DEVELOPMENT
OF A
GROUND-WATER MANAGEMENT
AQUIFER PROTECTION PLAN
A GUIDE TO CITIZEN PARTICIPATION
I
ANYTOWN, USA
THIS WATER SYSTEM IS
PROTECTED BY THE
PEOPLE
THAT IT SERVES
Prepared by
WAYNE A. PETTYJOHN
School of Geology
Oklahoma State University
StiUwater, OK 74078
1989
Under Subcontract to
Engineering Enterprises, Inc.
Norman, Oklahoma
EPA Contract No. 68-03-3416
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SECTION 1
DEVELOPMENT OF A GROUND-
| WATER MANAGEMENT
AND AQUIFER PROTECTION PLAN
I
! Introduction
i
I Communities smaller than
ICXOOOindividuals that depend on wells
asja source of water supply have spe-
cial cause to develop a ground-water
management and aquifer protection
plan. Generally their tax base and
other sources of income are small and
they can ill afford an expensive and
time consuming problem brought
about by contamination of their well
field. The best solution to the potential
forj contamination of a water supply is
the timely development, monitoring,
and enforcement of a plan that will
protect the ground-water system.
Prevention is far less costly than at-
tempts, commonly futile, to restore an
aquifer that has been contaminated
through use, neglect, ignorance, or
accident.
| The 1986 Amendments to the
Safe Drinking Water Act established a
national program to protect ground-
water resources that are used for public
wajter supplies. The U.S. Environ-
mejital Protection Agency is attempt-
ing to achieve the goals of the Act by
me|ans of individual state Wellhead
Protection Programs that "protect
wellhead areas within their jurisdic-
tion from contaminants which may
hajre any adverse effect on the health of
persons." The Wellhead Protection
Program includes what is known as
Wellhead Protection Areas, which are
defined as "the surface and subsur-
face area surrounding a water well or
wellfield, supplying a public water
system, through which contaminants
are reasonably likely to move toward
and reach such a water well or well-
field."
It should be noted that although
states are encouraged to develop a
Wellhead Protection Program, the
Environmental Protection Agency is
not authorized to establish such a
program in a state that does not wish
to participate. The only impact on a
state that does not so choose is the loss
of grant funds. On the other hand, it
makes good sense, both from a practi-
cal and monetary viewpoint, to develop
and implement some type of plan to
monitor and protect the water supply,
the one resource that is absolutely es-
sential to the survival and well being of
every community.
The Wellhead Protection Pro-
gram differs from a ground-water
management and aquifer protection
plan in that the former is concerned
with public health and individual public
water supply wells, while the latter
encompasses a broader scope by deal-
ing with the entire aquifer system,
both as it presently exists and in the
future. Furthermore, in many small
communities a large percentage of the
total water usage may be derived from
private rather than public sources.
The health of these users also needs to
be protected as do the workers in plants
and facilities that rely on private or
semiprivate supplies. Likewise, water
supplies used for :industrial process-
ing and the raising of livestock should
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meet certain chemical and biological movement so that a protection plan
criteria. can be developed by a municipality.
Contamination of ground-water
supplies is generally the result of (1)
selected past activities, (2) aproblem(s)
with the existing well or wellfield, in-
cluding pumping, inadequate con-
struction, operation, maintenance, or
training of personnel, (3) waste dis-
posal, (4) accidents, and (5) existing
activities. Once recognized, each of
these potential sources of contamina-
tion can be managed to reduce the
likelihood of an adverse impact on the
supply. For example, inadequacies of
the public water supply system can be
overcome with well construction codes,
inspections, repairs and modifications,
and operator training courses. Acci-
dents can not be avoided, but they can
be anticipated, at least as far as loca-
tion is concerned, and a response plan
that would have the least impact on
ground-water can be formulated. Po-
tential contamination brought about
by waste disposal can be addressed by
educational activities, by inventories,
by municipal ordinances and zoning,
by cleanup and restoration, and by
organizing alternative means of dis-
posal, such as collection stations.
The purpose of this report is to
provide a number of ideas, guidelines,
and techniques that can be used to
formulate aground-water management
and aquifer protection plan with mini-
mal cost. Of necessity, the report is
generalized because each ground-water
supply system is unique. Nonethe-
less, the concepts presented can be
used to develop a general understand-
ing of ground-water occurrence and
Most likely the plan could be
improved by hiring competent geologi-
cal and engineering consultants, al-
though this can be an expensive under-
taking. In most states, a variety of
local, state, or federal agency person-
nel, such as in health departments,
the state and federal Environmental
Protection Agency, or the state or fed-
eral geological survey, are more than
willing to provide data and evaluations.
Any ground-water protection
plan must consider potential sources
of contamination, the geology of the
area, and the local hydrogeology be-
cause they exert a major control on
water quality. In addition, once a plan
is developed there must be a move to-
ward education of the public, monitor-
ing, and enforcement. None of these
activities need be expensive, although
they can become time consuming. The
municipality and responsible individu-
als must not be allowed to become
complacent simply because no con-
tamination events have occurred.
In some cases the implementa-
tion of a ground-water management
and aquifer protection plan may be
hindered by local politics and special
interest groups, both of which work
against the common good. A prime
example is a small midwestern town
with a population of about 1500. Nearly
the entire income for the village is
derived from the sale of water, which is
pumped from shallow wells distrib-
uted through the corporation and on
the flood plain of an adjacent river.
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The wells produce from a mass of
suriicial sand that is particularly vul-
neriable to contamination from the
surface. The city commission was very
interested in an aquifer protection plan
uniil they realized the various implica-
tions: a spill of liquid fertilizer at a
local distribution plant that contami-
nated the ground water, a dry well at a
slaughter house that receives blood
and other wastes, a new landfill in a
most inappropriate location, and an
abundance of abandoned municipal
wells. The spill, the dry well, and the
lan'dfill are all directly upgradient from
one or more municipal wells; without
corrective action, it is only a matter of
tirrie until some of the wells become
contaminated. However, the owners of
the1 bulk plant and the slaughter house
are very influential citizens, the loca-
tion of the new landfill represents a
haij-d fought battle won by the commis-
sioners, and it would be a relatively ex-
pensive undertaking to adequately plug
all jof the abandoned city wells. The
ground-water management and aqui-
fer (protection plan was quickly tabled
and, consequently, the citizens of the
community will eventually suffer from
the effects of poor government.
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SECTION 2
states west of the Rocky Mountain
front (fig. 2.1).
INTRODUCTION TO GEOLOGY
A few basic principles of geology
are essential for the development of an
aquiferprotection planbecause ground
water occurs in rocks and unconsoli-
dated earth materials. Certain types of
rocks are characteristic of various
regions in the United States. More-
over, each rock type is sufficiently
uniform, even in widely separated
areas, so that some features can be
generalized.
The crust of the earth is com-
prised of three types of rocks igneous,
metamorphic, and sedimentary. Igne-
ous rocks, such as granite.solidified
from molten material either within the
earth or on or near the surface. Meta-
morphic rocks, such as slate and
marble, were formerly pre-existing
rocks that have changed by an In-
crease in temperature and pressure,
and by chemically active fluids. Sedi-
mentary rocks, examples being shale,
sandstone, and limestone, are the
result of weathering of pre-existing
rocks, their subsequent erosion, and
finally deposition.
Igneous and metamorphic rocks
are generally very hard, crystalline,
and fractured. For the most part they
occur in the central part of old or
existing mountain chains. They com-
prise but a small part of the land
surface of the United States and occur
notably in the Appalachian Mountains,
New England, New York, Michigan,
Wisconsin, Minnesota, and in several
For the most part, igneous and
metamorphic rocks neither store nor
transmit much water. Most, however,
are fractured to some degree and can
provide a modest amount of water to
wells.
Although igneous and metamor-
phic rocks are generally poor sources
of water, in several areas they are the
only source. In places such as these,
considerable care should be taken
because a number of these water-
bearing units can be easily contami-
nated. This vulnerability exists be-
cause the soil cover may be thin and
fractures in the rocks may extend to
land surface. The fractures may per-
mit direct infiltration of precipitation,
as well as contaminants, directly into
the aquifer. There are few, if any,
physical, chemical, or biological reac-
tions available within the rock to at-
tenuate the contaminant, other than
dilution. Moreover, the contaminated
water may flow rapidly in unantici-
pated directions.
Sedimentary rocks were depos-
ited in a body of water or on the land
surface by running water, by wind, or
by glaciers. The most common sedi-
mentary rocks are shale, siltstone,
sandstone, limestone, and glacial till.
Unconsolidated sedimentary deposits
include sand, gravel, silt, and clay;
they are changed to rock by the proc-
ess of lithification.
Although sedimentary rocks
appear (fig. 2.1) to be the dominant
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Limestone
Sand and gravel
Basalt
Rocks other than
those listed
Figure 2.1 Distribution of major rock types.
type, in reality they make up but a
small percentage of the earth. They do,
however, form a thin veneer over much
of the earth's surface, are the type
moist readily evident, and serve as the
pritnary source of ground water.
i
1 Many sedimentary rocks store
vasjt quantities of water, but some lack
pripiary openings, such as many lime-
stones and shales, and are poor sources
of yater. The latter serve as confining
units because water does not easily
move through them. Sedimentary
rocks that form the best aquifers in-
clude sandstone and limestone that
contains caves and other openings
enlarged by solution of the rock. Re-
gions typified by caves and solution
openings are called karst areas. Karst
areas are common in parts of Mis-
souri, Indiana, and Kentucky, as well
as many other regions underlain by
limestone.
Limestone with solution open-
ings and fractured sandstone also are
subject to contamination in the same
manner as the crystalline rocks. Karst
areas are particularly troublesome,
even though they can provide large
quantities of water to wells and springs.
Because of the pervasive nature of the
openings in the rocks, it is usually
difficult to trace the path of the con-
taminant, which may appear discharg-
ing from a spring miles away. In
addition, the water may flow very rap-
idly, and there is no filtering action to
degrade the waste. Not uncommonly
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in limestone areas, a well owner may
be totally unaware that he is consum-
ing or providing unsafe water. In fact,
in several places sinkholes, disposal
wells, or abandoned water wells have
been used to dispose of wastewaters
into limestone aquifers that also serve
as sources of drinking water.
Sand and gravel deposits, par-
ticularly those found alongmajorwater
must be remembered, however, that
coarse-grained, unconsolidated depos-
its not only provide large yields of
ground water but that they also may
be readily contaminated.
A few thousands of years ago,
glaciers covered a vast area in North
America, the southern boundary
stretching from Montana, across the
Dakotas, Nebraska, Kansas, and north-
Glacial lake deposits
Glacial deposits
Figure 2.2 Distribution of glacial deposits.
courses, such as the Ohio, Missis- ern Missouri into Illinois, Indiana, Ohio,
sippi, and Missouri Rivers and their and New York (fig. 2.2). Although less
tributaries, also are prolific suppliers widespread, glaciers also were present
of ground water. Likewise,.the coarse- in the northwestern states. The re-
grained alluvial fill in the intermoun- mains include deposits of sand and
tain valleys of the west and southwest gravel along streams and rivers, broad,
store vast quantities of water and relatively thin, sheet-like deposits of
provide significant yields to wells. It sand and gravel, called outwash, and
6
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glacial till, which in most places is a
miiture of clay, sand, gravel, and
boulders. The coarse-grained glacial
deposits serve as major aquifers, while
the till and clay act as confining layers.
j Sedimentary rocks usually are
deposited in a horizontal or nearly
hoijizontal position, which is easily
discernable because of bedding planes
within the rock. The fact that many
rocks are found overturned, displaced
vertically or laterally, and squeezed
into open or tight folds, clearly indi-
cat:es that the crust of the earth is not
at {rest. There is a constant battle
between the forces of destruction
(erosion) and construction (earth
movements).
i
Folded rocks are common in and
adjacent to former or existing moun-
tain ranges. Anticlines consist of rocks
folded upward into an arch and their
counterpart, synclines, are folded
downward like a valley (fig. 2.3). Al-
though the rocks may be dipping a few
degrees or more, the land surface
usually does not greatly reflect this
structure.
Fractures in rocks are either
joints or faults. A joint is a fracture
along which no movement has taken
place, but a fault implies movement.
The movement, the primary cause of
earthquakes, may range from a few
inches to several tens of miles. Frac-
tures, "whether joints or faults, may
exert a major control on ground-water
movement because water can easily
move through them unless they are
filled with clay or mineral matter.
The difficulty of evaluating wa-
ter and contaminant movement in
fractured rocks is that the actual di-
rection of movement may not be in the
direction of the water-level gradient,
but rather in some different though
related direction. The problem is fur-
ther compounded by the difficulty in
locating the fractures.
In summary, ground water oc-
curs in many types of rocks and un-
consolidated sediments. From the
point of view of contamination, regard-
less of the rock type, it is the permea-
bility or interconnection of the open-
ings in rocks that have the most sig-
Map View
Anticline
Syncline
Figure 2.3 Sedimentary strata folded Into an anticline
and a syncline.
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nlficance. That is, permeable materi-
als can readily allow the movement of
contaminants into the ground-water
system. Furthermore, permeable
materials at or near the land surface
are the most susceptible to contami-
nation because they permit contami-
nants direct access to the water-bear-
ing zone. It is ironic that shallow and
surficial aquifers, which are commonly
the most productive, the most readily
recharged by precipitation, and the
least costly for well construction, are
those that are the most vulnerable to
contamination to activities that occur
on the land surface.
8
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! SECTION 3
i
i
I
FUNDAMENTALS OF GROUND-
WATER OCCURRENCE AND MOVE-
i MENT
i
i The material in this section is
designed to provide a general intro-
duction to ground water, how it can be
evaluated, and some of the controls on
its jstorage and movement. It is not
intended to be a definitive discussion.
Sufficient material is included, how-
evejr, for an individual or group of
individuals to develop a generalized
understanding of their ground-water
sysjtem so that an aquifer protection
plan can be developed.
j
I If one were to dig a hole in the
ground, the first few feet or so would
probably be dry, but as the depth
increased, the soil would become moist
and eventually water would stand in
the! bottom of the hole. The surface of
the' water in the hole or well is called
theiwater table. The relatively dry zone
abojve the water table is the unsatu-
rated zone, while below the water table
lies; the saturated zone, in which all of
the[open spaces are filled with ground
water. The unsaturated zone is impor-
tant because many physical, chemi-
cal, and biological reactions occur
within it that tend to degrade waste
majterials and other contaminants. It
is commonly called the "living filter"
and the thicker it is, the more likely it
will provide protection against con-
tamination from surface or near sur-
face sources.
The water table, in a general
way, conforms to the contours of the
land surface, although it lies at a greater
depth under hills than it does beneath
valleys. In humid and semiarid re-
gions, the water table normally lies
between 0 and 25 feet below the land
surface. In some desert regions along
mountain fronts the water table may
occur at depths of hundreds of feet.
Below the water table, rocks
serve either as confining units or
aquifers. Confining units are charac-
terized by low permeability and water
does not readily pass through them,
although they may store large quanti-
ties. Examples include shale, clay,
and silt. An aquifer has sufficient
permeability to permit water to flow
through it with relative ease and, there-
fore, it will provide a usable quantity of
water to a well or spring. The most
common examples include sandstone,
limestone, fractured crystalline rocks,
and sand and gravel.
Water occurs in aquifers under
two different conditionsunconfined
and confined (fig. 3.1). An unconfined
or water-table aquifer has a free water
surface, which is the water table. The
water table rises and falls in response
to differences between inflow (recharge)
of water to the aquifer and outflow (dis-
charge) of water from it. As a general
rule, unconfined aquifers are most sub-
ject to contamination from the surface
and from shallow disposal wells.
A confined or: artesian aquifer is
overlain by a confining unit, such as
clay, and the water in the aquifer is
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S-S-V'V
^J1"^"!
*..*.*.'
l
ffj-tj-fj-lfi
1-1-1-1-1-N
fl+frffSff+f*
"iftft/W
'Sซ,Vป%-VซJ
1'
Flowing WeU
^ Water table ;'>.a<-.^ft'f4'fs'
jUnconfined aquifex
* '"'
Confining unit
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^^^^^^j'ซj|"^"^"j|"j|"j|"Jl"Af^,
,ป.. S.V. .%.-.. S-S-S. ...%. 1."S'-i'1.iy
tfV Confined aquifer^
Confining unit.
,
Confined aquifersj
frfftftfti'vflff
t.
*",'*,**,***'*****''
*>%%>
''
Figure 3.1 Major types of aquifer and confining units.
under sufficient pressure to rise above the water table lies below a stream or
the base of the confining unit, if it is canal, water may infiltrate from this
peetratedbyawell. In some cases, the source also. Interaquifer leakage, or
water is under enough pressure to flow flow from one aquifer to another, is
from a well at the surface (fig. 3.1). probably the major source of water in
These are called flowing artesian wells, deeper, confined aquifers.
The water level in a well tapping a
confined aquifer is called the potenti- An aquifer serves two functions,
ometric or water-pressure surface. The one as a conduit through which flow
confining unit that overlies, the aquifer occurs, and the other as a storage
may provide a considerable degree of reservoir. This is accomplished by
protection against the downward inftt- means of openings in the rock. The
tration of contaminants. openings include those between indi-
vidual grains and those present as
Fresh ground water is derived fractures, tunnels, and solution open-
largely by infiltration of precipitation, ings. The openings are primary if they
a process that is called recharge. Where were formed at the time the rock was
10
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deposited, or secondary if they devel-
oped after lithification. Examples of
the| latter include fractures and solu-
tion openings.
I
| Porosity, expressed as a per-
centage or decimal fraction, is the ratio
between the openings in the rock and
the total volume of the rock. It demies
thej amount of water a saturated rock
volume can contain. If a saturated
rock is allowed to drain by gravity, not
all jof the water it contains will be
released. The volume drained is called
the specific yield, a percentage, and
the; volume retained is called the spe-
cific retention. It is the specific yield
that is available to wells. Typical val-
ues for several rock types are listed in
Tab1 le 3.1.
Material Porosity Specific Specific
! % Yield Retention
Soil 55 40 15
Clay 50 2 48
Sailid 25 22 3
Gravel 20 19 1
Limestone 20 18 2
Sandstone 11 6 5
I
Table 3.1 Selected values of po-
rosity, specific yield,
! and specific retention
1
{ The term permeability (P) is used
in 3. qualitative sense, while hydraulic
conductivity (K) is a quantitative term.
In jthis report they are expressed in
units of gpd/ft2 (gallons per day per
square foot). Both terms refer to the
easp with which water can pass through
an (aquifer, that is, they are expres-
sions of the inteconnection of the
openings in the rock. The hydraulic
conductivity, which allows an aquifer
to serve as a conduit, ranges between
wide extremes from one rock type to
another and even, within the same
rock. Typical values for most common
water-bearing rocks are shown in Table
3.2.
Material
Coarse sand
Medium sand
Mixed sand
Sandy gravel
Clean gravel
Limestone
Hydraiolic Conductivity*
gpd/ft2
1500
1000
500
; 2000
4000
2000
*Hydraulic conductivity is closely
related to sorting and the size and
number of fractures. These values
are provided only as guidelines.
Table 3.2 Hydraulic conductivity of
selected rocks.
The hydraulic gradient (I), the
slope of the water table or potentiom-
eiric surface, is the change in water
level per unit of distance along the
direction of maximum "water-level
decline. It is determined by measuring
the water level in two or more wells (fig.
3.2). A general Impression of the
hydraulic gradient of the water table
can be obtained by examining a topo-
graphic map since the water table, in a
subdued manner, tends to parallel the
surface topography. The hydraulic
gradient is the driving force that causes
ground water to move. It is expressed
in consistent units, such as feet per
foot. For example, if the difference in
11
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1000 feet
fflfflftftftftftftfl^ Water Table
Elevation
.
Elevation = 87O
:*!*:*:*:*:*.
*****ป*****'
******
Figure 3.2 The hydraulic gradient (I) is the slope of the water
table or potentiometric surface.
altitude of the water level in two wells
1000 feet apart is 5 feet, the gradient is
5/1000 or .002.
A water-level map is a graphical
representation of the gradient. One
can be prepared by plotting water-level
measurements on a base map and
then contouring them. An example is
shown in Figure 3.3.
The direction of ground-water
flow is determined by drawing a series
of flow lines that intersect the water-
level contours at a right angle. Flow
lines are imaginary paths that would
be followed by particles of water flow-
ing through an aquifer (fig. 3.3).
Ground water moves both
through aquifers and confining units,
but it requires more energy to move
water through fine-grained material
than it does through coarse and, there-
fore, lateral flow in confining units is
small when compared to aquifers, but
vertical leakage through them can be
significant.
The average velocity of ground
water is generally much less than most
individuals anticipate. In general it
12
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Water-level contour
85
Waterrle.vel. elevation. - 88
Extent of aquifer
\
\
\
Scale (mi)
88 -
Figure 3.3 Water-level contour map and flow lines
i
ranges from less than 5 feet per year to (see Tables 3.1 and 3.2). The water
more than 5 feet per day. The very slow level in a well at the spill lies at an
movement is the major reason why altitude of 825 feet and in a well 1000
ground water, once contaminated, can feet directly down the hydraulic gradi-
rernain in an unusable or undesirable ent the water level lies at an altitude of
state for years or even decades. 815 feet. How long will it be before the
Ground-water velocity can be estimated second well is contaminated by fertil-
by pie following equation. izer?
j v = KI/7.48n
where v is the average velocity, in
feet per day,
; n is the specific yield,*
anol the other terms are as previ-
ously defined.
i
i
i For example, assume there is a
spill of liquid fertilizer that flows
thrjough the unsaturated zone and
quickly reaches a water-table aquifer.
Th<2 aquifer consists of sand and gravel
that has a hydraulic conductivity of
20J)0 gpd/ft2 and a specific yield of .20
v = (2000gpd/ft2HlOft/ 1000ft)/7.48 X .20
=13.4 ft/day
* Actually effective porosity, which is
slightly smaller than specific yield is
the proper term, but it makes little
difference in our analysis since we are
only interested in rather broad gener-
alizations.
Time = 1000ft/13.4 ft/day = 74.6
days or 2,,5 months
Both the velocity and time of travel are
only rather crude estimates, but they
13
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do provide a general impression of the
rate of contaminant movement.
Hydrogeologists commonly use
the term transmissivity (T) to describe
an aquifer's capacity to transmit
water.Transmissivity, described in
units of gpd/ft (gallons per day per foot
of aquifer thickness), is equal to the
product of the aquifer thickness and
hydraulic conductivity. That is:
T = Km
Anotherimportanttermis stora-
tMty (S), which describes the quantity
of water that an aquifer will release
from or take into storage per unit
surface area of the aquifer per unit
change in water level. In unconfined
aquifers the storativity is, for all prac-
tical purposes, equal to the specific
yield and, therefore, it should range
between about .01 and .3. The stora-
tivity of confined aquifers is substan-
tially smaller because the water re-
leased from storage when the head
declines conies from the expansion of
water and compression of the aquifer,
both of which are very small. For
confined aquifers storativity generally
ranges between .001 and .00001. The
consequence of the small storativity of
confined aquifers is that to obtain a
sufficient supply from a "well there
must be a large pressure change
throughout a wide area. This is not the
case with unconfined aquifers because
the water is derived from gravity drain-
age and dewatering of the aquifer.
Ground-water levels fluctuate
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878-
876-
874-
872-
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1989
1988
Figure 3.4 A hydrograph shows the fluctuation of the water level in a well.
14
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throughout the year in response to
natural changes in recharge and dis-
charge, to changes in pressure, and to
artificial stresses (fig. 3.4). Fluctua-
tions that involve changes in storage
are generally more long lived than those
caused by pressure changes. Most
ground-water recharge, which causes
thej water level to rise, takes place
duijing the spring and fall. After these
periods, which are a month or two
lon^, the water level generally declines
throughout the rest of the year be-
cause the ground water discharges
into streams, springs, seeps, lakes,
and wells, and is removed by plants
where the water table lies at depths
generally less than 15 feet.
; When a well is pumped, the water
level in its vicinity declines to provide a
gradient to drive water toward the well.
The gradient becomes steeper as the
well is approached because the flow is
converging from all directions and the
area through which the flow is occur-
ring becomes smaller. This results in
a cone of depression in the water table
or potentiometric surface around the
weU (fig. 3.5). Relatively speaking, the
cone of depression around a well tap-
ping an unconfined aquifer is small if
compared to that around a well in a
confined system. The former may be a
few tens to a few hundreds of feet in
diameter, while the: latter may extend
outward for miles.
Cones of depression from sev-
eral pumping wells may overlap and,
since their drawdown effects are addi-
tive, the water-level decline through-
out the area of influence is greater
than from a single cone. In ground-
water studies, and particularly con-
tamination problems, evaluation of the
cone or cones of depression can be
critical because they represent the area
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Confined
"-"--"-
er tf
-
". Confining unit
Figure 3.5 The cone of depression around a pumping well represents a
i steepening of the hydraulic gradient toward the well.
15
-------
of capture of water and contaminants
and the Increase in the hydraulic gra-
dient, controls ground-water velocity
and direction of flow. In fact, properly
spaced and pumped wells can be used
to provide a mechanism to control the
migration of contaminated ground
water.
Cone of Depression
mmmmmmmmmmmm
Figure 3.6 The water-level declined in and around a pumping well is called the
drawdown.
16
-------
! The decline of the water level
caused by a pumping well is called the
drawdown and the pre-pumping level
is the static level (fig. 3.6). The water
level in a well that is pumping is called
the! pumping level. During pumping
the! drawdown or water level in the
pumped well is greater than the
drawdown adjacent to the casing. The
difference is called well loss. Well loss
is related to flow conditions in the
vicinity of the screen and to the screen
proper. As the screen becomes en-
crusted, as they generally do over time,
the! well loss increases. The discharge
rate of the well divided by the differ-
ence between the static and the pump-
ing level is called the specific capacity.
The specific capacity indicates how
mu;ch water the well will produce per
foot of drawdown.
.j
i
i Specific capacity = Q/s
i
i
wh^re Q is the discharge rate, in
gpm, s is the drawdown, in feet.
i
i
j For example, if a well produces
100 gpm and the drawdown is 8 feet,
the' well will produce 12.5 gallons per
minute for each foot of available
drawdown. One can rather crudely
estimate the aquifer's transmissivity
by multiplying the specific capacity by
2000. The transmissivity can then be
divided by the thickness of the aquifer,
as Determined from well logs, to deter-
mine the hydraulic conductivity.
i
A Simple and Practical Approach To
| Estimate Velocity
i
The purpose of this generalized
description of hydrogeology is to pro-
vide the reader with an impression of
the manner in which ground water
occurs and an aquifer functions. One
of the purposes of the aquifer protec-
tion plan which follows is to indicate,
in a generalized way, the manner in
which contaminants might move in a
ground-water system so that appro-
priate and timely steps can be taken.to
evaluate a potential problem. Here,
the key word is "generalized", which
means that the directions of flow, the
velocity and rates, as well as the degree
of natural protection are not absolute
but rather are designed to provide only
an impression. Keeping these restric-
tions in mind, it is not unreasonable to
base some techniques on assumptions
that are not entirely correct for every
case, but yet are sufficiently near real
values to be useful for their intended
purpose.
Several field and laboratory
methods are available to calculate
hydraulic parameters, but rarely are
time and funds available to a small
municipality to conduct such tests.
Nonetheless, it maybe the responsibil-
ity of the water purveyor, city engineer,
or other designated person, to esti-
mate values in order to complete the
aquifer protection plan. The following
are four different approaches that can
be used to estimate hydraulic conduc-
tivity and ground-water velocity.
The first method is to contact
personnel in a state or federal agency,
such as the state geological survey or
the U.S. Geological Survey, and ask
for their expert opinion. The second
method is to compare the descriptions,
of the earth materials found in
17
-------
geologist's or driller's logs of the mu-
nicipal wells with tables of information
present in many textbooks. A third
method is merely to guess, perhaps
using the tables in this report. The
final technique is to estimate hydrau-
lic conductivity and velocity directly
from easily obtainable measurements.
It is a good management prac-
tice to periodically determine the spe-
cific capacity (Q/s) of each well in a
well field. When the specific capacity
begins to decline, one needs to con-
sider renovating the well because the
decline is probably related to incrusta-
tion of the well screen. The greater
drawdown caused by incrustation
increases the cost of pumping the
water.
Sample Calculation
Assume that the rate of dis-
charge of a municipal well is 200 gpm
(measured) and that after 8 hours the
drawdown in the pumping well is 10
feet (measured). This means that the
specific capacity of the well after 8
hours of pumping is 20 gpm/ft (200
gpm/10 ft of drawdown). In this case
well loss is ignored.
As described previously, trans-
missivity is equal to the hydraulic
conductivity (permeability) multiplied
fay the aquifer thickness and that an
estimate of transmissivity can be ob-
tained by multiplying specific capacity
by 2000. Therefore:
Specific capacity can be measured at
the well and the aquifer thickness can
be estimated from the driller's log of
the well. In this case, assume that the
log of the well indicates a saturated
thickness of 50 feet and, using the
specific capacity (20 gpm/ft) calcu-
lated above:
K= 2000X20 =8QO
50
Next measure the hydraulic gradient,
either by using the water-level differ-
ence between two wells or a water-level
map. Assume that the difference in
water lever between two wells is 20 feet
and that the wells are a mile apart.
That is:
I = 20/5280 = .004
The equation for ground-water veloc-
ity contains specific yield (effective
porosity) in the denominator. Assume
for all of the calculations that Specific
yield is . 15. The velocity equation can
now be written in the form:
v=.9KI
Therefore, using the data calculated
above:
v = .9 x 800 x .004 = 3 feet per day
2000 Q/S
Aquifer thickness
18
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SECTION 4
SOURCES OF GROUND-WATER
I CONTAMINATION
i Introduction
I
i
I One of the starting points in a
ground-water protection plan is to
determine all of the potential sources
of contamination, establish their loca-
tions, and become aware of the types of
chemicals that might be present. Once
this is done, each source can be evalu-
ated relative to the vulnerability of the
aqikifer. This, in turn, will provide an
indication of the degree of concern for
each source.
Locating potential sources of
contamination may not always be a
simple process. Certainly the most
obvious existing sources, such as
abandoned gas stations, the city
landfill, and various industrial works,
are readily apparent, but two other
areas also must be considered. The
first consists of minor sources, such as
the weekend auto repair shop, where
brake and power steering fluid, as well
as used oils, are dumped directly onto
the ground behind the garage or in a
dry well, or the part: time photographer
who disposes of spent developing
chemicals out by the garbage cans (fig.
4.1).
.'"
Mom & Pop's
Auto Repair and Photos
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'Figure 4.1 Minor sources of contamination, although difficult to
' locate, it may be of considerable importance in aquifer
i protection.
19
-------
The second consideration repre-
sents those facilities and activities that
have been gone for years or even dec-
ades. Where, for example, was the
gasworks plant that burned in 1918,
where was the city dump in 1923, the
shingle factory that was torn down in
the 1930's, or the military airfield that
was abandoned in 1945? Records of
facilities such as these may not be
available, but one vast, largely un-
tapped informational data base is at
hand ... the senior citizens. In fact,
senior citizens maybe the only source
of information.
As water moves from the land
surface, into and through the soil,
eventually reaching the water table,
the quality changes. The changes may
be either natural or man-influenced
and it is often impossible or at least
difficult to determine the origin of many
water-quality problems. Although the
chemical quality of water in surficial or
shallowaquifers mayrange within fairly
wide limits from one time to the next,
deeper ground water maintains nearly
constant chemical and physical prop-
erties where the aquifer is unstressed
by pumping.
In most places the greatest po-
tential for shallow ground-water con-
tamination is by selected activities that
occur on the land surface (table 4.1)
and by what are known as Class V
disposal wells (table 4.2).
Ground-Water Quality Problems that Origi-
nate on the Land Surface
1. Infiltration of contaminated
surface water
2. Land disposal of liquid and
solid waste
3. Stockpiles
4. Dumps
5. Disposal of sewage and water-
treatment plant sludge
6. Deicing salt usage and storage
7. Animal feedlots
8. Fertilizers and pesticides
9. Accidental spills
10. Particulate matter from air
borne sources
Ground-Water Quality Problems that Origi-
nate in the Ground Above the Water Table
1. Septic tanks, cesspools, and
privies
2. Holding ponds and lagoons
3. Sanitary landfills
4. Waste disposal in excavations
5.. Leakage from underground
storage tanks
6. Leakage from underground
pipelines
7. Artificial recharge
8. Sumps and dry wells
Ground-Water Quality Problems that Origi-
nate in the Ground Below the Water Table
1. Waste disposal in wet excava
tlons
2. Drainage wells and canals
3. Well disposal of wastes
4. Underground storage
5. Mines
6. Exploration wells
7. Abandoned wells
8. Water-supply wells
9. Ground-water development
Table 4.1
Generalized sources of ground-water
quality degradation.
20
-------
Drainage Wells (dry weiisj: agricui-
ฑirjal drainage wells, storm water drain-
age wells, improved sinkholes, indus-
Tial drainage wells, special drainage
Domestic Wastewater Disposal Wells:
anfreated sewage disposal wells, cess-
pools, septic systems (undifferentiated),
sepltic systems (well disposal method),
septic system (drainfield disposal
nethod), domestic wastewater treat-
cneht plant effluent disposal wells.
ndustrial/ Commercial/Utility Dis-
Dosal Wells: cooling water return flow
arells, industrial process water and
iva&te disposal wells, automobile serv-
ce |station disposal wells.
Recharge Wells: aquiier recharge wells,
saline water intrusion barrier wells,
subsidence control wells.
VLiijieral and Fossil Fuel Recovery Re-
ated Wells: mining, sand, or other
oackfill wells, solution mining wells,
n-situ fossil fuel recovery wells, spent-
arine return flow wells.
jepthermal Reinjection Wells: electric
wer reinjection wells, direct heat
einjection wells, heat pump/air con-
litioning return flow wells, ground-
vajter aquacultural return flow wells.
vusceiianeous wens: Radioactive waste
iisposal wells, experimental technol-
jgjr wells, aquifer remediation related
veils, abandoned drinkingwaterwells.
; Table 4.2
Generalized listing of Class V wells.
Class V disposal wells, which
likely exceed a half million units, in-
clude a diverse array of facilities, rang-
ing from grease pits and industrial
septic tank systems to storm runoff
collectors, that are used to inject a
broad range of waste waters into the
subsurface. Most, of these disposal
facilities are shallow, extending into
the unsaturated zone or a few feet into
a shallow or surficiial aquifer that has
sufficient permeability to accept the
waste. Although attempts are being
made at state and federal levels to
inventory and control their siting and
use, few individuals are fully aware of
the potential of the exceedingly high
adverse impact of many Class V wells
on underground sources of drinking
water in the United States. In addi-
tion, even fewer are; sufficiently knowl-
edgeable about the vulnerability of the
aquifers that provide their water sup-
piy-
Water Quality Problems Related to
Septic Systems
Probably the major cause of
ground-water contamination in the
United States is effluent from septic
tanks, cesspools, arid privies (fig. 4.2).
Individually of little significance, these
devices are important in the aggregate
because they are so abundant and
occur in every area not served by
municipal or privately owned sewage
treatment systems,, The area that each
point source affects is generally small,
since the quantity of effluent is small,
but in some limestone areas effluents
may travel long distances in subterra-
nean cavern systems. Residential or
21
-------
Figure 4.2 The cone of depression surrounding a water-supply well may
cause septic tank effluent to migrate to the well.
commercial septic systems serving 20
or more people are included in the
Class V well category.
Artificial Ground-Water Recharge.
Artificial recharge includes a
variety of techniques used to increase
the amount of water infiltrating to an
aquifer. It consists of spreading the
water over the land or placing it in pits,
ponds, or wells from which the water
will seep into the ground.
Waters used for artificial re-
charge consist of storm runoff, irriga-
tion return flows, stream water, cool-
ing water, and treated sewage effluent,
among others. Obviously the quality
of water artificially recharged can have
a major effect on the water in the
ground.
Water Quality Problems Related To
Dry Wells
Dry wells may locally cause some
contamination problems and in places
where these structures are adjacent to
a stream, bay, lake, or estuary, they
may pollute such surface water bodies
and lead to a proliferation of the growth
of algae and water weeds. These struc-
tures are commonly used to collect
runoff or spilled liquids, which will
infiltrate through the well (fig. 4.3).
Dry wells are typically installed to solve
surface drainage problems, so they
may transmit to ground water what-
ever pollutants are flushed into the
well.
Where surficial materials con-
sist of heavy clay, flat-lying land may
be poorly drained and contain an
abundance of marshes and ponds.
Drainage of this type of land is gener-
ally accomplished with field tiles and
drainage wells. A drainage well is
22
-------
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Figure 4.3 Sumps dry wells, and underground storage tanks are
| potential sources of ground-water contamination.
merely a vertical, cased hole in the
grdund or in the bottom of a pond that
allows the water to drain into deeper,
moire permeable materials (fig. 4.4).
The pond water may be highly miner-
alized which, in turn, leads to deterio-
ration of water quality in the receiving
aquifer.
Hazardous Waste Injection Wells
! For decades, man has disposed
of liquid wastes by pumping them into
wells. The wells are called Class I if
used to inject hazardous (and nonhaz-
ardous) waste below the lowermost
underground source of drinking wa-
ter I Since World War II, a considerable
number of Class I wells have come into
existence, usually at industrial sites.
These wells typically are several
hundred to several thousand feet deep.
In the past, injection of highly toxic
wastes into some of these wells has led
to contamination of fresh water due to
direct injection into the aquifer, as well
as leakage from the well head, through
the casing, along the outside of the
casing, or through fractures in confin-
ing beds.
It should be noted that wells
used for oil-field brine, injection are
class II wells. Exclusive of oil-field
brine, most deep-well injection (class I)
operations are tied to the chemical
industry. Well depths range from 1,000
to 9,000 feet and average 4,000. The
23
-------
Original pond surface New surface of pond
\ /
New potentiometric surface
Original potentiometric surface
^
'''''-''''' '
*"'**'*''*
'
.......
Figure 4.4 Drainage wells are designed to permit direct infiltration
of surface water into the subsurface.
deepest wells are found in Texas and
Mississippi.
Properly managed and designed
deep-well disposal systems can be ef-
fectively used for storage of wastes
deep underground and may permit
recovery of the waste in the future.
Before deep well disposal of wastes is
permitted, however, extensive evalu-
ations of the well system, the waste
fluids, and the rocks in the vicinity of
the proposed disposal well, are re-
quired and strictly enforced by state
and federal regulatory agencies.
Note thatwells injecting hazard-
ous or radioactive waste into or above
an underground source of drinking
water is classified as a Class IV injec-
tion well; these wells are prohibited.
Water Quality Problems Related to
Pumping/Well Construction
The yield of many wells tapping
streamside aquifers is sustained by
infiltration of surface water. In fact,
more than half of the well yield may be
derived directly from induced recharge
from a nearby stream (fig. 4.5). If the
water in the stream is of undesirable
quality, it may seep into the ground
and degrade the drinking water sup-
ply. In some coastal areas, particu-
larly in Florida, the construction of
extensive channel networks has per-
mitted tidal waters to flow consider-
able distances inland. The salty tidal
waters infiltrate, increasing the salt
24
-------
v%v^
Figure 4.5 A cone of depression that intersects a body of surface
j water will cause the surface water to flow into the ground.
coritent of the ground water in the more highly mineralized water toward
vicinity of the canal.
i
i For reasons such as these, it is
the well. Undeveloped coastal aquifers
are commonly full, the hydraulic gra-
dient slopes towards the sea, and fresh
important that streams not be allowed water discharges from them through
to become contaminated. Municipal springs and seeps into the ocean.
officials must carefully monitor all Extensive pumping lowers the fresh
activities within each stream water- water potentiometric surface, allowing
shed, particularly upstream of a well sea water to migrate; toward the pump-
field, in order to protect supplies that ing center. A similar predicament
depend on induced infiltration. occurs in inland areas where saline
! water is induced to flow upward,
I In certain situations pumping of downward, or laterally into a fresh
ground water can cause significant water aquifer due to the decreased
changes in ground-water quality. The head (pressure) in. the vicinity of a
principal reasons include interaquifer pumping well (fig. 4.6).
leakage, induced infiltration, and, in
coastal areas, landward migration of Improperly constructed water
sea; water. In these cases the lowering wells may either contaminate an aqui-
of the hydrostatic head in the fresh fer or produce contaminated water.
water aquifer leads to migration of Dug wells, generally of large diameter
25
-------
Figure 4.6 Pumping may Induce water of undesirable quality to flow from
one rock formation into another
and shallow depth, and typically poorly
protected, are commonly contaminated
by surface runoff flowing into the well.
Other contamination situations have
been caused by infiltration of water
through polluted fill around a well,
through the gravel pack, and still oth-
ers by barnyard, feedlot, septic tank,
or cesspool effluent draining directly
into the well.
Although construction of public
water-supply systems is presently
controlled by well construction codes
and standards, this is not necessarily
the case with private supplies. Fur-
thermore, many public and municipal
wells were installed long before con-
struction standards were established
and, consequently, they may have little
or no grout above the gravel pack, an
inadequate concrete pad surrounding
the well, and no sanitary well seal.
Water Quality Problems Related To
Abandoned Wells And Test Holes
Literally hundreds of thousands
of abandoned exploratory wells dot the
country side. Many were drilled to
determine the presence of underground
mineral resources (seismic shot holes,
coal, salt, oil, gas, etc.). The open holes
permit water to migrate freely from one
aquifer to another. Afresh water aquifer
could thus be joined with a deeper
saline aquifer, or mineralized surface
water could drain into fresh water
zones.
26
-------
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^tfr-**-*-*--^^^
Surface B vV^v^v/.v-"^v;,f".v^v.vV^vVy.v^vVyj-yi^jv
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Figure 4.7 Wells without casing may permit the movement of water
; from one aquifer to another.
! Another major cause of ground-
water contamination is the migration
of mineralized fluids through aban-
doned wells (fig. 4.7). Many times
whfen a well is abandoned, the casing
is pulled (if there was one) or eventu-
ally the casing may become so cor-
roded that holes develop. This permits
ready access for fluids under higher
pressure to migrate either upward or
dovynward through the abandoned well
to adjacent aquifers. In other cases,
improperly cased wells may allow high-
pre'ssure artesian saline water to spread
from an uncased or partly cased hole
into shallower, lower-pressure aqui-
fer^, resulting in widespread salt in-
tru!sion.
! Finally, upon well abandonment,
malny individuals remove the pump
and leave an open hole with neither a
protective cover nor any indication of
its presence. In addition to the likely-
hood of contaminants entering the well,
they can provide an imminent danger
to humans, particularly children, and
wild or domestic atnimals, as several
recent cases have so clearly shown.
Water Quality Problems Related To
Mining Activities
Following the removal of clay,
limestone, sand and gravel, or other
material, the remaining excavations
are commonly left unattended. Many
eventually fill with water, and often
they are used as unregulated dumps
into which are placed both solid and
liquid wastes. The quantity and vari-
ety of materials placed in them are
27
-------
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^f ป"ป* "a*"^" ^"^^^^"^^^^|' ***"*ซ"""ซ" i^"**" *""*ป" a"" ป"* ^""^"^
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Figure 4.8 Dewatering may cause upward migration of salty water,
almost limitless. The wastes may be in
direct connection with an aquifer.
Excavations also have been used
for the disposal of liquid wastes, such
as oil-field brines and spent acids from
steel mills. Many others serve as dis-
posal sites for snow removed from
surrounding streets and roadssnow
that commonly contains alarge amount
of deicing salt.
Mining has led to a number of
problems brought about by pumping
mine waters to the surface, by leaching
of the spoil material, by waters natu-
rally discharging through the mine,
and by milling wastes, among others.
laterally thousands of miles of stream
and hundreds of acres of aquifers have
been contaminated by highly corrosive
mineralized waters originating in coal
mines and dumps in Appalachia. In
many western states, mill wastes and
leachates have seriously affected both
surface water and ground water.
Many mines are deeper than the
water table, and in order to keep them
dry, large quantities of water are
pumped to waste. If salt water lies at
relatively shallow depths, the pump-
ing of fresh water for dewatering pur-
poses may cause an upward migration
of the salt water, which may be inter-
cepted by wells (fig. 4.8). The mineral-
ized water most commonly Is dis-
charged into a surface stream.
Water Quality Problems Related To
Product/Waste Storage
Another major cause of ground-
-------
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Unsaturate zone .ftftW
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Fjlgure 4.9 Leakage from holding ponds and lagoons may form a water mound
j that causes to flow In unanticipated directions.
water contamination is the storage of
cerjtain materials and the disposal of
waste matter directly onto the land
suijface. Examples include deicing
salt (sodium and calcium chloride),
treated lumber, manure, sludges,
garbage, industrial wastes, dumps,
septic tank wastes, etc. The material
may occur in individual units or it may
be jspread over the land. If the sub-
stahce contains soluble products, they
may cause ground-water contamina-
tion.
i
WJater Quality Problems Related To
Agricultural Activities
An increasing amount of fertiliz-
ers! and pesticides are being used each
yeair. Many of these substances are
highly toxic, their long term health
effects are largely unknown, and some
are! quite mobile in the subsurface. In
ma-ny heavily fertilized areas, the infil-
tration of nitrate, a decomposition
product of ammonia fertilizer, has
contaminated ground water. The
consumption of nitrate-rich water may
cause a disease in infants known as
"blue babies" (methemoglobinemia).
Furthermore, many types of pesticides
have been found in ^pround water within
the past few years*. In Iowa, for ex-
ample, where atrazine is the compound
most commonly detected, the estimated
number of individuals exposed to
pesticides in ground water is believed
to exceed 25 percent of the population.
In rural communities pesticide/
fertilizer bulk plants and spraying
operations are a very real concern.
Spills are the rule rather than the
exception at loading stations. In addi-
tion, individual as well as commercial
pesticide spraying operators commonly
rinse their tanks, allowing the pesti-
cide-enriched wash waters to flowfreely
29
-------
onto the ground where much of it can
infiltrate.
Animal feedlots, which cover
relatively small areas, provide a huge
volume of waste. These wastes have
polluted both surface and ground water
with large concentrations of nitrate
and other chemicals. Even small feed-
lots have created local but significant
problems.
Water Quality Problems Related To
Holding Ponds And Lagoons
Holding ponds and lagoons
consist of relatively shallow excava-
tions that range in area from a few
square feet to many acres (fig. 4.9).
They are used to store municipal sew-
age as well as large quantities of other
wastes, includingindustrial chemicals.
Special problems develop with
holding ponds and lagoons in lime-
stone terrain where extensive near-
surface solution openings have devel-
oped. In Florida, Alabama, Missouri,
and elsewhere municipal sewage la-
goons have collapsed into sinkholes
draining raw effluent into widespread
underground openings. In some cases
the sewage has reappeared in springs
and streams several miles away. Wells
producing from the caverns could easily
become contaminated, leading to epi-
demics of water-borne disease.
Oil-field brines, consisting of
.highly mineralized salt solutions, are
particularly noxious and they likley
have locally polluted both surface and
ground water in every state that pro-
duces oil. The brine, an unwanted by-
product, is produced with the oil. In
many states (in the past) it was stored
or disposed of by placing it in holding
ponds from which it infiltrated. Not
uncommonly the oil well was long
abandoned before it becomes appar-
ent that the adjacent ground water
was contaminated.
Water Quality Problems Related To
Landfills
Sanitary landfills generally are
constructed by placing wastes in exca-
vations and covering the material daily
with soil. Even though a landfill is
covered, however, leachate may be
generated by the infiltration of precipi-
tation. Fortunately many substances
are removed from the leachate as it
filters through the unsaturated zone,
but leachate may pollute ground water
and even streams if it discharges at the
surface as springs and seeps.
Water Quality Problems Related To
Underground Storage Tanks
And Transmission Lines
Many toxic materials are trans-
ported throughout the country by
truck, rail, and aircraft and stored in
above or below ground tanks; acciden-
tal spills of these materials are not
uncommon. There are virtually no
methods that can be used to quickly
and adequately clean up an accidental
spill or spills caused by explosion or
fires. Furthermore, immediately fol-
lowing an accident the usual proce-
dure is to spray the area, with water
and, of course, firefighters use great
30
-------
quantities of water to control fires. The
resulting fluid may then either flow
into a stream or infiltrate. In some
plaices the accepted prodedure is to
impound the fluids by dikes, which
leads to an even greater potential for
mffltration.
I A growing problem of substan-
tial; consequence is leakage from stor-
age! tenks an(i pipelines leading to
sucli tanks. Gasoline leakage has
caused sever pollution problems
tin-ought the nation. Gasoline, bein g
less dense, floats on the ground-water
surface and leaks into basements,
sewers, wells, and springs, causing
noxious odors, explosions, and fires. A
single wall steel tank has a life expec-
taricy of only about 18 years and costs
about $1 per gallon to replace. A
cleanup operation will generally ex-
ceejd $70,000 and some have cost
millions of dollars.
31
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SECTION 5
GROUND-WATER MANAGEMENT
AND AQUIFER PROTECTION PLAN
Introduction
Just because a water quality
problem is not known to exist at the
present time does not mean that one
may not appear tomorrow or at some
other time in the future. Contingency
plans should be developed so that
sufficient time is available for rational
decisions and planning should a prob-
lem occur. Several approaches can be
followed, any of which must be dic-
tated by the particular political, eco-
nomic, and technical situations that
exist. The contingency plans need not
be expensive nor should they neces-
sarily followtraditional methods. Some
of the best ideas are generated by
individuals with little or no scientific
training, but these same people are
characterized by a great deal of com-
mon sense and a need to quickly and
inexpensively solve a problem.
Although any ground-water
protection plan must be flexible, a
number of steps can be followed that
should make the plan easier to follow.
Certainly not inclusive , at least the
following steps could be taken: (1)
determine where the supply originates
and what problems might be associ-
ated with it, (2) learn the system, (3)
locate potential sources of contamina-
tion, (4) develop a system of situation
monitoring, (5) consider alternate
sources of supply, (6) locate and evalu-
ate existing germane laws and regula-
tions, (7) develop an aquifer sensitiv-
ity/vulnerability model, (8) determine
background chemical quality of the
supply, (9) develop an organization
structure, and (10) initiate an educa-
tional program.
Where Does The Supply Originate
A short distance from its border
with Kansas, Oklahoma's Cimarron
River contains more than 50,000 mg/
1 of dissolved solids during dry
weather. Scores of miles down stream
near its confluence with the Arkansas
River, the Cimarron still contains more
than 2000 mg/1 of dissolved solids
despite the dilution from several major
tributaries. The source for the calcium
sulfate and sodium chloride in the
river is natural, bring derived from a
series of saline springs and seeps.
In this case any wells drilled in
the flood plain that are dependent on
induced infiltration soon would be
contaminated as the river water flows
into the aquifer. On the other hand, if
the discharge of the wells was reduced
or they were constructed farther from
the river, their cones of depression
would not intercept the river and there
would be no induced infiltration.
At Minot, North Dakota two
municipal wells produce water that
contains higher concentrations of chlo-
ride than do the other wells in the field.
The two wells are also about 50 feet
deeper than the average. In this loca-
tion a buried interglacial river valley
trends through the center of town; it
had cut several tens of feet into the
underlying bedrock. One of the bed-
rock formations that subcrops along
32
-------
the; buried valley walls contains salty
water. Pumping the deeper municipal
wells causes salty water to flow from
thejbedrock, mixwith the fresher water
in the sand and gravel, and eventually
readh the municipal wells. This prob-
lem also is related to natural condi-
i
tioris and perhaps the most practical
control is to reduce the rate of pump-
ing! from the two wells or to blend the
water with that from other wells.
i
: Several years ago in an industri-
alized city in Michigan a plant water
manager decided to dredge the adja-
cerjt river in order to increase the yield
from their induced infiltration supply
wells. Not realizing the river contained
high concentrations of industrial
wastes, the river was dredged and
within days the chemical quality of the
well water deteriorated dramatically.
It was then recognized that waste pa-
peijmill products had sealed the river
bottom, providing a last line of defense
between the contaminated river and
the; well field.
I
I
i It is evident from the above that
a knowledge of the source of the water
supply can serve as a starting point in
the| development of management alter-
natives.
i
I Learn The System
! For the most part, geologic and
hydrologic evaluations of the subsur-
facje are based on an analysis of logs of
wells and test holes. These data can be
us^d to construct a number of maps
and cross sections of the aquifer sys-
tem. Cross sections should provide an
idea of how much protection the aqui-
fer and confining units provide against
contamination.
As illustrated in Figure 5.1, the
shallow or surficial aquifer, which
consists entirely of permeable mate-
rial that extends from land surface to
the base of the water-bearing zone
(aquifer A), is highly vulnerable to
contamination from the surface and
other shallow sources. The aquifer
has practically no natural protection
other than the unsaฑurated zone where
sorption and biological degradation will
partly attenuate the contaminant. It
could be easily contaminated by a spill
or nearly any type of waste disposal
scheme.
On the other hand, aquifer B is
overlain by a layer of clay of low per-
meability, one that might require years
for a contaminant to penetrate. Con-
taminants from the surface would be
required to migrate through the un-
saturated zone, where some degrada-
tion would occur, tlirough the surficial
aquifer, where additional dilution and
sorption would occur, and then through
the clay layer where not only would
more sorption occur, but the rate of
movement would be considerably re-
duced. Moreover, if aquifer B were
confined and its water level was above
the clay layer, then water movement
would be upward through the confin-
ing layer and there would be little or no
danger from surface spills. Therefore,
the deeper aquifer has some degree of
natural protection ,and, in the case of a
spill, time likely would be available to
develop plans to overcome a potential
contamination problem.
33
-------
g Water Table
?ปlJNUปi7Vฃfl^f^iftaMftpfMi^*
yy^^s^mKs^ffy!^^^}\fi^j^yffmfmj!&s
A
-
.^\^.^.^.\,^.\\^^\^^^^\\^\^-^
^^ Gravel A'
tftfs,Wtftftftftftfiftft^^^^^
''''''''''"'''"''^^
"Lป*,ซB-ปป^g*-|i*-j|*^j['Lj'^^
v. Confining Unit .v.v.v.v.v.v.v.v.;^^^^^^^^ .v.v
Figure 5.1 Aquifer A is readily subject to contamination from the
surface while aquifer B has a degree of natural protection
because of the overlying confining unit.
Unfortunately, the well logs that well is tested by pumping before it is
are required to obtained geologic data accepted by a municipality. During
commonly are not readily available, the test, the discharge rate and water
Experience has shown, however, that level are measured in the pumping
the logs of municipal wells and test well and, sometimes, in one or more
holes, as well as the logs of industrial observation wells during a period that
and domestic wells, are likely to be commonly exceeds eight hours. These
stored in a file some place, perhaps in data routinely are used to determine
the city engineers office, at the water how the well reacts, but they also can
plant, or in the city managers office. If be used to evaluate an aquifer's hy-
they can not be found, it might be draulic conductivity, transmissivity,
possible to obtain copies from the origi- and storativity,
nal driller, contractor, or consultant,
or they might be available from a state Of particular concern is the size
or federal agency. Along the same line, of the cone of depression around a
well construction details, such as pumping well. As described previ-
depth, length of screen, etc, also can ously, the radius of the cone of depres-
be of considerable value.
Nearly as important as geologic
information are records of well dis-
charge and water-level fluctuations,
the latter indicating how the aquifer
acts under stress. Generally a new
sion is controlled by the aquifer prop-
erties and the discharge rate of the
well. In an unconfined aquifer, the
radius of the cone may be in the order
of a few tens or a few hundred feet, but
in a confined aquifer it may extend
outward for miles. -Furthermore, the
-------
drawdown caused by overlapping cones
of ^depression is greater than that
caiised by a single well. Additionally,
horizontal and vertical variations in
aquifer properties, pumping schedules
and rates, and well interference will
tend to distort the shape of the com-
posite cone of depression in a well
field.
I The shape and area! extent of
thC| cone of depression are important
in contamination studies for two major
reasons. First, the cone represents a
change in the hydraulic gradient, which
steepens as it approaches the well.
This, in turn, increases the velocity of
gro;und-water flow. Secondly, con-
taminants that reach the aquifer and
are! within a cone will migrate toward
the pumping well. Therefore, what
eve'r happens within the radius of in-
fluence of a well is of concern to the
walier manager.
i
i
Likewise, the size of the area of
influence of a well field is important
because this is the area that should be
protected. Although the area of influ-
ence might well exceed several square
miles, the velocity of the ground water
near the outer margin should be rela-
tively low, as compared to that in the
vicinity of a well. Resultingly, if the
aquifer were contaminated in this
region, it might require several months
or Seven years for the contaminant to
appear at a well. In the meantime, the
contaminant might be diluted or de-
graded to such an extent that it would
not be of concern to the plant operator.
i
Locating Potential Sources Of Con-
i tamination
In order to develop an aquifer
protection plan, local sources or po-
tential sources of contamination must
be known. These include, in addition
to the more obvious ones discussed
previously, such things as the location
of railroads, major highways, streams
and rivers, shallow waste disposal and
drainage wells and sumps, gasoline
stations, and small, industrial or serv-
ice plants, particularly those small
concerns that might be operated in
someone's garage, basement, or out-
building. The latter are not likely to be
well known to regulatory agencies nor
are they likely to have discharge per-
mits.
In order to develop a data base
for potential sources of ground-water
pollution, several waste surveys could
be conducted. These should include
(1) an industrial waste survey, (2) a
municipal waste survey, and (3) a state
and federal properly survey. The sur-
veys themselves could be as simple as
examining a map to locate highways,
railroads, industrial sites, disposal
sites, etc, to actual interviews. Sur-
veys of this nature could become both
time consuming arid expensive.
One approach, which could be
both comprehensive and inexpensive,
would be to contact a number of local
service clubs, such as the Lion's Club,
and request their members to provide
information. Other than the obvious
advantages of this method, one impor-
tant consideration is that the mem-
bers of local service clubs represent a
wide spectrum of the population that,
as a whole, might well have a detailed
35
-------
knowledge of the area. Resultingly,
the data base that could be developed
would be comprehensive, inexpensive,
and flavored with community pride.
A second and probably essential
approach would be the development of
contacts with senior citizens, either
through local groups or the Senior
Citizen Center. Not only do these
individuals have a great deal to offer in
the way of time and experience, they
may well be the only source of informa-
tion concerning past activities within
the municipality.
Once the location of potential
sources of contamination are located,
it will then be possible to estimate the
time required for a contaminant to
migrate to a well. It must be remem-
bered, however, that what ever method
is used to predict travel time, it will be
only an estimate.
Situation Monitoring
Situation monitoring concerns
keeping ones finger on the pulse of the
community, that is, what has hap-
pened in the past, what is happening
at the present time, and what might
happen in the future. Situation moni-
toring should cover two main catego-
ries(1) monitoring of the existing
water supply system and plant and (2)
monitoring of other local situations.
The former can and should be accom-
plished by waterutility personnel, while
the latter can be carried out by inter-
views, the news media, and local agen-
cies.
It is surprising that so few op-
erators, particularly those involved with
small water systems, are aware of the
chemical quality of their supplies. Even
if routine chemical analyses are car-
ried out periodically, it is unlikely that
samples will be scanned for the more
exotic compounds, such as heavy
metals or organic compounds. This is
understandable in view of the cost. On
the other hand, without background
data it is commonly difficult if not im-
possible to detect many contaminants
or locate a source, especially if proof is
required in a legal action. Nonethe-
less, the costs of chemical analyses
must be accepted by the operator as a
part of the normal business practice.
Another part of the survey that
should be conducted by the water utility
personnel includes an examination of
their facilities addressing such items
as: possibility of back siphonage, cross-
connection, distribution system defi-
ciencies, and poor well construction or
location. Are there, for example, po-
tential sources of contamination, such
as fuel tanks or sewer lines, adjacent
to the well or well house?
The second part of situation
monitoring involves the collection and
evaluation of information in the com-
munity or area within the influence of
the cone of depression of the well field.
For example, have there been any fires
that might have resulted in the release
of chemicals that could reach the
aquifer? Have there been any spills
from truck or train wrecks? Might new
construction produce a hazard? Are
plans being developed for the place-
ment of hazardous waste storage or
disposal sites, or the construction'of a
36
-------
new golf course over a sensitive part of
the| aquifer? In other words, the pur-
pose of this type of monitoring, which
mu|st be continuous, is to keep in
touch with the community.
Alternate Sources of Supply
I A common solution to a water
quantity problem is to deepen a well
and to a contamination event is to
offset and drill another well. Unfortu-
nately, such potential solutions, al-
though simple, are rarely available. It
may not be possible to deepen a well
and merely offsetting a contaminated
well may only solve the problem for a
few hours or days. It appears that
human nature is such that we tend to
procrastinate, hoping that life will
continue uninterrupted. The far think-
ing individual, however, will consider
alternatives, formulate cost estimates,
and develop plans, both for design and
obtaining the necessary funds for
construction, for other sources of
supply.
i
; When addressing potential al-
ternate sources of either a surface
water supply (table 5.1) or a well field
(talple 5.2), a number of questions
shuld be asked, looked into, and
answers formulated. Is there a source
of surface water sufficiently nearby
that will meet water quality standards
after treatment? If so, is a site avail-
able and what are the potential costs of
constructing intake structures and
conveyance facilities, of treating the
water, and how much time would it
require to actually provide the water?
Is the supply dependable, or contami-
nated, or can water rights be obtained?
1. Is a practical source available?
2. Can water rights be obtained?
3. Is the supply sufficient for the needs?
4. Is it of acceptable quality?
5. Will treatment be necessary?
6. How much time will be required to
actually provide wa ter from the new
source?
7. How can the property be obtained?
8. What Is the cost to develop the supply?
a. Pipeline
b. Treatment (costs, how, where)
c. Source design/construction
9. Funding?
a. How much time to obtain?
b. How much vrill it cost?
Table 5.1 Considerations for alternate
sources of surface water
supply
1. Are other ground-water sources avail-
able?
2. What is the potential yield?
3. What is the chemical quality?
4. Is land available?
5. What are costs of construction for
a. Wells
b. Pipeline(s)
c. Treatment facilities
6. What kind of treatment & where?
7. How much time to put online?
8. Funding
a. How much?
b. How to obtain?
c. How long will it take?
9. Are the site characteristics adequate for
future development
10. Is the site vulnerable to future contami-
nation?
Pable 5.2 Considerations for alternate
sources of supply from
ground water
37
-------
Construction plans, either for a
surface or ground-water supply, can
be drawn and funding mechanisms
addressed when it is convenient. The
plans can be filed with the hope arid
expectation that they will never be
required. But if they are ever needed,
the preplanning may save several days
or months of work during a period
when time may be of the essence.
Furthermore, the plans might con-
sider an entire supply, a supplemental
supply, or a temporary supply.
Sometimes it might be possible
to use nontraditional concepts to de-
velop a water supply. One method
might be collection galleries, particu-
larly if the available streams are small.
In this case a ditch could be cut across
a stream into which is placed a gravel
bed (fig. 5.2). A well screen attached to
a suction line can be placed on the bed
and the ditch filled with gravel. This is
virtually a horizontal well whose sup-
ply depends on infiltration of surface
water through the gravel pack. Al-
though the filter pack might well re-
duce turbidity, it would have little or
no effect on many chemicals. None-
theless, this technique offers a simple
and relatively inexpensive alternative.
Along the same line is the sub-
surface dam. The village of Glenbum
in north-central -North Dakota had a
difficult time supplying sufficient wa-
ter for their needs. They overcame this
deficiency with an unusual and inex-
pensive design. Most of the surficial
rocks in the Glenbum area consist of
clay, but near the edge of town is a
stream channel, about 30 to 40 feet
wide, that is usually dry. The channel
contains 7 to 8 feet of coarse gravel and
sand. Upstream the deposit widens
and a half mile or so from the village
there is an abandoned gravel pit.
During the spring runoff a con-
siderable amount of water infiltrates
the gravel and the water table rises
dramatically. Because the deposits
are very permeable, however, the
ground water flows down gradient
quickly and the water table declines as
the aquifer is drained. The gravel
channel has a considerable capacity
for storage but no control to limit or
prohibit rapid drainage.
This problem was solved with
almost no cost by a volunteer work
force, representing nearly the entire
community, by excavating a ditch, 4 or
5 feet wide, across the channel and
entirely through the gravel deposit.
The excavation was backfilled with clay,
which formed a subsurface dam (fig.
5.3). Perforated culvert, serving as a
well, was installed on the upstream
side of the dam. Farther upstream a
diversion ditch was excavated from the
intermittent stream channel to the
abandoned gravel pit. During periods
of runoff, some of the surface water is
diverted into the gravel pit, where it
infiltrates and part of the remainder
infiltrates along the stream bottom.
Thus, during wet periods a consider-
able amount of water is collected in the
underground storage reservoir. The
subsurface dam impedes the flow of
the ground water down the gravel-
filled channel and the water table
remains at a high level, permitting
increased water usage and a sustained
supply.
38
-------
"^^^^^^^^^i Horizontal Well Screen -Xv^vXvXvIvJCvX
Plan View
Gravel Pack
Cross-Section
Figure 5.2 Plan view and cross-section of an infiltration
gallery.
| Water supply problems in arid
regions are particularly vexing because
of scanty rainfall and the high rate of
evaporation. In some situations, it
may be possible to augment supplies
by \ constructing artificial aquifers.
Artificial aquifers, by necessity, can
store only modest quantities of water,
bull they are labor intensive and, there-
fore, can be built with a minimal equip-
ment cost.
At the Santa Clara Indian Reser-
vation, New Mexico, a small gully,
several yards wide, was cleared of
vegetation, deepened, and sloped. Spoil
material was used to construct an
earthen dam across the gully. A trench
was cut adjacent to and parallel with
the dam into which was installed a
slotted plastic pipe. The slotted pipe
39
-------
was connected, at a right angle, to a
second pipe, extending through the
dam in the low point of the gully. Hie
second or discharge pipe was laid on a
slight downslope grade (fig. 5.4) arid
installed prior to dam construction.
Once the gully was shaped, the
pipes installed, and the dam built,
plastic lining was placed in the floor of
the excavation which was then back-
filled with uniform sand (gravel could
be used) and topped off with gravel
mulch.
During the rainy season, water
flows down the gully and infiltrates
through the gravel mulch to the artifi-
cial aquifer. (In some cases it might be
necessary to construct a spillway to
'^QJ^'^^^^^^^^^^SiJbsvafsice^Oarn ^^^^^^^^^^^^
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""""""""""'""""""""""~""""""*""'"'*"*"<*""*"'**'"*~"""'" "JVJVJVVVVVl"."-"-"-"ซVVV-"-"-"-"-"-".VVซ"JVVU"."."."
**.*ป-""-"- ...ปป.ป..ป..._ซ............-ซ-ซ-".-ป-.--ซซ--""--'
....v.v.v.^.^.sS53pj5->y
^ Water
4* Subsurface Dam
p"sl^&toavef^^^KSf^
&fewss*ifis*>ss^ssiSS: *b SSSSSS&
Direction of Ground-Water Flow
Figure 5.3 Plan view and cross-section of a subsurface dam.
40
-------
avoid excessive erosion of the dam.)
Water is removed from the reservoir by
gravity through the discharge pipe, the
rate being controlled by a valve.
i
i Another management alterna-
tive might be to consider developing
another aquifer or a different part of a
contaminated aquifer. In the latter
case, care would be required in the well
fielcl design to insure that the new
sysjtem would not be contaminated
due to changing hydraulic gradients.
; Generally newwellflelds require
considerable time and financing in
order to achieve a proper design and
adequate construction. The first ques-
tion to be addressed should be "is
thdre an aquifer available that will
supply the required needs and what
arej its characteristics?" If one is avail-
able, what is the quality of the water it
contains and what is an estimate of the
treatment requirements and costs?
How many wells will be required and
how much will they cost?
Periodically various regions suf-
fer from prolonged droughts,
streamflow decreases or may even
cease, and water rationing becomes
the rule. In many of these areas it is
only the surface water supply that is
decreasing, while billions of gallons of
ground water remain untapped in
naturally occurring underground res-
ervoirs that remain hidden from view.
Legal Controls On Waste Disposal
A variety of laws, regulations,
and rules exist to control waste dis-
posal. In addition to the often quoted
federal laws are those established by
state legislatures amd the regulations
formulated by state agencies. Local
zoning ordinances may play an impor-
Vy.A Uniform
r... , ,.W...-..,
Discharge line
Fjigure 5.4 Cross-section of an artifical aquifer.
i 41
-------
tant role in developing and maintain-
ing an aquifer protection program.
These need to be researched, under-
stood, and modified as the need arises.
Development Of A Ground-Water
Protection Plan
The basis of a ground-water
protection plan is at least a general
knowledge of the aquifer system and
the manner in which it functions.
Where are the inherent weaknesses of
the physical system, where are the
strong points, and where is a contami-
nation problem most likely to occur?
These questions can best be answered
or at least evaluated by means of a
series of maps. Once the maps have
been prepared, the next step is to
make a number of simple calculation
and estimates of ground-water veloc-
ity and potential contaminant travel
time from a-source to a well.
The key features of a ground-
water protection plan include an aqui-
fer sensitivity map, a water-level map,
a map of potential contamination
sources, estimates of ground-water
velocity and travel time from a poten-
tial source to a well, and finally an
organizational structure and educa-
tional program. These requirements
can be achieved through a logical se-
ries of 11 steps (table 5.3). The steps
do not need to be followed in sequence
and several can be carried out at the
same time.
Step l. Schedule all wells In area
Step 2. Plot well locations on basemap
Step 3. Map potential sources of contamina-
tion
Step. 4 Construct aquifer sensitivity map '
Step 5. Measure water levels in wells
Step 6. Draw water-level map
Step 7. Estimate permeability, specific yield,
and velocity
Step 8. Calculate travel time to wells
Step 9. Collect water samples for chemical
analyses
Step 10. Develop organizational structure
Step 11. Develop educational program
Table 5.3 Steps in the development
of an aquifer protection plan
The following is an explanation
of each step and an example of the type
of data that should be collected. These
data will be used to develop an aquifer
sensitivity map and protection plan.
Step 1.
Schedule all wells in the area. A
well schedule describes specific infor-
mation concerning a particular well.
The schedule should include the exact
well location (a generalized map could
be drawn on the reverse side of the
form), water-level notations or meas-
urements, well construction details,
availability of a driller's or geologist's
log, and chemical quality information.
The well inventory should include all
well (municipal, industrial, and do-
mestic) as well as test and exploration
holes. This survey could be conducted
by municipal workers, service clubs,
or senior citizens.
Very likely all of these data will
not be readily available and a search
will be required. This should include
42
-------
an I examination of municipal files,
contacts with contractors, consultants,
and local well drillers, as well as a visit
to the state or federal geological sur-
vey.
Step 2.
I On a base map of the area, plot
the location of all wells and test holes.
Us^ a variety of symbols to show the
typje of information that exists for each
well.
j
Step 3.
I Prepare a map showing the loca-
tion of all potential sources of contami-
nation, including roads, railroads,
streams, dumps, and landfills, as well
as 'industrial sites.
i
Step 4.
Using the well logs obtained in
Step 1, construct an aquifer sensitivity
map. The purpose of the sensitivity
map is to determine how much natural
protection the aquifer has, where it is,
and its characteristics. Some care
rmjst be taken here because drillers
commonly use different terminology to
describe rock types. For example a
geologic or driller's log may use the
term "sandy clay", which in reality may
be ja fine sand with minor amounts of
silt and clay that is substantially more
permeable than the log implies. The
general rule here is to assume that the
material is more permeable than it
would appear from the log. In addi-
tion, when constructing the sensitivity
map all sources of information should
be ichecked, including the location of
gravel and borrow pits, excavations,
mines, building foundations, pipeline
excavations, and even stream chan-
nels, j
Step 5.
Measure the water level in as
many wells as possible. The water
levels should be measured while the
well is pumping, if feasible, because
this will be the time of maximum
drawdown. Plot the altitude of the
water surface on the well location base
map.
Step 6.
Draw a water-level elevation map
using the data collected in Step 5. On
another map reproduce the water-level
contours and plot all of the potential
sources of contamination as deter-
mined in Step 3. Construct flowlines
that originate at each potential source
and continue them to the nearest well,
keeping in mind that the flow lines
must cross the water-level contours at
a right angle.
Step 7.
From specific capacity data, well
logs, tests, or tables, calculate or esti-
mate the hydraulic conductivity and
specific yield of the aquifer. Estimate
ground-water velocity.
Step 8.
Calculate the estimated time of
travel from each potential pollutant
source to the nearest well by dividing
the distance, measured along a flow
43
-------
line, between the source and the well legal action.
by the ground-water velocity.
Step 9.
Collect water samples from
municipal wells and test holes for
routine chemical analysis. Although
expensive it would be prudent to ana-
lyze for characteristic organic com-
pounds for those wells that are in a
sensitive area and relatively near (1500
feet or so) a potential source of con-
tamination that contains organic
compounds. The purpose of these
analyses is twofold. First to determine
if there is presently contamination and
second to establish background con-
centrations. The latter is essential to
prove subsequent contamination in a
Step 10.
Develop an organizational struc-
ture and chain of responsibility. Ulti-
mately, someone must be in charge of
the program. This needs to be an
individual who has the authority to
assign duties and act as a clearing
house for information. Depending on
the community organization, this indi-
vidual might be the city manager, fire-
chief, chief of police, city engineer, or a
senior citizen experienced in technical
matters.
Step 11.
The long term success or failure
POTENTIAL SOURCE
OF CONTAMINATION
Figure 5.5 Map showing location of all wells and test holes and potential
sources of contamination.
44
-------
of ail aquifer protection plan, to a large
extent, depends on the citizens of the
coriimunity, both young and old. They
need to knowwhy various things should
be jdone and what are the possible
consequences if they are done incor-
recjtly or not done at all. Education is
thej key. Again, this might be accom-
plished through educational programs
proyided to service clubs, garden clubs,
senior citizen centers, the Boy Scouts
and Girl Scouts, and in schools. This
method of public awareness also leads
to Community pride. A great many
pamphlets and reports , as well as
speakers, are available, free of charge,
from county extension agents, health
departments, and state and federal
agehcies, as well as a variety of asso-
ciations.
A topographic map of the area
shows that the city lies both within the
flood plain of a river and on the adja-
cent upland, which is about 200 feet
higher. The major aquifer is confined
to the river valley and consists of de-
posits of sand and gravel that are
interbedded with aind locally overlain
by glacial till. A base map was con-
structed from the topographic map.
Steps 1 and 2
All of the wells within the valley
were scheduled and their locations
plotted on the base map with a sequen-
tial numbering system (fig. 5.5).
Step 3
Another advantage of public
education and activity is peer pres-
sure. The owner of an abandoned
gasoline station might be reluctant to
remove old underground tanks, which
might be a source of contamination.
Once his neighbors and colleagues are
aware of his reluctance they might well Step 4
bring to his attention that he is endan-
gering their lives and property values.
Using data from the waste sur-
veys, the location of all potential sources
of contamination were plotted on a
base map (fig. 5.5). These include the
river, railroad tracks, and major high-
ways.
Example of a Ground-Water Protec-
i tion Plan
, The following example is based
on data obtained from a city in the
Northern Great Plains. The region was
glaciated and the earth materials con-
sist largely of glacial till and sand and
grayel that overlie nearly flat lying
sedimentary rocks that consist of al-
ternating layers of sand, shale, and
lignite.
An aquifer sensitivity map was
prepared on the ba,sis of the well logs
obtained in Step 1 (Appendix). In this
case a total of 30 logs were available
and they were divided into Potential
Contamination Classes. It was as-
sumed in this study that if the log
indicated that sand or sand and gravel
extended, more or less uninterrupted,
from land surface to the bottom of the
well that the aquifer was very sensitive
to contamination from the surface
(Class 1). If the log indicated that there
was a total of 25 to 45 feet of clay
45
-------
Critical: less than 25 feet of overlying clay
Caution: 25 to 45 feet of overlying clay
Moderately Safe: more than 45 feet of overlying clay
Figure 5.6 Map showing aquifer sensitivity
between the surface and the aquifer,
the site was considered to be only
questionably safe from surface con-
tamination (Class 2). Where more
than 45 feet of clay separated the
surface from the aquifer, it was as-
sumed the aquifer is moderately safe
from contamination from the surface
(Class 3).
*
The development of the sensitiv-
ity map, which is quite subjective, is
dependent on a reasonable evaluation
of existing well logs. Consequently,
one needs to be conservative in the
evaluation. The logs are not greatly
detailed and, therefore, some interpre-
tation is required. As an example,
many of the logs refer to a "sandy clay",
but this description does not clearly
indicate if this geologic unit consists of
clay with admixed sand, if it is pre-
dominantly sand with some clay, or if
it is actually layers of sand and clay.
The permeability of the three possible
types could differ significantly. Here
the key is to be conservative. The
estimated total thickness of fine-
grained material, largely clay or shale,
overlying the aquifer is shown on each
log in the Appendix.
Once the logs were evaluated,
the thickness or Potential. Contamina-
tion Class of each log was plotted on
the base map and the specific classes
were incorporated as units.
46
-------
SOURCE
:OF CONTAMINATION
Figure 5.7 Map showing water-level contours, potential sources of contamination,
; and flow lines extending from potential sources nearest dow-gradient
well.
i
; The degree of natural protection
afforded the aquifer is outlined in Fig-
ure 5.6. The map indicates that the
eastern part of the valley-fill aquifer is
projected by a considerable thickness
of clay through which contaminants
originating on the surface are not likely
to flow (Class 3). To the west, however,
thej valley fill consists of sand and
gravel that extends from land surface
to bedrock, a distance of more than
10Q feet (Class 1). Any contaminants
entering the ground here could reach
the' aquifer. In the central part of the
aquifer the major water-bearing zone
has some overlying protection in the
form of alternating layers of clay and
san;d (Class 2). Although a contami-
nant eventually might reach the aqui-
fer in this area, it would require a
substantial amoun t of time and proba-
bly the contaminant would be degraded
or sorbed to some extent and certainly
diluted as it migrated through 25 to 45
feet of fine-grained material.
The sensitivity-map rather clearly
indicates those areas of most and least
concern. The eastern part of the aqui-
fer is moderately safe, caution should
be exercised in the central part, and
the western part should be carefully
protected and monitored (fig. 5.6). The
latter critical area should be brought
to the attention of city officials and an
attempt made to protect it by local
47
-------
Figure 5.8 Map showing general range in ground-water velocity. Numbers are
velocity in feet per day.
zoning ordinances.
Steps 5 and 6
The next step was the measure-
ment of water levels in all available
.wells. The elevation of each well was
determined, either by estimation from
a topographic map or by actual sur-
veys. Added to the elevation of the well
house floor was the distance from the
floor to the top of the casing or what-
ever point was used for the measuring
point. The depth to water in the well
was subtracted from the elevation of
the measuring point and the difference
was recorded as the elevation of the
water-level surface (table 5.4). These
elevations were plotted on a base map
and contours or lines of equal water-
level elevation were constructed (fig.
5.7. Next, flow lines were extended
from each potential contamination
source to the nearest "well (fig. 5.7).
The map in Figure 5.7 shows a
large cone of depression around a well
field and the arrows indicate the gen-
eral direction of ground-water flow.
Notice that the contours indicate that
water is flowing into the pumping center
from all directions. Consequently, a
large area should be protected or at
least monitored because contaminants
reaching the aquifer in any part of the
area of pumping influence could even-
tually reach a well.
Step 7
As is evident from the well logs,
the material that forms the aquifer
ranges considerably in thickness and
grain size. Using specific capacity data
48
-------
tually reach a well.
Step?
aquifer and to establish a background
concentration.
Step 10 i
i As is evident from the well logs,
the' material that forms the aquifer
ranges considerably in thickness and
grain size. Using specific capacity data
and an estimation of the aquifer thick-
ness, as implied by the logs of wells Step 11
anci water-level measurements, the
generalized range in velocity of ground
water was calculated (fig. 5.8). The
estimates may be quite wrong, but
they are not likely to be incorrect by a
factor of more than 2 or 3. Further-
mojre, the purpose of this analysis is to
develop only a general impression of
the manner in which the aquifer func-
tions.
Ste|p8
I
[< The travel time from a potential
contaminant source to the nearest well
was calculated by dividing the dis-
tance between the source and the well,
measured along a flow line, by the
ground-water velocity.
i
Ste!p9
j
j The next step in this analysis
was the collection of water samples for
chemical analysis from all wells. In
this case there are no analyses for
organic compounds, which are the most
peijvasive and hazardous of all the
possible contaminants. The recom-
mejndation was to collect well water
samples specifically for the purpose of
evaluating the presence of potential
organic contaminants in order to de-
termine the existing load, if any, in the
An organizational structure was
established in cooperation with the
city council.
An educational program was devel-
oped and presented throughout the
city.
49
-------
Selected Reference
Deutsch, M., 1963, Ground-water contamination and legal controls in Michigan: U.S. Geologi-
cal Survey Water-Supply Paper 1691.
Heath, R.C., 1984, Ground-water regions of the United States: U.S. Geological Water-Supply
Paper 2242, U.S. Government Printing Office, Washington, D.C.
Heath, R.C., 1983, Basic ground-water hydrology: U.S. Geological Survey Water-Supply Paper
2220, U.S. Government Printing Office, Washington, D.C.
Helweg, O. J. and G. Smith, 1978, Appropriate technology for artificial aquifers: Ground Water,
v. 16, no. 3, pp. 144-148.
LeGrand, H.E., 1983, A standardized system for evaluating waste-disposal sites; National Water
Well Association, Dublin, OH.
Office of Ground-Water Protection, 1987, Guidelines for delineation of wellhead protection
areas: U.S. Environmental Protection Agency, EPA 440/6-87-010.
Pettyjohn, Wayne A., 1967, Geohydrology of the Souris River valley in the vicinity of Minot,
North Dakota: U.S. Geological Survey Water-Supply Paper 1844.
U.S. Environmental Protection Agency, 198.5, Protection of public water supplies from ground-
water contamination, seminar publication: U.S. Environmental Protection Agency, EPA/625/
4-85/016.
U.S. Environmental Protection Agency, 1987, Handbook groundwater: U.S. Environmental
Protection Agency, EPA/625/6-87/016.
Walton, W.C., 1970, Groundwater resource evaluation: McGraw-Hill Publications Co., New
York.
50
-------
Appendix
51
-------
WELL 1 (DOMESTIC)
Thickness
(feet)
Hard clay 18
Sand : 9
Yellow sand 11
Dark clay 24
Dark gravel and sand 13
Coal and sandy clay 5
Coal and clay 5
Blue clay 6
Coal and water 3
WELL 2 (TEST HOLE)
Fine yellow sand and silt,
some gravel streaks 24
Sand, gravel, some clay 4
Clay, gravel 24
Sand, gravel 2
Sand, gravel, boulders, some clay
lenses last 10 feet 44
Dirty sand, gravel 3
Clay, some gravel 13
WELL 3 (MUNICIPAL)
Fine yellow sand and silt, some
gravel streaks 24
Sand, gravel, clay 4
Clay and gravel 24
Sand, gravel, boulders 46
Sand, gravel, boulders, with
clay traces 3
Clay with gravel ' 13
WELL 4 (TEST HOLE)
Gravel, medium to coarse; rougr
drilling 11
Gravel, coarse; boulders, rough drilling,
lost circulation, abandoned hole r 9
* Major water-bearing zone
52
Depth
(feet)
18
27
38 *
62
75 *
80
85
91
94 *
24
28
52
54 *
98 *
101 *
114
24
28
52
98 *
101 *
114
11
20
-------
WELL 5 (MUNICIPAL)
Dirty sand 10
Sandy 16
Coarse gravel 46
Fine, gravel 8
Fine gravel and sand 5
Gravel with traces of clay 4
Hard clay 2
i
: WELL 6 (MUNICIPAL)
Silt i, sand, and clay 8
Sand and gravel 32
Small boulders, sand, and gravel ; 14
Coarse gravel, boulders 26
Clay and gravel 10
i
| WELL 7 (TEST HOLE)
I
Siltlandsand 8
i
Sand and gravel 32
Small boulders, sand, and gravel 14
SancI and gravel 31
Course gravel and boulders 26
Clay and gravel 10
I
; WELL 8 (TEST HOLE)
i
Clean, fine sand 70
Sand, gravel, and boulders 10
Sandy clay, blue in color 13
! WELL 9 (MUNICIPAL)
j
i
Sandy, some silt 20
Dirty sand 30
V^-lGcin SciIiQ. .11.- ...-.._ ___^^^__ ^
Sand and gravel 5
Coarse gravel 55
Clay 2
10
26
72 *
80 *
85 *
89 *
91
8
40 *
85 *
111 *
121
8
40 *
54 *
85 *
111 *
121
70 *
80 *
93
20
50*
55*
60*
115 *
117
53
-------
WELL 10 (MUNICIPAL)
Sandy clay, silt 11
Very fine sand, some clay and
Silt 27
Mostly clay, some sand layers 16
Sand (dirty) 3
Clean coarse sand 15
Clean sand, gravel 18
Dirty (clay) sand, gravel 7
Sandy clay, clay 14
WELL 11 (INDUSTRIAL)
' "" '"'"" ' J~ ' 2ง
Sandy clay 13
Sand and clay layers 15
Gravel, muddy water 7
Fine sand and muddy water 43
Clay and sand 10
Sand and watet 6
WELL 12 (MUNICIPAL)
Sandy clay 25
Blue clay 50
Sand and gravel 5
Gravel 9
Coarse gravel and boulders 25
o clIlCL *"* " ~" * ~" - /
Clay with gravel 2
WELL 13 (MUNICIPAL)
Clay, silty, some thin, fine
sand layers : 46
Dirty, medium to fine sand, some
lignite 22
Some clean sand, clay lenses,
lignite 10
dean, coarse sand and gravel 7
Mostly coarse gravel, rough
drilling 9
11
38
54
57 *
72 *
90 *
97 *
111
2
15
30
37 *
80 *
90 *
96 *
25
75
80 *
89 *
114 *
121 *
123 *
46
68 *
78 *
85 *
94 *
54
-------
Very coarse gravel, boulders, some
gfa-nrl i 17
oOllU -1 /
Sand, gravel and boulders 9
Gray clay 20
WELL 14 (TEST HOLE)
Sand, very fine to fine, brown- 15
Sand, very fine to coarse; minor
amount of fine gravel,
pelecypod valves 2.5
Sand, medium to very coarse, gray;
minor amount of fine gravel 7.5
Sand, very fine to medium 5
Sand, medium to coarse; minor
amount of fine gravel 5
Gravel, fine; sand, fine to coarse;
thin layer of clay 5
Sand, fine to coarse; gravel, very
fine; scattered lignite grains;
boulder at 85 feet; lost circulation 60
WELL 15 (MUNICIPAL)
1
Black soil 3
Sanely clay 81
Clay, some sand 6
Dirty sand 9
Coal 3
Coarse sand 2
Coarse gravel 21
Gravel and fine sand 5
! WELL 16 (MUNICIPAL)
|
Topsoil 2
Sand and clay 6
Sand 13
Plav AD
v^iciy t-r^
Sand and clay streaks 7
day 20
Mu&dysand 10
111 *
120 *
140
15 *
17.5 *
25 *
30 *
35 *
40 *
100 *
3
84
90
99 *
102 *
104 *
125 *
130 *
2
8
21
63
70
90
100 *
55
-------
Sand 18
Gravel and coarse sand 15
WELL 17 (MUNICIPAL)
Fill and topsoU 4
Sandy clay 4
Sand 8
Qay 70
Sand 4
Coarse sand 10
Fine sand 10
/"!*..Q. fป1 _________.___ <
\JL ctV CJL ~~"~ ~~"" ~~ ' '~ *}
Medium sand 7
Sand and gravel 3
WELL 18 (MUNICIPAL)
Sand 40
Clay, sandy; gravel 13
Clay, boulders 2
Clay, sandy 18
Sand, fine 17
Sand, fine; traces of lignite ; 29
Sand, fine; gravel = 16
Sand; boulders 4
WELL 19 (INDUSTRIAL)
Yellow sandy clay '- 5
Hard sand and clay 3
Yellow sandy clay 22
Hard sand 2
Yellow sandy clay 2
Hard sand 4
Sand and gravel 3
Sandy blue clay 11
Black sandy clay 11
Sand, gravel, and clay, mixed 23
ConrI 1
OcUlU ~" j
Coarse sand 2
Blue clay 5
Rock 1
Sand and clay 6
Blue clay and sand 5
118 *
133 *
4
8
16
86
90 *
100 *
110 *
115 *
122 *
125 *
40
53
55
73
90 *
119 *
135 *
139 *
5
8
30
32
34
38
41 *.
52
63
86 *
. 89 *
91 *
96
97
103
108
56
-------
Clay, sand and gravel mixed 3
Sand and gravel, water 7
! WELL 20 (INDUSTRIAL)
i
Tnncnil ', A ซ
1 OppOll \J.J
GraVelly yellow clay 5.5
Sandy yellow clay 32
Very sandy soft yellow clay 7
Sanely gray clay, some very sandy with
a little water 47
Mucldy sand and gravel, yellow ' 4
Fine muddy sand, yellow 12
! WELL 21 (TEST HOLE)
i
Soil, black 2
Sand, very fine, clayey 3
Cla^, silty and sandy, yellowish-brown 8
Gravel, fine to coarse; sand,
medium to coarse 4
Clay, silty, olive-gray; thin layers of sand
and gravel; lignite fragements 33
Sand, fine to medium; minor
amount of clay 11
Gravel, fine to coarse 3
Clay, silty, olive-gray, pebbles 8
Grajvel, fine to coarse 2
Clay, silty, olive-gray 6
Clay, sandy, ovlive-gray; abundance
of lignite fragments 43
Gravel, fine to medium; sand, coarse 27
Clay, silty, olive-gray; lignite fragments and
thin layers between 240 and 273 feet 100
GraVel, fine to coarse, rough
drilling; 6
San!d, clayey, greenish-gray 15
i WELL 22 (TEST HOLE)
Topsoil and clay 10
Clay; streak of sand 10
Clay and sand interbedded 10
Clay; streak of sand 35
Sand; trace of clay 5
111 *
118 *
0.5
6
38
45
92
96
108
2
5
13
17
72
83 *
86 *
94
96 *
102
145
172 *
272
278 *
293
10
20
30
65
70 *
57
-------
Sand, fine 64
Rocky, trace of hard clay 1
Rocky and clay, hard 5
wileLLG IT:.-. -. .ปซ,ซ.ซซ,ซป__ปซ___ I.. '~ 1
WELL 23 (MUNICIPAL)
Clay, hard and soft 67
Sand, "clean" 81
Sand; rocky 7
Sandy and clay 2
Clay, "blue" : 5
WELL 24 (MUNICIPAL)
Fill 4
Clay and streaks of sand 107
Coarse gravel and boulders 36
WELL 25 (MUNICIPAL)
FiU 6
Gumbo 2
Sand 6
day -68
Mud, sticks and sea shells 5
Clay 10
Muddy sand and clay 13
Clay and big gravel 3
Big gravel : ' .26
WELL 26 (INDUSTRIAL)
; A
*-r
Yellow clay 12
Sandy gray clay ' 24
Hard pan, rocks 8
Gravel 19
Clayey sand and gravel 4
Sand and gravel : 11
WELL 27 (TEST HOLE)
Soil, black- : 1
134 *
135
140
141
67
148 *
155 *
157
162
4
111
147 *
6
8
14
82
87
97
110
113
139 *
4
16
40
48
67 *
71 *
82 *
58
-------
Clay, jyellowish-gray 3
Sandjjvery fine to fine 4
Sand,|very fine to very coarse;
abundance of pelecypod valves 8
Clay, jsilty, dark-greenish-gray - 57
Clay, jsandy, brownish-gray 5
Sand,jfine to coarse; abundance of lignite
fragerbents; many fragement
of pelecypod valves 11
Gravel, fine to very coarse; lost circulation
from JLOO to 128 feet; used 41 bags of
bentonite; abondoned at 128 feet 39
i
WELL 28 (INDUSTRIAL)
i
ClayJ 10
Shalei dark (small amount of water) 2
Clay blue 22
Shalei dark (Small amount of water) 2
Clay,jblue 51
Clay,jgray : 162
Hard tnaterial 2
Shale (water) 3
Clay, blue 2
I WELL 29 (TEST HOLE)
i
Soil, black . 1
Clay, jsilty to sandy , yellow to.
olivje brown 9
Sand,,!meidum to coarse; gravel, fine,
clayey 22
Clay, isandy, dark-greenish-gray 7
Clay, Idark-greenish-gray; alternating
with sand, very fine to fine 33
Gravel, fineto medium; sand, coarse;
gastropodand pelecypod fragments 35
Sand,; very fine, light-greenish-gray clayey 19
j WELL 30 (DOMESTIC).
j
i
Brown clay 26
Quicksand 2
Sandy clay 6
4
8
16
73
78
89
128 *
10
12
34
36
87
249
251
254 *
256
1
10
32
39
72
107 *
126
26
28 *
34
59
-------
Blue clay
Soft blue clay
Sandy blue clay
Blue Clay
Sandy clay
19
11
1
15
4
53
64
65
80
84
60
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