EPA/600/R-11/108 I December 2011 I www.epa.gov/ada
United States
Environmental Protection
Agency
CIS Analysis to Assess where
Shallow Ground Water Supplies in
the United States are Vulnerable to
Contamination by Releases of Motor
Fuel from Underground Storage
Tanks
Office of Research and Development
National Risk Management Research Laboratory, Ada, Oklahoma 74820
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Inc.
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U.S.
U.S. EPA
U.S.
U.S.
Office of Research and Development
National Risk Management Research Laboratory, Ada, Oklahoma 74820
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The U.S. Environmental Protection Agency through its Office of Research
and Development funded and managed the research described here under
contract to Shaw Environmental Inc. (EP-C-08-034, work assignment CSMoS
2-04). It has been subjected to the Agency's peer and administrative review
and has been approved for publication as an EPA document.
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Foreword
The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting
the Nation's land, air, and water resources. Under a mandate of national environmental
laws, the Agency strives to formulate and implement actions leading to a compatible bal-
ance between human activities and the ability of natural systems to support and nurture life.
To meet this mandate, EPAs research program is providing data and technical support for
solving environmental problems today and building a science knowledge base necessary to
manage our ecological resources wisely, understand how pollutants affect our health, and
prevent or reduce environmental risks in the future.
The National Risk Management Research Laboratory (NRMRL) is the Agency's center for
investigation of technological and management approaches for preventing and reducing
risks from pollution that threatens human health and the environment. The focus of the
Laboratory's research program is on methods and their cost-effectiveness for prevention
and control of pollution to air, land, water, and subsurface resources; protection of water
quality in public water systems; remediation of contaminated sites, sediments and ground
water; prevention and control of indoor air pollution; and restoration of ecosystems. NRMRL
collaborates with both public and private sector partners to foster technologies that reduce
the cost of compliance and to anticipate emerging problems. NRMRL's research provides
solutions to environmental problems by: developing and promoting technologies that protect
and improve the environment; advancing scientific and engineering information to support
regulatory and policy decisions; and providing the technical support and information transfer
to ensure implementation of environmental regulations and strategies at the national, state,
and community levels.
Spills of motor fuel from underground storage tanks are an important source of contamina-
tion to ground water. This report provides a simple approach to identify those geographical
regions of the USA where shallow ground water that is used as a source of drinking water
is more vulnerable to contamination from fuel spills from underground storage tanks. This
screening approach identifies those geographical areas where efforts to prevent spills or
to manage spills from underground storage tanks will have the greatest benefit to protect
shallow ground water as a source of drinking water.
David G. Jewett,
Acting
i i rector
Ground Water arod Ecosystems Restoration Division
National Risk Management Research Laboratory
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Notice ii
Foreword iii
Acknowledgements xi
Abstract xiii
1.0 Introduction 1
2.0 Approach 3
3.0 Results and Discussion 11
4.0 Future Directions 15
5.0 References 17
6.0 List of Appendices 19
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Figures
Figure 1. The location of every active gasoline service station in 2009 - 91,308
Locations (ESR! Business Solutions, 2009) 4
Figure 2. The distribution of households with private wells. Each dot represents 10,000
households 6
Figure 3. AH 1990 US Census Block Groups - 226,320 block groups 6
Figure 4. Frequency distribution of the surface of all census block groups 7
Figure 5. 1990 US Census Block Groups Containing BOTH People Drinking Water from
a Private Source and Gasoline Service Stations - 33,167 block groups 7
Figure 6. Frequency distribution of the surface of those census block groups that
contain at one service station and at least one household that obtains
water from a private source 8
Figure 7: Locations of census block groups where the value of Wulnerability 3 is
in the upper 30% of all census block groups. This is the resource manager's
risk of an impact 11
Figure 8: Figure from Appendix F showing higher vulnerability in suburbs of
Minneapolis-St Paul, MN, Chicago, IL, Indianapolis, IN, Columbus, OH and
Detroit, Ml 12
Figure 9: Comparison between the distribution of MTBE contamination in water supply
wells in New Hampshire and the estimate of Vulnerability from Indices 1, 2
and 3 13
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Table 1. Range of numerical values calculated for Vulnerability Index 1 8
Table 2. Range of numerical values calculated for Vulnerability Index 2 9
Table 3. Range of numerical values calculated for Vulnerability Index 3 10
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Joel Hennessy (U.S. EPA Region 3) provided valuable guidance to this project.
Peer reviews were provided by Bob Pallarino (U.S. EPA Region 9), Joel Hennessy (U.S.
EPA Region 3), Jack Hwang (U.S. EPA Region 3), Frederick McGarry (New Hampshire
Department of Environmental Services), Mark Barolo (U.S. EPA Office of Underground
Storage Tanks), Hal White (U.S. EPA Office of Underground Storage Tanks), Stephen
Reuter (New Mexico Environmental Dept), Carol Eighmey (Missouri Petroleum Storage
Tank Insurance Fund), John Menatti (Utah Department of Environmental Quality) and Jeff
Kuhn (Montana Department of Environmental Quality).
Figure 1 from Ayotte et al., 2008 as included in Figure 9 is reprinted with permission from
Ayotte, J. D., D. M. Argue, F. J. McGarry, J. R. Degnan, L. Hayes, S. M, Flanagan and D.
R. Helsel. Methyl fe/f-Butyl Ether (MTBE) in public and private wells in New Hampshire:
occurrence, factors, and possible implications. Environmental Science & Technology 42,
677-684. (2008), copyright 2008, American Chemical Society.
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Geographic Information Systems (GIS) were used to the vulnerability of ground
water supplies to contamination. The analysis was conducted for the 48 contiguous
United States, and then again for groups of corresponding to the EPA Regions.
The long form of the 1990 census the respondents where they got the water for
their home. The choices were: (1) a public system such as a city water department or
private company; (2) an individual drilled well; (3) an individual dug well; or (4) some
other source such as a spring, creek, river, cistern, etc. The reported estimates for the
numbers of drilled wells, dug wells, and other supplies of water were summed to obtain
an estimate of the number of households in each census block group that obtained water
from a private source. The 1990 census also reported the surface [square miles] of
each census block group. A file was purchased from ESRI Business Solutions that
contained the latitude and longitude of active retail gasoline service stations in the United
States. Using Geographical Information System tools (GIS tools) and geo-referenced
GIS coverage files on each census block group, the latitude and longitude of each active
service station was used to assign the service station to a census block group. Then
the number of service stations in each census block group was summed. A simple
probability analysis was performed on the distribution of service stations and the
distribution of the households that obtained water from a private supply. Three
indices were calculated. Each index was calculated for those census block groups that
had at one service station and at one household that obtained water from a
private source.
Vulnerability Index 1 is simply the density of service stations in census block group.
It is calculated as the number of service stations in census block group divided by
the of each census block in square miles. It provides an estimate of the possibil-
ity that the water supplied to a household from a private source will be impacted by a
service station. Vulnerability Index 1 describes the consumer's risk of having his water
supply impacted.
Vulnerability Index 2 is the density of households in each census block group that
obtain water from a private source. It is calculated as the number of households in
each census block group that obtain water from a private source divided by the surface
of the block group in square miles. It provides an estimate of the possibility that
a from a particular service station will impact the water supplied to a household
that obtains water from a private source. Vulnerability Index 2 describes the risk to the
service station owner that a from his station will impact someone's private water
supply.
To describe the risk to the entire community that obtains ground water from shal-
low sources, the index that describes the possibility that a single household might be
impacted was multiplied by the number of households that are at risk. Vulnerability Index
3 was calculated by multiplying Vulnerability Index 1 for each block group by the number
of households in each block group that obtain water from a private source. Vulnerability
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Index 3 describes the resource manager's risk that a from a gasoline service sta-
tion in their geographic will impact the private water supply of a household in their
geographic
The report provides maps showing the distribution of census block groups that fell into
the highest 30%, the highest 10%, the highest 3% and the highest 1% of census block
groups for each Vulnerability Index.
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1.0
introduction
Petroleum gasoline contains, among many
other components, benzene, toluene, ethyl-
benzene, and xylenes (BTEX), Gasoline
may also contain ethanol, methyl tertiary
butyl ether (MTBE), tertiary butyl alcohol
(TBA), or other alcohols and ethers used
as fuel oxygenates. Leaded gasoline con-
tains an organolead compound such as tet-
raethyl lead (TEL) and the lead scavengers
ethylene dibromide (EDB) and 1,2-dichloro-
ethane (DCA). If gasoline is released from
an underground storage tank (UST) at a
gasoline service station, these compounds
can contaminate ground water. The US
Geological Survey (LJSGS) in a nationwide
study found that these gasoline compounds
are the third most commonly detected class
of organic contaminants in ground water
(Zogorski et al., 2006).
There are several factors that may contri-
bute to potential impacts of releases from
underground storage tanks on water sup-
plies. One factor deals with the composi-
tion of the fuels. The requirements of the
Renewable Fuel Standard (RFS) estab-
lished by the Energy Policy Act of 2005 and
amended by the Energy Independence and
Security Act of 2007 have increased the
use of biofuels in the nation's fuel supply.
This change in the fuel supply can alter the
spread of gasoline hydrocarbons in ground
water resulting from underground storage
tank releases.
Field demonstrations supported in part
by the U.S. EPA's Office of Research and
Development (Mackay et al., 2006) and
others (Corseuil et al., 2011) have shown
that ethanol can inhibit the natural anaero-
bic biodegradation of BTEX compounds,
causing dissolved plumes of BTEX in
ground water to be larger than they other-
wise would be. When a readily ferment-
able biofuel, such as ethanol, is included in
the fuel spill, the biofuel will be degraded
to acetate and molecular hydrogen. The
acetate and hydrogen will accumulate in
ground water until they make the anaerobic
biodegradation of benzene and other BTEX
compounds thermodynamically unfeasible
(Corseuil et al., 2011). As long as the bio-
fuel persists in ground water, degradation
of the biofuel to acetate and hydrogen will
preclude natural anaerobic biodegradation
of benzene and other BTEX compounds.
Anaerobic biodegradation of benzene
cannot begin until the biofuel, and its trans-
formation products, have been degraded
(Corseuil, et al, 2011). This means that if
ethanol is present in motor gasoline, there
is a greater chance that BTEX from a
spill of gasoline will impact a water supply
well. Given this projected impact on BTEX
contamination, it is reasonable to assume
that when a UST release occurs, the likeli-
hood of the plume reaching a water supply
well is greater when the release is from
a UST storing ethanol-blended fuel. The
increased use of biofuels makes it even
more important to understand the potential
interaction between releases of motor fuel
from underground storage tanks and the
impacts to ground water supply.
There are spatial and temporal interactions
that operate at a regional scale that may
affect the future supply of ground water.
As the population grows, the demand for
ground water will increase. This is par-
ticularly true in suburban landscapes that
are not served by a municipal or regional
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water supply. An increase in the number
of homes that are served by private wells
will increase the potential for an impact. If
climate change brings drought that reduces
precipitation and subsequent recharge
of ground water supplies, the potential
for impacts will increase. If pumping and
stream discharge exceed the recharge to
the aquifer, the water table in an aquifer
will drop. As the water table drops, the
zone of capture of a water supply well
must expand to be able to supply the same
amount of water. As the zone of capture
expands, the chance of pulling in contami-
nated ground water increases. Any useful
understanding of these potential interac-
tions at some time in the future must build
on an understanding of the current vulner-
ability of ground water to contamination.
There are many local conditions that may
contribute to potential impacts of releases
from underground storage tanks on water
supplies: the locations of the underground
storage tanks (USTs); the types of fuels
stored in USTs; the quality of installation;
the volume of fuel flowing through the UST
system and the number of dispensers; the
operating and maintenance practices of
the UST owner/operator; the local subsur-
face soil, geology and hydrogeology; the
distance to and density of nearby water
supply wells; and the depth and construc-
tion features of the wells. This information
is collected and organized by the individual
state agencies that implement the under-
ground storage tanks program. Each state
agency organizes the data in the manner
that best suits its purposes. Unfortunately,
these data are not compiled in a consis-
tent format that would allow comparisons
from one state to another. At the present
time, any analysis of these local condi-
tions must be carried out by the individual
states or local governments. However,
data are available at a national scale for
three important parameters - the density
of households that use shallow ground
water for drinking water, the density of UST
systems, and the co-location of gasoline
service stations and households that use
shallow ground water for drinking water,
Geographic Information Systems (CIS)
were used to assess the vulnerability of
ground water supplies to contamination
based on these three parameters. The
analysis was conducted for the 48 con-
tiguous United States, and then again for
groups of states corresponding to the EPA
Regions.
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2.0
Approach
The long form of the 1990 census asked
the respondents where they got the water
for their home. The choices were:
1) a public system such as a city water
department or private company;
2) an individual drilled well;
3) an individual dug well; or
4) some other source such as a spring,
creek, river, cistern, etc.
The respondents corresponded to a total
of 102 million households. Of these
households, 84% were served by a public
system, 13% were served by an individual
drilled well, 1.6% were served by an indi-
vidual dug well, and 1.0% were served by
some other private source. There are far
more private wells than there are public
water supply wells: 140,000 public water
supply systems rely on ground water, but
there are over 15 million private drinking
water wells in the United States (Toccalino
and Hopple, 2010).
Public water supply wells are regularly
monitored for water quality. In contrast, pri-
vate wells are rarely monitored (DeSimone
et al., 2009). It is less likely that con-
tamination in private water supplies will be
identified and remedied. For this reason,
this analysis will focus on private sources
of water supply.
There are several lines of evidence that
shallow ground water is vulnerable to
contamination from underground storage
tanks. Squillace et al. (2004) surveyed 518
shallow wells, and compared the detec-
tion frequency for the BTEX compounds to
the detection frequency reported in earlier
studies of urban wells and rural drinking
water wells. Averaged across the 518
wells, 1% had concentrations of benzene
exceeding 0.2 ug/L Concentrations of
benzene exceeded 0.2 ug/L in 3.2% of
urban wells compared to 0.3% of rural
wells. Urban wells were ten times more
likely to be contaminated with benzene.
In a survey of private domestic wells in the
US, 34% contained conform bacteria and
7.9% contained Escherichia co//bacteria
(DeSimone et al., 2009). E. coli is present
in human and animal feces. The presence
of coliform bacteria and E. coli bacteria in
particular are indications of fecal contami-
nation. Plausible sources of fecal contami-
nation are septic tank leach fields, leaking
sewer lines, and animal droppings. These
sources occur at or above the water table,
and will contaminate shallow ground water.
The prevalence of fecal contamination in
private domestic wells in the US indicates
that many of these wells produce water
from near the water table. Because motor
fuel is lighter than water, releases from
USTs also tend to accumulate at the water
table. As a result, the shallow ground
water is more vulnerable to contamination
from a release from a UST. Presumably,
private wells that are vulnerable to fecal
contamination are also vulnerable to a
release from a UST.
Shallow ground water also provides the
water to springs and contributes the base
flow to small creeks. For the purpose of
this analysis, if a respondent to the 1990
census identified their source of drinking
water as an individual drilled well, an indi-
vidual dug well, or some other source such
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as a spring, creek, river, cistern, etc., their
drinking water supply was considered to be
vulnerable to contamination by a release of
gasoline.
Based on the response from the long form,
the 1990 census provided estimates for
each census block group for the follow-
ing categories: Drill_well, Dug_well, and
Oth_water. The reported estimates for the
numbers of drilled wells, dug wells, and
other supplies of water were summed to
obtain an estimate of the number of house-
holds in each census block group that
obtained water from a private source. The
1990 census also reported the surface area
[square miles] of each census block group.
A data file was purchased from ESRI
Business Solutions (ESRI, 2009) that
contained the latitude and longitude of
active retail gasoline service stations in the
United States. Figure 1 presents a map
of gasoline service stations in the contigu-
ous United States- some 91,308 mapped
locations.
The data provided by ESRI may under-
estimate the number of retail gasoline
service stations. A report issued by the
Government Accountability Office (GAO,
2011) quoted an estimate that was pro-
vided by NPN magazine, a trade magazine
that serves the petroleum marketing indus-
try (www.npnweb.coni). As reported in
NPN MarketFacts 2010, there were approx-
imately 159,000 retail fueling outlets in
the United States in 2010. In 2005, there
were approximately 169,000 retail outlets.
^
:^.. :•. :.; .;• ; \T::
Figure 1. The location of every active gasoline service station in 2009 - 91,308 Locations (ESRI Business
Solutions, 2009).
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These numbers include Alaska and Hawaii,
while the 91,308 stations that were mapped
by ESRl did not. However, in 2009, Alaska
and Hawaii contained only 0,6% of the total
population of the United States. In addi-
tion, fuel that is stored in USTs that are
owned by non-retail facilities such as car
rentals, bus depots, and units of govern-
ment can also pose a risk to ground water
resources. This assessment only takes
into account the retail gasoline service sta-
tions that were contained in the ESRl data
file. The ESRl file may under repre-
sent the true number of service stations by
as much as one half.
Using Geographical Information System
tools (CIS tools) and geo-referenced CIS
coverage files on each census block group,
the latitude and longitude of each active
service station was used to assign the ser-
vice station to a census block group. Then
the number of service stations in each
census block group was summed.
A simple probability analysis was performed
based on the distribution of service sta-
tions and the distribution of the households
that obtained water from a private supply.
Specifically, GIS was used to compare:
• The relative possibility that an individual
household that obtains its water from
a private source will be impacted by a
release from any service station in the
immediate neighborhood;
• The relative possibility that a release
from an individual service station will
impact any household in the immediate
neighborhood that obtains water from a
private source;
• The relative possibility for a given sur-
face area of land that there will be an
impact from any service station to any
household that obtains its water from a
private source.
Figure 2 presents a map showing the
distribution of households whose primary
source of drinking water comes from pri-
vate sources. This was obtained from 1990
US Census statistics, which is the last
census that reported this data. Each dot
on this map represents 10,000 households
that obtained water from private sources.
Figure 3 presents the 1990 US Census
Tract Areas (block groups). This map of
the 1990 Census block groups provides a
geographic canvass which can serve as a
normalizing factor that allows for a simple
probability analysis based on areal distribu-
tion and densities. This simple probability
analysis yields an Index of Vulnerability
that can be displayed on a map.
The number of 1990 US Census block
groups shown in Figure 3 totals 226,320.
Each is represented by an individual closed
polygon. This is a very large number of
polygons on which to perform even simple
mathematical calculations in a GIS applica-
tion. It was therefore prudent to simplify
the analysis by reducing the total number
of pertinent census block groups. This
was done by superimposing the locations
of gasoline service stations and the loca-
tions of households of people who drink
water from private sources onto the census
block groups coverage and then dropping
out those census block groups that did not
contain at least one household with people
who drink water from a private source
and one service station. This left 33,167
census block groups on which to perform
the analysis.
Depending on population density, census
block groups vary widely in size. Figure 4
presents the frequency distribution of the
surface areas for all 226,320 census block
groups. Figure 5 presents a map of the
33,167 census block groups that contain
both households that consume water from
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Figure 2. The distribution of households with private wells. Each dot represents 10,000 households.
Figure 3. All 1990 US Census Block Groups - 226,320 block groups.
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private sources and gasoline service sta-
tions. Figure 6 presents the frequency dis-
tribution of the surface areas of the census
block groups that contain both households
that obtain water from private sources and
gasoline service stations. The distributions
in Figure 4 and Figure 6 are significantly
different because people who drink water
from a private source are more likely to
live in a rural area where the census block
group is larger. The median surface area
of all census block groups is 0.41 square
miles. The median surface area of the
census block groups that contain both
households that consume water from pri-
vate sources and gasoline service stations
is 5.0 square miles.
Census Block Group Area Frequency Distributioi
,100
0.001 0.01
10 100 1000 10000
Census Block Group Surface Area [mi2]
Figure 4. Frequency distribution of the surface
area of all census block groups.
Figure 5. 1990 US Census Block Groups Containing BOTH People Drinking Water from a Private Source
and Gasoline Service Stations - 33,167 block groups.
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Census Block Group Area Frequency Distribution
gioo
O 80
u
_0
m 60
c
0)
u
M—
o
4-1
c
u
OJ
Q.
40 -
20
0
0.001 0.01 0.1 1 10 100 1000
Census Block Group Surface Area [mi2]
F i g u re 6. Frequency distribution of the surface
area of those census block groups
that contain at least one service sta-
tion and at least one household that
obtains water from a private source.
With these CIS coverages in place, three
separate indices were calculated. Each
index was calculated for those census
block groups that had at least one service
station and at least one household that
obtained water from a private source.
Vulnerability Index 1 is simply the density
of service stations in each census block
group. It is calculated as the number
of service stations in each census block
group divided by the area of each census
block in square miles. It provides an
estimate of the possibility that the water
supplied to a household from a private
source will be impacted by a service sta-
tion. Vulnerability Index 1 describes the
consumer's risk of having his water supply
impacted. The higher the calculated index,
the higher the vulnerability.
Table 1 compares the distribution of cal-
culated values for Vulnerability Index 1
for the upper 30%, the upper 10%, the
upper 3% and the upper 1% of all values
in the 48 contiguous states and in each
EPA Region. The values of the vulnerabil-
ity index were calculated from data on the
census blocks groups in the 48 contigu-
ous states as a whole, and then the values
were ranked to identify the maximum value
and the lowest value in the upper 1%,
Table 1. Range of numerical values calculated for Vulnerability Index 1 [service stations per
square mile].
Area
48 States
EPA Region 1
EPA Region 2
EPA Region 3
EPA Region 4
EPA Region 5
EPA Region 6
EPA Region 7
EPA Region 8
EPA Region 9
EPA Region 10
Maximum
Value
201
36
201
46
58
46
55
23
22
82
19
Lowest Value in:
Upper
1%
11.6
13.6
32.6
12.2
7.5
10.6
9.0
5.4
8.4
15.7
7.7
Upper
3%
6.9
7.6
17.5
7.0
4.5
7.1
5.4
3.1
5.8
10.5
5.6
Upper
10%
3.0
3.5
6.3
3.1
2.0
3.1
2.5
1.1
2.3
5.4
2.6
Upper
30%
0.84
1.06
1.84
0.88
0.59
0.97
0.65
0.32
0.39
1.91
0.93
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3%, 10% and 30% of all values. Then the
values were calculated and ranked for the
census block groups in each individual EPA
Region,
Vulnerability Index 1 was highest in EPA
Region 2 and lowest in EPA Regions 7, 8
and 10.
Vulnerability Index 2 is simply the density
of households in each census block group
that obtain water from a private source. It
is calculated as the number of households
in each census block group that obtain
water from a private source divided by the
surface area of the block group in square
miles. It provides an estimate of the possi-
bility that a release from a particular ser-
vice station will impact the water supplied
to a household that obtains water from
a private source. Vulnerability 2
describes the risk to the service station
owner that a release from his station will
impact someone's private water supply.
The higher the calculated index, the higher
the vulnerability
Table 2 compares the distribution of cal-
culated values for Vulnerability
2 in the 48 contiguous states and in
each EPA Region. As was done previ-
ously, Vulnerability Index 2 was calcu-
lated and ranked for census block groups
in the 48 states as a whole, and then
again for each individual EPA Region.
Vulnerability 2 was highest in
Region 5 and lowest in Region 7.
To describe the risk to the entire com-
munity that obtains ground water from
shallow sources, the index that describes
the possibility that a single household
might be impacted was multiplied by the
number of households that are at risk.
Vulnerability 3 was calculated by
multiplying Vulnerability 1 for each
block group by the number of households
in each block group that obtain water from
a private source. Vulnerability 3
describes the resource manager's risk that
a release from a gasoline service station in
their geographic area will impact the private
Table 2. Range of numerical values calculated for Vulnerability Index 2 [households obtain-
ing water from a private source per square mile].
Area
48 States
EPA Region 1
EPA Region 2
EPA Region 3
EPA Region 4
EPA Region 5
EPA Region 6
EPA Region 7
EPA Region 8
EPA Region 9
EPA Region 10
Maximum
Value
2191
1251
2051
1432
1545
2191
698
488
797
626
808
Lowest Value in:
Upper
1%
361
337
531
331
347
498
210
100
140
306
233
Upper
3%
189
207
345
162
169
266
111
56
81
191
138
Upper 10%
81
107
140
83
68
111
46
24
30
89
67
Upper 30%
29
43
55
37
24
38
14
9
8
32
27
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water supply of a household in their geo-
graphic area. The higher the calculated
index, the higher the vulnerability.
Table 3 compares the distribution of cal-
culated values for Vulnerability Index 3
in the 48 contiguous states and in each
EPA Region. As was done previously,
Vulnerability Index 3 was calculated and
ranked for census block groups in the 48
states as a whole, and then again for each
individual EPA Region. Vulnerability
3 was highest in Region 2 and
lowest in Regions 7 and 8.
Table 3. Range of numerical values calculated for Vulnerability Index 3 [service stations per
square mile multiplied by the number of households obtaining water from a private
source].
Area
48 States
EPA Region 1
EPA Region 2
EPA Region 3
EPA Region 4
EPA Region 5
EPA Region 6
EPA Region 7
EPA Region 8
EPA Region 9
EPA Region
10
Maximum
Value
4213
1429
4213
3811
2678
2191
1118
975
836
2418
2540
Lowest Value in:
Upper
1%
547
547
970
524
538
704
354
760
223
420
394
Upper
3%
286
310
516
258
253
368
172
87
127
265
230
Upper 10%
720
754
202
122
770
756
77
35
46
128
104
Upper 30%
47
59
78
52
37
52
21
12
11
44
39
-------
3.0
Results and Discussion
The appendices contain maps that depict
the distribution of each of the Vulnerability
Indices. Maps are provided showing the
distribution of block groups with values
for the Indices that are in the upper 30%,
upper 10%, upper 3%, and upper 1% of all
block groups in the map. Maps are provid-
ed for the 48 contiguous United States as a
whole, and for those contiguous States that
are contained within each EPA Region.
This analysis provides a screening
approach to identify those areas in the US
where ground water that is used for drink-
ing water is most at risk from UST releas-
es. These areas are at the greatest risk for
potential impacts.
As an example, Figure 7 depicts the dis-
tribution across the US of those census
block groups that fall within the high-
est 30% of all census block groups for
Vulnerability Index 3. Those census
block groups are colored blue and give
a visual distribution of those areas in the
United States that are more vulnerable
from the point of view of a resource man-
ager. The most vulnerable census block
groups are concentrated in the suburban
fringe around major cities. This relation-
ship is even more apparent at smaller
scale in figures in the Appendix. See
Figure 8 for an example.
Figure 7. Locations of census block groups where the value of Vulnerability Index 3 is in the upper 30% of
all census block groups. This is the resource manager's risk of an impact.
-------
Vulnerability IndexS # Service stations *# Households USEPA Region 5 Upper 30%
Surf ace Area
Figure 8. Figure from Appendix F showing higher vulnerability in suburbs of Minneapolis-St Paul, MN,
Chicago, IL, Indianapolis, IN, Columbus, OH and Detroit, Ml.
The indices are based on only two envi-
ronmental parameters; and one of the
parameters describes the situation in 1990.
As a result, the indices can only provide a
screening level assessment of the risk to
water supply. The predictive value of the
approach is illustrated in Figure 9. Ayotte
et al. (2008) published information on
the distribution of MTBE in ground water
in New Hampshire. The most plausible
source of MTBE in ground water in New
Hampshire is leaks of motor fuel from
underground storage tanks.
Figure 9 compares the distribution of
ground water contamination from MTBE to
the distribution of Vulnerability Index 1,
Vulnerability Index 2 and Vulnerability
Index 3. In New Hampshire, there was
little difference in the distribution of MTBE
contamination between public wells and
private wells. This may be due, in part, to
the fact that most public and private wells
produce water from fractured rock aqui-
fers. In general, there is fair agreement
between the locations with high vulnerabil-
ity and the locations with actual impacts
to water supply wells; however, the spatial
correlations are far from perfect. For New
Hampshire, the distribution of Vulnerability
Index 1 (the density of service stations)
and Vulnerability Index 2 (the density
of households obtaining water from pri-
vate sources) were similar. However,
Vulnerability Index 3 (the product of the
density of service stations and the number
of households obtaining water from private
sources) had the strongest spatial associa-
tion with the actual distribution of MTBE
contamination in drinking water wells.
-------
MTBE concentrations in source
*atef to puMic ana private welH
m 2005 and 2006, ttl t.0rt-
Putfc
OlHtt* #
OJB-MC •
•:t'!.c *)
.-••:
Figure 1 of
Ayotteet al.
2008
Private weds
Vulnerability Index!
Upper 30%
Vulnerability Index 2 Vulnerability Index 3
Upper 30% Upper 30%
Figure 9. Comparison between the distribution of MTBE contamination in water supply wells in
New Hampshire and the estimate of Vulnerability from Indices 1, 2 and 3.
-------
This screening approach can assist com-
munities and States in identifying those
localities that are particularly vulnerable.
Additionally, the approach can serve as a
useful tool for communities as they develop
plans for sustainable water supply. These
plans will be especially valuable as popula-
tion growth in the US creates increasing
demands for water.
A simple comparison of vulnerabilities on
a local and regional scale is a first step
toward an integrated approach that will
allow communities to balance growth in the
demand for ground water against the cost
to protect existing supplies from contami-
nation, or the cost to reclaim ground water
that is already contaminated.
This study is one example of how vulner-
ability can be assessed. Other CIS-based
vulnerability assessments could be done in
a similar manner considering other path-
ways for exposure such as vapor intrusion.
Further improvements in such assessments
will require more detailed understanding
of the geological context, the local climate,
and other features of the landscape.
The maps of vulnerability indices that are provided in this document are organized by U.S.
EPA Regions. At this scale, it can be difficult to associate the census block groups used
to calculate the indices with political boundaries. If an employee of a regulatory agency in
any state, territory, county, city, or Native American government desires maps that pres-
ent the indices for the geographic area that is of particular concern to them, they should
request support from the Ground Water Technical Support Center, Ground Water and
Ecosystems Restoration Division (U.S. EPA). The request can be made to the Center
Director, Dr. David Burden, by email at burden.david@epa.gov or by telephone at 580-
436-8606. The request should mention the indices that are requested, and the political
boundaries that are included.
-------
4.0
Future Directions
One of the peer reviewers provided the
following warning. Their agency
... recently started an UST/LUST Risk
Project in which we [the state agency]
are identifying USTs with a high prob-
ability of leaking that are located in
environmentally sensitive areas. Our
initial efforts attempted to use "big pic-
ture" databases for our analysis, such as
what you have done. However, we have
found that this approach can produce
false negatives, i.e., it can identify UST
facilities as low risk, when in reality, they
are high risk. This can be a major prob-
lem for UST/LUST resource managers,
The next step will require tools to under-
stand the movement and redistribution
of contaminated ground water that might
impact water supply wells, distance to
receptor, and facility specific criteria such
as overfill protection, spill containment,
cathodic protection, etc. As an example
of such a tool, the state of New Mexico
has built a CIS system called Geographic
Information System Screening Tool of New
Mexico, or GoNM (Pruett and Arfman,
2011), The tool incorporates information on:
1) the physical surroundings of the
facility, including factors such as the
geology of the aquifer, the depth to
ground water, and soil permeability;
2) United States Census data including
population density, and
3) technical features of each UST facil-
ity, such as the composition of the
underground storage tank, how the
piping was constructed, the pres-
ence of secondary containment, the
type of overfill protection, the method
used to detect leaks, the age and
capacity of the tanks, the type of
cathodic protection if needed, and
the history of Notices of Violations.
The New Mexico Petroleum Storage Tank
Bureau uses GoNM to optimize their
resources. The tool is used to rate UST
facilities based on the chance that they
might have a release. The ratings are used
to prioritize inspections. The facilities with
the highest risk are inspected more often.
The tool is also used to identify remedial
technology that has been successful at
similar locations.
Understanding the interaction between the
supply of ground water, and the evolving
demand for water at both spatial and tem-
poral scales will help to ensure adequate
and safe water supplies for the future. The
U.S. EPA and USGS are working to move
this understanding from the national and
regional scale illustrated in this assess-
ment to the local scale where decisions
are made about ground water supply, UST
siting, and regulatory inspection and clean-
up prioritization.
-------
-------
5.0
References
Ayotte, J.D., D.M. Argue, FJ. McGarry,
J.R. Degnan, L. Hayes, S.M. Flanagan
and D.R. Helsel. Methyl te/t-Butyl
Ether (MTBE) in public and private
wells in New Hampshire: occurrence,
factors, and possible implications.
Environmental Science & Technology
42: 677-684 (2008).
Corseuil, H.X., A.L. Monier, M. Fernandes,
M.R. Schneider, C.C. Nunes, M.
do Rosario, and PJJ. Alvarez. BTEX
plume dynamics following an ethanol
blend release: geochemical footprint
and thermodynamic constraints on natu-
ral attenuation. Environmental Science
& Technology 45: 3422-3429 (2011).
DeSimone, L.A., P.A. Hamilton, and RJ.
Gilliom. Quality of water from domes-
tic wells in principal aquifers of the
United States, 1991-2004—Overview of
major findings: U.S. Geological Survey
Circular 1332, 48 p. (2009). Available:
http://pubs.usgs.gov/circ/circl332/
GAO Report. BIOFUELS - Challenges
to the transportation, sale, and use of
intermediate ethanol blends. GAO-11-
513. (June 2011). Available: http://www.
gao.gov/new.items/dn513.pdf
ESRI Business Solutions. (2009). T2009
Methodology Statement: ESRI Data—
Business Locations and Business
Summary: All Business Locations-SIC
Code-5514, Gasoline Service Stations.
Available: http://www.esri.com/indus-
tries/retail/index. html
Mackay, D.M., N.R. de Sieyes, M.D.
Einarson, K.P. Feris, A.A. Pappas, I.A.
Wood, L. Jacobson, L.G. Justice, M.N.
Noske, K.M. Scow, and J.T. Wilson.
Impact of ethanol on the natural attenu-
ation of benzene, toluene, and o-xylene
in a normally sulfate-reducing aquifer.
Environmental Science & Technology
40: 6123-6130(2006).
Pruett, J. and S. Arfman. The GISST of
GoNM. L.U.S.T. Line Bulletin 68, June
2011, pages 1-4 (2011). Available:
http://www. neiwpcc. org/lustline
Squillace, P.J., MJ. Moran, and C.V. Price.
VOCs in shallow groundwater in new
residential/commercial areas of the
United States. Environmental Science
& Technology 38:5327-5338 (2004).
Toccalino, PL., and J.A. Hopple. The qual-
ity of our Nation's waters - Quality of
water from public-supply wells in the
United States, 1993-2007 - Overview of
major findings: U.S. Geological Survey
Circular 1346, 58 p. (2010). Available:
http://pubs.usgs.gov/circ/1346/
United States 1990 Census Data. (1990).
Available: http://www.census.gov/
Zogorski, J.S., J.M. Carter, T. Ivahnenko,
W.W. Lapham, MJ. Moran, B.L. Rowe,
PJ. Squillace and PL. Toccalino. The
quality of our Nation's waters - Volatile
organic compounds in the Nation's
ground water and drinking-water supply
wells: U.S. Geological Survey Circular
1292, 101 p. (2006). Available: http//
pubs, usas. aov/circ 1292/
-------
-------
Appendix A
Appendix B
Appendix C
Appendix D
Appendix E
Appendix F
Appendix G
Appendix H
Appendix I
Appendix J
Appendix K
6.0
List of Appendices
US 48 States
USEPA Region 1
USEPA Region 2
USEPA Region 3
USEPA Region 4
USEPA Region 5
USEPA Region 6
USEPA Region 7
USEPA Region 8
USEPA Region 9
USEPA Region 10
Vulnerability
Vulnerability
Vulnerability
Vulnerability
Vulnerability
Vulnerability
Vulnerability
Vulnerability
Vulnerability
Vulnerability
Vulnerability
-------
-------
Appendix A
USA 48 States Vulnerability
-------
1990 US Census Blocks that contain BOTH Consumers of Shallow Drinking Water AND Service Stations
Vulnerability Index 1: Density of Service Stations (stations per square mile) USA: Upper 30%
-------
Vulnerability Index 1: Density of Service Stations (stations per square mile) USA: Upper 10%
Vulnerability Index 1: Density of Service Stations (stations per square mile) USA: Upper 3%
-------
Density of Households using Water from a Private Source
Vulnerability Index 2: (households per square mile) USA: Upper 30%
Density of Households using Water from a Private Source
Vulnerability Index 2: (households per square mile) USA: Upper 10%
-------
Density of Households using Water from a Private Source
Vulnerability Index 2: (households per square mile) USA: Upper 3%
Density of Households using Water from a Private Source
Vulnerability Index 2: (households per square mile) USA: Upper 1%
-------
Vulnerability Index 3:
# Service Stations * # Households
Surface Area
USA: Upper 30%
Vulnerability Index 3:
# Service Stations * # Households
Surface Area
USA: Upper 10%
-------
Vulnerability Index 3:
# Service Stations * # Households
Surface Area
USA: Upper 3%
Vulnerability Index 3:
# Service Stations * # Households
Surface Area
USA: Upper 1%
-------
-------
Appendix B
USEPA Region 1 Vulnerability
-------
1990 US Census Blocks that contain BOTH Consumers of Shallow Drinking Water
and Service Stations
-------
Vulnerability Index 1:
USEPA Region 1: Upper 30%
Density of Service Stations
(stations per square mile)
-------
USEPA Region 1: Upper 10%
Vulnerability Index 1: Density of Service Stations
(stations per square mile)
-------
USEPA Region 1: Upper 3%
Vulnerability Index 1: Density of Service Stations
(stations per square mile)
-------
Vulnerability Index 1:
USEPA Region 1: Upper 1%
Density of Service Stations
(stations per square mile)
-------
USEPA Region 1: Upper 30%
~ Density of Households using Water from a Private Source
Vulnerability Index 2: (households per square mile)
-------
USEPA Region 1: Upper 10%
. . ~ Density of Households using Water from a Private Source
Vulnerability Index 2: ,. ...
(households per square mile)
-------
Vulnerability Index 2:
USEPA Region 1: Upper 3%
Density of Households using Water from a Private Source
(households per square mile)
-------
Vulnerability Index 2:
USEPA Region 1: Upper 1%
Density of Households using Water from a Private Source
(households per square mile)
-------
Vulnerability Index 3:
# Service Stations * # Households
Surface Area
USEPA Region 1: Upper 30%
-------
Vulnerability Index 3: # Service Stations *# Households USEPA Region 1: Upper 10%
Surface Area
-------
Vulnerability Index 3:
# Service Stations * # Households
Surface Area
USEPA Region 1: Upper 3%
-------
Vulnerability Index 3: # Service Stations *# Households USEPA Region 1: Upper 1%
Surface Area
-------
Appendix C
USEPA Region 2 Vulnerability
-------
1990 US Census Blocks that contain BOTH Consumers
of Shallow Drinking Water and Service Stations
-------
USEPA Region 2: Upper 30%
Vulnerability Index 1: Density of Service Stations
(stations per square mile)
-------
USEPA Region 2: Upper 10%
Vulnerability Index 1: Density of Service Stations
(stations per square mile)
-------
USEPA Region 2: Upper 3%
Vulnerability Index 1: Density of Service Stations
(stations per square mile)
-------
USEPA Region 2: Upper 30%
Vulnerability Index 2: Density of Households using Water from a Private Source
(households per square mile)
-------
USEPA Region 2: Upper 10%
Vulnerability Index 2: Density of Households using Water from a Private Source
(households per square mile)
-------
USEPA Region 2: Upper 3%
Vulnerability Index 2: Density of Households using Water from a Private Source
(households per square mile)
-------
USEPA Region 2: Upper 1%
Vulnerability Index 2: Density of Households using Water from a Private Source
(households per square mile)
-------
Vulnerability Index 3: # Service Stations * # Households USEPA Region 2: Upper 30%
Surface Area
-------
Vulnerability Index 3: # Service Stations *# Households USEPA Region 2. Upper 10%
Surface Area
-------
Vulnerability Index 3:
# Service Stations * # Households
Surface Area
USEPA Region 2: Upper 3%
-------
Vulnerability Index 3:
# Service Stations * # Households
Surface Area
USEPA Region 2: Upper 1%
-------
-------
Appendix D
USEPA Region 3 Vulnerability
-------
1990 US Census Blocks that contain BOTH Consumers
of Shallow Drinking Water and Service Stations
-------
USEPA Region 3: Upper 30%
Vulnerability Index 1: Density of Service Stations
(stations per square mile)
-------
USEPA Region 3: Upper 10%
Vulnerability Index 1: Density of Service Stations
(stations per square mile)
-------
USEPA Region 3: Upper 3%
Vulnerability Index 1: Density of Service Stations
(stations per square mile)
-------
USEPA Region 3: Upper 1%
Vulnerability Index 1: Density of Service Stations
(stations per square mile)
-------
USEPA Region 3: Upper 30%
Vulnerability Index 2: Density of Households using Water from a Private Source
(households per square mile)
-------
USEPA Region 3: Upper 10%
Vulnerability Index 2: Density of Households using Water from a Private Source
(households per square mile)
-------
USEPA Region 3: Upper 3%
Vulnerability Index 2: Density of Households using Water from a Private Source
(households per square mile)
-------
USEPA Region 3: Upper 1%
Vulnerability Index 2: Density of Households using Water from a Private Source
(households per square mile)
-------
Vulnerability Index 3: # Service Stations * # Households USEPA Region 3: Upper 30o/o
Surface Area
-------
Vulnerability Index 3: # Service Stations * # Households USEPA Region 3: Upper 10o/o
Surface Area
-------
Vulnerability Index 3: # Service Stations *# Households USEPA Regjon 3. Upper 3o/o
Surface Area
-------
Vulnerability Index 3: # Service Stations * # Households USEPA Region 3: Upper 1%
Surface Area
-------
Appendix E
USEPA Region 4 Vulnerability
-------
1990 US Census Blocks that contain BOTH Consumers
of Shallow Drinking Water and Service Stations
-------
USEPA Region 4: Upper 30%
Vulnerability Index 1: Density of Service Stations
(stations per square mile)
-------
USEPA Region 4: Upper 10%
Vulnerability Index 1: Density of Service Stations
(stations per square mile)
-------
Vulnerability Index 1:
USEPA Region 4: Upper 3%
Density of Service Stations
(stations per square mile)
-------
USEPA Region 4: Upper 1%
Vulnerability Index 1: Density of Service Stations
(stations per square mile)
-------
USEPA Region 4: Upper 30%
Vulnerability Index 2: Density of Households using Water from a Private Source
(households per square mile)
-------
USEPA Region 4: Upper 10%
Vulnerability Index 2: Density of Households using Water from a Private Source
(households per square mile)
-------
USEPA Region 4: Upper 3%
Vulnerability Index 2: Density of Households using Water from a Private Source
(households per square mile)
-------
USEPA Region 4: Upper 1%
Vulnerability Index 2: Density of Households using Water from a Private Source
(households per square mile)
-------
Vulnerability Index 3: # Service Stations * # Households USEPA Region 4: Upper 30%
Surface Area
-------
Vulnerability Index 3: # Service Stations * # Households USEPA Region 4. Upper 10%
Surface Area
-------
Vulnerability Index 3: # Service Stations * # Households USEPA Region 4: Upper 3%
Surface Area
-------
Vulnerability Index 3:
# Service Stations * # Households
Surface Area
USEPA Region 4: Upper 1%
-------
Appendix F
USEPA Region 5 Vulnerability
-------
1990 US Census Blocks that contain BOTH Consumers of
Shallow Drinking Water AND Service Stations
-------
USEPA Region 5 : Worst 30%
Vulnerability Index 1: Density of Service Stations
(stations per square mile)
-------
USEPA Region 5 : Worst 10%
Vulnerability Index 1: Density of Service Stations
(stations per square mile)
-------
USEPA Region 5 : Worst 3%
Vulnerability Index 1: Density of Service Stations
(stations per square mile)
-------
USEPA Region 5 : Worst 1%
Vulnerability Index 1: Density of Service Stations
(stations per square mile)
-------
USEPA Region 5 : Worst 30%
Vulnerability Index 2: Density of Households using Water from a Private Source
(households per square mile)
-------
USEPA Region 5 : Worst 10%
Vulnerability Index 2: Density of Households using Water from a Private Source
(households per square mile)
-------
USEPA Region 5 : Worst 3%
Vulnerability Index 2: Density of Households using Water from a Private Source
(households per square mile)
-------
USEPA Region 5 : Worst 1%
Vulnerability Index 2: Density of Households using Water from a Private Source
(households per square mile)
-------
USEPA Region 5 : Worst 30%
Vulnerability Index 3: # Service Stations * # Households
Surface Area
-------
USEPA Region 5 : Worst 10%
Vulnerability Index 3: # Service Stations * # Households
Surface Area
-------
USEPA Region 5 : Worst 3%
Vulnerability Index 3: # Service Stations * # Households
Surface Area
-------
USEPA Region 5 : Worst 1%
Vulnerability Index 3: # Service Stations * # Households
Surface Area
-------
Appendix G
USEPA Region 6 Vulnerability
-------
1990 US Census Blocks that contain BOTH Consumers
of Shallow Drinking Water and Service Stations
-------
Vulnerability Index 1:
Density of Service Stations
(stations per square mile)
USEPA Region 6 : Upper 30%
-------
Vulnerability Index 1: DensitY of Service stations
(stations per square mile)
USEPA Region 6 : Upper 10%
-------
Vulnerability Index 1: DensitY of Service Stations
(stations per square mile)
USEPA Region 6 : Upper 3%
-------
Vulnerability Index 1: DensitY of Service stations
(stations per square mile)
USEPA Region 6 : Upper 1%
-------
USEPA Region 6 : Upper 30%
Vulnerability Index 2: Density of Households using Water from a Private Source
(households per square mile)
-------
USEPA Region 6 : Upper 10%
Vulnerability Index 2: Density of Households using Water from a Private Source
(households per square mile)
-------
USEPA Region 6 : Upper 3%
Vulnerability Index 2: Density of Households using Water from a Private Source
(households per square mile)
-------
USEPA Region 6 : Upper 1%
Vulnerability Index 2: Density of Households using Water from a Private Source
(households per square mile)
-------
Vulnerability Index 3:
# Service Stations * # Households
Surface Area
USEPA Region 6 : Upper 30%
-------
Vulnerability Index 3:
# Service Stations * # Households USEPA Region 6 : Upper 10%
Surface Area
-------
Vulnerability Index 3:
# Service Stations * # Households
Surface Area
USEPA Region 6: Upper 3%
-------
Vulnerability Index 3:
# Service Stations * # Households
Surface Area
USEPA Region 6 : Upper 1%
-------
Appendix H
USEPA Region 7 Vulnerability
-------
1990 US Census Blocks that contain BOTH Consumers
of Shallow Drinking Water and Service Stations
-------
Vulnerability Index 1:
Density of Service Stations
(stations per square mile)
USEPA Region 7 : Upper 30%
-------
Vulnerability Index 1:
Density of Service Stations
(stations per square mile)
USEPA Region 7 : Upper 10%
-------
Vulnerability Index 1:
Density of Service Stations
(stations per square mile)
USEPA Region 7: Upper 3%
-------
Vulnerability Index 1:
Density of Service Stations
(stations per square mile)
USEPA Region 7 : Upper 1%
-------
USEPA Region 7 : Upper 30%
Vulnerability Index 2: Density of Households using Water from a Private Source
(households per square mile)
-------
USEPA Region 7 : Upper 10%
Vulnerability Index 2: Density of Households using Water from a Private Source
(households per square mile)
-------
USEPA Region 7: Upper 3%
Vulnerability Index 2: Density of Households using Water from a Private Source
(households per square mile)
-------
USEPA Region 7 : Upper 1%
Vulnerability Index 2: Density of Households using Water from a Private Source
(households per square mile)
-------
Vulnerability Index 3:
# Service Stations * # Households
Surface Area
USEPA Region 7 : Upper 30%
-------
Vulnerability Index 3:
# Service Stations * # Households
Surface Area
USEPA Region 7 : Upper 10%
-------
Vulnerability Index 3:
# Service Stations * # Households
Surface Area
USEPA Region 7: Upper 3%
-------
Vulnerability Index 3:
# Service Stations * # Households USEPA Region 7 : Upper 1%
Surface Area
-------
Appendix I
USEPA Region 8 Vulnerability
-------
1990 US Census Blocks that contain BOTH Consumers
of Shallow Drinking Water and Service Stations
-------
USEPA Region 8: Upper 30%
Vulnerability Index 1: Density of Service Stations
(stations per square mile)
-------
USEPA Region 8: Upper 10%
Vulnerability Index 1: Density of Service Stations
(stations per square mile)
-------
USEPA Region 8: Upper 3%
Vulnerability Index 1: Density of Service Stations
(stations per square mile)
-------
USEPA Region 8: Upper 1%
Vulnerability Index 1: Density of Service Stations
(stations per square mile)
-------
USEPA Region 8: Upper 30%
Vulnerability Index 2: Density of Households using Water from a Private Source
(households per square mile)
-------
USEPA Region 8: Upper 10%
Vulnerability Index 2: Density of Households using Water from a Private Source
(households per square mile)
-------
USEPA Region 8: Upper 3%
Vulnerability Index 2: Density of Households using Water from a Private Source
(households per square mile)
-------
USEPA Region 8: Upper 1%
Vulnerability Index 2: Density of Households using Water from a Private Source
(households per square mile)
-------
Vulnerability Index 3: # Service Stations * # Households USEPA Region 8: Upper 30o/o
Surface Area
-------
Vulnerability Index 3: # Service Stations * # Households USEPA Regjon 8. Upper 10%
Surface Area
-------
Vulnerability Index 3:
# Service Stations * # Households
Surface Area
USEPA Region 8: Upper 3%
-------
Vulnerability Index 3:
# Service Stations * # Households
Surface Area
USEPA Region 8: Upper 1%
-------
Appendix J
USEPA Region 9 Vulnerability
-------
1990 US Census Blocks that contain BOTH Consumers
of Shallow Drinking Water and Service Stations
-------
USEPA Region 9: Upper 30%
Vulnerability Index 1: Density of Service Stations
-------
USEPA Region 9: Upper 10%
Vulnerability Index 1: Density of Service Stations
-------
USEPA Region 9: Upper 3%
Vulnerability Index 1: Density of Service Stations
-------
USEPA Region 9: Upper 1%
Vulnerability Index 1: Density of Service Stations
-------
USEPA Region 9: Upper 30%
Vulnerability Index 2: Density of Consumers of Shallow Drinking Water
-------
USEPA Region 9: Upper 10%
Vulnerability Index 2: Density of Consumers of Shallow Drinking Water
-------
USEPA Region 9: Upper 3%
Vulnerability Index 2: Density of Consumers of Shallow Drinking Water
-------
USEPA Region 9: Upper 1%
Vulnerability Index 2: Density of Consumers of Shallow Drinking Water
-------
Vulnerability Index 3: # Service Stations * # Consumers USEPA Regjon 9: Upper 30o/o
Surface Area
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Vulnerability Index 3: # Service Stations * # Consumers USEPA Regjon 9: Upper 10%
Surface Area
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Vulnerability Index 3: # Service Stations *# Consumers USEPA Regjon 9. Upper 3%
Surface Area
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Vulnerability Index 3: # Service Stations * # Consumers USEPA Regjon 9: Upper 1%
Surface Area
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Appendix K
USEPA Region 10 Vulnerability
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1990 US Census Blocks that contain BOTH Consumers
of Shallow Drinking Water and Service Stations
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Vulnerability Index 1:
Density of Service Stations
(stations per square mile) USEPA Region 10 : Upper 30%
-------
Vulnerability Index 1:
Density of Service Stations
(stations per square mile)
USEPA Region 10 : Upper 10%
-------
Vulnerability Index 1:
Density of Service Stations
(stations per square mile)
USEPA Region 10: Upper 3%
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Vulnerability Index 1:
Density of Service Stations
(stations per square mile)
USEPA Region 10 : Upper 1%
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Vulnerability Index 2:
Density of Households using Water from a Private Source
(households per square mile)
USEPA Region 10 : Upper 30%
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Vulnerability Index 2:
Density of Households using Water from a Private Source
(households per square mile)
USEPA Region 10 : Upper 10%
-------
Vulnerability Index 2:
Density of Households using Water from a Private Source
(households per square mile)
USEPA Region 10: Upper 3%
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Vulnerability Index 2:
Density of Households using Water from a Private Source
(households per square mile)
USEPA Region 10 : Upper 1%
-------
Vulnerability Index 3:
# Service Stations * # Households
Surface Area
USEPA Region 10 : Worst 30%
-------
Vulnerability Index 3:
# Service Stations * # Households
Surface Area
USEPA Region 10 : Worst 10%
-------
Vulnerability Index 3:
# Service Stations * # Households
Surface Area
USEPA Region 10 : Worst 3%
-------
Vulnerability Index 3:
# Service Stations * # Households
Surface Area
USEPA Region 10 : Worst 1%
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United States
Environmental Protection
Agency
PRESORTED STANDARD
POSTAGES FEES PAID
EPA
PERMIT NO. G-35
Office of Research and Development (8101R)
Washington, DC 20460
Official Business
Penalty for Private Use
$300
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