vvEPA
United States
Environmental Protection
Agency
Office of
Research and Development
Washington, DC 20460
EPA/600/2-91/043
August 1991
Regional Assessment of
Aquifer Vulnerability and
Sensitivity in the
Conterminous United States
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EPA/600/2-91/043
August 1991
REGIONAL ASSESSMENT OF AQUIFER
VULNERABILITY AND SENSITIVITY IN
THE CONTERMINOUS UNITED STATES
by
Wayne A. Pettyjohn
Mark Savoca
Dale Self
Oklahoma State University
Stillwater, Oklahoma 74078
Cooperative Agreement CR-815754
Project Officer
Jerry Thornhill
Extramural Activities And Assistance Division
Robert S. Kerr Environmental Research Laboratory
Ada, Oklahoma 74820
U S Environmental Protection Agency
Report 5, Library (PL-12J)
77\'ns« hckson Boulevard, 12th Floor
Chicago, IL 60604-3590
ROBERT S. KERR ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U. S. ENVIRONMENTAL PROTECTION AGENCY
ADA, OKLAHOMA 74820
Printed on Recycled Paper
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DISCLAIMER
The information in this document has been funded wholly or in part by the United States Environmental
Protection Agency under cooperative agreement CR-815754 to Oklahoma State University. The report has been
subjected to the Agency's peer and administrative review, and has been approved for publication as an EPA
document. Mention of trade names orcommercial products does not constitute endorsement or recommendation
for use.
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FOREWORD
EPA is charged by Congress to protect the Nation's land, air and water systems. Under a mandate of
national environmental laws focused on air and water quality, solid waste management and the control of
toxic substances, pesticides, noise and radiation, the Agency strives to formulate and implement actions
which lead to a compatible balance between human activities and the ability of natural systems to support
and nurture life.
The Robert S. Kerr Environmental Research Laboratory is the Agency's center of expertise for
investigation of the soil and subsurface environment. Personnel at the laboratory are responsible for
management of research programs to: (a) determine the fate, transport and transformation rates of
pollutants in the soil, the unsaturated and the saturated zones of the subsurface environment; (b) define
the processes to be used in characterizing the soil and subsurface environment as a receptor of
pollutants; (c) develop techniques for predicting the effect of pollutants on ground water, soil, and
indigenous organisms; and (d) define and demonstrate the applicability and limitations of using natural
processes, indigenous to the soil and subsurface environment, for the protection of this resource.
This report provides techniques for determining the vulnerability and sensitivity of shallow or surficial
aquifers to contamination from Class V wells. A representation of ground-water vulnerability, which is
determined by the geology of a system, precipitation distribution, population density, potential well yields,
and aquifer sensitivity, which is related to potential for contamination, is presented for each of the 48
conterminous states.
Clinton W. Hall
Director
Robert S. Kerr Environmental
Research Laboratory
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ABSTRACT
The EPA through the UIC program, is develop-
ing regulations for the protection of USDW's from
contamination by the subsurface emplacement of fluids
through wells. This report deals with Class V wells,
most of which inject into or above shallow or surficial
aquifers; that is, into or above USDW's.
The purpose of this report is to provide, in a
generalized, largely graphical format, a representation
of ground-water vulnerability, precipitation distribution,
population density, potential well yields, and aquifer
sensitivity for each of the 48 conterminous states.
The geology of the physical system determines
vulnerability. Population density and distribution are
important because people are associated with sources
of contamination. The greatest number of shallow in-
jection wells occurs in areas of high population density.
The distribution and quantity of precipitation has a
bearing on ground-water recharge. Well yield also plays
a role in prioritizing aquiferprotection. Aquifer sensitivity
is related to the potential for contamination. That is,
aquifers that have a high degree of vulnerability and are
in areas of high population density are considered to be
the most sensitive. This implies that even though an
aquifer is highly vulnerable, only that part covered by
population centers actually has a high degree of sen-
sitivity.
The classification scheme developed for this
report is based on an assessment of the vulnerability
of surficial and relatively shallow aquifers.
Class I (Surficial or shallow, permeable units;
highly vulnerable to contamination).
Unconsolidated Aquifers (Class la). Class la aquifers
consist of surficial, unconsolidated, and permeable
alluvial, terrace, outwash, beach, dune and other similar
deposits.
Soluble and Fractured Bedrock Aquifers (Class Ib).
Lithologies in this class include limestone, dolomite,
and, locally, evaporitic units that contain documented
karst features or solution channels, regardless of size.
Also included are sedimentary strata, and metamor-
phic and igneous rocks that are significantly faulted,
fractured, or jointed.
Semiconsolidated Aquifers (Class Ic). Semiconsolidated
systems generally contain poorly to moderately indu-
rated sand and gravel that is interbedded with clay and
silt.
Covered Aquifers (Class Id). This class consists of any
Class I aquiferthat is overlain by less than 50 feet of low
permeability, unconsolidated material, such as glacial
till, lacustrian, and loess deposits.
Class II (Consolidated bedrock aquifers, mod-
erately vulnerable)
Higher Yield Bedrock Aquifers (Class Ma). These
aquifers generally consist of fairly coarse sandstone or
conglomerate that contain lesser amounts of interbedded
fine-grained elastics and occasionally carbonate units.
In general, well yields must exceed 50 gpm to be
included in this class.
Lower Yield Bedrock Aquifers (Class Mb). Most com-
monly, lower yield systems consist of the same clastic
rock types present in the higher yield systems. Well
yields are commonly less than 50 gpm.
Covered Bedrock Aquifers (Class Me). This group
consists of a Class lla and lib aquifers that are overlain
by less than 50 feet of unconsolidated material of low
permeability.
Class III (Covered consolidated or unconsoli-
dated aquifers). This class includes those aquifers that
are overlain by more than 50 feet of low permeability
material.
Class U (Undifferentiated aquifers).This clas-
sification is used where several lithologic and hydrologic
conditions are present within a mappable area. This
class is intended to convey a wider range of vulnerability
than is usually contained within any other single class.
Subclass v (Variably covered aquifers). The
modifier "v" is used to describe areas where an unde-
termined or highly variable thickness of low permeability
sediments overlies the major water-bearing zone.
About 46 percent of the land area of the con-
terminous United States consists of vulnerable Class I
aquifers. Of this amount, 26.4 percent is Class la, 10.4
percent is Class Ib and Ib-v, 8.1 percent is Class Ic, and
IV
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Class Id accounts for an additional 1.4 percent. The
moderately vulnerable Class II aquifers cover about 14
percent of the United States, while the least vulnerable,
Class III, makes up about 19 percent. The undefined
systems, Class U, account for an additional 19 percent.
This report was submitted in fulfillment of contract
number EPA CR-815754-01 -0 by the School of Geology,
Oklahoma State University under the sponsorship of
the U.S. Environmental Protection Agency. This report
covers a period from 4-10-89 to 4-9-91, and work was
completed as of 4-9-91
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CONTENTS
Foreword iii
Abstract iv
Section 1. Introduction 1
Introduction 1
Aquifer vulnerability, potential yield and
sensitivity 2
Purpose and scope 4
Classification system 5
Characteristics of individual classes 6
Methodology 8
Scale dependency 8
Acknowledgments 12
Section 2. Regional evaluations 13
Summary 13
Table 1 14
Table 2 16
Tables 18
Region 1 19
Connecticut 20
Maine 26
Massachusetts 32
New Hampshire 38
Rhode Island 43
Vermont 48
Region 2 54
New Jersey 55
New York 61
Region 3 67
Delaware 68
Maryland 73
Pennsylvania 79
Virginia 85
West Virginia 91
Region 4 97
Alabama 98
Florida 104
Georgia 110
Kentucky 116
Mississippi 122
North Carolina 128
South Carolina 134
Tennessee 140
Region 5 146
Illinois 147
Indiana 153
Michigan 159
Minnesota 165
Ohio 170
Wisconsin 176
vii
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Region 6 182
Arkansas 183
Louisiana 188
New Mexico 193
Oklahoma 199
Texas 205
Region 7 211
Iowa 212
Kansas 217
Missouri 223
Nebraska 229
Region 8 235
Colorado 236
Montana 242
North Dakota 247
South Dakota 252
Utah 258
Wyoming 264
Region 9 270
Arizona 271
California 277
Nevada 283
Region 10 288
Idaho 289
Oregon 295
Washington 301
Section 3. Selected references 307
VIII
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Section 1
INTRODUCTION
In 1974Congress enacted theSafe Drinking
Water Act (PL 93-523) to protect public health and
welfare, as well as existing and future underground
sources of drinking water. To achieve this end, the
EPA (U.S. Environmental Protection Agency),
through the UIC (Underground Injection Control)
program, has and is developing regulations for the
protection of USDW's (Underground Sources of
Drinking Water) which contain less than 10,000
mg/L of dissolved solids) from contamination by
the subsurface emplacement of fluids through wells.
UIC regulations defined and established 5
classes of injection wells.
Class I—used to inject hazardous and non-
hazardous waste beneath the lowermost
formation containing a USDW.
Class n—used to inject brine from oil and
gas production.
Class ffl—used in conjunction with solution
mining of minerals.
Class IV—used to inject hazardous or
radioactive wastes into or above a USDW
(banned nationally).
Class V—none of above but which typically
inject non-hazardous waste into or above a
USDW. Also known as shallow injection wells.
UIC regulations define a well as a bored,
drilled, or driven shaft or dug hole, whose depth is
greater than its largest surface dimension. Well
injection is the subsurface emplacement of any
substance that flows or moves. There are two
general types of injection wells—high technology
and low technology. The latter include agricultural
drainage, storm water/industrial drainage, improved
sinkholes, raw sewage disposal and cesspools,
septic systems, some industrial process water and
waste disposal wells, auto service station waste
disposal wells, and abandoned water wells used for
disposal, among others.
Many, if not most, Class V wells inject into
or above shallow or surficial aquifers; that is, into
or above USDW's. According to the most recent
inventory reported by EPA, there are approximately
170,000 Class V or shallow injection wells in the
United States, but this estimate is probably far too
low. An assessment is provided in the Report to
Congress, Class V Injection Wells (EPA, 1987).
The greatest number of shallow injection
wells occurs in areas of high population density.
The types most likely to be present in industrial/
urban/suburban areas include storm water and
industrial drainage, improved sinkholes, domestic
waste water disposal, industrial process water and
waste, auto service station waste disposal, and
abandoned water supply wells used for waste
disposal.
Injection wells typically present in rural
areas are used primarily for agricultural drainage
and secondarily for raw sewage waste disposal.
As a group, abandoned wells are the most
pervasive and potentially dangerous of all the
shallow injection wells; they are found in both rural
and urban areas.
An evaluation of the potential for ground-
water contamination caused by shallow injection
wells is a major undertaking because of the vast
number of wells and their wide distribution
throughout an extensive array of diverse
hydrogeologic settings. To limit the potential
impact of shallow injection wells on the Nation's
1
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ground water, a scheme is needed to prioritize
regions so that, initially, the most sensitive and
productive or potentially productive ground-water
areas receive maximum attention.
Although this investigation was designed
specifically to answer a need in the Underground
Inj ection Control program, the products are equally
valuable to assess the potential for ground-water
contamination from other surface or near surface
sources.
Aquifer Vulnerability, Potential Yield,
and Sensitivity
There is a general relation of permeability
to geologic age and rock type in the conterminous
United States. The geologic age of the major rock
groups is shown in Figure 1. Figure 2 illustrates the
regional distribution of the principal types of water-
bearing rocks.
The geology of the physical system
EXPLANATION
GEOLOGIC AGE
Cenozoic
Mesozoic
Paleozoic
Precambrian
TYPE OF ROCK
Unconsolidated and
semiconsolidated
sedimentary
Unconsolidated and
semiconsolidated
sedimentary
consolidated
sedimentary
Extrusive
igneous
Intrusive
igneous
metamorpriic
sedimentary
and igneous
Figure 1. Geologic age of major rock groups (modified from Heath, 1984)
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Sand and gravel
Limestone and
dolomite
Basalt
EXPLANATION
| Sandstone
Igneous, metamorphic, and consolidated sedi-
mentary rocks exclusive of sandstones and
carbonate rocks
Figure 2. Generalized distribution of major types of aquifers (modified from Heath, 1984)
determines vulnerability. That is, aquifers that
have little or no natural protection, such as overlying
deposits of low permeability material (e.g., clay,
shale, or glacial till), are the most susceptible to
contamination from shallow or near-surf ace
sources.
Some of the most productive aquifers in the
United States lie along rivers; they are quickly
recharged and generally contain water of low
mineral content. But the characteristics that make
them desirable water-supply sources also make
them susceptible to contamination from surface or
near surface sources, and from shallow injection
wells, most of which are less than 50 feet deep.
These aquifers have little or no natural protection
other than that provided by the unsaturated zone.
Population density and distribution are
important because people are associated with
sources of contamination. The higher the population
density, the more likely there will be a greater
number of potential contamination sources. For
example, the probability of a large number of
sources is substantially higher in a municipal area
than it is in a rural region.
The distribution and quantity of
precipitation have a bearing on the potential for
ground-water contamination because infiltration
or ground-water recharge provides a driving force
that tends to leach water-soluble materials from the
surface or unsaturated zone to the water table.
As a practical matter, well yield also plays
a role in prioritizing aquifer protection.
Municipalities and industries are usually located in
areas where there is an adequate supply of water.
Therefore, a vulnerable, high yield aquifer in a
densely populated area is likely to have a higher
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priority for investigation and protection than an
area where the aquifer would provide only alimited
amount of water.
A municipality with a population of 10,000
would require a water supply capable of producing
at least 1.63 mgd (million gallons per day), which
is equal to a continuous pumping rate of nearly
1,200 gpm (gallons per minute). This yield could
be obtained from two wells each pumping 600 gpm
or a dozen wells producing 100 gpm continuously.
Most well fields, however, are operated only 8 to
10 hours per day and, consequently, larger yields,
longer pumping periods, or more wells would be
required to meet the average daily demand.
Well yields in the range of 100 gpm or
more can only be obtained from aquifers that are
quite permeable and quickly recharged or those
that contain a huge volume of water in storage.
Aquifers that meet these criteria are not common.
Aquifer sensitivity is related to the potential
for contamination. That is, aquifers that have a high
degree of vulnerability and are in areas of high
population density, are considered to be the most
sensitive, regardless of potential well yield or
ground-water recharge. In turn, this implies that
even though an aquifer is highly vulnerable, only
that part covered by population centers actually has
a high degree of sensitivity. For example, the
highly vulnerable sand deposits along Oklahoma's
Cimarron River cover about 1740 square miles, but
less than 6 square miles lie within or adjacent to
corporation boundaries. Consequently, even though
the aquifer is highly vulnerable, the aquifer
sensitivity is very small owing to the low population
density.
Purpose and Scope
The purpose of this report is not to classify
ground water or ground-water regions, but rather to
provide, in a generalized, largely graphical format,
a manual that displays, for each of the 48
conterminous states, a representation of ground-
water vulnerability, precipitation distribution,
population density, potential well yields, and aquifer
sensitivity. This manual can be used by local, state,
or federal regulatory agencies to rapidly assess
and, in a general manner, prioritize ground-water
protection activities relative to shallow injection
wells and other surface or near surface sources of
contamination.
In addition, the maps can be used to delineate
areas that provide or potentially provide the greatest
amount of ground water to the largest number of
people. Likewise, they also can be used to evaluate
the more remote areas. The maps can provide the
investigator with a quick, inexpensive means to
review the potential for ground-water
contamination and thus develop rapid but
generalized evaluations of large areas. This, in
turn, would permit agencies to develop a protocol
for shallow injection well permitting or impact
evaluations.
The generalized regional assessment can
be used to prioritize selected areas for additional
investigations where more detail is required.
Obviously, any assessment is scale dependent, and
a larger scale requires a more extensive data base.
Once a generalized evaluation has been
completed, it might then be appropriate to further
assess a region, area, or site by means of more
detailed approaches.
A number of methods have been available
for several years to evaluate a site relative to the
potential for ground-water contamination. These
rating techniques are valuable, in a qualitative
sense, for the formulation of adetailedinvestigation.
One of the most noted is the LeGrand (1983)
system, which takes into account the hydraulic
conductivity, sorption, thickness of the water-table
aquifer, position and gradient of the water table,
topography, and distance between a source of
contamination and a well or receiving stream. The
LeGrand system was modified by the EPA (1983)
for the Surface Impoundment Assessment study.
Fenn and others (1975) formulated a water
balance method to predict leachate generation at
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solid waste disposal sites. Gibb and others (1983)
devised a technique to set priorities for existing
sites relative to their threat to health. An
environmental contamination ranking system was
developed by the Michigan Department of Natural
Resources (1983). On a larger scale, DRASTIC,
prepared by the National Water Well Association
for EPA (Aller and others, 1985), is a method to
evaluate the potential for ground-water
contamination based on the hydrogeologic setting.
A methodology for the development of a ground-
water management and aquifer protection plan was
described by Pettyjohn (1990).
Although no specific ground-water
contamination prevention protocol is herein
suggested, it might be reasonable to first examine
those areas that have the greatest aquifer sensitivity
relative to vulnerability, high well yield, and
population density. A second priority would include
those areas that are less susceptible to contamination
owing to decreased aquifer vulnerability and a
lower population density.
Classification System
The classification scheme developed for
this report is based on an assessment of the
vulnerability of surficial and relatively shallow
aquifers to contamination from shallow injection
wells and other surface or near surface sources of
contamination. The investigation was not limited
to currently proven aquifers or aquifers of some
designated yield. Rather, an attempt was made to
evaluate all aquifers on the basis of their reported
physical properties and related hydrologic
characteristics and behavior, keeping in mind the
fact that the assessment had to be based entirely on
published reports and maps.
Physical properties that were considered
included:
1. Degree of consolidation (unconsolidated,
semiconsolidated, consolidated) resulting from
variable degrees of compaction, welding,
induration, etc.
2. Presence of primary porosity and permeability.
S.Presenceof secondary porosity and permeability,
such as solutional features, faults, fractures, joint
systems, bedding planes and schistocity,
vesiculation, and interformational breccia zones,
among others.
4. Presence of intercalated units of different
hydraulic characteristics.
The general ranges in well yield, as reported
by the U.S. Geological Survey and state agencies,
also was used to designate different aquiferclasses.
An arbitrary limit of 50 gpm was used to
differentiate between lower yield and higher yield
bedrock systems. It seems likely that higher yield
bedrock systems would be more permeable and,
therefore, more vulnerable than lower yield bedrock
systems, although yield is a function of several
different factors.
The degree to which a particular physical
feature is present also affects the classification. For
example, a densely jointed surficial sandstone
would be considered as Class Ib, which has a high
degree of vulnerability, but a similar unit that is
reported to be fractured only locally would be
considered as an undifferentiated (Class U) unit; it
is assumed that it would be less vulnerable.
Most surficial fine-grained material, which
appears to have a very low permeability, may
indeed be quite transmissive. Fine-grained alluvium,
for example, may be as permeable as a fractured
sandstone. Glacial till is commonly weathered and
fractured to a depth of 20 to 30 feet. Likewise, the
alternating layers of cemented, fine-grained
sandstone, siltstone, and mudstone of Late Paleozoic
age in the Southern Plains (and very likely elsewhere
as well), are fractured to a depth of 40 to 60 feet or
so. The postulated widespread fracturing has not
been well documented, but the few field studies
presently available indicate that there may be rapid
ground-water recharge through fine-grained
material and this makes an underlying aquifer quite
vulnerable to contamination despite the presence
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of a cover of fine-grained material. The presence
and potential effects of fracturing of surficial, fine-
grained materials, from whatever cause, were not
considered in this classification scheme.
Characteristics of Individual Classes
Class I (Surficial or shallow, permeable units;
highly vulnerable to contamination)
Unconsolidated Aquifers (Class la). Class la
aquifers consist of surficial, unconsolidated, and
permeable alluvial, terrace, outwash, beach, dune
and other similar deposits. These units generally
contain layers of sand and gravel that, commonly,
are interbedded to some degree with silt and clay.
Not all deposits mapped as Class la are important
water-bearing units, but they are likely to be both
permeable and vulnerable. The only natural
protection of aquifers of this class is the thickness
of the unsaturated zone and the presence of fine-
grained material.
Soluble and Fractured Bedrock Aquifers (Class
Ib). Lithologies in this class include limestone,
dolomite, and, locally, evaporitic units that contain
documented karst features or solution channels,
regardless of size. Generally these systems have a
wide range in permeability. A generalized map
showing the major karst areas and those locations
where soluble strata (carbonates and sulfates) lie at
a shallow depth or crop out is shown in Figure 3.
Also included in this class are sedimentary strata,
and metamorphic and igneous (intrusive and
extrusive) rocks that are significantly faulted,
fractured, or jointed. In all cases ground-water
movement is largely controlled by secondary
n vssyiM'v-.
""i »»«"?
f^^f^x^-^r
Hi'M^'SJV^
EXPLANATION
Karst Areas
Carbonate and sulfate rocks at
or near the surface
Figure 3. Generalized distribution of karst areas and regions where soluble rocks are at or near land
surface (modified from LeGrand and others, 1976)
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openings. Well yields range widely, but the
important feature is the potential for rapid vertical
and lateral ground-water movement along preferred
pathways, which result in a high degree of
vulnerability.
Semiconsolidated A quifers (Class I c).
Semiconsolidated systems generally contain
poorly- to moderately-indurated sand and gravel
that is interbedded with clay and silt. This group is
intermediate to the unconsolidated and consolidated
end members. These systems are common in the
Tertiary age rocks that are exposed throughout the
Gulf and Atlantic coastal states. Semiconsolidated
conditions also arise from the presence of
intercalated clay and caliche within primarily
unconsolidated to poorly consolidated units, such
as occurs in parts of the High Plains Aquifer.
Covered Aquifers (Class Id). This class consists of
any Class I aquifer that is overlain by less than 50
feet of low permeability, unconsolidated material,
such as glacial till, lacustrian, and loess deposits.
Class II (Consolidated bedrock aquifers;
moderately vulnerable)
Higher Yield Bedrock Aquifers (Class Ha). These
aquifers generally consist of fairly permeable
sandstone or conglomerate that contain lesser
amounts of interbedded fine-grainedclastics (shale,
siltstone, mudstone) and occasionally carbonate
units. In general, well yields must exceed 50 gpm
to be included in this class. Locally fracturing may
contribute to the dominant primary porosity and
permeability of these systems.
Lower Yield Bedrock Aquifers (Class lib). Inmost
cases these aquifers consist of sedimentary or
crystalline rocks. Most commonly, lower yield
systems consist of the same clastic rock types
present in the higher yield systems, but in the
former case grain size is generally smaller and the
degree of cementation or induration is greater, both
of which lead to a lower permeability. In many
existing and ancient mountain regions, such as the
Appalachians (Blue Ridge and Piedmont), the core
consists of crystalline rocks that are fractured to
some degree. Well yields are commonly less than
50 gpm, although they may be larger in valleys than
on interstream divides.
Covered Bedrock Aquifers (Class He). This group
consists of Class Ha and lib aquifers that are
overlain by less than 50 feet of unconsolidated
material of low permeability, such as glacial till,
lacustrian, or loess deposits. It is assumed that most
Class V wells are relatively shallow and, therefore,
50 feet or less of fine-grained cover could reduce
but not necessarily eliminate the vulnerability of
underlying Class II systems.
Class III (Consolidated or unconsolidated
aquifers that are overlain by more than 50 feet
of low permeability material; low vulnerability)
Aquifers of this type are the least vulnerable
of all the classes because they are naturally protected
by a thick layer of fine-grained material, such as
glacial till or shale. Examples include parts of the
Northern Great Plains where the Pierre Shale of
Cretaceous age crops out over thousands of square
miles and is hundreds of feet thick. In many of the
glaciated states, till forms an effective cover over
bedrock or buried outwash aquifers, and elsewhere
alternating layers of shale, siltstone, and fine-
grained sandstone insulate and protect the deeper
major water-bearing zones.
Class III aquifers are not likely to become
contaminated by surface sources, as a result of
leaching of contaminants stored in the unsaturated
zone, or by shallow injection wells. These aquifers
can become contaminated, however, largely by
waste disposal in abandoned wells, particularly
abandoned water wells or supply wells that were
not properly constructed.
Class U (Undifferentiated aquifers)
This classification is used where several
lithologic and hydrologic conditions are present
within a mappable area. Units are assigned to this
class because of constrains of mapping scale, the
presence of undelineated members within a
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formation or group, or the presence of nonuniformly
occurring features, such as fracturing. This class is
intended to convey a wider range of vulnerability
than is usually contained within any other single
class.
Subclass v (Variably covered aquifers)
The modifier "v", such as Class Ila-v, is
used to describe areas where an undetermined or
highly variable thickness of low permeability
sediments overlie the major water-bearing zone.
To provide the largest amount of information, the
underlying aquifer was mapped as if the cover were
absent, and the "v" designation was added to the
classification. The "v" indicates that a variable
thickness of low permeability material covers the
aquifer and, since the thickness of the cover, to a
large degree, controls vulnerability, this aspect is
undefined.
Methodology
This manual is based entirely on published
information. State and federal agency publications
catalogs were examined to obtain information that
appeared to fill the needs of the project. Several
workers were assigned states in which they had
actual experience to increase the accuracy of the
products.
In most cases, aquifer vulnerability maps
were prepared by outlining geologic units on a
1:500,000 scale base map. Each unit was assigned
a classification that reflected published geologic
andhydrogeologic descriptions. The geologic units
were transferred to a page size map of the state, and
the area of each unit was measured by planimeter.
Maps showing the distribution of
precipitation were prepared by means of national
climatological data that are stored on compact
disks and the software package, MapMaker II.
Climate data were stripped from the compact disks,
and manipulated to obtain combined files of
precipitation and latitude and longitude of each
station. Rather than using a predetermined time
interval, the entire period of record was used for
each station. This data set and state/county boundary
files were used as input to the MapMaker n program.
Population density maps were prepared by
means of MapMaker n files. The population data
are based on 1986 estimates.
Aquifer sensitivity maps represent
composite illustrations in that they show the location
of population centers that overlie vulnerable or
Class I aquifers. Maps of this type indicate that
even though the aquifer may be exceptionally
vulnerable, only a small part of the system is highly
susceptible to contamination, and these sites are
represented by the location of municipalities, both
large and small. Aquifer sensitivity maps were
prepared by overlaying scanned maps of aquifer
vulnerability and the latitude and longitude of
cities. All population centers that fell outside of
Class I aquifers were deleted.
U.S. Geological Survey reports and maps
proved to be the major sources of information on
potential well yield. The generalized maps were
prepared by transferring published information to
a map of appropriate scale. These data were then
incorporated into a computer generated map
Aquifer classification units do not
necessarily match at state borders. This is the result
of compiling geologic and hydrologic information
that was obtained for each state. Consequently, a
geologic unit in one state may have been described
in such a manner that it appeared to be largely, for
example, unconsolidated Class la material. The
same earth materials in an adjacent state may have
been described in such a broad sense that it only
could be classified as "undifferentiated" or Class
U.
Scale Dependency
The maps in this report are regional in
nature and provide only a broad, generalized
overview of aquifer vulnerability and sensitivity.
They are not designed for site specific evaluations.
Detailed investigations of a county or municipal
8
-------
area would require a large data base, and this, in
turn, would provide a greater degree of accuracy.
Oklahoma and North Dakota will serve as
examples of scale dependency. The major activity
in the lightly populated state of Oklahoma is
agriculture, which is coupled with a meager
aggregate of light industry and oil and gas
production. Ground water serves as a major source
of supply in several municipal and industrial
environs and throughout the rural area.
An accounting of the aquifer classifications
in Oklahoma indicates that of the 70,304 square
miles within the state borders, 36 percent is Class
I, 7.8 percent is Class II, and the remaining 61
percent is Class HI. Of these, Class la, the most
vulnerable, amounts to only 18.6 percent of the
entire state.
Areas where wells will yield more than 100
gpm and those that will yield less than 25 gpm
account for 36 and 64 percent of the total area,
respectively.
Precipitation ranges widely, decreasing
westward from nearly 58 inches in the Ouachita
Mountains to less than 15 inches in the Panhandle.
The population of Oklahoma is only about
3.3 million and the greatest density is in Tulsa and
Oklahoma counties. The Garber-Wellington or
Central Oklahoma Aquifer, which in conjunction
with surf ace reservoirs supplies much of Oklahoma
County, is a Class Ila system that has at least a
moderate degree of natural protection. Thus, despite
the high population density, and the moderate
precipitation and recharge, the aquifer is only
slightly vulnerable to contamination from shallow
injection wells, other than pervasive abandoned
wells.
The flood plain of the Arkansas River,
which trends through Tulsa County, is a vulnerable
Class la unit. In the vicinity of Tulsa there is some
ground-water contamination, but the aquifer
presently is not used as a major source of water
supply. In this case, the aquifer sensitivity is high
owing to the aquifer vulnerability, population
density, precipitation, and high rate of ground-
water recharge, but the aquifer, for all practical
purposes, is unused.
Likewise, the wide, highly vulnerable Class
la sandy flood plain and terrace deposits along the
Cimarron River, cover about 1740 square miles,
but the population density is so slight that there is
no significant widespread threat. In fact, urban and
suburban areas encompass less than 6 square miles
or .3 of 1 percent of the valley. Consequently, even
though the high yield aquifer has a high degree of
vulnerability to contamination, the regional aquifer
sensitivity is very low.
On the other hand, when examining the
Cimarron valley from the perspective of a county
or a municipality, the situation is quite different.
Payne County contains about 700 square miles of
which nearly 177 square miles or about 25 percent
consist of Class la materials (fig. 4). More than 70
square miles of these materials will yield no more
than a gallon or two per minute (fig. 5). The high
yield area in Payne County covers about 105 square
miles or about 15 percent.
Figure 4. Aquifer vulnerability map of Payne
County, Oklahoma
The village of Perkins (fig. 6), which lies
entirely on permeable terrace deposits adjacent to
the Cimarron, covers less than a square mile. All
the municipal wells lie downgradient of several
potential sources of contamination. Here both the
aquifer vulnerability and sensitivity are very high.
-------
> 50 gpm
< 25 gpm
Figure 5. Potential well yield map of Payne
County, Oklahoma
Figure 6. The village of Perkins, OK lies on
highly vulnerable, sandy terrace deposits and
the aquifer has a high degree of sensitivity.
North Dakota lies largely within the
glaciated Northern Great Plains and, in many
respects, is similar to Oklahoma. North Dakota
contains about 70,700 square miles, precipitation
ranges from about 13 to 22 inches annually, and the
total population is about 667,000 or about 9
individuals per square mile.
All but the southwestern quarter of the state
is mantled by glacial deposits. Vulnerable Class I
aquifers comprise about 13 percent of North Dakota,
and Class Ha and He make up about 36 percent. The
remaining 51 percent is Class III.
Ward County, which contains about 2300
square miles and lies in the north-central part of the
state, also is largely covered by glacial deposits.
These deposits range widely in thickness, reaching
more than 600 feet in preglacial or interglacial
buried valleys, but bedrock locally crops out along
several water courses. The Souris and Des Lacs
rivers, which trend southeastward across Ward
County, separate the relatively steep, northeast
sloping two-thirds of the county from the nearly
flat remainder.
Throughout most of the county, well yields
are quite small, except for several buried valleys
that, in places, contain a substantial thickness of
sand and gravel (fig. 7). In most places, aquifers in
buried valleys are covered by several tens to several
Potential Well Yields
I I Less than 15 gpm
I More than 25 gpm
More than 500 gpm
10
20
Scale, In miles
Figure 7. Potential well yield map of Ward
County, ND.
10
-------
hundreds of feet of glacial till. Even in present day
valleys the aquifers generally are covered by till
and fine-grained alluvium. Surficial outwash
deposits can provide moderate supplies, but they
are not widely used.
The county vulnerability map shows the
location of several Class la outwash deposits, but
most of the region consists of alternating layers of
unconsolidated sand, silt, clay, and lignite of the
Fort Union Formation of Paleocene age, which is
covered by glacial till (fig. 8) Throughout a wide
area the till is quite thick (Class III), but trending
diagonally across the middle of the copnty is a belt
of Class Id-v, which reflects a cover of glacial till
of variable thickness over the Fort Union. Similarly,
buried outwash in the valleys of the Souris and Des
Lacs rivers is classified as Class Id-v because of the
variable thickness of the cover. Thus, from the
WARD COUNTY, NORTH DAKOTA
AQUIFER VULNERABILITY
Class la
Class Id
[ | Class in
10
20
30
Scale, In miles
county perspective, the only areas of high
vulnerability are the Class la aquifers.
A vulnerability map of the Minot area,
which includes 15 square miles, indicates in greater
detail the susceptibility to contamination of the
buried outwash in the Souris River valley (fig. 9).
At this location Minot's municipal well field taps
sand and gravel that are confined within the valley
walls. By means of logs of wells and test holes, it
was possible to subdivide the regional Class Id-v
deposits into areas listed as "critical", "caution",
and "moderately safe", using as a criterion the
thickness of fine-grained material overlying the
aquifer. The city of Minot is spread throughout the
flood plain and the adjacent bluffs. Consequently,
the high population density in the area marked
"critical" makes the aquifer highly sensitive to
contamination, and the area shown as "caution" is
only slightly less sensitive. Several municipal wells
occur within these two zones.
Scale, milea
I < 25 ft of clay pi] 2S - SO ft of ct
SO ft of clay
Figure 8. Aquifer vulnerability map of Ward
County, ND.
Figure 9. Aquifer vulnerability and sensitivity
range widely in the area surrounding Minot's
municipal well field.
The examples of Oklahoma and North
Dakota indicate that the degree of accuracy and
detail is closely related to the scale of mapping. The
state maps of well yield, vulnerability, and
sensitivity in this report were designed only for
generalized regional assessments, but they can be
used to determine what areas require additional
evaluation.
11
-------
A considerable number of individuals were involved
in thisproject, which was under the overall direction
of Wayne A. Pettyjohn. Jerry Thornhill, Robert S.
Kerr Environmental Research Laboratory, served
as Project Officer for the U.S. Environmental
Protection Agency. Detailed management was
directed by Mark Savoca, Research Associate.
During the last few months of the project this
responsibility was assumed by Dale Self, a research
assistant.
Individuals involved in geologic and
hydrogeologic assessments included Carol Becker,
Tim Brandon, Scott Crouch, David Edwards, John
Field, Greg McCain, Betty Pierson, Dale Self,
Craig Stafford, Richard Shields, Alberta
Stephenson, Rex Stout, Vanessa Tigert, and Patti
Zietlow. Computer graphics were accomplished
by Lana Bruggeman, Melissa Hitch, and Cindy
McClellan, and areas were determined by Scott
Henderson. Kelly Goff, who was in charge of all
computer work, also prepared the population density
and precipitation maps.
12
-------
Section 2
REGIONAL EVALUATIONS
SUMMARY
Table 1 lists details concerning population, Specific examples of ground-water contamina-
area, and water use in each of the conterminous states, tion are not described in this report. A review of examples,
These data indicate that about 42.4 percent of the however, would show that no state is free from contami-
population served by public water-supply systems use nation. Moreover, no example is unique to any one state.
ground water as a source. Clearly, these subsurface
reservoirs need to be protected against contamination.
About 46 percent of the land area of the
conterminous United States consists of vulnerable
Class I aquifers. Of this amount, 26.4 percent is Class
la, 10.4 percent is Class Ib and Ib-v, 8.1 percent is
Class Ic, and Class Id accounts for an additional 1.4
percent. The moderately vulnerable Class II aquifers
cover about 14 percent of the United States, while the
least vulnerable, Class III, makes up about 19 percent.
The undefined systems, Class U, account for an ad-
ditional 19 percent. The percentage of each class of
aquifer present in each state is listed in Table 2.
Although large areas of several states consist
of vulnerable Class I aquifers, aquifer sensitivity is not
necessarily high. Aquifer sensitivity is related both to
vulnerability and population density. In aquifer sensi-
tivity investigations, the potential effect of population
density is best viewed by means of population centers,
which generally are concentrated along watercourses,
shorelines, and transportation routes. Consequently,
the areas where ground water is most likely to become
contaminated by means of shallow injection wells are
in and adjacent to towns, regardless of size. For
example, all of the population centers in a county may
amount to only a small percentage of the total area of
the county. Therefore, the areal extent of an investiga-
tion of aquifer sensitivity could be much smaller than
originally anticipated.
13
-------
State
Alabama
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Population
xlOOO
4102
3489
2395
28314
3301
3233
660
12335
6342
1003
11614
5556
2834
2495
3727
4408
1205
4662
5889
9240
4307
2620
5141
805
Area Square
51705
114000
53187
158706
104091
5018
2044
58664
58910
83564
56345
36185
56275
82277
40409
47752
33265
10460
8284
58527
84402
47689
69697
147046
Percent of Population Daily Fresh Ground Daily Saline Ground
Using Ground Water Water Use mgd Water Use mgd
35
62
48
67
15
19
53
89
31
87
39
49
74
50
1 1
50
26
17
30
19
69
92
36
37
343
3090
3810
14800
2310
144
79
4050
1000
4800
930
635
671
4800
205
1430
66
219
315
596
685
1580
640
203
3.4
8.4
0.0
284.0
32.0
0.0
0.0
0.0
0.0
0.0
38.0
0.0
0.0
0.0
0.0
5.6
0.0
0.0
0.0
4.5
0.0
0.0
0.3
0.0
Table 1. Population, area, and water use.
-------
State
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
Population
X1000
Area Square Miles
1602
1054
1085
7721
1507
17909
6489
667
10855
3242
2767
12001
993
3470
713
4895
16841
1690
557
6015
4648
1876
4855
479
77355
110561
9279
7787
121593
49108
52669
70702
41330
69956
97073
45308
1212
31113
77116
42144
266807
84899
9614
40767
68139
24231
56153
97803
Percent of Population
Using Ground Water
89
34
33
42
86
26
23
50
32
24
22
16
17
24
79
37
45
65
31
14
42
28
54
44
Daily Fresh Ground
Water Use mgd
5590
905
84
667
1510
1100
435
127
730
568
660
799
27
274
249
444
7180
790
37
341
1220
227
570
504
Daily Saline Ground
Water Use mgd
0.0
2.8
0.0
0.1
0.0
0.0
0.0
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
229.0
25.0
0.0
0.2
0.0
0.0
0.0
23.0
Table 1. Continued
-------
State
Alabama
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Total Area
51705
114000
53187
158706
104091
5018
2044
58664
58910
83564
56345
36185
56275
82277
40409
47752
33265
10460
8284
58527
84402
47689
69697
147046
la
11.3
27.7
50.8
32.1
9.8
38.8
92.4
42
13
38.4
13.8
27.2
14.3
28.8
10.1
39.7
19.9
55.7
29.4
13.6
21.7
39.5
18.3
16.4
Ib
10.9
7.2
16.7
16.8
0.2
0.2
25.1
17.5
31.3
0.6
6.1
11.9
12.7
7.1
1.5
44
5.2
Ibv
4.8
0.8
3.4
22.5
2.9
3.9
11.5
5.2
ic
35.7
9.4
0.6
8.9
15.8
30.7
30.1
0.8
24
1.31
16.8
35.7
0.5
5.7
Id
6
3.9
3
1.1
2.9
6
Ha
5.8
5.4
0.2
4.4
1.3
0.7
llav
3.2
15.7
lib
13.6
43.4
5.4
18.9
7.4
1.2
1.3
7.7
11.2
32.4
9.8
7.7
34.6
llbv
8.4
7.3
1
4.8
21.5
He
0.4
25.1
2.7
2.8
III
6.9
12.3
11.8
34.6
36.7
15.3
1.1
23.7
51.5
38.7
51.1
30.7
2.2
1.6
48.3
58.6
15.3
38
u
11.9
20.5
2.2
12.4
2.1
3
3
3.9
42.3
39.5
3.8
2.1
2
Uv
9.7
48
34.3
71.8
26.2
63.5
6
12.9
Table 2. Percent of state area covered by each vulnerability class.
-------
State
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
Total Area
77355
110561
9279
7787
121593
49108
52669
70702
31330
69956
97073
45308
1212
31113
77116
42144
266807
84899
9614
40767
68139
24231
56153
97803
ia
20.9
50.9
25.7
53.3
30.2
23.9
38.5
15
11.4
18.1
7.5
8.5
42.1
41.1
28.5
11.4
24.5
13.3
20.1
24.1
16.7
7.4
16.3
13.9
Ib
7.4
6.3
1.1
1.2
0.5
4.7
44.5
8.3
6.9
24.4
13.2
10.7
1.2
23.3
13.4
2.7
Ibv
5.2
8.4
15.2
0.6
0.9
19
9.5
1C
57.2
3.3
7.4
6.1
8.3
13.9
0.1
15.2
9.6
4.1
24.6
6.9
4.5
12.9
Id
35.6
10
Ha
6.4
28.2
8.1
1.9
27.3
3.3
39.1
llav
5
6.5
2.1
lib
1.9
22.2
55
15.4
10.9
6.6
48.3
7.5
4
llbv
1.9
17.9
22.1
6.9
lie
8.8
9.6
III
8.1
41.71
9.1
54.9
36.5
3.2
48
20.6
60.8
33.5
1.1
44.6
1.2
25.3
18.3
46.4
0.3
u
8.8
4
32.8
5.9
11.7
0.9
43.1
64.6
32.2
Uv
3.6
74.3
7
51
56.3
36.1
5.3
69.4
Table 2. Continued.
-------
CLASSIFICATION
CLASS! ^ Ib
HIGH __
VULNERABILITY [IIT1I Ic
CLASS II ^
MODERATE
VULNERABILITY ™
CLASS III . .
LOW HI
VULNERABILITY
CLASS U „„.
WIDE RANGE OF RSH u
VULNERABILITY
THE MODIFIER __
EXAMPLE
GENERAL AQUIFER
DESCRIPTION TYPES
• Unconsolidated Deposits 9 Alluvial, terrace, beach, glacial outwasr
• Highly fractured 4 Soluble carbonate, fractured limestone,
• Soluble Aquifers karst, fractured consolidated or
crystalline
• Semiconsolidated Deposits 9 Partially indurated sand and clay
* ic^^A^mgy^on W^^^<^^
• High Yield > 50 GPM « Consolidated sedimentary or
Consolidated Bedrock crystalline rock
• Low Yield < 50 GPM § Consolidated sedimentary or
Consolidated Bedrock crystalline rock
• .Covered Aquifer Classifjcattdn $ 4te or/lib overlain by < 50' of low
; perrhea&iiity deposits
• Not a
principal Aquifer 9 Shale, clay, glacial till
• Undiffereruiated « Crystalline aquifers
9 Undivided 9 Heterogeneous aquifers
9 Thin alternating layers
i§ "Covered Aquifer Ciassif icatioris 9 la, ib, ic,. n.ajjb, or u. overlain by a
••„• ., . COVERED AQUIFER CLASSIFICATIONS -
,.,;. , .. - ... Any. aquifer that Is overlain by low permeability deposits , .
' .= LOW PERMEABILITY DEPOSITS
Clay Glacial till
; Loess Lake Clay
Cover Thickness Classification
Id Less than 50' thick Class 1
lie Less than 50' thick Class II
• U-v Variable thickness for both Class U
_-v Variable thickness for both Class 1, II, U
Table 3. Explanation of aquifer classifications.
18
-------
REGION 1
Connecticut
Maine
Massachusetts
New Hampshire
Rhode Island
Vermont
19
-------
CONNECTICUT
General Setting
Connecticut contains approximately 5,018
square miles, and lies within the Connecticut Valley
Lowland, and Seaboard Lowland sections of the New
England physiographic province. The Connecticut Valley
Lowland, which extends north-south through central
Connecticut, is underlain by Lower Mesozoic
sedimentary and igneous extrusive rocks that have
been heavily faulted. Topographic relief is low except
for resistant ridges formed by extrusive rock. The
remainder of the state, characterized by a gently rolling
topography, is underlain by Precambrian to Middle
Paleozoic age metamorphic and extrusive igneous
rocks, which have been extensively folded and faulted.
With the exception of local bedrockoutcrops, Connecticut
is overlain by Pleistocene age glacial deposits of varying
lithology and thickness.
Connecticut is drained principally by the
Housatonic, Quinnipiac, Connecticut, and Thames
rivers, all of which flow generally north to south and
empty into Long Island Sound. Average annual
precipitation in the state, about 47 inches, is distributed
fairly evenly throughout the year. Connecticut's
population, approximately 3.2 million, is concentrated
along the southern coast and the central part of the
state. Daily use of fresh ground water amounts to about
144 million gallons.
Unconsolidated Aquifers (Class la)
Stratified drift aquifers are exposed extensively
in north-central Connecticut and intermittently throughout
the rest of the state. They consist of unconsolidated
sand and gravel and commonly are interbedded with
lenses of silt and clay. Well yields generally range from
50 to 500 gpm, and may exceed 2,000 gpm. Also
included in this class are gravel and sand-rich alluvial
deposits, which are exposed locally in the central part of
the state. Specific well yields for alluvial deposits were
not cited. About 39 percent of Connecticut is covered
by Class la aquifers.
Variably Covered Soluble and Fractured Bedrock
Aquifers (Class Ib-v)
Soluble bedrock aquifers overlain by an
undetermined thickness of glacial till occur in western
Connecticut. The bedrock consist of Early Paleozoic
age marble and dolomite marble, with some schist and
quartzite zones. Well yields commonly range from 1 to
50 gpm, and may exceed 200 gpm. Fractured bedrock
aquifers overlain by a variable thickness of glacial till
occur in central Connecticut. These Jurassic age
fractured rocks consist of basalt and diabase flows and
dikes. Well yields commonly range from 2 to 50 gpm,
and may exceed 500 gpm. The overlying glacial till
consist of a heterogeneous mixture gravel, sand, clay,
and silt. The vulnerability of this system is a function of
the thickness of the overlying till. Class Ib-v aquifers
occupy approximately 5 percent of the state.
Variably Covered Low Yield Bedrock Aquifers
(Class llb-v)
Low yield bedrock aquifers that are covered by
a variable thickness of glacial till occur in the central part
of Connecticut. The Triassic to Jurassic age bedrock
consist of sandstone, shale, siltstone, and conglomerate.
Well yields commonly range from 2 to 50 gpm, and may
exceed 500 gpm. Variably covered low yield bedrock
aquifers occupy about 8 percent of the state.
Variably Covered Undifferentiated Bedrock
Aquifers (Class U-v)
Variably covered undifferentiated crystalline
aquifers occur throughout Connecticut. These
Precambrian to Middle Paleozoic age rocks include
gneiss, schist, granite, and quartzite. Overlying them is
a variable thickness of glacial till. Well yields commonly
range from 1 to 25 gpm, and may exceed 200 gpm.
About 48 percent of Connecticut is occupied by variably
covered undifferentiated bedrock aquifers.
20
-------
Sensitivity
About 44 percent of Connecticut is covered by
vulnerable Class I aquifers. The areas most sensitive to
contamination from shallow injection wells generally
occur along water courses that contain permeable
deposits of sand and gravel, and these are widely
distributed throughout the state.
21
-------
Aquifer Vulnerability Map of Connecticut
22
-------
Potential Well Yteids In Connecticut
23
-------
I
I
w
o
E
•o
o
O
Areas covered by class I aquifers.
Each dot represents a population center.
-------
Population Density of Connecticut
riU .nnnls one person per square mde)
(Dot equals one person
39 to 42
42 to 46
46 to 50
50 to 53
53 to 57
Average
Annual Precipitation in Connecticut
25
-------
MAINE
General Setting
Maine, which contains approximately 33,200
square miles, lies within the New England physiographic
province of the Appalachian Highlands. The topography
ranges from gently rolling in southwestern Maine to
mountain regions elsewhere. Many surficial features
were formed or modified during Pleistocene glaciation.
The majority of Maine isunderlain by structurally complex
igneous and metamorphic rocks with minor amounts of
rather hard and dense sedimentary rock. With the
exception of a few local bedrock outcrops, the state is
overlain by glacial deposits of varying lithology and
thickness.
Northern Maine is drained by the northeast-
flowing St. John River and its tributaries. The remainder
of the state is drained by the south-flowing
Androscroggin, Kennebec, Penebscot, and St. Croix
rivers. Annual precipitation ranges from 34 inches in the
northeast to 55 inches in the north-central mountains.
The average precipitation, 42 inches, is distributed
somewhat uniformly throughout the year. The majority
of Maine's population, approximately 1.2 million, is
located in the southern part of the state in the vicinity of
Portland, Lewiston, and Augusta. The remainder of the
state is sparsely populated. Daily use of fresh ground
water is about 66 million gallons.
Unconsolidated Aquifers (Class la)
Glaciof luvial aquifers are exposed intermittently
throughout Maine andform some of the most vulnerable
aquifers in the state. Glacial outwash aquifers consist
of stratified sand and gravel with minor amounts of silt,
clay, and cobbles. Well yields commonly range from 10
to 100 gpm, and may exceed 2,000 gpm. Glacial ice-
contact deposits consist of well- to poorly-stratified
sand, gravel, and cobbles with some silt, clay, and
boulders. Well yields commonly range from 50 to 1,000
gpm, and may exceed 3000 gpm. Also included in
Class la are small exposures of Quaternary age alluvium,
stream terrace, and alluvial fan deposits, all of which
consist of sand, gravel, and silt. About 20 percent of
Maine is covered by Class la aquifers.
Variably Covered Soluble and Fractured Bedrock
Aquifers (Class Ib-v)
A soluble bedrock aquifer, which is overlain by
an undetermined thickness of glacial till, occurs in
northeast Maine. This Ordovician to Silurian age
carbonate bedrock unit consists of limestone, calcareous
shale, and calcareous siltstone. The overlying glacial
till consists of a heterogeneous mixture of sand, silt, and
clay with some boulders. The vulnerability of this
system is a function of the thickness of the overlying till.
Well yields commonly range from 10 to 30 gpm and may
exceed 600 gpm. Class Ib-v aquifers occupy about 3
percent of the state.
Undifferentiated Aquifers (Class U)
With the exception of the carbonate bedrock
unit in the northeast, Maine is underlain by lithologically
varied Precambrian and Paleozoic age crystalline rock.
Some of the rocks include schist, gneiss, quartzite, and
slate. These rocks are relatively impermeable, but they
do contain recoverable water in secondary openings,
such as fractures and joints. Surface exposures of
crystalline bedrock occur locally throughout the state.
Well yields commonly range from 2 to 10 gpm, and may
exceed 500 gpm. Surface exposures of undiff erentiated
crystalline bedrock occupy approximately 4 percent of
the state.
Variably Covered Undifferentiated Aquifers
(Class U-v)
Variably covered Undifferentiated crystalline
aquifers occur extensively throughout the state.
Overlying the crystalline bedrock is variable thickness
of glacial till, which consist of sand, silt, clay, and
boulders. The vulnerability of these systems is a
function of the thickness of the till. Wellyields commonly
range from 2 to 10 gpm, and may exceed 500 gpm.
26
-------
About 72 percent of Maine is underlain by variably
covered undifferentiated crystalline bedrock aquifers.
Sensitivity
About 23 percent of Maine is covered by Class
I aquifers. The most sensitive of these aquifers lie along
water courses that contain sand and gravel. Owing to
the relatively low population density, the potential for
ground-watercontamination from shallow injection wells
is quite small. In northeastern and southwestern Maine
a considerable number of population centers lie on
vulnerable aquifers.
27
-------
Aquifer Vulnerability Map of Maine
28
-------
<10GPM
10to30GPM
10 to 1000
CPM
Potential Well Yields in Maine
29
-------
Areas covered by class 1 aquifers.
Each dot represents a population center.
Aquifer Sensitivity Map of Maine
30
-------
Population Density of Maine (Dot equals one
person per square mile)
r~
^
•
'
•
>
Precipitation
IntDchu
• 32 to 41
• 41 to 49
+ 49 to 57
A 57 to 65
^ 65 to 74
Average Annual Precipitation in Maine
31
-------
MASSACHUSETTS
General Setting
Massachusetts contains approximately 9300
square miles. The extreme southeastern part of the
state, including Cape Cod, Martha's Vineyard and
Nantucket, lies within the flat lying Coastal Plain
physiographic province. The remainder of the state is
in the New England Upland province, which contains
gently rolling hills in the east that give way to increased
topographic relief westward. The Coastal Plain is covered
by thick sequences of unconsolidated glacial outwash
and Holocene age beach deposits that dip gently
eastward. The majority of the New England Upland is
underlain by faulted and folded Precambrian to Jurassic
age metamorphic and igneous crystalline rocks.
Precambrian to Ordovician age limestone, dolomite,
and marble underlie the western part of the state, and
Triassic and Jurassic age sedimentary rocks occur in
the west-central part. The entire New England Upland
is mantled by glacial outwash and till of variable thickness.
The northeastern part of Massachusetts is
drained by a network of northeast-flowing rivers, while
elsewhere the state is drained by several south-flowing
rivers. Annual precipitation averages about 45 inches
and is distributed fairly evenly throughout the year. The
majority of Massachusetts' population, approximately
5.9 million, is concentrated in the eastern part of the
state. The remainder of the state is moderately
populated. About 315 million gallons of fresh ground
water are used daily in Massachusetts.
Unconsolidated Aquifers (Class la)
Mantling the Coastal Plain in southeastern
Massachusetts are glacial outwash, delta, beach and
dune deposits, and glacial till. This continuous mass of
unconsolidated material forms a vulnerable and
productive aquifer. The aquiferconsists of sand, gravel,
and silt with minor amounts of clay and boulders.
Locally exposed throughout the state are small but very
permeable valley-fill aquifers that were deposited by
glacial meltwaters and recent streams. These
unconsolidated sediments consist of stratified sand and
gravel with some silt. Well yields commonly range from
100 to 1,000 gpm, and may exceed 2,000 gpm.
Approximately 29 percent of the state is overlain by
unconsolidated aquifers.
Variably Covered Soluble and Fractured Bedrock
Aquifers (Class Ib-v)
Variably covered soluble aquifers occur in far
western Massachusetts. The Cambrian to Ordovician
age bedrock, which is covered by till, consists of
limestone, dolomite, and marble units that are
interbedded with schist and quartzite. Where present,
solutional features contribute to the vertical and lateral
permeability of the rock. The vulnerability of these
systems is a function of the thickness and permeability
of the overlying glacial till. Well yields commonly range
from 1 to 50 gpm, and may exceed 1,000 gpm. Nearly
4 percent of the state is occupied by Class Ib-v aquifers.
Variably Covered Higher Yield Bedrock Aquifers
(Class lla-v)
Higher yield bedrock aquifers, which are
covered by a variable thickness of till, occur in the
central part of the state. The underlying Triassic and
Jurassic age bedrock consists of sandstone, shale,
arkosic conglomerate, and basaltic lava flows. Well
yields commonly range from 10 to 100 gpm, and may
exceed 500 gpm. The vulnerability of these systems is
a function of the thickness of the overlying low
permeability sediments. About 3 percent of
Massachusetts is occupied by Class lla-v aquifers.
Variably Covered Undifferentiated Aquifers
(Class U-v)
Occurring in the majority of the state are variably
covered undifferentiated aquifers. The underlying
bedrock consists largely of Precambrian to Paleozoic
age crystalline rock. The bedrock is covered by a
variable thickness of glacial till. Aquifer vulnerability is a
functionof the thickness and permeability of the overlying
glacial till. Well yields commonly range from 1 to 20
gpm, and may exceed 300 gpm. Nearly 64 percent of
the state is occupied by Class U-v aquifers.
32
-------
Sensitivity
About 33 percent of Massachusetts is covered
by vulnerable Class I aquifers. Along major river valleys
and Cape Cod there is a considerable number of
population centers. These areas have a high degree of
sensitivity. Elsewhere within the state the potential for
ground-watercontaminationfrom shallow injection wells
is relatively low.
33
-------
Aquifer Vulnerability Map of Massachusetts
34
-------
1
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Potential Well Yields in Massachusetts
-------
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ss
0)
•o
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Areas covered by class I aquifers.
Each dot represents a population center
-------
Population Density of Massachusetts (Dot equals one
person per square mile)
Average Annual Precipitation in Massachusetts
37
-------
NEW HAMPSHIRE
General Setting
New Hampshire, which lies within the Seaboard
Lowland, New England Upland, and White Mountain
sections of the New England physiographic province,
contains nearly 9300 square miles. The topography
varies from gently rolling hills to rugged mountains.
Bedrock consists of faulted and folded Precambrian
and Paleozoic age metasedimentary and intrusive
igneous rocks. The crystalline bedrock is overlain by
Pleistocene depositsof variable lithologyandthickness.
Glacial deposits generally are thicker in the lowlands
and valleys than they are on the upland mountainous
regions.
The extreme western part of the state is drained
by the south-flowing Connecticut River. The Merrimack
River, which also flows generally southward, drains the
central part of New Hampshire. Several easterly flowing
watercourses drain the eastern part of the state. Annual
precipitation averages about 43 inches, ranging from
about 34 inches in the Connecticut River Valley to more
than 80 inches in the White Mountains, which are
located in the north-central part of the state. The
precipitation is distributed fairly evenly throughout the
year. The majority of New Hampshire's population,
approximately 1,085,000, is located in the southeast
part of the state and the remainder of the state is
sparsely populated. Use of fresh ground water amounts
to about 27 mgd.
Unconsolidated Aquifers (Class la)
Stratified drift aquifers are exposed intermittently
throughout New Hampshire and form vulnerable and
productive aquifers. These aquifers consist of
unconsolidated glaciofluvial sand or sand and gravel.
Included in this class are finer-grained lacustrine
deposits, stratifiedoutwash, and coarser grained, higher
yielding toe-contact deposits. Well yields commonly
range from 100 to 500 gpm, and may exceed 600 gpm.
Approximately 26 percent of New Hampshire is covered
by unconsolidated stratified drift aquifers
Variably Covered Undifferentlated Aquifers
(Class U-V)
Variably covered undifferentiated crystalline
bedrock aquifers occur extensively throughout New
Hampshire. The bedrock consists of Ordovician to
Devonian age metasedimentary rock and Precambrian
to Mississippian age igneous rock. Overlying the bedrock
is a variable thickness of glacial till, which consists of an
unconsolidated, nonstratified, heterogeneous mixture
of clay to bou Ider size deposits. Water available to wells
occurs in fractures in the crystalline bedrock. These
fractures are few and, when present, decrease in size
and number with depth. Well yields commonly range
from 1 to 10 gpm, and may exceed 100 gpm. About 74
percent of New Hampshire is covered by Class U-v
aquifers.
Sensitivity
Nearly 26 percent of New Hampshire is covered
by Class I aquifers. These vulnerable areas generally
occur along water courses that contain masses of sand
and gravel. The number of population centers that
overlie vulnerable aquifers increases southward, but
most of these are small. The regional aquifer sensitivity
of New Hampshire is low.
38
-------
o
3g
-------
ItolOGPM
100to500GPM
Potential Well Yields in New Hampshire
40
-------
-------
Population Density of New Hampshire (Dot equals one
person per square mile)
Pr*eclpita.tion
Ixi iradaea
.
•
-*-
^^
•o-
32
44
56
68
SO
to 44
to 56
to 68
to 80
to 92
Average Annual Precipitation in New Hampshire
42
-------
RHODE ISLAND
General Setting
Rhode Island, which contains approximately
1,200 square miles, lies within the New England Upland
and Seaboard Lowland sections of the New England
physiographic province. The topography is gently rolling
with maximum elevations of about 800 feet in the hilly
northwest part of the state. The area arou nd Narragansett
Bay is underlain by folded sedimentary rock of
Pennsylvanian age, while the remainder of the state is
underlain by metasedimentary and igneous rocks that
range in age from Precambrian to Middle Paleozoic.
With the exception of a few local bedrock outcrops,
Rhode Island is overlain by glacial deposits of variable
lithology and thickness.
West of Narragansett Bay the state is drained
by the south-flowing Pawcatuck River. Central and
northern parts of Rhode Island are drained by the
Pawtuxet and Blackstone rivers, both of which empty
into Narragansett Bay. Rhode Island's annual
precipitation ranges from 45 to 48 inches, and is
distributed fairly evenly throughout the year The
population, approximately 993,000, is concentrated in
the eastern part of the state. About 27 million gallons of
fresh ground water are used each day.
Unconsolidated Aquifers (Class la)
Stratified drift aquifers occur intermittently
throughout Rhode Island and form the most vulnerable
aquifers in the state. They consist of unconsolidated,
moderately- to well-sorted lenses of gravel, sand, and
silt deposited by meltwater streams. In places these
deposits are interbedded with clay, silt, and silty sand
deposited in glacial lakes. Well yields commonly range
from 100 to 700 gpm, and may exceed 1500 gpm.
Approximately 42 percent of Rhode Island is covered by
Class la aquifers.
Semiconsolidated Aquifers (Class Ic)
Located on the higher elevations of Block Island,
which is just south of Rhode Island's coast, are surface
exposures of Upper Mesozoic age Semiconsolidated
sandstone. Well yields commonly range from 1 to 30
gpm (Hansen and Schiner, 1964). Surface exposures
of Semiconsolidated aquifers occupy about .13 percent
of the state.
Variably Covered Undifferentiated Aquifers
(Class U-v)
Variably covered undifferentiated bedrock
aquifers occur throughout Rhode Island. Near
Narragansett Bay bedrock is composed of well indurated
to metamorphosed sedimentary rock of Pennsylvanian
age. The units include conglomerate, sandstone, shale,
and anthracite. Elsewhere the bedrock consists of
igneous and metamorphic rocks, largely granite and
granite gneiss. Recoverable water from these rocks
occurs in a network of narrow and widely spaced
fracture systems that decrease both in size and number
with depth. Overly ing the bedrock is a variable thickness
of glacial till, which consists of heterogeneous mixture
of sand, silt, gravel, clay, and boulders. The vulnerability
of this system is a function of the thickness of the
overlying glacial till. Well yields commonly range from
1 to 20 gpm, and may exceed 50 gpm. Class U-v
aquifers occupy slightly more than 56 percent of Rhode
Island.
Sensitivity
About 42 percent of Rhode Island is covered by
vulnerable Class I aquifers. Population centers are
rather widely distributed in the vulnerable areas.
Consequently, the potential for ground-water
contamination from shallow injection wells is moderately
small.
43
-------
Aquifer Vulnerability Map of Rhode Island
44
-------
GPM
30GPM
100 to 700 GPM
LKl LAKE
Potential Well Yields in Rhode Island
45
-------
Areas covered by class I aquifers.
Each dot represents a population center.
Aquifer Sensitivity Map of Rhode Island
46
-------
'." *' >^:'.'••'''.' ' vr";./;• 2rtf'-fŁ..U'-
' ' • .•••'•. •• • '•••;s::-i\k-^Ł??:-'&*'
Population Density of Rhode Island (Dot equals one
person per square mile)
Average Annual Precipitation in Rhode Island
47
-------
VERMONT
General Setting
Vermont contains approximately 9,600 square
miles, and lies within the St. Lawrence Valley and New
England physiographic provinces. The predominant
topographic feature is a north-south trending mountain
belt, which extends the entire length of the state. The
remainder of Vermont generally exhibits rolling hills.
The eastern three-fourths of the state is underlain by
Precambrian to Early Paleozoic age igneous and
metamorphic rocks that have undergone folding and
faulting. The western quarter is composed of Ordovician
age carbonate strata with some crystalline rock that has
been thrust over the younger Ordovician bedrock.
Generally the bedrock is overlain by Pleistocene age
deposits of varying lithology and thickness.
Eastern Vermont is drained by the south-flowing
Connecticut River. The remainderof the state is drained
by several west- and northwest-flowing systems, which
empty into Lake Champlain. Annual precipitation ranges
from about 33 inches in the eastern and western valleys
to about 53 inches in the Green Mountain Belt.
Precipitation is lowest during the winter months and
somewhat evenly distributed throughout the rest of the
year. Of the state's 557,000 inhabitants, the largest
concentration is located in the vicinity of Burlington. The
remainder of Vermont is sparsely populated. About 37
million gallons of fresh ground water are used daily.
Unconsolidated Aquifers (Class la)
Stratified drift aquifers are exposed intermittently
throughout Vermont and form vulnerable and productive
aquifers. These aquifers, which generally occur in the
lowlands, consist of unconsolidated glaciofluvial sand
and gravel with minor amounts of silt. Included in this
stratified drift class are some thin, fine-grained lacustrine
deposits, stratified outwash deposits, and coarse-
grained ice contact deposits. Higher well yields can be
obtained from the thicker and coarser deposits. Well
yields commonly range from 30 to 400 gpm, and may
exceed 600 gpm. Approximately 20 percent of Vermont
is covered by Class la aquifers.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Locally, small exposures of carbonates are
present in western Vermont. These Ordovician age
rocks consist of limestone, dolomite, and marble, all of
which have been subjected to solution weathering
along fractures. Solutional features contribute to the
vertical and lateral permeability of the rock, creating
productive and vulnerable aquifers. Well yields
commonly range from 5 to 20 gpm, and may exceed 300
gpm. Surface exposures of Class Ib aquifers occupy
about 1.2 percent of Vermont.
Variably Covered Soluble and Fractured Bedrock
Aquifers
(Class Ib-v)
In some places in western Vermont, the
Ordovician age carbonate strata that have some
solutional features are overlain by glacial till of variable
thickness. The overlying till consists of a heterogeneous
mixture of sand, silt, clay and some boulders. The
vulnerability of this system is a function of the thickness
of the overlying till. Well yields commonly range from 5
to 20 gpm, and may exceed 300 gpm. Nearly 7 percent
of Vermont consists of Class Ib-v aquifers.
Undifferentiated Aquifers (Class U)
With the exception of the carbonate bedrock in
the west, Vermont is underlain by Precambrian to Early
Paleozoic age crystalline bedrock, which consists of
various metasedimentary, metavolcanic, and igneous
rock. These crystalline rock units contain recoverable
water in fractures and other similar openings. Fractures
decrease in size and number with depth. Local
exposures of undifferentiated crystalline bedrock occur
in western and central Vermont. Well yields commonly
range from 1 to 10 gpm, and may exceed 100 gpm.
Surface exposures of undifferentiated crystalline bedrock
occupy about 2.3 percent of Vermont.
48
-------
Variably Covered Undifferentiated Aquifers
(Class U-v)
Variably covered undifferentiated crystalline
bedrock aquifers occurextensivelythroughout the state.
Overlying the crystalline bedrock is glacial till, which is
quite variable in thickness. The vulnerability of these
systems is a function of the thickness and permeability
of the overlying till. Well yields commonly range from 1
to 10 gpm, and may exceed 100 gpm. Nearly 70 percent
of Vermont is underlain by variably covered
undifferentiated crystalline aquifers.
Sensitivity
About 21 percent of Vermont is covered by
vulnerable Class I aquifers. Owing to the low population
density, aquifer sensitivity to contamination by shallow
injection wells is low. The most sensitive areas lie in
north-south trending belts adjacent to the Connecticut
River and along the western part of the state.
49
-------
Aquifer Vulnerability Map of Vermont
50
-------
p1 <10GPM
5to20GPM
30to400GPM
potential WeU Yleldsmvermont
51
-------
Areas covered by class I aquifers.
Each dot represents a population center.
Aquifer Sensitivity Map of Vermont
52
-------
Population Density of Vermont (Dot equals one
person per square mile)
Average Annual Precipitation in Vermont
53
-------
REGION 2
New Jersey
New York
54
-------
NEW JERSEY
General Setting
New Jersey, which contains approximately
7,800 square miles, lies largely within four physiographic
provinces. The Coastal Plain, which occupies the
southern half of the state south of the Fall Line, is
characterized by Precambrian age basement rocks that
are overlain by Cretaceous to Quaternary age deposits
that dip and thicken southeastward. Exposures of the
surficial bedrock expresses the complex geology of the
northern half of New Jersey. In the Valley and Ridge,
Highlands, and Piedmont provinces, Precambrian
through Triassic age sedimentary and metamorphic
rock have been folded, faulted, and intruded by dikes
and sills; extrusive igneous rocks filled the low areas.
The northern quarter of New Jersey is covered by a
variable thickness of glacial deposits.
The western part of New Jersey is drained by
the south-flowing Delaware River and its tributaries.
Eastern New Jersey is drained by several southeasterly-
flowing watercourses that empty intothe Atlantic Ocean.
Annual average precipitation ranges from 44 inches in
the south to 52 inches in the northern part of the state.
New Jersey's population, about 6.1 million, is
concentrated in the northeast portion of the state. The
remainder is moderately populated. About 667 million
gallons of fresh and 100,000 gallons of saline ground
water are used daily in the state.
Unconsolidated Aquifers (Class la)
Exposed extensively in southern, and locally in
northern New Jersey, are Tertiary to Quaternary age
unconsolidated beach, marine terrace, and stratified
glacial outwash deposits. They are composed of sand,
gravel, silt, and clay. Well yields range from 500 to
1,000 gpm, and may exceed 2,000 gpm. About 53
percent of the state is covered by Class la aquifers.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Exposed in west central New Jersey are
fractured sedimentary rock aquifers. These densely
jointed and fractured Tertiary age strata consist of
shale, sandstone, and conglomerate, with lesser
amounts of limestone. Where present, fracturing and
jointing contribute to the vertical and lateral permeability
of the rock. Well yields commonly range from 10 to 500
gpm, and may exceed 1,500 gpm. About 6 percent of
the state is occupied by Class Ib aquifers.
Variably Covered Soluble and Fractured Bedrock
Aquifers
(Class Ib-v)
In northeastern New Jersey are variably covered
Tertiary age fractured sedimentary aquifers. The rocks
consist of shale, sandstone, and conglomerate, as well
as a small amount of limestone. Well yields commonly
range from 10 to 500, and may exceed 1,500 gpm. I n the
northwest are variably covered Ordovician to Silurian
age soluble and fractured aquifers. The bedrock consists
of limestone and shale. Well yields commonly range
from 5 to 500 gpm, and may exceed 1,500 gpm. The
vulnerability of these strata is a function of the thickness
and permeability of the overlying sediments. Class Ib-
v aquifers occupy about 8.4 percent of the state.
Semiconsolidated Aquifers (Class Ic)
Exposed in the central part of New Jersey are
Cretaceous age deposits that consist of sand and clay
that have been partially cemented by iron oxide. Well
yields commonly range from 50 to 500 gpm, and may
exceed 1,000 gpm. About 3 percent of the state is
covered by semiconsolidated aquifers.
Variably Covered Semiconsolidated Aquifers
(Class Ic-v)
A small area covered by glacial till of variable
thickness consists of Cretaceous age semiconsolidated
strata. These sediments consist of partially cemented
sand and clay, occurs east-central coastal part of the
state. Well yields commonly range from 50 to 500 gpm,
and may exceed 1,000 gpm. Less than a half percent
of the state is occupied by variably covered
semiconsolidated aquifers.
55
-------
Low Yield Bedrock Aquifers (Class lib)
Local exposures of low yield bedrock aquifers
occur in northwestern New Jersey. These Tertiary age
rocks are composed of sandstone, shale, and
conglomerate. Wells yield small quantities of water.
Nearly 2 percent of New Jersey is covered by Class Mb
aquifers.
Variably Covered Low Yield Bedrock Aquifers
(Class Mb-v)
Infar northern New Jersey are variably covered
Ordovician and Silurian age low yield aquifers. Bedrock
consists of sandstone and shale, which yields only
small quantities of water. Aquifer vulnerability is a
function of the thickness of the overlying low permeability
sediments. Nearly 2 percent of the state is occupied by
Class llb-v aquifers.
Undifferentiated Aquifers (Class U)
An undifferentiated series of Tertiary to
Cretaceous age sand and gravel deposits with bands of
shale is exposed in southern New Jersey. Well yields
range from 0 to 500 gpm, and may exceed 1,000 gpm.
Exposed in the northwest are Precambrian to Cambrian
age crystalline rock in which water occurs in fractures.
Well yields commonly range from 5 to 50 gpm, and may
exceed 400 gpm. Almost 9 percent of New Jersey is
covered by undifferentiated aquifers.
Variably Covered Undifferentiated Aquifers
(Class U-v)
Northern New Jersey contains variably covered
undifferentiated Precambrian and Cambrian crystalline
rock. Aquifer vulnerability is a function of the thickness
and permeability of the overlying sediments. Well
yields range from 5 to 50 gpm, and they may exceed 400
gpm. About 7 percent of the state is occupied by Class
U-v aquifers.
Sensitivity
About 71 percent of New Jersey is covered by
Class I aquifers. The potential for ground-water
contamination in the central, vulnerable part of the state
is moderately high owing to the distribution of population
and population centers. Elsewhere aquifer sensitivity is
low to moderate.
56
-------
Aquifer
of New Jersey
57
-------
CO
1
0)
I
c.
I
o-
-------
Areas covered by class I aquifers.
Each dot represents a population center.
Aquifer Sensitivity Map of New Jersey
59
-------
Population Density of New Jersey (Dot equals one
person per square mile)
•*• 7 ^41
/
+ -I
~^J
1
•f /
;
Precipitation
in inches
• 36 to 40
- 40 to 43
-f 43 to 47
•&• 47 to 50
Q 50 to 54
Average Annual Precipitation in New Jersey
60
-------
NEW YORK
General Setting
New York, which contains approximately 49,600
square miles, lies within the Central Lowland,
Appalachian Plateaus, Adirondack, St. Lawrence Valley,
Valley and Ridge, Piedmont, New England, and Coastal
Plain provinces. The topography ranges from level and
rolling plains near the Great Lakes in western New York
to the fairly rugged Adirondack and Catskill regions.
The bedrock underlying the western two-thirds of New
York is characterized by Early Paleozoic age
sedimentary rock that generally dips slightly southward.
The Adirondack Mountains in northeast New York consist
of metamorphicwith some igneous rock of Precambrian
age. Bedrock in the eastern part of New York is
composed of Precambrian to Mesozoic age sedimentary
and metamorphic rocks that have been folded and
faulted. Much of New York is mantled by Pleistocene
age glacial deposits, which are variable in both thickness
and lithology.
Eastern New York is drained by the Hudson
River and its tributaries, while the south-central part of
the state is drained by several south-flowing rivers.
Streams in western New York empty into Lake Ontario
and Lake Erie. Annual precipitation ranges from 30
inches in the lowlands to about 52 inches in the Catskill
and Adirondack Mountains. The majority of New York's
population, about 21.6 million, are located in or around
New York City, Buffalo, Rochester, Syracuse, and
Albany. The remainder of the state is moderately
populated. About 1.1 billion gallons of fresh ground
water are used daily in New York.
Unconsolidated Aquifers (Class la)
Unconsolidated aquifers are exposed on Long
Island and intermittently throughout upstate New York.
Quaternary age stratified outwash and valley-fill deposits
consist of sand and gravel with variable amounts of silt
and clay. Well yields commonly range from 10 to 1,200
gpm, and may exceed 3,000 gpm. About 24 percent of
New York is covered by Unconsolidated aquifers.
Variably Covered Soluble and Fractured Bedrock
Aquifers (Class Ib-v)
Variably covered Ordovician to Silurian age
karst carbonate aquifers are present in band-like trends
in upstate New York. The bedrock underlying the
glacial till cover is composed largely of limestone and
dolomite, although there is a minor amount of shale.
The vulnerability of this system is a function of the
thickness of the overlying low permeability glacial till.
Well yields commonly range from 50 to 150 gpm, and
they may exceed 200 gpm. About 15 percent of New
York is covered by Unconsolidated aquifers.
Variably Covered Higher Yield Bedrock Aquifers
(Class lla-v)
Occurring in northern and, locally in southern,
New York are higher yield sedimentary rock aquifers
that are covered with a variable thickness of glacial till.
The Cambrian to Ordovician age bedrock is composed
of sandstone, shale, and conglomerate. Well yields
commonly range from 5 to 100 gpm. The vulnerability of
these systems is a function of the thickness and
permeability of the overlying till. About 7 percent of New
York is occupied by Class lla-v aquifers.
Undifferentiated Aquifers (Class U-v)
In the Adirondack Mountains, and locally in
southeastern New York, are Precambrian to Ordovician
age undifferentiated crystalline rocks that are overlain
by glacial till of variable thickness. Due to lack of
published surficial maps of the Adirondack Mountains,
the variable modifier was used because surface
exposures of bedrock could not be delineated. Well
yields were not cited. About 18 percent of New York is
covered by Class U-v aquifers.
Sensitivity
Approximately 39 percent of New York is
covered by vulnerable Class I aquifers. The potential for
61
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ground-watercontaminationfrom shallow injection wells
is particularly high in western Long Island and in the
lower reaches of Hudson River valley. The potential is
moderate to high in the remainder of Long Island, and
along many of the other rivers and majortransportation
routes, such as 1-90. Although still significant, the
number of population centers on vulnerable aquifers in
the northern part of the state is considerably less than
it is in the south.
62
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Aquifer Vulnerability Map of New York
63
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/
f
I
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York
65
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Population Density of New York (Dot equals one
person per square mile)
• 28 to 36
- 36 to 44
-f 44(053
53 to 61
O 61 to 69
Average Annual Precipitation in New York
66
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REGION 3
Delaware
Maryland
Pennsylvania
Virginia
West Virginia
67
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DELAWARE
General Setting
Delaware, which contains approximately 2044
square miles, lies within two physiographic provinces.
North of the Fall Line, in the extreme northern part of the
state, lies the gently rolling Piedmont physiographic
province. Elsewhere is the flat-lying Coastal Plain
province. The Piedmont is underlain by Precambrianto
Paleozoic age crystalline bedrock, while the Coastal
Plain consists of Upper Cretaceous to Miocene age
alternating layers of unconsolidated sand and gravel
that dip and thicken toward the southeast. Overlying
these sediments is a continuous sheet of Quaternary
age unconsolidated deposits that range in thickness
from a few feet in the north to more than 180 feet in the
south (Johnson, 1977). These deposits consist of sand
and gravel with some silt and clay. Eastern Delaware
is drained by several small rivers that discharge into
Delaware Bay. Southwest Delaware is drained by the
southwest-flowing Nanticoke River and its tributaries.
Stream channel gradients are very low and some areas
of the state are poorly drained. Average annual
precipitation, about 43 inches statewide, is distributed
fairly evenly throughoutthe year. Delaware's population,
approximately 660,000 is concentrated in the northern
part of the state, in oraround Newcastle. The remainder
of the state is moderately populated. Daily use of fresh
ground water amounts to about 79 million gallons.
Unconsolidated Aquifers (Class la)
Marine, non-marine, and channel fill deposits
occur extensively throughout Delaware and form
productive, vulnerable aquifers. These unconsolidated
deposits consist of sand, gravel, silt and clay, with some
shell fragments. Well yields commonly range from 100
to 500 gpm ,and may exceed 1000 gpm. Slightly more
than 92 percent of Delaware is covered by permeable
Class la unconsolidated deposits.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Small local exposures of Paleozoic age dolomite
and marble with karst features occur in far northern
Delaware. Reports indicate that sinkholes can be
observed at numerous locations in the outcrop areas
(Talley, 1981). Well yield characteristics are not well
documented. About .24 percent of Delaware is covered
by karst carbonate aquifers.
Lower Yield Bedrock Aquifers (Class Mb)
Lower yield Precambrian to Paleozoic age
crystalline rocks are exposed in the extreme northern
part of Delaware. These exposures include gneiss,
schist, gabbro, granodiorite, and some marble. Well
yields commonly range from 5 to 20 gpm, and may
exceed 200 gpm. Surface exposures of lower yield
bedrock aquifers occupy about 7.4 percent of the state.
Sensitivity
Nearly 93 percent of Delaware consists of
vulnerable Class I aquifers. The distribution of population
centers indicates that, despite the vulnerability, the
regional sensitivity of the state is only moderate, except
along the majortransportation routes where the potential
for contamination is greater.
68
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Class la
Class Ib
Class lib
Aquifer Vulnerability Map of Delaware
69
-------
5 to 20 GPM
100to500GPM
No Weil Yield Characteristics Found
Potential Well Yields in Delaware
70
-------
-------
Population Density of Delaware
(Dot equals one person per square mile)
Average Annual Precipitation in Delaware
72
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MARYLAND
General Setting
Maryland, which contains approximately 10,460
square miles, lies within the Coastal Plain, Piedmont,
Blue Ridge, Valley and Ridge, and Appalachian Plateaus
provinces. The flat lying Coastal Plain, which is east of
the Fall Line, is underlain by gently dipping, Cretaceous
to Quaternary age sand and gravel deposits. West of
the Fall Line the topography ranges from gently rolling
to rugged, and is underlain by Precambrian to Middle
Paleozoic age folded and faulted consolidated
sedimentary, metamorphic, and igneous rocks.
Western Maryland is drained by the Potomac
River, and the Coastal Plain in eastern Delaware is
drained by several small river systems, which empty
into Chesapeake Bay. Average annual precipitation in
Maryland is about 42 inches, and the greatest amount,
more than 50 inches, occurs in far western Maryland.
Slightly more precipitation occurs in spring and summer
than in fall and winter. Maryland's population,
approximately 4.6 million, is centered in and around
Washington D.C. and Baltimore. The remainder of the
state is moderately populated. About 219 million gallons
of fresh ground water are used daily in Maryland.
Unconsolidated Aquifers (Class la)
A wedge of sediments underlies the Coastal
Plain. This mass varies in thickness from a few feet near
the Fall Line to more than 8,000 feet in the southeastern
part of Maryland. These Cretaceous to Quaternary age
deposits generally are unconsolidated with local areas
of slight cementation. The deposits consist of
interbedded sand, gravel, silt, and clay with some shell
beds. Well yields commonly range from 10 to 500 gpm,
and may exceed 2,000 gpm. About 56 percent of
Maryland is covered by Class la deposits.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
i
Carbonate aquifers occur intermittently west of
the Fall Line. Where present, solutional features
contribute to the vertical and lateral permeability of the
rock. These folded Cambrian to Late Paleozoic age
rocks consist of limestone, dolomite, marble, and some
shale. Well yields commonly range from 5 to 200 gpm,
and may exceed 500 gpm. Surface exposures of
soluble aquifers occupy about 7 percent of Maryland.
Higher Yield Bedrock Aquifers (Class Ma)
Higheryield sedimentary bedrock aquifers occur
in central Maryland. These Triassic age units include
sandstone, siltstone, and shale with some diabase
dikes and sills. Well yields commonly range from 10 to
100 gpm, and may exceed 800 gpm. Higher yield
bedrock aquifers occupy about 1.3 percent of Maryland.
Lower Yield Bedrock Aquifers (Class lib)
Exposed in western Maryland are folded and
faulted lower yield sedimentary units. These Middle to
Upper Paleozoic units consist of sandstone, shale, and
siltstone. Well yields commonly range from 2 to 50 gpm,
and may exceed 200 gpm. Lower yield bedrock aquifers
occupy nearly 10 percent of Maryland.
Variably Covered Undifferentiated Aquifers
(Class U-v)
Exposed in central Maryland are Precambrian
to Lower Paleozoic metamorphic and metamorphosed
igneous rocks, which include schist, gneiss, and phyllite.
Well yields commonly range from 2 to 60 gpm, and may
exceed 200 gpm. Even though these crystalline units
have a range that commonly exceeds 50 gpm, it was
classified as a lower yield aquifer because it better
represents the general yield characteristics. Class U-v
aquifers account for 26 percent of Maryland.
Sensitivity
About 63 percent of Maryland is covered by
vulnerable Class I deposits. Aquifersensitivitytoground-
water contamination from shallow injection wells is
73
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particularly high in the populated areas along the west
side of Chesapeake Bay, and to a smaller extent on the
east side of the Bay.
74
-------
I
f?
g
ff
•O
O
-------
I
•**
sr
I
9
a
I
2
10 to 100
GPM
-------
I
i
I
ss
«<
a
ff
3
ID
E.
Areas covered by class I aquifers.
Each dot represents a population center.
-------
Population Density of Maryland (Dot equals one
person per square mile)
• 31 to 35
• 35 to 38
-f 38 to 42
42 to 46
O 46 to 50
Average Annual Precipitation in Maryland
78
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PENNSYLVANIA
General Setting
Pennsylvania contains approximately 45,300
square miles, and lies within four physiographic
provinces. The western and northern parts of the state,
which are in the Appalachian Plateaus, are underlain by
Devonian to Permian age, generally horizontal
sedimentary rocks. The Valley and Ridge and Piedmont
provinces are characterized by folded and faulted
Cambrian to Mississippian age crystalline and
sedimentary rock. The Coastal Plain in southeastern
Pennsylvania is overlain by unconsolidated Quaternary
age deposits. Northwest and northeastern Pennsylvania
are mantled by glacial deposits.
Western Pennsylvania is drained largely by the
Allegheny River and its tributaries, while the central and
eastern parts of the state are drained by Susquehanna
and Delaware river systems. Average annual
precipitation ranges from 36 inches in the north and
west to 48 inches in the east. Pennsylvania's population,
about 12 million, is concentrated in the Philadelphia and
Pittsburgh areas. The remainder of the state is
moderately populated. About 799 million gallons of
fresh ground water are used daily in Pennsylvania.
Unconsolidated Aquifers (Class la)
Occurring generally along streams in the
northern part of Pennsylvania are Quaternary age
unconsolidated aquifers. These alluvial and stratified
glacial deposits consist of sand and gravel with varying
amounts of silt and clay. Well yields generally range
from 100 to 1,000 gpm, and may exceed 2,300 gpm.
About 8.5 percent of the state is covered by
unconsolidated aquifers.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Northeast-southwest trending bands of
Cambrian and Ordovician age karst carbonate rocks
occur in central and southeastern parts of the state.
These aquifers consist largely of limestone and dolomite,
although there are some units of shale and sandstone.
Where present, solutional features contribute to the
lateral and vertical permeability of the rock. Well yields
commonly range from 5 to 500 gpm, and may exceed
2,250 gpm. About 8 percent of the state is occupied by
Class Ib aquifers.
Variably Covered Soluble and Fractured Bedrock
Aquifers
(Class Ib-v)
A small exposure of variably covered Ordovician
age carbonate aquifer occurs in east-central
Pennsylvania. The bedrock is composed of limestone,
dolomite, shale, and sandstone. The vulnerability of
this system is a function of the thickness of the overlying
glacial till. Well yields commonly range from 5 to 500
gpm, and may exceed 2,250 gpm. About 1 percent of
the state is covered by Class Ib-v aquifers.
Lower Bedrock Aquifers (Class lib)
Underlying the majority of Pennsylvania are
Ordovician to Permian age sedimentary rock aquifers
that consist of cyclic sequences of sandstone and shale
with lesser amounts of limestone. Well yields commonly
range from 5 to 60 gpm, but they may exceed 600 gpm.
About 55 percent of the state is overlain with lower yield
bedrock aquifers.
Variably Covered Low Yield Bedrock Aquifers
(Class llb-v)
Variably covered lower yield bedrock aquifers
occur in the northwest and northeast parts of
Pennsylvania. These Devonian to Pennsylvanian age
rocks, which consist of sandstone, shale, and limestone,
are mantled by a variable thickness of glacial till. Their
vulnerability is a function of the thickness and
permeability of the overlying till. Well yields commonly
range from 5 to 60 gpm, and may exceed 600 gpm.
About 22 percent of the state is occupied by Class llb-
v aquifers.
79
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Undifferentiated Aquifers (Class U)
Undifferentiated Precambrian to Ordovician age
bedrock aquifers are present in the southeastern part of
Pennsylvania. These units consist of crystalline, clastic,
and some carbonate rock. Well yields commonly range
from 5 to 25 gpm, and may exceed 220 gpm. About 4
percent of the state is occupied by Undifferentiated
bedrock aquifers.
Sensitivity
Nearly 18 percent of Pennsylvania is covered
by vulnerable Class I aquifers. The most sensitive areas
lie in the vicinity of Philadelphia, along southwestward-
trending belts from Reading to York, Allentown through
Harrisburg, and from Williamsport to Altoona. Sensitive
reaches also occur along major rivers, such as the
Susquehanna and Allegheny rivers, among others.
80
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t/)
8
§
53
o
I
M
53
(S3 tfl
C 5
Aquifer Vulnerability Map of Pennsylvania
81
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I
f
-------
I
I
§
I
I
i
00
to
Areas covered by class I aquifers.
Each dot represents a population center.
-------
Population Density of Pennsylvania (Dot equals one
person per square mile)
Precipitation
in inches
• 32 to 37
- 37 to 43
+ 43 to 48
A. 48 to 54
<> 54 to 59
Average Annual Precipitation in Pennsylvania
84
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VIRGINIA
General Setting
Virginia contains approximately 40,800 square
miles. The mountainous western third of the state lies
in the Appalachian Plateaus and Valley and Ridge
physiographic provinces. Rolling hills and valleys of the
Blue Ridge and Piedmont in central Virginia give way to
the flat-lying Coastal Plain to the east. The Coastal Plain
is underlain by an eastward dipping sequence of
Cretaceous to Holocene age unconsolidated, marine-
terrace and alluvial deposits. The central part of the
state consists of a folded and faulted sequence of
Precambrian to Mesozoic age metamorphic, igneous,
and sedimentary rocks that are commonly overlain by
regolith. A thick sequence of folded and faulted
carbonate and clastic sedimentary rocks of Paleozoic
age underlie the western part of Virginia.
Western Virginia is drained by several
southwest-flowing rivers. The remainder of the state is
drained by a network of east-southeast flowing water
courses. Annual precipitation ranges from 50 inches in
the southeast and southwest to 36 inches along the
western part of the state. Precipitation is distributed
fairly evenly throughout the year. The majority of
Virginia's population, approximately 6 million, is
concentrated in the eastern part of the state. The
remainder of the state is only moderately populated.
Daily use of fresh and saline ground water amounts to
about 341 and .2 million gallons, respectively.
Unconsolidated Aquifers (Class la)
The unconsolidated sediments that make up
Virginia's Coastal Plain form vulnerable and productive
aquifers. Alluvial, marsh, lagoonal, and beach deposits
consist of unconsolidated sand and gravelthat commonly
is interbedded with silt and clay. Well yields range from
5 to 250 gpm, and may exceed 350 gpm. Marine-
terrace deposits consist of unconsolidated, shelly, and
moderately glauconitic sand that is interbedded with
silt, clay, gravel, and thin indurated shell beds. Well
yields commonly range from 5 to 1,500 gpm, and may
exceed 2,500 gpm. About 24 percent of the state is
covered by unconsolidated deposits.
Soluble and Fractured Bedrock Aquifers (Class
Karst features are present in limestone and
dolomite units in western Virginia. Minor amounts of
argellaceous sandstone and shale occur within these
units. Where present, karst features contribute to the
vertical and lateral permeability of the rock, creating
highly productive and vulnerable aquifers. Well yields
commonly range from 50 to 500 gpm, and locally may
exceed 3,000 gpm. Surface exposures of soluble
aquifers occupy about 23 percent of Virginia.
Higher Yield Bedrock Aquifers (Class Ha)
Higher yield bedrock aquifers are exposed
locally in the central part of the state. These aquifers
consist of arkosic sandstones, shales, and
conglomerates that have been intruded in the north.
Well yields commonly range from 10 to 100 gpm, and
may exceed 1 ,000 gpm. Surface exposures of higher
yield bedrock aquifers occupy about 3.3 percent of
Virginia.
Lower Yield Bedrock Aquifer (Class lib)
Lower yield bedrock aquifers are exposed
throughout southwestern Virginia. These Pennsylvanian
age aquifers consist of interbedded sandstone, shale,
siltstone and coal. Well yields commonly range from 1
to 50 gpm, and may exceed 200 gpm. Surface exposures
of tower yield bedrock aquifers occupy about 5 percent
of the state.
Undifferentiated Aquifers (Class U)
Several undivided and lithologically varied
Middle Paleozoic age formations, which crop out along
the western margin of Virginia, consist of folded and
faulted limestone, dolomite, shale, sandstone, siltstone,
85
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and chert. The lithologic and resultant hydrologic
variability of these undivided formations have not been
delineated. A wide range in aquifer productivity and
vulnerability should be expected. Surface exposures of
undiff erentiated aquifers occupy about .9 percent of the
state.
Variably Covered Undifferentiated Aquifers
(Class U-v)
Within the central part of the state, aquifers
consist of locally fractured metamorphic and igneous
rocks that are commonly overlain by regolith that may
exceed 100 feet in thickness. Well yields commonly
range from 1 to 15 gpm, and may exceed 200 gpm.
Aquifer productivity is dependent on the interception of
fractures and vulnerability is related to the thickness of
the regolith. The saturated regolith facilitates aquifer
recharge. Class U-v aquifers occupy about 43 percent
of Virginia.
Sensitivity
About 47 percent of Virginia is covered by
Class I aquifers. Aquifer sensitivity is moderate to high
in the eastern quarter of the state and moderate along
the western margin where vulnerable aquifers crop out.
86
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08 CO
6 O
O o
53 -Q
o
Aquifer Vulnerability Map of Virginia
87
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\
-------
13
fl?
-t
V)
o
w
•o
o
3
53"
oo
vo
Areas covered by class I aquifers.
Each dot represents a population center.
-------
Population Density of Virginia (Dot equals one
person per square mile)
Precipitation
in inches
• 31 to 36
• 36 to 41
+ 41 to 45
^ 45 to 50
O 50 to 54
Average Annual Precipitation in Virginia
90
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WEST VIRGINIA
General Setting
West Virginia contains approximately 24,200
square miles, and lies in the steep hills and incised
valleys and ridges of the Appalachian Plateaus, Valley
and Ridge, and Blue Ridge physiographic provinces.
Exposures of broadly folded Mississippian to Permian
age non-marine and marine cyclic sequences of
sandstone, siltstone, shale, limestone, coal, and
conglomerate occur throughout western and central
West Virginia. Faulted and tightly folded Ordovician to
Devonian age marine and non-marine limestone,
dolomite, shale, sandstone, conglomerate, and anhydrite
occur in the eastern part of the state. Carbonate units,
commonly cherty and argillaceous, range from non-
fossiliferous to bioclastic. Sandstones commonly are
hematitic and calcareous; shales may be fissile.
Except for the eastern part of West Virginia, the
entire state is drained by the Ohio River and its northwest
flowing tributaries. The eastern part of the state is
drained by the Potomac River. Annual precipitation,
which is distributed fairly evenly throughout the year,
ranges from about 30 inches in the east to about 60
inches in east-central West Virginia. The majority of
West Virginia's population, approximately 1.88 million,
is located along the Ohio and Kanawha river valleys.
The remainder of the state is sparsely to moderately
populated. About 227 million gallons of fresh ground
water are used daily.
Unconsolidated Aquifers (Class la)
Alluvial deposits largely occur along the Ohio,
Kanawha, and Little Kanawha river valleys. These
generally unconfined systems, which form vulnerable
and productive aquifers, consist of unconsolidated sand
and gravel that is interbedded with silt and clay. Well
yields commonly range from 50 to 1,500 gpm, and may
exceed 3,000. About 7.4 percent of the state is covered
by Class la aquifers.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Solutional features are present in the moderately
folded Mississippian age limestones that are exposed
in southeastern West Virginia. Marine and non-marine
shale and minor sandstone units occurwithinthe section.
Where present, solutional features contribute to the
vertical and lateral permeability of the rock. Well yields
commonly range from 1 to 100 gpm, and may exceed
200 gpm. Yields of springs range from 50 to 2,000 gpm.
Solutional features also are present in the highly folded
Cambrian and Ordovician age carbonate rocks that are
exposed in the extreme northeast part of the state.
These units primarily consist of limestone, and contain
sandstone, shale, and dolomite interbeds. Limestones
are commonly argillaceous, siliceous, and fossiliferous,
and well yields from them commonly range from 2 to
400 gpm, although yields may exceed 600 gpm.
Discharge from springs range from 50 to 5,000 gpm.
Surface exposures of soluble aquifers occupy nearly 3
percent of the state.
Higher Yield Bedrock Aquifers (Class Ha)
Higher yield Mississippian and Pennsylvanian
age aquifers, composed chiefly of broadly folded shale,
sandstone, siltstone, coal, and minor amounts of
limestone, crop out across southwest, east-central, and
northeast West Virginia. Well yields range from 1 to 100
gpm, and may exceed 300 gpm. Class Ma aquifers
occupy about 39 percent of West Virginia.
Lower Yield Bedrock Aquifers (Class Mb)
Lower yield Paleozoic age aquifers, composed
of nearly horizontal to tightly folded sandstone, shale,
siltstone, and minor limestone and coal, crop out across
northwestern, eastern, and southeastern West Virginia.
Well yields commonly range from 1 to 30 gpm, and may
exceed 200 gpm. Class lib aquifers occupy about 7.4
percent of the state.
91
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Undifferentiated Aquifers (Class U)
Several undivided and lithologically varied
Paleozoic age formations crop out in the eastern and
southeastern parts of the state. These strata largely
consist of folded, interbedded sandstone, shale,
limestone, dolomite, and siltstone, with a minor amount
of chert. The lithologic and hydrologic variability of
these undivided formations have not been delineated.
A wide range in aquiferyield and vulnerability should be
expected in these areas. Undifferentiated aquifers
occupy about 43 percent of West Virginia.
Sensitivity
About 10 percent of West Virginia is covered by
Class I aquifers. The potential for ground-water
contamination from shallow injection wells is small
owing to West Virginia's low population density. The
most sensitive areas lie along major river valleys,
particularly the Ohio River valley where there is a
considerable numberof population centers and industry.
92
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Aquifer Vulnerability Map of West Virginia
93
-------
•0
I
-------
Areas covered by class I aquifers.
Each dot represents a population center.
Aquifer Sensitivity Map of West Virginia
95
-------
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REGION
Alabama
Florida
Georgia
Kentucky
Mississippi
So"th Carolina
Tennessee
97
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ALABAMA
General Setting
Alabama contains approximately 51,700 square
miles. The southwestern three-fifths of the state is in the
low lying coast and moderate relief uplands of the
Coastal Plain physiographic province. The northeastern
two-fifths lies in the mountains and hilly plains of the
Piedmont, Valley and Ridge, Appalachian Plateaus,
and Interior Low Plateaus provinces. Alabama's Coastal
Plain is underlain by a south to southwest dipping
sequence of Cretaceous to Quaternary age,
semiconsolidated to unconsolidated, sand, clay, gravel,
lignite, marl, and limestone. These sediments locally
are overlain by alluvial and coastal deposits. Folded
andfaulted Precambrianto Paleozoic age metamorphic,
igneous, and sedimentary rocks underlie the remainder
of the state.
Northern Alabama is drained by the west-flowing
Tennessee River, while the remainder of the state is
drained by the south to southwest flowing Tombigbee,
Alabama, and Chattahoochee rivers. Annual
precipitation ranges from 49 inches in the north to 66
inches in the south.The majority of Alabama's population,
approximately 4.1 million, is distributed among several
mid-sized cities across the state. The remainder of the
state is sparsely populated. About 343 and 3.4 million
gallons of fresh and saline ground water, respectively,
are used daily in Alabama.
Unconsolidated Aquifers (Class la)
Alluvial and coastal deposits occur throughout
the southern half of the state, and form productive and
vulnerable aquifers. These generally unconfined
systems consist of interbedded and unconsolidated
deposits of sand, gravel, clay, and silt. Where saturated
sand and gravel deposits are of sufficient thickness,
well yields range from 10 to 350 gpm, and may exceed
700 gpm(Hinkle, 1984). About 11.3 percent of Alabama
is covered by unconsolidated deposits.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Solutional features are present in bioclastic
limestone and dolomite deposits of Paleozoic age,
which are exposed across northern Alabama and within
the Valley and Ridge province. Fractured chert and
fissile shale interbeds occur within this system. Where
present, karst features contribute to the vertical and
lateral permeability of the rock, creating highly productive
and vulnerable aquifers. Well yields range from 100 to
500 gpm, and may exceed 1,000. Springs discharging
from limestone and dolomite units yield as much as
1,000 and 4,800 gpm, respectively (Causey, 1965).
Solutional features also are present in sandy, glauconitic,
fossiliferous limestone and coquina, which is exposed
across southern Alabama. Locally these deposits are
overlain by residuum. Marl and sand interbeds also
occur within this Late Eocene to Oligocene age system.
Well yields commonly range from 100 to 500 gpm, and
may exceed 700 gpm. Surface exposures of soluble
aquifers occupy nearly 11 percent of Alabama.
Semiconsolidated Aquifers (Class Ic)
Exposures of semiconsolidated sediments
occur throughout Alabama's Coastal Plain, and consist
of partially to poorly indurated, Cretaceous to Miocene
age sand that is interbedded with clay, gravel, marl, and
sandy limestone. Clastic sediments are commonly
calcareous, glauconitic, fossiliferous, and micaceous.
Well yields commonly range from 300 to 1,000 gpm,
and may exceed 1,400 gpm. Surface exposures of
Class Ic aquifers occupy nearly 36 percent of the state.
Lower Yield Bedrock Aquifers (Class lib)
Lower yield bedrock aquifers crop out in north-
central and east-central Alabama. In the north,
Pennsylvanian age sandstones contain water in
openings along fractures, bedding planes, and joints,
98
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and within permeable zones. Fissile shale interbeds
are present withinthis system. Aquiferyields commonly
range from 1 to 10 gpm, and may exceed 100 gpm.
Surface exposures of lower yield bedrock aquifers
occupy about 14 percent of the state.
Undifferentiated Aquifers (Class U)
Several undivided and lithologically varied
Paleozoic age formations crop out across northern
Alabama and within the Valley and Ridge province.
These formations consist of folded and faulted,
argillaceous and cherty limestone, sandy dolomite,
calcareous shale, sandstone, siltstone, and mudstone.
Mississippian age limestones are commonly bioclastic
and oolitic. The lithologic and resultant hydrologic
variability of these undivided formations have not been
delineated. Undivided and lithologically varied Early
Cenozoic age formations crop out across the southern
part of the state, and consist of interbedded sandy and
fossiliferous limestone, massive clay, marl, sand, and
calcareous silt. Lithologically variable Quaternary age
sediments, which occur along coastal and adjacent
inland portions of southwestern Alabama, consist of
interbedded, unconsolidated sand, clay, and gravel.
Owing to the variable nature of these deposits there is
a wide range in aquifer yield and vulnerability.Surface
exposures of undifferentiated aquifers occupy about 18
percent of the state.
Variably Covered Undifferentiated Aquifers
(Class U-v)
Occurring in the eastern part of Alabama are
Precambrian to Paleozoic age folded, faulted
metamorphic and granitic rocks that are covered by
clay-saprolite of variable thickness. Well yields
commonly range from 1 to 10 gpm, and may exceed 100
gpm. Well yields are related to the number of fractures
encountered by the well bore, and vulnerability is related
to the thickness and permeability of the saprolite. Class
U-v aquifers incorporate nearly 10 percent of Alabama.
Sensitivity
About 57 percent of Alabama is covered by
Class I aquifers, and these generally occur in broad
belts that arc across the southwestern part of the state.
The potential for ground-water contamination from
shallow injection wells in these areas is moderate owing
to the rather evenly distributed population centers.
99
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Class Ic
Aquifer Vulnerability Map of Alabama
Class U
100
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< 10GPM
OT0500GPM
OTO 1000GPM
10T0350GPM
g$ 100T0500GPM
300 TO 1000
GPM
Potential Well Yields in Alabama
101
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Areas covered by class I aquifers.
Each dot represents a population center.
Aquifer Sensitivity Map of Alabama
102
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FLORIDA
General Setting
Florida, which contains 58,664 square miles,
lies entirely in the low relief coastal beaches, marshes,
and inland hills and swamps of the Coastal Plain
physiographic province. The Florida Peninsula is
underlain by a south-southeastward trending, elongate
ridge of Tertiary age limestone and dolomite, which
unconformably overlies Precambrian and Paleozoic
age rock. Interbedded clastic and carbonate sediments
of Quaternary and Tertiary age flank the ridge and cover
most of the state.
Florida contains a variety of surface-water
features including north-, south-, east-, and west-flowing
rivers and canals, as well as numerous swamps,
marshes, ponds, and lakes. Closed basins occur in
association with karst features. Annual precipitation
exceeds 50 inches over most of the state. The majority
of Florida's population, approximately 12.34 million,
occupies the coastal region of the Florida Peninsula
and a few inland cities. The remainder of the state is
sparsely populated. Daily use of fresh ground water
amounts to about 4050 million gallons.
Unconsolidated Aquifers (Class la)
Alluvial, marsh, coastal, and marine deposits
occur throughout the state, forming both productive and
vulnerable aquifers. These sediments consist of
Pliocene to Holocene age quartz sand and clay,
interbedded with lenses of gravel, limonite, occasional
shell layers, and minor limestone beds. Sands are
commonly phosphatic, ferrugenous, and, locally,
micaceous and clay rich. The presence of discontinuous,
poorly indurated sand layers that contain small quantities
of clay, limonite, and hematite cement, result in locally
confined conditions. Unconsolidated sediments, which
are commonly 5 to 50 feet thick, are as much as 700 feet
thick in the northwest corner of the state. Well yields
from Unconsolidated aquifers vary widely throughout
the state. In northwest Florida, yields commonly range
from 5 to 1,000 gpm, and may exceed 2,000 gpm
(Pascale, 1974). Surficial sediments in the Florida
Panhandle commonly yield less than 100 gpm, but
locally may exceed 1,000 gpm. About 40 percent of the
state is covered by Class la aquifers.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Solutional features are present in Late Eocene
to Pleistocene age carbonate units that are exposed
across Florida's Panhandle, and in the northwestern
and southern Florida Peninsula. Tertiary age
carbonates, associated with the Floridan aquifer system,
consist of finely crystalline to granular, fossiliferous to
bioclastic, sandy to argillaceous limestone. Dolomite
beds and lenses of clay, marl, and shale occur within
this system. Well yields range from 500 to 1,000 gpm,
and may exceed 20,000 gpm (Pascale, 1974).
Pleistocene age carbonates, associated with the
Biscayne aquifer system, crop out in southern Florida
and consist of oolitic, fossiliferous, pure to sandy
limestone, and interbedded sand, and calcareous
sandstone. This north and westward thinning system
reaches a maximum thickness of 200 feet along the
coast. Well yields commonly range from 500 to 1,000
gpm, and may exceed 7,000 gpm. Surface exposures
of soluble aquifers occupy about 25 percent of Florida.
Semiconsolidated Aquifers (Class Ic)
Exposures of semiconsolidated sediments
occur throughout Florida and consist of poorly to well
indurated, Miocene to Pleistocene age clastic and
carbonate units. Miocene age sediments in the Florida
Panhandle consist of quartz sand and gravel,
interbedded with lesser amounts of clay and shell
material, and minor phosphate, glauconite, and
limestone beds. Clay, and less commonly micrite, act
as cementing agents. Miocene and Pleistocene age
sediments, which are exposed throughout the northern
and western half of the Florida Peninsula, consist of
poorly indurated, clayey sand, interbedded with lenses
and laminae of dolomite and sandy limestone.
Phosphatic grain coatings and laminae are common
within this system. Semiconsolidated sediments
exposed in southeastern Florida consist of coarse sand
and shell fragments, locally cemented with calcium
104
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carbonate and shell marl. Grain size and degree of
induration decrease to the west. Semiconsolidated
sediments commonly yield less than 100 gpm, but may
exceed 1,000 gpm. Surface exposures of
semiconsolidated aquifers occupy nearly 31 percent of
the state.
Covered Aquifers (Class Id)
Semiconsolidated and carbonate aquifers,
overlain by less than 50 feet of fine-grained, argillaceous
sand, occur in the northwestern corner of the Florida
Peninsula. Well yields range from a few gallons to 1000
gpm. The reduced vulnerability of these covered systems
is a function of the thickness and permeability of the
overlying material. Class Id aquifers occupy about 1
percent of the state.
Sensitivity
The potential for shallow ground-water
contamination from shallow injection wells is very high
in Florida. Nearly the entire state consists of Class I
aquifers and many major urban and industrial centers
lie above highly vulnerable aquifers.
105
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Aquifer Vulnerability Map of Florida
106
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< 100GPM
m < i ooo GPM
500 TO 1000 GPM
LKl LAKE
Potential Well Yields in Florida
107
-------
Areas covered by class I aquifers.
Each dot represents a population center.
Aquifer Sensitivity Map of Florida
108
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Population Density of Florida
(Dot equals one person per square mile)
Average Annual Precipitation in Florida
109
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GEORGIA
General Setting
Georgia, which contains approximately 59,000
square miles, lies primarily in the low lying to hilly,
Coastal Plain and Piedmont provinces. The northern
part of the state is in the mountainous Blue Ridge,
Valley and Ridge, and Appalachian Plateaus provinces.
The southern half of Georgia is underlain by a southeast
dipping and thickening sequence of Cretaceous to
Holocene age consolidated to unconsolidated, marine,
beach, and alluvial deposits. The north-central and
northeastern parts of the state are underlain by folded
and faulted Precambrian to Mesozoic age igneous and
metamorphic rocks. Folded and faulted Paleozoic age
carbonate and clastic sedimentary rocks underlie the
northwestern corner of Georgia. Unconsolidated
weathered material locally overlies bedrock outcrops
throughout the state.
Streams in northern and northwestern Georgia
flow to the north and southwest. The remainder of the
state is drained by a network of south- to southeast-
flowing rivers. Annual precipitation ranges from less
than 44 inches in east-central Georgia to more than 76
inches in the north. Precipitation is distributed fairly
evenly throughout the year. The majority of Georgia's
population, approximately 6.3 million, is located in and
around metropolitan Atlanta, and several smaller cities
adjacent to major rivers. The remainder of the state is
moderately populated. Daily use of fresh ground water
amounts to about 1000 million gallons.
Unconsolidated Aquifers (Class la)
Alluvial, marsh, and beach deposits, which
occur along major rivers and across coastal Georgia,
form productive and vulnerable aquifers that have yet to
be heavily used. These generally unconfined systems
consist of interbedded, unconsolidated sand, gravel,
and clay. Expectable well yields range from 100 to 500
gpm (L. Gorday, Georgia Geological Survey, oral
communication, 1990). About 13 percent of the state is
covered by unconsolidated deposits.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Karst features are present in interbedded
carbonate and clastic units that are exposed in a belt
that extends from southwestern to east-central Georgia.
Where present, karst features contribute to the vertical
and lateral permeability of the rock, creating highly
productive and vulnerable aquifers. Well yields in
Oligocene age limestone, dolomite, and calcareous
sand aquifers, commonly range from 1,000 to 5,000
gpm, and may exceed 11,000 gpm. Well yields, in the
more widely exposed Late Eocene age sandy limestone
aquifers generally range from 150 to 600 gpm, but they
may exceed 1,500 gpm. The amount of clastic material
present in Upper Eocene strata increases to the
northeast. Karst features also are present in dolomite
and limestone units exposed in northwestern Georgia.
Well yields commonly range from 1 to 50 gpm, and may
exceed 3,500 gpm. Springs discharging from these
aquifers may flow as much as 5,000 gpm. Surface
exposures of soluble aquifers occupy about 17.5 percent
of Georgia.
Semiconsolidated Aquifers (Class Ic)
Exposures of semiconsolidated sediments,
which occurthroughout Georgia's Coastal Plain, consist
of partially to poorly indurated Cretaceous to Miocene
age sand that is interbedded with silt, clay, gravel, and
minor limestone units in the southwest. Sands vary
from glaconitic to calcareous and ferruginous, and are
locally phosphatic, fossiliferous, micaceous, and
carbonaceous. Well yields commonly range from 50 to
1,200 gpm, and may exceed 3,300 gpm. Surface
exposures of semiconsolidated aquifers occupy about
30 percent of the state.
Lower Yield Bedrock Aquifers (Class lib)
Lower yield bedrock aquifers, composed of
fractured sandstone, mudstone, and chert, crop out in
the northwest cornerof the state. Well yields range from
110
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1 to 20 gpm, and may reach 300 gpm (Sonderegger,
1978). Surf ace exposures of Class lib aquifers occupy
about 1 percent of the state.
Undifferentiated Aquifers (Class U)
Several undivided and lithologically varied
Paleozoic age formations, which crop out in the
northwestern corner of Georgia, consist of folded and
faulted, limestone, dolomite, sandstone, and mudstone.
The lithologic and resultant hydrologic variability of
these undivided formations has not been delineated. A
wide range in aquifer productivity and vulnerability
should be expected in these areas. Surface exposures
of undifferentiated aquifers occupy about 3 percent of
the state.
Variably Covered Undifferentiated Aquifers
(Class U-v)
Precambrian to Paleozoic age crystalline rocks
occur in northern Georgia. These bedrock aquifers
consist of granite, gneiss, schist, quartzite, and marble.
The rocks are mantled by saprolite of variable thickness.
Aquifer productivity relies on the presence of saturated
regolith and fractured bedrock. Well yields commonly
range from 1 to 25 gpm, and may exceed 500 gpm.
Slightly more than 34 percent of the state is covered by
Class U-v aquifers.
Sensitivity
About 60 percent of Georgia is covered by
Class I aquifers. The potential for ground-water
contamination from shallow injection wells is greatest in
the southeastern half of the state owing to the vulnerability
of the aquifers and the relatively uniform distribution of
population centers.
111
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Aquifer Vulnerability Map of Georgia
112
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\
°0
*.
\
-------
Areas covered by class I aquifers.
Each dot represents a population center.
Aquifer Sensitivity Map of Georgia
114
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Population Density of Georgia
(Dot equals one person per square mile)
Average Annual Precipitation in Georgia
115
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KENTUCKY
General Setting
Kentucky contains approximately 40,400
square miles, and lies primarily in the gently rolling
plateaus and dissected to mountainous terrain of the
Interior Low Plateaus and Appalachian Plateaus
provinces. The extreme southwestern part of the state
lies in the flat lying to gently rolling Coastal Plain. The
Appalachian Plateaus province in eastern Kentucky is
underlain by synclinally folded Pennsylvanian age
sandstone, siltstone, and shale. The eastern part of
InteriorLow Plateaus province, in east-central Kentucky,
is underlain by anticlinally folded Ordovician age
limestone, dolomite, shale, and sandstone. To the west,
synclinally folded interbedded, Mississippian age
limestone, sandstone, and shale, flank a core of
Pennsylvanian age elastics. Western Kentucky is
underlain by westward dipping, semiconsolidated to
unconsolidated Cretaceous and Tertiary age sand, silt,
and clay. Alluvial and eolian deposits occur throughout
western Kentucky and along the Ohio River.
Except for the southeastern part, the entire
state is drained by the Ohio and Mississippi rivers and
their numerous northwest flowing tributaries. The
southwest flowing Cumberland River drains
southeastern Kentucky. Annual precipitation ranges
from about 40 inches in the north to about 52 inches in
the southeast. Kentucky's population, approximately
3.7 million, is distributed among many municipalities
across the state. Jefferson, and Fayette are the most
densely populated counties. About 205 million gallons
of fresh ground water are used daily in Kentucky.
Unconsolidated Aquifers (Class la)
Alluvial and coastal deposits occur throughout
southwestern Kentucky, and along the major rivers in
the western and northern parts of the state. These
generally unconfined systems, which form vulnerable
and productive aquifers, consist of Tertiary and
Quaternary age unconsolidated sand, gravel, silt, and
clay. Well yields commonly range from 5 to 500 gpm,
and may exceed 5,000 gpm. About 10 percent of the
state is covered by Class la aquifers.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Solutional features are present in Mississippian
age chert and shale bearing limestone units that are
exposed across west-central Kentucky, and in
Ordovician age limestone and dolomite units in the
north-central part. Where present, karst features
contribute to the vertical and lateral permeability of the
rock. Well yields commonly range from 2 to 10 gpm, and
may exceed 500 gpm. Surface exposures of Class Ib
aquifers occupy about 13 percent of the state.
Semiconsolidated Aquifers (Class Ic)
Semiconsolidated sediments, which crop out in
southwestern Kentucky, consist of Cretaceous age
sand, silt, clay, and gravel. Well yields commonly range
from 5 to 25 gpm, and may exceed 1,100 gpm. Surface
exposures of Class Ic aquifers occupy about 1.3 percent
of the state.
Covered Aquifers (Class Id)
Unconsolidated alluvial and coastal deposits
that are overlain by less than 50 feet of low permeability
materials, occur throughout the extreme southwestern
part of Kentucky. The reduced vulnerability of these
covered systems is a function of the thickness of the
overlying fine-grained material. Covered alluvial and
coastal aquifers occupy about 1 percent of the state.
Lower Yield Bedrock Aquifers (Class lib)
Lower yield Pennsylvanian age bedrock
aquifers, composed of interbedded sandstone, shale,
siltstone, and coal, crop out throughout eastern and
parts of western Kentucky. Well yields commonly range
from 1 to 5 gpm, and may exceed 200 gpm. Surface
exposures of lower yield bedrock aquifers occupy about
32.4 percent of the state.
116
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Undifferentiated Aquifers (Class U)
Several undivided and lithologically varied
Paleozoic age formations crop out across central
Kentucky, and consist of interbedded limestone, shale,
and sandstone. The lithologic and resultant hydrologic
variability of these undivided formations has not been
delineated. A wide range in aquifer productivity and
vulnerability should be expected. Surface exposures of
undifferentiated aquifers occupy about 42.3 percent of
the state.
Sensitivity
About 25 percent of Kentucky is covered by
Class I aquifers. The potential for ground-water
contamination from shallow injection wells is moderately
low. Sensitivity is high both in karst areas and locally
along the Ohio River where there is an abundance of
industry.
117
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CO
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CO
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CO
CO
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CO
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Aquifer Vulnerability Map of Kentucky
118
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Potential Well Yields in Kentucky
119
-------
I
I
OT
-------
Population Density of Kentucky
(Dot equals one person per square mile)
Average Annual Precipitation in Kentucky
121
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MISSISSIPPI
General Setting
Mississippi contains nearly 48,000 square miles,
and lies largely in the relatively flat lying Coastal Plain
physiographic province. The extreme northeastern
corner of the state is in the Central Lowland province.
The Coastal Plain is underlain by a south- to southwest-
dipping sequence of Cretaceous to Tertiary age
semiconsolidated to unconsolidated sand, silt, clay,
gravel, marl, and limestone. These sediments are
mantled by unconsolidated Mississippi River alluvium
and loess deposits in the west and, locally, by river
alluvium and coastal deposits. Devonian and
Mississippian age carbonate and clastic rocks crop out
in the extreme northeast corner of the state.
The Mississippi Riverand its southwest-flowing
tributaries drain western Mississippi. The remainder of
the state is drained by a network of south-flowing rivers.
Annual precipitation ranges from about 46 inches in the
north to 65 inches in the south. The late winter and
spring months generally have the highest precipitation.
Evapotranspiration is high due to the state's flat
topography and warm climate. The majority of
Mississippi's population, about 2.6 million, is located in
and around metropolitan Jackson, and along the Gulf
Coast. The remainder of the state is rural, and sparsely
populated. About 1580 million gallons of fresh ground
water are used daily in the state.
Unconsolidated Aquifers (Class la)
Alluvial and coastal deposits occur throughout
the state, and form productive and vulnerable aquifers.
These semiconfined to unconfined systems consist of
unconsolidated sand, gravel, silt, clay, and loam.
Alluvium in the Mississippi River flood plain average
about 140 feet in thickness, and well yields range from
500 to 3,000 gpm, and may exceed 5,000 gpm. Yields
from other alluvial and coastal aquifers range from 50 to
300 gpm, and may exceed 500 gpm. Nearly 40 percent
of the state is covered by Class la aquifers.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Solutional features are present in M ississippian
age limestone units exposed in the extreme northeast
corner of the state. Chert, sandstone, and shale
interbeds occur within this system. Where present,
solutional features contribute to the vertical and lateral
permeability of the rock, creating highly productive and
vulnerable aquifers. Well yields range from 100 to 900
gpm, and may exceed 1,000 gpm. Karst features are
present in Oligocene age limestones exposed across
the southern mid-section of the state. Marl, clay, and
sand interbeds occur within this system. Well yields
range from 10 to 150 gpm, and may exceed 400 gpm.
Surface exposures of karst carbonate aquifers occupy
about 1.3 percent of Mississippi.
Semiconsolidated Aquifers (Class Ic)
Exposures of semiconsolidated sediments
occur throughout Mississippi. This thick sequence
consists of partially to poorly indurated, Cretaceous to
Tertiary age calcareous and glauconitic sand with
interbedded clay, gravel, marl, and limestone. Well
yields range from 10 to 2,000 gpm, and may exceed
5,000 gpm. The presence of numerous intercalated
layers of low permeability strata reduces the vulnerability
of this system. Surface exposures of semiconsolidated
aquifers occupy nearly 36 percent of the state.
Covered Aquifers (Class Id)
Semiconsolidated and soluble aquifers, overlain
by less than 50 feet of loess, occur along the eastern
marginof the Mississippi Riverflood plain. The reduced
vulnerability of these covered systems is a function of
the thickness of the overlying low permeability material.
Covered semiconsolidated and soluble aquifers occupy
about 6 percent of the state.
122
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Undifferentiated Aquifers (Class U)
Lit ho logically varied Quaternary age sediments
occur along coastal and adjacent inland parts of
southeastern Mississippi, and consist of interbedded
unconsolidated clay, silt, sand, and gravel. Due to their
textural heterogeneity, a wide range in aquifer
productivity and vulnerability should be expected in
these areas. About 2 percent of the state is covered by
Class U aquifers.
Sensitivity
Nearly 83 percent of Mississippi is covered by
Class I aquifers. Owing to the high permeability of these
systems, the potential for ground-water contamination
from shallow injection wells is significant. On the other
hand, the population centers, which are rather evenly
distributed throughout the state, are generally quite
small.
123
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Class Ic
Aquifer Vulnerability Map of Mississippi
124
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<10GPM
10tol50GPM
I 10to300GPM
i§3
3 10to2000GPM
A
50to300GPM
100to900GPM
500 to 3000 GPM
Potential Well Yields in Mississippi
125
-------
Areas covered by class I aquifers.
Each dot represents a population center.
Aquifer Sensitivity Map of Mississippi
126
-------
i
I
•e
•e
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NORTH CAROLINA
Genera! Setting
North Carolina, which contains approximately
52,700 square miles, lies within four distinct
physiographic provinces. The Coastal Plain province
occupies the eastern two-fifths of the state, and contains
the low lying to flat, poorly drained, outer or tide-water
part, and the gently rolling, well drained, inner part
(Stuckey and Steel, 1953). The central part of the state
lies in the hills of the Piedmont province, while the
mountainous western fifth of the state is in the Blue
Ridge and Valley and Ridge. The Coastal Plain is
underlain by an eastward thickening wedge of
Cretaceous to Holocene age consolidated to
unconsolidated, marine, marine-terrace, and alluvial
deposits. The central and western parts of the state are
underlain by faulted and folded Precambrian to Mesozoic
age metamorphic, igneous, and sedimentary rocks,
which commonly are overlain by regolith.
The western part of North Carolina is drained
by several northwest-flowing rivers. The remainder of
the state is drained by a network of southeast-flowing
rivers. Annual precipitation ranges from 40 to 82 inches
in the mountainous Blue Ridge province. Elsewhere
annual precipitation ranges from 44 inches in the west
to 52 inches in the southeast. The majority of North
Carolina's population, nearly 6.5 million, is located in
the Piedmont. The remainder of the state is moderately
populated. About 435 million gallons of fresh ground
water are used daily in North Carolina.
Unconsolidated Aquifers (Class la)
The unconsolidated sediments in North
Carolina's Coastal Plain form vulnerable and productive
aquifers. Alluvial, marsh, lagoonal, and beach deposits
consist of unconsolidated sand, silt, gravel, and clay,
which locally are overlain by dune sand. Well yields
commonly range from 25 to 200 gpm, and may exceed
500 gpm. Marine-terrace deposits consist of
unconsolidated sand and clay, sandy shell beds and
interbedded marls, and massive marine clays. Well
yields commonly range from 15 to 90 gpm, and may
exceed 500 gpm. About 38.5 percent of the state is
covered by unconsolidated deposits.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Solutional features are present in carbonate
rocks, which are locally exposed in stream cuts in the
eastern part of the state. Lithologies range from sandy
shell limestone and marl to dense silicified limestone
with calcareous sand facies. Solutional features
contribute to the vertical and lateral permeability of the
rock, creating highly productive and vulnerable aquifers.
Well yields commonly range from 200 to 500 gpm, and
may exceed 2,000 gpm. Surface exposures of soluble
aquifers occupy about 1.2 percent of the state.
Semiconsolidated Aquifers (Class Ic)
Exposures of Semiconsolidated marine
sediments occur along a northeasterly trend in south-
central North Carolina, and in several stream valleys in
the eastern part of the state. These Cretaceous age
sediments consist of sand, clayey sand, and clay, and
locally contain marls and shell limestones. Well yields
commonly range from 200 to 400 gpm, and may exceed
1400 gpm. Surface exposures of Class Ic aquifers
occupy about 6 percent of the state.
Variably Covered Undifferentiated Aquifers
(Class U-v)
Undifferentiated aquifers are exposed
throughout the western two-thirds of North Carolina.
These bedrock units consist of fractured, metamorphic
and igneous rocks that commonly are overlain by a clay-
rich regolith of variable thickness. Well yields normally
range from 5 to 35 gpm, and may exceed 200 gpm. Well
yields are dependent on the number of fractures
penetrated by the well bore. Sustained well yields are
related to the thickness of the saturated regolith. Class
U-v aquifers occupy about 51 percent of the state.
128
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Sensitivity
About 46 percent of North Carolina is covered
by Class I aquifers. The potential for ground-water
contamination from shallow injection wells is highest in
the eastern part of the state where population centers
are rather evenly distributed.
129
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Potential Well Yields in North Carolina
131
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>
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NJ
-by class I aquifers.
dot represents a population center.
-------
Population Density of North Carolina (Dot equals
one person per square mile)
Average Annual Precipitation in North Carolina
133
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SOUTH CAROLINA
General Setting
South Carolina, which contains approximately
31,100 square miles, lies primarily in the low relief to
hilly Coastal Plain and Piedmont physiographic
provinces. The extreme northwestern part of the state
includes the mountainous Blue Ridge province. The
southeastern two-thirds of the state is underlain by a
southeastward thickening wedge of consolidated to
unconsolidated marine, marine-terrace, and alluvial
deposits that range from Cretaceous to Holocene in
age. The northwestern third of the state is underlain by
folded and faulted metamorphic and igneous rocks,
Precambrian to Mesozoic in age, that commonly are
overlain by regolith.
South Carolina is drained by a network of
southeast flowing rivers. The Savannah River and its
many tributaries drain the western margin of the state.
Annual precipitation ranges from less than 48 inches in
the southeast to more than 80 inches in the northwest.
Precipitation is greatest during the summer and least in
the fall. The majority of South Carolina's population,
nearly 3.5 million, is divided among several mid-sized
cities that are distributed throughout the state. Elsewhere
the state is moderately populated. About 214 million
gallons per day of fresh ground water are used in the
state.
Unconsolidated Aquifers (Class la)
The unconsolidated sediments, which form
South Carolina's Coastal Plain, are vulnerable and
productive aquifers. Alluvial, marsh and beach deposits
consist of unconsolidated sand, gravel, and clay. Well
yields commonly range from 5 to 10 gpm, and may
exceed 500 gpm. Marine-terrace deposits consist of
unconsolidated glauconitic, quartzose sand, interbedded
with clay, marl, and coquina. Well yields from these
deposits commonly range from 50 to 200 gpm, and may
exceed 700 gpm. About 40 percent of the state is
covered by Class la aquifers.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Solutional features are present in fossiliferous
limestones and coquina beds that are locally exposed
by stream cuts throughout the southwestern half of the
Coastal Plain. Karst features create highly productive
and vulnerable aquifers. Well yields commonly range
from 100 to 300 gpm, and may exceed 2,000 gpm.
Surface exposures of soluble aquifers occupy about 8
percent of the state.
Semiconsolidated Aquifers (Class Ic)
Exposures of semiconsolidated continental and
marine sediments occur along a northeastern trend
across central South Carolina, and in stream cut valleys
throughout the Coastal Plain. These Cretaceous age
sediments consist of phosphatic, glauconitic, and
calcareous sand, interbedded with clay. Well yields
commonly range from 50 to 700 gpm, and may exceed
2,000 gpm. Surface exposures of semiconsolidated
aquifers occupy about 15 percent of the state.
Variably Covered Undifferentiated Aquifers
(Class U-v)
Class U-v aquifers occur throughout the
northwestern half of the state. These bedrock aquifers
consist of fractured igneous and metamorphic rocks
that are commonly covered by a saprolite that ranges
from about 30 to 60 feet in thickness. The clay-rich,
unconsolidated saprolite stores a large quantity of water,
but it has a low permeability. Well yields generally range
from 10 to 30 gpm, and may exceed 300 gpm. The
occurrence of water bearing fractures decreases with
depth. Class U-v aquifers occupy approximately 36
percent of the state.
Sensitivity
About 63 percent of South Carolina is covered
by Class I aquifers. The potential for ground-water
134
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contamination from shallow injection wells is low to
moderate, particularly in the southeastern half of the
state where unconsolidated Coastal Plain deposits
crop out.
135
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Aquifer Vulnerability Map of South Carolina
136
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Potential Well Yields in South Carolina
137
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U)
00
ff
"O
o
ff
I
s
Areas covered by class I aquifers.
Each dot represents a population center.
-------
(Dot e^als
v
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TENNESSEE
General Setting
Tennessee, which contains approximately
42,150 square miles, is in a physiographically diverse
region. The eastern half of the state lies among the
mountains, ridges, hills, and incised valleys of the Blue
Ridge, Valley and Ridge, and Appalachian Plateaus
provinces. West-central Tennessee is in the rolling
plains of the Interior Low Plateaus and the surrounding
gently rolling to highly dissected plateaus of the Highland
Rim. Western Tennessee lies in the north-south trending
Western Valley and the westward sloping plains of the
Coastal Plain. The eastern third of Tennessee is
underlain by faulted and tightly folded Cambrian to
Pennsylvanian age carbonate and clastic strata. The
central part of the state consists of a broadly folded
dome of Ordovician to Mississippian age carbonate and
clastic sedimentary rocks. Westward dipping,
semiconsolidated to unconsolidated, Cretaceous to
Holocene age clastic sediments underlie the western
third of the state. Alluvial and eolian deposits occur
throughout western Tennessee.
Western Tennessee is drained by the
Mississippi River, and the remainder of the state by the
west- and north-flowing Tennessee and Cumberland
rivers. Annual precipitation rangesf rom47 inches inthe
west to 80 inches in the mountainous east. The majority
of Tennessee's population, approximately 4.9 million, is
located in Shelby, Davidson, Hamilton, and Knox
Counties. Elsewhere the state is moderately populated.
Each day Tennessee uses about 444 million gallons of
fresh ground water.
Unconsolidated Aquifers (Class la)
Alluvial deposits occur throughout western
Tennessee, and form vulnerable and productive aquifers.
These generally unconf ined systems consist of Tertiary
to Quaternary age interbedded and unconsoiidated
sand, gravel, clay, silt, and lignite. Well yields commonly
range from 20 to 1,000 gpm, and may exceed 2,000
gpm. About 11.4 percent of the state is covered by
Class la aquifers.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Karst features are present in Mississippian age
dolomitic and cherty limestone, which is exposed
throughout central Tennessee's Highland Rim. These
rocks commonly contain calcareous sandstone and
shale in the north and east. Where present, karst
features contribute to the vertical and lateral permeability
of the rock. Well yields commonly range from 5 to 50
gpm, and may exceed 400 gpm. Extensively faulted
and folded, Cambrian to Ordovician age clastic and
karstic carbonate rocks crop out across eastern
Tennessee. These units consist of highly fractured
calcareous shale, sandstone, conglomerate, and
limestone with dolomite interbeds. Well yields commonly
range from 5 to 200 gpm, and may exceed 2,000 gpm.
Class Ib aquifers occupy 24.4 percent of the state.
Semiconsolidated Aquifers (Class Ic)
Semiconsolidated sediments crop out in west-
central Tennessee. These Cretaceous age units consist
of fine-grained, glauconitic sand that is interbedded with
silt, clay, marl, and cherty gravel. Well yields commonly
range from 50 to 500 gpm, and may exceed 1000 gpm.
Surface exposures of semiconsolidated aquifers occupy
about 4 percent of the state.
Covered Aquifers (Class Id)
Unconsolidated alluvial aquifers that are
overlain by less than 50 feet of low permeability deposits
occur throughout western Tennessee's Coastal Plain.
The reduced vulnerability of these covered systems is
a function of the thickness of the overlying material.
Covered alluvial aquifers occupy about 10 percent of
the state.
Lower Yield Bedrock Aquifers (Class lib)
Lower yield Pennsylvanian age bedrock
aquifers, composed of sandstone and conglomerate
that is interbedded with shale, siltstone, and coal, crop
140
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out throughout eastern Tennessee's Cumberland
Plateau. Well yields commonly range from 5 to 50 gpm,
and may exceed 200 gpm. Class Mb aquifers cover 11
percent of the state.
Undifferentiated Aquifers (Class U)
Several undivided and lithologically varied
Paleozoic age formations crop out across the eastern
three-fourths of the state, and consist of interbedded
limestone, shale, dolomite and sandstone. Lithologically
varied Tertiary age sediments extend across the eastern
margin of the Coastal Plain in western Tennessee, and
consist of interbedded clay, glauconitic sand, and a
basal limestone unit. The lithologic and resultant
hydrologic variability of these undivided formations has
not been delineated, but a wide range in aquifer
productivity and vulnerability should be expected.
Surface exposures of undifferentiated aquifers occupy
about 33 percent of the state.
Undifferentiated Aquifers (Class U-v)
Undifferentiated bedrock aquifers crop out
across eastern Tennessee's Blue Ridge. These units
consist of Precambrian age igneous, metamorphic, and
metasedimentary rocks that are mantled by regolith of
variable thickness. Aquifer productivity relies on the
presence of saturated regolith and fractured bedrock.
Well yields commonly range from 5 to 50 gpm, and may
exceed 1,000 gpm. Class U-v aquifers occupy about 5
percent of the state.
Sensitivity
About 50 percent of Tennessee is covered by
Class I aquifers. The potential for ground-water
contamination from shallow injection wells is relatively
low owing to the moderate population density. The most
sensitive areas lie in southwest-trending belts in the
eastern part of the state where the density of population
centers is rather high. Elsewhere in vulnerable areas,
population centers are rather evenly distributed.
141
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-------
e
0,
00
o
o
O
\r\
a
00
o
o
o
o
-------
i
g
E
g
Areas covered by class I aquifers.
Each dot represents a population center.
-------
Population Density of Tennessee (Dot equals one
person per square mile)
Precipitation
In inches
• 41 to 49
- 49 to 57
+ 57 to 65
^ 65 to 73
O 73 to 81
Average Annual Precipitation in Tennessee
145
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REGION 5
Illinois
Indiana
Michigan
Minnesota
Ohio
Wisconsin
146
-------
ILLINOIS
General Setting
Illinois contains approximately 56,400 square
miles, and mainly lies in the Central Lowland
physiographic province. Small areas in the southwestern
and southern parts of the state lie within the Ozark
Plateaus province. The topography varies from flat-
lying to gently rolling. The state is underlain by gently
dipping Paleozoic age sediments that are mantled by a
variable thickness of glacial material. Glacial deposits,
which range from 0 to 600 feet in thickness, are absent
in extreme northwest and southern Illinois.
The southern part of the state is drained by
several rivers that empty into the Ohio River. The
southwesterly-flowing Illinois and Rock rivers drain
central and northern Illinois, respectively. Annual
average precipitation ranges from 36 inches in the north
to about 46 inches in the southern part of the state. The
majority of Illinois' population, approximately 11.6 million,
is concentrated in the Chicago metropolitan area. The
remainderof the state is moderately populated. Ground-
water usage amounts to about 930 million gallons of
fresh and 38 million gallons of saline ground water each
day.
Unconsolidated Aquifers (Class la)
Exposed intermittently throughout the state are
unconsolidated alluvial and glaciofluvial aquifers. These
aquifers consist of sand and gravel with variable amounts
of silt and clay. Well yields commonly range from 10 to
1,000 gpm, and may exceed 3,000 gpm. Approximately
14 percent of the state is covered by permeable
unconsolidated aquifers.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Local exposures of Ordovician to Mississippian
age carbonate rocks occur in northeastern, western,
and far southern Illinois. These rocks consist of dolomite,
limestone, chert, and shale. Where present, solutional
features contributeto the vertical and lateral permeability
of the rock. Well yields commonly range from 5 to 1,000
gpm, and may exceed 1,500 gpm. About .6 percent of
Illinois is covered by Class Ib aquifers.
Semiconsolidated aquifers (Class Ic)
In the south and west-central parts of Illinois
are local exposures of Cretaceous age semiconsolidated
deposits. These consist of sand, silt, and clay. Well
yields commonly range from 10 to 1,000 gpm, and may
exceed 3,000 gpm. About .8 percent of the state is
occupied by semiconsolidated aquifers.
Covered Aquifers (Class Id)
Soluble strata that are overlain by less than 50
feet of low permeability sediments occur in northern,
western, and southern Illinois. These Ordovician to
Mississippian age units consist of dolomite, limestone,
chert, and shale. Well yields commonly range from 5 to
1,000 gpm, and may exceed 1,500 gpm. Class Id
aquifers occupy about 4 percent of the state.
Lower Yield Bedrock Aquifers (Class lib)
Local exposures of lower yield sedimentary
rock aquifers occur in southern Illinois. These
Pennsylvanian age strata are predominantly sandstone
with minor amounts of shale, coal, and limestone. Well
yields commonly range from 5 to 25 gpm, and may
exceed 1,000 gpm. Class lib aquifers are exposed in
about 1.3 percent of Illinois
Covered Aquifers (Class lie)
Exposed intermittently throughout Illinois are
low yield aquifers that are overlain by less than 50 feet
of low permeability sediments. These Pennsylvanian
age rocks consist of sandstone, shale, and chert with
minor amounts of limestone and coal. Well yields
commonly range from 5 to 25 gpm, and may exceed
1,000 gpm. About 25 percent of Illinois is occupied by
Class lie aquifers.
147
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Undifferentiated Aquifers (Class U)
Exposed locally in western and southern Illinois
are undifferentiated Upper Mississippian rocks that
consist of shale, sandstone, and limestone. Well yields
commonly range from 5 to 25 gpm, and may exceed
1,000 gpm. About 2 percent of the state is occupied by
undifferentiated aquifers.
Covered Undifferentiated Aquifers (Class U-v)
Occurring in southwestern Illinois are
undifferentiated Mississippian age clastic and carbonate
rocks that are overlain by a variable thickness of low
permeability sediments. Well yields commonly range
from 5-25 gpm, and may exceed 100 gpm. About 1
percent of Illinois is occupied by Class U-v aquifers.
Sensitivity
Nearly 15 percent of Illinois is covered by Class
I aquifers. Most of the areas consist of linear belts of
sand and gravel that lie along streams and the Mississippi
River. Population centers are rather dense along parts
of the Mississippi and Illinois rivers. These areas are
particularly sensitive because of the population
distribution and abundance of industry.
148
-------
Aquifer Vulnerability Map of Illinois
149
-------
*)
v°
-------
Areas covered by class I aquifers.
Each dot represents a population center.
Aquifer Sensitivity Map of Illinois
151
-------
Population Density of Illinois
(Dot equals one person per square mile)
Precipitation
In inches
• 28 to 32
• 32 to 36
+ 36 to 40
•^ 40 to 45
0 45 to 49
Average Annual Precipitation in Illinois
152
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INDIANA
General Setting
Indiana, which contains approximately 36,200
square miles, lies within the unglaciated Interior Low
Plateaus in the southern part of the state, and the
remainder is in the glaciated Central Lowland. The
topography ranges from flat to gently rolling. Indiana is
underlain by Paleozoic age sedimentary rocks that dip
gently off the northwest-southeast trending Cincinnati-
Kankakee Arch.
The state is drained by the Wabash and other
southwest-flowing river systems. Average annual
precipitation varies from 36 inches in the north to 44
inches in the southern part of the state. Indiana's
population, approximately 5.5 million, is concentrated
in Indianapolis and several other metropolitan areas.
The remainder of the state is moderately populated.
About 635 million gallons of fresh ground water are
used daily in Indiana.
Unconsolidated Aquifers (Class la)
Exposed along river channels, and locally
elsewhere, are unconsolidated outwash, glaciofluvial,
and alluvial deposits, which consist of sand and gravel
with lesser amounts of silt and clay. Well yields commonly
range from 100 to 500 gpm, and may exceed 1,500
gpm. Approximately 27 percent of Indiana is covered by
Class la aquifers.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Soluble aquifers are exposed in south-central
and southeastern Indiana. These Ordovician and
Mississippian age rocks consist of limestone with lesser
amounts of shale and sandstone. Well yields commonly
range from 10 to 100 gpm, and may exceed 600 gpm.
Where present, karst features contribute to the vertical
and lateral permeability of the rock. Class Ib aquifers
occupy about 6 percent of Indiana.
Variably Covered Soluble and Fractured Bedrock
Aquifers
(Class Ib-v)
Carbonate aquifers overlain by a variable
thickness of glacial till occur in southwest and, locally,
in south-central Indiana. These Ordovician to
Mississippian age strata, which contain solutional
features, consist of limestone with lesser amounts of
shale and sandstone. Well yields commonly range from
10to 100 gpm, and may exceed 600gpm. Approximately
3 percent of the state is covered by Class Ib-v aquifers.
Covered Aquifers (Class Id)
Soluble aquifers that are overlain by less than
50 feet of glacial till occur in the central part of Indiana.
The bedrock consists of Ordovician to Mississippian
age limestone with lesser amounts of shale and
sandstone. The vulnerability of these covered systems
is af unction of the overlying low permeability sediments.
Well yields commonly range from 10 to 100 gpm, and
may exceed 600 gpm. About 3 percent of Indiana is
overlain by Class Id aquifers.
Lower Yield Bedrock Aquifers (Class lib)
Occurring in south-central Indiana are lower
yield bedrock aquifers. These Mississippian to
Pennsylvanian age aquifers consist of sandstone,
shale, and limestone with some coal. Well yields are
generally less than 25 gpm. About 8 percent of
Indiana is occupied by Class lib aquifers.
Covered Low Yield Bedrock Aquifers (Class He)
Occurring locally in west-central Indiana are
lower yield sedimentary aquifers that are overlain by
less than 50 feet of low permeability glacial till. These
Mississippian to Pennsylvanian age rocks consist of
siltstone, sandstone, and shale with some limestone
153
-------
and coal. Specific well yields are not well defined, but
yields of a few tens of gallons per minute are to be
expected. About 3 percent of Indiana is covered by
Class Me aquifers.
Undifferentiated Aquifers (Class U)
Undifferentiated glacial deposits locally occur
throughout the state. These aquifers consist of a
heterogeneous mix of stratified drift and till deposits.
Well yields are not defined. Approximately 4 percent of
Indiana is covered by Undifferentiated glacial aquifers.
Sensitivity
Class I aquifers occupy nearly 37 percent of
Indiana. The potential for ground-water contamination
from shallow injection wells is moderately low. Although
several areas are quite vulnerable, the density of
population centers is not great. The most sensitive
regions occur in the southeastern and southern parts of
the state and along several rivers, such as the Ohio,
Wabash, and Kankakee rivers.
154
-------
Aquifer Vulnerability Map of Indiana
155
-------
10 to 100 GPM
100 to 500 GPM
Low Well Yield
Undefined
Potential Well Yields in Indiana
156
-------
Areas covered by class I aquifers.
Each dot represents a population center.
Aquifer Sensitivity Map of Indiana
157
-------
Population Density of Indiana
(Dot equals one person per square mile)
Average Annual Precipitation in Indiana
158
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MICHIGAN
General Setting
Michigan contains approximately 58,200 square
miles. The rugged western part of the Upper Peninsula,
which lies within the Superior Upland physiographic
province, is underlain by Precambrian to Paleozoic age
crystalline and sedimentary rock. The gently rolling
eastern part of the Upper Peninsula and the gently
rolling to rugged hills of the Lower Peninsula lie within
the Central Lowlands. This province is underlain by
Paleozoic to Mesozoic age sedimentary rock, which
has been structurally formed into the Michigan Basin.
Overlying the bedrock throughout most of the state are
permeable glaciofluvial and relatively low permeable
glacial till deposits. These glacial deposits range in
thickness from a few feet in the western part of the
Upper Peninsula to overSOOfeetinthe Lower Peninsula.
The Upper Peninsula is drained by several
streams that empty into Lake Superior and Lake
Michigan. The western half of the Lower Peninsula is
drained by rivers that terminate in Lake Michigan.
Eastern Michigan is drained by several northerly- and
easterly-flowing rivers that discharge into Lake Huron.
Average annual precipitation in the Upper Peninsula is
about 34 inches, while in the Lower Peninsula it ranges
from 28 inches in the east to about 40 inches in the
southwest. Michigan's population, about 9.2 million, is
concentrated in Detroit and other large cities in the
southern part of the state. About 596 million gallons of
fresh and 4.5 million gallons of saline water are used
daily in Michigan.
Unconsolidated Aquifers (Class la)
Exposed intermittently in the Upper Peninsula
and fairly extensively in the Lower Peninsula are
unconsolidated glacial outwash, glaciofluvial, and
lacustrian deposits. They consist of sand, gravel, and
variable amounts of locally interbedded silt and clay.
Well yields commonly range from 1 to 1,000 gpm, and
may exceed 2,000 gpm. Approximately 14 percent of
Michigan is covered by permeable unconsolidated
aquifers.
Variably Covered Soluble and Fractured Bedrock
Aquifers
(Class Ib-v)
Underlying the southwestern part of the Upper
Peninsula, as well as the southwest and northern parts
of the Lower Peninsula, are carbonate bedrock aquifers
that are overlain by a variable thickness of glacial till.
The bedrock consists of Silurian to Devonian age
limestone and dolomite with some sandstone and shale
units. The vulnerability of these aquifers is a function of
the thickness of the overlying glacial till. Well yields
commonly range from 10 to 300 gpm, and may exceed
500 gpm. Nearly 12 percent of Michigan is underlain by
Class Ib-v aquifers.
Variably Covered High Yield Bedrock Aquifers
(Class lla-v)
Occurring intermittently throughout the Lower
Peninsula are variably covered high yield sedimentary
bedrock aquifers. This Mississippian to Pennsylvanian
age sequence consists of sandstone and siltstone with
some shale, limestone, and coal. The vulnerability of
these aquifers is a function of the thickness of the
overlying low permeability sediments. Well yields
commonly range form 100 to 500 gpm, and may exceed
1,500 gpm. About 16 percent of the state is covered by
Class lla-v aquifers.
Variably Covered Lower Yield Bedrock Aquifers
(Class llb-v)
Underlying parts of the Upper Peninsula are
variably covered lower yield sedimentary bedrock
aquifers. These Precambrian age rocks consist of well-
cemented sandstone that is interbedded with shale.
The vulnerability of the system is dependent on the
thickness of the overlying till. Well yields commonly
159
-------
range from 5 to 50 gpm, and may exceed 100 gpm.
About 5 percent of Michigan is underlain by Class llb-v
aquifers.
Variably Covered Undifferentlated Aquifers
(Class U-v)
In parts of the eastern side of the Upper
Peninsula are variably covered undifferentiated
sedimentary bedrock aquifers. These Cambrian to
Ordovician age units consist of sandstone, limestone,
and dolomite. Vulnerability is a function of the thickness
of the overlying glacial till. Well yields commonly range
from 10 to 100 gpm, and may exceed 500 gpm. About
6 percent of the state is underlain by Class U-v aquifers.
Sensitivity
About 25 percent of Michigan is covered by
vulnerable Class I deposits. Many of these consist of
permeable sand and gravel that lie along water cou rses.
The Upper Peninsula is lightly populated and most of
the population centers are generally quite small and
adjacent to the Lake Michigan shore. The Lower
Peninsula is more densely populated, particularly in the
southern half where there is more industry and the
towns are larger. The potential for ground-water
contamination from shallow injection wells is very small
in the Upper Peninsula, small in the northern part of the
Lower Peninsula, and moderate to high elsewhere.
160
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[ I Class la
Biaasslbv
[Classllav
DClass HI
II Class Uv
Aquifer Vulnerability Map of Michigan
161
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-------
I
!
o
1
Ł
0>
-------
Population Density of Michigan (Dot equals
person per square mile)
one
• 26 to 29
• 29 to 32
•*• 32 to 35
A 35 to 38
<> 38 to 41
Average Annual Precipitation in Michigan
164
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MINNESOTA
General Setting
Minnesota contains approximately 84,000
square miles, and lies primarily in the Central Lowland
physiographic province. The northeastern part of the
state is in the Superior Upland province. The majority
of the state is underlain by Precambrian age igneous
and metamorphic rock, with minor amounts of
sedimentary rock in east-central Minnesota. In the
southeastern part of Minnesota are southwestward
dipping clastic and carbonate rocks of Paleozoic age.
Minnesota is mantled by unconsolkJatedoutwash, glacial
lake deposits, and glacial till.
The Mississippi Riversystemdrainsthe majority
of central and southern Minnesota, while the
northwestern and western sections are principally
drained by the Red River of the North. Annual average
precipitation ranges from about 20 inches in the
northwest to about 32 inches in the southeast. The
population of Minnesota, approximately 4.3 million, is
concentrated in the Minneapolis - St. Paul metropolitan
area. About 685 million gallons of fresh ground water
are used daily in Minnesota.
Unconsolidated Aquifers (Class la)
Exposed intermittently throughout the southern
three quarters of Minnesota are unconsolidated alluvial,
glacial, terrace, and outwash deposits. These deposits
generally consist of stratified sand and gravel with some
intercalated beds of silt and clay. Well yields commonly
range from 100 to 800 gpm, and may exceed 2,000
gpm. Approximately 22 percent of the state is covered
by Class la deposits.
Covered Aquifers (Class Id)
Carbonate bedrock aquifers with solutional
features, which are overlain by less than 50 feet of
glacial till, occur in the southeast corner of Minnesota.
The bedrock aquifer consists of Cambrian to Devonian
age limestone and dolomite with minor amounts of
sandstone. The reduced vulnerability of these systems
is a function of the thickness of the overlying till. Well
yields commonly range from 200 to 1,000 gpm, and may
exceed 2,700 gpm. About 3 percent of Minnesota is
underlain by Class Id aquifers.
Covered Bedrock Aquifers (Class lie)
Higheryield bedrock aquifers, which are overlain
by less than 50 feet of glacial till, occur in the southeastern
corner of the state. The aquifers consist of Cambrian to
Ordovician age sandstone with some thin beds of shale
and siltstone. The vulnerability of these reservoirs is a
function of the thickness of the overlying till. Well yields
commonly range from 100 to 250 gpm, and may exceed
1,000 gpm. Nearly 3 percent of the state is underlain by
Class lie aquifers.
Variably Covered Undifferentiated Bedrock
Aquifers (Class U-v)
Variably covered undifferentiated bedrock
aquifers occur extensively throughout the northeastern
part of the state. Small local exposures also are present
in central and southwestern Minnesota. These bedrock
aquifers consist of Precambrian age crystalline rock
and sandstone. Locally in the northeast, bedrock is
exposed. The vulnerability of these systems is related
to the thickness of the overlying low permeability material.
Well yields commonly range from 5 to 750 gpm, and
may exceed 1,000 gpm. Variably covered
undifferentiated bedrock aquifers occupy nearly 13
percent of Minnesota.
Sensitivity
About 22 percent of Minnesota is covered by
Class I aquifers. Most of the vulnerable aquifers lie
along rivers. The potential for ground-water
contamination from shallow injection wells is small in
the northern part of the state. Along the Mississippi and
Minnesota rivers and in the southeastern part of the
state sensitivity increases because of the number of
population centers.
165
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-------
Ł91
-------
Areas covered by class I aquifers.
Each dot represents a population center.
Aquifer Sensitivity Map of Minnesota
168
-------
Population Density of Minnesota (Dot equals one
person per square mile)
Average Annual Precipitation in Minnesota
169
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OHIO
Genera! Setting
Ohio, which contains about 41,300 square miles,
lies in the rolling till plains, end moraines, and beach
ridges of the Central Lowland, Interior Lowland, and
Appalachian Plateaus physiographic provinces. The
state is underlain by gently dipping Paleozoic rocks.
Along the Cincinnati Arch in southwestern Ohio,
Ordovician shale and limestone crop out, while Silurian
and Devonian carbonates underlie the west-central and
northwestern parts of the state. An eastward-thickening
sequence of shale, sandstone, and coal-bearing units
of Mississippian to Permian age underlies the eastern
third of the state. All but the southeastern third of Ohio
is covered by glacial till, outwash, and glacial lake
deposits of Quaternary age. These deposits range in
thickness from less than 10 to more than 500 feet
(Goldthwait, White, and Forsyth, 1961).
Much of Ohio is drained by the Muskingum,
Scioto, and Great Miami rivers, all of which discharge
into the Ohio River. The Maumee and Cuyahoga rivers,
among others, drain the northern third of the state and
empty into Lake Erie. Annual precipitation ranges from
less than 34 inches in the north to 42 in the south. In
northeastern Ohio moisture derived from Lake Erie
leads to a yearly precipitation of as much as 44 inches.
The majority of Ohio's population, nearly 11 million, is
located along major rivers in the southwestern and
central parts of the state, and along the shores of Lake
Erie. The remainderof the state is moderately populated.
Use of fresh and saline ground water in Ohio amounts
to about 730 and .1 mgd, respectively.
Unconsolidated Aquifers (Class la)
Glacial outwash and alluvial deposits form the
most productive aquifers in the Ohio. These generally
unconfined systems, which lie along modern streams
and throughout the glaciated parts of the state, consist
of unconsolidated deposits of sand and gravel, with
lesser amounts of clay and silt. Well yields commonly
range from 100 to 500 gpm, and may exceed 2,000
gpm. Less productive aquifers, composed of
unconsolidated, fine-grained, sand, clay, silt, and gravel,
occur as localized lenses within glaciated areas, and as
valley fill in abandoned stream valleys. These aquifers
locally may be confined by clay or till. Well yields
commonly range from 25 to 50 gpm, and may exceed
200 gpm. About 11.4 percent of the state is covered by
Class la aquifers.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Minor outcrops of fractured limestone and
dolomite occur in southern Ohio. The presence of
fractures and weathered strata contribute to the
permeability and vulnerability of these aquifers. Shale
and gypsiferous interbeds occur locally. Well yields
commonly range from 5 to 300 gpm, and may exceed
500 gpm. Surface exposures of fractured bedrock
aquifers occupy about a half of a percent of the state.
Covered Aquifers (Class Id)
Buried outwash and fractured bedrock aquifers
that are overlain by less than 50 feet of glacial till and
lacustrine deposits, occur throughout the glaciated part
of the state. Well yields commonly range from 5 to 500
gpm, and they may exceed 2,000 gpm. The reduced
vulnerability of these covered systems is a function of
the thickness of the overlying low permeability material.
About 36 percent of Ohio is underlain by Class Id
aquifers.
Lower Yield Bedrock Aquifers (Class lib)
Lower yield bedrock aquifers, consisting
primarily of fine-to medium-grained sandstone, occur in
eastern and southeastern Ohio. Sandstone aquifers,
which contain interbedded limestone, shale, coal, and
siltstone, are unconfined in the outcrop area. Well
yields range from about 1 to about 25 gpm, and may
exceed 250 gpm. Surface exposures of lower yield
bedrock aquifers occupy about 22 percent of the state.
170
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Covered Bedrock Aquifers (Class He)
Lower yield bedrock aquifers that are overlain
by less than 50 feet of glacial till and lacustrine deposits,
occur along the eastern and northeastern glaciated
parts of the state. The reduced vulnerability of these
systems is a function of the thickness of the overlying
low permeability material. About 9.6 percent of the state
is underlain by Class Me aquifers.
Sensitivity
Nearly 48 percent of Ohio is covered by Class
I aquifers. The potentialforground-watercontamination
from shallow injection wells is moderately high owing to
the high population density on and near many of these
aquifers, particularly the stream valleys. Additionally,
the permeable nature of many of the carbonate rocks,
which are mantled by glacial till, has led to the fairly
widespread practice of using sinkholes and wells for
waste disposal in north-central Ohio.
171
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I Class Id
Aquifer Vulnerability Map of Ohio
172
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5to300GPM
5to500GPM
25to50GPM
25to500GPM
Undefined
Potential Well Yields In Ohio
173
-------
Areas covered by class I aquifers.
Each dot represents a population center.
Aquifer Sensitivity Map of Ohio
174
-------
Population Density of Ohio (Dot equals one
person per square mile)
Average Annual Precipitation in Ohio
175
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WISCONSIN
General Setting
Wisconsin, which contains approximately
56,150 square miles, lies within the Superior Upland
province in the north, and the Central Lowland province
inthe southern part of the state. Underlying northwestern,
north-central, and northeastern Wisconsin is
Precambrian material, which consists of sedimentary
rock in the extreme northwest and igneous rock
elsewhere. Western, southern, and eastern Wisconsin
is underlain by a series of Cambrian to Devonian age
clastic and carbonate rocks that dip to the southeast,
south, and west. With the exception of so called
"driftless area" in southwestern Wisconsin, the state is
covered by a variable thickness of unconsolidated
glacial deposits, which can be several hundreds of feet
thick.
Northeastern Wisconsin is drained by several
streams that empty into Green Bay. The remainder of
the state is drained by southwesterly-flowing water
courses that discharge into the Mississippi River on the
state's western boundary. Average annual precipitation
averages about 32 inches, with the least amount
occurring during the winter months. Wisconsin's
population, nearly 4.9 million, is concentrated in the
Milwaukee, Madison, and Green Bay metropolitan areas.
Use of fresh ground water amounts to about 570 million
gallons per day.
Unconsolidated Aquifers (Class la)
Exposed intermittently from the northwest to
the south are unconsolidated alluvial and glacial outwash
deposits, which consist predominantly of stratified sand
and gravel with variable amounts of silt and clay. Well
yields commonly range from 10 to 100 gpm, and may
exceed 2,000 gpm. Approximately 16 percent of the
state is overlain by unconsolidated aquifers.
Variable Covered Soluble and Fractured Bedrock
Aquifers (Class Ib-v)
Carbonate aquifers with solutionalfeaturesthat
are overlain by a variable thickness of glacial till occur
in eastern Wisconsin. The bedrock aquifers consist of
Ordovician to Devonian age dolomite and lesseramounts
of limestone and shale. Well yields commonly range
from 5 to 50 gpm, and may exceed 200 gpm. Nearly 10
percent of the state is occupied by Class Ib-v aquifers.
Undifferentiated Aquifers (Class U)
(Class Uw-v)
Undifferentiated crystalline bedrock aquifers
that are overlain by a variable thickness of glacial till
occur in northwest and central Wisconsin. The
underlying Precambrian age igneous and metamorphic
rocks yield small quantities of water from fractures and
crevices. Well yields commonly range from .5 to 10
gpm, and may exceed 50 gpm. The reduced vulnerability
of these systems is a function of the thickness of the
overlying low permeability material. Variably covered
Undifferentiated crystalline bedrock aquifers occupy
about 8 percent of Wisconsin.
(Class U-x)
Exposed in northern and south-central
Wisconsin is an Undifferentiated mass of outwash, till,
and glaciolacustrian deposits. These deposits consist
of variable amounts of sand, gravel, silt, and clay, which
vary in thickness from a few feet to hundreds of feet. A
wide range of well yields could be expected from these
aquifers, the highest being in the areas of outwash.
About 25 percent of Wisconsin is covered by
Undifferentiated class U-x aquifers
(Class U-y)
Exposed in the "driftless area" in southwestern
Wisconsin are Undifferentiated deposits of Cambrian to
Ordovician age sandstone, dolomite with solutional
features, dolomitic sandstone, and shale beds. Well
yields commonly range from 10 to 500 gpm, and may
exceed 1,000 gpm. Approximately 13 percent of
Wisconsin is occupied by Class U-y aquifers.
(Class Uz-v)
Undifferentiated clastic and carbonate bedrock
aquifers, which are covered by a variable thickness of
glacial till, occur intermittently in western and eastern
176
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Wisconsin. The underlying Cambrian to Ordovician
age sediments consist of sandstone, dolomite, dolomitic
sandstone, and shale units. The reduced vulnerability
of these systems is a function of the thickness of the
overlying low permeable material. Well yields commonly
range from 10 to 500 gpm, and may exceed 1,000 gpm.
Approximately 19 percent of Wisconsin is underlain by
Class Uz-v aquifers.
Sensitivity
Nearly 26 percent of Wisconsin is covered by
Class I aquifers. The most sensitive area extends
southwestward from Green Bay. Elsewhere in vulnerable
areas population centers are widely distributed. On a
county scale, several other areas that are shown as
Class U-x would be considered moderately sensitive
owing to the presence of masses of outwash.
177
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\
\
\
11 \ *
c* **
d ^
Ci
-------
.5 to 10 GPM
5 to 50 GPM
10 to 100 GPM
10 to 500 GPM
Undefined
Wide Range
Potential Well Yields in Wisconsin
179
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180
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REGION 6
Arkansas
Louisiana
New Mexico
Oklahoma
Texas
182
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ARKANSAS
General Setting
Arkansas contains approximately 53,000
square miles, and is somewhat equally divided by the
northeast-southwest trending Fall Line. Northwest of
this line lies the gently rolling to rugged terrain of the
Ozark Plateaus and Ouachita province. This area is
underlain by Ordovician to Pennsylvanian age faulted
and folded sedimentary rock. Southeast of the Fall Line
is the generally flat-lying Gulf Coastal Plain province,
which is underlain by southeastward-dipping
unconsolidated strata of Cretaceous to Quaternary
age. These deposits range in thickness from the out
crop along the Fall Line to over 4500 feet at the
southeastern corner of the state.
Arkansas is principally drained by the southeast-
flowing White, Arkansas, and Ouachita river systems.
Average annual precipitation varies 40 inches to 56
incheswith the greatest amount occurring inthe southern
half of the state. The population of Arkansas, about 2.4
million, is distributed fairly evenly throughout the state,
with Little Rock being the largest city. About 381 billion
gallons of fresh ground water are used daily in Arkansas.
Unconsolidated Aquifers (Class la)
Streamside alluvial and marine terrace deposits
occur along the Arkansas River and extensively in the
southeastern half of the state. These unconsolidated
Quaternary age deposits consist of sand, gravel, silt
and clay. Well yields commonly range from 50 to 2,000
gpm, and may exceed 5,000 gpm. About 51 percent of
Arkansas is covered by unconsolidated aquifers.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Karst features are present in carbonate units in
northern Arkansas. These Ordovician to Pennsylvanian
age rocks consist of limestone, dolomite, shale, and
lesser amounts of sandstone. Where present, karst
and other solutional features contribute to the vertical
and lateral permeability of the rocks. Well yields
commonly range from 150 to 300 gpm, and may exceed
500 gpm. Soluble aquifers occupy about 17 percent of
the state.
Semiconsolidated Aquifers (Class Ic)
Small exposures of Semiconsolidated strata
occur in southwestern Arkansas. These Cretaceous to
Tertiary age deposits consist of fine-grained quartz
sand, silt, clay, and lignite. Well yields commonly range
from 150 to 300 gpm, and may exceed 500 gpm. About
.6 percent of Arkansas is covered by Class Ic aquifers.
Undifferentiated Aquifers (Class U)
Pennsylvanian age sedimentary rocks, which
occur in northern Arkansas, are undifferentiated and
consist of shale and lesser amounts of sandstone.
Small quantities of water are derived from bedding
planes and local fracturing. Well yields commonly
range from 1 to 3 gpm, and may exceed 25 gpm
(Lamonds, 1972). Undifferentiated aquifers occur in
about 21 percent of Arkansas.
Sensitivity
About 68 percent of Arkansas is covered by
Class I aquifers. A large wedge of less vulnerable
deposits occurs in the west-central part of the state and
in a few relatively narrow belts, largely in the southern
half. Although the population of Arkansas is not large,
population centers are rather evenly distributed
throughout the state.
183
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Aquifer Vulnerability Map of Arkansas
184
-------
Potential Well Yields in Arkansas
185
-------
Areas covered by class I aquifers.
Each dot represents a population center.
Aquifer Sensitivity Map of Arkansas
186
-------
Population Density in Arkansas (Dot equals one
person per square mile)
Average Annual Precipitation in Arkansas
187
-------
LOUISIANA
General Setting
Louisiana contains approximately 48,000
square miles, and lies entirely in the relatively flat lying
Coastal Plain physiographic province. The state is
underlain by a southward dipping wedge of
semiconsolidated to unconsolidated, interbedded silt,
clay, sand, gravel, shale, limestone, and tuff aceous and
lignitic beds that range in age from Cretaceous to
Holocene.
Louisiana is drained by the south to southeast
flowing Sabine, Red, and Mississippi rivers, and their
numerous tributaries. Annual precipitation ranges from
less than 48 inches in the northwest to more than 66
inches in the southeast. Evapotranspiration rates,
which average about 20 to 22 in/yr are high due to the
flat topography, low surface runoff, warm climate, and
dense vegetation (McGuinness, 1963). The majority of
Louisiana's population, about 4.4 million, occurs in
several large cities located along major rivers. The
remainder of the state is sparsely populated. Use of
fresh ground water within the state averages 1430
million gallons per day.
Unconsolidated Aquifers (Class la)
Streamside alluvial and terrace deposits occur
throughout the state and form vulnerable and productive
aquifers. These confined to unconf ined systems consist
of fining upward sequences of interbedded and
unconsolidated deposits of silt, clay, sand, and gravel.
Glacial outwash deposits in northeastern Louisiana
consist of unconsolidated, fine to coarse sand, and
lesser amounts of clay, silt, and gravel that are locally
overlain by loess. Well yields range from 500 to 2,500
gpm, and may exceed 7,000 gpm. Nearly 40 percent of
the state is covered by Class la aquifers.
Semiconsolidated Aquifers (Class Ic)
Exposures of semiconsolidated sediments
occur throughout northern Louisiana. Early Tertiary
age sediments that consist of partially indurated, fine to
medium sand that is interbedded with silt and clay occur
in northwestern Louisiana. Lignite, limestone, and
glauconite also are present within the section. Well
yields range from 40 to 150 gpm, and may exceed 350
gpm. Exposures of Eocene to Pliocene age sediments
extend across north-central and western Louisiana,
and consist of interbedded, sand, clay, silt, gravel,
sandstone, siltstone, marl, and shale. These strata
contain tuffaceous beds, ironstone concretions,
glauconite, and other diagenetic constituents. Well
yields commonly range from 50 to 1,800 gpm, and may
exceed 3,000 gpm. Surface exposures of
semiconsolidated aquifers occupy 17 percent of the
state.
Undifferentiated Aquifers (Class U)
Lithologically varied sediments of Quaternary
age occur throughout Louisiana, and consist of
interbedded and unconsolidated deposits of clay, silt,
sand, and gravel, locally overlain by loess. Due to their
textural heterogeneity, a wide range in aquifer
productivity and vulnerability should be expected in
these areas. About 40 percent of the state is covered
by Class U aquifers.
Sensitivity
Nearly 57 percent of Louisiana is covered by
Class I aquifers. In addition, another 40 percent has
been mapped as Class U, and much of this area also is
likely to be quite vulnerable. The potential for ground-
water contamination from shallow injection wells in
Louisiana is high due to the extensive occurrence of
vulnerable aquifers and the abundance of population
centers, which are rather evenly distributed throughout
the state.
188
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Aquifer Vulnerability Map of Louisiana
189
-------
061
* »«*«„,
-------
Areas covered by class I aquifers.
Each dot represents a population center.
Aquifer Sensitivity Map of Louisiana
-------
-------
NEW MEXICO
General Setting
New Mexico, containing 121,593 square miles,
lies in the mountains, intermountain basins, dissected
plateaus, and high plains of the Basin and Range,
Southern Rocky Mountains, Colorado Plateau, and
Great Plains physiographic provinces. The mountains
of northern, central, and southwestern New Mexico
consist largely of Tertiary and Quaternary age basalt,
andesite, and rhyolite flows, pyroclastic deposits, and
associated sediments. Scattered throughout the state
are isolated exposures of Precambrian age metamorphic
rocks, Paleozoic and Mesozoic sedimentary units, and
Cretaceous and Tertiary age intrusives. Intermountain
basins contain thick accumulations of Cenozoic age
alluvial, bolson, eolian, lacustrine, and volcanic deposits.
The plateaus and plains of northwestern and eastern
New Mexico are underlain by relatively flat-lying
Paleozoic, Mesozoic, andTertiary age sandstone, shale,
limestone, and gypsum deposits.
The extreme western part of New Mexico is
drained by the west-flowing San Juan River system,
and several tributaries of the Colorado River. The
remainder of the state is drained by the Rio Grande and
Pecos systems, and the east-flowing Canadian River.
Annual precipitation ranges from 6 inches in the desert
valleys to 35 inches at higher elevations in the mountains.
Evapotranspiration, caused by direct evaporation and
loss to phreatophytes, ranges from 40 to 80 in/yr. The
majority of New Mexico's population, approximately 1.5
million, is located in the vicinity of Albuquerque, Santa
Fe, and Las Cruces. The remainder of the state is
sparsely populated. Daily use of fresh ground water
amounts to about 1510 million gallons.
Unconsolidated Aquifers (Class la)
Alluvial, bolson, eolian, and lacustrine deposits
occur in basins and valleys throughout the state, forming
vulnerable and productive aquifers. These unconfined
and confined systems consist of unconsolidated deposits
of sand, gravel, silt, clay, and volcanic material of
Quaternary age. In most places, these strata range
fromafew hundred to as much as 2,000feetinthickness,
but they may be as much as 20,000 feet thick in the Rio
Grande Valley. Well yields commonly range from 100
to 500 gpm, and may exceed 3,000 gpm. About 30
percent of New Mexico is covered by Class la aquifers.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Karst features are present in fractured Permian
age limestone, which is exposed in southeastern New
Mexico. Where present, karst features and fractures
contribute to the vertical and lateral permeability of the
rock, creating highly productive and vulnerable aquifers.
Well yields commonly range from 400 to 800 gpm, and
may exceed 3,000. Surface exposures of karst
carbonate aquifers occupy slightly more than 1 percent
of the state.
Semiconsolidated Aquifers (Class Ic)
The High Plains Aquifer, exposed along the
eastern margin of New Mexico, consists of the Tertiary
age Ogallala Formation. The Ogallala contains
semiconsolidated, fine- to coarse-grained sand, gravel,
clay, silt, and thin beds of caliche. Well yields commonly
range from 100 to 500 gpm, and may exceed 3,000
gpm. The presence of intercalated layers of low
permeability strata coupled with an unsaturated zone of
substantial thickness reduces the physical vulnerability
of the aquifer system. Surface exposures of
semiconsolidated aquifers occupy about 7.4 percent of
the state.
Higher Yield Bedrock Aquifers (Class Ma)
Higher yield bedrock aquifers crop out in
northwestern New Mexico, and consist of a series of
hydraulically connected Mesozoic and Tertiary age
very fine- and medium-grained sandstones of both
marine and continental origin. Well yields commonly
range from 50 to 100 gpm, and may exceed 1,200 gpm.
Surface exposures of higher yield bedrock aquifers
occupy about 6.4 percent of the state.
193
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Sensitivity
Nearly 39 percent of New Mexico is covered by
Class I aquifers. Owing to the light population density,
aquifer sensitivity is low. In a few vulnerable areas there
are a considerable numberof population centers that lie
along the major transportation routes.
194
-------
Class Ib
Class Ic
Class I la
Class III
Aquifer Vulnerability Map of New Mexico
195
-------
Y » C**^wJi,Jl«TwTvTv'T*fr'IV Y Y^
50 to 100GPM
100to500GPM
400 to 800 GPM
i—I Undefined
Potential Well Yields In New Mexico
196
-------
Areas covered by class I aquifers.
Each dot represents a population center.
Aquifer Sensitivity Map of New Mexico
197
-------
Population Density of New Mexico (Dot equals one
person per square mile)
Average Annual Precipitation in New Mexico
198
-------
OKLAHOMA
General Setting
Oklahoma, which contains approximately
70,000 square miles, lies primarily in the rolling plains
and low hills of the Central Lowlands, the Great Plains,
and the Coastal Plains physiographic provinces.
Mountainous regions along Oklahoma's eastern margin
lie within the Ozark Plateaus and Ouachita provinces.
The less extensive Arbuckle and Wichita Mountains
occur in the south-central and southwestern parts of the
state, respectively. Most of Oklahoma is underlain by
thick sequences of westward dipping Paleozoic age
limestone, dolomite, and shale. The Anadarko, Ardmore,
and Arkoma basins in west-central, south-central, and
east-central Oklahoma, respectively, contain as much
as 40,000 feet of marine, and minor terrigenous
sediments. Folded and faulted Paleozoic age rocks
crop out in the Wichita, Arbuckle, and Ouachita
Mountains, and in the Ozark Plateaus, while
Precambrian crystalline rocks are exposed in the Wichita
and Arbuckle Mountains. Flat lying clastic and carbonate
units of Mesozoic age are exposed in the northwestern
part of the Panhandle, and southward-dipping clastic
and carbonate strata of Cretaceous age crop out in the
southeastern part of the state. Exposures of
semiconsolidated to consolidated sand and gravel,
forming the Ogallala Formation of Tertiary age .dominate
northwestern Oklahoma. Unconsolidated Quaternary
age alluvial and terrace deposits, which lie along all of
Oklahoma's major rivers, may extend as much as 15
miles from the rivers.
The Arkansas River and its eight principal
tributaries drain the northern two thirds of Oklahoma.
The Red River and itsfive principal tributaries drains the
southern third of the state. Annual precipitation ranges
from less than 16 inches in the west to more than 54
inches in the southeast. April and September are the
months that generally have the greatest precipitation.
Evapotranspiration ranges from about 16 in/yr in the
west to 36 in the northeast. The majority of Oklahoma's
population, approximately 3.2 million, is located in
Oklahoma, Tulsa, and Cleveland counties. The
remainderof the state is sparsely populated. About 568
million gallons of fresh ground water are used daily in
the state.
Unconsolidated Aquifers (Class la)
Streamside alluvial and terrace deposits form
some of the most vulnerable aquifers in the state. These
unconfined systems generally consist of permeable,
Unconsolidated, gravel, sand, silt, and clay that
commonly are tens of feet thick. Well yields normally
range from 20 to 600 gpm, and may exceed 1,200 gpm.
Dune sands locally overlie alluvium and terrace deposits.
About 18 percent of the state is covered by Class la
aquifers.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Solutional features are present in carbonate
and gypsiferous units in southwestern, south-central
and northeastern Oklahoma. Where present, karst
features contribute to the vertical and lateral permeability
of the rock, creating both productive and vulnerable
aquifers. Well yields generally range from 90 to 600
gpm, but locally may exceed 2,500 gpm. Several
springs discharge from 50 to 18,000 gpm. In northeast
Oklahoma, well yields of 10 gpm or less are common,
but springs may discharge as much as 3,500 gpm.
Soluble aquifers and fractured bedrock aquifers occupy
about 4.7 percent of the state.
Semiconsolidated Aquifers (Class Ic)
The High Plains Aquifer, located in northwestern
Oklahoma, consists of the Ogallala Formation and
overlying alluvial and basin-fill deposits of reworked
Ogallala. The Ogallala contains semiconsolidated,
fine-grained sandstone and siltstone, with lesser
amounts of clay and gravel, and thin beds of limestone
and caliche. The overlying alluvial deposits consist of
Unconsolidated sand, silt, clay, and gravel. The High
Plains Aquifer is largely unconfined and the saturated
199
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thickness ranges from a few feet to as much as 500 feet.
Well yields commonly range from 100 to 1,000 gpm,
and may locally exceed 2,000 gpm. The presence of
numerous intercalated layers of low permeability strata,
coupled with an unsaturated zone of substantial
thickness, reduces the vulnerability of the aquifer system.
Surface exposures of Class Ic aquifers occupy slightly
more than 8 percent of the state.
Higher Yield Bedrock Aquifers (Class Ha)
Higher yield bedrock aquifers, consisting
primarily of sandstone, occur throughout much of the
state. Sandstone aquifers, which contain variable
amounts of siltstone, shale, dolomite, and gypsum, are
unconfined in the outcrop area. Well yields range from
50 to 600 gpm, and may exceed 1,700 gpm. Surface
exposures of Class lla aquifers occupy about 8 percent
of the state.
Sensitivity
Although 31 percent of the state is covered by
Class I aquifers, the potential for ground-water
contamination from shallow injection wells is small
owing to Oklahoma's low population density. The most
sensitive areas are the Class la aquifers, most of which
lie along the major rivers, and these amount to only
about 18 percent of the state. The number of population
centers within Class la also is very small. Class Ic,
which reflects the lightly populated High Plains Aquifer,
covers about 8.3 percent of the state, but in this area the
water table generally lies at a considerable depth, and
several zones of caliche tend to reduce ground-water
recharge.
200
-------
201
-------
.——,..-!.—•--l"""
^«%«v«
tftftf
&W
Potential Well Yields in Oklahoma
202
-------
J3
0)
(D
Q>
"O
O
0>
N9
O
Areas covered by class I aquifers.
Each dot represents a population center
-------
Population Density of Oklahoma (Dot equals one
person per square mile)
• 0 to 20
• 20 to 30
+ 30 to 40
^. 40 to 50
^ 50 to 70
Average Annual Precipitation in Oklahoma
204
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TEXAS
General Setting
Texas, which contains approximately 266,800
square miles, lies primarily in the low hills and dissected
plains of the Coastal Plain, Central Lowland, and Great
Plains physiographic provinces. The mountainous
southwest corner of the state lies within the Basin and
Range province. Most of Texas is underlain by gently
dipping carbonate and clastic sedimentary rocks of
Paleozoic age. These units crop out throughout the
central and north-central parts of the state. Folded and
faulted Paleozoic age rocks, which are intruded and
locally overlain by Tertiary age igneous rocks, crop out
in the southwest corner of Texas. Exposures of
Precambrian age igneous and metamorphic rocks occur
within anticlinal Paleozoic strata in the Llano Uplift in
central Texas. Mesozoic age carbonate and clastic
rocks, which unconformably overlie the Paleozoic
section, are exposed across south-central and
northeastern Texas. Semiconsolidated, clastic
sediments of the Tertiary age Ogallala Formation mantle
Paleozoic rocks in northwestern Texas. The Coastal
Plain is underlain by an eastward thickening wedge of
Cretaceous to Holocene age semiconsolidated to
unconsolidated, interbedded, sand, silt, clay, gravel,
and marl.
Several north- and east-flowing rivers drain the
Texas Panhandle. The remainder of the state is drained
by numerous south to southeast-flowing waterways.
Annual precipitation ranges from less than 8 inches in
the west to more than 56 inches in the east. The
majority of Texas' population, nearly 17 million, is
located in and around several large cities. Elsewhere
the state is sparsely populated. More than 7180 and
229 million gallons of fresh and saline ground water,
respectively, are used in Texas each day.
Unconsolidated Aquifers (Class la)
Alluvial, marsh, lagoonal, and beach deposits
occur throughout the Texas Coastal Plain, and form
both vulnerable and productive aquifers. These confined
to unconfined, multi-layered systems consist of
interbedded and interfingering, unconsolidated deposits
of clayey sand, silt, clay, sand, and gravel. Well yields
range from 300 to 1,500 gpm, and may exceed 4,500
gpm. Alluvial and bolson deposits provide important
sources of ground water in north-central and west
Texas. These generally unconfined aquifers consist of
unconsolidated sand, gravel, silt, and clay. Locally
bolson deposits in western Texas reach several
thousand feet in thickness. Well yields range from 500
to 900 gpm, and may exceed 2,500 gpm. Nearly 25
percent of the state is covered by Class la aquifers.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Karstfeatures are present inthe folded, faulted,
and fractured limestone, dolomite, and marls that are
exposed along the Balcones fault zone in south-central
Texas. Where present, karst features contribute to the
vertical and lateral permeability of the the rock, creating
highly productive and vulnerable aquifers. Well yields
range from 400 to 1,200 gpm, and may exceed 16,000
gpm. Karst features also are present in the limestone
and dolomitic rocks that are widely exposed throughout
west-central Texas. Minor clay, sand, and sandstone
interbeds occur within the carbonate section. Well
yields range from 50 to 200 gpm, and may exceed 3,000
gpm. Exposures of karstic evaporite deposits, which
extend southward from the eastern Texas Panhandle,
consist of beds of anhydrite, gypsum, halite, silty shale,
and dolomite. Ground water occurs primarily in solution
channels and cavities within beds of anhydrite and
gypsum. Several formations, consisting of karstic
limestone, dolomite, and evaporites, locally crop out in
west Texas. Fractured volcanic aquifers occur in west
Texas. These systems are unconfined in the outcrop
area, and consist of interbedded lava flows, tuffs, and
volcanic breccia. Ground-water movement is controlled
by the density of jointing and secondary fractures, the
degree of welding, and the presence of permeable
breccias. Surface exposures of karst and fractured
bedrock aquifers occupy about 13 percent of the state.
205
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Semiconsolidated Aquifers (Class Ic)
The High Plains Aquifer in the Panhandle
consists of the Ogallala Formation, which is overlain
locally by eolian and alluvial deposits. The Ogallala
contains as much as 900 feet of unconsolidated, fine- to
coarse-grained sand that is interbedded with loam,
gravel, clay, silt, and caliche zones. Well yields
commonly range from 100 to 1,000 gpm, and may
exceed 2,000 gpm. The presence of intercalated layers
of low permeability strata coupled with an unsaturated
zone of substantial thickness reduces the physical
vulnerability of the aquifer system. Semiconsolidated
continental and marine sediments crop out along a
northeast trend across eastern Texas. These
Cretaceous to Tertiary age sediments consist of
ferruginous, glauconitic, and calcareous sand and
interbedded clay, sandstone, shale, silt, marl, and chalk.
Well yields commonly range from 100 to 1,000 gpm,
and may exceed 3,000 gpm. Surface exposures of
Class Ic aquifers occupy nearly 25 percent of the state.
Higher Yield Bedrock Aquifers (Class Ha)
Higher yield bedrock aquifers, consisting of
sandstone and sand, interbedded with clay, shale,
conglomerate, caliche, limestone, and evaporite
deposits, crop out in north-central and northwest Texas.
Well yields range from 100 to 300 gpm, and may exceed
1,000 gpm. Surface exposures of Class lla aquifers
occupy nearly 7 percent of the state.
Undifferentiated Aquifers (Class U)
Lithologically varied Quaternary age sediments,
which occurthroughout the Texas Coastal Plain, consist
of interbedded and interfingering, unconsolidated, clay,
mud, sand, silt, and gravel. Due to their textural
heterogeneity, a wide range in aquifer productivity and
vulnerability should be expected in these areas. Nearly
6 percent of the state is covered by undifferentiated
aquifers.
Sensitivity
About 62 percent of Texas is covered by Class
I aquifers. The potentialforground-watercontamination
from shallow injection wells is moderately high in those
critical areas that have a high population density, such
as the coastal plain sediments in the southeastern part
of the state. Although vulnerable strata exist in the
Panhandle and in other western parts of Texas, aquifer
sensitivity is less because the water table generally lies
at a greater depth and, commonly, units of low
permeability lie above major reservoirs.
206
-------
Aquifer Vulnerability Map of Texas
207
-------
r~l Undefined
0 to 1500GPM
50 to 300 GPM
100 to 500 GPM
100 to 1000 GPM
300 to 1500 GPM
400 to 1200 GPM
Potential Well Yields In Texas
208
-------
I
I
o
i
NS
O
vŁ>
Areas covered by class 1 aquifers.
Each dot represents a population center.
-------
Popu.af.on Density of Texas (Dot equate one
person per square mile)
. 7 to 18
. 18 to 28
.4. 28 to 39
39 to 49
49 to 60
Average
Annual Precipitation in Texas
210
-------
REGION 7
Iowa
Kansas
Missouri
Nebraska
211
-------
IOWA
General Setting
Iowa, which contains approximately 56,275
square miles, lies within the Central Lowland
physiographic province. The topography varies from
steep hills and high bluffs in the northeast to gently
rolling hills in the southwest. Sculptured by five
successive major glacial advances, Iowa's bedrock is
mantled by a variable thickness of unconsolidated
glacial drift and wind blown loess that averages roughly
200 feet in thickness. These deposits cover most of the
state. The underlying bedrock is predominantly
sandstone, limestone, and dolomite that ranges in age
from Cambrian to Cretaceous. These strata have been
gentlyfolded and downwarped, dipping from structurally
higher areas in the north and northeast into a broad
basin in the south and southwest.
Western Iowa is drained by several southwest-
flowing rivers that empty into the Missouri River. Central
and eastern Iowa, situated in the Mississippi Valley, are
drained by many southeasterly-flowing streams. Annual
average precipitation varies from 28 inches in the
northwest to 34 inches in the southeast. Iowa's
population, about 2.8 million, is distributed among several
moderately sized cities that lie along major rivers and
throughout a lightly populated rural area. About 671
million gallons of fresh ground water are used daily in
the state.
Unconsolidated Aquifers (Class la)
Unconsolidated Quaternary age alluvium occurs
along the flood plains and terrains of Iowa's principle
streams and rivers. These deposits consist of fine- to
coarse-grained sand and gravel with varying amounts
of silt and clay. Well yields commonly range from 200
to 1,000 gpm, and may exceed 2,000 gpm. About 14.3
percent of Iowa is covered by Class la aquifers.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Exposed in the northeast and locally along
major rivers in eastern Iowa are carbonate aquifers.
These Ordovician to Mississippian age rocks consist of
limestone and dolomite with shale and some sandstone.
Where present, solutional features contribute to the
vertical and lateral permeability of the rock, creating
productive and vulnerable aquifers. Well yields
commonly range from 50 to 1,000 gpm, and may
exceed 4,000 gpm. Class Ib aquifers are exposed in
nearly 12 percent of the state.
Variably Covered Soluble and Fractured Bedrock
Aquifers (Class Ib-v)
Occurring in central and eastern Iowa are
Ordovician to Mississippian age carbonate rocks with
solutional features that are overlain by a variable
thickness of glacial till and loess. Aquifer vulnerability
is a f u nction of the thickness of the overlying sediments.
Well yields commonly range from 50 to 1,000, and may
exceed 4,000 gpm. About 22.5 percent of Iowa is
underlain by Class Ib-v aquifers.
Higher Yield Bedrock Aquifers (Class lla)
Exposed in far northeastern Iowa is a small
area of Cambrian age sandstone. Well yields commonly
range from 100 to 1,000 gpm. About .2 percent of Iowa
is covered by higher yield bedrock aquifers.
Sensitivity
About 49 percent of Iowa contains Class I
aquifers. The largest area lies in the northeastern half of
the state, while a rather extensive band of alluvium
occurs along the western margin. Population centers
are rather evenly distributed throughout the vulnerable
areas, but most of the towns are small. The potential for
ground-watercontamination from shallow injection wells
in Iowa is moderately low.
212
-------
a
c
Aquifer Vulnerability Map of Iowa
213
-------
50tolOOGPM
100to300GPM
150 to 400 GPM
gg 100 to 1000 GPM
j~~] 200 to 1000 GPM
|~~| Undefined
Potential Well Yields In Iowa
214
-------
Areas covered by class I aquifers.
Each dot represents a population center.
Aquifer Sensitivity Map of Iowa
215
-------
Population Density of Iowa
(Dot equals one person per square mile)
Precipitation
in inches
• 24 to 27
• 27 to 30
+ 30 to 32
A 32 to 35
$ 35 to 38
Average Annual Precipitation in Iowa
216
-------
KANSAS
General Setting
Kansas contains approximately 82,000 square
miles, and lies primarily in the high plains and mesas,
rolling plains, and low hills of the Great Plains and
Central Lowlands physiographic provinces. The Ozark
Plateau province occupies the southeastern corner of
the state. Kansas is underlain by Paleozoic age rocks
that dip gently westward from the structurally higher
Ozark Plateaus in Missouri, into the north-trending
shallow structural basin beneath the Great Plains.
Pennsylvanian and Permian age shale, limestone, and
sandstone crop out in the southeastern part of the state
and dip to the northwest. Pleistocene age glacial
deposits mantle large areas of Pennsylvanian and
Permian rocks in the northeast. Paleozoic rocks lie
beneath Cretaceous age shale, sandstone, limestone,
and chalk in central Kansas. Cretaceous strata are
mantled, especially to the west, by the Tertiary age
Ogallala Formation, as well as by younger fluvial and
eolian sediments. Quaternary age alluvial deposits are
present along major river valleys throughout the state.
Several east-flowing tributaries of the Missouri River
drain the northern half of Kansas. A network of east- to
southeast-flowing rivers drains the southern half of the
state.
Annual precipitation ranges from 15 inches in
the west to 45 inches in the east. The spring and early
summer months generally have the greatest
precipitation. Evapotranspiration from lake surfaces
ranges from 44 in/yr in the northeast to 68 in/yr in the
southwest (Farnsworth and others, 1982). Themajority
of Kansas' population, approximately 2.5 million, is
located in Johnson, Wabaunsee, and Sedgwick
counties. The remainder of the state is sparsely
populated. About 4800 million gallons of fresh ground
water are used each day in Kansas.
Unconsolidated Aquifers (Class la)
Streamside alluvial deposits form some of the
most productive and vulnerable aquifers in the state.
These unconfined systems generally consist of
unconsolidated clay, silt, sand, and gravel. Well yields
commonly range from 10 to 500 gpm, and may exceed
1,000 gpm. Glacial outwash aquifers, consisting of
unconsolidated clay, silt, sand, and gravel, occur within
the northeast corner of the state, and may reach 500
feet in thickness. Well yields commonly range from 10
to 100 gpm, and may exceed 500 gpm. About 29
percent of the state is covered by Class la aquifers.
Semiconsolidated Aquifers (Class Ic)
The High Plains Aquifer, exposed throughout
the western half of the state, consists of the Ogallala
Formation, which is locally overlain by eolian and alluvial
deposits. The Ogallala contains lenses of
Semiconsolidated, poorly- to moderately-sorted sand,
gravel, and silt. Limestone, marl, and clay interbeds
occurthroughoutthe section, and, along with carbonate-
and silica-cemented sandstone beds, produce locally
confined conditions. The overlying eolian deposits
consist of unconsolidated fine-grained sand and silt.
The saturated thickness of the High Plains Aquifer
commonly ranges from a few feet to 400 feet, and may
exceed 600 feet in southwestern Kansas (Weeks and
Gutentag, 1981). Well yields commonly range from 500
to 1,000 gpm, and may locally exceed 1,500 gpm.
Surface exposures of Semiconsolidated aquifers occupy
about 24 percent of the state.
Higher Yield Bedrock Aquifers (Class lla)
Higher yield bedrock aquifers, consisting
primarily of sandstone of Cretaceous age, crop out in
northern and north-central Kansas. Sandstone aquifers,
which contain minor shale beds, are unconfined in the
outcrop area. Well yields range from 10 to 100 gpm, and
may exceed 1,000 gpm. Surface exposures of higher
yield bedrock aquifers occupy about 4.4 percent of the
state.
Lower Yield Bedrock Aquifers (Class lib)
Class lib aquifers, composed of limestone,
sandstone, and minor shale beds of Pennsylvanian
age, crop out in the eastern third of the state. Well yields
commonly range from 10 to 40 gpm, and may exceed
217
-------
200 gpm. Surface exposures of lower yield bedrock
aquifers occupy about 11 percent of the state.
Covered Bedrock Aquifers (Class llb-v)
Lower yield limestone aquifers, overlain by an
undetermined thickness of glacial till, occur in
northeastern Kansas. The vulnerability of these systems
is a function of the thickness of the overlying low
permeability sediments. Only about 1 percent of the
state is covered by Class llb-v aquifers.
Sensitivity
About 53 percent of Kansas is covered by
Class I aquifers, largely in the western half of the state.
The potential for ground-water contamination from
shallow injection wells is relatively small due to the
state's low population density. Many of the population
centers are located along major highways.
218
-------
Aquifer Vulnerability Map of Kansas
219
-------
CL
o
o
2 *
c
2 i
o -o
o c
2*
o. o
o o o
XT — lA
B S 3
o o o
Potential Well Yields In Kansas
220
-------
I
-------
Population Density of Kansas
(Dot equals one person per square mile)
Precipitation
in inches
• 14 to 20
• 20 to 26
+ 26 to 32
A 32 to 38
0 38to44
Average Annual Precipitation in Kansas
222
-------
MISSOURI
General Setting
Missouri contains approximately 69,700 square
miles. The far southeastern part of the state lies within
the Coastal Plain physiographic province, while central
and northern parts lie within the Ozark Plateaus and
Central Lowland provinces, respectively. The
topography varies from gently rolling to rugged, maturely
dissected rolling uplands. The Ozark Uplift in the
southeastern quarter of the state is the predominant
structural feature in Missouri. At the center of the uplift,
Precambrian age igneous rocks are exposed and the
overlying Paleozoic rocks dip predominantly to the west
and northwest. Glacial deposits are present in the
northern third of the state and their southern limit
roughly parallels the Missouri River. Theglacial deposits,
which overlie Ordovician to Pennsylvanian age
sedimentary rock, range in thickness from 0 to 400 feet.
Missouri is drained principally by the Missouri
and Osage river systems, which flow eastward to the
Mississippi River. Annual average precipitation ranges
from 36 inches in the north to 48 inches in the southeast.
Missouri's population, approximately 5.1 million, is
concentrated in the Kansas City and St. Louis
metropolitan areas. The remainderof the state is lightly
populated. About 640 million gallons of fresh ground
water are used daily in Missouri.
Unconsolidated Aquifers (Class la)
Alluvial and terrace deposits occur along many
rivers and tributaries throughout the state. Also included
as Class la are local glaciofluvial deposits. In the
northern part of Missouri these unconsolidated aquifers
consist of sand and gravel with variable amounts of silt
and clay. Well yields commonly range from 100 to
1,000 gpm, and they may exceed 2,500 gpm. Exposed
in far southeastern Missouri are alluvial aquifers that
form the Mississippi River flood plain. These
unconsolidated deposits consist of Quaternary age
sand, gravel, silt, and clay. Well yields commonly range
from 1,000 to 2,000 gpm, and may exceed 4,000 gpm.
About 18 percent of Missouri is covered by
unconsolidated aquifers.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Exposed extensively in southern Missouri are
Cambrian to Pennsylvanian age carbonate aquifers.
These deposits consist of dolomite and limestone with
lesser amounts of sandstone and shale. Solution activity
has created karstic features, which enhance vertical
and lateral permeability of the aquifer. Well yields
commonly range from 15 to 700 gpm, and may exceed
1,000 gpm. Approximately 44 percent of the state is
underlain by Class Ib aquifers.
Variably Covered Soluble and Fractured Bedrock
Aquifers (Class Ib-v)
In eastern and central Missouri Ordovician to
Pennsylvanian age carbonate aquifers are overlain by
a variable thickness of glacial till. The underlying
bedrock consists of limestone and dolomite with lesser
amounts of sandstone and shale. Aquifer vulnerability
is afunction of the overlying low permeability sediments.
Well yields commonly range from 15 to 700, and may
exceed 1,000 gpm. About 6 percent of the state is
occupied by Class Ib-v aquifers.
Semiconsolidated Aquifers (Class Ic)
A relatively small exposure of Semiconsolidated
sediments occurs in far southeastern Missouri. These
Tertiary to Cretaceous age Semiconsolidated deposits
consist of interbedded sand and clay. Well yields
commonly range from 100 to 1600 gpm, and may
exceed 2,000 gpm. Only .5 percent of the state is
occupied by Class Ic aquifers.
Higher Yield Bedrock Aquifers (Class Ha)
Small local exposures of higher yield bedrock
aquifers, consisting of Cambrian age sandstone, occur
223
-------
in the eastern part of the state. Well yields commonly
range from 5 to 100 gpm, and they may exceed 250
gpm. Only .7 percent of the state is occupied by higher
yield bedrock aquifers.
Lower Yield Bedrock Aquifers (Class lib)
Occurring in western and, locally, in eastern
Missouri are Pennsylvanian age lower yield aquifers,
which consist of shale and sandstone with lesser
amounts of limestone and coal. Well yields commonly
range from 1 to 15 gpm, and may exceed 25 gpm. About
8 percent of the state is covered by Class lib aquifers.
Variable Covered Lower Yield Bedrock Aquifers
(Class llb-v)
Throughout much of northern Missouri are
variably covered toweryield aquifers. The Pennsylvanian
age bedrock aquifer, which consists of shale and
sandstone with lesser amounts of limestone and coal,
is covered by till. The vulnerability of these aquifers is
a function of thickness of the overlying glacial till. Well
yields commonly range from 1 to 15 gpm, and may
exceed 25 gpm. Nearly 21 percent of the state is
occupied by Class llb-v aquifers.
Undifferentiated Aquifers (Class U)
Exposed in east-central Missouri are
undifferentiated Pennsylvanian age sedimentary rock.
Precambrian age intrusive and extrusive crystalline
bedrock occurs in the southwestern part of the state.
About 2 percent of Missouri is occupied by
undifferentiated aquifers.
Sensitivity
Approximately 68 percent of Missouri consists
of vulnerable Class I aquifers. The potential for ground-
water contamination from shallow injection wells is high
owing to the permeable nature of the rocks in the karst
areas. Population centers are rather evenly distributed
throughout the state.
224
-------
Class la
Class Ib
Class I la
Class lib
Class Ilbv
Class U
Aquifer Vulnerability Map of Missouri
225
-------
5 to 200 GPM
!5to700GPM
100 to 200 GPM
100 to 1000 GPM
100 to 1600 GPM
1000 to 2000 GPM
Potential Well Yields in Missouri
226
-------
Areas covered by class I aquifers.
Each dot represents a population center.
Aquifer Sensitivity Map of Missouri
227
-------
-------
NEBRASKA
General Setting
Nebraska, which contains approximately 77,400
square miles, lies in the dissected plains and rolling hills
of the Great Plains and Central Lowland physiographic
provinces. Nebraska is underlain by Precambrian and
Mesozoic age clastic and carbonate sedimentary rocks
that crop out in the eastern part of the state, and dip
gently westward into shallow structural basins beneath
the Great Plains. These bedrock units are mantled by
semiconsolidated, Tertiary age clastic sediments
throughout central and western Nebraska, and locally
by Quaternary age deposits in eastern Nebraska.
Unconsolidated alluvial, eolian, lacustrian, and glacial
deposits occur along recent stream and in preglacial
bedrock valleys, as well as in other areas throughout the
state. Although variable, the thickness of glacial deposits
may exceed 400 feet in places (Burchett and others,
1972; Burchett and others, 1975; Dreeszen and others,
1973).
The Missouri River and its many southeastward
flowing tributaries drain the entire state. Annual
precipitation ranges from less than 16 inches in the west
to more than 32 inches in the southeast. The majority of
Nebraska's population, approximately 1.6 million, is
located in and around metropolitan Omaha and Lincoln.
The remainder of the state is sparsely populated. About
5590 million gallons of fresh ground water are used
daily in Nebraska.
Unconsolidated Aquifers (Class la)
Alluvium and glacial outwash, which occurs
along majorstreamsandwithinpaleovalleys throughout
the state, forms both vulnerable and productive aquifers.
These generally unconfined systems consist of
Unconsolidated deposits of sand, gravel, silt, and clay
that are commonly tens of feet thick. Well yields
commonly range from 300 to 1,000 gpm, and locally
may exceed 1,500 gpm. About 21 percent of the state
is covered by Class la aquifers.
Variably Covered Soluble and Fractured Bedrock
Aquifers (Class Ib-v)
Karst features are present in fractured, Upper
Cretaceous chalk and silty marlstone in eastern
Nebraska. These rocks are overlain by a variable
thickness of glacial till. The vulnerability of these
systems is afunction of the thickness of the overlying till,
and the occurrence of solutional features and fractures.
Well yields commonly range from 300 to 750 gpm, and
may exceed 1,000 gpm. Slightly more than 5 percent of
the state is underlain by Class Ib-v aquifers.
Semiconsolidated Aquifers (Class Ic)
Exposures of semiconsolidated sediments
occur throughout central and western Nebraska, and
consist of Tertiary age, poorly- to well-indurated,
tuffaceous sand, silt, gravel, and intercalated beds of
clay and marl. In many places hydraulically connected
Quaternary age glacial and eolian deposits overlie the
semiconsolidated sediments and are included in the
system. Saturated thicknesses locally exceed 1,000
feet, and well yields commonly range from 500 to 1,000
gpm, and may exceed 2,500 gpm. Surface exposures
of semiconsolidated aquifers occupy about 57 percent
of the state.
Variably Covered Higher Yield Bedrock Aquifers
(Class lla-v)
Higher yield bedrock aquifers, composed of
Lower Cretaceous sandstone and interbedded clay,
occur in eastern Nebraska. These rocks are overlain by
a variable thickness of low permeability glacial till. The
vulnerability of these systems is a function of the
thickness and permeability of the overlying sediments.
Well yields commonly range from 300 to 750 gpm, and
may exceed 1,000 gpm. About 5 percent of the state is
underlain by Class lla-v aquifers.
229
-------
Variably Covered Undifferentiated Aquifers
(Class U-v)
Undivided and lithologically varied Paleozoic
age formations occur in southeastern Nebraska, and
consist of interbedded shale, limestone, dolomite,
sandstone, and evaporite and coal beds. These strata
are overlain by a variable thickness of glacial till. The
vulnerability of these systems is a function of the
thickness and permeability of the overlying sediments.
In addition, the lithologic and resultant hydrologic
variability of the undivided bedrock formations have not
been delineated. A wide range in aquifer permeability
and vulnerability should be expected in these areas.
About 3.6 percent of the state is underlain by Class U-
v aquifers.
Sensitivity
About 83 percent of Nebraska is covered by
vulnerable Class I aquifers. The potential for ground-
water contamination from shallow injection wells is
quite low because of the light population density. Most
of the population centers are small and lie along major
highways. Consequently, vast expanses are unlikely to
be affected.
230
-------
Aquifer Vulnerability Map of Nebtaska
231
-------
•o
0>
d
-------
I
(0_
3?
<
•o
a
i
N3
LO
CO
Areas covered by class I aquifers.
Each dot represents a population center.
-------
Population Density of Nebraska (Dot equals one
person per square mile)
Average Annual Precipitation in Nebraska
234
-------
REGION 8
Colorado
Montana
North Dakota
South Dakota
Utah
Wyoming
235
-------
COLORADO
General Setting
Colorado contains approximately 104,100
square miles, and lies in the high plains, mountains,
valleys, and dissected plateaus of the Great Plains,
Southern and Middle Rocky Mountains, Wyoming Basin,
and Colorado Plateaus provinces. The mountains of
central and northern Colorado consist largely of faulted
Precambrian age metamorphic and igneous rocks,
flanked by steeply dipping Paleozoic and Mesozoic age
clastic and carbonate sedimentary units. The mountains
of southern and west-central Colorado are composed of
Tertiary age volcanic and granitic rocks, as well as
Paleozoic and Mesozoic age clastic and carbonate
sediments. The plateaus and plains of western and
eastern Colorado are underlain by relatively flat lying,
consolidated to semiconsolidated, Mesozoic and
Cenozoic age clastic rocks. Unconsolidated alluvial,
eolian, and glacial deposits occur throughout the state.
The eastern half of Colorado is drained by the east-
flowing South Platte and Arkansas rivers, and their
many tributaries. The western half of the state is
drained by the Colorado River and several other smaller
systems.
Annual precipitation ranges from less than 8
inches in south-central and western Colorado to about
40 inches in the Rocky Mountains. Extreme variations
in monthly precipitation are the resu It of regional climatic
variations and orographic effects. The majority of
Colorado's population, approximately 3.3 million, is
located along the eastern front of the Rocky Mountains.
The remainder of the state is sparsely populated. About
2310 and 32 million gallons of fresh and saline ground
water, respectively, are used each day in Colorado.
Unconsolidated Aquifers (Class la)
Alluvial, lacustrine, and glacial deposits occur
in river valleys and basins throughout the state, and
form vulnerable and productive aquifers. These
generally unconfined systems consist of Unconsolidated
Late Tertiary and Quaternary age gravel, sand, silt, and
clay. Glacial material includes cobbles and boulders.
Volcanic rock interbeds occur within basin-fill deposits
in southern Colorado. Well yields in river valley deposits
commonly range from 100 to 1,500 gpm, and may
exceed 3,000 gpm. Well yields in basin-fill deposits of
the San Luis Valley in southern Colorado commonly
range from 500 to 1,200 gpm, and may exceed 2,000
gpm. Nearly 10 percent of the state is covered by Class
la aquifers.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Limited exposures of solutional features are
present in fractured Devonian and Mississippian age
limestone and dolomite in the west-central Rocky
Mountains. Sandstone and chert interbeds occur within
these units. Where present, solutional features and
fractures contribute to the vertical and lateral permeability
of the rock. Well yields in this largely undeveloped
aquifer may exceed 500 gpm. Class Ib aquifers occupy
about .2 percent of the state.
Semiconsolidated Aquifers (Class Ic)
Exposures of semiconsolidated sediments
occur throughout eastern Colorado, and as isolated
units in central and western parts of the state. These
generally unconfined systems consist of poorly- to
moderately- consolidated Tertiary and Quaternary age
gravel, sand, silt, and clay with thin beds of caliche and
limestone. Calcite is a common cementing agent. In
northeastern Colorado, the semiconsolidated High
Plains Aquifer reaches a thickness of 400 feet (Pearl,
1974). Semiconsolidated sediments locally are overlain
by eolian and alluvial deposits. Well yields in the High
Plains Aquifer commonly range from 350 to 2,000 gpm,
and may exceed 2,500 gpm. Surface exposures of
semiconsolidated aquifers occupy about 16 percent of
the state.
Higher Yield Bedrock Aquifers (Class Ma)
Higher yield bedrock aquifers crop out in
northern and southern parts of western Colorado and in
the east-central part of the state. These systems
consist of Cretaceous and Tertiary age sandstone and
236
-------
conglomerate with interbedded shale, siltstone, coal,
and fractured dolomitic marlstone. Well yields in
northwestern and east-central Colorado commonly
range from 5 to 500 gpm, and may exceed 2,000 gpm;
well yields in the southwest generally range from 5 to
1,000 gpm, and may exceed 1,500 gpm. Surface
exposures of higher yield bedrock aquifers occupy
nearly 6 percent of the state.
Lower Yield Bedrock Aquifers (Class lib)
Lower yield bedrock aquifers, which crop out
throughout western and parts of southeastern Colorado,
consist of Mesozoic and Early Tertiary age sandstone
with interbedded shale, siltstone, and conglomerate.
Well yields in western Colorado commonly range from
1 to 25 gpm, and may exceed 500 gpm; moderate well
yields are reported for similar units in southeastern
Colorado (McGuinness, 1963). Surface exposures of
Class lib aquifers occupy about 19 percent of the state.
Undifferentiated Aquifers (Class U)
Precambrian age igneous and metamorphic
rocks are exposed throughout the Rocky Mountains,
and function as aquifers only in areas where faulting
and jointing have produced fractures. An incomplete
understanding of the distribution and hydrologic behavior
of fractures results in a wide range in aquifer productivity
and vulnerability. Well yields from crystalline aquifers
along the Front Range commonly range from 0.5 to 5
gpm, and may exceed 15 gpm. Similar hydrologic
conditions within othercrystalline rocks may exist outside
those areas documented. Undivided and lithologically
varied Cretaceous age rocks, which crop out throughout
western Colorado, consist of interbedded shale,
sandstone, and limestone. The lithologic and resultant
hydrologic variability of these undivided units has not
been delineated. Well yields in locally weathered or
fractured producing zones commonly range from 1 to
10 gpm, and may exceed 25 gpm. Surface exposures
of undifferentiated aquifers occupy about 12 percent of
the state.
Sensitivity
Nearly 26 percent of Colorado consists of Class
I aquifers. Aquifer sensitivity in most places in Colorado
is quite low owing to the low population density. The
greatest number of population centers occurs along
major highways in the eastern quarter of the state.
Several of the highways follow major water courses,
such as along the South Platte and Arkansas rivers.
237
-------
Aquifer Vulnerability Map of Colorado
238
-------
TJ
a
o
••*
fil
2.
Q.
V)
ET
g
o
3
S9
w
VO
1 to 25 GPM
5 to 500 GPM
5 to 1000 GPM
100 to 1500 GPM
350 to 2000 GPM
500 to 1200 GPM
Undefined
May Exceed 500 GPM
Moderate Well
-------
Is)
*»
O
f
V)
S!
s:
"O
o
-*
5?
o
Areas covered by class I aquifers.
Each dot represents a population center.
-------
Population Density of Colorado (Dot equals one
person per square mile)
Precipitation
in inches
• 7 to 14
- 14 to 21
+ 21 to 29
^ 29 to 36
O 36 to 43
Average Annual Precipitation in Colorado
241
-------
MONTANA
General Setting
Montana contains approximately 147,000
square miles, and lies in the mountains, valleys, and
dissected plains of the Northern and Middle Rocky
Mountain and the Great Plains physiographic provinces.
The mountains of western and southwestern Montana
are underlain by folded and faulted Precambrian to
Paleozoic age metamorphic and sedimentary rocks
that, locally, are intruded by Precambrian, Cretaceous,
and Tertiary age basic and acidic bodies. The remainder
of the state is underlain by gently dipping Paleozoic to
Tertiary age marine and nonmarine sediments, locally
intruded by minor Tertiary age granitic bodies. Alluvial
and glacial deposits occur along rivers and within
intermontane valleys.
Except for northwestern Montana, the entire
state is drained by the east-flowing Missouri and
Yellowstone rivers. Kootenai and Clark Fork rivers
drain northwestern Montana. Annual precipitation ranges
from 8 to 120 inches in the west, and from 12 to 30
inches in the eastern plains. The majority of Montana's
precipitation is received from April to September. The
majority of Montana's population, approximately
805,000, is located in Cascade, Silver Bow, Missoula,
and Yellowstone counties. The remainder of the state
is sparsely populated. Daily use of fresh ground water
amounts to about 203 million gallons.
U neon sol idated Aquifers (Class la)
Alluvial and glacial-outwash deposits occur
throughoutthe state, and form vulnerable and productive
aquifers. These generally unconfined systems consist
of Late Tertiary and Quaternary age unconsolidated
sand, gravel, silt, and clay. Outwash deposits generally
include cobbles and boulders. Well yields commonly
range from 5 to 50 gpm, and may exceed 3,500 gpm.
About 16.4 percent of the state is covered by Class la
aquifers.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Solutional features are present in Paleozoic
age limestone units exposed in west-central and
southwestern Montana. Dolomite, anhydrite, and halite
interbeds occur within this system. Where present,
solutional features contribute to the vertical and lateral
permeability of the rock, creating highly productive and
vulnerable aquifers. Well yields may exceed 1,000
gpm. Class Ib aquifers occupy about 5.2 percent of the
state.
Semiconsolidated Aquifers (Class Ic)
Exposures of semiconsolidated sediments
occur throughout northeastern and southwestern
Montana, and consist of poorly to moderately
consolidated, interbedded, Tertiary age gravel, sand,
silt, clay, tuffaceous material, and lenses of lignite. Well
yields range from 15 to 25 gpm, and may exceed 100
gpm. Surface exposures of semiconsolidated aquifers
occupy about 5.7 percent of the state.
Lower Yield Bedrock Aquifers (Class lib)
Lower yield bedrock aquifers, consisting
primarily of Cretaceous and Paleocene age sandstone,
occur throughout the eastern two-thirds of the state.
Sandstone aquifers contain variable amounts of
siltstone, shale, lignite, and limestone, and are
unconfined in the outcrop area. Well yields range from
5 to 25 gpm, and may exceed 200 gpm.
Sensitivity
Although about 27 percent of Montana is
covered by Class I aquifers, the potential for ground-
water contamination from shallow injection wells is
relatively small owing to Montana's low population
density. Population centers generally follow the trend of
major river valleys and highways. Elsewhere there are
only a few relatively isolated towns.
242
-------
Aquifer Vulnerability Map of Montana
243
-------
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Poten,,alWellyte,dsinMon|ana
244
-------
Q
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Population Density of Montana (Dot equals one
person per square mile)
Precipitation
in inches
.
•
+
^
o
6 to 13
13 to 20
20 to 27
27 to 33
33 to 40
Average Annual Precipitation in Montana
246
-------
NORTH DAKOTA
General Setting
North Dakota, which contains approximately
70,700 square miles, lies in the rolling to hilly, largely
glaciated prairies of the Great Plains and Central Lowland
physiographic provinces. The Badlands of southwestern
North Dakotacontain rugged hills along the Little Missouri
River. All but the southwestern quarter of North Dakota
is covered with unconsolidated glacial deposits of
Quaternary age. These sediments range from less than
10 to more than 600 feet in thickness(Bluemle, 1986).
The glacial boundary roughly parallels the present
course of the Missouri River. The Williston structural
basin in western North Dakota contains thick
accumulations of Paleozoic to Tertiary age limestone,
sandstone, siltstone, and shale. These deposits
gradually thin toward the margins of the basin, and
Precambrian age granitic rocks locally underlie glacial
deposits in the eastern part of the state.
The Great Plains province is drained by the
Missouri River and its five principal tributaries, and the
Little Missouri River. The north-flowing Red and Souris
rivers drain most of the Central Lowlands province.
Poorly defined drainage patterns over much of the
province reduce surface runoff to rivers. North Dakota
has a semiarid continental climate with extremes in
winter and summer temperatures. Annual precipitation
ranges from about 13 inches in the west to more than 22
inches in the east. The majority of North Dakota's
population, approximately 667,000, is located in Burleigh,
Morton, Cass, and Ward counties. Theremainderofthe
state is sparsely populated. Daily use of fresh ground
water amounts to about 127 million gallons.
Unconsolidated Aquifers (Class la)
Glacial outwash and alluvial deposits form the
most productive and vulnerable aquifers in the state.
Glacial outwash deposits consist of unconsolidated,
interbedded, linear bodies of sand, gravel, silt, and clay.
These deposits occur throughout much of the state and
locally exceed 100 feet in thickness. Alluvial deposits,
consisting of unconsolidated sand, gravel, and silt are
best developed along the Missouri River and its
tributaries, and the Little Missouri River. Well yields in
glacial outwash and alluvial aquifers range from about
1 to 1,000 gpm, and may exceed 1,500 gpm. About 13
percent of the state is covered by glacial outwash and
alluvial deposits.
Higher Yield Bedrock Aquifers (Class Ma)
Higher yield bedrock aquifers, consisting of
interbedded sandstone, siltstone, claystone, and shale
of Cretaceous and Tertiary age, crop out throughout the
unglaciated southwestern part of the state. Well yields
range from 1 to 150 gpm, and may exceed 300 gpm.
Surface exposures of higher yield bedrock aquifers
occupy 27 percent of the state.
Covered Bedrock Aquifers (Class lie)
Higher yield bedrock aquifers of Cretaceous
and Tertiary age, overlain by less than 50 feet of glacial
till, occur sporadically throughout the glaciated part of
the state. Well yields commonly range from 1 to 150
gpm. Class lie aquifers occupy 9 percent of the state.
Sensitivity
Although 15 percent of the state is covered by
Class I aquifers, the potential for shallow ground-water
contamination from shallow injection wells is very low
due to North Dakota's low population density. Population
centers that lie on Class I aquifers are very few and
these generally occur along major highways.
247
-------
Qciass
[Class Ha
Class He QciassIII
-------
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Potential Well Yields In North Dakota
249
-------
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Areas covered by class I aquifers.
Each dot represents a population center.
-------
Population Density of North Dakota (Dot equals one
person per square mile)
Precipitation
in inches
• 8 to 12
• 12 to 15
+ 15 to 18
* 18 to 22
0 22 to 25
Average Annual Precipitation in North Dakota
251
-------
SOUTH DAKOTA
General Setting
South Dakota contains approximately 77,100
square miles, and is divided into two physiographic
provinces by the Missouri River. The area west of the
Missouri lies in the Great Plains province and is
characterized by deep valleys and canyons, buttes, and
broad flat uplands. East of the Missouri River, low
rolling hills and potholes typify the glaciated part of the
Central Lowland province. South Dakota is underlain by
gently dipping, Paleozoic and Mesozoic age limestone,
shale, and sandstone. These rocks are locally overlain
by Tertiary age semiconsolidated to consolidated
sandstone, silt, and clay in the western two-thirds of the
state, and by Quaternary age glacial deposits in the
eastern third of the state. Glacial deposits average
about 150 feet in thickness, but may be as much as 800
feet thick in the northeast part of the state (U.S.G.S.,
1986). Precambrian age metamorphic and igneous
rocks crop out in the Black Hills in western South
Dakota, and along the partially buried Sioux Uplift in the
east. Unconsolidated Quaternary age alluvial and
terrace deposits lie along all of South Dakota's major
rivers.
South Dakota is drained by the southeast-
flowing Missouri River and its seven principal tributaries.
The state has a continental climate with extreme summer
heat, extreme winter cold, and rapidly changing
temperatures. Annual precipitation commonly ranges
from 13 inches in the northwest to 25 inches in the
southeast. The majority of South Dakota's population,
approximately three-quarters of a million, is located in
Minnehaha and Pennington counties. The remainderof
the state is sparsely populated. About 249 million gallons
of fresh ground water are used daily.
Unconsolidated Aquifers (Class la)
Alluvial deposits occur in narrow bands along
larger streams, and form some of the most vulnerable
aquifers in the state. These unconfined systems
generally consist of Unconsolidated sand, gravel, and
silt. Glacial outwash aquifers, consisting of
Unconsolidated sand, gravel, and silt occur throughout
the glaciated eastern third of the state. Well yields
commonly range from 3 to 50 gpm, and may exceed
2,000 gpm. About 28.5 percent of the state is covered
by Class la aquifers.
Semiconsolidated Aquifers (Class Ic)
The High Plains Aquifer, located in south-central
South Dakota, consists of the lower part of the Ogallala
and the Arikaree Formation of Miocene age. The
Ogallala is composed of semiconsolidated to
consolidated sand and silt, while the Arikaree consists
of semiconsolidated to consolidated sand, clay, and silt.
Sediments associated with the largely unconfined High
Plains Aquifer are as much as 700 feet thick. Well yields
commonly range from 5 to 100 gpm, and may locally
exceed 1,500 gpm. Surface exposures of
semiconsolidated aquifers occupy nearly 10 percent of
the state.
Higher Yield Bedrock Aquifers (Class Ha)
Higher yield bedrock aquifers, consisting of a
variety of interbedded lithologies including sandstone,
shale, siltstone, limestone, dolomite, and evaporites,
are exposed around the Black Hills in western South
Dakota. Well yields commonly range from 3 to 100 gpm
but as much as 4,000 gpm are obtainable locally in
areas of significant artesian pressure. Surface
exposures of higher yield bedrock aquifers occupy
nearly 2 percent of the state.
Lower Yield Bedrock Aquifers (Class lib)
Lower yield bedrock aquifers, consisting of
sandstone that is interbedded with shale, siltstone, and
lignite, occur in the western and northwestern parts of
the state. Sandstone aquifers are unconfined in the
outcrop area. Well yields range from 2 to 50 gpm, and
may exceed 1,500 gpm. Surface exposures of lower
yield bedrock aquifers occupy about 15.4 percent of the
state.
252
-------
Sensitivity
About 38 percent of South Dakota is covered
by Class I aquifers. The potential for ground-water
contamination from shallow injection wells is small
owing to low population density. In the Class I areas in
the eastern part of the state, most of the population
centers lie along major highways and the towns are
small.
253
-------
Aquifer Vulnerability Map of South Dakota
254
-------
Potential Well Yields In South Dakota
255
-------
I
I
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-------
Population Density of South Dakota (Dot equals one
person per square mile)
Precipitation
in inches
• 13 to 16
- 16 to 19
+ 19 to 22
^. 22 to 25
^ 25 to 28
Average Annual Precipitation in South Dakota
257
-------
UTAH
General Setting
Utah contains approximately 84,900 square
miles, and lies in the mountains, intermountain basins,
and dissected plateaus of the Basin and Range, Middle
Rocky Mountains, and Colorado Plateaus physiographic
provinces. The mountains of northern and western
Utahconsist largely of folded andfaulted, metamorphic,
clastic, and carbonate rocks that range from Paleozoic
to Precambrianinage. Tertiary age granitic and volcanic
rocks form mountains in parts of western Utah. Paleozoic
and Mesozoic age clastic and carbonate sediments
f lankthe northern mountains and crop out in large areas
of the Colorado Plateaus to the south. Basin and valley
fill generally consistsof thick accumulations of Cenozoic
age alluvial, playa, and volcanic deposits.
Eastern Utah is drained by the Colorado River
system. Most of the rivers in western Utah terminate in
closed basins. Annual precipitation ranges from less
than 10 inches in the west to more than 40 inches in the
mountains of north and southwest Utah. The distribution
of precipitation is relatively uniform throughout the year.
The majority of Utah's population, nearly 1.7 million, is
located in the north-central part of the state. Elsewhere
the state is sparsely populated. The daily use of fresh
and saline ground water in Utah is about 790 and 25
million gallons, respectively.
Unconsolidated Aquifers (Class la)
Quaternary age valley-fill and basin-fill deposits
form vulnerable and productive aquifers, and constitute
the principal source of ground water in Utah. These
unconf ined to confined systems consist of interbedded,
unconsolidated deposits of clay, sand, silt, gravel, and
boulders. Evaporite and volcanic deposits occur locally.
Valley-fill, alluvial, colluvial, and glacial deposits, which
generally extend from southwestern to northeastern
Utah, commonly reach thicknesses of several hundred
feet. Well yields usually range from 10 to 750 gpm, and
may exceed 2,000 gpm. Basin-fill deposits occur
throughout western Utah, where they reach thicknesses
of several thousand feet. Well yields commonly range
from 200 to 1,000 gpm, and may exceed 6,000 gpm.
About 13.3 percent of the state is covered by permeable,
unconsolidated sediments.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Solutional features and fractures are present in
folded and faulted limestone and dolomite units that
range in age from Middle Cambrian to Triassic in
western, central, and northeastern Utah. Sandstone
and shale interbeds occur within these units. Where
present, solutional features and fractures contribute to
the vertical and lateral permeability of the rock, creating
productive and vulnerable aquifers. Well yields in this
largely undeveloped aquifer system are generally less
than 10 gpm, but may exceed 200 gpm. Solutional
features also are present in the Tertiary age limestone
units that are exposed across southwestern and south-
central Utah. Fractured volcanic rock aquifers,
composed of Tertiary and Quaternary age basalt and
rhyolite, have been documented in central and northern
Utah. Ground-water yield and movement are controlled
by the density of joints and fractures. Well yields usually
are less than 10 gpm. Similar hydrologic conditions
within other volcanic units may exist outside those
areas documented. Fractured rock aquifers also are
present in the Pennsylvanian age quartzite exposed
along the Wasatch Front in north-central Utah. Class Ib
aquifers occupy about 10.7 percent of the state.
Semiconsolidated Aquifers (Class Ic)
Exposures of Semiconsolidated sediments
occur in isolated areas throughout Utah, and consist of
Tertiary and Quaternary age poorly- to well-indurated,
tuff aceous sand, gravel, and intercalated layers of clay.
Calcium carbonate is a common cementing agent. Low
to moderate permeabilities are reported for these
sediments (Hood and Waddell, 1969; Hood, 1972).
Surface exposures of Semiconsolidated aquifers occupy
about 7 percent of the state.
258
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Higher Yield Bedrock Aquifers (Class lla)
Higher yield bedrock aquifers, composed of
Pennsylvanian, Permian, and Mesozoic age fine to
coarse-grained sandstone, with some shale, coal, and
limestone, crop out in southern, eastern, and
northeastern Utah. Well yields commonly range from
50 to 500 gpm, and may exceed 3,000 gpm. Higher
yield Late Cretaceous and Tertiary age aquifers, which
are composed of sandstone interbedded with shale,
conglomerate, and coal, crop out across central and
east-central Utah. Well yields commonly range from 25
to 100 gpm (Waddell and others, 1981). Maximumwell
yields are associated with local fracturing. Surface
exposures of Class I la aquifers occupy about 27 percent
of the state.
Variably Covered Aquifers (Class lla-v)
Higher yield bedrock aquifers that are overlain
by an undetermined thickness of low permeability
material, occur throughout southeastern Utah. The
vulnerability of these systems is a function of the
thickness of the overlying sediments. Variably covered,
higher yield bedrock aquifers occupy about 2 percent of
the state.
Lower Yield Bedrock Aquifers (Class lib)
Lower yield bedrock aquifers of Tertiary age
that are composed of sandstone, conglomerate, and
shale, crop out in northern and northeastern Utah.
Limited amounts of ground water are produced from
wells and springs in these units (Taylor and others,
1986; Holmes, 1987). Maximum well yields are
associated with local fracturing. Surface exposures of
Class Mb aquifers occupy about 6.6 percent of the state.
Undifferentiated Aquifers (Class U)
Undivided and lithologically varied
Pennsylvanian, Permian, and Triassic age strata crop
out in parts of southeastern and southwestern Utah.
They consist of interbedded limestone, shale, sandstone,
and conglomerate. Moderate amounts of ground water
are produced from the Triassic sandstone and
conglomerate units (McGuinness, 1963;Goode, 1966);
Paleozoic limestones are known to yield water to wells
(McGuinness, 1963). Undivided and lithologically varied
Cretaceous and Eocene age formations crop out across
eastern and south-central Utah, and consist of shales
that contain permeable sandstone and limestone
interbeds (Waddell and others, 1981 ;Taylor and others,
1986; Holmes, 1987). Maximum well yields are
associated with local fracturing. Surface exposures of
undifferentiated aquifers occupy about 12 percent of
the state.
Sensitivity
Although nearly 31 percent of Utah consists of
Class I units, aquifer sensitivity is very low because of
the light population density. Most of the population
centers that lie on Class I aquifers occur along major
highways.
259
-------
Class Ic
Lake
Aquifer Vulnerability Map of Utah
260
-------
10to750GPM
25tolOOGPM
50to500GPM
200tolOOOGPM
Undefined
Low Well Yields
Low to Moderate Permeabilities
Moderate Well Yields
Variable Permeability
Potential Well Yields in Utah
261
-------
Areas covered by class I aquifers.
Each dot represents a population center.
Aquifer Sensitivity Map of Utah
262
-------
Population Density of Utah (Dot equals one
person per square mile)
Average Annual Precipitation in Utah
263
-------
WYOMING
General Setting
Wyoming, whichcontains approximately 97,800
square miles, lies in the high plains, basins, and
mountains of the Great Plains, Wyoming Basin, Middle
and Southern Rocky Mountains physiographic
provinces. Wyoming's mountains consist of exposed
cores of Precambrian age metamorphic and igneous
rocks, flanked by Paleozoic and Mesozoicage carbonate
and clastic stratathat dip steeply into adjacent structu ral
basins. Semiconsolidated to consolidated Tertiary age
clastic deposits comprise the majority of the basin fill.
Alluvial, glacial, and eolian deposits occur along rivers,
and within intermontane valleys.
The northern half of Wyoming is drained by the
west-flowing Snake River and the north- and east-
flowing Yellowstone, Bighorn, Powder, Belle Fourche,
and Cheyenne rivers and their tributaries. The southern
half of the state is drained by the south- and east-flowing
Green and North Platte rivers. Annual precipitation
ranges from less than 8 inches at lower elevations to
more than 24 inches in the western mountains
(McGuinness,1963). Approximately 50 percent of the
state receives lessthan 12 inches peryear. The majority
of Wyoming's population, approximately 479,000, is
located in Natrona, Cheyenne, Laramie, and Kemmerer
Counties. The remainder of the state is sparsely
populated. About 504 and 23 million gallons of fresh
and saline ground water, respectively, are used daily in
Wyoming.
Unconsolidated Aquifers (Class la)
Alluvial and outwash deposits, which occur
throughout the state, form vulnerable and productive
aquifers. These generally unconfined systems consist
of Quaternary age gravel, sand, silt, and clay. Glacial
outwash locally contains boulders. Alluvial aquifers
generally are less than 50 feet thick, but may exceed
200 feet in the Bear and Snake River structural basins.
Well yields commonly range from 50 to 100 gpm, and
may exceed 3,000 gpm. About 14 percent of the state
is covered by Class la aquifers.
Semiconsolidated Aquifers (Class Ic)
Exposures of Semiconsolidated sediments,
which occur throughout the southern half of Wyoming,
consist of poorly- to moderately-consolidated,
interbedded, Tertiary and Quaternary age tuffaceous
sand, clay, silt, and gravel. Thicknesses are generally
less than 400 feet, but may locally exceed 1,000 feet.
Semiconsolidated sediments are locally overlain by
eolian deposits. Well yields commonly range from 150
to 800 gpm, and may exceed 2,000 gpm. Surface
exposures of Semiconsolidated aquifers occupy about
13 percent of the state.
Lower Yield Bedrock Aquifers (Class lib)
Lower yield bedrock aquifers occur within
structural basins across the state, and consist of
interbedded, Late Cretaceous and Tertiary age
sandstone, shale, claystone, siltstone, marlstone, coal
beds, and conglomerate. Sandstones are commonly
arkosic and tuffaceous; coal beds may contain oil.
Locally in southwestern Wyoming, these units are
overlain by eolian deposits. Well yields commonly
range from 1 to 50 gpm, but may exceed 1,000 gpm.
Surface exposures of lower yield bedrock aquifers
occupy 37 percent of the state.
Undifferentiated Aquifers (Class U)
Several undivided and lithologically varied
Paleozoic and Triassic age formations crop out along
the flanks of mountains throughout the state, and consist
of interbedded limestone, dolomite, sandstone, shale,
siltstone, phosphorite, gypsum, and halite. The lithologic
and resultant hydrologic variability of these undivided
formations has not been delineated. A wide range in
aquiferproductivity and vulnerability should beexpected
in these areas. Surface exposures of undifferentiated
aquifers occupy about 32 percent of the state.
264
-------
Sensitivity
Although nearly 27 percent of Wyoming is
covered by Class I aquifers, the potential for shallow
ground-watercontaminationfrom shallow injection wells
is relatively small due to Wyoming's low population
density. Even in the most vulnerable areas, population
centers are quite widely distributed, and most lie along
major highways.
265
-------
Aquifer Vulnerability Map of Wyoming
266
-------
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Potentla. Well Yields in Wyornmg
267
-------
Areas covered by class I aquifers.
Each dot represents a population center.
Aquifer Sensitivity Map of Wyoming
268
-------
Population Density of Wyoming (Dot equals one
person per square mile)
Average Annual Precipitation in Wyoming
269
-------
REGION 9
Arizona
California
Nevada
270
-------
ARIZONA
General Setting
Arizona, which contains approximately 114,000
square miles, lies in the dissected plateaus, mountains,
and intermountain basins of the Colorado Plateaus and
Basin and Range physiographic provinces.The
mountains of central and southern Arizona consist
largely of Precambrian and Cenozoic age metamorphic,
sedimentary, and igneous extrusive and intrusive rocks.
Similar rocks of Paleozoic and Mesozoic age crop out
locally in the mountains of western and southeastern
Arizona. Intermountain basins contain thick
accumulations of variably indurated, Cenozoic age
alluvial, eolian, lacustrine, and volcanic deposits. The
northern and northeastern parts of the state are underlain
by thick sequences of flat lying Paleozoicand Mesozoic
age clastic and carbonate rocks. These units are locally
overlain by Cenozoic age volcanic and sedimentary
deposits.
The entire state is drained by the Colorado
River and its west-flowing tributaries. Annual
precipitation ranges from less than 5 inches in the
southwest to more than 25 inches at higher elevations
across the state. July and August are the wettest
months of the year; May and June are the driest. The
majority of Arizona's population, nearly 3.5 million, is
located in and around metropolitan Phoenix andTucson.
The remainder of the state is sparsely populated. Daily
use of fresh and saline ground water amounts to 3090
and 8.4 million gallons, respectively.
Unconsolidated Aquifers (Class la)
Alluvial, eolian, and lacustrine deposits occur
throughout the basins of southern Arizona, and within
isolated depressions in the north, forming sensitive and
productive aquifers that constitute the state's major
ground-water reservoirs. These unconf ined to confined
systems consist of Quaternary age unconsolidated
sand, silt, clay, and volcanic material, that range from a
few hundred to about 10,000 feet in thickness. Well
yields of 1,000 gpm are common and locally they may
exceed 2,500 gpm. About 28 percent of the state is
covered by unconsolidated basin-fill deposits.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Solutional features are present in fractured,
sandy, Permo-Triassic age limestone units exposed in
north-central and northwestern Arizona. Where present,
solutionalfeaturesandfractures contribute to the vertical
and lateral permeability of the rock. Although ground
water is not currently being obtained from these rocks,
reports indicate that there is a potential for development
(Arizona Geological Survey, oral, communication, 1990).
Class Ib aquifers occupy about 7 percent of the state.
Semiconsolidated Aquifers (Class Ic)
Exposures of semiconsolidated sediments,
which occur within intermountain basins in west-central
and southeastern Arizona, consist of poorly- to well-
indurated, Tertiary and Quaternary age gravel, sand,
silt, clay, gypsum, limestone, diatomite, and some
intercalated basalt flows and f elsic tuff beds. Well yields
of 1,000 gpm are common, and locally they may exceed
2,500 gpm. Surface exposures of semiconsolidated
aquifers occupy about 9 percent of the state.
Lower Yield Bedrock Aquifers (Class lib)
Lower yield bedrock aquifers, composed of
sedimentary and igneous rocks, occur throughout the
state. Throughout northern Arizona, these units consist
of Paleozoic and Mesozoic age fine-grained sandstone
and interbedded siltstone, shale, and carbonate rocks.
Elsewhere Late Mesozoic and Cenozoic age,
interbedded basalt and rhyolite flows, agglomerate,
and variable welded pyroclastic material are exposed.
Well yields for sedimentary and volcanic aquifers
commonly range from 0.5 to 2 gpm, but they may
exceed 200 gpm. Maximum well yields, and increased
aquifer vulnerability are associated with the density of
joints and fractures, and the degree of pyroclastic
271
-------
welding. Surface exposures of lower yield bedrock
aquifers occupy about 43 percent of the state.
Sensitivity
About 44 percent of Arizona is covered by
Class I aquifers. On the other hand, the distribution of
population centers and the population density indicate
that the potential for the contamination of ground water
from shallow injection wells is generally small. The most
sensitive part of the state is in the vicinity of Phoenix.
272
-------
I I Class I a
Class Ib H| Class lib
Classic | |Class III
Aquifer Vulnerability Map of Arizona
273
-------
GPM
Undefined
Potential Well Yields in Arizona
274
-------
Areas covered by class I aquifers.
Each dot represents a population center.
Aquifer Sensitivity Map of Arizona
275
-------
Population Density of Arizona (Dot equals one
person per square mile)
Average Annual Precipitation in Arizona
276
-------
CALIFORNIA
General Setting
California, which contains approximately
158,700 square miles, lies in a physiographically diverse
region. The broad and flat, northwest trending, Central
Valley is bounded by the rugged mountains and valleys
of the Coast Ranges, Klamath Mountains, Southern
Cascade Range, Sierra Nevada, and Transverse and
Peninsular Ranges subprovinces. Northeastern and
southeastern California lie in the arid, block-faulted
mountains, valleys, and plateaus of the Basin and
Range, as well as the Southern California Desert.
California's mountains are composed of a variety of
folded and faulted, Precambrian to Cenozoic age
sedimentary, igneous, and metamorphic rocks.
Sedimentary and metasedimentary units include
consolidated Precambrian to Mesozoic age marine
shale, sandstone, conglomerate, limestone, and
dolomite, and their metamorphic equivalents, as well as
metavolcanic and granitic rocks. Cenozoic units include
partially consolidated, marine and nonmarine,
sandstone, shale, conglomerate, and siltstone, as well
as igneous intrusive and extrusive rocks. Valley- and
basin-fill deposits generally consist of considerable
thicknesses of interbedded, unconsolidated, marine
and nonmarine, sand, gravel, silt, and clay of Cenozoic
age.
Most of California is drained by rivers that
originate in the mountainous parts of the state and flow
westward to the Pacific Ocean. Rivers in northeast and
southeast California commonly terminate in closed
basins. Annual precipitation is highly variable, ranging
from less than 5 inches in the desert southeast to more
than 80 inches along the northwest coast. The majority
of California's population, approximately 28.3 million, is
located in and around several large coastal cities and
within the Central Valley. The remainder of the state is
sparsely populated. Use of fresh and saline ground
water amounts to about 14,800 and 284 mgd,
respectively.
Unconsolidated Aquifers (Class la)
A variety of unconsolidated deposits occurs
throughout the state, forming both vulnerable and
productive aquifers. These unconfined to confined
systems, which are present along modern streams and
within basins and valleys, consist of unconsolidated,
continental and marine origin sand, gravel, silt, and
clay. Well yields for Central Valley and desert basin-fill
unconsolidated aquifers commonly range from 50 to
1,500 gpm, and may exceed 4,000 gpm. Well yields for
coastal and adjacent inland unconsolidated aquifers
commonly range from 500 to 1,500 gpm, and may
exceed 4,000 gpm. About 32 percent of the state is
covered by Class la aquifers.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Fractured volcanic bedrock aquifers occur
throughout northeastern California, and locally in the
east-central part of the state. This system consists of
faulted and jointed, Tertiary and Quaternary age
andesite, rhyolite, and basalt flows, pyroclastic rocks,
and associated sedimentary deposits. Ground-water
movement is controlled by the density of joints and
faults, as well as the occurrence of permeable rubble
zones and clastic interbeds. Well yields commonly
range from 100 to 1,000 gpm, and may exceed 4,000
gpm. Precambrian to Mesozoic age granitic and
metamorphic rocks crop out across southern California.
These units are strongly jointed, weathered, and contain
springs. Ground-water movement is controlled by the
density of joints, faults, and fractures, the presence of
openings along schistocity, bedding, and sheeting
planes, and the occurrence of permeable weathered
material (Eckis, 1934; Wiese, 1950 ;Larsen and others,
1951). Similar hydrologic conditions may exist beyond
those areas documented. Surface exposures of
fractured volcanic and crystalline bedrock aquifers
occupy about 17 percent of the state.
Semiconsolidated Aquifers (Class Ic)
Exposures of semiconsolidated, marine and
nonmarine sediments occur along coastal and adjacent
inland parts of California. These Tertiary age sediments
consist of poorly- to well-indurated sand, silt, clay, and
277
-------
gravel. Calcite and hematite are common cementing
agents. Volcanic material and minor limestone units
occur within the section. Moderate to large well yields
and spring discharges are associated with these
sediments. Surface exposures of semiconsolidated
aquifers occupy about 9 percent of the state.
Lower Yield Bedrock Aquifers (Class lib)
Lower yield Jurassic and Cretaceous age
aquifers, composed of sandstone, shale, and
conglomerate, interbedded with limestone and
pyroclastic rocks, crop out within the coastal mountains
of central and northern California. Low quantities of
ground water are produced from wells and springs in
these units. About 5.4 percent of California consists of
Class lib aquifers.
Undifferentiated Aquifers (Class U)
Several undivided and lithologically varied
Precambrian and Paleozoic age formations, which crop
out in the mountains of eastern California, consist of
folded andfaulted limestone, dolomite, sandstone, shale
and metasedimentary rocks. The presence of karst
features, numerous springs, and complexly faulted and
fractured rock, provide the potential for ground-water
movement in this region (Kunkel, 1962; Winograd and
Thordarson, 1975). The lithologic, structural, and
resultant hydrologic variability of these undivided
formations have not been delineated. A wide range in
aquiferpermeability and vulnerability should be expected
in these areas. In addition, undivided and lithologically
varied Cretaceous and Tertiary age formations, which
crop out along part of the southern California coast,
consist of consolidated and semiconsolidated clastic
sediments, as well as intrusive and extrusive igneous
rocks. Surface exposures of undifferentiated aquifers
occupy about 2 percent of the state.
Sensitivity
About 58 percent of California contains Class I
aquifers. The potential for ground-water contamination
from shallow injection wells is high in the densely
populated, vulnerable areas in the vicinity of Los Angeles,
San Francisco, and muchof the Central Valley. Although
vulnerable, wide areas between the major metropolitan
areas and in the desert in the eastern part of the state
are not particularly sensitive owing to the light distribution
of population centers.
278
-------
Aquifer Vulnerability Map of California
279
-------
/
-------
Areas covered by class I aquifers.
Each dot represents a population center
Aquifer Sensitivity Map of California
281
-------
-------
NEVADA
General Setting
Nevada contains approximately 110,561 square
miles, and lies primarily in the structurally controlled
mountain ranges and intermountain basins of the Basin
and Range physiographic province. Small areas in
northeastern and western Nevada lie within the Columbia
Plateaus and Cascade-Sierra Mountains provinces.
The mountains of eastern and southeastern Nevada
consist largely of Paleozoic age limestone, dolomite,
and shale. Mesozoic and Cenozoic age siliciclastic and
igneous rocks become increasingly abundant in the
mountainsof central and western Nevada. Intermontane
basins contain thick accumulations of Cenozoic age
alluvial, lacustrine, and volcanic deposits.
Nevada receives water from the Truckee,
Carson, and Walker rivers, which originate in the Sierra
Nevada and end in closed basins within the state. The
Humboldt River drains north-central Nevada and
terminates in the Humboldt Sink, while the Colorado
Riverdrains southeastern Nevada. Annual precipitation
ranges from 4 inches in low-altitude valleys to about 16
inches at higher elevations; locally precipitation exceeds
30 inches in the higher mountains. Nevada's average
annual precipitation, 9 inches, is the lowest in the
Nation. Ground-water recharge occurs primarily in the
mountains and adjacent alluvial fans. The majority of
Nevada's population, approximately 1,054,000, is
located in Clark, Washoe, and Carson City counties.
The remainderof the state is sparsely populated. About
905 and 2.8 million gallons of fresh and saline ground
water, respectively, are used daily in Nevada.
Unconsolidated Aquifers (Class la)
Basin fill, alluvial, colluvial, and lacustrine
deposits form some of the most vulnerable aquifers in
the state, and comprise Nevada's major ground-water
resource. These unconfined to confined systems
generally consist of permeable, unconsolidated gravel,
sand, silt, and clay that commonly range from 2,000 to
5,000 feet in thickness, and may exceed 10,000 feet.
The upper 1,000 feet are generally the most permeable
(Bedinger and others, 1984). Well yields commonly
range from 200 to 1,000 gpm, and may exceed 5,000
gpm. Evaporite deposits, limestone, and volcanic rocks
are locally interbedded within the basin-fill deposits.
About 51 percent of the state is covered by Class la
deposits.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Solutional features and fractures are present in
carbonate rocks in eastern and southeastern Nevada.
Where present, solutional features and fractures
contribute to the vertical and lateral permeability of the
rock, creating highly productive and vulnerable aquifers.
Interbasin ground-water flow is facilitated by secondary
permeability. Well yields generally range from 50 to
1,000 gpm, but locally may exceed 3,400 gpm. Fractured
volcanic bedrock aquifers occur in the south-central
part of the state. These aquifers, unconfined in the
outcrop area, consist of interbedded, nonwelded to
densely welded ash-flow tuff, bedded ash-fall tuff, and
rhyolite and basalt flows. Ground-water movement is
controlled by the density of jointing and secondary
fractures, the degree of welding, and the presence of
rubble between flows. Well yields commonly range
from 20 to 1,000 gpm, and may exceed 3,000 gpm.
Class Ib aquifers occupy 7.4 percent of the state.
Sensitivity
Although 58 percent of Nevada is covered by
Class I aquifers, the potential for ground-water
contamination from shallow injection wells is low owing
to Nevada's low population density. The potential for
contamination is greater along major transportation
routes and in the vicinity of large population centers.
283
-------
Aquifer Vulnerability Map of Nevada
Class la
Class Ib
Class III
284
-------
<10GPM
20tolOOOGPM
200tolOOOGPM
Potential Well Yields In Nevada
285
-------
Areas covered by class I aquifers.
Each dot represents a population center.
Aquifer Sensitivity Map of Nevada
286
-------
Population Density of Nevada
(Dot equals one person per square mile)
Average Annual Precipitation in Nevada
287
-------
REGION 10
Idaho
Oregon
Washington
288
-------
IDAHO
General Setting
Idaho, which contains 83,564 square miles,
lies among the mountains and plateaus of the Northern
and Middle Rocky Mountains, Columbia Plateaus, and
Basin and Range physiographic provinces. The
mountains of northern and central Idaho are underlain
by folded and faulted Precambrian age sedimentary
and metamorphic rocks and Cretaceous age granitic
intrusives. To the south, these units are intruded and
overlain by Eocene age granites, lava flows, and
pyroclastic material. The mountains of east-central and
southeastern Idaho are composed of structurally
complex, Paleozoic to Mesozoic age marine and
nonmarine sediments and Late Te rtiary and Quaternary
age lava flows and pyroclastic material. Exposures of
Mesozoic age volcaniclastics and metasediments occur
locally in west-central Idaho. The remainderof the state
is underlain by jointed and locally faulted basalt flows
and associated pyroclastic and interbedded detrital
material and by glacial and alluvial deposits of Tertiary
and Quaternary age. Except for the southeastern
corner of Idaho, the entire state is drained by the west-
and north-flowing Snake River, and the west- and
northwest-flowing Spokane, Pend.Oreille, and Kootenai
rivers. The Bear River drains southeastern Idaho.
Annual precipitation varies with topography
and ranges from about 10 to 30 inches in the Snake
River Plain and surrounding highlands, and from 40 to
more than 60 inches in the central mountains. The
majority of Idaho's population, approximately a million,
is located along the Snake, Boise, and Coeur d' Alene
rivers. The remainderof the state is sparsely populated.
Daily use of fresh ground water amounts to about 4800
million gallons.
Unconsolidated Aquifers (Class la)
Glacial outwash and alluvial deposits occur
throughoutthe state, forming vulnerable and productive
aquifers. These generally unconfined systems are
present along modern streams and valleys, and consist
of gravel, sand, silt, and clay. Well yields commonly
range from 2 to 2,000 gpm, and may exceed 3,500 gpm.
About 38 percent of the state is covered by permeable
unconsolidated sediments.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Fractured volcanic bedrock aquifers occur
throughout the Snake River Plain in southern Idaho,
and locally along the state's western border. This
system consists of jointed and locally faulted, Tertiary
and Quaternary age basaltic and silicicf lows, associated
pyroclastics, and thin interbedded layers of gravel,
sand, silt, and clay. Ground-water movement is
controlled by the density of joints andfau Its, the presence
of rubble between flows, and other voids and cavities
produced by cooling and flow processes. Well yields
commonly range from 300 to 3,300 gpm, and may
exceed 7,000 gpm. Mississippian age limestone and
dolomite of the Madison Group crop out in southeastern
Idaho. Little data are available concerning these rocks
in Idaho because they are found in rugged, sparsely
populated areas. However, solutional features in the
Madison Group have been documented in Idaho. Class
Ib aquifers occupy about 31 percent of the state.
Variably Covered Aquifers (Class Ib-v)
Fractured volcanic bedrock aquifers, overlain
by an undetermined thickness of loess, occur along the
northwestern border of Idaho. Well yields commonly
range from 300 to 3,300 gpm, and may exceed 7,000
gpm. The vulnerability of this system is a function of the
thickness of the overlying cover. About 1 percent of the
state is underlain by Class Ib-v aquifers.
Semiconsolidated Aquifers (Class lla)
Exposures of Semiconsolidated sedimentary
and volcanic rocks occurlocallythroughout mountainous
parts of Idaho. These Tertiary age deposits consist of
poorly- to moderately-indurated gravel, sand, silt, and
clay that is interbedded with basalt and pyroclastic
material. Well yields commonly range from 100 to 2,500
289
-------
gpm, and may exceed 3,000 gpm. Surface exposures
of semiconsolidated aquifers occupy about 5.4 percent
of the state.
Sensitivity
About 70 percent of Idaho is covered by Class
I aquifers. The potentialfor ground-water contamination
from shallow injection wells is relatively low due to
Idaho's low population. The greatest sensitivity is along
major transportation routes, which include the most
dense concentration of population centers. An
abundance of agricultural drainage wells occurs in the
Snake River valley.
290
-------
Aquifer Vulnerability Map of Idaho
-------
2to2000GPM
100to2500GPM
300to3300GPM
Undefined
Potential Well Yields In Idaho
292
-------
Areas covered by class I aquifers.
Each dot represents a population center.
Aquifer Sensitivity Map of Idaho
293
-------
Population Density of Idaho
(Dot equals one person per square mile)
Average Annual Precipitation in Idaho
294
-------
OREGON
General Setting
Oregon contains approximately 97,073 square
miles, and is in a physiographically diverse region. The
western third of the state lies in the structural valleys
and rugged, extensively forested mountains of the
Pacific Border and Cascade-Sierra physiographic
provinces. South-central Oregon is in the block-faulted
mountains and valleys of the Basin and Range province,
while the remainder of the state lies in the arid plateaus,
lava plains, and mountains of the Columbia Plateaus
physiographic province. Oregon's coastal mountains
are composed of gently folded, Early to Middle Cenozoic
age marine sedimentary rocks and basalt and, to the
south, Late Paleozoic to Mesozoic age metamorphic,
sedimentary, and igneous rocks. To the east,
semiconsolidated nonmarine terrace deposits of the
Willamette Valley are bounded by altered Tertiary age
volcanic rocks of the Western Cascade Range. Except
for the Blue Mountains in northeastern Oregon, the
remainder of the state is underlain by Quaternary and
Tertiary age basalt and andesite flows, volcanic ash,
and glacial and alluvial deposits. The Blue Mountains
consist of Paleozoic to Mesozoic age metamorphic,
igneous, sedimentary, and altered volcanic rocks.
Eastern Oregon is drained by the Snake River
and its many tributaries. North-central and western
Oregon are drained by the Columbia River and its north
flowing tributaries, as well as by numerous shorter
rivers that discharge directly into the Pacific Ocean.
Annual precipitation varies with altitude and ranges
from about 25 to 180 inches in western Oregon and from
about 10 to 80 inches in the east. The majority of
Oregon's population, approximately 2.7 million, is located
along the Willamette Valley. The remainder of the state
is sparsely populated. Daily use of fresh ground water
amounts to about 660 million gallons.
Unconsolidated Aquifers (Class la)
A variety of unconsolidated deposits occusr
throughoutthe state, forming vulnerable and productive
aquifers. These generally unconfined systems are
present along modern streams, on terraces and
pediments above present flood plains, and within basins.
Alluvial sediments and exposures of outwash and
pediment deposits adjacent to the Columbia River
consist of unconsolidated sand, gravel, silt, and
pyroclastic debris. Outwash, terrace, and pediment
deposits in southeastern Oregon consist of
unconsolidated gravel, cobbles, and boulders, with
clay, silt, and sand. Unconsolidated dacite ash-flow
and ash-fall deposits floor parts of the Klamath Basin in
southwestern Oregon. Dune sands contain ash and
pumice. Well yields commonly range from 100 to 500
gpm, and may exceed 2,000 gpm. About 7.5 percent of
the state is covered by Class la aquifers.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Fractured volcanic bedrock aquifers occur
throughoutthe eastern three-fourths of the state, locally
within the Willamette Valley, and in northwestern Oregon.
These aquifers consists of faulted and jointed Miocene
and Quaternary age basalt, andesite, and minor rhyolite
flows, flow breccias, ash-flow tuffs, and interbeds of
tuffaceous sand, gravel, silt, and clay. Some flows
range from vesicular to scoriaceous. Ground-water
movement is controlled by the density of joints and
faults, andthe occurrence of permeable clastic interbeds.
Well yields commonly range from 50 to 500 gpm, and
may exceed 3,000 gpm. Surface exposures of fractured
volcanic bedrock aquifers occupy 44.5 percent of the
state.
Variably Covered Aquifers (Class Ib-v)
Fractured volcanic bedrock aquifers, overlain
by an undetermined thickness of low permeability wind-
blown clayey silt and fine sand, occur adjacent to the
Columbia River in northeastern Oregon. The
vulnerability of these aquifers is afunctionof the thickness
and permeability of the overlying sediments. About .6
percent of the state is covered by Class Ib-v aquifers.
295
-------
Semiconsolidated Aquifers (Class Ic)
Exposures of semiconsolidated nonmarine and
marine sediments occur along Oregon's coast, within
the Willamette Valley, and throughout the eastern part
of the state. These Quaternary to Tertiary age sediments
consist of poorly- to moderately-indurated sand, silt,
gravel, and clay. Nonmarine sediments east of the
Cascade Range are tuffaceous and pumiceous, and
locally grade into Miocene age basalt, andesite, and
rhyolite flows. Lignite and diatomite beds occur within
the section. Nonmarine sediments within the Willamette
Valley contain peat beds and boulderysoilsthat, locally,
are cemented with caliche. Marine sands are commonly
silty and contain lenses of gravel, peat, and clay. Well
yields generally range from 100 to 500 gpm, and may
exceed 2,000 gpm. Surface exposures of
semiconsolidated aquifers occupy about 14 percent of
the state.
Sensitivity
About 66.5 percent of Oregon is covered by
Class I aquifers. Aquifer sensitivity, however, is quite
low except in the upper reaches of the Willamette
Valley. Although the western two-thirds of the state
contains a large expanse of Class I aquifers, vulnerability
is low owing to the small population density. Most
population centers lie along major highways.
296
-------
Aquifer Vulnerability Map of Oregon
297
-------
"8
fe
•o
c
CL
O
o
o
o
o
O
O
\n
2
o
Potential Well Yields In Oregon
298
-------
I
CO
CD
W
O
O
I
O
NS
VO
VO
Areas covered by class I aquifers.
Each dot represents a population center.
-------
Population Density of Oregon (Dot equals one
person per square mile)
Precipitation
in inches
• 8 to 26
- 26 to 44
+ 44 to 62
A. 62 to 80
^ 80 to 98
Average Annual Precipitation in Oregon
300
-------
WASHINGTON
General Setting
Washington contains approximately 68,140
square miles, and lies in a physiographically diverse
region. The north trending Cascade-Sierra Mountains,
which contains many rugged and glaciated peaks,
roughly bisects the state. To the east lie the mountains
and arid high plateaus of the Northern Rocky Mountains
and Columbia Plateaus provinces. In the west, lies the
Puget Trough and Olympic Mountains subdivisions of
the Pacific Border province. The oldest exposed rocks
in the state, which crop out in the Northern Rocky
Mountains in northeastern Washington, consist of folded
and faulted Precambrian age sedimentary and
metamorphic rocks that are overlain by Paleozoic age
marine sediments. The Cascade Range in north-
central Washington is composed of structurally complex,
pre-Jurassic age metamorphic rocks that are flanked by
Paleozoic and Mesozoic age marine sediments.
Exposures of Mesozoic and Early Tertiary age granitic
rocks occur throughout the mountains in northeastern
and north-central Washington. Cretaceous and
Paleocene age continental deposits crop out in the
northwestern and central parts of the Cascade Range,
and nonmarine and marine sediments of similar age are
exposed in the Olympic Mountains in northwestern
Washington. The remainder of the state is underlain by
Tertiary to Holocene age volcanic rocks, continental
and marine sediments, and glacial and alluvial deposits.
Eastern Washington is drained by the south-
and westward-flowing Columbia River and its three
principal tributaries. Western Washington is drained by
numerous shorter rivers, which discharge directly into
Puget Sound and Pacific Ocean. Annual precipitation
rangesfromS inches in the eastto more than 200 inches
in the northwest. The majority of Washington's
population, approximately 4.65 million, is located in the
Puget Sound region and in several cities along major
rivers. The remainder of the state is sparsely populated.
About 1220 million gallons of fresh ground water are
used daily in Washington.
Unconsolidated Aquifers (Class la)
Glacial, alluvial, and eolian deposits form
vulnerable and productive aquifers. These generally
unconfined systems are present along streams and
throughout the glaciated and coastal parts of the state.
Outwash deposits and locally permeable till units consist
of unconsolidated sand, silt, gravel, and clay. Well
yields commonly range from 1 to 1,000 gpm, and may
exceed 10,000 gpm. Alluvial deposits consist of
unconsolidated silt, sand, gravel, cobbles, and clay.
Well yields range from 5 to 50 gpm, and may exceed
200 gpm. Eolian deposits consist of active dune and
beach sands. About 16.7 percent of Washington is
covered by unconsolidated aquifers.
Soluble and Fractured Bedrock Aquifers (Class
Ib)
Fractured volcanic rock aquifers occur
throughout southeastern and south-central Washington,
and consist of dense, columnartoplaty jointed, Miocene
age basalt flows with interbeds of unconsolidated sand
and gravel. Some flows range from vesicular to
scoriaceous. Ground-water movement is controlled by
the density of jointing, and the occurrence of permeable
clastic interbeds. Well yields commonly range from 150
to 3,000 gpm, and may exceed 6,000 gpm. Surface
exposures of fractured volcanic bedrock aquifers occupy
13.4 percent of the state.
Variably Covered Aquifers (Class Ib-v)
Fractured volcanic rock aquifers, overlain by
an undetermined thickness of silt, occur throughout
southeastern and south-central Washington. The
vulnerability of these systems is a function of the
thickness of the overlying low permeability sediments.
Class Ib-v aquifers occupy about 19 percent of the
state.
301
-------
Semiconsolidated Aquifers (Class Ic)
Ex posuresof semiconsolidated, nonmarine and
marine sediments occur along the Washington coast,
as well as in southwestern and south-central parts of the
state. These Tertiary to Quaternary age sediments
consist of poorly-to moderately-indurated sand, gravel,
silt, and clay. Nonmarine sands commonly are
tuffaceous and pumiceous, and locally calcareous;
marine sands tend to be shaley. Basalt flows and
diatomite beds occur locally within the section. Well
yields commonly range from 10 to 1,000 gpm, and may
exceed 4,500 gpm. Surface exposures of
semiconsolidated aquifers occupy about 4.5 percent of
the state.
Sensitivity
About 50 percent of Washington is covered by
Class I aquifers.The potential for ground-water
contamination from shallow injection wells is relatively
high in areas of high population density and along major
highways.
302
-------
Aquifer Vulnerability Map of Washington
303
-------
T3
0
-o
c
Potential Well Yields in Washington
304
-------
I
(0
0)
(0
o
Areas covered by class I aquifers.
Each dot represents a population center.
-------
•HI O*
,,«t>e^^\e>
».*«*
Ufl
,tsotv
-------
Section 3
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