
statistics, such as the  number or percent of samples or systems with detections of a given contaminant.
For example, the lower the MRL, the greater the number of detections. Multiple MRLs arise because of
many reasons. Improvement in analytical methods over time can result in a lowering of the MRL.
Within reason, MRLs can even vary from laboratory to laboratory using the same method, or they can
vary with sample batch, of for other reasons.  There can be more dramatic variation of MRLs when
different methods are used to quantify the same contaminant. Within the drinking water program,
methods have become well standardized so this was not a major issue for this study, particularly for the
SOCs and VOCs. However, the use of multiple MRLs within a State was not uncommon.

Another general data quality issue that can affect a large-scale summary of results  is the different
sampling schedules that may be used by different public water systems. A system with a known
contaminant problem usually has to sample more frequently than a system that has never detected the
contaminant. Obviously, the results of a simple computation of the percentage of analytical detections (or
other statistics) can be skewed by the more  frequent sampling results reported by the contaminated site.
Therefore, this analysis is focused on occurrence at the system level (rather than on a total sample basis),
which avoids the skewness inherent in the sample data, particularly over the multi-year period covered.


IV.  STAGE 1 ANALYSIS

The initial step in estimating the occurrence of regulated contaminants, the Stage 1 analysis, develops
general occurrence assessments which are more straightforward and conservative than the subsequent
Stage 2 analysis. Stage 1 analyses were conducted on the compliance monitoring data sets from the initial
eight cross-section States at the system-level.  There are inherent vulnerability, occurrence pattern, and
some regulatory differences between surface water-supplied and ground water-supplied PWSs, so
separate analyses were generated for surface water (SW) systems and ground water (GW) systems.  All of
the Stage 1 findings are presented separately for the three contaminant groups (i.e., lOCs, SOCs, and
VOCs). The contaminant group classifications relate partly to the contaminants' sources, fate, and
transport, to their chemical properties and general methods of laboratory analyses, and to regulatory
requirements that vary somewhat according to these contaminant groupings.  For IOC occurrence
analyses, arsenic was not evaluated because it is being evaluated and addressed separately through the
new arsenic rule. There were too few data to  evaluate for asbestos (an IOC), nickel (an IOC), and dioxin
(an SOC).  Therefore, these contaminants were also excluded from the occurrence analyses.

Stage 1 analysis provides a conservative assessment of occurrence by simply counting the number of
public water systems  with at least one analytical result that exceeds a concentration equal to the MRL,  !/2
MCL, and the MCL for each particular contaminant.  Hence, these Stage 1 analyses are essentially based
on the single maximum analytical value recorded at each public water system. Assessed relative to
MCLs, which reflect  public health considerations for long-term exposure to contaminants in drinking
water, 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.
Estimates based on the population served by PWSs provides a "Stage  1" preliminary characteristic of
exposure potential.

Following the Stage 1 analysis, the contaminants were then ranked, from highest to lowest, based on the
percentage of systems with at least one analytical result greater than the MRL, !/> MCL,  and the MCL for
each particular contaminant. These rankings were conducted separately for the percent of systems and for
the population served by those systems. The "highest ranking contaminants" were defined as being the
contaminants which occur in the highest percentage of public water systems at a concentration greater
than the MCL ("% >  MCL"). The "lowest ranking concentrations" were defined as the contaminants
which occur in the lowest percentage of public water systems at any concentration greater than the


Occurrence Estimation Methodology                 10                                      June 2003

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Minimum Reporting Level ("% > MRL"). The high to low occurrence rank-ordering list of contaminants
was then divided into quartiles. The "top quartile contaminants" were the upper 25 percent of the highest
occurrence contaminants, and the "bottom quartile contaminants" were the lower 25 percent of the lowest
occurrence contaminants. It should be noted that the different contaminant groups have different total
numbers of contaminants so the respective quartiles contain different numbers of contaminants.

There are additional, more involved statistical methods that can be applied to analyze limited data, such as
those comprising the cross-section State data sets.  However, for these initial analyses, a simple approach
was developed to be clear and repeatable, resulting in aggregate numbers that could be easily understood,
and that would rank the occurrence of the contaminants, from high (frequent occurrence at levels greater
than the MCL) to low (infrequent occurrence at any level greater than the MRL).

IV.A.  Summary of Contaminant Occurrence Ranking Findings

Table IV.A. 1 lists the Stage 1 analysis "high occurrence" contaminants, as based on the percent of
systems and population served by all systems (served by ground water and/or surface water) with at least
one analytical result greater than the MCL. The percent systems and percent population "> MCL"
indicates the proportion of all cross-section State public water supply systems or population-served by
systems with any analytical results exceeding the concentration value of the MCL. (Note: This does not
necessarily indicate an MCL  violation.  An MCL violation occurs when the MCL is exceeded by the
average results from four consecutive quarterly confirmation samples as required by the primacy States.)
Most contaminants ranked as high occurrence based on the percent systems were also ranked as high
occurrence based on the percent population served.
Table IV.A.l.  Stage 1 Analysis - High Occurrence Contaminants Ranked by MCL for All Systems
in the Eight Cross-Section States
Contaminant
(MCL in mg/L)
Percent
Systems
>MCL
Contaminant
(MCL in mg/L)
Percent
Pop. Served
by Systems
>MCL
Inorganic Chemicals
Fluoride (4.0)
Cadmium (0.005)
Thallium (0.002)
1.41%
0.69%
0.45%
Fluoride (4.0)
Chromium (0.1)
Cadmium (0.005)
7.31%
1.06%
0.54%
Synthetic Organic Chemicals
Bis(2-ethylhexyl)phthalate1 (0.006)
1 ,2-Dibromo-3-chloropropane (0.0002)
Atrazine (0.003)
Ethylene Dibromide (0.00005)
Lindane (0.0002)
Toxaphene (0.004)
PCBs (0.0005)
2.17%
1.95%
0.94%
0.92%
0.11%
0.09%
0.08%
Ethylene Dibromide (0.00005)
1 ,2-Dibromo-3-chloropropane (0.0002)
Bis(2-ethylhexyl)phthalate1 (0.006)
Atrazine (0.003)
Lindane (0.0002)
PCBs (0.0005)
Endrin (0.002)
17.17%
16.07%
2.74%
1.39%
0.86%
0.49%
0.35%
Volatile Organic Chemicals
Tetrachloroethylene (0.005)
Trichloroethylene (0.005)
1.18%
0.94%
Tetrachloroethylene (0.005)
Trichloroethylene (0.005)
22.24%
21.11%
Occurrence Estimation Methodology
11
June 2003

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Contaminant
(MCL in mg/L)
Dichloromethane2 (0.005)
1,1-Dichloroethylene (0.007)
Carbon Tetrachloride (0.005)
Benzene (0.005)
Percent
Systems
>MCL
0.74%
0.25%
0.24%
0.23%
Contaminant
(MCL in mg/L)
Dichloromethane2 (0.005)
1,2-Dichloroethane (0.005)
1,1-Dichloroethylene (0.007)
Carbon Tetrachloride (0.005)
Percent
Pop. Served
by Systems
>MCL
15.00%
14.09%
13.59%
12.44%
1. The high occurrences of phthalate are, in part, considered false positives related to sample contamination by plastics and laboratory analytical
problems.
2. The high occurrences of dichloromethane are, in part, considered to be false positives related to laboratory analytical problems.


Table IV.A.2 lists the Stage  1 analysis "low occurrence" contaminants,  as based on the proportion of all
cross-section State systems  or population-served by systems with at least one analytical result exceeding
the concentration value of the MRL. Note that the contaminant concentration value of a minimum
reporting level is a characteristic of the analytical method employed to  conduct the laboratory analysis for
any particular contaminant.  The actual analytical concentration of an MRL, therefore, generally differs
for different contaminants.  There can also be several different approved analytical methods for analysis
of the same contaminant, and therefore, multiple MRLs for even a single contaminant. Given this, the
occurrence measures presented in Table IV.A.2 are relative to the variable MRLs, with each MRL
representing the lowest level that can be reliably achieved within specified limits of precision and
accuracy under routine laboratory operating conditions.  Most contaminants ranked as low occurrence
based on the percent systems were also ranked as low occurrence based on the percent population served.
These contaminants are indicated in italics.
Table IV.A.2. Stage 1 Analysis - Low Occurrence Contaminants Ranked by MRL for All Systems
in the Eight Cross-Section States
Contaminant
(MCL in mg/L)
Percent
Systems
>MRL
Contaminant
(MCL in mg/L)
Percent
Pop. Served
by Systems
>MRL
Inorganic Chemicals
Antimony (0.006)
Cyanide (0.2)
Beryllium (0.004)
3.24%
2.38%
2.10%
Cyanide (0.2)
Beryllium (0.004)
Thallium (0.002)
3.35%
3.24%
2.29%
Synthetic Organic Chemicals
PCBs (0.0005)
Carbofuran (0.003)
Carbofuran (0.04)
Glyphosate (0.7)
Oxamyl (0.2)
Chlordane (0.002)
Hexachlorobenzene (0.001)
0.20%
0.16%
0.11%
0.10%
0.09%
0.05%
0.04%
PCBs (0.0005)
Heptachlor (0.0004)
Heptachlor Epoxide (0.0002)
Oxamyl (0.2)
Hexachlorobenzene (0.001)
Glyphosate (0.7)
Chlordane (0.002)
0.57%
0.34%
0.16%
0.10%
0.09%
0.02%
0.01%
Volatile Organic Chemicals
Occurrence Estimation Methodology
12
June 2003

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Contaminant
(MCL in mg/L)
1,2-Dichloropropane (0.005)
1,2,4-Trichlorobenzene (0.07)
1,1,2-Trichloroethane (0.005)
trans- 1,2-Dichloroethylene (0.1)
Vinyl Chloride (0.002)
Percent
Systems
>MRL
1.12%
1.08%
1.00%
0.80%
0.64%
Contaminant
(MCL in mg/L)
1,4-Dichlorobenzene (0.075)
o-Dichlorobenzene (0.6)
Vinyl Chloride (0.002)
1,2,4-Trichlorobenzene (0.07)
Styrene (0.1)
Percent
Pop. Served
by Systems
>MRL
6.50%
5.28%
4.92%
2.76%
2.69%
As mentioned above, Stage 1 analyses were also generated separately by ground water and surface source
water type. The same lists of high and low occurrence contaminants (included in Tables IV. A.I and
IV.A.2) were determined by all the ranking approaches (i.e., ground water ranking, surface water ranking,
or combined ground and surface water ranking) for the eight cross-section States data sets. See Appendix
A for summary tables of Stage 1 occurrence findings for all regulated contaminants.  For a detailed
review of the Stage 1 analytical approach and a presentation of the complete Stage 1  analytical findings,
please refer to the report titled First Stage Occurrence and Exposure Report for Six-Year Review
(Cadmus 2000).

Fluoride was consistently ranked as the highest occurrence IOC on most of the various ranking
approaches. Chromium and cadmium were also consistently ranked high in many of the ranking
approaches. Antimony and mercury were occasionally ranked with high occurrence.

For low occurrence of lOCs, beryllium was the most consistent contaminant of low ranking occurrence.
Antimony, cyanide and thallium were also commonly ranked as low occurrence contaminants using the
various ranking approaches.

Note there are seemingly contradictory occurrence findings for antimony because it occurs on both the
high occurrence list and the low occurrence list. However, these two occurrence measures are valid.  In
the case of antimony, the MCL is relatively close to the MRL, so when an analytical  concentration is
detected for antimony (above the MRL), the detection is likely to also be above the MCL.  Antimony is
detected relatively infrequently compared to other lOCs; its presence is infrequently  identified above the
MRL making it a "low occurrence contaminant." Yet on those few occasions when antimony is detected,
it is often detected at concentrations greater than the MCL. A large proportion of antimony results exceed
its MCL, relative to the other lOCs' detections exceeding their respective MCLs.  By this measure,
antimony is also considered a "high occurrence contaminant."  This apparent occurrence contradiction is
also possible in the findings for several other contaminants (e.g., the VOC vinyl chloride). These subtle
differences in occurrence measures must be noted when considering what type of occurrence assessment
and conclusions are to be made.

Ethylene dibromide (EDB), l,2-dibromo-3-chloropropane (DBCP), and bis(2-ethylhexyl)phthalate
(DEHP) were consistently ranked as the highest occurrence SOCs on most of the ranking approaches.
The next most frequent contaminant was atrazine, which was ranked high in many of the ranking
approaches. (Atrazine occurrence is being considered separately under other occurrence and exposure
analyses.) This was followed by benzo(a)pyrene, diquat, and endrin, which were occasionally ranked
with high occurrence. The high occurrences of phthalate are, in part, considered false positives related to
sample contamination by plastics and laboratory analytical problems.5
5 The false positive issue was informally evaluated. The issue was discussed with several national laboratories, and
available State occurrence data were evaluated over time. The opinions of the laboratory staff contacted
corresponded to the evaluation of the occurrence data; there appears to be no distinct time period or date after which
phthalate occurrence data can clearly be considered free of false positives.
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Carbofuran, glyphosate, chlordane, oxamyl, hexachlorocyclopentadiene, carbofuran, hexachlorobenzene,
and PCBs were consistently ranked as the lowest occurrence SOCs.

Dichloromethane, tetrachloroethylene, and trichloroethylene were consistently ranked as the highest
occurrence VOCs on most or all of the separate ranking approaches. The next most frequent contaminant
was 1,1-dichloroethylene which was ranked high in many of the ranking approaches. This was followed
by carbon tetrachloride, 1,1,1-trichloroethane, and, to a lessor degree, vinyl chloride and 1,4-
dichlorobenzene, which were occasionally ranked with high occurrence. Note that the high occurrences
of dichloromethane are, in part, considered false positives related to laboratory analytical problems.

For low occurrence of VOCs, 1,2-dichloropropane, 1,2,4-trichlorobenzene, vinyl chloride, styrene, and
o-dichlorobenzene were the most consistent contaminants of low rank occurrence based on the various
ranking approaches.

IV.B.  Comparison of State Data and URCIS  Stage 1 Findings

As an additional evaluation of the national "representativeness" of the initial eight cross-section States,
occurrence analyses from the cross-section States' were compared to similar occurrence analyses
aggregated from another cross-section of compliance monitoring data - the Unregulated Contaminant
Information System (URCIS) 24-State Cross-Section.  The URCIS data set includes information on sixty
regulated and unregulated VOCs, and two regulated SOCs from atotal of 40 U.S. States or Territories.
A group of 24 URCIS States was selected from the URCIS database, using the same cross-section
development approach described in Section II.  The majority of the data are from the first round of
required unregulated contaminant monitoring from 1987 through 1992.  It is important to note that
because of the age of the data, in relation to rapid improvements made in data processing systems, the
quality of data received by EPA for URCIS is highly variable.  For a detailed description of the URCIS
rankings, please refer to Section 4.5, in First Stage Occurrence and Exposure Report for Six-Year Review
(Cadmus 2000).

The URCIS data are from an earlier time period than are the data for this current. The URCIS data also
are largely limited to occurrence monitoring results for VOCs. Nonetheless, in aggregation, the
comparison to the URCIS data provides  an additional evaluation of the use of the cross-section States for
broad occurrence assessments indicative of national  occurrence. The comparison is qualitative,  but still
provides information for comparative assessments of, for example, the relative occurrence of the different
VOCs across  different time periods and different (yet presumably nationally-balanced) cross-sections of
States.

URCIS VOC  occurrence findings were ranked  according to systems and population served, and then
compared to the initial eight cross-section State data occurrence findings for VOCs. A general summary
of the determined high and low occurrence contaminants based on these rankings is described below.

High and low contaminant occurrence rankings, based on the number of systems and population served,
were conducted separately for surface water-supplied and ground water-supplied systems using  URCIS
Round 1 data from a group of 24 States.  Generally, there was agreement between the findings of high
and low occurrence contaminants for both systems and population served rankings and for surface and
ground water systems.  The URCIS rankings were also in general agreement with the rankings of the
eight cross-section States' data.  Again, please note that the high occurrences of dichloromethane are, in
part, considered false positives related to analytical problems.

The high occurrence VOCs common to both surface and ground water systems ranked by the proportion
of systems with at least one analytical result greater than the MCL were 1,1-dichloroethylene,
dichloromethane, tetrachloroethylene, and trichloroethylene. The low occurrence VOCs common  to both
surface and ground water systems ranked by proportion of systems were vinyl chloride,
o-dichlorobenzene, and 1,2,4-trichlorobenzene.

Based on the proportion of population served by systems with at least one analytical result greater than
the MCL, the high occurrence VOCs common to  both surface and ground water systems were


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1,1-dichloroethylene, dichloromethane, tetrachloroethylene, and trichloroethylene. The low occurrence
VOCs common to both surface and ground water systems ranked by population served were styrene and
1,2,4- trichlorobenzene.

As an additional comparison, tetrachloroethylene Stage 1 occurrence findings from the URCIS 24-State
cross-section were directly compared to the 8-State cross-section tetrachloroethylene findings.  While
URCIS does contain data on other regulated VOCs, tetrachloroethylene was selected for this comparison
because of its relatively large amount of occurrence data and analytical detections. Generally, the
findings for the other VOCs in URCIS were consistent with the 8-State cross-section. As Table IVB. 1
illustrates, the percent of systems and population served by systems estimated to exceed each threshold
was comparable for both cross-sections, though the 8-State cross-section occurrence findings were
consistently higher than those based on URCIS data.  A relatively small percentage of systems had any
analytical results that exceeded the MCL and 1A MCL for both cross-sections (less than 3 percent for
ground water and/or surface water).

The percentages of population served by systems with at least one analytical result of tetrachloroethylene
exceeding the MCL, 1A MCL, and MRL were also comparable. The proportion of population served by
ground water systems in the 8-State cross-section that exceeded the MCL, 1A MCL, and MRL equaled
32%, 37%, and 47%, respectively. This compares to  approximately  18%, 25%, and 34% of population
served by systems in the URCIS 24-State cross-section that had at least one analytical result greater than
the MCL, !/2 MCL, and MRL, respectively. The proportion of population served by surface water systems
exceeding each threshold also compares favorably between each cross-section.  A relatively small
percentage of population served by systems had any analytical results that exceeded the MCL and 1A
MCL for both cross-sections (less than 5 percent for either cross-section). However, there is a much
greater percentage of population served by surface water systems with any analytical detections (> MRL)
for both cross-sections.
Table IV.B.l.  Stage 1 Analysis Comparison of Tetrachloroethylene Occurrence in Different
Cross-Sections
Source Water
Type
Ground Water
Threshold
MCL
!/2 MCL
MRL
Percent of Systems
Exceeding Threshold
Initial 8-State
Cross-Section
1.2%
1.9%
4.5%
URCIS 24-State
Cross-Section
0.9%
1.5%
3.4%
Percent of Population Served by
Systems Exceeding Threshold
Initial 8-State
Cross-Section
32.1%
37.3%
46.7%
URCIS 24-State
Cross-Section
17.7%
25.3%
33.7%

Surface Water
MCL
!/2 MCL
MRL
1.7%
2.9%
8.7%
0.7%
1.0%
2.7%
3.2%
4.9%
29.0%
2.1%
3.5%
17.5%
The MCL for tetrachloroethylene is 0.005 mg/L. One-half the MCL is 0.0025 mg/L. The MRL is variable.
V.  FULL SIXTEEN STATE DATA SETS AND CROSS-SECTION

The coverage suggests that the initial eight cross-section State data sets are indicative of national
occurrence and the aggregate size of the data sets is substantial (representing approximately 10 million
analytical results from nearly 22,000 PWSs). Nonetheless, the addition of data from other States would
Occurrence Estimation Methodology
15
June 2003

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contribute to more nationally representative occurrence analyses and greater confidence in the
conclusions derived from the analyses.

Consideration was first made regarding the expanded use of State data sets that were already in hand (i.e.,
the 6 data sets not used in the initial 8-State cross-section).  For example, Indiana's data set had been
previously volunteered, and was available for use. The data set, which is quite complete and of
satisfactory  quality, was carefully considered for addition to the national cross-section (as long as other
State data sets were added from other quartiles for balance). The other five States, however, were not
usable for expanding the national cross-section of State data. For instance, Iowa had an adequate and
complete data set,6 but using Iowa data would over-represent the Midwestern "Cornbelt" States, with
Illinois and possibly Indiana (see above) already included in the national cross-section of State data. The
other four data sets were in-hand (specifically Kansas, Massachusetts, Missouri, and Ohio) were
incomplete,  biased, or not functionally suitable for expanding the national cross-section.

The acquisition of additional State data sets to expand the national cross-section in a balanced and
representative way was conducted using the same pollution potential quartile distribution and geographic
diversity criteria that were used to develop the balanced and representative initial 8-State cross-section.
As with the  selection of the initial 8 cross-section States, consideration of the additional cross-section
States was based primarily on the ranking indicator of the number of manufacturing establishments per
square mile, but total farm agricultural expenditures and TRI releases were also considered to insure that
the occurrence data from the selected States were, collectively, representative or indicative of national
occurrence.

Maintaining a geographic balance, to the extent possible, also contributes to  an aggregate data set that is
more representative of the variety of geographic conditions present nationally.  Regarding this balance,
further representation from the New England area, the southeast and south-central States would contribute
to balancing an expanded national coverage. Based on the consideration of States' pollution potential
rankings, how they best fit into the quartile distribution, and how their spatial or geographic coverage
contributed to a representative national cross-section of States, the States considered for addition to the
national cross-section contaminant occurrence data set were:

        Quartile 1) Rhode Island, Pennsylvania, Florida;
        Quartile 2) Indiana,  New Hampshire, Tennessee, South Carolina, Vermont;
        Quartile 3) Kentucky, Minnesota,  Texas, Mississippi, West Virginia, Oklahoma; and
        Quartile 4) Utah, Nebraska, South Dakota.

As new State data sets were  added to the initial group of eight cross-section States, the data sets were
added in specific groups to further build the cross-section sample in a balanced manner. Based on data
availability and quality, the additional group of eight States added to the cross-section were: Florida -
Quartile 1; Indiana, South Carolina, and Vermont - Quartile 2; Kentucky,  and Texas  - Quartile 3;
Nebraska, and South Dakota - Quartile 4.  A summary of these additional eight State data sets is presented
in Table V.I.
6 For the CMR Report, contaminant occurrence results from Iowa were included, but the Iowa data set was not
directly used.  Iowa has a published report that provided the necessary occurrence figures, which provided
occurrence information without conducting additional analyses. Therefore, the actual Iowa data set has not yet been
procured, but likely could be, if necessary.

Occurrence Estimation Methodology                  16                                       June 2003

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Table V.I. Additional State Data Sets Used for Analyses
State
Florida
Indiana
Kentucky
Nebraska
South Carolina
South Dakota
Texas
Vermont
Total
Contaminant Groups
Represented '
lOCs, SOCs, VOCs
IOCS, SOCs, VOCs, 0
lOCs, SOCs, VOCs, O
lOCs, SOCs, VOCs
lOCs, SOCs, VOCs
lOCs, SOCs, VOCs
lOCs, SOCs, VOCs
lOCs, SOCs, VOCs, 0
lOCs, SOCs, VOCs, O
Number of
Analytical Results
713,543
257,428
177,070
189,959
501,286
55,526
947,615
248,438
3,090,865
Number of PWSs
Represented
6,297
1,488
570
1,555
2,352
965
5,350
873
19,450
Time Period 2
1993-1997
1982-1997
1993-1997
1993-1999
1989-2000
1990-2000
1990-2000
1987-2000
1982-2000
1) lOCs = the 13 regulated inorganic chemicals; SOCs = the 30 regulated synthetic organic chemicals; VOCs = the 21 regulated volatile organic
chemicals; O = Other regulated or unregulated chemicals.
2) Data from 1999 and 2000 were excluded from analysis.  Most data sets contained complete data only through 1998.


Table V.2 shows quartile rankings for the 16 States contained in the national cross-section.  Figure V.2
shows the distribution of the initial eight cross-section States included with the additional eight cross-
section States. The distribution is broad and relatively uniform across all four quartiles (columns) of the
manufacturing pollution potential indicators and across all four quartiles (rows) of the agriculture
pollution potential indicators. Note that the manufacturing pollution potential indicator was the primary
ranking factor with agricultural and TRI indicators considered  in a secondary sense.  Figure V.3 is a map
illustrating the geographic distribution of the initial eight cross-section States, as well as the additional
eight cross-section States.  Together, the 16 States provide a broad representation of the geologic,
hydrologic, and climatic variability across the United States.
Occurrence Estimation Methodology
17
June 2003

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Table V.2.  National Cross-Section States with Ranking of Pollution Potential Indicators
Quartiles
for Rank-Order of
All States Based on
Manufacturing Ranking
1
2
3
4
States in 16-State
National
Cross-Section
NJ
IL
CA
FL
MI
IN
SC
VT
AL
KY
TX
OR
NE
NM
SD
MT
National Ranking of
Pollution Potential Indicators
Manufacturing1
2
10
11
12
13
15
21
23
25
27
30
34
42
44
45
48
Agriculture2
37
2
1
4
18
7
32
47
26
27
6
22
9
40
21
34
TRI Releases3
8
11
38
13
16
6
10
45
7
21
20
39
41
40
49
34
The additional eight cross-section States are listed in bold.

1) "Manufacturing" = the number of manufacturing facilities per square mile
2) "Agriculture" = total expenditures on farm agricultural chemicals
3) "TRI" = TRI releases (in total pounds) per square mile
Occurrence Estimation Methodology
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June 2003

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Figure V.2.  Distribution of State Ranking for Manufacturing Establishments/ Sq. Mile vs. Farm
Ag. Chemical Expenses (Highlighting Initial 8 & Additional 8 Cross-Section States)
                                   Ranking of the No. of Manufacturing Establishments/ Sq. Mile
                  CA
                  IL
                  MI

                  OR

                  .IL
                  MT

                   NJ

                  MM
                                                                                           3
                                                                                           "o
                                                                                           H
                                                                                           i>
                                                                                           •3
                                                                   MI CA IL      NJ
                                                 TX  KY   VT SC     IN  FL
                       ^ Initial 8-State Cross-Section
                       ^ Additional 8-State Cross-Section
                       O  All Other States
Occurrence Estimation Methodology
19
June 2003

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Figure V.3. Map of the 16 Cross-Section States
                                                           Initial 8-State Cross-Section
                                                           Additional 8-State Cross-Section
                                                           States not included in Cross-Section
V.A.   Data Use and Editing

Similar to the initial eight cross-section States, a considerable amount of data editing was necessary for
the additional eight cross-section States.  Each data set was reviewed to ensure it contained the basic data
elements necessary to conduct a consistent analysis for this study. These elements were reviewed with
State contacts to ensure consistent and appropriate interpretations.  Once data quality issues were
resolved, each data set was converted into a consistent format.

A common data quality issue associated with the additional eight States involved data that appeared to
have been recorded or mislabeled in incorrect units. In many State databases, analytical results are
presented as integers in one column with a corresponding column to identify how many decimal points
are associated with that integer.  Because these data are often entered manually by a data entry person,
there is a large potential for error. If the "decimal point" column is incorrectly entered, the analytical
results are recorded in the data set in the wrong units.  In many cases, detailed double-checking with the
analytical results for similar contaminants in other States showed that the analytical results appeared to be
incorrect (either too low or too high) by a factor of 1,000.  The interpretation was that the data were
mistakenly recorded in micrograms per liter (• g/L) in the database, but actually represented data in
milligrams per liter (mg/L) (or vice versa). These data corrections were somewhat straightforward after
identifying, reviewing, and cross-checking the analytical results. The criteria for excluding outliers
required the evaluation of each individual analytical result. Other data that appeared to be in incorrect
units, but were not off by the typical factor of 1,000, were either left in the database or excluded from
analysis, depending on how much of an outlier it appeared to be.

Values evaluated were both high and low value outliers. Therefore, by removing incorrect values, both
large and small questionable values were removed. Less than  0.02 percent of the total number records
were identified as analytical results recorded in the incorrect units.  Less than 0.25 percent of the
analytical results were identified and changed to non-detections. Of the total number of records excluded
from analysis, only 0.002 percent of the total data were removed as suspected or confirmed outliers.
Occurrence Estimation Methodology
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June 2003

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V.B.  Comparison of 8-State vs. 16-State National Cross-Sections

To further evaluate the representativeness of the cross-section, occurrence analyses from the 8-State
cross-section were compared to occurrence analyses from the 16-State cross-section. The percent of
systems (and population served by systems) with at least one analytical result greater than the MCL and
MRL in the eight States were compared to the same measures for the 16-State cross-section. The 8-State
and 16-State  Stage 1 findings were quite similar. Generally, the contaminants found with high, medium
or low relative occurrence based on the 8-State Stage  1 analyses were the same contaminants with high,
medium or low occurrence, respectively, based on the 16-State data set.  The ranking from highest to
lowest occurrence was not identical in the 8-State and 16-State data sets but, for this simple non-
parametric evaluation, the dissimilarities were small.

Table V.B. 1 compares the 8-State and 16-State cross-sections based on the percent of systems with at
least one analytical results greater than the MRL or MCL. The percentages are generally consistent
between the two cross-sections. For the SOCs and VOCs, the proportion of systems with analytical
detections (i.e., "% Systems > MRL") is generally higher for the 8-State cross-section than the 16-State
cross-section. With the exception of a few contaminants, the proportion of systems with at least one
analytical result greater than the MCL (i.e., "% Systems > MCL") is also higher for the 8-State cross-
section than the 16-State cross-section.

The greatest discrepancy between the 8-State and 16-State proportion of systems with analytical
detections is seen in the contaminant cyanide. The 16-State percentage of systems with analytical
detection of cyanide is almost 8 times greater than the 8-State percentage of systems with analytical
detection of cyanide. Based on the proportion of systems with at least one analytical result greater than
the MCL, the greatest discrepancy between the 8-State and 16-State cross-section is seen in the
contaminant diquat. The percentage of systems in the 8 States with at least one analytical result greater
than the MCL for diquat is almost three times greater than the percentage of systems in the 16  States with
at least one analytical result greater than the MCL for diquat.
Table V.B.I. Comparison of Stage 1 Analyses for 8-State vs. 16-State National Cross-Sections
Based on the Percent of Systems
Contaminant
MCL
(mg/L)
% Systems > MRL
8 States
16 States
% Systems > MCL
8 States
16 States
Inorganic Chemicals
Antimony
Barium
Beryllium
Cadmium
Chromium
Cyanide
Fluoride
Mercury
Selenium
Thallium
0.006
2
0.004
0.005
0.1
0.2
4
0.002
0.05
0.002
3.25%
49.7%
1.80%
5.14%
16.8%
2.27%
81.0%
5.69%
9.27%
2.49%
14.4%
71.2%
3.32%
17.6%
18.3%
17.0%
83.8%
17.3%
22.1%
4.22%
0.416%
0.25%
0.295%
0.741%
0.214%
0.234%
1.04%
0.336%
0.164%
0.295%
0.623%
0.174%
0.217%
0.544%
0.127%
0.167%
1.28%
0.263%
0.107%
0.679%
Occurrence Estimation Methodology
21
June 2003

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Contaminant
MCL
(mg/L)
% Systems > MRL
8 States
16 States
% Systems > MCL
8 States
16 States
Synthetic Organic Chemicals
Alachlor
Atrazine
Benzo(a)pyrene
Bis(2-ethylhexyl)adipate
Bis(2-ethylhexyl)phthalate
Carbofuran
Chlordane
2,4-D
Dalapon
1 ,2-Dibromo-3-chloropropane
Dinoseb
Diquat
Endothall
Endrin
Ethylene Dibromide
Glyphosate
Heptachlor
Heptachlor Epoxide
Hexachlorobenzene
Hexachlorocyclopentadiene
Lindane
Methoxychlor
Oxamyl
PCBs
Pentachlorophenol
Picloram
Simazine
Toxaphene
2,4,5-TP
0.002
0.003
0.0002
0.4
0.006
0.04
0.002
0.07
0.2
0.0002
0.007
0.02
0.1
0.002
0.0000
0.7
0.0004
0.0002
0.001
0.05
0.0002
0.04
0.2
0.0005
0.001
0.5
0.004
0.003
0.05
0.911%
3.89%
0.407%
6.56%
12.0%
0.103%
1.81%
0.0580%
1.66%
2.31%
0.457%
0.915%
0.238%
0.347%
1.02%
0.0687%
0.195%
0.199%
0.0367%
0.951%
0.279%
0.230%
0.0793%
0.202%
0.781%
0.812%
3.02%
0.156%
0.658%
0.670%
3.83%
0.443%
7.31%
12.5%
0.0646%
1.19%
0.121%
1.10%
1.61%
0.237%
0.491%
0.151%
0.179%
1.06%
0.102%
0.0842%
0.0920%
0.0928%
0.891%
0.162%
0.193%
0.0760%
0.0894%
0.431%
0.411%
1.80%
0.0797%
0.399%
0.000%
1.01%
0.0479%
0.000%
1.97%
0.000%
0.0134%
0.000%
0.000%
1.49%
0.0305%
0.0590%
0.0297%
0.0533%
0.768%
0.000%
0.0177%
0.0362%
0.000%
0.000%
0.0798%
0.0136%
0.000%
0.0865%
0.0459%
0.000%
0.103%
0.0173%
0.000%
0.000%
0.676%
0.0531%
0.00944%
2.20%
0.000%
0.00637%
0.0152%
0.000%
0.912%
0.0203%
0.0218%
0.0348%
0.0247%
0.724%
0.000%
0.00702%
0.0283%
0.00714%
0.000%
0.0373%
0.00622%
0.000%
0.0335%
0.0270%
0.000%
0.0550%
0.00724%
0.000%
Volatile Organic Chemicals
Benzene
Carbon Tetrachloride
1 ,4-Dichlorobenzene
0.005
0.005
0.075
1.54%
2.37%
2.28%
1.31%
1.99%
1.76%
0.235%
0.254%
0.000%
0.189%
0.204%
0.000%
Occurrence Estimation Methodology
22
June 2003

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Contaminant
o-Dichlorobenzene
1 ,2-Dichloroethane
1 , 1 -Dichloroethy lene
cis-1 ,2-Dichloroethylene
trans- 1 ,2-Dichloroethylene
Dichloromethane
1 ,2-Dichloropropane
Ethylbenzene
Monochlorobenzene
Styrene
Tetrachloroethylene
Toluene
1 ,2,4-Trichlorobenzene
1,1,1 -Trichloroethane
1 ,1 ,2-Trichloroethane
Trichloroethylene
Vinyl Chloride
Xylenes (Total)
MCL
(mg/L)
0.6
0.005
0.007
0.07
0.1
0.005
0.005
0.7
0.1
0.1
0.005
1
0.07
0.2
0.005
0.005
0.002
10
% Systems > MRL
8 States
1.13%
1.70%
2.03%
1.96%
0.838%
14.5%
1.12%
2.52%
1.30%
1.49%
5.12%
4.57%
0.953%
3.83%
1.21%
3.97%
0.673%
4.86%
16 States
0.608%
1.31%
1.58%
1.37%
0.526%
8.59%
0.673%
3.62%
0.748%
0.988%
3.36%
4.73%
0.610%
2.50%
0.619%
2.61%
0.606%
4.16%
% Systems > MCL
8 States
0.000%
0.188%
0.301%
0.0194%
0.000%
0.896%
0.117%
0.000%
0.000%
0.000%
1.30%
0.000%
0.000%
0.0166%
0.0804%
1.00%
0.0914%
0.000%
16 States
0.000%
0.126%
0.236%
0.0305%
0.000%
0.669%
0.0682%
0.000%
0.000%
0.000%
0.778%
0.000%
0.000%
0.00811%
0.0404%
0.647%
0.110%
0.000%
Note: All percentages are shown to three significant figures.
Table V.B.2 compares the 8-State and 16-State cross-sections based on the percent of population served
by systems. The percentages are generally consistent between the two cross-sections. For the lOCs, the
proportion of population served by systems "> MRL" is always smaller for the 8-State cross-section than
the 16-State cross-section.  For the SOCs, the proportion of population served by systems "> MRL" and
"> MCL" is generally higher for the 8-State cross-section than the 16-State cross-section. For the VOCs,
the proportion of population served by systems "> MRL" and "> MCL" is always higher for the 8-State
cross-section than the 16-State cross-section.

The greatest discrepancy between the 8-State and 16-State proportion of population served by systems
with analytical detections is seen in the contaminant chlordane. The 16-State percentage of systems with
analytical detection of chlordane is about 12 times the 8-State percentage of systems with analytical
detection of chlordane.  Based on the proportion of systems with at least one analytical result  greater than
the MCL, the greatest discrepancy between the 8-State and 16-State cross-section is seen in the
contaminant endothall.  The percentage of systems in the  16 States with at least one analytical result
greater than the MCL for endothall is approximately 34 times the percentage of systems in the 8 States
with at least one analytical  result greater than the MCL  for endothall.
Occurrence Estimation Methodology
23
June 2003

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Table V.B.2. Comparison of Stage 1 Analyses for 8-State vs. 16-State National Cross-Sections
Based on the Percent of Population Served by Systems
Contaminant
MCL
(mg/L)
% Population Served by Systems
>MRL
8 States
16 States
% Population Served by Systems
>MCL
8 States
16 States
Inorganic Chemicals
Antimony
Barium
Beryllium
Cadmium
Chromium
Cyanide
Fluoride
Mercury
Selenium
Thallium
0.006
2
0.004
0.005
0.1
0.2
4
0.002
0.05
0.002
4.03%
82.3%
3.26%
5.84%
26.6%
3.34%
96.2%
6.01%
7.59%
2.26%
14.5%
84.1%
6.65%
14.9%
28.7%
10.7%
96.9%
21.6%
22.8%
6.49%
0.210%
0.346%
0.098%
0.537%
1.01%
0.246%
6.84%
0.391%
0.506%
0.144%
0.234%
0.309%
0.621%
1.56%
0.666%
0.399%
4.56%
0.275%
0.309%
1.85%
Synthetic Organic Chemicals
Alachlor
Atrazine
Benzo(a)pyrene
Bis(2-ethylhexyl)adipate
Bis(2-ethylhexyl)phthalate
Carbofuran
Chlordane
2,4-D
Dalapon
1 ,2-Dibromo-3-chloropropane
Dinoseb
Diquat
Endothall
Endrin
Ethylene Dibromide
Glyphosate
Heptachlor
Heptachlor Epoxide
Hexachlorobenzene
0.002
0.003
0.0002
0.4
0.006
0.04
0.002
0.07
0.2
0.0002
0.007
0.02
0.1
0.002
0.00005
0.7
0.0004
0.0002
0.001
1.31%
11.9%
0.988%
9.87%
32.6%
0.938%
0.0133%
3.12%
2.20%
18.4%
0.665%
0.984%
0.703%
1.68%
18.5%
0.0214%
0.336%
0.157%
0.0924%
2.55%
16.1%
1.39%
6.66%
28.0%
0.541%
0.164%
2.76%
1.86%
13.5%
0.432%
0.764%
0.505%
1.30%
13.5%
0.0402%
0.191%
0.101%
0.329%
0.000%
1.39%
0.294%
0.000%
2.74%
0.000%
0.000%
0.189%
0.000%
16.3%
0.0278%
0.325%
0.00127%
0.352%
17.0%
0.000%
0.000699%
0.0306%
0.000%
0.00%
2.99%
0.243%
0.0292%
3.19%
0.00%
0.000477%
0.117%
0.00%
11.3%
0.0252%
0.208%
0.0429%
0.206%
12.3%
0.00%
0.000398%
0.0226%
0.0399%
Occurrence Estimation Methodology
24
June 2003

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Contaminant
Hexachlorocyclopentadiene
Lindane
Methoxychlor
Oxamyl
PCBs
Pentachlorophenol
Picloram
Simazine
Toxaphene
2,4,5-TP
MCL
(mg/L)
0.05
0.0002
0.04
0.2
0.0005
0.001
0.5
0.004
0.003
0.05
% Population Served by Systems
>MRL
8 States
3.54%
1.03%
1.36%
0.098%
0.568%
1.70%
0.970%
9.51%
1.47%
1.57%
16 States
2.28%
0.744%
1.06%
0.166%
0.338%
1.24%
0.584%
11.2%
0.851%
1.08%
% Population Served by Systems
>MCL
8 States
0.000%
0.852%
0.215%
0.000%
0.494%
0.00128%
0.000%
0.0663%
0.230%
0.000%
16 States
0.00%
0.497%
0.125%
0.00%
0.293%
0.000761%
0.00%
0.0471%
0.131%
0.000%
Volatile Organic Chemicals
Benzene
Carbon Tetrachloride
1 ,4-Dichlorobenzene
o-Dichlorobenzene
1 ,2-Dichloroethane
1 , 1 -Dichloroethy lene
cis-1 ,2-Dichloroethylene
trans- 1 ,2-Dichloroethylene
Dichloromethane
1 ,2-Dichloropropane
Ethylbenzene
Monochlorobenzene
Styrene
Tetrachloroethylene
Toluene
1 ,2,4-Trichlorobenzene
1,1,1 -Trichloroethane
1 ,1 ,2-Trichloroethane
Trichloroethylene
Vinyl Chloride
Xylenes (Total)
0.005
0.005
0.075
0.6
0.005
0.007
0.07
0.1
0.005
0.005
0.7
0.1
0.1
0.005
1
0.07
0.2
0.005
0.005
0.002
10
17.4%
19.7%
6.50%
5.22%
19.3%
24.1%
24.8%
16.8%
44.0%
17.9%
18.3%
7.64%
2.69%
36.3%
26.2%
2.75%
30.3%
16.7%
37.3%
4.89%
31.0%
12.0%
14.8%
4.38%
2.30%
12.3%
16.0%
18.2%
10.5%
28.6%
11.1%
16.6%
5.54%
2.08%
27.2%
22.0%
1.96%
20.2%
10.4%
24.9%
3.81%
24.0%
0.701%
12.4%
0.000%
0.000%
14.1%
13.6%
0.0725%
0.000%
15.0%
1.30%
0.000%
0.000%
0.000%
22.2%
0.000%
0.000%
0.0733%
11.8%
21.1%
2.64%
0.000%
0.518%
7.35%
0.000%
0.000%
8.40%
8.68%
0.247%
0.000%
9.50%
1.18%
0.000%
0.000%
0.000%
13.5%
0.000%
0.000%
0.0432%
6.97%
13.3%
1.86%
0.000%
Note: All percentages are shown to three significant figures.
Occurrence Estimation Methodology
25
June 2003

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The occurrence findings in Tables V.B.I and V.B.2 are broadly consistent between the two cross-sections
regarding contaminant occurrence rankings and "orders of magnitude" values. The 16-State cross-section
contains twice as much data as the 8-State cross-section while also covering a broader range
geographically and across pollution potential indicators.  Therefore, all additional analyses were
conducted on the 16-State cross-section.


VI.  STAGE 2 ANALYSIS

Stage 1 analysis is based on the proportion of systems with at least one analytical result greater than a
specified threshold.  Stage 2 analysis, however, is based on the proportion of systems with a mean
concentration value greater than a specified threshold. Thus, the Stage 1 analysis roughly assesses
"peak" contaminant concentrations in public water systems while the Stage 2 analyses roughly assess
"long-term" contaminant concentrations in public water systems. Stage 1 analysis are generally reported
as "less than MRL"  rather than as actual numerical values. The numerical concentration value of a non-
detection lies somewhere between zero and the specified Minimum Reporting Level. (The Minimum
Reporting Level represents the lowest level that can be reliably achieved within specified limits of
precision and accuracy under routine laboratory operating conditions.) Historically, three  approaches have
been commonly used to  determine the mean of such data: assume non-detection data are equal to zero,
assume all non-detection data are equal to half the MRL, or assume all non-detection data are  equal to the
MRL.  An arithmetic mean is then calculated using these fabricated numbers together with values above
the MRL. While these methods are widely used, they all "introduce a bias and result in erroneous
estimates of the mean and standard deviation" (Porter et. al., as cited in Travis and Land, 1990).  Setting
all non-detections equal  to zero likely underestimates the true  analytical value of the sample, and setting
all non-detections equal  to the MRL or half the MRL likely over estimates the true analytical value.

VI.A.  Preparation of State Data for the Stage 2 Analysis

The contaminant occurrence rankings (described in Section IV) provided a preliminary means by which
EPA began to assess the occurrence of regulated contaminants considered for Six-Year Review. The
subsequent Stage 2 analyses were more rigorous and required several intermediate data management and
analysis steps prior to conducting any parametric statistical analyses. A summary of the data editing
necessary to enable  Stage 2 analysis is described below.

As previously noted, no  IOC data were originally available from the State of Michigan. As part of the
preparation for Stage 2 analysis, Michigan State data management staff were contacted.  Compliance
monitoring data were acquired for fluoride, beryllium, chromium, mercury, and thallium.  The data were
checked and edited for quality, and were added to the cross-section data set.

Once the 16-State cross-section was established (including Michigan IOC data), the data still required
further computational manipulation prior to estimating national occurrence.  Because the  Stage 2 analysis
generates mean concentration values for each system, this analysis is affected by all observations
including non-detections and detections.  Therefore, each analytical record for each contaminant had to be
checked to prepare the data for Stage 2 analysis. Many data quality issues appeared that were not
discovered in the first round of data quality review.  For example, South Dakota data contained 91
analytical detections for beryllium.  Fifty-six of these detections were equal to 0.0005. It is very unusual
to have such a large proportion (62 percent) of analytical detections all equal to the same value. Because
0.0005 mg/L is well below the MCL for beryllium (0.004 mg/L), these data would not affect Stage 1
analysis.  However,  so many analytical results equal to the same concentration value would greatly
influence the mean concentration value used in Stage 2 analysis.  After consultation with  State data
management staff in South Dakota, it was determined that these analytical results were actually non-
detections. Apparently, the values were simply entered into the database at the MRL, and no flag was
included to specify whether the result was a detection or non-detection.

Decisions also had to be made on how to quantitatively include non-detection data. Some States record
the MRL in the analytical result column and also include a "<" in a corresponding column to flag the
record as a non-detection. Other  States simply include a zero  in the analytical result column to signify a


Occurrence Estimation Methodology                26                                       June 2003

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non-detection. Although non-detection data were not a concern in the Stage 1 analysis, they pose a
problem within Stage 2 analysis where mean concentration values are estimated for each system. In order
to estimate a mean concentration value for each system, a non-zero MRL must be included for all
analytical results that were reported either as zero or alphanumerically as "non-detection" or "ND," etc.
(The method used to estimate mean concentration values for each system is described in Section VI.D) A
convention was developed to set all such records equal to "less-than" the State's non-zero modal MRL.
However, for the States that set all non-detections equal to zero, the non-detections were set equal to "less
than" the non-zero modal MRL for all  16 States. (Note: This is not the same type of substitution method
described in the first paragraph of this Section.  When non-detection values are set equal to the non-zero
modal MRL, they are still considered "less-than" that non-zero modal MRL.  The substitution method
mentioned early simply set the non-detection values equal to the MRL, as if that were the true numerical
concentration value.)

The final element of the Stage 2 data quality analysis is related to the source water type and population
served for each system.  For the Stage 2 analysis, it was necessary to define each system in a unique
source water type/population size strata.  Systems using both ground water and surface water,  and
systems using ground water under direct influence of surface water, were included with surface water
data. Systems with more than one specified value of their population served in the  original data were
included using the largest population served value. Because these data management decisions were not
conducted until after the completion of the Stage 1 analysis, some very slight differences (based on the
very few number of systems so affected) may occur between Stage 1 and Stage 2 findings.

Table VI.A. 1 describes the occurrence data from the 16-State cross-section data set used for Stage 2
analysis. For each contaminant, this table includes the MCL values, as well as the total number of
analyses, systems, and population served by systems  that have data represented in the 16 cross-section
States. All population numbers were rounded to the nearest hundred. Also presented are the non-zero
modal MRL values substituted for all non-detection data that were originally set equal to zero  by the
States. The final column in Table VI.A. 1 lists the range of MRL values as reported by the States. As
illustrated, these values ranged from 0 to as high as 100 mg/L.  For the Stage 2 analysis, the non-zero
modal MRL (also included in Table VI.A. 1) was substituted for all non-detection data that were  originally
equal to zero.
Table VI.A.l. Contaminant Occurrence Data From the 16-State Cross-Section Used in Stage 2
Analysis
Contaminant
Total
Number of
Analyses
Total
Number of
Systems
Total
Population
Served by
Systems
MCL
(mg/L)
Non-Zero
Modal MRL
(mg/L)
Range of
MRLs
Reported by
the States
(mg/L)
Inorganic Chemicals
Antimony
Barium
Beryllium
Cadmium
Chromium
Cyanide
Fluoride
Mercury
Selenium
43,757
64,076
47,761
62,600
65,437
27,648
93,062
64,764
61,978
15,725
17,780
18,933
16,924
19,695
9,559
20,803
18,995
16,820
101,194,400
102,837,700
104,573,700
102,672,300
105,380,000
73,497,500
107,075,700
105,096,700
102,480,300
0.006
2
0.004
0.005
0.1
0.2
4
0.002
0.05
0.002
0.1
0.001
0.001
0.01
0.1
0.1
0.001
0.005
0-0.2
0-2
0- 1
0-0.5
0-5
0- 10
0- 100
0-0.5
0-0.5
Occurrence Estimation Methodology
27
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Contaminant
Thallium
Total
Number of
Analyses
46,959
Total
Number of
Systems
17,972
Total
Population
Served by
Systems
104,291,600
MCL
(mg/L)
0.002
Non-Zero
Modal MRL
(mg/L)
0.001
Range of
MRLs
Reported by
the States
(mg/L)
0-2.2
Synthetic Organic Chemicals
Alachlor
Atrazine
Benzo(a)pyrene
Bis(2-ethylhexyl)adipate
Bis(2-ethylhexyl)phthalate
Carbofuran
Chlordane
2,4-D
Dalapon
1 ,2-Dibromo-3-chloropropane
Dinoseb
Diquat
Endothall
Endrin
Ethylene Dibromide
Glyphosate
Heptachlor
Heptachlor Epoxide
Hexachlorobenzene
Hexachlorocyclopentadiene
Lindane
Methoxychlor
Oxamyl
PCBs
Pentachlorophenol
Picloram
Simazine
Toxaphene
2,4,5-TP
58,700
67,492
46,522
42,757
41,052
51,994
59,689
59,952
44,440
98,559
49,287
36,443
32,606
66,100
121,327
33,957
57,489
57,731
52,931
52,614
62,383
66,046
47,664
33,336
53,344
46,323
68,176
52,429
58,246
14,330
14,797
11,292
10,597
9,418
13,925
13,184
15,688
11,644
14,042
14,780
9,159
8,624
16,209
15,688
7,862
14,245
14,133
14,011
13,922
16,098
16,089
13,157
8,950
14,838
12,907
14,533
13,805
15,539
95,678,600
98,200,900
88,210,900
59,319,700
78,293,000
94,338,000
97,459,900
107,117,600
89,946,800
87,727,200
94,611,700
73,602,900
69,914,100
99,994,100
88,839,500
70,081,900
96,563,400
96,222,900
94,035,300
93,429,200
99,942,600
99,925,500
92,345,800
82,625,900
95,138,200
93,235,500
98,178,100
95,108,100
106,937,300
0.002
0.003
0.0002
0.4
0.006
0.04
0.002
0.07
0.2
0.0002
0.007
0.02
0.1
0.002
0.00005
0.7
0.0004
0.0002
0.001
0.05
0.0002
0.04
0.2
0.0005
0.001
0.5
0.004
0.003
0.05
0.0002
0.001
0.00002
0.0006
0.0006
0.0009
0.0002
0.0001
0.001
0.00002
0.001
0.0004
0.009
0.00001
0.00002
0.006
0.00004
0.00002
0.0001
0.005
0.00002
0.0001
0.002
0.0001
0.00004
0.0001
0.001
0.001
0.005
0-0.2
0-0.1
0 - 0.02
0-0.4
0-0.2
0-0.9
0-0.2
0-0.5
0 - 0.488
0-0.5
0-0.2
0-0.4
0-0.25
0 - 0.26
0-0.01
0-6
0-0.1
0-0.1
0-0.1
0-0.1
0-0.1
0-0.5
0-2
0-0.01
0 - 0.306
0-0.2
0-0.1
0-2.2
0-0.2
Occurrence Estimation Methodology
28
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Contaminant
Total
Number of
Analyses
Total
Number of
Systems
Total
Population
Served by
Systems
MCL
(mg/L)
Non-Zero
Modal MRL
(mg/L)
Range of
MRLs
Reported by
the States
(mg/L)
Volatile Organic Chemicals
Benzene
Carbon Tetrachloride
1 ,4-Dichlorobenzene
o-Dichlorobenzene
1 ,2-Dichloroethane
1 , 1 -Dichloroethylene
cis-Dichloroethylene
trans-Dichloroethylene
Dichloromethane
1 ,2-Dichloropropane
Ethylbenzene
Monochlorobenzene
Styrene
Tetrachloroethylene
Toluene
1 ,2,4-Trichlorobenzene
1,1,1 -Trichloroethane
1 , 1 ,2-Trichloroethane
Trichloroethylene
Vinyl Chloride
Xylenes (Total)
188,811
182,944
123,229
133,512
180,631
170,411
180,839
177,541
170,899
180,920
184,179
134,461
174,650
195,239
184,358
167,546
191,476
173,927
201,235
187,950
170,946
23,266
23,028
18,961
20,714
23,038
19,101
22,920
23,570
21,530
21,988
23,935
20,730
22,272
22,362
23,949
21,483
24,653
22,284
23,035
24,607
22,111
110,866,600
110,605,500
72,994,500
74,066,200
110,794,100
106,607,600
110,777,600
107,446,600
110,146,100
110,450,100
111,061,000
74,082,400
110,550,900
110,557,800
111,250,100
109,956,600
111,206,600
110,366,500
110,612,900
111,200,800
105,314,200
0.005
0.005
0.075
0.6
0.005
0.007
0.07
0.1
0.005
0.005
0.7
0.1
0.1
0.005
1
0.07
0.2
0.005
0.005
0.002
10
0.0005
0.0005
0.0005
0.0005
0.0005
0.0005
0.0005
0.0005
0.0005
0.0005
0.0005
0.0005
0.0005
0.0005
0.0005
0.0005
0.0005
0.0005
0.0005
0.0005
0.0005
0-0.5
0-0.5
0-0.5
0 - 0.006
0- 1
0-0.5
0 - 0.07
0-0.01
0 - 0.62
0-0.5
0 - 0.02
0-0.01
0 - 0.02
0-0.5
0 - 0.02
0 - 0.07
0 - 0.039
0-0.5
0-0.5
0-0.018
0-0.1
The reduced number of systems sampling for SOC data, as compared to lOCs and VOCs, likely relates to State waivers for pesticides and
herbicides.
VLB.   Previous Occurrence Estimation Methods

It is very difficult to calculate a simple arithmetic mean for each PWS because most compliance
monitoring data are non-detections.  Such concentrations are generally reported as "less than MPvL" rather
than as actual numerical values. The numerical concentration value of a non-detection lies somewhere
between zero and the specified MRL. In the past, several estimation approaches have been implemented
to estimate system mean concentrations when non-detection data are present. Substitution is a common
method used to determine the mean of such data. This method assumes that all non-detection data are
equal to zero, equal to half the MRL, or equal to the MRL. An arithmetic mean is then calculated using
these fabricated numbers together with values above the MRL.  While these methods are widely used,
they all "introduce a bias and result in erroneous estimates of the mean and standard deviation" (Porter et.
al. as cited in Travis and Land 1990). Setting all non-detections equal to  zero likely underestimates the
Occurrence Estimation Methodology
29
June 2003

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true analytical value of the sample, and setting all non-detections equal to the MRL or half the MRL
likely overestimates the true analytical value.

Other estimation procedures have been developed and used to estimate system mean concentrations which
avoid the inherent bias of the substitution method. Each method handles non-detection data, characterizes
the distribution of the data, and generates occurrence estimates somewhat differently. The occurrence
estimation approach developed for and used in this report reflects, to some degree, an evolution of
analytical approaches. Previously, EPA had developed an approach to estimate radon occurrence in
drinking water, as well as another approach to estimate arsenic occurrence in drinking water.

Multiple data sets, containing different proportions of non-detection data, were used in the radon analysis.
(These are described in detail in Methods, Occurrence, and Monitoring Document for Radon in Drinking
Water; U.S. EPA 2000a.) For most of the data sets, a log-normal distribution assumption was used to
generate system mean concentration values. When data sets contained less than 5 percent non-detection
data, the log mean (natural log of the geometric mean) and log standard deviation (natural log of the
geometric standard deviation) were the primary statistics used. When the data contained a higher
proportion of non-detection data, the log mean and log variance parameters were estimated by a
maximum likelihood estimation (MLE) method, which involves the iterative calculation of log likelihood
ratios while updating the estimates of the non-detection values of the data until the likelihood ratio is
optimized within specified limits. To calculate the proportion of systems above certain radon levels and
the confidence limits on the proportions, two different approaches were employed: a distributional
approach and a non-distributional approach. The distributional approach simply applied the known
properties of the cumulative normal distribution to the estimated log mean and log standard deviation of
radon occurrence in a given population of sources/systems to estimate the proportion that would be
expected to be above a specified threshold of concern. A non-distributional approach was used when the
fits of the radon distributions to log-normal distributions were not very good. This method calculated the
upper and lower confidence limits on the estimated proportion of systems above a certain level. This
method, which is based on counts of actual systems/sources above specified levels, makes no assumptions
about the underlying shape of the distribution of radon levels.

Although MLE is an alternative method for estimating the log-normal distribution parameters, its
approach was somewhat more computationally involved than the Regression on Ordered Statistics (ROS)
method, developed by Helsel and Cohn (1988). In comparing methods for estimating distributional
parameters, Helsel and Gilliom (1988) found that the MLE method was preferred for estimating percentile
values for non-detection water quality data, but that the regression methods (such as ROS) were preferred
for estimating the distributional parameters (mean and standard deviation). For this reason, and the
relative ease of calculation compared with MLE approaches, the ROS method was used in estimating
arsenic occurrence.  The arsenic analysis used five steps for estimating national occurrence. First, system
arithmetic means were calculated using ROS. This approach, which assumes that the underlying
distribution of occurrence data are reasonably well characterized by a log-normal distribution, "fills-in"
values for non-detection data based on the values of the detection data. Once the system means were
generated, State exceedance probability distributions for ground water and surface water were calculated.
Weighted sums of the exceedance probabilities generated for each State were then used to develop
regional exceedance probability distributions for ground water and surface water. National exceedance
probability distributions were developed as the weighted sum of the exceedance probability distributions
derived for each Region. Finally, the estimated numbers of systems exceeding levels of interest were
generated as the product of the national probability distributions and the total number of ground water or
surface water systems. For a detailed description of the protocol, refer to Arsenic Occurrence in Public
Drinking Water Supplies (U.S. EPA 2000b).

The arsenic "ROS approach" for estimating occurrence and exposure was used for preliminary
estimations in this Six-Year Review of contaminant occurrence estimation. However, since this
occurrence modeling approach could not provide a complete quantitative estimation of statistical error,
alternative modeling approaches were considered, and the Bayesian-based modeling approach was
subsequently developed.
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The Bayesian-based hierarchical model has important advantages. This model fully uses information
about all detection and non-detection (censored) data and provides a single approach for estimating
occurrence that is unified and consistent for estimates between and within systems. Also, the Bayesian
model quantifies estimation of statistical error. The model provides uncertainty intervals around each
estimate, taking into account both sampling variability over time and across systems, as well as
uncertainty due to non-detection concentrations. The model also generates occurrence estimates across
the broad range of high to low proportion of censored data for the 60 contaminant-specific data sets
analyzed.

VI.C.   General Description of Bayesian Statistics

Bayesian statistics are named after an English mathematician, Thomas Bayes, who first used probability
inductively and established a mathematical basis for probability inference. The Bayesian approach is
based on the concept that more may be known about an actual situation than is contained in the data from
a single experiment regarding that situation. Bayesian methods, for example, can be used to combine
results and information from several different,  but related situations or experiments. This type of
approach considers not only what information  is contained in the specific situation (or data) directly being
assessed, but what outside expertise or information might also contribute to an understanding of the
situation being assessed (such as an assessment of the likelihood of an event occurring).  The Bayesian
view of probability is related to a "degree of belief' and measures the feasibility of an event occurring in
the context of incomplete knowledge.

Bayesian inference is best suited to problems that involve making decisions under uncertainty.  Bayes'
Theorem begins with a statement of what is known prior to performing the experiment. In the context of
statistical modeling, this prior knowledge is typically in the form of a probability density function, a
mathematical expression that defines the likelihood of an event occurring. The prior knowledge, or
"prior," can be based on the results  of other experiments, on expert opinion, or actual existing data. The
Bayesian analytical approach is designed to start with a statement of initial or "prior" knowledge, and
then use that knowledge and related information to improve upon the initial state of knowledge.

In the context of statistical estimations of contaminant occurrence, a "prior" is first specified and could be
the analytical monitoring results of contaminant occurrence at a public water system. The prior is then
supplemented with the inclusion of a likelihood function, which mathematically presents the distribution
of similar, related data. The modeling process then revises the prior distribution based on this additional
(likelihood) information to generate an updated estimate (the "posterior" distribution). This "posterior"
distribution represents what is now  believed about the original parameter (the "prior") in light of the
supplemental data. This updating process is repeated again and again in an iterative process; the posterior
from one distribution becomes the prior for the next, and so on.  This updating proceeds until the model
"converges" (meaning that two successive estimates of the repeated updating process are equal, and no
further updating is necessary).  Sections VI.D.  - VI.G. summarize the Bayesian-based estimation model.
A more detailed, technical description of the Bayesian model, and its programming code, are included in
Appendix B.

VI.D.   Estimating System Mean  Concentrations

The general Stage 2 approach is to use the available 16-State cross-section data to model contaminant
concentrations in drinking water as a function of system characteristics, such as source water type and
system size. As stated above, Bayesian methods allow various sources of variability and uncertainty in
occurrence to be explicitly quantified.  For these analyses, a Bayesian-based hierarchical model is fit to
characterize uncertainty in the estimates.

The model is based on the assumption that each system is log-normally distributed with an unknown
mean and unknown variance.  (It  is a common  assumption that water data follow a log normal
distribution.7)  The "priors" in this analysis are for the means and variance. For each system, a constant
7 Ott, W.R. 1995. Environmental Statistics and Data Analysis. Lewis Publishers, Boca Raton.

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variance, but non-constant mean, is assumed. Once the prior distribution has been established, a two-
level statistical model is built. The lower level features the observed concentrations (analytical detections
and non-detections), which are treated as coming from a log-normal distribution.  The upper level features
the unknown parameters of the log-normal probability distribution of each system, whose values are
estimated based on the detections and non-detections.  Thus, the Bayesian-based approach allows the
model to produce a conditional distribution of the unknown features of interest (system mean and
standard deviation) as a function of the known data (both detections and non-detections 8).

By pooling evidence  from many observations for thousands of PWSIDs, this model estimates the mean
concentration and standard deviation for each system using a Bayesian-based approach.  An advantage of
this model is that it allows for "borrowing of strength" in estimation between neighboring strata
(Lockwood et al. 2001). In particular, when a stratum (e.g., all ground water systems serving less than
500 people) has either no or very few observations, its parameter estimates are shrunk toward the nearest
strata that have data (e.g., all ground water systems serving between 501-3,301 people).  Thus, this
process improves estimates for entire  strata.

A historical limitation of using Bayesian methods was that analytical solutions for the required
computations were available for a limited number of parameters (Qian, 2001).  The amount of parameters
in this analysis exceeded this limit, making it impossible to generate estimates by use of Bayes' Theorem.
However, the advent  of fast and  inexpensive computing has promoted the development of several
methods of performing  Bayesian inference (Qian, 2001). The method used for this analysis is based on
Monte Carlo sampling.

The Monte Carlo method is, in general terms, any technique using random numbers to model some sort of
a process. (This technique works particularly well when the process is one where the underlying
probability distributions are known, but the results are more difficult to determine.) During a Monte Carlo
simulation, the value  used for each variable is selected randomly from the defined probability
distribution. Many simulations are then performed and the desired result is taken as an average over the
number of observations (which may be a single observation or perhaps millions of observations).

A Markov chain Monte Carlo (MCMC) method was used for this analysis.  Markov chain Monte Carlo
(MCMC) is an important technique used by Bayesian practitioners to sample from the posterior
distribution. MCMC generates a chain that converges, in distribution, on the posterior parameter
distribution, that can  be regarded as a sample from the posterior distribution (Qian et al., 2001). Using
these samples, it is then possible to calculate the statistics of interest (mean concentration and standard
deviation).  This technique also provides a means to generate a random sequence of model output that
may be used to make inferences  about the model uncertainties that derive from measurement
uncertainties.

VI.E.   Estimation of Probabilities of Threshold Exceedance

Approximately 500 Monte Carlo simulations,9 using the stratum-level mean and standard deviation as
model input, were used to estimate the number of systems that are expected to exceed each specified
concentration threshold for each source water type and system-size category. The estimated number of
systems that exceed each threshold for a given stratum is then divided by the total number of systems in
that stratum, resulting in the percent of systems estimated to exceed a specified threshold for a specific
stratum (the estimated mean "probability of threshold exceedance").
8 Although actual numerical values are unknown for the non-detections, they are known to be less than the MRL

9 To test the number of Monte Carlo simulations necessary for this analysis, preliminary model runs were
conducted using 500 simulations, 1,000 simulations, and 2,000 simulations.  Expanding the amount of simulations
did not alter the results.  Thus, 500 simulations proved adequate and were used for computational efficiency
reasons.

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The estimates for population served exceedances are generated in a separate model run. In the process of
the system exceedance estimation steps, the actual population served by each system in the data set is
mathematically "attached" to each system. Therefore, when the Monte Carlo simulations are run to
estimate the number of systems for each source water type and system-size category that are expected to
exceed each specified concentration threshold, there are corresponding population served values along
with the system number estimates. So, the estimated population served by systems that exceed each
threshold for a given stratum is then divided by the total population served in that stratum, resulting in the
percent of population estimated to be served by systems with a mean concentration that exceeds a
specified concentration threshold for a specific stratum (the estimated mean "probability of threshold
exceedance").

VI.F.   Credible Intervals

In Bayesian analysis, credible intervals are generated to quantify the uncertainty of each estimated mean
probability of exceedance. A Bayesian credible interval (CI) defines the range of values within which the
true value of the parameter is believed to occur.  In our case, a 90% credible interval of the  exceedance
probability is interpreted as a 90% probability that the true value of the exceedance probability lies in the
interval. The actual upper and lower numeric values of the credible interval are referred to as the "upper
credible bound" and the "lower credible bound," respectively.  Because the probability of exceedance is
estimated using approximately 500 Monte Carlo simulations, there exists 500, instead of one, estimates of
the probability. A credible interval is the central region within which a specified  percentage of the
posterior density lies equally within the distribution (e.g., the 95% CI would be the region of the posterior
density which lies between 2.5% and 97.5%). Thus, a 90% credible interval is an interval between the 5th
and 95th percentiles of the 500 Monte Carlo values of probability of exceedance.

The Bayesian "credible interval" probability that the actual parameter lies within  the interval is different
from standard definition of "confidence interval", which is based on (hypothetical) repeated experiments.
Because the credible interval directly relates to the distribution of the actual data, this interval may or may
not include the mean, depending on the skewness of the estimated distribution. In other words, the
credible interval is not an interval around the mean (like the more traditional confidence interval).  The
traditional statistical ("frequentist") 90% confidence interval is an interval that will contain the true value
of the mean 90% of the time.  For a particular study, a confidence interval provides qualitative
information since they are really a measure of how precise an estimated effect is.  If a confidence interval
is wide, the estimated mean is less reliable.  In contrast, a Bayesian credible interval, has the precise
probabilistic meaning. In our case, a 90% credible interval of the exceedance probability is interpreted as
a 90% probability that the true value of the exceedance probability lies in the interval.

For some extremely skewed estimated distributions,  it is possible that the Monte Carlo estimated 5th and
95th percentiles are the same.  For example, several estimates of the probability of a system mean
exceeding a given threshold have  an upper 90% credible bound of zero and a lower 90% credible bound
also equal to zero, but a mean ("best estimate") probability of exceedance NOT equal to zero. This is
because the probability of a threshold exceedance is  evaluated by several Monte Carlo  samples and at
least 95% of the samples are equal to zero. Under such a situation, one should conclude that the chance is
less than 5% to have an exceedance probability that is greater than zero.

It is also important to note that the credible intervals for estimates of the totals (total ground water, total
surface water, and total combined ground plus surface water) are always narrower than the  credible
intervals for each individual stratum.  Because the estimates, and the associated standard errors, of the
totals are based on a much larger sample size, the standard errors for totals are less and the credible
intervals are narrower than for the individual stratum.

VI.G.   Using the Occurrence Probability Estimates to Obtain National Occurrence Estimates

Once the probability of exceedance has been estimated through Stage 2 analysis,  a straightforward
extrapolation can be used to estimate national occurrence. 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 probability of exceedance by the national numbers for systems (and


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population served by systems) documented in the Water Industry Baseline Handbook, Second Edition -
2000 (U.S. EPA 2000c). The total number of ground water and surface water CWSs plus NTNCWSs in
the Baseline Handbook is 65,030, and the total population served by ground water and surface water
CWSs plus NTNCWSs is 213,008,182 persons.  (The handbook presents the system and population
served numbers stratified by source water type and population served, as well.) To derive the national
occurrence estimate for a specific threshold/source water type/population served size category, the
national number of PWSs (or population served by PWSs) from the handbook is simply multiplied by the
probability of exceedance estimated by the statistical model.  The process of generating the probabilities
of exceedance are described in Section VI.E.

Table VI.G. 1 illustrates the calculation of national estimates of exceedance. For example, to estimate the
number of systems nationally expected to have mean concentration values of fluoride exceeding 4 mg/L
for ground water systems serving 500 people or less, the best estimate probability of exceedance
(0.5895%) is multiplied by the total number of ground water systems nationally that serve 500 people or
less (43,498 systems).  The resulting  estimate equals 256 systems (43,498*0.005895=256). The national
estimate of population  exposed to a given contaminant is extrapolated in a similar fashion (i.e., the
probability of exceedance is multiplied by the total population served nationally).
Table VI.G.l.  Calculating National Estimates of Exceedance
Population-
Served Size
Category
<500
501 - 3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total2
Total
Number of
Systems
Nationally 1
43,498
12,158
2,405
1,190
189
59,440
Probability of Exceedance
Best Estimate
0.5895%
0.4803%
0.6018%
0.1355%
0.0160%
0.5496%
Lower 95%
CB
0.4881%
0.3283%
0.2988%
0.0000%
0.0000%
0.4685%
Upper 95%
CB
0.6878%
0.6313%
0.8964%
0.3484%
0.0000%
0.4685%
National Estimate of Exceedance
Best
Estimate2
256
58
14
2
0
327
Lower 95%
CB
212
40
7
0
0
278
Upper 95%
CB
299
77
22
4
0
378
1. System inventory data from the Water Industry Baseline Handbook, Second Edition - 2000 (U.S. EPA 2000c).
2. Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated
totals at the source water level of aggregation, and estimates for the source water strata ("GW Total" and "S W Total") will not add to the total
estimated for all systems ("Total Ground & Surface Water").


The estimated number of systems and population served by systems in the 16 States were also
extrapolated from the Stage 2 probabilities of exceedance. To generate the 16-State estimates, the
probabilities of exceedance were simply multiplied by the total number of systems (or population served
by systems) with 16-State data for that particular contaminant/source  water type/system size. (For the
total number of systems and population served by systems for each contaminant, please refer to Table
VI.A.l.)

VI.H.  Summary of Occurrence Estimations

The Stage 2 analytical findings are summarized below.  The complete Stage 2 analytical findings,
presented in Appendix C, include estimated contaminant mean concentrations, the statistical best
estimates of exceeding contaminant concentration thresholds, and both the 90% and 95% credible
intervals for the best estimates. All  findings presented in Appendix C are stratified by source water type
and system size, and are presented relative to multiple thresholds.  These findings also include a single
aggregate result for each contaminant/threshold which provides a mean concentration, best estimate for
exceeding that threshold, and the 90% and 95% credible intervals for the best estimate aggregated across
all system sizes for all source water types. Additionally, the best estimates and credible intervals have
been used to extrapolate to national  values. These national extrapolations (including both stratified and
Occurrence Estimation Methodology
34
June 2003

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aggregate values) present the modeled best estimates for the national number of systems, and the
population served by those systems, that are expected to exceed the specified threshold concentrations for
each evaluated contaminants.

The Stage 2 best estimate findings (based on the 16-State national cross-section data) are presented in
comparison to the Stage 1  (16-State) findings in Table VI.H.l. The findings are presented as the percent
of systems, and population-served by those systems, that exceed the current MCL for each contaminant.
Note that this table compares the two different types of analytical findings of the Stage 1 (non-parametric
"peak" concentration values) and the Stage 2 (parametric "long-term" mean concentration values)
analyses.  This comparison is included as a general, qualitative evaluation of the  Stage 2 model as well as
a means to develop a sense of how straightforward Stage 1 findings relate to the more complex Stage 2
findings. With the exception of l,2-dibromo-3-chloropropane and toluene,10 the  Stage 1 findings (percent
of systems with at least one analytical results greater than the MCL) are always higher than the Stage 2
findings (percent of systems with an estimated mean concentration greater than the MCL). For one of the
60 contaminants, pentachlorophenol, the Stage 2 findings based on population served were greater than
the corresponding Stage 1  findings based on population served.
Table VI.H.1. Comparison of Aggregate Stage 1 and Stage 2 Analytical Results Based on the 16-
State National Cross-Section - Percent of Systems and Population Served by Systems Greater than
the MCL
Contaminant
MCL
(mg/L)
% Systems
>MCL
Stage 1
(one result > MCL)
Stage 2
(mean > MCL)
% Population-Served by Systems
>MCL
Stage 1
(one result > MCL)
Stage 2
(mean > MCL)
Inorganic Chemicals
Antimony
Barium
Beryllium
Cadmium
Chromium
Cyanide
Fluoride
Mercury
Selenium
Thallium
0.006
2
0.004
0.005
0.1
0.2
4
0.002
0.05
0.002
0.623%
0.174%
0.217%
0.544%
0.127%
0.167%
1.28%
0.263%
0.107%
0.679%
0.248%
0.0887%
0.0781%
0.412%
0.00424%
0.0757%
0.511%
0.0672%
0.0267%
0.283%
1.00%
0.309%
0.621%
1.56%
0.666%
0.399%
4.56%
0.276%
0.309%
1.85%
0.0475%
0.0137%
0.0208%
0.07520%
0.00139%
0.0110%
0.0897%
0.00627%
0.00167%
0.0743%
10 Exceptions to the general rule can occur, however. A phenomenon referred to as "Bayesian shrinkage" can force
the higher and lower values of a range of estimated values to shift (or shrink) toward the mean, thereby increasing
the lower values and decreasing the higher values. Also, a Monte Carlo simulation step is used in the model to
estimate the number of systems with mean concentrations above a specified threshold concentration. The input for
this Monte Carlo step is the estimated system mean concentration and variance about the mean estimate.  A high
variance can affect the Monte Carlo simulation results which, in turn, affects the final Stage 2 results.
Occurrence Estimation Methodology
June 2003

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Contaminant
MCL
(mg/L)
% Systems
>MCL
Stage 1
(one result > MCL)
Stage 2
(mean >MCL)
% Population-Served by Systems
>MCL
Stage 1
(one result > MCL)
Stage 2
(mean >MCL)
Synthetic Organic Chemicals
Alachlor
Atrazine
Benzo(a)pyrene
Bis(2-ethylhexyl)adipate
Bis(2-ethylhexyl)phthalate
Carbofuran
Chlordane
2,4-D
Dalapon
1 ,2-Dibromo-3-chloropropane
Dinoseb
Diquat
Endothall
Endrin
Ethylene Dibromide
Glyphosate
Heptachlor
Heptachlor Epoxide
Hexachlorobenzene
Hexachlorocyclopentadiene
Lindane
Methoxychlor
Oxamyl
PCBs
Pentachlorophenol
Picloram
Simazine
Toxaphene
2,4,5-TP
0.002
0.003
0.0002
0.4
0.006
0.04
0.002
0.07
0.2
0.0002
0.007
0.02
0.1
0.002
0.00005
0.7
0.0004
0.0002
0.001
0.05
0.0002
0.04
0.2
0.0005
0.001
0.5
0.004
0.003
0.05
0.0419%
0.676%
0.0531%
0.00944%
2.20%
0.000%
0.0152%
0.00637%
0.000%
0.912%
0.0203%
0.0218%
0.0348%
0.0247%
0.746%
0.000%
0.00702%
0.0283%
0.00714%
0.000%
0.0373%
0.00622%
0.000%
0.0335%
0.0270%
0.000%
0.0550%
0.00724%
0.000%
0.000%
0.0625%
0.0000354%
0.000%
0.256%
0.000%
0.000%
0.000%
0.000%
1.41%
0.00765%
0.000%
0.000%
0.000%
0.116%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.00369%
0.00164%
0.000%
0.000%
0.000%
0.000%
0.259%
2.99%
0.243%
0.0292%
3.19%
0.000%
0.000477%
0.117%
0.000%
11.4%
0.0252%
0.208%
0.0429%
0.206%
12.3%
0.000%
0.000398%
0.0291%
0.0399%
0.000%
0.497%
0.125%
0.000%
0.293%
0.000761%
0.000%
0.0469%
0.131%
0.000%
0.000%
0.0385%
0.00000134%
0.000%
0.119%
0.000%
0.000%
0.000%
0.000%
2.60%
0.0141%
0.000%
0.000%
0.000%
0.142%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.0297%
0.00105%
0.000%
0.000%
0.000%
0.000%
Occurrence Estimation Methodology
36
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Contaminant
MCL
(mg/L)
% Systems
>MCL
Stage 1
(one result > MCL)
Stage 2
(mean >MCL)
% Population-Served by Systems
>MCL
Stage 1
(one result > MCL)
Stage 2
(mean >MCL)
Volatile Organic Chemicals
Benzene
Carbon Tetrachloride
1 ,4-Dichlorobenzene
o-Dichlorobenzene
1 ,2-Dichloroethane
1 , 1 -Dichloroethy lene
cis-Dichloroethylene
trans-Dichloroethylene
Dichloromethane
1 ,2-Dichloropropane
Ethylbenzene
Monochlorobenzene
Styrene
Tetrachloroethy lene
Toluene
1 ,2,4-Trichlorobenzene
1,1,1 -Trichloroethane
1 , 1 ,2-Trichloroethane
Trichloroethylene1
Vinyl Chloride
Xylenes (Total)
0.005
0.005
0.075
0.6
0.005
0.007
0.07
0.1
0.005
0.005
0.7
0.1
0.1
0.005
1
0.07
0.2
0.005
0.005
0.002
10
0.189%
0.204%
0.000%
0.000%
0.126%
0.236%
0.0305%
0.000%
0.669%
0.0682%
0.000%
0.000%
0.000%
0.778%
0.000%
0.000%
0.00811%
0.0404%
0.647%
0.110%
0.000%
0.0313%
0.0159%
0.000%
0.000%
0.00479%
0.0144%
0.000401%
0.000%
0.0131%
0.00358%
0.000%
0.000%
0.000%
0.202%
0.00000835%
0.000%
0.000235%
0.000%
0.236%
0.00350%
0.000%
0.518%
7.35%
0.000%
0.000%
8.40%
8.69%
0.247%
0.000%
9.50%
1.18%
0.000%
0.000%
0.000%
13.5%
0.000%
0.000%
0.0432%
6.97%
13.3%
1.86%
0.000%
0.00947%
0.0316%
0.000%
0.000%
0.000331%
0.0135%
0.00000449%
0.000%
0.119%
0.0358%
0.000%
0.000%
0.000%
0.685%
0.0000000539%
0.000%
0.00000698%
0.000%
8.19%
0.0244%
0.000%
Note that this table provides a qualitative comparison between the different estimation approaches of the Stage 1 (non-parametric "peak"
concentration values) and the Stage 2 (parametric mean concentration values) analyses.

All percentages are shown to three significant figures.
1. The low percentage of systems with trichloroethylene MCL exceedances, as compared to the very higher percentage of population served by
those systems with trichloroethylene MCL exceedances, is the result of a few systems with MCL exceedances that serve very large populations.


Based on the generated Stage 2 probability of exceedance percentages, national extrapolations can be
calculated.  The Stage 2 probability of exceedance percentages are multiplied by the known national total
number of systems, and population served by systems (based on national PWS inventory information
from the Baseline Handbook). The result  is an extrapolated national estimate of the number of systems
(Table VI.H.2), and population served by systems (Table VI.H.3), that are expected to exceed the MCL.
In general,  l,2-dibromo-3-chloropropane has the largest number of systems estimated to exceed the MCL
(almost 200 systems in  the 16 States, and over 900 systems nationally). The second largest number of
systems estimated to exceed the MCL was for fluoride (just over 100 systems in the 16 States, and over
Occurrence Estimation Methodology
37
June 2003

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300 systems nationally).  Trichloroethylene had, by far, the largest estimated population served by
systems exceeding the MCL (over 9 million people in the 16 States, and approximately 17 million people
nationally). The next largest population potentially exposed to a contaminant greater than the MCL was
l,2-dibromo-3-chloropropane (approximately 2.3 million people in the 16 States and about 5.5 million
people nationally).  For 35 of the 60 contaminants, zero systems were estimated to exceed the MCL in the
16 States and nationally.  Range estimates (based on the 95% credible bounds around the best estimate)
for the number of systems, and population served by those systems, are also included in Tables VI.H.2
andVI.H.3.
Table VI.H.2. Best Estimate and Range of the Number of Systems Exceeding the MCL in the 16
Cross-Section States and Nationally
Contaminant
MCL
(in mg/L)
Best Estimate of
Systems Estimated to
Exceed the MCL
16 States
National
Range Estimate of Systems Estimated to
Exceed the MCL
16 States
National
Inorganic Chemicals
Antimony
Barium
Beryllium
Cadmium
Chromium
Cyanide
Fluoride
Mercury
Selenium
Thallium
0.006
2
0.004
0.005
0.1
0.2
4
0.002
0.05
0.002
39
16
15
70
1
7
106
13
4
51
162
58
51
268
3
49
332
44
17
184
26-54
10-22
7-24
55-86
0-3
3- 11
91 - 123
8-18
1 -8
35-66
107 - 223
37-80
24-82
211-330
0- 10
20-75
284 - 385
27-62
4-31
127 - 239
Synthetic Organic Chemicals
Alachlor
Atrazine
Benzo(a)pyrene
Bis(2-ethylhexyl)adipate
Bis(2-ethylhexyl)phthalate
Carbofuran
Chlordane
2,4-D
Dalapon
l,2-Dibromo-3-chloropropane
Dinoseb
Diquat
0.002
0.003
0.0002
0.4
0.006
0.04
0.002
0.07
0.2
0.0002
0.007
0.02
0
9
0
0
24
0
0
0
0
199
1
0
0
41
0
0
166
0
0
0
0
920
5
0
0-0
6- 13
0-0
0-0
14-37
0-0
0-0
0-0
0-0
171 -231
0-2
0-0
0-0
26-57
0-0
0-0
97 - 256
0-0
0-0
0-0
0-0
792 - 1,070
0-9
0-0
Occurrence Estimation Methodology
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Contaminant
Endothall
Endrin
Ethylene Dibromide
Glyphosate
Heptachlor
Heptachlor Epoxide
Hexachlorobenzene
Hexachlorocyclopentadiene
Lindane
Methoxychlor
Oxamyl
PCBs
Pentachlorophenol
Picloram
Simazine1
Toxaphene
2,4,5-TP
MCL
(in mg/L)
0.1
0.002
0.00005
0.7
0.0004
0.0002
0.001
0.05
0.0002
0.04
0.2
0.0005
0.001
0.5
0.004
0.003
0.05
Best Estimate of
Systems Estimated to
Exceed the MCL
16 States
0
0
18
0
0
0
0
0
0
0
0
1
1
0
0
0
0
National
0
0
76
0
0
0
0
0
0
0
0
2
1
0
1
0
0
Range Estimate of Systems Estimated to
Exceed the MCL
16 States
0-0
0-0
7-32
0-0
0-0
0-0
0-0
0-0
0-0
0-0
0-0
0-2
0- 1
0-0
0-0
0-0
0-0
National
0-0
0-0
28 - 133
0-0
0-0
0-0
0-0
0-0
0-0
0-0
0-0
0- 15
0-4
0-0
0-0
0-0
0-0
Volatile Organic Chemicals
Benzene
Carbon Tetrachloride
1 ,4-Dichlorobenzene
o-Dichlorobenzene
1 ,2-Dichloroethane
1 , 1 -Dichloroethylene
cis-Dichloroethylene
trans-Dichloroethylene
Dichloromethane
1 ,2-Dichloropropane
Ethylbenzene
Monochlorobenzene
Styrene
Tetrachloroethylene
Toluene
0.005
0.005
0.075
0.6
0.005
0.007
0.07
0.1
0.005
0.005
0.7
0.1
0.1
0.005
1
7
4
0
0
1
3
0
0
3
1
0
0
0
45
0
20
10
0
0
3
9
0
0
9
2
0
0
0
132
0
4- 12
2-5
0-0
0-0
0-3
1-6
0- 1
0-0
1 -6
0-2
0-0
0-0
0-0
37-53
0-0
11 -34
6- 14
0-0
0-0
0-8
3-20
0-3
0-0
3- 18
0-6
0-0
0-0
0-0
108 - 154
0-0
Occurrence Estimation Methodology
June 2003

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Contaminant
1,2,4-Trichlorobenzene
1,1,1 -Trichloroethane
1 , 1 ,2-Trichloroethane
Trichloroethylene
Vinyl Chloride
Xylenes (Total)
MCL
(in mg/L)
0.07
0.2
0.005
0.005
0.002
10
Best Estimate of
Systems Estimated to
Exceed the MCL
16 States
0
0
0
54
1
0
National
0
0
0
154
2
0
Range Estimate of Systems Estimated to
Exceed the MCL
16 States
0-0
0- 1
0-0
47-63
0- 1
0-0
National
0-0
0-3
0-0
133 - 178
0-3
0-0
The estimates for the number of systems in the 16 States and nationally are both based on the same modeled best estimate. The 16-State values
are obtained by multiplying the probability of exceedance by the actual number of systems in the 16-State cross-section for each particular
contaminant.  The national values are obtained by multiplying the same probability of exceedance by the total number of systems nationally based
on inventory numbers identified in the Water Industry Baseline Handbook (U.S. EPA 2000c). The range of values are based on the 95% credible
bounds around the best estimate.

Note: All system values are rounded to the nearest whole system.

1. Model output resulted in an estimate of less than half a system; however, the fraction was rounded up to 1.
Table VI.H.3. Best Estimate and Range of the Population-Served by Systems Exceeding the MCL
in the 16 Cross-Section States and Nationally
Contaminant
MCL
(in mg/L)
Best Estimate of
Population Served by
Systems Estimated to
Exceed the MCL
16 States
National
Range Estimate of Population Served by
Systems Estimated to Exceed the MCL
16 States
National
Inorganic Chemicals
Antimony
Barium
Beryllium
Cadmium
Chromium
Cyanide
Fluoride
Mercury
Selenium
Thallium
0.006
2
0.004
0.005
0.1
0.2
4
0.002
0.05
0.002
48,000
14,100
21,800
77,200
1,500
8,100
96,000
6,600
1,700
77,500
101,100
29,200
44,400
160,100
3,000
23,300
191,000
13,400
3,600
158,300
10,300 - 124,500
2,700 - 68,500
2,900-81,700
30,500-212,500
0 - 8,400
900-31,800
59,400- 151,300
1,000-23,400
100 - 6,200
16,300 - 256,900
21,700-262,000
5,600 - 142,000
5,900 - 166,300
63,300 - 440,900
0 - 16,900
2,700-92,100
118,200-301,000
2,000 - 47,400
200 - 12,900
33,300 - 524,600
Synthetic Organic Chemicals
Alachlor
Atrazine
0.002
0.003
0
37,800
0
82,100
0-0
11,300- 120,000
0-0
24,400 - 260,300
Occurrence Estimation Methodology
40
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Contaminant
Benzo(a)pyrene
Bis(2-ethylhexyl)adipate
Bis(2-ethylhexyl)phthalate
Carbofuran
Chlordane
2,4-D
Dalapon
l,2-Dibromo-3-chloropropane
Dinoseb
Diquat
Endothall
Endrin
Ethylene Dibromide
Glyphosate
Heptachlor
Heptachlor Epoxide
Hexachlorobenzene
Hexachlorocyclopentadiene
Lindane
Methoxychlor
Oxamyl
PCBs
Pentachlorophenol
Picloram
Simazine
Toxaphene
2,4,5-TP
MCL
(in mg/L)
0.0002
0.4
0.006
0.04
0.002
0.07
0.2
0.0002
0.007
0.02
0.1
0.002
0.00005
0.7
0.0004
0.0002
0.001
0.05
0.0002
0.04
0.2
0.0005
0.001
0.5
0.004
0.003
0.05
Best Estimate of
Population Served by
Systems Estimated to
Exceed the MCL
16 States
0
0
93,400
0
0
0
0
2,278,300
13,300
0
0
0
126,200
0
0
0
0
0
0
0
0
24,600
1,000
0
100
0
0
National
0
0
254,100
0
0
0
0
5,531,800
29,900
0
0
0
302,700
0
0
0
0
0
0
0
0
63,300
2,200
0
200
0
0
Range Estimate of Population Served by
Systems Estimated to Exceed the MCL
16 States
0-0
0-0
14,600 - 284,500
0-0
0-0
0-0
0-0
1,853,700 - 3,307,300
0 - 48,600
0-0
0-0
0-0
62,600-384,100
0-0
0-0
0-0
0-0
0-0
0-0
0-0
0-0
0 - 230,000
0 - 1,200
0-0
0-0
0-0
0-0
National
0-0
0-0
39,700-774,100
0-0
0-0
0-0
0-0
4,500,900 - 8,030,400
0 - 109,500
0-0
0-0
0-0
150,100-921,000
0-0
0-0
0-0
0-0
0-0
0-0
0-0
0-0
0 - 593,000
0 - 2,700
0-0
0-0
0-0
0-0
Volatile Organic Chemicals
Benzene
Carbon Tetrachloride
1 ,4-Dichlorobenzene
o-Dichlorobenzene
0.005
0.005
0.075
0.6
10,500
35,000
0
0
20,200
67,400
0
0
2,100-33,200
800 - 47,500
0-0
0-0
4,000 - 63,800
1,500-91,400
0-0
0-0
Occurrence Estimation Methodology
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Contaminant
1 ,2-Dichloroethane
1 , 1 -Dichloroethylene
cis-Dichloroethylene
tmas-Dichloroethylene
Dichloromethane
1 ,2-Dichloropropane
Ethylbenzene
Monochlorobenzene
Styrene
Tetrachloroethylene
Toluene
1,2,4-Trichlorobenzene
1,1,1 -Trichloroethane
1 , 1 ,2-Trichloroethane
Trichloroethylene
Vinyl Chloride
Xylenes (Total)
MCL
(in mg/L)
0.005
0.007
0.07
0.1
0.005
0.005
0.7
0.1
0.1
0.005
1
0.07
0.2
0.005
0.005
0.002
10
Best Estimate of
Population Served by
Systems Estimated to
Exceed the MCL
16 States
400
14,400
0
0
131,100
39,500
0
0
0
757,200
0
0
0
0
9,062,500
27,200
0
National
700
28,800
0
0
253,500
76,200
0
0
0
1,458,900
0
0
0
0
17,451,800
52,000
0
Range Estimate of Population Served by
Systems Estimated to Exceed the MCL
16 States
0-800
0 - 136,900
0-100
0-0
200 - 275,300
0 - 142,000
0-0
0-0
0-0
519,700-965,100
0-0
0-0
0-200
0-0
8,828,000 - 9,302,500
0-31,500
0-0
National
0- 1,500
100 - 273,500
0- 100
0-0
300 - 532,300
0 - 273,900
0-0
0-0
0-0
1,001,400- 1,859,300
0-0
0-0
0-300
0-0
17,000,200- 17,914,000
0 - 60,300
0-0
The estimates for the number of systems in the 16 States and nationally are both based on the same modeled best estimate. The 16-State values
are obtained by multiplying the probability of exceedance by the actual number of systems in the 16-State cross-section for each particular
contaminant. The national values are obtained by multiplying the same probability of exceedance by the total number of systems nationally based
on inventory numbers identified in the Water Industry Baseline Handbook (U.S. EPA 2000c). The range of values are based on the 95% credible
bounds around the best estimate.

Note: All population values are rounded to the nearest hundred.


VI.I.   Stage  2 Model Verification

Several approaches for model verification were undertaken. The first verification assessment partially
assesses both the modeling process and a key component of the cross-section construction. A simulation
data study was also conducted to compare the Bayesian-based approach to the "ROS" method, and to test
the assumption of constant variance and log-normality at the system level for the national distribution of
system means.

To partially assess the modeling process and a key component of the cross-section construction, the mean
concentration values for  select contaminants were estimated for groups of top quartile and bottom quartile
States.  (For a  description of how quartiles are determined, please see Section II.B.) The cross-section
development approach presumes that the top quartile  States have a higher pollution potential than the
bottom quartile States, and, therefore, the estimated mean concentrations for the top quartile States should
be greater than those for the bottom quartile States. The estimated mean concentration values for the top
quartile States were always higher than the mean concentration for the bottom quartile States with the
exception of glyphosate and heptachlor (two very low occurrence SOCs).
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Table VI.I.l.  Stage 2 Comparison of Top Quartile and Bottom Quartile States' Mean
Concentration Values
Contaminant Name
Mean Concentration (in mg/L)
Top Quartile States
Bottom Quartile States
Inorganic Chemicals 1
Fluoride
0.68951748
0.29773017
Synthetic Organic Chemicals 2
Alachlor
Carbofuran
Diquat
Glyphosate
Heptachlor
Heptachlor Epoxide
Hexachlorobenzene
Oxamyl
Picloram
0.00000407
0.00001795
0.00004839
0.00012887
0.00000069
0.00000057
0.00000135
0.00002879
0.00000247
0.00000355
0.00001654
0.00004012
0.00014761
0.00000073
0.00000051
0.00000105
0.00002540
0.00000211
Volatile Organic Chemicals 3
1 ,4-Dichlorobenzene
Tetrachloroethylene
0.00002310
0.00007779
0.00002157
0.00003378
1. IOC - Ranking based on CDC Fluoridation Census - Top Quartile States = IN, IL, KY, SD; Bottom Quartile States = CA, NJ, MT, OR.
2. SOC - Ranking based on Total Farm Ag. Chemical Expenses - Top Quartile States = CA, FL, IL, TX; Bottom Quartile States = MT, NJ, NM,
VT.
3. VOC - Ranking Based on Number of Manufacturing Establishments / Sq. Mile - Top Quartile States = CA, FL, IL, NJ; Bottom Quartile States
= MT, NE, NM, SD.


A rigorous, quantitative model verification was conducted through a simulation study, using six synthetic
data sets.  This study was designed to explore the impact of the log-normal, as well as the constant
variance, assumption made on the system level for the national distribution of system means. In addition,
the Bayesian-based hierarchical modeling approach was compared to the ROS plotting position method.

The six simulated data sets were divided into three groups. The first group was designed to emphasize
the comparison of the Bayesian and ROS methods. The second group was generated to evaluate the
constant variance assumption.  Finally, the third group of simulated data sets tested the impact of a log-
normal assumption at the system level on the national distribution of system means. Please refer to
Appendix B for details regarding the simulated data study.

Both the simulated study and the mixture model indicated that the Bayesian-based hierarchical model
used for the study is appropriate. The simulated study showed that the prior assumptions about the
contaminant distribution do not have an undue influence on the posterior estimate of the national
distribution of system means. The mixture model study showed that using a log-normal distribution at the
system level is appropriate. When the log-normal assumption is not used, the estimated national
distribution has a slightly larger variance, which may result in an overestimate of the exceedance
probabilities.

Another direct verification of the model consists of a traditional bounding analysis.  A bounding analysis
enables an assessment of how well the model estimates  system mean concentrations, and by inference,
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how well the model estimates values for the non-detection values used in the mean concentration
estimations. This is of interest because non-detections typically comprise a significant proportion of
drinking water analytical records for any particular contaminant. For the bounding analysis, EPA
generated a data set based on the raw analytical results for each contaminant. In this data set, a "lower
bound" was generated by substituting the value of 0 (zero) for all non-detections, and an "upper bound"
was generated by substituting a value equal to the non-zero modal MRL for all non-detections. For
additional comparative detail, a value equal to 1A the MRL was also substituted for all non-detection
records for each contaminant assessed.

Fifteen contaminants were assessed with this bounding analysis.  For all contaminants, the modeled
system mean concentration was 'bracketed' by the bounding values, with the lower bound mean below
and the upper bound mean above the modeled values. In all cases except for fluoride,  the bounding value
substituting !/> MRL for non-detections also was above the modeled system mean. A complete
presentation of the bounding analysis is included in Appendix D, including graphs showing the 90%
Credible Bounds of model prediction.

VI.J.    Stage 2 Model Validation

Another assessment of the model is based on the comparison of the modeled occurrence estimations to
other known measures of contaminant occurrence in drinking water.  In the next section, the Stage 2
occurrence estimates for fluoride conducted for the Six-Year Review were assessed relative  to system
fluoridation findings reported in the US Department of Health and Human Services Centers for Disease
Control and Prevention (CDC) Fluoridation Census 1992. Additional information was provided by the
CDC regarding the unpublished Fluoridation Census 2000. And in the following section, a general
assessment of the Stage 2 model findings relative to MCL violation records in SDWIS/Fed was
conducted.

VI.J.I. Centers for Disease Control and Prevention Fluoridation Census

This section provides a general  comparative assessment between the Six-Year Review's Stage 2 national
fluoride occurrence estimates (based on the 16-State national cross-section) primarily with public water
system fluoridation findings reported in the CDC Fluoridation Census 1992 as well as with findings
provided by CDC staff from the unpublished Fluoridation Census 2000 (CDC 2002).  The fluoride data
contained in the CDC and the 16-State cross-section are inherently different. The CDC census findings
report the voluntary provision of qualitative/semi-quantitative information from public drinking water
systems that identify if a particular system is operating as a fluoridating system (with either natural or
"adjusted" concentrations of fluoride within the optimum range of fluoride). On the other hand, the
OGWDW Six-Year Review Stage 2 findings are quantitative, parametric statistical estimations of fluoride
occurrence based on compliance monitoring analytical results of fluoride concentrations in public
drinking water systems from the 16-State cross-section (with the results from the 16-State cross-section
then extrapolated to national occurrence estimates).

Despite the significant differences in the underlying sources of fluoride occurrence information, the
comparison between the CDC and OGWDW Stage 2 findings is informative. The comparison suggests
that the Stage 2 modeled national estimates are valid, broadly reflecting and correlating with the general
fluoride concentrations implied by the fluoridation census findings when considering details of the
differences between the census and  statistical estimation approaches.  Details of the comparative
assessment are included below.

The CDC periodically conducts a national fluoridation census which records the total national number of
public  water systems, and population served by those systems, that operate with natural or adjusted levels
of fluoride in drinking water at optimum levels.  The "optimum range" of fluoride in drinking water
(regarding prevention of dental  cavities) is from 0.7 mg/L to 1.2 mg/L (although a system can be
considered to be operating as a fluoridating system if it operates within the broader "control range" of
Occurrence Estimation Methodology                 44                                      June 2003

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fluoride concentrations from 0.6 mg/L to 1.7 mg/L).11  To complete the fluoridation census, States
voluntarily report: the name, location, and public water system identification number of each fluoridated
water system; the population served by each system; whether the system operates with adjusted, or
natural, levels of fluoride; the chemical used for fluoridation, if adjusted; and whether or not the system
purchased water. However, no quantitative analytical results are presented, no information is provided
for systems with fluoride occurrence less than 0.7 mg/L (the low end of the optimum range), and the
source water type is not specified. Therefore, the implication is that all systems that reported as
fluoridating (i.e., all systems listed in the CDC census) are considered for comparison purposes to have a
minimum average fluoride concentration of 0.7 mg/L, the low end of the optimum fluoridation range.

Table VI.J. l.a shows  a comparison between the quantitative results based on the 16-State cross-section
data and the qualitative reported findings of the CDC Fluoridation Census 1992 and the unpublished
CDC Fluoridation Census 2000.  The table specifically presents the Stage 2 modeled estimates based on
the Six-Year Review  16-State cross-section compared to the number of fluoridating systems (and
population served by  those systems) as reported to the  CDC.


Table VI. J.I.a.  Comparison of the National Extrapolations of the Stage 2 Modeled Estimates with
the CDC Fluoridation Census Findings
Stage 2 Modeled Estimates based on
Compliance Monitoring Results of the
16-State Cross-Section
Fluoride
Threshold
(mg/L)
4
2
0.7
Total Number of Systems Nationally
Estimated to Exceed Threshold
Best Estimate
332
1,885
13,390
Range
284-385
1,769 - 2,000
13,156- 13,624
Total Population Served by Systems
Nationally Estimated to
Exceed Threshold
Best Estimate
191,000
1,978,600
57,022,300 2
Range
118,200-301,000
1,505,100-3,293,100
51,803,600-61,346,400 2
CDC Fluoridation Census
1992 and unpublished
2000 l Findings
Total
Number of
Systems
Fluoridating
145 '
746 '
14,496 3
Total Population
Served by
Systems
Fluoridating
152,527'
849,591 '
141,107,164 3
For a detailed description of how the Stage 2 modeled estimations are derived, please refer to Section VI.A. through VI. H. of this report.

1.  The number of systems and population-served by systems with reported fluoride concentrations greater than 2 mg/L and 4 mg/L were
provided by the CDC from the unpublished Fluoridation Census 2000. (These measures of fluoride occurrence relative to these specific fluoride
thresholds are not included in the 1992 or earlier census publications.)
2.  There were no compliance monitoring records for fluoride for the Chicago Water System in the State of Illinois compliance monitoring data
set. Therefore, since Illinois is one of the States in the 16-State cross-section and the Chicago Water System is known to fluoridate, the Stage 2
modeled estimates presented here do not reflect the population served by the fluoridated water provided by the Chicago Water System (and its
consecutive systems).  (The Chicago Water System fluoride data were received after the completion of the Stage 2 analysis and were, therefore,
not included.)
3.  This estimate includes public water systems that operate within the "control range" of optimum fluoride concentrations. Therefore, this
estimate includes systems that maintain fluoride concentrations as low as 0.6 mg/L while the Stage 2 model estimates are based on the 0.7 mg/L
fluoride concentration values which is the low end of the optimum range.
1'  The optimum amount of fluoride in drinking water at PWSs is the range of fluoride that assists in the prevention
of dental cavities. The specific optimum level of fluoride for a given PWS is generally inversely proportional to
temperature. It is assumed that individuals drink more water in warmer climates and higher temperatures. The
ingestion of fluoride via drinking water is directly related to the volume of water consumed. Therefore, since high
temperatures result in consumption of higher volumes of water, the amount of fluoride considered optimal is at the
low end of the optimal range (0.7 mg/L) in warmer regions (or warmer seasons) and at the high end of the optimum
range (1.2 mg/L) in cooler regions (or cooler seasons).  For example, the optimum level of fluoride for PWSs in
southern Florida is 0.7 mg/L and for PWSs in Maine it is 1.2 mg/L. The "control range" recommended by CDC for
the optimum concentration is 0.1 mg/L below to 0.5 mg/L above the optimum.
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The CDC Fluoridation Census 1992 indicates that a total of 14,496 public water systems, serving
141,107,164 people, report that they operate as a fluoridated system.12 In comparison, the Stage 2
national occurrence estimates based on the 16-State cross-section indicate a total of 13,390 systems,
serving 57,022,300 people, with estimated mean concentrations of fluoride greater than 0.7 mg/L. (For a
detailed presentation of Stage 2 modeled estimations of fluoride occurrence, please refer to Appendix C,
Tables C.16.f and C.16.n.) A system with a mean concentration of fluoride greater than 0.7 mg/L is
approximately equivalent to a "fluoridated" system (in the CDC census) that reports operation at optimum
fluoride levels, though systems are included in the CDC census as fluoridating if systems operate within
the broader control range and above 0.6 mg/L fluoride.

The differences between the national estimates for fluoridating systems (CDC-14,496 PWSs and national
cross-section-13,390 PWSs) and population served by fluoridating systems (CDC-141,107,164 people
and national cross-section-57,022,300 people) appear to relate to several factors. First, the lack of
fluoride occurrence data from the Chicago Water System certainly results in an underestimate for the
model estimated number of systems, and population served by those systems.  (Fluoride data for Chicago
were not included in the original compliance monitoring data sets obtained directly from the State of
Illinois. Fluoride compliance monitoring data are reported to the State's public health agency. These
fluoride data were subsequently requested, but were received after the Stage 2 estimations had been
completed.)

The system size distribution of fluoridating systems is a second factor influencing the difference in
population served between the State data and the CDC census data. Table Vl.J.l.b illustrates the
distribution of fluoridating systems based on six population served size categories. Although the number
of systems serving 1,000 people or less is similar in the State data and CDC data (2,824 and 2,540
respectively), this equals a much larger percentage of the smallest systems in the cross-section data set (66
percent) than are represented in the CDC census (only 42 percent).  Therefore, the  cross-section data set
(comprised of compliance monitoring data records acquired directly from the States) has a
proportionately larger amount of the smallest systems than does the CDC census (based on voluntary
reporting of which systems fluoridate).  This differing system size profile can result in a smaller
population served by a similar number of systems as is the case for the national extrapolations based on
the cross-section data.
Table Vl.J.l.b. Size Distribution of Fluoridating Systems in the 16 Cross-Section States and the
CDC Fluoridation Census 1992
Population
Served
• -1,000
1,001-5,000
5,001 - 10,000
10,001 - 50,000
50,001 - 100,000
> 100,000
Number of Systems
that Fluoridate -
State Data 1
2,824
750
244
347
54
42
Percent of State
Total Number of
Fluoridating
Systems
66%
18%
6%
8%
1%
1%
Number of Systems
that Fluoridate -
CDC Data 2
2,540
1,983
578
716
103
79
Percent of CDC
Total Number of
Fluoridating
Systems
42%
33%
10%
12%
2%
1%
12 The system and population totals listed here are equal to the exact system and population summations of the 50
States. These total sums do not equal the sums presented in the CDC Fluoridation Census 1992, in part due to the
inclusion of the District of Columbia.
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Population
Served
Total
Number of Systems
that Fluoridate -
State Data 1
4,261
Percent of State
Total Number of
Fluoridating
Systems
100%
Number of Systems
that Fluoridate -
CDC Data 2
5,999
Percent of CDC
Total Number of
Fluoridating
Systems
100%
1. The State data results of "number of systems that fluoridate" are derived by using the cross-section data, calculating a simple arithmetic mean
fluoride concentration for each system in a particular population served system size category, and then counting all systems with a mean
concentration greater than 0.7mg/L (which represents the low end of the range of optimum fluoride concentration for fluoridation).
2. CDC "number of systems that fluoridate" are derived from qualitative reported findings of the CDC 1992 Fluoridation Census.


A third factor influencing the  system number and population differences between the CDC and national
cross-section estimates relates to systems that report as "fluoridated systems." In the CDC Fluoridation
Census 1992, systems that operate within the control range (of optimum fluoride concentration) of 0.6
mg/L and 1.7 mg/L are considered to fluoridate. The Stage 2 statistical  estimations and related national
extrapolations were based on a fluoride concentration threshold of 0.7 mg/L (the low end of the optimum,
not the control, range of fluoride levels).  Therefore, the  Six-Year Review Stage 2 estimates of systems
with estimated mean concentrations of fluoride  greater than 0.7 mg/L will likely be lower than the CDC
census number of systems reported to operate within the control range (between 0.6 mg/L and 1.7 mg/L
fluoride).

Other factors relate to the type of systems included in EPA's  Six-Year Review and the CDC fluoridation
census.  The Six-Year Review, based on compliance monitoring, does not include analytical results for
consecutive (i.e., purchased) systems. Because compliance monitoring requirements for consecutive
systems are at the discretion of the individual States, the consecutive system compliance monitoring
record is not uniform from State to State.  Therefore, systems identified as consecutive were removed in
the raw data sets prior to Stage 2 estimations. The CDC fluoridation census does include consecutive
systems.  (CDC estimates that there may be approximately 1,696 consecutive systems serving a
population  of 12,850,000 in the 16 States that comprise the 16-State cross-section used in this Six-Year
Review analysis.) Also, while the Six-Year Review 16-State cross-section data does include monitoring
results from NTNCWSs, the CDC fluoridation census does not.

In summary, given the differences between the CDC census numbers and the EPA model estimates,
direct comparisons cannot made between the two assessments of fluoride occurrence in public water
systems.  However, considering the underlying  differences between the  CDC census findings and the  Six-
Year Review model estimates, general comparisons suggest that the Stage 2 modeling approach tracks
relatively closely to CDC voluntarily reported qualitative census findings.

The comparison of the number of systems estimated by the Six-Year model to have an estimated mean
fluoride concentration greater than 0.7 mg/L compared to the number of systems reporting to the CDC
census as fluoridating exhibits the largest difference between the two fluoride occurrence assessments.
Three likely causes for this discrepancy are:

1.     The CDC fluoridating systems include systems operating within the "control range" (i.e., as low
       as 0.6  mg/L).
2.     The Six-Year Review estimates did not have data for the Chicago Water System.
3.     The Six-Year Review estimates generally do not include consecutive systems.

The comparison between the Six-Year Review model estimates and the unpublished 2000 Census
numbers for systems with fluoride concentrations above 2 mg/L and 4 mg/L are generally good. For
example, relative to 4 mg/L, the Six-Year Review model estimates are not dramatically higher than the
CDC estimates, especially when comparing the total population  served.  The EPA system numbers are
modeled estimates, and therefore, it is appropriate to consider the estimated range of results rather than
the single "best estimate." The modeled estimates indicate that from 118,200 people to 301,000 people
could be served by systems with a mean fluoride concentration greater than 4 mg/L.  The CDC estimate
(of approximately 153,000 people) falls into this range.  The  other comparisons with the unpublished
2000 CDC  census findings, while not within the statistical model estimate ranges, are relatively similar
Occurrence Estimation Methodology
47
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(not orders of magnitude apart) given the differences between the CDC and EPA sources of
information/data. The differences in hundreds of systems or hundreds of thousands of population served
by systems can be interpreted as somewhat close when considered relative to the total United States'
population or the total United States'  population served by fluoridated water.

VI.J.2.  SDWIS/Fed Comparison

A preliminary comparison was conducted of Stage 2 model findings and MCL violation records in
SDWIS/Fed. Due to many qualifying factors, this must be regarded as a very general, indirect
comparison. A primary factor that inhibits a direct comparison is the somewhat incomplete State
reporting to the SDWIS/Fed database over the time frame of interest (roughly 1993-1999). Also, the
method for calculating a contaminant's concentration in a system is somewhat different for the Stage 2
analysis as compared to MCL violation determinations. A brief description of some key topics related to
MCL compliance information is presented below to  provide background on SDWIS/Fed MCL violation
data.

For systems that monitor more frequently than annually, compliance with the MCL is determined by a
running annual average  of results from all samples taken at each sampling point. If this contaminant
mean concentration exceeds the MCL, then the system is out of compliance.  For systems that monitor
annually or less frequently, if the level of a contaminant at any sampling point exceeds the MCL, the
system is out of compliance with the MCL.

More systems have MCL exceedances than actual MCL violations. A system with an MCL violation
always has an MCL exceedance. However, a system with an MCL exceedance may not always incur an
MCL violation.  For example, if a system that conducts quarterly monitoring has one quarter in which the
concentration is above the MCL, but the running annual average based on this high analytical  result and
those from the three preceding quarters is below the  MCL, the system would have an MCL exceedance
but not an MCL violation.  Also, if the State requires a confirmation sample, compliance with  the MCL is
calculated using the average of the routine and confirmation sample.  If the average is below the MCL,
the system would have an exceedance but not an MCL violation.

Many States experienced delays in implementing the Phase II/V rule. In some cases, approval of State
primacy took many years. Laboratory capacity, resource and staffing levels, and waivers were recurring
issues.  States are required to report MCL violations to SDWIS/Fed. However, delays in determining
MCL violations and reporting them to SDWIS/Fed were commonplace.  States  had to create new
databases or modify existing databases for Phase II/V compliance tracking and  reporting.  As a result,
many States had delays  in reporting chemical violation data to SDWIS/Fed. Under-reporting of
violations for chemicals is still an issue for some States.  SDWIS/Fed has the capability of storing data on
MCL exceedances; however, reporting of these is optional.

When comparing the modeled national occurrence estimates to the SDWIS/Fed MCL violation data, one
must also consider the different time frames at hand. The SDWIS/Fed MCL violation data are roughly
from 1993-1999.  The Stage 2 estimate is based on compliance monitoring analytical results that are
predominantly from between 1992 and 1997. (Potentially more than five years of monitoring  results are
used to estimate a single system mean concentration). The Stage 2 estimated number of systems with a
mean concentration greater than the MCL (based on data for many years) is an  approximation of, though
not directly comparable to, the number of SDWIS/Fed MCL violations for a single year.

Table VI.J.2.a compares the reported  SDWIS/Fed MCL violations (between January 1, 1993 and
December 31, 1999) to the  Stage 2 estimates of mean concentration MCL exceedances for beryllium,
chromium, fluoride, and tetrachloroethylene. Based on the qualifying factors described above, it is not
surprising that the Stage 2 estimates are higher than  the reported SDWIS/Fed MCL violations  (with the
exception of chromium). Even given the inherent differences between the SDWIS/Fed MCL violation
records and the Stage 2  analytical findings measured relative to the MCL, the comparison between the
two assessments of occurrence are reasonably comparable, providing additional measures that suggest a
validation of the Stage 2 modeling approach.
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Table VI. J.2.a. Preliminary Comparison of Stage 2 Analytical Findings and SDWIS/Fed MCL
Violation Information
Contaminant
(MCL in mg/L)
Beryllium (0.004)
Chromium (0.1)
Fluoride (4)
Tetrachloroethylene (0.005)
Number of Systems
SDWIS/Fed
MCL Violations
17
9
247
128
Stage 2 Estimates of
Mean Concentration
Greater than the MCL
51
3
332
132
VII. CONCLUSION

A broad evaluation of regulated contaminant occurrence in public drinking water systems was conducted
in support of the Six-Year Review of National Primary Drinking Water Regulations. Safe Drinking
Water Act compliance monitoring analytical results reported to the States provided the occurrence data
used in the occurrence estimates.  States were evaluated through a methodology that included a ranking of
States' based on measures of pollution potential, dividing States into quartiles based on these rankings,
and then selecting States that equally represent the four pollution potential quartiles. By also considering
geographic distribution of the selected States, a "cross-section" of States was selected to reflect a national
representation of pollution potentials and climatic/hydrologic differences.

The analyses presented in this report are based on compliance monitoring data from the 16 selected cross-
section States, which include: Alabama, California, Florida, Illinois, Indiana, Kentucky, Michigan,
Montana, Nebraska, New Jersey, New Mexico,  Oregon, South Carolina, South Dakota, Texas, and
Vermont.  These data have undergone extensive quality review and editing, including discussions with
State data management staff. This 16-State national cross-section represents the largest compliance
monitoring data set compiled to date by the USEPA.

The 16-State cross-section contains compliance monitoring data for the following: 10 inorganic
contaminants with occurrence data from approximately 22,000 public water systems that serve an
approximate total of 110,000,000 persons; 29 synthetic organic contaminants with occurrence data from
approximately 20,000 public water systems that serve an approximate total of 116,000,000 persons, and;
21 volatile organic contaminants with occurrence data from approximately 25,000 public water systems
that serve  an approximate total of 113,000,000 persons. For comparison, the total number of (non-
purchased) public water systems nationally is approximately 65,000 and the total population served by
these public  water systems is approximately 213,000,000.

A two-stage  occurrence assessment approach was developed to evaluate the assembled 16-State cross-
section occurrence data. The first stage of analysis (Stage 1) provides a straightforward, non-parametric,
and preliminary assessment of occurrence.  The primary  Stage  1 measure is a simple statistical count and
percentage of PWSs with at least one analytical result that exceeds  a specified contaminant concentration
threshold. These initial statistics were developed for each contaminant according to water system source
water type.

For the second stage of analysis (Stage 2), a Bayesian-based hierarchical model was developed for use to
generate detailed, stratified national occurrence estimates from the 16-State cross-section data. This
statistical estimation method has been peer-reviewed, has been assessed relative to another drinking water
contaminant occurrence estimation method (i.e., ROS), and has been evaluated with simulated data sets
designed to assess the impact of the log-normal, as well as the constant variance, assumption made on the
system level regarding the national distribution of system means.
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All model assessments suggest the Bayesian-based hierarchical model used for the occurrence estimations
in this report is appropriate. The peer-review generally supported the use and application of the model.
Peer-review suggestions, such as a simulation study, have been conducted and incorporated into this
report. Compared to the ROS approach, the Bayesian-based model estimates system means that are closer
to the true system means of the simulated data sets. The simulated study also  showed that the assumption
of log-normal contaminant distribution does not have an undue influence  on the estimate of the national
distribution of system means.  When the log-normal assumption is not used, the estimated national
distribution has a slightly larger variance, which may result in an overestimate of the exceedance
probabilities. The detailed evaluations of the Bayesian-based model suggest that the occurrence
estimations, based on the 16-State cross-section of public water system compliance monitoring, are valid.
The occurrence of 60 regulated contaminants was evaluated in this analysis. The Stage 1 and Stage 2
estimates for these contaminants generally yielded very similar results. For instance, when evaluated
relative to their respective MCLs, the same contaminants exhibit the highest occurrence in their
contaminant group for both the Stage 1 and Stage 2 analyses. Based on the 16-State cross-section Stage 1
estimates, the highest occurrence IOC was fluoride, the highest occurrence SOC was bis(2-
ethylhexyl)phthalate and the highest occurrence VOC was tetrachloroethylene. Based on the  16-State
cross-section Stage 2 estimates, the highest occurrence IOC was fluoride, the highest occurrence  SOC
was l,2-dibromo-3-chloropropane (bis[2-ethylhexyl]phthalate was the second highest occurrence SOC)
and the highest occurrence VOC was trichloroethylene (tetrachloroethylene was the second highest
occurrence VOC).

Sixteen out of the 60 contaminants reviewed for this analysis were determined to have no compliance
monitoring analytical results greater than their MCL in any of the 16 cross-section States. (Not a single
analytical result for sixteen reviewed contaminants exceeded  the MCL concentration.) Thus, the Stage 1
estimates (based  on at least one analytical result greater than the MCL) and the Stage 2 estimates (based
on a system mean concentration greater than the MCL) were  equal to 0% for these 16 contaminants.
Seven of the 16 contaminants were SOCs, including carbofuran, dalapon, glyphosate,
hexachlorocyclopentadiene, oxamyl, picloram, and 2,4,5-TP.  The  remaining nine contaminants were
VOCs, including 1,4-dichlorobenzene, o-dichlorobenzene, trans-dichloroethylene, ethylbenzene,
monochlorobenzene, styrene, toluene, 1,2,4-trichlorobenzene, and xylenes.

Another fifteen contaminants had Stage 1 estimates relative to the MCL which were not equal to zero but
had Stage 2 estimates relative to the MCL that were equal to zero.  These differences between Stage 1  and
Stage 2 findings can relate to specific occurrence details.  For example, a contaminant with widespread
and frequent occurrence at low concentrations (just about the MRL) would be characterized by relatively
high Stage 1 values yet very low (even zero) Stage 2 values.  Fourteen of these 15 contaminants were
SOCs, including  alachlor, bis(2-ethylhexyl)adipate, chlordane, 2,4-d, diquat, endrin, endothall,
heptachlor, heptachlor epoxide, hexachlorobenzene, lindane,  methoxychlor, simazine, and toxaphene.
One of the 15 contaminants, 1,1,2-trichloroethane, was a VOC.

Complete Stage 1 analytical occurrence findings for each of the 60 regulated contaminants are presented
in Appendix A. Complete Stage 2 analytical occurrence findings  for each of the 60 regulated
contaminants are presented in Appendix C. A summary of the Stage 2 findings for 14 of the regulated
contaminants was presented in a Federal Register notice announcing EPA's preliminary decisions
regarding  its Six-Year Review of National Primary Drinking Water Regulations (U.S. EPA 2002). Stage
2 summary findings for two additional regulated contaminants are presented in EPA's announcement of
its final decisions (yet to be published). The Stage 2 summary findings for all  16 contaminants are
presented  in Appendix E.
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                                       REFERENCES


Center for Disease Control and Prevention (CDC).  1992.  Fluoridation Census 1992. Atlanta, GA:
       Centers for Disease Control and Prevention, Public Health Service, U.S.  Department of Health
       and Human Services.

Center for Disease Control and Prevention (CDC).  2002.  Written comments (including information from
       the unpublished Fluoridation Census 2000) from CDC staff to OGWDW staff, January 8, 2002.

Hall, B., and M.L. Kerr.  1993.  1991-1992 Green Index: A State-By-State Guide to the Nation's
       Environmental Health. Washington, DC: Island Press.

Helsel, D.R., and T.A. Cohn.  1988.  "Estimation of Descriptive Statistics for Multiply Censored Water
       Quality Data." Water Resources Research, 24, 1997-2004.

Helsel, D.R., and R.J. Gilliom.  1988. "Estimation  of Distributional Parameters for Censored Trace Level
       Water Quality Data.  2.  Verification and Applications." Water Resources Research, 24,  147-155.

Lockwood, J.R. Ill, M.J. Schervish, P. Gurian, and M.J. Small.  2001. Characterization of Arsenic
       Occurrence in US Drinking Water Treatment Facility Source Waters (Revised Version).
       accepted by Journal of the American Statistical Association (March 2001).

Porter, P., R.C. Ward and H.F Bell.  1988. Environ. Sci.  Technol.  v.22, pp. 856-61.

Squillace,  P.J.,  M.J. Moran, W.W. Lapham, C.V. Price, RM. Clawges, and J.S. Zogorski.  1999.
       "Volatile Organic Compounds in Untreated Groundwater of the United States, 1985-1995."
       Environ.  Sci. Technol.  v.33, no. 23, pp. 4176-4187.

The Cadmus Group, Inc. 2000. First Stage Occurrence and Exposure Report for Six-Year Review. Draft
       report submitted to EPA for review May 12, 2000.

Travis, C.C. and M.L. Land.  1990. Estimating the  mean of data sets with nondetectable values. Environ.
       Sci.  Technol. v.24, no.  7, pp. 961.

U.S. Department of Commerce (U.S. DOC), Bureau of the Census.  1994.  1992 Census of Agriculture.
       Washington, D.C.: U.S. Government Printing Office.

U.S. DOC, Bureau of the Census.  1996.  1992 Census of Manufactures. Washington, D.C.: U.S.
       Government Printing Office.

U.S. DOC, Bureau of the Census.  1997.  1995 Annual Survey of Manufactures.  Washington, D.C.: U.S.
       Government Printing Office.

U.S. Environmental Protection Agency (U.S. EPA). 1999. A Review of Contaminant Occurrence in
       Public Water Systems.  EPA Report # 816-R-99-006, Office of Water, 78  pp.

U.S. EPA.  2000a. Methods,  Occurrence, and Monitoring Document for Radon in Drinking Water. EPA
       Office  of Ground Water and Drinking Water.

U.S. EPA.  2000b. Arsenic Occurrence in Public Drinking Water Supplies. EPA Office of Ground
       Water and Drinking Water.

U.S. EPA.  2000c. Water Industry Baseline Handbook, Second Edition (Draft). March 17.
Occurrence Estimation Methodology                51                                     June 2003

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U.S. EPA. 2001. TRI Explorer (Data from 1988-1995).  Available on the Internet at:
       http://www.epa.gov/triexplorer/chemical.htm.  (The version of this website last modified on
       October 4, 2001 was used for this report.)

U.S. EPA. 2002. National Primary Drinking Water Regulations - Announcement of the Results of
       EPA's Review of Existing Drinking Water Standards and Request for Public Comment; Proposed
       Rule. Federal Register. Vol. 67, No. 74. p. 19030, April 17, 2002.
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                                         DEFINITIONS


Bayesian inference is an approach to statistics in which all forms of uncertainty are expressed in terms of
probability.  A Bayesian approach to a problem starts with the formulation of a "prior distribution" of the
unknown parameters (or measurements) of the system being modeled. This prior distribution is meant to
capture the beliefs and reflect the characteristics of the system being modeled before analyzing the data
(that has been collected to represent the system being modeled). After reviewing the data, Bayes' Rule is
applied to obtain a "posterior distribution" for the unknown parameters, which takes account of both the
formulated "priors" and the data that represent the system being modeled. From this posterior
distribution, predictive distributions can be computed from which the best estimates (e.g., the mean,
median, or mode) as well as the uncertainty of the estimates (the credible intervals) can be presented.

Best estimate (in the context of this analysis) refers to the average (mean) probability of exceeding a
threshold (i.e., the average probability that a public water system will have an estimated mean
contaminant concentration that exceeds a specific threshold).

Censored data (see non-detection data).

Central tendency is  a measure of the typicality or centrality of a set of values; the three main measures of
central tendency are mean, median and mode.

Community water system (CWS) is a public water system that serves at least 15 service connections used
by year-round residents or regularly serves at least 25 year-round residents.

Compliance monitoring data refer to drinking water regulated contaminant occurrence dat from required
sampling conducted at public drinking water systems.  Compliance monitoring sampling is conducted by
trained water system staff and the samples are analyzed using EPA drinking water-certified laboratory
methods.

Credible interval (CI) is the calculated interval that has a specified probability of containing a parameter
of interest. For example, if one obtained a 95% CI of (0.85, 0.96) for the best estimate probability of
exceedance, then we would be 95% certain that the true value of the best estimate probability of
exceedance was between 0.85 and 0.96.

Credible bounds (CB) are the upper and lower bounds of the credible interval.

Extrapolation is the estimation of unknown values by  extending or projecting from known values. In this
report, occurrence estimates generated using data from the 16-State national cross-section are extrapolated
to national estimates (since contaminant occurrence in the cross-section of 16 States is indicative of
national occurrence).

Log-normal distribution is a specific distribution of values in which the logarithms of the values follow a
normal distribution.

Maximum contaminant level (MCL) is the maximum permissible level of a contaminant in water which is
delivered to any user of a public water system.  An MCL is specified for each regulated drinking water
contaminant based primarily on the known heal effects associated with that contaminant.

Minimum reporting level (MRL) is the lowest laboratory analytical concentration that can be reliably
achieved (and subsequently reported) within specified limits of precision and accuracy under routine
laboratory operating conditions.  The MRL is essentially equal to the "censoring" level for a particular
analytical method; therefore, sample analytical results that are below, or less than, the MRL are referred
to as non-detection (or censored) data. (See non-detection data.)
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                                   DEFINITIONS (Continued)

Monte Carlo method is, in general terms, any technique using random numbers to model a process. This
technique works particularly well when the process is one where the underlying probability distributions
are known, but the results are more difficult to determine.

Non-detection data (sometimes referred to non-detect or censored data) are the sample analytical results
when a contaminant either is not detected analytically or is detected at a concentration less than the
minimum reporting level (MRL).

Non-community water system (NCWS) is a public water system that is not a community water system.
There are two types of NCWSs: transient non-community water systems (TNCWS) and non-transient
non-community water systems (NTNCWS).  A TNCWS does not regularly serve at least 25 of the same
persons during six months of the year (for example, a gas station or a campground). A NTNCWS
regularly serves at least 25 of the same persons during at least 6 months per year (for example,  a school).

Non-parametric statistics do not rely on parameter estimation nor do they involve assumptions about the
underlying distribution of variables. Non-parametric statistics can be used to describe the relationship
between or among variables ordinally or by scenarios rather than in terms of statistical parameters.  The
Stage 1 analyses in this report are non-parametric because no assumptions are made about the underlying
data and no parameters are estimated.  Stage 1 analyses  are simple counts based directly on the actual data
(e.g., the number of systems with at least one exceedance of the MCL).  (See parametric statistics.)

Non-transient non-community water system (NTNCWS) is a public water system that is not a community
water system and that regularly serves at least 25 of the  same persons during at least 6 months per year
(for example, a school).

Non-zero modal MRL refers to the most commonly occurring MRL value, other than zero.

Normal distribution is a specific distribution of values having a characteristic bell-shaped, symmetrical
form.

Parameters are numerical values summarizing the data (e.g., the minimum, mean, or maximum
concentration of a contaminant in a public water system).

Parametric statistics are a type of inferential statistic that involves the estimation of at least one
parameter, with the statistical estimates typically requiring some assumptions about the variables under
investigation.  Often, an assumption is made that the data are a sample from a certain distribution,
commonly a normal distribution. (Most environmental data generally follow a normal distribution.) The
Stage 2 analyses in this report are parametric because the data are assumed to follow a log-normal
distribution and mean contaminant concentrations (a parameter) are estimated for public water  systems.

Percentile is the point below which a specified percentage of the observations fall.

Pollution potential indicators are environmental factors which indicate the likelihood of pollution (or
contaminant occurrence) in a particular State or Region. For this analysis, the number of manufacturing
establishments per square mile was considered to be the best indicator of the potential for manufacturing
pollution (mainly volatile organic contaminant occurrence).  Total farm agricultural chemical expenses
was considered to be the best indicator of the potential for agricultural pollution (primarily synthetic
organic contaminant occurrence).

Population-served refers to the number of persons that consume water from a particular public  water
system or group of public water systems.

Population-Served by Systems > MCL refers to the total number of persons that consume water from
public water systems that have had at least one analytical result  greater than the MCL of the contaminant
in question.


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                                   DEFINITIONS (Continued)

Posterior probability is a concept associated with Bayesian statistics. The posterior probability is the
probability of an event occurring after making use of new, additional information. In other words, it is the
prior probability of an event after updating it with new data.

Prior probability is the probability of an event as it could best be assessed initially.  The prior probability
can be based on the results of other experiments, on expert opinion, or actual existing data.

Probability ofexceedance refers to the probability that a public water system will have an estimated mean
contaminant concentration that exceeds  a specific concentration threshold.  Probabilities ofexceedance
are estimated in the Stage 2 analyses and are presented as best estimates, with credible intervals.

Public water system (PWS) is a system that provides water for human consumption through pipes or other
constructed conveyances to at least 15 service connections or serves an average of at least 25 people for at
least 60 days a year.

Public water system identification number (PWSID) is a unique 9-digit number assigned by EPA to
uniquely identify each public water system in the States, territories, and tribes of the United States.

Quantitative data are numerical data, obtained by measuring objects or events.

Qualitative data are non-numerical data, often in the form of categorical data.

Quartiles are the points which break the distribution of values into fourths.

Range is a measure of variability indicating the difference between the highest and lowest values in a
distribution of values.

Ranked data are data for which the observations have been replaced by their numerical ranks (typically
from lowest to highest).

Sample level analyses are based on the total number of samples where an event has occurred (e.g., the
total number of analytical results greater than the MCL).  PWS contaminant occurrence sample level
analyses can be biased (over-representing contaminant occurrence) because more frequent sampling is
typically conducted and reported by public water systems experiencing problems with contaminant
occurrence.

Scatterplot is a figure in which the individual data points are plotted in two-dimensional space.

Skewness is a measure of the degree to which a distribution is asymmetrical.

Stage 1 analysis, a non-parametric analysis, is based on the number of public water systems that have had
at least one analytical result which exceeds a specified concentration threshold for a particular
contaminant. Stage 1 analyses are simple counts of the number of systems which are not based on
modeled estimates. Stage 1 analyses are very approximate measures if of peak concentrations.

Stage 2 analysis, a parametric analysis,  is based on the number of systems with an estimated mean
concentration value which exceeds a specified concentration threshold for a particular contaminant.

Stage 2 analyses are generated using the Bayesian-based hierarchical model. Stage 2 analyses are
measures of average, or mean, concentrations.

Standard deviation is a descriptive statistic used to measure the degree of variability within a set of
values. Standard deviation is equal to the square root of the variance.
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                                   DEFINITIONS (Continued)

Stratification is the partitioning of subjects into subgroups. For example, stratification of results by
source water type means that the analyses are generated separately for ground water and surface water
public water systems.

System level analyses are based on the number of systems for which an event occurred (e.g., the number
of systems that have had at least one analytical result greater than the MCL). System level analysis
avoids the potential bias of results of public water system contaminant occurrence assessments that can
occur through sample level analyses.

System mean refers to the average concentration value of a given contaminant for a public water system.
System means are estimated in the Stage 2 analysis by the Bayesian-based model.

Systems > MCL refers to the total number public water systems that have had at least one analytical result
greater than the MCL. This is an example of the non-parametric, Stage  1 analyses.

Transient non-community water system (TNCWS) is a non-community water system that does not
regularly serve at least 25 of the same  persons during six months of the year (for example, a gas station
or a campground).

Variance is a measure of dispersion  or variability (spread of values), calculated by squaring the value of
the standard deviation.
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                         APPENDICES
Appendix A.




Appendix Bl.




Appendix B2.




Appendix C.




Appendix D.




Appendix E.
Stage 1 Analytical Findings




Detailed Description of Bayesian Hierarchical Model




16-State Cross-Section Data Used for Stage 2 Analysis




Stage 2 Analytical Findings




Model Bounding Analysis




Summary of Stage 2 Analytical Findings

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                  Appendix A.  Stage 1 Analytical Findings
Table A. 1 .a.    Summary of Occurrence of IOC Regulated Contaminants in Surface Water Systems from
              the Initial Eight Cross-Section States - Based on Systems
Table A. 1 .b.    Summary of Occurrence of IOC Regulated Contaminants in Ground Water Systems from
              the Initial Eight Cross-Section States - Based on Systems

Table A.2.a.    Summary of Occurrence of IOC Regulated Contaminants in Surface Water Systems from
              the Initial Eight Cross-Section States - Based on Population Served
Table A.2.a.    Summary of Occurrence of IOC Regulated Contaminants in Ground Water Systems from
              the Initial Eight Cross-Section States - Based on Population Served

Table A.3 .a.    Summary of Occurrence of SOC Regulated Contaminants in Surface Water Systems from
              the Initial Eight Cross-Section States - Based on Systems
Table A.3 .b.    Summary of Occurrence of SOC Regulated Contaminants in Ground Water Systems from
              the Initial Eight Cross-Section States - Based on Systems

Table A.4.a.    Summary of Occurrence of SOC Regulated Contaminants in Surface Water Systems from
              the Initial Eight Cross-Section States - Based on Population Served
Table A.4.a.    Summary of Occurrence of SOC Regulated Contaminants in Ground Water Systems from
              the Initial Eight Cross-Section States - Based on Population Served

Table A.5.a.    Summary of Occurrence of VOC Regulated Contaminants in Surface Water Systems
              from the Initial Eight Cross-Section States - Based on Systems
Table A.S.b.    Summary of Occurrence of VOC Regulated Contaminants in Ground Water Systems
              from the Initial Eight Cross-Section States - Based on Systems

Table A.6.a.    Summary of Occurrence of VOC Regulated Contaminants in Surface Water Systems
              from the Initial Eight Cross-Section States - Based on Population Served
Table A.6.a.    Summary of Occurrence of VOC Regulated Contaminants in Ground Water Systems
              from the Initial Eight Cross-Section States - Based on Population Served

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Occurrence Estimation Methodology and Findings
Appendix A. Stage 1 Analytical Findings
Six-Year Review
      Table A.l.a.  Summary of Occurrence of IOC Regulated Contaminants in Surface Water Systems from the
      Initial Eight Cross-Section States - Based on Systems
Inorganic Chemicals
(MCL in mg/L)
Antimony (0.006)
Arsenic (0.05)
Barium (2.0)
Beryllium (0.004)
Cadmium (0.005)
Chromium (0.10)
Cyanide (0.20)
Fluoride (4.0)
Mercury (0.002)
Selenium (0.05)
Thallium (0.002)
Surface Water Systems
Number of
Analyses in
Cross-Section
2,932
5,601
5,425
2,924
5,351
5,346
2,326
8,186
5,329
5,339
2,928
Number of
Systems in
Cross-Section
561
686
680
558
682
681
489
685
680
682
558
% Systems
>MRL
4.10%
13.70%
49.85%
2.51%
5.13%
11.75%
5.52%
79.12%
8.82%
10.70%
2.69%
% Systems
> 0.5 MCL
0.89%
1.02%
0.59%
0.54%
1.47%
0.73%
1.02%
2.19%
1.76%
0.15%
0.90%
% Systems
>MCL
0.36%
0.87%
0.44%
0.00%
0.29%
0.44%
0.41%
1.17%
0.74%
0.00%
0.18%
      Too few data to evaluate asbestos.
      " % > MCL " indicates the proportion of systems with any analytical results exceeding the concentration value of the MCL; it does not necessarily indicate
      an MCL violation. An MCL violation occurs when the MCL is exceeded by the average results from four quarterly samples or confirmation samples as
      required by the primacy State.

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Occurrence Estimation Methodology and Findings
Appendix A. Stage 1 Analytical Findings
Six-Year Review
      Table A.l.b.  Summary of Occurrence of IOC Regulated Contaminants in Ground Water Systems from the
      Initial Eight Cross-Section States - Based on Systems
Inorganic Chemicals
(MCL in mg/L)
Antimony (0.006)
Arsenic (0.05)
Barium (2.0)
Beryllium (0.004)
Cadmium (0.005)
Chromium (0.10)
Cyanide (0.20)
Fluoride (4.0)
Mercury (0.002)
Selenium (0.05)
Thallium (0.002)
Ground Water Systems
Number of
Analyses in
Cross-Section
17,752
37,975
36,507
17,591
36,037
36,157
13,389
44,023
35,824
36,189
17,623
Number of
Systems in
Cross-Section
5,099
6,644
6,665
5,095
6,669
6,671
4,067
6,968
6,637
6,636
5,089
% Systems
>MRL
3.10%
19.25%
48.03%
2.02%
4.74%
13.07%
1.97%
73.39%
4.41%
8.54%
3.46%
% Systems
> 0.5 MCL
1.27%
1.67%
0.80%
0.51%
1.39%
0.61%
0.44%
4.02%
0.74%
0.39%
1.36%
% Systems
>MCL
0.43%
0.98%
0.24%
0.24%
0.72%
0.27%
0.25%
1.42%
0.39%
0.23%
0.47%
      Too few data to evaluate asbestos.
      " % > MCL " indicates the proportion of systems with any analytical results exceeding the concentration value of the MCL; it does not necessarily indicate
      an MCL violation. An MCL violation occurs when the MCL is exceeded by the average results from four quarterly samples of confirmation samples as
      required by the primacy States.

-------
Occurrence Estimation Methodology and Findings
Appendix A.  Stage 1 Analytical Findings
Six-Year Review
     Table A.2.a. Summary of Occurrence of IOC Regulated Contaminants in Surface Water Systems from
     the Initial Eight Cross-Section States - Based on Population Served
Inorganic Chemicals
(MCL in mg/L)
Fluoride (4.0)
Arsenic (0.05)
Chromium (0.10)
Barium (2.0)
Mercury (0.002)
Antimony (0.006)
Cadmium (0.005)
Cyanide (0.20)
Selenium (0.05)
Beryllium (0.004)
Thallium (0.002)
Surface Water Systems
Number of
Analyses in Cross-
Section
8,021
5,380
5,176
5,251
5,159
2,827
5,181
2,243
5,165
2,819
2,815
Number of Systems
in
Cross-Section
641
646
642
641
641
532
643
467
642
529
529
Total Population
Served by Systems
40,956,768
40,662,132
40,621,592
40,619,748
40,596,090
38,871,834
40,652,812
33,238,140
40,621,592
38,764,439
38,766,394
% Population
Served by Systems
>MRL
94.47%
8.86%
10.61%
76.56%
5.47%
4.71%
6.20%
3.39%
8.03%
4.08%
2.14%
% Population
Served by Systems
> 1/2 MCL
5.76%
1.19%
3.85%
0.31%
0.30%
2.00%
0.65%
0.59%
0.57%
0.16%
1.41%
% Population
Served by Systems
>MCL
5.69%
1.05%
0.41%
0.28%
0.14%
0.10%
0.07%
0.02%
0.00%
0.00%
0.00%
     Too few data to evaluate asbestos.
     " % > MCL " indicates the proportion of population served with any analytical results exceeding the concentration value of the MCL; it does not necessarily indicate an MCL violation. An MCL
     violation occurs when the MCL is exceeded by the average results from four quarterly samples of confirmation samples as required by the primacy States.

-------
Occurrence Estimation Methodology and Findings
Appendix A. Stage 1 Analytical Findings
Six-Year Review
     Table A.2.b. Summary of Occurrence of IOC Regulated Contaminants in Ground Water Systems from
     the Initial Eight Cross-Section States - Based on Population Served
Inorganic Chemicals
(MCL in mg/L)
Fluoride (4.0)
Arsenic (0.05)
Chromium (0.10)
Selenium (0.05)
Cadmium (0.005)
Barium (2.0)
Mercury (0.002)
Cyanide (0.20)
Antimony (0.006)
Thallium (0.002)
Beryllium (0.004)
Ground Water Systems
Number of
Analyses in Cross-
Section
39,940
34,630
33,035
33,042
32,914
33,342
32,670
12,738
16,692
16,582
16,565
Number of Systems
in
Cross-Section
6,184
6,221
6,253
6,219
6,251
6,245
6,221
3,904
4,866
4,865
4,877
Total Population
Served by Systems
38,473,294
38,496,759
38,678,416
38,471,623
38,678,035
38,656,452
38,495,894
33,517,398
36,692,016
36,763,051
36,822,894
% Population
Served by Systems
>MRL
97.10%
12.29%
29.98%
3.98%
2.97%
81.46%
3.70%
2.06%
1.59%
1.50%
0.99%
% Population
Served by Systems
> 1/2 MCL
11.88%
5.05%
23.15%
0.85%
0.96%
0.97%
1.10%
0.50%
1.03%
0.54%
0.34%
% Population
Served by Systems
>MCL
8.14%
3.63%
1.68%
0.81%
0.78%
0.51%
0.50%
0.40%
0.36%
0.31%
0.08%
     Too few data to evaluate asbestos.
     " % > MCL " indicates the proportion of population served with any analytical results exceeding the concentration value of the MCL; it does not necessarily indicate an MCL violation. An MCL
     violation occurs when the MCL is exceeded by the average results from four quarterly samples of confirmation samples as required by the primacy States.

-------
Occurrence Estimation Methodology and Findings
Appendix A.  Stage 1 Analytical Findings
Six-Year Review
            Table A.3.a.  Summary of Occurrence of SOC Regulated Contaminants in Surface Water Systems from the Initial
            Eight Cross-Section States - Based on Systems
Synthetic Organic Chemicals
(MCL in mg/L)
Atrazine (0.003)
Ethylene Dibromide (0.00005)
bis(2-ethylhexyl) phthalate (0.006)
l,2-Dibromo-3-chloropropane (0.0002)
Simazine (0.004)
Lindane (0.0002)
Alaohlor (0.002)
PCBs (0.0005)
Toxaphene (0.003)
2,4-D (0.07)
Endrin (0.002)
Methoxyohlor (0.04)
2,4,5-TP (0.05)
Benzo[a]pyrene (0.0002)
bis(2-ethylhexyl) adipate (0.4)
Carboforan (0.04)
Chlordane (0.002)
Dalapon (0.2)
Dinoseb (0.007)
Diquat (0.02)
Endothall (0.1)
Glyphosate (0.7)
Heptaohlor (0.0004)
Heptachlor Epoxide (0.0002)
Hexaohlorobenzene (0.001)
Hexaohlorocyclopentadiene (0.05)
Oxamyl (0.2)
Pentaohlorophenol (0.001)
Pioloram (0.5)
Surface Water Systems
Number of
Analyses in
Cross-Section
4,786
9,252
3,175
7,610
4,590
5,046
4,289
2,990
3,721
4,329
5,060
5,025
4,274
3,479
3,085
3,157
4,372
3,044
3,160
2,233
2,096
2,158
4,438
4,391
4,059
3,813
2,716
3 212
3,156
Number of
Systems in
Cross-Section
550
585
289
585
528
624
535
426
545
620
625
625
621
459
416
523
496
443
491
401
399
406
529
521
521
518
493
496
493
% Systems
>MRL
20.91%
4.62%
28.37%
5.81%
15.91%
1.28%
7.48%
0.47%
0.73%
10.97%
2.08%
0.96%
1.77%
0.44%
6.73%
0.76%
0.00%
8.80%
2.24%
2.74%
0.25%
0.00%
0.19%
0.38%
0.38%
8.88%
0.00%
3.23%
3.45%
% Systems
> 0.5 MCL
12.91%
4.27%
3.11%
1.88%
2.65%
0.48%
1.68%
0.23%
0.18%
0.32%
0.16%
0.16%
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%
0.40%
0.00%
% Systems
>MCL
10.55%
3.59%
2.08%
1.54%
1.14%
0.48%
0.37%
0.23%
0.18%
0.16%
0.16%
0.16%
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%
           Too few data to evaluate dioxin.
           The high rates of phthalate and adipate are, in part, considered false positives related to sample contamination by plastics and analytical problems.

           "% > MCL" indicates the proportion of systems with any analytical results exceeding the concentration value of the MCL; it does not necessarily indicate an MCL violation. An MCL violation
           occurs when the MCL is exceeded by the average results from four quarterly samples or confirmation samples as required by the primacy State.

-------
Occurrence Estimation Methodology and Findings
Appendix A. Stage 1 Analytical Findings
Six-Year Review
            Table A.3.b.  Summary of Occurrence of SOC Regulated Contaminants in Ground Water Systems from the Initial
            Eight Cross-Section States - Based on Systems
Synthetic Organic Chemicals
(MCL in mg/L)
bis(2-ethylhexyl) phthalate (0.006)
l,2-Dibromo-3-ohloropropane (0.0002)
Ethylene Dibromide (0.00005)
Atrazine (0.003)
Lindane (0.0002)
Diquat (0.02)
PCBs (0.0005)
Pentachlorophenol (0.001)
Endrin (0.002)
Benzo[a]pyrene (0.0002)
Dinoseb (0.007)
Heptachlor Epoxide (0.0002)
Endothall (0.1)
Heptachlor (0.0004)
Alaohlor (0.002)
2,4,5-TP (0.05)
2,4-D (0.07)
bis(2-ethylhexyl) adipate (0.4)
Carboforan (0.04)
Chlordane (0.002)
Dalapon (0.2)
Glyphosate (0.7)
Hexachlorobenzene (0.001)
Hexachlorocyclopentadiene (0.05)
Methoxychlor (0.04)
Oxamyl (0.2)
Picloram (0.5)
Simazine (0.004)
Toxaphene (0.003)
Ground Water Systems
Number of
Analyses in
Cross-Section
17,705
65,119
81,902
37,180
31,469
18,099
15,605
22,227
31,180
19,996
21,846
27,457
15,566
28,170
27,726
28,859
30,787
15,888
25,599
29,431
19,297
17,901
23,416
22,667
30,591
21,415
20,984
36,429
26,780
Number of
Systems in
Cross-Section
3,039
7,683
7,819
6,242
5,946
3,142
3,193
4,921
5,922
3,985
5,090
5,356
3,231
5,463
5,547
5,614
5,887
3,270
5,725
5,081
3,656
2,682
5,194
5,103
5,698
4,912
4,598
6,019
5,672
% Systems
>MRL
10.50%
2.66%
1.02%
2.15%
0.25%
0.83%
0.16%
0.81%
0.25%
0.43%
0.45%
0.19%
0.22%
0.22%
0.25%
0.75%
1.22%
7.13%
0.05%
0.06%
0.85%
0.11%
0.00%
0.10%
0.21%
0.10%
0.57%
1.63%
0.11%
% Systems
> 0.5 MCL
3.52%
2.32%
0.90%
0.26%
0.12%
0.10%
0.09%
0.14%
0.07%
0.18%
0.06%
0.04%
0.06%
0.09%
0.05%
0.00%
0.02%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.03%
0.02%
% Systems
>MCL
2.17%
1.99%
0.73%
0.08%
0.07%
0.06%
0.06%
0.06%
0.05%
0.05%
0.04%
0.04%
0.03%
0.02%
0.02%
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%
            Too few data to evaluate dioxin.
            The high rates of phthalate and adipate are, in part, considered false positives related to sample contamination by plastics and analytical problems.

            "% > MCL" indicates the proportion of systems with any analytical results exceeding the concentration value of the MCL; it does not necessarily indicate an MCL violation. An MCL violation
            occurs when the MCL is exceeded by the average results from four quarterly samples or confirmation samples as required by the primacy State.

-------
Occurrence Estimation Methodology and Findings
Appendix A. Stage 1 Analytical Findings
Six-Year Review
    Table A.4.a.  Summary of Occurrence of SOC Regulated Contaminants in Surface Water Systems from the Initial
    Eight Cross-Section States - Based on Population Served
Synthetic Organic Chemicals
(MCL in mg/L)
l,2-Dibromo-3-chloropropane (0.0002)
Ethylene Dibromide (0.00005)
Atrazine (0.003)
Lindane (0.0002)
PCBs (0.0005)
bis(2-ethylhexyl) phthalate (0.006)
Toxaphene (0.003)
Methoxychlor (0.04)
2,4-D (0.07)
Alachlor (0.002)
Endrin (0.002)
Simazine (0.004)
Dalapon (0.2)
Diquat (0.02)
Endothall (0.1)
Glyphosate (0.7)
bis(2-ethylhexyl) adipate (0.4)
Oxamyl (0.2)
Picloram (0.5)
Dinoseb (0.007)
Hexachlorocyclopentadiene (0.05)
Carbofuran (0.04)
Heptachlor (0.0004)
Heptachlor Epoxide (0.0002)
2,4,5-TP (0.05)
Hexachlorobenzene (0.001)
Benzo[a]pyrene (0.0002)
Pentachlorophenol (0.001)
Chlordane (0.002)
Surface Water Systems
Number of Analyses
in
Cross-Section
7,541
9,183
4,723
4,957
2,925
3,109
3,689
4,937
4,252
4,223
4,971
4,525
2,970
2,162
2,033
2,094
3,029
2,649
3,089
3,094
3,749
3,090
4,360
4,313
4,197
3,995
3,415
3,146
4,297
Number of Systems
in
Cross-Section
575
575
541
608
415
281
535
609
605
525
609
519
434
393
392
399
410
484
484
482
510
514
517
509
606
513
451
487
484
Total Population
Served by Systems
36,775,874
36,287,757
33,612,243
35,324,374
29,555,126
27,404,128
32,869,028
35,324,603
42,897,324
32,593,972
35,351,865
33,549,549
27,826,964
27,318,992
27,214,510
27,914,653
13,288,441
29,396,354
29,556,415
29,262,719
29,434,915
29,981,346
32,662,080
32,429,919
42,916,224
29,761,430
28,549,179
29,398,501
33,712,241
% Population
Served by Systems
>MRL
25.31%
6.18%
11.46%
1.44%
0.79%
38.28%
2.33%
1.61%
3.55%
1.99%
1.97%
7.95%
2.60%
0.32%
0.13%
0.00%
1.96%
0.00%
0.57%
0.69%
6.11%
1.66%
0.02%
0.09%
1.29%
0.16%
0.82%
0.98%
0.00%
% Population
Served by Systems
> 1/2 MCL
23.01%
5.33%
2.95%
1.26%
0.78%
0.58%
0.38%
0.35%
0.29%
0.34%
0.19%
0.25%
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%
0.02%
0.00%
% Population
Served by Systems
>MCL
22.75%
5.27%
1.90%
1.26%
0.78%
0.54%
0.38%
0.35%
0.29%
0.22%
0.19%
0.11%
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%
    Too few data to evaluate dioxin.
    "% > MCL" indicates the proportion of population served with any analytical results exceeding the concentration value of the MCL; it does not necessarily indicate an MCL violation. An MCL
    violation occurs when the MCL is exceeded by the average results from four quarterly samples or confirmation samples as required by the primacy States.

-------
Occurrence Estimation Methodology and Findings
Appendix A. Stage 1 Analytical Findings
Six-Year Review
    Table A.4.b.  Summary of Occurrence of SOC Regulated Contaminants in Ground Water Systems from the Initial
    Eight Cross-Section States - Based on Population Served
Synthetic Organic Chemicals
(MCL in mg/L)
Ethylene Dibromide (0.00005)
l,2-Dibromo-3-chloropropane (0.0002)
bis(2-ethylhexyl) phthalate (0.006)
Diquat (0.02)
Benzo[a]pyrene (0.0002)
Atrazine (0.003)
Endrin (0.002)
Lindane (0.0002)
Heptachlor Epoxide (0.0002)
Dinoseb (0.007)
PCBs (0.0005)
Endothall (0.1)
Alachlor (0.002)
Pentachlorophenol (0.001)
Heptachlor (0.0004)
Methoxychlor (0.04)
Toxaphene (0.003)
Dalapon (0.2)
Glyphosate (0.7)
bis(2-ethylhexyl) adipate (0.4)
Oxamyl (0.2)
Simazine (0.004)
Picloram (0.5)
Hexachlorocyclopentadiene (0.05)
Carbofuran (0.04)
2,4-D (0.07)
2,4,5-TP (0.05)
Hexachlorobenzene (0.001)
Chlordane (0.002)
Ground Water Systems
Number of Analyses
in
Cross-Section
78,182
60,295
16,253
16,948
18,900
34,161
28,872
29,142
25,588
20,480
14,522
14,687
25,881
21,038
26,194
28,484
24,944
18,261
16,636
15,422
20,078
33,204
19,923
21,447
23,939
28,632
27,067
22,113
27,226
Number of Systems
in
Cross-Section
7,344
7,092
2,833
3,032
3,789
5,765
5,567
5,585
5,072
4,731
3,090
3,036
5,236
4,699
5,178
5,443
5,308
3,545
2,551
3,224
4,599
5,368
4,484
4,896
5,338
5,520
5,372
4,980
4,741
Total Population
Served by Systems
38,913,299
39,436,663
29,160,368
30,156,678
31,745,303
38,443,753
38,892,442
38,918,871
36,651,094
35,740,628
30,011,043
26,637,191
35,705,526
35,878,071
36,995,500
38,797,783
37,117,798
31,911,316
30,628,529
7,240,096
32,426,769
38,246,225
34,481,953
34,548,177
35,250,302
38,976,761
38,796,035
34,829,449
37,511,301
% Population
Served by Systems
>MRL
24.26%
5.74%
14.68%
1.25%
0.77%
7.48%
0.73%
0.24%
0.15%
0.43%
0.15%
1.02%
0.16%
1.74%
0.48%
0.57%
0.09%
1.13%
0.03%
23.88%
0.15%
7.07%
0.98%
0.11%
0.00%
1.37%
1.23%
0.00%
0.02%
% Population
Served by Systems
> 1/2 MCL
23.09%
5.37%
6.20%
0.52%
0.54%
1.34%
0.37%
0.15%
0.05%
0.09%
0.08%
0.06%
0.07%
0.02%
0.42%
0.00%
0.05%
0.00%
0.00%
0.00%
0.00%
0.01%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
% Population
Served by Systems
>MCL
22.78%
4.73%
3.75%
0.51%
0.45%
0.38%
0.36%
0.13%
0.05%
0.04%
0.04%
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%
    Too few data to evaluate dioxin.
    "% > MCL" indicates the proportion of population served with any analytical results exceeding the concentration value of the MCL; it does not necessarily indicate an MCL violation. An MCL
    violation occurs when the MCL is exceeded by the average results from four quarterly samples or confirmation samples as required by the primacy State.

-------
Occurrence Estimation Methodology and Findings
Appendix A. Stage 1 Analytical Findings
Six-Year Review
    Table A.5.a.  Summary of Occurrence of VOC Regulated Contaminants in Surface Water Systems from the
    Initial Eight Cross-Section States - Based on Systems
Volatile Organic Chemicals
(MCL in mg/L)
Dichloromethane (0.005)
Tetrachloroethylene (0.005)
Trichloroethylene (0.005)
Vinyl chloride (0.002)
1,2-Dichloroethane (0.005)
1,2-Dichloropropane (0.005)
Benzene (0.005)
1,1-Dichloroethylene (0.007)
Carbon Tetrachloride (0.005)
Chlorobenzene (0.1)
cis-l,2-Dichloroethylene (0.07)
Ethyl benzene (0.7)
o-Dichlorobenzene (0.6)
1,4-Dichlorobenzene (0.075)
Styrene (0.1)
Toluene (1.0)
trans-l,2-Dichloroethylene (0.1)
1,1,1-Trichloroethane (0.2)
1,1,2-Trichloroethane (0.005)
1,2,4-Trichlorobenzene (0.07)
Xylenes (10.0)
Surface Water Systems
Number of
Analyses in
Cross-Section
9,598
12,270
12,701
10,630
10,581
9,783
10,414
11,615
10,434
6,789
9,829
9,860
6,682
6,706
9,552
9,847
8,184
10,756
9,884
8,719
9,724
Number of
Systems in
Cross-Section
633
690
704
699
702
684
698
702
700
529
688
684
529
490
683
685
603
700
685
628
680
% Systems
>MRL
24.33%
8.70%
7.81%
3.00%
3.28%
3.07%
4.15%
3.42%
8.43%
8.13%
3.78%
6.43%
3.21%
5.71%
3.22%
10.80%
2.49%
8.14%
5.69%
2.87%
11.91%
% Systems
> 0.5 MCL
8.85%
2.90%
2.13%
0.29%
0.28%
0.29%
0.57%
0.43%
0.57%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.44%
0.00%
0.00%
% Systems
>MCL
3.00%
1.74%
0.71%
0.29%
0.28%
0.15%
0.14%
0.14%
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%
    "% > MCL" indicates the proportion of systems with any analytical results exceeding the concentration value of the MCL; it does not necessarily indicate an MCL violation. An MCL violation occurs
    when the MCL is exceeded by the average results from four quarterly samples or confirmation samples as required by the primacy State.

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Occurrence Estimation Methodology and Findings
Appendix A. Stage 1 Analytical Findings
Six-Year Review
    Table A.5.b.  Summary of Occurrence of VOC Regulated Contaminants in Ground Water Systems from
    the Initial Eight Cross-Section States - Based on Systems
Volatile Organic Chemicals
(MCL in mg/L)
Tetrachloroethylene (0.005)
Trichloroethylene (0.005)
Dichloromethane (0.005)
Carbon Tetrachloride (0.005)
1,1-Dichloroethylene (0.007)
Benzene (0.005)
1,2-Dichloroethane (0.005)
1,2-Dichloropropane (0.005)
Vinyl chloride (0.002)
1,1,2-Trichloroethane (0.005)
cis-l,2-Dichloroethylene (0.07)
Toluene (1.0)
1,1,1-Trichloroethane (0.2)
trans-l,2-Dichloroethylene (0.1)
Xylenes (10.0)
Ethyl benzene (0.7)
Chlorobenzene (0.1)
o-Dichlorobenzene (0.6)
1,4-Dichlorobenzene (0.075)
Styrene (0.1)
1,2,4-Trichlorobenzene (0.07)
Ground Water Systems
Number of
Analyses in
Cross-Section
129,348
133,026
105,825
116,057
115,205
111,554
113,116
105,751
110,603
109,026
102,666
108,967
113,868
103,547
107,591
109,027
52,259
51,508
49,505
96,171
90,603
Number of
Systems in
Cross-Section
11,751
12,402
10,965
12,402
12,403
12,383
12,411
10,476
12,392
11,708
9,361
11,703
12,405
11,358
11,631
11,698
6,318
6,299
6,192
7,994
7,374
% Systems
>MRL
4.46%
3.37%
11.00%
1.69%
1.64%
1.19%
1.42%
0.98%
0.50%
0.73%
1.94%
3.61%
3.39%
0.70%
3.97%
2.10%
1.00%
1.19%
1.97%
1.20%
0.91%
% Systems
> 0.5 MCL
1.86%
1.47%
1.74%
0.39%
0.40%
0.38%
0.33%
0.26%
0.15%
0.13%
0.10%
0.02%
0.02%
0.02%
0.01%
0.01%
0.00%
0.00%
0.02%
0.00%
0.00%
% Systems
>MCL
1.20%
0.96%
0.61%
0.25%
0.25%
0.23%
0.15%
0.12%
0.09%
0.07%
0.03%
0.02%
0.02%
0.01%
0.01%
0.01%
0.00%
0.00%
0.00%
0.00%
0.00%
    "% > MCL" indicates the proportion of systems with any analytical results exceeding the concentration value of the MCL; it does not necessarily indicate an MCL violation. An MCL violation occurs
    when the MCL is exceeded by the average results from four quarterly samples or confirmation samples as required by the primacy States.

-------
Occurrence Estimation Methodology and Findings
Appendix A. Stage 1 Analytical Findings
Six-Year Review
 Table A.6.a.  Summary of Occurrence of VOC Regulated Contaminants in Surface Water Systems from the Initial
 Eight Cross-Section States - Based on Population Served
Volatile Organic Chemicals
(MCL in mg/L)
Vinyl chloride (0.002)
1,2-Dichloroethane (0.005)
Tetrachloroethylene (0.005)
Dichloromethane (0.005)
Trichloroethylene (0.005)
1,2-Dichloropropane (0.005)
1,1-Dichloroethylene (0.007)
Benzene (0.005)
1,2,4-Trichlorobenzene (0.07)
cis-l,2-Dichloroethylene (0.07)
Xylenes (10.0)
o-Dichlorobenzene (0.6)
1,4-Dichlorobenzene (0.075)
trans- 1 ,2-Dichloroethylene (0.1)
1,1,1-Trichloroethane (0.2)
Carbon Tetrachloride (0.005)
1,1,2-Trichloroethane (0.005)
Chlorobenzene (0.1)
Toluene (1.0)
Ethyl benzene (0.7)
Styrene (0.1)
Surface Water Systems
Number of
Analyses
10,495
10,446
12,136
9,464
12,566
9,649
11,480
10,279
8,595
9,696
9,590
6,605
6,629
8,127
10,621
10,299
9,749
6,712
9,712
9,725
9,428
Number of
Systems
676
679
667
610
681
661
679
675
605
665
657
523
484
586
677
677
662
523
662
661
660
Total Population
Served by Systems
39,822,670
40,104,511
40,120,168
39,735,767
40,163,388
39,780,006
39,977,500
39,815,370
39,444,625
39,887,447
39,311,533
17,803,174
17,526,833
37,314,132
39,877,321
39,973,520
39,780,122
17,803,690
39,951,706
39,772,606
39,772,706
% Population
Served by Systems
>MRL
6.14%
5.75%
29.01%
49.66%
31.78%
2.89%
4.60%
2.41%
2.51%
5.95%
20.07%
5.06%
6.30%
2.01%
11.62%
5.66%
4.76%
9.77%
10.97%
3.08%
2.34%
% Population
Served by Systems
> 1/2 MCL
3.44%
3.25%
4.91%
20.66%
22.34%
0.20%
0.35%
0.72%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.03%
0.21%
0.00%
0.00%
0.00%
0.00%
% Population
Served by Systems
>MCL
3.44%
3.25%
3.18%
1.92%
1.32%
0.17%
0.17%
0.01%
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%
"% > MCL" indicates the proportion of population served with any analytical results exceeding the concentration value of the MCL; it does not necessarily indicate an MCL violation. An MCL violation occurs when the
MCL is exceeded by the average results from four quarterly samples of confirmation samples as required by the primacy States.

-------
Occurrence Estimation Methodology and Findings
Appendix A. Stage 1 Analytical Findings
Six-Year Review
 Table A.6.b.  Summary of Occurrence of VOC Regulated Contaminants in Ground Water Systems from the Initial
 Eight Cross-Section States - Based on Population Served
Volatile Organic Chemicals
(MCL in mg/L)
Tetrachloroethylene (0.005)
Trichloroethylene (0.005)
Dichloromethane (0.005)
1,1-Dichloroethylene (0.007)
Carbon Tetrachloride (0.005)
1,2-Dichloroethane (0.005)
1,1,2-Trichloroethane (0.005)
1,2-Dichloropropane (0.005)
Benzene (0.005)
Vinyl chloride (0.002)
1,1,1-Trichloroethane (0.2)
cis-l,2-Dichloroethylene (0.07)
Xylenes (10.0)
Ethyl benzene (0.7)
Toluene (1.0)
1,2,4-Trichlorobenzene (0.07)
o-Dichlorobenzene (0.6)
1,4-Dichlorobenzene (0.075)
trans- 1 ,2-Dichloroethylene (0.1)
Chlorobenzene (0.1)
Styrene (0.1)
Ground Water Systems
Number of
Analyses
116,766
120,512
95,239
104,657
105,019
102,497
98,442
96,181
100,888
100,074
103,165
94,709
97,254
98,393
98,338
83,593
50,969
48,966
93,536
51,720
89,276
Number of
Systems
9,423
10,078
8,639
10,077
10,074
10,081
9,387
8,833
10,066
10,073
10,076
8,372
9,323
9,385
9,387
7,020
6,244
6,137
9,089
6,263
7,724
Total Population
Served by Systems
43,883,073
44,091,721
43,562,902
44,089,203
44,089,695
44,095,527
43,847,546
43,677,151
44,086,485
44,087,462
42,701,428
43,551,622
43,374,987
43,847,474
43,852,683
43,063,532
11,560,698
11,466,073
42,059,111
11,572,759
43,333,336
% Population
Served by Systems
>MRL
46.68%
45.88%
37.53%
31.79%
24.11%
23.37%
20.41%
23.92%
23.61%
1.73%
36.26%
32.59%
28.35%
24.55%
29.60%
1.79%
4.99%
6.00%
22.84%
3.72%
1.86%
% Population
Served by Systems
> 1/2 MCL
37.25%
33.36%
23.34%
21.98%
19.62%
19.33%
18.19%
4.67%
1.78%
0.85%
0.11%
0.42%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
% Population
Served by Systems
>MCL
32.14%
30.49%
20.51%
19.94%
18.40%
17.94%
17.54%
1.77%
1.03%
0.82%
0.11%
0.11%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
"% > MCL" indicates the proportion of population served with any analytical results exceeding the concentration value of the MCL; it does not necessarily indicate an MCL violation. An MCL violation occurs when the
MCL is exceeded by the average results from four quarterly samples of confirmation samples as required by the primacy States.

-------
Appendix Bl. Detailed Description of Bayesian Hierarchical Model

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Occurrence Estimation Methodology and Findings                                       Six-Year Review
Appendix Bl. Detailed Description of Bayesian Based Model


    The Hierarchical Modeling Approach for Estimating National Distributions of
                Contaminant Concentrations in Public Water Systems
I.  INTRODUCTION

       The goal of this analysis is to estimate contaminant occurrence in public water systems (PWSs)
nationally by estimating system mean contaminant concentrations, as well as the probability that those
estimated system means will exceed specified health thresholds. However, it is difficult to measure
contaminant occurrence in drinking water because concentrations are generally quite low. As a result,
concentration values below the Minimum Reporting Level (MRL) are common. (The Minimum
Reporting Level is the lowest level that can be reliably achieved within specified limits of precision and
accuracy under routine laboratory operating conditions.) When a concentration is below the MRL (a
"non-detection"), the exact concentration value is only known to be less than that specified MRL.  When
the underlying probability distribution of the contaminant concentration is of interest, a non-detection
contributes less information than an exactly measured value (a "detection") does. Nevertheless, it has
information that cannot be disregarded when estimating the probabilistic distribution parameters.

       Historically, many different methods have been used for estimating distribution parameters when
non-detection data are present. The simplest method is to replace all non-detection values by a specific
number (e.g., zero, !/2 the MRL, or the MRL). However, this substitution method is unreliable, since it
likely underestimates occurrence (when zero is used) and likely overestimates occurrence (when !/2 the
MRL or the MRL is used).

       Alternatively, Gilliom and Helsel (1986) and Helsel and Gilliom (1986) proposed a regression on
ordered statistics (ROS) method for estimating the mean and variance of a log-normal distribution.  The
ROS method is based on the fact that a  straight line is formed when plotting the quantiles of a normally
distributed random variable (with mean m and variance s2) against the same quantiles of a standard
normal random variate.  The intercept of the line is m and the slope of the line is s. ROS  was the method
used by the Environmental Protection Agency (EPA) to estimate PWS mean concentrations of arsenic in
drinking water (U.S. EPA 2000a).

       Another frequently used method for estimating distribution parameters of data containing non-
detection values is the maximum likelihood estimator (MLE). As in the conventional MLE, the
likelihood of a detection (a value above the MRL) is the  corresponding density value.  For a non-
detection, the likelihood is evaluated as the probability of observing a value that is less than the MRL, or
the cumulative density of the MRL. For a given family of probability distributions, both the probability
density and the cumulative density can be (in principle) explicitly expressed as a function of the
probability distribution parameters. By assuming observations are independent random samples from the
same distribution (or Independently, Identically Distributed, i.i.d.), the likelihood function is the product
of the likelihoods  of all observations. The MLE is the estimator that maximizes the likelihood function.
However, the presence of non-detections makes computation of the MLE more difficult.  A commonly
used computational method is the Expectation-Maximization (EM) algorithm (Tanner  1991). The MLE
method was used in EPA's radon analysis to generate system mean concentration values  (U.S. EPA
2000b).

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Occurrence Estimation Methodology and Findings                                        Six-Year Review
Appendix Bl.  Detailed Description of Bayesian Based Model


        Because both the ROS and MLE methods assume observations are i.i.d., when used for
estimating the national distribution, it is necessary to apply both methods separately for each PWS, since
it is a reasonable assumption that the contaminant concentration distribution varies from system to
system. Those separately estimated system means are then pooled to form the national distribution of
system means. Separately estimating distribution parameters for each PWS may lead to  a biased estimate
of the national distribution of system means, because (1) uncertainty of the estimated system means varies
from system to system due to differences in  sample size and other factors; systems with a large sample
size will have much less uncertainty than systems with a small sample  size and (2) systems with a large
number of non-detection values may be excluded since their distribution parameters may not be
adequately estimated, which will result in an overestimate of the contaminant mean concentration.  In
addition, because the national distribution of system means is the primary target, it is less important
whether the distribution parameters for each system can be estimated or not.

        Drinking water contaminant occurrence data exhibit a hierarchical structure.  In  other words, it is
possible to imagine that there is a "super" probability distribution that governs the mean concentrations,
as well as the variance, of PWSs in the United States. These means and variances determine the
magnitude and spread of contaminant concentrations observed from each system. This national
distribution is on the top, which generates a  series of system distributions of concentration values. Thus,
the data can be seen as having a two level structure: the top level is the national distribution, and the
bottom level is the collection of system distributions. When analyzing hierarchically structured data, a
hierarchical modeling approach is preferred  (Gelman et al. 1995).  This appendix presents  a hierarchical
model for estimating the national distribution of system mean contaminant concentrations. The model is
inherently Bayesian because (1) the mean concentration of an unknown system is treated as a random
variable and (2) (non-informative) prior distributions for all parameters are used in the numerical
procedure.

II. METHOD

        Bayesian methods are currently experiencing an increasing popularity in the sciences as a means
of probabilistic inference (Malakoff 1999). Among their advantages is the ability to incorporate prior
information, the  ease of incorporation into a formal decision analytic context, the explicit handling of
uncertainty, and the straightforward ability to assimilate new information in contexts such  as adaptive
management. In some problems, a Bayesian approach has been shown to lead to very different
conclusions than a classical approach (Ludwig 1996; Al-Khatib et al. 2001). Introduction  to Bayesian
statistics and decision theory can be found in Box and Tiao (1973) and Bernardo and Smith (1994).

        Under the Bayesian paradigm, random variables are inferred by using probability distributions.
Since distributions have unknown parameters, it is necessary to infer the distributions of parameters at
many levels.  If linkages among the data at various levels in the hierarchical structure can be assumed,
then information at the various levels can be used to support the parameter estimation at higher levels, or
within the same level. Such hierarchical thinking helps in understanding multiple parameter problems,
and also plays an important role in developing computational strategies.

        Perhaps  even more important in practice is that non-hierarchical models are usually inappropriate
for hierarchical data: with few parameters, they usually cannot fit large data sets accurately, whereas with
many parameters, they tend to "overfit" such data in the sense of producing models that  fit the existing
data well but lead to inferior predictions for  new data. In contrast, hierarchical models can have enough
parameters to fit the data well, while using a population distribution to structure some dependence into

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Occurrence Estimation Methodology and Findings                                        Six-Year Review
Appendix Bl.  Detailed Description of Bayesian Based Model


parameters, thereby avoiding problems of overfitting. Details of the Bayesian-based hierarchical
modeling approach can be found in German, et al. (1995) and Congdon (2001).

        The model is based on the assumption that each contaminant concentration distribution at the
system level can be approximated by a log-normal distribution.  The national distribution is then
estimated as a mixture of system distributions. The model is summarized in Equation 1:
                                                                                  (i)
where yijk is the k*1 observed concentration value (in logarithm) from system /', in strata/,  Hy is the mean
and T] is the precision (or the inverse of variance, I/a2).  The notation I(,S) indicates the corresponding
concentration value is less than S (or non-detection). For a detection, S is set to be infinity. The mean Hy
is modeled as the sum of three normal random variables, representing the grand mean (//), the strata's
adjustment (a0, and the system adjustment (by).  The prior distributions //, dp and by are normal
distributions with means equal to zero and unknown variances.  By selecting a widely dispersed prior
distribution for the precision parameters (Gamma (0.01, 0.01), the prior distributions used here are
essentially flat and non-informative.

        The objective of the model is to estimate the posterior distributions of//, ap bip and i^. It should
be noted an a priori constant precision T\ is used. This constant variance assumption is necessary because
many systems in the data have only one observation. However, this prior constant variance assumption
will not result in a constant posterior variance for all systems. This is because the mean //^ is modeled as
a random variable. In another words, the posterior distribution of yijk is estimated by:
where 7i(^Y) and TJ^T^Y) are the posterior distributions of the system mean and precision, respectively.
Unless two systems have exactly the same posterior distribution of the mean, two systems will have
different posterior variances. This setting will also result in the separation of between and within system
variances. In addition, by modeling the mean as another normal random variable, the resulting log-
concentration distribution is more robust against unusually large concentration values.

        Intuitively, a two-level statistical model is built, reflecting all the sources of variability and
uncertainty. The lower level features the observed concentration values (both detections and non-
detections).  Those observed log concentrations are treated as though they come from a normal
distribution. When the concentration value is below the MRL, its value is uncertain and is imputed based
on the fact that the value is known to be below  a given value (i.e., below the MRL). The upper level
represents those (for the most part, completely uncertain) features of the model that govern groups of or

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Occurrence Estimation Methodology and Findings                                       Six-Year Review
Appendix Bl. Detailed Description of Bayesian Based Model


perhaps all of the observations, about which information may be learned by pooling the evidence from
many observations at thousands of PWSs. The upper level of the model uses widely-dispersed normal
distributions to model //, dp and by, and widely-dispersed gamma distribution to model il to reflect broad
uncertainty about them.

        A Markov chain Monte Carlo simulation (MCMC) method (Gilks, et al. 1996) is used for
simultaneously estimating the distribution parameters by sampling the parameters from their joint
posterior distribution. The MCMC is implemented using a freely available software WinBUGS
(Spiegelhalter, et al. 1996).  The national distribution, as well as the probabilities of exceeding certain
thresholds, is estimated in the same Monte Carlo simulation.  The MCMC method allows the  sampling of
Hy and T] from their joint posterior distribution.

        Since the PWSs included in the  16-State cross-section data set is a representative sample of PWSs
nationally, the system means estimated for these systems are considered to be a sample from the national
system mean distribution. (Since it is assumed that the concentration values follow a log-normal
distribution at the system level, the arithmetic system mean, mip is  calculated from the generated log-
normal mean /^ and variance Tl5 (i.e., mtj = expf/^ + 0.5/Tj]).)  For each set of system mean
concentrations, an empirical cumulative distribution function (CDF) of the national distribution, as well
as probabilities of system mean concentrations exceeding certain thresholds, can be estimated. By
repeated sampling of the system means, there exist many empirical CDFs of the national distribution and
many estimates of the exceedance probabilities. These empirical CDFs are used to summarize the
national distribution, as well as the uncertainty about the distribution.  Note that the estimated means and
variances are based on log-transformed concentration values. Thus, it is necessary to obtain the system
means in the original metric.

        Comparing the samples of system means to a threshold value, many samples of the proportion of
systems with a mean concentration value exceeding the threshold are obtained. (These proportions are
samples of the probability of a system mean exceeding the threshold.) If the MCMC process  produces
500 pairs of random samples of nl}and Tb there exist 500 empirical CDFs of the national distribution, 500
random samples  of the arithmetic system mean, and hence, 500 exceedence  probabilities for each
threshold. From these 500 probabilities, the mean, median, and the 2.5th and 97.5th percentiles (or the
95% credible interval) can be calculated to summarize the uncertainty on the quantity.

        It is worthwhile to discuss the method of presenting uncertainty used by a Bayesian.  The
Bayesian method treats an unknown parameter as a random variable. The uncertainty of the parameter is
reflected in the estimated posterior distribution. This posterior distribution is a combination of
uncertainty about the data, the prior knowledge, and maybe the model. A 95% credible interval is the
interval between the 2.5th and 97.5th percentiles of the posterior distribution. This interval may or may not
include the mean, depending on the skewness of the posterior distribution. In other words, the credible
interval is not an interval  of the mean (such as the frequentist confidence interval). For some  extremely
skewed posterior distributions, it is quite possible that the Monte Carlo estimated 2.5th and 97.5th
percentiles are the same.  For example, the several estimates of the probability of system mean exceeding
a given threshold have a lower 90% credible bound of zero, as well as an upper 90% credible  bound of
zero.  This is because the  posterior distribution of the probability is evaluated by Monte Carlo samples
and at least 95% of the samples are equal to zero.  Under such a situation, one should conclude that the
chance is less than or equal to 5% to have an exceedence probability that is larger than zero.

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Occurrence Estimation Methodology and Findings                                       Six-Year Review
Appendix Bl. Detailed Description of Bayesian Based Model


III. EVALUATION OF THE MODEL

       Various tests were performed to evaluate the proposed model.  A simulation study, conducted
with six simulated data sets, was designed to explore the impact of the log-normal, as well as the constant
variance, assumption made on the system level.  In addition, the Bayesian-based hierarchical modeling
approach was compared to the ROS plotting position method.

       The six synthetic (or simulated) data sets were divided into three groups.  The first group
emphasized the comparison of the Bayesian and ROS methods.  The second group of the simulated data
sets were generated to evaluate the constant variance assumption.  Finally, the third group of simulated
data sets tested the impact of a log-normal assumption at the system level on the national distribution of
system means.

       The ROS method was compared to the Bayesian-based model by applying both methods to a
series of synthetic data sets. The two synthetic data sets in the first group were constructed to represent
both a high and low information case. The high information case was modeled after the fluoride data set,
where approximately 80% of the total observations were detections. The low information case was
modeled after the thallium data set, where only about 2% of the total observations were detections.

       The fluoride-like and thallium-like data  sets were generated, each containing the same number of
PWSs and the  same number of observations per  PWS, as contained in the actual 16-State cross-section
data set for fluoride and thallium, respectively. A number of system means were generated from a log-
normal distribution.  These means, along with a  constant variance, were used to generate a number of log-
concentration values for each system. These generated log-concentration values were censored (i.e.,
considered non-detections) at a fixed value: log(O.ll) for the fluoride-like data and log(O.OOl) for the
thallium-like data. This operation resulted in about 25% of the values below MRL of 0.11 for fluoride,
and almost 90% of the values below the MRL of 0.001 for thallium. The system means of the simulated
high information data sets were generated to approximately followed a log-normal distribution, 7V(-1.15,
1.33), while the system means of the simulated low information data sets were generated to approximately
followed a log-normal distribution, 7V(-10, 2.4).

       The second group of the simulated data  sets were generated to evaluate the constant variance
assumption. It is worth mentioning that although a constant variance was used to specify the model, the
constant variance is the Bayesian prior model specification. However, the posterior variance of each
system is not necessarily the same for all systems.  However, two simulated data sets were produced to
evaluate the constant variance assumption. Again, one data set was modeled after the 16-State fluoride
data and the other modeled after the 16-State thallium data.  The system means were generated in the
same way as in the first group and the system variance were generated from an inverse gamma
distribution.

       The third group of simulated data sets tested the impact of a log-normal assumption at the system
level on the national distribution of system means. Instead of using a normal distribution to generate log-
concentration values for each system, two other  distributions were used: (1) a Weibull distribution and
(2) a 50-50 mixture of log-normal and Weibull distributions. The Weibull distribution was chosen
because it is a feasible probability distribution for water quality data and it has the largest tail area
difference from the log-normal distribution (Ott  1995). Both data sets were modeled after the 16-State
fluoride data. Again, a log-normal distribution was used to  generate the mean and an inverse gamma
distribution was used to generate the variance for each system. The mean and variance were used to

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Occurrence Estimation Methodology and Findings
Appendix Bl. Detailed Description of Bayesian Based Model
Six-Year Review
calculate the scale parameter of the Weibull distribution. The shape parameter was fixed at 2, which
resulted in a skewed distribution.

       Tables 1-3 summarizes the six synthetic data sets. Table 1 presents general summary statistics
describing each of the six synthetic data sets. The simulated system means and variances for each data set
are described Tables 2 and 3, respectively.
Table 1. Summary Statistics of the Six Synthetic Data Sets
High/Low
Information
High
Low
High
Low
High
High
Distribution
Assumption
Constant
Variance
Constant
Variance
Variable
Variance
Variable
Variance
Weibull
Mixed
Distribution
Minimum
0.11
0.001
0.11
0.001
0.11
0.11
25th
Percentile
0.2389
0.00163
0.2317
0.001618
0.2422
0.2502
Median
0.4668
0.002975
0.4339
0.002989
0.4659
0.4892
Mean
0.9881
0.01554
0.8627
0.02073
0.9149
0.9744
75th
Percentile
1.019
0.007449
0.9282
0.007388
0.9735
1.041
Maximum
66.98
6.179
88.45
35.92
47.79
69.87
%
Non-
Detections
20.3%
86.4%
20.0%
87.6%
19.2%
19.0%

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Occurrence Estimation Methodology and Findings
Appendix Bl. Detailed Description of Bayesian Based Model
Six-Year Review
Table 2. Summary Statistics of Simulated System Means
High/Low
Information
High
Low
High
Low
High
High
Distribution
Assumption
Constant
Variance
Constant
Variance
Variable
Variance
Variable
Variance
Weibull
Mixed
Distribution
Minimum
-5.698
-20.12
-5.323
-19.26
0.00158
0.003666
1st Quarter
-1.94
-11.6
-1.941
-11.59
0.184
0.185
Median
-1.156
-9.981
-1.17
-9.984
0.4022
0.4026
Mean
-1.159
-9.993
-1.152
-9.994
0.7867
0.7896
3rd Quarter
-0.3816
-8.375
-0.3642
-8.378
0.8839
0.8829
Maximum
2.959
0.2593
3.356
-1.279
31.72
34.38
Table 3. Summary Statistics of Simulated System Variances
High/Low
Information
High1
Low1
High
Low
High
High
Distribution
Assumption
Constant
Variance
Constant
Variance
Variable
Variance
Variable
Variance
Weibull
Mixed
Distribution
Minimum


0.04
0.32
0.001
0.002
1st Quarter


0.16
1.33
0.10
0.10
Median
0.49
2.25
0.21
1.86
0.21
0.21
Mean


0.24
2.20
0.41
0.41
3rd Quarter


0.28
2.66
0.46
0.46
Maximum


1.91
20.81
16.58
17.97
1. These two data sets have a constant variance. Therefore, summary statistics, other than the median, could not be generated.
        Simulation results are presented in Figures 1-6.  The national distribution estimated by the
Bayesian-based hierarchical model was almost identical to the true distribution (Figure 1), while the ROS
plotting position method yielded a distribution with a slightly larger variance and smaller median.
Although the ROS plotting method yielded an estimate that was very close to the true CDF, the ROS
method is unable to quantify the uncertainty in the estimated CDF. When the log-normal distribution was
used at the system level, results similar to Figure 1 were obtained. (These results, however, are not

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 Occurrence Estimation Methodology and Findings
 Appendix Bl. Detailed Description of Bayesian Based Model
                                                                                    Six-Year Review
 shown.) A numerical summary of the simulated results is not presented since the graphical presentation
 clearly indicates that the Bayesian-based model tracks most closely to the true distribution. In addition,
 the assumptions of log-normality and constant variance made in the model do not appear to influence the
 results.
 Figure 1.  High Information-Constant Variance Synthetic Data Set
                                    Run 2.9: Fluoride,
    0.999
    0.990
>,
^

ll   °'95e
-g   0.900

CL
dj   0.750
>

-|   0.500

E
O
    0.2
      50
    0.100
-g   0.050
    0.01-0
    O.Otfr
             	 Bayes Mean
             	 Bayes Cl
                  Empirical CDF
                  Empirical Bounds
             	 True CDF
             	ROS
                       0.01
                                          I
                                         0.1
                                                                               \
                                                                              10
                                       Concentration (mg/L)

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Occurrence Estimation Methodology and Findings
Appendix Bl. Detailed Description of Bayesian Based Model
                                                                                  Six-Year Review
Figure 2. Low Information-Constant Variance Synthetic Data Set
                                        Run 9.9: Thallium,
    0.999


    0.996
CL
       0.906


       0.756
   -§  0.506

   E
   Q  0.256
   M—
   2  0.106

   -g  0.056

   CL
       0.01-6


       0.001
           L
                         Bayes Mean
                         Bayes Cl
                         Empirical CDF
                         Empirical Bounds
                         True CDF
                         ROS
               I

             1e-009
                     1e-008
                             I
                          1e-007
  I
1e-006
  1
1e-005
  T

0.0001
                                                               0.001
                                                                        0.01
 \
0.1
                                           Concentration (mg/L)

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Occurrence Estimation Methodology and Findings
Appendix Bl. Detailed Description of Bayesian Based Model
                                                                               Six-Year Review
Figure 3. High Information-Variable Variance Synthetic Data Set
                                       Run 2.95:  Fluoride,
   &
   o
   CL
   E
   =3
0.999


0.990


0.950
0.900


0.750


0.500


0.250
   .2  0.100
   •9  0.050
      o.o-ro
      o.ooi
           n
           0.001
                   	  Bayes Mean
                   	  Bayes Cl
                         Empirical CDF
                         Empirical Bounds
                   	  True CDF
                   	  ROS
                             0.01
                                               0.1
                                                                                   10
                                           Concentration (mg/L)
                                                 10

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Occurrence Estimation Methodology and Findings
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                                                                                  Six-Year Review
Figure 4. Low Information-Variable Variance Synthetic Data Set
                                       Run 9.95: Thallium,
      0.999


      0.990


   1  0-958
   -g  0.900

   CL
   a,  0.750


   -|  0.500

   E
   Q  0.250
   °  0.100


   CL
•g   0.050
      0.01-0
      O.OOt
                  	  Bayes Mean
                  	  Bayes Cl
                        Empirical CDF
                        Empirical Bounds
                  	  True CDF
                  	  ROS
                 I

               1e-009
  I

1e-008
                              I
                            1e-007
  I
1e-006
  1
1e-005
  r
0.0001
  I
0.001
                                                                        0.01
                                                                                 0.1
                                           Concentration (mg/L)
                                                 11

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Occurrence Estimation Methodology and Findings
Appendix Bl. Detailed Description of Bayesian Based Model
                                                                                   Six-Year Review
Figure 5. High Information-Weibull Distribution Synthetic Data Set
                                       Run 2.96:  Fluoride,
    0.999


    0.996
>,
±±

ll   °-958
-g   0.906

CL
Oj   0.756

^
-|   0.506

E
=3
O
M—
O


o
CL
      0.256


      0.106
      0.056


      0.01-6


      0.001
           1

          0.001
                        Bayes Mean
                        Bayes Cl
                        Empirical CDF
                        Empirical Bounds
                        True CDF
                        ROS
                            0.01
                                               0.1                 1

                                           Concentration (mg/L)
                                                                                   10
                                                 12

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Occurrence Estimation Methodology and Findings
Appendix Bl.  Detailed Description of Bayesian Based Model
                                                                            Six-Year Review
Figure 6.  High Information-Mixed Distribution Synthetic Data Set
                                     Run 2.99: Fluoride,
  *
  CL
0.999


0.990


0.950

0.900


0.750
  -§  0.500

  E
  Q  0.2501
  M—
  2  0.100

  -g  0.050

  CL
      0.01-0


      Q.QCrt
                             Bayes Mean
                             Bayes Cl
                             Empirical CDF
                             Empirical Bounds
                             True CDF
                             ROS
                 \

                0.001
                                0.01
                                           I
                                          0.1
                                                                                10
                                         Concentration (mg/L)
        The second evaluation of the proposed model involved a test of the assumption of log-normality.
This assumption was tested using the 16-State fluoride data set.  The log-normal distribution is commonly
used in analyzing environmental  data and one can argue its adequacy on both empirical and physical basis
(Ott 1995).  It is, however, an assumption that is rarely tested. A mixture of two normal distributions was
                                               13

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Occurrence Estimation Methodology and Findings                                       Six-Year Review
Appendix Bl.  Detailed Description of Bayesian Based Model


used at the system level to determine whether a better model can be found without using log-normal
distribution at the system level.  In other words, the first line of equation (1) was replaced by:
where 0 


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Occurrence Estimation Methodology and Findings
Appendix Bl.  Detailed Description of Bayesian Based Model
                                                                          Six-Year Review
Figure 7.  Mixture of Normal Distributions Model
    CO
    _Q
    O
    0>
.9999-

.999

 .99

 .95
 0.9

0.75-

 0.5 -

0.25-
    _CD

    1     0.1
    O
 05
          .01 -

         .001 •

         .0001'
^^—

	
	
	

Log-normal Mean
Log-normal Cl
Mixed Mean
Mixed Cl
0-line
0.5-line
1-line
Thresholds
                        <-18033 (of 93062)censored
                        0.001
                              0.01
0.1
10
                                          Concentration (mg/L)
        This graphical comparison is favorable since the four CDFs converge at higher concentration
values where non-detection values are less likely to occur. Since the substitutions occur at the lower end
of the distribution, the differences among the four CDFs, therefore, appear at the left tail of the
distribution. When examining the MRLs, it is important to note that the majority of the MRL values are
equal to 0.1 mg/L. This is reflected in the figure as the widest gap between the model estimated CDF and
the 1-line.  The second most occurring MRL value is 0.2 mg/L, where the 1-line diverted from the model
estimated CDF slightly.  As expected, the estimated CDF is bounded by the 0- and 1- lines, and is close to
the 0.5-line.

        Table 4 presents a comparison of selected percentiles of the estimated national distribution, based
on model prediction, to three empirical CDFs, based on the substitutions.  As expected, the differences
between the model predicted and the empirical percentiles are mainly in the lower half of the distribution.
                                                15

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Occurrence Estimation Methodology and Findings
Appendix Bl. Detailed Description of Bayesian Based Model
Six-Year Review
Table 4. Comparison of Selected Percentiles (mg/L) of Five Estimated National Distributions of
System Mean Fluoride Concentrations
Estimated
National
Distribution
Low1
Middle 2
High3
Mixed4
Model Prediction
5th
Percentile
0
0.05
0.10
0.03
0.05
10th
Percentile
0
0.05
0.10
0.05
0.07
25th
Percentile
0.08
0.10
0.13
0.13
0.13
50th
Percentile
0.21
0.23
0.24
0.30
0.27
75th
Percentile
0.59
0.60
0.60
0.74
0.60
90th
Percentile
1.10
1.10
1.10
1.51
1.11
95th
Percentile
1.68
1.68
1.68
2.34
1.57
1. The "low" estimated national distribution was calculated from system means where all non-detection values were substituted with zero.
2. The "middle" estimated national distribution was calculated from system means where all non-detection values were substituted with 1/2 the
modal MRL.
3. The "high" estimated national distribution was calculated from system means where all non-detection values were substituted with the modal
MRL.
4. The "mixed" estimated national distribution was calculated using a mixture of two normal distributions at the system level.
        In conclusion, both the simulated study and the mixture model indicated that the Bayesian-based
hierarchical model is appropriate for use in this study.  The simulated study showed that the prior
assumptions about the contaminant distribution do not have an undue influence on the posterior estimate
of the national distribution of system means. The mixture model study showed that using a log-normal
distribution at the system level is appropriate. When the log-normal assumption is not used, the estimated
national distribution has a slightly larger variance, which may result in an overestimate of the exceedance
probabilities.

IV.  DISCUSSION

        There are three advantages of using the hierarchical modeling approach in this study. First, the
log-normal assumption has much less of an impact on the final estimate of the national distribution. This
can be explained in two levels: (1) The national distribution is expressed as a mixture of many log-normal
distributions, and the resulting national distribution is not subject to the log-normality assumption. This
flexibility makes the model prediction more realistic; (2) At the system level, the log-normality is
conditional on the system mean, and the  system mean is modeled as a sum of two random variables.  As a
consequence, the log-normal assumption at the system level is also relaxed.

        The second advantage of the hierarchical approach is the relatively light computational burden.
This is because the hierarchical model produces the national distribution in one model run, while for the
ROS plotting position  method to be used properly, mean concentration distribution for each water supply
system has to be estimated separately.

        The third advantage of using the hierarchical modeling approach is its Bayesian feature that
allows combining information from all systems.  This is a desired feature because not all the water supply
systems have the same amount of data and some systems have all measurements below the MRL. As a
result, if the national distribution were estimated based on individual system distributions, as in the ROS
                                                 16

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Occurrence Estimation Methodology and Findings                                       Six-Year Review
Appendix Bl. Detailed Description of Bayesian Based Model


plotting position method, uncertainty in estimated individual system distributions would vary
significantly.

V. REFERENCES

Al-Khatib, S., R.M. Califf, V. Hasselblad, J.H. Alexander, D.C. McCrory, and J. Sugarman. 2001.
        Placebo-Controls in short-term clinical trials of hypertension. Science, 292:2013-2015.

Bernardo, J.M.  and A.P.M. Smith.  1994. Bayesian Theory. Wiley, West Sussex, England.

Box, G.E.P.  andG.C. Tiao.  1973. Bayesian Inference in Statistical Analysis. Addison-Wesley,
        Reading, MA.

Congdon, P., 2001. Bayesian Statistical Modelling.  Wiley, West Sussex, England.

Ferguson, T.S., 1983. Bayesian density estimation by mixtures of normal distributions, In: Recent
        Advances in Statistics: Papers in Honor of Herman Chernoffon His Sixtieth Birthday. Academic,
        New York, pp:287-302.

Gelman, A., J.B. Carlin, H.S. Stern, and D.B. Rubin. 1995. Bayesian Data Analysis.  Chapman & Hall,
        London.

Gilks, W.R., S. Richardson, and D.J. Spiegelhalter. 1996. Markov Chain Monte Carlo in Practice.
        Chapman & Hall, London.

Gilliom, R.J. and D.R. Helsel.  1986. Estimation of distribution parameters for censored trace level water
        quality data 1: estimation techniques. Water Resources Research. 22:135-146.

Helsel, D.R. and R.J. Gilliom.  1986.  Estimation of distribution parameters for censored trace level water
        quality data 2: verification and applications. Water Resources Research. 22:147-155.

Ludwig, D. 1996. Uncertainty and the assessment of extinction probabilities. Ecological Applications, 6:
        1067-1076.

Malakoff, D.M. 1999. Bayes offers "new" way to make sense of numbers. Science, 286: 1460-1464.

Ott, W.R. 1995. Environmental Statistics and Data Analysis. Lewis Publishers, Boca Raton.

Spiegelhalter, D.J., A. Thomas, N. Best, and W.R. Gilks. 1996. BUGS 0.5:  Bayesian inference Using
        Gibbs Sampling Manual.  Medical Research Council Biostatistics Unit, Institute of Public Health,
        Cambridge, UK.

Tanner, M.A.,  1991. Tools for Statistical Inference: Observed Data and Data Augmentation Methods.
        Springer-Verlag, New York.

United States Environmental Protection Agency (U.S. EPA).  2000a  Arsenic Occurrence in Public
        Drinking Water Supplies. EPA Office of Ground Water and Drinking Water.
                                               17

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Occurrence Estimation Methodology and Findings                                       Six-Year Review
Appendix Bl. Detailed Description of Bayesian Based Model


U.S. EPA. 2000b.  Methods, Occurrence, and Monitoring Document for Radon in Drinking Water.  EPA
       Office of Ground Water and Drinking Water.
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Appendix Bl. Detailed Description of Bayesian Based Model
                                           ADDENDUM

This addendum includes the WinBUGS program of the hierarchical model, as well as the S-Plus programs
used for creating input files and processing output from the hierarchical model. These programs are
included for review purpose only. They are not to be distributed without written consent from the
developer.
A. The WinBUGS Program of the Hierarchical Model

# Song S. Qian, 30 March 2001, revised 17 April 2001, 25 May 2001
# National distribution of regulated contaminants concentrations.
# A hierarchical modeling for normally distributed data containing detections and non-detections
#
#Data:
#     y - contaminant concentrations (sorted by system id)
#     n-length of y
#     cj - minimum reporting levels (if detection cj = exp(lOOO))
#     pwsid - public water system id
#     strata - M (10) level strata indicating source water type and population served
#     mstrata - strata id of each system
#           npwsid - incremental # of observations in water systems
#           cr - water quality criteria
#     K - length of cr
#
# Output to be monitored:
#      beta - slope of strata
#      prob - prob. of system mean exceeding cr (for each strata)
#      cdf - cdf of the system mean distribution
#      cbar - system means
#           cbarsys - mean of cbar
#      cbarstrata - mean concentrations in each strata
model{
        for (i in l:n){
                y[i] ~ dnorm(mu[i], tau)I(, cj[i]);
                mu[i] <- mul[pwsid[i]] + beta[strata[i]] ;
        }
        for(iinl:M){
                beta[i] ~ dnorm(0, prec[2]);
                cbarstrata[i] <-sum(cbarst[l:L, i])/nstrata[i];
        }
        for(linl:L){
                mul[l] ~ dnorm(0, prec[3]);
                cbar[l] <- exp(mul[l] +beta[mstrata[l]] + 0.5/tau);
                for(kinl:K){
                        exced[k, 1] <- step(cbar[l] -  cr[k]);
                }
                for(kinl:(CUTS[3] + l)){
                        cdfsys[l,k] <- step(cut[k] - cbar[l]);
                }
                for(jinl:M){
                                                   19

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Occurrence Estimation Methodology and Findings                                           Six-Year Review
Appendix Bl.  Detailed Description of Bayesian Based Model


                        cbarst[l, j] <- cbar[l] * equals(mstrata[l], j);


        for(kinl:K){
                for(iinl:L){
                        for(jinl:M){
                                 ex[k, i, j] <- exced[k, i] * equals(mstrata[i], j);


                for(jinl:M){
                        prob[j, k] <- sum(ex[k,l:L, j])/nstrata[j];

                probAll[k] <- sum(ex[k,,])/L;
                probG[k] <-(sum(ex[k,,l])+sum(ex[k,,2])+sum(ex[k,,3])+sum(ex[k,,4])+sum(ex[k,,5]))/nG;
                probS[k] <- (sum(ex[k,,6])+sum(ex[k,,7])+sum(ex[k,,8])+sum(ex[k,,9])+sum(ex[k,.

        for(iinl:3){
     prec[i] ~dgamma(0.01, 0.01);

        for(kinO:CUTS[3]){
                cut[k+l] <- pow(10, CUTS[1] + k*CUTS[2]);
                cdf[k+l] <- mean(cdfsys[l:L, k+1]); # mean of system means

        tau ~ dgamma(0.01, 0.01);
        sigma <- sqrt(l/tau);
  cbarsys <- mean(cbar[l:L]);
B. S-Plus Program for Creating the BUGS Input Data Files

# creating input data files for BUGS run
# Necessary inputs for function bugs.in:
#               y [i]: concentration data log-transformed.
#               source [i]:  type of source water 1 or 2
#               pops[i]: population served 1,..., 5
#               cj[i]: minimum reporting levels (log-transformed).
# Initial values:
#               y [i]: non-detection y values, use 0.5 *cj
#               e[i]: residuals: rep(0, n)
#               prec[l:4]: precision of ei, betal, beta2, mul
#               betal [j], beta2[k], rep(0,1), rep(0, K); I: # of source type, K: number of population category
#               mul[l]: rep(0, L); L: # of systems
#               tau: 0.1
to2 <- function(n)  { if(n<10) paste("0",as.character(n),sep="") else
                        as.character(n) }
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Appendix Bl.  Detailed Description of Bayesian Based Model


  #11IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
  TrTrTrTrf/"//77f/"fr7777f/"// UTrTi~ii~TrTrU 11 a~Trii~ II U~H~ii~TrTrTrTrTrU 11O~
# Input Data                              #
#####################################

pops.fun <- function(x){
        ifelse(x<=500,        1, x)->x
        ifelse(x>500  & x<=3300, 2, x)->x
        ifelse(x>3300  & x<=10000, 3, x)->x
        ifelse(x>10000 & x<=50000, 4, x)->x
        ifelse(x>50000,       5, x)->x
        return(x)
}
bugs.in <- function(run = 0, base = "c:\\users\\song\\cadmus\\occurrence",
        infile = Flu, contaminant = "Fluoride", cuts=c(-4, 2), ncuts=40,
        cr=c(4, 2,0.5, 0.1)){
                # This version sorts the data by system id (pwsid)
                # for calculating both strata means and systems means.
                # cuts: concentration range where CDF will be estimated
                # cr: critical values in original scale
        rundir <- paste(base, "runs", to2(run), sep="\\")
# input data
        oo <- order(infile$PWSID)
        infile <- infile [oo,]
        y <- log(infile$VALUE)
        n <- length(y)
        m <- sum(infile$DETECT==l)
        y[infile$DETECT==0] <- NA
        source <- as.numeric(ordered(infile$SOURCE)) # 1=G, 2=S
        I <- length(unique(source))
        pops <- pops.fun(infile$POPSERV)
        strata <- paste(source, pops, sep=".")
        M <-  length(unique(strata))
        strata <- as.numeric(ordered(strata))
        pwsid <- as.numeric(ordered(infile$PWSID))
        L <- length(unique(pwsid))
        npwsid <- as.vector(table(ordered(infile$PWSID)))
        mstrata <- strata[cumsum(npwsid)]
        nstrata <- as.vector(table(mstrata))
        if(sum(nstrata)!=L)stop("number of systems not equal")
        J <- length(nstrata)
        nG <- length(unique(pwsid[source==l]))
        nS <- length(unique(pwsid[source==2]))
        if(L!=(nG+nS))stop("S+G!=All")
        cj <- log(infile$VALUE)
        cj[infile$DETECT==l] <-1000
        bugs.dat <- list(n=n, M=M, K=length(cr), L=L, y=y, cj=cj, strata=strata, nstrata = nstrata, mstrata=mstrata,
                pwsid=pwsid, npwsid=c(0,cumsum(npwsid)), CUTS=c(cuts[l], (cuts[2]-cuts[l])/ncuts, ncuts),
                cr=cr, nS=nS, nG=nG)
# initial values
        yi <- 0.5*cj
        yi[infile$DETECT==l] <-NA
        mul <- rep(0, L)
        beta <- rep(0, M)

                                                    21

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Occurrence Estimation Methodology and Findings                                            Six-Year Review
Appendix Bl. Detailed Description of Bayesian Based Model


        tau<-0.01
        bugs.ini <- list(y=yi, mul=mul, beta=beta, tau=tau, prec=rep(0.01, 3), tt = rep(0, n))
# log file
        bugs.log <- list(run=run, contaminant=contaminant, rundir=rundir,
                                 CUTS=c(cuts[l], (cuts[2]-cuts[l])/ncuts, ncuts), cr=cr, K=length(cr),
nstrata=nstrata)
# BUGS files
 dput(bugs.dat, paste(rundir,"occdat.txt",sep="\\"));
 dput(bugs.ini, paste(rundir, "occini.txt", sep="\\"));
 dput(bugs.log, paste(rundir,"occlog.txt",sep="\\"));
invisible()
C. S-Plus Program for Processing the BUGS Output Data Files

# Routines for plotting CDF's and saving summary statistics.
#
# Gamma priors on s.d. scale
fsig <- function(s, a, t) { return(fs <- 2 * exp(-t/sA2) / sA(2*a+l)); }
pfsig <- function(a, t, lab=NA, hi=0) {
        md<-sqrt(t/(a + 0.5));
     if(a>.5) {mu <- sqrt(t)*exp(lgamma(a - 0.5)-lgamma(a)); }
     else { mu <- Inf; }
        if(a>l) { sd<- sqrt(t/(a-l)-muA2); }
     else { sd<-Inf; }
     hi <- max(hi,3*md);
        x<-seq(0, hi,, 101);
        y <- fsig(x, a, t);
     if(is.na(lab)) {lab <- paste("sd = l/sqrt(t) if t~Ga(",
       signif(a,2),",", signif(t,2),")",sep="") }
        plot(x, y, type = "1", axes=F, ylab="Prob Density", xlab=lab);
     axis(side=l);
     abline(v=0);
     if(a>.5) { abline(v=mu); }
     list(mode=md, mean=mu, sdev=sd);
}
if(!exists("ps.colors.hsb")) source("c:/users/song/cadmus/water/bugs/hsb.q");
# Finds (approximate) quantiles from cdf vector
p2q <- function(x, cdf, p, cut=c(-6,.25,40), con) {
         if(missing(con)||is.null(con))  con<- c(-5:2)
     if(missing(x))   x <- log(10)*seq(cut[l],,cut[2],l+cut[3]);
     if(missing(cdf)) cdf <- pnorm(x);
     if(missing(p))   p <- .01*c(5, 10,25,50,75,80,90,95);
     xj <- seq(nx <- length(x));
     np <- length(p<-c(p));
     q <- rep(NA,np);
     for(iin l:np) {
      j <- sum(cdf<=p[i]);
      if(G==l)IIG==nx))
       q[i]<-xO];
      else
                                                     22

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Occurrence Estimation Methodology and Findings                                           Six-Year Review
Appendix Bl. Detailed Description of Bayesian Based Model
                ] + (xU+l]-xU])*(p[i]-cdfD])/(cdf[]+l]-cdf[j]);

                 nc <- length(con)
                 pc <- rep(NA, nc)
                 for (i in l:nc){
                        j <- sum(x <= log(10)*con[i])
                                 pc[i] <-
                         else
                                 pc[i] <- cdfO] + (cdfU+l]-cdfU])*(con[i]-x[j])/(x[j+l]-x[j])
                 }
     myj <- round(l+(con-cut[l])/cut[2]);
     myj[myjcut[3]] <- l+cut[3];
     invisible(list(pl=p,    ql=signif(exp(q),3),
             p2=cdf[myj], q2=exp(x[myj]),
             p3=pc,    q3=signif(10A(con),3),
             y=cdf, x=exp(x)));
# Plot posterior cdf from BUGS run of EPA data:
 my.cdf <-
function(run = 0, base = "c:/users/song/cadmus/occurrence", ps = T, wmf = F, infile=Flu, ifname="Flu",
Con=NULL, unit="mg/L")
        rundir <- paste(base, "runs", to2(run), sep = "/")
        print(paste("Using directory ", rundir,".", sep = ""))
        psw <- dget(paste(rundir, "occlog.txt", sep = "/"))
        run <- psw$run
        cr <- psw$cr
        mycon <- pswScontaminant
        mytitle <- paste("Run", run,": ", mycon,",", sep = "")
        new.wmf <- function(n, name = "", dir = rundir){
                if (wmf) {
                         fname <- paste(dir,"/", name, to2(n), ".wmf', sep = "")
                         win.printer(file=fname, height=6, width=8, format="metafile")
                         print(paste("Writing Windows Meta file ", fname, sep = ""))
        new.ps <- function(n, name = "", dir = rundir)
        {
                if(ps) {
                        fname <- paste(dir,"/", name, to2(n), ".ps", sep = "")
                        postscript(fname, hori = T, colors = ps.colors.hsb[c("black", "white", "RoyalBluel",
"redl", "purple",
                                 "green4",  "yellow2"),  ])
                        print(paste("Writing postscript file ", fname, sep = ""))
        mswcoK-1;
        rawcol <- 6      # Green for empirical stuff
        ps.off <- function()
                if(ps) {

                                                    23

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Occurrence Estimation Methodology and Findings                                         Six-Year Review
Appendix Bl. Detailed Description of Bayesian Based Model


                        dev.offO


        wmf.off <- function()

                if(wmf) {
                        dev.offQ


        cdf <- read.table(paste(rundir, "cdf.txt", sep = "/"), head = T, sep = "\t")

        prob <- read.table(paste(rundir, "prob.txt", sep = "/"), head = T, sep = "\t")
        probG <- read.table(paste(randir, "probG.txt", sep = "/"), head = T, sep = "\t")
        probS <- read.table(paste(rundir, "probS.txt", sep = "/"), head = T, sep = "\t")
        probAll <- read.table(paste(rundir, "probAll.txt", sep = "/"), head = T, sep = "\t")
        cbarstrata <- read.table(paste(rundir, "cbarstrata.txt", sep = "/"), head = T, sep = "\t")
        cbarsys <- read.table(paste(rundir, "cbarsys.txt", sep = "/"), head = T, sep = "\t")
        cbarG<- sum(cbarstrata$mean[l: 5]*psw$nstrata[l: 5])/sum(psw$nstrata[l: 5])
        cbarS <- sum(cbarstrata$mean[6:10]*psw$nstrata[6:10])/sum(psw$nstrata[6:10])
        cbarG.sd<-sum(cbarstrata$sd[l: 5]*psw$nstrata[l: 5])/sum(psw$nstrata[l: 5])
        cbarS.sd<-sum(cbarstrata$sd[6:10]*psw$nstrata[6:10])/sum(psw$nstrata[6:10])
        K <- psw$K
        meaaprob <- rbind(matrix(prob$mean, ncol=K, nrow=10, byrow=T), probGSmean, probS$mean,
                                        probAll$mean)
        prob2.5 <- rbind(matrix(prob$X2.5, ncol=K, nrow=10, byrow=T), probG$X2.5, probS$X2.5,
probAll$X2.5)
        prob97.5 <- rbind(matrix(prob$X97.5, ncol=K, nrow=10, byrow=T), probG$X97.5, probS$X97.5,
                                        probAll$X97.5)
        prob5 <- rbind(matrix(prob$X5.0, ncol=K, nrow=10, byrow=T), probG$X5.0, probS$X5.0, probAll$X5.0)
        prob95 <- rbind(matrix(prob$X95.0, ncol=K, nrow=10, byrow=T), probG$X95.0, probS$X95.0,
                                        probAll$X95.0)

        out.table <- data.frame(mean.conc=c(cbarstrata$mean, cbarG, cbarS, cbarsys$mean),
                                                               sd.mean = c(cbarstrata$sd, cbarG.sd,
cbarS.sd, cbarsys$sd));
        nm <- names(out.table)
        for(iinl:K){
                out.table <- cbind(out.table, mean.prob[,i], prob2.5[, i], prob97.5[,i], prob5[, i], prob95[,i])
                nm<- c(nm, paste("prob.MCL", i, sep=""), paste("CI95L", i, sep="."), paste("CI95H", i, sep="."),
                paste("CI90L", i, sep="."), paste("CI90H", i, sep="."))
        names(out.table) <- nm
        ncut<-psw$CUTS[3] + l
        cdf.raw <- rep(0, ncut)
        temp <- p2q(cdf = cdf$mean, cut = psw$CUT, con=Con)
        new.ps(ran, "cdf', rundir)
        new.wmf(run, "cdf', randir)
        x <- log(10) * seq(psw$CUTS[l],  , psw$CUTS[2], psw$CUTS[3] + 1)
        xx <- log(10) * psw$CUTS[2] + x  # Trailing edge of step
        xat <- log(10) * seq(psw$CUTS[l], psw$CUTS[l] + psw$CUTS[2] * psw$CUTS[3])
        xlab <- as.character(signif(10Aseq(psw$CUTS[l], psw$CUTS[l] +psw$CUTS[2] * psw$CUTS[3]), 1))
                                                  24

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Occurrence Estimation Methodology and Findings                                            Six-Year Review
Appendix Bl. Detailed Description of Bayesian Based Model


        plot(x, cdf$mean, type = "n", axes = F, xlab = paste("Concentration (", unit, ")",sep=""), ylab =
"Cumulative Probability", ylim=c(-0.04, 1))
        disclaimer <-paste("Draft for Discussion:",  substring(date(), 4, 10),",", substring(date(), 20), sep = "")
        stamp(disclaimer)
        axis(side = 1, at = xat, labels = xlab)
        axis(side = 2, at = seq(0, 1,  , 11))
        lines(x, cdf$mean, col = mswcol, Iwd = 2)   # Mean
        lines(x, cdf$X5.0, col = mswcol, Ity = 2)    # 5%
        lines(x, cdf$X95.0, col = mswcol, Ity = 2)   # 95%
        old.ht <-1000000000
        xraw <- log(infile$VALUE)
        nraw <- length(xraw)
        xraw.clean <- xraw[infile$DETECT==l]

        segments(log(cr), rep(0, length(cr)), log(cr), rep(l, length(cr)), col=3)
        nok <- length(xraw.clean) # Eliminates O's, NA's and non-detections
        nzip <- sum(infile$DETECT==0)  # number of non-detections
        ntot <- nraw
        xtem <- jitter(xraw.clean)
        segments(xtem, rep(-0.02, nok), xtem, rep(0, nok), col = rawcol)
        text(xat[l] + 4, -0.04, paste("<-", nzip," (of", ntot,") non-detection", sep = ""), col = rawcol)
        title(mytitle)
        ps.offQ
        wmf.off()
        sink(paste(rundir, "/cdf', to2(run), ".out", sep = ""))
        print("Estimated Quantiles")
        pred.quant <- temp$ql
        print(rbind(temp$p 1 ,temp$ql));
        print("Quantiles of the Raw Data")
        print(quantile(infile$VALUE, prob=c(0.05, 0.1, 0.25, 0.5, 0.75, 0.8, 0.9, 0.95)))
        print(rbind(temp$q3 ,temp$p3));
        print(paste("Run: ", psw$run,", Contaminant: ", psw$contaminant, sep = ""))
        print(disclaimer)
        sink()
        invisible(out.table)
                                                    25

-------
                Appendix B2.  16-State Cross-Section Data

                            Used for Stage 2 Analysis

Table B.I.a.    Alachlor - Number of Records and Number of Systems in the 16-State Cross-Section by
              Source Water Type and Population-Served Size Category

Table B.2.a.    Antimony - Number of Records and Number of Systems in the 16-State Cross-Section by
              Source Water Type and Population-Served Size Category

Table B.S.a.    Atrazine - Number of Records and Number of Systems in the 16-State Cross-Section by
              Source Water Type and Population-Served Size Category

Table B.4.a.    Barium - Number of Records and Number of Systems in the 16-State Cross-Section by
              Source Water Type and Population-Served Size Category

Table B.S.a.    Benzene - Number of Records and Number of Systems in the 16-State Cross-Section by
              Source Water Type and Population-Served Size Category

Table B.6.a.    Benzo(a)pyrene - Number of Records and Number of Systems in the 16-State
              Cross-Section by Source Water Type and Population-Served Size Category

Table B.V.a.    Beryllium - Number of Records and Number of Systems in the 16-State Cross-Section by
              Source Water Type and Population-Served Size Category

Table B.S.a.    Bis(2-ethylhexyl)adipate - Number of Records and Number of Systems in the 16-State
              Cross-Section by Source Water Type and Population-Served Size Category

Table B.9.a.    Bis(2-ethylhexyl)phthalate - Number of Records and Number of Systems in the 16-State
              Cross-Section by Source Water Type and Population-Served Size Category

Table B. lO.a.   Cadmium - Number of Records and Number of Systems  in the 16-State Cross-Section by
              Source Water Type and Population-Served Size Category

Table B.ll.a.   Carbofuran - Number of Records and Number of Systems in the 16-State Cross-Section
              by Source Water Type and Population-Served Size Category

Table B. 12.a.   Carbon Tetrachloride - Number of Records and Number  of Systems in the 16-State
              Cross-Section by Source Water Type and Population-Served Size Category

Table B. 13.a.   Chlordane - Number of Records and Number of Systems in the 16-State Cross-Section by
              Source Water Type and Population-Served Size Category

Table B. 14.a.   Chromium - Number of Records and Number of Systems in the 16-State Cross-Section
              by Source Water Type and Population-Served Size Category

Table B. 15.a.   Cyanide - Number of Records and Number of Systems in the 16-State Cross-Section by
              Source Water Type and Population-Served Size Category

Table B. 16.a.   2,4-D - Number of Records and Number of Systems in the  16-State Cross-Section by
              Source Water Type and Population-Served Size Category

-------
Table B. IV.a.   Dalapon - Number of Records and Number of Systems in the 16-State Cross-Section by
              Source Water Type and Population-Served Size Category

Table B. 18.a.   l,2-Dibromo-3-chloropropane - Number of Records and Number of Systems in the
              16-State Cross-Section by Source Water Type and Population-Served Size Category

Table B.I 9.a.   1,4-Dichlorobenzene - Number of Records and Number of Systems in the 16-State
              Cross-Section by Source Water Type and Population-Served Size Category

Table B.20.a.   o-Dichlorobenzene  - Number of Records and Number of Systems in the 16-State
              Cross-Section by Source Water Type and Population-Served Size Category

Table B.21.a.   1,2-Dichloroethane -Number of Records and Number of Systems in the 16-State
              Cross-Section by Source Water Type and Population-Served Size Category

Table B.22.a.   1,1-Dichloroethylene - Number of Records and Number of Systems in the  16-State
              Cross-Section by Source Water Type and Population-Served Size Category

Table B.23.a.   cis-l,2-Dichloroethylene - Number of Records and Number of Systems in the 16-State
              Cross-Section by Source Water Type and Population-Served Size Category

Table B.24.a.   trans-1,2-Dichloroethylene - Number of Records and Number of Systems in the 16-State
              Cross-Section by Source Water Type and Population-Served Size Category

Table B.25.a.   Dichloromethane - Number of Records and Number of Systems in the 16-State
              Cross-Section by Source Water Type and Population-Served Size Category

Table B.26.a.   1,2-Dichloropropane - Number of Records and Number of Systems in the 16-State
              Cross-Section by Source Water Type and Population-Served Size Category

Table B.27.a.   Dinoseb - Number of Records and Number of Systems in the 16-State Cross-Section by
              Source Water Type and Population-Served Size Category

Table B.28.a.   Diquat - Number of Records and Number of Systems in the 16-State Cross-Section by
              Source Water Type and Population-Served Size Category

Table B.29.a.   Endothall - Number of Records and Number of Systems in the 16-State Cross-Section by
              Source Water Type and Population-Served Size Category

Table B.SO.a.   Endrin - Number of Records and Number of Systems in the 16-State Cross-Section by
              Source Water Type and Population-Served Size Category

Table B.Sl.a.   Ethylbenzene - Number of Records and Number of Systems in the 16-State Cross-Section
              by Source Water Type and Population-Served Size Category

Table B.32.a.   Ethylene Dibromide - Number of Records and Number of Systems in the 16-State
              Cross-Section by Source Water Type and Population-Served Size Category

Table B.33.a.   Fluoride - Number of Records and Number of Systems in the 16-State Cross-Section by
              Source Water Type and Population-Served Size Category

Table B.34.a.   Glyphosate - Number of Records and Number of Systems in the  16-State Cross-Section
              by Source Water Type and Population-Served Size Category

-------
Table B.35.a.   Heptachlor - Number of Records and Number of Systems in the 16-State Cross-Section
              by Source Water Type and Population-Served Size Category

Table B.36.a.   Heptachlor Epoxide - Number of Records and Number of Systems in the 16-State
              Cross-Section by Source Water Type and Population-Served Size Category

Table B.37.a.   Hexachlorobenzene - Number of Records and Number of Systems in the 16-State
              Cross-Section by Source Water Type and Population-Served Size Category

Table B. 3 8 .a.   Hexachlorocyclopentadiene - Number of Records and Number of Systems in the 16-State
              Cross-Section by Source Water Type and Population-Served Size Category

Table B.39.a.   Lindane - Number of Records and Number of Systems in the 16-State Cross-Section by
              Source Water Type and Population-Served Size Category

Table B.40.a.   Mercury - Number of Records and Number of Systems in the 16-State Cross-Section by
              Source Water Type and Population-Served Size Category

Table B.41.a.   Methoxychlor - Number of Records and Number of Systems in the 16-State
              Cross-Section by Source Water Type and Population-Served Size Category

Table B.42.a.   Monochlorobenzene - Number of Records and Number of Systems in the 16-State
              Cross-Section by Source Water Type and Population-Served Size Category

Table B.43.a.   Oxamyl - Number of Records and Number of Systems in the 16-State Cross-Section by
              Source Water Type and Population-Served Size Category

Table B.44.a.   PCBs - Number of Records and Number of Systems in the 16-State Cross-Section by
              Source Water Type and Population-Served Size Category

Table B.45.a.   Pentachlorophenol - Number of Records and Number of Systems in the 16-State
              Cross-Section by Source Water Type and Population-Served Size Category

Table B.46.a.   Picloram - Number of Records and Number of Systems in the  16-State Cross-Section by
              Source Water Type and Population-Served Size Category

Table B.47.a.   Selenium - Number of Records and Number of Systems in the 16-State Cross-Section by
              Source Water Type and Population-Served Size Category

Table B.48.a.   Simazine - Number of Records and Number of Systems in the 16-State Cross-Section by
              Source Water Type and Population-Served Size Category

Table B.49.a.   Styrene - Number of Records and Number of Systems in the 16-State Cross-Section by
              Source Water Type and Population-Served Size Category

Table B.SO.a.   Tetrachloroethylene - Number of Records and Number of Systems in the 16-State
              Cross-Section by Source Water Type and Population-Served Size Category

Table B.Sl.a.   Thallium - Number of Records and Number of Systems in the 16-State Cross-Section by
              Source Water Type and Population-Served Size Category

Table B.52.a.   Toluene - Number of Records and Number of Systems in the 16-State Cross-Section by
              Source Water Type and Population-Served Size Category

-------
Table B.53.a.   Toxaphene - Number of Records and Number of Systems in the 16-State Cross-Section
               by Source Water Type and Population-Served Size Category

Table B.54.a.   2,4,5-TP - Number of Records and Number of Systems in the 16-State Cross-Section by
               Source Water Type and Population-Served Size Category

Table B.55.a.   1,2,4-Trichlorobenzene - Number of Records and Number of Systems in the 16-State
               Cross-Section by Source Water Type and Population-Served Size Category

Table B.56.a.   1,1,1-Trichloroethane - Number of Records and Number of Systems in the 16-State
               Cross-Section by Source Water Type and Population-Served Size Category

Table B.57.a.   1,1,2-Trichloroethane - Number of Records and Number of Systems in the 16-State
               Cross-Section by Source Water Type and Population-Served Size Category

Table B. 5 8 .a.   Trichloroethylene - Number of Records and Number of Systems in the 16-State
               Cross-Section by Source Water Type and Population-Served Size Category

Table B.59.a.   Vinyl Chloride  - Number of Records and Number of Systems in the  16-State
               Cross-Section by Source Water Type and Population-Served Size Category

Table B.60.a.   Xylenes (Total) - Number of Records and Number of Systems in the 16-State
               Cross-Section by Source Water Type and Population-Served Size Category
Table B. 1 .b.    Alachlor - Summary of Analytical Detections in the 16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B.2.b.    Antimony - Summary of Analytical Detections in the  16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B.S.b.    Atrazine - Summary of Analytical Detections in the 16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B.4.b.    Barium - Summary of Analytical Detections in the 16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B.S.b.    Benzene - Summary of Analytical Detections in the 16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B.6.b.    Benzo(a)pyrene - Summary of Analytical Detections in the 16-State Cross-Section by
               Source Water Type and Population-Served Size Category

Table B.V.b.    Beryllium - Summary of Analytical Detections in the  16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B.S.b.    Bis(2-ethylhexyl)adipate - Summary of Analytical Detections in the 16-State
               Cross-Section by Source Water Type and Population-Served Size Category

Table B.9.b.    Bis(2-ethylhexyl)phthalate - Summary of Analytical Detections in the 16-State
               Cross-Section by Source Water Type and Population-Served Size Category

-------
Table B. lO.b.   Cadmium - Summary of Analytical Detections in the 16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B. 11 .b.   Carbofuran - Summary of Analytical Detections in the 16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B.12.b.   Carbon Tetrachloride - Summary of Analytical Detections in the  16-State Cross-Section
               by Source Water Type and Population-Served Size Category

Table B. 13.b.   Chlordane - Summary of Analytical Detections in the 16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B.14.b.   Chromium - Summary of Analytical Detections in the 16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B. 15.b.   Cyanide - Summary of Analytical Detections in the 16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B.16.b.   2,4-D - Summary of Analytical Detections in the 16-State Cross-Section by Source Water
               Type and Population-Served Size Category

Table B. 17.b.   Dalapon - Summary of Analytical Detections in the 16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B.lS.b.   l,2-Dibromo-3-chloropropane - Summary of Analytical Detections in the 16-State
               Cross-Section by Source Water Type and Population-Served Size Category

Table B. 19.b.   1,4-Dichlorobenzene - Summary of Analytical Detections in the 16-State Cross-Section
               by Source Water Type and Population-Served Size Category

Table B.20.b.   o-Dichlorobenzene - Summary of Analytical Detections in the 16-State Cross-Section by
               Source Water Type and  Population-Served Size Category

Table B.21.b.   1,2-Dichloroethane - Summary of Analytical Detections in the 16-State Cross-Section by
               Source Water Type and  Population-Served Size Category

Table B.22.b.   1,1-Dichloroethylene - Summary of Analytical Detections in the  16-State Cross-Section
               by Source Water Type and Population-Served Size Category

Table B.23.b.   cis-l,2-Dichloroethylene - Summary of Analytical Detections in the 16-State
               Cross-Section by Source Water Type and Population-Served Size Category

Table B.24.b.   trans-1,2-Dichloroethylene - Summary of Analytical Detections in the  16-State
               Cross-Section by Source Water Type and Population-Served Size Category

Table B.25.b.   Dichloromethane - Summary of Analytical Detections in the 16-State Cross-Section by
               Source Water Type and  Population-Served Size Category

Table B.26.b.   1,2-Dichloropropane - Summary of Analytical Detections in the 16-State Cross-Section
               by Source Water Type and Population-Served Size Category

Table B.27.b.   Dinoseb - Summary of Analytical Detections in the 16-State Cross-Section by Source
               Water Type and Population-Served Size Category

-------
Table B.28.b.   Diquat - Summary of Analytical Detections in the 16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B.29.b.   Endothall - Summary of Analytical Detections in the 16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B.SO.b.   Endrin - Summary of Analytical Detections in the 16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B.31 .b.   Ethylbenzene - Summary of Analytical Detections in the 16-State Cross-Section by
               Source Water Type and Population-Served Size Category

Table B.32.b.   Ethylene Dibromide - Summary of Analytical Detections in the 16-State Cross-Section
               by Source Water Type and Population-Served Size Category

Table B.33.b.   Fluoride - Summary of Analytical Detections in the 16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B.34.b.   Glyphosate - Summary of Analytical Detections in the 16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B.35.b.   Heptachlor - Summary of Analytical Detections in the 16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B.36.b.   Heptachlor Epoxide - Summary of Analytical Detections in the 16-State Cross-Section by
               Source Water Type and Population-Served Size Category

Table B.37.b.   Hexachlorobenzene - Summary of Analytical Detections in the 16-State Cross-Section by
               Source Water Type and Population-Served Size Category

Table B.38.b.   Hexachlorocyclopentadiene - Summary of Analytical Detections in the 16-State
               Cross-Section by Source Water Type and Population-Served Size Category

Table B.39.b.   Lindane - Summary of Analytical Detections in the  16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B.40.b.   Mercury - Summary of Analytical Detections in the 16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B.41.b.   Methoxychlor - Summary of Analytical Detections in the 16-State Cross-Section by
               Source Water Type and Population-Served Size Category

Table B.42.b.   Monochlorobenzene - Summary of Analytical Detections in the  16-State Cross-Section
               by Source Water Type and Population-Served Size Category

Table B.43.b.   Oxamyl - Summary of Analytical Detections in the  16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B.44.b.   PCBs - Summary of Analytical Detections in the 16-State Cross-Section by Source Water
               Type and Population-Served Size Category

Table B.45.b.   Pentachlorophenol - Summary of Analytical Detections in the 16-State Cross-Section by
               Source Water Type and Population-Served Size Category

-------
Table B.46.b.   Picloram - Summary of Analytical Detections in the 16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B.47.b.   Selenium - Summary of Analytical Detections in the 16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B.48.b.   Simazine - Summary of Analytical Detections in the 16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B.49.b.   Styrene - Summary of Analytical Detections in the  16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B.SO.b.   Tetrachloroethylene - Summary of Analytical Detections in the 16-State Cross-Section by
               Source Water Type and Population-Served Size Category

Table B.51 .b.   Thallium - Summary of Analytical Detections in the 16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B.52.b.   Toluene - Summary of Analytical Detections in the 16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B.53.b.   Toxaphene - Summary of Analytical Detections in the 16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B.54.b.   2,4,5-TP - Summary of Analytical Detections in the 16-State Cross-Section by Source
               Water Type and Population-Served Size Category

Table B.55.b.   1,2,4-Trichlorobenzene - Summary of Analytical Detections in the 16-State
               Cross-Section by Source Water Type and Population-Served Size Category

Table B.56.b.   1,1,1-Trichloroethane - Summary of Analytical Detections in the 16-State Cross-Section
               by Source Water Type and Population-Served Size Category

Table B.57.b.   1,1,2-Trichloroethane - Summary of Analytical Detections in the 16-State Cross-Section
               by Source Water Type and Population-Served Size Category

Table B.58.b.   Trichloroethylene - Summary of Analytical Detections in the 16-State Cross-Section by
               Source Water Type and Population-Served Size Category

Table B.59.b.   Vinyl Chloride - Summary of Analytical Detections in the 16-State Cross-Section by
               Source Water Type and Population-Served Size Category

Table B.60.b.   Xylenes (Total) - Summary of Analytical Detections in the 16-State Cross-Section by
               Source Water Type and Population-Served Size Category

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.I.a. Alachlor - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
3,090
7,320
4,641
5,291
2,901
1,743
1,278
1,621
1,660

4,264
593
5,806
773
3,742
949
45,672
255
613
1,972
1,737
1,298
1,197
743
1,062
799

2,033
394
2,452
376
1,820
746
17,497
57
405
1,380
505
893
169
644
647
443

531
327
664
145
1,178
404
8,392
966
901
708
2,090
707
368
391
262
567

858
116
1,452
176
950
160
10,672
154
227
443
379
377
47
271
77
178

126
68
147
60
423
57
3,034
1,105
1,015
383
558
386
129
101
127
109

366
35
1,249
131
627
43
6,364
77
115
122
89
79
16
53
11
23

23
12
44
14
135
8
821
599
2,403
774
697
405
37
31
170
173

620
46
425
90
303

6,773
24
139
139
55
38
5
13
2
9

17
12
14
4
54

525
165
2,388
804
209
105
12
12

12

387
2
228

42

4,366
1
58
62
3
4
1
4

1

2
1
2

6

145
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
801
2,578
79
2,107
603
1,519
240
247
160

250
424
667
161
2,828
364
13,028
38
30
2
71
36
182
5
35
6

56
67
56
21
544
54
1,203
8
9
1
3
6
26
4
19
2

17
43
9
9
90
32
278
67
20
10
785
91
389
66
77
21

60
131
174
14
724
116
2,745
11
9
5
36
11
48
16
18
3

12
59
21
7
121
31
408
117
70
10
414
100
429
73
60
20

44
80
120
48
498
54
2,137
16
8
3
22
16
53
15
9
3

5
18
12
8
70
8
266
355
462
34
590
171
444
76
64
19

39
105
246
48
613
132
3,398
32
21
7
32
13
57
19
3
1

4
21
24
7
65
6
312
224
1,996
23
247
205
75
20
11
94

51
41
71
30
449
8
3,545
9
52
5
16
8
5
6
2
1

1
4
7
2
30
1
149
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.2.a.  Antimony - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
686
6,977
5,206
160
2,897
877
0
1,096
991
3,469
1,689
616
3,658
372
5,379
1,090
35,163
69
1,045
2,169
53
1,579
584

624
350
1,645
885
446
2,183
256
2,541
889
15,318
50
674
1,255
51
900
195

410
232
1,017
459
377
682
241
2,327
479
9,349
248
1,023
956
62
839
196

339
372
623
325
120
678
79
2,014
169
8,043
152
288
396
52
376
47

69
162
243
113
74
145
58
1,131
60
3,366
229
971
428
17
237
73

56
134
381
125
22
524
22
538
32
3,789
77
135
95
15
81
16

10
23
71
22
11
43
12
296
8
915
110
2,097
731
15
208
19

77
130
679
208
27
189
15
221

4,726
24
156
115
7
38
5

2
9
64
16
12
11
4
86

549
30
1,841
922
13
34
5


5
141
146
1
84

65

3,287
1
65
52
2
4
1


1
4
2
1
2

11

146
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
523
2,838
92
67
371
1,000
0
254
59
432
62
528
497
42
1,447
382
8,594
36
76
6
2
27
116

47

4
10
102
40
9
260
72
807
8
28
1
2
6
34

19

1
5
44
9
9
100
28
294
53
98
24
30
58
262

106
4
18
16
187
96
6
381
177
1,516
11
30
5
30
11
48

18
2
4
7
59
20
6
123
33
407
84
83
12
13
84
280

42
9
29
14
75
110
8
291
47
1,181
16
23
2
13
16
53

9
3
5
2
18
12
7
71
8
258
209
459
29
16
96
303

47
11
112
7
122
190
5
272
79
1,957
32
28
5
16
13
57

3
3
11
2
21
25
4
66
6
292
141
2,122
21
6
106
39

12
35
269
15
42
61
14
243
7
3,133
9
61
3
6
8
4

2
1
12
1
4
7
2
30
1
151
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.3.a. Atrazine - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
3,100
13,673
4,631
5,294
2,989
1,829
1,278
1,646
1,660
0
4,257
603
5,813
771
3,771
872
52,187
255
1,293
1,974
1,735
1,332
1,265
743
1,069
799

2,020
402
2,459
376
1,826
685
18,233
57
767
1,379
505
892
169
644
646
443

531
331
666
145
1,178
386
8,739
966
1,860
708
2,091
716
383
391
266
567

860
121
1,452
174
951
146
11,652
154
334
443
379
377
47
271
77
178

126
69
147
60
423
55
3,140
1,118
1,959
378
557
403
130
101
131
109

369
35
1,249
131
628
41
7,339
77
140
122
89
79
16
53
11
23

23
12
44
14
135
8
846
596
4,336
776
699
417
39
31
180
173

624
43
425
90
324

8,753
24
152
139
55
38
5
13
2
9

17
12
14
4
55

539
165
4,225
795
212
121
12
12

12

384
2
228

42

6,210
1
63
62
3
4
1
4

1

2
1
2

6

150
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
815
4,904
74
2,138
725
1,575
241
252
130
0
251
429
658
168
2,732
213
15,305
43
26
2
71
37
193
5
35
6

54
67
49
16
492
27
1,123
8
10
1
3
6
26
4
19
2

17
43
7
6
77
14
243
67
50
9
787
125
406
66
80
21

60
129
174
14
706
88
2,782
11
18
4
36
11
48
16
18
3

12
59
21
7
118
27
409
119
108
10
426
142
431
73
61
9

44
83
118
48
498
47
2,217
16
14
3
22
16
53
15
9
1

5
18
12
8
70
8
270
359
1,049
30
597
188
472
77
64


44
109
246
54
587
44
3,920
32
24
6
32
13
57
19
3


4
21
24
7
63
5
310
227
3,671
23
257
233
73
20
12
94

49
41
71
36
449
7
5,263
9
54
5
16
8
5
6
2
1

1
4
7
2
30
1
151
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.4.a.  Barium - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
1,491
18,088
5,109
311
2,989
961
0
1,400
167
3,636
1,859
1,787
3,761
365
6,341
1,664
49,929
150
1,810
2,131
66
1,588
655

1,037
19
1,715
1,006
1,422
2,222
256
3,453
1,346
18,876
56
868
1,256
53
899
202

641
18
1,037
485
1,046
690
244
3,142
543
11,180
549
2,955
945
136
857
210

227
46
650
357
245
728
80
2,057
264
10,306
153
378
396
71
376
47

78
20
245
118
111
146
60
1,164
63
3,426
480
2,967
396
47
262
72

59
56
402
132
63
535
22
544
54
6,091
77
157
95
22
81
16

11
14
72
23
18
43
13
299
9
950
261
5,451
716
47
248
19

77
43
725
218
55
191
7
222

8,280
24
161
115
12
38
5

2
8
65
17
13
11
4
86

561
51
4,905
921
15
34
5


3
144
146
2
85

65

6,376
1
66
52
2
4
1


1
4
2
1
2

11

147
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
840
7,239
91
69
373
1,153
0
265
26
460
78
946
510
35
1,472
590
14,147
58
130
6
2
27
138

65

4
20
234
43
9
279
148
1,163
8
37
1
2
6
36

22

1
12
72
9
9
106
44
365
82
346
24
30
58
303

95

18
20
326
99
7
386
261
2,055
11
51
5
30
11
48

18

4
9
63
20
7
123
33
433
146
304
12
13
84
315

42
5
34
14
130
111
8
292
67
1,577
16
31
2
13
16
53

9
3
5
2
18
12
7
71
8
266
360
1,368
29
16
99
350

51
6
124
9
190
193
6
272
101
3,174
32
33
5
16
13
57

3
3
11
3
22
25
5
66
6
300
194
5,091
20
8
105
47

12
15
280
15
66
64
5
243
13
6,178
9
63
3
6
8
5

2
1
12
1
4
7
2
30
1
154
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.S.a. Benzene - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
5,136
38,818
18,951
23,749
3,781
1,575
1,996
3,333
4,767
10,778
5,515
1,926
8,855
720
24,168
3,965
158,033
406
4,009
8,946
9,531
1,953
1,044
884
2,339
2,604
4,819
2,833
1,506
4,143
472
10,594
3,201
59,284
56
2,166
1,974
659
871
180
666
678
592
1,296
562
936
769
288
2,812
550
15,055
1,632
4,441
2,948
8,626
974
364
631
538
1,357
1,861
1,009
286
2,014
199
7,375
680
34,935
152
488
549
436
372
48
279
78
183
261
133
110
154
82
1,236
62
4,623
1,602
4,655
1,168
2,852
403
135
336
184
376
1,176
377
62
1,660
29
3,924
84
19,023
76
158
126
109
79
16
56
11
24
73
24
17
45
16
328
8
1,166
1,189
11,351
2,572
2,317
385
28
134
272
405
2,301
808
70
674
20
1,930

24,456
24
162
141
60
38
5
14
2
9
65
17
13
14
4
95

663
307
14,362
3,317
423
66
4
11

25
621
488
2
364

345

20,335
1
66
62
3
4
1
4

1
4
2
1
2

12

163
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,297
11,915
136
2,827
526
1,715
437
391
155
761
343
924
1,140
75
6,324
812
30,778
146
81
6
58
36
176
20
80
13
6
87
231
52
12
1,044
172
2,220
8
27
1
3
6
30
4
21
3
1
20
53
8
9
117
36
347
166
188
30
917
82
409
95
131
27
21
69
356
210
9
1,379
336
4,425
11
38
5
37
11
47
17
18
3
4
12
61
22
8
124
33
451
283
406
19
621
110
417
120
89
26
44
65
107
163
14
1,230
82
3,796
16
25
3
26
16
53
15
9
3
5
5
18
14
8
72
8
296
847
1,880
43
777
148
664
181
60
25
159
61
182
563
13
1,448
185
7,236
32
32
7
33
13
54
19
3
1
11
4
22
27
7
66
6
337
855
9,360
38
454
150
49
21
31
64
531
61
48
152
27
1,223
37
13,101
9
56
5
18
8
4
5
2
1
12
1
4
7
2
30
1
165
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.6.a.  Benzo(a)pyrene - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
3,121
2,708
4,659
5,242
2,844
1,020
17
1,614
1,974
0
4,116
549
5,777
932
533
884
35,990
255
312
2,005
1,740
1,273
703
6
1,062
963

1,946
358
2,489
453
160
724
14,449
57
206
1,381
505
892
169
4
647
453

525
300
687
153
123
407
6,509
970
224
716
2,055
698
210
3
253
639

817
117
1,175
215
64
134
8,290
154
99
442
379
377
47
3
77
180

123
67
150
59
43
56
2,256
1,114
298
387
553
365
68
7
126
145

359
32
1,373
148
208
26
5,209
77
61
122
89
79
16
5
11
23

23
12
44
14
80
8
664
601
736
770
687
403
27
1
173
213

610
41
485
116
90

4,953
24
102
138
55
38
5
1
2
9

17
12
12
4
33

452
181
1,138
781
207
105
12


14

384
1
255

11

3,089
1
52
62
3
4
1


1

2
1
2

2

131
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
807
1,316
77
1,784
544
968
11
229
158
0
145
410
696
179
2,931
277
10,532
38
24
2
63
35
123

35
5

19
58
48
25
502
39
1,016
8
7
1
3
6
26

19
2

6
39
9
9
78
20
233
67
1
10
664
60
225

70
21

31
128
138
18
663
97
2,193
11
1
5
36
11
48

18
3

7
59
22
7
114
27
369
125
20
10
325
93
222
1
60
22

32
79
123
53
600
47
1,812
16
4
3
22
16
53
1
9
3

2
18
12
8
71
8
246
355
177
32
505
165
329
7
54
23

17
104
310
53
683
88
2,902
32
17
7
32
13
57
7
3
1

2
21
26
7
66
6
297
222
1,094
23
227
191
69
3
10
87

46
41
77
30
483
6
2,609
9
41
5
16
8
5
3
2
1

1
4
7
2
30
1
135
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.7.a. Beryllium - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
771
7,692
5,121
252
2,896
820
3,767
1,000
980
3,454
1,738
615
3,307
245
6,343
902
39,903
66
1,037
2,132
58
1,579
539
2,455
625
346
1,640
907
443
1,971
172
3,449
733
18,152
49
669
1,255
53
899
195
1,896
410
229
1,017
471
375
676
165
3,140
452
11,951
238
1,016
957
107
835
190
942
243
370
619
340
120
664
51
2,057
142
8,891
147
290
396
72
376
47
424
69
162
243
117
74
145
42
1,164
59
3,827
229
989
396
38
239
67
238
55
132
379
127
22
443
8
545
27
3,934
77
140
95
22
81
16
55
10
23
71
23
11
43
7
299
8
981
156
2,256
729
35
209
19
94
77
128
674
217
29
148
14
227

5,012
30
164
115
12
38
5
13
2
9
64
17
13
12
3
87

584
82
2,394
907
14
34
5
38

4
142
147
1
81

65

3,914
4
78
52
2
4
1
4

1
4
2
1
2

11

166
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
371
2,080
91
68
372
959
279
256
55
432
128
527
429
5
1,468
338
7,858
26
73
6
2
27
115
17
46

4
35
102
37
3
279
61
833
8
26
1
2
6
34
7
18

1
15
44
9
3
106
28
308
41
84
24
30
58
253
57
106
3
18
30
187
91

386
167
1,535
9
27
5
30
11
48
18
18
2
4
10
59
20

123
32
416
75
55
12
13
85
263
60
43
8
29
23
76
91
2
292
39
1,166
15
16
2
13
16
53
16
9
3
5
4
18
12
2
71
8
263
142
273
28
16
95
289
115
49
10
112
23
119
157

268
65
1,761
25
20
5
16
13
57
27
3
1
11
4
20
24

65
6
297
87
1,595
21
7
107
39
30
12
34
269
17
43
53

243
6
2,563
6
48
3
6
8
4
7
2
1
12
1
4
7

30
1
140
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.S.a. Bis(2-ethylhexyl)adipate - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Catego
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
3,175
0
4,662
5,260
2,862
1,025
17
1,621
1,974
0
4,121
555
6,698
927
374
973
34,244
263

2,008
1,752
1,286
708
6
1,067
963

1,948
363
3,022
451
98
800
14,735
57

1,380
505
891
169
4
646
453

525
299
677
154
74
422
6,256
975

716
2,049
693
210
3
255
639

818
118
1,558
212
17
144
8,407
154

442
378
377
47
3
77
180

123
68
148
60
13
56
2,126
1,130

376
552
367
68
7
126
145

360
32
1,384
148
163
29
4,887
77

122
89
79
16
5
11
23

23
12
44
14
64
8
587
620

780
695
411
27
1
173
213

611
41
466
116
86

4,240
24

138
55
38
5
1
2
9

17
12
13
4
30

348
187

782
212
105
12


14

384
1
268

10

1,975
1

62
3
4
1


1

2
1
2

2

79
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
887
0
77
1,771
548
969
11
233
158
0
145
411
750
179
2,079
295
8,513
39

2
62
35
123

36
5

19
58
60
25
422
49
935
8

1
3
6
26

19
2

6
39
9
9
78
21
227
67

10
662
60
226

70
21

31
129
178
18
397
103
1,972
11

5
36
11
48

18
3

7
59
21
7
107
28
361
124

10
326
92
222
1
62
22

32
80
135
53
421
48
1,628
16

3
22
16
53
1
9
3

2
18
12
8
70
8
241
403

32
493
166
329
7
54
23

17
102
299
53
510
88
2,576
32

7
32
13
57
7
3
1

2
21
25
7
65
6
278
254

23
228
195
69
3
11
87

46
42
78
30
329
7
1,402
9

5
16
8
5
3
2
1

1
4
7
2
30
1
94
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.9.a. Bis(2-ethylhexyl)phthalate - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Gate
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
3,403
4,409
4,728
5,302
3,004
177
12
1,622
1,613



7,150
787
80
917
33,204
293
373
2,047
1,757
1,325
114

1,068
792



2,991
387
26
750
11,923
57
247
1,382
505
893
19

646
443



668
149
13
410
5,432
1,081
447
722
2,070
720
35
3
255
532



2,048
179
4
137
8,233
154
160
442
380
377
5
3
77
178



149
60
3
55
2,043
1,196
561
384
560
386
1
8
126
109



1,386
131
42
30
4,920
77
90
123
89
79
1
5
11
23



44
14
7
8
571
642
1,278
786
701
452
15
1
173
168



497
90
7

4,810
24
123
138
55
38
3
1
2
9



14
4
2

413
191
1,750
789
214
121
12


12



228

1

3,318
1
57
62
3
4
1


1



2

1

132
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
927
1,625
79
1,820
574
404
11
231
121



672
161
971
252
7,848
63
26
2
62
40
47

35
5



28
21
324
41
694
8
9
1
3
6
11

19
2



4
9
70
21
163
71
4
10
662
61
59

70
19



166
14
238
98
1,472
11
4
5
36
11
9

18
3



19
7
48
30
201
132
35
12
344
102
10
1
61
17



127
48
117
39
1,045
16
7
3
22
16
4
1
9
3



12
8
21
8
130
402
154
32
510
171
223
7
54
19



281
48
181
68
2,150
32
19
7
32
13
36
7
3
1



24
7
29
6
216
259
1,406
23
242
200
65
3
11
61



70
30
111
6
2,487
9
45
5
16
8
5
3
2
1



7
2
13
1
117
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.lO.a. Cadmium - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
1,502
17,835
5,159
251
2,989
953
0
1,408
162
3,570
1,854
1,727
3,723
366
5,383
1,666
48,548
152
1,803
2,164
58
1,586
648

1,040
17
1,699
1,002
1,403
2,217
256
2,543
1,353
17,941
56
869
1,256
53
899
202

641
16
1,041
485
1,046
685
244
2,329
543
10,365
549
2,945
949
106
857
210

231
43
636
357
230
704
81
2,016
261
10,175
154
377
396
71
376
47

78
19
245
118
111
146
61
1,131
64
3,394
486
2,827
404
38
263
71

59
56
389
132
50
527
22
538
52
5,914
77
157
95
22
81
16

11
14
72
23
18
43
13
296
8
946
263
5,482
718
35
248
19

78
43
704
217
42
191
7
221

8,268
24
161
115
12
38
5

2
8
65
17
13
11
4
86

561
52
4,778
924
14
35
5


3
142
146
2
84

65

6,250
1
66
52
2
4
1


1
4
2
1
2

11

147
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
839
7,183
94
67
374
1,147
0
266
26
450
78
939
508
35
1,447
599
14,052
58
127
6
2
27
138

65

4
20
232
41
9
260
148
1,137
8
37
1
2
6
36

22

1
12
72
9
9
100
44
359
82
345
24
30
58
302

95

18
20
326
100
7
381
262
2,050
11
51
5
30
11
48

18

4
9
63
21
7
123
33
434
147
301
15
13
84
311

42
5
34
14
130
110
8
291
69
1,574
16
31
2
13
16
53

9
3
5
2
18
12
7
71
8
266
361
1,373
29
16
100
352

51
6
116
9
185
193
6
272
100
3,169
32
33
5
16
13
57

3
3
11
3
22
25
5
66
6
300
191
5,037
20
6
105
44

13
15
278
15
66
64
5
243
20
6,122
9
63
3
6
8
5

2
1
12
1
4
7
2
30
1
154
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.ll.a. Carbofuran - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
3,087
6,450
4,670
4,662
2,843
1,015
1,264
1,593
585

4,156
591
5,787
760
3,467
913
41,843
255
694
2,000
1,619
1,275
703
744
1,056
129

1,998
395
2,262
384
1,730
721
15,965
57
511
1,380
506
891
169
645
647
68

529
329
674
151
1,149
413
8,119
966
902
714
1,750
702
207
384
245
369

828
118
1,549
184
907
157
9,982
154
232
444
380
377
47
270
77
106

126
69
148
65
407
57
2,959
1,105
898
378
506
365
68
95
121
34

350
34
1,309
102
501
35
5,901
77
120
122
89
79
16
53
11
12

23
12
44
14
122
8
802
596
2,039
774
613
398
25
30
171
51

593
42
430
90
289

6,141
24
133
139
55
38
5
12
2
5

17
12
14
4
54

514
165
1,917
804
174
103
12
11

2

387
2
237

40

3,854
1
52
62
3
4
1
4

1

2
1
2

4

137
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
796
2,370
79
988
505
967
184
229
43

237
422
662
163
2 232
274
10,151
38
32
2
27
35
122
5
34
2

55
67
46
22
354
40
881
8
10
1
3
6
26
4
19
2

17
43
9
9
88
20
265
67
16
10
357
59
222
40
70
3

57
130
165
14
609
101
1,920
11
8
5
36
11
48
16
18
3

12
59
22
7
121
31
408
117
62
10
179
91
221
57
62
3

43
80
120
49
421
43
1,558
16
9
3
22
16
53
15
9
3

5
18
12
8
70
8
267
354
336
34
270
156
335
63
54
9

37
104
262
48
490
84
2,636
32
20
7
32
13
57
19
3
1

4
21
25
7
65
6
312
220
1,924
23
155
164
67
19
9
26

45
41
69
30
358
6
3,156
9
45
5
16
8
5
6
2
1

1
4
7
2
30
1
142
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.I 2. a. Carbon Tetrachloride - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Categor
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
5,122
41,407
18,542
23,747
3,765
1,591
1,972
3,334
3,855
10,784
5,512
1,916
8,323
495
19,146
2,930
152,441
406
4,046
8,948
9,529
1,936
1,051
884
2,340
2,131
4,807
2,841
1,497
3,767
346
8,583
2,342
55,454
56
2,173
1,973
659
872
180
666
678
572
1,296
563
934
751
230
2,748
523
14,874
1,627
4,400
2,935
8,627
971
371
631
538
1,071
1,861
1,020
285
1,966
126
5,857
520
32,806
152
490
549
436
371
48
279
78
181
261
133
110
156
64
1,225
61
4,594
1,601
4,768
1,145
2,840
406
135
310
184
320
1,179
378
62
1,567
20
3,000
68
17,983
76
158
126
109
79
16
56
11
24
73
24
17
45
12
325
8
1,159
1,189
12,125
2,186
2,320
386
30
136
272
325
2,317
786
70
665
3
1,458

24,268
24
162
141
60
38
5
14
2
9
65
17
13
15
3
96

664
299
16,068
3,328
431
66
4
11

8
620
487
2
358

248

21,930
1
66
62
3
4
1
4

1
4
2
1
2

12

163
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,298
13,508
136
2,831
527
1,720
441
391
95
762
347
924
1,003
55
4,777
667
30,482
145
80
6
58
36
176
20
80
13
6
88
231
47
5
939
136
2,066
8
27
1
3
6
30
4
21
3
1
20
53
8
5
117
36
343
166
189
30
921
83
422
95
131
12
21
69
356
195
5
1,164
275
4,134
11
38
5
37
11
47
17
18
2
4
12
61
20
4
123
33
443
283
407
19
620
110
415
120
89
17
44
65
107
150
10
845
66
3,367
16
26
3
26
16
53
15
9
3
5
5
18
14
5
71
8
293
848
1,886
43
778
148
658
185
60
19
161
61
182
472
8
972
155
6,636
32
32
7
33
13
54
19
3
1
11
4
22
25
4
64
6
330
856
10,946
38
454
150
49
21
31
34
530
64
48
139
27
857
35
14,279
9
56
5
18
8
4
5
2
1
12
1
4
7
2
30
1
165
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.I 3. a. Chlordane - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
3,087
8,964
4,667
5,294
2,822
1,012

1,548
290
598
4,265
591
9,053
764
3,615
966
47,536
255
810
1,986
1,737
1,263
698

1,030
135
167
2,034
395
3,844
374
1,765
752
17,245
57
535
1,379
505
892
169

632
86
133
531
329
672
142
1,145
404
7,611
966
1,245
716
2,091
694
208

221
100
109
858
117
2,377
169
905
165
10,941
154
271
443
379
377
47

72
52
76
126
69
148
60
402
57
2,733
1,105
1,254
385
558
365
68

126
31
112
366
34
1,814
131
584
49
6,982
77
128
122
89
79
16

11
13
42
23
12
44
14
124
8
802
596
2,866
774
699
396
26

171
22
197
620
43
620
90
320

7,440
24
144
139
55
38
5

2
4
51
17
12
14
4
54

563
165
2,789
806
209
104
12


2
13
387
2
398

41

4,928
1
61
62
3
4
1


1
2
2
1
2

5

145
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
800
3,278
76
2,144
549
952

209
12
71
250
424
1,088
156
1,887
257
12,153
38
30
2
72
36
123

21
2

56
67
72
16
415
47
997
8
9
1
3
6
27

15
2

17
43
7
6
76
27
247
67
40
9
801
63
224

75
3
1
60
131
258
14
440
104
2,290
11
11
4
36
11
48

18
3
1
12
59
21
7
110
28
380
117
85
10
411
94
223

43
1
8
44
81
185
48
319
49
1,718
16
11
3
22
16
53

9
1
5
5
18
12
8
70
8
257
354
580
32
611
165
319

61

25
39
104
479
48
418
49
3,284
32
23
6
32
13
57

3

7
4
21
25
7
59
5
294
224
2,543
23
249
191
63

9
6
37
51
41
94
30
295
8
3,864
9
52
5
16
8
5

2
1
10
1
4
7
2
29
1
152
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.14.a.  Chromium - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
1,522
18,855
5,108
252
2,988
898
2,976
1,404
154
3,560
1,901
1,756
3,311
271
6,344
1,084
52,384
166
1,810
2,130
58
1,585
596
2,156
1,038
14
1,691
1,024
1,413
1,973
193
3,451
878
20,176
56
870
1,257
53
899
202
1,654
642
13
1,043
495
1,047
676
185
3,141
472
12,705
548
2,960
940
107
857
208
606
230
41
635
371
236
665
61
2,057
172
10,694
154
377
396
72
376
47
325
78
18
245
120
111
145
50
1,164
61
3,739
491
2,929
398
38
263
70
151
59
54
390
134
54
443
10
544
34
6,062
77
160
95
22
81
16
40
11
14
72
24
18
43
9
299
8
989
266
5,685
720
35
248
19
39
77
43
700
225
51
149
7
227

8,491
24
166
115
12
38
5
11
2
8
65
16
13
12
4
87

578
51
5,471
920
14
35
5
24

2
144
147
2
81

65

6,961
1
74
52
2
4
1
3

1
4
2
1
2

11

158
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
844
6,250
94
69
373
1,147
149
265
23
450
153
930
434
14
1,467
391
13,053
58
121
6
2
27
138
6
64

4
45
230
38
4
279
83
1,105
8
35
1
2
6
36
2
22

1
17
71
9
4
106
31
351
82
346
24
30
58
302
24
95

18
38
319
91
1
386
178
1,992
11
51
5
30
11
48
14
18

4
11
63
20
1
123
31
441
150
272
15
13
84
312
25
42
4
34
26
130
91
4
292
43
1,537
16
28
2
13
16
53
9
9
2
5
4
18
12
4
71
8
270
363
1,071
29
17
99
351
73
51
5
117
26
185
159
1
267
72
2,886
32
28
5
16
13
57
24
3
1
11
4
22
24
1
65
6
312
191
4,440
20
7
105
44
21
13
14
277
18
66
55
4
243
15
5,533
9
55
3
6
8
5
7
2
1
12
1
4
7
1
30
1
152
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.lS.a. Cyanide - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
685
4,896
5,101
161
2,350
801
0
356
982
2,723
1,775
609
897
0
0
1,094
22,430
70
375
2,130
53
1,492
516

161
347
1,489
892
441
754


900
9,620
50
221
1,252
51
870
182

127
230
962
523
372
456


483
5,779
245
694
944
63
600
195

128
370
456
344
119
119


168
4,445
152
188
396
52
325
47

55
162
213
126
73
46


61
1,896
229
746
400
17
116
66

24
132
283
168
22
15


26
2,244
77
105
95
15
57
16

8
23
61
24
11
5


8
505
111
1,725
718
15
125
19

43
128
464
228
26
6



3,608
24
137
115
7
31
5

2
9
54
17
12
1



414
30
1,356
909
13
17
5


5
31
143
1
3



2,513
1
58
52
2
3
1


1
3
2
1
1



125
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
491
2,216
90
70
124
942
0
115
59
194
57
529
5
0
0
326
5,218
36
55
6
3
13
109

13

2
11
102
3


62
415
8
15
1
3
5
33

8

1
7
44
3


29
157
53
76
23
30
20
245

50
3
10
15
186



142
853
11
20
5
30
9
48

18
2
3
8
59



33
246
84
58
12
13
32
262

20
9
29
5
77



46
647
16
9
2
13
15
53

9
3
5
1
18



8
152
202
439
28
17
29
286

27
12
82
11
123
2


70
1,328
32
23
5
16
12
57

3
3
10
2
21
1


6
191
116
1,588
21
7
30
40

5
35
71
15
41



6
1,975
9
52
3
6
6
4

2
1
7
1
4



1
96
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.16.a. 2,4-D - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
3,154
9,885
4,634
4,745
2,918
1,498
2,800
1,648
632
54
4,060
629
4,962
867
3,469
1,007
46,962
261
805
1,982
1,628
1,302
1,003
2,099
1,085
300
10
1,920
416
1,951
434
1,727
799
17,722
57
518
1,383
506
892
175
1,897
650
212
9
526
340
666
150
1,149
440
9,570
984
1,478
705
1,806
723
337
572
268
165
4
807
123
1,018
203
903
174
10,270
154
291
442
379
377
47
411
77
59
4
123
69
146
60
406
58
3,103
1,144
1,533
392
507
391
108
97
124
100
10
366
41
1,298
114
518
34
6,777
77
145
122
89
79
16
57
11
20
8
23
12
44
14
120
8
845
600
3,308
783
624
399
32
24
171
66
29
599
47
427
116
281

7,506
24
158
139
55
38
5
12
2
8
9
17
12
12
4
52

547
165
2,761
772
180
103
18
8

1
1
368
2
268

40

4,687
1
64
62
3
4
1
3

1
1
2
1
2

5

150
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
969
3,604
78
1,474
516
1,674
175
228
34
14
155
608
655
183
2,263
360
12,990
50
41
3
48
34
221
6
35


26
118
41
27
364
51
1,065
8
16
1
3
6
32
5
19


11
51
9
9
87
26
283
82
80
10
571
61
382
34
67

2
32
183
124
18
611
128
2,385
11
28
5
36
11
48
17
18

1
8
61
21
7
121
33
426
145
122
10
300
100
443
49
61
4
5
32
107
116
53
417
56
2,020
16
24
3
22
16
53
14
9
2
3
2
18
12
8
70
8
280
415
702
32
363
158
544
66
54
6
5
17
146
299
55
514
118
3,494
32
29
7
32
13
57
23
3
1
3
2
21
26
7
66
6
328
277
2,659
23
192
163
84
20
11
24
2
48
54
75
30
357
7
4,026
9
56
5
16
8
5
7
2
1
2
1
4
7
2
30
1
156
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.17.a. Dalapon - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
3,111
3,996
4,680
4,745
2,828
1,020
36
446
632
0
3,674
583
5,111
867
3,469
72
35,270
255
464
2,000
1,631
1,270
706
9
241
300

1,740
388
2,058
434
1,727
58
13,281
57
320
1,382
507
891
169
9
181
212

512
321
667
150
1,149
56
6,583
984
499
716
1,801
695
209
19
61
165

720
116
1,048
203
903
13
8,152
154
168
443
379
377
47
18
24
59

120
68
146
60
406
9
2,478
1,110
542
401
507
362
68
4
25
100

318
35
1,315
114
518
1
5,420
77
100
122
89
79
16
3
8
20

23
12
44
14
120
1
728
597
1,315
788
626
398
25
3
119
66

529
43
428
116
281

5,334
24
118
139
55
38
5
3
2
8

16
12
12
4
52

488
165
1,176
775
180
103
12
1

1

367
1
262

40

3,083
1
53
62
3
4
1
1

1

2
1
2

5

136
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
889
1,534
81
1,416
513
948
22
66
34
0
132
427
646
183
2,263
16
9,170
45
27
3
47
35
123

7


21
66
43
27
364
6
814
8
9
1
3
6
27

5


6
42
9
9
87
4
216
76
21
11
550
61
225
4
11


28
133
122
18
611
2
1,873
11
8
5
36
11
48
2
7


7
59
21
7
121
2
345
136
36
10
290
98
222
6
21
4

30
84
118
53
417
6
1,531
16
6
3
22
16
53
3
8
2

2
18
12
8
70
3
242
397
269
34
340
161
315
7
23
6

11
103
291
55
514
1
2,527
32
17
7
32
13
57
4
3
1

2
21
26
7
66
1
289
235
1,181
23
189
158
63
5
4
24

42
41
72
30
357
1
2,425
9
45
5
16
8
5
3
2
1

1
4
7
2
30
1
139
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.lS.a. l,2-Dibromo-3-chloropropane - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
3,079
26,193
4,623
5,690
2,741
1,870
1,678
1,435
5,962
9,114
5,126
591
9,691
1,411

328
79,532
247
1,565
1,934
1,903
1,198
1,287
772
863
2,975
4,078
2,459
390
3,705
828

284
24,488
56
636
1,347
499
843
170
634
594
592
1,157
547
323
748
288

217
8,651
965
3,095
706
2,113
681
390
527
244
1,919
1,545
995
119
2,308
403

37
16,047
152
288
440
385
370
47
264
74
183
236
130
67
154
82

29
2,901
1,105
2,880
385
647
357
140
263
128
530
975
407
34
2,372
131

7
10,361
76
125
121
95
78
16
55
11
24
70
24
12
45
16

5
773
597
7,902
787
791
401
39
108
200
508
1,988
864
46
822
49


15,102
24
143
139
57
38
5
13
2
9
64
17
12
14
4


541
165
10,751
811
236
104
14
8

30
528
401
2
484



13,534
1
57
62
3
4
1
4

1
4
2
1
2



142
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
830
10,700
77
1,389
516
1,586
320
219
217
560
321
436
1,514
258

75
19,018
46
36
2
39
42
196
15
23
15
5
79
69
66
39

8
680
8
10
1
3
6
26
4
20
3
1
20
43
8
9

8
170
71
35
10
459
59
378
72
63
34
16
69
132
315
27

22
1,762
11
16
5
36
11
47
17
17
3
3
12
58
22
8

14
280
126
114
10
262
95
442
91
80
33
32
49
77
227
67

2
1,707
16
9
3
24
16
53
15
9
3
5
5
18
14
8

2
200
364
1,505
32
409
157
490
125
36
36
125
44
113
733
68

43
4,280
32
24
7
32
13
54
19
3
1
11
4
21
26
7

3
257
223
9,010
23
220
163
80
17
17
99
382
80
45
173
57


10,589
9
51
5
17
8
4
4
2
1
12
1
4
7
2


127
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.19.a. 1,4-Dichlorobenzene - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
5,117

18,535
23,484
3,801
1,580
1,973

3,855
10,127
5,504
1,920
8,313
495
19,146
2,929
106,779
406

8,946
9,461
1,977
1,051
884

2,131
4,619
2,843
1,499
3,763
346
8,566
2,342
48,834
56

1,973
659
877
180
666

572
1,282
563
934
749
230
2,744
523
12,008
1,623

2,948
8,555
970
357
633

1,071
1,743
1,012
287
1,956
126
5,874
519
27,674
152

549
436
371
48
279

181
254
133
110
154
64
1,229
61
4,021
1,600

1,156
2,786
402
141
310

320
1,062
377
62
1,567
20
3,000
68
12,871
76

126
109
79
16
56

24
72
24
17
45
12
325
8
989
1,189

2,162
2,264
385
27
135

325
2,100
785
70
669
3
1,458

11,572
24

141
60
38
5
14

9
65
17
13
15
3
96

500
299

3,323
418
67
4
11

8
603
487
2
358

248

5,828
1

62
3
4
1
4

1
4
2
1
2

12

97
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,297

136
2,799
526
1,706
438

95
667
345
924
1,020
55
4,776
666
16,450
145

6
58
36
181
20

13
6
88
231
53
5
915
136
1,893
8

1
3
6
30
4

3
1
20
53
10
5
116
36
296
166

30
913
82
414
95

12
20
69
356
205
5
1,179
274
3,820
11

5
37
11
47
17

2
4
12
61
22
4
123
33
389
283

19
616
110
404
120

17
36
65
107
150
10
842
65
2,844
16

3
26
16
53
15

3
5
5
18
14
5
71
8
258
848

43
768
148
658
182

19
134
62
182
472
8
983
155
4,662
32

7
33
13
54
19

1
11
4
22
25
4
65
6
296
855

38
444
150
49
21

34
471
61
48
140
27
857
36
3,231
9

5
18
8
4
5

1
12
1
4
7
2
30
1
107
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.20.a. o-Dichlorobenzene - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
5,117
0
18,450
23,440
3,764
1,148
4,155
3,334
4,767
10,150
5,248
647
8,330
683
23,193
3,678
116,104
406

8,921
9,459
1,942
788
2,833
2,340
2,604
4,622
2,742
448
4,017
449
10,415
2,953
54,939
56

1,973
657
873
173
1,933
678
592
1,280
557
328
763
278
2,806
543
13,490
1,623

2,933
8,538
969
238
915
538
1,357
1,754
957
125
1,812
188
6,853
643
29,443
152

549
435
372
47
429
78
183
256
130
66
154
82
1,235
62
4,230
1,600

1,140
2,780
402
80
308
184
376
1,072
360
31
1,544
27
3,760
82
13,746
76

126
109
79
16
58
11
24
72
24
12
45
15
328
8
1,003
1,189

2,152
2,245
385
28
91
272
405
2,077
703
41
633
19
1,835

12,075
24

141
60
38
5
14
2
9
65
17
12
14
4
95

500
299

3,304
418
66
14
8

25
625
486
2
324

330

5,901
1

62
3
4
1
3

1
4
2
1
2

12

96
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,295
0
135
2,793
526
1,152
506
391
154
694
209
447
1,091
70
6,183
762
17,408
145

6
58
36
131
29
80
13
6
40
80
55
10
1,031
160
1,880
8

1
3
6
27
6
21
3
1
10
44
10
8
117
36
301
166

29
913
82
257
102
131
27
20
40
145
204
9
1,348
315
3,788
11

5
37
11
48
19
18
3
4
8
58
22
8
124
33
409
283

19
614
110
251
116
89
26
36
53
71
161
13
1,200
76
3,118
16

3
26
16
53
14
9
3
5
2
18
14
7
72
8
266
846

43
765
148
443
235
60
25
148
18
115
533
11
1,407
175
4,972
32

7
33
13
57
23
3
1
11
2
21
27
6
66
6
308
855

38
443
150
70
24
31
63
484
58
36
138
27
1,197
36
3,650
9

5
18
8
5
6
2
1
12
1
4
7
2
30
1
111
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.21.a. 1,2-Dichloroethane - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
5,128
39,785
18,615
23,714
3,783
1,571
1,972
3,328
3,857
10,780
5,521
1,916
8,319
495
19,146
2,935
150,865
406
4,057
8,942
9,523
1,940
1,044
884
2,334
2,131
4,812
2,841
1,497
3,765
346
8,583
2,345
55,450
56
2,177
1,973
659
872
180
666
678
572
1,296
563
934
751
230
2,748
523
14,878
1,633
4,421
2,937
8,607
975
360
630
538
1,072
1,864
1,018
285
1,964
126
5,857
522
32,809
152
491
550
436
372
48
279
78
181
262
134
110
156
64
1,225
61
4,599
1,600
4,711
1,154
2,844
409
135
313
184
320
1,176
377
62
1,567
20
3,000
68
17,940
76
158
126
109
79
16
56
11
24
73
24
17
45
12
325
8
1,159
1,190
11,472
2,261
2,306
393
28
134
272
326
2,308
798
70
665
3
1,458

23,684
24
162
141
60
38
5
14
2
9
65
17
13
15
3
96

664
299
15,124
3,321
434
66
4
11

8
620
487
2
358

248

20,982
1
66
62
3
4
1
4

1
4
2
1
2

12

163
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,297
12,791
136
2,832
530
1,705
437
390
95
763
344
924
1,001
55
4,777
668
29,745
145
80
6
58
38
176
20
80
13
6
88
231
47
5
939
136
2,068
8
27
1
3
6
30
4
21
3
1
20
53
8
5
117
36
343
166
189
30
919
82
412
95
131
12
21
69
356
195
5
1,164
275
4,121
11
38
5
37
11
47
17
18
2
4
12
61
20
4
123
33
443
284
408
19
621
111
410
120
89
17
44
65
107
150
10
845
66
3,366
16
26
3
26
16
53
15
9
3
5
5
18
14
5
71
8
293
847
2,112
43
781
149
658
181
60
19
161
61
182
470
8
972
156
6,860
32
32
7
33
13
54
19
3
1
11
4
22
25
4
64
6
330
855
10,002
38
453
150
49
21
30
34
531
61
48
139
27
857
35
13,330
9
57
5
18
8
4
5
2
1
12
1
4
7
2
30
1
166
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.22.a. 1,1-Dichloroethylene - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
5,135
40,131
15,773
23,768
3,736
1,550
1,968
3,334
3,399
10,816
5,504
1,919
8,289
291
9,922
2,226
137,761
406
4,052
6,553
9,548
1,909
1,024
884
2,340
1,719
4,804
2,841
1,501
3,743
178
4,477
1,705
47,684
56
2,176
1,342
659
846
168
666
678
435
1,296
563
934
739
113
1,160
358
12,189
1,631
4,359
9 593
Z,DZ.5
8,625
967
356
630
538
1,051
1,865
1,013
285
1,956
96
9 71 3
z, /1J
456
29,064
152
490
442
436
369
47
279
78
176
261
133
110
154
46
424
53
3,650
1,609
4,901
1,129
2,838
402
138
309
184
295
1,186
377
62
1,567
14
1,607
65
16,683
76
158
122
109
78
16
56
11
23
73
24
17
45
10
135
8
961
1,189
11,365
2,246
2,320
391
28
134
272
326
2,339
785
69
665
3
911

23,043
24
162
138
60
38
5
14
2
9
65
17
13
15
3
54

619
300
15,454
3,322
437
67
4
11

8
622
488
2
358

214

21,287
1
66
62
3
4
1
4

1
4
2
1
2

6

157
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,296
15,557
136
2,830
526
2,000
437
391
92
763
345
922
1,019
54
4,710
572
32,650
145
80
6
58
36
176
20
80
10
6
88
231
53
5
857
89
1,940
8
27
1
3
6
26
4
21
2
1
20
53
10
5
91
21
299
166
189
30
919
82
416
95
131
12
21
70
354
205
4
1,175
229
4,098
11
38
5
37
11
47
17
18
2
4
12
61
22
3
121
29
438
284
415
19
621
110
416
120
89
17
44
65
107
150
10
838
66
3,371
16
26
3
26
16
53
15
9
3
5
5
18
14
5
70
8
292
846
2,941
43
779
148
943
181
60
19
161
61
182
472
8
983
154
7,981
32
32
7
33
13
54
19
3
1
11
4
22
25
4
65
6
331
855
11,932
38
453
150
49
21
31
34
531
61
48
139
27
857
34
15,260
9
56
5
18
8
4
5
2
1
12
1
4
7
2
30
1
165
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.23.a. cis-l,2-Dichloroethylene - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Categ
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
5,116
34,585
18,841
23,582
3,891
1,148
4,256
3,320
4,767
10,960
5,251
655
8,319
683
23,193
3,652
152,219
406
2,464
8,928
9,504
1,977
788
2,832
2,338
2,604
4,772
2,742
456
4,012
449
10,415
2,863
57,550
56
1,231
1,974
657
873
173
1,933
678
592
1,295
557
332
763
278
2,806
537
14,735
1,622
3,662
2,931
8,561
994
238
934
537
1,357
1,905
959
125
1,812
188
6,853
710
33,388
152
397
549
435
371
47
429
78
183
261
131
66
154
82
1,235
62
4,632
1,600
4,018
1,136
2,804
412
80
366
173
376
1,230
360
31
1,543
27
3,760
79
17,995
76
154
126
109
80
16
58
11
24
73
24
12
45
15
328
8
1,159
1,189
10,955
2,524
2,277
429
28
113
272
405
2,377
703
41
628
19
1,835

23,795
24
162
141
60
38
5
14
2
9
65
17
12
14
4
95

662
299
13,486
3,322
436
79
14
11

25
676
487
2
324

330

19,491
1
65
62
3
4
1
3

1
4
2
1
2

12

161
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,301
11,058
136
2,808
528
1,177
536
385
154
786
209
446
1,091
70
6,183
752
28,620
145
73
6
58
36
138
29
80
13
6
40
80
55
10
1,031
154
1,954
8
27
1
3
6
27
6
21
3
1
10
44
10
8
117
36
328
166
167
29
919
82
256
102
130
27
21
40
144
204
9
1,348
313
3,957
11
36
5
37
11
48
19
18
3
4
8
58
22
8
124
33
445
283
363
19
617
110
251
116
84
26
44
53
71
161
13
1,200
76
3,487
16
25
3
26
16
53
14
9
3
5
2
18
14
7
72
8
291
846
1,711
43
767
148
460
265
60
25
176
18
115
534
11
1,407
174
6,760
32
32
7
33
13
57
23
3
1
11
2
21
27
6
66
6
340
861
8,744
39
447
152
72
24
31
63
539
58
36
137
27
1,197
35
12,462
9
56
5
18
8
5
6
2
1
12
1
4
7
2
30
1
167
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.24.a. trans-l,2-Dichloroethylene - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Cal
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
0
38,711
18,555
23,603
3,761
1,146
4,161
3,332
4,766
10,748
5,248
651
8,319
683
23,193
3,556
150,433

4,023
8,929
9,500
1,934
786
2,833
2,339
2,603
4,761
2,742
452
4,012
449
10,415
2,863
58,641

2,174
1,973
657
871
173
1,933
678
591
1,295
557
330
763
278
2,806
537
15,616

4,340
2,932
8,584
968
238
915
537
1,357
1,863
957
125
1,812
188
6,853
614
32,283

489
550
435
371
47
429
78
183
260
130
66
154
82
1,235
62
4,571

4,639
1,142
2,811
402
80
314
184
376
1,185
360
31
1,543
27
3,760
79
16,933

158
126
109
79
16
58
11
24
73
24
12
45
15
328
8
1,086

10,877
2,241
2,285
390
28
91
272
405
2,296
703
41
628
19
1,835

22,111

162
141
60
38
5
14
2
9
65
17
12
14
4
95

638

14,832
3,311
423
67
14
8

25
643
486
2
324

330

20,465

66
62
3
4
1
3

1
4
2
1
2

12

161
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
0
11,899
135
2,806
526
1,157
506
391
154
783
209
446
1,091
70
6,183
752
27,108

80
6
58
36
131
29
80
13
6
40
80
55
10
1,031
154
1,809

27
1
3
6
27
6
21
3
1
10
44
10
8
117
36
320

189
29
919
82
260
102
131
27
21
40
144
204
9
1,348
313
3,818

38
5
37
11
48
19
18
3
4
8
58
22
8
124
33
436

408
19
617
110
251
116
89
26
44
53
71
161
13
1,200
76
3,254

26
3
26
16
53
14
9
3
5
2
18
14
7
72
8
276

1,866
43
768
148
443
235
60
25
171
18
115
534
11
1,407
174
6,018

32
7
33
13
57
23
3
1
11
2
21
27
6
66
6
308

9,356
38
444
150
72
24
31
63
541
58
36
137
27
1,197
35
12,209

56
5
18
8
5
6
2
1
12
1
4
7
2
30
1
158
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.25.a. Dichloromethane - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
5,130
38,708
18,606
23,627
3,963
1,149
1,971

3,855
10,750
4,830
659
7,804
495
19,146
2,820
143,513
406
4,055
9,003
9,488
2,033
788
884

2,131
4,763
2,455
459
3,663
346
8,583
2,264
51,321
56
2,175
1,976
657
879
173
666

572
1,295
555
334
747
230
2,748
516
13,579
1,630
4,343
2,977
8,556
1,022
238
630

1,071
1,861
906
128
1,764
126
5,857
491
31,600
152
490
549
436
375
47
279

181
260
133
66
156
64
1,225
61
4,474
1,601
4,627
1,147
2,839
428
81
312

320
1,193
348
31
1,440
20
3,000
65
17,452
76
158
126
109
79
16
56

24
73
23
12
45
12
325
8
1,142
1,194
10,875
2,162
2,308
414
28
134

325
2,288
639
40
619
3
1,458

22,487
24
162
141
60
38
5
14

9
65
17
12
15
3
96

661
299
14,808
3,317
436
66
14
11

8
645
482
1
318

248

20,653
1
66
62
3
4
1
4

1
4
2
1
2

12

163
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,327
11,902
135
2,844
546
1,148
439

95
737
309
449
946
55
4,777
656
27,365
145
83
6
58
43
129
20

13
6
72
80
43
5
939
131
1,773
8
27
1
3
6
27
4

3
1
20
44
8
5
117
36
310
166
195
29
911
86
256
95

12
21
66
145
188
5
1,164
271
3,610
11
38
5
37
11
48
17

2
4
12
58
20
4
123
33
423
284
408
19
636
117
251
120

17
44
60
71
148
10
845
66
3,096
16
26
3
26
16
53
15

3
5
5
18
14
5
71
8
284
850
1,692
43
778
149
442
183

19
169
58
116
443
8
972
154
6,076
32
32
7
33
13
57
19

1
11
4
21
25
4
64
6
329
882
9,524
38
461
151
70
21

34
497
53
37
124
27
857
34
12,810
9
57
5
18
8
5
5

1
12
1
4
7
2
30
1
165
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.26.a. 1,2-Dichloropropane - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
5,122
36,571
18,465
23,517
3,758
1,138
1,967
3,333
4,769
10,074
5,501
648
8,348
720
23,780
3,966
151,677
406
3,217
8,928
9,486
1,937
778
884
2,339
2,604
4,592
2,840
447
4,039
472
10,541
3,202
56,712
56
1,644
1,973
657
871
172
666
678
592
1,281
562
330
765
288
2,812
550
13,897
1,628
4,105
2,930
8,567
968
238
630
538
1,358
1,739
1,012
127
1,812
199
7,206
680
33,737
152
452
549
436
371
47
279
78
183
255
133
66
154
82
1,236
62
4,535
1,600
4,462
1,129
2,795
402
80
308
184
376
1,066
377
31
1,544
29
3,810
84
18,277
76
153
126
109
79
16
56
11
24
71
24
12
45
16
328
8
1,154
1,189
10,638
2,174
2,253
385
28
134
272
406
2,055
785
41
629
20
1,880

22,889
24
161
141
60
38
5
14
2
9
65
17
12
14
4
95

661
299
14,149
3,304
416
66
14
11

25
622
487
2
324

343

20,062
1
66
62
3
4
1
4

1
4
2
1
2

12

163
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,295
11,660
135
2,798
526
1,146
437
391
155
668
344
448
1,084
75
6,251
812
29,225
145
80
6
58
36
138
20
80
13
6
88
80
48
12
1,032
172
2,014
8
26
1
3
6
27
4
21
3
1
20
44
8
9
117
36
334
166
185
29
915
82
247
95
131
27
20
69
145
203
9
1,367
336
4,026
11
38
5
37
11
47
17
18
3
4
12
58
22
8
124
33
448
283
398
19
615
110
251
120
89
26
36
65
71
161
14
1,216
82
3,556
16
25
3
26
16
53
15
9
3
5
5
18
14
8
72
8
296
846
1,827
43
766
148
445
181
60
25
145
61
115
534
13
1,431
185
6,825
32
31
7
33
13
54
19
3
1
11
4
21
27
7
66
6
335
855
9,170
38
444
150
65
21
31
64
461
61
37
138
27
1,205
37
12,804
9
56
5
18
8
4
5
2
1
12
1
4
7
2
30
1
165
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.27.a. Dinoseb - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
3,096
4,538
4,613
4,755
2,832
1,018
2,800
448
632
0
4,059
585
4,981
867
3,469
1,003
39,696
255
660
1,975
1,631
1,265
704
2,099
235
300

1,920
389
1,954
434
1,727
798
16,346
57
501
1,378
507
892
169
1,897
175
212

526
322
666
150
1,149
439
9,040
972
583
703
1,801
694
209
572
74
165

806
116
1,016
203
903
171
8,988
154
201
442
379
377
47
411
22
59

123
68
146
60
406
58
2,953
1,106
625
382
516
370
68
97
24
100

366
35
1,301
114
518
34
5,656
77
109
122
89
79
16
57
8
20

23
12
44
14
120
8
798
598
1,455
781
627
400
25
24
115
66

599
44
427
116
281

5,558
24
128
139
55
38
5
12
2
8

17
12
12
4
52

508
165
1,215
772
180
103
12
8

1

368
1
283

40

3,148
1
55
62
3
4
1
3

1

2
1
2

5

140
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
833
1,567
79
1,411
507
949
175
63
34
0
146
427
642
183
2,263
312
9,591
41
29
3
47
34
123
6
7


21
66
41
27
364
37
846
8
9
1
3
6
27
5
5


6
42
9
9
87
20
237
73
11
10
549
60
225
34
11


29
133
122
18
611
108
1,994
11
6
5
36
11
48
17
7


7
59
21
7
121
29
385
117
29
10
284
93
223
49
19
4

32
84
114
53
417
51
1,579
16
6
3
22
16
53
14
8
2

2
18
12
8
70
8
258
378
288
33
341
157
315
66
22
6

16
103
292
55
514
110
2,696
32
20
7
32
13
57
23
3
1

2
21
26
7
66
6
316
224
1,210
23
190
163
63
20
4
24

48
41
73
30
357
6
2,476
9
47
5
16
8
5
7
2
1

1
4
7
2
30
1
145
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.2S.a. Diquat - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
3,144
3,703
4,670
4,646
2,841
1,017
35
2
714

3,085
547
5,113
595

53
30,165
255
249
2,003
1,621
1,279
701
2
1
665

1,552
353
2,163
310

44
11,198
57
174
1,380
508
890
169
2
1
446

488
296
670
134

42
5,257
990
364
709
1,734
696
210
19
1
39

667
116
1,155
158

8
6,866
154
118
442
380
377
47
19
1
29

117
67
147
59

8
1,965
1,116
480
377
502
365
68
5

4

233
34
1,185
93

1
4,463
77
82
122
89
79
16
4

4

23
12
44
13

1
566
618
1,314
780
615
398
26
7

3

326
43
391
34


4,555
24
106
138
55
38
5
7

3

14
12
13
4


419
165
1,296
801
174
103
12
2

3

307
1
219



3,083
1
51
62
3
4
1
2

1

2
1
2



130
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
874
1,468
77
964
507
972
19

17

208
415
594
161

2
6,278
38
27
2
27
34
122




51
58
41
21

1
422
8
8
1
3
6
26




17
39
9
9

1
127
74
5
10
340
60
226
1

3

47
129
134
14

1
1,044
11
4
5
36
11
48
1

3

12
60
22
7

1
221
123
31
11
176
95
222
6

8

33
81
107
48


941
16
4
3
22
16
53
4

3

5
18
12
8


164
406
225
32
267
156
337
7

1

31
106
244
48


1,860
32
15
7
32
13
57
3

1

4
21
25
7


217
233
1,180
22
154
162
65
5

5

46
41
68
30


2,011
9
33
5
16
8
5
2

1

1
4
7
2


93
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.29.a. Endothall - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
3,104
2,522
4,662
4,618
2,829
1,051
35
2
10
0
2,997
546
4,386
680
0
52
27,494
255
358
1,989
1,609
1,272
723
5
1
5

1,454
354
1,790
351

43
10,209
57
252
1,379
506
891
169
5
1
4

480
298
641
135

41
4,859
967
205
713
1,734
695
217
19
1
3

645
114
844
187

8
6,352
154
100
442
379
377
47
19
1
3

114
68
143
58

8
1,913
1,105
303
375
495
366
71
5

1

244
35
1,147
104

1
4,252
77
62
122
88
79
16
4

1

22
12
45
13

1
542
596
799
792
609
393
28
4



334
42
360
38


3,995
24
92
138
55
38
5
4



16
12
12
4


400
181
857
793
171
103
12
2

1

320
1
245



2,686
1
42
62
3
4
1
2

1

2
1
2



121
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
797
476
77
955
508
987
20
0
5
0
108
405
594
178
0
2
5,112
38
25
2
29
33
115




19
57
41
24

1
384
8
8
1
3
6
26




6
39
9
9

1
116
68
4
10
332
60
227
1



25
127
111
18

1
984
11
3
5
36
11
48
1



7
59
21
7

1
210
117
28
10
178
91
231
6

2

12
78
99
52


904
16
5
3
22
16
53
4

2

2
18
12
8


161
354
67
32
264
156
348
9

1

8
103
282
54


1,678
32
11
7
32
13
57
6

1

2
21
26
7


215
220
352
23
152
168
66
4

2

44
40
61
30


1,162
9
27
5
16
8
5
2

1

1
4
7
2


87
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.30.a. Endrin - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
3,103
9,607
4,685
5,285
2,838
1,462
2,845
1,609
1,974
50
4,131
632
6,410
902
4,044
963
50,540
256
863
1,996
1,737
1,271
974
2,139
1,063
963
11
1,961
418
2,992
436
1,901
781
19,762
57
546
1,380
505
891
175
1,912
646
453
10
526
342
677
148
1,182
424
9,874
970
1,511
717
2,087
695
327
571
249
639
4
815
123
1,353
202
963
151
11,377
154
305
443
378
377
47
419
77
180
4
123
69
148
60
429
58
3,271
1,111
1,460
386
558
368
110
102
127
145
10
359
40
1,351
148
750
31
7,056
77
148
122
89
79
16
57
11
23
8
23
12
44
14
145
8
876
601
3,007
775
695
400
33
24
170
213
24
609
49
447
116
378

7,541
24
157
139
55
38
5
12
2
9
8
17
12
12
4
54

548
165
2,766
811
208
104
18
9

14
1
387
2
267

52

4,804
1
63
62
3
4
1
3

1
1
2
1
2

6

150
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
931
3,674
77
2,142
545
1,595
181
248
170
13
156
598
745
179
3,944
362
15,560
50
41
2
72
36
209
5
35
5

26
119
60
25
642
68
1,395
8
16
1
3
6
32
4
19
2

11
51
9
9
91
34
296
76
88
10
802
61
362
35
77
21
2
33
182
174
18
885
126
2,952
11
28
5
36
11
48
17
18
3
1
8
61
21
7
122
31
428
140
132
10
412
95
414
51
60
22
5
32
100
133
53
802
59
2,520
16
24
3
22
16
53
14
9
3
3
2
18
12
8
71
8
282
398
695
32
609
162
528
68
64
23
4
17
143
300
53
949
101
4,146
32
30
7
32
13
57
23
3
1
3
2
21
25
7
66
6
328
267
2,718
23
247
191
82
22
12
99
2
48
54
78
30
666
8
4,547
9
56
5
16
8
5
7
2
1
2
1
4
7
2
30
1
156
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.31.a. Ethylbenzene - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
5,118
38,590
18,552
23,591
3,785
1,154
4,166
3,321
4,767
10,057
5,238
656
8,328
683
23,193
3,682
154,881
406
4,004
8,965
9,500
1,956
786
2,834
2,339
2,604
4,586
2,734
456
4,016
449
10,415
2,954
59,004
56
2,168
1,975
657
871
173
1,933
678
592
1,279
556
333
763
278
2,806
543
15,661
1,622
4,345
2,948
8,583
974
246
915
537
1,357
1,737
955
126
1,811
188
6,853
646
33,843
152
488
549
435
371
47
429
78
183
255
130
67
154
82
1,235
62
4,717
1,602
4,600
1,149
2,815
402
80
317
173
376
1,063
360
31
1,544
27
3,760
82
18,381
76
158
126
109
79
16
58
11
24
71
24
12
45
15
328
8
1,160
1,189
11,328
2,188
2,275
387
28
92
272
405
2,050
703
41
633
19
1,835

23,445
24
162
141
60
38
5
14
2
9
65
17
12
14
4
95

662
299
14,313
3,302
418
66
14
8

25
621
486
2
324

330

20,208
1
66
62
3
4
1
3

1
4
2
1
2

12

162
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,300
11,894
135
2,799
526
1,151
512
385
154
671
209
448
1,094
70
6,182
768
29,298
146
79
6
58
36
129
34
80
13
6
39
80
55
10
1,031
160
1,962
8
27
1
3
6
27
6
21
3
1
10
44
10
8
117
36
328
167
188
29
917
82
256
102
130
27
20
40
146
206
9
1,347
317
3,983
11
38
5
37
11
48
19
18
3
4
8
58
22
8
124
33
447
283
409
19
616
110
255
117
84
26
36
53
71
162
13
1,200
76
3,530
16
25
3
26
16
53
14
9
3
5
2
18
14
7
72
8
291
849
1,878
43
765
148
441
235
60
25
147
18
115
533
11
1,407
177
6,852
32
32
7
33
13
57
23
3
1
11
2
21
27
6
66
6
340
855
9,340
38
443
150
70
24
31
63
462
59
36
138
27
1,197
38
12,971
9
56
5
18
8
5
6
2
1
12
1
4
7
2
30
1
167
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.32.a. Ethylene Dibromide - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
3,165
22,144
4,820
28,721
2,822
1,900
4,183
991
5,977
9,291
4,897
604
9,706
1,352
0
1,007
101,580
270
1,385
2,034
11,290
1,262
1,313
2,847
656
2,985
4,182
2,358
397
3,728
798

810
36,315
57
637
1,392
665
892
171
1,934
535
595
1,202
544
326
757
283

443
10,433
990
2,375
717
10,580
699
392
924
169
1,923
1,582
931
121
2,308
381

162
24,254
154
289
443
435
377
47
430
71
184
243
127
68
154
82

59
3,163
1,143
2,331
409
3,315
362
142
310
77
530
997
392
34
2,364
126

35
12,567
77
132
121
109
79
16
58
11
24
71
24
12
46
16

8
804
597
7,085
845
2,940
396
39
93
89
509
1,971
816
50
822
47


16,299
24
142
139
60
38
5
14
2
9
64
17
12
14
4


544
165
8,968
815
596
103
14
9

30
559
400
2
484



12,145
1
58
62
3
4
1
3

1
4
2
1
2



142
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
834
8,654
78
3,938
508
1,640
515
153
218
567
199
433
1,508
250
0
252
19,747
58
37
2
97
41
200
29
20
15
5
29
69
74
36

32
744
8
10
1
3
6
26
6
19
3
1
10
43
10
9

19
174
78
37
11
1,351
59
391
103
49
34
16
37
131
301
27

87
2,712
11
17
5
37
11
48
19
17
3
3
7
59
22
8

27
294
124
117
10
827
94
444
118
49
33
36
35
77
227
65

31
2,287
16
12
3
26
16
53
14
9
3
5
2
18
14
8

8
207
354
1,477
32
1,112
157
513
237
27
36
124
16
112
733
65

101
5,096
32
24
7
33
13
57
23
3
1
11
2
21
26
7

6
266
220
6,986
23
551
157
92
28
8
100
386
82
44
173
57

1
8,908
9
49
5
18
8
5
7
2
1
12
1
4
7
2

1
131
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.33.a. Fluoride - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
1,487
22,678
5,595
224
2,863
1,143
14,479
1,494
4,296
4,340
2,226
1,820
3,588
215
6,549
1,453
74,450
152
1,900
2,190
67
1,511
776
8,310
1,076
716
2,057
1,160
1,424
2,148
188
3,558
1,177
28,410
56
862
1,259
53
883
215
2,130
644
247
1,046
481
1,030
718
181
3,189
528
13,522
540
3,509
976
91
820
248
4,677
274
2,694
784
458
254
700
25
2,127
229
18,406
154
376
395
53
372
48
443
78
162
244
113
110
148
20
1,181
63
3,960
484
3,887
454
26
251
96
1,174
60
599
495
195
71
476
2
569
47
8,886
77
157
96
15
80
16
62
11
23
71
24
19
43
2
300
8
1,004
259
7,186
791
26
252
22
263
84
240
817
270
69
170

230

10,679
24
162
115
7
38
5
16
2
9
65
17
13
14

87

574
52
6,196
1,184
14
29
1
55

47
187
143
2
94

65

8,069
1
66
52
2
4
1
3

1
4
2
1
2

11

150
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
853
10,535
288
70
348
935
725
527
246
535
196
974
353
3
1,502
522
18,612
57
126
6
2
28
117
47
58

4
53
239
33
3
287
140
1,200
8
38
1
2
6
38
8
22

1
17
72
9
3
106
44
375
83
355
23
30
54
256
146
200
35
23
49
327
83

398
234
2,296
11
51
5
30
11
50
23
18
2
4
11
63
21

123
33
456
152
659
32
13
86
305
145
100
99
49
27
135
64

289
56
2,211
16
30
2
13
16
53
21
9
3
5
4
18
12

71
8
281
359
1,582
167
17
94
234
299
129
58
139
49
212
129

282
80
3,830
32
32
5
16
13
56
31
3
1
11
4
22
24

65
6
321
202
7,813
60
8
86
23
88
40
54
320
18
61
44

246
12
9,075
9
63
3
6
8
5
8
2
1
12
1
4
7

30
1
160
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.34.a. Glyphosate - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
3,087
5,096
4,622
1,705
1,767
1,022
12
1


4,092
553
5,120
748

52
27,877
255
291
1,981
466
1,159
706
2
1


1,983
356
2,238
386

43
9,867
57
188
1,379
144
827
169
2
1


528
299
673
145

41
4,453
966
604
705
647
345
209
7



822
116
1,204
170

8
5,803
154
162
443
203
206
47
6



125
68
148
60

8
1,630
1,105
531
375
129
101
68
2



336
36
1,118
102

1
3,904
77
91
122
37
26
16
2



23
12
43
14

1
464
596
1,719
778
300
93
27




565
44
358
90


4,570
24
132
138
29
18
5




17
12
13
4


392
165
1,951
783
163
69
12
1



386
1
202



3,733
1
55
62
3
2
1
1



2
1
2



130
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
796
2,055
77
661
103
990
18



237
417
562
162

2
6,080
38
31
2
16
1
123




55
60
43
21

1
391
8
11
1
3
1
26




17
41
9
9

1
127
67
14
10
212
2
226
8



60
128
126
15

1
869
11
6
5
36
1
48
2



12
59
21
7

1
209
117
43
10
137
8
225
4



43
80
101
48


816
16
7
3
22
4
53
1



5
17
12
8


148
354
264
32
196
33
348
4



32
107
229
48


1,647
32
15
7
32
8
57
1



4
21
25
7


209
220
1,703
23
100
59
68
2



47
42
63
30


2,357
9
44
5
15
6
5
2



1
4
7
2


100
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.35.a. Heptachlor - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
3,090
8,029
4,664
5,290
2,833
1,011
1,250
1,172
1,614

4,265
595
5,808
763
3,749
843
44,976
257
766
1,986
1,737
1,269
697
728
748
793

2,034
393
2,452
371
1,826
680
16,737
57
499
1,380
505
892
169
637
475
443

531
326
664
143
1,178
390
8,289
966
1,178
715
2,090
693
208
382
163
532

858
118
1,454
171
950
132
10,610
154
265
443
379
377
47
265
52
178

126
69
147
60
423
57
3,042
1,105
1,176
383
558
369
68
99
91
109

366
35
1,249
131
628
31
6,398
77
127
122
89
79
16
53
11
23

23
12
44
14
135
8
833
597
2,468
774
697
398
26
29
170
168

620
47
425
90
303

6,812
24
139
139
55
38
5
13
2
9

17
12
14
4
54

525
165
2,441
806
208
104
12
12

12

387
2
228

42

4,419
1
59
62
3
4
1
4

1

2
1
2

6

146
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
800
2,893
79
2,147
547
950
167
184
121

249
423
667
161
2,833
292
12,513
38
30
2
72
36
123
5
19
5

55
67
56
21
544
56
1,129
8
9
1
3
6
27
4
12
2

17
43
9
9
90
33
273
67
40
10
802
61
223
33
64
19

60
131
174
14
726
105
2,529
11
11
5
36
11
48
16
17
3

12
59
21
7
121
29
407
117
83
10
413
98
223
53
36
17

44
80
120
48
498
47
1,887
16
9
3
22
16
53
15
9
3

5
18
12
8
70
8
267
354
520
34
611
164
319
57
58
19

39
104
246
48
616
77
3,266
32
23
7
32
13
57
19
3
1

4
21
24
7
65
6
314
224
2,220
23
249
188
62
19
7
61

51
41
71
30
449
7
3,702
9
52
5
16
8
5
6
2
1

1
4
7
2
30
1
149
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.36.a. Heptachlor Epoxide - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
3,098
7,663
4,648
5,291
2,833
1,544
1,249
966
1,614

4,265
595
5,805
763
3,749
844
44,927
255
768
1,986
1,737
1,269
1,075
728
602
793

2,034
394
2,451
371
1,826
681
16,970
57
504
1,380
505
892
169
637
380
443

531
327
663
143
1,178
390
8,199
966
1,103
713
2,092
693
316
381
136
532

858
118
1,452
171
950
132
10,613
154
262
443
379
377
47
265
43
178

126
69
147
60
423
57
3,030
1,110
1,125
380
558
369
103
99
74
109

366
35
1,249
131
628
31
6,367
77
126
122
89
79
16
53
10
23

23
12
44
14
135
8
831
602
9 347
Z,J4/
772
696
398
38
29
154
168

620
46
425
90
303

6,688
24
138
139
55
38
5
13
2
9

17
12
14
4
54

524
165
2,320
797
208
104
12
12

12

387
2
228

42

4,289
1
58
62
3
4
1
4

1

2
1
2

6

145
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
800
2,841
77
2,147
543
1,337
167
146
121

250
423
666
161
2,833
292
12,804
38
30
2
72
36
169
5
11
5

56
67
56
21
544
56
1,168
8
9
1
3
6
27
4
8
2

17
43
9
9
90
33
269
67
36
10
802
61
344
33
49
19

60
131
174
14
726
105
2,631
11
10
5
36
11
48
16
15
3

12
59
21
7
121
29
404
117
78
10
413
94
345
53
31
17

44
80
120
48
498
47
1,995
16
10
3
22
16
53
15
9
3

5
18
12
8
70
8
268
354
510
32
611
164
412
57
50
19

39
104
246
48
616
77
3,339
32
23
7
32
13
57
19
3
1

4
21
24
7
65
6
314
224
2,187
23
249
188
67
19
5
61

51
41
70
30
449
7
3,671
9
52
5
16
8
5
6
2
1

1
4
7
2
30
1
149
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.37.a. Hexachlorobenzene - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
3,087
4,180
4,634
5,296
2,851
1,010
1,250
1,563
1,614

4,265
592
5,836
761
3,749
761
41,449
255
434
1,980
1,738
1,275
697
728
1,026
793

2,034
391
2,466
371
1,826
613
16,627
57
283
1,380
505
892
169
637
624
443

531
323
664
143
1,178
367
8,196
966
495
711
2,094
699
207
382
249
532

858
119
1,468
169
950
120
10,019
154
169
443
380
377
47
265
77
178

126
69
147
60
423
54
2,969
1,105
637
379
560
369
68
99
118
109

366
35
1,249
131
628
28
5,881
77
99
122
89
79
16
53
11
23

23
12
44
14
135
8
805
596
1,276
770
696
403
26
29
170
168

620
46
425
90
303

5,618
24
127
138
55
38
5
13
2
9

17
12
14
4
54

512
165
1,338
794
208
105
12
12

12

387
1
228

42

3,304
1
56
62
3
4
1
4

1

2
1
2

6

143
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
799
1,899
77
2,093
547
952
167
243
121

250
424
665
167
2,833
245
11,482
38
28
2
71
36
122
5
33
5

56
68
56
21
544
37
1,122
8
8
1
3
6
26
4
18
2

17
44
9
9
90
21
266
67
18
10
782
60
222
33
77
19

60
131
174
14
726
91
2,484
11
7
5
36
11
48
16
18
3

12
59
21
7
121
27
402
117
40
10
406
96
223
53
59
17

44
81
118
48
498
40
1,850
16
5
3
22
16
53
15
9
3

5
18
12
8
70
8
263
355
279
32
589
164
322
57
62
19

39
103
246
48
616
71
3,002
32
21
7
32
13
57
19
3
1

4
21
24
7
65
6
312
222
1,534
23
245
191
63
19
12
61

51
41
71
36
449
6
3,024
9
46
5
16
8
5
6
2
1

1
4
7
2
30
1
143
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.3S.a. Hexachlorocyclopentadiene - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Ca
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
3,087
3,537
4,663
5,247
2,832
1,301
1,250
1,611
1,614

4,265
585
5,734
761
3,857
765
41,109
255
365
1,992
1,741
1,265
918
728
1,063
793

2,026
385
2,430
371
1,848
617
16,797
57
233
1,379
505
892
169
637
647
443

531
319
656
143
1,180
368
8,159
966
384
718
2,058
692
256
382
251
532

860
119
1,451
169
991
120
9,949
154
140
444
380
377
47
265
77
178

126
68
147
60
423
54
2,940
1,105
495
384
555
368
80
99
127
109

369
33
1,242
131
682
28
5,807
77
85
122
89
79
16
53
11
23

23
12
44
14
136
8
792
596
1,001
772
688
402
35
29
170
168

626
47
391
90
294

5,309
24
120
138
55
38
5
13
2
9

17
12
13
4
52

502
165
1,292
797
205
105
12
12

12

384
1
220

42

3,247
1
56
62
3
4
1
4

1

2
1
2

6

143
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
799
1,858
79
1,853
570
1,136
167
261
121

252
424
684
161
2,888
252
11,505
38
28
2
64
42
146
5
35
5

54
68
49
21
549
40
1,146
8
8
1
3
6
26
4
19
2

17
44
7
9
91
22
267
67
5
10
707
60
279
33
83
19

60
132
173
14
737
94
9 473
^^ i j
11
4
5
36
11
48
16
18
3

12
59
21
7
122
29
402
117
37
10
339
110
262
53
60
17

44
80
117
48
500
40
1,834
16
5
3
22
16
53
15
9
3

5
18
12
8
69
8
262
355
284
34
515
165
383
57
71
19

44
103
274
48
634
71
3,057
32
21
7
32
13
57
19
3
1

4
21
25
7
66
6
314
222
1,504
23
228
193
66
19
12
61

50
41
71
30
468
7
2,995
9
44
5
16
8
5
6
2
1

1
4
7
2
30
1
141
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.39.a. Lindane - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
3,117
9,771
4,686
5,286
2,833
1,491
2,844
1,609
1,974
50
4,131
638
2,740
902
4,044
962
47,078
261
887
1,994
1,737
1,265
997
2,138
1,064
963
11
1,961
420
1,158
436
1,901
781
17,974
57
561
1,380
505
891
175
1,912
647
453
10
526
344
574
148
1,182
425
9,790
976
1,519
717
2,087
694
333
571
248
639
4
815
125
370
202
963
150
10,413
154
305
443
378
377
47
419
77
180
4
123
70
121
60
429
58
3,245
1,114
1,468
386
558
372
110
102
127
145
10
359
41
731
148
750
31
6,452
77
147
122
89
79
16
57
11
23
8
23
12
44
14
145
8
875
601
3,042
111
696
398
33
24
170
213
24
609
50
260
116
378

7,391
24
157
139
55
38
5
12
2
9
8
17
12
12
4
54

548
165
2,855
812
208
104
18
9

14
1
387
2
221

52

4,848
1
63
62
3
4
1
3

1
1
2
1
2

6

150
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
916
3,759
77
2,146
529
1,616
181
246
170
13
156
597
416
179
3,944
360
15,305
46
41
2
72
36
213
5
35
5

26
119
24
25
642
68
1,359
8
16
1
3
6
32
4
19
2

11
51
9
9
91
34
296
76
89
10
802
61
368
35
76
21
2
33
181
71
18
885
126
2,854
11
28
5
36
11
48
17
18
3
1
8
61
21
7
122
31
428
133
131
10
413
94
418
51
59
22
5
32
99
86
53
802
58
2,466
16
24
3
22
16
53
14
9
3
3
2
18
12
8
71
8
282
394
693
32
611
163
536
68
64
23
4
17
144
187
53
949
100
4,038
32
30
7
32
13
57
23
3
1
3
2
21
25
7
66
6
328
267
2,805
23
248
175
81
22
12
99
2
48
54
48
30
666
8
4,588
9
56
5
16
8
5
7
2
1
2
1
4
7
2
30
1
156
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.40.a. Mercury - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
1,508
17,677
5,110
168
2,986
930
3,089
1,397
154
3,597
1,893
1,724
3,332
272
5,400
1,480
50,717
153
1,806
2,138
54
1,586
625
2,243
1,031
14
1,718
1,020
1,400
1,982
194
2,551
1,192
19,707
56
872
1,256
52
899
202
1,762
640
13
1,044
492
1,044
681
186
2,335
528
12,062
558
2,930
944
69
856
210
625
222
41
638
369
230
674
61
2,013
238
10,678
154
377
396
53
376
47
329
78
18
245
119
111
146
50
1,126
62
3,687
485
2,828
399
17
262
71
157
59
54
392
132
52
448
10
547
50
5,963
77
157
95
15
81
16
39
11
14
72
23
18
43
9
299
9
978
261
5,346
714
15
248
19
39
85
43
705
225
40
147
7
223

8,117
24
161
115
7
38
5
11
2
8
65
17
13
12
4
85

567
51
4,767
915
13
34
5
25

2
144
147
2
81

66

6,252
1
66
53
2
4
1
3

1
4
2
1
2

11

151
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
836
7,159
91
69
373
1,149
148
261
23
445
159
931
412
14
1,451
526
14,047
57
129
6
2
27
138
5
64

4
47
231
25
4
260
140
1,139
8
37
1
2
6
36
2
22

1
18
72
5
4
100
44
358
82
344
24
30
58
300
27
95

17
40
322
85
1
386
232
2,043
11
51
5
30
11
48
14
18

4
12
63
19
1
124
33
444
147
304
12
13
85
313
23
42
4
34
28
130
91
4
290
58
1,578
16
31
2
13
16
53
9
9
2
5
5
18
12
4
70
8
273
358
1,361
29
17
99
349
72
48
5
116
26
182
158
1
263
84
3,168
32
32
5
16
13
57
24
3
1
11
4
22
24
1
64
6
315
192
5,021
20
7
104
49
21
12
14
274
18
66
53
4
252
12
6,119
9
63
3
6
8
5
7
2
1
12
1
4
7
1
30
1
160
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.41.a. Methoxychlor - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
3,098
9,284
4,687
5,288
2,847
1,490
2,845
1,614
1,974
50
4,130
636
6,699
902
4,044
960
50,548
256
710
1,996
1,737
1,277
997
2,139
1,066
963
11
1,961
420
3,018
436
1,901
779
19,667
57
438
1,381
505
891
175
1,912
647
453
10
526
343
677
148
1,182
424
9,769
969
1,468
717
2,087
695
332
571
251
639
4
815
125
1,560
202
963
150
11,548
154
291
443
378
377
47
419
77
180
4
123
70
148
60
429
58
3,258
1,107
1,448
387
558
371
110
102
127
145
10
358
40
1,387
148
750
31
7,079
77
146
122
89
79
16
57
11
23
8
23
12
44
14
145
8
874
601
2,928
775
698
400
33
24
170
213
24
609
49
466
116
378

7,484
24
156
139
55
38
5
12
2
9
8
17
12
13
4
54

548
165
2,730
812
208
104
18
9

14
1
387
2
268

52

4,770
1
63
62
3
4
1
3

1
1
2
1
2

6

150
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
912
3,584
77
2,147
547
1,617
181
246
170
13
156
598
766
179
3,944
361
15,498
46
41
2
72
36
213
5
34
5

26
119
60
25
642
68
1,394
8
16
1
3
6
32
4
19
2

11
52
9
9
91
34
297
76
88
10
802
61
368
35
76
21
2
33
180
181
18
885
126
2,962
11
28
5
36
11
48
17
18
3
1
8
61
21
7
122
31
428
133
130
10
413
95
417
51
60
22
5
32
101
137
53
802
58
2,519
16
24
3
22
16
53
14
9
3
3
2
18
12
8
71
8
282
392
681
32
611
164
536
68
64
23
4
17
144
308
53
949
101
4,147
32
29
7
32
13
57
23
3
1
3
2
21
25
7
66
6
327
265
2,644
23
249
191
83
22
12
99
2
48
54
80
30
666
8
4,476
9
56
5
16
8
5
7
2
1
2
1
4
7
2
30
1
156
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.42.a. Monochlorobenzene - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
5,119
0
18,497
23,601
3,754
1,151
4,155
3,332
4,767
10,737
5,249
649
8,328
683
23,193
3,669
116,884
406

8,927
9,500
1,933
790
2,833
2,339
2,604
4,756
2,743
449
4,016
449
10,415
2,946
55,106
56

1,972
657
871
173
1,933
678
592
1,293
557
329
763
278
2,806
543
13,501
1,625

2,932
8,584
968
239
915
537
1,357
1,859
957
125
1,811
188
6,853
641
29,591
152

550
435
371
47
429
78
183
260
130
66
154
82
1,235
62
4,234
1,600

1,152
2,813
402
80
308
184
376
1,184
360
31
1,544
27
3,760
82
13,903
76

126
109
79
16
58
11
24
73
24
12
45
15
328
8
1,004
1,189

2,178
2,281
385
28
91
272
405
2,295
703
42
633
19
1,835

12,356
24

141
60
38
5
14
2
9
65
17
12
14
4
95

500
299

3,308
423
66
14
8

25
643
486
2
324

330

5,928
1

62
3
4
1
3

1
4
2
1
2

12

96
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,296
0
135
2,808
526
1,215
506
391
154
782
210
447
1,091
70
6,183
763
17,577
145

6
58
36
138
29
80
13
6
41
80
55
10
1,031
160
1,888
8

1
3
6
27
6
21
3
1
10
44
10
8
117
36
301
166

29
920
82
256
102
131
27
21
40
145
204
9
1,348
316
3,796
11

5
37
11
48
19
18
3
4
8
58
22
8
124
33
409
283

19
618
110
251
116
89
26
44
53
71
161
13
1,200
76
3,130
16

3
26
16
53
14
9
3
5
2
18
14
7
72
8
266
846

43
768
148
485
235
60
25
170
18
115
533
11
1,407
175
5,039
32

7
33
13
57
23
3
1
11
2
21
27
6
66
6
308
856

38
444
150
85
24
31
63
541
58
36
138
27
1,197
36
3,724
9

5
18
8
5
6
2
1
12
1
4
7
2
30
1
111
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.43.a. Oxamyl - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
3,087
4,231
4,666
4,661
2,832
1,002
1,264
382
585

4,157
586
5,787
760
3,467
910
38,377
255
588
2,005
1,619
1,271
691
744
193
129

1,998
392
2,262
384
1,730
719
14,980
57
429
1,381
506
889
169
645
152
68

529
327
674
151
1,149
412
7,538
966
541
712
1,750
698
206
384
52
369

828
118
1,549
184
907
156
9,420
154
175
443
380
377
47
270
21
106

126
69
148
65
407
57
2,845
1,105
600
378
505
365
68
95
18
34

351
33
1,309
102
501
35
5,499
77
96
122
89
79
16
53
6
12

23
12
44
14
122
8
773
596
1,329
771
613
395
25
30
119
51

593
42
430
90
289

5,373
24
126
139
55
38
5
12
2
5

17
12
14
4
54

507
165
1,173
800
174
103
12
11

2

387
1
237

40

3,105
1
50
62
3
4
1
4

1

2
1
2

4

135
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
796
1,668
79
988
506
971
184
63
43

237
423
662
163
2 232
272
9,287
38
30
2
27
35
121
5
7
2

55
68
46
22
354
38
850
8
9
1
3
6
26
4
5
2

17
44
9
9
88
21
252
67
6
10
357
60
223
40
13
3

57
130
165
14
609
102
1,856
11
5
5
36
11
48
16
7
3

12
59
22
7
121
31
394
117
33
10
179
91
221
57
19
3

43
80
120
49
421
43
1,486
16
7
3
22
16
53
15
9
3

5
18
12
8
70
8
265
354
257
34
270
156
341
63
21
9

37
104
262
48
490
83
2,529
32
20
7
32
13
57
19
3
1

4
21
25
7
65
6
312
220
1,342
23
155
164
65
19
3
26

45
41
69
30
358
6
2,566
9
40
5
16
8
5
6
1
1

1
4
7
2
30
1
136
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.44.a. PCBs - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
3,096
3,446
4,655
4,821
430
11
0
658
0
596
0
561
0
905
4,044
910
24,133
255
335
1,994
1,663
139
11

386

166

378

439
1,901
725
8,392
57
241
1,380
506
126
4

275

132

314

147
1,182
410
4,774
966
490
714
1,831
92


83

108

109

202
963
151
5,709
154
147
443
379
79


33

75

69

60
429
58
1,926
1,107
506
379
511
54


54

112

33

148
750
34
3,688
77
78
122
89
31


11

42

12

14
145
8
629
603
1,140
772
638
99


135

197

39

116
378

4,117
24
117
139
55
19


2

51

11

4
54

476
165
975
796
178
46




13

2


52

2,227
1
44
62
3
2




2

1


6

121
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
796
1,445
77
1,432
449
19
0
104
0
71
0
416
0
179
3,944
271
9,203
38
21
2
40
29
1

8



62

25
642
34
902
8
8
1
3
6
1

6



39

9
91
20
192
67
20
10
507
55
7

32

i

132

18
885
95
1,829
11
8
5
36
11
3

12

1

59

7
122
27
302
117
35
10
288
85
1

23

8

78

53
802
47
1,547
16
5
3
22
16
1

8

5

18

8
71
8
181
354
324
32
401
136


36

25

104

53
949
88
2,502
32
20
7
32
13


3

7

21

7
66
6
214
220
1,045
23
196
144
10

5

37

40

30
666
7
2,423
9
46
5
16
8
2

2

10

4

2
30
1
135
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.45.a. Pentachlorophenol - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
3,113
4,590
4,622
4,752
2,840
1,018
2,802
638
632
0
4,064
586
5,146
867
4,183
1,005
40,858
257
603
1,981
1,632
1,265
704
2,099
339
300

1,925
390
2,055
434
2,035
800
16,819
57
397
1,377
507
892
169
1,897
228
212

526
323
666
150
1,178
440
9,019
977
566
704
1,806
695
209
574
100
165

806
117
1,046
203
984
171
9,123
154
199
442
380
377
47
411
30
59

123
68
146
60
433
58
2,987
1,106
654
383
511
373
68
97
37
100

366
34
1,333
114
732
34
5,942
77
111
122
89
79
16
57
9
20

23
12
44
14
143
8
824
608
1,389
778
627
403
25
24
162
66

599
43
429
116
375

5,644
24
130
138
55
38
5
12
2
8

17
12
12
4
55

512
165
1,378
776
176
104
12
8

1

368
2
283

57

3,330
1
60
62
3
4
1
3

1

2
1
2

6

146
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
826
1,913
82
1,412
535
945
175
70
34
0
146
427
654
183
4,772
312
12,486
45
29
6
47
34
122
6
7


21
67
41
27
850
38
1,340
8
9
1
3
6
26
5
5


6
43
9
9
90
21
241
67
17
10
547
61
224
34
16


29
132
124
18
1,163
108
2,550
11
7
5
36
11
48
17
9


7
59
21
7
122
29
389
124
40
10
287
94
227
49
19
4

32
84
116
53
893
50
2,082
16
6
3
22
16
53
14
8
2

2
18
12
8
71
8
259
370
310
33
340
166
315
66
24
6

16
103
299
55
1,090
110
3,303
32
20
7
32
13
57
23
3
1

2
21
26
7
66
6
316
220
1,517
23
191
180
57
20
4
24

48
41
74
30
776
6
3,211
9
47
5
16
8
5
7
2
1

1
4
7
2
30
1
145
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.46.a. Picloram - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
3,105
4,018
4,614
4,748
2,839
1,022
1,242
435
317

4,193
584
4,618
721
3,472
893
36,821
255
464
1,976
1,631
1,272
708
721
223
51

1,993
388
1,812
364
1,725
702
14,285
57
318
1,381
507
892
169
634
169
33

532
321
655
146
1,149
407
7,370
969
513
703
1,804
694
209
388
75
132

849
118
997
169
903
157
8,680
154
169
442
380
377
47
262
23
50

126
68
145
60
406
56
2,765
1,106
536
384
507
372
68
93
22
75

373
34
1,188
98
518
34
5,408
77
98
122
89
79
16
53
8
18

23
12
44
13
120
8
780
610
1,304
780
626
398
25
29
115
58

610
43
376
90
286

5,350
24
118
139
55
38
5
13
2
8

17
12
13
4
53

501
165
1,201
771
180
103
12
11

1

368
1
245

40

3,098
1
53
62
3
4
1
4

1

2
1
2

5

139
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
806
1,568
80
1,412
508
949
161
58
31

250
432
562
162
2,257
266
9,502
41
29
3
47
34
123
5
7


56
67
35
22
364
35
868
8
9
1
3
6
27
4
5


17
43
9
9
87
20
248
69
19
10
550
60
225
32
7


60
132
118
14
610
96
2,002
11
8
5
36
11
48
16
6


12
59
21
7
121
29
390
117
34
10
284
94
223
51
18
4

44
86
97
48
417
41
1,568
16
5
3
22
16
53
15
8
2

5
18
12
8
70
8
261
359
290
34
341
157
315
56
22
4

39
106
247
48
509
89
2,616
32
19
7
32
13
57
19
3
1

4
21
25
7
65
6
311
220
1,196
23
190
163
63
17
4
23

51
41
65
30
357
5
2,448
9
45
5
16
8
5
6
2
1

1
4
7
2
30
1
142
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.47.a. Selenium - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
1,514
18,069
5,097
161
2,984
946
0
1,403
162
3,552
1,854
1,728
3,636
366
5,385
1,259
48,116
154
1,800
2,127
53
1,585
630

1,036
17
1,684
1,002
1,399
2,172
256
2,544
1,024
17,483
56
869
1,256
51
899
202

643
16
1,039
485
1,046
681
244
2,329
493
10,309
554
2,950
939
62
856
218

231
43
638
357
232
669
81
2,017
197
10,044
154
377
396
52
376
47

78
19
245
118
111
146
61
1,131
62
3,373
490
2,870
397
17
261
74

59
56
392
132
50
522
22
538
38
5,918
77
157
95
15
81
16

11
14
72
23
18
43
13
296
8
939
264
5,572
715
15
248
19

77
43
696
217
45
189
7
221

8,328
24
161
115
7
38
5

2
8
65
17
13
11
4
86

556
52
4,877
919
14
34
5


3
142
146
2
84

65

6,343
1
66
52
2
4
1


1
4
2
1
2

11

147
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
839
7,166
91
67
373
1,152
0
260
26
450
78
938
499
35
1,447
441
13,862
58
131
6
2
27
138

64

4
20
231
39
9
260
86
1,075
8
37
1
2
6
36

22

1
12
72
9
9
100
30
345
82
343
24
30
58
304

95

18
20
323
99
7
381
208
1,992
11
51
5
30
11
48

18

4
9
63
20
7
123
33
433
146
304
12
13
85
317

42
5
34
14
131
110
8
291
52
1,564
16
31
2
13
16
53

9
3
5
2
18
12
7
71
8
266
361
1,356
29
16
99
348

47
6
116
9
188
190
6
272
87
3,130
32
33
5
16
13
57

3
1
11
3
22
25
5
66
6
298
192
5,032
20
6
104
45

12
15
278
15
65
61
5
243
8
6,101
9
63
3
6
8
5

2
1
12
1
4
7
2
30
1
154
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.48.a. Simazine - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
3,104
13,942
4,647
5,281
2,857
1,019
1,278
398
1,973

4,255
596
6,207
936
4,334
913
51,740
255
1,455
1,975
1,735
1,274
699
743
191
963

2,018
398
2,641
450
1,964
745
17,506
57
911
1,379
505
891
169
644
153
453

531
328
682
150
1,188
416
8,457
971
1,935
710
2,083
699
212
391
66
639

860
120
1,513
218
1,168
140
11,725
154
345
443
379
377
47
271
24
180

126
69
150
61
453
57
3,136
1,117
1,992
384
556
380
68
101
28
145

369
34
1,328
151
775
28
7,456
77
139
122
89
79
16
53
9
23

23
12
44
14
150
8
858
596
4,335
778
696
399
28
31
113
213

624
43
455
117
375

8,803
24
151
139
55
38
5
13
2
9

17
12
14
4
53

536
165
4,225
800
211
105
12
12

13

384
1
270

52

6,250
1
62
62
3
4
1
4

1

2
1
2

6

149
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
822
4,941
79
2,112
625
1,073
240
81
158

251
425
655
183
4,496
292
16,433
38
30
2
71
35
127
5
8
5

54
67
29
26
749
42
1,288
8
10
1
3
6
26
4
5
2

17
43
4
9
93
21
252
67
58
10
782
90
257
66
19
21

60
129
148
18
1,050
103
2,878
11
22
5
36
11
48
16
7
3

12
59
19
7
123
27
406
117
109
10
420
110
269
73
18
22

44
82
131
54
898
48
2,405
16
15
3
22
16
53
15
8
3

5
18
12
8
70
8
272
380
1,048
34
594
178
352
76
31
23

44
106
269
55
1,055
93
4,338
32
25
7
32
13
57
19
3
1

4
21
24
7
66
6
317
220
3,696
23
245
212
68
20
5
87

49
41
78
30
744
6
5,524
9
53
5
16
8
5
6
2
1

1
4
7
2
30
1
150
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.49.a. Styrene - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
5,119
31 222
18,430
23,503
3,795
1,146
4,171
3,331
4,766
10,044
5,248
646
8,328
683
23,193
3,676
147,301
406
1,564
8,914
9,484
1,965
786
2,836
2,338
2,603
4,580
2,742
447
4,016
449
10,415
2,950
56,495
56
661
1,972
657
874
173
1,933
678
591
1,279
557
328
763
278
2,806
543
14,149
1,622
3,382
2,937
8,552
974
238
925
537
1,357
1,736
957
125
1,811
188
6,853
644
32,838
152
353
549
435
371
47
429
78
183
255
130
66
154
82
1,235
62
4,581
1,601
3,851
1,138
2,796
405
80
310
184
376
1,060
360
31
1,544
27
3,760
82
17,605
76
150
126
109
79
16
58
11
24
71
24
12
45
15
328
8
1,152
1,189
10,066
2,139
2,254
385
28
92
272
405
2,046
703
41
633
19
1,835

22,107
24
161
141
60
38
5
14
2
9
65
17
12
14
4
95

661
301
12,359
3,302
417
66
14
8

25
622
486
2
324

330

18,256
1
65
62
3
4
1
3

1
4
2
1
2

12

161
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,295
9,948
135
2,798
528
1,151
511
391
154
671
209
450
1,091
70
6,183
764
27,349
145
70
6
58
37
131
30
80
13
6
40
80
55
10
1,031
160
1,952
8
26
1
3
6
27
6
21
3
1
10
44
10
8
117
36
327
166
171
29
915
82
256
102
131
27
20
40
145
204
9
1,348
316
3,961
11
36
5
37
11
48
19
18
3
4
8
58
22
8
124
33
445
283
335
19
615
110
251
116
89
26
36
53
74
161
13
1,200
76
3,457
16
24
3
26
16
53
14
9
3
5
2
18
14
7
72
8
290
846
1,491
43
766
149
443
239
60
25
147
18
115
533
11
1,407
176
6,469
32
31
7
33
13
57
23
3
1
11
2
21
27
6
66
6
339
855
7,881
38
444
150
70
24
31
63
462
58
36
138
27
1,197
36
11,510
9
56
5
18
8
5
6
2
1
12
1
4
7
2
30
1
167
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.SO.a. Tetrachloroethylene - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
5,120
49,815
18,663
23,690
3,859
1,146
2,013
3,335
3,855
11,150
5,537
699
7,817
495
19,146
2,958
159,298
406
4,112
8,952
9,512
1,961
786
886
2,340
2,131
4,765
2,848
483
3,659
346
8,566
2,342
54,095
56
2,176
1,974
657
872
173
666
678
572
1,294
563
337
745
230
2,744
523
14,260
1,622
4,779
2,941
8,601
985
238
656
537
1,071
1,914
1,016
135
1,753
126
5,874
548
32,796
152
490
550
436
371
47
279
78
181
259
134
69
154
64
1,229
61
4,554
1,601
5,311
1,145
2,814
425
80
321
186
320
1,236
377
31
1,457
20
3,000
68
18,392
76
158
126
109
80
16
56
11
24
73
24
12
45
12
325
8
1,155
1,192
16,278
2,290
2,324
390
28
137
272
325
2,421
808
48
630
3
1,458

28,604
24
162
141
60
38
5
14
2
9
65
17
12
15
3
96

663
299
19,335
3,335
439
98
14
13

8
814
488
2
318

248

25,411
1
66
62
3
4
1
4

1
4
2
1
2

12

163
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,343
19,944
136
2,813
526
1,179
437
391
95
788
347
459
963
55
4,777
667
35,920
145
82
6
58
36
138
20
80
13
6
88
85
49
5
916
136
1,863
8
27
1
3
6
27
4
21
3
1
20
44
10
5
116
36
332
166
206
30
919
82
256
95
131
12
21
70
151
198
5
1,179
274
3,795
11
38
5
37
11
48
17
18
2
4
12
58
22
4
123
33
443
283
426
19
617
110
251
120
89
17
44
65
71
148
10
842
66
3,178
16
26
3
26
16
53
15
9
3
5
5
18
14
5
71
8
293
854
3,490
43
770
148
462
181
60
19
176
61
115
443
8
983
155
7,968
32
32
7
33
13
57
19
3
1
11
4
21
25
4
65
6
333
895
15,740
38
449
150
72
21
31
34
541
63
37
125
27
857
36
19,116
9
56
5
18
8
5
5
2
1
12
1
4
7
2
30
1
166
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.Sl.a. Thallium - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
686
6,979
5,287
163
2,891
911
3,762
1,000
980
3,463
1,732
614
3,234
255
5,384
890
38,231
69
1,051
2,196
53
1,580
611
2,453
627
346
1,644
905
444
1,945
177
2,468
720
17,289
50
676
1,254
51
900
195
1,896
410
229
1,015
469
376
670
167
2,252
451
11,061
247
1,027
970
65
834
203
940
241
370
622
338
120
630
55
2,030
143
8,835
151
288
396
53
376
47
424
69
162
243
116
74
145
42
1,126
59
3,771
230
959
435
17
234
73
237
56
132
376
125
23
432
9
568
27
3,933
77
134
95
15
81
16
55
10
23
71
22
11
43
7
293
8
961
111
2,095
765
15
209
19
94
76
128
680
217
26
147
14
253

4,849
24
156
115
7
38
5
13
2
9
64
17
12
12
3
84

561
29
1,847
921
13
34
5
38

4
141
147
1
80

65

3,325
1
65
52
2
4
1
4

1
4
2
1
2

11

150
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
513
2,826
92
67
369
1,039
279
252
55
433
134
530
425
5
1,395
314
8,728
36
76
6
2
27
118
17
46

4
36
102
35
3
256
60
824
8
28
1
2
6
34
7
18

1
16
44
9
3
98
28
303
53
99
24
30
57
274
57
107
3
18
33
188
91

367
146
1,547
11
30
5
30
11
48
18
18
2
4
12
59
20

123
32
423
84
84
12
13
84
288
60
42
8
29
25
76
90
2
276
39
1,212
16
23
2
13
16
53
16
9
3
5
5
18
12
2
71
8
272
196
459
29
16
95
318
115
45
10
112
23
121
156

259
63
2,017
32
28
5
16
13
57
27
3
1
11
4
21
24

65
6
313
144
2,108
21
6
106
41
30
12
34
270
17
43
53

237
6
3,128
9
62
3
6
8
4
7
2
1
12
1
4
7

30
1
157
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.52.a. Toluene - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
5,130
38,611
18,637
23,627
3,869
1,164
4,181
3,322
4,766
10,067
5,242
663
8,323
683
23,193
3,681
155,159
406
4,011
9,008
9,499
2,032
796
2,833
2,340
2,603
4,588
2,736
463
4,015
449
10,415
2,953
59,147
56
2,167
1,973
657
882
173
1,933
678
591
1,279
556
336
763
278
2,806
543
15,671
1,627
4,348
2,973
8,587
977
246
921
537
1,357
1,738
954
126
1,811
188
6,853
646
33,889
152
488
550
435
373
47
429
78
183
255
130
66
154
82
1,235
62
4,719
1,607
4,580
1,146
2,827
404
80
324
173
376
1,062
360
31
1,544
27
3,760
82
18,383
77
158
126
109
79
16
58
11
24
71
24
12
45
15
328
8
1,161
1,190
11,329
2,199
2,290
389
28
94
272
405
2,055
706
41
629
19
1,835

23,481
24
162
141
60
38
5
14
2
9
65
17
12
14
4
95

662
300
14,343
3,311
424
67
14
9

25
624
486
2
324

330

20,259
1
66
62
3
4
1
3

1
4
2
1
2

12

162
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,304
11,697
135
2,811
527
1,238
508
385
154
671
208
451
1,092
70
6,183
765
29,199
145
79
6
58
37
145
29
80
13
6
39
80
55
10
1,031
160
1,973
8
27
1
3
6
27
6
21
3
1
10
44
10
8
117
36
328
168
187
29
917
82
266
103
130
27
20
40
149
204
9
1,348
317
3,996
11
38
5
37
11
48
19
18
3
4
8
58
22
8
124
33
447
283
409
19
621
110
273
116
84
26
36
53
71
161
13
1,200
76
3,551
16
25
3
26
16
53
14
9
3
5
2
18
14
7
72
8
291
849
1,713
43
770
148
478
236
60
25
147
18
115
534
11
1,407
176
6,730
32
32
7
33
13
57
23
3
1
11
2
21
27
6
66
6
340
859
9,309
38
445
150
76
24
31
63
462
58
36
138
27
1,197
36
12,949
9
57
5
18
8
5
6
2
1
12
1
4
7
2
30
1
168
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.53.a. Toxaphene - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States

9,581
4,724
4,822
2,821
1,494
1,250
1,613
260
50
4,265
631
4,797
766
3,555
887
41,516

926
2,008
1,664
1,261
1,000
728
1,065
124
11
2,034
420
1,946
376
1,752
696
16,011

594
1,380
506
891
175
637
648
79
10
531
344
674
142
1,146
392
8,149

1,530
719
1,836
693
333
382
249
91
4
859
124
1,084
169
901
153
9,127

319
443
380
377
47
265
77
51
4
126
70
150
60
399
58
2,826

1,449
389
507
369
110
99
128
24
10
366
39
1,148
131
575
38
5,382

147
122
89
79
16
53
11
12
8
23
12
44
14
127
8
765

2,975
793
637
394
33
29
171
19
24
620
46
402
90
286

6,519

157
139
55
38
5
13
2
4
8
17
12
13
4
52

519

2,701
815
178
104
18
12

2
1
386
2
217

41

4,477

63
62
3
4
1
4

1
1
2
1
2

5

149
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States

3,644
77
1,488
525
1,615
167
249
26
15
264
596
561
161
1,180
345
10,913

41
2
41
36
213
5
34

2
61
120
24
21
239
61
900

16
1
3
6
32
4
19

2
19
52
4
9
88
34
289

88
10
527
63
368
33
77
3
2
65
180
118
14
249
116
1,913

28
5
36
11
48
16
18
3
1
12
61
19
7
112
31
408

132
10
298
95
421
53
62
3
5
46
99
107
48
199
51
1,629

24
3
22
16
53
15
9
3
3
5
18
12
8
67
8
266

694
32
423
161
531
57
64
3
4
41
143
246
48
285
109
2,841

30
7
32
13
57
19
3
1
3
4
21
25
7
61
6
289

2,689
23
199
170
82
19
12
17
2
51
54
66
30
208
8
3,630

56
5
16
8
5
6
2
1
2
1
4
7
2
29
1
145
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.54.a. 2,4,5-TP - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
3,131
8,689
4,630
4,750
2,838
1,492
2,800
1,648
632
54
4,060
626
4,983
867
3,469
1,006
45,675
256
651
1,984
1,631
1,262
1,003
2,099
1,085
300
10
1,920
414
1,954
434
1,727
799
17,529
57
390
1,384
507
892
175
1,897
650
212
9
526
340
666
150
1,149
439
9,443
985
1,377
705
1,805
695
331
572
268
165
4
807
123
1,018
203
903
173
10,134
154
276
442
379
377
47
411
77
59
4
123
69
146
60
406
58
3,088
1,117
1,439
388
507
377
108
97
124
100
10
366
41
1,301
114
518
34
6,641
77
143
122
89
79
16
57
11
20
8
23
12
44
14
120
8
843
608
2,824
781
627
398
32
24
171
66
29
599
46
427
116
281

7,029
24
156
139
55
38
5
12
2
8
9
17
12
12
4
52

545
165
2,398
772
180
106
18
8

1
1
368
2
283

40

4,342
1
63
62
3
4
1
3

1
1
2
1
2

5

149
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
914
3,275
78
1,468
544
1,628
175
227
34
13
155
603
658
183
2,263
353
12,571
46
41
3
48
49
211
6
34


26
118
41
27
364
46
1,060
8
16
1
3
6
32
5
19


11
51
9
9
87
25
282
76
78
10
569
68
371
34
67

2
32
182
125
18
611
126
2,369
11
28
5
36
11
48
17
18

1
8
61
21
7
121
33
426
133
121
10
294
104
422
49
61
4
5
32
106
116
53
417
56
1,983
16
24
3
22
16
53
14
9
2
3
2
18
12
8
70
8
280
397
634
32
363
159
538
66
54
6
4
17
143
301
55
514
118
3,401
32
28
7
32
13
57
23
3
1
3
2
21
26
7
66
6
327
262
2,401
23
194
164
86
20
11
24
2
48
54
75
30
357
7
3,758
9
56
5
16
8
5
7
2
1
2
1
4
7
2
30
1
156
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.55.a. 1,2,4-Trichlorobenzene - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Catego
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
5,119
31,171
18,436
20,798
3,762
1,147
4,155
0
4,769
10,557
5,248
647
8,318
683
23,193
3,251
141,254
406
1,667
8,917
8,124
1,940
787
2,833

2,604
4,661
2,742
449
4,015
449
10,415
2,627
52,636
56
743
1,973
623
872
173
1,933

592
1,282
557
330
763
278
2,806
515
13,496
1,623
3,343
2,932
7,516
968
238
915

1,358
1,814
957
125
1,812
188
6,853
555
31,197
152
364
549
433
371
47
429

183
259
130
66
154
82
1,235
62
4,516
1,601
3,771
1,138
2,595
403
80
308

376
1,169
360
31
1,534
27
3,760
69
17,222
76
148
126
109
79
16
58

24
73
24
12
45
15
328
8
1,141
1,190
9,953
2,149
2,174
385
28
91

406
2,270
703
41
633
19
1,835

21,877
24
161
141
60
38
5
14

9
65
17
12
14
4
95

659
299
12,437
3,300
389
66
14
8

25
643
486
1
324

330

18,322
1
65
62
3
4
1
3

1
4
2
1
2

12

161
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,295
9,881
136
2,277
527
1,153
506
0
155
732
209
448
1,091
70
6,183
629
26,292
145
72
6
33
36
131
29

13
6
40
80
55
10
1,031
131
1,818
8
26
1
3
6
27
6

3
1
10
44
10
8
117
32
302
166
162
29
636
83
256
102

27
20
40
145
204
9
1,348
278
3,505
11
35
5
37
11
48
19

3
4
8
58
22
8
124
33
426
283
324
19
534
110
251
116

26
44
53
71
161
13
1,200
62
3,267
16
24
3
26
16
53
14

3
5
2
18
14
7
72
8
281
846
1,485
44
688
148
443
235

25
165
18
116
533
11
1,407
132
6,296
32
31
7
33
13
57
23

1
11
2
21
27
6
66
6
336
855
7,838
38
386
150
72
24

64
497
58
36
138
27
1,197
26
11,406
9
56
5
18
8
5
6

1
12
1
4
7
2
30
1
165
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.56.a. 1,1,1-Trichloroethane . Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Categor
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
5,148
39,796
18,576
23,732
3,862
1,589
4,169
3,334
4,769
10,982
5,250
1,919
8,828
683
23,193
3,678
159,508
406
4,079
8,928
9,521
1,975
1,059
2,835
2,340
2,604
4,819
2,742
1,501
4,116
449
10,415
2,951
60,740
56
2,177
1,973
659
880
180
1,933
678
592
1,296
557
933
767
278
2,806
543
16,308
1,634
4,398
2,938
8,602
979
363
919
538
1,358
1,895
957
286
2,014
188
6,853
645
34,567
152
488
549
435
372
48
429
78
183
261
130
110
154
82
1,235
62
4,768
1,614
4,667
1,145
2,837
408
135
314
184
376
1,239
360
62
1,660
27
3,760
82
18,870
76
158
126
109
79
16
58
11
24
73
24
17
45
15
328
8
1,167
1,194
11,287
2,245
2,312
400
28
93
272
406
2,388
703
68
674
19
1,835

23,924
24
162
141
60
38
5
14
2
9
65
17
13
14
4
95

663
300
15,365
3,320
460
100
4
8

25
641
488
2
364

330

21,407
1
66
62
3
4
1
3

1
4
2
1
2

12

162
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,313
13,356
136
2,816
528
1,704
507
391
155
764
210
925
1,147
70
6,183
763
31,968
146
80
6
58
36
176
29
80
13
6
40
231
59
10
1,031
160
2,161
8
27
1
3
6
30
6
21
3
1
10
53
10
8
117
36
340
167
189
30
919
82
406
103
131
27
21
40
358
210
9
1,348
316
4,356
11
38
5
37
11
47
19
18
3
4
8
61
22
8
124
33
449
285
416
19
622
110
411
116
89
26
45
53
107
163
13
1,200
76
3,751
16
26
3
26
16
53
14
9
3
5
2
18
14
7
72
8
292
849
1,990
43
770
148
662
235
60
25
161
18
182
563
11
1,407
175
7,299
32
32
7
33
13
54
23
3
1
11
2
22
27
6
66
6
338
866
10,681
38
447
152
49
24
31
64
531
59
47
152
27
1,197
36
14,401
9
56
5
18
8
4
6
2
1
12
1
4
7
2
30
1
166
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.57.a. 1,1,2-Trichloroethane - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Categor
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
5,117
38,672
18,523
23,525
3,755
1,144
1,967
3,334
3,857
10,069
5,503
647
7,799
495
19,196
2,930
146,533
406
4,044
8,921
9,486
1,934
786
884
2,340
2,131
4,586
2,841
449
3,665
346
8,566
2,342
53,727
56
2,172
1,972
657
871
173
666
678
572
1,280
563
330
747
230
2,744
523
14,234
1,623
4,350
2,929
8,567
968
238
630
538
1,072
1,746
1,012
125
1,753
126
5,878
520
32,075
152
489
549
436
371
47
279
78
181
255
133
66
154
64
1,230
61
4,545
1,600
4,630
1,130
2,797
402
80
308
184
320
1,065
377
31
1,440
20
3,000
68
17,452
76
158
126
109
79
16
56
11
24
71
24
12
45
12
325
8
1,152
1,189
10,882
2,238
2,259
385
26
134
272
326
2,051
786
41
623
3
1,504

22,719
24
162
141
60
38
5
14
2
9
65
17
12
15
3
97

664
299
14,766
3,305
416
66
14
11

8
621
487
1
318

248

20,560
1
66
62
3
4
1
4

1
4
2
1
2

12

163
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,296
11,945
125
2,798
526
1,154
437
391
64
670
344
455
957
54
4,606
551
27,373
145
80
6
58
36
131
20
80
13
6
88
80
43
5
838
104
1,733
8
27
1
3
6
27
4
21
3
1
20
44
8
5
102
27
307
166
189
22
915
82
256
95
131
12
20
69
149
198
4
1,149
228
3,685
11
38
4
37
11
48
17
18
2
4
12
58
22
3
120
29
434
283
409
19
617
110
252
120
89
5
36
65
73
148
10
842
66
3,144
16
26
3
26
16
53
15
9
1
5
5
18
14
5
71
8
291
847
1,885
39
766
148
443
181
60

147
61
116
443
8
920
118
6,182
32
32
6
33
13
57
19
3

11
4
21
25
4
63
5
328
855
9,382
39
442
150
72
21
31
34
461
61
37
125
27
857
35
12,629
9
56
5
18
8
5
5
2
1
12
1
4
7
2
30
1
166
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.58.a. Trichloroethylene - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
5,151
51,708
18,904
23,744
3,908
1,593
2,069
3,333
3,855
11,122
5,531
1,932
8,323
495
19,146
2,972
163,786
407
4,170
8,987
9,530
1,972
1,050
884
2,340
2,131
4,815
2,841
1,513
3,767
346
8,583
2,343
55,679
56
2,177
1,974
659
873
180
666
678
572
1,296
563
934
751
230
2,748
523
14,880
1,639
4,474
2,939
8,607
980
376
671
537
1,071
1,930
1,015
286
1,966
126
5,857
561
33,035
152
489
549
436
371
48
279
78
181
261
134
110
156
64
1,225
61
4,594
1,614
5,326
1,151
2,823
433
135
361
184
320
1,254
392
62
1,567
20
3,000
68
18,710
76
158
126
109
80
16
56
11
24
73
24
17
45
12
325
8
1,160
1,191
17,794
2,502
2,317
416
28
140
272
325
2,422
795
69
665
3
1,458

30,397
24
162
141
60
38
5
14
2
9
65
17
13
15
3
96

664
300
19,944
3,325
467
107
4
13

8
701
488
2
358

248

25,965
1
66
62
3
4
1
4

1
4
2
1
2

12

163
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,375
20,417
136
2,814
527
1,702
437
391
95
763
345
925
1,003
55
4,777
666
37,428
146
80
6
58
36
176
20
80
13
6
88
233
47
5
939
136
2,069
8
27
1
3
6
30
4
21
3
1
20
53
8
5
117
36
343
166
189
30
919
82
407
95
131
12
21
70
355
195
5
1,164
274
4,115
11
38
5
37
11
47
17
18
2
4
12
61
20
4
123
33
443
285
439
19
619
110
409
120
89
17
44
65
107
150
10
845
66
3,394
16
26
3
26
16
53
15
9
3
5
5
18
14
5
71
8
293
853
3,103
43
770
148
661
181
60
19
161
61
182
471
8
972
155
7,848
32
32
7
33
13
54
19
3
1
11
4
22
25
4
64
6
330
925
16,606
38
448
151
49
21
31
34
531
61
48
140
27
857
35
20,002
9
56
5
18
8
4
5
2
1
12
1
4
7
2
30
1
165
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.59.a. Vinyl Chloride - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
5,117
38,299
19,021
23,526
3,764
1,566
4,161
3,333
4,766
10,767
5,248
1,917
8,831
683
23,193
3,251
157,443
406
4,038
8,957
9,487
1,934
1,037
2,833
2,340
2,603
4,803
2,742
1,500
4,116
449
10,415
2,627
60,287
56
2,173
1,974
659
871
179
1,933
678
591
1,296
557
934
767
278
2,806
515
16,267
1,623
4,307
2,939
8,556
970
361
915
537
1,357
1,865
957
285
2,013
188
6,853
555
34,281
152
489
549
435
371
48
429
78
183
261
130
110
154
82
1,235
62
4,768
1,600
4,585
1,155
2,797
403
136
309
184
376
1,175
360
62
1,660
27
3,760
69
18,658
76
158
126
109
79
16
58
11
24
73
24
17
45
15
328
8
1,167
1,189
10,806
2,643
2,269
389
28
96
272
405
2,304
703
68
678
19
1,835

23,704
24
162
141
60
38
5
14
2
9
65
17
13
14
4
95

663
299
14,563
3,327
417
68
4
8

25
620
486
2
364

330

20,513
1
66
62
3
4
1
3

1
4
2
1
2

12

162
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,296
12,140
136
2,801
526
1,634
506
391
154
762
209
923
1,147
70
6,183
629
30,507
145
80
6
58
36
174
29
80
13
6
40
231
59
10
1,031
131
2,129
8
27
1
3
6
30
6
21
3
1
10
53
10
8
117
32
336
167
186
30
915
82
405
102
131
27
21
40
356
211
9
1,348
278
4,308
11
37
5
37
11
47
19
18
3
4
8
61
22
8
124
33
448
283
408
19
617
110
408
116
89
26
43
53
107
163
13
1,200
62
3,717
16
26
3
26
16
53
14
9
3
5
2
18
14
7
72
8
292
846
1,874
43
768
148
598
235
60
25
161
18
182
563
11
1,407
132
7,071
32
32
7
33
13
54
23
3
1
11
2
22
27
6
66
6
338
855
9,592
38
443
150
49
24
31
63
531
58
47
151
27
1,197
26
13,282
9
56
5
18
8
4
6
2
1
12
1
4
7
2
30
1
166
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2.  16-State Cross-Section Data for Stage 2 Analysis
Six-Year Review
  Table B.60.a. Xylenes (Total) - Number of Records and Number of Systems in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
<500
Number of
Records
Number of
Systems
501 - 3,300
Number of
Records
Number of
Systems
3,301 - 10,000
Number of
Records
Number of
Systems
10,001 - 50.000
Number of
Records
Number of
Systems
> 50,000
Number of
Records
Number of
Systems
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
sc
SD
TX
VT
All States
5,118
37,609
18,682
23,210
3,782
4
4,171
3,269
1
10,271
4,619
654
4,916
0
23,193
3,558
143,057
406
3,980
8,989
9,473
1,952
4
2,834
2,299
1
4,502
2,375
453
3,033

10,415
2,863
53,579
56
2,163
1,975
655
871
3
1,933
676
1
1,242
550
334
686

2,806
537
14,488
1,623
4,292
3,003
8,545
975

916
531

1,755
857
127
853

6,853
616
30,946
152
487
549
434
371

429
78

249
129
67
144

1,235
62
4,386
1,600
4,527
1,163
2,663
401

321
173

1,149
333
31
667

3,760
79
16,867
76
158
126
107
78

58
11

73
23
12
43

328
8
1,101
1,190
11,272
2,201
2,152
388

92
266

2,244
573
41
264

1,835

22,518
24
162
141
60
38

14
2

65
17
12
13

95

643
299
13,538
3,326
377
66

8


621
481
2
99

330

19,147
1
66
62
3
4

3


4
2
1
2

12

160
Suface Water
AL
CA
FL
LL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,297
12,768
135
2,465
529
2
527
371
0
757
186
442
473
0
6,183
754
27,889
145
79
6
58
39

40
80

6
32
80
39

1,031
154
1,789
8
27
1
3
6

6
21

1
9
44
9

117
36
288
166
187
29
906
82
2
104
122

16
36
147
82

1,348
314
3,541
11
38
5
37
11
1
19
17

3
8
58
21

124
33
386
283
409
19
513
110

119
84

43
50
71
102

1,200
76
3,079
16
25
3
26
16

14
9

5
2
18
12

72
8
226
847
1,853
43
628
148

240
55

159
18
114
196

1,407
175
5,883
32
32
7
33
13

23
3

11
2
21
26

66
6
275
856
10,240
38
360
150

24
30

533
50
30
54

1,197
35
13,597
9
56
5
18
8

6
2

12
1
3
7

30
1
158
  * Blank cells indicate that there were no analytical results for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                            Six-Year Review
 Table B.l.b. Alachlor - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
3,090
7,320
4,641
5,291
2,901
1,743
1,278
1,621
1,660
0
4,264
593
5,806
773
3,742
949
45,672
2
5

9
3
2
1

20



3

1

46
0.06%
0.07%
0.00%
0.17%
0.10%
0.11%
0.08%
0.00%
1.20%
0.00%
0.00%
0.00%
0.05%
0.00%
0.03%
0.00%
0.10%

0.0002

0.00023
0.0003
0.00003


0.00018







0.00003

0.0006

0.00023
0.0006
0.00003


0.00018







0.00024

0.001

0.00025
0.0009
0.00003


0.00018







0.001

0.001

0.0002

0.00198


0.00011



0.00046



0.00011

0.001

0.000475

0.00198


0.000425



0.00046



0.000485

0.001

0.003

0.00198


0.00057



0.00108



0.003








0.00004







0.00004








0.00078







0.00078








0.0016







0.0016
0.00008
0.0002




0.0014







0.0008

0.00008
0.00049
0.0002




0.0014







0.0008

0.0008
0.0009
0.0002




0.0014







0.0008

0.0014



















































Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
801
2,578
79
2,107
603
1,519
240
247
160
0
250
424
667
161
2,828
364
13,028
3
1

62
14
11
5

3





25

124
0.37%
0.04%
0.00%
2.94%
2.32%
0.72%
2.08%
0.00%
1.88%
0.00%
0.00%
0.00%
0.00%
0.00%
0.88%
0.00%
0.95%



0.00043
0.0001









0.00012

0.0001



0.000495
0.0001









0.00046

0.00043



0.00056
0.0001









0.0058

0.0058
0.00003


0.0002
0.0001
0.00006
0.0005







0.00013

0.00003
0.000045


0.000315
0.00015
0.00198
0.0013







0.0003

0.00031
0.00006


0.0017
0.00062
0.008
0.0021







0.00042

0.008
0.00009


0.00024
0.00132
0.00004
0.0004

0.00009





0.00012

0.00004
0.00009


0.00038
0.00134
0.00015
0.0012

0.00009





0.00018

0.00033
0.00009


0.0012
0.00136
0.00026
0.002

0.00009





0.00034

0.002



0.0002

0.00003
0.0004







0.00016

0.00003



0.00031

0.000055
0.0004







0.00025

0.00027



0.0019

0.00006
0.0004







0.00041

0.0019

0.009

0.0002
0.0002
0.00003


0.00007





0.0001

0.00003

0.009

0.00083
0.00038
0.00003


0.0001





0.00014

0.000215

0.009

0.001
0.0064
0.00003


0.00013





0.00022

0.009
Note: All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                           Six-Year Review
 Table B.2.b.  Antimony - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
686
6,977
5,206
160
2,897
877
0
1,096
991
3,469
1,689
616
3,658
372
5,379
1,090
35,163
6
1
316

1,716
118

81
226
145
10
5
22
149
41
17
2,853
0.87%
0.01%
6.07%
0.00%
59.23%
13.45%
0.00%
7.39%
22.81%
4.18%
0.59%
0.81%
0.60%
40.05%
0.76%
1.56%
8.11%


0.0003

0.00005
0.001

0.001
0.001
0.001
0.00084
0.00003
0.003
0.00028
0.002
0.003
0.00003


0.00345

0.002
0.004

0.001
0.001
0.0049
0.0011
0.006
0.004
0.002
0.0026
0.0075
0.002


0.3

0.04
0.175

0.017
0.002
3.8
0.002
0.032
0.025
0.01
0.0053
0.012
3.8
0.002

0.0008

0.0001
0.001

0.001
0.001
0.0002
0.0006
0.002
0.003
0.00024
0.002
0.003
0.0001
0.003

0.003

0.002
0.004

0.003
0.001
0.00285
0.0006
0.00215
0.003
0.002
0.0038
0.003
0.002
0.005

0.0165

0.03
0.019

0.034
0.003
0.05
0.002
0.0023
0.004
0.005
0.0053
0.003
0.05


0.0004

0.0002
0.002

0.001
0.001
0.001


0.003
0.0003
0.0022

0.0002


0.0038

0.002
0.004

0.001
0.001
0.004


0.003
0.002
0.0032

0.002


0.041

1
0.007

0.006
0.001
0.034


0.003
0.005
0.0032

1
0.002

0.001

0.0002
0.004


0.001
0.0004
0.0002

0.006
0.0004


0.0002
0.002

0.003

0.002
0.004


0.001
0.0028
0.0005

0.015
0.001


0.002
0.002

0.02

0.006
0.004


0.001
0.037
0.0006

0.024
0.0015


0.037

0.16
0.0002

0.0002



0.001







0.0002

0.16
0.003

0.0004



0.001







0.0025

0.16
0.027

0.005



0.001







0.16
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
523
2,838
92
67
371
1,000
0
254
59
432
62
528
497
42
1,447
382
8,594
12

1

228
112

7
22
16

6

19
9
5
437
2.29%
0.00%
1.09%
0.00%
61.46%
11.20%
0.00%
2.76%
37.29%
3.70%
0.00%
1.14%
0.00%
45.24%
0.62%
1.31%
5.08%
0.003



0.002
0.001

0.001





0.0003
0.0021

0.0003
0.003



0.005
0.004

0.001





0.0004
0.0023

0.003
0.003



0.005
0.007

0.001





0.002
0.0026

0.007
0.003



0.0002
0.0002

0.001
0.001


0.00003

0.0003
0.0028
0.005
0.00003
0.0035



0.0025
0.003

0.001
0.001


0.000765

0.0004
0.00345
0.005
0.003
0.004



0.006
0.007

0.001
0.001


0.0015

0.0005
0.0041
0.005
0.007
0.002



0.0004
0.001


0.001
0.002

0.003

0.00036
0.002

0.00036
0.002



0.003
0.004


0.5005
0.002

0.003

0.0004
0.0021

0.003
0.002



0.005
0.017


1
0.002

0.003

0.0004
0.0024

1
0.002



0.0002
0.001

0.001
0.001
0.002

0.002

0.0002
0.0028

0.0002
0.00275



0.001
0.0035

0.001
0.001
0.0029

0.008

0.0003
0.0028

0.0025
0.0392



0.005
0.009

0.001
0.001
0.006

0.01

0.0005
0.0028

0.0392
0.0009

0.012

0.0002
0.0004

0.002
0.001
0.0005






0.0002
0.00245

0.012

0.001
0.002

0.002
0.001
0.004






0.001
0.004

0.012

0.006
0.003

0.002
0.001
0.006






0.012
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                            Six-Year Review
 Table B.3.b.  Atrazine - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
3,100
13,673
4,631
5,294
2,989
1,829
1,278
1,646
1,660
0
4,257
603
5,813
771
3,771
872
52,187
10
187

165
39
17
1
1
700

9

1

39
3
1,172
0.32%
1.37%
0.00%
3.12%
1.30%
0.93%
0.08%
0.06%
42.17%
0.00%
0.21%
0.00%
0.02%
0.00%
1.03%
0.34%
2.25%

0.0002

0.00012
0.0001
0.00002

0.00039
0.00008

0.0003



0.0003
0.0002
0.00002

0.00034

0.00035
0.00025
0.00008

0.00039
0.00022

0.000355



0.001
0.0002
0.00024

0.002

0.0014
0.0019
0.00025

0.00039
0.00294

0.00037



0.0018
0.0002
0.00294
0.00006
0.0005

0.0001
0.0001
0.00001


0.00008







0.00001
0.000128
0.0005

0.000345
0.0003
0.000175


0.00022







0.00023
0.000196
0.0005

0.0079
0.006
0.0027


0.00585







0.0079
0.00014
0.00021

0.0001
0.00018
0.00009


0.00008



0.00093

0.0002
0.00027
0.00008
0.000264
0.00056

0.00033
0.00023
0.00016


0.00016



0.00093

0.00065
0.00027
0.000285
0.002
0.0017

0.0021
0.0003
0.00044


0.00083



0.00093

0.0033
0.00027
0.0033

0.00011

0.0001
0.0001
0.00022
0.0009

0.00008

0.00025



0.001

0.00008

0.0005

0.00023
0.0002
0.00024
0.0009

0.00022

0.00025



0.001

0.0003

0.0024

0.0027
0.0003
0.00026
0.0009

0.00385

0.00025



0.001

0.00385

0.00011

0.0001
0.0001



0.00011







0.0001

0.00056

0.00036
0.000125



0.0002







0.0005

0.0023

0.0062
0.0011



0.00075







0.0062
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
815
4,904
74
2,138
725
1,575
241
252
130
0
251
429
658
168
2,732
213
15,305
7
42

1,369
243
139
35

28




2
474
2
2,341
0.86%
0.86%
0.00%
64.03%
33.52%
8.83%
14.52%
0.00%
21.54%
0.00%
0.00%
0.00%
0.00%
1.19%
17.35%
0.94%
15.30%
0.00029


0.00012
0.0001
0.00002


0.00016





0.0001

0.00002
0.00029


0.0027
0.0009
0.00034


0.000595





0.00036

0.00045
0.00029


0.019
0.0061
0.0008


0.00103





0.0105

0.019
0.00009


0.0001
0.00006
0.00002
0.0001

0.00042





0.0001

0.00002
0.00009


0.0013
0.00082
0.000555
0.0003

0.000745





0.00037

0.001
0.00009


0.019
0.0085
0.008
0.0036

0.001





0.0039

0.019
0.0007
0.0005

0.00011
0.00015
0.00001
0.0001

0.00016





0.00011
0.0001
0.00001
0.0007
0.000555

0.00089
0.000595
0.00015
0.0002

0.00016





0.00051
0.0001
0.00066
0.0007
0.00061

0.042
0.0042
0.0048
0.003

0.00016





0.0096
0.0001
0.042
0.000133
0.00011

0.0001
0.0001
0.00002
0.0001






0.000456
0.0001

0.00002
0.0003625
0.00075

0.00079
0.00041
0.00031
0.0003






0.000456
0.0005

0.0006
0.000592
0.002

0.012
0.0071
0.023
0.0038






0.000456
0.0029

0.023
0.00008
0.00012

0.00008
0.00013
0.0001


0.00008




0.0001
0.0001

0.00008
0.000175
0.0005

0.00069
0.0008
0.000255


0.00017




0.0001
0.000445

0.00057
0.00027
0.0017

0.014
0.014
0.00096


0.0105




0.0001
0.0031

0.014
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                             Six-Year Review
 Table B.4.b. Barium - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
1,491
18,088
5,109
311
2,989
961
0
1,400
167
3,636
1,859
1,787
3,761
365
6,341
1,664
49,929
298
4,092
2,706
305
2,800
715

888
142
1,804
1,067
510
847
340
6,140
651
23,305
19.99%
22.62%
52.97%
98.07%
93.68%
74.40%
0.00%
63.43%
85.03%
49.61%
57.40%
28.54%
22.52%
93.15%
96.83%
39.12%
46.68%
0.0034
0.051
0.0003
0.008
0.00001
0.001

0.005
0.026
0.0018
0.0009
0.001
0.003
0.0017
0.0005
0.002
0.00001
0.025
0.14
0.01415
0.078
0.093
0.2915

0.0915
0.1675
0.06
0.1
0.01765
0.05
0.1
0.0884
0.03
0.065
0.74
7.6
0.88
1.4
7.1
9.15

1.131
0.31
9.2
0.8
4.75
0.72
0.857
5.75
0.5
9.2
0.002
0.051
0.002
0.006
0.00002
0.002

0.006
0.079
0.001
0.0007
0.0016
0.003
0.004
0.0007
0.01
0.00002
0.049
0.13
0.015
0.078
0.09
0.0445

0.066
0.21
0.042
0.0432
0.0175
0.05
0.1
0.0736
0.038
0.068
0.621
1.31
0.86
6.8
14
1.54

0.498
0.895
2
0.3
1
0.36
0.665
1.33
0.34
14
0.006
0.051
0.001
0.005
0.006
0.004

0.01
0.1
0.0015
0.0072
0.004
0.003
0.002
0.0025
0.01
0.001
0.05
0.14
0.0147
0.0855
0.06
0.023

0.0825
0.195
0.06
0.07155
0.009
0.036
0.1
0.085
0.02
0.1
0.65
3.14
0.53
2.4
1
0.54

0.3
0.33
1.6
1.03
0.1
0.63
0.256
0.559
0.1
3.14
0.01
0.051
0.0017
0.013
0.005
0.007

0.1
0.1
0.0038
0.0006
0.003
0.003
0.1
0.002

0.0006
0.03
0.124
0.016
0.11
0.094
0.022

0.2
0.18
0.082
0.06435
0.013
0.017
0.15
0.059

0.103
0.47
0.9891
4
6.2
1.26
0.04

0.5
0.48
3.8
0.228
0.08
0.07
0.16
0.358

6.2
0.02
0.051
0.0017
0.026
0.033
0.017


0.118
0.025
0.00019

0.05

0.004

0.00019
0.024
0.12
0.018
0.071
0.088
0.034


0.215
0.085
0.0695

0.06

0.046

0.099
0.028
0.91
41
0.4
0.322
0.036


0.225
0.48
0.2

0.11

1.51

41
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
840
7,239
91
69
373
1,153
0
265
26
460
78
946
510
35
1,472
590
14,147
406
1,621
43
69
339
657

94
22
253
55
189
70
32
1,456
115
5,421
48.33%
22.39%
47.25%
100.00%
90.88%
56.98%
0.00%
35.47%
84.62%
55.00%
70.51%
19.98%
13.73%
91.43%
98.91%
19.49%
38.32%
0.002
0.11
0.05
0.016
0.008
0.002

0.008


0.0084
0.0005
0.01
0.028
0.003
0.01
0.0005
0.02
0.225
0.05
0.03
0.019
0.027

0.05


0.0775
0.017
0.06
0.05
0.0635
0.0192
0.0415
0.09
0.66
0.05
0.044
0.9
0.45

0.22


0.2
0.25
0.1
0.1
0.469
0.2
0.9
0.008
0.094
0.0013
0.008
0.006
0.006

0.005

0.0089
0.0058
0.0016
0.008
0.009
0.016
0.01
0.0013
0.02
0.15
0.027
0.0315
0.042
0.025

0.063

0.014
0.0143
0.0085
0.02
0.0245
0.07099
0.02
0.04115
0.25
0.39
0.07
0.065
1
0.44

0.1

0.033
0.13
23
0.07
0.15
0.333
0.2
23
0.005
0.1
0.01
0.02
0.008
0.003

0.006
0.14
0.01
0.0002
0.002
0.004
0.031
0.004
0.002
0.0002
0.02
0.15
0.017
0.023
0.03
0.029

0.043
0.2875
0.0185
0.01745
0.00545
0.013
0.03845
0.06619
0.016
0.042
0.058
0.304
0.0254
0.051
0.9
0.75

0.154
0.305
1.32
0.1
0.3
0.08
0.11
0.389
0.02
1.32
0.005
0.0506
0.01
0.01
0.01
0.002

0.006
0.0679
0.002
0.011
0.001
0.003
0.021
0.007
0.01
0.001
0.021
0.097
0.016
0.0185
0.05
0.029

0.02
0.1175
0.0342
0.07225
0.00715
0.0145
0.05
0.069995
0.027
0.043
0.19
0.71
0.029
0.048
0.9
1

0.05
0.14
6
0.2
0.206
0.18
0.18
0.299
0.132
6
0.00244
0.0505
0.015
0.011
0.004
0.02

0.035
0.0174
0.0062
0.1
0.001
0.013
0.021
0.007

0.001
0.024
0.1465
0.045
0.0195
0.045
0.031

0.043
0.1675
0.15
0.2
0.0035
0.018
0.0764
0.068

0.124
0.21
1
0.15
40
0.146
0.106

0.056
0.34
0.77
1.1
0.027
0.019
0.1
0.26

40
Note: All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                           Six-Year Review
 Table B.S.b.  Benzene - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
5,136
38,818
18,951
23,749
3,781
1,575
1,996
3,333
4,767
10,778
5,515
1,926
8,855
720
24,168
3,965
158,033
43
299
143
105
7
5
30
5
60
65
111
10
42
4
125
21
1,075
0.84%
0.77%
0.75%
0.44%
0.19%
0.32%
1.50%
0.15%
1.26%
0.60%
2.01%
0.52%
0.47%
0.56%
0.52%
0.53%
0.68%

0.0006
0.00001
0.0005
0.0007
0.001
0.0005
0.0062
0.0001
0.00032
0.0004
0.0003
0.00056

0.0005
0.0002
0.00001

0.0068
0.0026
0.0006
0.0007
0.001
0.00155
0.0062
0.013
0.0029
0.0013
0.0029
0.00103

0.0016
0.0014
0.0017

0.243
0.0037
0.008
0.0007
0.001
0.0025
0.0062
0.2486
0.0299
0.0045
0.012
0.0068

0.15
0.0127
0.2486
0.0005
0.0006
0.0027
0.0005
0.0005
0.00055
43.213
0.001
0.0002
0.00023

0.0001
0.00021
0.000582
0.0005

0.0001
0.0021
0.00195
0.0029
0.001
0.0007
0.00055
43.213
0.00215
0.0005
0.00054

0.0001
0.001095
0.00112
0.0011

0.0016
0.247
0.0072
0.0034
0.163
0.0028
0.00055
43.213
0.003
0.2388
0.0048

0.0001
0.0204
0.004348
0.0062

43.213
0.0007
0.00053
0.00056
0.0005
0.0017
0.0007
0.0005

0.0003
0.0005
0.0009
0.0013
0.0011

0.0005

0.0003
0.0013405
0.011
0.001
0.0007
0.0017
0.000705
0.0032

0.00125
0.00085
0.0009
0.0013
0.0011

0.0017

0.0021
0.00275
1.3
0.011
0.0098
0.0017
0.00071
0.0351

0.0022
0.0012
0.0009
0.0013
0.0011

0.0044

1.3
0.00065
0.00051
0.00011
0.000098




0.00012
0.0002
0.0004
0.0006


0.0007

0.000098
0.00263
0.0011
0.0011
0.0016




0.001005
0.00072
0.00215
0.0006


0.0007

0.0012
0.0034
0.012
0.0251
0.005




0.01222
0.021
0.0264
0.0006


0.0007

0.0264
0.00083
0.0006
0.00014
0.00017





0.00118
0.0018





0.00014
0.0028
0.001
0.000727
0.0005





0.00118
0.0018





0.001
0.0098
0.007
0.00312
0.0031





0.00118
0.0018





0.0098
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,297
11,915
136
2,827
526
1,715
437
391
155
761
343
924
1,140
75
6,324
812
30,778
4
17

26

13
1


1
3
1
17

9
1
93
0.17%
0.14%
0.00%
0.92%
0.00%
0.76%
0.23%
0.00%
0.00%
0.13%
0.87%
0.11%
1.49%
0.00%
0.14%
0.12%
0.30%
0.005













0.0005

0.0005
0.005













0.0005

0.00275
0.005













0.0005

0.005
0.00072


0.0005

0.00055
0.0008


0.0004

0.0005
0.00072

0.0006

0.0004
0.00072


0.0032

0.000795
0.0008


0.0004

0.0005
0.00072

0.0006

0.00071
0.00072


0.0059

0.0015
0.0008


0.0004

0.0005
0.00072

0.0014

0.0059



0.00013

0.00052










0.00013



0.0005

0.00055










0.00051



0.002

0.00061










0.002
0.00083
0.00063

0.0005

0.001






0.00139

0.0006
0.0005
0.0005
0.001615
0.00078

0.0005

0.00227






0.00323

0.0006
0.0005
0.00203
0.0024
0.00097

0.0005

0.116






0.00856

0.001
0.0005
0.116

0.0006

0.0005






0.0008



0.0011

0.0005

0.0008

0.0005






0.0063



0.001465

0.0008

0.0029

0.003






0.128



0.00183

0.128
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                           Six-Year Review
 Table B.6.b.  Benzo(a)pyrene - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
3,121
2,708
4,659
5,242
2,844
1,020
17
1,614
1,974
0
4,116
549
5,777
932
533
884
35,990
8

21
4

6

2




1


3
45
0.26%
0.00%
0.45%
0.08%
0.00%
0.59%
0.00%
0.12%
0.00%
0.00%
0.00%
0.00%
0.02%
0.00%
0.00%
0.34%
0.13%


0.00002
0.00003

0.0001

0.0001




0.00007


0.000096
0.00002


0.00004
0.00003

0.00014

0.00025




0.00007


0.00053
0.000099


0.000199
0.00011

0.00026

0.0004




0.00007


0.00053
0.00053
0.00002

0.0000166













0.0000166
0.000025

0.000031













0.000026
0.00016

0.00011













0.00016
0.0002

0.00003













0.00003
0.0002

0.00005













0.000128
0.0002

0.000056













0.0002
0.0002















0.0002
0.0002















0.0002
0.0002















0.0002


0.00001
0.000281












0.00001


0.0002035
0.000281












0.000281


0.000397
0.000281












0.000397
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
807
1,316
77
1,784
544
968
11
229
158
0
145
410
696
179
2,931
Til
10,532
4


1
2
2






1

1

11
0.50%
0.00%
0.00%
0.06%
0.37%
0.21%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.14%
0.00%
0.03%
0.00%
0.10%




0.00019







0.00002

0.00004

0.00002




0.00019







0.00002

0.00004

0.00004




0.00019







0.00002

0.00004

0.00019
0.00002




0.00019










0.00002
0.000025




0.00019










0.00003
0.00003




0.00019










0.00019
0.00006















0.00006
0.00006















0.00006
0.00006















0.00006





0.00013










0.00013





0.00013










0.00013





0.00013










0.00013
0.00002


0.00005
0.00002











0.00002
0.00002


0.00005
0.00002











0.00002
0.00002


0.00005
0.00002











0.00005
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                            Six-Year Review
 Table B.7.b.  Beryllium - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
771
7,692
5,121
252
2,896
820
3,767
1,000
980
3,454
1,738
615
3,307
245
6,343
902
39,903
1

346
1
117
47
24
7
10
130
4
6

32
19
6
750
0.13%
0.00%
6.76%
0.40%
4.04%
5.73%
0.64%
0.70%
1.02%
3.76%
0.23%
0.98%
0.00%
13.06%
0.30%
0.67%
1.88%


0.0001

0.00003
0.001
0.0001
0.00006
0.0005
0.00005
0.001
0.0003

0.00022
0.0009
0.0003
0.00003


0.001

0.0012
0.001
0.0001
0.002
0.001
0.001
0.0065
0.0005

0.0007
0.001
0.00125
0.001


0.005

0.003
0.019
0.0162
0.002
0.001
0.014
0.029
0.0008

0.004
0.008
0.016
0.029
0.001

0.0001
0.001
0.00002
0.001
0.0001

0.0005
0.00002

0.0012

0.0003
0.0009

0.00002
0.001

0.00145
0.001
0.003
0.001
0.00455

0.0005
0.001

0.0012

0.0003
0.001

0.001
0.001

0.06
0.001
0.0039
0.002
0.0133

0.0005
0.017

0.0012

0.001
0.002

0.06


0.0001

0.0008

0.0001
0.002
0.0005
0.0008



0.0007


0.0001


0.0007

0.003

0.0098
0.002
0.50025
0.0041



0.00085


0.001


0.0039

0.1

0.0738
0.002
1
0.008



0.001


1


0.0002

0.0001

0.0306


0.0002

0.0006




0.0001


0.00065

0.0008

0.0306


0.001

0.0006




0.001


0.02

0.003

0.0306


0.006

0.0006




0.0306


0.0002

0.0008











0.0002


0.001

0.0019











0.001


0.007

0.003











0.007
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
371
2,080
91
68
372
959
279
256
55
432
128
527
429
5
1,468
338
7,858
6

1

35
40
1


16

4


4
7
114
1.62%
0.00%
1.10%
0.00%
9.41%
4.17%
0.36%
0.00%
0.00%
3.70%
0.00%
0.76%
0.00%
0.00%
0.27%
2.07%
1.45%




0.003
0.001








0.001

0.001




0.003
0.001








0.001

0.001




0.003
0.002








0.001

0.003
0.001

0.0002

0.0012
0.001









0.001
0.0002
0.001

0.0002

0.0012
0.001









0.012
0.0012
0.001

0.0002

0.003
0.002









0.08
0.08
0.001



0.0001
0.001



0.004




0.001

0.0001
0.001



0.0001
0.001



0.004




0.001

0.001
0.001



0.0001
0.001



0.004




0.001

0.004
0.001



0.0001
0.00018



0.001




0.01

0.0001
0.002



0.0008
0.001



0.0015




0.01

0.001
0.003



0.003
0.003



0.003




0.01

0.01
0.001



0.0008

0.0001


0.0004

0.00001




0.00001
0.001



0.0008

0.0001


0.0014

0.00004




0.0008
0.001



0.0028

0.0001


0.002

0.00006




0.0028
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                                   Six-Year Review
 Table B.8.b.  Bis(2-ethylhexyl)adipate - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NI
NM
OR
SC
SD
TX
VT
All States
3,175
0
4,662
5,260
2,862
1,025
17
1,621
1,974
0
4,121
555
6,698
927
374
973
34,244
46

36
6
8
422

18
21

507
3
163

1
120
1,351
1.45%
0.00%
0.77%
0.11%
0.28%
41.17%
0.00%
1.11%
1.06%
0.00%
12.30%
0.54%
2.43%
0.00%
0.27%
12.33%
3.95%
0.0003

0.000758

0.0009
0.0001

0.0004
0.000295

0.00001
0.0002
0.0006


0.00014
0.00001
0.0019

0.00263

0.0012
0.000365

0.0005
0.00052

0.00007
0.0004
0.00106


0.0012
0.00035
0.00836

0.16

0.0035
0.019

0.0273
0.00085

0.028
0.003
0.01


0.017
0.16
0.0003

0.0000055
0.0007

0.0001

0.0014
0.00041

0.00001

0.0005


0.00016
0.0000055
0.000825

0.000899
0.0007

0.00036

0.009845
0.005705

0.00003

0.00102


0.00048
0.00042
0.0136

0.00793
0.0007

0.003

0.0133
0.0278

0.029

0.01


0.0068
0.029
0.0003

0.000884
0.0009
0.0009
0.00012

0.0004
0.000362

0.00001

0.0006

0.001
0.00024
0.00001
0.002

0.017
0.0009
0.0009
0.00031

0.0004
0.000555

0.00002

0.000955

0.001
0.00024
0.00046
0.00593

0.0482
0.0009
0.0009
0.01

0.0004
0.02203

0.00208

0.0299

0.001
0.02
0.0482
0.0003


0.0008
0.001


0.00012
0.00033

0.00001

0.0006



0.00001
0.0014


0.0022
0.00105


0.000455
0.00597

0.00005

0.00099



0.00009
0.0045


0.0045
0.0011


0.00079
0.01161

0.132

0.00227



0.132
0.0035

0.00152







0.00001

0.0023



0.00001
0.0071

0.00152







0.00002

0.0023



0.00003
0.0107

0.00152







0.035

0.0023



0.035
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NI
NM
OR
SC
SD
TX
VT
All States
887
0
77
1,771
548
969
11
233
158
0
145
411
750
179
2,079
295
8,513
42



2
305

2


15
1
25


16
408
4.74%
0.00%
0.00%
0.00%
0.36%
31.48%
0.00%
0.86%
0.00%
0.00%
10.34%
0.24%
3.33%
0.00%
0.00%
5.42%
4.79%
0.0003




0.0001

0.0022


0.00002

0.0006


0.00024
0.00002
0.0003




0.00043

0.0022


0.00002

0.00101


0.00273
0.00051
0.0003




0.005

0.0022


0.00002

0.00117


0.021
0.021





0.0001




0.00001

0.00095


0.00018
0.00001





0.00033




0.000045

0.006145


0.0011
0.00034





0.005




0.00036

0.00896


0.00177
0.00896
0.0008




0.00011

0.0005


0.00001
0.055
0.0006


0.0082
0.00001
0.0014




0.00034

0.0005


0.00002
0.055
0.00073


0.0096
0.00034
0.0016




0.004

0.0005


0.00005
0.055
0.0299


0.011
0.055
0.0002




0.00013






0.0006



0.00013
0.002245




0.00099






0.00625



0.0014
0.0415




5.09






0.01



5.09
0.0002



0.0021





0.00002

0.00086


0.00549
0.00002
0.00575



0.00385





0.00002

0.00086


0.006895
0.00424
0.18



0.0056





0.00009

0.00086


0.0083
0.18
 Note: All results are expressed in mg/L.
 * Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                                   Six-Year Review
 Table B.9.b.  Bis(2-ethylhexyl)phthalate - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NI
NM
OR
SC
SD
TX
VT
All States
3,403
4,409
4,728
5,302
3,004
177
12
1,622
1,613
0
0
0
7,150
787
80
917
33,204
252
106
104
191
101
6
5
45
63



1,044

6
247
2,170
7.41%
2.40%
2.20%
3.60%
3.36%
3.39%
41.67%
2.77%
3.91%
0.00%
0.00%
0.00%
14.60%
0.00%
7.50%
26.94%
6.54%
0.0002
0.00011
0.0000022
0.0006
0.0006
0.00098

0.0000063
0.0021



0.0006

0.0046
0.00022
0.0000022
0.001075
0.0062
0.00216
0.0012
0.0012
0.0012

0.00115
0.0049



0.001115

0.013
0.0012
0.00124
0.0145
0.0227
0.0444
0.0091
0.01
0.0021

0.0268
0.0183



2.83

0.0225
2.5
2.83
0.0002
0.0028
0.001
0.0006
0.0004

0.0015
0.0000049
0.0022



0.00021


0.00024
0.0000049
0.0012
0.006
0.00225
0.001025
0.0012

0.0015
0.0005
0.00756



0.00124


0.001
0.00127
0.0244
0.025
0.00509
0.0048
0.0067

0.0015
0.0021
0.03752



0.0867


1.1
1.1
0.00029
0.00342
0.000299
0.00066
0.0007

0.0006
0.0004
0.0007



0.0006

0.00782
0.00044
0.00029
0.00122
0.00457
0.00094
0.0009
0.00107

0.0007
0.00255
0.008485



0.001505

0.00782
0.0009
0.00137
0.0124
0.069
0.00683
0.0023
0.007

0.0068
0.0047
0.0145



1.42

0.00782
0.0086
1.42
0.00014
0.0008
0.00063
0.0006
0.0002
0.00015

0.00014
0.0011



0.0006



0.00014
0.00118
0.00465
0.00242
0.00125
0.0009
0.00015

0.000255
0.011355



0.00139



0.001385
0.0074
0.105
0.0115
0.0099
0.005
0.00015

0.0012
0.044



3



3
0.0002
0.0006
0.0009
0.0006
0.0008







0.00061



0.0002
0.001125
0.001305
0.0035
0.0008
0.001







0.0007



0.001
0.0088
0.058
0.015
0.0019
0.0014







1.2



1.2
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NI
NM
OR
SC
SD
TX
VT
All States
927
1,625
79
1,820
574
404
11
231
121
0
0
0
672
161
971
252
7,848
99
43
1
68
43
30
9
4




160

16
26
499
10.68%
2.65%
1.27%
3.74%
7.49%
7.43%
81.82%
1.73%
0.00%
0.00%
0.00%
0.00%
23.81%
0.00%
1.65%
10.32%
6.36%
0.0007
0.00012

0.00069
0.0008
0.002

0.0012




0.0006

0.0021
0.00084
0.00012
0.00125
0.00023

0.00069
0.00115
0.00774

0.0012




0.0008

0.0046
0.0012
0.0012
0.0031
0.0006

0.00069
0.0015
0.00774

0.0012




0.00268

0.022
0.0031
0.022
0.0004


0.0006

0.00012






0.00062

0.0023
0.00071
0.00012
0.00105


0.0009

0.0007






0.00238

0.0054
0.00115
0.0013
0.007


0.0028

0.001






0.00939

0.011
0.007
0.011
0.0001
0.0037
0.0006
0.0006
0.0007

0.0009
0.0006




0.0006

0.0031

0.0001
0.00091
0.0037
0.0006
0.0011
0.0015

0.0009
0.0007




0.00114

0.0031

0.0011
0.002
0.0037
0.0006
0.004
0.00315

0.0009
0.0016




0.0129

0.0031

0.0129
0.0002


0.00061
0.0007
0.0008
0.0006





0.0006

0.0029
0.0009
0.0002
0.00125


0.00094
0.00085
0.00175
0.0008





0.00148

0.0029
0.0009
0.00146
0.0222


0.025
0.0025
0.0077
0.0011





1.17

0.0029
0.0823
1.17
0.000002
0.00011

0.0006
0.00052
0.0012
0.0006





0.00062

0.0078

0.000002
0.00175
0.00314

0.000795
0.0009
0.0017
0.00075





0.001225

0.0079

0.0012
0.007
0.0271

0.011
0.0054
0.00211
0.0009





0.00431

0.0084

0.0271
 Note: All results are expressed in mg/L.
 * Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                                 Six-Year Review
  Table B.lO.b. Cadmium - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
1,502
17,835
5,159
251
2,989
953
0
1,408
162
3,570
1,854
1,727
3,723
366
5,383
1,666
48,548
26
8
570
3
1,858
163

28
1
201
36
70
411
169
245
39
3,828
1.73%
0.04%
11.05%
1 .20%
62.16%
17.10%
0.00%
1 .99%
0.62%
5.63%
1.94%
4.05%
11.04%
46.17%
4.55%
2.34%
7.88%
0.001

0.0001

0.00004
0.0002

0.0001

0.00004
0.0002
0.0001
0.0001
0.00022
0.0001
0.0006
0.00004
0.001

0.0003

0.001
0.002

0.002

0.001
0.0006
0.001
0.0002
0.0005
0.0003
0.002
0.001
0.01

0.045

0.005
0.12

0.011

0.044
0.0074
0.014
0.0026
0.0016
0.0042
0.04
0.12
0.001
0.079
0.0001
0.003
0.00004
0.001

0.001

0.0001
0.0002
0.001
0.0001
0.00022
0.0001
0.002
0.00004
0.01
0.5395
0.0006
0.003
0.001
0.001

0.002

0.00085
0.002
0.003
0.0003
0.00047
0.0003
0.002
0.001
0.09
1
0.018
0.007
0.005
0.008

0.002

0.018
0.003
0.009
0.002
0.0028
0.0078
0.002
1
0.0002
0.11
0.0001

0.00004
0.003

0.003
0.001
0.00006
0.00014

0.0001
0.00047
0.0001
0.002
0.00004
0.00145
0.12
0.0003

0.002
0.003

0.003
0.001
0.001
0.0002

0.0002
0.0005
0.0004
0.002
0.001
0.004
0.14
0.013

0.011
0.003

0.003
0.001
0.005
0.0004

0.003
0.00106
0.0024
0.002
0.14
0.0001
0.06
0.0001

0.00004


0.001

0.0001
0.00012
0.0002
0.0002
0.00029
0.0002

0.00004
0.001
0.1
0.0003

0.001


0.001

0.001
0.000135
0.001
0.0008
0.00047
0.0004

0.001
0.02
0.355
0.0029

0.005


0.001

0.27
0.00015
0.001
0.0024
0.0005
0.0009

0.355


0.0001

0.00008




0.0005
0.0003

0.0002



0.00008


0.0003

0.00017




0.001
0.0003

0.0002



0.0003


0.008

0.005




0.0011
0.0003

0.0002



0.008
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
839
7,183
94
67
374
1,147
0
266
26
450
78
939
508
35
1,447
599
14,052
7
1
4
1
232
56

11

13
3
16
16
14
43
13
430
0.83%
0.01%
4.26%
1 .49%
62.03%
4.88%
0.00%
4.14%
0.00%
2.89%
3.85%
1.70%
3.15%
40.00%
2.97%
2.17%
3.06%



0.003
0.0001
0.001

0.005


0.003
0.001

0.00047
0.0001
0.002
0.0001



0.003
0.001
0.002

0.0055


0.003
0.002

0.0005
0.0002
0.0025
0.001



0.003
0.003
0.004

0.006


0.003
0.009

0.0005
0.0008
0.014
0.014


0.0001

0.00007
0.00012

0.002

0.00015
0.0006
0.0006
0.0002
0.0005
0.0001
0.0009
0.00007


0.0001

0.00135
0.001

0.002

0.00015
0.0006
0.0006
0.0003
0.0005
0.0003
0.002
0.001


0.0001

0.005
0.004

0.004

0.00015
0.0006
0.001
0.001
0.0005
0.0008
0.002
0.005
0.001

0.002

0.00004
0.00013

0.001

0.004
0.00034
0.0004
0.0001
0.00029
0.0001
0.003
0.00004
0.001

0.002

0.0004
0.001

0.001

0.004
0.00034
0.001
0.0004
0.00047
0.0003
0.003
0.0005
0.001

0.002

0.005
0.005

0.001

0.004
0.00034
0.0018
0.005
0.0005
0.001
0.003
0.005
0.0005
0.108
0.0002

0.00004
0.001

0.001

0.0001

0.0001
0.0001
0.0005
0.0001

0.00004
0.001
0.108
0.0002

0.0002
0.001

0.001

0.0007

0.0009
0.0002
0.0005
0.00025

0.0005
0.01
0.108
0.0002

0.003
0.002

0.0012

0.0027

0.001
0.001
0.0005
0.0003

0.108
0.00001



0.0001




0.00005


0.0004
0.0005
0.0001
0.002
0.00001
0.00003



0.0002




0.00026


0.0007
0.0006
0.0003
0.002
0.0003
0.00009



0.005




0.005


0.001
0.001
0.0059
0.002
0.0059
 Note:  All results are expressed in mg/L.
 * Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                           Six-Year Review
 Table B.ll.b. Carbofuran - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
3,087
6,450
4,670
4,662
2,843
1,015
1,264
1,593
585
0
4,156
591
5,787
760
3,467
913
41,843

1

1
1
1










4
0.00%
0.02%
0.00%
0.02%
0.04%
0.10%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.01%

0.005

0.0009
0.02531











0.0009

0.005

0.0009
0.02531











0.005

0.005

0.0009
0.02531











0.02531





0.00396










0.00396





0.00396










0.00396





0.00396










0.00396

























































































































































Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
796
2,370
79
988
505
967
184
229
43
0
237
422
662
163
2,232
274
10,151



2

1





2




5
0.00%
0.00%
0.00%
0.20%
0.00%
0.10%
0.00%
0.00%
0.00%
0.00%
0.00%
0.47%
0.00%
0.00%
0.00%
0.00%
0.05%






















































0.00061












0.00061



0.002355












0.002355



0.0041












0.0041





0.00066










0.00066





0.00066










0.00066





0.00066










0.00066











0.0009




0.0009











0.0009




0.0009











0.0009




0.0009











0.0009




0.0009











0.0009




0.0009











0.0009




0.0009
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                                 Six-Year Review
   Table B.12.b. Carbon Tetrachloride - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NI
NM
OR
SC
SD
TX
VT
All States
5,122
41,407
18,542
23,747
3,765
1,591
1,972
3,334
3,855
10,784
5,512
1,916
8,323
495
19,146
2,930
152,441
17
1,057
67
172
10
13
5
1
77
103
25
6
25
6
55
9
1,648
0.33%
2.55%
0.36%
0.72%
0.27%
0.82%
0.25%
0 03%
2.00%
0.96%
0.45%
0.31%
0.30%
1.21%
0.29%
0.31%
1.08%
0.0005

0.00001
0.0005
0.002
0.0002
0.0009
0.00056
0.0002
0.00018
0.0009
0.0004
0.00052
0.000547
0.0005
0.0004
0.00001
0.00065

0.00098
0.0007
0.00205
0.001
0.0009
0.00056
0.0019
0.00142
0.0009
0.0008
0.006515
0.0005735
0.0008
0.0055
0.001
0.0008

0.0247
0.012
0.0021
0.00122
0.0009
0.00056
0.0239
0.03574
0.0009
0.0013
0.0148
0.0006
0.0041
0.027
0.03574
0.0005
0.0006
0.0006
0.0005
0.0005
0.0007
0.0005

0.0006
0.000005
0.0002

0.0005
0.000863
0.0002
0.0008
0.000005
0.001
0.00195
0.00085
0.001
0.00068
0.00125
0.00055

0.0206
0.0008
0.0018

0.002025
0.007225
0.0008
0.0008
0.001
0.1192
0.01
0.0026
0.011
0.00096
0.00244
0.0006

0.0404
0.0013
0.006

0.00917
0.007225
0.014
0.0008
0.1192
0.0005
0.00051
0.000047
0.0005
0.0006
0.0017
0.0007

0.0005
0.00028
0.0146



0.0003

0.000047
0.0006
0.0006
0.000575
0.0006
0.0016
0.0017
0.0007

0.001
0.00205
0.0146



0.00066

0.0008
0.0007
0.0117
0.00614
0.012
0.0063
0.0017
0.0007

0.0015
0.00657
0.0146



0.0012

0.0146
0.0024
0.00053
0.0001
0.000234
0.0009

0.0004

0.0005
0.00018
0.0004

0.00093

0.00059

0.0001
0.0024
0.0022
0.001
0.001
0.0009

0.0004

0.0012
0.0007
0.0004

0.00123

0.0006

0.002
0.0024
0.029
0.0028
0.00203
0.0009

0.0004

0.005
0.005
0.0004

0.00442

0.0027

0.029

0.00052
0.0000005
0.00013












0.0000005

0.0011
0.0007
0.0009












0.0011

0.0085
0.0035
0.0021












0.0085
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NI
NM
OR
SC
SD
TX
VT
All States
2,298
13,508
136
2,831
527
1,720
441
391
95
762
347
924
1,003
55
4,777
667
30,482
7
956
13
56
1
17
5
1

9

1
22

31
2
1,121
0.30%
7.08%
9.56%
1.98%
0.19%
0.99%
1.13%
0.26%
0.00%
1.18%
0.00%
0.11%
2.19%
0.00%
0.65%
0.30%
3.68%
0.00257


0.001



0.0012






0.0005

0.0005
0.00257


0.001



0.0012






0.0006

0.00085
0.00257


0.001



0.0012






0.0007

0.00257


0.0027
0.0005
0.0005
0.0001



0.0002


0.00111

0.0004
0.0006
0.0001


0.00285
0.0008
0.0005
0.000615



0.0003


0.00111

0.00072
0.0006
0.00071


0.003
0.0033
0.0005
0.005



0.0004


0.00111

0.0017
0.0006
0.005



0.0005

0.00051
0.0004


0.003




0.0005

0.0004



0.0006

0.001255
0.0004


0.003




0.00064

0.00064



0.002

0.002
0.0004


0.003




0.0013

0.003
0.0005
0.0026

0.0005

0.0005
0.0004


0.00078

0.0005
0.00052

0.0003
0.0005
0.0003
0.001
0.0026

0.0006

0.0005
0.00065


0.001

0.0005
0.001815

0.0007
0.0005
0.0008
0.0021
0.0026

0.0014

0.0005
0.0008


0.0018

0.0005
0.00341

0.0012
0.0005
0.00341
0.00082
0.00051
0.0005


0.0003



0.0001




0.0004

0.0001
0.00082
0.0025
0.0005


0.00035



0.000325




0.0004

0.0024
0.00082
0.021
0.0017


0.0004



0.00055




0.001

0.021
   Note: All results are expressed in mg/L.
   * Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                           Six-Year Review
 Table B.13.b. Chlordane - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
3,087
8,964
4,667
5,294
2,822
1,012
0
1,548
290
598
4,265
591
9,053
764
3,615
966
47,536

1
2






2


31



36
0.00%
0.01%
0.04%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.33%
0.00%
0.00%
0.34%
0.00%
0.00%
0.00%
0.08%









0.00057


0.00051



0.00051









0.00057


0.001255



0.00125









0.00057


0.00469



0.00469


0.0006






0.00044






0.00044


0.0006






0.00044






0.00052


0.0006






0.00044






0.0006

0.0004










0.00075



0.0004

0.0004










0.00075



0.00075

0.0004










0.00075



0.00075












0.00058



0.00058












0.00058



0.00058












0.00058



0.00058


0.0000953













0.0000953


0.0000953













0.0000953


0.0000953













0.0000953
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
800
3,278
76
2,144
549
952
0
209
12
71
250
424
1,088
156
1,887
257
12,153





2










2
0.00%
0.00%
0.00%
0.00%
0.00%
0.21%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.02%






























































































































































0.0001










0.0001





0.0001










0.0001





0.0001










0.0001



















































Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                           Six-Year Review
 Table B.14.b. Chromium - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
1,522
18,855
5,108
252
2,988
898
2,976
1,404
154
3,560
1,901
1,756
3,311
271
6,344
1,084
52,384
29
26
1,143
3
820
151
707
42
97
355
824
248
61
52
510
13
5,081
1.91%
0.14%
22.38%
1.19%
27.44%
16.82%
23.76%
2.99%
62.99%
9.97%
43.35%
14.12%
1.84%
19.19%
8.04%
1.20%
9.70%
0.005
0.12
0.0002
0.005
0.00005
0.001
0.0007
0.001
0.001
0.00008
0.00012
0.0003
0.003
0.00117
0.004
0.002
0.00005
0.0275
0.12
0.002
0.005
0.002
0.003
0.002
0.0063
0.001
0.002
0.0027
0.002
0.005
0.00463
0.01
0.006
0.0021
0.55
0.12
0.227
0.005
0.1
1.1
0.038
0.043
0.005
0.25
0.029
0.04
0.15
0.02
0.064
0.37
1.1
0.001
0.07
0.0003
0.063
0.00005
0.001
0.001
0.002
0.001
0.0007
0.00014
0.0004
0.003
0.00104
0.002

0.00005
0.005
0.11
0.00185
0.063
0.0028
0.003
0.002
0.0033
0.001
0.003
0.002
0.002
0.0035
0.002275
0.01

0.0032
0.011
0.219
0.072
0.063
0.1
0.023
0.039
0.02
0.004
0.04
0.0408
0.035
0.004
0.0189
0.08

0.219
0.001
0.057
0.0002
0.007
0.00005
0.001
0.0001
0.03
0.001
0.00012
0.00007
0.001
0.003

0.0052

0.00005
0.0025
0.0735
0.002
0.007
0.004
0.003
0.002
0.03
0.002
0.0012
0.002
0.004
0.003

0.01

0.0021
0.035
0.14
0.04
0.007
0.1
0.085
0.008
0.03
0.013
0.03
0.018
0.013
0.003

0.03

0.14
0.001
0.06
0.0003

0.00005

0.002
0.006
0.001
0.0005
0.00012
0.001
0.003

0.01

0.00005
0.0035
0.087
0.0023

0.0033

0.003
0.006
0.001
0.002
0.0024
0.002
0.003

0.015

0.0025
0.17
1.1
0.038

0.1

0.006
0.006
0.004
0.21
0.0554
0.01
0.004

0.02

1.1
0.001
0.052
0.0001

0.0002
0.003
0.001

0.001
0.0008
0.000274



0.01

0.0001
0.001
0.064
0.0017

0.00145
0.003
0.002

0.001
0.003
0.002



0.01

0.0018
0.001
0.12
0.04

0.011
0.003
0.005

0.001
0.08
0.032



0.01

0.12
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
844
6,250
94
69
373
1,147
149
265
23
450
153
930
434
14
1,467
391
13,053
27
12
15
1
74
246
43
4
22
51
59
41

2
40
4
641
3.20%
0.19%
15.96%
1.45%
19.84%
21.45%
28.86%
1.51%
95.65%
11.33%
38.56%
4.41%
0.00%
14.29%
2.73%
1.02%
4.91%
0.001




0.001

0.001


0.0007
0.001


0.0063
0.05
0.0007
0.001




0.002

0.001


0.0047
0.002


0.01
0.05
0.003
0.001




0.055

0.001


0.12
0.035


0.02
0.05
0.12
0.002

0.0012
0.024
0.0001
0.00016
0.001


0.0011
0.0008
0.0003


0.004
0.001
0.0001
0.002

0.0031
0.024
0.004
0.002
0.001


0.0011
0.0017
0.005


0.01
0.001
0.002
0.002

0.005
0.024
0.1
0.02
0.003


0.0011
0.0068
0.032


0.03
0.001
0.1
0.005

0.004

0.00075
0.0005
0.001
0.02
0.001
0.0008
0.00012
0.001


0.0048
0.018
0.00012
0.0105

0.005

0.0183
0.002
0.0015
0.02
0.0015
0.004
0.0014
0.004


0.0074
0.018
0.002
0.17

0.006

0.05
0.02
0.003
0.02
0.002
0.01
0.0072
0.007


0.01
0.018
0.17
0.002

0.0006

0.00005
0.0007
0.001

0.001
0.0007
0.001
0.001


0.0045
0.11
0.00005
0.01

0.002

0.00125
0.002
0.001

0.0015
0.00155
0.00275
0.001


0.00525
0.11
0.002
0.07

0.006

0.0075
0.05
0.004

0.002
0.01
0.005
0.004


0.011
0.11
0.11
0.00015
0.051
0.0008

0.0008
0.001
0.001

0.001
0.00005
0.001


0.0021
0.0043

0.00005
0.002
0.09
0.0025

0.0009
0.0026
0.001

0.001
0.0024
0.005


0.00605
0.01

0.002
0.035
0.89
0.007

0.0058
0.0035
0.004

0.003
0.01
0.02


0.01
0.01

0.89
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                            Six-Year Review
 Table B.lS.b. Cyanide - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
685
4,896
5,101
161
2,350
801
0
356
982
2,723
1,775
609
897
0
0
1,094
22,430
11
3
375
2
1,483
25

2
4
46
16
12
16


14
2,009
1.61%
0.06%
7.35%
1.24%
63.11%
3.12%
0.00%
0.56%
0.41%
1.69%
0.90%
1.97%
1.78%
0.00%
0.00%
1.28%
8.96%


0.0004

0.00001
0.002

0.013
0.02
0.002
0.1
0.003
0.01


0.01
0.00001


0.0112

0.01
0.02

0.0735
0.02
0.01
0.34
0.0045
0.01


0.02
0.01


6.01

0.15
0.056

0.134
0.02
0.25
32.7
0.017
0.02


0.2
32.7
0.0119

0.001
0.02
0.00001
0.003


0.02
0.003
0.1
0.003
0.01


0.01
0.00001
0.01555

0.012
0.025
0.01
0.017


0.02
0.013
0.145
0.004
0.01


0.01
0.01
0.0362

0.314
0.03
0.16
0.064


0.02
0.06
0.19
0.005
0.01


0.01
0.314
0.006
0.56
0.002

0.005
0.02



0.02






0.002
0.008
0.56
0.0225

0.01
0.02



0.02






0.01
0.01
0.56
0.195

0.2
0.02



0.38






0.56
0.005
0.065
0.005

0.00001




0.003
0.13





0.00001
0.053
0.065
0.025

0.01




0.01
0.13





0.01
0.1
0.065
5.735

0.2




0.1
0.13





5.735
0.008
0.35
0.001

0.005











0.001
0.008
0.35
0.02

0.02











0.02
0.008
0.35
0.701

0.03











0.701
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
491
2,216
90
70
124
942
0
115
59
194
57
529
5
0
0
326
5,218
10

3
1
97
21

4

12
1
7



2
158
2.04%
0.00%
3.33%
1.43%
78.23%
2.23%
0.00%
3.48%
0.00%
6.19%
1.75%
1.32%
0.00%
0.00%
0.00%
0.61%
3.03%
0.005



0.005
0.02





0.002




0.002
0.008



0.005
0.02





0.003




0.006
0.029



0.02
0.02





0.03




0.03
0.005



0.005
0.001

0.001


0.15
0.001



0.01
0.001
0.006



0.01
0.035

0.005


0.15
0.002



0.01
0.01
0.007



0.05
0.06

0.2


0.15
0.003



0.01
0.2




0.005
0.002

0.002

0.002






0.002




0.005
0.018

0.002

0.005






0.0075




0.021
0.04

0.002

0.024






0.04
0.002

0.011
0.005
0.00001
0.02



0.003

0.003




0.00001
0.005

0.07
0.005
0.01
0.02



0.006

0.003




0.01
0.08

0.071
0.005
0.06
0.03



0.008

0.003




0.08
0.025



0.004
0.001



0.02

0.02




0.001
0.025



0.02
0.002



0.07

0.02




0.02
0.025



0.06
0.002



0.12

0.02




0.12
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                            Six-Year Review
 Table B.16.b. 2,4-D - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
3,154
9,885
4,634
4,745
2,918
1,498
2,800
1,648
632
54
4,060
629
4,962
867
3,469
1,007
46,962
18
11
4
42
3
9

1



2
1


2
93
0.57%
0.11%
0.09%
0.89%
0.10%
0.60%
0.00%
0.06%
0.00%
0.00%
0.00%
0.32%
0.02%
0.00%
0.00%
0.20%
0.20%
0.000083
0.002
0.000005
0.00011

0.0001

0.00041



0.007
0.0002


0.000055
0.000005
0.0003415
0.0088
0.000005
0.00023

0.00013

0.00041



0.0075
0.0002


0.0001325
0.00021
0.0006
0.046
0.000005
0.016

0.00022

0.00041



0.008
0.0002


0.00021
0.046
0.000176
0.0004

0.00011
0.001
0.00009










0.00009
0.0003
0.0004

0.000305
0.001
0.00009










0.00034
0.000823
0.0013

0.0014
0.001
0.00011










0.0014
0.0001788
0.00093
0.00112
0.00014
0.001











0.00014
0.001
0.00093
0.02806
0.00042
0.001











0.00093
0.005
0.00093
0.055
0.0012
0.001











0.055

0.002

0.00011












0.00011

0.00295

0.00015












0.000495

0.0039

0.00083












0.0039


0.0009
0.00012












0.00012


0.0009
0.00012












0.00051


0.0009
0.00012












0.0009
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
969
3,604
78
1,474
516
1,674
175
228
34
14
155
608
655
183
2,263
360
12,990
16
6

72
8
24





2
1

2
i
132
1.65%
0.17%
0.00%
4.88%
1.55%
1.43%
0.00%
0.00%
0.00%
0.00%
0.00%
0.33%
0.15%
0.00%
0.09%
0.28%
1.02%
0.0004
0.00032

0.00037

0.00013








0.0343
0.00021
0.00013
0.0004
0.00032

0.00055

0.00023








0.0343
0.00021
0.00037
0.0004
0.00032

0.00073

0.005








0.0343
0.00021
0.0343
0.0002


0.000119

0.00006





0.0006
0.00011



0.00006
0.0008


0.0004

0.000085





0.0293
0.00011



0.00035
0.0014


0.0017

0.0002





0.058
0.00011



0.058
0.000646
0.001

0.00011
0.00024
0.00008










0.00008
0.000773
0.001

0.000325
0.0021
0.00011










0.0003
0.0009
0.001

0.00083
0.00265
0.00113










0.00265
0.0001
0.001

0.000119
0.0003
0.00008










0.00008
0.0008
0.001

0.00026
0.0004
0.0001










0.00037
0.0018
0.001

0.002
0.0005
0.00096










0.002
0.0002
0.01

0.0001
0.000242
0.00011








0.008

0.0001
0.0007
0.02

0.0002
0.00038
0.00011








0.008

0.00028
0.0014
0.1

0.0005
0.00394
0.00011








0.008

0.1
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                                   Six-Year Review
  Table B.17.b. Dalapon - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
3,111
3,996
4,680
4,745
2,828
1,020
36
446
632
0
3,674
583
5,111
867
3,469
72
35,270
10
8
73
9
1



2

1





104
0.32%
0.20%
1 .56%
0.19%
0.04%
0.00%
0.00%
0.00%
0.32%
0.00%
0.03%
0.00%
0.00%
0.00%
0.00%
0.00%
0.29%
0.0004
0.002
0.00001
0.0011












0.00001
0.0004
0.002
0.002
0.0015












0.0019
0.0004
0.002
0.0388
0.0019












0.0388
0.002
0.001
0.0000016
0.0011
0.001











0.0000016
0.00405
0.003
0.0019
0.0016
0.001











0.0022
0.025
0.004
0.011
0.00243
0.001











0.025
0.006995

0.00045





0.00209

0.02





0.00045
0.006995

0.00215





0.00222

0.02





0.002375
0.006995

0.0052





0.00235

0.02





0.02
0.00037
0.002
0.0002
0.001












0.0002
0.000685
0.008
0.00175
0.001












0.00175
0.001
0.017
0.00338
0.001












0.017


0.00142
0.002












0.00142


0.00173
0.002












0.001865


0.0094
0.002












0.0094
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
889
1,534
81
1,416
513
948
22
66
34
0
132
427
646
183
2,263
16
9,170
37
4
4
34
5
1

1








86
4.16%
0.26%
4.94%
2.40%
0.97%
0.11%
0.00%
1 .52%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.94%
0.011
0.001

0.0016
0.0012











0.001
0.03
0.001

0.001685
0.00125











0.0016
0.049
0.001

0.00177
0.0013











0.049
0.018

0.004
0.0013

0.0011










0.0011
0.03

0.004
0.0021

0.0011










0.00296
0.068

0.0073
0.025

0.0011










0.068
0.001


0.0011



0.0153








0.001
0.009


0.0025



0.0153








0.00367
0.0153


0.00537



0.0153








0.0153
0.001
0.019
0.0016
0.0025
0.0012











0.001
0.02
0.019
0.0016
0.0025
0.00124











0.013
0.064
0.019
0.0016
0.0025
0.0018











0.064
0.001
0.001

0.00441












0.001
0.013
0.001

0.00441












0.003705
0.045
0.001

0.00441












0.045
  Note:  All results are expressed in mg/L.
  * Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                               Six-Year Review
  Table B.18.b.  l,2-Dibromo-3-chloropropane - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
3,079
26,193
4,623
5,690
2,741
1,870
1,678
1,435
5,962
9,114
5,126
591
9,691
1,411
0
328
79,532
13
4,951
6
2
14




7
9

37


8
5,047
0.42%
18.90%
0.13%
0.04%
0.51%
0.00%
0.00%
0.00%
0.00%
0.08%
0.18%
0.00%
0.38%
0.00%
0.00%
2.44%
6.35%
0.00008
0.00011

0.00002
0.000082




0.00002
0.000013

0.00004


0.00005
0.000013
0.00008
0.00032

0.00002
0.001391




0.00026
0.00006

0.00013


0.00005
0.0003
0.00008
0.0062

0.00002
0.0027




0.0005
0.0001

0.056


0.00005
0.056
0.00002
0.00011
0.000011
0.00007
0.00019




0.0005
0.0001

0.00004


0.00005
0.000011
0.00003
0.0004
0.00001 1
0.00007
0.00028




0.0005
0.0001

0.00052


0.00005
0.0004
0.00003
0.00616
0.000011
0.00007
0.00037




0.001
0.0001

0.00093


0.00005
0.00616
0.000024
0.00011


0.000027





0.00003

0.00052



0.000024
0.000043
0.00024


0.00009





0.00003

0.00055



0.00023
0.000139
0.00411


0.00015





0.00003

0.00055



0.00411
0.00001
0.000105
0.000076

0.00005





0.00008

0.00006



0.00001
0.00001
0.00031
0.000076

0.000052





0.000085

0.00007



0.00031
0.00001
0.074
0.000076

0.00011





0.00009

0.00009



0.074

0.00011
0.00005

0.00004







0.00009



0.00004

0.00028
0.00006

0.00004







0.00009



0.00028

0.034
0.000091

0.00004







0.00009



0.034
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
830
10,700
77
1,389
516
1,586
320
219
217
560
321
436
1,514
258
0
75
19,018
15
2,187

9
4
3

1

4
5

18



2,246
1.81%
20.44%
0.00%
0.65%
0.78%
0.19%
0.00%
0.46%
0.00%
0.71%
1.56%
0.00%
1.19%
0.00%
0.00%
0.00%
11.81%
0.000034


0.00003
0.000078
0.0001




0.000013

0.00061



0.000013
0.000034


0.00003
0.000078
0.0001




0.0000265

0.00061



0.00004
0.000034


0.00003
0.000078
0.0001




0.00004

0.00061



0.00061



0.00002












0.00002



0.000025












0.000025



0.00007












0.00007
0.00002
0.00011

0.00002
0.000034


0.000269








0.00002
0.000026
0.00013

0.00002
0.00004


0.000269








0.000078
0.000061
0.00019

0.00002
0.000078


0.000269








0.000269
0.00002
0.00011

0.00002

0.00001




0.00014

0.00013



0.00001
0.00003
0.00014

0.000025

0.000015




0.00014

0.00031



0.00014
0.00005
0.0016

0.00003

0.00002




0.00014

0.229



0.229

0.000101

0.00004





0.00000001
0.00045





0.00000001

0.00034

0.00004





0.0005
0.00045





0.00034

0.0152

0.00004





0.0005
0.00045





0.0152
  Note: All results are expressed in mg/L.
  * Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                           Six-Year Review
 Table B.19.b. 1,4-Dichlorobenzene - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
5,117
0
18,535
23,484
3,801
1,580
1,973
0
3,855
10,127
5,504
1,920
8,313
495
19,146
2,929
106,779
2

81
113
37
16
9

4
102
4
6
9

92
19
494
0.04%
0.00%
0.44%
0.48%
0.97%
1.01%
0.46%
0.00%
0.10%
1.01%
0.07%
0.31%
0.11%
0.00%
0.48%
0.65%
0.46%


0.00001
0.0005
0.0005
0.00057
0.0004

0.0004
0.00019
0.00014
0.0006
0.00059

0.0005
0.0005
0.00001


0.001
0.0024
0.0013
0.00108
0.0009

0.00055
0.0008
0.00048
0.0013
0.0006

0.0009
0.0011
0.001


0.0046
0.042
0.0081
0.01
0.0014

0.0017
0.0072
0.0032
0.0026
0.00061

0.004
0.0067
0.042
0.001

0.0006
0.0005
0.0005
0.00067
0.0004


0.000032

0.0001
0.0005

0.0005

0.000032
0.00105

0.002035
0.0006
0.0005
0.00067
0.0005


0.00054

0.00015
0.00238

0.00065

0.000615
0.0011

0.00264
0.0086
0.0005
0.00067
0.0006


0.00135

0.0002
0.00728

0.0022

0.0086


0.0012
0.0002

0.00059



0.000656


0.0005

0.0005

0.0002


0.0012
0.0005

0.0008



0.0008875


0.0005

0.0007

0.0006


0.0012
0.0007

0.00093



0.001


0.0005

0.0015

0.0015


0.00051
0.00032





0.0001




0.0006

0.0001


0.0012
0.0009





0.00054




0.0011

0.0007


0.0097
0.0016





0.0026




0.006

0.0097


0.00016
0.00003
0.00063




0.00054






0.00003


0.0007
0.0015
0.00063




0.00054






0.0007


0.0068
0.0049
0.00063




0.00054






0.0068
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,297
0
136
2,799
526
1,706
438
0
95
667
345
924
1,020
55
4,776
666
16,450
6


28

6
5

1

1
1


25
2
75
0.26%
0.00%
0.00%
1.00%
0.00%
0.35%
1.14%
0.00%
1.05%
0.00%
0.29%
0.11%
0.00%
0.00%
0.52%
0.30%
0.46%





0.00125








0.0005

0.0005





0.00125








0.0006

0.0006





0.00125








0.001

0.00125
0.0016


0.0005

0.00053


0.0003


0.0013


0.0005

0.0003
0.0016


0.0021

0.00112


0.0003


0.0013


0.0009

0.0013
0.0016


0.0046

0.002


0.0003


0.0013


0.0018

0.0046
0.0006


0.0005

0.0005








0.0007

0.0005
0.000735


0.0005

0.0005








0.0007

0.0006
0.00087


0.0009

0.0005








0.0011

0.0011
0.00053


0.0005


0.0006



0.0016



0.0006
0.0005
0.0005
0.0007


0.0005


0.001



0.0016



0.0008
0.0005
0.00065
0.00124


0.0005


0.0015



0.0016



0.001
0.0005
0.0016



0.0005


0.0017







0.0006
0.0005
0.0005



0.0005


0.0017







0.0015
0.0005
0.0008



0.0008


0.0017







0.0021
0.0005
0.0021
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                           Six-Year Review
 Table B.20.b. o-Dichlorobenzene - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
5,117
0
18,450
23,440
3,764
1,148
4,155
3,334
4,767
10,150
5,248
647
8,330
683
23,193
3,678
116,104
1

39
57
8

3
9

86
1

1

3
13
221
0.02%
0.00%
0.21%
0.24%
0.21%
0.00%
0.07%
0.27%
0.00%
0.85%
0.02%
0.00%
0.01%
0.00%
0.01%
0.35%
0.19%


0.00005
0.0005
0.0009

0.0015
0.00057

0.0003





0.0005
0.00005


0.0007225
0.031
0.0035

0.0017
0.00057

0.00065





0.0011
0.000885


0.0034
0.18
0.0094

0.0019
0.0015

0.00904





0.0024
0.18
0.0005

0.000688
0.0005
0.0011

0.0013
0.00053

0.0002


0.0005

0.002

0.0002
0.0005

0.000894
0.00125
0.0011

0.0013
0.00068

0.00065


0.0005

0.00265

0.001
0.0005

0.0011
0.0074
0.0011

0.0013
0.001

0.0025


0.0005

0.0033

0.0074



0.0005





0.00065




0.0013

0.0005



0.0005





0.00065




0.0013

0.0005



0.0005





0.00065




0.0013

0.0013


0.00026
0.000328





0.00019
0.0006





0.00019


0.0014
0.000414





0.00065
0.0006





0.00065


0.004
0.0005





0.0008
0.0006





0.004


0.000624
0.00014





0.0006






0.00014


0.00338
0.00117





0.00065






0.00141


0.0064
0.0022





0.00065






0.0064
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,295
0
135
2,793
526
1,152
506
391
154
694
209
447
1,091
70
6,183
762
17,408
1


16





1
1




1
20
0.04%
0.00%
0.00%
0.57%
0.00%
0.00%
0.00%
0.00%
0.00%
0.14%
0.48%
0.00%
0.00%
0.00%
0.00%
0.13%
0.11%
















0

































0



0.0005





0.0004






0.0004



0.0005





0.0004






0.00045



0.0005





0.0004






0.0005



0.0005






0.0013





0.0005



0.0005






0.0013





0.0005



0.0005






0.0013





0.0013
0.00486


0.0005











0.0005
0.0005
0.00486


0.0005











0.0005
0.0005
0.00486


0.0005











0.0005
0.00486



0.0005












0.0005



0.0005












0.0005



0.001












0.001
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                           Six-Year Review
 Table B.21.b. 1,2-Dichloroethane - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
5,128
39,785
18,615
23,714
3,783
1,571
1,972
3,328
3,857
10,780
5,521
1,916
8,319
495
19,146
2,935
150,865
37
496
37
78
27
10
6
2
91
122
29
4
68
3
20
7
1,037
0.72%
1.25%
0.20%
0.33%
0.71%
0.64%
0.30%
0.06%
2.36%
1.13%
0.53%
0.21%
0.82%
0.61%
0.10%
0.24%
0.69%

0.0006
0.00003
0.0005
0.00055
0.0002

0.00099
0.0002
0.00013
0.0063
0.0006
0.0005

0.0059
0.0004
0.00003

0.000945
0.0006
0.0006
0.00096
0.00052

0.00099
0.0016
0.00173
0.00715
0.0045
0.00095

0.0059
0.00065
0.001

0.0049
0.0029
0.0029
0.0067
0.001

0.00099
0.0242
0.017
0.008
0.009
0.00307

0.0059
0.0008
0.0242
0.0005
0.00052

0.0005
0.00077


0.00068
0.0002
0.000017
0.0003

0.00036
0.00178
0.00037
0.0003
0.000017
0.000975
0.00068

0.0007
0.00086


0.00068
0.0004
0.000785
0.00055

0.00059
0.00296
0.0012
0.0004
0.00072
0.0069
0.006

0.0019
0.001


0.00068
0.0251
0.0034
0.0023

0.00167
0.004648
0.0022
0.0009
0.0251
0.000519
0.00051
0.00051
0.0005
0.00056
0.0003
0.0005

0.0002
0.0003


0.00058



0.0002
0.0011
0.0018
0.002
0.0007
0.00071
0.00035
0.00055

0.0002
0.0007


0.00234



0.00105
0.00415
0.018
0.0034
0.0034
0.0012
0.0004
0.0027

0.0075
0.00121


0.00345



0.018
0.0005
0.00051
0.00027
0.000244
0.00058
0.0003


0.0002
0.0005
0.0002





0.0002
0.00072
0.0025
0.001
0.00078
0.00084
0.0003


0.0005
0.0018
0.0007





0.0021
0.0013
0.0125
0.001
0.011
0.0022
0.0003


0.0042
0.012
0.005





0.0125

0.00051
0.0000553
0.00017

0.0005










0.0000553

0.00076
0.00017
0.00145

0.0009










0.0007

0.007
0.0076
0.003

0.0013










0.0076
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,297
12,791
136
2,832
530
1,705
437
390
95
763
344
924
1,001
55
4,777
668
29,745
5
380
1
20
4
7

1


4

2

2
3
429
0.22%
2.97%
0.74%
0.71%
0.75%
0.41%
0.00%
0.26%
0.00%
0.00%
1.16%
0.00%
0.20%
0.00%
0.04%
0.45%
1.44%




0.001







0.00059



0.00059




0.0011







0.00059



0.001




0.0012







0.00059



0.0012


0.001
0.0005

0.0005

0.022







0.0006
0.0005


0.001
0.0005

0.0005

0.022







0.0006
0.0006


0.001
0.0005

0.0005

0.022







0.0006
0.022
0.0007


0.0005
0.0009











0.0005
0.0009


0.0005
0.0009











0.0007
0.0021


0.0015
0.0009











0.0021
0.0018
0.00051

0.0005
0.00058
0.0002






0.00099

0.0005
0.0003
0.0002
0.0034
0.0009

0.0006
0.00058
0.0003






0.00099

0.00065
0.0004
0.0008
0.005
0.0084

0.0024
0.00058
0.0004






0.00099

0.0008
0.0005
0.0084

0.00051

0.0005






0.0007





0.0005

0.00137

0.0005






0.0009





0.0013

0.0092

0.0005






0.003





0.0092
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                           Six-Year Review
 Table B.22.b. 1,1-Dichloroethylene - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
5,135
40,131
15,773
23,768
3,736
1,550
1,968
3,334
3,399
10,816
5,504
1,919
8,289
291
9,922
2,226
137,761
48
1,224
102
121
14
2
1
3
30
245
8
15
106

29
6
1,954
0.93%
3.05%
0.65%
0.51%
0.37%
0.13%
0.05%
0.09%
0.88%
2.27%
0.15%
0.78%
1.28%
0.00%
0.29%
0.27%
1.42%

0.00097
0.00007
0.0005
0.0005
0.001

0.00086
0.0002
0.00015

0.0008
0.00058

0.0005
0.0005
0.00007

0.0052
0.0033
0.0034
0.0006
0.001

0.0016
0.0049
0.0011555

0.0034
0.0018

0.0023
0.003
#REF!

0.0422
0.006
0.011
0.0038
0.001

0.0023
0.016
0.07

0.0352
0.824

0.0054
0.00582
0.824
0.0005
0.00068

0.0005
0.0006



0.0004
0.0002
0.0002

0.0005

0.0011
0.032
0.0002
0.004
0.0046

0.00065
0.0006



0.0006
0.000545
0.0002

0.00192

0.0081
0.0505
#REF!
0.0164
0.0238

0.0018
0.0006



0.0031
0.011
0.0002

0.0073

0.014
0.069
0.069
0.0008
0.00051
0.000243
0.0005
0.00086

0.0014

0.0011
0.00034
0.0004

0.00054



0.000243
0.0032
0.0021
0.0008
0.0005
0.00086

0.0014

0.0024
0.0006
0.001025

0.001485



#REF!
0.0076
0.011
0.001
0.001
0.00086

0.0014

0.003
0.00701
0.00165

0.00601



0.011
0.0007
0.00053
0.001
0.000197
0.0006



0.0002
0.00016
0.0002

0.00235



0.00016
0.0064
0.0028
0.0027
0.0009
0.00077



0.00055
0.0009
0.00069

0.00235



#REF!
0.0082
0.1525
0.0068
0.011
0.0026



0.0098
0.0077
0.0012

0.00235



0.1525
0.0006
0.00055
0.00015
0.0005
0.0008




0.00051
0.00022

0.00307



0.00015
0.0006
0.0019
0.002205
0.0019
0.0008




0.000865
0.00022

0.003635



#REF!
0.0006
0.019099
0.0108
0.0077
0.0008




0.00117
0.00022

0.0042



0.019099
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,296
15,557
136
2,830
526
2,000
437
391
92
763
345
922
1,019
54
4,710
572
32,650
7
2,327

16

5



3
2

9


1
2,370
0.30%
14.96%
0.00%
0.57%
0.00%
0.25%
0.00%
0.00%
0.00%
0.39%
0.58%
0.00%
0.88%
0.00%
0.00%
0.17%
7.26%




















































0.0014

0.0005

0.0005




0.0009





0.0005

0.0014

0.0005

0.0005




0.0009





#REF!

0.0014

0.0005

0.0005




0.0009





0.0014
0.0007
0.0006

0.0005








0.00058



0.0005
0.0007
0.0009

0.0005








0.00062



#REF!
0.0007
0.002

0.0005








0.0024



0.0024
0.0006
0.0006

0.0005

0.0011






0.00155


0.0005
0.0005
0.0006
0.0021

0.0005

0.00125






0.00344


0.0005
#REF!
0.0006
0.0107

0.0015

0.0018






0.0158


0.0005
0.0158
0.0005
0.00051

0.0005





0.0005






0.0005
0.0015
0.0014

0.0005





0.0008






#REF!
0.0019
0.184

0.0005





0.0009






0.184
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                            Six-Year Review
 Table B.23.b. cis-l,2-Dichloroethylene - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
5,116
34,585
18,841
23,582
3,891
1,148
4,256
3,320
4,767
10,960
5,251
655
8,319
683
23,193
3,652
152,219
7
1,855
650
365
135
5
141
5
110
434
5
9
69

4
145
3,939
0.14%
5.36%
3.45%
1.55%
3.47%
0.44%
3.31%
0.15%
2.31%
3.96%
0.10%
1.37%
0.83%
0.00%
0.02%
3.97%
2.59%


0.00001
0.0005
0.00058
0.0016
0.0005
0.0047
0.0002
0.00024

0.0005
0.0005

0.0029
0.0005
0.00001


0.0013
0.0011
0.00155
0.002
0.0006
0.005
0.0012
0.0014

0.0013
0.00068

0.0047
0.0008
0.0013


0.26
0.019
0.027
0.0021
0.0009
0.007
0.0306
0.015

0.0049
0.00341

0.0148
0.0013
0.26
0.0009
0.0006
0.000666
0.0005
0.0005

0.0004

0.00029
0.000035
0.0006

0.0005


0.0005
0.000035
0.0009
0.0027
0.00071
0.0055
0.00165

0.0005

0.0006
0.00431
0.00105

0.00063


0.0031
0.0026
0.0009
0.0052
0.00093
0.023
0.025

0.0013

0.0027
0.0948
0.0025

0.00341


2.6
2.6
0.0006
0.00054
0.00027
0.0002
0.0007

0.0004

0.0002
0.00018


0.00051



0.00018
0.00065
0.0013
0.00078
0.001
0.00095

0.0013

0.0008
0.0016


0.0009



0.0011
0.0008
0.0092
0.00264
0.0093
0.0034

0.0388

0.0039
0.0226


0.00228



0.0388

0.00051
0.00015
0.0005
0.0005

0.0004

0.0002
0.00018


0.00053



0.00015

0.00134
0.0017
0.002
0.00135

0.0009

0.0008
0.0018


0.00053



0.0014

0.09
0.14
0.013
0.03

0.005

0.008
0.043


0.00097



0.14

0.00052
0.00006
0.00015
0.0005

0.0008


0.00021
0.00002

0.00068



0.00002

0.00135
0.002195
0.0015
0.00081

0.0018


0.00068
0.00002

0.001005



0.00158

0.064
0.114
0.028
0.0065

0.0019


0.0079
0.00002

0.00133



0.114
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,301
11,058
136
2,808
528
1,177
536
385
154
786
209
446
1,091
70
6,183
752
28,620
30
687

26
2

59


7

1
2

2
1
817
1.30%
6.21%
0.00%
0.93%
0.38%
0.00%
11.01%
0.00%
0.00%
0.89%
0.00%
0.22%
0.18%
0.00%
0.03%
0.13%
2.85%














0.00498

0.00498














0.00498

0.00498














0.00498

0.00498



0.0005








0.0121

0.00498

0.0005



0.00065








0.0121

0.00498

0.00289



0.0008








0.0121

0.00498

0.0121



0.0005












0.0005



0.0005












0.0005



0.0032












0.0032

0.00051

0.0005


0.0004


0.0006





0.0005
0.0004

0.0013

0.0005


0.0009


0.0006





0.0005
0.0011

0.0047

0.0005


0.003


0.0006





0.0005
0.0047
0.0005
0.00051

0.0005
0.00055




0.0005

0.0002
0.0198



0.0002
0.001
0.0016

0.0012
0.000575




0.0012

0.0002
0.0198



0.0016
0.0043
0.0119

0.0043
0.0006




0.0018

0.0002
0.0198



0.0198
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                           Six-Year Review
 Table B.24.b. trans-l,2-Dichloroethylene - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
0
38,711
18,555
23,603
3,761
1,146
4,161
3,332
4,766
10,748
5,248
651
8,319
683
23,193
3,556
150,433

61
146
54
6

2

46
21
1
4
1


3
345
0.00%
0.16%
0.79%
0.23%
0.16%
0.00%
0.05%
0.00%
0.97%
0.20%
0.02%
0.61%
0.01%
0.00%
0.00%
0.08%
0.23%

0.00169
0.00006
0.0005




0.0002
0.000172

0.002



0.0005
0.00006

0.00201
0.0009
0.0005




0.0057
0.0007

0.00305



0.0006
0.0008

0.00233
0.00139
0.0013




0.0532
0.00077

0.008



0.0007
0.0532


0.0006
0.0005





0.00046
0.0009

0.0005



0.00046


0.0012
0.001





0.000561
0.0009

0.0005



0.00085


0.005
0.061





0.00118
0.0009

0.0005



0.061

0.00077
0.0001
0.0005


0.0004


0.00051






0.0001

0.0016
0.001
0.0005


0.00205


0.00055






0.00055

0.0083
0.001
0.0006


0.0037


0.0007






0.0083

0.00053
0.00016
0.000162
0.0006



0.0002
0.0006






0.00016

0.000895
0.00061
0.0021
0.001



0.000645
0.0007






0.0009

0.047
0.0016
0.033
0.015



0.007
0.0241






0.047

0.0006
0.000265
0.00017
0.00372











0.00017

0.0019
0.0014
0.00017
0.00372











0.00149

0.017
0.0033
0.00017
0.00372











0.017
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
0
11,899
135
2,806
526
1,157
506
391
154
783
209
446
1,091
70
6,183
752
27,108

7

15

1









1
24
0.00%
0.06%
0.00%
0.53%
0.00%
0.09%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.13%
0.09%
















0

































0



0.0005

0.004










0.0005



0.0005

0.004










0.00225



0.0005

0.004










0.004



0.0005












0.0005



0.0005












0.0005



0.0005












0.0005



0.0005











0.0005
0.0005



0.0005











0.0005
0.0005



0.0005











0.0005
0.0005

0.0007

0.0005












0.0005

0.0014

0.0005












0.0007

0.0029

0.0005












0.0029
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                                 Six-Year Review
  Table B.25.b.  Dichloromethane - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
SOI - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NI
NM
OR
SC
SD
TX
VT
All States
5,130
38,708
18,606
23,627
3,963
1,149
1,971
0
3,855
10,750
4,830
659
7,804
495
19,146
2,820
143,513
230
242
200
1,329
203
20
15

4
372
16
13
51
2
145
17
2,859
4.48%
0.63%
1.07%
5.62%
5.12%
1.74%
0.76%
0.00%
0.10%
3.46%
0.33%
1.97%
0.65%
0.40%
0.76%
0.60%
1.99%
0.0005
0.00059
0.0000011
0.0005
0.0005
0.00052
0.0007

0.0012
0.00023
0.0006
0.0007
0.0005
0.000726
0.0005
0.0005
0.0000011
0.00115
0.00095
0.0012
0.0008
0.0013
0.001525
0.0009

0.0019
0.001
0.0019
0.0012
0.00121
0.000754
0.0014
0.000955
#REF!
0.0046
0.0105
0.0473
0.016
0.0135
0.0025
0.0045

0.0026
0.0786
0.11
5.4
0.0281
0.000782
0.391
0.01
5.4
0.0005
0.0006
0.0000007
0.0005
0.00058
0.00053
0.0006

0.0013
0.00007
0.0008
0.0008
0.0005

0.0005
0.0024
0.0000007
0.0015
0.001
0.00157
0.0008
0.0012
0.00231
0.00105

0.0013
0.0008
0.008
0.0009
0.00192

0.00165
0.0024
AREF!
0.00987
0.12
0.017
0.007
0.013
0.00784
0.0022

0.0013
0.0048
0.27
0.0017
0.0184

0.1
0.0024
0.27
0.00052
0.00053
0.00006
0.0001
0.0005
0.00182
0.0006


0.0004


0.0005

0.0005

0.00006
0.00078
0.00093
0.001145
0.00095
0.00089
0.002135
0.00075


0.00107


0.00172

0.00125

#REF!
0.0039
0.005
0.0209
0.17
0.01
0.0033
0.0009


0.00793


0.00294

0.011

0.17
0.0004
0.00053
0.00044
0.00035
0.0005



0.003
0.00041
0.0006

0.00087

0.0006

0.00035
0.002
0.001
0.00145
0.001
0.00094



0.003
0.0009
0.0009

0.00087

0.0013

AREF!
0.0173
0.034
0.0091
0.013
0.008



0.003
0.014
0.0017

0.00087

0.0089

0.034
0.001
0.00051
0.00051
0.00009





0.00017
0.0002





0.00009
0.003
0.00135
0.00253
0.002





0.00114
0.0002





#REF!
0.004
0.1
0.0054
0.028





0.0023
0.0002





0.1
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NI
NM
OR
SC
SD
TX
VT
All States
2,327
11,902
135
2,844
546
1,148
439
0
95
737
309
449
946
55
4,777
656
27,365
189
75
1
244
20
40
2


15
4
2
10

44
7
653
8.12%
0.63%
0.74%
8.58%
3.66%
3.48%
0.46%
0.00%
0.00%
2.04%
1.29%
0.45%
1.06%
0.00%
0.92%
1.07%
2.39%
0.00053
0.0008

0.0005
0.00068
0.00065



0.0005
0.009
0.0004


0.0005
0.0001
0.0001
0.0014
0.0022

0.0008
0.0013
0.00065



0.002215
0.0095
0.0004


0.0007
0.00155
#REF!
0.0016
0.0036

0.0015
0.0015
0.00065



0.00393
0.01
0.0004


0.0221
0.0026
0.0221
0.00063
0.0009
0.0067
0.0005
0.00059
0.0006



0.0007
0.0063
0.0011
0.0006

0.0005

0.0005
0.000845
0.0009
0.0067
0.0012
0.00078
0.002795



0.0007
0.0067
0.0011
0.00102

0.0011

AREF!
0.0011
0.0009
0.0067
0.0081
0.0021
0.0031



0.0007
0.0071
0.0011
0.00811

0.0026

0.00811
0.00052
0.0012

0.00035
0.00055
0.00053








0.0006

0.00035
0.0017
0.003365

0.0016
0.00087
0.0012








0.00105

#REF!
0.00797
0.00553

0.017
0.0024
0.00341








0.0018

0.017
0.000513
0.00055

0.0005
0.0022
0.00072
0.0009


0.0002


0.0008

0.0006
0.0005
0.0002
0.00145
0.0027

0.0012
0.0022
0.001595
0.0009


0.000555


0.00098

0.00085
0.0005
AREF!
0.00798
0.025

0.0071
0.0022
0.006
0.0009


0.0014


0.00176

0.0013
0.0005
0.025
0.00051
0.00055

0.0005
0.0009

0.0012


0.00023




0.0006

0.00023
0.0015
0.000975

0.002
0.0009

0.0012


0.00079




0.0092

#REF!
0.0042
0.018

0.011
0.0009

0.0012


0.0017




0.0178

0.018
  Note: All results are expressed in mg/L.
  * Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                           Six-Year Review
 Table B.26.b. 1,2-Dichloropropane - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
5,122
36,571
18,465
23,517
3,758
1,138
1,967
3,333
4,769
10,074
5,501
648
8,348
720
23,780
3,966
151,677
26
130
50
38
3



11
28

2
12

10
2
312
0.51%
0.36%
0.27%
0.16%
0.08%
0.00%
0.00%
0.00%
0.23%
0.28%
0.00%
0.31%
0.14%
0.00%
0.04%
0.05%
0.21%

0.00055
0.00001
0.0005
0.0006



0.0025
0.00019


0.00089

0.0005
0.0005
0.00001

0.00083
0.001
0.0005
0.0008



0.0025
0.000818


0.003255

0.0006
0.00075
0.00083

0.053
0.002
0.065
0.0038



0.0025
0.0083


0.00516

0.0028
0.001
0.065
0.0005
0.00059
0.0009
0.0005




0.0002
0.0005

0.0023
0.0005



0.0002
0.00125
0.00101
0.0009
0.0005




0.00062
0.0012

0.35115
0.00089



0.00089
0.0035
0.0028
0.0009
0.01




0.00243
0.0016

0.7
0.00089



0.7


0.000223
0.0005





0.0003




0.0005

0.000223


0.000223
0.0005





0.00075




0.0013

0.0005


0.000223
0.0024





0.0024




0.0019

0.0024
0.00054
0.00058
0.00013
0.000182





0.00045






0.00013
0.00064
0.00145
0.00205
0.00055





0.0009






0.0012
0.0018
0.01
0.004
0.001





0.00136






0.01

0.0006
0.000568
0.00007












0.00007

0.001
0.00211
0.00007












0.001

0.007
0.039
0.00007












0.039
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,295
11,660
135
2,798
526
1,146
437
391
155
668
344
448
1,084
75
6,251
812
29,225
3
46

16



1

6

1
2


1
76
0.13%
0.39%
0.00%
0.57%
0.00%
0.00%
0.00%
0.26%
0.00%
0.90%
0.00%
0.22%
0.18%
0.00%
0.00%
0.12%
0.26%






















































0.0005



0.00098




0.0083



0.0005



0.0005



0.00098




0.0083



0.00464



0.0005



0.00098




0.0083



0.0083



0.0005





0.0005






0.0005



0.0005





0.0005






0.0005



0.0025





0.0005






0.0025
0.0033
0.00052

0.0005







0.003



0.0005
0.0005
0.0033
0.00066

0.0005







0.003



0.0005
0.000605
0.0033
0.00076

0.0005







0.003



0.0005
0.0033
0.0008
0.0007

0.0005





0.0006






0.0005
0.0012
0.0028

0.0005





0.0009






0.00215
0.0016
0.0067

0.0005





0.0018






0.0067
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                            Six-Year Review
 Table B.27.b. Dinoseb - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
3,096
4,538
4,613
4,755
2,832
1,018
2,800
448
632
0
4,059
585
4,981
867
3,469
1,003
39,696
5
5
2
8
1


8







1
30
0.16%
0.11%
0.04%
0.17%
0.04%
0.00%
0.00%
1.79%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.10%
0.08%

0.001
0.000002
0.00076



0.001







0.000185
0.000002

0.001
0.000002
0.000775



0.007







0.000185
0.0012

0.001
0.000002
0.00079



0.025







0.000185
0.025
0.0002
0.00018














0.00018
0.00025
0.00018














0.0002
0.0004
0.00018














0.0004



0.000139












0.000139



0.000277












0.000277



0.001












0.001
0.0003
0.1
0.00131

0.00068











0.0003
0.0003
0.1
0.00131

0.00068











0.000995
0.0003
0.1
0.00131

0.00068











0.1
















0

































0
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
833
1,567
79
1,411
507
949
175
63
34
0
146
427
642
183
2,263
312
9,591
14


10











1
25
1.68%
0.00%
0.00%
0.71%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.32%
0.26%



0.00031












0.00031



0.000525












0.000525



0.00074












0.00074
0.0002


0.00021












0.0002
0.00045


0.000345












0.000345
0.0007


0.00082












0.00082



0.000381











0.0136
0.000381



0.00042











0.0136
0.0004705



0.000521











0.0136
0.0136
0.0002


0.000447












0.0002
0.0005


0.000447












0.0004735
0.004


0.000447












0.004
0.0002


0.001167












0.0002
0.0002


0.001167












0.0006835
0.0021


0.001167












0.0021
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                            Six-Year Review
 Table B.28.b. Diquat - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
3,144
3,703
4,670
4,646
2,841
1,017
35
2
714
0
3,085
547
5,113
595
0
53
30,165
37
2
8
1
8











56
1.18%
0.05%
0.17%
0.02%
0.28%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.19%


0.000475

0.00036











0.00036


0.00176

0.000615











0.00074


0.00395

0.004











0.004
0.0004

0.0022

0.0009











0.0004
0.0008

0.0026

0.0009











0.00088
0.019

0.0043

0.0009











0.019
0.0004

0.00053













0.0004
0.00075

0.00053













0.00053
0.0016

0.00053













0.0016
0.0003
0.002


0.0024











0.0003
0.0007
0.003


0.0024











0.001
0.0085
0.004


0.0024











0.0085


0.00089
0.0418












0.00089


0.00089
0.0418












0.021345


0.00089
0.0418












0.0418
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
874
1,468
77
964
507
972
19
0
17
0
208
415
594
161
0
2
6,278
35


1












36
4.00%
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%
0.00%
0.00%
0.57%
0.0006















0.0006
0.0006















0.0006
0.0006















0.0006
0.0004


0.0004












0.0004
0.00058


0.0004












0.00049
0.0015


0.0004












0.0015
0.0003















0.0003
0.0006















0.0006
0.0014















0.0014
0.0004















0.0004
0.0013















0.0013
0.024















0.024
0.0003















0.0003
0.0005















0.0005
0.004















0.004
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                            Six-Year Review
 Table B.29.b. Endothall - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
3,104
2,522
4,662
4,618
2,829
1,051
35
2
10
0
2,997
546
4,386
680
0
52
27,494
1
1
1
1
1





2





7
0.03%
0.04%
0.02%
0.02%
0.04%
0.00%
0.00%
0.00%
0.00%
0.00%
0.07%
0.00%
0.00%
0.00%
0.00%
0.00%
0.03%


0.009

0.018





0.0019





0.0019


0.009

0.018





0.0019





0.00545


0.009

0.018





0.0019





0.018



4.548












4.548



4.548












4.548



4.548












4.548
0.017















0.017
0.017















0.017
0.017















0.017

0.1














0.1

0.1














0.1

0.1














0.1
















0

































0
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
797
476
77
955
508
987
20
0
5
0
108
405
594
178
0
2
5,112

2


1
4





1




8
0.00%
0.42%
0.00%
0.00%
0.20%
0.41%
0.00%
0.00%
0.00%
0.00%
0.00%
0.25%
0.00%
0.00%
0.00%
0.00%
0.16%
















0

































0
















0

































0
















0

































0

0.0025


0.013
0.55





0.009




0.0025

0.0025


0.013
1.725





0.009




0.55

0.0025


0.013
2.9





0.009




2.9

0.0025














0.0025

0.0025














0.0025

0.0025














0.0025
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                                   Six-Year Review
  Table B.30.b.  Endrin - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NI
NM
OR
SC
SD
TX
VT
All States
3,103
9,607
4,685
5,285
2,838
1,462
2,845
1,609
1,974
50
4,131
632
6,410
902
4,044
963
50,540
6
3
3







3





15
0.19%
0.03%
0.06%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.07%
0.00%
0.00%
0.00%
0.00%
0.00%
0.03%


0.00002







0.00011





0.00002


0.00002







0.00011





0.000065


0.00002







0.00011





0.00011
0.000008
0.3














0.000008
0.000019
0.3














0.00002
0.000037
0.3














0.3
0.000014









0.0001





0.000014
0.000027









0.0006





0.00007
0.00004









0.0011





0.0011

0.013














0.013

0.013














0.013

0.013














0.013

0.0002
0.00028













0.0002

0.0002
0.000305













0.00028

0.0002
0.00033













0.00033
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NI
NM
OR
SC
SD
TX
VT
All States
931
3,674
77
2,142
545
1,595
181
248
170
13
156
598
745
179
3,944
362
15,560
7
4

4
1






1




17
0.75%
0.11%
0.00%
0.19%
0.18%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.17%
0.00%
0.00%
0.00%
0.00%
0.11%
0.000051















0.000051
0.000051















0.000051
0.000051















0.000051



0.00001












0.00001



0.00001












0.00001



0.00001












0.00001
0.000008










0.00002




0.000008
0.000018










0.00002




0.000019
0.000089










0.00002




0.000089
0.000008















0.000008
0.000038















0.000038
0.000038















0.000038

0.0002

0.0001
0.00003











0.00003

0.0101

0.0001
0.00003











0.0002

0.09

0.0001
0.00003











0.09
  Note: All results are expressed in mg/L.
  * Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                           Six-Year Review
 Table B.31.b. Ethylbenzene - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
5,118
38,590
18,552
23,591
3,785
1,154
4,166
3,321
4,767
10,057
5,238
656
8,328
683
23,193
3,682
154,881
72
60
96
161
17
5
16
7
35
55
16
6
59
6
689
15
1,315
1.41%
0.16%
0.52%
0.68%
0.45%
0.43%
0.38%
0.21%
0.73%
0.55%
0.31%
0.91%
0.71%
0.88%
2.97%
0.41%
0.85%
0.0009
0.0006
0.00001
0.0005
0.0005

0.0005
0.0006
0.0002
0.00017
0.0008
0.0006
0.00055
0.000676
0.0005
0.0002
0.00001
0.0011
0.0009
0.001
0.0007
0.00072

0.0009
0.00191
0.0008
0.0011
0.0014
0.00135
0.001
0.000711
0.001
0.0031
0.001
0.0091
0.004
0.016
0.044
0.0096

0.0015
0.0049
0.0145
0.0264
0.03
0.0064
0.0076
0.00144
0.3
0.01
0.3
0.0005
0.0008
0.0005
0.0005
0.0005
0.00058
0.0007
0.0006
0.0004
0.0002
0.00051
0.0008
0.0005
0.00065
0.00016
0.0006
0.00016
0.0009
0.00147
0.00156
0.001
0.00068
0.0006
0.0007
0.0006
0.0012
0.0005
0.0014
0.0009
0.00104
0.00065
0.0009
0.0007
0.0009
0.0893
0.1525
0.0794
0.027
0.002
0.002
0.0007
0.0006
0.0085
0.0054
0.003
0.001
0.00473
0.00065
0.05843
0.005
0.1525
0.000511
0.00054
0.00024
0.0002


0.0006

0.0007
0.0003


0.00051

0.00017

0.00017
0.00111
0.013
0.001
0.0005


0.0023

0.0022
0.00065


0.00087

0.0011

0.0011
0.009976
0.14
0.0081
0.0024


0.0047

0.003
0.00189


0.00232

0.38607

0.38607
0.0005
0.0006
0.000183
0.000205
0.0008



0.0005
0.00029
0.0004



0.0005

0.000183
0.00286
0.0029
0.0022
0.0006
0.0009



0.00379
0.0007
0.00098



0.001

0.0012
0.0118
0.019
0.00971
0.0094
0.001



0.00475
0.00527
0.0018



0.0071

0.019
0.0005
0.0007
0.0001
0.00069




0.00471



0.00119

0.0005

0.0001
0.001
0.0031
0.00175
0.005595




0.00471



0.00119

0.00075

0.001725
0.004
0.01
0.03
0.0105




0.00471



0.00119

0.001

0.03
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,300
11,894
135
2,799
526
1,151
512
385
154
671
209
448
1,094
70
6,182
768
29,298
26
19

18

13
11
2
1
2
2
1
12
1
105
7
220
1.13%
0.16%
0.00%
0.64%
0.00%
1.13%
2.15%
0.52%
0.65%
0.30%
0.96%
0.22%
1.10%
1.43%
1.70%
0.91%
0.75%
0.0005
0.0011



0.0005
0.0005





0.00177
0.000803
0.00012

0.00012
0.00055
0.0011



0.00297
0.0006





0.00177
0.000803
0.0013

0.00116
0.0006
0.0011



0.00505
0.0018





0.00177
0.000803
0.0189

0.0189
0.0006
0.0067

0.0005

0.0002
0.0006




0.001
0.0008

0.0003
0.0005
0.0002
0.0016
0.0067

0.0005

0.0006
0.0016




0.001
0.00089

0.000785
0.0005
0.000835
0.00172
0.0067

0.0005

0.0008
0.0026




0.001
0.0035

0.004
0.0005
0.0067
0.0005
0.0013

0.0005

0.0004
0.0019
0.0023
0.0006



0.00089

0.0005

0.0004
0.0013
0.0053

0.0005

0.00082
0.0019
0.00245
0.0006



0.000895

0.001035

0.0013
0.0072
0.028

0.0022

0.00199
0.0019
0.0026
0.0006



0.0009

0.0058

0.028
0.0006
0.00168

0.0005

0.00064
0.0005


0.0003




0.0005
0.0005
0.0003
0.0008
0.00168

0.0005

0.00081
0.0005


0.0017




0.0007
0.0006
0.0007
0.0017
0.00168

0.0016

0.00098
0.0005


0.0031




0.0011
0.005
0.005
0.000529
0.0006

0.0005






0.0004

0.0008

0.00017
0.0009
0.00017
0.0014
0.0017

0.0005






0.000785

0.0008

0.0007
0.0031
0.0007
0.00141
0.0176

0.0005






0.00117

0.0008

0.002
0.005
0.0176
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                          Six-Year Review
 Table B.32.b. Ethylene Dibromide - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
3,165
22,144
4,820
28,721
2,822
1,900
4,183
991
5,977
9,291
4,897
604
9,706
1,352
0
1,007
101,580
18
51
19
16
1
2


52
8
25
5
48
1

9
255
0.57%
0.23%
0.39%
0.06%
0.04%
0.11%
0.00%
0.00%
0.87%
0.09%
0.51%
0.83%
0.49%
0.07%
0.00%
0.89%
0.25%

0.00016
0.00002
0.00001

0.00005


0.00001
0.0004
0.000014
0.00001
0.00005


0.000013
0.00001

0.00016
0.00007
0.000015

0.00023


0.00007
0.0004
0.00032
0.000035
0.000155


0.00003
0.0001

0.00016
0.0053
0.00002

0.00041


0.001372
0.0062
0.00104
0.00015
0.052


0.00005
0.052
0.00002
0.00017
0.000013
0.000104
0.00002



0.00001
0.0004
0.00032

0.00004
0.00329

0.00003
0.00001
0.00003
0.0005235
0.0000135
0.0005
0.00002



0.000017
0.0005
0.00061

0.00058
0.00329

0.00003
0.000097
0.000192
0.0059
0.000014
0.0009
0.00002



0.000027
0.0005
0.0009

0.00247
0.00329

0.00003
0.0059
0.00002
0.0002
0.000025
0.00004




0.00001
0.0005


0.00004



0.00001
0.000036
0.0003
0.000057
0.0003




0.000027
0.0007


0.00043



0.00004
0.00016
0.0004
0.000089
0.0005




0.000086
0.0009


0.0312



0.0312
0.00004
0.00011
0.000018
0.0002






0.00003
0.00005
0.00272



0.000018
0.00004
0.000238
0.00003
0.0002






0.00004
0.00005
0.00272



0.00021
0.00004
0.00087
0.0007
0.0002






0.00102
0.00005
0.00272



0.00272

0.00011
0.00002
0.00001






0.00002





0.00001

0.00017
0.00138
0.00008






0.00002





0.00015

0.0011
0.00525
0.0004






0.00002





0.00525
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
834
8,654
78
3,938
508
1,640
515
153
218
567
199
433
1,508
250
0
252
19,747
5
11

12

12

1

3
24
1
13



82
0.60%
0.13%
0.00%
0.30%
0.00%
0.73%
0.00%
0.65%
0.00%
0.53%
12.06%
0.23%
0.86%
0.00%
0.00%
0.00%
0.42%
0.0003




0.00002










0.00002
0.00031




0.000025










0.0003
0.00036




0.00003










0.00036
0.00034


0.00002



0.000029


0.00014

0.00107



0.00002
0.00041


0.00002



0.000029


0.00014

0.001165



0.00034
0.00048


0.00002



0.000029


0.00014

0.00126



0.00126



0.0001






0.00021

0.00056



0.0001



0.0033






0.00021

0.00056



0.00056



0.013






0.00021

0.00056



0.013



0.00005

0.00001



0.00068
0.00014
0.00004
0.00005



0.00001



0.0015

0.000035



0.00068
0.00014
0.00004
0.00034



0.000135



0.0064

0.0002



0.00068
0.00014
0.00004
0.00095



0.0064

0.00012

0.0044





0.00000001
0.0001





0.00000001

0.0008

0.0044





0.00050001
0.0013





0.000995

0.006755

0.0044





0.001
0.0032





0.006755
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                                  Six-Year Review
  Table B.33.b. Fluoride - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
1,487
22,678
5,595
224
2,863
1,143
14,479
1,494
4,296
4,340
2,226
1,820
3,588
215
6,549
1,453
74,450
770
18,607
4,967
224
1,764
1,086
12,873
1,230
4,168
2,275
2,163
946
2,116
215
6,100
294
59,798
51.78%
82.05%
88.78%
100.00%
61.61%
95.01%
88.91%
82.33%
97.02%
52.42%
97.17%
51.98%
58.97%
100.00%
93.14%
20.23%
80.32%
0.04
0.06
0.012
0.06
0.0001
0.004
0.1
0.01
0.1
0.002
0.1
0.001
0.08
0.077
0.1
0.06
0.0001
0.48
0.21
0.188
0.66
0.58
0.34
0.3
0.3
0.38
0.19
0.5
0.21
0.28
0.36
0.4
0.3
0.3
1.79
140
7.62
3.5
22
29
2.3
10.1
4.48
3
24
6.1
6.3
4.16
44
3.35
140
0.02
0.06
0.003
0.17
0.0001
0.057
0.1
0.02
0.2
0.03
0.1
0.02
0.1
0.2
0.1
0.1
0.0001
0.32
0.34
0.19
0.87
0.7
0.9015
0.3
0.42
0.92
0.2
0.5
0.2
0.4
1.16
0.4
0.35
0.4
3.29
49
3.98
4.6
7.6
40
17.8
5.9
6.45
8.23
8.4
2.2
5.5
3.51
70
3.6
70
0.01
0.051
0.01
0.15
0.0014
0.018
0.1
0.07
0.2
0.02
0.1
0.031
0.1
0.27
0.1
0.2
0.0014
0.75
0.4
0.3
1.03
0.72
0.9635
0.6
0.295
0.9
0.18
0.7
0.2
0.92
0.785
0.4
0.83
0.5
4.22
24
2.57
5.3
39.9
4.55
21.5
0.97
3.42
9
4.9
3.5
6
1.3
4
2 2
39.9
0.034
0.06
0.01
0.18
0.0001
0.781
0.1
0.1
0.2
0.036
0.17
0.039
0.1

0.1

0.0001
0.88
0.3825
0.3455
0.97
0.9
1.075
0.3
0.15
0.4
0.2
0.9
0.22
0.85

0.5

0.4
3.67
42
1.77
1.49
2.6
1.62
1.3
0.6
8.71
3.82
4.7
0.92
5.1

4.8

42
0.05
0.06
0.0001
0.86
0.7
1.18
0.1

0.42
0.01
0.2

0.1

0.2

0.0001
0.71
0.34
0.3585
1.07
1.175
1.18
0.5

0.98
0.08
0.6

0.78

0.2

0.37
3
15
3.54
1.38
1.3
1.18
1

1.1
1
1.5

1.28

3.4

15
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
853
10,535
288
70
348
935
725
527
246
535
196
974
353
3
1,502
522
18,612
732
9,055
280
69
227
888
667
456
244
278
185
386
254
3
1,377
130
15,231
85.81%
85.95%
97.22%
98.57%
65.23%
94.97%
92.00%
86.53%
99.19%
51.96%
94.39%
39.63%
71.95%
100.00%
91 .68%
24.90%
81 .83%
0.017
0.06
0.28
0.56
0.036
0.01
0.1
0.057

0.2
0.1
0.01
0.1
0.21
0.1
0.14
0.01
0.73
0.155
0.745
0.74
0.118
0.078
0.1
0.365

0.2
0.21
0.1
0.58
0.26
0.3
0.58
0.2
3.49
2
i
0.92
0.782
3.81
1.3
0.84

0.2
0.9
0.7
0.91
0.43
4.5
1.5
4.5
0.05
0.08
0.06
0.12
0.053
0.03
0.1
0.098
0.33
0.03
0.1
0.019
0.1

0.1
0.02
0.019
0.2625
0.3
0.24
0.87
0.7
0.974
0.6
0.67
0.95
0.12
0.4
0.12
0.81

0.2
0.3
0.485
2.25
7.15
1.1
1.81
3.5
2.75
1.3
2.38
1.25
0.3
1.5
1.36
4.8

3.3
1.73
7.15
0.046
0.07
0.17
0.08
0.01
0.052
0.1
0.1
0.29
0.03
0.1
0.05
0.13

0.1
0.4
0.01
0.9
0.6035
0.7
1.04
0.8085
1.03
0.9
0.89
0.97
0.08
0.3
0.42
0.76

0.4
1.02
0.8
2.85
25.7
1.2
1.24
1.4
42
1.7
1.16
3.62
1.36
2.5
1.8
1.32

2.4
2.1
42
0.034
0.08
0.05
0.11
0.0002
0.077
0.1
0.05
0.31
0.02
0.1
0.02
0.13

0.1
0.1
0.0002
0.895
0.3
0.7
0.95
0.897
1.03
0.9
0.98
0.82
0.15
0.3
0.59
0.83

0.7
0.94
0.66
2.81
21.8
1.53
1.15
1.4
12.2
5.6
1.43
1.3
1.14
1.9
1.8
4.14

2.7
1.3
21.8
0.00077
0.06
0.11
0.2
0.21
0.87
0.1
0.16
0.24
0.02
0.1
0.061
0.44

0.1
0.9
0.00077
0.936
0.31
0.69
0.9
0.975
1.07
0.9
0.4
0.81
0.2
0.3
0.126
0.84

0.7
1.025
0.34
4.06
600
1.1
1.07
1.9
1.64
3
1.6
1.15
1.1
0.8
0.29
1.42

4.1
1.18
600
 Note: All results are expressed in mg/L.
 * Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                            Six-Year Review
 Table B.34.b. Glyphosate - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
3,087
5,096
4,622
1,705
1,767
1,022
12
1
0
0
4,092
553
5,120
748
0
52
27,877
2

4

1











7
0.06%
0.00%
0.09%
0.00%
0.06%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.03%


0.006

0.0089











0.006


0.0086

0.0089











0.00875


0.036

0.0089











0.036



















































0.007

0.006













0.006
0.009

0.006













0.007
0.011

0.006













0.011






































































































Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
796
2,055
77
661
103
990
18
0
0
0
237
417
562
162
0
2
6,080





1










1
0.00%
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%
0.02%











































































































0.00902










0.00902





0.00902










0.00902





0.00902










0.00902






































































































Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                                   Six-Year Review
  Table B.35.b.  Heptachlor - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NI
NM
OR
SC
SD
TX
VT
All States
3,090
8,029
4,664
5,290
2,833
1,011
1,250
1,172
1,614
0
4,265
595
5,808
763
3,749
843
44,976
4
2








7



1

14
0.13%
0.02%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.16%
0.00%
0.00%
0.00%
0.03%
0.00%
0.03%
0.00134













0.0002

0.0002
0.00134













0.0002

0.00077
0.00134













0.0002

0.00134
0.000003









0.00011





0.000003
0.0000315









0.00015





0.00011
0.00006









0.00015





0.00015










0.0001





0.0001










0.000226





0.000226










0.000352





0.000352
0.00004









0.0002





0.00004
0.00004









0.000225





0.0002
0.00004









0.00025





0.00025

0.00015














0.00015

0.000185














0.000185

0.00022














0.00022
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NI
NM
OR
SC
SD
TX
VT
All States
800
2,893
79
2,147
547
950
167
184
121
0
249
423
667
161
2,833
292
12,513



1






2





3
0.00%
0.00%
0.00%
0.05%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.80%
0.00%
0.00%
0.00%
0.00%
0.00%
0.02%









































































































0.000043












0.000043



0.000043












0.000043



0.000043












0.000043





























































0.00036





0.00036










0.000374





0.000374










0.000388





0.000388
  Note: All results are expressed in mg/L.
  * Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                           Six-Year Review
 Table B.36.b. Heptachlor Epoxide - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
3,098
7,663
4,648
5,291
2,833
1,544
1,249
966
1,614
0
4,265
595
5,805
763
3,749
844
44,927
10

1









1



12
0.32%
0.00%
0.02%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.02%
0.00%
0.00%
0.00%
0.03%
0.000005















0.000005
0.000005















0.000005
0.000005















0.000005
0.000007















0.000007
0.0000105















0.0000105
0.000012















0.000012
0.000036

0.00021









0.00035



0.000036
0.000513

0.00021









0.00035



0.00028
0.00099

0.00021









0.00035



0.00099
0.00005















0.00005
0.00008















0.00008
0.00029















0.00029



















































Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
800
2,841
77
2,147
543
1,337
167
146
121
0
250
423
666
161
2,833
292
12,804
1


1












2
0.13%
0.00%
0.00%
0.05%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.02%






















































0.00002












0.00002



0.00002












0.00002



0.00002












0.00002



















































0.000032















0.000032
0.000032















0.000032
0.000032















0.000032



















































Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                           Six-Year Review
 Table B.37.b. Hexachlorobenzene - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
3,087
4,180
4,634
5,296
2,851
1,010
1,250
1,563
1,614
0
4,265
592
5,836
761
3,749
761
41,449




6









1
1
8
0.00%
0.00%
0.00%
0.00%
0.21%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.03%
0.13%
0.02%




0.0001










0.0001
0.0001




0.0001










0.0001
0.0001




0.0001










0.0001
0.0001




0.0001











0.0001




0.0001











0.0001




0.0001











0.0001

































































0.0088

0.0088














0.0088

0.0088














0.0088

0.0088




0.0001











0.0001




0.0001











0.0001




0.0001











0.0001
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
799
1,899
77
2,093
547
952
167
243
121
0
250
424
665
167
2,833
245
11,482



2









1

2
5
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%
0.60%
0.00%
0.82%
0.04%















0.0001
0.0001















0.0001
0.0001















0.0001
0.0001






















































0.000018











0.0001
0.000018



0.000018











0.0001
0.000059



0.000018











0.0001
0.0001



0.000027












0.000027



0.000027












0.000027



0.000027












0.000027













0.0001


0.0001













0.0001


0.0001













0.0001


0.0001
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                          Six-Year Review
 Table B.38.b. Hexachlorocyclopentadiene - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
3,087
3,537
4,663
5,247
2,832
1,301
1,250
1,611
1,614
0
4,265
585
5,734
761
3,857
765
41,109


17
3

2




1





23
0.00%
0.00%
0.36%
0.06%
0.00%
0.15%
0.00%
0.00%
0.00%
0.00%
0.02%
0.00%
0.00%
0.00%
0.00%
0.00%
0.06%


0.0000138







0.00077





0.0000138


0.000235







0.00077





0.00036


0.0006







0.00077





0.00077


0.0000822
0.000184

0.00094










0.0000822


0.0003
0.000942

0.00094










0.00036


0.00061
0.0017

0.00094










0.0017


0.000198
0.00074

0.00008










0.00008


0.000198
0.00074

0.00008










0.000198


0.000198
0.00074

0.00008










0.00074






































































































Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
799
1,858
79
1,853
570
1,136
167
261
121
0
252
424
684
161
2,888
252
11,505
4
4

80
7
50

26






28
2
201
0.50%
0.22%
0.00%
4.32%
1.23%
4.40%
0.00%
9.96%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.97%
0.79%
1.75%



0.00011
0.00033
0.00005








0.00034

0.00005



0.0002
0.00033
0.00022








0.00034

0.00023



0.00032
0.00033
0.00034








0.00034

0.00034



0.0001

0.00005

0.000029






0.00024

0.000029



0.00017

0.00007

0.000135






0.00091

0.00018



0.000884

0.00014

0.00042






0.0019

0.0019



0.00011
0.00011
0.00004








0.0002
0.0001
0.00004



0.0003
0.0002
0.00008








0.00035
0.0001
0.00018



0.000863
0.00021
0.0003








0.0017
0.0001
0.0017
0.000051
0.008

0.00011
0.0002
0.00005

0.00002








0.00002
0.000074
0.008

0.000273
0.0002
0.000065

0.000051








0.000085
0.00015
0.008

0.000885
0.0002
0.0018

0.00045








0.008
0.000068
0.000108

0.00013



0.000033








0.000033
0.000068
0.000122

0.000269



0.000033








0.000122
0.000068
0.000146

0.000408



0.000033








0.000408
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                           Six-Year Review
 Table B.39.b. Lindane - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
3,117
9,771
4,686
5,286
2,833
1,491
2,844
1,609
1,974
50
4,131
638
2,740
902
4,044
962
47,078
11

1


1


1
2
1



2

19
0.35%
0.00%
0.02%
0.00%
0.00%
0.07%
0.00%
0.00%
0.05%
4.00%
0.02%
0.00%
0.00%
0.00%
0.05%
0.00%
0.04%
0.00013




0.00002


0.00008
0.00026




0.0001

0.00002
0.00013




0.00002


0.00008
0.000275




0.00015

0.00013
0.00013




0.00002


0.00008
0.00029




0.0002

0.00029
0.000008















0.000008
0.0000485















0.0000485
0.0002















0.0002
0.000042















0.000042
0.0000675















0.0000675
0.00019















0.00019










0.00004





0.00004










0.00004





0.00004










0.00004





0.00004


0.000006













0.000006


0.000006













0.000006


0.000006













0.000006
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
916
3,759
77
2,146
529
1,616
181
246
170
13
156
597
416
179
3,944
360
15,305
4
3

1





1

1




10
0.44%
0.08%
0.00%
0.05%
0.00%
0.00%
0.00%
0.00%
0.00%
7.69%
0.00%
0.17%
0.00%
0.00%
0.00%
0.00%
0.07%
















0

































0
0.000022


0.00002












0.00002
0.000022


0.00002












0.000021
0.000022


0.00002












0.000022











0.00002




0.00002











0.00002




0.00002











0.00002




0.00002
0.000005








0.00026






0.000005
0.000042








0.00026






0.0000435
0.000045








0.00026






0.00026

0.0004














0.0004

0.001














0.001

0.004














0.004
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                           Six-Year Review
 Table B.40.b. Mercury - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
1,508
17,677
5,110
168
2,986
930
3,089
1,397
154
3,597
1,893
1,724
3,332
272
5,400
1,480
50,717
24
8
420
1
1,832
146
183
7

238
8
88
5
257
570
37
3,824
1.59%
0.05%
8.22%
0.60%
61.35%
15.70%
5.92%
0.50%
0.00%
6.62%
0.42%
5.10%
0.15%
94.49%
10.56%
2.50%
7.54%
0.0004

0.0001

0.00002
0.0001
0.00001
0.0001

0.00004
0.0006
0.0001
0.0013
0.00012
0.00013
0.0002
0.00001
0.0005

0.0003

0.0002
0.0004
0.000015
0.0002

0.0005
0.0006
0.0005
0.2
0.0002
0.0002
0.0005
0.0002
0.0005

0.0035

0.002
0.02
0.0003
0.0003

3.9
0.002
0.0034
0.37
0.0004
0.00959
0.0015
3.9
0.0002
0.073
0.0001
0.0053
0.0001
0.0002
0.00001
0.0003

0.0001
0.0006
0.0003

0.00012
0.00013
0.0003
0.00001
0.0007
0.1
0.0004
0.0053
0.0002
0.0003
0.00002
0.0003

0.000385
0.00065
0.0006

0.0002
0.00023
0.0005
0.0002
0.0059
0.13
0.0048
0.0053
0.002
0.0008
0.0018
0.0003

0.005
0.0007
0.001

0.0005
0.00848
0.0005
0.13
0.0001

0.0001

0.0001
0.0001
0.00001


0.00014

0.0003

0.00013
0.00013
0.0005
0.00001
0.0006

0.0005

0.0002
0.0002
0.00001


0.000305

0.0005

0.0002
0.00018
0.0005
0.0002
0.0029

0.0098

0.002
0.0003
0.0003


0.0011

0.0006

0.00021
0.00974
0.0005
0.0098
0.0001
0.07
0.0001

0.0001

0.00001
0.0002

0.0001
0.0007
0.0001

0.0002
0.00014

0.00001
0.0001
0.215
0.0004

0.0002

0.00001
0.0002

0.000325
0.0007
0.0005

0.0002
0.00016

0.0002
0.0005
0.3
0.002

0.002

0.00001
0.0002

0.0045
0.0007
0.0007

0.0002
0.00099

0.3


0.0001

0.0001




0.0005




0.00013

0.0001


0.0003

0.0001




0.0005




0.000185

0.0002


0.0011

0.0005




0.0006




0.00154

0.00154
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
836
7,159
91
69
373
1,149
148
261
23
445
159
931
412
14
1,451
526
14,047
13

5

233
174
9
10

26
3
33
4
14
168
18
710
1.56%
0.00%
5.49%
0.00%
62.47%
15.14%
6.08%
3.83%
0.00%
5.84%
1.89%
3.54%
0.97%
100.00%
11.58%
3.42%
5.05%
0.00028



0.0001
0.0002

0.0002


0.0024
0.0002

0.0002
0.00013
0.0005
0.0001
0.00028



0.0002
0.0003

0.0002


0.0024
0.0009

0.0002
0.0002
0.0005
0.000205
0.00028



0.0005
0.0009

0.0002


0.0024
0.0011

0.00025
0.0015
0.0005
0.0024


0.0008

0.0001
0.0002
0.00001
0.0008

0.00016
0.0011
0.0002

0.0002
0.00013
0.0002
0.00001


0.0008

0.0002
0.0003
0.00001
0.0008

0.000265
0.0011
0.0004

0.0002
0.00023
0.0005
0.000225


0.0008

0.002
0.0013
0.00001
0.0008

0.0003
0.0011
0.005

0.0002
0.00254
0.0007
0.005
0.001

0.0005

0.0001
0.0001
0.00001
0.0002

0.0002

0.0002

0.00013
0.00013
0.0005
0.00001
0.0011

0.0005

0.0002
0.0003
0.00001
0.0006

0.0002

0.0005

0.0002
0.000175
0.0006
0.0002
0.0012

0.0005

0.002
0.001
0.00001
0.0007

0.0004

0.001

0.0002
0.0013
0.0007
0.002
0.0004

0.0003

0.0001
0.0001
0.00001
0.0004

0.00013
0.0005
0.0001

0.0002
0.00013
0.0005
0.00001
0.0007

0.00035

0.0002
0.0003
0.00001
0.0112

0.0005
0.0005
0.0004

0.0002
0.000205
0.0005
0.00023
0.003

0.0004

0.001
0.0009
0.00001
0.022

0.0018
0.0005
0.0014

0.0002
0.00171
0.0005
0.022
0.0005

0.001

0.0001
0.0001
0.00004
0.0002

0.00014

0.0006
0.0004
0.0002
0.00013

0.00004
0.0005

0.001

0.0002
0.0002
0.00004
0.001

0.0003

0.00065
0.0004
0.0002
0.00022

0.0002
0.0018

0.001

0.0008
0.0003
0.00004
0.001

0.001

0.0007
0.0004
0.0002
0.00125

0.0018
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                           Six-Year Review
 Table B.41.b. Methoxychlor - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
3,098
9,284
4,687
5,288
2,847
1,490
2,845
1,614
1,974
50
4,130
636
6,699
902
4,044
960
50,548
3
6
1
1








37

1

49
0.10%
0.06%
0.02%
0.02%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.55%
0.00%
0.02%
0.00%
0.10%












0.00073

0.0005

0.0005












0.00079

0.0005

0.00079












0.0051

0.0005

0.0051
0.00005
0.0005










0.00088



0.00005
0.00005
0.0005










0.00088



0.00088
0.00005
0.0005










0.00088



0.00088
0.00005


0.0001












0.00005
0.0000665


0.0001












0.000083
0.000083


0.0001












0.0001

0.0005










0.00083



0.0005

0.001










0.00083



0.000915

0.005










0.00083



0.005

0.0016
0.0005













0.0005

0.0016
0.0005













0.00105

0.0016
0.0005













0.0016
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
912
3,584
77
2,147
547
1,617
181
246
170
13
156
598
766
179
3,944
361
15,498
3
3

3
2
1








1

13
0.33%
0.08%
0.00%
0.14%
0.37%
0.06%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.03%
0.00%
0.08%





0.0001










0.0001





0.0001










0.0001





0.0001










0.0001
















0

































0



0.001










0.00028

0.00028



0.001










0.00028

0.00064



0.001










0.00028

0.001
0.00006



0.00014











0.00006
0.00006



0.00014











0.00006
0.00006



0.00014











0.00014

0.001

0.001
0.0009











0.0009

0.01

0.001
0.0009











0.001

0.1

0.001
0.0009











0.1
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                                  Six-Year Review
   Table B.42.b.  Monochlorobenzene - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NI
NM
OR
SC
SD
TX
VT
All States
5,119
0
18,497
23,601
3,754
1,151
4,155
3,332
4,767
10,737
5,249
649
8,328
683
23,193
3,669
116,884
4

112
62


1
2
1
44
3
2
1

5
1
238
0.08%
0.00%
0.61%
0.26%
0.00%
0.00%
0.02%
0.06%
0.02%
0.41%
0.06%
0.31%
0.01%
0.00%
0.02%
0.03%
0.20%


0.00001
0.0005


0.0042
0.0000027
0.00273
0.000044
0.0011
0.0005


0.0011
0.0005
0.0000027


0.00105
0.0005


0.0042
0.00025135
0.00273
0.0005455
0.0022
0.0005


0.0011
0.0005
0.0009


0.0125
0.0019


0.0042
0.0005
0.00273
0.0028
0.0046
0.0005


0.0011
0.0005
0.0125
0.0012

0.0011
0.0005





0.0002


0.0005

0.0016

0.0002
0.00135

0.00193
0.00245





0.0005


0.0005

0.0016

0.0015
0.00171

0.0028
0.027





0.0008


0.0005

0.0016

0.027


0.00096
0.0005





0.0003




0.00091

0.0003


0.001
0.0005





0.0003




0.00091

0.00091


0.00446
0.0025





0.0003




0.00091

0.00446


0.0002
0.0001





0.0002

0.0009




0.0001


0.0012
0.0005





0.0007285

0.0009




0.001


0.024
0.001





0.012

0.0009




0.024


0.00025
0.00016










0.0013

0.00016


0.001
0.00098










0.00225

0.0011


0.0033
0.0018










0.0032

0.0033
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NI
NM
OR
SC
SD
TX
VT
All States
2,296
0
135
2,808
526
1,215
506
391
154
782
210
447
1,091
70
6,183
763
17,577
2


57





3
2
1


3
1
69
0.09%
0.00%
0.00%
2.03%
0.00%
0.00%
0.00%
0.00%
0.00%
0.38%
0.95%
0.22%
0.00%
0.00%
0.05%
0.13%
0.39%










0.0065



0.0012

0.0012










0.0065



0.0012

0.00385










0.0065



0.0012

0.0065



0.0005





0.0001

0.0009




0.0001



0.0006





0.0004

0.0009




0.0006



0.002





0.0008

0.0009




0.002



0.0005






0.0052



0.0022

0.0005



0.00175






0.0052



0.0022

0.00195



0.007






0.0052



0.0022

0.007
0.003


0.0005











0.0005
0.0005
0.003


0.00105











0.0005
0.00105
0.003


0.0037











0.0005
0.0037
0.0005


0.0005










0.0009

0.0005
0.0005


0.0005










0.0009

0.0005
0.0005


0.0014










0.0009

0.0014
   Note: All results are expressed in mg/L.
   * Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                           Six-Year Review
 Table B.43.b. Oxamyl - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
3,087
4,231
4,666
4,661
2,832
1,002
1,264
382
585
0
4,157
586
5,787
760
3,467
910
38,377

3
2
1
1
1










8
0.00%
0.07%
0.04%
0.02%
0.04%
0.10%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.02%

0.005
0.000118
0.02












0.000118

0.005
0.000118
0.02












0.005

0.005
0.000118
0.02












0.02




0.028
0.00054










0.00054




0.028
0.00054










0.01427




0.028
0.00054










0.028

































0


















0.008














0.008

0.009














0.009

0.01














0.01


0.0044













0.0044


0.0044













0.0044


0.0044













0.0044
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
796
1,668
79
988
506
971
184
63
43
0
237
423
662
163
2,232
272
9,287





2










2
0.00%
0.00%
0.00%
0.00%
0.00%
0.21%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.02%

































0


















































0






















0.00052










0.00052





0.00052










0.00052





0.00052










0.00052





0.0044










0.0044





0.0044










0.0044





0.0044










0.0044

































0

















Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                           Six-Year Review
 Table B.44.b. PCBs - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
3,096
3,446
4,655
4,821
430
11
0
658
0
596
0
561
0
905
4,044
910
24,133
2


1





4





1
8
0.06%
0.00%
0.00%
0.02%
0.00%
0.00%
0.00%
0.00%
0.00%
0.67%
0.00%
0.00%
0.00%
0.00%
0.00%
0.11%
0.03%









0.0057





0.0004
0.0004









0.0057





0.0004
0.00305









0.0057





0.0004
0.0057



0.0001












0.0001



0.0001












0.0001



0.0001












0.0001
















0

































0
0.0002








0.000611






0.0002
0.00025








0.000611






0.000611
0.0003








0.000611






0.000611
















0

































0
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
796
1,445
77
1,432
449
19
0
104
0
71
0
416
0
179
3,944
271
9,203
1








1






2
0.13%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
1.41%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.02%
















0

































0
















0

































0
0.0002















0.0002
0.0002















0.0002
0.0002















0.0002
















0

































0









0.0029






0.0029









0.0029






0.0029









0.0029






0.0029
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                                  Six-Year Review
   Table B.45.b.  Pentachlorophenol - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NI
NM
OR
SC
SD
TX
VT
All States
3,113
4,590
4,622
4,752
2,840
1,018
2,802
638
632

4,064
586
5,146
867
4,183
1,005
40,858
18
6
5
5
1

17




3
6


4
65
0.58%
0.13%
0.11%
0.11%
0.04%
0.00%
0.61%
0.00%
0.00%
0.00%
0.00%
0.51%
0.12%
0.00%
0.00%
0.40%
0.16%
0.00004
0.0002
0.0000005



0.00016




0.0001
0.00005


0.00004
0.0000005
0.000845
0.00035
0.000015



0.00025




0.0001
0.00011


0.00159
0.000185
0.00164
0.0006
0.000118



0.00109




0.0021
0.00019


0.0031
0.0031
0.00004
0.0002

0.000047


0.0001









0.00004
0.00014
0.0002

0.00009


0.00039









0.0003
0.0007
0.0002

0.00023


0.0008









0.0008
0.00005











0.00002



0.00002
0.00006











0.00002



0.00005
0.001











0.00002



0.001
0.00005



0.00008











0.00005
0.0001



0.00008











0.00009
0.00015



0.00008











0.00015

0.00015
0.000042













0.000042

0.00015
0.0000441













0.0000462

0.00015
0.0000462













0.00015
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NI
NM
OR
SC
SD
TX
VT
All States
826
1,913
82
1,412
535
945
175
70
34
0
146
427
654
183
4,772
312
12,486
13

1
10

1

1








26
1.57%
0.00%
1.22%
0.71%
0.00%
0.11%
0.00%
1.43%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.21%
0.00009

0.00069
0.00006












0.00006
0.00009

0.00069
0.00006












0.00009
0.00009

0.00069
0.00006












0.00069
0.00006


0.00004



0.000067








0.00004
0.000065


0.00007



0.000067








0.000067
0.00007


0.00073



0.000067








0.00073
0.00008




0.00007










0.00007
0.000305




0.00007










0.00008
0.00053




0.00007










0.00053
0.00005


0.00006












0.00005
0.00008


0.00008












0.00008
0.000336


0.00009












0.000336
0.00007


0.0001












0.00007
0.00007


0.0001












0.000085
0.00007


0.0001












0.0001
   Note: All results are expressed in mg/L.
   * Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                                   Six-Year Review
   Table B.46.b.  Picloram - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NI
NM
OR
SC
SD
TX
VT
All States
3,105
4,018
4,614
4,748
2,839
1,022
1,242
435
317
0
4,193
584
4,618
721
3,472
893
36,821
4
5
2
9
1
0

1
6



1

1

32
0.13%
0.12%
0.04%
0.19%
0.04%
0.20%
0.00%
0.23%
1.89%
0.00%
0.00%
0.00%
0.02%
0.00%
0 03%
0.00%
0.09%

0.001
0.000002

0.0025



0.0003



0.00075

0.00069

0.000002

0.001
0.000002

0.0025



0.00045



0.00075

0.00069

0.0005

0.001
0.000002

0.0025



0.0005



0.00075

0.00069

0.0025
0.0005
0.001

0.00011

0.00003

0.00036








0.00003
0.0005
0.001

0.00012

0.00003

0.00036








0.000145
0.0005
0.001

0.0002

0.00003

0.00036








0.001


0.0023
0.00012












0.00012


0.0023
0.00012












0.00121


0.0023
0.00012












0.0023
0.0003
0.0048

0.00012












0.00012
0.0004
0.0048

0.00014












0.0003
0.0004
0.0048

0.00016












0.0048

0.0011














0.0011

0.0011














0.0011

0.0011














0.0011
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NI
NM
OR
SC
SD
TX
VT
All States
806
1,568
80
1,412
508
949
161
58
31
0
250
432
562
162
2,257
266
9,502
5


25

4








1

35
0.62%
0.00%
0.00%
1.77%
0.00%
0.42%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.04%
0.00%
0.37%














0.0032

0.0032














0.0032

0.0032














0.0032

0.0032
0.0002


0.0001

0.00005










0.00005
0.0004


0.00013

0.00005










0.00013
0.0006


0.00056

0.00005










0.0006



0.000108

0.00004










0.00004



0.00012

0.000055










0.00011



0.000631

0.00007










0.000631
0.0002


0.000536

0.00003










0.00003
0.00065


0.000536

0.00003










0.000368
0.0011


0.000536

0.00003










0.0011
0.0002


0.0002












0.0002
0.0002


0.0002












0.0002
0.0002


0.0002












0.0002
   Note: All results are expressed in mg/L.
   * Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                             Six-Year Review
 Table B.47.b. Selenium - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
1,514
18,069
5,097
161
2,984
946
0
1,403
162
3,552
1,854
1,728
3,636
366
5,385
1,259
48,116
20
16
410
6
1,818
254

168
45
134
565
85
43
303
698
26
4,591
1.32%
0.09%
8.04%
3.73%
60.92%
26.85%
0.00%
11.97%
27.78%
3.77%
30.47%
4.92%
1.18%
82.79%
12.96%
2.07%
9.54%
0.001
0.058
0.0002
0.0013
0.00001
0.001

0.001
0.005
0.0005
0.0011
0.001
0.002
0.0006
0.002
0.0005
0.00001
0.005
0.058
0.003
0.002
0.002
0.004

0.002
0.006
0.0042
0.0044
0.004
0.004
0.001955
0.0072
0.005
0.003
0.027
0.058
0.023
0.002
0.05
0.034

1.02
0.015
0.112
0.0495
0.0141
0.008
0.05
0.1562
0.01
1.02
0.0005

0.0003
0.0027
0.0002
0.001

0.001
0.005
0.0007
0.0011
0.001
0.002
0.0006
0.002
0.002
0.0002
0.002

0.003
0.00295
0.002
0.005

0.002
0.006
0.0026
0.0022
0.003
0.005
0.0014
0.0044
0.005
0.003
0.016

0.0317
0.0032
0.01
0.09

0.026
0.022
0.013
0.0124
0.0088
0.021
0.013
0.074
0.03
0.09
0.002
0.06
0.0006
0.0045
0.0001
0.002

0.001
0.0037
0.0003
0.0012
0.0006
0.005
0.0007
0.0021
0.005
0.0001
0.00875
0.07
0.003
0.0045
0.002
0.004

0.0015
0.009
0.002
0.0029
0.002
0.005
0.00125
0.0051
0.005
0.004
0.03
0.078
0.049
0.0045
0.015
0.017

0.002
0.032
0.039
0.0081
0.008
0.005
0.0211
0.0209
0.005
0.078
0.005
0.052
0.0003

0.0004
0.004


0.005
0.001
0.0011
0.002

0.0006
0.002

0.0003
0.005
0.064
0.0029

0.003
0.004


0.007
0.0022
0.00455
0.0055

0.00075
0.00515

0.00395
0.005
0.2
0.015

0.01
0.004


0.009
0.022
0.0247
0.008

0.0013
0.0109

0.2

0.082
0.0002

0.001





0.0011





0.0002

0.082
0.002

0.001





0.00236





0.002

0.082
0.0094

0.005





0.0102





0.082
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
839
7,166
91
67
373
1,152
0
260
26
450
78
938
499
35
1,447
441
13,862
33
1
1
5
230
301

20
1
13
26
33

28
272
4
968
3.93%
0.01%
1.10%
7.46%
61.66%
26.13%
0.00%
7.69%
3.85%
2.89%
33.33%
3.52%
0.00%
80.00%
18.80%
0.91%
6.98%
0.002



0.002
0.001

0.001


0.0019
0.001

0.0012
0.0021
0.002
0.001
0.002



0.005
0.004

0.002


0.004
0.003

0.002
0.00325
0.002
0.003
0.002



0.01
0.049

0.003


0.0047
0.008

0.0366
0.0237
0.002
0.049
0.001


0.001
0.001
0.001

0.001

0.001
0.0012
0.001

0.0007
0.0022

0.0007
0.003


0.00135
0.0021
0.004

0.001

0.001
0.0022
0.003

0.0037
0.0043

0.004
0.009


0.0017
0.01
0.018

0.001

0.001
0.0052
0.007

0.0198
0.0281

0.0281
0.002


0.001
0.001
0.001

0.001


0.00054
0.001

0.0006
0.0021
0.005
0.00054
0.002


0.001
0.002
0.004

0.002


0.0021
0.005

0.00151
0.0045
0.005
0.00395
0.02


0.001
0.01
0.023

0.011


0.0099
0.005

0.0064
0.0249
0.005
0.0249
0.0012

0.002
0.0016
0.001
0.001



0.002
0.0019
0.0009

0.0008
0.002
0.005
0.0008
0.004

0.002
0.0016
0.002
0.0035



0.003
0.0031
0.003

0.001
0.0039
0.005
0.003
0.025

0.002
0.0016
0.01
0.015



0.006
0.007
0.008

0.0036
0.0122
0.005
0.025
0.00041
0.082

0.001
0.001
0.0008

0.001
0.005
0.0006

0.007

0.002
0.002

0.00041
0.0025
0.082

0.001
0.002
0.00105

0.001
0.005
0.004

0.007

0.002
0.0036

0.003
0.024
0.082

0.001
0.01
0.0018

0.001
0.005
0.026

0.007

0.005
0.0162

0.082
Note: All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                           Six-Year Review
 Table B.48.b. Simazine - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
3,104
13,942
4,647
5,281
2,857
1,019
1,278
398
1,973
0
4,255
596
6,207
936
4,334
913
51,740
6
187

38
8
7
1

1





3
1
252
0.19%
1.34%
0.00%
0.72%
0.28%
0.69%
0.08%
0.00%
0.05%
0.00%
0.00%
0.00%
0.00%
0.00%
0.07%
0.11%
0.49%

0.00013

0.00007
0.00007
0.00004
0.0005

0.00015






0.00016
0.00004

0.001

0.00013
0.00007
0.00005
0.0005

0.00015






0.00016
0.00015

0.001

0.0004
0.00007
0.00013
0.0005

0.00015






0.00016
0.001
0.000861
0.00025

0.00011
0.00018
0.00003










0.00003
0.000861
0.001

0.00027
0.00037
0.00006










0.000415
0.000861
0.00202

0.0019
0.00226
0.00009










0.00226
0.0001
0.00017

0.00018

0.00055








0.00011

0.0001
0.000284
0.00054

0.00025

0.00055








0.00012

0.000305
0.000549
0.001

0.00031

0.00055








0.00013

0.001

0.00011

0.00007
0.000079









0.00056

0.00007

0.0005

0.00039
0.000079









0.00056

0.0005

0.0019

0.00099
0.000079









0.00056

0.0019

0.00011

0.00029












0.00011

0.0004

0.000565












0.0004

0.0014

0.00084












0.0014
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
822
4,941
79
2,112
625
1,073
240
81
158
0
251
425
655
183
4,496
292
16,433
11
60

310
49
63
11

7



4

87

602
1.34%
1.21%
0.00%
14.68%
7.84%
5.87%
4.58%
0.00%
4.43%
0.00%
0.00%
0.00%
0.61%
0.00%
1.94%
0.00%
3.66%



0.00012
0.00011
0.00005








0.0001

0.00005



0.00046
0.00011
0.00018








0.00015

0.00017



0.0074
0.00011
0.00024








0.00074

0.0074



0.00007
0.00015
0.00006
0.0001

0.00017





0.00013

0.00006



0.00049
0.00056
0.0002
0.0001

0.00018837





0.00023

0.000435



0.0049
0.0021
0.008
0.0001

0.00051





0.00028

0.008

0.0005

0.00008
0.000079
0.00003
0.0001





0.00285

0.00011

0.00003

0.0005

0.00032
0.00019
0.000195
0.0001





0.0049

0.00011

0.00022

0.0005

0.0033
0.00202
0.00107
0.0001





0.00695

0.00018

0.00695
0.0001
0.0003

0.00007
0.000075
0.00003
0.0001







0.00011

0.00003
0.0002495
0.001

0.000455
0.000195
0.0002
0.0001







0.00023

0.00038
0.00489
0.00137

0.003
0.00393
0.00081
0.0001







0.00037

0.00489
0.00009
0.00017

0.00007
0.00011
0.00009


0.00024





0.0001

0.00007
0.00009
0.000515

0.00014
0.000195
0.000145


0.00024





0.00016

0.00025
0.00009
0.0017

0.00054
0.00097
0.0002


0.00024





0.00071

0.0017
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                            Six-Year Review
 Table B.49.b. Styrene - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
5,119
31,222
18,430
23,503
3,795
1,146
4,171
3,331
4,766
10,044
5,248
646
8,328
683
23,193
3,676
147,301
7
8
22
71
38
2
43

15
16


1

24
1
248
0.14%
0.03%
0.12%
0.30%
1.00%
0.17%
1.03%
0.00%
0.31%
0.16%
0.00%
0.00%
0.01%
0.00%
0.10%
0.03%
0.17%


0.00001
0.0005
0.0006
0.0006
0.0005

0.0004
0.000188




0.00037
0.0005
0.00001


0.0007
0.00065
0.00295
0.0013
0.0006

0.001
0.001159




0.001
0.0005
0.0008


0.00216
0.0029
0.0366
0.002
0.0035

0.0017
0.0078




0.033
0.0005
0.0366
0.00094
0.0006
0.0005
0.0005
0.0008

0.0005

0.0004
0.0002


0.0005

0.0006

0.0002
0.003275
0.0006
0.00103
0.00065
0.0011

0.0005

0.0004
0.00035


0.0005

0.0007

0.0007
0.00561
0.0006
0.00463
0.0086
0.002

0.004

0.0004
0.0005


0.0005

0.0026

0.0086
0.00051

0.0007
0.0005
0.0006



0.0019
0.00193




0.0006

0.0005
0.002385

0.0007
0.0005
0.00085



0.0019
0.00193




0.001

0.0007
0.00426

0.0016
0.0023
0.0011



0.0019
0.00193




0.027

0.027

0.00056
0.001
0.000173




0.0004





0.0007

0.000173

0.00175
0.001
0.0003365




0.0008





0.0007

0.001

0.00287
0.001
0.0005




0.0034





0.0007

0.0034
0.0005
0.007
0.0011
0.00003




0.00183







0.00003
0.0024
0.007
0.0011
0.000715




0.00183







0.001615
0.0031
0.007
0.0011
0.0014




0.00183







0.007
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,295
9,948
135
2,798
528
1,151
511
391
154
671
209
450
1,091
70
6,183
764
27,349
2
6

19
2

4


1

1


6
6
47
0.09%
0.06%
0.00%
0.68%
0.38%
0.00%
0.78%
0.00%
0.00%
0.15%
0.00%
0.22%
0.00%
0.00%
0.10%
0.79%
0.17%




0.0016

0.0008







0.0005
0.0002
0.0002




0.0016

0.0008







0.000705
0.003
0.0016




0.0016

0.0008







0.027
0.0056
0.027



0.0005










0.0051

0.0005



0.0005










0.0051

0.0028



0.0005










0.0051

0.0051



0.0005







0.0027




0.0005



0.0005







0.0027




0.0005



0.0014







0.0027




0.0027
0.0006


0.0005
0.0008

0.0005


0.000044





0.0005
0.000044
0.0006


0.0005
0.0008

0.0006


0.000044





0.0005
0.00055
0.0006


0.0015
0.0008

0.001


0.000044





0.0005
0.0015
0.0007
0.0009

0.0005










0.016

0.0005
0.0007
0.00135

0.0005










0.016

0.0008
0.0007
0.0044

0.0031










0.016

0.016
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                                       Six- Year Review
   Table B.50.b.  Tetrachloroethylene - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NI
NM
OR
SC
SD
TX
VT
All States
5,120
49,815
18,663
23,690
3,859
1,146
2,013
3,335
3,855
11,150
5,537
699
7,817
495
19,146
2,958
159,298
137
9,256
410
369
100
22
71
121
78
884
180
64
271
6
137
78
12,184
2.68%
18.58%
2.20%
1.56%
2.59%
1 .92%
3.53%
3.63%
2.02%
7.93%
3.25%
9.16%
3.47%
1.21%
0.72%
2.64%
7.65%
0.00065
0.00053
0.000019
0.0005
0.0005
0.0005
0.0004
0.00054
0.0004
0.00016
0.0001
0.0004
0.00051
0.000563
0.0005
0.0003
0.000019
0.00115
0.00245
0.00089
0.002
0.0008
0.003
0.0008
0.0013
0.0008
0.00085
0.0012
0.00135
0.00185
0.0015615
0.0011
0.0011
0.001385
0.0016
0.087
0.03
0.011
0.0044
0.03
0.0089
0.0076
0.0051
0.199
0.0028
0.07
0.0787
0.0024
0.137
0.009
0.199
0.0001
0.00051
0.00019
0.0005
0.00059
0.001
0.0004
0.0000012
0.0005
0.000115
0.00085
0.0007
0.0005

0.00011
0.0005
0.0000012
0.00133
0.0018
0.000443
0.0009
0.00145
0.00134
0.0014
0.0000012
0.0035
0.000903
0.0014
0.0012
0.00088

0.00075
0.0013
0.0014
0.0063
0.21
0.00079
0.035
0.026
0.003
0.0241
0.0000012
0.0135
0.0277
0.0019
0.002
0.00748

0.0061
0.0067
0.21
0.0005
0.00051
0.0012
0.0005
0.0011

0.0004
0.0000019
0.0004
0.00012


0.00058

0.0016

0.0000019
0.00187
0.0022
0.0016
0.0007
0.0023

0.0006
0.00056
0.0007
0.0016


0.00263

0.0018

0.0019
0.00877
0.2
0.0018
0.0043
0.004

0.0009
0.00094
0.0031
0.0521


0.0263

0.002

0.2
0.0005
0.00051
0.0000004
0.000202
0.0013


0.0001
0.0003
0.00016
0.0001

0.00056

0.0006

0.0000004
0.0015
0.002
0.001
0.0012
0.0056


0.0015
0.0008
0.00178
0.00083

0.00157

0.0006

0.00197
0.017
1.2
0.0121
0.013
0.0058


0.0043
0.032
0.06
0.0038

0.0263

0.0006

1.2
0.0011
0.00051
0.00006
0.00004
0.0005

0.0009


0.00013
0.00001

0.00084

0.00034

0.00001
0.0013
0.0021
0.001185
0.0017
0.00106

0.00095


0.001125
0.0008

0.00697

0.00065

0.0019
0.0015
2.4
0.0927
0.0062
0.0031

0.001


0.0235
0.0064

0.0378

0.002

2.4
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NI
NM
OR
SC
SD
TX
VT
All States
2,343
19,944
136
2,813
526
1,179
437
391
95
788
347
459
963
55
4,777
667
35,920
207
6,203

24
4
2

6

21
2
17
31

4
4
6,525
8.83%
31.10%
0.00%
0.85%
0.76%
0.17%
0.00%
1.53%
0.00%
2.66%
0.58%
3.70%
3.22%
0.00%
0.08%
0.60%
18.17%

0.0006



0.001





0.0003


0.0011

0.0003

0.0007



0.001





0.0017


0.0011

0.00155

0.0016



0.001





0.0195


0.0011

0.0195

0.00053

0.0005

0.002




0.0006
0.0005
0.00452

0.0006
0.0009
0.0005

0.00082

0.0005

0.003




0.0008
0.0007
0.00452

0.0006
0.001
0.00084

0.065

0.0005

0.003




0.001
0.0028
0.00452

0.0006
0.0011
0.065

0.0007

0.00031





0.0009






0.00031

0.0012

0.0005





0.0009






0.0011

0.0018

0.0013





0.0009






0.0018
0.0001
0.00051

0.0005

0.002

0.00049

0.000037


0.00069


0.0005
0.000037
0.0028
0.0031

0.00075

0.002

0.000975

0.00081


0.00211


0.0005
0.003
0.0365
0.2

0.002

0.002

0.0015

0.0017


0.00677


0.0005
0.2
0.00053
0.00051

0.0005





0.00021

0.0009


0.0005
0.0006
0.00021
0.00165
0.0021

0.0005





0.0007

0.0009


0.0005
0.0006
0.0021
0.0581
0.097

0.002





0.0039

0.0009


0.0005
0.0006
0.097
   Note: All results are expressed in mg/L.
   * Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                             Six-Year Review
 Table B.Sl.b. Thallium - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
686
6,979
5,287
163
2,891
911
3,762
1,000
980
3,463
1,732
614
3,234
255
5,384
890
38,231
3

289
2
83
108
8
5
4
100
158
6
5
26
108
2
907
0.44%
0.00%
5.47%
1.23%
2.87%
11.86%
0.21%
0.50%
0.41%
2.89%
9.12%
0.98%
0.15%
10.20%
2.01%
0.22%
2.37%


0.0001

0.0001
0.001
0.0001
0.001

0.0002
0.00004
0.0006
0.003
0.00011
0.0008
0.001
0.00004


0.0016

0.0005
0.001
0.0003
0.0015

0.002
0.00019
0.001
0.003
0.00091
0.0012
0.001
0.001


1.5

0.004
0.218
0.0035
0.002

0.21
0.002
0.0069
0.003
0.006
0.0028
0.001
1.5
0.002

0.0002
0.0012
0.0001
0.001
0.0001
0.002
0.0001
0.0001
0.00004

0.003
0.00019


0.00004
0.002

0.0017
0.00355
0.0005
0.001
0.0001
0.002
0.0001
0.0011
0.0001

0.0145
0.000345


0.001
0.002

0.032
0.0059
0.005
0.02
0.0001
0.002
0.0001
0.004
0.0025

0.026
0.0005


0.032


0.0006

0.0005
0.001
0.0001
0.002
0.001
0.00075
0.00009
0.002


0.001

0.00009


0.0024

0.0005
0.0014
0.0001
0.002
0.001
0.0025
0.0001
0.002


0.00105

0.0018


0.086

0.5
0.0018
0.0001
0.002
0.001
0.019
0.00014
0.002


0.003

0.5
0.002

0.001



0.0008


0.001
0.00004





0.00004
0.002

0.002



0.0008


0.0011
0.000095





0.001
0.002

0.013



0.0008


0.007
0.0011





0.013


0.0001

0.0005



0.001
0.001
0.000039





0.000039


0.001

0.0005



0.001
0.001
0.00005





0.0007


0.02

0.0005



0.001
0.001
0.00019





0.02
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
513
2,826
92
67
369
1,039
279
252
55
433
134
530
425
5
1,395
314
8,728
4

1

12
87

4

6
8
3

1
26
1
153
0.78%
0.00%
1.09%
0.00%
3.25%
8.37%
0.00%
1.59%
0.00%
1.39%
5.97%
0.57%
0.00%
20.00%
1.86%
0.32%
1.75%
0.001




0.001




0.00011
0.0004

0.0009
0.0008

0.00011
0.001




0.001




0.00011
0.0004

0.0009
0.001

0.001
0.001




0.027




0.00011
0.0004

0.0009
0.0012

0.027




0.0008
0.0007

0.002


0.00036
0.0004


0.0008
0.001
0.00036




0.0015
0.001

0.002


0.00047
0.0004


0.0011
0.001
0.001




0.005
0.005

0.002


0.00058
0.0004


0.0012
0.001
0.005




0.0005
0.0007

0.001


0.00004



0.001

0.00004




0.0005
0.001

0.0015


0.0002



0.0011

0.001




0.0005
0.005

0.002


0.00035



0.0032

0.005
0.001



0.0001
0.0001



0.001

0.001


0.0009

0.0001
0.001



0.0001
0.001



0.001

0.001


0.00095

0.001
0.001



0.0005
0.005



0.001

0.001


0.001

0.005
0.002

0.004

0.0001
0.0016



0.001




0.0008

0.0001
0.0025

0.004

0.0006
0.00205



0.002




0.00105

0.0012
0.003

0.004

0.0011
0.0025



0.002




0.0012

0.004
Note: All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                                   Six-Year Review
  Table B.52.b.  Toluene - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
SOI - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NI
NM
OR
SC
SD
TX
VT
All States
5,130
38,611
18,637
23,627
3,869
1,164
4,181
3,322
4,766
10,067
5,242
663
8,323
683
23,193
3,681
155,159
91
115
145
158
93
27
90
21
59
132
33
17
99
8
390
72
1,550
1.77%
0.30%
0.78%
0.67%
2.40%
2.32%
2.15%
0.63%
1.24%
1.31%
0.63%
2.56%
1.19%
1.17%
1.68%
1.96%
1.00%
0.001
0.00055
0.00001
0.0005
0.0005
0.00056
0.0005
0.00053
0.0002
0.0001
0.0006
0.0005
0.00051
0.0006
0.00038
0.0002
0.00001
0.00255
0.0018
0.001
0.0009
0.0013
0.001
0.00085
0.00145
0.0015
0.0009205
0.0014
0.0007
0.00106
0.00075
0.0015
0.00145
0.0011
0.02
0.0472
0.01
0.016
0.0353
0.089
0.009
0.027
0.417
0.0085
0.15
0.0277
0.00574
0.00122
0.41649
0.0717
0.417
0.0005
0.00058
0.000521
0.0005
0.00068
0.00053
0.0005
0.00072
0.0002
0.0001
0.0012
0.0005
0.0005
0.0006
0.00013
0.0005
0.0001
0.0021
0.001
0.00108
0.0007
0.00215
0.00239
0.00075
0.0013
0.00049
0.00046
0.00215
0.00095
0.00182
0.0006
0.00142
0.0019
0.0012
0.139
0.11
0.0611
0.059
0.022
0.008
0.0227
0.002
0.003
0.0014
0.0031
0.0014
0.00949
0.011944
0.13751
0.9
0.9
0.0005
0.0007
0.00072
0.0005
0.0007
0.00064
0.0005

0.0003
0.00008


0.00064

0.00025

0.00008
0.001595
0.018
0.00125
0.00058
0.0034
0.00064
0.00175

0.00045
0.0009


0.00064

0.0011

0.0012
0.008
0.48
0.00425
0.027
0.0061
0.00064
0.0048

0.001
0.00866


0.00064

0.041

0.48
0.0005
0.00051
0.00011
0.000069
0.0006

0.0005

0.0002
0.00013
0.0008
0.0006


0.0005

0.000069
0.0012
0.0015
0.00104
0.00135
0.001195

0.0006

0.00064
0.0009
0.00135
0.0006


0.001

0.0011
0.0177
0.022
0.03
0.012
0.0052

0.0007

0.0029
0.00672
0.0031
0.0006


0.013

0.03
0.0007
0.00056
0.00041
0.00063
0.0013




0.00347
0.0022



0.0006

0.00041
0.0014
0.00314
0.00113
0.000785
0.0013




0.010735
0.0022



0.0006

0.0013
0.0017
0.0272
0.123
0.003
0.0013




0.018
0.0022



0.0006

0.123
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NI
NM
OR
SC
SD
TX
VT
All States
2,304
11,697
135
2,811
527
1,238
508
385
154
671
208
451
1,092
70
6,183
765
29,199
43
31

53
1
21
7
7

5
1
5
8

110
10
302
1.87%
0.27%
0.00%
1.89%
0.19%
1.70%
1.38%
1.82%
0.00%
0.75%
0.48%
1.11%
0.73%
0.00%
1.78%
1.31%
1.03%
0.0008



0.0005
0.00052
0.0005







0.0005

0.0005
0.0012



0.0005
0.00076
0.0005







0.00159

0.0014
0.0018



0.0005
0.001
0.0005







0.0313

0.0313
0.00094


0.0005

0.00056
0.001
0.00057

0.0002

0.0005
0.00056

0.0005
0.0005
0.0002
0.0021


0.0016

0.00114
0.00175
0.00057

0.0002

0.0026
0.00056

0.0012
0.0006
0.001185
0.005


0.002

0.00429
0.0047
0.00057

0.0002

0.004
0.0025

0.0077
0.0016
0.0077
0.00056
0.0008

0.0005

0.00053

0.0014




0.00084

0.0005

0.0005
0.00286
0.00205

0.0006

0.0007

0.0014




0.00084

0.0007

0.00075
0.0313
0.0027

0.0015

0.00411

0.0014




0.00084

0.0024

0.0313
0.0005
0.0017

0.0003

0.00057
0.0005
0.00082

0.00005


0.00082

0.00047
0.0005
0.00005
0.00105
0.0026

0.00093

0.0008
0.00065
0.0014

0.00005


0.00082

0.0008
0.0007
0.0009
0.0084
0.0103

0.004

0.165
0.0008
0.002

0.00005


0.00082

0.033
0.0016
0.165
0.0005
0.00059

0.00043

0.0009



0.0006
0.00265

0.00056

0.0005

0.00043
0.00265
0.0013

0.0005

0.0009



0.0008
0.00265

0.001255

0.0008

0.00086
0.0132
0.0313

0.0014

0.0009



0.0009
0.00265

0.00195

0.0074

0.0313
  Note: All results are expressed in mg/L.
  * Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                           Six-Year Review
 Table B.53.b. Toxaphene - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
0
9,581
4,724
4,822
2,821
1,494
1,250
1,613
260
50
4,265
631
4,797
766
3,555
887
41,516

6














6
0.00%
0.06%
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%
0.01%

0.0005














0.0005

0.0005














0.0005

0.0005














0.0005

0.001














0.001

0.001














0.001

0.001














0.001




















































0.0005














0.0005

0.00125














0.00125

0.002














0.002



















































Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
0
3,644
77
1,488
525
1,615
167
249
26
15
264
596
561
161
1,180
345
10,913

5



2










7
0.00%
0.14%
0.00%
0.00%
0.00%
0.12%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.06%





0.003










0.003





0.003










0.003





0.003










0.003
























































0.002










0.002





0.002










0.002





0.002










0.002




















































0.0005














0.0005

0.001














0.001

0.005














0.005
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                            Six-Year Review
 Table B.54.b. 2,4,5-TP - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
3,131
8,689
4,630
4,750
2,838
1,492
2,800
1,648
632
54
4,060
626
4,983
867
3,469
1,006
45,675
22
5
1

3





21

8


1
61
0.70%
0.06%
0.02%
0.00%
0.11%
0.00%
0.00%
0.00%
0.00%
0.00%
0.52%
0.00%
0.16%
0.00%
0.00%
0.10%
0.13%
0.00016
0.001
0.0000005







0.0017




0.000054
0.0000005
0.00016
0.001
0.0000005







0.0017




0.000054
0.00016
0.00016
0.001
0.0000005







0.0017




0.000054
0.0017
0.00007
0.0002








0.0032

0.00004



0.00004
0.0009025
0.0002








0.0032

0.00004



0.0009025
0.001623
0.001








0.0032

0.00004



0.0032
0.00004



0.00028





0.0031





0.00004
0.0001



0.00064





0.0064





0.0031
0.000962



0.001





0.0105





0.0105
0.00006
0.0002








0.0017

0.00013



0.00006
0.0002445
0.0002








0.00205

0.0004



0.0004
0.001224
0.0002








0.0024

0.0004



0.0024




0.00021











0.00021




0.00021











0.00021




0.00021











0.00021
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
914
3,275
78
1,468
544
1,628
175
227
34
13
155
603
658
183
2,263
353
12,571
23
5

1
5
2










36
2.52%
0.15%
0.00%
0.07%
0.92%
0.12%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.29%
0.00023



0.00015
0.0005










0.00015
0.00023



0.000245
0.0005










0.000285
0.00023



0.00034
0.0005










0.0005
0.00006


0.00021
0.00029











0.00006
0.00006


0.00021
0.00029











0.00021
0.0003


0.00021
0.00029











0.0003
0.0003
0.001


0.00816
0.00007










0.00007
0.0003
0.001


0.00816
0.00007










0.00065
0.0003
0.001


0.00816
0.00007










0.00816
0.00004
0.001


0.0009











0.00004
0.000129
0.001


0.0009











0.00018
0.000574
0.001


0.0009











0.001
0.00005
0.001














0.00005
0.00006
0.002














0.00008
0.00009
0.01














0.01
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                           Six-Year Review
 Table B.55.b. 1,2,4-Trichlorobenzene - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
5,119
31,171
18,436
20,798
3,762
1,147
4,155
0
4,769
10,557
5,248
647
8,318
683
23,193
3,251
141,254
14
7
46
30
6
1



66


2
1
16
2
191
0.27%
0.02%
0.25%
0.14%
0.16%
0.09%
0.00%
0.00%
0.00%
0.63%
0.00%
0.00%
0.02%
0.15%
0.07%
0.06%
0.14%

0.0012
0.00002
0.0005
0.0005
0.0006



0.0003


0.00056

0.0005
0.0005
0.00002

0.0012
0.000694
0.0005
0.00081
0.0006



0.00066


0.00056

0.0006
0.0031
0.00066

0.0012
0.0014
0.0005
0.0014
0.0006



0.00066


0.00056

0.00075
0.0057
0.0057
0.0005

0.0008
0.0005





0.0002


0.0005
0.000663
0.0006

0.0002
0.0009

0.00348
0.0005





0.00066


0.0005
0.000663
0.0007

0.00066
0.0041

0.0043
0.0005





0.001326


0.0005
0.000663
0.00274

0.0043
0.0005
0.011
0.00082
0.0005
0.00072




0.00066




0.0005

0.0005
0.000643
0.0145
0.00082
0.0005
0.00072




0.00066




0.0007

0.0006
0.0007
0.021
0.00082
0.0007
0.00072




0.00066




0.00282

0.021
0.0006
0.00058
0.001
0.000246





0.00066




0.0017

0.000246
0.002
0.00058
0.001
0.0005





0.00066




0.0017

0.00066
0.0048
0.00058
0.0015
0.0009





0.00093




0.0017

0.0048

0.007
0.000381






0.0006






0.000381

0.007
0.00135






0.00066






0.0009055

0.007
0.00928






0.00066






0.00928
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,295
9,881
136
2,277
527
1,153
506
0
155
732
209
448
1,091
70
6,183
629
26,292
4


16
1









2
1
24
0.17%
0.00%
0.00%
0.70%
0.19%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.03%
0.16%
0.09%














0.0008

0.0008














0.0008

0.0008














0.0008

0.0008



0.0005
0.00071











0.0005



0.0005
0.00071











0.000605



0.0005
0.00071











0.00071



0.0005












0.0005



0.0005












0.0005



0.0005












0.0005
0.000889


0.0005










0.00066
0.00005
0.00005
0.000889


0.0005










0.00066
0.00005
0.0005
0.000889


0.0005










0.00066
0.00005
0.000889
0.000785


0.0005












0.0005
0.0008


0.0005












0.0005
0.0018


0.003












0.003
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                           Six-Year Review
 Table B.56.b. 1,1,1-Trichloroethane - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
5,148
39,796
18,576
23,732
3,862
1,589
4,169
3,334
4,769
10,982
5,250
1,919
8,828
683
23,193
3,678
159,508
77
984
31
450
104
16
58
24
67
811
13
29
107
3
22
28
2,824
1.50%
2.47%
0.17%
1.90%
2.69%
1.01%
1.39%
0.72%
1.40%
7.38%
0.25%
1.51%
1.21%
0.44%
0.09%
0.76%
1.77%

0.0006
0.00003
0.0005
0.0005
0.0006
0.0004
0.0005
0.0004
0.000016
0.00053
0.0001
0.0005
0.00216
0.0006
0.0005
0.000016

0.0011
0.00096
0.0012
0.0012
0.0025
0.0008
0.0021
0.0097
0.0015
0.00096
0.0013
0.000815
0.00908
0.001955
0.0028
0.0013

0.2022
0.00305
0.037
0.056
0.012
0.0265
0.029
0.0769
0.042
0.0027
0.1169
0.0208
0.016
0.011
0.0045
0.2022
0.0006
0.0006
0.00013
0.00022
0.00056
0.001
0.0004
0.0007
0.0003
0.000083
0.001
0.0008
0.00002
0.00051
0.0005
0.0008
0.00002
0.003025
0.0015
0.0006
0.0022
0.0043
0.001
0.0005
0.0022
0.00084
0.0007
0.001
0.0026
0.00073
0.00051
0.0015
0.0008
0.001
0.0112
0.00273
0.001
0.077
0.0069
0.001
0.0008
0.0024
0.00394
0.01
0.001
0.0044
0.00228
0.00051
0.0037
0.0008
0.077
0.0006
0.00051
0.0005
0.0004
0.0005

0.0004
0.000001
0.0003
0.00013

0.0006
0.0005



0.000001
0.00157
0.000855
0.0005
0.001
0.0011

0.00045
0.0006005
0.001945
0.0012

0.0006
0.000785



0.0011
0.01
0.057
0.0005
0.012
0.0015

0.0008
0.0012
0.0037
0.00986

0.0006
0.00228



0.057
0.0005
0.00055
0.0003
0.000288
0.0005

0.0006

0.0002
0.00014
0.0001
0.0014




0.0001
0.00185
0.00235
0.00084
0.001
0.0059

0.0023

0.0006
0.00127
0.00066
0.0014




0.0016
0.0341
0.4617
0.005
0.013
0.0155

0.0024

0.00404
0.0417
0.0007
0.0014




0.4617
0.0008
0.00051
0.0000435
0.0005
0.0007




0.00012
0.0001





0.0000435
0.0008
0.0014
0.00056175
0.0046
0.00285




0.000425
0.00075





0.0014
0.0008
0.0971
0.00108
0.031
0.011




0.002
0.0014





0.0971
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,313
13,356
136
2,816
528
1,704
507
391
155
764
210
925
1,147
70
6,183
763
31,968
28
813

31
2
8
2

5
29
1
4
17

2
2
944
1.21%
6.09%
0.00%
1.10%
0.38%
0.47%
0.39%
0.00%
3.23%
3.80%
0.48%
0.43%
1.48%
0.00%
0.03%
0.26%
2.95%
0.00279
0.0009






0.0004



0.00056


0.0007
0.0004
0.003195
0.0009






0.00155



0.00121


0.0007
0.00155
0.0036
0.0009






0.0032



0.00186


0.0007
0.0036
0.0094
0.0072

0.0005

0.0017
0.0004



0.0009
0.001
0.00073



0.0004
0.0094
0.0072

0.0006

0.00228
0.0004



0.0009
0.001
0.00073



0.00135
0.0094
0.0072

0.0007

0.0032
0.0004



0.0009
0.002
0.00073



0.0094
0.00077
0.0006

0.0005

0.003


0.0011
0.001

0.0007
0.00058



0.0005
0.00097
0.0006

0.0005

0.003


0.0011
0.0016

0.0007
0.001335



0.000655
0.006
0.0006

0.002

0.003


0.0011
0.0022

0.0007
0.00228



0.006
0.0007
0.00059

0.0005

0.0019
0.0006





0.00059

0.0006
0.0005
0.0005
0.00466
0.001

0.0006

0.00195
0.0006





0.0018

0.0006
0.0005
0.001
0.018
0.013

0.0006

0.002
0.0006





0.0079

0.0006
0.0005
0.018
0.0005
0.00052

0.0005
0.00053




0.0001




0.0016

0.0001
0.00105
0.0018

0.0005
0.000715




0.0006




0.0016

0.0017
0.0202
0.073

0.014
0.0009




0.0017




0.0016

0.073
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                           Six-Year Review
 Table B.57.b. 1,1,2-Trichloroethane - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
5,117
38,672
18,523
23,525
3,755
1,144
1,967
3,334
3,857
10,069
5,503
647
7,799
495
19,196
2,930
146,533
4
17
15
34


1
1
2
59
2
1
1


1
138
0.08%
0.04%
0.08%
0.14%
0.00%
0.00%
0.05%
0.03%
0.05%
0.59%
0.04%
0.15%
0.01%
0.00%
0.00%
0.03%
0.09%

0.0011
0.00003
0.0005


0.0007
0.0005

0.00018

0.0005



0.0005
0.00003

0.00215
0.0028
0.0005


0.0007
0.0005

0.00059

0.0005



0.0005
0.00059

0.0032
0.013
0.0056


0.0007
0.0005

0.0099

0.0005



0.0005
0.013
0.0009
0.0012

0.0005





0.0005


0.0005



0.0005
0.001
0.0012

0.0005





0.00059


0.0005



0.00059
0.0011
0.0012

0.0005





0.0048


0.0005



0.0048
0.00636
0.0006

0.0002






0.0003





0.0002
0.00636
0.0006

0.0005






0.0003





0.0005
0.00636
0.0006

0.0008






0.0003





0.00636
0.00062
0.0006
0.0007
0.000258




0.0014
0.00039
0.0002





0.0002
0.00062
0.0063
0.0012
0.00055




0.00195
0.00059
0.0002





0.00059
0.00062
0.009
0.0044
0.0017




0.0025
0.00132
0.0002





0.009

0.0007
0.00009
0.00015





0.00059






0.00009

0.0043
0.00052
0.00015





0.00059






0.001025

0.007
0.00095
0.00015





0.00059






0.007
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NJ
NM
OR
SC
SD
TX
VT
All States
2,296
11,945
125
2,798
526
1,154
437
391
64
670
344
455
957
54
4,606
551
27,373
45
43

18





2

7


2
1
118
1.96%
0.36%
0.00%
0.64%
0.00%
0.00%
0.00%
0.00%
0.00%
0.30%
0.00%
1.54%
0.00%
0.00%
0.04%
0.18%
0.43%
0.0012
0.00061












0.0007

0.00061
0.0012
0.00061












0.0007

0.0007
0.0012
0.00061












0.0007

0.0012
0.00053


0.0005







0.0005


0.0009

0.0005
0.00053


0.0005







0.0007


0.0009

0.0007
0.00053


0.0005







0.0011


0.0009

0.0011
0.00051
0.000946

0.0005





0.0013

0.0005




0.0005
0.00117
0.000946

0.0005





0.0013

0.00065




0.000745
0.0037
0.000946

0.00078





0.0013

0.0008




0.0037
0.0007


0.0005





0.000056

0.001



0.0005
0.000056
0.00107


0.0005





0.000056

0.001



0.0005
0.00094
0.0046


0.0005





0.000056

0.001



0.0005
0.0046
0.00054
0.0006

0.0005












0.0005
0.00099
0.0012

0.0005












0.001
0.0034
0.0081

0.0005












0.0081
Note:  All results are expressed in mg/L.
* Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                                   Six-Year Review
   Table B.58.b.  Trichloroethylene - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NI
NM
OR
SC
SD
TX
VT
All States
5,151
51,708
18,904
23,744
3,908
1,593
2,069
3,333
3,855
11,122
5,531
1,932
8,323
495
19,146
2,972
163,786
81
9,334
484
476
148
47
125
8
127
792
59
65
221
3
40
71
12,081
1.57%
18.05%
2.56%
2.00%
3.79%
2.95%
6.04%
0.24%
3.29%
7.12%
1.07%
3.36%
2.66%
0.61%
0.21%
2.39%
7.38%
0.0008
0.00054
0.00001
0.0005
0.0005
0.001
0.0009
0.00091
0.0001
0.00012
0.0024
0.0002
0.0005

0.00044
0.0005
0.00001
0.0012
0.0027
0.0015
0.0043
0.00335
0.0015
0.0009
0.001
0.001
0.001
0.0024
0.0017
0.0012

0.0006
0.0008
0.0018
0.0016
0.014
0.01
0.023
0.076
0.002
0.0009
0.0023
0.0953
0.14
0.0024
0.0272
0.069

0.151
0.058
0.151
0.0005
0.00054
0.002
0.0005
0.0005
0.0005
0.0004

0.0002
0.00018
0.001

0.00001
0.002202
0.0005
0.0005
0.00001
0.00102
0.0015
0.002
0.0009
0.0013
0.002
0.001

0.0003
0.001594
0.00185

0.000995
0.002202
0.0008
0.002
0.0013
0.0067
0.005
0.00689
0.023
0.004
0.013
0.0045

0.0008
0.0624
0.0036

0.00846
0.01423
0.0013
0.7
0.7
0.0005
0.00051
0.000142
0.0002
0.0012
0.0002
0.0004

0.0002
0.00014
0.0002

0.0005

0.00043

0.00014
0.0009
0.0014
0.0006
0.0021
0.0035
0.0017
0.001

0.02025
0.0015
0.0013

0.00305

0.0007

0.00158
0.0052
0.41
0.0015
0.021
0.006
0.003
0.0149

0.186
0.0209
0.00374

0.0086

0.0014

0.41
0.00052
0.00051
0.000001
0.000221
0.0005

0.0004
0.0012
0.0002
0.00012
0.0001

0.00051



0.000001
0.0007
0.0028
0.00168
0.001
0.0009

0.0007
0.0012
0.003
0.0011
0.0016

0.0008



0.0025
0.002
1.062
0.064
0.019
0.0029

0.0027
0.0012
0.009
0.116
0.005

0.00658



1.062
0.0005
0.00051
0.00006
0.0005
0.0005

0.0009


0.00012
0.00001

0.00119



0.00001
0.0005
0.0025
0.0021
0.0021
0.00126

0.001


0.00073
0.000355

0.00459



0.0023
0.0005
7.5
0.0886
0.0087
0.0046

0.0011


0.0073
0.0007

0.00846



7.5
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NI
NM
OR
SC
SD
TX
VT
All States
2,375
20,417
136
2,814
527
1,702
437
391
95
763
345
925
1,003
55
4,777
666
37,428
165
6,994

24
1
13



38
5
6
24


1
7,271
6.95%
34.26%
0.00%
0.85%
0.19%
0.76%
0.00%
0.00%
0.00%
4.98%
1.45%
0.65%
2.39%
0.00%
0.00%
0.15%
19.43%
0.0005




0.001





0.0002




0.0002
0.0005




0.0015





0.0005




0.0005
0.0005




0.002





0.0006




0.002



0.0005






0.0006
0.0007




0.0005



0.0005






0.0006
0.00085




0.0006



0.0005






0.0015
0.001




0.0015
0.001
0.0006

0.0005





0.0004






0.0004
0.0013
0.0008

0.0005





0.0004






0.0006
0.0016
0.0034

0.00075





0.0004






0.0034
0.0005
0.00052

0.0005

0.0005



0.0006


0.00062


0.0005
0.0005
0.0009
0.0017

0.0005

0.0007



0.00097


0.00125


0.0005
0.0016
0.006
0.0883

0.00075

0.001



0.0023


0.0859


0.0005
0.0883
0.0005
0.00051

0.00035
0.0005




0.0001






0.0001
0.002
0.0027

0.0005
0.0005




0.0006






0.0027
0.011
0.47

0.0019
0.0005




0.0014






0.47
   Note: All results are expressed in mg/L.
   * Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                                        Six- Year Review
   Table B.59.b.  Vinyl Chloride - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NI
NM
OR
SC
SD
TX
VT
All States
5,117
38,299
19,021
23,526
3,764
1,566
4,161
3,333
4,766
10,767
5,248
1,917
8,831
683
23,193
3,251
157,443
7
8
243
68
8
5
5


11
1

4
1
14
3
378
0.14%
0.02%
1.28%
0.29%
0.21%
0.32%
0.12%
0.00%
0.00%
0.10%
0.02%
0.00%
0.05%
0.15%
0.06%
0.09%
0.24%
0.0007
0.0021
0.00004
0.0005

0.001



0.000213


0.0005

0.00052
0.0005
0.00004
0.0007
0.00225
0.00104
0.0005

0.001



0.00068


0.0005

0.0007
0.0023
0.0007
0.0009
0.0024
0.00661
0.0016

0.00145



0.0014


0.0005

0.00288
0.0051
0.00661
0.00053

0.0013
0.0005
0.001
0.002



0.0005


0.00024
0.000612
0.0005

0.00024
0.00109

0.0013
0.0008
0.001
0.002



0.00065


0.00033
0.000612
0.0011

0.0008
0.002

0.0013
0.0035
0.001
0.002



0.0008


0.0005
0.000612
0.0016

0.0035

0.0007
0.0007
0.0005
0.0049









0.0005

0.0005

0.0007
0.001
0.0009
0.0049









0.00056

0.001

0.0007
0.001
0.0067
0.0049









0.00159

0.0067

0.023
0.000185
0.000304
0.0005

0.0005



0.0007





0.000185

0.023
0.00197
0.00065
0.00095

0.0007



0.0007





0.00158

0.023
0.71
0.001
0.0017

0.0009



0.0007





0.71

0.0016
0.00021
0.00028
0.00099











0.00021

0.00475
0.006955
0.00028
0.001275











0.005685

0.0127
0.0598
0.00028
0.00156











0.0598
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NI
NM
OR
SC
SD
TX
VT
All States
2,296
12,140
136
2,801
526
1,634
506
391
154
762
209
923
1,147
70
6,183
629
30,507
1
1

16

2



2

0
3

7
2
36
0.04%
0.01%
0.00%
0.57%
0.00%
0.1 2%
0.00%
0.00%
0.00%
0.26%
0.00%
0.22%
0.26%
0.00%
0.11%
0.32%
0.1 2%












0.0005

0.001

0.0005












0.0005

0.001055

0.00101












0.0005

0.00498

0.00498
0.0021


0.0005







0.0008


0.0008
0.0006
0.0005
0.0021


0.0005







0.0008


0.00289
0.0006
0.0008
0.0021


0.0005







0.0008


0.00498
0.0006
0.00498



0.0005

0.00065





0.0007




0.0005



0.0005

0.002325





0.0007




0.0005



0.0005

0.004





0.0007




0.004



0.0005








0.0005

0.0023
0.0005
0.0005



0.0005








0.0005

0.0023
0.0005
0.0005



0.0005








0.0005

0.0023
0.0005
0.0023

0.00222

0.0005





0.000266


0.0005



0.000266

0.00222

0.0005





0.000306


0.0005



0.0005

0.00222

0.0007





0.000346


0.0005



0.00222
   Note: All results are expressed in mg/L.
   * Blank cells indicate that there were no analytical detections for that State.

-------
Occurrence Estimation Methodology and Findings
Appendix B2. 16-State Cross-Section Data for Stage 2 Analysis
                                                                                                                                                                                                  Six-Year Review
   Table B.60.b.  Xylenes (Total) - Summary of Analytical Detections in the 16-State Cross-Section by Source Water Type and Population-Served Size Category
State
Total #
Records
# Detects
% Detects
<500
Minimum
Median
Maximum
501 - 3,300
Minimum
Median
Maximum
3,301 - 10,000
Minimum
Median
Maximum
10,001 - 50.000
Minimum
Median
Maximum
> 50,000
Minimum
Median
Maximum
Ground Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NI
NM
OR
SC
SD
TX
VT
All States
5,118
37,609
18,682
23,210
3,782
4
4,171
3,269
1
10,271
4,619
654
4,916
0
23,193
3,558
143,057
120
109
227
446
13

53
4

140
35
8
51

228
3
1,437
2.34%
0.29%
1.22%
1.92%
0.34%
0.00%
1.27%
0.12%
0.00%
1.36%
0.76%
1.22%
1.04%
0.00%
0.98%
0.08%
1.00%
0.00052
0.00075
0.00002
0.0005
0.0021

0.0005
0.00084

0.00012
0.0005
0.0008
0.00092

0.00017
0.0002
0.00002
0.0014
0.0064
0.002
0.0015
0.0033

0.0009
0.00215

0.00112
0.0018
0.0044
0.00232

0.0034
0.00045
0.001755
0.0448
0.573
0.071
0.172
0.012

0.0087
0.134

0.183
0.118
0.0646
0.0342

1.6
0.0007
1.6
0.00052
0.0007
0.00039
0.0005
0.00058

0.0005


0.000053
0.0005
0.0014
0.0005

0.00023
0.001
0.000053
0.00194
0.0039
0.001865
0.0014
0.0007

0.00155


0.001
0.0022
0.0025
0.0014

0.0022
0.001
0.0016
0.2402
0.669
0.266
0.13
0.0012

0.0035


0.04546
0.0171
0.0045
0.00501

0.31856
0.001
0.669
0.00054
0.0006
0.0001
0.0005


0.0005


0.0005


0.00167

0.00026

0.0001
0.002
0.0054
0.001
0.0007


0.0009


0.001614


0.00167

0.0024

0.0017
0.0135
0.28
0.0282
0.054


0.0084


0.0037


0.00167

0.19155

0.28
0.0005
0.0006
0.0002
0.000275
0.0029

0.002


0.00012
0.0004



0.0006

0.00012
0.00302
0.0018
0.00469
0.0011
0.0031

0.002


0.000635
0.00105



0.0016

0.0014
0.066
0.198
0.0315
0.214
0.0053

0.002


0.0207
0.00314



0.0111

0.214
0.002
0.00099
0.000159
0.0007





0.003




0.0025

0.000159
0.00305
0.002
0.001375
0.0007





0.01635




0.00445

0.002
0.0041
0.058
0.088
0.0007





0.0297




0.0064

0.088
Suface Water
AL
CA
FL
IL
IN
KY
MI
MT
NE
NI
NM
OR
SC
SD
TX
VT
All States
2,297
12,768
135
2,465
529
2
527
371
0
757
186
442
473
0
6,183
754
27,889
30
26

48
3

48
2

7
2
6
1

59
2
234
1.31%
0.20%
0.00%
1.95%
0.57%
0.00%
9.11%
0.54%
0.00%
0.92%
1.08%
1.36%
0.21%
0.00%
0.95%
0.27%
0.84%
0.0058
0.0071

0.0018
0.00051

0.0005




0.0008


0.00052

0.0005
0.0065
0.0071

0.0018
0.00067

0.0035




0.0013


0.00538

0.004
0.0072
0.0071

0.0018
0.0009

0.0112




0.0018


0.0975

0.0975
0.00099
0.04

0.0005


0.0006




0.0006
0.0015

0.00043
0.0043
0.00043
0.00394
0.04

0.00085


0.0019




0.00075
0.0015

0.00155
0.0043
0.0015
0.00939
0.04

0.0029


0.016




0.0065
0.0015

0.11285
0.0043
0.11285
0.00062
0.0052

0.0005


0.0005
0.0053


0.0007



0.0006

0.0005
0.00655
0.02945

0.001


0.0009
0.00615


0.0007



0.0019

0.00185
0.0497
0.125

0.012


0.0085
0.007


0.0007



0.014

0.125
0.00054
0.0012

0.0005


0.0005


0.0005




0.0007
0.0028
0.0005
0.0013
0.0042

0.0009


0.0006


0.00204




0.0014
0.0028
0.001
0.0041
0.022

0.0054


0.0008


0.00358




0.003
0.0028
0.022
0.0012
0.0006

0.0005





0.000001
0.06391



0.0006

0.000001
0.00408
0.0021

0.0005





0.0005
0.06391



0.00082

0.0008
0.0078
0.1033

0.0008





0.0025
0.06391



0.0037

0.1033
   Note: All results are expressed in mg/L.
   * Blank cells indicate that there were no analytical detections for that State.

-------
                  Appendix C.  Stage 2 Analytical Findings
Table C.I.a.    Alachlor - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on the Number of Systems
Table C. 1 .b.    Alachlor - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.002 mg/L)
Table C. 1 .c.    Alachlor - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.002 mg/L)
Table C.l.d.    Alachlor - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on Population Served
Table C. 1 .e.    Alachlor - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.002 mg/L)
Table C. 1 .f.    Alachlor - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.0002 mg/L)

Table C.2.a.    Antimony - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on the Number of Systems
Table C.2.b.    Antimony - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.024 mg/L)
Table C.2.c.    Antimony - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.018 mg/L)
Table C.2.d.    Antimony - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.012 mg/L)
Table C.2.e.    Antimony - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.006 mg/L)
Table C.2.f    Antimony - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.003 mg/L)
Table C.2.g.    Antimony - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.002 mg/L)
Table C.2.h.    Antimony - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.0015 mg/L)
Table C.2.i.    Antimony - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on Population Served
Table C.2.J.    Antimony - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.024 mg/L)
Table C.2.k.    Antimony - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.018 mg/L)
Table C.2.1.    Antimony - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.012 mg/L)
Table C.2.m.   Antimony - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.006 mg/L)
Table C.2.n.    Antimony - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.003 mg/L)
Table C.2.o.    Antimony - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.002 mg/L)
Table C.2.p.    Antimony - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.0015 mg/L)

Table C.3.a.    Atrazine - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on the Number of Systems

-------
Table C.S.b.   Atrazine - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.050 mg/L)
Table C.S.c.   Atrazine - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.012 mg/L)
Table C.S.d.   Atrazine - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.010 mg/L)
Table C.S.e.   Atrazine - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.003 mg/L)
Table C.S.f    Atrazine - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on Population Served
Table C.S.g.   Atrazine - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.050 mg/L)
Table C.S.h.   Atrazine - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.012 mg/L)
Table C.S.i.    Atrazine - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.010 mg/L)
Table C.3.J.    Atrazine - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.003 mg/L)

Table C.4.a.   Barium - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on the Number of Systems
Table C.4.b.   Barium - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 2 mg/L)
Table C.4.c.   Barium - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 1 mg/L)
Table C.4.d.   Barium - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.5 mg/L)
Table C.4.e.   Barium - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.1 mg/L)
Table C.4.f.    Barium - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on Population Served
Table C.4.g.   Barium - Population Served - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 2 mg/L)
Table C.4.h.   Barium - Population Served - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 1 mg/L)
Table C.4.i.    Barium - Population Served - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.5 mg/L)
Table C.4.J.    Barium - Population Served - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.1 mg/L)

Table C.5.a.   Benzene - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on the Number of Systems
Table C.5.b.   Benzene - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.005 mg/L)
Table C.5.c.   Benzene - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.0005 mg/L)
Table C.5.d.   Benzene - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.0004 mg/L)
Table C.5.e.   Benzene - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on Population Served
Table C.5.f    Benzene - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.005 mg/L)

-------
Table C.S.g.   Benzene - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.0005 mg/L)
Table C.S.h.   Benzene - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.0004 mg/L)

Table C.6.a.   Benzo(a)pyrene - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on the Number of Systems
Table C.6.b.   Benzo(a)pyrene - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.0002 mg/L)
Table C.6.c.   Benzo(a)pyrene - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.0001 mg/L)
Table C.6.d.   Benzo(a)pyrene - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.00005 mg/L)
Table C.6.e.   Benzo(a)pyrene - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.00002 mg/L)
Table C.6.f.   Benzo(a)pyrene - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on Population Served
Table C.6.g.   Benzo(a)pyrene - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.0002 mg/L)
Table C.6.h.   Benzo(a)pyrene - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.0001 mg/L)
Table C.6.i.   Benzo(a)pyrene - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.00005 mg/L)
Table C.6.J.   Benzo(a)pyrene - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.00002 mg/L)

Table C.7.a.   Beryllium - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on the Number of Systems
Table C.7.b.   Beryllium - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.01 mg/L)
Table C.7.c.   Beryllium - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.004 mg/L)
Table C.7.d.   Beryllium - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.001 mg/L)
Table C.7.e.   Beryllium - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on Population Served
Table C.7.f   Beryllium - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.01 mg/L)
Table C.7.g.   Beryllium - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.004 mg/L)
Table C.7.h.   Beryllium - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.001 mg/L)

Table C.S.a.   Bis(2-ethylhexyl)adipate - 16 Cross-Section States - Mean Concentration, Best Estimate,
              and Credible Intervals Based on the Number of Systems
Table C.S.b.   Bis(2-ethylhexyl)adipate - Systems - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.4 mg/L)
Table C.S.c.   Bis(2-ethylhexyl)adipate - Systems - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.2 mg/L)
Table C.S.d.   Bis(2-ethylhexyl)adipate - Systems - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.1 mg/L)
Table C.S.e.   Bis(2-ethylhexyl)adipate - Systems - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.0006 mg/L)

-------
Table C.S.f    Bis(2-ethylhexyl)adipate - 16 Cross-Section States - Mean Concentration, Best Estimate,
              and Credible Intervals Based on Population Served
Table C.S.g.   Bis(2-ethylhexyl)adipate - Population Served - National Best Estimate Including
              Estimate Range Based on Credible Bounds (Threshold = 0.4 mg/L)
Table C.S.h.   Bis(2-ethylhexyl)adipate - Population Served - National Best Estimate Including
              Estimate Range Based on Credible Bounds (Threshold = 0.2 mg/L)
Table C.S.i.    Bis(2-ethylhexyl)adipate - Population Served - National Best Estimate Including
              Estimate Range Based on Credible Bounds (Threshold = 0.1 mg/L)
Table C.S.j.    Bis(2-ethylhexyl)adipate - Population Served - National Best Estimate Including
              Estimate Range Based on Credible Bounds (Threshold = 0.0006 mg/L)

Table C.9.a.   Bis(2-ethylhexyl)phthalate - 16 Cross-Section States - Mean Concentration, Best
              Estimate, and Credible Intervals Based on the Number of Systems
Table C.9.b.   Bis(2-ethylhexyl)phthalate - Systems - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.006 mg/L)
Table C.9.c.   Bis(2-ethylhexyl)phthalate - Systems - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.003 mg/L)
Table C.9.d.   Bis(2-ethylhexyl)phthalate - Systems - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.0006 mg/L)
Table C.9.e.   Bis(2-ethylhexyl)phthalate - 16 Cross-Section States - Mean Concentration, Best
              Estimate, and Credible Intervals Based on Population Served
Table C.9.f.    Bis(2-ethylhexyl)phthalate - Population Served - National Best Estimate Including
              Estimate Range Based on Credible Bounds (Threshold = 0.006 mg/L)
Table C.9.g.   Bis(2-ethylhexyl)phthalate - Population Served - National Best Estimate Including
              Estimate Range Based on Credible Bounds (Threshold = 0.003 mg/L)
Table C.9.h.   Bis(2-ethylhexyl)phthalate - Population Served - National Best Estimate Including
              Estimate Range Based on Credible Bounds (Threshold = 0.0006 mg/L)

Table C.lO.a.  Cadmium - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on the Number of Systems
Table C. lO.b.  Cadmium - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.005 mg/L)
Table C. lO.c.  Cadmium - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.0025 mg/L)
Table C. lO.d.  Cadmium - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.00125 mg/L)
Table C. lO.e.  Cadmium - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.001 mg/L)
Table C.lO.f  Cadmium - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on Population Served
Table C. lO.g.  Cadmium - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.005 mg/L)
Table C. lO.h.  Cadmium - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.0025 mg/L)
Table C. lO.i.  Cadmium - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.00125 mg/L)
Table C. lO.j.  Cadmium - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.001 mg/L)

Table C. 11 .a.  Carbofuran - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on the Number of Systems
Table C. 11 .b.  Carbofuran - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.04 mg/L)

-------
Table C. 11 .c.  Carbofuran - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.007 mg/L)
Table C. 11 .d.  Carbofuran - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.004 mg/L)
Table C. 11 .e.  Carbofuran - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on Population Served
Table C. 11 .f.  Carbofuran - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.04 mg/L)
Table C. 11 .g.  Carbofuran - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.007 mg/L)
Table C. 11 .h.  Carbofuran - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.004 mg/L)

Table C.12.a.  Carbon Tetrachloride - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on the Number of Systems
Table C. 12.b.  Carbon Tetrachloride - Systems - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.005 mg/L)
Table C. 12.c.  Carbon Tetrachloride - Systems - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.0025 mg/L)
Table C. 12.d.  Carbon Tetrachloride - Systems - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.0005 mg/L)
Table C.12.e.  Carbon Tetrachloride - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on Population Served
Table C. 12.f.  Carbon Tetrachloride - Population Served - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.005 mg/L)
Table C. 12.g.  Carbon Tetrachloride - Population Served - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.0025 mg/L)
Table C. 12.h.  Carbon Tetrachloride - Population Served - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.0005 mg/L)

Table C.I3.a.  Chlordane - 16 Cross-Section States - Mean Concentration, Best Estimate,  and Credible
              Intervals Based on the Number of Systems
Table C. 13.b.  Chlordane - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.002 mg/L)
Table C. 13.c.  Chlordane - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.001 mg/L)
Table C. 13.d.  Chlordane - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.0002 mg/L)
Table C.13.e.  Chlordane - 16 Cross-Section States - Mean Concentration, Best Estimate,  and Credible
              Intervals Based on Population Served
Table C. 13.f  Chlordane - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.002 mg/L)
Table C. 13.g.  Chlordane - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.001 mg/L)
Table C. 13.h.  Chlordane - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.0002 mg/L)

Table C. 14.a.  Chromium - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on the Number of Systems
Table C. 14.b.  Chromium - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.1 mg/L)
Table C. 14.c.  Chromium - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.07 mg/L)

-------
Table C. 14.d.  Chromium - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.05 mg/L)
Table C. 14.e.  Chromium - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.02 mg/L)
Table C. 14.f.  Chromium - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.01 mg/L)
Table C.14.g.  Chromium - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on Population Served
Table C.14.h.  Chromium - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.1 mg/L)
Table C. 14.i.  Chromium - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.07 mg/L)
Table C. 14.j.  Chromium - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.05 mg/L)
Table C.14.k.  Chromium - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.02 mg/L)
Table C. 14.1.  Chromium - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.01 mg/L)

Table C.I5.a.  Cyanide - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on the Number of Systems
Table C. 15.b.  Cyanide - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.2 mg/L)
Table C. 15.c.  Cyanide - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.1 mg/L)
Table C. 15.d.  Cyanide - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.05 mg/L)
Table C.15.e.  Cyanide - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on Population Served
Table C. 15.f.  Cyanide - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.2 mg/L)
Table C. 15.g.  Cyanide - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.1 mg/L)
Table C. 15.h.  Cyanide - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.05 mg/L)

Table C.16.a.  2,4-D - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on the Number of Systems
Table C. 16.b.  2,4-D - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.07 mg/L)
Table C. 16.c.  2,4-D - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.035 mg/L)
Table C. 16.d.  2,4-D - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.0175 mg/L)
Table C. 16.e.  2,4-D - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.0001 mg/L)
Table C.16.f  2,4-D - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on Population Served
Table C. 16.g.  2,4-D - Population Served - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.07 mg/L)
Table C. 16.h.  2,4-D - Population Served - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.035 mg/L)

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Table C. 16.i.   2,4-D - Population Served - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.0175 mg/L)
Table C. 16.j.   2,4-D - Population Served - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.0001 mg/L)

Table C.17.a.   Dalapon - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on the Number of Systems
Table C. IV.b.   Dalapon - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.2 mg/L)
Table C. 17.c.   Dalapon - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.1 mg/L)
Table C. IV.d.   Dalapon - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.05 mg/L)
Table C. 17.e.   Dalapon - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.001 mg/L)
Table C.lV.f.   Dalapon - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on Population Served
Table C. 17.g.   Dalapon - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.2 mg/L)
Table C. IV.h.   Dalapon - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.1 mg/L)
Table C. 17.i.   Dalapon - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.05 mg/L)
Table C. IV.j.   Dalapon - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.001 mg/L)

Table C.lS.a.   l,2-Dibromo-3-chloropropane - 16 Cross-Section States - Mean Concentration, Best
              Estimate, and Credible Intervals Based on the Number of Systems
Table C. 18.b.   l,2-Dibromo-3-chloropropane - Systems - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.0002 mg/L)
Table C. 18.c.   l,2-Dibromo-3-chloropropane - Systems - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.0001 mg/L)
Table C. 18.d.   l,2-Dibromo-3-chloropropane - Systems - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.00002 mg/L)
Table C.lS.e.   l,2-Dibromo-3-chloropropane - 16 Cross-Section States - Mean Concentration, Best
              Estimate, and Credible Intervals Based on Population Served
Table C.lS.f.   l,2-Dibromo-3-chloropropane - Population Served - National Best Estimate Including
              Estimate Range Based on Credible Bounds (Threshold = 0.0002 mg/L)
Table C.lS.g.   l,2-Dibromo-3-chloropropane - Population Served - National Best Estimate Including
              Estimate Range Based on Credible Bounds (Threshold = 0.0001 mg/L)
Table C.lS.h.   l,2-Dibromo-3-chloropropane - Population Served - National Best Estimate Including
              Estimate Range Based on Credible Bounds (Threshold = 0.00002 mg/L)

Table C.19.a.   1,4-Dichlorobenzene - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on the Number of Systems
Table C. 19.b.   1,4-Dichlorobenzene - Systems - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.075 mg/L)
Table C. 19.c.   1,4-Dichlorobenzene - Systems - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.005 mg/L)
Table C. 19.d.   1,4-Dichlorobenzene - Systems - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.0005 mg/L)
Table C.19.e.   1,4-Dichlorobenzene - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on Population Served

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Table C. 19.f.    1,4-Dichlorobenzene - Population Served - National Best Estimate Including Estimate
               Range Based on Credible Bounds (Threshold = 0.075 mg/L)
Table C. 19.g.   1,4-Dichlorobenzene - Population Served - National Best Estimate Including Estimate
               Range Based on Credible Bounds (Threshold = 0.005 mg/L)
Table C. 19.h.   1,4-Dichlorobenzene - Population Served - National Best Estimate Including Estimate
               Range Based on Credible Bounds (Threshold = 0.0005 mg/L)

Table C.20.a.   o-Dichlorobenzene - 16 Cross-Section States - Mean Concentration, Best Estimate, and
               Credible Intervals Based on the Number of Systems
Table C.20.b.   o-Dichlorobenzene - Systems - National Best Estimate Including Estimate Range Based
               on Credible Bounds (Threshold = 0.6 mg/L)
Table C.20.C.   o-Dichlorobenzene - Systems - National Best Estimate Including Estimate Range Based
               on Credible Bounds (Threshold = 0.3 mg/L)
Table C.20.d.   o-Dichlorobenzene - Systems - National Best Estimate Including Estimate Range Based
               on Credible Bounds (Threshold = 0.15 mg/L)
Table C.20.e.   o-Dichlorobenzene - Systems - National Best Estimate Including Estimate Range Based
               on Credible Bounds (Threshold = 0.0005 mg/L)
Table C.20.f.    o-Dichlorobenzene - 16 Cross-Section States - Mean Concentration, Best Estimate, and
               Credible Intervals Based on Population Served
Table C.20.g.   o-Dichlorobenzene - Population Served - National Best Estimate Including Estimate
               Range Based on Credible Bounds (Threshold = 0.6 mg/L)
Table C.20.h.   o-Dichlorobenzene - Population Served - National Best Estimate Including Estimate
               Range Based on Credible Bounds (Threshold = 0.3 mg/L)
Table C.20.L    o-Dichlorobenzene - Population Served - National Best Estimate Including Estimate
               Range Based on Credible Bounds (Threshold = 0.15 mg/L)
Table C.20.J.    o-Dichlorobenzene - Population Served - National Best Estimate Including Estimate
               Range Based on Credible Bounds (Threshold = 0.0005 mg/L)

Table C.21.a.   1,2-Dichloroethane - 16 Cross-Section States - Mean Concentration, Best Estimate, and
               Credible Intervals Based on the Number of Systems
Table C.21.b.   1,2-Dichloroethane - Systems - National Best Estimate Including Estimate Range Based
               on Credible Bounds (Threshold = 0.005 mg/L)
Table C.21.C.   1,2-Dichloroethane - Systems - National Best Estimate Including Estimate Range Based
               on Credible Bounds (Threshold = 0.0025 mg/L)
Table C.21.d.   1,2-Dichloroethane - Systems - National Best Estimate Including Estimate Range Based
               on Credible Bounds (Threshold = 0.0005 mg/L)
Table C.21.e.   1,2-Dichloroethane - 16 Cross-Section States - Mean Concentration, Best Estimate, and
               Credible Intervals Based on Population Served
Table C.21.f    1,2-Dichloroethane - Population Served - National Best Estimate Including Estimate
               Range Based on Credible Bounds (Threshold = 0.005 mg/L)
Table C.21.g.   1,2-Dichloroethane - Population Served - National Best Estimate Including Estimate
               Range Based on Credible Bounds (Threshold = 0.0025 mg/L)
Table C.21.h.   1,2-Dichloroethane - Population Served - National Best Estimate Including Estimate
               Range Based on Credible Bounds (Threshold = 0.0005 mg/L)

Table C.22.a.   1,1-Dichloroethylene - 16 Cross-Section States - Mean Concentration, Best Estimate, and
               Credible Intervals Based on the Number of Systems
Table C.22.b.   1,1-Dichloroethylene - Systems - National Best Estimate Including Estimate Range
               Based on Credible Bounds (Threshold = 0.3 mg/L)
Table C.22.C.   1,1-Dichloroethylene - Systems - National Best Estimate Including Estimate Range
               Based on Credible Bounds (Threshold = 0.03 mg/L)
Table C.22.d.   1,1-Dichloroethylene - Systems - National Best Estimate Including Estimate Range
               Based on Credible Bounds (Threshold = 0.007 mg/L)

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Table C.22.e.   1,1-Dichloroethylene - Systems - National Best Estimate Including Estimate Range
               Based on Credible Bounds (Threshold = 0.005 mg/L)
Table C.22.f.   1,1-Dichloroethylene - Systems - National Best Estimate Including Estimate Range
               Based on Credible Bounds (Threshold = 0.001 mg/L)
Table C.22.g.   1,1-Dichloroethylene - Systems - National Best Estimate Including Estimate Range
               Based on Credible Bounds (Threshold = 0.0005 mg/L)
Table C.22.h.   1,1-Dichloroethylene - 16 Cross-Section States - Mean Concentration, Best Estimate, and
               Credible Intervals Based on Population Served
Table C.22.L   1,1-Dichloroethylene - Population Served - National Best Estimate Including Estimate
               Range Based on Credible Bounds (Threshold = 0.3 mg/L)
Table C.22.J.   1,1-Dichloroethylene - Population Served - National Best Estimate Including Estimate
               Range Based on Credible Bounds (Threshold = 0.03 mg/L)
Table C.22.k.   1,1-Dichloroethylene - Population Served - National Best Estimate Including Estimate
               Range Based on Credible Bounds (Threshold = 0.007 mg/L)
Table C.22.1.   1,1-Dichloroethylene - Population Served - National Best Estimate Including Estimate
               Range Based on Credible Bounds (Threshold = 0.005 mg/L)
Table C.22.m.  1,1-Dichloroethylene - Population Served - National Best Estimate Including Estimate
               Range Based on Credible Bounds (Threshold = 0.001 mg/L)
Table C.22.n.   1,1-Dichloroethylene - Population Served - National Best Estimate Including Estimate
               Range Based on Credible Bounds (Threshold = 0.0005 mg/L)

Table C.23.a.   cis-l,2-Dichloroethylene - 16 Cross-Section States - Mean Concentration, Best Estimate,
               and Credible Intervals Based on the Number of Systems
Table C.23.b.   cis-l,2-Dichloroethylene - Systems - National Best Estimate Including Estimate Range
               Based on Credible Bounds (Threshold = 0.07 mg/L)
Table C.23.C.   cis-l,2-Dichloroethylene - Systems - National Best Estimate Including Estimate Range
               Based on Credible Bounds (Threshold = 0.035 mg/L)
Table C.23.d.   cis-l,2-Dichloroethylene - Systems - National Best Estimate Including Estimate Range
               Based on Credible Bounds (Threshold = 0.0175 mg/L)
Table C.23.e.   cis-l,2-Dichloroethylene - Systems - National Best Estimate Including Estimate Range
               Based on Credible Bounds (Threshold = 0.0005 mg/L)
Table C.23.f.   cis-l,2-Dichloroethylene - 16 Cross-Section States - Mean Concentration, Best Estimate,
               and Credible Intervals Based on Population Served
Table C.23.g.   cis-l,2-Dichloroethylene - Population Served - National Best Estimate Including
               Estimate Range Based on Credible Bounds (Threshold = 0.07 mg/L)
Table C.23.h.   cis-l,2-Dichloroethylene - Population Served - National Best Estimate Including
               Estimate Range Based on Credible Bounds (Threshold = 0.035 mg/L)
Table C.23.L   cis-l,2-Dichloroethylene - Population Served - National Best Estimate Including
               Estimate Range Based on Credible Bounds (Threshold = 0.0175 mg/L)
Table C.23.J.   cis-l,2-Dichloroethylene - Population Served - National Best Estimate Including
               Estimate Range Based on Credible Bounds (Threshold = 0.0005 mg/L)

Table C.24.a.   trans-1,2-Dichloroethylene - 16 Cross-Section States - Mean Concentration, Best
               Estimate, and Credible Intervals Based on the Number of Systems
Table C.24.b.   trans-1,2-Dichloroethylene - Systems - National Best Estimate Including Estimate Range
               Based on Credible Bounds (Threshold = 0.1 mg/L)
Table C.24.C.   trans-1,2-Dichloroethylene - Systems - National Best Estimate Including Estimate Range
               Based on Credible Bounds (Threshold = 0.05 mg/L)
Table C.24.d.   trans-1,2-Dichloroethylene - Systems - National Best Estimate Including Estimate Range
               Based on Credible Bounds (Threshold = 0.025 mg/L)
Table C.24.e.   trans-1,2-Dichloroethylene - Systems - National Best Estimate Including Estimate Range
               Based on Credible Bounds (Threshold = 0.0005 mg/L)

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Table C.24.f.   trans- 1,2-Dichloroethylene - 16 Cross-Section States - Mean Concentration, Best
              Estimate, and Credible Intervals Based on Population Served
Table C.24.g.  trans-1,2-Dichloroethylene - Population Served - National Best Estimate Including
              Estimate Range Based on Credible Bounds (Threshold = 0.1 mg/L)
Table C.24.h.  trans-1,2-Dichloroethylene - Population Served - National Best Estimate Including
              Estimate Range Based on Credible Bounds (Threshold = 0.05 mg/L)
Table C.24.L   trans-1,2-Dichloroethylene - Population Served - National Best Estimate Including
              Estimate Range Based on Credible Bounds (Threshold = 0.025 mg/L)
Table C.24.J.   trans-1,2-Dichloroethylene - Population Served - National Best Estimate Including
              Estimate Range Based on Credible Bounds (Threshold = 0.0005 mg/L)

Table C.25.a.  Dichloromethane - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on the Number of Systems
Table C.25.b.  Dichloromethane - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.005 mg/L)
Table C.25.C.  Dichloromethane - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.0025 mg/L)
Table C.25.d.  Dichloromethane - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.002 mg/L)
Table C.25.e.  Dichloromethane - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.001 mg/L)
Table C.25.f.   Dichloromethane - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.0005 mg/L)
Table C.25.g.  Dichloromethane - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.00025 mg/L)
Table C.25.h.  Dichloromethane - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on Population Served
Table C.25.L   Dichloromethane - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.005 mg/L)
Table C.25.J.   Dichloromethane - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.0025 mg/L)
Table C.25.k.  Dichloromethane - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.002 mg/L)
Table C.25.1.   Dichloromethane - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.001 mg/L)
Table C.25.m.  Dichloromethane - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.0005 mg/L)
Table C.25.n.  Dichloromethane - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.00025 mg/L)

Table C.26.a.  1,2-Dichloropropane - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on the Number of Systems
Table C.26.b.  1,2-Dichloropropane - Systems - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.005 mg/L)
Table C.26.C.  1,2-Dichloropropane - Systems - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.0005 mg/L)
Table C.26.d.  1,2-Dichloropropane - Systems - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.0004 mg/L)
Table C.26.e.  1,2-Dichloropropane - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on Population Served
Table C.26.f.   1,2-Dichloropropane - Population Served - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.005 mg/L)

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Table C.26.g.   1,2-Dichloropropane - Population Served - National Best Estimate Including Estimate
               Range Based on Credible Bounds (Threshold = 0.0005 mg/L)
Table C.26.h.   1,2-Dichloropropane - Population Served - National Best Estimate Including Estimate
               Range Based on Credible Bounds (Threshold = 0.0004 mg/L)

Table C.27.a.   Dinoseb - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
               Intervals Based on the Number of Systems
Table C.27.b.   Dinoseb - Systems - National Best Estimate Including Estimate Range Based on Credible
               Bounds (Threshold = 0.007 mg/L)
Table C.27.C.   Dinoseb - Systems - National Best Estimate Including Estimate Range Based on Credible
               Bounds (Threshold = 0.0035 mg/L)
Table C.27.d.   Dinoseb - Systems - National Best Estimate Including Estimate Range Based on Credible
               Bounds (Threshold = 0.00175 mg/L)
Table C.27.e.   Dinoseb - Systems - National Best Estimate Including Estimate Range Based on Credible
               Bounds (Threshold = 0.001 mg/L)
Table C.27.f.   Dinoseb - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
               Intervals Based on Population Served
Table C.27.g.   Dinoseb - Population Served - National Best Estimate Including Estimate Range Based
               on Credible Bounds (Threshold = 0.007 mg/L)
Table C.27.h.   Dinoseb - Population Served - National Best Estimate Including Estimate Range Based
               on Credible Bounds (Threshold = 0.0035 mg/L)
Table C.27.L   Dinoseb - Population Served - National Best Estimate Including Estimate Range Based
               on Credible Bounds (Threshold = 0.00175 mg/L)
Table C.27.J.   Dinoseb - Population Served - National Best Estimate Including Estimate Range Based
               on Credible Bounds (Threshold = 0.001 mg/L)

Table C.28.a.   Diquat - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
               Intervals Based on the Number of Systems
Table C.28.b.   Diquat - Systems - National Best Estimate Including Estimate Range Based on Credible
               Bounds (Threshold = 0.02 mg/L)
Table C.28.C.   Diquat - Systems - National Best Estimate Including Estimate Range Based on Credible
               Bounds (Threshold = 0.004 mg/L)
Table C.28.d.   Diquat - Systems - National Best Estimate Including Estimate Range Based on Credible
               Bounds (Threshold = 0.002 mg/L)
Table C.28.e.   Diquat - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
               Intervals Based on Population Served
Table C.28.f.   Diquat - Population  Served - National Best Estimate Including Estimate Range Based on
               Credible Bounds (Threshold = 0.02 mg/L)
Table C.28.g.   Diquat - Population  Served - National Best Estimate Including Estimate Range Based on
               Credible Bounds (Threshold = 0.004 mg/L)
Table C.28.h.   Diquat - Population  Served - National Best Estimate Including Estimate Range Based on
               Credible Bounds (Threshold = 0.002 mg/L)

Table C.29.a.   Endothall - 16 Cross-Section  States - Mean Concentration, Best Estimate, and Credible
               Intervals Based on the Number of Systems
Table C.29.b.   Endothall - Systems - National Best Estimate Including Estimate Range Based on
               Credible Bounds (Threshold = 0.1 mg/L)
Table C.29.C.   Endothall - Systems - National Best Estimate Including Estimate Range Based on
               Credible Bounds (Threshold = 0.05 mg/L)
Table C.29.d.   Endothall - Systems - National Best Estimate Including Estimate Range Based on
               Credible Bounds (Threshold = 0.025 mg/L)
Table C.29.e.   Endothall - Systems - National Best Estimate Including Estimate Range Based on
               Credible Bounds (Threshold = 0.009 mg/L)

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Table C.29.f.   Endothall - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on Population Served
Table C.29.g.  Endothall - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.1 mg/L)
Table C.29.h.  Endothall - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.05 mg/L)
Table C.29.L   Endothall - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.025 mg/L)
Table C.29.J.   Endothall - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.009 mg/L)

Table C.SO.a.  Endrin - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on the Number of Systems
Table C.SO.b.  Endrin - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.002 mg/L)
Table C.SO.c.  Endrin - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.001 mg/L)
Table C.SO.d.  Endrin - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.0005 mg/L)
Table C.SO.e.  Endrin - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.00001 mg/L)
Table C.SO.f.   Endrin - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on Population Served
Table C.SO.g.  Endrin - Population Served - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.002 mg/L)
Table C.SO.h.  Endrin - Population Served - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.001 mg/L)
Table C.SO.i.   Endrin - Population Served - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.0005 mg/L)
Table C.30.J.   Endrin - Population Served - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.00001 mg/L)

Table C.Sl.a.  Ethylbenzene - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on the  Number of Systems
Table C.Sl.b.  Ethylbenzene - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.7 mg/L)
Table C.31 .c.  Ethylbenzene - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.35 mg/L)
Table C.Sl.d.  Ethylbenzene - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.175 mg/L)
Table C.31 .e.  Ethylbenzene - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.0005 mg/L)
Table C.Sl.f.   Ethylbenzene - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on Population Served
Table C.31.g.  Ethylbenzene - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.7 mg/L)
Table C.31.h.  Ethylbenzene - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.35 mg/L)
Table C.Sl.i.   Ethylbenzene - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.175 mg/L)
Table C.31 j.   Ethylbenzene - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.0005 mg/L)

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Table C.32.a.  Ethylene Dibromide - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on the Number of Systems
Table C.32.b.  Ethylene Dibromide - Systems - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.00005 mg/L)
Table C.32.C.  Ethylene Dibromide - Systems - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.000025 mg/L)
Table C.32.d.  Ethylene Dibromide - Systems - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.00002 mg/L)
Table C.32.e.  Ethylene Dibromide - Systems - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.0000125 mg/L)
Table C.32.f.  Ethylene Dibromide - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on Population Served
Table C.32.g.  Ethylene Dibromide - Population Served - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.00005 mg/L)
Table C.32.h.  Ethylene Dibromide - Population Served - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.000025 mg/L)
Table C.32.L  Ethylene Dibromide - Population Served - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.00002 mg/L)
Table C.32.J.  Ethylene Dibromide - Population Served - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.0000125 mg/L)

Table C.33.a.  Fluoride - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on the Number of Systems
Table C.33.b.  Fluoride - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 4 mg/L)
Table C.33.C.  Fluoride - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 3 mg/L)
Table C.33.d.  Fluoride - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 2 mg/L)
Table C.33.e.  Fluoride - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold =1.5 mg/L)
Table C.33.f  Fluoride - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold =1.2 mg/L)
Table C.33.g.  Fluoride - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.7 mg/L)
Table C.33.h.  Fluoride - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.5 mg/L)
Table C.33.L  Fluoride - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.1 mg/L)
Table C.33.J.  Fluoride - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on Population Served
Table C.33.k.  Fluoride - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 4 mg/L)
Table C.33.1.  Fluoride - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 3 mg/L)
Table C.33.m.  Fluoride - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 2 mg/L)
Table C.33.n.  Fluoride - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold =1.5 mg/L)
Table C.33.O.  Fluoride - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold =1.2 mg/L)
Table C.33.p.  Fluoride - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.7 mg/L)

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Table C.33.q.  Fluoride - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.5 mg/L)
Table C.33.r.   Fluoride - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.1 mg/L)

Table C.34.a.  Glyphosate -  16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on the Number of Systems
Table C.34.b.  Glyphosate -  Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.7 mg/L)
Table C.34.C.  Glyphosate -  Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.06 mg/L)
Table C.34.d.  Glyphosate -  Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.006 mg/L)
Table C.34.e.  Glyphosate -  16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on Population Served
Table C.34.f.   Glyphosate -  Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.7 mg/L)
Table C.34.g.  Glyphosate -  Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.06 mg/L)
Table C.34.h.  Glyphosate -  Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.006 mg/L)

Table C.35.a.  Heptachlor -  16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on the Number of Systems
Table C.35.b.  Heptachlor - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.0004 mg/L)
Table C.35.C.  Heptachlor - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.0001 mg/L)
Table C.35.d.  Heptachlor - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.00004 mg/L)
Table C.35.e.  Heptachlor -  16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on Population Served
Table C.35.f   Heptachlor - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.0004 mg/L)
Table C.35.g.  Heptachlor - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.0001 mg/L)
Table C.35.h.  Heptachlor - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.00004 mg/L)

Table C.36.a.  Heptachlor Epoxide - 16 Cross-Section States  - Mean  Concentration, Best Estimate, and
              Credible Intervals Based on the Number of Systems
Table C.36.b.  Heptachlor Epoxide - Systems - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.0002 mg/L)
Table C.36.C.  Heptachlor Epoxide - Systems - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.0001 mg/L)
Table C.36.d.  Heptachlor Epoxide - Systems - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.00002 mg/L)
Table C.36.e.  Heptachlor Epoxide - 16 Cross-Section States  - Mean  Concentration, Best Estimate, and
              Credible Intervals Based on Population Served
Table C.36.f   Heptachlor Epoxide - Population Served - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.0002 mg/L)
Table C.36.g.  Heptachlor Epoxide - Population Served - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.0001 mg/L)

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Table C.36.h.  Heptachlor Epoxide - Population Served - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.00002 mg/L)

Table C.37.a.  Hexachlorobenzene - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on the Number of Systems
Table C.37.b.  Hexachlorobenzene - Systems - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.001 mg/L)
Table C.37.C.  Hexachlorobenzene - Systems - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.0005 mg/L)
Table C.37.d.  Hexachlorobenzene - Systems - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.0001 mg/L)
Table C.37.e.  Hexachlorobenzene - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on Population Served
Table C.37.f.  Hexachlorobenzene - Population Served - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.001 mg/L)
Table C.37.g.  Hexachlorobenzene - Population Served - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.0005 mg/L)
Table C.37.h.  Hexachlorobenzene - Population Served - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.0001 mg/L)

Table C.38.a.  Hexachlorocyclopentadiene - 16 Cross-Section States - Mean Concentration, Best
              Estimate, and Credible Intervals Based on the Number of Systems
Table C.38.b.  Hexachlorocyclopentadiene - Systems - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.0004 mg/L)
Table C.38.C.  Hexachlorocyclopentadiene - Systems - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.0001 mg/L)
Table C.38.d.  Hexachlorocyclopentadiene - Systems - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.00004 mg/L)
Table C.38.e.  Hexachlorocyclopentadiene - 16 Cross-Section States - Mean Concentration, Best
              Estimate, and Credible Intervals Based on Population Served
Table C.38.f  Hexachlorocyclopentadiene - Population Served - National Best Estimate Including
              Estimate Range Based on Credible Bounds (Threshold = 0.004 mg/L)
Table C.38.g.  Hexachlorocyclopentadiene - Population Served - National Best Estimate Including
              Estimate Range Based on Credible Bounds (Threshold = 0.0001 mg/L)
Table C.38.h.  Hexachlorocyclopentadiene - Population Served - National Best Estimate Including
              Estimate Range Based on Credible Bounds (Threshold = 0.00004 mg/L)

Table C.39.a.  Lindane -  16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on the Number of Systems
Table C.39.b.  Lindane -  Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.001 mg/L)
Table C.39.C.  Lindane -  Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.0002 mg/L)
Table C.39.d.  Lindane -  Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.0001 mg/L)
Table C.39.e.  Lindane -  Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.00005 mg/L)
Table C.39.f  Lindane -  Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.00002 mg/L)
Table C.39.g.  Lindane -  16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on Population Served
Table C.39.h.  Lindane -  Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.001 mg/L)

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Table C.39.L   Lindane - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.0002 mg/L)
Table C.39.J.   Lindane - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.0001 mg/L)
Table C.39.k.  Lindane - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.00005 mg/L)
Table C.39.1.   Lindane - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.00002 mg/L)

Table C.40.a.  Mercury - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on the Number of Systems
Table C.40.b.  Mercury - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.0004 mg/L)
Table C.40.C.  Mercury - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.0001 mg/L)
Table C.40.d.  Mercury - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.00004 mg/L)
Table C.40.e.  Mercury - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on Population Served
Table C.40.f.   Mercury - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.004 mg/L)
Table C.40.g.  Mercury - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.0001 mg/L)
Table C.40.h.  Mercury - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.00004 mg/L)

Table C.41.a.  Methoxychlor - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on the  Number of Systems
Table C.41.b.  Methoxychlor - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.04 mg/L)
Table C.41.C.  Methoxychlor - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.02 mg/L)
Table C.41.d.  Methoxychlor - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.01 mg/L)
Table C.41.e.  Methoxychlor - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.0001 mg/L)
Table C.41.f   Methoxychlor - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on Population Served
Table C.41.g.  Methoxychlor - Population Served - National Best Estimate Including Estimate  Range
              Based on Credible Bounds (Threshold = 0.04 mg/L)
Table C.41.h.  Methoxychlor - Population Served - National Best Estimate Including Estimate  Range
              Based on Credible Bounds (Threshold = 0.02 mg/L)
Table C.41.L   Methoxychlor - Population Served - National Best Estimate Including Estimate  Range
              Based on Credible Bounds (Threshold = 0.01 mg/L)
Table C.41.J.   Methoxychlor - Population Served - National Best Estimate Including Estimate  Range
              Based on Credible Bounds (Threshold = 0.0001 mg/L)

Table C.42.a.  Monochlorobenzene - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on the  Number of Systems
Table C.42.b.  Monochlorobenzene - Systems - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.1 mg/L)
Table C.42.C.  Monochlorobenzene - Systems - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.05 mg/L)

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Table C.42.d.  Monochlorobenzene - Systems - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.025 mg/L)
Table C.42.e.  Monochlorobenzene - Systems - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.0005 mg/L)
Table C.42.f.  Monochlorobenzene - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on Population Served
Table C.42.g.  Monochlorobenzene - Population Served - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.1 mg/L)
Table C.42.h.  Monochlorobenzene - Population Served - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.05 mg/L)
Table C.42.L   Monochlorobenzene - Population Served - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.015 mg/L)
Table C.42.J.   Monochlorobenzene - Population Served - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.0005 mg/L)

Table C.43.a.  Oxamyl - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on the Number of Systems
Table C.43.b.  Oxamyl - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.2 mg/L)
Table C.43.C.  Oxamyl - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.04 mg/L)
Table C.43.d.  Oxamyl - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.03 mg/L)
Table C.43.e.  Oxamyl - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.02 mg/L)
Table C.43.f.  Oxamyl - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.01 mg/L)
Table C.43.g.  Oxamyl - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on Population Served
Table C.43.h.  Oxamyl - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.2 mg/L)
Table C.43.L   Oxamyl - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.04 mg/L)
Table C.43.J.   Oxamyl - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.03 mg/L)
Table C.43.k.  Oxamyl - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.02 mg/L)
Table C.43.1.   Oxamyl - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.01 mg/L)

Table C.44.a.  PCBs - 16 Cross-Section States - Mean Concentration,  Best Estimate, and Credible
              Intervals Based on the Number of Systems
Table C.44.b.  PCBs - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.0005 mg/L)
Table C.44.C.  PCBs - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.00025 mg/L)
Table C.44.d.  PCBs - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.000125 mg/L)
Table C.44.e.  PCBs - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.0001 mg/L)
Table C.44.f  PCBs - 16 Cross-Section States - Mean Concentration,  Best Estimate, and Credible
              Intervals Based on Population Served

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Table C.44.g.  PCBs - Population Served - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.0005 mg/L)
Table C.44.h.  PCBs - Population Served - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.00025 mg/L)
Table C.44.L   PCBs - Population Served - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.000125 mg/L)
Table C.44.J.   PCBs - Population Served - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.0001 mg/L)

Table C.45.a.  Pentachlorophenol - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on the Number of Systems
Table C.45.b.  Pentachlorophenol - Systems - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.001 mg/L)
Table C.45.C.  Pentachlorophenol - Systems - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.0005 mg/L)
Table C.45.d.  Pentachlorophenol - Systems - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.00025 mg/L)
Table C.45.e.  Pentachlorophenol - Systems - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.00004 mg/L)
Table C.45.f.   Pentachlorophenol - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on Population Served
Table C.45.g.  Pentachlorophenol - Population Served - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.001 mg/L)
Table C.45.h.  Pentachlorophenol - Population Served - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.0005 mg/L)
Table C.45.L   Pentachlorophenol - Population Served - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.00025 mg/L)
Table C.45.J.   Pentachlorophenol - Population Served - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.00004 mg/L)

Table C.46.a.  Picloram - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on the Number of Systems
Table C.46.b.  Picloram - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 1 mg/L)
Table C.46.C.  Picloram - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.5 mg/L)
Table C.46.d.  Picloram - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.05 mg/L)
Table C.46.e.  Picloram - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on Population Served
Table C.46.f   Picloram - Population Served - National  Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 1 mg/L)
Table C.46.g.  Picloram - Population Served - National  Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.5 mg/L)
Table C.46.h.  Picloram - Population Served - National  Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.05 mg/L)

Table C.47.a.  Selenium - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on the Number of Systems
Table C.47.b.  Selenium - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.05 mg/L)
Table C.47.C.  Selenium - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.025 mg/L)

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Table C.47.d.   Selenium - Systems - National Best Estimate Including Estimate Range Based on
               Credible Bounds (Threshold = 0.0125 mg/L)
Table C.47.e.   Selenium - Systems - National Best Estimate Including Estimate Range Based on
               Credible Bounds (Threshold = 0.005 mg/L)
Table C.47.f.   Selenium - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
               Intervals Based on Population Served
Table C.47.g.   Selenium - Population Served - National Best Estimate Including Estimate Range Based
               on Credible Bounds (Threshold = 0.05 mg/L)
Table C.47.h.   Selenium - Population Served - National Best Estimate Including Estimate Range Based
               on Credible Bounds (Threshold = 0.025 mg/L)
Table C.47.L   Selenium - Population Served - National Best Estimate Including Estimate Range Based
               on Credible Bounds (Threshold = 0.0125 mg/L)
Table C.47.J.   Selenium - Population Served - National Best Estimate Including Estimate Range Based
               on Credible Bounds (Threshold = 0.005 mg/L)

Table C.48.a.   Simazine - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
               Intervals Based on the Number of Systems
Table C.48.b.   Simazine - Systems - National Best Estimate Including Estimate Range Based on
               Credible Bounds (Threshold = 0.004 mg/L)
Table C.48.C.   Simazine - Systems - National Best Estimate Including Estimate Range Based on
               Credible Bounds (Threshold = 0.002 mg/L)
Table C.48.d.   Simazine - Systems - National Best Estimate Including Estimate Range Based on
               Credible Bounds (Threshold = 0.001 mg/L)
Table C.48.e.   Simazine - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
               Intervals Based on Population Served
Table C.48.f.   Simazine - Population Served - National Best Estimate Including Estimate Range Based
               on Credible Bounds (Threshold = 0.004 mg/L)
Table C.48.g.   Simazine - Population Served - National Best Estimate Including Estimate Range Based
               on Credible Bounds (Threshold = 0.002 mg/L)
Table C.48.h.   Simazine - Population Served - National Best Estimate Including Estimate Range Based
               on Credible Bounds (Threshold = 0.001 mg/L)

Table C.49.a.   Styrene - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
               Intervals Based on the Number of Systems
Table C.49.b.   Styrene - Systems - National Best Estimate Including Estimate Range Based on Credible
               Bounds (Threshold = 0.1 mg/L)
Table C.49.C.   Styrene - Systems - National Best Estimate Including Estimate Range Based on Credible
               Bounds (Threshold = 0.05 mg/L)
Table C.49.d.   Styrene - Systems - National Best Estimate Including Estimate Range Based on Credible
               Bounds (Threshold = 0.025 mg/L)
Table C.49.e.   Styrene - Systems - National Best Estimate Including Estimate Range Based on Credible
               Bounds (Threshold = 0.0005 mg/L)
Table C.49.f   Styrene - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
               Intervals Based on Population Served
Table C.49.g.   Styrene - Population Served - National Best Estimate Including Estimate Range Based on
               Credible Bounds (Threshold = 0.1 mg/L)
Table C.49.h.   Styrene - Population Served - National Best Estimate Including Estimate Range Based on
               Credible Bounds (Threshold = 0.05 mg/L)
Table C.49.L   Styrene - Population Served - National Best Estimate Including Estimate Range Based on
               Credible Bounds (Threshold = 0.015 mg/L)
Table C.49.J.   Styrene - Population Served - National Best Estimate Including Estimate Range Based on
               Credible Bounds (Threshold = 0.0005 mg/L)

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Table C.SO.a.  Tetrachloroethylene - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on the Number of Systems
Table C.SO.b.  Tetrachloroethylene - Systems - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.005 mg/L)
Table C.SO.c.  Tetrachloroethylene - Systems - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.0005 mg/L)
Table C.SO.d.  Tetrachloroethylene - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on Population Served
Table C.SO.e.  Tetrachloroethylene - Population Served - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.005 mg/L)
Table C.SO.f.  Tetrachloroethylene - Population Served - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.0005 mg/L)

Table C.51.a.  Thallium - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on the Number of Systems
Table C.51 .b.  Thallium - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.002 mg/L)
Table C.51 .c.  Thallium - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.001 mg/L)
Table C.51.d.  Thallium - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on Population Served
Table C.51 .e.  Thallium - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.002 mg/L)
Table C.51 .f  Thallium - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.001 mg/L)

Table C.52.a.  Toluene - 16  Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on the Number of Systems
Table C.52.b.  Toluene - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 1 mg/L)
Table C.52.C.  Toluene - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.5 mg/L)
Table C.52.d.  Toluene - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.3 mg/L)
Table C.52.e.  Toluene - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.25 mg/L)
Table C.52.f  Toluene - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.05 mg/L)
Table C.52.g.  Toluene - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.0005 mg/L)
Table C.52.h.  Toluene - 16  Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on Population Served
Table C.52.L  Toluene - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 1 mg/L)
Table C.52.J.  Toluene - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.5 mg/L)
Table C.52.k.  Toluene - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.3 mg/L)
Table C.52.1.  Toluene - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.25 mg/L)
Table C.52.m.  Toluene - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.05 mg/L)

-------
Table C.52.n.  Toluene - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.0005 mg/L)

Table C.53.a.  Toxaphene - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on the Number of Systems
Table C.53.b.  Toxaphene - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.003 mg/L)
Table C.53.C.  Toxaphene - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.0015 mg/L)
Table C.53.d.  Toxaphene - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.001 mg/L)
Table C.53.e.  Toxaphene - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on Population Served
Table C.53.f.  Toxaphene - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.003 mg/L)
Table C.53.g.  Toxaphene - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.0015 mg/L)
Table C.53.h.  Toxaphene - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.001 mg/L)

Table C.54.a.  2,4,5-TP - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on the Number of Systems
Table C.54.b.  2,4,5-TP - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.05 mg/L)
Table C.54.C.  2,4,5-TP - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.025 mg/L)
Table C.54.d.  2,4,5-TP - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.0125 mg/L)
Table C.54.e.  2,4,5-TP - Systems - National Best Estimate Including Estimate Range Based on Credible
              Bounds (Threshold = 0.005 mg/L)
Table C.54.f  2,4,5-TP - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible
              Intervals Based on Population Served
Table C.54.g.  2,4,5-TP - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.05 mg/L)
Table C.54.h.  2,4,5-TP - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.025 mg/L)
Table C.54.L  2,4,5-TP - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.0125 mg/L)
Table C.54.J.  2,4,5-TP - Population Served - National Best Estimate Including Estimate Range Based
              on Credible Bounds (Threshold = 0.005 mg/L)

Table C.55.a.  1,2,4-Trichlorobenzene - 16 Cross-Section States - Mean Concentration, Best Estimate,
              and Credible Intervals Based on the Number of Systems
Table C.55.b.  1,2,4-Trichlorobenzene - Systems - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.07 mg/L)
Table C.55.C.  1,2,4-Trichlorobenzene - Systems - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.035 mg/L)
Table C.55.d.  1,2,4-Trichlorobenzene - Systems - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.0175 mg/L)
Table C.55.e.  1,2,4-Trichlorobenzene - Systems - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.0005 mg/L)
Table C.55.f  1,2,4-Trichlorobenzene - 16 Cross-Section States - Mean Concentration, Best Estimate,
              and Credible Intervals Based on Population Served

-------
Table C.55.g.

Table C.55.h.

Table C.551

Table C.55.J.


Table C.56.a.

Table C.56.b.

Table C.56.C.

Table C.56.d.

Table C.56.e.

Table C.56.f.

Table C.56.g.

Table C.56.h.

Table C.56.i.

Table C.56.J.


Table C.57.a.

Table C.57.b.

Table C.57.C.

Table C.57.d.

Table C.57.e.

Table C.57.f.


Table C.58.a.

Table C.58.b.

Table C.58.C.

Table C.58.d.

Table C.58.e.
1,2,4-Trichlorobenzene -
Range Based on Credible
1,2,4-Trichlorobenzene -
Range Based on Credible
1,2,4-Trichlorobenzene -
Range Based on Credible
1,2,4-Trichlorobenzene -
Range Based on Credible
Population Served - National Best Estimate Including Estimate
Bounds (Threshold = 0.07 mg/L)
Population Served - National Best Estimate Including Estimate
Bounds (Threshold = 0.035  mg/L)
Population Served - National Best Estimate Including Estimate
Bounds (Threshold = 0.0175 mg/L)
Population Served - National Best Estimate Including Estimate
Bounds (Threshold = 0.0005 mg/L)
1,1,1-Trichloroethane - 16 Cross-Section States - Mean Concentration, Best Estimate,
and Credible Intervals Based on the Number of Systems
1,1,1-Trichloroethane - Systems - National Best Estimate Including Estimate Range
Based on Credible Bounds (Threshold = 0.2 mg/L)
1,1,1-Trichloroethane - Systems - National Best Estimate Including Estimate Range
Based on Credible Bounds (Threshold = 0.1 mg/L)
1,1,1-Trichloroethane - Systems - National Best Estimate Including Estimate Range
Based on Credible Bounds (Threshold = 0.05 mg/L)
1,1,1-Trichloroethane - Systems - National Best Estimate Including Estimate Range
Based on Credible Bounds (Threshold = 0.0005 mg/L)
1,1,1-Trichloroethane - 16 Cross-Section States - Mean Concentration, Best Estimate,
and Credible Intervals Based on Population Served
1,1,1-Trichloroethane - Population Served - National Best Estimate Including Estimate
Range Based on Credible Bounds (Threshold = 0.2 mg/L)
1,1,1-Trichloroethane - Population Served - National Best Estimate Including Estimate
Range Based on Credible Bounds (Threshold = 0.1 mg/L)
1,1,1-Trichloroethane - Population Served - National Best Estimate Including Estimate
Range Based on Credible Bounds (Threshold = 0.05 mg/L)
1,1,1-Trichloroethane - Population Served - National Best Estimate Including Estimate
Range Based on Credible Bounds (Threshold = 0.0005 mg/L)

1,1,2-Trichloroethane - 16 Cross-Section States - Mean Concentration, Best Estimate,
and Credible Intervals Based on the Number of Systems
1,1,2-Trichloroethane - Systems - National Best Estimate Including Estimate Range
Based on Credible Bounds (Threshold = 0.005 mg/L)
1,1,2-Trichloroethane - Systems - National Best Estimate Including Estimate Range
Based on Credible Bounds (Threshold = 0.003 mg/L)
1,1,2-Trichloroethane - 16 Cross-Section States - Mean Concentration, Best Estimate,
and Credible Intervals Based on Population Served
1,1,2-Trichloroethane - Population Served - National Best Estimate Including Estimate
Range Based on Credible Bounds (Threshold = 0.005 mg/L)
1,1,2-Trichloroethane - Population Served - National Best Estimate Including Estimate
Range Based on Credible Bounds (Threshold = 0.003 mg/L)

Trichloroethylene - 16 Cross-Section States - Mean Concentration, Best Estimate, and
Credible Intervals Based on the Number of Systems
Trichloroethylene - Systems - National Best Estimate Including Estimate Range Based on
Credible Bounds (Threshold = 0.005 mg/L)
Trichloroethylene - Systems - National Best Estimate Including Estimate Range Based on
Credible Bounds (Threshold = 0.0025 mg/L)
Trichloroethylene - Systems - National Best Estimate Including Estimate Range Based on
Credible Bounds (Threshold = 0.001 mg/L)
Trichloroethylene - Systems - National Best Estimate Including Estimate Range Based on
Credible Bounds (Threshold = 0.0005 mg/L)

-------
Table C.58.f.   Trichloroethylene - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on Population Served
Table C.58.g.  Trichloroethylene - Population Served - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.005 mg/L)
Table C.58.h.  Trichloroethylene - Population Served - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.0025 mg/L)
Table C.58.L   Trichloroethylene - Population Served - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.001 mg/L)
Table C.58.J.   Trichloroethylene - Population Served - National Best Estimate Including Estimate
              Range Based on Credible Bounds (Threshold = 0.0005 mg/L)

Table C.59.a.  Vinyl Chloride - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on the Number of Systems
Table C.59.b.  Vinyl Chloride - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.002 mg/L)
Table C.59.C.  Vinyl Chloride - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.001 mg/L)
Table C.59.d.  Vinyl Chloride - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.0005 mg/L)
Table C.59.e.  Vinyl Chloride - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on Population Served
Table C.59.f.   Vinyl Chloride - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.002 mg/L)
Table C.59.g.  Vinyl Chloride - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.001 mg/L)
Table C.59.h.  Vinyl Chloride - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.0005 mg/L)

Table C.60.a.  Xylenes (Total) - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on the Number of Systems
Table C.60.b.  Xylenes (Total) - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold =10 mg/L)
Table C.60.C.  Xylenes (Total) - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 5 mg/L)
Table C.60.d.  Xylenes (Total) - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 4 mg/L)
Table C.60.e.  Xylenes (Total) - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 2.5 mg/L)
Table C.60.f   Xylenes (Total) - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.005 mg/L)
Table C.60.g.  Xylenes (Total) - Systems - National Best Estimate Including Estimate Range Based on
              Credible Bounds (Threshold = 0.0005 mg/L)
Table C.60.h.  Xylenes (Total) - 16 Cross-Section States - Mean Concentration, Best Estimate, and
              Credible Intervals Based on Population Served
Table C.60.i.   Xylenes (Total) - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold =10 mg/L)
Table C.60.J.   Xylenes (Total) - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 5 mg/L)
Table C.60.k.  Xylenes (Total) - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 4 mg/L)
Table C.60.1.   Xylenes (Total) - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 2.5 mg/L)

-------
Table C.60.m.  Xylenes (Total) - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.005 mg/L)
Table C.60.n.  Xylenes (Total) - Population Served - National Best Estimate Including Estimate Range
              Based on Credible Bounds (Threshold = 0.0005 mg/L)

-------
   Occurrence Estimation Methodology and Findings
   Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.l.a.  Alachlor -16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on the Number of Systems
Source Water
Type
Ground Water
Population
Served
<500
501 -3,300
3,301 - 10,000
10,001 -50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.00000293
0.00000395
0.00000268
0.00000243
0.00000129
0.00000311

Surface Water
<500
501 -3,300
3,301 - 10,000
10,001 -50,000
> 50,000
Total
0.00000936
0.0000185
0.0000118
0.0000100
0.0000108
0.0000128

All Systems - Combined
Ground & Surface Water
0.00000406
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.002 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0002 mg/L
0.0126%
0.0451%
0.109%
0.0217%
0.000%
0.0266%
0.000% - 0.0358%
0.000% - 0.132%
0.000% - 0.244%
0.000% - 0.191%
0.000% - 0.000%
0.00774% - 0.0542%
0.000% - 0.0358%
0.000% - 0.0989%
0.000% - 0.122%
0.000% - 0.191%
0.000% - 0.000%
0.00774% - 0.0465%

0.399%
0.691%
0.0970%
0.0526%
0.146%
0.323%
0.000% - 0.719%
0.000% - 1.47%
0.000% - 0.752%
0.000% - 0.321%
0.000% - 0.671%
0.0708% - 0.566%
0.360% - 0.719%
0.245% - 1.23%
0.000% - 0.376%
0.000% - 0.321%
0.000% - 0.671%
0.142% - 0.495%

0.0559%
0.0279% - 0.0907%
0.0279% - 0.0837%
All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.l.b.  Alachlor - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.002 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.l.c.  Alachlor - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.0002 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
5
5
o
J
1
0
16
6
12
1
1
1
18
36
using lower
95% CB
0
0
0
0
0
5
0
0
0
0
0
4
18
using upper
95% CB
16
16
6
2
0
32
11
25
8
3
3
32
59
using lower
90% CB
0
0
0
0
0
5
6
4
0
0
0
8
18
using upper
90% CB
16
12
o
J
2
0
28
11
21
4
o
J
3
28
54
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
  Occurrence Estimation Methodology and Findings
  Appendix C. Stage 2 Analytical Findings
Six-Year Review
Table C.l.d. Alachlor -16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on Population Served
Source Water
Type
Ground Water
Population
Served
<500
501 -3,300
3,301 - 10,000
10,001 -50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.00000293
0.00000395
0.00000268
0.00000243
0.00000129
0.00000311

Surface Water
<500
501 -3,300
3,301 - 10,000
10,001 -50,000
> 50,000
Total
0.00000936
0.0000185
0.0000118
0.0000100
0.0000108
0.0000128

All Systems - Combined
Ground & Surface Water
0.00000406
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.002 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0002 mg/L
0.00657%
0.0534%
0.178%
0.0375%
0.00227%
0.0385%
0.000% - 0.0363%
0.000% - 0.139%
0.000% - 0.379%
0.000% - 0.286%
0.000% - 0.000%
0.00383% - 0.112%
0.000% - 0.0310%
0.000% - 0.124%
0.000% - 0.303%
0.000% - 0.207%
0.000% - 0.000%
0.00985% - 0.105%

0.152%
0.840%
0.155%
0.0692%
0.0862%
0.0956%
0.000% - 1.01%
0.0859% - 1.85%
0.000% - 0.831%
0.000% - 0.627%
0.000% - 0.376%
0.0479% - 0.770%
0.115% - 1.68%
0.000% - 0.612%
0.000% - 0.479%
0.000% - 0.376%
0.00250% - 0.408% 0.00360% - 0.343%

0.0716%
0.0104% - 0.258%
0.0123% - 0.225%
All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
  Table C.l.e.  Alachlor - Population Served - National Best Estimate Including Estimate Range Based on
  Credible Bounds (Threshold = 0.002 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
  Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
  level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground &
  Surface Water").

  An additional rounding convention is applied to population-served estimates.  The primary model estimation output is the number of systems. In a specific size
  category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value.
  For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate
  is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
  Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
  Table C.l.f.  Alachlor - Population Served - National Best Estimate Including Estimate Range Based on
  Credible Bounds (Threshold = 0.0002 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
427
8,296
24,552
10,001
0
33,022
444
23,670
9,443
15,128
82,954
121,660
152,471
using lower
95% CB
0
0
0
0
0
3,279
0
2,420
0
0
0
3,186
22,110
using upper
95% CB
2,358
21,552
52,134
69,978
0
96,221
2,942
52,256
50,586
136,970
362,393
519,747
548,709
using lower
90% CB
0
0
0
0
0
8,439
140
3,244
0
0
0
4,586
26,094
using upper
90% CB
2,013
19,301
41,710
50,522
0
90,051
2,253
47,324
37,255
104,673
362,393
436,984
479,694
  Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
  level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground &
  Surface Water").


  An additional rounding convention is applied to population-served estimates.  The primary model estimation output is the number of systems. In a specific size
  category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value.
  For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate
  is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
  Population estimates are rounded to the nearest hundred.

-------
     Occurrence Estimation Methodology and Findings
     Appendix C.  Stage 2 Analytical Findings
                                                                                                                                                                                                                     Six-Year Review
Table C.2.a. Antimony - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on the Number of Systems
Source Water
Type
Ground Water
Population
Served
<500
501 - 3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.000714
0.000666
0.000581
0.000511
0.000446
0.000684
Best Estimate
of Exceeding
Threshold
95% Credible
Interval
90% Credible
Interval
Threshold = 0.024 mg/L
0.00357%
0.000535%
0.000219%
0.000%
0.000%
0.00247%
0.000% - 0.0107%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.00698%
0.000% - 0.0107%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.00698%
Best Estimate
of Exceeding
Threshold
95% Credible
Interval
90% Credible
Interval
Threshold = 0.018 mg/L
0.00764%
0.00285%
0.000874%
0.000%
0.000%
0.00571%
0.000% - 0.0214%
0.000% - 0.0297%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.0209%
0.000% - 0.0214%
0.000% - 0.0297%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.0140%
Best Estimate
of Exceeding
Threshold
95% Credible
Interval
90% Credible
Interval
Threshold = 0.012 mg/L
0.0283%
0.0134%
0.00525%
0.00219%
0.000%
0.0220%
0.000% - 0.0642%
0.000% - 0.0594%
0.000% - 0.109%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.0419%
0.0107% - 0.0535%
0.000% - 0.0594%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.00698% - 0.0419%
Best Estimate
of Exceeding
Threshold
95% Credible
Interval
90% Credible
Interval
Threshold = 0.006 mg/L
0.313%
0.214%
0.139%
0.110%
0.0466%
0.268%
0.203% - 0.439%
0.0891% - 0.386%
0.000% - 0.437%
0.000% - 0.364%
0.000% - 0.685%
0.182% - 0.363%
0.214% - 0.417%
0.0891% - 0.357%
0.000% - 0.437%
0.000% - 0.364%
0.000% - 0.685%
0.189% - 0.349%

Surface Water
<500
501 - 3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.000442
0.000449
0.000667
0.000527
0.000330
0.000491
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.00068%
0.000%
0.00233%
0.000%
0.000%
0.00057%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.0456%
0.0246%
0.0775%
0.0759%
0.0119%
0.0480%
0.000% - 0.340%
0.000% - 0.246%
0.000% - 0.388%
0.000% - 0.690%
0.000% - 0.000%
0.000% - 0.214%
0.000% - 0.340%
0.000% - 0.246%
0.000% - 0.388%
0.000% - 0.345%
0.000% - 0.000%
0.000% - 0.143%

All Systems - Combined
Ground & Surface Water
0.000666
0.00225%
0.000% - 0.00636%
0.000% - 0.00636%
0.00520%
0.000% - 0.0191%
0.000% - 0.0127%
0.0201%
0.000% - 0.0382%
0.00636% - 0.0382%
0.248%
0.165% - 0.343%
0.178% - 0.324%
Source Water
Type
Ground Water
Population
Served
<500
501 - 3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.000714
0.000666
0.000581
0.000511
0.000446
0.000684
Best Estimate
of Exceeding
Threshold
95% Credible
Interval
90% Credible
Interval
Threshold = 0.003 mg/L
2.39%
1.97%
1.57%
1.34%
1.07%
2.19%
2.01% - 2.77%
1.49% - 2.47%
0.984% - 2.40%
0.546% - 2.19%
0.000% - 2.74%
1.88% - 2.48%
2.09% - 2.72%
1.55% - 2.38%
0.984% - 2.19%
0.729% - 2.00%
0.000% - 2.74%
1.95% - 2.44%
Best Estimate
of Exceeding
Threshold
95% Credible
Interval
90% Credible
Interval
Threshold = 0.002 mg/L
6.16%
5.32%
4.28%
3.62%
3.11%
5.71%
5.54% - 6.77%
4.52% - 6.09%
3.17% - 5.57%
2.37% - 5.10%
1.37% - 4.80%
5.26% - 6.18%
5.66% - 6.69%
4.66% - 5.97%
3.28% - 5.36
2.55% - 4.74
1.37% - 4.80
5.31% - 6.11
Best Estimate
of Exceeding
Threshold
95% Credible
Interval
90% Credible
Interval
Threshold = 0.0015 mg/L
10.8%
9.53%
7.71%
6.28%
5.20%
10.1%
9.89% - 11.6%
8.44% - 10.6%
6.01% - 9.62%
4.74% - 8.20%
2.74% - 8.22%
9.42% - 10.7%
10.1% - 11.5%
8.62% - 10.5%
6.23% - 9.40%
4.92% - 7.83%
3.43% - 7.53%
9.52% - 10.6%

Surface Water
<500
501 - 3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.000442
0.000449
0.000667
0.000527
0.000330
0.000491
0.774%
0.712%
1.83%
1.32%
0.703%
1.06%
0.000% - 1.70%
0.000% - 1.47%
0.388% - 3.49%
0.345% - 2.41%
0.000% - 1.99%
0.571% - 1.57%
0.000% - 1.70%
0.246% - 1.23%
0.775% - 3.10%
0.345% - 2.41%
0.000% - 1.99%
0.714% - 1.50%
2.35%
2.34%
5.81%
3.63%
2.03%
3.21%
1.02% - 4.08%
1.23% - 3.69%
3.10% - 8.53%
2.07% - 5.52%
0.662% - 3.97%
2.43% - 4.00%
1.02% - 3.74
1.23% - 3.44
3.49% - 8.14
2.41% - 5.17
1.33% - 3.31
2.57% - 3.93
4.45%
4.59%
10.6%
6.48%
3.33%
5.93%
2.38% - 7.14%
2.95% - 6.63%
6.98% - 14.7%
4.48% - 8.97%
1.99% - 5.30%
4.93% - 7.00%
2.72% - 6.46%
3.19% - 6.39%
7.75% - 13.6%
4.83% - 8.62%
1.99% - 5.30%
5.00% - 6.93%

All Systems - Combined
Ground & Surface Water
0.000666
2.09%
1.79% - 2.37%
1.87% - 2.31%
5.49%
5.06% - 5.93%
5.13% - 5.87%
9.69%
9.11% - 10.3%
9.20% - 10.2%
All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.2.b.  Antimony - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.024 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
2
0
0
0
0
1
0
0
0
0
0
0
1
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
5
0
0
0
0
4
0
0
0
0
0
0
4
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
5
0
0
0
0
4
0
0
0
0
0
0
4
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.2.c.  Antimony - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.018 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
3
1
0
0
0
o
5
0
0
0
0
0
0
3
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
9
4
0
0
0
12
0
0
0
0
0
0
12
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
9
4
0
0
0
8
0
0
0
0
0
0
8
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.2.d.  Antimony - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.012 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
12
2
0
0
0
13
0
0
0
0
0
0
13
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
28
7
3
0
0
25
0
0
0
0
0
0
25
using lower
90% CB
5
0
0
0
0
4
0
0
0
0
0
0
4
using upper
90% CB
23
7
0
0
0
25
0
0
0
0
0
0
25
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.2.e.  Antimony - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.006 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
136
26
o
J
1
0
159
1
1
1
1
0
o
3
162
using lower
95% CB
88
11
0
0
0
108
0
0
0
0
0
0
107
using upper
95% CB
191
47
11
4
1
216
5
4
4
6
0
12
223
using lower
90% CB
93
11
0
0
0
112
0
0
0
0
0
0
116
using upper
90% CB
181
43
11
4
1
207
5
4
4
o
5
0
8
211
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.2.f. Antimony - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.003 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
1,040
239
38
16
2
1,299
12
12
19
12
3
59
1,356
using lower
95% CB
875
181
24
7
0
1,116
0
0
4
o
6
0
32
1,166
using upper
95% CB
1,205
300
58
26
5
1,473
26
25
35
23
8
88
1,539
using lower
90% CB
907
188
24
9
0
1,158
0
4
8
3
0
40
1,216
using upper
90% CB
1,182
289
53
24
5
1,448
26
21
31
23
8
84
1,501
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.2.g.  Antimony - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.002 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
2,678
646
103
43
6
3,395
36
40
59
34
8
180
3,569
using lower
95% CB
2,410
549
76
28
3
3,125
16
21
31
19
3
136
3,288
using upper
95% CB
2,945
740
134
61
9
3,672
63
63
86
52
16
224
3,858
using lower
90% CB
2,461
567
79
30
3
3,157
16
21
35
23
5
144
3,333
using upper
90% CB
2,908
726
129
56
9
3,631
57
59
82
48
13
220
3,817
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.2.h.  Antimony - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.0015 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
4,689
1,159
185
75
10
5,980
68
78
107
61
13
331
6,304
using lower
95% CB
4,304
1,026
145
56
5
5,602
37
50
71
42
8
276
5,926
using upper
95% CB
5,063
1,294
231
98
16
6,336
110
113
149
84
21
391
6,679
using lower
90% CB
4,380
1,048
150
59
6
5,660
42
54
78
45
8
280
5,980
using upper
90% CB
5,007
1,272
226
93
14
6,301
99
109
137
81
21
387
6,633
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
    Occurrence Estimation Methodology and Findings
    Appendix C.  Stage 2 Analytical Findings
                                                                                                                                                                                                                                     Six-Year Review
Table C.2.i. Antimony -16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on Population Served
 Source Water
     Type
Population
  Served
    Mean
Concentration
Value (mg/L)
Best Estimate
of Exceeding
  Threshold
95% Credible
   Interval
90% Credible
   Interval
                                                          Threshold = 0.024 mg/L
Best Estimate
of Exceeding
  Threshold
95% Credible
   Interval
90% Credible
   Interval
                                                                                                              Threshold = 0.018 mg/L
Best Estimate
of Exceeding
  Threshold
95% Credible
   Interval
90% Credible
   Interval
                                                                                                                                                                 Threshold = 0.012 mg/L
Best Estimate
of Exceeding
  Threshold
95% Credible
   Interval
90% Credible
   Interval
                                                                                                                                                                                                                     Threshold = 0.006 mg/L
                                                                                                                                                                                                                     0.142% -  0.448%
                                                                                                                                                                                                                                      0.0843% -  0.341%
                3,301 - 10,000
               10,001 - 50,000
                   Total
                                                                                                             0.000%  -  0.00399%
                                                                                                                                0.000%  -  0.00301%
                 501-3,300
 Surface Water
                3,301 - 10,000
               10,001 - 50,000
    All Systems - Combined
    Ground & Surface Water
                                                         0.000%  -  0.000129%  0.000% -  0.0000445%   0.000188%
Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.000714
0.000666
0.000581
0.000511
0.000446
0.000684
Best Estimate
of Exceeding
Threshold
95% Credible
Interval
90% Credible
Interval
Threshold = 0.003 mg/L
2.41%
1.85%
1.58%
1.45%
0.650%
1.20%
1.99% - 2.87%
1.32% - 2.40%
0.911% - 2.45%
0.709% - 2.32%
0.000% - 1.86%
0.744% - 1.77%
2.04% - 2.80%
1.41% - 2.31%
0.994% - 2.22%
0.763% - 2.21%
0.000% - 1.77%
0.827% - 1.68%
Best Estimate
of Exceeding
Threshold
95% Credible
Interval
90% Credible
Interval
Threshold = 0.002 mg/L
6.24%
5.06%
4.31%
3.55%
2.09%
3.28%
5.57% - 7.00%
4.24% - 5.92%
3.10% - 5.66%
2.36% - 4.92%
0.738% - 3.87%
2.51% - 4.09%
5.69% - 6.86%
4.34% - 5.80%
3.25% - 5.41%
2.58% - 4.71%
0.807% - 3.50%
2.65% - 3.93%
Best Estimate
of Exceeding
Threshold
95% Credible
Interval
90% Credible Interval
Threshold = 0.0015 mg/L
10.9%
9.16%
7.75%
6.03%
3.76%
5.79%
9.99% - 11.9%
7.94% - 10.4%
6.04% - 9.80%
4.48% - 7.92%
1.64% - 6.97%
4.69% - 7.22%
10.1% - 11.7%
8.21% - 10.2%
6.29% - 9.29%
4.71% - 7.60%
1.89% - 6.01%
4.87% - 6.66%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.000442
0.000449
0.000667
0.000527
0.000330
0.000491
0.799%
0.790%
1.81%
1.18%
0.725%
0.804%
0.000% - 2.21%
0.000% - 1.61%
0.297% - 3.66%
0.214% - 2.24%
0.000% - 2.14%
0.108% - 2.03%
0.000% - 1.94%
0.155% - 1.51%
0.504% - 3.27%
0.343% - 2.01%
0.000% - 1.97%
0.135% - 1.97%
2.54%
2.57%
5.73%
3.03%
2.29%
2.46%
0.674% - 4.95%
1.18% - 4.20%
3.06% - 8.62%
1.63% - 4.73%
0.337% - 4.51%
0.825% - 4.20%
0.958% - 4.48%
1.39% - 3.93%
3.42% - 8.03%
1.79% - 4.47%
0.630% - 3.79%
1.08% - 3.76%
4.80%
4.95%
10.5%
5.55%
3.48%
3.91%
2.25% - 8.00%
2.97% - 7.20%
7.12% - 14.5%
3.62% - 8.01%
1.97% - 6.48%
2.63% - 6.38%
2.48% - 7.46%
3.32% - 6.62%
7.39% - 13.8%
3.80% - 7.68%
2.14% - 5.14%
2.74% - 5.39%

All Systems - Combined
Ground & Surface Water
0.000666
0.963%
0.462% - 1.77%
0.485% - 1.69%
2.79%
1.70% - 3.97%
1.97% - 3.66%
4.67%
3.74% - 6.57%
3.82% - 5.81%
All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
     Table C.2.J.  Antimony - Population Served - National Best Estimate Including Estimate Range Based on
     Credible Bounds (Threshold = 0.024 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
100
0
0
0
0
100
0
0
0
0
0
0
100
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
300
0
0
0
0
300
0
0
0
0
0
0
300
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
100
0
0
0
0
100
0
0
0
0
0
0
100
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").

    An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size
    category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional
    value. For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the
    population estimate is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
    Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
     Table C.2.k. Antimony - Population Served - National Best Estimate Including Estimate Range Based on
     Credible Bounds (Threshold = 0.018 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
200
500
0
0
0
400
0
0
0
0
0
0
400
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
1,300
4,500
0
0
0
3,400
0
0
0
0
0
0
3,400
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
900
2,800
0
0
0
2,600
0
0
0
0
0
0
2,600
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").

    An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size
    category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional
    value. For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the
    population estimate is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
    Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
     Table C.2.1. Antimony - Population Served - National Best Estimate Including Estimate Range Based on
     Credible Bounds (Threshold = 0.012 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
1,200
1,800
0
0
0
2,700
0
0
0
0
0
0
2,800
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
4,200
9,600
14,600
0
0
16,100
0
0
0
0
0
0
16,500
using lower
90% CB
100
0
0
0
0
100
0
0
0
0
0
0
100
using upper
90% CB
3,700
8,900
0
0
0
10,400
0
0
0
0
0
0
10,900
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").

    An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size
    category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional
    value. For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the
    population estimate is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
    Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
     Table C.2.m.  Antimony - Population Served - National Best Estimate Including Estimate Range Based on
     Credible Bounds (Threshold = 0.006 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
18,700
30,700
18,700
29,700
0
82,000
100
700
4,300
16,200
0
18,800
101,100
using lower
95% CB
9,200
11,500
0
0
0
18,000
0
0
0
0
0
0
21,700
using upper
95% CB
29,100
58,800
65,600
123,200
90,400
216,600
1,600
9,000
37,000
150,100
0
123,000
262,000
using lower
90% CB
11,000
13,100
0
0
0
22,600
0
0
0
0
0
0
26,400
using upper
90% CB
26,800
52,900
53,100
110,100
88,300
192,200
900
6,600
27,000
150,100
0
97,200
223,900
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").

    An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size
    category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional
    value. For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the
    population estimate is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
    Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
     Table C.2.n. Antimony - Population Served - National Best Estimate Including Estimate Range Based on
     Credible Bounds (Threshold = 0.003 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
156,900
287,000
217,300
354,400
165,300
1,026,500
2,300
22,300
110,100
257,200
697,500
1,023,300
2,051,500
using lower
95% CB
129,300
205,100
125,400
173,200
0
637,800
0
0
18,100
46,800
0
137,300
983,200
using upper
95% CB
186,500
373,300
337,500
567,300
474,000
1,519,100
6,500
45,500
222,400
489,700
2,064,200
2,589,800
3,772,400
using lower
90% CB
132,300
218,300
136,800
186,400
0
708,500
0
4,400
30,700
74,900
0
171,900
1,033,100
using upper
90% CB
182,000
358,700
305,800
540,900
449,600
1,436,000
5,700
42,500
198,700
438,100
1,899,600
2,509,600
3,604,100
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").

    An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size
    category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional
    value. For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the
    population estimate is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
    Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
     Table C.2.o.  Antimony - Population Served - National Best Estimate Including Estimate Range Based on
     Credible Bounds (Threshold = 0.002 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
405,300
786,000
593,200
868,700
532,500
2,810,400
7,400
72,400
348,400
662,800
2,200,000
3,133,500
5,947,200
using lower
95% CB
362,000
658,100
427,400
577,600
187,700
2,148,900
2,000
33,200
186,300
356,000
324,800
1,050,200
3,625,400
using upper
95% CB
454,600
918,500
779,000
1,202,300
985,700
3,507,000
14,500
118,300
524,400
1,033,200
4,345,100
5,351,500
8,460,700
using lower
90% CB
369,700
674,400
447,000
631,300
205,400
2,267,100
2,800
39,100
208,000
390,900
606,500
1,371,300
4,192,000
using upper
90% CB
445,800
899,800
745,000
1,151,000
889,500
3,370,700
13,100
110,900
488,700
975,700
3,650,900
4,788,700
7,804,600
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").

    An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size
    category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional
    value. For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the
    population estimate is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
    Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
     Table C.2.p. Antimony - Population Served - National Best Estimate Including Estimate Range Based on
     Credible Bounds (Threshold = 0.0015 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
707,700
1,422,800
1,067,600
1,474,800
956,900
4,959,300
14,000
139,400
635,800
1,212,400
3,347,600
4,974,600
9,941,100
using lower
95% CB
648,900
1,233,100
831,200
1,093,800
418,000
4,021,000
6,600
83,700
433,000
791,500
1,899,600
3,342,300
7,964,400
using upper
95% CB
770,700
1,608,700
1,349,900
1,935,300
1,772,600
6,188,800
23,400
202,800
881,600
1,749,500
6,234,000
8,119,600
13,986,100
using lower
90% CB
656,400
1,275,100
866,600
1,152,000
481,900
4,172,700
7,200
93,600
449,900
830,600
2,064,200
3,486,200
8,141,200
using upper
90% CB
759,700
1,585,400
1,278,800
1,857,300
1,529,600
5,708,100
21,800
186,600
842,100
1,678,900
4,951,600
6,864,200
12,367,300
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").

    An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size
    category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional
    value. For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the
    population estimate is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
    Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
            Table C.3.a. Atrazine - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on the Number of Systems
Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (nig/L)
0.0172
0.0280
0.0301
0.0411
0.0449
0.0218
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.05 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.012 mg/L
0.0000229%
0.000%
0.000%
0.000%
0.000%
0.0000149%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.123
0.280
0.200
0.175
0.152
0.199
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000%
0.00196%
0.000%
0.000%
0.000%
0.000579%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

All Systems - Combined
Ground & Surface Water
0.0384
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.0000676%
0.000% - 0.000%
0.000% - 0.000%

Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.0172
0.0280
0.0301
0.0411
0.0449
0.0218
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.010 mg/L
0.0000458%
0.000%
0.000%
0.000%
0.000%
0.0000298%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% 0.000%
0.000% 0.000%
0.000% 0.000%
0.000% 0.000%
0.000% 0.000%
0.000% 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.003 mg/L
0.00156%
0.00261%
0.000473%
0.00260%
0.00267%
0.00179%
0.000% - 0.0114%
0.000% - 0.0319%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.00746%
0.000% - 0.0114%
0.000% - 0.0319%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.00746%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.123
0.280
0.200
0.175
0.152
0.199
0.000%
0.00831%
0.000%
0.000%
0.000%
0.00246%
0.000% - 0.000%
0.000% - 0.245%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.0723%
0.000% 0.000%
0.000% 0.000%
0.000% 0.000%
0.000% 0.000%
0.000% 0.000%
0.000% 0.000%
0.430%
1.35%
0.606%
0.256%
0.0185%
0.652%
0.412% - 0.823%
0.734% - 2.20%
0.000% - 1.11%
0.000% - 0.968%
0.000% - 0.662%
0.434% - 0.940%
0.412% - 0.412%
0.734% - 1.96%
0.000% - 1.11%
0.000% - 0.645%
0.000% - 0.00%
0.434% - 0.868%

All Systems - Combined
Ground & Surface Water
0.0384
0.000257%
0.000% - 0.00676%
0.000% 0.000%
0.0625%
0.0406% - 0.0879%
0.0406% - 0.0879%
            All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.3.b.  Atrazine - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.005 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.3.c.  Atrazine - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.0025 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.3.d.  Atrazine - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.00125 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
4
0
0
0
4
4
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.3.e. Atrazine - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.001 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
1
1
0
0
0
1
7
23
6
2
0
36
41
using lower
95% CB
0
0
0
0
0
0
6
13
0
0
0
24
26
using upper
95% CB
5
4
0
0
0
4
13
38
11
9
3
53
57
using lower
90% CB
0
0
0
0
0
0
6
13
0
0
0
24
26
using upper
90% CB
5
4
0
0
0
4
6
33
11
6
0
49
57
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "S
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
           Table C.3.f. Atrazine - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on Population Served
Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.0172
0.0280
0.0301
0.0411
0.0449
0.0218
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.005 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate of
Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0025 mg/L
0.0000145%
0.000%
0.000%
0.000%
0.000%
0.000000480%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.123
0.280
0.200
0.175
0.152
0.199
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000%
0.00175%
0.000%
0.000%
0.000%
0.0000217%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

All Systems - Combined
Ground & Surface Water
0.0384
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.0000127%
0.000% - 0.000%
0.000% - 0.000%

Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.0172
0.0280
0.0301
0.0411
0.0449
0.0218
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.00125 mg/L
0.0000666%
0.000%
0.000%
0.000%
0.000%
0.00000220%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate of
Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.001 mg/L
0.00220%
0.00278%
0.000459%
0.00176%
0.00115%
0.00144%
0.000% - 0.0260%
0.000% - 0.0360%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.00771%
0.000% - 0.0260%
0.000% - 0.0220%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.00357%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.123
0.280
0.200
0.175
0.152
0.199
0.000%
0.00425%
0.000%
0.000%
0.000%
0.0000528%
0.000% - 0.000%
0.000% - 0.0962%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.00119%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.554%
0.883%
0.747%
0.208%
0.00859%
0.0659%
0.545% - 0.619%
0.332% - 1.72%
0.000% - 1.35%
0.000% - 0.745%
0.000% - 0.172%
0.0197% - 0.212%
0.545% - 0.545%
0.353% - 1.52%
0.000% - 1.35%
0.000% - 0.606%
0.000% - 0.000%
0.0225% - 0.133%

All Systems - Combined
Ground & Surface Water
0.0384
0.0000313%
0.000% - 0.000687%
0.000% - 0.000%
0.0385%
0.0115% - 0.122%
0.0129% - 0.0770%
           All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.3.g.  Atrazine - Population Served - National Best Estimate Including Estimate Range Based on Credible
Bounds (Threshold =  0.005 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
Estimates are generated separately for each level of aggregation.  Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.3.h.  Atrazine - Population Served - National Best Estimate Including Estimate Range Based on Credible
Bounds (Threshold = 0.0025 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
Estimates are generated separately for each level of aggregation.  Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems.  In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.3.i.  Atrazine - Population Served - National Best Estimate Including Estimate Range Based on Credible
Bounds (Threshold = 0.00125 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
2,700
0
0
0
1,500
1,500
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
Estimates are generated separately for each level of aggregation.  Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems.  In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.3.J. Atrazine - Population Served - National Best Estimate Including Estimate Range Based on Credible
Bounds (Threshold = 0.001 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
100
500
0
0
0
1,200
1,600
24,900
45,400
45,400
0
83,800
82,100
using lower
95% CB
0
0
0
0
0
0
1,600
9,400
0
0
0
25,100
24,400
using upper
95% CB
1,700
5,600
0
0
0
6,600
1,800
48,500
82,400
162,800
165,400
269,900
260,300
using lower
90% CB
0
0
0
0
0
0
1,600
9,900
0
0
0
28,600
27,600
using upper
90% CB
1,700
3,400
0
0
0
3,100
1,600
42,900
82,400
132,400
0
169,700
163,900
Estimates are generated separately for each level of aggregation.  Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
                                                                                                                                                                           Six-Year Review
                  Table C.4.a. Barium - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on the Number of Systems
Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.103
0.106
0.100
0.0901
0.0704
0.102
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 2 mg/L
0.108%
0.0949%
0.0194%
0.0442%
0.0327%
0.0969%
0.0716% - 0.161%
0.0292% - 0.175%
0.000% - 0.105%
0.000% - 0.178%
0.000% - 0.680%
0.0615% - 0.135%
0.0716% - 0.152%
0.0292% - 0.175%
0.000% - 0.105%
0.000% - 0.178%
0.000% - 0.000%
0.0676% - 0.129%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 1 mg/L
0.505%
0.508%
0.306%
0.568%
0.342%
0.495%
0.403% - 0.617%
0.321% - 0.730%
0.000% - 0.737%
0.178% - 1.07%
0.000% - 0.680%
0.412% - 0.584%
0.420% - 0.599%
0.350% - 0.671%
0.000% - 0.632%
0.178% - 0.891%
0.000% - 0.680%
0.424% - 0.572%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.0567
0.0579
0.0644
0.0581
0.0730
0.0603
0.00164%
0.000%
0.000%
0.000%
0.00130%
0.000528%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.0241%
0.00970%
0.00977%
0.00134%
0.0234%
0.0129%
0.000% - 0.274%
0.000% - 0.231%
0.000% - 0.376%
0.000% - 0.000%
0.000% - 0.649%
0.000% - 0.132%
0.000% - 0.274%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.0660%

All Systems - Combined
Ground & Surface Water
0.0989
0.0887%
0.0562% - 0.124%
0.0619% - 0.118%
0.454%
0.377% - 0.534%
0.388% - 0.523%

Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.103
0.106
0.100
0.0901
0.0704
0.102
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.5 mg/L
2.53%
2.64%
2.27%
2.10%
0.878%
2.51%
2.28% - 2.82%
2.16% - 3.12%
1.47% - 3.16%
1.43% - 3.03%
0.000% - 2.04%
2.28% - 2.74%
2.31% - 2.76%
2.28% - 3.01%
1.58% - 2.95%
1.43% - 2.85%
0.000% - 1.36%
2.31% - 2.71%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.1 mg/L
29.1%
30.8%
30.1%
25.1%
19.0%
29.3%
28.4% - 29.9%
29.7% - 32.0%
28.2% - 32.1%
22. 8 /o - 27. 1 /o
15.0% - 22.5%
28.7% - 29.9%
28.5% - 29.7%
29.9% - 31.8%
28.4% - 31.9%
23.4% - 26.9%
15.7% - 21.8%
28.8% - 29.8%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.0567
0.0579
0.0644
0.0581
0.0730
0.0603
0.358%
0.217%
0.299%
0.157%
0.310%
0.263%
0.000% - 1.10%
0.000% - 0.693%
0.000% - 1.13%
0.000% - 0.671%
0.000% - 1.30%
0.0660% - 0.528%
0.000% - 0.822%
0.000% - 0.693%
0.000% - 1.13%
0.000% - 0.671%
0.000% - 1.30%
0.0660% - 0.528%
15.9%
17.1%
19.3%
15.9%
24.5%
17.7%
13.2% - 18.6%
14.3% - 19.6%
15.8% - 22.6%
13.1% - 19.1%
20.8% - 27.9%
16.3% - 19.0%
13.7% - 18.4%
15.0% - 19.4%
16.2% - 22.2%
13.4% - 18.5%
21.4% - 27.3%
16.6% - 18.8%

All Systems - Combined
Ground & Surface Water
0.0989
2.32%
2.10% - 2.53%
2.14% - 2.50%
28.3%
27.8 /o - 28.8 /o
27.9% - 28.8%
                  All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.4.b.  Barium - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 2 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
47
12
1
1
0
58
0
0
0
0
0
0
58
using lower
95% CB
31
4
0
0
0
37
0
0
0
0
0
0
37
using upper
95% CB
70
21
3
2
1
80
0
0
0
0
0
0
80
using lower
90% CB
31
4
0
0
0
40
0
0
0
0
0
0
40
using upper
90% CB
66
21
o
J
2
0
77
0
0
0
0
0
0
77
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.4.c.  Barium - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 1 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
220
62
7
7
1
294
1
1
0
0
0
1
295
using lower
95% CB
175
39
0
2
0
245
0
0
0
0
0
0
245
using upper
95% CB
268
89
18
13
1
347
4
4
4
0
3
7
347
using lower
90% CB
183
43
0
2
0
252
0
0
0
0
0
0
252
using upper
90% CB
261
82
15
11
1
340
4
0
0
0
0
4
340
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.4.d.  Barium - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.5 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
1,101
321
54
25
2
1,491
6
4
o
J
1
1
15
1,506
using lower
95% CB
992
263
35
17
0
1,356
0
0
0
0
0
4
1,368
using upper
95% CB
1,226
380
76
36
4
1,630
17
12
11
6
5
29
1,646
using lower
90% CB
1,004
277
38
17
0
1,374
0
0
0
0
0
4
1,390
using upper
90% CB
1,202
365
71
34
3
1,612
13
12
11
6
5
29
1,628
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.4.e.  Barium - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.1 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
12,671
3,746
724
299
36
17,422
244
291
196
149
99
991
18,416
using lower
95% CB
12,366
3,606
678
272
28
17,071
202
244
160
122
84
911
18,052
using upper
95% CB
12,993
3,889
772
322
42
17,755
286
335
228
179
112
1,062
18,755
using lower
90% CB
12,410
3,634
684
278
30
17,131
211
256
164
125
86
926
18,117
using upper
90% CB
12,936
3,869
767
320
41
17,713
282
331
224
172
110
1,051
18,716
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
               Table C.4.f.  Barium - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on Population Served
Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.103
0.106
0.100
0.0901
0.0704
0.102
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 2 mg/L
0.139%
0.0833%
0.0204%
0.0310%
0.0160%
0.0331%
0.0872% - 0.199%
0.0157% - 0.181%
0.000% - 0.181%
0.000% - 0.130%
0.000% - 0.334%
0.00643% - 0.163%
0.0934% - 0.190%
0.0157% - 0.163%
0.000% - 0.154%
0.000% - 0.130%
0.000% - 0.000%
0.00722% - 0.105%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 1 mg/L
0.562%
0.474%
0.318%
0.616%
0.170%
0.368%
0.413% - 0.727%
0.258% - 0.722%
0.000% - 0.731%
0.130% - 1.15%
0.000% - 0.334%
0.175% - 0.580%
0.444% - 0.702%
0.298% - 0.678%
0.000% - 0.635%
0.247% - 1.07%
0.000% - 0.334%
0.199% - 0.557%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.0567
0.0579
0.0644
0.0581
0.0730
0.0603
0.00229%
0.000%
0.000%
0.000%
0.000344%
0.000294%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.0386%
0.0107%
0.00680%
0.00181%
0.00734%
0.00678%
0.000% - 0.558%
0.000% - 0.205%
0.000% - 0.221%
0.000% - 0.000%
0.000% - 0.172%
0.000% - 0.146%
0.000% - 0.558%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.00712%

All Systems - Combined
Ground & Surface Water
0.0989
0.0137%
0.00263% - 0.0667%
0.00295% - 0.0632%
0.154%
0.0745% - 0.249%
0.0818% - 0.235%

Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.103
0.106
0.100
0.0901
0.0704
0.102
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.5 mg/L
2.66%
2.61%
2.21%
2.12%
0.484%
1.51%
2.33% - 3.07%
2.05% - 3.17%
1.46% - 3.02%
1.44% - 2.98%
0.000% - 1.46%
1.19% - 1.94%
2.38% - 2.94%
2.15% - 3.09%
1.54% - 2.90%
1.50% - 2.79%
0.000% - 1.07%
1.24% - 1.85%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.1 mg/L
29.7%
30.9%
29.4%
24.8%
14.9%
22.0%
28.9% - 30.6%
29.7% - 32.1%
27.4% - 31.5%
22.6% - 27.1%
11.2% - 18.6%
20.2% - 23.7%
29.00/ - 30.5%
29.90/ - 31.9%
27.70/ - 31.2%
23. 0°/ - 26.6%
11. 9°/ - 17.9%
20.60/ - 23.5%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.0567
0.0579
0.0644
0.0581
0.0730
0.0603
0.474%
0.221%
0.226%
0.136%
0.0982%
0.108%
0.000% - 1.72%
0.000% - 0.772%
0.000% - 0.858%
0.000% - 0.570%
0.000% - 0.498%
0.000509% - 0.465%
0.000% - 1.31%
0.000% - 0.686%
0.000% - 0.749%
0.000% - 0.544%
0.000% - 0.394%
0.000797% - 0.398%
16.7%
17.6%
18.4%
15.1%
46.7%
42.0%
13.4% - 20.3%
14.8% - 20.5%
14.9% - 21.7%
12.0% - 18.2%
32.9% - 51.7%
30.2% - 46.2%
14.10/ - 19.5%
15. W - 20.1%
15. 6°/ - 21.2%
12.50/ - 17.6%
34.70/ - 50.7%
31.6V - 45.4%

All Systems - Combined
Ground & Surface Water
0.0989
0.678%
0.504% - 0.953%
0.527% - 0.895%
33.8%
26.9% - 36.6%
28.0% - 35.9%
               All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.4.g.  Barium - Population Served - National Best Estimate Including Estimate Range Based on Credible
Bounds (Threshold = 2 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
9,000
12,900
3,300
10,000
0
28,400
0
0
0
0
0
0
29,200
using lower
95% CB
5,700
2,400
0
0
0
5,500
0
0
0
0
0
0
5,600
using upper
95% CB
12,900
28,000
24,900
31,800
84,900
139,600
0
0
0
0
0
0
142,000
using lower
90% CB
6,100
2,400
0
0
0
6,200
0
0
0
0
0
0
6,300
using upper
90% CB
12,400
25,400
21,200
31,800
0
90,200
0
0
0
0
0
0
134,600
Estimates are generated separately for each level of aggregation.  Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.4.h.  Barium - Population Served - National Best Estimate Including Estimate Range Based on Credible
Bounds (Threshold = 1 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
36,500
73,600
43,800
150,500
50,000
315,600
100
500
0
0
0
8,600
328,700
using lower
95% CB
26,900
40,100
0
31,800
0
149,500
0
0
0
0
0
0
158,600
using upper
95% CB
47,200
112,200
100,600
280,400
84,900
496,700
1,600
5,800
13,500
0
165,600
185,400
530,000
using lower
90% CB
28,900
46,300
0
60,400
0
170,300
0
0
0
0
0
0
174,300
using upper
90% CB
45,600
105,300
87,500
260,800
84,900
477,200
1,600
0
0
0
0
9,100
500,400
Estimates are generated separately for each level of aggregation.  Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.4.i.  Barium - Population Served - National Best Estimate Including Estimate Range Based on Credible
Bounds (Threshold = 0.5 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
173,100
404,700
303,800
517,400
123,200
1,289,500
1,400
6,200
13,700
29,700
94,600
137,300
1,444,000
using lower
95% CB
151,200
318,500
200,600
351,500
0
1,023,000
0
0
0
0
0
600
1,074,400
using upper
95% CB
199,600
491,500
416,400
727,400
372,200
1,663,900
5,000
21,800
52,200
124,600
479,400
591,600
2,030,800
using lower
90% CB
154,700
333,500
211,800
367,100
0
1,059,000
0
0
0
0
0
1,000
1,122,100
using upper
90% CB
191,300
479,300
398,900
682,200
271,500
1,580,800
3,800
19,300
45,600
118,900
379,200
506,500
1,907,100
Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.4.J. Barium - Population Served - National Best Estimate Including Estimate Range Based on Credible
Bounds (Threshold = 0.1 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
1,930,800
4,798,100
4,051,200
6,056,700
3,788,500
18,858,500
48,900
495,200
1,120,100
3,291,000
44,991,100
53,477,100
72,082,000
using lower
95% CB
1,874,900
4,604,000
3,773,100
5,514,100
2,842,000
17,299,100
39,200
416,600
906,600
2,617,900
31,714,200
38,414,400
57,192,700
using upper
95% CB
1,985,400
4,987,500
4,332,100
6,628,700
4,737,500
20,340,800
59,300
578,900
1,322,800
3,974,900
49,756,900
58,799,400
77,854,500
using lower
90% CB
1,883,300
4,639,700
3,807,500
5,619,200
3,017,500
17,616,200
41,300
425,300
948,000
2,727,200
33,389,500
40,273,400
59,621,000
using upper
90% CB
1,980,200
4,959,500
4,296,300
6,508,900
4,544,100
20,152,300
57,100
566,000
1,289,900
3,841,600
48,851,800
57,831,700
76,512,500
Estimates are generated separately for each level of aggregation.  Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
    Occurrence Estimation Methodology and Findings
    Appendix C. Stage 2 Analytical Findings
                                                                                                                                                                                   Six-Year Review
Table C.S.a.  Benzene - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on the Number of Systems
Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.0000153
0.0000201
0.0000269
0.0000247
0.00000823
0.0000172
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.005 mg/L
0.0216%
0.0723%
0.0446%
0.0148%
0.000%
0.0332%
0.00664% - 0.0399%
0.0216% - 0.130%
0.000% - 0.172%
0.000% - 0.151%
0.000% - 0.000%
0.0138% - 0.0554%
0.0133% - 0.0332%
0.0433% - 0.108%
0.000% - 0.172%
0.000% - 0.151%
0.000% - 0.000%
0.0185% - 0.0508%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0005 mg/L
0.194%
0.325%
0.890%
0.972%
0.0331%
0.282%
0.120% - 0.286%
0.216% - 0.454%
0.600% - 1.20%
0.754% - 1.21%
0.000% - 0.614%
0.198% - 0.369%
0.126% - 0.272%
0.216% - 0.433%
0.686% - 1.12%
0.754% - 1.21%
0.000% - 0.614%
0.208% - 0.360%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0004 mg/L
0.247%
0.399%
1.01%
1.06%
0.0687%
0.344%
0.153% - 0.352%
0.260% - 0.562%
0.686% - 1.37%
0.754% - 1.36%
0.000% - 0.614%
0.249% - 0.452%
0.159% - 0.339%
0.281% - 0.541%
0.772% - 1.29%
0.754% - 1.36%
0.000% - 0.614%
0.258% - 0.438%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.00000543
0.0000141
0.0000143
0.0000168
0.00000959
0.0000123
0.000%
0.00710%
0.000%
0.00772%
0.000%
0.00363%
0.000% - 0.000%
0.000% - 0.222%
0.000% - 0.000%
0.000% - 0.297%
0.000% - 0.000%
0.000% - 0.0627%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.0627%
0.0277%
0.255%
0.137%
0.605%
0.0570%
0.237%
0.000% - 0.288%
0.000% - 0.887%
0.000% - 0.676%
0.297% - 1.19%
0.000% - 0.606%
0.0627% - 0.501%
0.000% - 0.288%
0.000% - 0.665%
0.000% - 0.676%
0.297% - 1.19%
0.000% - 0.606%
0.0627% - 0.439%
0.0478%
0.351%
0.220%
0.759%
0.120%
0.323%
0.000% - 0.288%
0.000% - 0.887%
0.000% - 1.01%
0.297% - 1.48%
0.000% - 0.606%
0.125% - 0.627%
0.000% - 0.288%
0.000% - 0.887%
0.000% - 0.676%
0.297% - 1.19%
0.000% - 0.606%
0.125% - 0.564%

All Systems - Combined
Ground & Surface Water
0.0000168
0.0313%
0.0172% - 0.0516%
0.0172% - 0.0473%
0.279%
0.198% - 0.370%
0.206% - 0.352%
0.343%
0.245% - 0.456%
0.258% - 0.434%
All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
Table C.S.b.  Benzene - Systems - National Best Estimate Including Estimate Range Based on Credible Bounds
(Threshold = 0.005 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
9
9
1
0
0
20
0
0
0
0
0
1
20
using lower
95% CB
3
3
0
0
0
8
0
0
0
0
0
0
11
using upper
95% CB
17
16
4
2
0
33
0
4
0
3
0
4
34
using lower
90% CB
6
5
0
0
0
11
0
0
0
0
0
0
11
using upper
90% CB
14
13
4
2
0
30
0
0
0
0
0
4
31
Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").
System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
Table C.S.c.  Benzene - Systems - National Best Estimate Including Estimate Range Based on Credible Bounds
(Threshold = 0.0005 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
84
40
21
12
0
168
1
4
1
6
1
13
181
using lower
95% CB
52
26
14
9
0
118
0
0
0
3
0
4
129
using upper
95% CB
124
55
29
14
1
219
4
15
7
11
2
28
240
using lower
90% CB
55
26
17
9
0
123
0
0
0
o
J
0
4
134
using upper
90% CB
118
53
27
14
1
214
4
11
7
11
2
25
229
Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").
System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
Table C.S.d.  Benzene - Systems - National Best Estimate Including Estimate Range Based on Credible Bounds
(Threshold = 0.0004 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
108
49
24
13
0
204
1
6
2
7
1
18
223
using lower
95% CB
66
32
17
9
0
148
0
0
0
3
0
7
159
using upper
95% CB
153
68
33
16
1
269
4
15
10
14
2
35
296
using lower
90% CB
69
34
19
9
0
154
0
0
0
o
J
0
7
168
using upper
90% CB
147
66
31
16
1
261
4
15
7
11
2
32
282
Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

System estimates are rounded to the nearest whole number.

-------
    Occurrence Estimation Methodology and Findings
    Appendix C. Stage 2 Analytical Findings
                                                                                                                                                                                   Six-Year Review
Table C.S.e. Benzene - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on Population Served
Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.0000153
0.0000201
0.0000269
0.0000247
0.00000823
0.0000172
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.005 mg/L
0.0303%
0.0683%
0.0497%
0.0135%
0.000%
0.0204%
0.0148% - 0.0517%
0.0231% - 0.120%
0.000% - 0.202%
0.000% - 0.150%
0.000% - 0.000%
0.00407% - 0.0629%
0.0185% - 0.0490%
0.0376% - 0.114%
0.000% - 0.202%
0.000% - 0.150%
0.000% - 0.000%
0.00546% - 0.0557%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0005 mg/L
0.222%
0.354%
1.03%
0.962%
0.0238%
0.481%
0.135% - 0.327%
0.216% - 0.504%
0.671% - 1.37%
0.677% - 1.31%
0.000% - 0.323%
0.340% - 0.632%
0.148% - 0.309%
0.235% - 0.478%
0.743% - 1.34%
0.677% - 1.26%
0.000% - 0.274%
0.360% - 0.616%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0004 mg/L
0.277%
0.432%
1.16%
1.05%
0.0484%
0.546%
0.169% - 0.403%
0.272% - 0.621%
0.805% - 1.57%
0.677% - 1.41%
0.000% - 0.433%
0.399% - 0.758%
0.187% - 0.380%
0.294% - 0.594%
0.857% - 1.49%
0.677% - 1.36%
0.000% - 0.369%
0.417% - 0.707%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.00000543
0.0000141
0.0000143
0.0000168
0.00000959
0.0000123
0.000%
0.00405%
0.000%
0.00448%
0.000%
0.000625%
0.000% - 0.000%
0.000% - 0.130%
0.000% - 0.000%
0.000% - 0.172%
0.000% - 0.000%
0.000% - 0.0220%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.00163%
0.0264%
0.214%
0.134%
0.404%
0.0266%
0.0805%
0.000% - 0.399%
0.000% - 0.817%
0.000% - 0.768%
0.151% - 1.04%
0.000% - 0.286%
0.0194% - 0.283%
0.000% - 0.175%
0.000% - 0.657%
0.000% - 0.629%
0.151% - 0.922%
0.000% - 0.143%
0.0210% - 0.206%
0.0473%
0.309%
0.214%
0.525%
0.0472%
0.117%
0.000% - 0.638%
0.000% - 1.05%
0.000% - 1.03%
0.151% - 1.20%
0.000% - 0.451%
0.0244% - 0.451%
0.000% - 0.399%
0.000% - 0.860%
0.000% - 0.867%
0.151% - 1.11%
0.000% - 0.266%
0.0322% - 0.315%

All Systems - Combined
Ground & Surface Water
0.0000168
0.00947%
0.00188% - 0.0300%
0.00244% - 0.0258%
0.260%
0.176% - 0.389%
0.183% - 0.353%
0.309%
0.211% - 0.514%
0.222% - 0.445%
All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.S.f. Benzene - Population Served - National Best Estimate Including Estimate Range Based on Credible
Bounds (Threshold = 0.005 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
2,000
10,600
6,800
0
0
17,500
0
0
0
0
0
800
20,200
using lower
95% CB
1,000
3,600
0
0
0
3,500
0
0
0
0
0
0
4,000
using upper
95% CB
3,400
18,600
27,800
36,600
0
53,900
0
3,700
0
37,500
0
28,000
63,800
using lower
90% CB
1,200
5,800
0
0
0
4,700
0
0
0
0
0
0
5,200
using upper
90% CB
3,200
17,600
27,800
36,600
0
47,700
0
0
0
0
0
2,100
54,800
Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.S.g.  Benzene - Population Served - National Best Estimate Including Estimate Range Based on Credible
Bounds (Threshold = 0.0005 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
14,400
54,900
142,200
235,200
0
412,100
100
6,000
8,200
88,400
25,600
102,500
553,400
using lower
95% CB
8,800
33,600
92,400
165,500
0
291,700
0
0
0
33,000
0
24,700
374,000
using upper
95% CB
21,300
78,200
188,500
321,200
82,300
541,300
1,200
23,000
46,700
226,400
275,000
359,800
828,800
using lower
90% CB
9,600
36,600
102,300
165,500
0
308,000
0
0
0
33,000
0
26,700
389,800
using upper
90% CB
20,100
74,200
185,100
307,200
69,800
527,500
500
18,500
38,300
201,400
137,200
262,000
750,900
Estimates are generated separately for each level of aggregation.  Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.S.h.  Benzene - Population Served - National Best Estimate Including Estimate Range Based on Credible
Bounds (Threshold = 0.0004 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
18,000
67,000
160,300
256,900
0
468,200
100
8,700
13,000
114,700
45,400
148,500
658,000
using lower
95% CB
11,000
42,300
110,900
165,500
0
341,800
0
0
0
33,000
0
31,100
449,900
using upper
95% CB
26,200
96,300
215,800
345,100
110,200
649,200
1,900
29,700
62,900
262,400
434,300
574,200
1,095,300
using lower
90% CB
12,100
45,700
118,000
165,500
0
356,900
0
0
0
33,000
0
40,900
472,500
using upper
90% CB
24,700
92,200
204,600
332,200
93,800
605,600
1,200
24,200
52,800
243,200
256,100
401,500
948,500
Estimates are generated separately for each level of aggregation.  Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
     Table C.6.a.  Benzo(a)pyrene - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on the Number of Systems
Source Water Type
Ground Water
Population
Served
<500
501 - 3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (nig/L)
0.000000730
0.000000540
0.000000420
0.000000239
0.00000116
0.000000650
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0002 mg/L
0.0000307%
0.000%
0.000%
0.000%
0.000%
0.0000200%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0001 mg/L
0.000307%
0.0000887%
0.000%
0.000%
0.000%
0.000220%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

Surface Water
<500
501 - 3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.00000173
0.00000103
0.000000441
0.000000716
0.00000103
0.000000970
0.000858%
0.000%
0.000%
0.000%
0.000%
0.000156%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000858%
0.000542%
0.000%
0.000%
0.000%
0.000313%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

All Systems - Combined
Ground & Surface Water
0.000000686
0.0000354%
0.000% - 0.000%
0.000% - 0.000%
0.000230%
0.000% - 0.00886%
0.000% - 0.000%

Source Water Type
Ground Water
Population
Served
<500
501 - 3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.000000730
0.000000540
0.000000420
0.000000239
0.00000116
0.000000650
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.00005 mg/L
0.00234%
0.000266%
0.000%
0.000%
0.00458%
0.00164%
0.000% - 0.0154%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.0100%
0.000% - 0.0154%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.0100%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.00002 mg/L
0.0329%
0.00789%
0.00241%
0.000%
0.0992%
0.0247%
0.000% - 0.108%
0.000% - 0.0443%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.763%
0.000% - 0.0699%
0.000% - 0.0922%
0.000% - 0.0443%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.763%
0.000% - 0.0599%

Surface Water
<500
501 - 3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.00000173
0.00000103
0.000000441
0.000000716
0.00000103
0.000000970
0.00773%
0.00542%
0.000%
0.00269%
0.00296%
0.00391%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.0781%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.303%
0.0916%
0.00407%
0.0377%
0.0504%
0.0964%
0.000% - 1.72%
0.000% - 0.542%
0.000% - 0.000%
0.000% - 0.337%
0.000% - 0.741%
0.000% - 0.313%
0.000% - 1.29%
0.000% - 0.542%
0.000% - 0.000%
0.000% - 0.337%
0.000% - 0.741%
0.000% - 0.313%

All Systems - Combined
Ground & Surface Water
0.000000686
0.00190%
0.000% - 0.0177%
0.000% - 0.00886%
0.0328%
0.000% - 0.0886%
0.000% - 0.0797%
     All mean concentration and percentage estimates are expressed to three significant figures

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
                                                                               Six-Year Review
    Table C.6.b.  Benzo(a)pyrene
    Credible Bounds (Threshold
Systems - National Best Estimate Including Estimate Range Based on
0.0002 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
                                                                               Six-Year Review
    Table C.6.c.  Benzo(a)pyrene
    Credible Bounds (Threshold
Systems - National Best Estimate Including Estimate Range Based on
0.0001 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
6
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
                                                                               Six-Year Review
    Table C.6.d.  Benzo(a)pyrene
    Credible Bounds (Threshold
Systems - National Best Estimate Including Estimate Range Based on
0.00005 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
1
0
0
0
0
1
0
0
0
0
0
1
1
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
7
0
0
0
0
6
0
0
0
0
0
4
12
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
7
0
0
0
0
6
0
0
0
0
0
0
6
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
                                                                               Six-Year Review
    Table C.6.e.  Benzo(a)pyrene
    Credible Bounds (Threshold
Systems - National Best Estimate Including Estimate Range Based on
0.00002 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
14
1
0
0
0
15
5
2
0
1
0
5
21
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
47
5
0
0
1
42
26
9
0
3
3
17
58
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
40
5
0
0
1
36
20
9
0
o
J
3
17
52
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
        Table C.6.f.  Benzo(a)pyrene - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on Population Served
Source Water Type
Ground Water
Population
Served
<500
501 - 3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.000000730
0.000000540
0.000000420
0.000000239
0.00000116
0.000000650
Best Estimate of
Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0002 mg/L
0.0000176%
0.000%
0.000%
0.000%
0.000%
0.000000514%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0001 mg/L
0.000305%
0.000162%
0.000%
0.000%
0.000%
0.0000226%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

Surface Water
<500
501 - 3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.00000173
0.00000103
0.000000441
0.000000716
0.00000103
0.000000970
0.00226%
0.000%
0.000%
0.000%
0.000%
0.00000188%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.00226%
0.000766%
0.000%
0.000%
0.000%
0.0000111%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

All Systems - Combined
Ground & Surface Water
0.000000686
0.00000134%
0.000% - 0.000%
0.000% - 0.000%
0.0000157%
0.000% - 0.000102%
0.000% - 0.000%

Source Water Type
Ground Water
Population
Served
<500
501 - 3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.000000730
0.000000540
0.000000420
0.000000239
0.00000116
0.000000650
Best Estimate of
Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.00005 mg/L
0.00263%
0.000274%
0.000%
0.000%
0.00298%
0.00156%
0.000% - 0.0274%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.00100%
0.000% - 0.0245%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000713%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.00002 mg/L
0.0383%
0.00675%
0.00162%
0.000%
0.0677%
0.0352%
0.000% - 0.129%
0.000% - 0.0683%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.580%
0.000% - 0.285%
0.000% - 0.108%
0.000% - 0.0442%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.492%
0.000% - 0.242%

Surface Water
<500
501 - 3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.00000173
0.00000103
0.000000441
0.000000716
0.00000103
0.000000970
0.0117%
0.00760%
0.000%
0.00203%
0.000802%
0.00103%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.00462%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.404%
0.106%
0.00300%
0.0315%
0.0393%
0.0384%
0.000% - 2.31%
0.000% - 0.703%
0.000% - 0.000%
0.000% - 0.254%
0.000% - 0.277%
0.000% - 0.243%
0.000% - 1.85%
0.000% - 0.514%
0.000% - 0.000%
0.000% - 0.254%
0.000% - 0.165%
0.000% - 0.140%

All Systems - Combined
Ground & Surface Water
0.000000686
0.00124%
0.000% - 0.00289%
0.000% - 0.000527%
0.0371%
0.000% - 0.230%
0.000% - 0.147%
        All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
                                                                                         Six-Year Review
Table C.6.g.  Benzo(a)pyrene
Credible Bounds (Threshold
Population Served - National Best Estimate Including Estimate Range Based on
0.0002 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
                                                                                         Six-Year Review
Table C.6.h.  Benzo(a)pyrene
Credible Bounds (Threshold
Population Served - National Best Estimate Including Estimate Range Based on
0.0001 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
200
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates.  The primary model estimation output is the number of systems. In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
                                                                                          Six-Year Review
Table C.6.i.  Benzo(a)pyrene
Credible Bounds (Threshold
Population Served - National Best Estimate Including Estimate Range Based on
 0.00005 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
200
0
0
0
0
1,300
0
0
0
0
0
1,300
2,600
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
1,800
0
0
0
0
900
0
0
0
0
0
5,900
6,200
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
1,600
0
0
0
0
600
0
0
0
0
0
0
1,100
Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
                                                                                         Six-Year Review
Table C.6.J.  Benzo(a)pyrene
Credible Bounds (Threshold
Population Served - National Best Estimate Including Estimate Range Based on
 0.00002 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
2,500
1,000
0
0
0
30,100
1,200
3,000
0
10,000
0
48,900
79,000
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
8,400
10,600
0
0
147,600
244,500
6,700
19,800
0
55,400
266,400
309,500
488,900
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
7,000
6,900
0
0
125,100
207,200
5,400
14,500
0
55,400
159,200
178,400
312,100
Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
    Occurrence Estimation Methodology and Findings
    Appendix C. Stage 2 Analytical Findings
                                                                                                                                                                                    Six-Year Review
Table C.I.a.  Beryllium - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on the Number of Systems
Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.0000797
0.0000638
0.0000662
0.0000911
0.0000940
0.0000760
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.01 mg/L
0.00956%
0.00481%
0.0181%
0.00308%
0.00121%
0.00870%
0.000% - 0.0335%
0.000% - 0.0261%
0.000% - 0.102%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.0229%
0.000% - 0.0251%
0.000% - 0.0261%
0.000% - 0.102%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.0229%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.004 mg/L
0.0878%
0.0666%
0.129%
0.0408%
0.0277%
0.0833%
0.0335% - 0.151%
0.000% - 0.157%
0.000% - 0.306%
0.000% - 0.343%
0.000% - 0.602%
0.0400% - 0.137%
0.0418% - 0.142%
0.000% - 0.131%
0.000% - 0.306%
0.000% - 0.171%
0.000% - 0.000%
0.0514% - 0.126%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.001 mg/L
1.16%
0.875%
0.894%
1.62%
1.27%
1.10%
0.929% - 1.39%
0.575% - 1.23%
0.510% - 1.43%
0.856% - 2.57%
0.000% - 3.01%
0.908% - 1.29%
0.962% - 1.36%
0.627% - 1.15%
0.510% - 1.33%
1.03% - 2.40%
0.000% - 2.41%
0.942% - 1.26%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.0000446
0.0000530
0.0000699
0.0000778
0.0000627
0.0000604
0.000%
0.000481%
0.000%
0.00202%
0.000%
0.000562%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.0117%
0.0111%
0.0107%
0.0303%
0.000%
0.0140%
0.000% - 0.325%
0.000% - 0.240%
0.000% - 0.380%
0.000% - 0.337%
0.000% - 0.000%
0.000% - 0.0702%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.337%
0.000% - 0.000%
0.000% - 0.0702%
0.439%
0.734%
0.639%
1.07%
0.823%
0.731%
0.000% - 1.30%
0.240% - 1.44%
0.000% - 1.90%
0.000% - 2.36%
0.000% - 2.14%
0.351% - 1.19%
0.000% - 1.30%
0.240% - 1.44%
0.000% - 1.52%
0.337% - 2.02%
0.000% - 2.14%
0.421% - 1 .12%

All Systems - Combined
Ground & Surface Water
0.0000748
0.00809%
0.000% - 0.0211%
0.000% - 0.0211%
0.0781%
0.0370% - 0.127%
0.0475% - 0.116%
1.07%
0.882% - 1.25%
0.914% - 1.23%
All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.7.b.  Beryllium - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.01 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
4
1
1
0
0
5
0
0
0
0
0
1
5
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
15
3
2
0
0
14
0
0
0
0
0
0
14
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
11
3
2
0
0
14
0
0
0
0
0
0
14
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.7.c.  Beryllium - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.004 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
38
8
3
1
0
50
0
1
0
1
0
1
51
using lower
95% CB
15
0
0
0
0
24
0
0
0
0
0
0
24
using upper
95% CB
66
19
7
4
1
81
5
4
4
3
0
4
82
using lower
90% CB
18
0
0
0
0
31
0
0
0
0
0
0
31
using upper
90% CB
62
16
7
2
0
75
0
0
0
o
J
0
4
76
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.7.d.  Beryllium - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.001 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
505
106
21
19
2
653
7
13
6
10
o
J
41
696
using lower
95% CB
404
70
12
10
0
540
0
4
0
0
0
20
574
using upper
95% CB
604
149
34
31
6
764
20
25
19
22
9
67
814
using lower
90% CB
419
76
12
12
0
560
0
4
0
3
0
24
594
using upper
90% CB
590
140
32
29
5
750
20
25
15
19
9
63
801
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
    Occurrence Estimation Methodology and Findings
    Appendix C. Stage 2 Analytical Findings
                                                                                                                                                                                    Six-Year Review
Table C.T.e.  Beryllium - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on Population Served
Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.0000797
0.0000638
0.0000662
0.0000911
0.0000940
0.0000760
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.01 mg/L
0.0112%
0.00506%
0.0165%
0.00260%
0.000603%
0.00403%
0.000% - 0.0449%
0.000% - 0.0445%
0.000% - 0.114%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.0255%
0.000% - 0.0387%
0.000% - 0.0437%
0.000% - 0.114%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.0153%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.004 mg/L
0.0985%
0.0658%
0.121%
0.0372%
0.0146%
0.0430%
0.0304% - 0.187%
0.000% - 0.167%
0.000% - 0.304%
0.000% - 0.335%
0.000% - 0.301%
0.00586% - 0.174%
0.0380% - 0.162%
0.000% - 0.150%
0.000% - 0.284%
0.000% - 0.210%
0.000% - 0.000%
0.00787% - 0.142%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.001 mg/L
1.25%
0.869%
0.799%
1.68%
1.02%
1.17%
0.949% - 1.54%
0.551% - 1.22%
0.408% - 1.31%
0.680% - 2.87%
0.000% - 2.58%
0.595% - 1.96%
1.02% - 1.51%
0.610% - 1.18%
0.469% - 1.22%
0.844% - 2.64%
0.000% - 2.35%
0.646% - 1.89%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.0000446
0.0000530
0.0000699
0.0000778
0.0000627
0.0000604
0.000%
0.000830%
0.000%
0.00187%
0.000%
0.000227%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.0106%
0.0151%
0.0101%
0.0254%
0.000%
0.00341%
0.000% - 0.130%
0.000% - 0.357%
0.000% - 0.225%
0.000% - 0.368%
0.000% - 0.000%
0.000% - 0.0427%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.241%
0.000% - 0.000%
0.000% - 0.0280%
0.408%
0.989%
0.633%
1.06%
0.210%
0.330%
0.000% - 1.44%
0.357% - 2.02%
0.000% - 1.93%
0.000% - 2.26%
0.000% - 0.885%
0.0558% - 0.911%
0.000% - 1.21%
0.357% - 1 .82%
0.000% - 1.66%
0.169% - 2.09%
0.000% - 0.793%
0.0854% - 0.808%

All Systems - Combined
Ground & Surface Water
0.0000748
0.00190%
0.000% - 0.0128%
0.000% - 0.00720%
0.0208%
0.00278% - 0.0781%
0.00380% - 0.0632%
0.699%
0.356% - 1.18%
0.417% - 1.07%
All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
  Table C.7.f.  Beryllium - Population Served - National Best Estimate Including Estimate Range Based on
  Credible Bounds(Threshold = 0.01 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
700
800
3,300
0
0
3,500
0
0
0
0
0
300
4,100
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
2,900
6,900
15,800
0
0
21,900
0
0
0
0
0
0
27,200
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
2,500
6,800
15,800
0
0
13,100
0
0
0
0
0
0
15,300
  Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
  level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground &
  Surface Water").
  An additional rounding convention is applied to population-served estimates.  The primary model estimation output is the number of systems. In a specific size
  category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value.
  For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate
  is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).

  Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
  Table C.7.g. Beryllium - Population Served - National Best Estimate Including Estimate Range Based on
  Credible Bounds (Threshold = 0.004 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
6,400
10,200
16,700
10,000
0
36,800
0
500
0
10,000
0
4,300
44,400
using lower
95% CB
2,000
0
0
0
0
5,000
0
0
0
0
0
0
5,900
using upper
95% CB
12,100
25,900
41,900
81,900
76,700
148,700
400
10,100
13,700
80,500
0
54,400
166,300
using lower
90% CB
2,500
0
0
0
0
6,700
0
0
0
0
0
0
8,100
using upper
90% CB
10,600
23,300
39,100
51,400
0
121,700
0
0
0
52,700
0
35,600
134,500
  Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
  level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground &
  Surface Water").
  An additional rounding convention is applied to population-served estimates.  The primary model estimation output is the number of systems. In a specific size
  category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value.
  For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate
  is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).

  Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
  Table C.7.h. Beryllium - Population Served - National Best Estimate Including Estimate Range Based on
  Credible Bounds(Threshold = 0.001 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
81,000
134,900
110,100
410,600
260,000
1,002,500
1,200
27,900
38,500
231,400
201,900
419,500
1,489,600
using lower
95% CB
61,600
85,500
56,200
166,200
0
509,700
0
10,100
0
0
0
71,000
758,500
using upper
95% CB
100,000
188,800
180,100
701,200
657,400
1,681,900
4,200
56,900
117,200
494,100
851,900
1,159,600
2,519,900
using lower
90% CB
66,100
94,700
64,600
206,300
0
553,100
0
10,100
0
37,000
0
108,700
887,400
using upper
90% CB
98,000
182,900
168,400
645,500
598,200
1,616,800
3,500
51,300
100,900
455,600
763,100
1,028,400
2,283,400
  Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
  level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground &
  Surface Water").
  An additional rounding convention is applied to population-served estimates.  The primary model estimation output is the number of systems. In a specific size
  category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value.
  For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate
  is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).

  Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
     Table C.S.a.  Bis(2-ethylhexyl)adipate - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on the Number of Systems
Source Water Type
Ground Water
Population
Served
<500
501 - 3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.0000922
0.0000648
0.0000878
0.0000381
0.0000250
0.0000832
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.4 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.2 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

Surface Water
<500
501 - 3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.000216
0.000180
0.000296
0.000190
0.0000654
0.000203
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

All Systems - Combined
Ground & Surface Water
0.0000968
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%

Source Water Type
Ground Water
Population
Served
<500
501 - 3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.0000922
0.0000648
0.0000878
0.0000381
0.0000250
0.0000832
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.1 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0006 mg/L
2.76%
1.65%
2.52%
0.426%
0.311%
2.39%
2.30% - 3.23%
1.13% - 2.21%
1.36% - 3.75%
0.000% - 1.15%
0.000% - 1.27%
2.02% - 2.77%
2.37% - 3.17%
1.22% - 2.12%
1.53% - 3.75%
0.000% - 1.15%
0.000% - 1.27%
2.08% - 2.71%

Surface Water
<500
501 - 3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.000216
0.000180
0.000296
0.000190
0.0000654
0.000203
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
8.77%
7.00%
13.1%
6.49%
1.82%
8.03%
5.29% - 12.8%
4.43% - 9.97%
9.54% - 17.0%
3.96% - 8.99%
0.000% - 4.26%
6.66% - 9.41%
5.29% - 11.9%
4.71% - 9.42%
9.96% - 16.2%
4.68% - 8.63%
0.000% - 3.19%
6.83% - 9.24%

All Systems - Combined
Ground & Surface Water
0.0000968
0.000%
0.000% - 0.000%
0.000% - 0.000%
3.03%
2.66% - 3.39%
2.71% - 3.34%
     All mean concentration and percentage estimates are expressed to three significant figures

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.S.b.  Bis(2-ethylhexyl)adipate - Systems - National Best Estimate Including Estimate Range Based
    on Credible Bounds (Threshold = 0.4 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.S.c.  Bis(2-ethylhexyl)adipate - Systems - National Best Estimate Including Estimate Range Based
    on Credible Bounds (Threshold = 0.2 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.S.d.  Bis(2-ethylhexyl)adipate - Systems - National Best Estimate Including Estimate Range Based
    on Credible Bounds (Threshold = 0.1 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.S.e.  Bis(2-ethylhexyl)adipate - Systems - National Best Estimate Including Estimate Range Based
    on Credible Bounds (Threshold = 0.0006 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
1,201
200
60
5
1
1,418
135
119
132
61
7
449
1,968
using lower
95% CB
1,001
137
o o
JJ
0
0
1,202
81
76
97
37
0
372
1,730
using upper
95% CB
1,405
269
90
14
2
1,645
196
170
172
84
17
526
2,203
using lower
90% CB
1,029
149
37
0
0
1,233
81
80
101
44
0
382
1,761
using upper
90% CB
1,377
257
90
14
2
1,613
183
161
164
81
13
517
2,173
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
         Table C.S.f. Bis(2-ethylhexyl)adipate - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on Population Served
Source Water
Type
Ground Water
Population
Served
<500
501 - 3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (nig/L)
0.0000922
0.0000648
0.0000878
0.0000381
0.0000250
0.0000832
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.4 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.2 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

Surface Water
<500
501 - 3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.000216
0.000180
0.000296
0.000190
0.0000654
0.000203
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

All Systems - Combined
Ground & Surface Water
0.0000968
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%

Source Water
Type
Ground Water
Population
Served
<500
501 - 3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (nig/L)
0.0000922
0.0000648
0.0000878
0.0000381
0.0000250
0.0000832
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.1 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0006 mg/L
2.89%
1.66%
2.35%
0.382%
0.267%
0.814%
2.36% - 3.46%
1.05% - 2.25%
1.28% - 3.77%
0.000% - 1.31%
0.000% - 1.16%
0.483% - 1.35%
2.42% - 3.37%
1.16% - 2.16%
1.42% - 3.53%
0.000% - 1.07%
0.000% - 0.837%
0.517% - 1.24%

Surface Water
<500
501 - 3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.000216
0.000180
0.000296
0.000190
0.0000654
0.000203
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
9.31%
6.80%
12.6%
5.90%
1.02%
2.54%
5.42% - 13.8%
3.87% - 10.1%
8.93% - 16.5%
3.33% - 8.47%
0.000% - 4.11%
1.57% - 4.86%
5.90% - 13.0%
4.46% - 9.56%
9.30% - 16.1%
3.79% - 8.14%
0.000% - 2.13%
1.67% - 3.74%

All Systems - Combined
Ground & Surface Water
0.0000968
0.000%
0.000% - 0.000%
0.000% - 0.000%
1.78%
1.20% - 3.28%
1.24% - 2.57%
         All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.S.g.  Bis(2-ethylhexyl)adipate - Population Served - National Best Estimate Including Estimate Range
Based on Credible Bounds (Threshold = 0.4 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.S.h.  Bis(2-ethylhexyl)adipate - Population Served - National Best Estimate Including Estimate Range
Based on Credible Bounds (Threshold = 0.2 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.8.1.  Bis(2-ethylhexyl)adipate - Population Served - National Best Estimate Including Estimate Range
Based on Credible Bounds (Threshold  = 0.1 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.S.j.  Bis(2-ethylhexyl)adipate - Population Served - National Best Estimate Including Estimate Range
Based on Credible Bounds (Threshold = 0.0006 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
187,600
257,900
324,000
93,400
68,000
697,800
27,200
191,700
768,500
1,290,200
977,200
3,237,900
3,800,100
using lower
95% CB
153,200
162,300
176,800
0
0
414,200
15,900
108,900
543,000
728,600
0
1,993,900
2,558,200
using upper
95% CB
224,800
349,700
518,700
319,200
295,100
1,155,800
40,400
285,800
1,004,500
1,851,300
3,960,900
6,183,000
6,986,700
using lower
90% CB
157,000
180,000
195,000
0
0
443,100
17,200
125,600
565,800
828,600
0
2,126,400
2,647,700
using upper
90% CB
219,200
336,000
486,500
260,800
212,900
1,059,900
38,100
269,400
979,000
1,778,600
2,045,900
4,760,700
5,476,400
Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates.  The primary model estimation output is the number of systems. In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
    Occurrence Estimation Methodology and Findings
    Appendix C. Stage 2 Analytical Findings
                                                                                                                                                                                   Six-Year Review
Table C.9.a.  Bis(2-ethylhexyl)phthalate - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on the Number of Systems
Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.000287
0.000231
0.000251
0.000276
0.000208
0.000269
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.006 mg/L
0.305%
0.155%
0.155%
0.443%
0.121%
0.263%
0.147% - 0.479%
0.000% - 0.343%
0.000% - 0.525%
0.000% - 0.969%
0.000% - 0.758%
0.151% - 0.396%
0.166% - 0.442%
0.0490% - 0.294%
0.000% - 0.525%
0.000% - 0.726%
0.000% - 0.758%
0.163% - 0.373%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.003 mg/L
1.05%
0.715%
0.719%
1.07%
0.785%
0.944%
0.681% - 1.40%
0.392% - 1.13%
0.175% - 1.58%
0.484% - 1.70%
0.000% - 2.27%
0.698% - 1.23%
0.773% - 1.36%
0.441% - 1.03%
0.175% - 1.40%
0.484% - 1.70%
0.000% - 1.52%
0.722% - 1.20%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0006 mg/L
10.5%
8.50%
9.98%
9.22%
6.64%
9.85%
9.30% - 11.7%
7.20% - 9.99%
7.71% - 12.4%
6.78% - 11.6%
3.03% - 10.6%
8.93% - 10.8%
9.43% - 11.5%
7.39% - 9.74%
8.06% - 12.1%
7.26% - 11.4%
3.79% - 9.85%
9.07% - 10.7%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.000382
0.000274
0.000226
0.000333
0.000351
0.000314
0.350%
0.107%
0.0323%
0.262%
0.111%
0.184%
0.000% - 1.23%
0.000% - 0.995%
0.000% - 0.769%
0.000% - 0.926%
0.000% - 0.855%
0.000% - 0.484%
0.000% - 1.23%
0.000% - 0.498%
0.000% - 0.000%
0.000% - 0.926%
0.000% - 0.855%
0.000% - 0.484%
1.42%
0.705%
0.277%
1.41%
0.889%
0.988%
0.000% - 3.68%
0.000% - 1.99%
0.000% - 1.54%
0.463% - 2.78%
0.000% - 3.42%
0.363% - 1.69%
0.000% - 3.07%
0.000% - 1.99%
0.000% - 1.54%
0.463% - 2.32%
0.000% - 2.56%
0.484% - 1.57%
16.3%
11.5%
9.44%
13.8%
15.6%
13.3%
9.82% - 23.9%
6.97% - 16.4%
4.62% - 14.6%
1 0.2% - 17.6%
10.3% - 22.2%
10.8% - 15.7%
11.0% - 22.1%
7.96% - 15.4%
5.39% - 13.9%
10.7% - 17.1%
10.3% - 21.4%
11.4% - 15.4%

All Systems - Combined
Ground & Surface Water
0.000273
0.256%
0.149% - 0.393%
0.159% - 0.372%
0.948%
0.690% - 1.24%
0.733% - 1.20%
10.2%
9.22% - 11.1%
9.45% - 11.0%
All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.9.b.  Bis(2-ethylhexyl)phthalate - Systems - National Best Estimate Including Estimate Range
    Based on Credible Bounds (Threshold = 0.006 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
132
19
4
5
0
156
5
2
1
2
1
10
166
using lower
95% CB
64
0
0
0
0
90
0
0
0
0
0
0
97
using upper
95% CB
208
42
13
12
1
235
19
17
8
9
3
27
256
using lower
90% CB
72
6
0
0
0
97
0
0
0
0
0
0
104
using upper
90% CB
192
36
13
9
1
221
19
8
0
9
o
J
27
242
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.9.c.  Bis(2-ethylhexyl)phthalate - Systems - National Best Estimate Including Estimate Range
    Based on Credible Bounds (Threshold = 0.003 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
456
87
17
13
1
561
22
12
3
13
4
55
616
using lower
95% CB
296
48
4
6
0
415
0
0
0
4
0
20
449
using upper
95% CB
609
137
38
20
4
733
57
34
16
26
14
95
808
using lower
90% CB
336
54
4
6
0
429
0
0
0
4
0
27
476
using upper
90% CB
592
125
34
20
o
J
713
47
34
16
22
10
88
780
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.9.d.  Bis(2-ethylhexyl)phthalate - Systems - National Best Estimate Including Estimate Range
    Based on Credible Bounds (Threshold = 0.0006 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
4,554
1,033
240
110
13
5,856
251
196
96
129
63
745
6,607
using lower
95% CB
4,044
875
185
81
6
5,307
151
119
47
95
41
601
5,993
using upper
95% CB
5,085
1,214
299
138
20
6,420
368
280
148
164
89
879
7,199
using lower
90% CB
4,100
899
194
86
7
5,390
170
136
54
99
41
636
6,145
using upper
90% CB
5,020
1,184
291
135
19
6,354
340
263
140
160
86
859
7,147
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
    Occurrence Estimation Methodology and Findings
    Appendix C. Stage 2 Analytical Findings
                                                                                                                                                                                   Six-Year Review
Table C.9.e. Bis(2-ethylhexyl)phthalate - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on Population Served
Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.000287
0.000231
0.000251
0.000276
0.000208
0.000269
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.006 mg/L
0.299%
0.164%
0.151%
0.407%
0.0678%
0.189%
0.133% - 0.524%
0.000% - 0.378%
0.000% - 0.515%
0.000% - 0.998%
0.000% - 0.409%
0.0215% - 0.463%
0.160% - 0.452%
0.0217% - 0.339%
0.000% - 0.459%
0.000% - 0.938%
0.000% - 0.342%
0.0411% - 0.414%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.003 mg/L
1.00%
0.720%
0.688%
1.09%
0.410%
0.676%
0.647% - 1.38%
0.399% - 1.17%
0.119% - 1.58%
0.280% - 1.84%
0.000% - 1.28%
0.326% - 1.19%
0.702% - 1.31%
0.432% - 1.06%
0.166% - 1.40%
0.394% - 1.75%
0.000% - 0.999%
0.369% - 1.02%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0006 mg/L
10.2%
8.89%
10.2%
9.25%
4.98%
7.22%
8.91% - 11.6%
7.47% - 10.4%
7.97% - 12.7%
6.67% - 12.0%
1.69% - 9.72%
5.45% - 9.92%
9.15% - 11.4%
7.68% - 10.2%
8.26% - 12.4%
7.07% - 11.4%
2.17% - 8.88%
5.69% - 9.27%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.000382
0.000274
0.000226
0.000333
0.000351
0.000314
0.510%
0.0839%
0.0278%
0.182%
0.0575%
0.0712%
0.000% - 2.36%
0.000% - 0.757%
0.000% - 0.477%
0.000% - 0.997%
0.000% - 0.475%
0.000% - 0.426%
0.000% - 1.85%
0.000% - 0.591%
0.000% - 0.000%
0.000% - 0.760%
0.000% - 0.356%
0.000% - 0.311%
1.84%
0.558%
0.251%
1.00%
0.595%
0.634%
0.000% - 4.76%
0.000% - 1.96%
0.000% - 1.32%
0.222% - 2.50%
0.000% - 3.19%
0.0312% - 3.00%
0.000% - 4.19%
0.000% - 1.59%
0.000% - 1.25%
0. 222% - 2.21%
0.000% - 2.15%
0.0461% - 2.03%
17.7%
11.3%
9.16%
12.3%
11.6%
11.6%
10.5% - 25.7%
6.70% - 16.1%
4.60% - 14.1%
8.17% - 17.0%
5.07% - 19.3%
5.81% - 18.2%
11.6% - 24.5%
7.45% - 15.5%
5.45% - 13.3%
8.94% - 16.1%
6.32% - 18.2%
7.01% - 17.2%

All Systems - Combined
Ground & Surface Water
0.000273
0.119%
0.0186% - 0.363%
0.0230% - 0.304%
0.652%
0.220% - 2.02%
0.241% - 1.50%
9.82%
6.20% - 13.9%
7.00% - 13.3%
All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
  Table C.9.f.  Bis(2-ethylhexyl)phthalate - Population Served - National Best Estimate Including Estimate Range
  Based on Credible Bounds (Threshold = 0.006 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
19,400
25,400
20,800
99,600
0
161,500
1,500
2,400
3,300
39,700
55,300
90,600
254,100
using lower
95% CB
8,600
0
0
0
0
18,400
0
0
0
0
0
0
39,700
using upper
95% CB
34,100
58,700
71,000
243,900
104,100
396,400
6,900
21,300
29,000
217,900
457,300
542,400
774,100
using lower
90% CB
10,400
3,400
0
0
0
35,200
0
0
0
0
0
0
49,100
using upper
90% CB
29,400
52,700
63,200
229,100
87,000
354,800
5,400
16,600
0
166,100
342,600
395,900
647,100
  Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
  level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground &
  Surface Water").
  An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems.  In a specific size
  category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value.
  For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate
  is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).

  Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
  Table C.9.g.  Bis(2-ethylhexyl)phthalate - Population Served - National Best Estimate Including Estimate
  Range Based on Credible Bounds (Threshold = 0.003 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
65,100
111,800
94,700
266,200
104,300
579,600
5,400
15,700
15,300
218,500
572,500
807,500
1,387,700
using lower
95% CB
42,100
61,900
16,400
68,500
0
278,900
0
0
0
48,400
0
39,700
468,600
using upper
95% CB
89,600
181,200
218,000
450,700
324,400
1,019,600
13,900
55,300
80,300
547,000
3,067,400
3,824,900
4,300,600
using lower
90% CB
45,600
67,000
22,800
96,400
0
316,100
0
0
0
48,400
0
58,700
513,100
using upper
90% CB
85,000
164,100
192,400
428,500
254,100
876,500
12,200
44,700
75,800
482,500
2,073,800
2,583,500
3,184,500
  Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
  level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground &
  Surface Water").
  An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems.  In a specific size
  category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value.
  For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate
  is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).

  Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
  Table C.9.h. Bis(2-ethylhexyl)phthalate - Population Served - National Best Estimate Including Estimate
  Range Based on Credible Bounds (Threshold = 0.0006 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
665,500
1,380,100
1,407,300
2,261,600
1,267,300
6,187,900
51,700
319,100
557,500
2,696,600
11,149,100
14,795,300
20,911,000
using lower
95% CB
578,800
1,160,500
1,097,800
1,630,500
429,500
4,668,800
30,600
189,000
279,600
1,785,300
4,881,300
7,391,300
13,202,200
using upper
95% CB
755,100
1,619,500
1,754,300
2,942,800
2,471,800
8,498,800
75,200
453,500
859,700
3,706,200
18,543,300
23,198,900
29,522,900
using lower
90% CB
594,600
1,193,100
1,136,900
1,726,800
552,900
4,878,700
34,000
209,800
331,400
1,952,500
6,080,000
8,919,200
14,904,200
using upper
90% CB
740,200
1,583,800
1,702,000
2,796,200
2,260,400
7,939,300
71,800
436,300
808,600
3,522,600
17,503,500
21,900,200
28,223,600
  Estimates are generated separately for each level of aggregation.  Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
  level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground &
  Surface Water").
  An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size
  category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value.
  For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate
  is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).

  Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
            Table C.lO.a. Cadmium - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on the Number of Systems
Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.000291
0.000234
0.000222
0.000179
0.0000977
0.000269
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.005 mg/L
0.502%
0.322%
0.467%
0.147%
0.0708%
0.443%
0.376% - 0.637%
0.147% - 0.530%
0.106% - 0.951%
0.000% - 0.535%
0.000% - 0.680%
0.344% - 0.558%
0.405% - 0.608%
0.177% - 0.471%
0.211% - 0.846%
0.000% - 0.357%
0.000% - 0.680%
0.357% - 0.532%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0025 mg/L
1.73%
1.36%
1.76%
0.878%
0.429%
1.61%
1.48% - 1.97%
1.00% - 1.74%
1.16% - 2.43%
0.178% - 1.60%
0.000% - 1.36%
1.42% - 1.80%
1.52% - 1.93%
1.06% - 1.68%
1.27% - 2.33%
0.357% - 1.43%
0.000% - 1.36%
1.43% - 1.78%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.000163
0.0000978
0.000186
0.000100
0.0000773
0.000127
0.183%
0.0442%
0.166%
0.0336%
0.0247%
0.0945%
0.000% - 0.557%
0.000% - 0.230%
0.000% - 0.752%
0.000% - 0.336%
0.000% - 0.649%
0.000% - 0.265%
0.000% - 0.557%
0.000% - 0.230%
0.000% - 0.752%
0.000% - 0.336%
0.000% - 0.000%
0.000% - 0.199%
0.714%
0.366%
0.940%
0.280%
0.210%
0.517%
0.000% - 1.67%
0.000% - 0.922%
0.000% - 1.88%
0.000% - 1.01%
0.000% - 0.649%
0.265% - 0.860%
0.000% - 1.39%
0.000% - 0.922%
0.376% - 1.88%
0.000% - 0.671%
0.000% - 0.649%
0.265% - 0.794%

All Systems - Combined
Ground & Surface Water
0.000256
0.412%
0.325% - 0.508%
0.337% - 0.490%
1.51%
1.33% - 1.70%
1.36% - 1.67%

Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.000291
0.000234
0.000222
0.000179
0.0000977
0.000269
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.00125 mg/L
4.76%
3.96%
4.11%
3.06%
1.19%
4.45%
4.36% - 5.16%
3.42% - 4.57%
3.17% - 4.97%
1.96% - 4.28%
0.000% - 2.04%
4.15% - 4.80%
4.43% - 5.10%
3.48% - 4.48%
3.38% - 4.86%
2.14% - 3.92%
0.680% - 2.04%
4.19% - 4.72%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.001 mg/L
6.31%
5.23%
5.08%
4.13%
1.51%
5.88%
5.87% - 6.81%
4.57% - 5.92%
4.12% - 6.03%
3.03% - 5.35%
0.680% - 2.72%
5.51% - 6.24%
5.92% - 6.73%
4.71% - 5.80%
4.23% - 5.92%
3.03% - 5.17%
0.680% - 2.72%
5.59% - 6.19%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.000163
0.0000978
0.000186
0.000100
0.0000773
0.000127
2.23%
1.34%
2.89%
1.23%
0.944%
1.76%
0.836% - 3.62%
0.691% - 2.07%
1.50% - 4.51%
0.336% - 2.35%
0.000% - 1.95%
1.19% - 2.25%
1.11% - 3.62%
0.691% - 2.07%
1.50% - 4.14%
0.336% - 2.01%
0.000% - 1.95%
1.32% - 2.18%
3.04%
1.82%
3.83%
1.78%
1.38%
2.41%
1.67% - 4.74%
0.922% - 2.77%
2.26% - 5.64%
0.671% - 3.02%
0.649% - 2.60%
1.79% - 3.04%
1.67% - 4.46%
1.15% - 2.54%
2.63% - 5.26%
1.01% - 2.69%
0.649% - 2.60%
1.92% - 2.91%

All Systems - Combined
Ground & Surface Water
0.000256
4.21%
3.94% - 4.52%
3.98% - 4.47%
5.57%
5.24% - 5.89%
5.28% - 5.86%
            All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.lO.b. Cadmium - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.005 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
218
39
11
2
0
263
3
1
2
0
0
5
268
using lower
95% CB
164
18
o
J
0
0
204
0
0
0
0
0
0
211
using upper
95% CB
277
64
23
6
1
332
9
4
8
3
3
15
330
using lower
90% CB
176
21
5
0
0
212
0
0
0
0
0
0
219
using upper
90% CB
264
57
20
4
1
316
9
4
8
o
5
0
11
319
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.lO.c.  Cadmium - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.0025 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
750
166
42
10
1
954
11
6
10
o
6
i
29
980
using lower
95% CB
642
122
28
2
0
845
0
0
0
0
0
15
864
using upper
95% CB
856
211
58
19
3
1,068
26
16
19
9
3
48
1,103
using lower
90% CB
659
129
30
4
0
852
0
0
4
0
0
15
884
using upper
90% CB
840
204
56
17
3
1,057
21
16
19
6
3
44
1,083
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.lO.d. Cadmium - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.00125 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
2,072
481
99
36
2
2,645
34
23
29
11
4
99
2,738
using lower
95% CB
1,897
416
76
23
0
2,468
13
12
15
o
6
0
67
2,559
using upper
95% CB
2,245
555
119
51
4
2,854
56
35
46
22
8
126
2,939
using lower
90% CB
1,926
423
81
25
1
2,491
17
12
15
3
0
74
2,586
using upper
90% CB
2,220
544
117
47
4
2,807
56
35
42
19
8
122
2,909
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.lO.e. Cadmium - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.001 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
2,746
636
122
49
3
3,492
47
31
39
17
6
135
3,620
using lower
95% CB
2,552
555
99
36
1
3,274
26
16
23
6
3
100
3,404
using upper
95% CB
2,963
720
145
64
5
3,710
73
47
57
28
10
170
3,831
using lower
90% CB
2,577
573
102
36
1
3,320
26
20
27
9
3
107
3,435
using upper
90% CB
2,929
706
142
62
5
3,679
69
43
53
25
10
163
3,808
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "S
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
            Table C.lO.f. Cadmium - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on Population Served
Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.000291
0.000234
0.000222
0.000179
0.0000977
0.000269
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.005 mg/L
0.529%
0.302%
0.474%
0.112%
0.0359%
0.162%
0.379% - 0.694%
0.101% - 0.511%
0.128% - 0.985%
0.000% - 0.403%
0.000% - 0.346%
0.0698% - 0.316%
0.401% - 0.670%
0.149% - 0.482%
0.155% - 0.873%
0.000% - 0.319%
0.000% - 0.346%
0.0785% - 0.289%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0025 mg/L
1.79%
1.28%
1.77%
0.676%
0.212%
0.726%
1.51% - 2.11%
0.892% - 1.69%
1.19% - 2.44%
0.176% - 1.24%
0.000% - 0.697%
0.495% - 1.00%
1.55% - 2.06%
0.952% - 1.65%
1.23% - 2.37%
0.257% - 1.17%
0.000% - 0.627%
0.517% - 0.955%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.000163
0.0000978
0.000186
0.000100
0.0000773
0.000127
0.188%
0.0474%
0.145%
0.0178%
0.0103%
0.0154%
0.000% - 0.804%
0.000% - 0.272%
0.000% - 0.764%
0.000% - 0.161%
0.000% - 0.291%
0.000% - 0.247%
0.000% - 0.765%
0.000% - 0.272%
0.000% - 0.649%
0.000% - 0.161%
0.000% - 0.000%
0.000% - 0.0412%
0.777%
0.399%
0.843%
0.166%
0.0852%
0.119%
0.000% - 2.00%
0.000% - 1.10%
0.000% - 1.82%
0.000% - 0.666%
0.000% - 0.406%
0.0128% - 0.377%
0.000% - 1.75%
0.000% - 0.949%
0.250% - 1.73%
0.000% - 0.617%
0.000% - 0.291%
0.0166% - 0.321%

All Systems - Combined
Ground & Surface Water
0.000256
0.0752%
0.0297% - 0.207%
0.0338% - 0.153%
0.366%
0.232% - 0.555%
0.244% - 0.529%

Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.000291
0.000234
0.000222
0.000179
0.0000977
0.000269
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.00125 mg/L
4.93%
3.77%
4.07%
2.54%
0.604%
2.13%
4.44% - 5.46%
3.13% - 4.37%
3.11% - 4.98%
1.65% - 3.49%
0.000% - 1.33%
1.74% - 2.54%
4.50% - 5.35%
3.27% - 4.29%
3.31% - 4.85%
1.77% - 3.35%
0.281% - 1.04%
1.80% - 2.47%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.001 mg/L
6.52%
4.97%
5.03%
3.46%
0.814%
2.80%
6.00% - 7.11%
4.31% - 5.64%
4.06% - 6.01%
2.40% - 4.55%
0.281% - 2.83%
2.32% - 3.61%
6.09% - 7.01%
4.41% - 5.57%
4.18% - 5.93%
2.54% - 4.35%
0.346% - 1.67%
2.43% - 3.25%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.000163
0.0000978
0.000186
0.000100
0.0000773
0.000127
2.52%
1.48%
2.81%
0.931%
0.420%
0.557%
0.827% - 4.66%
0.660% - 2.38%
1.21% - 4.54%
0.152% - 1.90%
0.000% - 1.92%
0.139% - 1.87%
1.14% - 4.23%
0.733% - 2.27%
1.51% - 4.18%
0.208% - 1.79%
0.000% - 1.08%
0.183% - 1.21%
3.46%
2.00%
3.80%
1.40%
0.736%
0.910%
1.46% - 5.81%
1.07% - 2.94%
2.06% - 5.75%
0.435% - 2.51%
0.109% - 2.32%
0.292% - 2.24%
1.93% - 5.44%
1.16% - 2.84%
2.28% - 5.42%
0.521% - 2.30%
0.142% - 2.09%
0.378% - 2.11%

All Systems - Combined
Ground & Surface Water
0.000256
1.20%
0.888% - 1.97%
0.931% - 1.70%
1.68%
1.28% - 2.55%
1.32% - 2.40%
            All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.lO.g.  Cadmium - Population Served - National Best Estimate Including Estimate Range Based on
Credible Bounds (Threshold = 0.005 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
34,400
46,900
65,300
27,300
0
139,000
600
1,300
8,800
0
0
19,600
160,100
using lower
95% CB
24,600
15,700
17,600
0
0
59,800
0
0
0
0
0
0
63,300
using upper
95% CB
45,100
79,300
135,700
98,500
88,000
270,600
2,400
7,700
46,500
35,200
280,200
314,200
440,900
using lower
90% CB
26,000
23,200
21,300
0
0
67,200
0
0
0
0
0
0
72,000
using upper
90% CB
43,500
74,800
120,300
78,100
88,000
247,200
2,200
7,700
39,500
35,200
0
52,500
326,800
Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates.  The primary model estimation output is the number of systems. In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.lO.h. Cadmium - Population Served - National Best Estimate Including Estimate Range Based on
Credible Bounds (Threshold = 0.0025 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
116,600
199,100
243,200
165,300
54,000
621,600
2,300
11,200
51,300
36,200
82,100
151,500
779,600
using lower
95% CB
98,300
138,600
163,600
42,900
0
423,700
0
0
0
0
0
16,300
494,600
using upper
95% CB
136,900
263,000
335,600
302,600
177,300
858,500
5,800
30,900
110,400
145,600
390,400
479,800
1,181,800
using lower
90% CB
100,800
147,800
169,500
62,900
0
443,200
0
0
15,200
0
0
21,100
520,600
using upper
90% CB
133,600
255,600
326,100
286,900
159,500
818,600
5,100
26,700
105,000
134,900
280,200
409,000
1,127,500
Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates.  The primary model estimation output is the number of systems. In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.lO.i. Cadmium - Population Served - National Best Estimate Including Estimate Range Based on
Credible Bounds (Threshold = 0.00125 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
320,200
584,600
559,800
620,600
153,700
1,821,600
7,400
41,800
171,200
203,400
404,400
708,800
2,547,600
using lower
95% CB
288,500
485,700
428,100
403,800
0
1,494,300
2,400
18,600
73,800
33,300
0
176,300
1,892,200
using upper
95% CB
354,800
678,200
686,300
852,300
337,400
2,179,700
13,600
67,000
276,000
415,400
1,847,600
2,382,300
4,189,900
using lower
90% CB
292,400
507,000
456,100
432,100
71,500
1,544,800
3,300
20,700
91,600
45,400
0
233,300
1,983,100
using upper
90% CB
347,700
666,000
667,300
819,300
265,600
2,119,800
12,400
64,000
254,400
390,300
1,039,800
1,545,700
3,621,100
Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates.  The primary model estimation output is the number of systems. In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.lO.j.  Cadmium - Population Served - National Best Estimate Including Estimate Range Based on
Credible Bounds (Threshold = 0.001 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
423,500
771,600
693,100
845,900
207,100
2,401,700
10,100
56,400
231,000
305,100
708,300
1,159,100
3,580,700
using lower
95% CB
389,700
668,500
559,300
585,400
71,500
1,983,500
4,300
30,100
125,500
95,100
104,600
372,300
2,730,800
using upper
95% CB
461,900
875,300
828,000
1,113,100
720,500
3,093,100
17,000
82,800
349,700
547,800
2,237,500
2,850,800
5,429,600
using lower
90% CB
395,400
685,200
575,200
620,600
88,000
2,078,600
5,600
32,600
138,700
113,900
136,300
480,800
2,801,100
using upper
90% CB
455,600
864,400
816,700
1,063,200
425,900
2,784,700
15,900
80,100
329,600
501,700
2,011,300
2,685,300
5,112,200
Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
    Occurrence Estimation Methodology and Findings
    Appendix C. Stage 2 Analytical Findings
                                                                                                                                                                                  Six-Year Review
Table C.ll.a.  Carbofuran - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on the Number of Systems
Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.0000142
0.0000223
0.0000175
0.00000725
0.0000311
0.0000162
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.040 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.007 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.004 mg/L
0.000172%
0.000%
0.000%
0.000%
0.000%
0.000112%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.0000292
0.0000500
0.0000191
0.0000429
0.0000139
0.0000349
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000%
0.000490%
0.000%
0.000%
0.000%
0.000144%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

All Systems - Combined
Ground & Surface Water
0.0000181
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000115%
0.000% - 0.000%
0.000% - 0.000%
All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.ll.b. Carbofuran - Systems - National Best Estimate Including Estimate Range Based on
    Credible Bounds (Threshold = 0.040 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.I I.e.  Carbofuran - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.007 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.ll.d. Carbofuran - Systems - National Best Estimate Including Estimate Range Based on
    Credible Bounds (Threshold = 0.004 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
    Occurrence Estimation Methodology and Findings
    Appendix C. Stage 2 Analytical Findings
                                                                                                                                                                                  Six-Year Review
Table C.ll.e.  Carbofuran - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on Population Served
Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.0000142
0.0000223
0.0000175
0.00000725
0.0000311
0.0000162
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.040 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.007 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.004 mg/L
0.000247%
0.000%
0.000%
0.000%
0.000%
0.00000806%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.0000292
0.0000500
0.0000191
0.0000429
0.0000139
0.0000349
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000%
0.000171%
0.000%
0.000%
0.000%
0.00000217%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

All Systems - Combined
Ground & Surface Water
0.0000181
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.00000461%
0.000% - 0.000%
0.000% - 0.000%
All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
  Table C.ll.f.  Carbofuran - Population Served - National Best Estimate Including Estimate Range Based on
  Credible Bounds (Threshold = 0.040 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
  Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
  level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground &
  Surface Water").
  An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size
  category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value.
  For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate
  is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).

  Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
  Table C.ll.g.  Carbofuran - Population Served - National Best Estimate Including Estimate Range Based on
  Credible Bounds (Threshold = 0.007 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
  Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
  level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground &
  Surface Water").
  An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size
  category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value.
  For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate
  is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).

  Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
  Table C.ll.h.  Carbofuran - Population Served - National Best Estimate Including Estimate Range Based on
  Credible Bounds (Threshold = 0.004 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
  Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
  level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground &
  Surface Water").
  An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size
  category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value.
  For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate
  is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).

  Population estimates are rounded to the nearest hundred.

-------
    Occurrence Estimation Methodology and Findings
    Appendix C. Stage 2 Analytical Findings
                                                                                                                                                                                  Six-Year Review
Table C.12.a.  Carbon Tetrachloride - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on the Number of Systems
Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.0000126
0.0000239
0.0000179
0.0000324
0.0000310
0.0000160
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.005 mg/L
0.00820%
0.0367%
0.000690%
0.112%
0.000%
0.0171%
0.00672% - 0.0135%
0.0218% - 0.0435%
0.000% - 0.000%
0.000% - 0.151%
0.000% - 0.000%
0.00932% - 0.0233%
0.00672% - 0.0135%
0.0218% - 0.0435%
0.000% - 0.000%
0.000% - 0.151%
0.000% - 0.000%
0.00932% - 0.0233%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0025 mg/L
0.0142%
0.0535%
0.0192%
0.161%
0.000%
0.0273%
0.00672% - 0.0269%
0.0435% - 0.0871%
0.000% - 0.0863%
0.151% - 0.301%
0.000% - 0.000%
0.0186% - 0.0373%
0.00672% - 0.0269%
0.0435% - 0.0871%
0.000% - 0.0863%
0.151% - 0.301%
0.000% - 0.000%
0.0186% - 0.0373%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0005 mg/L
0.106%
0.316%
0.324%
0.708%
1.67%
0.193%
0.0605% - 0.161%
0.174% - 0.457%
0.173% - 0.604%
0.602% - 0.904%
1.23% - 2.45%
0.140% - 0.242%
0.0672% - 0.155%
0.218% - 0.435%
0.173% - 0.518%
0.602% - 0.904%
1.23% - 1.84%
0.149% - 0.238%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.0000134
0.0000309
0.0000289
0.0000253
0.0000486
0.0000274
0.000%
0.000452%
0.000683%
0.000606%
0.000%
0.000381%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.00175%
0.00406%
0.00137%
0.00303%
0.00242%
0.00267%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.0635%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.0566%
0.410%
0.230%
0.320%
1.94%
0.441%
0.000% - 0.292%
0.000% - 0.903%
0.000% - 1.02%
0.000% - 0.909%
1.21% - 3.03%
0.254% - 0.699%
0.000% - 0.292%
0.000% - 0.903%
0.000% - 0.683%
0.000% - 0.909%
1 .21% - 2.42%
0.254% - 0.635%

All Systems - Combined
Ground & Surface Water
0.0000168
0.0159%
0.00869% - 0.0217%
0.00869% - 0.0217%
0.0256%
0.0174% - 0.0347%
0.0174% - 0.0347%
0.210%
0.161% - 0.265%
0.169% - 0.256%
All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.12.b. Carbon Tetrachloride - Systems - National Best Estimate Including Estimate Range Based
    on Credible Bounds (Threshold = 0.005 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
4
4
0
1
0
10
0
0
0
0
0
1
10
using lower
95% CB
o
J
3
0
0
0
6
0
0
0
0
0
0
6
using upper
95% CB
6
5
0
2
0
14
0
0
0
0
0
0
14
using lower
90% CB
3
3
0
0
0
6
0
0
0
0
0
0
6
using upper
90% CB
6
5
0
2
0
14
0
0
0
0
0
0
14
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.12.C.  Carbon Tetrachloride - Systems - National Best Estimate Including Estimate Range Based
    on Credible Bounds (Threshold = 0.0025 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
6
6
1
2
0
16
0
0
0
0
0
1
17
using lower
95% CB
o
J
5
0
2
0
11
0
0
0
0
0
0
11
using upper
95% CB
12
11
2
4
0
22
0
0
0
0
0
4
23
using lower
90% CB
3
5
0
2
0
11
0
0
0
0
0
0
11
using upper
90% CB
12
11
2
4
0
22
0
0
0
0
0
0
23
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.12.d. Carbon Tetrachloride - Systems - National Best Estimate Including Estimate Range Based
    on Credible Bounds (Threshold = 0.0005 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
46
38
8
8
o
J
115
1
7
2
o
J
8
25
137
using lower
95% CB
26
21
4
7
2
83
0
0
0
0
5
14
105
using upper
95% CB
70
56
15
11
5
144
4
15
10
8
12
39
172
using lower
90% CB
29
26
4
7
2
89
0
0
0
0
5
14
110
using upper
90% CB
67
53
12
11
o
J
141
4
15
7
8
10
36
167
    Estimates are generated separately for each level of aggregation.  Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
    Occurrence Estimation Methodology and Findings
    Appendix C. Stage 2 Analytical Findings
                                                                                                                                                                                  Six-Year Review
Table C.12.e.  Carbon Tetrachloride - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on Population Served
Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.0000126
0.0000239
0.0000179
0.0000324
0.0000310
0.0000160
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.005 mg/L
0.00866%
0.0189%
0.000476%
0.234%
0.000%
0.0705%
0.00681% - 0.0159%
0.0104% - 0.0220%
0.000% - 0.000%
0.000% - 0.313%
0.000% - 0.000%
0.00158% - 0.0950%
0.00681% - 0.0159%
0.0104% - 0.0220%
0.000% - 0.000%
0.000% - 0.313%
0.000% - 0.000%
0.00172% - 0.0942%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0025 mg/L
0.0159%
0.0367%
0.0133%
0.335%
0.000%
0.104%
0.00681% - 0.0366%
0.0220% - 0.0894%
0.000% - 0.0608%
0.313% - 0.626%
0.000% - 0.000%
0.0938% - 0.191%
0.00681% - 0.0321%
0.0220% - 0.0828%
0.000% - 0.0608%
0.313% - 0.626%
0.000% - 0.000%
0.0938% - 0.187%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0005 mg/L
0.124%
0.286%
0.307%
1.06%
0.915%
0.764%
0.0598% - 0.195%
0.164% - 0.431%
0.118% - 0.584%
0.962% - 1.34%
0.691% - 1.62%
0.627% - 1.05%
0.0680% - 0.185%
0.191% - 0.408%
0.118% - 0.552%
0.962% - 1.28%
0.691% - 1.22%
0.633% - 0.907%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.0000134
0.0000309
0.0000289
0.0000253
0.0000486
0.0000274
0.000%
0.000263%
0.000886%
0.000333%
0.000%
0.0000713%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.00188%
0.00180%
0.00183%
0.00160%
0.00133%
0.00139%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.00104%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.0500%
0.349%
0.256%
0.201%
15.3%
12.7%
0.000% - 0.490%
0.000% - 0.985%
0.000% - 1.03%
0.000% - 0.742%
14.9% - 16.7%
12.4% - 13.9%
0.000% - 0.382%
0.000% - 0.870%
0.000% - 0.916%
0.000% - 0.600%
14.9% - 15.9%
1 2.4% - 13.2%

All Systems - Combined
Ground & Surface Water
0.0000168
0.0316%
0.000707% - 0.0429%
0.000772% - 0.0422%
0.0474%
0.0420% - 0.0865%
0.0420% - 0.0842%
7.37%
7.16% - 8.00%
7.1 8% - 7.71 %
All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
  Table C.12.f.  Carbon Tetrachloride - Population Served - National Best Estimate Including Estimate Range
  Based on Credible Bounds (Threshold = 0.005 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
600
2,900
0
57,100
0
60,400
0
0
0
0
0
100
67,400
using lower
95% CB
400
1,600
0
0
0
1,400
0
0
0
0
0
0
1,500
using upper
95% CB
1,000
3,400
0
76,500
0
81,400
0
0
0
0
0
0
91,400
using lower
90% CB
400
1,600
0
0
0
1,500
0
0
0
0
0
0
1,600
using upper
90% CB
1,000
3,400
0
76,500
0
80,700
0
0
0
0
0
0
89,900
  Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
  level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground &
  Surface Water").
  An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems.  In a specific size
  category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value.
  For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate
  is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).

  Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
  Table C.12.g.  Carbon Tetrachloride - Population Served - National Best Estimate Including Estimate Range
  Based on Credible Bounds (Threshold = 0.0025 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
1,000
5,700
3,300
81,900
0
89,300
0
0
0
0
0
1,800
101,100
using lower
95% CB
400
3,400
0
76,500
0
80,400
0
0
0
0
0
0
89,500
using upper
95% CB
2,400
13,900
8,400
153,100
0
163,300
0
0
0
0
0
1,300
184,300
using lower
90% CB
400
3,400
0
76,500
0
80,400
0
0
0
0
0
0
89,500
using upper
90% CB
2,100
12,900
8,400
153,100
0
160,000
0
0
0
0
0
0
179,300
  Estimates are generated separately for each level of aggregation.  Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
  level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground &
  Surface Water").
  An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size
  category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value.
  For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate
  is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).

  Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
  Table C.12.h.  Carbon Tetrachloride - Population Served - National Best Estimate Including Estimate Range
  Based on Credible Bounds (Threshold = 0.0005 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
8,100
44,500
42,200
259,800
232,800
654,600
100
9,800
15,600
43,900
14,711,400
16,221,400
15,705,100
using lower
95% CB
3,900
25,500
16,200
235,100
175,700
537,200
0
0
0
0
14,355,200
15,788,500
15,245,000
using upper
95% CB
12,700
66,900
80,400
327,300
410,900
902,200
1,400
27,800
62,700
162,100
16,078,600
17,698,400
17,042,800
using lower
90% CB
4,400
29,700
16,200
235,100
175,700
542,700
0
0
0
0
14,355,200
15,801,200
15,298,200
using upper
90% CB
12,000
63,300
76,000
312,400
310,900
777,000
1,100
24,500
55,800
131,100
15,298,700
16,832,600
16,414,400
  Estimates are generated separately for each level of aggregation.  Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
  level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground &
  Surface Water").
  An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size
  category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value.
  For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate
  is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).

  Population estimates are rounded to the nearest hundred.

-------
    Occurrence Estimation Methodology and Findings
    Appendix C. Stage 2 Analytical Findings
                                                                                                                                                                                  Six-Year Review
Table C.13.a.  Chlordane - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on the Number of Systems
Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.00000334
0.00000320
0.00000421
0.00000338
0.00000331
0.00000337
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.002 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.001 mg/L
0.000158%
0.000%
0.000%
0.000%
0.000%
0.000101%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0002 mg/L
0.0563%
0.0149%
0.0100%
0.000711%
0.000%
0.0403%
0.0394% - 0.0920%
0.000% - 0.0732%
0.000% - 0.125%
0.000% - 0.000%
0.000% - 0.000%
0.0253% - 0.0591%
0.0394% - 0.0788%
0.000% - 0.0732%
0.000% - 0.125%
0.000% - 0.000%
0.000% - 0.000%
0.0253% - 0.0591%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.00000190
0.000000917
0.000000497
0.00000211
0.00000222
0.00000143
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000810%
0.000%
0.000%
0.000680%
0.000%
0.000301%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

All Systems - Combined
Ground & Surface Water
0.00000317
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.0000910%
0.000% - 0.000%
0.000% - 0.000%
0.0363%
0.0228% - 0.0531%
0.0228% - 0.0531%
All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.13.b. Chlordane - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.002 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.13.C.  Chlordane - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.001 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.13.d. Chlordane - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.0002 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
25
2
0
0
0
24
0
0
0
0
0
1
24
using lower
95% CB
17
0
0
0
0
15
0
0
0
0
0
0
15
using upper
95% CB
40
9
3
0
0
35
0
0
0
0
0
0
35
using lower
90% CB
17
0
0
0
0
15
0
0
0
0
0
0
15
using upper
90% CB
34
9
3
0
0
35
0
0
0
0
0
0
35
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
  Occurrence Estimation Methodology and Findings
  Appendix C.  Stage 2 Analytical Findings
                                                                                                                                                                                         Six-Year Review
Table C.13.e.  Chlordane - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on Population Served
Source Water
Type
Ground Water
Population
Served
<500
501 - 3,300
3,301 - 10,000
10,001 -50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.00000334
0.00000320
0.00000421
0.00000338
0.00000331
0.00000337
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.002 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.001 mg/L
0.000119%
0.000%
0.000%
0.000%
0.000%
0.00000350%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0002 mg/L
0.0485%
0.0111%
0.00777%
0.000463%
0.000%
0.00346%
0.0322% - 0.0789%
0.000% - 0.0570%
0.000% - 0.103%
0.000% - 0.000%
0.000% - 0.000%
0.000945% - 0.0166%
0.0322% - 0.0731%
0.000% - 0.0492%
0.000% - 0.0728%
0.000% - 0.000%
0.000% - 0.000%
0.000945% - 0.0116%

Surface Water
<500
501 - 3,300
3,301 - 10,000
10,001 -50,000
> 50,000
Total
0.00000190
0.000000917
0.000000497
0.00000211
0.00000222
0.00000143
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000555%
0.000%
0.000%
0.000399%
0.000%
0.0000479%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

All Systems - Combined
Ground & Surface Water
0.00000317
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.00000146%
0.000% - 0.000%
0.000% - 0.000%
0.00147%
0.000394% - 0.00701%
0.000394% - 0.00486%
All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
  Table C.13.f.  Chlordane - Population Served - National Best Estimate Including Estimate Range Based on
  Credible Bounds (Threshold = 0.002 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
  Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
  level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground &
  Surface Water").

  An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size
  category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value.
  For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate
  is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to  10,000 size category).
  Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
  Table C.13.g.  Chlordane - Population Served - National Best Estimate Including Estimate Range Based on
  Credible Bounds (Threshold = 0.001 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
  Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
  level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground &
  Surface Water").

  An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size
  category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value.
  For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate
  is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to  10,000 size category).
  Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
  Table C.13.h.  Chlordane - Population Served - National Best Estimate Including Estimate Range Based on
  Credible Bounds (Threshold = 0.0002 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
3,200
1,700
0
0
0
3,000
0
0
0
0
0
100
3,100
using lower
95% CB
2,100
0
0
0
0
800
0
0
0
0
0
0
800
using upper
95% CB
5,100
8,900
14,200
0
0
14,200
0
0
0
0
0
0
14,900
using lower
90% CB
2,100
0
0
0
0
800
0
0
0
0
0
0
800
using upper
90% CB
4,800
7,600
10,000
0
0
9,900
0
0
0
0
0
0
10,400
  Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
  level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground &
  Surface Water").

  An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size
  category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value.
  For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate
  is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
  Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
                                                                                                                                                                                                           Six- Year Review
         Table C.14.a. Chromium - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on the Number of Systems
Source Water
Type
Ground Water
Population
Served
<500
501 - 3,300
3,301 - 10,000
10,001 -50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.00124
0.00189
0.00119
0.000819
0.000676
0.00135
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.1 mg/L
0.00376%
0.00754%
0.00607%
0.00242%
0.000%
0.00459%
0.000% - 0.0157%
0.000% - 0.0535%
0.000% - 0.101%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.0165%
0.000% - 0.0157%
0.000% - 0.0268%
0.000% - 0.101%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.0165%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.07 mg/L
0.0117%
0.0245%
0.0176%
0.00727%
0.000%
0.0144%
0.000% - 0.0315%
0.000% - 0.0802%
0.000% - 0.101%
0.000% - 0.173%
0.000% - 0.000%
0.000% - 0.0385%
0.000% - 0.0315%
0.000% - 0.0802%
0.000% - 0.101%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.0275%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.05 mg/L
0.0312%
0.0721%
0.0388%
0.0177%
0.000%
0.0393%
0.00787% - 0.0630%
0.000% - 0.161%
0.000% - 0.202%
0.000% - 0.173%
0.000% - 0.000%
0.0110% - 0.0716%
0.00787% - 0.0551%
0.000% - 0.161%
0.000% - 0.101%
0.000% - 0.173%
0.000% - 0.000%
0.0165% - 0.0661%

Surface Water
<500
501 - 3,300
3,301 - 10,000
10,001 -50,000
> 50,000
Total
0.000759
0.000997
0.000994
0.000763
0.000617
0.000856
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.00114%
0.00136%
0.000%
0.000641%
0.000%
0.000786%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.00456%
0.00680%
0.00444%
0.00128%
0.000%
0.00406%
0.000% - 0.000%
0.000% - 0.227%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.0655%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.0655%

All Systems - Combined
Ground & Surface Water
0.00132
0.00424%
0.000% - 0.0152%
0.000% - 0.0152%
0.0133%
0.000% - 0.0355%
0.000% - 0.0254%
0.0366%
0.0152% - 0.0660%
0.0152% - 0.0609%
Source Water
Type
Ground Water
Population
Served
<500
501 - 3,300
3,301 - 10,000
10,001 -50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.00124
0.00189
0.00119
0.000819
0.000676
0.00135
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.02 mg/L
0.310%
0.759%
0.310%
0.213%
0.00886%
0.396%
0.205% - 0.417%
0.508% - 1.07%
0.000% - 0.607%
0.000% - 0.519%
0.000% - 0.000%
0.292% - 0.501%
0.228% - 0.401%
0.535% - 0.990%
0.101% - 0.607%
0.000% - 0.519%
0.000% - 0.000%
0.308% - 0.479%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.01 mg/L
1.35%
2.98%
1.27%
0.764%
0.220%
1.65%
1.10% - 1.60%
2.35% - 3.61%
0.607% - 1.92%
0.346% - 1.38%
0.000% - 0.633%
1.40% - 1.89%
1.13% - 1.55%
2.49% - 3.50%
0.708% - 1.82%
0.346% - 1.21%
0.000% - 0.633%
1.45% - 1.85%

Surface Water
<500
501 - 3,300
3,301 - 10,000
10,001 -50,000
> 50,000
Total
0.000759
0.000997
0.000994
0.000763
0.000617
0.000856
0.0803%
0.129%
0.0511%
0.0212%
0.00395%
0.0696%
0.000% - 0.570%
0.000% - 0.454%
0.000% - 0.370%
0.000% - 0.321%
0.000% - 0.000%
0.000% - 0.262%
0.000% - 0.285%
0.000% - 0.454%
0.000% - 0.370%
0.000% - 0.321%
0.000% - 0.000%
0.000% - 0.197%
0.526%
0.713%
0.433%
0.296%
0.0974%
0.474%
0.000% - 1.43%
0.000% - 1.59%
0.000% - 1.48%
0.000% - 0.962%
0.000% - 0.658%
0.131% - 0.786%
0.000% - 1.14%
0.227% - 1.36%
0.000% - 1.11%
0.000% - 0.962%
0.000% - 0.658%
0.197% - 0.721%

All Systems - Combined
Ground & Surface Water
0.00132
0.371%
0.274% - 0.467%
0.289% - 0.447%
1.56%
1.33% - 1.78%
1.38% - 1.75%
         All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.14.b. Chromium - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.1 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
2
1
0
0
0
o
J
0
0
0
0
0
0
3
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
7
7
2
0
0
10
0
0
0
0
0
0
10
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
7
3
2
0
0
10
0
0
0
0
0
0
10
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.14.C.  Chromium - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.07 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
5
3
1
0
0
9
0
0
0
0
0
1
9
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
14
10
2
2
0
23
0
0
0
0
0
0
23
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
14
10
2
0
0
16
0
0
0
0
0
0
17
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.14.d. Chromium - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.05 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
14
9
1
1
0
23
0
0
0
0
0
1
24
using lower
95% CB
o
5
0
0
0
0
7
0
0
0
0
0
0
10
using upper
95% CB
27
20
5
2
0
43
0
4
0
0
0
4
43
using lower
90% CB
3
0
0
0
0
10
0
0
0
0
0
0
10
using upper
90% CB
24
20
2
2
0
39
0
0
0
0
0
4
40
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.14.e.  Chromium - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.02 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
135
92
7
o
J
0
236
1
2
1
0
0
4
241
using lower
95% CB
89
62
0
0
0
173
0
0
0
0
0
0
178
using upper
95% CB
181
130
15
6
0
298
9
8
4
3
0
15
304
using lower
90% CB
99
65
2
0
0
183
0
0
0
0
0
0
188
using upper
90% CB
175
120
15
6
0
285
4
8
4
o
J
0
11
291
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.14.f.  Chromium - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.01 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
585
362
30
9
1
980
8
12
4
o
J
1
26
1,013
using lower
95% CB
479
286
15
4
0
834
0
0
0
0
0
7
865
using upper
95% CB
695
439
46
16
1
1,122
22
27
15
9
3
44
1,156
using lower
90% CB
493
302
17
4
0
864
0
4
0
0
0
11
895
using upper
90% CB
675
426
44
14
1
1,099
18
23
11
9
o
J
40
1,139
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
                                                                                                                                                                                                            Six- Year Review
         Table C.14.g.  Chromium - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on Population Served
Source Water
Type
Ground Water
Population
Served
<500
501 - 3,300
3,301 -10,000
10,001 -50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.00124
0.00189
0.00119
0.000819
0.000676
0.00135
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.1 mg/L
0.00427%
0.00748%
0.00666%
0.00493%
0.000%
0.00325%
0.000% - 0.0266%
0.000% - 0.0607%
0.000% - 0.124%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.0186%
0.000% - 0.0215%
0.000% - 0.0455%
0.000% - 0.0745%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.0157%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.07 mg/L
0.0120%
0.0234%
0.0188%
0.0156%
0.000%
0.00987%
0.000% - 0.0438%
0.000% - 0.0963%
0.000% - 0.124%
0.000% - 0.394%
0.000% - 0.000%
0.000% - 0.113%
0.000% - 0.0374%
0.000% - 0.0804%
0.000% - 0.124%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.0281%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.05 mg/L
0.0326%
0.0680%
0.0397%
0.0383%
0.000%
0.0248%
0.00140% - 0.0768%
0.000% - 0.175%
0.000% - 0.198%
0.000% - 0.394%
0.000% - 0.000%
0.00124% - 0.130%
0.00323% - 0.0685%
0.000% - 0.161%
0.000% - 0.143%
0.000% - 0.394%
0.000% - 0.000%
0.00254% - 0.125%

Surface Water
<500
501 - 3,300
3,301 -10,000
10,001 -50,000
> 50,000
Total
0.000759
0.00100
0.000994
0.000763
0.000617
0.000856
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.00120%
0.000727%
0.000%
0.000785%
0.000%
0.000104%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.00568%
0.00425%
0.00436%
0.00133%
0.000%
0.000336%
0.000% - 0.000%
0.000% - 0.0744%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.00182%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000655%

All Systems - Combined
Ground & Surface Water
0.00132
0.00139%
0.000% - 0.00793%
0.000% - 0.00670%
0.00427%
0.000% - 0.0481%
0.000% - 0.0125%
0.0108%
0.000580% - 0.0559%
0.00113% - 0.0536%
Source Water
Type
Ground Water
Population
Served
<500
501 - 3,300
3,301 -10,000
10,001 -50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.00124
0.00189
0.00119
0.000819
0.000676
0.00135
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.02 mg/L
0.323%
0.746%
0.283%
0.325%
0.00984%
0.228%
0.187% - 0.473%
0.462% - 1.09%
0.000% - 0.618%
0.000% - 0.665%
0.000% - 0.000%
0.0959% - 0.357%
0.215% - 0.445%
0.486% - 1.04%
0.0650% - 0.564%
0.000% - 0.638%
0.000% - 0.000%
0.109% - 0.337%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.01 mg/L
1.38%
3.00%
1.18%
0.868%
0.242%
0.893%
1.09% - 1.67%
2.35% - 3.70%
0.550% - 1.84%
0.458% - 1.48%
0.000% - 0.812%
0.635% - 1.32%
1.14% - 1.63%
2.48% - 3.57%
0.675% - 1.75%
0.493% - 1.31%
0.000% - 0.812%
0.664% - 1.27%

Surface Water
<500
501 - 3,300
3,301 -10,000
10,001 -50,000
> 50,000
Total
0.000759
0.000997
0.000994
0.000763
0.000617
0.000856
0.0767%
0.124%
0.0535%
0.0221%
0.00112%
0.00667%
0.000% - 0.625%
0.000% - 0.637%
0.000% - 0.497%
0.000% - 0.358%
0.000% - 0.000%
0.000% - 0.0532%
0.000% - 0.545%
0.000% - 0.510%
0.000% - 0.394%
0.000% - 0.190%
0.000% - 0.000%
0.000% - 0.0335%
0.516%
0.691%
0.448%
0.313%
0.0333%
0.0866%
0.000% - 1.64%
0.000% - 1.62%
0.000% - 1.43%
0.000% - 1.16%
0.000% - 0.363%
0.00604% - 0.358%
0.000% - 1.45%
0.0714% - 1.51%
0.000% - 1.31%
0.000% - 0.975%
0.000% - 0.184%
0.00981% - 0.221%

All Systems - Combined
Ground & Surface Water
0.00132
0.101%
0.0447% - 0.159%
0.0479% - 0.149%
0.431%
0.298% - 0.649%
0.307% - 0.611%
        All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
   Table C.14.h.  Chromium - Population Served - National Best Estimate Including Estimate Range Based on
   Credible Bounds (Threshold = 0.1 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
300
1,200
0
0
0
2,800
0
0
0
0
0
0
3,000
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
1,700
9,400
17,100
0
0
15,900
0
0
0
0
0
0
16,900
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
1,400
7,100
10,300
0
0
13,500
0
0
0
0
0
0
14,300
   Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source
   water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground
   & Surface Water").
   An additional rounding convention is applied to population-served estimates.  The primary model estimation output is the number of systems. In a specific size
   category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional
   value. For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the
   population estimate is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).

   Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
   Table C.14.1. Chromium - Population Served - National Best Estimate Including Estimate Range Based on
   Credible Bounds (Threshold = 0.07 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
800
3,600
3,300
0
0
8,500
0
0
0
0
0
100
9,100
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
2,800
15,000
17,100
96,400
0
96,600
0
0
0
0
0
0
102,400
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
2,400
12,500
17,100
0
0
24,100
0
0
0
0
0
0
26,600
   Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source
   water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground
   & Surface Water").
   An additional rounding convention is applied to population-served estimates.  The primary model estimation output is the number of systems. In a specific size
   category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional
   value. For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the
   population estimate is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).

   Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
   Table C.14.J. Chromium - Population Served - National Best Estimate Including Estimate Range Based on
   Credible Bounds (Threshold = 0.05 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
2,100
10,600
5,500
10,000
0
21,200
0
0
0
0
0
400
22,900
using lower
95% CB
100
0
0
0
0
1,100
0
0
0
0
0
0
1,200
using upper
95% CB
5,000
27,200
27,300
96,400
0
111,600
0
2,100
0
0
0
2,300
119,000
using lower
90% CB
200
0
0
0
0
2,200
0
0
0
0
0
0
2,400
using upper
90% CB
4,500
25,000
19,600
96,400
0
107,300
0
0
0
0
0
800
114,100
   Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source
   water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground
   & Surface Water").
   An additional rounding convention is applied to population-served estimates.  The primary model estimation output is the number of systems. In a specific size
   category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional
   value. For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the
   population estimate is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).

   Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
   Table C.14.k.  Chromium - Population Served - National Best Estimate Including Estimate Range Based on
   Credible Bounds (Threshold = 0.02 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
21,000
115,800
39,000
79,400
0
195,500
200
3,500
3,300
0
0
8,500
215,600
using lower
95% CB
12,100
71,700
0
0
0
82,200
0
0
0
0
0
0
95,200
using upper
95% CB
30,800
169,700
85,100
162,500
0
306,000
1,800
17,900
30,300
78,200
0
67,700
338,900
using lower
90% CB
14,000
75,400
9,000
0
0
93,500
0
0
0
0
0
0
102,100
using upper
90% CB
28,900
161,000
77,700
156,000
0
288,700
1,600
14,400
24,000
41,600
0
42,700
316,500
   Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source
   water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground
   & Surface Water").
   An additional rounding convention is applied to population-served estimates.  The primary model estimation output is the number of systems. In a specific size
   category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional
   value. For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the
   population estimate is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).

   Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
   Table C.14.1. Chromium - Population Served - National Best Estimate Including Estimate Range Based on
   Credible Bounds (Threshold = 0.01 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
89,900
466,300
162,900
212,200
61,600
764,900
1,500
19,500
27,200
68,300
50,000
110,200
917,000
using lower
95% CB
70,800
364,900
75,700
112,000
0
544,200
0
0
0
0
0
7,700
634,100
using upper
95% CB
108,500
574,800
253,500
362,000
206,500
1,129,300
4,800
45,800
87,100
252,600
349,800
455,400
1,382,400
using lower
90% CB
74,100
385,400
92,900
120,500
0
568,800
0
2,000
0
0
0
12,500
653,300
using upper
90% CB
105,900
554,200
241,500
321,200
206,500
1,083,900
4,300
42,600
79,400
213,000
176,800
281,800
1,301,900
   Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source
   water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground
   & Surface Water").
   An additional rounding convention is applied to population-served estimates.  The primary model estimation output is the number of systems. In a specific size
   category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional
   value. For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the
   population estimate is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).

   Population estimates are rounded to the nearest hundred.

-------
   Occurrence Estimation Methodology and Findings
   Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.lS.a.  Cyanide - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on the Number of Systems
Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.00834
0.00793
0.00627
0.00707
0.00606
0.00804
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.2 mg/L
0.103%
0.0425%
0.0269%
0.0812%
0.00320%
0.0827%
0.0346% - 0.173%
0.000% - 0.158%
0.000% - 0.198%
0.000% - 0.242%
0.000% - 0.000%
0.0344% - 0.126%
0.0519% - 0.156%
0.000% - 0.106%
0.000% - 0.198%
0.000% - 0.242%
0.000% - 0.000%
0.0459% - 0.126%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.1 mg/L
0.493%
0.440%
0.311%
0.435%
0.0928%
0.463%
0.346% - 0.675%
0.158% - 0.738%
0.000% - 0.792%
0.000% - 0.966%
0.000% - 0.800%
0.321% - 0.596%
0.363% - 0.640%
0.211% - 0.686%
0.000% - 0.792%
0.242% - 0.725%
0.000% - 0.800%
0.356% - 0.585%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.05 mg/L
2.25%
2.33%
1.69%
1.84%
1.69%
2.21%
1.85% - 2.65%
1.74% - 2.95%
0.792% - 2.77%
0.966% - 2.90%
0.000% - 3.20%
1.93% - 2.51%
1.94% - 2.58%
1.85% - 2.85%
0.990% - 2.38%
0.966% - 2.66%
0.000% - 3.20%
1.97% - 2.48%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.00159
0.00227
0.00225
0.00289
0.00182
0.00223
0.00127%
0.0106%
0.000%
0.00106%
0.000%
0.00357%
0.000% - 0.000%
0.000% - 0.407%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.119%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.00255%
0.0740%
0.00263%
0.00952%
0.00417%
0.0252%
0.000% - 0.000%
0.000% - 0.407%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.119%
0.000% - 0.000%
0.000% - 0.407%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.119%
0.0242%
0.316%
0.0934%
0.278%
0.0708%
0.185%
0.000% - 0.637%
0.000% - 0.813%
0.000% - 0.658%
0.000% - 1.06%
0.000% - 1.04%
0.000% - 0.476%
0.000% - 0.000%
0.000% - 0.813%
0.000% - 0.658%
0.000% - 1.06%
0.000% - 1.04%
0.000% - 0.357%

All Systems - Combined
Ground & Surface Water
0.00753
0.0757%
0.0314% - 0.115%
0.0419% - 0.115%
0.424%
0.293% - 0.555%
0.324% - 0.534%
2.03%
1.77% - 2.32%
1.80% - 2.27%
All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.lS.b. Cyanide - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.2 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
45
5
1
1
0
49
0
0
0
0
0
1
49
using lower
95% CB
15
0
0
0
0
20
0
0
0
0
0
0
20
using upper
95% CB
75
19
5
3
0
75
0
7
0
0
0
7
75
using lower
90% CB
23
0
0
0
0
27
0
0
0
0
0
0
27
using upper
90% CB
68
13
5
o
6
0
75
0
0
0
0
0
0
75
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.lS.c.  Cyanide - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.1 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
215
53
7
5
0
275
0
1
0
0
0
1
276
using lower
95% CB
151
19
0
0
0
191
0
0
0
0
0
0
190
using upper
95% CB
294
90
19
11
2
355
0
7
0
0
0
7
361
using lower
90% CB
158
26
0
3
0
211
0
0
0
0
0
0
211
using upper
90% CB
278
83
19
9
2
348
0
7
0
0
0
7
347
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.lS.d. Cyanide - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.05 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
978
283
41
22
3
1,311
1
5
1
o
6
0
10
1,319
using lower
95% CB
806
212
19
11
0
1,145
0
0
0
0
0
0
1,150
using upper
95% CB
1,152
359
67
34
6
1,493
10
14
7
10
4
27
1,510
using lower
90% CB
843
224
24
11
0
1,173
0
0
0
0
0
0
1,170
using upper
90% CB
1,121
346
57
32
6
1,472
0
14
7
10
4
20
1,476
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
   Occurrence Estimation Methodology and Findings
   Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.lS.e.  Cyanide - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on Population Served
Source Water
Type
Ground Water
Population
Served
<500
501 -3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.00834
0.00793
0.00627
0.00707
0.00606
0.00804
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.2 mg/L
0.152%
0.0378%
0.0333%
0.0482%
0.00157%
0.0260%
0.0851% - 0.247%
0.000% - 0.159%
0.000% - 0.290%
0.000% - 0.320%
0.000% - 0.000%
0.00301% - 0.103%
0.0880% - 0.230%
0.000% - 0.141%
0.000% - 0.290%
0.000% - 0.205%
0.000% - 0.000%
0.00340% - 0.0741%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.1 mg/L
0.541%
0.395%
0.350%
0.307%
0.0536%
0.201%
0.340% - 0.760%
0.141% - 0.705%
0.000% - 0.977%
0.000% - 0.847%
0.000% - 0.531%
0.0680% - 0.488%
0.382% - 0.740%
0.178% - 0.652%
0.000% - 0.832%
0.121% - 0.730%
0.000% - 0.446%
0.0776% - 0.422%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.05 mg/L
2.31%
2.19%
1.80%
1.71%
0.905%
1.38%
1.83% - 2.81%
1.54% - 2.98%
0.755% - 3.00%
0.662% - 3.10%
0.000% - 2.37%
0.797% - 2.23%
1.91% - 2.74%
1.67% - 2.82%
1.04% - 2.70%
0.777% - 2.80%
0.000% - 2.06%
0.882% - 2.05%

Surface Water
<500
501 -3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.00159
0.00227
0.00225
0.00289
0.00182
0.00223
0.000%
0.00839%
0.000%
0.000725%
0.000%
0.000160%
0.000% - 0.000%
0.000% - 0.312%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.00317%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000978%
0.0579%
0.00173%
0.00610%
0.000542%
0.00173%
0.000% - 0.000%
0.000% - 0.312%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.00948%
0.000% - 0.000%
0.000% - 0.312%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.00317%
0.0272%
0.275%
0.0847%
0.215%
0.0165%
0.0412%
0.000% - 0.326%
0.000% - 0.771%
0.000% - 0.775%
0.000% - 0.946%
0.000% - 0.209%
0.000% - 0.194%
0.000% - 0.000%
0.000% - 0.771%
0.000% - 0.691%
0.000% - 0.861%
0.000% - 0.136%
0.000% - 0.161%

All Systems - Combined
Ground & Surface Water
0.00753
0.0110%
0.00128% - 0.0432%
0.00143% - 0.0310%
0.0849%
0.0294% - 0.204%
0.0332% - 0.177%
0.602%
0.350% - 0.949%
0.382% - 0.897%
All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.lS.f.  Cyanide - Population Served - National Best Estimate Including Estimate Range Based on Credible
Bounds (Threshold = 0.2 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
9,800
5,900
4,600
11,800
0
22,300
0
0
0
0
0
200
23,300
using lower
95% CB
5,500
0
0
0
0
2,600
0
0
0
0
0
0
2,700
using upper
95% CB
16,100
24,800
39,900
78,200
0
88,600
0
8,800
0
0
0
4,000
92,100
using lower
90% CB
5,700
0
0
0
0
2,900
0
0
0
0
0
0
3,100
using upper
90% CB
14,900
21,900
39,900
50,200
0
63,500
0
0
0
0
0
0
66,100
Estimates are generated separately for each level of aggregation.  Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.lS.g.  Cyanide - Population Served - National Best Estimate Including Estimate Range Based on Credible
Bounds (Threshold = 0.1 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
35,200
61,300
48,300
74,900
0
171,900
0
1,600
0
0
0
2,200
180,900
using lower
95% CB
22,100
21,900
0
0
0
58,200
0
0
0
0
0
0
62,600
using upper
95% CB
49,400
109,400
134,500
207,000
135,200
418,300
0
8,800
0
0
0
12,100
435,000
using lower
90% CB
24,800
27,600
0
29,600
0
66,500
0
0
0
0
0
0
70,700
using upper
90% CB
48,100
101,300
114,500
178,500
113,500
361,900
0
8,800
0
0
0
4,000
376,400
Estimates are generated separately for each level of aggregation.  Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.lS.h. Cyanide - Population Served - National Best Estimate Including Estimate Range Based on Credible
Bounds (Threshold = 0.05 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
150,300
340,500
248,400
417,700
230,200
1,183,300
100
7,700
5,200
47,000
0
52,400
1,281,200
using lower
95% CB
119,200
238,700
104,000
161,800
0
682,500
0
0
0
0
0
0
746,200
using upper
95% CB
182,700
462,300
413,400
758,200
601,700
1,914,100
1,000
21,700
47,100
206,700
201,100
247,000
2,022,300
using lower
90% CB
123,900
258,800
142,700
189,900
0
755,400
0
0
0
0
0
0
813,700
using upper
90% CB
178,100
438,300
371,400
683,400
523,400
1,753,900
0
21,700
42,000
188,200
130,600
205,400
1,910,000
Estimates are generated separately for each level of aggregation.  Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems.  In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
                Table C.16.a. 2,4-D - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on the Number of Systems
Source Water
Type
Ground Water
Population
Served
<500
501 -3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.00000220
0.00000480
0.00000554
0.00000270
0.00000256
0.00000299
Best Estimate
of Exceeding
Threshold
95% Credible
Interval
90%
Credible Interval
Threshold = 0.07 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.035 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

Surface Water
<500
501 -3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.0000290
0.0000378
0.0000219
0.0000126
0.0000271
0.0000263
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

All Systems - Combined
Ground & Surface Water
0.00000518
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%

Source Water
Type
Ground Water
Population
Served
<500
501 -3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.00000220
0.00000480
0.00000554
0.00000270
0.00000256
0.00000299
Best Estimate
of Exceeding
Threshold
95% Credible
Interval
90%
Credible Interval
Threshold = 0.0175 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0001 mg/L
0.0334%
0.188%
0.273%
0.0541%
0.0293%
0.0820%
0.000% - 0.0940%
0.0322% - 0.516%
0.000% - 0.710%
0.000% - 0.366%
0.000% - 0.667%
0.0211% - 0.183%
0.000% - 0.0836%
0.0322% - 0.451%
0.000% - 0.710%
0.000% - 0.183%
0.000% - 0.000%
0.0281% - 0.162%

Surface Water
<500
501 -3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.0000290
0.0000378
0.0000219
0.0000126
0.0000271
0.0000263
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
5.59%
8.05%
3.54%
1.41%
5.11%
4.93%
1.77% - 11.3%
3.76% - 13.2%
1.07% - 7.14%
0.000% - 3.66%
1.28% - 10.3%
2.99% - 7.54%
2.12% - 10.6%
4.46% - 12.2%
1.43% - 6.79%
0.305% - 3.35%
1.92% - 8.97%
3.26% - 7.13%

All Systems - Combined
Ground & Surface Water
0.00000518
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.537%
0.332% - 0.854%
0.357% - 0.797%
                All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.16.b. 2,4-D - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.07 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
    Estimates are generated separately for each level of aggregation.  Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.16.C. 2,4-D - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.035 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
    Estimates are generated separately for each level of aggregation.  Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.16.d. 2,4-D - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.0175 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.16.e. 2,4-D - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.0001 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
15
23
7
1
0
49
86
137
36
13
21
276
349
using lower
95% CB
0
4
0
0
0
13
27
64
11
0
5
167
216
using upper
95% CB
41
63
17
4
1
109
174
224
72
34
41
421
555
using lower
90% CB
0
4
0
0
0
17
33
76
14
3
8
182
232
using upper
90% CB
36
55
17
2
0
96
163
208
69
31
36
398
518
    Estimates are generated separately for each level of aggregation.  Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
              Table C.16.f.  2,4-D - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on Population Served
Source Water
Type
Ground Water
Population
Served
<500
501 -3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.00000220
0.00000480
0.00000554
0.00000270
0.00000256
0.00000299
Best Estimate
of Exceeding
Threshold
95% Credible
Interval
90%
Credible Interval
Threshold = 0.07 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.035 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

Surface Water
<500
501 -3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.0000290
0.0000378
0.0000219
0.0000126
0.0000271
0.0000263
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

All Systems - Combined
Ground & Surface Water
0.00000518
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%

Source Water
Type
Ground Water
Population
Served
<500
501 -3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.00000220
0.00000480
0.00000554
0.00000270
0.00000256
0.00000299
Best Estimate
of Exceeding
Threshold
95% Credible
Interval
90%
Credible Interval
Threshold = 0.0175 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0001 mg/L
0.0318%
0.193%
0.275%
0.0554%
0.0289%
0.0817%
0.000% - 0.101%
0.0132% - 0.508%
0.000% - 0.780%
0.000% - 0.356%
0.000% - 0.370%
0.00651% - 0.315%
0.000% - 0.0859%
0.0231% - 0.440%
0.000% - 0.685%
0.000% - 0.280%
0.000% - 0.000%
0.0115% - 0.192%

Surface Water
<500
501 -3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.0000290
0.0000378
0.0000219
0.0000126
0.0000271
0.0000263
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
5.80%
7.69%
3.70%
1.50%
3.45%
3.28%
1.39% - 12.7%
3.39% - 13.1%
1.23% - 7.96%
0.000% - 3.71%
0.399% - 16.4%
0.622% - 14.2%
1.86% - 11.4%
4.26% - 11.8%
1.53% - 6.96%
0.136% - 3.41%
0.578% - 12.7%
0.840% - 11.1%

All Systems - Combined
Ground & Surface Water
0.00000518
0.000%
0.000% - 0.000%
0.000% - 0.000%
2.04%
0.408% - 8.70%
0.551% - 6.86%
              All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.16.g.  2,4-D - Population Served - National Best Estimate Including Estimate Range Based on Credible
Bounds (Threshold = 0.07 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.16.h. 2,4-D - Population Served - National Best Estimate Including Estimate Range Based on Credible
Bounds (Threshold = 0.035 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
Estimates are generated separately for each level of aggregation.  Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.16.1.  2,4-D - Population Served - National Best Estimate Including Estimate Range Based on Credible
Bounds (Threshold = 0.0175 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
Estimates are generated separately for each level of aggregation.  Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.16.J.  2,4-D - Population Served - National Best Estimate Including Estimate Range Based on Credible
Bounds (Threshold = 0.0001 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
2,100
29,900
37,800
13,500
0
70,000
17,000
216,600
225,400
327,800
3,325,500
4,180,100
4,336,800
using lower
95% CB
0
2,100
0
0
0
5,600
4,100
95,600
74,900
0
383,700
791,700
869,100
using upper
95% CB
6,600
78,800
107,300
86,900
94,200
269,700
37,100
368,400
484,600
810,900
15,809,000
18,105,800
18,527,500
using lower
90% CB
0
3,600
0
0
0
9,900
5,400
120,100
93,100
29,800
556,200
1,069,500
1,174,500
using upper
90% CB
5,600
68,300
94,300
68,500
0
164,700
33,300
332,900
423,300
745,200
12,198,500
14,120,500
14,616,600
Estimates are generated separately for each level of aggregation.  Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
                Table C.17.a. Dalapon - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on the Number of Systems
Source Water
Type
Ground Water
Population
Served
<500
501 -3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (nig/L)
0.0000287
0.0000386
0.0000300
0.0000251
0.0000366
0.0000311

Surface Water
<500
501 -3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.0000788
0.000211
0.0000791
0.0000899
0.0000337
0.000113

All Systems - Combined
Ground & Surface Water
0.0000398
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.2 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.1 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000%
0.00116%
0.000%
0.000%
0.000%
0.000325%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

0.000%
0.000% - 0.000%
0.000% - 0.000%
0.0000344%
0.000% - 0.000%
0.000% - 0.000%

Source Water
Type
Ground Water
Population
Served
<500
501 -3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (nig/L)
0.0000287
0.0000386
0.0000300
0.0000251
0.0000366
0.0000311
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.05 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.001 mg/L
0.188%
0.289%
0.236%
0.215%
0.329%
0.219%
0.0911% - 0.319%
0.0807% - 0.605%
0.000% - 0.550%
0.000% - 0.615%
0.000% - 1.47%
0.125% - 0.346%
0.0911% - 0.304%
0.121% - 0.525%
0.000% - 0.550%
0.000% - 0.410%
0.000% - 1.47%
0.134% - 0.317%

Surface Water
<500
501 -3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.0000788
0.000211
0.0000791
0.0000899
0.0000337
0.000113
0.000%
0.00116%
0.000%
0.000%
0.000%
0.000325%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
1.06%
4.12%
1.06%
1.38%
0.332%
1.91%
0.000% - 2.78%
1.74% - 6.96%
0.000% - 2.48%
0.692% - 2.77%
0.000% - 1.44%
1.14% - 2.76%
0.000% - 2.78%
2.03% - 6.38%
0.000% - 2.07%
0.692% - 2.42%
0.000% - 1.44%
1.22% - 2.68%

All Systems - Combined
Ground & Surface Water
0.0000398
0.0000344%
0.000% - 0.000%
0.000% - 0.000%
0.397%
0.275% - 0.533%
0.301% - 0.515%
                All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.lT.b. Dalapon - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.2 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.17.C.  Dalapon - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.1 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.17.d. Dalapon - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.05 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
    Table C.lT.e.  Dalapon - Systems - National Best Estimate Including Estimate Range Based on Credible
    Bounds (Threshold = 0.001 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
82
35
6
o
5
i
130
16
70
11
13
1
107
258
using lower
95% CB
40
10
0
0
0
74
0
30
0
6
0
64
179
using upper
95% CB
139
74
13
7
3
205
43
119
25
26
6
154
346
using lower
90% CB
40
15
0
0
0
80
0
35
0
6
0
68
195
using upper
90% CB
132
64
13
5
3
188
43
109
21
23
6
150
335
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C. Stage 2 Analytical Findings
Six-Year Review
                 Table C.17.f. Dalapon - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on Population Served
Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.0000287
0.0000386
0.0000300
0.0000251
0.0000366
0.0000311

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.0000788
0.000211
0.0000791
0.0000899
0.0000337
0.000113

All Systems - Combined
Ground & Surface Water
0.0000398
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.2 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.1 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000%
0.00162%
0.000%
0.000%
0.000%
0.0000182%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%

0.000%
0.000% - 0.000%
0.000% - 0.000%
0.0000107%
0.000% - 0.000%
0.000% - 0.000%

Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.0000287
0.0000386
0.0000300
0.0000251
0.0000366
0.0000311
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.05 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.001 mg/L
0.244%
0.308%
0.202%
0.270%
0.214%
0.238%
0.0953% - 0.428%
0.0872% - 0.631%
0.000% - 0.549%
0.000% - 0.712%
0.000% - 0.801%
0.0343% - 0.524%
0.116% - 0.391%
0.0971% - 0.566%
0.000% - 0.459%
0.000% - 0.573%
0.000% - 0.736%
0.0495% - 0.505%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.0000788
0.000211
0.0000791
0.0000899
0.0000337
0.000113
0.000%
0.00162%
0.000%
0.000%
0.000%
0.0000182%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
1.39%
4.17%
1.10%
1.40%
0.292%
0.497%
0.000% - 3.87%
1.64% - 7.18%
0.000% - 2.70%
0.507% - 2.79%
0.000% - 1.05%
0.144% - 1.23%
0.000% - 3.44%
2.07% - 6.59%
0.000% - 2.34%
0.624% - 2.49%
0.000% - 0.991%
0.162% - 1.11%

All Systems - Combined
Ground & Surface Water
0.0000398
0.0000107%
0.000% - 0.000%
0.000% - 0.000%
0.390%
0.144% - 0.860%
0.155% - 0.794%
                All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.17.g.  Dalapon - Population Served - National Best Estimate Including Estimate Range Based on Credible
Bounds (Threshold = 0.2 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
Estimates are generated separately for each level of aggregation.  Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems.  In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.lT.h. Dalapon - Population Served - National Best Estimate Including Estimate Range Based on Credible
Bounds (Threshold = 0.1 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
Estimates are generated separately for each level of aggregation.  Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems. In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.17.1. Dalapon - Population Served - National Best Estimate Including Estimate Range Based on Credible
Bounds (Threshold = 0.05 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
Estimates are generated separately for each level of aggregation.  Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems.  In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
Table C.17.J.  Dalapon - Population Served - National Best Estimate Including Estimate Range Based on Credible
Bounds (Threshold = 0.001 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
15,800
47,900
27,800
66,000
54,500
204,100
4,100
117,400
66,700
305,700
281,000
632,800
831,600
using lower
95% CB
6,200
13,500
0
0
0
29,400
0
46,100
0
110,900
0
183,200
306,100
using upper
95% CB
27,800
98,000
75,500
174,000
203,700
449,300
11,300
202,300
164,200
609,500
1,008,000
1,564,800
1,832,500
using lower
90% CB
7,500
15,100
0
0
0
42,400
0
58,300
0
136,400
0
206,700
330,600
using upper
90% CB
25,400
87,900
63,100
140,100
187,400
432,300
10,100
185,800
142,400
545,000
954,000
1,414,600
1,691,500
Estimates are generated separately for each level of aggregation.  Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground & Surface
Water").

An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems.  In a specific size category,
model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value. For this
reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate is greater
than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
Population estimates are rounded to the nearest hundred.

-------
    Occurrence Estimation Methodology and Findings
    Appendix C. Stage 2 Analytical Findings
                                                                                                                                                                                 Six-Year Review
Table C.lS.a.  l,2-Dibromo-3-chloropropane - 16 Cross-Section States - Mean Concentration, Best Estimate, Credible Intervals Based on the Number of Systems
Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.000288
0.000182
0.0000481
0.0000971
0.000137
0.000241
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0002 mg/L
1.24%
1.39%
1.92%
2.74%
3.27%
1.40%
0.994% - 1.51%
1.03% - 1.83%
1.42% - 2.72%
2.03% - 3.51%
2.11% - 4.93%
1.19% - 1.61%
1.02% - 1.48%
1.10% - 1.76%
1.42% - 2.59%
2.22% - 3.33%
2.11% - 4.23%
1.22% - 1.59%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0001 mg/L
1.72%
1.89%
2.54%
3.63%
4.00%
1.91%
1.39% - 2.08%
1.41% - 2.52%
1.81% - 3.62%
2.77% - 4.44%
2.82% - 5.63%
1.65% - 2.18%
1.46% - 2.01%
1.48% - 2.41%
1.94% - 3.36%
2.96% - 4.25%
2.82% - 5.63%
1.68% - 2.15%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.0000653
0.00000502
0.0000239
0.0000133
0.000739
0.000111
2.25%
0.251%
1.63%
1.18%
4.83%
1.64%
0.000% - 4.71%
0.000% - 1.07%
0.500% - 3.50%
0.389% - 2.34%
3.94% - 6.30%
1.06% - 2.32%
0.588% - 4.71%
0.000% - 1.07%
0.500% - 3.00%
0.389% - 2.34%
3.94% - 6.30%
1.16% - 2.22%
3.57%
0.490%
2.32%
1.93%
5.53%
2.33%
0.588% - 7.06%
0.000% - 1.79%
1.00% - 4.00%
0.778% - 3.50%
3.94% - 7.87%
1.55% - 3.19%
1.18% - 6.47%
0.000% - 1.43%
1.00% - 4.00%
0.778% - 3.50%
3.94% - 7.87%
1.64% - 3.00%

All Systems - Combined
Ground & Surface Water
0.000231
1.41%
1.22% - 1.65%
1.25% - 1.60%
1.94%
1.70% - 2.21%
1.72% - 2.17%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.00002 mg/L
3.72%
3.92%
5.03%
6.21%
6.20%
3.97%
3.10% - 4.27%
3.03% - 5.41%
3.49% - 6.73%
4.81% - 7.76%
4.23% - 9.16%
3.41% - 4.52%
3.20% - 4.20%
3.10% - 5.24%
3.88% - 6.34%
4.99% - 7.58%
4.23% - 8.45%
3.52% - 4.44%

8.89%
1.76%
4.91%
6.16%
9.29%
5.56%
3.53% - 14.7%
0.357% - 4.29%
2.00% - 8.00%
3.11% - 9.34%
5.51% - 13.4%
4.06% - 7.06%
4.12% - 13.5%
0.357% - 3.57%
2.50% - 7.50%
3.89% - 8.56%
6.30% - 12.6%
4.45% - 6.87%

4.09%
3.53% - 4.63%
3.66% - 4.55%
All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.lS.b.  l,2-Dibromo-3-chloropropane - Systems - National Best Estimate Including Estimate Range
    Based on Credible Bounds (Threshold = 0.0002 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
539
169
46
33
6
830
35
4
17
11
19
92
920
using lower
95% CB
432
126
34
24
4
709
0
0
5
4
16
59
792
using upper
95% CB
659
222
65
42
9
959
72
18
35
22
25
130
1,070
using lower
90% CB
442
134
34
26
4
726
9
0
5
4
16
65
810
using upper
90% CB
644
214
62
40
8
946
72
18
30
22
25
124
1,042
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.lS.c.  l,2-Dibromo-3-chloropropane - Systems - National Best Estimate Including Estimate Range
    Based on Credible Bounds (Threshold = 0.0001 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
749
230
61
43
8
1,136
55
8
23
18
22
130
1,263
using lower
95% CB
603
172
44
o o
JJ
5
978
9
0
10
7
16
86
1,102
using upper
95% CB
905
306
87
53
11
1,298
108
30
40
33
32
178
1,436
using lower
90% CB
633
180
47
35
5
1,001
18
0
10
7
16
92
1,120
using upper
90% CB
875
293
81
51
11
1,275
99
24
40
33
32
168
1,408
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.lS.d.  l,2-Dibromo-3-chloropropane - Systems - National Best Estimate Including Estimate Range
    Based on Credible Bounds (Threshold = 0.00002 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
1,616
477
121
74
12
2,360
137
30
50
57
37
311
2,658
using lower
95% CB
1,348
369
84
57
8
2,025
54
6
20
29
22
227
2,297
using upper
95% CB
1,855
658
162
92
17
2,687
226
73
81
87
54
395
3,010
using lower
90% CB
1,393
377
93
59
8
2,093
63
6
25
36
25
249
2,380
using upper
90% CB
1,825
637
152
90
16
2,641
208
61
76
80
51
384
2,960
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
    Occurrence Estimation Methodology and Findings
    Appendix C. Stage 2 Analytical Findings
                                                                                                                                                                                 Six-Year Review
Table C.lS.e.  l,2-Dibromo-3-chloropropane - 16 Cross-Section States - Mean Concentration, Best Estimate, Credible Intervals Based on the Population Served
Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.000288
0.000182
0.0000481
0.0000971
0.000137
0.000241
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0002 mg/L
1.21%
1.48%
2.21%
2.82%
4.41%
3.27%
0.905% - 1.55%
1.11% - 1.96%
1.63% - 3.02%
1.94% - 3.80%
3.48% - 6.41%
2.71% - 4.20%
0.940% - 1.49%
1.17% - 1.88%
1.72% - 2.90%
2.09% - 3.62%
3.48% - 5.62%
2.77% - 3.80%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0001 mg/L
1.70%
1.97%
2.82%
3.94%
5.04%
4.03%
1.34% - 2.13%
1.52% - 2.63%
2.10% - 3.89%
3.12% - 4.78%
3.97% - 8.17%
3.40% - 5.38%
1.39% - 2.03%
1.56% - 2.49%
2.16% - 3.64%
3.27% - 4.63%
3.97% - 6.93%
3.45% - 4.96%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.00002 mg/L
3.68%
3.99%
5.25%
6.35%
7.05%
6.21%
2.99% - 4.35%
3.07% - 5.54%
3.78% - 6.85%
4.93% - 7.93%
4.57% - 15.9%
4.92% - 9.98%
3.08% - 4.24%
3.14% - 5.30%
4.03% - 6.64%
5.10% - 7.69%
4.84% - 14.7%
5.06% - 9.46%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.0000653
0.00000502
0.0000239
0.0000133
0.000739
0.000111
2.31%
0.255%
1.83%
0.910%
2.26%
2.07%
0.000% - 5.69%
0.000% - 1.20%
0.330% - 3.59%
0.197% - 2.14%
1.71% - 4.49%
1.51% - 3.97%
0.0971% - 5.18%
0.000% - 0.926%
0.596% - 3.29%
0.197% - 1.97%
1.71% - 4.08%
1.52% - 3.56%
3.61%
0.503%
2.55%
1.63%
2.75%
2.58%
0.410% - 8.32%
0.000% - 1.76%
1.10% - 4.41%
0.409% - 3.25%
1.71% - 5.90%
1.60% - 5.24%
0.771% - 7.16%
0.000% - 1.59%
1.10% - 4.16%
0.547% - 3.05%
1.71% - 4.82%
1.66% - 4.33%
8.87%
1.77%
5.21%
5.81%
5.37%
5.39%
3.17% - 15.2%
0.206% - 4.12%
2.41% - 8.38%
3.03% - 8.95%
2.24% - 15.7%
2.74% - 14.2%
3.84% - 14.5%
0.374% - 3.66%
2.98% - 7.87%
3.45% - 8.29%
2.55% - 10.9%
2.97% - 9.85%

All Systems - Combined
Ground & Surface Water
0.000231
2.60%
2.11% - 3.77%
2.16% - 3.46%
3.22%
2.49% - 4.96%
2.53% - 4.60%
5.75%
3.99% - 10.4%
4.18% - 8.84%
All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
  Table C.lS.f.  l,2-Dibromo-3-chloropropane - Population Served - National Best Estimate Including Estimate
  Range Based on Credible Bounds (Threshold = 0.0002 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
78,699
229,033
304,737
688,287
1,121,018
2,799,221
6,761
7,173
111,223
198,747
2,179,751
2,630,565
5,531,822
using lower
95% CB
58,813
172,357
223,767
473,198
884,907
2,319,404
0
0
20,066
42,984
1,642,516
1,920,083
4,500,863
using upper
95% CB
100,730
304,653
416,276
929,041
1,631,200
3,600,345
16,645
33,936
218,552
466,547
4,323,879
5,052,315
8,030,408
using lower
90% CB
61,114
182,140
236,574
511,083
884,907
2,371,669
284
0
36,233
42,984
1,642,516
1,939,182
4,594,586
using upper
90% CB
96,701
291,765
399,890
885,779
1,428,878
3,251,620
15,136
26,106
200,299
430,272
3,928,173
4,530,276
7,376,473
  Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
  level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground &
  Surface Water").
  An additional rounding convention is applied to population-served estimates.  The primary model estimation output is the number of systems.  In a specific size
  category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value.
  For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate
  is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).

  Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
                                                                   Six-Year Review
  Table C.lS.g.  l,2-Dibromo-3-chloropropane -
  Range Based on Credible Bounds (Threshold
Population Served - National Best Estimate Including Estimate
 0.0001 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
110,543
305,740
388,185
963,505
1,283,344
3,454,686
10,551
14,186
155,152
355,319
2,646,703
3,290,116
6,867,384
using lower
95% CB
86,953
235,710
288,488
762,591
1,009,323
2,912,321
1,198
0
66,807
89,354
1,642,516
2,034,677
5,299,644
using upper
95% CB
138,487
408,223
535,803
1,168,818
2,077,419
4,607,962
24,330
49,551
268,018
710,856
5,680,446
6,674,454
10,571,596
using lower
90% CB
90,137
241,921
297,439
798,032
1,009,323
2,952,591
2,254
0
66,807
119,423
1,642,516
2,112,346
5,382,717
using upper
90% CB
131,924
386,018
501,652
1,132,643
1,764,216
4,246,385
20,923
44,844
253,111
667,151
4,635,822
5,513,237
9,802,637
  Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
  level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground &
  Surface Water").
  An additional rounding convention is applied to population-served estimates.  The primary model estimation output is the number of systems.  In a specific size
  category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value.
  For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate
  is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).

  Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
                                                                   Six-Year Review
  Table C.lS.h.  l,2-Dibromo-3-chloropropane -
  Range Based on Credible Bounds (Threshold
Population Served - National Best Estimate Including Estimate
 0.00002 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
239,347
618,933
722,252
1,552,313
1,793,221
5,321,690
25,944
50,002
316,754
1,268,964
5,173,057
6,861,624
12,252,231
using lower
95% CB
193,986
476,700
519,829
1,205,725
1,163,762
4,212,969
9,264
5,798
146,878
662,562
2,157,607
3,486,199
8,507,547
using upper
95% CB
282,629
860,699
943,679
1,937,764
4,047,978
8,546,749
44,507
116,210
509,569
1,955,783
15,086,881
18,029,430
22,216,753
using lower
90% CB
200,030
488,035
555,356
1,245,566
1,230,423
4,338,921
11,214
10,539
181,194
753,031
2,451,257
3,777,777
8,903,742
using upper
90% CB
275,740
822,656
914,761
1,878,370
3,729,941
8,104,632
42,285
103,216
479,086
1,811,339
10,475,128
12,542,932
18,829,923
  Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
  level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground &
  Surface Water").
  An additional rounding convention is applied to population-served estimates.  The primary model estimation output is the number of systems. In a specific size
  category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value.
  For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate
  is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).

  Population estimates are rounded to the nearest hundred.

-------
    Occurrence Estimation Methodology and Findings
    Appendix C. Stage 2 Analytical Findings
                                                                                                                                                                                  Six-Year Review
Table C.19.a.  1,4-Dichlorobenzene - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on the Number of Systems
Source Water
Type
Ground Water
Population
Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.0000239
0.0000209
0.0000183
0.0000223
0.0000302
0.0000229
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.075 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.005 mg/L
0.000400%
0.000%
0.000%
0.000%
0.000%
0.000273%
0.000% - 0.00833%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.00568%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0005 mg/L
0.153%
0.0356%
0.0129%
0.118%
0.0268%
0.117%
0.100% - 0.225%
0.000% - 0.0995%
0.000% - 0.101%
0.000% - 0.400%
0.000% - 1.03%
0.0738% - 0.170%
0.108% - 0.208%
0.000% - 0.0746%
0.000% - 0.101%
0.000% - 0.400%
0.000% - 0.000%
0.0795% - 0.153%

Surface Water
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
Total
0.0000195
0.0000301
0.0000277
0.0000181
0.0000364
0.0000252
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.0216%
0.197%
0.0233%
0.0128%
0.0692%
0.0746%
0.000% - 0.338%
0.000% - 0.514%
0.000% - 0.388%
0.000% - 0.338%
0.000% - 0.935%
0.000% - 0.223%
0.000% - 0.338%
0.000% - 0.514%
0.000% - 0.388%
0.000% - 0.000%
0.000% - 0.935%
0.000% - 0.149%

All Systems - Combined
Ground & Surface Water
0.0000231
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000253%
0.000% - 0.00527%
0.000% - 0.000%
0.114%
0.0738% - 0.164%
0.0791% - 0.153%
All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.19.b. 1,4-Dichlorobenzene - Systems - National Best Estimate Including Estimate Range Based on
    Credible Bounds (Threshold = 0.075 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.19.C.  1,4-Dichlorobenzene - Systems - National Best Estimate Including Estimate Range Based on
    Credible Bounds (Threshold = 0.005 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
4
0
0
0
0
3
0
0
0
0
0
0
3
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
    Table C.19.d. 1,4-Dichlorobenzene - Systems - National Best Estimate Including Estimate Range Based on
    Credible Bounds (Threshold = 0.0005 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001-50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Systems Exceeding the Specified Threshold
using best estimate
66
4
0
1
0
69
1
3
0
0
0
4
74
using lower
95% CB
43
0
0
0
0
44
0
0
0
0
0
0
48
using upper
95% CB
98
12
2
5
2
101
5
9
4
3
4
12
106
using lower
90% CB
47
0
0
0
0
47
0
0
0
0
0
0
51
using upper
90% CB
91
9
2
5
0
91
5
9
4
0
4
8
99
    Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the
    source water level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems
    ("Total Ground & Surface Water").
    System estimates are rounded to the nearest whole number.

-------
  Occurrence Estimation Methodology and Findings
  Appendix C. Stage 2 Analytical Findings
                                                                                                                                                                                       Six-Year Review
Table C.19.e.  1,4-Dichlorobenzene - 16 Cross-Section States - Mean Concentration, Best Estimate, and Credible Intervals Based on Population Served
Source Water
Type
Ground Water
Population
Served
<500
501 - 3,300
3,301 - 10,000
10,001 -50,000
> 50,000
Total
Mean
Concentration
Value (mg/L)
0.0000239
0.0000209
0.0000183
0.0000223
0.0000302
0.0000229
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.075 mg/L
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0050 mg/L
0.0000838%
0.000%
0.000%
0.000%
0.000%
0.00000416%
0.000% - 0.00139%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.0000691%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
Best Estimate
of Exceeding
Threshold
95%
Credible Interval
90%
Credible Interval
Threshold = 0.0005 mg/L
0.149%
0.0341%
0.0114%
0.107%
0.0168%
0.0505%
0.0912% - 0.221%
0.000% - 0.119%
0.000% - 0.121%
0.000% - 0.454%
0.000% - 0.382%
0.00580% - 0.187%
0.103% - 0.209%
0.000% - 0.103%
0.000% - 0.0780%
0.000% - 0.372%
0.000% - 0.000%
0.00709% - 0.143%

Surface Water
<500
501 - 3,300
3,301 - 10,000
10,001 -50,000
> 50,000
Total
0.0000195
0.0000301
0.0000277
0.0000181
0.0000364
0.0000252
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.000% - 0.000%
0.0189%
0.162%
0.0237%
0.0107%
0.0258%
0.0255%
0.000% - 0.377%
0.000% - 0.529%
0.000% - 0.442%
0.000% - 0.207%
0.000% - 0.229%
0.000% - 0.193%
0.000% - 0.0755%
0.000% - 0.443%
0.000% - 0.257%
0.000% - 0.000%
0.000% - 0.229%
0.000% - 0.177%

All Systems - Combined
Ground & Surface Water
0.0000231
0.000%
0.000% - 0.000%
0.000% - 0.000%
0.00000206%
0.000% - 0.0000343%
0.000% - 0.000%
0.0379%
0.00390% - 0.167%
0.00456% - 0.119%
All mean concentration and percentage estimates are expressed to three significant figures.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
  Table C.19.f.  1,4-Dichlorobenzene - Population Served - National Best Estimate Including Estimate Range
  Based on Credible Bounds (Threshold = 0.075 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
  Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
  level of aggregation, and estimates for the source water strata ("GW Total" and "SW Total") will not add to the total estimated for all systems ("Total Ground &
  Surface Water").
  An additional rounding convention is applied to population-served estimates. The primary model estimation output is the number of systems.  In a specific size
  category, model output can be a fraction of a system and therefore, the raw model output for the associated population-served estimate can also be a fractional value.
  For this reason, fractional population-served estimates are rounded up to the value of the lower bound of the population-served size category if the population estimate
  is greater than one-half the value of the lower bound (e.g. 1,651 is rounded up to 3,300 for the 3,301 to 10,000 size category).
  Population estimates are rounded to the nearest hundred.

-------
Occurrence Estimation Methodology and Findings
Appendix C.  Stage 2 Analytical Findings
Six-Year Review
  Table C.19.g.  1,4-Dichlorobenzene - Population Served - National Best Estimate Including Estimate Range
  Based on Credible Bounds (Threshold = 0.005 mg/L)
Source Water Type
Ground Water
Surface Water
Population Served
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
GW Total
<500
501-3,300
3,301 - 10,000
10,001 - 50,000
> 50,000
SW Total
Total Ground & Surface Water
National Estimate of Population Served by Systems Exceeding the Specified Threshold
using best estimate
0
0
0
0
0
0
0
0
0
0
0
0
0
using lower
95% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
95% CB
<100
0
0
0
0
<100
0
0
0
0
0
0
<100
using lower
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
using upper
90% CB
0
0
0
0
0
0
0
0
0
0
0
0
0
  Estimates are generated separately for each level of aggregation. Therefore, estimates for the individual size stratum will not add to estimated totals at the source water
  level of aggregation, and estimates for the source water strata ("GW Total" and "S