Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water


vvEPA

United States
Environmental Protection
Agency

INVENTORY OF
SITES WITH
THE POTENTIAL
TO RELEASE
CONTAMINANTS
TO SOURCES OF
DRINKING WATER

Office of Water	EPA 817-R-23-001	August 2023

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Disclaimer

The Water Infrastructure and Cyber Resilience Division of the Office of Groundwater and Drinking Water
has reviewed and approved the report "Inventory of Sites with the Potential to Release Contaminants to
Sources of Drinking Water" for publication. This document is intended for use by the drinking water
sector to better understand the risk of potential threats to sources of drinking water. It may provide
information useful for conducting risk and resilience assessments, as required under America's Water
Infrastructure Act of 2018.

This report is new. It does not modify or replace any previously published EPA documents. This
document does not impose legally binding requirements on any party. The information in this document
is intended solely as an information resource and does not imply any requirements. Neither the U.S.
Government nor any of its employees, contractors or their employees make any warranty, expressed or
implied, or assumes any legal liability or responsibility for any third party's use of any information,
product, or process discussed in this document, or represents that its use by such party would not
infringe on privately owned rights. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.

Questions concerning this document should be addressed to Steve Allgeier, allgeier.steveffiepa.gov.
513-569-7131.

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Acknowledgements

The document was developed by the U.S. EPA Water Infrastructure and Cyber Resilience Division, with
support provided under U.S. EPA contract EP-C-15-022. The following individuals contributed to the
development of this document:

•	Emily Smith, Corona Environmental Consulting

•	Margaret Kearns, Corona Environmental Consulting

•	Monica Weisenbach, Corona Environmental Consulting

Peer review of this document was provided by the following individuals:

•	April Byrne, U.S. EPA, Office of Groundwater and Drinking Water, Drinking Water Capacity and
Compliance Assistance Division

•	Chandler Klawitter, U.S. EPA, Office of Groundwater and Drinking Water, Drinking Water
Capacity and Compliance Assistance Division

•	Cary McElhinney, U.S. EPA, Region 5

•	Richard Stuck, Greater Cincinnati Water Works

•	Terrell Tiendrebeogo, U.S. EPA, Office of Groundwater and Drinking Water, Drinking Water
Capacity and Compliance Assistance Division

ii

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Table of Contents

DISCLAIMER	 I

ACKNOWLEDGEMENTS	 II

TABLE OF CONTENTS	 Ill

LIST OF FIGURES	IV

LIST OF TABLES	V

ABBREVIATIONS	VI

SECTION 1.0: INTRODUCTION	1

1.1	Introduction	1

1.2	Previous Efforts	2

1.3	Objectives	4

1.4	Scope	4

SECTION 2.0: METHODOLOGY	5

2.1	Study Area	5

2.2	Zones of Concern	5

2.3	Threat Type and Contaminant Class Definitions	9

2.4	Information Resources for Building SWCTIs	11

2.5	Data Processing	11

2.6	Limitations of the Methodology	12

SECTION 3.0: RESULTS AND DISCUSSION	13

3.1	Occurrence ofThreats byThreatType	13

3.2	Occurrence ofThreats by Contaminant Classification	16

3.3	Occurrence of CWA-HS Threats	21

3.4	Threat Occurrence by ZOC	24

3.5	Evaluation of Information Resources	32

SECTION 4.0: SUMMARY AND CONCLUSIONS	36

SECTION 5.0: RECOMMENDATIONS	38

REFERENCES	39

GLOSSARY	45

Appendix A: Unit Conversion Multipliers	46

Appendix B: Supplemental Analyses of Threat Occurrence in Specific ZOCs	47

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List of Figures

Figure 1. Example of a Site with Multiple Threats	

Figure 2. Example of NHD Flowline and Waterbody Representations	

Figure 3. Example of a Surface Water Zone of Concern	

Figure 4. Example of Groundwater Zones of Concern	

Figure 5. Threat Type Percentages for all Ten States	1

Figure 6. Total GW and SW Threat Counts per State	1

Figure 7. Percentage of Threats Located Inside and Outside of ESRI Industrial Areas	1

Figure 8. Total Number of Threats and Average Volume for Each Contaminant Class	1

Figure 9. Total Number of Threats and Average Volume for Each CWA-HS Contaminant Class	2

Figure 10. Geographic Distribution of CWA-HS Threats and Releases	2

Figure 11. Example of Overlapping SW ZOCs	2

Figure 12. Example of Overlapping GW ZOCs	2

Figure 13. Total and Average ZOC Threat Count in Each State	2

Figure 14. Geographic Distribution ofSW ZOCs Containing Threat Counts Within the Indicated Range	2

Figure 15. Geographic Distribution of GW ZOCs Containing Threat Counts Within the Indicated Range	2

Figure 16. Percentage ofSW and GWZOCs Containing "n"TotalThreats Within the Indicated Range	2

Figure 17. Correlation between Number of Threats and Number of Releases in SW ZOCs	3

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List of Tables

Table 1. Statistics for SW ZOC Areas, per State 8

Table 2. Threat Types used to Classify Sites 9

Table 3. Contaminant Classes and Most Common Materials 10

Table 4. Excluded Material Categories and Examples 10

Table 5. ThreatType Coverage byState and National Information Resources 11

Table 6. ThreatType Counts for allTen States 13

Table 7. Total Number of Threats in Each Contaminant Class byState 17

Table 8. Total Number of Threats Containing a Volume within the Indicated Range for Each Contaminant Class 18

Table 9. Most Commonly Occurring Material in each Contaminant Class 18

Table 10. Ten Most Commonly Occurring Materials in the Organic Chemical Class 19

Table 11. Ten Most Commonly Occurring Materials in the Inorganic Chemical Class 19

Table 12. Ten Most Commonly Occurring Materials Across All Contaminant Classes 20

Table 13. Total Number of CWA-HS Threats for Each Contaminant Class byState 22

Table 14. Total Number of CWA-HS Threats Containing a Volume within the Indicated Range for Each Contaminant

Class 22

Table 15. Ten Most Commonly Occurring CWA-HS Materials in the Organic Chemical Class 24

Table 16. Ten Most Commonly Occurring CWA-HS Materials in the Inorganic Chemical Class 24

Table 17. Total Number ofSW and GW ZOCs Delineated for Each State 26

Table 18. Threat Count Statistics for SW and GW ZOCs per State 30

Table 19. National Information Resources used in this Study, Organized byThreatType 32

Table 20. State Information Resources used in this Study, Organized byThreatType 33

Table 21. Threat Attributes Available in National and State Information Resources 34

Table 22. Count of Threats (byThreatType Category) Identified through National and State Information Resources...35
Table 23. SW ZOCs Containing the Greatest Number of Contamination Threats. (Unique sites are discrete locations that

MANUFACTURE, USE, STORE, OR DISCHARGE CONTAMINANTS OF CONCERN. THREAT COUNTS REFLECT THE INDIVIDUAL
CONTAMINATION THREATS LOCATED AT THESE DISCRETE LOCATIONS.) 47

Table 24. GW ZOCs Containing the Greatest Number of Contamination Threats. (Unique sites are discrete locations

THAT MANUFACTURE, USE, STORE, OR DISCHARGES CONTAMINANTS OF CONCERN. THREAT COUNTS REFLECT THE INDIVIDUAL
CONTAMINATION THREATS LOCATED AT THESE DISCRETE LOCATIONS.) 48

Table 25. SW ZOCs Containing the Greatest Number of Threats in each State. (Unique sites are discrete locations that

MANUFACTURE, USE, STORE, OR DISCHARGES CONTAMINANTS OF CONCERN. THREAT COUNTS REFLECT THE INDIVIDUAL
CONTAMINATION THREATS LOCATED AT THESE DISCRETE LOCATIONS.) 49

Table 26. GW ZOCs Containing the Greatest Number of Threats in each State. (Unique sites are discrete locations that

MANUFACTURE, USE, STORE, OR DISCHARGES CONTAMINANTS OF CONCERN. THREAT COUNTS REFLECT THE INDIVIDUAL
CONTAMINATION THREATS LOCATED AT THESE DISCRETE LOCATIONS.) 50

Table 27. SW ZOCs Containing the MostThreats Along the Mississippi and Ohio Rivers. (Unique sites are discrete

LOCATIONS THAT MANUFACTURE, USE, STORE, OR DISCHARGES CONTAMINANTS OF CONCERN. THREAT COUNTS REFLECT THE
INDIVIDUAL CONTAMINATION THREATS LOCATED AT THESE DISCRETE LOCATIONS.) 51

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Abbreviations

AST

Aboveground storage tank

AWIA

America's Water Infrastructure Act

CAFO

Concentrated animal feeding operation

CASRN

Chemical Abstracts Service Registry Number

CCR

Coal combustion residuals

CWA-HS

Clean Water Act Hazardous Substances

CWS

Community water system

EPCRA

Emergency Planning and Community Right-to-Know Act

ESRI

Environmental Systems Research Institute

FRP

Facility Response Plan

GIS

Geographic information system

GW

Groundwater

kgal

One thousand gallons

lat/long

Latitude and longitude

LUST

Leaking underground storage tank

NHD

National Hydrography Dataset

NPDES

National Pollutant Discharge Elimination System

NRC

National Response Center

PFAS

Perfluoroalkyl and polyfluoroalkyl substances

PWS

Public water system

RCRA

Resource Conservation and Recovery Act

SDWA

Safe Drinking Water Act

SDWIS

Safe Drinking Water Information System

STCM

Storage tank and contamination monitoring

SW

Surface water

SWAP

Source Water Assessment Program

SWCTI

Source water contamination threat inventory

TRI

Toxics Release Inventory

TSCA

Toxic Substances Control Act

U.S. EIA

United States Energy Information Administration

U.S. EPA

United States Environmental Protection Agency

UST

Underground storage tank

ZOC

Zone of concern

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Section 1.0: Introduction

1.1 Introduction

Releases of hazardous substances into sources of drinking water can cause significant problems for
public water systems (PWSs), such as process upsets, contaminated infrastructure, exposure of
customers to harmful contaminants, and costs incurred to respond to the release. Note that throughout
this report the terms "release" and "spill" are used interchangeably, and refer to the sudden, transient
release of a contaminant into source water. Persistent, diffuse sources of contamination, such as
agricultural runoff, are not covered in the scope of this report.

Congress recognized the importance of this risk to source water by enacting Section 2018 of America's
Water Infrastructure Act (AWIA), which authorizes water systems to access chemical inventory data as
well as receive prompt notification of spills contaminating their source water (U.S. Congress, 2018).
Furthermore, Section 2013 of AWIA requires community water systems (CWSs) serving a population
greater than 3,300 to conduct risk and resilience assessments every five years. One of the assets that
must be considered in this assessment is source water.

An important step in preparing for releases to sources of drinking water is to develop an understanding
of source water contamination threats in a PWS's source water protection area. This understanding can
be acquired by conducting a source water contamination threat inventory (SWCTI), which is an
inventory of potential sources of acute contamination (e.g., spills, untreated discharges) identified
within a source water protection area. A source water contamination threat can be any site that
manufactures, uses, stores, or discharges contaminants of concern that could enter a source of drinking
water. Examples of source water contamination threats include aboveground storage tanks (ASTs),
underground storage tanks (USTs), chemical facilities, mining operations, animal feeding operations, or
facilities with National Pollutant Discharge Elimination System (NPDES) permits, among others.
Contaminants of concern refer to any chemical or substance, which if released to a surface water or
groundwater source would adversely impact drinking water operations or cause harm to the customers
served by the drinking water system. Examples of contaminants of concern include gasoline, crude
petroleum, benzene, styrene, coal combustion residuals (CCR), and untreated wastewater.

A SWCTI generally intends to capture two types of information, characteristics of a site and
characteristics of contaminants of concern present at a site. In this document, the term site refers to any
facility, storage container, outfall, plot of land, or other feature that produces, stores, handles, uses, or
discharges a contaminant of concern. Note that a site (i.e., the physical location) may represent multiple
threats (i.e., the specific contaminants of concern present at the site). Thus, a SWCTI will typically
contain many more threats than sites. Figure 1 shows an example of a site with multiple threats.

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Figure 1. Example of a Site with Multiple Threats

1.2 Previous Efforts

Significant efforts previously conducted to inventory source water contamination threats are briefly
described in this section. Most notably, source water assessments for PWSs often include a SWCTI,
although scope and comprehensiveness can vary. The 1996 Safe Drinking Water Act (SDWA)
Amendments required that states create a Source Water Assessment Program (SWAP) to inform source
water protection activities (U.S. EPA, 2022a). Specifically, state drinking water programs were required
to:

• Identify the land area(s) which provide source water to each PWS in their state;

• Complete an inventory of existing and potential sources of contamination in those areas;

• Determine the susceptibility of each PWS to contamination; and

• Distribute the results of the assessment to water users and other interested entities.

By the early 2000s, source water assessments were completed by all state drinking water programs. The
1996 SDWA Amendments do not require states to update their source water assessments, although
some states do maintain and periodically update their SWCTIs. A brief description of the processes used
to maintain contamination threat inventories in Idaho and Indiana is provided below.

The Idaho Department of Environmental Quality annually inventories facilities, land uses, and
environmental conditions within delineated source water assessment areas that are potential sources of

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

contamination to groundwater or surface water (Idaho Department of Environmental Quality, 2022).
Idaho's SWCTI involves searching electronic databases and other files to identify potential sources of
contamination within the delineated area. Base maps detailing the delineated source water protection
area(s) along with the potential contaminant sources are produced. This initial inventory is enhanced
using on-the-ground surveys, local record review, and local knowledge to identify additional source
water contamination threats not identified during the preliminary inventory (Idaho Department of
Environmental Quality, 2007).

The Indiana Department of Environmental Management administers a Wellhead Protection Program,
which requires all PWSs using groundwater sources to develop a plan to protect the areas around their
wellheads, including development of a SWCTI. The inventory describes the location, nature, and status
of identified threats. PWSs are required to update their management strategy, including updates to the
SWCTI, if needed. PWSs are also required to perform ongoing maintenance to update the inventory and
plan on a 5-year cycle as long as the PWS is operating (Indiana Department of Environmental
Management, 2022).

The United States Environmental Protection Agency (U.S. EPA) hosts several databases and resources
useful for developing a SWCTI. One such platform is the Drinking Water Mapping Application to Protect
Source Waters, which provides a geographic information system (GIS) platform for accessing datasets
important for source water protection activities. This application compiles information from national
information resources, such as Toxic Substances Control Act (TSCA), NPDES, and Resource Conservation
and Recovery Act (RCRA), but does not include information resources managed by individual states, such
as Emergency Planning and Community Right-to-Know Act (EPCRA) Tier II chemical inventory systems
(U.S. EPA, 2022c). Another U.S. EPA resource is the UST Finder Application, which compiles data from
states and other jurisdictions about USTs. The database allows users to locate USTs in a specific area,
with details on the material stored in the tanks, and indicates whether the tank is further categorized as
a leaking underground storage tank (LUST) (U.S. EPA, 2022b).

Outside of the SDWA SWAP and other federal programs, several studies conducted contaminant threat
inventories for specific contaminants or groups of contaminants. One example is a 2016 study to identify
and compile information about facilities likely to store or handle substances containing per- and
polyfluoroalkyl substances (PFAS) in order to examine the correlation of PFAS contamination to point
sources (Hu et al., 2016) and identify water supplies that may be vulnerable to PFAS contamination
(George & Dixit, 2021; McMahon et al., 2022; Xindi et al., 2021). EPA has also published PFAS Analytical
Tools that provide location-specific information related to PFAS manufacture, release, and occurrence in
the environment, as well as facilities potentially handling PFAS. Another example is an inventory
conducted in the source water protection area for the City of Las Vegas to identify point and nonpoint
sources of pollution. This study involved field work to identify possible sources of contamination,
including facilities such as chemical manufacturers/warehouses, manufacturing sites, petroleum storage
and distribution sites, research laboratories, airports, and dry-cleaning sites. The information collected
included facility description and address, geographic coordinates, site pictures, and contaminants at the
facility (Reginato, 2002).

The resources and studies described in this section are limited in geographic coverage, threat coverage,
or information resources utilized. The authors were unable to identify a published multi-state SWCTI
that uses both national and state information resources to document the full range of acute
contamination threats to both surface water and groundwater sources of drinking water.

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

1.3 Objectives

The study described in this report characterized the occurrence of source water contamination threats
within zones of concern (ZOCs) for CWSs located in the states included in this study. A ZOC is a portion
of a source water protection area, typically in close proximity to an intake or wellhead, considered to be
at greater risk from an acute contamination incident due to decreased opportunities for attenuation and
mitigation. The objectives of this study were to evaluate the following:

• Distribution of the number of threats within ZOCs evaluated in this study

• Geographic occurrence of source water contamination threats

• Frequency of occurrence for classes of contaminants of concern

• Distribution of volumes of contaminants of concern

• Relationship between the number of source water contamination threats and the number of
releases in a ZOC

• Relative value of different information resources in building a SWCTI and ease of accessing and
using the information

1.4 Scope

The scope of this analysis was limited to the following:

• Community water systems. This analysis was limited to threats in source water ZOCs for CWSs,
as defined in Section 1401(15) of the Safe Drinking Water Act. CWSs were considered in this
analysis, rather than all PWSs, because the former serves established populations year-round.

• Availability of detailed state-level data. The study area included ten states (Florida, Illinois,
Indiana, Iowa, Kentucky, Louisiana, New Jersey, New Hampshire, Ohio, and Texas) which were
selected based on the availability of detailed state-level information resources that included
statewide Tier II hazardous chemical inventories, oil and gas wells, discharge information,
chemical facilities, ASTs, LUSTs, concentrated animal feeding operations (CAFOs), hazardous
waste information, and releases.

• Active sites. This analysis was limited to active sites. Sites with inactive permits or wells that
were not drilled were removed for this analysis.

• Scope of information resources considered. Potential sources of acute contamination were
identified through national and state information resources in the study area; however, the
analysis was limited to only those resources that were available to U.S. EPA. When possible,
data were collected through publicly available resources (e.g., U.S. EPA, Texas Commission on
Environmental Quality) or through a public records request. The data used in this study were
reviewed and selected based on availability of specific information (e.g., site location,
contaminant identity, contaminant mass or volume, container size) as well as the quality of that
information.

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Section 2.0: Methodology

2.1 Study Area

Ten states were selected for a statewide SWCTI: Florida, Illinois, Indiana, Iowa, Kentucky, Louisiana, New
Jersey, New Hampshire, Ohio, and Texas. These states were selected to provide a diversified sample of
source water contamination threats. For example, Louisiana and Texas have multiple industrial regions
involved in chemical manufacturing; Ohio and Kentucky have a mix of mining operations, industrial
regions, and agricultural areas; Iowa, Illinois, Indiana, and New Hampshire have extensive agricultural
areas; and Florida and New Jersey have a mix of agricultural and large urbanized areas. The diversity of
threat profiles provided by these ten states is intended to provide a reasonable representation of
national trends in the occurrence of potential sources of contamination.

Furthermore, information resources considered essential to a SWCTI had to be available for selected
states. Specifically, the study only considered states which were willing to provide a complete, statewide
Tier II hazardous chemical storage dataset to U.S. EPA. Additionally, states were selected only if the
available state-level information resources covered a significant portion of the threat types described in
Section 2.3.

2.2 Zones of Concern

ZOCs were developed using the locations of drinking water intakes and groundwater wells, along with
hydrography information. ZOCs extending into neighboring states not included in the assessment were
clipped at the state boundary. For example, if the ZOC of a CWS in Kentucky (included in this study)
extended into Tennessee (not included), the portion of the ZOC located in Tennessee was not included.
Data sources used to develop ZOCs included:

• National Hydrography Dataset (NHD) served as the primary source of information about
locations of surface waterbodies. The high-resolution NHD waterbody areas and flowlines were
used when available; otherwise, medium resolution NHD flowlines and waterbody boundaries
were used. Figure 2 provides an example of NHD waterbody and flowline representations.

• Safe Drinking Water Information System (SDWIS) was used to identify CWSs from among the
larger universe of PWSs and to obtain the population served and source water type (e.g., surface
water, groundwater) for each CWS. The restricted access version of SDWIS was used to obtain
the location of surface water intakes and groundwater wellheads for each CWS with a
population served greater than 1,000.

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Figure 2. Example of NHD Flowline and Waterbody Representations

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Surface water (SW) ZOCs extend 50 miles upstream, V* mile downstream, include all major tributaries,
and include a % mile buffer inland from the waterbody area boundary (see Figure 3 for an example) This
definition for a SW intake ZOC is consistent with the general principles for establishing source water
area delineations for conducting a SWCTI, specifically in a targeted ZOC (U.S. EPA, 2006; ORSANCO,
2022). SW ZOCs were developed for 1,152 SW intakes in the study area.

Figure 3. Example of a Surface Water Zone of Concern

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Groundwater (GW) ZOCs are defined by a % mile radius around a wellhead (see Figure 4 for an
example). Guidance from U.S. EPA states that an "arbitrary fixed radius" can be used as a first
approximation for a source water area delineation (U.S. EPA, 2006). GW ZOCs were developed for
31,441 GW wellheads in the study area.

• Wellhead Location

Ground Water Zone of Concern

Figure 4. Example of Groundwater Zones of Concern

The SW ZOCs developed for this study were defined to be conservative, meaning they cover a large area
in order to capture most threats that could impact water quality at the intake. Some SW ZOCs cross
state boundaries, and when the neighboring state was included in this study, the threats from the
neighboring state were included in the threat inventory for that SW ZOC. However, if a SW ZOC
extended into a state that was not included in this study, the ZOC was clipped at the state border. Table
1 presents a summary of ZOC statistics per state, including the distribution of ZOC areas for SW ZOCs.
The area statistics are not included for GW ZOCs, because, with only a few exceptions, GW ZOCs have a
uniform area of 0.78 sq mi, corresponding to a !4 mile radius.

Table 1. Statistics for SW ZOC Areas, per State

OH

TX

NH

IA

IL

IN

FL

KY

LA

NJ

Total

Total No. of Zones

2,929

11,319

1,232

2,072

2,949

2,041

5,509

364

2,213

1,965

32,593

Total No. of SW Zones

231 (8%)

405 (4%)

39 (3%)

38 (2%)

137 (5%)

37 (2%)

31 (1%)

139 (38%)

52 (2%)

43 (2%)

1,152

Total No. of GW Zones

2,698 (92%)

10,914(96%) 1,193(97%) 2,034(98%)

2,812 (95%)

2,004 (98%)

5,478 (99%)

225 (62%)

2,161 (98%)

1,922 (98%)

31,441

Mean SW Zone (sq mi)

78.09

148.94

45.76

149.80

101.99

37.21

146.87

165.74

171.29

39.52

120.99

Minimum SW Zone (sq mi)

0.30

0.14

0.18

0.70

0.20

0.34

0.43

0.20

0.19

0.44

0.14

10th Percentile SW Zone (sq mi)

1.03

0.36

0.65

1.81

2.52

1.21

0.44

0.82

13.71

1.71

0.74

50th Percentile SW Zone (sq mi)

24.36

61.89

4.01

30.19

32.78

27.04

47.27

46.72

39.08

25.08

34.89

90th Percentile SW Zone (sq mi)

243.78

408.39

102.86

454.13

307.98

82.55

552.34

452.51

496.93

80.17

372.60

Maximum SW Zone Area (sq mi)

828.56

912.76

718.41

785.02

786.30

218.42

725.45

759.01

1,517.59

259.01

1,517.59

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

2.3 Threat Type and Contaminant Class Definitions

Sites were classified according to the threat types defined in Table 2 based on the nature of the site.

Table 2. Threat Types used to Classify Sites

Threat Type

Threat Type Description

Aboveground Storage Tanks
(AST)

AST threats include sites with chemicals stored in ASTs. Most AST
information resources acquired for this study tracked storage of petroleum
products, including diesel and gasoline, as well as a few organic chemicals
and trade name chemicals.

Chemical Facilities

Chemical facility threats include sites that handle, manufacture, use, or
store toxic substances. These include sites reporting under the TSCA for
chemicals that were determined to cause unreasonable risk to public health
or the environment, and facilities required to develop a risk management
plan (RMP) for handling, manufacturing, using, or storing certain flammable
or toxic substances that exceed a threshold quantity.

Concentrated Animal Feeding
Operation (CAFO)

CAFO threats include large-scale industrial agricultural facilities where
animals are kept and raised in confined areas or facilities.

Energy Infrastructure

Energy infrastructure threats include refineries and processing plants.

Hazardous Waste

Hazardous waste threats include sites that handle and dispose of
hazardous waste. Facilities with RCRA permits for large quantity (waste)
generators are included, while small quantity were excluded. State
regulated hazardous waste treatment, storage, and disposal sites were
included.

Injection and Resource
Extraction Wells

Injection and resource extraction well threats include waste injection wells
as well as active oil and gas wells (including fracking sites). Dry and non-
drilled wells were omitted from this analysis.

Leaking Underground Storage
Tanks (LUST)

LUST threats include sites with leaking underground storage tanks.

National Pollutant Discharge
Elimination System (NPDES)

NPDES threats include sites with a permit for discharging pollutants into
nearby waters. Stormwater NPDES permits were omitted from this analysis.

Oil Storage Facilities

Oil storage facility threats include facilities required to submit an EPA
Facility Response Plan (FRP) for storing and using oil. Facilities are required
to develop an FRP if they have a total oil storage capacity of 1 million gallons
or greater or if they have an oil storage capacity of 42,000 gallons or greater
and transfer oil over water.

Resource Extraction

Resource extraction threats include sites involved in mining operations,
natural gas market hubs, and natural gas underground storage.

Storage Tanks

Storage tank threats include sites storing petroleum in ASTs or USTs.

Tier II Hazardous Chemical
Storage

Tier II threats include sites reporting tier II hazardous chemical inventory
data under EPCRA. This includes facilities storing more than 10,000 pounds
of a hazardous substance or more than a threshold quantity (between 1
and 500 pounds) of an extremely hazardous substance.

Toxic Release

Toxic release threats include releases reported to the National Response
Center (NRC) of 100 gallons or more and sites reporting under the Toxic
Release Inventory (TRI).

Sites were also characterized according to the types of chemicals stored or handled onsite. Given the
very large number of unique materials identified in this study (16,827), it was necessary to group
materials into classes to facilitate analysis of contaminant occurrence. The contaminant classes used in
this study are listed in Table 3, along with examples of the most commonly occurring contaminant
within each class. While these contaminant classes are useful for a high-level aggregate analysis, many

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

contaminants within the same class behave differently with respect to important characteristics, such as
fate and transport, treatability, and toxicity.

Table 3. Contaminant Classes and Most Common Materials

Contaminant Class

Most Common Materials within these Categories

Acid

Sulfuric Acid, Hydrochloric Acid, Fluorosilicic Acid

Antifreeze/Ethylene Glycol

Ethylene Glycol, Propylene Glycol, Triethylene Glycol

Caustic Material

Sodium Hydroxide, Potassium Hydroxide, Calcium Hydroxide

Chlorine

Liquified Chlorine Gas, Sodium Hypochlorite

Coal Combustion Residuals (CCR)

Fly Ash, Carbon Black, Bottom Ash

Cyanide Compounds

Sodium Cyanide, Potassium Cyanide

Diesel or Gasoline

Diesel No 2 Fuels, Natural Gasoline, Diesel

Drilling Fluid

Produced Water, Brine

Fertilizer/Ammonia

Ammonia, Nitrogen, Ammonium Sulfate

Firefighting Foam

Ansul Purple K, Aer-O-Lite 3%, Buckeye 3% AFFF

Food Products

Soybean Oil, Xanthan Gum

Inorganic Chemical

Sodium Chloride, Aluminum Sulfate, Sodium Bisulfite

Organic Chemical

Methanol, Ethanol

Paint

Paint, C.I. Pigment Yellow 42, Pigment Blue 15

Pesticides or Herbicides

Acetochlor, Atrazine, S-Metachlor

Petroleum Products

Crude Oil, Fuel Oil Number 2. (Excludes Diesel and Gasoline,
which are covered under a dedicated class.)

Radiological

Americium-141, Radioactive Material

Trade Name

Nettles P.E. Extract, Nalco Product. (Unidentified composition.)

Waste Material

Hazardous Waste N.O.S., Waste & Slop Polyols

Materials unlikely to change water quality due to the nature or form of the material were excluded from
the analysis. The material categories, with examples, excluded from this study are listed in Table 4.

Table 4. Excluded Material Categories and Examples

Excluded Material Category

Material Examples

Abrasives

Blast Media - Mineral Sands, Blast Media (Almandine Garnet)

Ammunition/Explosives

l.ld Emulsion Explosives, Bulk Emulsion Explosives, High Explosives (Class A)

Batteries and Related Products

Lead Acid Batteries, Electrodes

Coal

CWS Charcoal

Construction Materials

Roofing Shingles, Cement, Concrete, Brick Rubble, Glass, Lumber

Earth/Mineral Products

Gravel, Gypsum, Limestone, Aggregate, Mica, Kaolin, Quartz, Bentonite, Clay, GMA Garnet

Food Products

Corn Dust, Corn Flour, Wheat Flour, Whole Grain, Corn Cob Grits, Corn Germ

Gaseous Products

Compressed Air, Argon, Carbon Dioxide, Helium, Oxygen, Landfill Gas, LP Gas

Metal and Scrap

Alloys, Aluminum, Carbon Steel, Brass, Iron, Metal Dust, Metal Shavings, Lead

Miscellaneous Waste

Waste Aerosol Cans, Waste Sandblasting Media, Metals Water Tank

Non-Hazardous

No Hazardous Ingredients, None Listed

Other

Molecular Sieve

Resin Products

Amberlite IR-120+ Industrial Resin, Dowex Monosphere 550a oh Anion Exchange Resin

Volatile Chemicals

Propane, Butane, Methane, Natural Gas, 1-Pentene, Aerosol, Refrigerants

Water

Water, Pond Water, Treated Freshwater

10

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

2.4 Information Resources for Building SWCTIs

To build the SWCTI, information about potential sources of acute contamination were collected from
national and state information resources. Available resources were reviewed and selected based on the
quality of data and amount of information available, such as site name, address, and contaminant
information. A full list of information resource references used in this assessment is provided in the
References section of this report. The national organizations that provided the greatest number of
information resources were the U.S. EPA, U.S. Energy Information Administration (U.S. EIA), and Center
for Effective Government Right-to-Know Network. Although these references were the top contributing
information resources across the ten states, these datasets often provided only a site name and address,
and lacked site attributes important to a SWCTI, such as the identity and quantity of material present at
a site.

Based on their content, each information resource was classified according to the threat type (see Table
2) for which it was most relevant. These classifications are summarized in Table 5. The threat categories
covered by the greatest number of state and national information resources include Resource Extraction
(13), Hazardous Waste (12), and NPDES (11). At the state level, Ohio (9), Florida (9), and Kentucky (9)
provided the greatest number of information resources, while Louisiana (5), Texas (5), New Hampshire
(4), and New Jersey (3) provided the fewest.

Table 5. Threat Type Coverage by State and National Information Resources

Threat Type

National

Total

Resource Extraction

Hazardous Waste

NPDES

Tier II

Injection and Resource Extraction Wells

Chemical Facilities

Energy Infrastructure

Toxic Release

CAFOs

AST

LUST

Oil Storage Facilities

Storage Tanks

Total

2.5 Data Processing

Data entry errors occurred in data fields within most of the information resources used in this study.
Most of these errors involved inconsistent naming of record attributes, such as material names and
location names. In many information resources, the material name and volume units were not
standardized, which resulted in the use of synonymous or ambiguous names and various volumetric
units. Other errors included missing latitude and longitude (lat/long) coordinates for site locations.

To improve the quality of the analysis, the following data processing was performed:

• Location data was standardized to identify the best geospatial data for a supplied address if the
lat/long coordinates were not given. When a street address was provided, this information was
used to geocode the record.

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

• Names of materials were reviewed and standardized to a specific material name or general
group if the material name was vague and lacking a Chemical Abstracts Service Registry Number
(CASRN). For some information resources that did not provide a material name, the name could
be inferred from the purpose or scope of that resource. For example, it was assumed that the
information resource "Facilities with Anhydrous Ammonia" tracks sites that store ammonia.

• CASRNs were used to correct material names. Trade name materials that list the CASRN of the
main component of the mixture were categorized according to the provided CASRN. Incorrect
CASRNs or those with missing digits were also reviewed and standardized to a specific material
name when the correct CASRN or material name could be inferred. Materials missing CASRNs
were assigned a specific material name by using its synonym or other identifier.

• Units for amount of material were standardized to a common unit, gallons, using the conversion
factors listed in Appendix A. In some cases, contextual information from the record was used to
assign a unit of measure (e.g., EPCRA specifies Tier II reporting thresholds in pounds, thus it was
assumed that values for Tier II storage quantities were provided in pounds unless otherwise
noted).

• Sites considered to pose a minimal threat of rapidly releasing contaminants into drinking water
sources were excluded from the analysis. Examples of excluded sites include those associated
with inactive permits, wells that were not drilled, dry wells, small quantity generators (as
designated under RCRA), and stormwater discharges. Additionally, sites that reported a material
volume or mass of "0" were excluded from the analysis; however, sites with unreported volume
or mass were retained.

2.6 Limitations of the Methodology

• Collected information resources may be incomplete and missing data essential to the analysis,
such as site location, contaminant identity, and volume or mass.

• State information resources were sought for all threat types listed in Table 2, however, not all
states track all sites of interest in publicly available resources.

• The criteria used to develop ZOCs were generic and there is a possibility that a release from a
threat outside of a ZOC could significantly impact a source of drinking water. Conversely, it is
possible that a release from threats within a ZOC may not significantly impact a source of
drinking water.

• The analyses presented in this report focus on occurrence of threats in ZOCs, and each unique
combination of a specific threat and specific ZOC constitute a unique occurrence record. An
artifact of this approach is that a single threat is counted multiple times if it occurs in multiple
ZOCs. Specifically, the occurrence of overlapping ZOCs results in inflated threat counts and
cumulative volumes reported in aggregate analyses. Section 3.4 provides more details regarding
analysis of threats in overlapping ZOCs.

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Section 3.0: Results and Discussion

Results from the inventory of sites with the potential to rapidly release contaminants to sources of
drinking water are presented in the following subsections:

•	3.1 provides a summary of the number of threats in each threat category and presents the
geographic occurrence of threats involving different threat types

•	3.2 provides a summary of the number of threats in each contaminant class, presents the
geographic occurrence of contaminant classes, and presents the relation between
contamination threat occurrence and contaminant releases

•	3.3 provides a summary of the number and geographic occurrence of Clean Water Act
Hazardous Substance (CWA-HS) threats

•	3.4 provides a summary of source water contamination threat occurrence by ZOC

•	3.5 presents the evaluation of information resources

3.1 Occurrence of Threats by Threat Type

After the records were processed according to the methodology described in Section 2, a total of
506,413 threats were identified in the SWCTI across the ten states. These 506,413 threats are associated
with 110,745 unique sites, resulting in an average of 4.57 threats per site.

As shown in Table 6 and Figure 5, the threat types with the largest counts in the SWCTI were Tier II with
234,040 threats (46%), followed by Injection and Resource Extraction Wells with 93,774 threats (19%),
and NPDES with 71,086 threats (14%). Note that these trends are influenced by the availability of state-
level resources that track occurrence of threats in each threat type category. Some threat type
categories may be underrepresented because only a portion of the ten states included in this study had
information resources that track sites relevant to those threat types, as shown in Table 5 of Section 2.4.

Table 6. Threat Type Counts for all Ten States

Threat Type

Percentage

Threat Count

Tier II

46.2%

234,040

Injection and Resource Extraction Wells

18.5%

93,774

NPDES

14.0%

71,086

LUST

6.7%

33,808

Chemical Facilities

5.3%

26,696

Storage Tanks

2.7%

13,656

Toxic Release

2.5%

12,561

Hazardous Waste

1.4%

7,084

AST

1.4%

6,858

Resource Extraction

0.8%

4,203

Energy Infrastructure

0.2%

1,230

CAFOs

0.2%

764

Oil Storage Facilities

0.1%

653

Total

100%

506,413

i Tier II

i Injection and Resource Extraction Wells

¦	NPDES
i LUST

i Chemical Facilities
i Storage Tanks
Toxic Release
i Hazardous Waste

¦	AST

i Resource Extraction
i Energy Infrastructure
i CAFOs

i Oil Storage Facilities

Figure 5. Threat Type Percentages for all Ten States

13

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Figure 6 shows threat counts by state, including the total count, the threat count in SW ZOCs, and the
threat count in GW ZOCs. The states with the largest number of threats in SW ZOCs include Louisiana
(77,199), Ohio (58,330), and Texas (55,948). The states with the largest number of threats in GW zones
include Florida (48,994), Louisiana (39,535), and Texas (29,428).

NH — 237624 I I riGW Threat Count

6,330 | | | BSW Threat Count

, a T!" 15,340

IA 21599 ¦ Total Threat Count

IN 6.193

— 21,885

i KY

15,692

22,876

37,164

2850 37,331

40,181

23,005

1/1 IL 26.113 _. ...

49,118

FL
OH
TX

48,994
— 52,584

75,442

85,376

¦116,734

0 20,000 40,000 60,000 80,000 100,000 120,000

THREAT COUNT

Figure 6. Total GW and SW Threat Counts per State

Further analysis of the geographic distribution of threats evaluated occurrence within the following
types of designated regions: Environmental Systems Research Institute (ESRI) industrial areas, shale play
areas, and census urban areas. This analysis included the following six threat types that occurred with
high frequency or in high volume: Petroleum Products, Organic Chemical, Inorganic Chemical, Trade
Name, Fertilizer/Ammonia, and Pesticides or Herbicides. Also, this analysis was limited to threats
identified through the national information resources. State information resources were not included
due to interstate variability in the availability of this data.

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Figure 7 shows the relative percentage of threat counts in each of four categories located in ESRI
industrial areas for the ten states included in this study. As can be seen in the figure, the majority of
threats across all four categories were located outside of ESRI industrial areas. Oil Storage Facilities
(77%) and Energy Infrastructure (83%) had the greatest percentage of threats falling outside of industrial
areas. While more than half of the inventoried threats were located outside of ESRI industrial areas
across the ten states, there were exceptions to this average trend for individual states. For example, in
New Jersey between 73% and 100% of threats in each of the four categories were located within ESRI
industrial areas.

54% 56% 77% 83%

Threat Type

¦ Threats Outside Industrial Areas Threats Inside Industrial Areas

Figure 7. Percentage of Threats Located Inside and Outside of ESRI Industrial Areas

The geographic occurrence of Oil Storage Facilities threats was also evaluated relative to the locations of
shale plays. Only 20% (130) of Oil Storage Facilities were located within the boundaries of shale plays.
Similarly, the occurrence of NPDES permits was compared to census designated urban areas, and for the
data evaluated in this study, 60% (27,690) of NPDES threats fell within the census designated urban
areas.

Collectively, these results indicate that the designated regions evaluated in this study: ESRI industrial
areas, shale play areas, and census designated urban areas, are not always reliable predictors of threat
occurrence. However, they may serve as better predictors in some states relative to others.

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

3.2 Occurrence of Threats by Contaminant Classification

Of the 506,413 threats
identified in the SWCTI,

276,816 (55%) threats reported
a material name. These
276,816 threats included
16,827 unique materials, which
were grouped into the
contaminant classes listed in
Table 3. A mass or volume was

reported for 227,449 (82%) of the 276,816 threats with material names.

i Threats with
Material Names
Threats without
Material Names

i Threats with
Mass or Volume
Threats without
Mass or Volume

The threat count and average volume per threat by contaminant class is shown in Figure 8. Materials in
the Organic Chemical class occurred at the greatest frequency, with 59,402 (21%), and the most
commonly occurring materials in the Organic Chemical class were methanol, 5,472 (9%); ethanol, 2,003
(3%); and paraffinic petroleum distillates, 1,332 (2%). The next most commonly occurring contaminant
class was Trade Name, with 45,991 (16%) threats, which includes proprietary chemical mixtures
comprised of two or more components. The contaminant classes with the third and fourth highest
threat counts were Petroleum Products, with 36,517 (13%), and Diesel or Gasoline, with 36,250 (13%).
The Petroleum Products class had the highest average volume per threat across all contaminant classes,
with 12,387 kgal.

70,000

¦ Threat Count

59,402 12,387
5,520 *

11,714

• Avg. Volume (kgal)

50,000

40,000

30,000

20,000

10,000

45,991
41

36,250
36,517 59

23,336
794

_ 14,504

I 3,657 12,777

• 13,409

979 77 11,999

77 38 8,751

535 5,835

20 nCr

2,465 lj965 g20 568

2,405

1 87 28 l."4

¦ 9 ¦

x> jy

<<>N

& v# ,0

& >

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Table 7 shows the total number of threats for each contaminant class by state. A red font gradient
indicates the first (darkest red), second, and third (lightest red) most frequently occurring contaminant
class in each state. The states with the largest total threat count include Louisiana, 73,583 (27%), Texas,
63,323 (23%), and Ohio, 26,442 (10%). The majority of threats in Louisiana fell into the Trade Name
class, 24,616 (33%), followed by Organic Chemical, 15,850 (22%), and Petroleum Products, 6,750 (9%).
The Organic Chemical contaminant class represented the largest threat count in Texas, Ohio, New
Jersey, and Illinois.

Table 7. Total Number of Threats in Each Contaminant Class by State

Total

Organic Chemical

15,850

14,169

5,437

13,406

1,783

4,258

1,686

1,675

922

216

59,402

Trade Name

24,616

892

1,085

1,228

1,283

45,991

Petroleum Products

13,651

4,645

1,515

1,926

1,870

1,373

2,036

939

1,812

36,517

Diesel or Gasoline

4,277

8,536

2,459

2,972

9,960

3,754

782

715

930

36,250

Inorganic Chemical

5,262

4,227

3,709

1,324

2,499

1,477

1,110

136

23,336

Fertilizer/Ammonia

2,834

2,404

1,177

635

1,522

2,241

2,060

655

747

229

14,504

Acid

2,830

1,777

1,220

738

1,692

1,158

730

1,048

131

13,409

Chlorine

2,023

5,051

784

128

2,775

434

707

265

573

12,777

Pesticides or Herbicides

2,704

1,063

472

434

910

2,449

2,833

418

714

11,999

Caustic Material

2,560

1,154

1,309

555

1,359

668

547

288

199

112

8,751

Antifreeze/Ethylene Glycol

1,765

1,202

377

1,161

275

487

261

145

119

5,835

Food Products

448

317

203

823

304

200

2,465

Paint

777

157

600

108

1,965

CCR

143

388

199

219

174

202

106

1,574

Cyanide Compounds

128

149

175

135

820

Drilling Fluid

338

195

568

Waste Material

121

369

Firefighting Foam

179

263

Radiological

Total

73,583

63,323

26,442

26,423

25,306

23,534

15,730

10,072

8,442

3,961

276,816

Table 8 shows the number of threats within a specified range of volumes for each contaminant class. A
red font gradient indicates the first (darkest red), second, and third (lightest red) most frequently
occurring contaminant class in each volume range. Four volume ranges were considered: less than 1
kgal; between 1 and 10 kgal; between 10 and 100 kgal; and greater than 100 kgal. Most threats, 86,784
(31%), reported volumes within the range of 1 and 10 kgal, followed by those reporting volumes less
than 1 kgal, 73,022 (26%). With the exception of Cyanide Compounds and Waste Material, all other
classes had significantly fewer threats in the greater than 100 kgal volume range compared with the
other three volume ranges. The contaminant classes with the largest number of threats in the greater
than 100 kgal volume range include: Organic Chemical, 5,161 (26%); Trade Name, 4,071 (21%); and
Petroleum Products, 2,523 (13%). The contaminant classes with the greatest total volume include
Petroleum Products, 452,352,011 kgal (51%); Organic Chemical, 327,924,764 kgal (37%);
Fertilizer/Ammonia, 53,036,862 kgal (6%); and Inorganic Chemical, 18,527,671 kgal (2%). Note that
percentages are calculated relative to the total count or volume in the corresponding volume range.

The threat counts in Table 7 show that Organic Chemical, Trade Name, and Petroleum Products classes
make up 51% of the total number of threats, and the values for total volume in Table 8 show that
Petroleum Products, Organic Chemical, Fertilizer/Ammonia, and Inorganic Chemical are responsible for
95% of the total material volume.

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Table 8. Total Number of Threats Containing a Volume within the Indicated Range for Each
Contaminant Class

Contaminant Class

No. of
Threats

Total Volume
(kgal)

Avg. Volume
(kgal)

Number of Threats in Volume Range

Largest Volume
(kgal)

Not Reported

< 1 (kgal)

1 -10 (kgal)

10 -100 (kgal)

> 100 (kgal)

TOTAL

276,816

894,972,878

3,233

49,367

73,022

86,784

47,992

19,651

N/A

Petroleum Products

452,352,011

12,387

7,133

11,087

6,558

9,113,000

Organic Chemical

59,402

327,924,764

20,794

12,157

13,949

5,161

13,000,000

Fertilizer/Ammonia

14,504

3,657

1,562

3,198

5,063

3,220

1,461

793,248

Inorganic Chemical

23,336

18,527,671

794

3,955

5,335

7,776

4,181

2,089

CCR

1,574

18,437,595

11,714

335

352

597

206

1,009,115

Acid

13,409

13,122,004

979

967

6,295

3,688

1,548

911

1,092,000

Caustic Material

8,751

4,685,280

535

661

1,788

3,187

2,152

963

230,000

Diesel or Gasoline

36,250

2,138,227

3,891

6,749

11,145

1,044

60,000

Trade Name

45,991

1,904,139

13,615

15,014

7,494

4,071

33,225

Chlorine

12,777

986,800

907

8,027

2,894

841

108

48,446

Waste Material

369

887,598

2,405

118

114,002

Pesticides or Herbicides

11,999

454,717

528

2,777

7,125

1,166

403

36,183

Food Products

2,465

214,874

958

246

564

470

227

9,274

Antifreeze/Ethylene Glycol

5,835

114,867

854

2,289

1,735

766

191

1,200

Cyanide Compounds

820

65,528

225

179

219

122

1,200

Drilling Fluid

568

64,297

113

103

124

235

1,200

Paint

1,965

54,692

686

781

322

128

6,055

Firefighting Foam

263

944

175

Radiological

0.4

Table 9 shows the most frequently occurring material in each contaminant class, displaying the threat
count for the listed material and percentage relative to the total threat count in the corresponding
contaminant class.

Table 9. Most Commonly Occurring Material in each Contaminant Class

Contaminant Class

Material Name

CASRN

Threat Count for
Material Name

% of Total
Class Count

Diesel or Gasoline

Fuels, diesel no. 2

068476-34-6

13,491

37%

Acid

Sulfuric acid

007664-93-9

6,698

50%

Chlorine

Liquified Chlorine Gas

007782-50-5

6,669

52%

Petroleum Products

Crude oil

148002-05-9

5,887

16%

Caustic Material

Sodium hydroxide

001310-73-2

5,508

63%

Organic Chemical

Methanol

000067-56-1

5,472

Fertilizer/Ammonia

Ammonia

007664-41-7

3,678

25%

Antifreeze/Ethylene Glycol

Ethylene glycol

000107-21-1

2,422

42%

Pesticides or Herbicides

Acetochlor

034256-82-1

1,616

13%

Inorganic Chemical

Sodium chloride

007647-14-5

1,260

CCR

Fly ash

068131-74-8

959

61%

Trade Name

Water-based
hydraulic fluid

178

0.4%

Drilling Fluid

Produced water

007782-44-7

157

28%

Paint

157

Food Products

Soybean oil, me ester

067784-80-9

148

Cyanide Compounds

Polymeric
Diphenylmethane
diisocyanate

009016-87-9

114

14%

Waste Material

Haz Waste, N.O.S.
(Only if EHS RPTD) liq

101

27%

Firefighting Foam

Ansul Purple K

12%

Radiological

Americium-241

014596-10-2

90%

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

The Organic Chemical class had the greatest number of threats across all contaminant classes.
Contaminant occurrence within this category was further evaluated to identify the ten most commonly
occurring organic chemicals, which are shown iri Table 10.

Table 10. Ten Most Commonly Occurring Materials in the Organic Chemical Class

Material Name

CASRN

Threat Count for
Material Name

% of Total Class
Count

Methanol

000067-56-1

5,472

Ethanol

000064-17-5

2,003

Paraffinic petroleum
distillates

064742-65-0

1,332

Isopropyl alcohol

000067-63-0

1,127

Toluene

000108-88-3

952

Heavy paraffinic petroleum
distillates

064741-88-4

814

Naphthalene

000091-20-3

781

Xylene

001330-20-7

751

2-Butoxyethanol

000111-76-2

667

Acetone

000067-64-1

643

Table 11 lists the most frequently occurring materials in the Inorganic Chemical class. Notably, several of
these inorganic chemicals are used in water treatment, including sodium chloride, aluminum sulfate,
sodium bisulfite, hydrogen peroxide, and ferric chloride.

Table 11. Ten Most Commonly Occurring Materials in the Inorganic Chemical Class

Material Name

CASRN

Threat Count for
Material Name

% of Total Class
Count

Sodium chloride

007647-14-5

1,260

Aluminum sulfate

010043-01-3

956

Sodium bisulfite

007631-90-5

809

Calcium chloride

010043-52-4

761

Hydrogen peroxide

007722-84-1

657

Ferric chloride

007705-08-0

491

Titanium dioxide

013463-67-7

471

Aluminum oxide

001344-28-1

470

Lead compounds

007439-92-1

449

Potassium chloride

007447-40-7

437

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Table 12 shows the ten most frequently occurring materials across all contaminant classes. Out of the
ten most frequently occurring materials, three are in the Diesel or Gasoline contaminant class and two
are in the Chlorine contaminant class. Again, several chemicals used in water treatment are on this top
ten list: chlorine, sodium hypochlorite, sodium hydroxide, ammonia, and sulfuric acid.

Table 12. Ten Most Commonly Occurring Materials Across All Contaminant Classes

Contaminant Class

Material Name

CASRN

Threat Count for
Material Name

% of Total
Class Count

Diesel or Gasoline

Fuels, diesel no. 2

068476-34-6

13,491

37%

Diesel or Gasoline

Gasoline, natural

008006-61-9

6,954

19%

Diesel or Gasoline

Diesel

6,809

19%

Acid

Sulfuric acid

007664-93-9

6,698

50%

Chlorine

Liquified Chlorine Gas

007782-50-5

6,669

52%

Petroleum Products

Crude oil

148002-05-9

5,887

16%

Caustic Material

Sodium hydroxide

001310-73-2

5,508

63%

Organic Chemical

Methanol

000067-56-1

5,472

Chlorine

Sodium hypochlorite

007681-52-9

4,039

32%

Fertilizer/Ammonia

Ammonia

007664-41-7

3,678

25%

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

3.3 Occurrence of CWA-HS Threats

The SWCTI developed for this study includes Clean Water Act Hazardous Substances (CWA-HS). The
Clean Water Act, Section 311 (b)(2)(A) requires U.S. EPA to compile a list of hazardous substances which
pose a threat to the public health or welfare when discharged into navigable waters or adjoining
shorelines (U.S. EPA, 2021a). The CWA-HS list was published in 1978 and includes 296 substances. A
complete listing of CWA-HS can be found at 40 CFR 116. Of the 506,413 threats identified in the SWCTI,
46,281 (9%) threats were identified as a CWA-HS.

The frequency of CWA-HS threats and average volume by contaminant class is shown in Figure 9. CWA-
HS materials in the Chlorine class occur at the greatest frequency, with 11,271 threats (24%). This CWA-
HS contaminant class includes liquified chlorine gas (59%), sodium hypochlorite (36%), and calcium
hypochlorite (5%). The total volume of material in the CWA-HS Chlorine class is 818,102 kgal, most of
which is liquified chlorine gas, 778,795 kgal (95%). The average volume of material in the Chlorine class
is 73 kgal per threat (i.e., {total Chlorine volume 818,102 kgal} / {total Chlorine threat count 11,271}).

12,000
| 10,000

e 8,000

-C

H
c

.1 6,000
E

ro
c

3 4,000

oo
X

5 2,000

11,271
73

10,798
1'209 15,645

7,055

6,433

163

•

5,127
6,816

4,689
68

697
187

202
31
•

9
11

C°

\<>

¦TO

18,000
16,000
14,000
12,000 j?
10,000 E

8,000 >

CtO
ra

6,000 fc
<

4,000
2,000
0

Contaminant Class

Figure 9. Total Number of Threats and Average Volume for Each CWA-HS Contaminant Class

The next most commonly occurring CWA-HS contaminant class is Acid, with 10,798 (23%) threats.

Sulfuric acid is the most common CWA-HS material in the Acid class with 6,698 (62%) threats. The total
CWA-HS Acid class volume is 13,059,473 kgal, and nitric acid is the material in this class with the greatest
total volume at 7,484,673 kgal (57%). The average volume within the Acid class is 1,209 kgal per threat.

The third most commonly occurring CWA-HS contaminant class is Caustic, with 6,433 (14%) threats.
Within the Caustic class, sodium hydroxide is the most common CWA-HS material with 5,508 (86%)
threats, followed by potassium hydroxide with 925 (14%) threats. The total CWA-HS Caustic class
volume is 1,047,819 kgal, and potassium hydroxide is the material in this class with the greatest total
volume at 604,353 kgal (58%). The average volume within the Caustic class is 163 kgal per threat.

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

The fourth most commonly occurring contaminant class for CWA-HS materials is Organic Chemical, with
7,055 (15%) threats. Within the Organic Chemical class, the most commonly occurring material is
toluene with 952 (13%) threats followed by naphthalene with 781 (11%) threats. The total CWA-HS
Organic Chemical class volume is 110,377,573 kgal, most of which is ethylbenzene, 105,795,963 kgal
(96%). The Organic Chemical class had the highest average volume of all contaminant classes at 15,645
kgal per threat.

Table 13 shows the total number of CWA-HS threats for each contaminant class by state. The dark red
font color indicates the most frequently occurring contaminant class for each state followed by lighter
shades of red highlighting the second and third most frequently occurring contaminant class. The states
with the most CWA-HS threats include Louisiana, 11,309 (24%); Texas, 9,802 (21%); and Florida, 6,430
(14%).

Table 13. Total Number of CWA-HS Threats for Each Contaminant Class by State

Total

Chlorine

1,837

3,964

2,696

745

408

657

117

567

243

11,271

Acid

2,369

1,407

1,371

1,029

1,527

951

616

797

608

123

10,798

Caustic Material

2,023

901

1,045

831

425

343

416

149

197

103

6,433

Organic Chemical

2,336

1,891

145

859

380

191

954

130

156

7,055

Fertilizer

1,191

609

728

442

584

817

153

261

164

178

5,127

Inorganic Chemical

1,296

981

346

663

378

262

212

330

195

4,689

Pesticides or Herbicides

238

114

697

Cyanide Compounds

202

Trade Name

Total

11,309

9,802

6,430

4,611

3,834

3,305

2,563

2,347

1,585

495

46,281

Table 14 shows the number of CWA-HS threats in each contaminant class that fall within a specified
volume range. Similar to Table 8, four volume ranges are shown: less than 1 kgal; between 1 and 10
kgal; between 10 and 100 kgal; and greater than 100 kgal. With the exception of Cyanide Compounds
and Organic Chemical classes, all other contaminant classes had significantly fewer CWA-HS threats in
the greater than 100 kgal volume range compared with the lower volume ranges. The contaminant
classes with the most CWA-HS threats in the greater than 100 kgal volume range include Organic
Chemical, 1,261 (35%); Acid, 845 (24%); and Caustic Material, 618 (17%). The contaminant classes with
the largest CWA-HS total volumes include Organic Chemical, 110,377,573 kgal (69%);
Fertilizer/Ammonia, 34,945,388 kgal (22%); and Acid, 13,059,474 kgal (8%). Note that percentages are
calculated relative to the total count or volume in the corresponding volume range.

Table 14. Total
Contaminant C

Number of CWA-HS Threats Containing a Volume within the Indicated Range for Each
ass

Contaminant Class

No. of Threats

Total Volume
(kgal)

Avg. Volume
(kgal)

Number of Threats in Volume Range

Largest Volume
(kgal)

Not Reported

< 1 (kgal)

1 -10 (kgal)

10 -100 (kgal)

> 100 (kgal)

TOTAL

46,281

160,704,144

3,472

4,745

18,767

12,483

6,701

3,585

N/A

Organic Chemical

110,377,573

15,645

1,912

1,368

816

1,261

2,958,030

Fertilizer/Ammonia

5,127

34,945,388

6,816

483

1,694

1,437

1,140

373

Acid

10,798

13,059,474

1,209

725

5,421

2,483

1,324

845

1,092,000

Caustic Material

6,433

1,047,819

163

332

1,593

2,554

1,336

16,900

Chlorine

11,271

818,103

587

7,072

2,737

788

48,446

Inorganic Chemical

4,689

318,948

980

1,604

302

25,972

Pesticides or Herbicides

697

130,441

187

223

279

110

36,183

Cyanide Compounds

202

6,298

120

Trade Name

101

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

To investigate the geographic distribution of CWA-HS threats and releases, the threat locations were
mapped in Figure 10. The states with the most CWA-HS threats and releases include Louisiana, 11,309
(24%); Texas, 9,802 (21%); and Florida, 6,430 (14%). The map shows a high density of CWA-HS threats in
southeastern Louisiana, northern New Jersey, eastern Texas, and northeastern Illinois. As expected,
occurrence of CWA-HS threats and releases was greater in more industrialized areas, including the
following cities: Newark, NJ; Baton Rouge, LA; Dallas, TX; Houston, TX; and Chicago, IL. However, CWA-
HS threats are widely distributed across many of the states, and dense occurrence of CWA-HS threats
can occur outside industrialized areas.

Figure 10. Geographic Distribution of CWA-HS Threats and Releases

(The total number of threats and releases displayed on this map is 46,281, which are associated with
only 6,838 unique sites. This results in significant overlap of symbols on this map.)

The threat counts in Table 13 show Chlorine, Acid, and Caustic Material classes make up 62% of the
CWA-HS contaminant threats in the SWCTI. These three contaminant classes contain only a few specific
CWA-HS materials. The most frequently occurring materials in these three classes are: liquified chlorine
gas (Chlorine), sulfuric acid (Acid), and sodium hydroxide (Caustic).

There are significantly more CWA-HS materials in the Organic Chemical (62) and Inorganic Chemical (49)
classes. Thus, these two important contaminant classes were selected for a more detailed assessment.

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Table 15 shows the ten most commonly occurring CWA-HS materials in the Organic Chemical class,
displaying the count for the listed material and percentage relative to the total count in the Organic
Chemical class. The most commonly occurring CWA-HS material in the Organic Chemical class was
toluene, 952 (13%); followed by naphthalene, 781 (11%); and xylene, 751 (11%).

Table 15. Ten Most Commonly Occurring CWA-HS Materials in the Organic Chemical Class

Material Name

CASRN

Threat Count for
Material Name

% of Total Class
Count

Toluene

000108-88-3

952

13%

Naphthalene

000091-20-3

781

11%

Xylene

001330-20-7

751

11%

Formaldehyde

000050-00-0

438

Styrene

000100-42-5

431

Acetic acid

000064-19-7

349

Ethylbenzene

000100-41-4

294

Phenol

000108-95-2

281

Benzene

000071-43-2

243

Aniline

000062-53-3

205

Table 16 lists the most frequently occurring CWA-HS materials in the Inorganic Chemical class, with the
top three commonly used in water treatment: aluminum sulfate, 956 (20%); sodium bisulfite, 809 (17%);
and ferric chloride, 491 (10%).

Table 16. Ten Most Commonly Occurring CWA-HS Materials in the Inorganic Chemical Class

Material Name

CASRN

Threat Count for
Material Name

% of Total Class
Count

Aluminum sulfate

010043-01-3

956

20%

Sodium bisulfite

007631-90-5

809

17%

Ferric chloride

007705-08-0

491

10%

Lead acetate

000301-04-2

435

Potassium permanganate

007722-64-7

272

Sodium nitrite

007632-00-0

261

Ferric sulfate

010028-22-5

231

Ferrous sulphate

007720-78-7

120

Zinc sulfate

007733-02-0

114

Zinc chloride

007646-85-7

105

3.4 Threat Occurrence by ZOC

The results presented in Sections 3.1 through 3.3 aggregated threat occurrence within each state and
across all ten states in the study area. This section provides details on the occurrence of threats within a
source water ZOC for the CWS intakes and wells included in this study. It is important to consider that
multiple intakes located in close proximity to each other have overlapping ZOCs, which results in the
same threat impacting multiple ZOCs. Examples of SW and GW overlapping ZOCs are displayed in
Figures 11 and 12. Both figures show the intake or wellhead location as a blue triangle, one ZOC as light
pink, the second ZOC as orange, and the overlapping ZOC areas as red.

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Figure 11. Example of Overlapping SW ZOCs

Figure 12. Example of Overlapping GW ZOCs

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Table 17 shows the total number of SW and GW ZOCs delineated for each state and the total number of
ZOCs with and without threats for each state. Of the 32,593 ZOCs delineated for this analysis, 1,152 are
SW ZOCs, with 1,003 (87%) containing at least 1 threat; and 31,441 are GW ZOCs, with 19,955 (63%)
containing at least 1 threat. The states with the highest percentage of SW ZOCs containing at least 1
threat include Illinois, 131 (96%); Texas, 343 (85%); and Ohio, 196 (85%). The states with the highest
percentage of GW ZOCs containing at least 1 threat include Florida, 4,358 (80%); Ohio, 2,090 (77%); and
Texas, 4,582 (42%).

Table 17. Total Number of SW and GW ZOCs Delineated for Each State

Total

Total No. of SW Zones

231

405

137

139

1,152

Total No. of SW Zones with 0 Threats

149

Total No. of SW Zones with >0 Threats

196

343

131

125

1,003

Total No. of GW Zones

2,698

10,914

1,193

2,034

2,812

2,004

5,478

225

2,161

1,922

31,441

Total No. of GW Zones with 0 Threats

608

6,332

669

614

760

439

1,120

441

454

11,486

Total No. of GW Zones with >0 Threats

2,090

4,582

524

1,420

2,052

1,565

4,358

176

1,720

1,468

19,955

Figure 13 shows the total threat count per state (blue shading and number within state boundary) as
well as the average threat count per ZOC (black circles) in the state. The average ZOC threat count is
computed as the total number of threats in the state divided by the total number of ZOCs with at least
one threat in the state.

; t /T

21,599

49'118 I 21,885 "j!42

o © ©

37,164

40,181

Threat Count

6,330 116,734

Figure 13. Total and Average ZOC Threat Count in Each State

The states with the highest average ZOC threat counts include Kentucky (133), Louisiana (66), and Ohio
(33). The large average ZOC threat counts in Kentucky were driven by a small number of ZOCs covering

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

large resource extraction wellfields where individual wells are represented as a single threat. Out of the
301 ZOCs with at least 1 threat in Kentucky, 8 of the SW ZOCs contained more than 1,000 threats, and
the total number of threats in these 8 SW ZOCs was 12,259, of which 6,706 (55%) were Injection and
Resource Extraction Wells.

Figures 14 and 15 represent each ZOC containing at least one threat as a point on the map. The
symbology on these two figures uses a color designation to indicate the threat count bin into which each
ZOC falls. The five threat count bins used in these figures are: 1; 2 to 25; 26 to 100; 101 to 1,000; and
greater than 1,000.

Figure 14 shows the geographic distribution of SW ZOCs containing at least 1 threat. There were 327
(33%) SW ZOCs with threat counts that fell within the 101 to 1,000 bin, followed by 308 (31%) in the 2 to
25 bin. Only 78 (7%) SW ZOCs had threat counts that fell in the greater than 1,000 bin. The states with
the most SW ZOCs containing more than 1,000 threats include: Louisiana, 28 (36%); Ohio, 16 (21%); and
Texas, 12 (15%) - percentages are calculated relative to the 78 SW ZOCs that had threat counts in the
greater than 1,000 range.

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Figure 15 shows the geographic distribution of GW ZOCs containing at least 1 threat. There were 14,577
(73%) GW ZOCs containing 2 to 25 threats, followed by 3,835 (19%) containing 1 threat. Only 2 GW
ZOCs, one located in New Jersey and the other in Texas, contained more than 1,000 threats. The states
with the most GW ZOCs containing at least 1 threat include Texas, 4,582 (23%); Florida, 4,358 (22%); and
Ohio, 2,090 (10%).

Threat Count

¦ 1000+

¦ 101-1000
26-100

¦ 2-25

¦ 1

Figure 15. Geographic Distribution of GW ZOCs Containing Threat Counts Within the Indicated Range

Comparison of distribution of threat counts between SW and GW ZOCs displayed in Figures 14 and 15
clearly show that a greater proportion of SW ZOCs fail into the higher threat count bins compared with
GW ZOCs. These differences in threat occurrence between SW and GW ZOCs are explored further in the
following analysis.

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Figure 16 presents the distribution of threat counts for SW and GW ZOCs using thirteen threat count
bins: 1; 2; 3; 4; 5; 6-24; 25-49; 50-99; 100-299; 300-499; 500-999; 1,000-2,999; and greater than or
equal to 3,000. Of the 1,003 SW ZOCs containing a least one threat, 17% (173) had threat counts that fell
into the 6-24 bin, followed by 17% (172) in the 100-299 bin. Of the 19,955 GW ZOCs containing a least
one threat, 36% (7,148) had threat counts that fell into the 6-24 bin, followed by 19% (3,835) in the 1
bin The distribution of threats in Figure 16 show that threat counts in SW ZOCs skew towards higher
threat count bins compared to GW ZOCs. Using 25 threats per zone as a reference, 62% (624) of SW
ZOCs contain 25 or more threats compared to 8% (1,671) of GW ZOCs that contain 25 or more threats.
At the upper end of the distribution, 8% (78) of SW ZOCs contain more than 1,000 threats while only
0.01% (2) of GW ZOCs contain more than 1,000 threats.

40%

I SW Zones
I GW Zones

30%

« 20%

15%

19%

17%

i J il

17%

12%

10.1% ¦0.196 ¦ 0.01% 0.01%

j? y
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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Table 18 shows the SW and GW ZOC threat count statistics per state, including minimum, mean,
maximum, 10th percentile, 50th percentile, and 90th percentile. States that had the highest 50th
percentile SW ZOC threat counts include Louisiana (1,218), New Jersey (224), and Kentucky (90). States
that had the highest 50th percentile GW ZOC threat counts include Kentucky (11), Florida (7), Illinois (6),
Indiana (6), and Louisiana (6).

Table 18. Threat Count Statistics for SW and GW ZOCs per State

Overall

Mean Zonal Threats

133

Minimum Zonal Threats

10th Percentile Zonal Threats

50th Percentile Zonal Threats

90th Percentile Zonal Threats

440

Maximum Zonal Threats

4,027

2,393

2,417

1,563

2,137

1,666

932

2,894

6,779

3,309

6,779

Mean SW Zonal Threats

298

163

173

184

199

172

120

299

1,485

408

288

Minimum SW Zonal Threats

10th Percentile SW Zonal Threats

50th Percentile SW Zonal Threats

1,218

224

90th Percentile SW Zonal Threats

843

384

129

459

578

359

194

791

2,898

1,129

764

Maximum SW Zonal Threats

4,027

2,393

2,417

1,563

2,137

1,666

932

2,894

6,779

2,322

6,779

Mean GW Zonal Threats

Minimum GW Zonal Threats

10th Percentile GW Zonal Threats

50th Percentile GW Zonal Threats

90th Percentile GW Zonal Threats

Maximum GW Zonal Threats

226

2,293

78 207

184

310

105

889

3,309

The ten SW ZOCs that had the maximum threat counts in each state collectively contained a total of
27,130 (9%) threats. The ten GW ZOCs that had the maximum threat counts in each state collectively
contained a total of 7,700 (4%) threats. Additional analyses of SW and GW ZOCs with the largest threat
counts can be found in Appendix B.

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Throughout Section 3.4, attention has been drawn to ZOCs that contain a large number of threats,
working from the hypothesis that ZOCs that contain a large number of threats are at greater risk of
experiencing a release. A 2021 study evaluated the occurrence of releases between 2010 and 2019 that
had the potential to impact sources of drinking water (U.S. EPA, 2021b). The 2021 study used the same
ZOC definitions as are used in this SWCTI study, thus it was possible to compare the number of threats in
a ZOC with the number of releases that occurred in the same ZOC between 2010 and 2019. Figure 17
presents a scatter plot of the number of releases versus the number of threats in SW ZOCs included in
this study. No correlation was observed between the number of threats and number of releases in a SW
ZOC. In fact, there were a number of SW ZOCs with fewer than 100 threats which experienced more
than ten releases over the 10-year period. Conversely, there were several SW ZOCs that contained more
than 1,000 threats but experienced fewer than ten releases.

0 500 1,000 1,500 2,000

Number of Threats in a SW ZOC

Figure 17. Correlation between Number of Threats and Number of Releases in SW ZOCs

The reasons for the lack of a correlation between threat count and release occurrence is unclear.
However, the release report shows that the most frequent known cause of releases to source waters is
equipment failure (U.S. EPA, 2021b). Thus, it may be that the characteristics of individual sites that store
or handle chemicals and other materials is a more important factor in the risk of a release than is the
number of threats in a ZOC. Another factor to consider is that some sites (i.e., specific facilities) are
associated with more than 100 threats. Such large facilities may have more resources and incentive to
invest in spill prevention and response. And while the presence of such large facilities with 100s of
threats in a ZOC may elevate a water system's raw threat count, the results in this study suggest that
this does not necessarily translate into a greater risk of releases. However, this is only a hypothesis
based on the data available from these two studies, and more research is needed to gain a better
understanding of the factors that increase the risk of releases into sources of drinking water.

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

¦ Threats from a
State Resource

¦ Threats from a
National Resource

3.5 Evaluation of Information Resources

As discussed in Section 2, it was necessary to utilize
both state and national information resources to
build a comprehensive SWCT1 because no single
resource covers all threat types. A total of 88
information resources were collected, consisting of
25 (28%) national information resources and 63
(72%) state information resources. State information
resources proved to be more valuable than national
information resources because the state information

resources generally contained more complete information and fewer data gaps, however, national
resources provided more uniform data for interstate SWCTIs. Table 19 and Table 20 show the national
and state information resources that were collected for each threat type.

Table 19. National Information Resources used in this Study, Organized by Threat Type

Threat Type Covered

Number of
Resources

Names of Resources

Chemical Facilities

EPA RMP Facilities
RMP Facilities with Anhydrous Ammonia
Facilities with Anhydrous Ammonia
TSCA Consumer and Commercial Use Information
TSCA Industrial Processing and Use Information
TSCA Manufacturing Information

Energy infrastructure

Coal Power Plants
Ethylene Crackers
Natural Gas Processing Plants
Petroleum Refineries
Power Plants

Toxic Release

NRC Incident Reports
Toxic Release Inventory System

TRI - Releases to Land
TRI - Releases to Underground
TRI - Releases to Water & POTW

Resource Extraction

Coal Mines
Natural Gas Market Flubs
Natural Gas Underground Storage

Injection and Resource
Extraction Wells

Hydraulic Fracturing Wells by Type of Toxin - Gas
Hydraulic Fracturing Wells by Type of Toxin - Oil

LUST

UST Finder App

Oil Storage Facilities

EPA FRP Facilities

Hazardous Waste

RCRA

NPDES

National Pollutant Discharge Elimination System

Storage Tanks

AST

CAFOs

Tier II

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Table 20. State Information Resources used in this Study, Organized by Threat Type

Threat Type Covered

Number of
Resources

Names of Resources

Hazardous Waste

FL- Hazardous Waste Transfer Facilities
FL - Hazardous Waste Transport Facilities
FL - HAZWASTE
FL - Waste Cleanup Open Responsible Party Sites

IL - IEPA Coal Ash Ponds
KY - Hazardous Waste Large Quantity Generators
KY - Solid Waste Landfills Points
LA - Hazardous Waste Permits
NH - Hazardous Waste Generators
NH - Solid Waste Facilities
TX - Industrial and Hazardous Waste

Tier II

Statewide Tier II Dataset

Resource Extraction

IA - Coal Mines Points
IL - All Mine Points
IN - Active Industrial Mineral Operations
KY - Active Coal Mines
KY - Mineral Operations

LA - Coal Mines
OH - Coal Mines Current
OH - Coal Mines Locations
OH - Industrial Mineral Locations
TX - Historical Coal Sites

NPDES

FL - NPDES Facilities (both Domestic and Industrial)
IA - Wastewater NPDES Facility
IL-NPDES Permits
IN - Water NPDES Facilities
IN - Water NPDES Pipe Locations
KY - KPDES Permitted Facilities
LA - LPDES

NJ - NJPDES Active Permit List with Contacts
NJ - Surface Water Discharge
OH - NPDES Individual Permits

Injection and Resource Extraction Wells

FL - Permitted Oil and Gas Wells

IN - Petroleum Wells
KY - Class 1 Wells, Waste Injection
KY - Class II Wells, Injection Wells Associated with Oil and Gas Production
KY - Oil & Gas Wells
LA - Well Information
OH - Active Oil and Gas Wells
OH - Oil and Gas Wells

CAFOs

Statewide CAFOs Dataset (IA, IL, IN, OH, TX)

AST

Statewide AST Dataset (IA, OH, NH, TX)

LUST

Statewide LUST Dataset (IA, IL)

Chemical Facilities

FL - Fuel Facilities

Storage Tanks

FL - Registered Tanks from Storage Tank and Contamination Monitoring (STCM)

Energy Infrastructure

IN - Ethanol Production Facilities

Oil Storage Facilities

Toxic Release

The national and state information resources used in this study were selected in an effort to obtain
specific threat attributes, including material identification (name/CASRN), material volume/mass,
discharge flow information, and facility/tank operation status. Table 21 shows the number of national or
state information resources that included information about each of the listed attributes. Key findings
from the evaluation of information resources include:

• State information resources generally had more complete reporting of material identity and
volume/mass stored on-site compared with national information resources.

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

• Tier II was the most valuable information resource due to broad coverage of facilities that

handle or store chemicals, the consistent availability of the identity and mass of material on-site,
and the annual updating of Tier II chemical inventories. This valuable dataset is only available
from state information resources.

Table 21. Threat Attributes Available in National and State Information Resources

Attribute

National Threat Type (Count)

Total National
Resources

State Threat Type (Count)

Total State
Resources

Material Identification
(Name/CASRN)

Energy Infrastructure (1)

Chemical Facilities (5)

Injection and Resource Extraction Wells (2)
LUST (1)

Toxic Release (4)

13 (52%)

AST (4)
Chemical Facilities (1)
Resource Extraction (2)
Energy Infrastructure (1)
Tier II (10)

18 (29%)

Material Volume/Mass

Chemical Facilities (3)
Toxic Release (3)

6 (24%)

AST (4)
Chemical Facilities (1)
Resource Extraction (1)
Tier II (10)

16 (25%)

Discharge Flow Information

0(0%)

NPDES (3)

3 (5%)

Facility/Tank/Operation Status

0(0%)

Injection and Resource Extration Wells
(3)

Storage Tanks (1)

AST (2)

LUST (1)

NPDES (1)

CAFOs (1)

Hazardous Waste (1)

10(16%)

Of the 506,413 threats identified in the SWCTI, 391,880 (77%) threats were identified through a state
information resource and 114,533 (23%) threats were identified through a national information
resource. Table 22 shows the number of threats, categorized by threat type, identified using national
and state information resources. All except the following four threat type categories are represented in
national information resources: Tier II, Storage Tanks, AST, and CAFOs. State information resources
covered all threat types except Toxic Release and Oil Storage Facilities (i.e., EPA Facility Response Plan
[FRP] Facilities), although this coverage varied widely across the ten states. Information resources for
some threat types were identified in only one or two of the ten states (e.g., information resources
covering Energy Infrastructure were identified only in KY and IN).

Comparing the total threat counts across all threat type categories shows that the number of threats
identified using state information resources exceeds the number identified using national resources,
with the following five exceptions: LUSTs, Toxic Release, Oil Storage Facilities, Energy Infrastructure, and
NPDES. The national LUST information resource is a compilation of state and national databases, and
thus would be expected to provide a comprehensive inventory of LUSTs. Toxic releases are tracked
through EPA's Toxics Release Inventory (TRI) and the National Response Center (NRC) Spill Reporting
Hotline. Large Oil Storage Facilities are tracked through EPA's FRP regulation. Thus, while state
information resources may collectively provide a larger raw threat count, there are gaps in threat type
coverage by state resources, and some states (e.g., NJ, NH) lack information resources for several of the
listed threat types.

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Table 22. Count of Threats (by Threat Type Category) Identified through National and State
Information Resources

Total

Tier II - National

N/A

Tier II - State

71,354

50,840

23,191

20,181

19,492

8,981

15,685

7,855

14,335

2,126

234,040

Injection and Resource Extraction Wells - National

7,886

7,942

Injection and Resource Extraction Wells - State

27,866

8,759

31,873

12,732

N/A

4,534

N/A

85,832

NPDES-National

8,277

5,742

6,875

7,962

5,437

4,264

2,333

3,579

1,343

661

46,473

NPDES - State

5,444

242

4,035

1,006

3,332

2,461

4,318

2,848

927

N/A

24,613

LUST - National

362

862

1,565

3,020

2,953

7,047

2,411

814

409

310

19,753

LUST - State

N/A

12,652

N/A

182

1,221

N/A

14,055

Chemical Facilities - National

1,903

2,994

2,441

649

1,361

701

10,649

546

921

22,214

Chemical Facilities - State

N/A

4,482

N/A

4,482

Storage Tanks - National

N/A

Storage Tanks - State

N/A

13,656

N/A

13,656

Toxic Release - National

882

2,213

2,925

820

1,938

1,011

904

1,003

686

179

12,561

Toxic Release - State

N/A

Hazardous Waste - National

360

125

810

226

529

201

772

255

3,412

Hazardous Waste - State

1,332

482

535

1,161

3,672

AST - National

N/A

AST - State

3,668

588

N/A

103

N/A

736

1,753

6,858

Resource Extraction - National

219

298

Resource Extraction - State

122

653

N/A

831

1,883

N/A

414

N/A

3,905

Energy Infrastructure - National

304

240

214

132

1,227

Energy Infrastructure - State

N/A

CAFOs - National

N/A

CAFOs - State

N/A

178

384

N/A

764

Oil Storage Facilities - National

146

198

653

Oil Storage Facilities - State

N/A

Total - National

12,031

20,349

14,984

12,748

12,546

13,577

17,147

6,282

3,579

1,290

114,533

Total - State

104,703

65,027

60,458

39,836

36,572

26,604

20,017

15,603

18,020

5,040

391,880

The results of this analysis demonstrate that under the current paradigm of fractured data collection for
potential sources of source water contamination, a comprehensive SWCTI can only be developed
through use of multiple information resources from both national and state information resources.
National information resources were found to be important for identifying threat types including Toxic
Release, Energy Infrastructure, Oil Storage Facilities, Hazardous Waste, and NPDES. State information
resources were found to be important for identifying threat types including Tier II, Resource Extraction
sites (including wells), Storage Tanks (including ASTs and LUSTs), Hazardous Waste sites, NPDES, and
CAFOs. Notably, the single most valuable information resource, in terms of both threat coverage and
availability of important threat attributes, were the Tier II datasets, which are only available through
State Emergency Response Commissions or Local Emergency Planning Committees. Fortunately,
amendments to the EPCRA, enacted under Section 2018 of AWIA, provide CWSs with the legal authority
to access this important dataset (U.S. EPA, 2019).

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Section 4.0: Summary and Conclusions

A SWCTI conducted for ten states (Florida, Illinois, Indiana, Iowa, Kentucky, Louisiana, New Jersey, New
Hampshire, Ohio, and Texas) identified 506,413 threats and 110,745 unique sites within the ZOCs
delineated for CWSs that serve a population of 1,000 customers or more. Threats identified in this
SWCTI include any material that is manufactured, used, stored, or discharged at an active site that fell
within a ZOC. Regardless of their proximity to intakes or wellheads, threats considered to pose a
minimal risk of releasing a significant volume of a contaminant to drinking water sources over a short
duration were excluded, such as dry wells, wells that were not drilled, small quantity generators as
designated under RCRA, stormwater discharges, and threats reporting a material volume or mass of "0."
Additionally, materials unlikely to change water quality (e.g., lead acid batteries, limestone, propane)
were excluded from the analysis (see Table 4 in Section 2.3 for additional materials excluded from the
analysis). Finally, this analysis did not consider releases that can occur during transportation accidents.

Of the 506,413 threats, 288,875 (57%) threats were within 1,003 SW ZOCs and 217,538 (43%) were
within 19,955 GW ZOCs. Threats in the SWCTI existed across all ten states, with the highest density of
threats near industrial areas, resource extraction hubs, and urban areas. States with the greatest
number of threats included Louisiana, 116,734 (23%); Texas, 85,376 (17%); and Ohio, 75,442 (15%). Of
the 506,413 threats, the threat types with the largest threat counts in the SWCTI included Tier II,

234,040 (45%); Injection and Resource Extraction Wells, 93,774 (19%); and NPDES, 71,086 (14%).

Material names were reported for 276,816 (55%) of the 506,413 threats identified in the SWCTI. A mass
or volume was reported for 227,449 (82%) of the 276,816 threats with material names. The most
commonly occurring contaminant class was Organic Chemical with 59,402 (21%) threats, followed by
Trade Name with 45,991 (16%) threats, Petroleum Products with 36,517 (13%) threats, and Diesel or
Gasoline with 36,250 (13%) threats. The contaminant categories with the largest total volumes were
Petroleum Products with 452,352,011 kgal (51%), Organic Chemical with 327,924,764 kgal (37%), and
Fertilizer/Ammonia with 53,036,862 kgal (6%). Within the Organic Chemical class, the most commonly
occurring materials were methanol, 5,472 (9%); ethanol, 2,003 (3%); and paraffinic petroleum distillates,
1,332 (2%).

Of the 506,413 threats identified in the SWCTI, 46,281 (9%) were identified as a CWA-HS. The most
commonly occurring contaminant classes for CWA-HS were Chlorine with 11,271 (24%) threats, Acid
with 10,798 (23%) threats, and Caustic Material with 6,433 (14%) threats. The contaminant categories
with the largest total volumes of CWA-HS were: Organic Chemical, 110,377,573 kgal (69%);
Fertilizer/Ammonia, 34,945,388 kgal (22%); and Acid, 13,059,474 kgal (8%). Within the Organic Chemical
class, the most commonly occurring CWA-HS threats were toluene, 952 (13%); naphthalene, 781 (11%);
and xylene, 751 (11%). CWA-HS threats were widely distributed across all ten states, with a high density
of CWA-HS threats in more industrialized areas including southeastern Louisiana, northern New Jersey,
northeastern/southeastern Texas, and northeastern Illinois.

A total of 32,593 ZOCs were delineated for this analysis, including 1,152 SW ZOCs and 31,441 GW ZOCs.
Of the 1,152 SW ZOCs, 1,003 (87%) contained at least 1 threat. There were 327 (33%) SW ZOCs with
threat counts between 101 and 1,000, and 78 (7%) SW ZOCs with threat counts greater than 1,000. Of
the 31,441 GW ZOCs, 19,955 (63%) contained at least 1 threat. Of these, 14,577 (73%) had a threat
count between 2 and 25, while only 2 (<1%) contained more than 1,000 threats: one GW ZOC located in
NJ and the other in Texas.

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

The study identified 12,561 releases of a substance, but there was not a statistically significant
correlation between the number of threats and number of releases in a SW ZOC. The reasons for this
lack of correlation are unclear and warrant further research.

Both state and national information resources were necessary to build a comprehensive SWCTI due to
gaps in information available from any single information resource. Of the 88 information resources
collected, 25 (28%) were national information resources and 63 (72%) were state information resources.
Some threat types were better covered by national resources, such as Energy Infrastructure, Oil Storage
Facilities, and Toxic Release, while others were better covered by state resources, such as Tier II
Hazardous Chemical Storage, Storage Tanks, and Resource Extraction. Tier II datasets were found to be
the single most valuable information resource, in terms of both threat coverage and availability of
important threat attributes. Tier II datasets are only available through states or Local Emergency
Planning Committees; however, the amendments to EPCRA under AWIA, Section 2018 explicitly grant
CWSs with access to Tier II data for facilities located in a corresponding source water protection area.

The results of this SWCTI indicate that threats are prevalent across all industrial, agricultural, urban, and
resource extraction regions that fall within SW and GW ZOCs. Although 11,635 (36%) ZOCs out of 32,593
did not have a threat present within the ZOC, there is a possibility that a release from a threat outside of
a ZOC could significantly impact a source of drinking water. The following section provides
recommendations to help CWSs develop a SWCTI and use it to understand risk and prepare for releases.

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Section 5.0: Recommendations

The findings from this SWCTI demonstrate a variety of threat types occurring in SW and GW ZOCs across
the ten states inventoried. However, the analysis of threat occurrence within individual ZOCs showed
that threat occurrence varied by as much as three orders of magnitude and that the specific types of
threats in a ZOC depend on local conditions, such as land use, characteristics of the drainage area, and
the prevalence of industry, resource extraction, or agriculture in the region. Thus, for a water system to
understand its unique risk of acute source water contamination incidents, it is necessary to develop a
system-specific SWCTI. Once a SWCTI is developed, it should be analyzed to characterize and prioritize
those threats identified in the inventory that present the greatest risk, considering factors such as:

• The identity and quantity of a material stored at the site

• Overland flow distance from the site to the waterbody, including consideration of direct
conveyance that may occur through waste or storm water collection systems, or other
infrastructure

• Flowpath within the waterbody from the site to the drinking water intake or wellhead

• Groundwater fate and transport modeling through an aquifer

• History of releases in the ZOC, including those that reached the waterbody

If the results of the SWCTI indicate the risk of releases to source water is significant, the following
actions should be considered to prepare for and mitigate that risk:

• Identify the materials stored, used, or released at sites that pose the greatest risk to a source
water

• Identify methods and laboratories that can analyze for these materials

• Evaluate the ability of current treatment processes, including intermittent pretreatment, such as
addition of powdered activated carbon, to remove or neutralize these materials

• Reach out to site owners to share contact information and coordinate communications in the
event of a release from that site

• Ensure that notifications of releases that are reported under EPCRA are promptly reported to
CWSs that could be impacted (U.S. EPA, 2019)

• Create relationships with first responders and Local Emergency Planning Committees to
coordinate communications for notification of releases that could impact a source water

• Consider methods for monitoring and early detection of releases

• Update emergency response plans to include procedures to respond to releases from threats
identified in the SWCTI

• Periodically update the SWCTI to capture new threats and update information about previously
identified threats

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

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inventory

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Glossary

Census Designated Urban Areas. An area that encompasses at least 5,000 people or at least 2,000
housing units.

Clean Water Act Hazardous Substances. A list of substances defined under authorities of Section
311(b)(2) of the Clean Water Act (Title 40 of the CFR, Part 116).

Community Water System. A system that provides water for human consumption through pipes or
other constructed conveyances and has at least fifteen service connections or regularly serves at least
twenty-five individuals, and which serves the same population year-round (SDWA section 1401(15)).

Contaminants of Concern. Any contaminant that enters a body of water and is likely to cause adverse
human health effects, impact water system operations, or damage water system infrastructure.

ESRI Industrial Areas. Geographical areas zoned for industrial use by a government jurisdiction.

National Hydrography Dataset. A dataset maintained by the United States Geological Survey that
represents the water drainage network of the United States with features such as rivers, streams,
canals, lakes, ponds, coastline, dams, and stream gages.

National Response Center. The designated federal point of contact for reporting all oil, chemical,
radiological, biological, and etiological discharges into the environment, anywhere in the United States
and its territories. The National Response Center is part of the federally established National Response
System and staffed 24 hours a day by the U.S. Coast Guard.

Safe Drinking Water Information System. A system maintained by U.S. EPA that contains basic
information about each public water system, violation information for each public water system, and
enforcement information.

Shale Plays. A set of discovered, undiscovered, or possible natural gas accumulations that exhibit similar
geological characteristics. Shale plays are located within basins, which are large scale geologic
depressions, often hundreds of miles across, which may contain oil and natural gas resources.

Source Water Contamination Threat Inventory. A record of sites (e.g., facilities) that store or handle
materials, which if suddenly released, could contaminate a source of drinking water. A source water
contamination threat inventory (SWCTI) can be developed for systems using either surface water or
groundwater. The scope of a SWCTI is generally defined by threat types of most concern to a system
(e.g., above ground storage tanks, waste storage facilities) and a zone of concern (defined below).

Toxic Release Inventory. A program created under the Emergency Planning and Community Right-to-
Know Act that requires certain industries to file an annual report documenting releases of certain toxic
chemicals that may pose a threat to human health and to the environment. Reporting is limited to a list
of approximately 755 individual chemicals and 33 chemical categories.

Zone of Concern. For surface water intakes, an area that extends 50 miles upstream, / mile
downstream, includes all major tributaries, and includes a % mile buffer inland from the waterbody area
boundary. For groundwater wells, an area defined by a Vz mile radius around the well location. This
definition was used solely for the purposes of the study presented in this report.

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Appendix A: Unit Conversion Multipliers

For each unit of measure below, multiply the available value by the multiplier to convert to gallons (U.S.,
liquid).

• Barrels (petroleum) = 42.0

• Barrels (not petroleum) = 31.5

• Cubic Meters = 264.172

• Cubic Yards = 201.974

• Cups = 0.0625

• Drops = 0.0000132086

• Gallons = 1.0

• Liters = 0.264

• Ounces = 0.0078125

• Pints = 0.125

• Pounds = 0.12 (assuming a density of water of 8.345 pounds/gallon)

• Quarts = 0.25

• Tablespoons = 0.00390625

• Tons = 269.0 (assuming a density of water of 8.345 pounds/gallon)

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Appendix B: Supplemental Analyses of Threat Occurrence in Specific

ZOCs

Table 23 presents attributes of the ten SW ZOCs that contain the greatest number of threats. The threat
count for these ten SW ZOCs ranged from 2,775 to 6,779 threats, and the most common contaminant
classes occurring were the Organic and Inorganic Chemical classes. Note that the ZOCs with the
following IDs partially overlapped adjacent zones: 1, 2, 79, and 80. The two SW ZOCs (1 and 2) with the
greatest number of threats, 6,753 and 6,779, represent multiple intakes located near one another and
thus overlap almost completely, resulting in the two zones containing a nearly identical inventory of
threats. These two SW ZOCs are located south of Baton Rouge, LA, and most threats in these ZOCs are
Injection and Resource Extraction Wells: 3,931 (58%) and 4,131 (61%), for zones 1 and 2, respectively.

Table 23. SW ZOCs Containing the Greatest Number of Contamination Threats. (Unique sites are
discrete locations that manufacture, use, store, or discharge contaminants of concern. Threat counts
reflect the individual contamination threats located at these discrete locations.)

Threat Count

Zone Area
(sq mi)

Normalized
Threat Count

Unique Sites

Threat Type with Highest Threat
Count

Contaminant Class with
Highest Threat Count

1, 2

6,753 & 6,779

1,505 &
1,518

4.50

4,276 &
4,308

Injection and Resource Extraction
Wells (3,931 & 4,131)

Organic Chemical (371 & 389)

6,141

562

2,088

Tier II (3,593)

Organic Chemical (1,194)

5,575

108

274

Tier II (5,265)

Organic Chemical (1,588)

4,027

243

2,041

Injection and Resource Extraction
Wells (3,789)

Organic Chemical (36)

3,908

200

Tier II (3,651)

Organic Chemical (1,159)

79, 80

2,898

64 & 65

206

Tier II (2,639)

Organic Chemical (973)

2,894

291

2,103

Injection and Resource Extraction
Wells (1,590)

Organic Chemical (218)

2,877

386

1,277

Injection and Resource Extraction
Wells (1,469)

Inorganic Chemical (218)

2,788

297

1,407

Injection and Resource Extraction
Wells (2,431)

Organic Chemical (66)

2,775

356

1,233

Injection and Resource Extraction
Wells (1,346)

Inorganic Chemical (224)

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Table 24 presents attributes of the ten GW ZOCs that contain the greatest number of threats. Note that
the ZOCs with the following IDs partially overlapped adjacent zones: 138, 139, 140, 141, 132, and 155.
The threat count for these ten GW ZOCs ranged from 560 to 3,309 threats, and the most common
contaminant class was the Organic Chemical class. The GW ZOC (ID-95) with the greatest number of
threats was located near Madison, NJ and contained 3,309 threats, which are associated with five
unique sites (i.e., one or more of these five sites handle a very large number of chemicals). Of the 3,309
threats within this GW ZOC, 3,304 (99.8%) were chemical facility threats.

Table 24. GW ZOCs Containing the Greatest Number of Contamination Threats. (Unique sites are
discrete locations that manufacture, use, store, or discharges contaminants of concern. Threat counts
reflect the individual contamination threats located at these discrete locations.)

Threat Count

Zone Area
(sq mi)

Normalized
Threat Count

Unique Sites

Threat Type with Highest
Threat Count

Contaminant Class with
Highest Threat Count

3,309

0.78

4,217

Chemical Facilities (3,304)

Organic Chemical (2,339)

2,293

0.78

2,923

Tier II (2,265)

Organic Chemical (51)

889

0.78

1,133

Tier II (849)

Organic Chemical (257)

765

0.78

975

Tier II (741)

Organic Chemical (128)

714

0.78

910

Tier II (625)

Organic Chemical (142)

138, 139

708

0.78

902

Chemical Facilities (660)

Organic Chemical (609)

140, 141

684

0.78

872

Chemical Facilities (660)

Organic Chemical (588)

131

683

0.78

871

Tier II (646)

Organic Chemical (167)

132, 155

614 & 666

0.78

783 & 849

34 & 35

Tier II (554 & 606)

Organic Chemical (46 & 58)

142

560

0.78

714

Chemical Facilities (552)

Organic Chemical (324)

The ten SW ZOCs that had the maximum threat counts in each state collectively contained a total of
27,130 (9%) threats. The ten GW ZOCs that had the maximum threat counts in each state collectively
contained a total of 7,700 (4%) threats. The characteristics of these ten SW ZOCs and ten GW ZOCs are
presented in Tables 25 and 26, respectively.

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Table 25 presents attributes of the SW ZOC that contains the largest number of threats in each state.
Note that the ZOCs with the following IDs partially overlapped adjacent zones: 6 and 7; 1 and 2; 51 and
52. The states containing the SW ZOCs with the largest threat counts include Louisiana (largest SW ZOC
threat count = 6,779), Ohio (largest SW ZOC threat count = 4,027), and Kentucky (largest SW ZOC threat
count = 2,894). The two SW ZOCs in Louisiana with the largest threat count were previously described in
Table 23. The SW ZOC with the second largest threat count was in Ohio with 4,027 threats. This SW ZOC
was located near Alliance, OH, and the threats in this SW ZOC consisted mostly of resource extraction
wells, 3,789 (94%). The most commonly occurring contaminant classes in these SW ZOCs are the Organic
Chemical, Petroleum Products, Diesel or Gasoline, and Inorganic Chemical classes.

Table 25. SW ZOCs Containing the Greatest Number of Threats in each State. (Unique sites are
discrete locations that manufacture, use, store, or discharges contaminants of concern. Threat counts
reflect the individual contamination threats located at these discrete locations.)

State

Threat Count

Zone Area
(sq mi)

Normalized
Threat Count

Unique Sites

Threat Type with Highest Threat
Count

Contaminant Class with
Highest Threat Count

6,7

918 & 932

358 & 387

2 & 3

463 & 464

Tier II (408 & 427)

Diesel or Gasoline (123 & 131)

1,563

463

363

Tier II (1,178)

Organic Chemical (302)

2,137

876

Tier II (996)

Organic Chemical (182)

1,666

109

648

Tier II (861)

Inorganic Chemical (128)

2,894

291

2,103

Injection and Resource Extraction
Wells (1,590)

Organic Chemical (218)

1,2

6,753 & 6,779

1,505 & 1,518

4,276 & 4,308

Injection and Resource Extraction
Wells (3,931 & 4,131)

Organic Chemical (371 & 389)

2,417

718

1,097

Tier II (984)

Petroleum Products (657)

2,322

126

706

Tier II (1,639)

Organic Chemical (705)

4,027

243

2,041

Injection and Resource Extraction
Wells (3,789)

Organic Chemical (36)

51, 52

2,393

751

2,108

Injection and Resource Extraction
Wells (2,059)

Organic Chemical (54)

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Table 26 presents attributes of the GW ZOC in each state that contains the largest number of threats.
Note that the ZOCs with the following IDs partially overlapped adjacent zones: 118, 119, and 120; and
144 and 145. The states containing the GW ZOCs with the largest threat counts include New Jersey
(largest GW ZOC threat count = 3,309), Texas (largest GW ZOC threat count = 2,293), and Louisiana
(largest GW ZOC threat count = 889). The GW ZOC in New Jersey with the largest threat count was
previously described in Table 24. The GW ZOC with the second largest threat count was located near
Orange, TX, and the threats consisted mostly of Tier II threats, 2,265 (99%). The most commonly
occurring contaminant classes in these GW ZOCs are the Organic Chemical, Pesticides or Herbicides, and
Fertilizer/Ammonia classes.

Table 26. GW ZOCs Containing the Greatest Number of Threats in each State. (Unique sites are
discrete locations that manufacture, use, store, or discharges contaminants of concern. Threat counts
reflect the individual contamination threats located at these discrete locations.)

State

Threat
Count

Zone Area
(sq mi)

Normalized
Threat Count

Unique
Sites

Threat Type with Highest
Threat Count

Contaminant Class with
Highest Threat Count

100

310

0.78

395

Tier II (183)

Organic Chemical (209)

105

207

0.78

264

Tier II (204)

Pesticides or Herbicides (40)

112

184

0.78

235

Tier II (121)

Organic Chemical (30)

118, 119,
120

0.78

126

Tier II (96)

Pesticides or Herbicides (45)

126

105

0.78

134

Tier II (94)

Organic Chemical (19)

889

0.78

1,133

Tier II (849)

Organic Chemical (257)

133

0.78

Tier II (57)

Fertilizer (43)

3,309

0.78

4,217

Chemical Facilities (3,304)

Organic Chemical (2,339)

144, 145

225 & 226

0.78

287 & 288

2 & 3

Tier II (221)

Organic Chemical (179)

2,293

0.78

2,923

Tier II (2,265)

Organic Chemical (51)

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Inventory of Sites with the Potential to Release Contaminants to Sources of Drinking Water

Two major rivers in the ten-state study area, Mississippi River and Ohio River, intersected fifty-two SW
ZOCs. All SW ZOCs that intersected these rivers contained at least one threat. Table 27 presents
attributes of the five SW ZOCs containing the greatest number of threats that intersect each of these
two rivers. The five SW ZOCs that intersect the Mississippi River with the greatest number of threats
were all located along the river between Baton Rouge and New Orleans, LA. Note that the SW ZOCs with
the following IDs partially overlapped adjacent zones: 4, 35, 79, 80, and 155. Two SW ZOCs (79 and 80)
represent multiple intakes located near one another and thus overlap almost completely, resulting in
the two zones containing the same 2,898 threats. The threat count for these five SW ZOCs ranged from
1,738 to 6,141 threats. The most common contaminant class occurring in these five SW ZOCs along the
Mississippi River was Organic Chemicals.

The five SW ZOCs containing the greatest number of threats that intersect the Ohio River were mostly
located along the river near Ashland, KY, although one was located near Evansville, IN. Note that the SW
ZOCs with the following IDs partially overlapped adjacent zones: 31, 157, 156, and 158. The threat count
for these five SW ZOCs ranged from 1,305 to 2,894 threats. The most common contaminant classes
occurring in these five SW ZOCs along the Ohio River was Petroleum Products and Organic Chemical.

Table 27. SW ZOCs Containing the Most Threats Along the Mississippi and Ohio Rivers. (Unique sites
are discrete locations that manufacture, use, store, or discharges contaminants of concern. Threat
counts reflect the individual contamination threats located at these discrete locations.)

State

Potentially
Impacted
Waterbody

Threat
Count

Zone Area
(sq mi)

Normalized
Threat Count

Unique Sites

Threat Type with Highest
Threat Count

Contaminant Class with
Highest Threat Count

Mississippi River

6,141

562

2,088

Tier II (3,593)

Organic Chemical (1,194)

Mississippi River

5,575

108

274

Tier II (5,265)

Organic Chemical (1,588)

Mississippi River

3,908

200

Tier II (3,651)

Organic Chemical (1,159)

79, 80

Mississippi River

2,898

64 & 65

206

Tier II (2,369)

Organic Chemical (973)

155

Mississippi River

1,738

Tier II (1,599)

Organic Chemical (327)

Ohio River

2,894

291

2103

Injection and Resource
Extraction Wells (1,590)

Organic Chemical (218)

156

Ohio River

1,595

829

758

Tier II (625)

Petroleum Products (181)

Ohio River

1,516

493

692

Injection and Resource
Extraction Wells (614)

Petroleum Products (158)

157

Ohio River

1,313

443

675

Tier II (427)

Petroleum Products (164)

158

Ohio River

1,305

452

667

Tier II (426)

Petroleum Products (164)

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