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STATE OF FLORIDA
STATE BOARD OF CONSERVATION

FLORIDA GEOLOGICAL SURVEY
Robert O. Vernon, Director





INFORMATION CIRCULAR NO. 28





RECONNAISSANCE OF THE GROUND-WATER RESOURCES
OF THE
FERNANDINA AREA, NASSAU COUNTY, FLORIDA






By
Gilbert W. Leve, Geologist
U. S. Geological Survey



Prepared by the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with the
FLORIDA GEOLOGICAL SURVEY




Tallahassee, Florida
1961




400(. q


F O. L "



AGRI-
CULTURAL
LIRARY













TABLE OF CONTENTS


Page


Abstract . . . . . .
Introduction . . . . . .
Previous investigations . . .
Acknowledgments ................
Well-numbering system. ...... .
Geography. ......................
Geologic formations and their water-bearing
properties ....................
Ground water .....................
Artesian aquifer.................
Piezometric surface . . ..
Quality of water ....................
Salt-water contamination . . .
Conclusions ......................
References . . . . . .










ILLUSTRATIONS


Figure Page

1 Map of the Florida Peninsula showing the
location of Nassau County and the
Fernandina area ................. 6
2 Geologic section showing the formations
penetrated by well 038-127-4 at Fernandina .. 8
3 Map of the Fernandina area showing the
location of wells. ... ............. 10
4 Maps of the Fernandina area showing the
piezometric surface in 1946 and 1959 .... .13
5 Hydrograph of well 040-126-1 in Fernandina 14
6 Graphs showing the chloride content of water
from wells 039-128-3, 039-127-2, and
038-127-4 in the Fernandina area. . .. 20
7 Graph showing the chloride content of water
sampled at different depths in well 041-127-2 21


Table

1 Chemical analyses of water from artesian
wells in the Fernandina area ...... .16 and 17
2 Chloride content of water from artesian
wells in the Fernandina area . . 18












RECONNAISSANCE OF THE GROUND-WATER RESOURCES
OF THE
FERNANDINA AREA, NASSAU COUNTY, FLORIDA


By
Gilbert W. Leve




ABSTRACT

This report describes an area approximately 8- miles
long and 6 miles wide, adjacent to the Atlantic Ocean in
northeastern Florida. Sand and alluvium of Pleistocene and
Recent age are exposed at the surface. They are immedi-
ately underlain by undifferentiated deposits of marl, sand,
and shell of undetermined age. These, in turn, are under-
lain by the Hawthornformation of middle Miocene age which
consists predominantly of clay beds. The Hawthorn forma-
tion is underlain bylimestones of Eocene age whose top was
found to be 550 feet below land surface in one well.

The limestones of Eocene age contain water under ar-
tesian pressure and are the principal source of water in the
area. The artesian aquifer is recharged to the north and
west of the area where the limestones crop out or are hydro-
logically connected to bodies of surface water.

Water is discharged from the aquifer in the Fernan-
dina area by municipal and industrial wells. This discharge
has created a depression in the piezometric surface in the






FLORIDA GEOLOGICAL SURVEY


Fernandina area. Since 1946, there has been a decline in
the piezometric surface of about 10 to more than 20 feet and
the area in which the altitude of the piezometric surface is
at or below mean sea level has approximately tripled. Hy-
drographs of water levels show that in the area of discharge,
the artesian pressure has declined more than 50 feet since
1939.

The chloride content of water in 1959 ranged from 26
to 41 ppm (parts per million) from wells less than 1,400
feet deep and from 50 to 1, 060 ppm from wells more than
1, 400 feet deep. Recently there has been a general increase
in the chloride content of water from wells tapping the ar-
tesian aquifer. This increase averaged less than 10 ppm
since 1940 in wells less than 1, 400 feet deep, and from 20
to 640 ppm since 1952 in wells more than 1, 400 feet deep.

Possible sources of salt-water contamination may be
salt zones in the lower part of the aquifer below the fresh-
water zone or thin zones of mineralized water within the
fresh-water zone. Most water samples collected did not
indicate sufficient saline content to endanger municipal and
industrial supplies. However, as more water is withdrawn
from the artesian aquifer and wells are drilled deeper into
the lower part of the aquifer, it is possible that increasing
amounts of saline water maymove into the fresh-water zones
and make them unsuitable for domestic and industrial use.


INTRODUCTION

Practically all water for municipal and industrial use
in the Fernandina area is supplied by artesian wells. In
recent years, the use of artesian water in the area has in-
creased to meet the needs of expanding industry and increas-
ing population. The total industrial and municipal pumpage
has increased from approximately 35 million gallons per day
in 1941 to approximately 50 million gallons per day in 1959.
Correlated with the increase in water use is the constant
decline in the artesian pressure in the area. In many other
areas in Florida, such a decline in artesian pressure has
resulted in salt-water intrusion into the fresh-water supply.






FLORIDA GEOLOGICAL SURVEY


Fernandina area. Since 1946, there has been a decline in
the piezometric surface of about 10 to more than 20 feet and
the area in which the altitude of the piezometric surface is
at or below mean sea level has approximately tripled. Hy-
drographs of water levels show that in the area of discharge,
the artesian pressure has declined more than 50 feet since
1939.

The chloride content of water in 1959 ranged from 26
to 41 ppm (parts per million) from wells less than 1,400
feet deep and from 50 to 1, 060 ppm from wells more than
1, 400 feet deep. Recently there has been a general increase
in the chloride content of water from wells tapping the ar-
tesian aquifer. This increase averaged less than 10 ppm
since 1940 in wells less than 1, 400 feet deep, and from 20
to 640 ppm since 1952 in wells more than 1, 400 feet deep.

Possible sources of salt-water contamination may be
salt zones in the lower part of the aquifer below the fresh-
water zone or thin zones of mineralized water within the
fresh-water zone. Most water samples collected did not
indicate sufficient saline content to endanger municipal and
industrial supplies. However, as more water is withdrawn
from the artesian aquifer and wells are drilled deeper into
the lower part of the aquifer, it is possible that increasing
amounts of saline water maymove into the fresh-water zones
and make them unsuitable for domestic and industrial use.


INTRODUCTION

Practically all water for municipal and industrial use
in the Fernandina area is supplied by artesian wells. In
recent years, the use of artesian water in the area has in-
creased to meet the needs of expanding industry and increas-
ing population. The total industrial and municipal pumpage
has increased from approximately 35 million gallons per day
in 1941 to approximately 50 million gallons per day in 1959.
Correlated with the increase in water use is the constant
decline in the artesian pressure in the area. In many other
areas in Florida, such a decline in artesian pressure has
resulted in salt-water intrusion into the fresh-water supply.






INFORMATION CIRCULAR NO. 28


An intrusion of salt water in the Fernandina area would con-
taminate the existing fresh-water supply and would result
in a hardship for the population and seriously injure the
economy.

Recognizing the threat to the fresh-water supplies of
this area, the U. S. Geological Survey in cooperation with
the Florida Geological Surveymade a reconnaissance to de-
termineif there has been any intrusion of salt water into the
fresh-water supply or if there is any danger of future intru-
sion.

This report presents the information collected during
October and November, 1959, and discusses the results of
this reconnaissance. The major phases of the reconnais-
sance included the following:

(1) Collection and compilation of existing ground-water
data.

(2) An inventory of wells to determine their number,
distribution, depths, diameters, yields, artesian
pressure, and other pertinent information.

(3) The study of existing geologic information to de-
termine the thickness, character, and extent of the
different geologic formations.

(4) The collection and study of artesian-pressure data
to determine the seasonal fluctuations and progres-
sive trends.

(5) A study of the quality of the artesianwater to deter-
mine if the decline in artesianpressure had caused
an intrusion of saltwater into the artesian aquifer.

The investigation was made under the general super-
vision of Philip E. LaMoreaux, chief, Ground Water Branch,
U. S. Geological Survey, and under the immediate super-
vision of M. I. Rorabaugh, district engineer for Florida.






FLORIDA GEOLOGICAL SURVEY


Previous Investigations

Detailed studies of the ground-water resources and
geology of the Fernandina area were made by Cooper (1944,
p. 169-185) and Derragon (1955). Much of the field data
collected during these earlier studies were used in prepar-
ing this report.

Chemical analyses of water from a number of wells in
the area are included in a report byBlack and Brown (1951,
p. 81-82).

Numerous reports by the U. S. Geological Survey and
the Florida Geological Survey have included general infor-
mation on the ground-water resources and geology of the
Fernandina area.


Acknowledgments

The writer wishes to express his appreciation to Mr.
T. Oliver, power superintendent, Container Corporation of
America; Mr. H. G. Taylor, chief chemist, Rayonier Inc.;
and to Mr. Revells, engineer, Florida Public Utilities Co.,
all of whom supplied valuable data and permitted the meas-
uring and sampling of wells.


Well-numbering System

Wells inventoried during this investigation were each
assigned an identifying well number. The well number was
determined by first locating each well on a map which was
divided into 1-minute quadrangles of latitude and longitude,
then numbering consecutively each inventoried well in a
quadrangle. The well number is composed of the last three
digits of the degrees and minutes of latitude south of the
well, followed by the last three digits of the degrees and
minutes of longitude east of the well, followed by the number
of the well in the quadrangle. For example, well 039-128-2
is the well numbered 2 in the quadrangle bounded by latitude
30039' on the south and longitude 81028' on the east. With






INFORMATION CIRCULAR NO. 28


this system, a well referred to by number in the text can be
located on figure 3.


GEOGRAPHY

This report describes an area approximately 81 by 6
miles adjacent to the Atlantic Ocean in northeastern Florida
(fig. 1). It includes the city of Fernandina and adjacentparts
of Nassau County.

The easternpart of the area, which includes the city of
Fernandina, is an offshore bar separated from the mainland
by the Amelia River and its tributaries. The western part
of the area is a dissected plain which slopes irregularly
eastward toward the ocean.

The land surface is relatively low and flat, ranging in
altitude from sea level to about 20 feet. Small scattered
sand hills and dunes in the eastern part attain altitudes of
more than 50 feet.

Surface drainage is principally by the Amelia River
and its tributaries. Drainage is sluggish in the streamval-
leys and on the irregular marsh plain west of the river.





6 FLORIDA GEOLOGICAL SURVEY




Figure 1. Map of the Florida Peninsula showing the location
of Nassau County and the Fernandina area.






INFORMATION CIRCULAR NO. 28


GEOLOGIC FORMATIONS
AND THEIR WATER-BEARING PROPERTIES1

The principal source of water in the Fernandina area
is permeable limestones of Eocene age. As shown in fig-
ure 2, the top of the limestone section is about 550 feet
below the land surface, and more than 1, 500 feet thick in
well 038-127-4.

Thelower three Eocene formations, the Oldsmar, Lake
City, and Avon Park limestones, consist of alternating beds
of soft, porous limestone and hard, dense crystalline lime-
stone and dolomite. The upper three Eocene formations,
the Inglis, Williston, and Crystal River formations, con-
sist of a homogeneous sequence of soft, porous limestone
containing a few dolomite lenses near the base.

The Hawthorn formation of middle Miocene age over-
lies the Crystal River formation throughout the area. It
consists of greenish gray, phosphatic, calcareous clay con-
taining lenses of dolomite, limestone, and sand.

Undifferentiated deposits of greenish gray sandy, shelly
marl overlie the Hawthorn formation. The author did not
attempt to determine the exact age of these beds. As shown
in figure 2, they are referred to as post-Hawthorn deposits.

The relatively impermeable clay, marl, and dolomite
beds in the Hawthorn formation and the post-Hawthorn de-
posits serve as confining beds for the artesian water in the
underlying limestones of Eocene age. The combined thick-
ness of these confining beds is more than 500 feet in well
038-127-4 (fig. 2).

Sand and alluvium of Pleistocene and Recent age cover
the surface of the area. The sand is 40 feet thick in well
038-127-4 (fig. 2).


'The classification and nomenclature of the rock units used
in this report conform to the usage of the Florida Geological
Survey and are not necessarily those of the U. S. Geological
Survey.






INFORMATION CIRCULAR NO. 28


this system, a well referred to by number in the text can be
located on figure 3.


GEOGRAPHY

This report describes an area approximately 81 by 6
miles adjacent to the Atlantic Ocean in northeastern Florida
(fig. 1). It includes the city of Fernandina and adjacentparts
of Nassau County.

The easternpart of the area, which includes the city of
Fernandina, is an offshore bar separated from the mainland
by the Amelia River and its tributaries. The western part
of the area is a dissected plain which slopes irregularly
eastward toward the ocean.

The land surface is relatively low and flat, ranging in
altitude from sea level to about 20 feet. Small scattered
sand hills and dunes in the eastern part attain altitudes of
more than 50 feet.

Surface drainage is principally by the Amelia River
and its tributaries. Drainage is sluggish in the streamval-
leys and on the irregular marsh plain west of the river.







FLORIDA GEOLOGICAL SURVEY


Geologic section showing the formations penetrated
by well 038-127-4 at Fernandina.


GEOLOGIC DEPTH
AGE FORMATION BELOW SECTION LITHOLOGY
AGESURFACE I


AO
IN 7--


- 550 -
55-







"9300'

-,028'-


i;'' *:; .I Snd, mediua-grained, clear to brown stained.


..- .- .L


5 ~ 'I-


i


S Harl greeonish-gray, sandy, shully.


Clay, anrl. land, and limestone.
Predominantly greenish-gray, sandy calcareous,
phosphoritic clay with bade of cream-colored
very sandyj phosphorltic, soft, slightly,
porous limestone and some thin layers of
dolomite and sand. The limestone and sand
bede yield water to some wells.


Limestono, cream-colored soft to hard, panty to
granular, porous. Parts of the formation
consist of a coquina of large foraminifera.


RECENT
PLEISTOCENE
HAWT RN

Z L
u z
wJ _
S5
0






w
I-
.J






W
z



W W
0
0J


I80' -E-- clay, gray, waxy, dane.
Dolomite, can to brown, hard, donse, black speckled,
cryutalline,
> I I Limestones cream-colored to dark-gray, soft, pasty,
I~ Z atirly porous, hard, granular to dense,
0 I0 foslliferous.
I-
i U Limestone, cream-colored to tan, hard, dense,
M crystalline In part, dolomitic.
-_J Dolomite, tan, hard, denser crystalline and some
cream-colored, soft porous limestone.


LII


Dolomite, tan,bhrd, dense, crystalline.
Limestone, cream-colored, soft, pasty, granular,
porous, tosiliferous and some dolomite,
chalcedony, and glauconite (?).
Limestone, cream-colored, soft, granular, porous
and tan to brown, hard, finely crystalline,
dense dolomite.


Figure 2.


POST HAWTHOI
OEPOStTS


CRYSTAL
RIVER
FORMATION

WILLISTON
FORMATION
INGLIS
FORMATION
-J
z
0 n it
0. W /


Llmestone, cream-colored to tan, softgranular,
porous, foseolifrous, dolomitic in part.

Limestone, cream-colored, hard to soft, pasty.
Dolomite. tan to brown, hard, dense crystalline,
slightly porous.
Limestone, cream-colored, soft, granular, dolomitic.
Dolomite, tan to brown, hard, donee.


2,130'


1,756'


' '-'


**


--1---1,756'






INFORMATION CIRCULAR NO. 28


Manydomestic wells obtain water from the Pleistocene
and Recent sand and from the thin sand, limestone, and shell
lenses in the Hawthorn and post-Hawthorn deposits. How-
ever, the small quantity of water available from these beds
necessitates the drilling of deeper wells into the more pro-
ductive limestones of Eocene age for municipal and industrial
purposes.


GROUND WATER

Ground water is that part of the subsurface water that
is in the zone of saturation, in which all pore spaces in the
rock are filled with water. It is derived almost entirely
from precipitation but not all precipitation becomes ground
water. Part of it is returned to the atmosphere by evapo-
transpiration and part of it drains overland into lakes,
streams, and the ocean.

Ground water may occur under either nonartesian or
artesian conditions. Where the ground water is not con-
fined and its surface is free to rise and fall, it is said to be
under nonartesian conditions. Where the water is confined
in a permeable bed that is overlain by impermeable beds so
that its surface is not free to rise and fall, it is said to be
under artesian conditions. The term "artesian" is applied
to ground water that is confined under sufficient pressure to
rise in a well above the top of the permeable bed that con-
tains it. The artesian pressure head is the height to which
water will rise in an artesian well and the piezometric sur-
face is the imaginary surface to which water will rise in
tightly cased wells that penetrate the artesian aquifer. The
location of the wells inventoried in the area are shown on
figure 3.

An aquifer is a formation, group of formations, or
part of a formation in the zone of saturation that is perme-
able enough to transmit usable quantities of water. Areas
in which aquifers are replenished are called recharge areas
and areas in which water is lost fromthe aquifer are called
discharge areas.






10 FLORIDA GEOLOGICAL SURVEY


Figure 3. Map of the Fernandina area showing the location
of wells.

31' 81030' 29' 28' 27' 26' 81025'







INFORMATION CIRCULAR NO. 28


Artesian Aquifer

The artesian aquifer is the principal source of water in
the Fernandina area, therefore nearly all of the information
collected and studied during this investigation concerns the
artesian aquifer.

The artesian aquifer in the Fernandina area consists
of the limestone beds of Eocene age. Water is confined un-
der pressure in the limestones by beds of clay, marl, and
dolomite in the overlying Hawthorn formation and post-
Hawthorn deposits.

The artesian aquifer is recharged to the north and west
of the Fernandina area in southeastern Georgia and north-
central Florida. In the recharge area the limestones of
Eocene age either crop out at the surface and are recharged
directly by rainfall or the formations are hydrologically
connected to lakes, streams, sinkholes, and the nonartesian
aquifer.

Ground water moves laterally away from the recharge
areas through the permeable limestones toward areas where
discharge is occurring. In the Fernandina area, water is
discharged by numerous wells that penetrate the artesian
aquifer.

Figure 2 shows that below the Inglis formation, the
artesian aquifer contains beds of hard, dense, crystalline
dolomite and limestone. These relativelyimpermeable beds
tend to restrict the vertical movement of water in the aqui-
fer. Differences in static head and chloride content of the
water at different depths indicate that there are several
separate zones within the artesian aquifer in the Fernandina
area.

In the past, the Inglis, Williston, and Crystal River
formations have supplied sufficient quantities of water to
industrial and municipal wells and the underlying forma-
tions were not used as a source of water. Recently, because
of increasing demands for water a number of municipal and
industrial wells have been drilled into the underlying forma-
tions.






FLORIDA GEOLOGICAL SURVEY


Piezometric Surface

Since 1939, large quantities of ground water have been
withdrawn in the Fernandina area, principally by industrial
and municipal wells. This withdrawal has reduced the ar-
tesian pressure and has created a depression in the piezo-
metric surface in the area. The contours in figure 4 show
the piezometric surface in the Fernandina area in 1946 and
1959. As the piezometric surface fluctuates continuously in
response to changes in pressure within the artesian aquifer,
figure 4 can only approximate the piezometric surface dur-
ing these years.

Within the O-contour in figure 4, the piezometric sur-
face has been depressed to or below mean sea level. The
maps show that between 1946 and 1959 the area enclosed by
the O-contour line has approximately tripled. The slope of
the piezometric surface toward the discharge area repre-
sents the hydraulic gradient created by the discharging wells
in the Fernandina area. The maps reveal that the gradient
has decreased slightly, and that there has been a general
decline in the altitude of the piezometric surface of about
10 to more than 20 feet since 1946.

Periodic measurements of the artesian pressure have
been made since 1939 in well 040-126-1 in Fernandina. The
hydrograph(fig. 5) of this wellshows theprogressive trends
of the artesian pressure and the effect of withdrawal of ar-
tesian water by nearby industrial and municipal wells. The
artesianpressurehas declinedmore than50 feet since 1939.
Fluctuations in the artesian pressure indicate periods of
increased or decreased pumpage by the nearby industrial
and municipal wells. The artesian pressure in the well in-
creases when discharge decreases and vice versa. Fluc-
tuations of more than 10 feet are common, especiallyduring
periods when the industrial wells are shut down.


QUALITY OF WATER

The chemical character of ground water largely de-
pends upon the type of material with which the water has







INFORMATION CIRCULAR NO. 28


Figure 4. Maps of the Fernandina area showing the piezo-
metric surface in 1946 and 1959.

1946







Figure 5. Hydrograph of well 040-126-1 in Fernandina.


"!-- -


















-104 42 44 45 46 1948 49 2 56 1
1939 ;19401941 1942 1945 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959






INFORMATION CIRCULAR NO. 28


come in contact or by contamination with sea water. When
the water first enters the ground it is only slightlymineral-
ized. As it moves through the ground it may become more
mineralized by dissolving mineral matter from the rocks
and by mixing with mineralized water already in the rocks.

Chemical analyses of water from 14 artesian wells of
various depths in the Fernandina area are shown in table 1.
The degree of mineralization, expressed by the dissolved-
solid content, generally does not differ significantly among
wells less than 1,400 feet deep. Water from wells more
than 1, 400 feet deep generally show a higher degree of min-
eralization than the shallower wells. The dissolved-solid
content of water from well 038-127-4, which is 1, 826 feet
deep, was found to be 5 to 6 times as great as water from
wells less than 1, 400 feet deep.


Salt-water Contamination

In many parts of Florida, where there has been a de-
cline in artesian pressure, the existing fresh-water supply
has been contaminated by intrusions of salt water. These
intrusions have occurred in various ways, depending upon
the location and the geologic and hydrologic characteristics
of the different areas. In some areas, particularly near
the coast, salt water from the ocean has moved laterally or
vertically into the zones of reduced pressure. In other
areas, salt water has moved upward from deeper, highly
mineralized zones or laterally from relatively thin miner-
alized zones within the aquifer into the fresh-water zones.


Table 2 shows the chloride content by years of water
from wells of different depths that penetrate the artesian
aquifer in the Fernandina area. The chloride content, which
is an index of salt-water contamination, generally increases
with depth. In 1959, the chloride content of water from wells
less than 1, 400 feet deep ranged from 26 to 41 ppm and in
wells more than 1, 400 feet deep the chloride content ranged
from 50 to 1, 060 ppm.







16 FLORIDA GEOLOGICAL SURVEY








Table 1. Chemical Analyses of Water from Artesian Wells

in the Fernandina Area

(Chemical constituents in parts per million)



a s


number (feet) (feet) sampled -q a






039-127-1 750 ----- 1- 8-24 496 37 0.06 73 40 28 194 173 31 346 ---
4- 1-59 527 -- .0 80 37 -- 192 163 33 354 7.4

040-127-5 731 ----- 9-28-37 --- 22 .31 60 44 19 195 159 33 330 7.3
4- 2-50 480 33 .01 71 39 21 200 166 33 334 7.4
4- 1-59 509 -- .06 72 28 -- 202 144 29 300 7.4

042-126-1 800 550 5-15-59 583 -- .06 76 37 -- 192 228 36 344 7.2

042-127-1 800 534 5-15-59 535 -- .0 72 32 -- 190 198 33 316 7.7

042-127-2 800 520 5-15-59 552 -- .06 72 34 -- 180 193 32 320 7.3

Well 1,000 to 1,400 feet deep


038-126-2







039-128-2


039-128-3 1065 550


6-25-37
5-30-50
4-17-56
12- 6-56
8- 7-57
8-20-57
4- 1-59

5-30-50
4-17-56
12- 6-56
3- 7-58
12- 1-58
3-10-59
6-18-59
9- 3-59

1- 8-24
8- 7-57
3- 7-58
12- 1-58
3-10-59
6-18-59
9- 3-59








INFORMATION CIRCULAR NO. 28 17










Table 1. (Continued)

(Chemical constituents in parts per million)



2 8

Well Depth Cased Date 0 -- e .
number (feet) (feet) sampled S g

2 0 0 6 0 -7 2 '16 30
oa v- 0 BO na u
'- 4 a oo -^ 3 3 5 a


040-127-1 1100 552 9-28-37 --- 22 0.32 60 44 19 195 159 33 330 7.3
9-27-49 570 -- .0 82 35 14 205 162 30 350 7.4
4- 2-50 467 34 .01 66 39 27 204 160 36 326 7.3
5-15-59 524 -- .04 61 34 -- 192 224 29 296 7.4

040-127-2 1025 500 9-27-49 520 -- .10 80 35 16 205 161 30 344 7.4
4- 2-50 463 34 .0 69 41 23 204 168 34 338 7.3
4- 1-59 520 -- .0 72 42 -- 190 153 33 356 7.3

040-127-4 1203 550 4- 1-59 570 -- .09 77 40 -- 192 157 38 360 7.3

Wells more than 1,400 feet deep

038-127-4 1826 --- 4-17-56 1955 -- ---- 178 86 -- --- 360 644 790 --
12- 6-56 2475 -- --- 166 96 -- --- 375 687 808 --
8- 7-57 2805 -- ---- 163 85 -- --- 355 770 758 --
3- 7-58 2375 -- ---- 170 94 -- --- 364 790 812 --
12- 1-58 2365 -- ---- 168 104 -- --- 379 865 849 ---
3-10-59 2748 -- ---- 170 101 -- --- 372 860 841 --
6-18-59 3095 -- ---- 172 105 --- 382 960 864 --
9- 3-59 3048 -- ---- 170 101 -- --- 403 864 841 ---

039-127-2 1700 545 4-17-56 694 -- ---- 62 37 -- --- 169 44 308 ---
12- 6-56 579 -- ---- 79 35 -- ---168 38 341 ---
8- 7-57 611 -- ---- 70 39 -- --- 152 47 334 ---
3- 7-58 605 -- ---- 72 35 --- 177 47 324 ---
12- 1-58 622 -- ---- 74 38 -- --- 184 52 344 --
3-10-59 629 -- ---- 73 41 -- --- 172 50 351 --
6-18-59 548 -- ---- 73 41 --- 184 51 352
9- 3-59 622 -- ---- 74 44 -- --- 177 50 367 --

039-127-4 1820 545 4-17-56 820 -- ---- 92 36 -- --- 190 107 376
12- 6-56 730 -- ---- 80 45 -- --- 185 99 388 ---
8- 7-57 874 -- ---- 80 45 -- --- 197 112 386 --
3- 7-58 788 -- ---- 84 43 -- -- 206 112 387
12- 1-58 760 -- ---- 85 48 ----- 197 127 409 --
3-10-59 754 -- ---- 85 46 ----- 198 121 400
6-18-59 800 -- ---- 92 48 -- --- 203 126 436
9- 3-59 860 -- ---- 84 48 -- --- 182 125 409 --








18 FLORIDA GEOLOGICAL SURVEY








Table 2. Chloride Content of Water from Artesian Wells in

the Fernandina Area


(Deflnition of use: A, abandoned; D, domestic; 1, industrial; PS, public supply; S, stock)


Wall IDepth ICased I
number I(feet)I(feet) UseI


Chloride content In parts per million
11940 1948 1949 1950 19523 1953 19541 1955 1956
Wells less than 1,000 feet deep


035-127-1 580 350 D -------- 25 26-31 --- --- ---- ---- --- --- ----- ---- ---- 30

035-127-2 540 --- D ---- -------- ---------- -------- ----- --- 26 ------ ----- ----- 27

037-129-1 578 --- D.S --------- 27 ---------- ----- ---------- 27 ---------------- 28

037-!30-1 540 504 D ---- ---- 27 28 ---- --------- ---- ------- ---------------- 3

038-L26-1 550- --- A ---- ---- 28 ----- ----- -------------- --- 29 ------ ----------- 36

039-127-1 750 --- I ---- ---- 26 ------------- -------------- --- ---------------- 33

039-131-2 550- --- D ---- ---- ---- ----- -------- ----- ----------- 29 ------ ----- ----- 33

040-127-6 940 550 ---- ---- ---- ----- ----- --------- ----- ----- ----- 54-58 52-56 ----- 32

042-126-1 800 550 PS ---- --- 32 ------------------ ----- ----- ---------- --------- 36-40

042-127-1 800 550 PS ---- ---- 28 --------- ---------------------------------- ----- 3

042-127-2 800 520 PS ---- --------- --- --------- ----- ----- ----- 30 ------ ---------- 32

Wells between 1,000 and 1,400 feet deep

013-126-2 1203 572 PS -------- ----- --- ------ -- ---- ----- ----- -------- ------ 27 --- 29-30

039-128-1 1054 549 I ---- 34 30 ------ --- ------ ----- -- 33 30-35 29-32 26 38-40 37-38

039-128-2 1054 549 I 33 ---- 30 ----- ---- 30 ----- ----- ----- ----- 23-34 34 37-41 37-41

039-128-3 1065 625 I ---- -------- ----- ----- 30 ----- ----- ----- 30-32 30-32 35 32-40 33-37

040-127-1 1100 552 PS 33 ---- 29 ----- 30 36 ----- ----- -------------------------- 26-29

040-127-2 1100 --- PS 39 ---- 30 --- 30 34 --------- ------------------------- 33-35

Wells over 1,400 feet deep

038-127-4 1826 --- I -- -- ---- ----- --- -------- 420- 480- ----- 560- 644- 770 790- 860-
450 580 630 687 865 1060

039-127-2 1700 545 I ------------- ----- --------- 32-38 36-43 40-43 37-43 38-44 47 47-52 50-52

039-127-3 1840 551 I ---- ---- ---- ----- ---- ---- 65-68 70-77 77-85 82-96 89-90 99 102- 109-
116 130

039-127-4 1820 545 1 ---------- ------------- ---- 104 106- --------- 99-107 112 112- 121-
127 127 140

041-126-1 1404 550 I ---- ---- ---- ----- -- -- ----- --- -- ----- 142- 112- ----- 120
148 118






INFORMATION CIRCULAR NO. 28


The graphs (fig. 6) and the analyses (table 2) show that
in the past few years there has been a general increase in
the chloride content of water from wells that penetrate the
artesian aquifer in the Fernandina area. In wells less than
1, 400 feet deepthis increase has been small, averagingless
than 10 ppm since 1940. The increase in chloride content
of the water has been much greater in wells more than 1, 400
feetdeep. During 1952-59 the chloride content has increased
from 31 to 52 ppm in well 039-127-2 (1, 700 feet deep), and
it has increased from 420 to 1, 060 ppm in well 038-127-4
(1, 826 feet deep).

The increase in salt content of water from artesian
wells in the Fernandina area indicates that salty water is
entering the zone of reduced pressure and gradually con-
taminating the zone. The higher chloride content in water
from the deeper wells indicates that the salty water is being
drawn from deeper, highly mineralized zones. If this is
true, the recent drilling and deepening of artesian wells in
the Fernandina area may tend to hasten contamination of the
water in the upper zones. The deeper wells have penetrated
relatively impermeable beds in the lower part of the aquifer
that restricted vertical movement of water. When these
impermeable barriers are penetrated by wells, it is possible
that the salty water in the lower part of the aquifer will flow
up the well bore and into the zone of reduced artesian pres-
sure in the upper part of the aquifer.

An indication that salt water may also be present in
the upper zones of the artesian aquifer was found during the
construction of well 041-127-2. The chloride content of
water samples taken at 10-foot intervals in this well indi-
cated a zone of relatively saltywater between 1, 230 feet and
1, 450 feet. As shown graphically in figure 7, the chloride
content of the water in this depth zone increases from less
than 100 ppm to more than 500 ppm. The graph also shows
a gradual increase in the chloride content of the water in the
zone below 2, 020 feet.

Most water samples collected during this investigation
did not indicate sufficient saline content to endanger the mu-
nicipal or industrial supplies. However, as more fresh







Figure 6. Graphs showing chloride content of water from wells
039-128-3, 039-127-2, and 038-127-4 in the Fernan-
dina area.
40 Well 039-128-3
35Total depth 1,065 ft.

0 30
-j
.I
2 60
c- Well 039-127-2
S50-_Total depth 1,700 ft.___
a. 50-




S1,100 Well 038-127-4
1 0oo Total depth 1,826ft-

'- 900
z

U 800

S700
-J
o 600--
' 500

400

300
1952 1953 1954 1955 1956 1957 1958 1959







INFORMATION :CIRCULAR NO. 28


Figure 7.






0
1,100




1,200 -




1,300-




S1,400
rr


o 1,500-
z


-J
Z



1 1,600-


I-

LL 1,700 -
2

I-
S1,800
Q


Graph showing the chloride content of water
sampled at different depths in well 041-127-2.


CHLORIDE CONTENT, IN PARTS PER MILLION






FLORIDA GEOLOGICAL SURVEY


water is withdrawn from the artesian aquifer, it is likely
that increasing amounts of salty water may move into the
fresh-water zones and make them unsuitable for domestic
or industrial use.


CONCLUSIONS

The following conclusions can be made as a result of
this reconnaissance.

The principal source of water in the Fernandina area
is permeable limestone of Eocene age whose top was found
to be 550 feet below land surface in well 038-127-4. These
limestones are overlain by the Hawthorn formation of middle
Miocene age which consists of beds of clay containing dolo-
mite, limestone, and sand lenses. The Hawthorn formation
is overlain by undifferentiated deposits of marl, sand, and
shell of undetermined age. The impermeable beds in the
Hawthorn formation and post-Hawthorn deposits confine ar-
tesian water in the underlying limestones of Eocene age.
Sand and alluvium of Pleistocene and Recent age cover the
surface of the area.

The piezometric surface has declined in the Fernandina
area because of withdrawals of artesian water by municipal
and industrialwells. Between 1946 and 1959 the piezometric
surface declined about 10 to 20 feetand the area inwhich the
piezometric surface was at or below mean sea level approxi-
mately tripled. Water-level records show that in the dis-
charge area the artesian pressure has declined more than
50 feet since 1939 and commonly fluctuations of more than
10 feet occur in response to variations in discharge of in-
dustrial and municipal wells.

The chloride content of water from wells in the arte-
sian aquifer generally increases with depth. In 1959, the
chloride content of water from wells less than 1, 400 feet
deep ranged from 26 to 41 ppm and inwells more than 1, 400
feet deep ranged from 50 to 1, 060 ppm.

Recently there has been a general increase in the







INFORMATION CIRCULAR NO. 28


chloride content of water from artesian wells. In wells less
than 1, 400 feet deep this increase has been small, averag-
ing less than 10 ppm since 1940. In wells more than 1, 400
feetdeep this increase has been much greater, ranging from
20 to 640 ppm since 1952.

The higher chloride content of water from deeper wells
indicates that salty water is entering the fresh-water zone
from mineralized zones in the lower part of the aquifer. It
is possible that deep wells penetrating relatively impermea-
ble beds in the lower part of the aquifer will allow salty
water to move up into the fresh-water zones at a fast rate.
A relatively salty zone within the fresh-water zone was found
during the construction of well 041-127-2.

Mostwater samples collected did not indicate sufficient
saline content to endanger municipal or industrial supplies.
However, the increase in chloride content of water from
wells in the past years shows that salty water is gradually
contaminating the fresh-water supplies. If this trend con-
tinues the water from the artesian aquifer in the Fernandina
area could become progressively saltier than at present.
It is then conceivable that at some future date it maybecome
unsuitable for domestic and industrial use.






FLORIDA GEOLOGICAL SURVEY


REFERENCES


Black, A. P.
1951


(and Brown, Eugene) Chemical character of
Florida's waters 1951: Florida State Board
of Cons., Div. Water Survey and Research,
Paper 6.


Brown, Eugene (see Black, A. P.)

Cooper, H.H., Jr.
1944 Ground-water investigations in Florida (with
special reference to Duval and Nassau coun-
ties): Am. Water Works Assoc. Jour., v. 36,
no. 2, p. 169-185.

Derragon, Eugene
1955 Basic data of the 1955 study of ground-water
resources of Duval and Nassau counties,
Florida: U. S. Geol. Survey, open-file infor-
mation.










FLRD GEOLOSk ( IC SUfRiW


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