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 Transmittal letter
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 Geology and hydrology
 References


FGS






STATE OF FLORIDA

STATE BOARD OF CONSERVATION

DIVISION OF GEOLOGY



FLORIDA GEOLOGICAL SURVEY
Robert O. Vernon, Director



REPORT OF INVESTIGATIONS NO. 29


AQUIFERS

ALONG THE


AND QUALITY OF GROUND WATER

GULF COAST OF WESTERN FLORIDA


By
Jack T. Barraclough and Owen T. Marsh
U. S. Geological Survey


Prepared by the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with the
FLORIDA GEOLOGICAL SURVEY,
ESCAMBIA COUNTY, SANTA ROSA COUNTY,
and the
CITY OF PENSACOLA


TALLAHASSEE
1962




40t '





CULTUR4
LIBRARY
FLORIDA STATE BOARD

OF

CONSERVATION







FARRIS BRYANT
Governor


Tom Adams
Secretary of State



J. Edwin Larson
Treasurer



Thomas D. Bailey
Superintendent of Public Instruction


Richard Ervin
Attorney General



Ray E. Green
Comptroller



Doyle Conner
Commissioner of Agriculture


W. Randolph Hodges
Director







LETTER OF TRANSMITTAL


lonaida Gjeologica Suve

Tallahassee
August 8, 1962



Honorable Farris Bryant, Chairman
Florida State Board of Conservation
Tallahassee, Florida
Dear Governor Bryant:
The Division is publishing, as Florida Geological Survey Report of
Investigations No. 29, a comprehensive report on the aquifers and qual-
ity of ground water along the gulf coast of western Florida, written
by Mr. J. T. Barraclough,' engineer, and Mr. Owen T. Marsh, geologist,
U. S. Geological Survey. This report was prepared in cooperation with
this department, Escambia County, Santa Rosa County, and the City
of Pensacola.
Three separate aquifers have been identified, each being separated
by clay aquicludes. With the definition of the geology in this area, it
becomes possible to make some tentative plans for deep well waste
disposal, as well as the wise and comprehensive management of the
fresh water resources contained in the shallow aquifers.

Respectfully yours,
Robert O. Vernon, Director
and State Geologist




























Completed manuscript received
February 21, 1962

Published for the Florida Geological Survey
By Rose Printing Company, Inc.
Tallahassee, Florida
August 8, 1962







CONTENTS

Page
Abstract 1______________

Introduction 1___ ___ ______-____- -
Purpose and scope -_____
Location of the area -- ----2-------__------__ ---- 2
Previous work __2_____-------
Acknowledgments ---__---_-----___ 3

Geology and hydrology 4______ .___._____ 4
Geologic setting -- --_ ___- _-______ 4
Hydrologic principles 4_____
Aquifers 7_______ ___ 7
Sand-and-gravel aquifer 7-_ ------7
Floridan aquifer 9----------
Upper limestone 10
Lower limestone _____ 16
Aquicludes _____ _____________ 17
Miocene clay 17
Bucatunna Clay Member __17
Middle Eocene clay and shale 18

Chemical quality of ground water 18
Definitions and general discussion ----- ---- 18
Water in the sand-and-gravel aquifer 20
Dissolved solids ___- ------20
Hardness 20
Chloride 20
Fluoride _20
Iron _____ -- 20
Dissolved gases __-20
Water in the Floridan aquifer ---- 20
Upper limestone of the Floridan aquifer __21
Dissolved solids _--21
Hardness ___ 21
Chloride .- --- ___ _22
Fluoride ___ -- -23
Iron ____ 24
Dissolved gases --_________ 24
Lower limestone of the Floridan aquifer --- 24

Summary and conclusions ----- -------25

References --- ------------- ---- 27







ILLUSTRATIONS

Figure Page
1 Location of area described in this report ....-----...........-----... 3
2 Aquifers and aquicludes along the gulf coast of western Florida as
shown in representative test well near Pensacola ---.......--.---..... --- ---... 5
3 Geologic cross section A-A' along the gulf coast of western Florida 6
4 Water levels in a well in the sand-and-gravel aquifer and a well in the
Floridan aquifer compared with rainfall at Pensacola --------- 9
5 Western Florida gulf coast showing structure contours on top of the
upper limestone of the Floridan aquifer -..---- ......-------- -- 11
6 Western Florida gulf coast showing thickness of the upper limestone of
the Floridan aquifer --......---.---. ........----- ---------------------------- 12
7 Hydrographs of three wells tapping the upper limestone of the Floridan
aquifer, showing decline of artesian pressure head in southern Okaloosa
County ....-----.....................--- ------------- ----------------------.. 14
8 Western Florida gulf coast showing net decline of artesian pressure head
in wells tapping the upper limestone of the Floridan aquifer, January
1948 to September 1960 ..--...-----.-- --------------------- ------.------- 15
9 Western Florida gulf coast showing the dissolved-solids content of
water from the upper limestone of the Floridan aquifer .......----. _facing 22
10 Western Florida gulf coast showing hardness of water from the upper
limestone of the Floridan aquifer .......------------------facing 22
11 Western Florida gulf coast showing chloride content of water from the
upper limestone of the Floridan aquifer .----------- -----facing 24
12 Western Florida gulf coast showing fluoride content of water from the
upper limestone of the Floridan aquifer -------facing 24






AQUIFERS AND QUALITY OF GROUND WATER ALONG
THE GULF COAST OF WESTERN FLORIDA
By
Jack T. Barraclough and Owen T. Marsh

ABSTRACT

A study of electric logs, well cuttings, and chemical analyses of water
from wells in the western Florida Panhandle reveals the relation of
the quality of ground water to the geology. Three aquifers separated by
clay aquicludes underlie the panhandle west of the Choctawhatchee
River: (1) the sand-and-gravel aquifer at the surface, (2) the upper
limestone of the Floridan aquifer, and (3) the lower limestone of the
Floridan aquifer. The remarkably soft and relatively unmineralized water
in the sand-and-gravel aquifer supplies most of the wells in the western
half of the area. In the eastern half of the area, where this aquifer is
thin, most wells obtain water from the upper limestone of the Floridan
aquifer. Electric logs suggest that some fresh water may be present at
the top of the lower limestone of the Floridan aquifer in the area north
and east of Fort Walton Beach.
Dissolved solids, chloride, and fluoride in water from the upper lime-
stone of the Floridan aquifer increase in a southwesterly direction (down-
dip) across the area according to a simple, mappable pattern. Hardness
of the water decreases downdip as a result of ion exchange by clays
in the upper limestone. Areas of usable and unusable water have been
delineated on maps.
Two water problems in the Fort Walton Beach area are brought to
light by this study: (1) a sharp decline of water levels amounting to as
much as 82 feet since 1936, and (2) incipient salt-water intrusion at
the Fort Walton Beach Elementary School, induced by the drop in water
levels. The magnitude of this decline probably is related to the low
permeability of the clay in the upper limestone of the Floridan aquifer.

INTRODUCTION
PURPOSE AND SCOPE
The rapid growth of population in the western part of the Florida
Panhandle in recent years has resulted primarily from three factors: (1)
The abundance of excellent ground water has attracted more and more
industries to the area; (2) two large military bases, the Naval Air Station
at Pensacola and Eglin Air Force Base at Niceville, are in the area;
and (3) the unsurpassed beaches, numerous waterways, and agreeable






FLORIDA GEOLOGICAL SURVEY


climate have been attracting greater numbers of tourists as well as
permanent residents.
A key factor in both present and anticipated future growth is the
supply of fresh ground water. The present use of ground water in the
area probably exceeds 100 million gallons per day. The future develop-
ment and efficient utilization of the ground-water resources requires a
knowledge of both geologic and hydrologic conditions. For example,
what water-bearing formations underlie the area? How deep is the fresh
water? What is the chemical quality of the water? Is the water level
rising, falling, or remaining constant? These are some of the questions
that the authors of this report seek to answer.
This paper is a byproduct of an intensive investigation of the water
resources of Escambia and Santa Rosa counties being made by the U.S.
Geological Survey in cooperation with the Florida Geological Survey,
Escambia and Santa Rosa counties, and the city of Pensacola.

LOCATION OF THE AREA
The area discussed in this report (fig. 1) includes about 2,370
square miles in the western part of the Florida Panhandle. It includes
the southern half of the following counties: Escambia, Santa Rosa, Oka-
loosa, and Walton. This area extends about 74 miles along the gulf coast
from Perdido Bay (near Pensacola) to the east end of Choctawhatchee
Bay, and about 32 miles inland from the Gulf of Mexico, as far north as
Crestview and De Funiak Springs.

PREVIOUS WORK
Prior to 1961 relatively little was known about the geology and ground
water of westernmost Florida. A few reports contained information of a
reconnaissance or strictly local nature. The earliest published report that
describes the water resources of this area was by Sellards and Gunter
(1912). During the following year, a report on the geology and ground
water of the entire State by Matson and Sanford (1913) was published.
Jacob and Cooper (1940, unpublished manuscript) made a detailed
investigation of ground water in the Pensacola area; their report included
a section on geology by Stubbs. Heath and Clark (1951) made a detailed
investigation of the potential yield of ground water in the vicinity of
Gulf Breeze near Pensacola. Chemical analyses of ground water in the
area were prepared by Collins and Howard (1928) and by Black and
Brown (1951). Cooke (1945) included in his "Geology of Florida" a
reconnaissance of the area in which he described the marine terraces
and gave data from wells. The first detailed geologic study of Escambia






REPORT OF INVESTIGATIONS No. 29


Figure 1. Location of area described in this report.

and Santa Rosa counties was made by Marsh (1962) in connection with
a comprehensive investigation of the water resources of the area that is
currently being made by the U.S. Geological Survey. An interim report
of that investigation (Musgrove, Barraclough, and Marsh, 1961) sum-
marizes the geology and water resources of the western half of the area
discussed in the present paper.

ACKNOWLEDGMENTS
The writers would like to express appreciation to M. E. Batz and C. A.
Witcher, Jr., of the Chemstrand Corp. for various courtesies extended; to
Lehmon Spillers of Pensacola, as well as to Docie Bass and E. L. Thoma-
son of Fort Walton Beach for supplying data on wells; and to Earl
Campbell, Okaloosa County sanitarian, A. G. Symons of the Layne-
Central Co., and Shelby Sanders of Shelby Sanders and Associates for
furnishing chemical analyses of water samples.






FLORIDA GEOLOGICAL SURVEY


GEOLOGY AND HYDROLOGY
GEOLOGIC SETTING
The part of the Florida Panhandle described in this paper lies in the
Coastal Plain province and is situated along the north flank of the vast
sinking trough known as the gulf coast geosyncline. Long-continued sub-
sidence of this trough has resulted in the deposition of sand, clay, and
limestone beds, most of which thicken toward the gulf. These beds dip
about 30-35 feet per mile toward the southwest in the area of this report.
Fresh water occurs in parts of three principal aquifers: (1) the sand-
and-gravel aquifer, (2) the upper limestone of the Floridan aquifer, and
(3) the lower limestone of the Floridan aquifer (fig. 2). East of the
Choctawhatchee River the limestone of the Floridan aquifer forms the
land surface, which is pock-marked with countless sinkholes. West of the
river the limestone slopes uniformly southwestward until at Pensacola
it lies more than 1,200 feet below the surface. West of the Choctawhat-
chee River a westward-thickening wedge of sand and gravel underlies
the land surface. Throughout most of the area two thick beds of clay
separate the sand-and-gravel aquifer from the upper limestone of the
Floridan aquifer. A thinner but more extensive bed of clay divides the
Floridan aquifer into an upper limestone and a lower limestone (fig. 3).
The lower two clay beds pinch out near the eastern border of the area,
bringing the upper and lower limestones of the Floridan aquifer together
and causing the sand-and-gravel aquifer to rest directly upon the Floridan
aquifer. The uppermost clay bed ends abruptly farther west. The
Floridan aquifer is underlain by impermeable clay and shale.
HYDROLOGIC PRINCIPLES
Part of the rain that falls on the land surface runs off into lakes and
streams; part returns to the atmosphere by evaporation, either directly
or through the leaves of plants evapotranspirationn); and part seeps
into the ground to become ground water. A simple analogy would be to
compare the ground with a pail of sand. If you sprinkle water on the sand
(in imitation of rain) until the water rises nearly to the top of the sand,
you have a rough example of ground water that occurs under water-
table conditions. But to bring the analogy closer to reality, the pail must
have a few holes in the sides and bottom so that the water is continually
leaking out. Unless you keep sprinkling water on the sand, the water
level-called the water table-will drop steadily lower and lower.
Similarly, ground water keeps leaking away through seeps and springs
into streams, lakes, and oceans. This subterranean water supply must be
replenished periodically by rainfall (and snowmelt in northern areas)
if the water table is to remain near a given level. The quantity of rainfall










REPORT OF ,INVESTIGATIONS No. 29


DESCRIPTIVE SAMPLE LOG SCT IONO


Sand, light-brown, medium to very coarse


Sand, light-brown, very coarse;
and grovel


Sand, light gray, fine to very coarse;
mollusk shells
Claoy sandy
Sand, very coarse, shells; and grovel

Mollusk shels with some fine to very
coarse sdnd


Gravel with shells and medium
to very coarse sand
Cloy, gray
Grovel and shell fragments


300-


400-


500-


600-


700-


2 800


:3 900
i-
o OO

0
z
4 1000-
_j

3 1100-
0
o





. 1300-

z
S1400-

-.
w, 1500-


1600-


1700-


1800-


1900-


2000-


2100-
-

















2200-


2300


Cloy, dark-gray, sandy


L Limestone, grayish while, and dark -
z gray clay

0 Limestone, light gray fossils rare
o on, medium to very coarse, an

o Limestone, grayish whie, some
-J foraminifers in tower half

SJ
w z
j .J Cloy, dark gray a little pyrite and
So carbonaceous material
- o
s_j
0




z
uj
0 Limestone, white, abundant
Sforaminifers

I-


Cloy, gray, with forominifers


I---


. .. I


RESISTIVITY IN OHM-METERS
20 40 60 80 100 120 14C


I I I I I I I


: -::
-







~~ i~
ii --


Figure 2. Aquifers and aquicludes along the gulf coast of western Florida as

shown in representative test well near Pensacola.


Cloy, gray, sandy

Grovel, very coarse sand, shells


'


I


SAND AND- GRAVEL




SLOQUIFER




EXPLANATION


Relatively permeable bed


Relatively impereable bed*








AQUICLUDE
(Absent in northern haf of Escomblo
and Santa Roso Counties)







FLORIDAN AQUIFER
(Upper limestone)






A UICLUDE
(Bucotunno Cloy Member of
Byrom Formation)








FLORIDAN AQUIFER
(Lower limestone)










A 0OUICLUDE

















BALDWIN COUN
AL ABA


S--...--.-.-..-..---..-- -- --AREA DESCRIBED IN THIS PAPER ---------

TI ESCAMBIA COUNT SANTA ROS COUNTY SA OKALOOSA COUNTY
MA FLORIDA Polo lo C C \H T C
c _Slto ion A uo po tPNo1n60 SAWA ROSA SOUA O ISlond bo C Ole S
.... A. r


A
WEST
MO8LAV
01


EXPLANATION
Length of section 115 miles
Vertcol ecaggeraolon about 52 times
- Unconformily
I Well in plane of section

SWell projeced into plane of
election along Strike of boed


WALTON COUNTY A

H =E f A P c |voltar. ;IEAST


200
400
-600
-800
-1000
1200
1400

-'1800
-1600


2000
2200
-2400
-2600
-2800
-3000
3200


eI~wlncoN~r i~sn~a\.i~ 5 ~l ;3~os c.! 111As COUNTY WALTON COUNT Y
44 LA 13A M COUNTY



andl F1 Walton Dsi

OF Air r x It C


0 5 10 20 30miles
Map showing location of Cros Seclion A-A.


Figure 8. Geologic cross section A-A' along the gulf coast of western Florida.


SAND 8 AND I- GRAVEL :AQUIFER Sa8

Auj%.uE

CLAI
tMA li C, E ii~


AIDOCNE '~l0IFE R ......
G LO AN FORM 416R,15
mE FLOR
oM AQUIFER




SY LLOtNE. L AND GLA

ES1 14 i. 0 Itie
AIND



5 0 15 ie


Seoa levi


S200-
400-
600-
800-
S1000-
1200-
1400-
S1600-
W 1800-
IB0 -
1 2000-
2200-
, 2400-
2600-
- 2800-
s'ooo-


][ --


--


~300-


C, 41







REPORT OF INVESTIGATIONS No. 29


varies from month to month and year to year in an unpredictable man-
ner, although the average for a given period may be fairly constant. In
times of above-average rainfall the water table rises, and in times of
below-average rainfall the water table declines. Figure 4 shows this
relationship.
The type of ground water just described is called nonartesian. Com-
monly, however, the water is confined in a permeable bed of sand or
limestone, for example, that is sandwiched between relatively imperme-
able beds, such as clay. Such confined water is under artesian pressure.
Ground water is termed artesian if it is confined under enough pressure
to make it rise in a well above the top of the permeable bed that
contains the water. It is not necessary that the water rise to or above
the land surface to be classified as artesian. A rough demonstration of
water under artesian pressure can be made with a 3-foot piece of garden
hose filled with water. If you hold your thumb over one end and raise
the other end, you can feel the pressure against your thumb. But if some-
one were to cut a small hole into the upper surface of the hose near
its middle, a jet of water would shoot upward, just as water rises in a
well drilled through a confining bed of clay into a water-bearing bed of
sand or limestone. The height to which water will rise in an artesian
well is called the artesian pressure head.
An aquifer is a formation (such as a thick layer of sand or limestone),
a part of a formation, or a group of interconnected formations that are
permeable enough to transmit usable quantities of water. An aquiclude
is a bed (such as clay or shale) that is too impermeable to transmit
water in usable quantities.. Areas where aquifers are replenished are
called recharge areas, and areas where aquifers lose water are called
discharge areas.
AQUIFERS
SAND-AND-GRAVEL AQUIFER
The wedge-shaped deposit of sand and gravel that underlies the
land surface west of the Choctawhatchee River is known as the sand-
and-gravel aquifer (Musgrove, Barraclough, and Marsh, 1961). The aqui-
fer is exposed from Escambia County, Alabama, on the north to the
Gulf of Mexico on the south, and from the Choctawhatchee River on the
east at least to Mobile Bay on the west. Although the aquifer generally
thickens downdip to the west and southwest from its thin outcrop along
the Choctawhatchee River, considerable variations in thickness occur
throughout the area, as indicated in figure 3: 150 feet at Fort Walton
Beach, 500 feet at the Santa Rosa-Okaloosa County line, 300 feet in
downtown Pensacola, 700 feet at Perdido Bay, and 1,200 feet at Mobile
Bay. The aquifer overlies thick layers of relatively impermeable clay






FLORIDA GEOLOGICAL SURVEY


everywhere in the area except the eastern part, where it rests upon
the upper limestone of the Floridan aquifer.
The sand-and-gravel aquifer consists predominantly of white to
reddish brown quartz sand ranging from very fine to very coarse and in
places mixed with granules and small pebbles of quartz and chert. Lenses
and stringers of gravel and clay occur throughout the aquifer. The clay
lenses range from a few inches to several tens of feet in thickness and
may extend from a few feet to several miles in length. Impermeable
layers of hardpan also are found within the sand-and-gravel aquifer.
This dense, rusty brown material-referred to simply as "rock" by local
drillers-is formed through cementation of sand by iron oxides precipi-
tated from ground water. It occurs extensively throughout western
Florida and southern Alabama and ranges in thickness from a fraction
of an inch to 3 or 4 feet. Little is known about the lateral extent of
these layers, but probably no layer extends for more than a few thousand
yards.
Fossils, including snails, clams, and microscopic animals, indicate
that the lower part of the sand-and-gravel aquifer is of Late Miocene
Age (roughly 10-15 million years old); the upper part is much younger.
The sand-and-gravel aquifer contains ground water under both ar-
tesian and water-table conditions. Where the water is confined by clay
or hardpan, it is under artesian pressure. Where the water is not confined
by impermeable layers, it is under water-table conditions.
Changes of the water level within the sand-and-gravel aquifer are the
result of both natural and artificial causes. The principal natural cause
is variation in the amount of rainfall which affects recharge of the aquifer.
Manmade causes include intensive pumping and the erection of struc-
tures, such as dams or canals, which alter the natural pattern of drainage
or infiltration. Figure 4 compares variations in the annual rainfall at
Pensacola with changes of the artesian pressure head in a well drilled
into the upper limestone of the Floridan aquifer, as well as with changes
of the water level in a well drilled into the sand-and-gravel aquifer. The
hydrograph for the latter well (Santa Rosa 10) shows water-level
changes from 1947 to 1960 in an area where this aquifer is virtually
unaffected by pumping. The graph shows close correlation of ground-
water levels with rainfall. The high water levels from 1947 to 1949
reflect a very wet period, the lowered levels from 1950 to 1955 indicate
a relatively dry period, and the rise of the water table from 1956 to 1960
reflects the increase in rainfall during that period. The 1959-60 water
level is about the same as it was in 1948. The maximum change observed
during the period of record was 13 feet, the highest water level at 56
feet above sea level in 1949 and the lowest water level at 43 feet above
sea level in 1955.







REPORT OF INVESTIGATIONS NO. 29


f- us- T--r
juJ Well Walton 14, at Point Washington
(in the upper limestone of the Floridan aquifer)

LZ 25

20 -


00 OD PERIOD PERIOD
In




-z60
S40


1936 194 1947 94 949 950 1951 952 195 4 955 1956197 95 1959 960


the Floridan aquifer compared with rainfall at Pensacola.

Wells in the sand-and-gravel aquifer furnish almost all the ground
water used in Escambia and Santa Rosa counties, as well as a substantial
part of the smaller supplies in Okaloosa County. The temperature of

water from the aquifer increases with depth from about 680F near the
ground surface to about 74oF at about 400 feet below the.land surface.
The aquifer becomes less important in the eastern half of the area because
larger quantities of fresh water are obtainable from the upper limestone
of the Floridan aquifer at moderate depths.
FLORIDAN AQUIFER

In peninsular Florida the limestone formations that range in age
from Eocene to Miocene are collectively referred to as the Floridan
aquifer. Although it is much thinner than in central Florida, this aquifer
also underlies the entire Florida Panhandle and southwestern Alabama
at least as far as Mobile Bay.
groun surac toaou74F tabu71fetblw h ln Arae
Th qufrbeoesls iprtn n h asen afofte40abeas






FLORIDA GEOLOGICAL SURVEY


East of the Choctawhatchee River the Floridan aquifer forms the
land surface, which is dotted with sinkholes. West of the river the top
of the aquifer slopes uniformly southwestward (fig. 5) until at the
eastern shore of Mobile Bay it lies about 2,100 feet below the land
surface. Thus, the top of the Floridan aquifer has an average apparent
dip (along section A-A', fig. 3) of about 20 feet per mile from east to
west.
Within the area of this report the Bucatunna Clay Member of the
Byram Formation separates the Floridan aquifer into an "upper lime-
stone" and a lower limestone." The Bucatunna thins to the east and
finally pinches out a few miles east of Destin. The maximum thickness
of the Floridan aquifer within the area, including both the upper and
the lower limestones, is about 1,900 feet in southern Walton County.
Upper limestone. Along section A-A' (fig. 3) between the
Choctawhatchee River and Mobile Bay the upper limestone ranges from
350 to 450 feet in thickness. The upper limestone thins northward from
the Gulf of Mexico (fig. 6). This thinning is much more rapid in the
eastern part of the area than in the western. The thinnest known section
of the upper limestone (45 feet) is in southern Okaloosa County, north
of Niceville: the thickest known section (455 feet) is near the mouth of
Perdido Bay.
The upper limestone is composed of light gray to brown dolomitic
limestone and some dolomite which has a distinctive "spongy-looking"
texture and contains abundant shell fragments of clams, snails, and
microscopic animals. In much of the area the upper limestone contains
layers of green and brown clay. In some wells this limestone section
must be screened and gravel packed, or the clay beds cased off, to
prevent the water that is withdrawn from becoming turbid.
The upper limestone of the Floridan aquifer is recharged directly by
rain where the limestone lies at or near the surface of the ground, or
indirectly by percolation from the sand-and-gravel aquifer. The Floridan
aquifer discharges water continuously by seepage into the gulf, by upward
leakage, and by pumping or flowing from wells.
The water in the Floridan aquifer within the area of study is under
artesian pressure. Changes in the artesian pressure head are dependent-
upon variations in rainfall and the quantity of water withdrawn by wells.
Pumping from the upper limestone has the greatest effect on the artesian
pressure in the central part of the area.
Figure 4 shows the artesian pressure head in a well drilled into the
upper limestone of the Floridan aquifer at Point Washington, near the
east end of Choctawhatchee Bay. Although the well is in an area where




















.104 B -5 h303h










SGU F OF MEXICO



0 5 10 1H mll e

1715 87"00' 645' 86' 0'

EXPL A N A T I N
.360
Well
Number indicates altitude of top 'of limestone of the
Florldon oqulfer in feet below mean seao level
----500--
Contour of top of Upper limestone of the Floridon
aquifer, in feet below mean sea level
Contour Interval, 100 feet

Figure 5. Western Florida gulf coast showing structure contours on top of
the upper limestone of the Floridan aquifer.









UNITED STATES DEPARTMENT OF THE INTERIOR
GEOLOGICAL SURVEY


FLORIDA BOARD OF CONSERVATION
DIVISION OF GEOLOGY tz


Bail taken from Army Map
Service topographic quadrangle
|i 250,000


Figure 6. Western Florida gulf coast showing thickness of the
upper limestone of the Floridan aquifer.







REPORT OF INVESTIGATIONS No. 29


very little water is pumped from the aquifer, the head has dropped
about 3 feet since 1948. This lowering may be the result of heavy
pumping from the upper limestone elsewhere in the area. From 1946 to
1949 the artesian pressure rose, from 1949 to 1956 it declined slightly,
and from 1956 to 1960 it rose slightly. These trends reflect periods of
abundant or deficient rainfall.
Formerly, artesian wells in low areas in the Fort Walton Beach area
would flow but they no longer flow because of the considerable decline
in the artesian pressure head. This decline doubtless has been caused
by increased use of water, especially by Eglin Air Force Base, the city
of Fort Walton Beach, and other nearby water users. In 1986, the artesian
pressure head in wells tapping the upper limestone at Fort Walton Beach
averaged about 56 feet above sea level. By 1960, however, the average
artesian pressure head had declined to about 18 feet below sea level.
This means that the average net decline of the artesian pressure head in
the upper limestone at Fort Walton Beach has been about 74 feet since
1936.
Figure 7 illustrates part of this striking decline. The top graph shows
that the artesian pressure head in a well that is 17 miles northwest of
Fort Walton Beach has declined about 16 feet since 1948. The hydrograph
shows very little correlation with rainfall. The gradual decrease of the
artesian pressure may be attributed mainly to pumping. The middle
graph shows the decline of the artesian pressure in a well that is 7
miles north of Fort Walton Beach. During the period of record the aver-
age decline was about 30 feet. The bottom graph represents the most
striking decline of artesian pressure in the area, in a well (Okaloosa 3)
at the Fort Walton Beach Elementary School. This decline was 95 feet
between 1936 and 1957. The artesian pressure head recovered about
18 feet from August 1957 to December 1960. It should be noted, however,
that this recovery was a result of above-average rainfall from 1958 to
1960. If rainfall returns to or below average and present pumping con-
tinues, the downward trend of the artesian pressure head may be ex-
pected to continue. In 1951 the well stopped flowing and since then has
flowed only intermittently for short periods. The artesian pressure head
dropped below sea level in 1954 and has remained below this level most
of the time since then. Low points on the hydrograph of Okaloosa 3
generally reflect the increased use of water during the summer for
watering lawns and other purposes.
Figure 8 is a contour map of the area showing the net decline of
artesian pressure in wells tapping the upper limestone, from January
1948 to September 1960. The map is based on an analysis of the hydro-
graphs of wells in the area. It shows that the greatest decline, about 56






WATEf< LEVEL, IN FEET HEfE RRFD 10 MEAN S f A LEV F'L.
1 -L Z I .. ... _. _.^ ......-. ....-... .- ......... ..
(A,, ,,,,


I!
i5





R








* 1 ,


\o Santa Ro Counly
S Okoloolo County

Ia


I


























lBose token from Army Mop
* Service topographic quadrangle
I 250,000


0
^.


*1

0
z
: p


Figure 8. Western Florida gulf coast showing net decline of artesian pressure head in wells tapping the
upper limestone of Floridan aquifer, January 1948 to September 1960.


I II ~-s I






FLORIDA GEOLOGICAL SURVEY


feet, was at Fort Walton Beach, and the smallest decline, about 2
feet, was at Point Washington, near the east end of Choctawhatchee Bay.
It is interesting to note that the water level in a well drilled into the
sand-and-gravel aquifer 8 miles northeast of Holley and located well
within the cone of depression of water in the upper limestone of the
Floridan aquifer (fig. 4) had a net rise of 1.3 feet during this same
period.
Little is known about the water-transmitting and water-storing abilities
of the upper limestone. Well-yield figures indicate that the aquifer trans-
mits water readily in some places and reluctantly in others. In some
localities large quantities of clay have been found and probably the clay
fils some voids in the limestone. This clay may have been deposited
in the voids during later advances of the sea, after solution cavities had
been formed. Electric logs and well samples also indicate that fairly con-
tinuous beds of clay are present in the upper limestone.
The drawdown in the Fort Walton Beach area (fig. 8) appears to
be much greater than would be expected from the amount of pumping
in the area. The presence of the clay in the upper limestone provides a
reasonable explanation. This clay would reduce both the permeability
and the effective porosity of the aquifer, and would result in unusually
large drawdowns. In addition, the erratic occurrence of clay-filled voids
would explain the great variation observed in the yield of otherwise
similar wells.

The temperature of water from the upper limestone of the Floridan
aquifer ranges from about 700F in the eastern part of the area to as high
as 95'F near Pensacola.
Lower limestone. The lower limestone of the Floridan aquifer is much
more variable in thickness than the upper limestone. From its maximum
thickness of about 1,500 feet in southern Walton County, it thins abruptly
to about 700 feet just west of Destin. The limestone continues to thin to
the west, although at a much more uniform rate, until at Mobile Bay
it is less than 300 feet thick. The limestone also thins southward, toward
the gulf, from about 1,000 feet in northern Santa Rosa County to about
450 feet in central Escambia County. Thus, unlike most geologic forma-
tions along the gulf coast, this limestone thins rather than thickens down-
dip. The lower limestone is white to grayish cream and is rather soft
and chalky. It consists mainly of microscopic animals, corals, sand dollars,
clams, and many other types of shells. Thick, lens-shaped masses of hard,
light gray shale and siltstone, as well as a small amount of gray clay, are
irregularly distributed in the lower half of the limestone.






REPORT OF INVESTIGATIONS No. 29


AQUICLUDES
In most of the area the aquifers are separated by relatively imperme-
able formations (aquicludes) which greatly retard the upward and down-
ward movement of ground water.

MIOCENE CLAY
Two thick masses of clay (Marsh, 1962) separated by a thin bed of
sand lie between the sand-and-gravel aquifer and the Floridan aquifer
over most of the area. Along section A-A' (fig. 8) the upper clay thickens
from about 300 feet at Mobile Bay to about 670 feet at Pensacola. East of
Pensacola the clay thins, and just west of the Santa Rosa-Okaloosa County
line it terminates rather abruptly by interfingering with the sand-and-
gravel aquifer. The lower clay thins from about 500 feet at Mobile Bay
to 150 feet at the Santa Rosa-Okaloosa County line. East of this point
it thickens again to about 300 feet at Fort Walton Beach and then thins
and finally pinches out in southwestern Walton County. Both the upper
and lower clays appear to interfinger with the sand-and-gravel aquifer
about 20 miles north of Pensacola. The sand bed between the two clays
thickens from about 30 feet at Pensacola to about 90 feet at Mobile Bay
and about 130 feet just northwest of upper Perdido Bay. A flowing well
in Warrington obtains water from this bed of sand.
Fossil clams, snails, and shells of microscopic animals date these thick
clays as late Miocene in age (10 to 15 million years old). The clay is gray
to dark gray and contains much silt, very fine to coarse sand, and a little
gravel.

BUCATUNNA CLAY MEMBER
Throughout most of the area the upper and lower limestones of the
Floridan aquifer are separated by the Bucatunna Clay Member of the
Byram Formation (Marsh, 1962). This clay bed differs from the Miocene
clays discussed above in being much thinner, more uniform in thickness,
and more regionally extensive. The Bucatunna underlies most of western-
most Florida and parts of Alabama, Mississippi, and Louisiana. Within
the area discussed in this report the Bucatunna attains a maximum thick-
ness of 215 feet just north of Escambia Bay. It thins northward and east-
ward, pinching out in southern Walton County, 17 miles west of the
Choctawhatchee River.
The Bucatunna consists of soft gray silty to sandy clay containing a
variety of fossils. The clay rests unconformably upon the eroded surface
of the lower limestone of the Floridan aquifer and is overlain conformably






FLORIDA GEOLOGICAL SURVEY


by the flat, even base of the upper limestone, with which it interfingers
locally.

MIDDLE EOCENE CLAY AND SHALE
In the western part of the Florida Panhandle the limestones of the
Floridan aquifer are underlain by gray clay and shale of Middle Eocene
Age (roughly 50 million years old). The top of this formation dips gen-
erally southwestward and undulates broadly. Eastward along the coast
from Mobile Bay the top of the formation is relatively flat, except in
southern Walton County where it plunges abruptly downward.

CHEMICAL QUALITY OF GROUND WATER
Ground water contains various amounts of substances dissolved from
the air, soil, or rocks, as well as mineral matter introduced from bodies
of surface water such as streams and oceans. For example, salt water may
enter the aquifer from the sea. The amount of such substances dissolved
by ground water depends on the climate, type of soil or rock, and other
factors. The chemical content of ground water differs considerably from
one aquifer to another and even from place to place within a given
aquifer. Ground water along the gulf coast of western Florida is of sev-
eral types: Some is so free of dissolved substances that it can be used
even in automobile batteries in place of distilled water; some, although
mineralized to a moderate degree, can be made entirely satisfactory for
most uses by simple treatment; and some is so highly mineralized that it
cannot be made suitable for ordinary use by any practical treatment.

DEFINITIONS AND GENERAL DISCUSSION
The standard unit for reporting the concentration of various mineral
constituents in ground water is part per million (ppm), which means
that if a sample of water is reported to contain one part per million of
iron, a million pounds of such water would contain one pound of iron.
The term total dissolved solids indicates approximately the total quan-
tity of mineral matter in solution. The U.S. Public Health Service (1946)
recommends that the concentration of dissolved solids in a drinking-
water supply should not exceed 500 ppm, although water with 1,000 ppm
is acceptable where nothing better is available. Water with more than
1,000 ppm of dissolved solids usually contains enough of some constitu-
ents to produce a noticeable taste or to make the water unsuitable for
many domestic and industrial uses.
Hardness of water is caused principally by compounds of calcium
and magnesium. Hardness of water is generally recognized by the







REPORT OF INVESTIGATIONS No. 29


amount of soap required to produce lather. Many U.S. Geological Survey
reports have classified water ranging in hardness from 0 to 60 ppm as
soft, from 61 to 120 ppm as moderately hard, from 121 to 200 ppm as
hard, and more than 200 ppm as very hard.
The chloride content of ground water is a good indication of the extent
to which it has been contaminated by sea water, for about 90 percent of
the dissolved-solids content of sea water consists of chloride salts. Ground
water with a chloride content of less than 30 ppm generally has not
been contaminated by water from present or ancient seas. Chloride salts
do not usually affect the potability of water except when present in
quantities sufficient to cause a salty taste. The U.S. Public Health Service
recommends 250 ppm of chloride as the upper limit for public drinking
water supplies. Water with a chloride content of 500 ppm tastes salty
to most people. Water with a chloride content of more than about 800 ppm
may cause damage to plants, shrubs, and irrigated crops. In addition, a
high-chloride content makes the water more corrosive.
The fluoride content of water used for drinking has aroused con-
siderable public interest in recent years. Evidence indicates that the
presence of about 1.0 ppm of fluoride in drinking water decreases the
occurrence of dental caries (tooth decay) when the water is habitually
consumed by children during the period of formation of their teeth. For
this reason, fluoride is added to many public water supplies. Drinking
water containing more than 1.5 ppm of fluoride may cause dental
fluorosis (mottled enamel) in children's teeth. The U.S. Public Health
Service (1946) specifies 1.5 ppm of fluoride as the maximum concen-
tration allowable for water that is to be used for drinking.
Iron is dissolved by ground water and surface water (streams, lakes,
and oceans) from nearly all rocks and soils and from iron pipes. A con-
centration of more than about 0.3 ppm of iron in water is objectionable
as it stains porcelain, plumbing fixtures, and clothing; it imparts an
undesirable taste to the water; and upon oxidation it forms a reddish
brown sediment. Excess iron usually can be removed from water by
aeration and filtration, but some water supplies require the addition of
hydrated lime or soda ash. Along the gulf coast of western Florida, the
concentration of iron in the ground water varies considerably from place
to place and from one depth to another.
Hydrogen sulfide gas is present in ground water in some areas and
gives the water a distinctive taste and odor. Water containing it are
usually called "sulfur water." This gas, which is probably caused by the
reduction of sulfates, can be removed by aerating the water, by chlorina-
tion, or by allowing it to stand in an open container.






FLORIDA GEOLOGICAL SURVEY


Carbon dioxide in water from the sand-and-gravel aquifer causes the
water to be acidic and therefore corrosive. Most industries and munici-
palities in the western part of the Florida Panhandle treat the water
from this aquifer to reduce its corrosiveness in order to protect water
pipes, water heaters, and other metallic objects with which the water
comes into contact.

WATER IN THE SAND-AND-GRAVEL AQUIFER
Water in the sand-and-gravel aquifer is not only abundant but also
extraordinarily soft and relatively unmineralized. The availability of a
water supply of such excellent quality is the prime reason that major
industries, such as the Chemstrand Corp. and St. Regis Paper Co., have
chosen to locate in this part of the State. The Columbia National Corp.
extracts zirconium from minerals mined at Starke, Florida, and trans-
ports the ore 345 miles to its processing plant in Santa Rosa County in
order to utilize ground water in the area.
Dissolved solids. The dissolved-solids content of water from the sand-
and-gravel aquifer in this area generally is extremely low, ranging from
15 to 40 ppm. However, water from this aquifer in some localities may
contain as much as 300 ppm of dissolved solids.
Hardness. Water from the sand-and-gravel aquifer is exceptionally
soft, generally containing 4 to 30 ppm of calcium and magnesium car-
bonates. In places, water from deeper parts of this aquifer may be
considerably harder, containing as much as 150 ppm of these carbonates.
Chloride. The chloride content of water from the sand-and-gravel
aquifer generally ranges from 2 to 30 ppm except where salty water has
not been completely flushed from the aquifer or where lateral encroach-
ment from salt-water bodies has occurred.
Fluoride. The water from the sand-and-gravel aquifer usually con-
tains less than 0.2 ppm fluoride.
Iron. The iron content of water from the sand-and-gravel aquifer
ranges from 0.06 to 4.9 ppm, although it is usually less than 0.25 ppm.
Dissolved gases. Water from the sand-and-gravel aquifer contains
enough carbon dioxide to make the water acidic. Some water from this
aquifer contains hydrogen sulfide in solution.

WATER IN THE FLORIDAN AQUIFER
'The upper limestone of the Floridan aquifer is of more economic
unportance to the area than the lower limestone as a source of fresh
water, for both present and future use. Few, if any, wells in the area







REPORT OF INVESTIGATIONS No. 29


uDoamn water trom the lower limestone, whereas the upper limestone is
the principal aquifer for wells in the eastern part of the area.
UPPER LIMESTONE OF THE FLORIDAN AQUIFER
Water in the upper limestone of the Floridan aquifer is suitable for
most uses in the eastern two-thirds of the area. However, increasing
concentrations of dissolved solids, chloride, and fluoride in the western
third of the area makes the water unsuitable for most purposes.
Dissolved solids. In the western part of the Florida Panhandle, the
dissolved-solids content of water from the upper limestone ranges from
92 ppm at De Funiak Springs to 3,960 pp.m at Pensacola Beach. As shown
in figure 9, dissolved-solids content increases in a southwesterly direction
across the area. In the region between De Funiak Springs, Crestview,
Holley, Fort Walton Beach, and Freeport, water from the upper lime-
stone contains less than 500 ppm of dissolved solids. The dissolved-solids
content increases toward Point Washington and in a small area in Fort
Walton Beach, as well as southward and westward from Holley. At
Pensacola, Gulf Breeze, and Pensacola Beach, the dissolved-solids con-
tent of water from the upper limestone exceeds 1,000 ppm (fig. 9).
Hardness. Figure 10 shows that the hardness of water from the upper
limestone ranges from 24 to 146 ppm across the area. The hardest water
occurs in the area between Crestview and Destin (including Niceville
and Valparaiso) and around Point Washington. Moderately hard water
(hardness range from 60-120 ppm) from the upper limestone is found
at Pensacola, Gulf Breeze, Crestview, De Funiak Springs, and Freeport.
Soft water (hardness range 0-60 ppm) is found at Fort Walton Beach,
Destin, Navarre, and Holley.
The dissolved-solids content of the water from the upper limestone
increases in a southwesterly direction within the area (fig. 9). It would
be reasonable to expect the water to become increasingly harder in this
direction also, for the hardness of ground water in limestone usually
increases as the dissolved-solids content increases. This actually happens
in the area between De Funiak Springs and Niceville and around Point
Washington. However, from Niceville to Fort Walton Beach the hardness
decreases rather abruptly; and at Pensacola and Pensacola Beach, where
the water is highly mineralized, it is only moderately hard.
A possible explanation for this decrease of hardness may be natural
softening of the water by ion exchange between the water and clay
minerals, as considerable clay occurs in the upper limestone of the
Floridan aquifer. Glauconite, an ion-exchange mineral commonly found
in marine sediments, also has been noted in many well cuttings from this
area. Carlston (1942, p. 16) suggests that the increase in bicarbonate





FLORIDA GEOLOGICAL 'SURVEY


content of water from northern Alabama is ,caused by carbon dioxide
reacting with calcium and magnesium carboniates in the sediments. The
calcium and magnesium ions that were taken into solution by this reac-
tion are exchanged for sodium ions on glauconite and on clay minerals.
Such a process would explain the softening of the water and the increase
in sodium and bicarbonate ion contents.
A less important process that may tend to reduce thei hardness of the
water is indirectly a result of the dip of the upper limestone. In general,
where the top of the upper limestone is more than 400 feet below sea
level, the water in it is softer than farther updip. The temperature of the
ground water down to a depth of about 50 feet is usually about the same
as the average annual temperature of the air, which at Pensacola is
about 680F. Below a depth of 50 feet the temperature of ground water
increases steadily downward for a considerable distance. In the western
Florida Panhandle the temperature of ground water increases about
1'F for each 50 to 80 feet of depth. Thus, the temperature of water in
the upper limestone of the Floridan aquifer increases in a southwesterly
direction as the aquifer gets deeper. In the areas where the water is
relatively soft, its temperature is at least 750F. As water becomes warmer
the amount of carbon dioxide gas that it can hold in solution decreases.
The less carbon dioxide in the water, the smaller the amount of calcium
and magnesium carbonate that can remain in solution. Therefore, as the
temperature of the water increases, these carbonates tend to precipitate
out of solution, leaving the water softer.
Chloride. The chloride content of water from the upper limestone of
the Floridan aquifer ranges from 2 to more than 2,000 ppm. Figure 11
shows how the chloride content varies in the area. The chloride con-
centration is very low between Crestview, De Funiak Springs, and Nice-
vile, and increases in a southwesterly direction. The 250-ppm contour
crosses Fairpoint Peninsula west of Navarre and crosses Santa Rosa
Island near the Santa Rosa-Okaloosa County line. Except in a small area
at Fort Walton Beach and another south of Point Washington, the
chloride content of water east of this contour meets the U.S. Public
Health Service recommended standards for a public supply. West of the
250-ppm contour much of the water from the upper limestone is too
salty for a public supply.
This study revealed evidence of incipient salt-water encroachment in
the upper limestone of the Floridan aquifer in a small area at Fort
Walton Beach. During 1948, the chloride content of water from the well
at the Fort Walton Beach Elementary School was determined at three
different times to be 70, 68, and 72 ppm. On October 7, 1960, the






UNITED STATES DEPARTMENT OF THE INTERIOR
GEOLOGICAL SURVEY


FLORIDA BOARD OF CONSERVATION
DIVISION OF GEOLOGY


87000'


SANTA ROSA


OKAL


Milton


87015'


IR () S 776

G IU L F OF


MEX/CO37 --
352 500 '-
MEXICO


6030'


Number is


Less than 500 ppm
Water suitable for
municipal supplies


E X P L A N AT ION
.450
Well


dissolved solids in


500-1000 ppm


Water suitable for some
purposes
Contour interval variable


ppm


More than 1000 ppm
Water too highly mineralized
for most purposes


--e tzken from Army Mop
"-,,'e topographic Map
1 250,000


Figure 9. Western Florida gulf coast showing the dissolved-solids content of water from the upper limestone of the Floridan aquifer.


86015'
;lTOL 7: -'COUNTY




qA

.4 s.









-..- -

K C


87 00'


0 5 10 15 miles

86045'I 8
8645' 81


86015'


I I ~- L~ IL '' I~ = 'C- CL -- L II






UNITED STATES DEPARTMENT OF THE INTERIOR
GEOLOGICAL SURVEY

875' 870
SANTA ROSA f


FLORIDA BOARD OF CONSERVATION
DIVISION OF GEOLOGY

86015'
LTON I COUNTY I- -I


Milton


0105


,. I



I-H alley


K.* I t`
No?6Nvai~
lmir-z ~24i
4 -.o


ROSA

G U


87*15'


0-60 ppm
Soft


-e- 82 -2 2 48\2\---
28
LF OF MEXICO
O 5 15 miles

86045' 8
E X P L A N A T I O N


*24
Well
Number is hardness in

E I
61-120 ppm
Moderately hard


Hardness expressed as CoCo3
Contour interval, 20 ppm


ppm


121-200 ppm
Hard


tcS? taken from Army Mop
'r~v:e topographic Map
1250,000


Figure 10. Western Florida gulf coast showing hardness of water from the upper limestone of the Floridan aquifer.


,'"' c'


86015'






REPORT OF INVESTIGATIONS No. 29


chloride content was 262 ppm, and about 2 weeks later it was 290 ppm.
This is an increase of more than 200 ppm in the last 12 years. Salt-
water encroachment may be a result of the drastic lowering of the water
level in this well (fig. 7). Before much water was withdrawn from the
upper limestone, the artesian pressure head in the upper limestone prob-
ably was about the same as in the lower limestone. Extensive pumping
of water from the upper limestone has doubtless reduced the artesian
pressure head considerably below that in the lower limestone. This differ-
ence in head would cause the water in the lower limestone to move
upward, under the higher artesian pressure. Salt water from! the lower
limestone probably is moving upward through about 60 feet of the
Bucatunna Clay Member (fig. 3) into the upper limestone. This upward
encroachment may have been facilitated by the presence of old wells
that penetrated the Bucatunna Clay Member and were later plugged
or partially plugged. Salt water may have moved upward through part
of the borehole.
As the water level in the upper limestone at Fort Walton Beach is
below sea level most of the time, salt water from the Gulf of Mexico or
Choctawhatchee Bay would have the potential head to percolate down-
ward to this limestone. However, the possibility that this has happened
seems remote, because a bed of clay about 300 feet thick overlies the
limestone and-would greatly retard the movement of water from! above
into the aquifer. In contrast, the clay bed below the upper limestone
is relatively thin and, moreover, is perforated by open-hole sections of
several old wells; this situation, coupled with the fact that water in
the lower limestone has a higher head than water in the upper lime-
stone, makes intrusion of salt water from below much more likely.
Furthermore, no appreciable increase in the chloride content has been
noted in water from wells closer to the gulf or the bay than the high-
chloride well at the elementary school.
The implications of the data collected at the school well in Fort
Walton Beach warrant continued measurement of the water level and
the initiation of a periodic sampling program to keep a check on the
chloride content. In addition, the chloride content of water from nearby
wells, especially the city wells, should be checked periodically to deter-
mine any significant change in the salinity of the water.
Fluoride. The fluoride content of water from the upper limestone of
the Floridan aquifer ranges from 0.0 ppm in the vicinity of Niceville to
6.5 ppm at Pensacola Beach. Figure 12 indicates that the fluoride con-
tent of water from this aquifer increases in a southwesterly direction
across the area. Patterns on the map indicate areas in which the fluoride





24 FLORIDA GEOLOGICAL SURVEY

content of the water (from 0.5 to 1.5 ppm) would reduce tooth decay
among children drinking the water (Black and Brown, 1951, p. 15).
An area of beneficial fluoride content lies between Destin and Holley,
and another south of Point Washington. An area in which the fluoride
content (more than 1.5 ppm) of water from the upper limestone is so
high that it might cause mottling of children's teeth also is shown on
figure 12 (Black and Brown, 1951, p. 15). This area includes Fairpoint
Peninsula west of Navarre and the western part of Santa Rosa Island.
It is interesting to note that the fluoride content of water from a test well
at Pensacola Beach (6.5 ppm) was almost twice as high as that from any
other well in Florida known to the writers (excluding ground water con-
taminated by industrial wastes). In the area between Niceville, Crest-
view, and De Funiak Springs the fluoride content of water from the
upper limestone is less than 0.5 ppm and probably would have little or
no effect on children's teeth (Dean, 1943, p. 1173).
There are several possible sources of this fluoride. Certain minerals
common in marine sediments contain fluoride. Among these are glau-
conite, phosphate, and muscovite, which have been noted in well samples
in West Florida. The mica (muscovite) is especially abundant. According
to Hem (1959, p. 112), "Cederstrom (1945) attributes fluoride in ground
waters of the Virginia coastal plain to solution of micas which contain
fluoride." Another possible source, mentioned by LaMoreaux (1948, p.
32-34) is sea water that has not been completely flushed from the aquifer.
Fluoride is a normal, although minor, constituent of sea water. In West
Florida, the fluoride content of water from the upper limestone gener-
ally increases with increasing depth of the aquifer. LaMoreaux noted a
similar correlation in certain marine sands of southern Alabama. He also
observed a relation between high-fluoride content of ground water and
marine glauconitic sands. Some of the.fluoride may be derived from the
clay beds located within the aquifer.
Iron. The concentration of iron in water from the upper limestone
of the Floridan aquifer ranges from 0.0 to 5.0 ppm.
Dissolved gases. Most waters from the Floridan aquifer within the
study area contain hydrogen sulfide gas in solution.
LOWER LIMESTONE OF THE FLORIDAN AQUIFER
Unfortunately, no water samples could be obtained from the lower
limestone of the Floridan aquifer. However, electric-log resistivities indi-
cate that most of the water in this limestone is salty. The upperpart of the
lower limestone possibly contains fresh: water north and east of Fort
Walton Beach (updip), but until samples of the water can be analyzed,
this possibility can be only speculative.







UNITED STATES DEPARTMENT OF THE INTERIOR
GEOLOGICAL SURVEY


3C45


30o30'


FLORIDA BOARD OF CONSERVATION
DIVISION OF GFOI OGY


Chloride content in

-500 -


ppm


Contour interval variable


less than 250 ppm
Water suitable for
municipal supplies


E X P L A N AT IO N
o64
Well
Number is chloride content in


250-1000 ppm
Water suitable for some
manufacturing and
irrigation uses


ppm


more than 1000 ppm
Water too salty for
most uses


Base taken from Army Map
Service topographic
I: 250,000


Figure 11. Western Florida gulf coast showing chloride content of water from the upper limestone of the Floridan aquifer.


_


__


~~ -~ ----~~'








UNITED STATES DEPARTMENT OF THE INTERIOR
GEOLOGICAL SURVEY


FLORIDA BOARD OF CONSERVATION
DIVISION OF GEOLOGY


8715' 87000'


Less than 0.5 ppm
Fluoride content too low
to have any appreciable
effect on children's teeth


E X P L A N AT ION

I I
0.5 to 1.5 ppm
Fluoride content beneficial
to children's teeth


Contour interval, 0.5 ppm


More than 1.5 ppm
Fluoride content
injurious to children's
teeth


3Bse taken from Army Map
Service topographic Map
1: 250,000


Figure 12. Western Florida gulf coast showing fluoride content of water from the upper limestone of the Floridan aquifer.


86045'


300435'

















3C-30'


86030'


86 15'


30045'

















3n-030'


I I ~ I ~ L I ~ ~C~s~CI ,,


I I I ~-- I ~ 1 l- Ir~ e -arl ,- ~~s ae ~s -.1 L-






REPORT OF INVESTIGATIONS No. 29


SUMMARY AND CONCLUSIONS
Three aquifers separated by clay aquicludes underlie the area dis-
cussed in this paper. The sand-and-gravel aquifer at the surface contains
soft, relatively unmineralized water and supplies most of the wells in
the western half of the area. The deeper lying upper limestone of the
Floridan aquifer contains water that is more mineralized and supplies
most of the wells in the eastern half of the area. Most of the lower lime-
stone of the Floridan aquifer is too salty for use.
Maps showing hardness, dissolved solids, chloride, and fluoride in
water from the upper limestone indicate that this water is suitable for
most uses in the eastern two-thirds of the area. The concentrations of
the mineral constituents increase in a southwesterly direction, making
the water unsuitable for most purposes in the western third of the area.
The hardest water occurs in the eastern part of the area and the water
becomes softer in a southwesterly direction.
A decline in head in the upper limestone at Fort Walton Beach has
amounted to about 82 feet since 1986. Apparently, this caused salt water
from the lower limestone to move upward through the Bucatunna Clay
Member into the upper limestone. Clay in the upper limestone of the
Floridan aquifer has played a significant role in the production of large
drawdowns by decreasing both the permeability and the effective poros-
ity of the aquifer. It has also effectively softened the water in the aquifer
by ion exchange.







REPORT OF INVESTIGATIONS No. 29


REFERENCES

Barraclough, J. T. (see Musgrove, R. H.)


Black, A. P.
1951


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


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


Carlston, C. W.
1942


Fluoride in the ground water of the Cretaceous area of Alabama:
Alabama Geol. Survey Bull. 52.


Cederstrom, D. J.
1945 Geology and ground-water resources of the Coastal Plain in south-
eastern Virginia: Virginia Geol. Survey Bull. 63.
Clark, W. E. (see Heath, R. C.)


Collins, W. D.
1928


(and Howard, C. S.) Chemical character of waters of Florida:
U. S, Geol, Survey Water-Supply Paper 596-G.


Cooke, C. Wythe
1945 Geology of Florida: Florida Geol. Survey Bull. 29.

Cooper, H. H., Jr. (see Jacob, C. E.)

Dean, H. Trendley
1943 Domestic water and dental caries: Am. Water Works Assoc. Jour.,
v. 35, no. 9, p. 1161-1183.

Gunter, Herman (see Sellards, E. H.)


Heath, R. C.
1951



Hem, J. D.
1959


(and Clark, W. E.) Potential yield of ground water on the Fair
Point Peninsula, Santa Rosa County, Florida: Florida Geol. Survey
Rept. Inv. 7.


Study and interpretation of the chemical characteristics of natural
water: U. S. Geol. Survey Water-Supply Paper 1473.


Howard, C. S. (see Collins, W. D.)

Jacob, C. E.
1940 (and Cooper H. H., Jr.) Report on the ground-water resources of the
Pensacola area in Escambia County, Florida, with a section on the
geology by S. A. Stubbs: U.S. Geol. Survey open-file report.

LaMoreaux, P.E.
1948 Fluoride in the ground water of the Tertiary area of Alabama:
Alabama Geol. Survey Bull. 59.






FLORIDA GEOLOGICAL SURVEY


Marsh, O.T. (also see Musgrove, R.H.)
1962 Relation of Bucatunna Clay Member (Byram Formation, Oligocene)
to geology and ground water of westernmost Florida: Geol. Soc.
America Bull., v. 73, p. 243-251.
Matson, G.C.
1913 (and Sanford, Samuel) Geology and ground waters of Florida:
U.S. Geol. Survey Water-Supply Paper 319.
Musgrove, R.H.
1961 (and Barraclough, J.T., and Marsh, O.T.) Interim report on the
water resources of Escambia and Santa Rosa counties,. Florida:
Florida Geol. Survey Inf. Circ. 30.
Sanford, Samuel (see Matson, G.C.)


Sellards, E.H.
1912


(and Gunter, Herman) The water supply of west-central and west
Florida: Florida Geol. Survey 4th Ann. Rept., p. 81-155.


Stubbs, S.A. (see Jacob, C.E.)
US. Public Health Service
1946 Drinking water standards: Public Health Rcpts., v. 61, no. 11,
p. 371-384.




Aquifers and quality of ground water along the gulf coast of Western Florida ( FGS: Report of investigations 29 )
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Title: Aquifers and quality of ground water along the gulf coast of Western Florida ( FGS: Report of investigations 29 )
Series Title: ( FGS: Report of investigations 29 )
Physical Description: vii, 28 p. : maps (part fold., part col.) diagrs. ; 24 cm.
Language: English
Creator: Barraclough, Jack T
Marsh, Owen Thayer
Geological Survey (U.S.)
Florida -- Bureau of Geology
Publisher: s.n.
Place of Publication: Tallahassee
Publication Date: 1962
 Subjects
Subjects / Keywords: Groundwater -- Florida   ( lcsh )
Geology -- Florida   ( lcsh )
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 Notes
Statement of Responsibility: by Jack T. Barraclough and Owen T. Marsh.
Bibliography: "References": p. 27-28.
General Note: "Prepared by the United States Geological Survey in cooperation with the Florida Geological Survey, Escambia County, Santa Rosa County, and the city of Pensacola."
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Table of Contents
    Front Cover
        Page i
    Florida State Board of Conservation
        Page ii
    Transmittal letter
        Page iii
        Page iv
    Contents
        Page v
        Page vi
        Page vii
        Page viii
    Abstract and introduction
        Page 1
        Page 2
        Page 3
    Geology and hydrology
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        22a
        22b
        Page 23
        Page 24
        Page 26
        24b
        Page 25
        Page 26
    References
        Page 27
        Page 28
        Copyright
            Copyright
Full Text


STATE OF FLORIDA

STATE BOARD OF CONSERVATION

DIVISION OF GEOLOGY



FLORIDA GEOLOGICAL SURVEY
Robert 0. Vernon, Director



-REPORT OF INVESTIGATIONS NO. 29


AQUIFERS

ALONG THE


AND QUALITY OF GROUND WATER

GULF COAST OF WESTERN FLORIDA


By
Jack T. Barraclough and Owen T. Marsh
U. S. Geological Survey


Prepared by the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with the
FLORIDA GEOLOGICAL SURVEY,
ESCAMBIA COUNTY, SANTA ROSA COUNTY,
and the
CITY OF PENSACOLA


TALLAHASSEE
1962











CULTUR4
LIBRARY
FLORIDA STATE BOARD

OF

CONSERVATION







FARRIS BRYANT
Governor


Tom Adams
Secretary of State



J. Edwin Larson
Treasurer



Thomas D. Bailey
Superintendent of Public Instruction


Richard Ervin
Attorney General



Ray E. Green
Comptroller



Doyle Conner
Commissioner of Agriculture


W. Randolph Hodges
Director







LETTER OF TRANSMITTAL


Jlonaida Gjeological Sireu

Tallahassee
August 8, 1962



Honorable Farris Bryant, Chairman
Florida State Board of Conservation
Tallahassee, Florida
Dear Governor Bryant:
The Division is publishing, as Florida Geological Survey Report of
Investigations No. 29, a comprehensive report on the aquifers and qual-
ity of ground water along the gulf coast of western Florida, written
by Mr. J. T. Barraclough,' engineer, and Mr. Owen T. Marsh, geologist,
U. S. Geological Survey. This report was prepared in cooperation with
this department, Escambia County, Santa Rosa County, and the City
of Pensacola.
Three separate aquifers have been identified, each being separated
by clay aquicludes. With the definition of the geology in this area, it
becomes possible to make some tentative plans for deep well waste
disposal, as well as the wise and comprehensive management of the
fresh water resources contained in the shallow aquifers.

Respectfully yours,
Robert 0. Vernon, Director
and State Geologist




























Completed manuscript received
February 21, 1962

Published for the Florida Geological Survey
By Rose Printing Company, Inc.
Tallahassee, Florida
August 8, 1962







CONTENTS

Page
Abstract I__ _1_-__- -- --

Introduction _1____________ -____-_
Purpose and scope 1____
Location of the area ____2-----------------------
Previous work 2
Acknowledgments -3--- 3

Geology and hydrology 4
Geologic setting ----_-- 4
Hydrologic principles 4
Aquifers 7
Sand-and-gravel aquifer 7
Floridan aquifer 9-------------
Upper limestone 10
Lower limestone _16
Aquicludes 17
Miocene clay 17
Bucatunna Clay Member _-17
Middle Eocene clay and shale 18

Chemical quality of ground water 18
Definitions and general discussion 18
Water in the sand-and-gravel aquifer 20
Dissolved solids 20
Hardness 20
Chloride 20
Fluoride 20
Iron -- 20
Dissolved gases 20
Water in the Floridan aquifer 20
Upper limestone of the Floridan aquifer 21
Dissolved solids 21
Hardness 21
Chloride _. __22
Fluoride 23
Iron 24
Dissolved gases -____--__ 24
Lower limestone of the Floridan aquifer 24

Summary and conclusions --- --------- 25

References ------ -------- ---- 27










ILLUSTRATIONS

Figure Page
1 Location of area described in this report .............--- ............ -- .. 3
2 Aquifers and aquicludes along the gulf coast of western Florida as
shown in representative test well near Pensacola --...........--------........--... 5
3 Geologic cross section A-A' along the gulf coast of western Florida 6
4 Water levels in a well in the sand-and-gravel aquifer and a well in the
Floridan aquifer compared with rainfall at Pensacola ______- 9
5 Western Florida gulf coast showing structure contours on top of the
upper limestone of the Floridan aquifer ... ..........----- 11
6 Western Florida gulf coast showing thickness of the upper limestone of
the Floridan aquifer ......-..............-- -- ....----------------------- --- 12
7 Hydrographs of three wells tapping the upper limestone of the Floridan
aquifer, showing decline of artesian pressure head in southern Okaloosa
County ...........................---- ....-----------------------------------------------.. 14
8 Western Florida gulf coast showing net decline of artesian pressure head
in wells tapping the upper limestone of the Floridan aquifer, January
1948 to September 1960 .-..............----------------------------------------.----------- 15
9 Western Florida gulf coast showing the dissolved-solids content of
water from the upper limestone of the Floridan aquifer ........------- facing 22
10 Western Florida gulf coast showing hardness of water from the upper
limestone of the Floridan aquifer ............----- facing 22
11 Western Florida gulf coast showing chloride content of water from the
upper limestone of the Floridan aquifer ------- -----facing 24
12 Western Florida gulf coast showing fluoride content of water from the
upper limestone of the Floridan aquifer facing 24









AQUIFERS AND QUALITY OF GROUND WATER ALONG
THE GULF COAST OF WESTERN FLORIDA
By
Jack T. Barraclough and Owen T. Marsh

ABSTRACT

A study of electric logs, well cuttings, and chemical analyses of water
from wells in the western Florida Panhandle reveals the relation of
the quality of ground water to the geology. Three aquifers separated by
clay aquicludes underlie the panhandle west of the Choctawhatchee
River: (1) the sand-and-gravel aquifer at the surface, (2) the upper
limestone of the Floridan aquifer, and (3) the lower limestone of the
Floridan aquifer. The remarkably soft and relatively unmineralized water
in the sand-and-gravel aquifer supplies most of the wells in the western
half of the area. In the eastern half of the area, where this aquifer is
thin, most wells obtain water from the upper limestone of the Floridan
aquifer. Electric logs suggest that some fresh water may be present at
the top of the lower limestone of the Floridan aquifer in the area north
and east of Fort Walton Beach.
Dissolved solids, chloride, and fluoride in water from the upper lime-
stone of the Floridan aquifer increase in a southwesterly direction (down-
dip) across the area according to a simple, mappable pattern. Hardness
of the water decreases downdip as a result of ion exchange by clays
in the upper limestone. Areas of usable and unusable water have been
delineated on maps.
Two water problems in the Fort Walton Beach area are brought to
light by this study: (1) a sharp decline of water levels amounting to as
much as 82 feet since 1936, and (2) incipient salt-water intrusion at
the Fort Walton Beach Elementary School, induced by the drop in water
levels. The magnitude of this decline probably is related to the low
permeability of the clay in the upper limestone of the Floridan aquifer.

INTRODUCTION
PURPOSE AND SCOPE
The rapid growth of population in the western part of the Florida
Panhandle in recent years has resulted primarily from three factors: (1)
The abundance of excellent ground water has attracted more and more
industries to the area; (2) two large military bases, the Naval Air Station
at Pensacola and Eglin Air Force Base at Niceville, are in the area;
and (3) the unsurpassed beaches, numerous waterways, and agreeable






FLORIDA GEOLOGICAL SURVEY


climate have been attracting greater numbers of tourists as well as
permanent residents.
A key factor in both present and anticipated future growth is the
supply of fresh ground water. The present use of ground water in the
area probably exceeds 100 million gallons per day. The future develop-
ment and efficient utilization of the ground-water resources requires a
knowledge of both geologic and hydrologic conditions. For example,
what water-bearing formations underlie the area? How deep is the fresh
water? What is the chemical quality of the water? Is the water level
rising, falling, or remaining constant? These are some of the questions
that the authors of this report seek to answer.
This paper is a byproduct of an intensive investigation of the water
resources of Escambia and Santa Rosa counties being made by the U.S.
Geological Survey in cooperation with the Florida Geological Survey,
Escambia and Santa Rosa counties, and the city of Pensacola.

LOCATION OF THE AREA
The area discussed in this report (fig. 1) includes about 2,370
square miles in the western part of the Florida Panhandle. It includes
the southern half of the following counties: Escambia, Santa Rosa, Oka-
loosa, and Walton. This area extends about 74 miles along the gulf coast
from Perdido Bay (near Pensacola) to the east end of Choctawhatchee
Bay, and about 32 miles inland from the Gulf of Mexico, as far north as
Crestview and De Funiak Springs.

PREVIOUS WORK
Prior to 1961 relatively little was known about the geology and ground
water of westernmost Florida. A few reports contained information of a
reconnaissance or strictly local nature. The earliest published report that
describes the water resources of this area was by Sellards and Gunter
(1912). During the following year, a report on the geology and ground
water of the entire State by Matson and Sanford (1913) was published.
Jacob and Cooper (1940, unpublished manuscript) made a detailed
investigation of ground water in the Pensacola area; their report included
a section on geology by Stubbs. Heath and Clark (1951) made a detailed
investigation of the potential yield of ground water in the vicinity of
Gulf Breeze near Pensacola. Chemical analyses of ground water in the
area were prepared by Collins and Howard (1928) and by Black and
Brown (1951). Cooke (1945) included in his "Geology of Florida" a
reconnaissance of the area in which he described the marine terraces
and gave data from wells. The first detailed geologic study of Escambia






REPORT OF INVESTIGATIONS No. 29


Figure 1. Location of area described in this report.

and Santa Rosa counties was made by Marsh (1962) in connection with
a comprehensive investigation of the water resources of the area that is
currently being made by the U.S. Geological Survey. An interim report
of that investigation (Musgrove, Barraclough, and Marsh, 1961) sum-
marizes the geology and water resources of the western half of the area
discussed in the present paper.

ACKNOWLEDGMENTS
The writers would like to express appreciation to M. E. Batz and C. A.
Witcher, Jr., of the Chemstrand Corp. for various courtesies extended; to
Lehmon Spillers of Pensacola, as well as to Docie Bass and E. L. Thoma-
son of Fort Walton Beach for supplying data on wells; and to Earl
Campbell, Okaloosa County sanitarian, A. G. Symons of the Layne-
Central Co., and Shelby Sanders of Shelby Sanders and Associates for
furnishing chemical analyses of water samples.






FLORIDA GEOLOGICAL SURVEY


GEOLOGY AND HYDROLOGY
GEOLOGIC SETTING
The part of the Florida Panhandle described in this paper lies in the
Coastal Plain province and is situated along the north flank of the vast
sinking trough known as the gulf coast geosyncline. Long-continued sub-
sidence of this trough has resulted in the deposition of sand, clay, and
limestone beds, most of which thicken toward the gulf. These beds dip
about 30-35 feet per mile toward the southwest in the area of this report.
Fresh water occurs in parts of three principal aquifers: (1) the sand-
and-gravel aquifer, (2) the upper limestone of the Floridan aquifer, and
(3) the lower limestone of the Floridan aquifer (fig. 2). East of the
Choctawhatchee River the limestone of the Floridan aquifer forms the
land surface, which is pock-marked with countless sinkholes. West of the
river the limestone slopes uniformly southwestward until at Pensacola
it lies more than 1,200 feet below the surface. West of the Choctawhat-
chee River a westward-thickening wedge of sand and gravel underlies
the land surface. Throughout most of the area two thick beds of clay
separate the sand-and-gravel aquifer from the upper limestone of the
Floridan aquifer. A thinner but more extensive bed of clay divides the
Floridan aquifer into an upper limestone and a lower limestone (fig. 3).
The lower two clay beds pinch out near the eastern border of the area,
bringing the upper and lower limestones of the Floridan aquifer together
and causing the sand-and-gravel aquifer to rest directly upon the Floridan
aquifer. The uppermost clay bed ends abruptly farther west. The
Floridan aquifer is underlain by impermeable clay and shale.
HYDROLOGIC PRINCIPLES
Part of the rain that falls on the land surface runs off into lakes and
streams; part returns to the atmosphere by evaporation, either directly
or through the leaves of plants evapotranspirationn); and part seeps
into the ground to become ground water. A simple analogy would be to
compare the ground with a pail of sand. If you sprinkle water on the sand
(in imitation of rain) until the water rises nearly to the top of the sand,
you have a rough example of ground water that occurs under water-
table conditions. But to bring the analogy closer to reality, the pail must
have a few holes in the sides and bottom so that the water is continually
leaking out. Unless you keep sprinkling water on the sand, the water
level--called the water table-will drop steadily lower and lower.
Similarly, ground water keeps leaking away through seeps and springs
into streams, lakes, and oceans. This subterranean water supply must be
replenished periodically by rainfall (and snowmelt in northern areas)
if the water table is to remain near a given level. The quantity of rainfall









REPORT OF ,INVESTIGATIONS No. 29


DESCRIPTIVE SAMPLE LOG SCTIONO


Sand, light-brown, medium to very coarse


Sand, light-brown, very coarse; -
and gravel


Sand, light gray, fine to very coarse;
mollusk shells
Claoy sandy
Sand, very coarse, shells; and grovel

Mollusk sheUs with some fine to very
coarse sdnd


Gravel with shells and medium
to very coarse sand
Cloy. gray
Grovel and shell fragments


300-


400-


500-


600-


700-

TOO

2 800






-n
OO


z
. 1000-
_j




3 1100-
- -








1200
^ 1300-


1400












50
uj 1500-


1600-


1700-


1800-


1900-


2000-


2100-


2200-


2300


Cloy, dark-gray, sandy


L Limestone, grayish while, and dark -
z gray clay

0 Limestone, light gray, fossils rare
o' bond, medium to ver coarse, an

o Limestone, grayish while, some
-J foraminifers in tower half

SJ
wu z
.j 1.J Cloy, dark gray a little pyrite and
So0 carbonaceous material
- o





z
uj
0 Limestone, while, abundant
wU foraminifers

W-


Cloy, gray, with forominifers


I---


----II


RESISTIVITY IN OHM-METERS
20 40 60 80 100 120 14C


I I I I I I


Figure 2. Aquifers and aquicludes along the gulf coast of western Florida as
shown in representative test well near Pensacola.


Cloy, gray, sandy

Grovel, very coarse sand, shells


-


I


SAND AND- GRAVEL




A AQUIFER




FRI EXPLANATION


SRelatively permeable bed


Relatively impermeable bed*







AQUICLUDE
(Absent in northern half of Escomblo
and Santa Roso Counties)







FLORIDAN AQUIFER
(Upper limestone)






A QU INCLUDE
(Bucotunno Cloy Member of
Byrom Formation)







FLORIDAN AQUIFER
(Lower limestone)









A 0U INCLUDE


















BALDWIN COUN
AL ABA


--..-.......-..- -...--- --AREA DESCRIBED IN THIS PAPER ---------

TI ESCAMNIA COUNTY SANTA ROSA COUNTY I OKLOSA COUNTY
MA FLORIDA PenoCOI Fapolno O llon C H 0 C A\H A TP C
f _tSltoion A2. P1apont11o 0 SAWA ROSA SOUNO Ilaond o 0CH Oe S
.... A. r


A
WEST
MOltS i
8A


EXPLANATION
Length of section 115 miles
Vertical ecaggeralion about 52 times
- Unconformily

Well in plane of section

SWell projected into plane of
Section along Strike of bed$


WALTON COUNTY A

H =E f A P c |voltwa IEAST


-- -00


2800

-1000
-1200
1400
-1600
-'-1800
2000
2200
-2400
2600
-2800
-3000
3200


each
BALDWIN COUNTY I ESCAMBIA%. I, ANTA ROSA COA OKALOOSA COUNTY I WALTON COUNTY
111A COUNTY WALTON COUNT Y
44 L A 13 A M A COUNTY
F L 0 1 DA
Colo flow ten 0 a
A
and F1 Walton Deslin
art a ach

OF Air r x It C 0


0 5 10 20 30miles
Map showing location of Cross Seclion A-A.


Figure 8. Geologic cross section A-A' along the gulf coast of western Florida.


SAND 8 AND i-GRAVEL ::AQUIFER Sa8,t





CLA
ii ii C, Ei


mE FLOR
II AQUIFER

o1_ V1 fLOSDAN
E I A C ~U IC LU DE
o'Y' L~otNE. ~ AND GA




5ii 10 I5nides


Seoa levi


J 200-
400-
600-
800-

1000-
S1200-
1400-
1600-
W 1800-
S2000-
2200-
, 2400-
2600-
ao 2800-
00ooo-


][ --1


--


~300-


C, 41







REPORT OF INVESTIGATIONS No. 29


varies from month to month and year to year in an unpredictable man-
ner, although the average for a given period may be fairly constant. In
times of above-average rainfall the water table rises, and in times of
below-average rainfall the water table declines. Figure 4 shows this
relationship.
The type of ground water just described is called nonartesian. Com-
monly, however, the water is confined in a permeable bed of sand or
limestone, for example, that is sandwiched between relatively imperme-
able beds, such as clay. Such confined water is under artesian pressure.
Ground water is termed artesian if it is confined under enough pressure
to make it rise in a well above the top of the permeable bed that
contains the water. It is not necessary that the water rise to or above
the land surface to be classified as artesian. A rough demonstration of
water under artesian pressure can be made with a 3-foot piece of garden
hose filled with water. If you hold your thumb over one end and raise
the other end, you can feel the pressure against your thumb. But if some-
one were to cut a small hole into the upper surface of the hose near
its middle, a jet of water would shoot upward, just as water rises in a
well drilled through a confining bed of clay into a water-bearing bed of
sand or limestone. The height to which water will rise in an artesian
well is called the artesian pressure head.
An aquifer is a formation (such as a thick layer of sand or limestone),
a part of a formation, or a group of interconnected formations that are
permeable enough to transmit usable quantities of water. An aquiclude
is a bed (such as clay or shale) that is too impermeable to transmit
water in usable quantities.. Areas where aquifers are replenished are
called recharge areas, and areas where aquifers lose water are called
discharge areas.
AQUIFERS
SAND-AND-GRAVEL AQUIFER
The wedge-shaped deposit of sand and gravel that underlies the
land surface west of the Choctawhatchee River is known as the sand-
and-gravel aquifer (Musgrove, Barraclough, and Marsh, 1961). The aqui-
fer is exposed from Escambia County, Alabama, on the north to the
Gulf of Mexico on the south, and from the Choctawhatchee River on the
east at least to Mobile Bay on the west. Although the aquifer generally
thickens downdip to the west and southwest from its thin outcrop along
the Choctawhatchee River, considerable variations in thickness occur
throughout the area, as indicated in figure 3: 150 feet at Fort Walton
Beach, 500 feet at the Santa Rosa-Okaloosa County line, 300 feet in
downtown Pensacola, 700 feet at Perdido Bay, and 1,200 feet at Mobile
Bay. The aquifer overlies thick layers of relatively impermeable clay






FLORIDA GEOLOGICAL SURVEY


everywhere in the area except the eastern part, where it rests upon
the upper limestone of the Floridan aquifer.
The sand-and-gravel aquifer consists predominantly of white to
reddish brown quartz sand ranging from very fine to very coarse and in
places mixed with granules and small pebbles of quartz and chert. Lenses
and stringers of gravel and clay occur throughout the aquifer. The clay
lenses range from a few inches to several tens of feet in thickness and
may extend from a few feet to several miles in length. Impermeable
layers of hardpan also are found within the sand-and-gravel aquifer.
This dense, rusty brown material-referred to simply as "rock" by local
drillers-is formed through cementation of sand by iron oxides precipi-
tated from ground water. It occurs extensively throughout western
Florida and southern Alabama and ranges in thickness from a fraction
of an inch to 3 or 4 feet. Little is known about the lateral extent of
these layers, but probably no layer extends for more than a few thousand
yards.
Fossils, including snails, clams, and microscopic animals, indicate
that the lower part of the sand-and-gravel aquifer is of Late Miocene
Age (roughly 10-15 million years old); the upper part is much younger.
The sand-and-gravel aquifer contains ground water under both ar-
tesian and water-table conditions. Where the water is confined by clay
or hardpan, it is under artesian pressure. Where the water is not confined
by impermeable layers, it is under water-table conditions.
Changes of the water level within the sand-and-gravel aquifer are the
result of both natural and artificial causes. The principal natural cause
is variation in the amount of rainfall which affects recharge of the aquifer.
Manmade causes include intensive pumping and the erection of struc-
tures, such as dams or canals, which alter the natural pattern of drainage
or infiltration. Figure 4 compares variations in the annual rainfall at
Pensacola with changes of the artesian pressure head in a well drilled
into the upper limestone of the Floridan aquifer, as well as with changes
of the water level in a well drilled into the sand-and-gravel aquifer. The
hydrograph for the latter well (Santa Rosa 10) shows water-level
changes from 1947 to 1960 in an area where this aquifer is virtually
unaffected by pumping. The graph shows close correlation of ground-
water levels with rainfall. The high water levels from 1947 to 1949
reflect a very wet period, the lowered levels from 1950 to 1955 indicate
a relatively dry period, and the rise of the water table from 1956 to 1960
reflects the increase in rainfall during that period. The 1959-60 water
level is about the same as it was in 1948. The maximum change observed
during the period of record was 13 feet, the highest water level at 56
feet above sea level in 1949 and the lowest water level at 43 feet above
sea level in 1955.







REPORT OF INVESTIGATIONS NO. 29


f- us-T--r
juJ J Well Walton 14, at Point Washington
| \ (in the upper limestone of the Floridan aquifer)



20 -


W 40
955 1956197 9 in1
Figure 4. Water levels in well in the sand-and-gravel aquifer and a well in

00 Escambia and Santa PERIOD ties, as well as a substantiaRIOD






part of the smaller supplies in Okaloosa County. The temperature of
FLORIDAN AQUIFENORMAL RAINFALL




1936 194 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 960
Figure 4. Water levels in a well in the sand-and-gravel aquifer and a well in
the Floridan aquifer compared souith rainfall at Pensacola.

Wells in the sand-and-gravel aquifer furnish almost all the ground
water used in Escambia and Santa Rosa counties, as well as a substantial
part of the smaller supplies in Okaloosa County. The temperature of
water from the aquifer increases with depth from about 68F near the
ground surface to about 74F at about 400 feet below the land surface.
The aquifer becomes less important in the eastern half of the area because
larger quantities of fresh water are obtainable from the upper limestone
of the Floridan aquifer at moderate depths.
FLORIDAN AQUIFER
In peninsular Florida the limestone formations that range in age
from Eocene to Miocene are collectively referred to as the Floridan
aquifer. Athough it is much thinner than in central Florida, this aquifer
also underlies the entire Florida Panhandle and southwestern Alabama
at least as far as Mobile Bay.






FLORIDA GEOLOGICAL SURVEY


East of the Choctawhatchee River the Floridan aquifer forms the
land surface, which is dotted with sinkholes. West of the river the top
of the aquifer slopes uniformly southwestward (fig. 5) until at the
eastern shore of Mobile Bay it lies about 2,100 feet below the land
surface. Thus, the top of the Floridan aquifer has an average apparent
dip (along section A-A', fig. 3) of about 20 feet per mile from east to
west.
Within the area of this report the Bucatunna Clay Member of the
Byram Formation separates the Floridan aquifer into an "upper lime-
stone" and a "lower limestone." The Bucatunna thins to the east and
finally pinches out a few miles east of Destin. The maximum thickness
of the Floridan aquifer within the area, including both the upper and
the lower limestones, is about 1,900 feet in southern Walton County.
Upper limestone. Along section A-A' (fig. 3) between the
Choctawhatchee River and Mobile Bay the upper limestone ranges from
350 to 450 feet in thickness. The upper limestone thins northward from
the Gulf of Mexico (fig. 6). This thinning is much more rapid in the
eastern part of the area than in the western. The thinnest known section
of the upper limestone (45 feet) is in southern Okaloosa County, north
of Niceville: the thickest known section (455 feet) is near the mouth of
Perdido Bay.
The upper limestone is composed of light gray to brown dolomitic
limestone and some dolomite which has a distinctive "spongy-looking"
texture and contains abundant shell fragments of clams, snails, and
microscopic animals. In much of the area the upper limestone contains
layers of green and brown clay. In some wells this limestone section
must be screened and gravel packed, or the clay beds cased off, to
prevent the water that is withdrawn from becoming turbid.
The upper limestone of the Floridan aquifer is recharged directly by
rain where the limestone lies at or near the surface of the ground, or
indirectly by percolation from the sand-and-gravel aquifer. The Floridan
aquifer discharges water continuously by seepage into the gulf, by upward
leakage, and by pumping or flowing from wells.
The water in the Floridan aquifer within the area of study is under
artesian pressure. Changes in the artesian pressure head are dependent-
upon variations in rainfall and the quantity of water withdrawn by wells.
Pumping from the upper limestone has the greatest effect on the artesian
pressure in the central part of the area.
Figure 4 shows the artesian pressure head in a well drilled into the
upper limestone of the Floridan aquifer at Point Washington, near the
east end of Choctawhatched Bay. Although the well is in an area where























.1045B 85h 3063






S L n F OF MEXICO



0 5 10 I miles

5 87"00' 645' 86' 30

EX PL A N A TI O N
.360
Well
Number indicates altitude of top of limestone of the
Florldon aqulfer In feet below mean seao level
----00--
Contour of top of Upper limestone of the Floridan
aquifer, in feet below mean sea level
Contour Interval, 100 feet

Figure 5. Western Florida gulf coast showing structure contours on top of
the upper limestone of the Floridan aquifer.









UNITED STATES DEPARTMENT OF THE INTERIOR
GEOLOGICAL SURVEY


FLORIDA BOARD OF CONSERVATION
DIVISION OF GEOLOGY tz


Bai taken from Army Map
Service topographic quadrangle
i 250,000


Figure 6. Western Florida gulf coast showing thickness of the
upper limestone of the Floridan aquifer.







REPORT OF INVESTIGATIONS No. 29


very little water is pumped from the aquifer, the head has dropped
about 3 feet since 1948. This lowering may be the result of heavy
pumping from the upper limestone elsewhere in the area. From 1946 to
1949 the artesian pressure rose, from 1949 to 1956 it declined slightly,
and from 1956 to 1960 it rose slightly. These trends reflect periods of
abundant or deficient rainfall.
Formerly, artesian wells in low areas in the Fort Walton Beach area
would flow but they no longer flow because of the considerable decline
in the artesian pressure head. This decline doubtless has been caused
by increased use of water, especially by Eglin Air Force Base, the city
of Fort Walton Beach, and other nearby water users. In 1986, the artesian
pressure head in wells tapping the upper limestone at Fort Walton Beach
averaged about 56 feet above sea level. By 1960, however, the average
artesian pressure head had declined to about 18 feet below sea level.
This means that the average net decline of the artesian pressure head in
the upper limestone at Fort Walton Beach has been about 74 feet since
1936.
Figure 7 illustrates part of this striking decline. The top graph shows
that the artesian pressure head in a well that is 17 miles northwest of
Fort Walton Beach has declined about 16 feet since 1948. The hydrograph
shows very little correlation with rainfall. The gradual decrease of the
artesian pressure may be attributed mainly to pumping. The middle
graph shows the decline of the artesian pressure in a well that is 7
miles north of Fort Walton Beach. During the period of record the aver-
age decline was about 30 feet. The bottom graph represents the most
striking decline of artesian pressure in the area, in a well (Okaloosa 3)
at the Fort Walton Beach Elementary School. This decline was 95 feet
between 1936 and 1957. The artesian pressure head recovered about
18 feet from August 1957 to December 1960. It should be noted, however,
that this recovery was a result of above-average rainfall from 1958 to
1960. If rainfall returns to or below average and present pumping con-
tinues, the downward trend of the artesian pressure head may be ex-
pected to continue. In 1951 the well stopped flowing and since then has
flowed only intermittently for short periods. The artesian pressure head
dropped below sea level in 1954 and has remained below this level most
of the time since then. Low points on the hydrograph of Okaloosa 3
generally reflect the increased use of water during the summer for
watering lawns and other purposes.
Figure 8 is a contour map of the area showing the net decline of
artesian pressure in wells tapping the upper limestone, from January
1948 to September 1960. The map is based on an analysis of the hydro-
graphs of wells in the area. It shows that the greatest decline, about 56





WATER< LEVEL, IN FEET REF FRRFD 10 MEAN S f A LEVFL.
(AZ.L.


II
U



I. R
i
i"
Eo

i^


\O Santa Rom County
Okoloolo County
Ia


I































lBase taken from Army Mop
* Service, topographic uadrangle
I'250,000


0
.0


*1

0

z
p


Figure 8. Western Florida gulf coast showing net decline of artesian pressure head in wells tapping the
upper limestone of Floridan aquifer, January 1948 to September 1960.


L I II ~-s I






FLORIDA GEOLOGICAL SURVEY


feet, was at Fort Walton Beach, and the smallest decline, about 2
feet, was at Point Washington, near the east end of Choctawhatchee Bay.
It is interesting to note that the water level in a well drilled into the
sand-and-gravel aquifer 8 miles northeast of Holley and located well
within the cone of depression of water in the upper limestone of the
Floridan aquifer (fig. 4) had a net rise of 1.3 feet during this same
period.
Little is known about the water-transmitting and water-storing abilities
of the upper limestone. Well-yield figures indicate that the aquifer trans-
mits water readily in some places and reluctantly in others. In some
localities large quantities of clay have been found and probably the clay
fills some voids in the limestone. This clay may have been deposited
in the voids during later advances of the sea, after solution cavities had
been formed. Electric logs and well samples also indicate that fairly con-
tinuous beds of clay are present in the upper limestone.
The drawdown in the Fort Walton Beach area (fig. 8) appears to
be much greater than would be expected from the amount of pumping
in the area. The presence of the clay in the upper limestone provides a
reasonable explanation. This clay would reduce both the permeability
and the effective porosity of the aquifer, and would result in unusually
large drawdowns. In addition, the erratic occurrence of clay-filled voids
would explain the great variation observed in the yield of otherwise
similar wells.
The temperature of water from the upper limestone of the Floridan
aquifer ranges from about 700F in the eastern part of the area to as high
as 95'F near Pensacola.
Lower limestone. The lower limestone of the Floridan aquifer is much
more variable in thickness than the upper limestone. From its maximum
thickness of about 1,500 feet in southern Walton County, it thins abruptly
to about 700 feet just west of Destin. The limestone continues to thin to
the west, although at a much more uniform rate, until at Mobile Bay
it is less than 300 feet thick. The limestone also thins southward, toward
the gulf, from about 1,000 feet in northern Santa Rosa County to about
450 feet in central Escambia County. Thus, unlike most geologic forma-
tions along the gulf coast, this limestone thins rather than thickens down-
dip. The lower limestone is white to grayish cream and is rather soft
and chalky. It consists mainly of microscopic animals, corals, sand dollars,
clams, and many other types of shells. Thick, lens-shaped masses of hard,
light gray shale and siltstone, as well as a small amount of gray clay, are
irregularly distributed in the lower half of the limestone.






REPORT OF INVESTIGATIONS No. 29


AQUICLUDES
In most of the area the aquifers are separated by relatively imperme-
able formations (aquicludes) which greatly retard the upward and down-
ward movement of ground water.

MIOCENE CLAY
Two thick masses of clay (Marsh, 1962) separated by a thin bed of
sand lie between the sand-and-gravel aquifer and the Floridan aquifer
over most of the area. Along section A-A' (fig. 8) the upper clay thickens
from about 300 feet at Mobile Bay to about 670 feet at Pensacola. East of
Pensacola the clay thins, and just west of the Santa Rosa-Okaloosa County
line it terminates rather abruptly by interfingering with the sand-and-
gravel aquifer. The lower clay thins from about 500 feet at Mobile Bay
to 150 feet at the Santa Rosa-Okaloosa County line. East of this point
it thickens again to about 300 feet at Fort Walton Beach and then thins
and finally pinches out in southwestern Walton County. Both the upper
and lower clays appear to interfinger with the sand-and-gravel aquifer
about 20 miles north of Pensacola. The sand bed between the two clays
thickens from about 30 feet at Pensacola to about 90 feet at Mobile Bay
and about 130 feet just northwest of upper Perdido Bay. A flowing well
in Warrington obtains water from this bed of sand.
Fossil clams, snails, and shells of microscopic animals date these thick
clays as late Miocene in age (10 to 15 million years old). The clay is gray
to dark gray and contains much silt, very fine to coarse sand, and a little
gravel.

BUCATUNNA CLAY MEMBER
Throughout most of the area the upper and lower limestones of the
Floridan aquifer are separated by the Bucatunna Clay Member of the
Byram Formation (Marsh, 1962). This clay bed differs from the Miocene
clays discussed above in being much thinner, more uniform in thickness,
and more regionally extensive. The Bucatunna underlies most of western-
most Florida and parts of Alabama, Mississippi, and Louisiana. Within
the area discussed in this report the Bucatunna attains a maximum thick-
ness of 215 feet just north of Escambia Bay. It thins northward and east-
ward, pinching out in southern Walton County, 17 miles west of the
Choctawhatchee River.
The Bucatunna consists of soft gray silty to sandy clay containing a
variety of fossils. The clay rests unconformably upon the eroded surface
of the lower limestone of the Floridan aquifer and is overlain conformably






FLORIDA GEOLOGICAL SURVEY


by the flat, even base of the upper limestone, with which it interfingers
locally.

MIDDLE EOCENE CLAY AND SHALE
In the western part of the Florida Panhandle the limestones of the
Floridan aquifer are underlain by gray clay and shale of Middle Eocene
Age (roughly 50 million years old). The top of this formation dips gen-
erally southwestward and undulates broadly. Eastward along the coast
from Mobile Bay the top of the formation is relatively flat, except in
southern Walton County where it plunges abruptly downward.

CHEMICAL QUALITY OF GROUND WATER
Ground water contains various amounts of substances dissolved from
the air, soil, or rocks, as well as mineral matter introduced from bodies
of surface water such as streams and oceans. For example, salt water may
enter the aquifer from the sea. The amount of such substances dissolved
by ground water depends on the climate, type of soil or rock, and other
factors. The chemical content of ground water differs considerably from
one aquifer to another and even from place to place within a given
aquifer. Ground water along the gulf coast of western Florida is of sev-
eral types: Some is so free of dissolved substances that it can be used
even in automobile batteries in place of distilled water; some, although
mineralized to a moderate degree, can be made entirely satisfactory for
most uses by simple treatment; and some is so highly mineralized that it
cannot be made suitable for ordinary use by any practical treatment.

DEFINITIONS AND GENERAL DISCUSSION
The standard unit for reporting the concentration of various mineral
constituents in ground water is part per million (ppm), which means
that if a sample of water is reported to contain one part per million of
iron, a million pounds of such water would contain one pound of iron.
The term total dissolved solids indicates approximately the total quan-
tity of mineral matter in solution. The U.S. Public Health Service (1946)
recommends that the concentration of dissolved solids in a drinking-
water supply should not exceed 500 ppm, although water with 1,000 ppm
is acceptable where nothing better is available. Water with more than
1,000 ppm of dissolved solids usually contains enough of some constitu-
ents to produce a noticeable taste or to make the water unsuitable for
many domestic and industrial uses.
Hardness of water is caused principally by compounds of calcium
and magnesium. Hardness of water is generally recognized by the







REPORT OF INVESTIGATIONS No. 29


amount of soap required to produce lather. Many U.S. Geological Survey
reports have classified water ranging in hardness from 0 to 60 ppm as
soft, from 61 to 120 ppm as moderately hard, from 121 to 200 ppm as
hard, and more than 200 ppm as very hard.
The chloride content of ground water is a good indication of the extent
to which it has been contaminated by sea water, for about 90 percent of
the dissolved-solids content of sea water consists of chloride salts. Ground
water with a chloride content of less than 30 ppm generally has not
been contaminated by water from present or ancient seas. Chloride salts
do not usually affect the potability of water except when present in
quantities sufficient to cause a salty taste. The U.S. Public Health Service
recommends 250 ppm of chloride as the upper limit for public drinking
water supplies. Water with a chloride content of 500 ppm tastes salty
to most people. Water with a chloride content of more than about 800 ppm
may cause damage to plants, shrubs, and irrigated crops. In addition, a
high-chloride content makes the water more corrosive.
The fluoride content of water used for drinking has aroused con-
siderable public interest in recent years. Evidence indicates that the
presence of about 1.0 ppm of fluoride in drinking water decreases the
occurrence of dental caries (tooth decay) when the water is habitually
consumed by children during the period of formation of their teeth. For
this reason, fluoride is added to many public water supplies. Drinking
water containing more than 1.5 ppm of fluoride may cause dental
fluorosis (mottled enamel) in children's teeth. The U.S. Public Health
Service (1946) specifies 1.5 ppm of fluoride as the maximum concen-
tration allowable for water that is to be used for drinking.
Iron is dissolved by ground water and surface water (streams, lakes,
and oceans) from nearly all rocks and soils and from iron pipes. A con-
centration of more than about 0.3 ppm of iron in water is objectionable
as it stains porcelain, plumbing fixtures, and clothing; it imparts an
undesirable taste to the water; and upon oxidation it forms a reddish
brown sediment. Excess iron usually can be removed from water by
aeration and filtration, but some water supplies require the addition of
hydrated lime or soda ash. Along the gulf coast of western Florida, the
concentration of iron in the ground water varies considerably from place
to place and from one depth to another.
Hydrogen sulfide gas is present in ground water in some areas and
gives the water a distinctive taste and odor. Water containing it are
usually called "sulfur water." This gas, which is probably caused by the
reduction of sulfates, can be removed by aerating the water, by chlorina-
tion, or by allowing it to stand in an open container.






FLORIDA GEOLOGICAL SURVEY


Carbon dioxide in water from the sand-and-gravel aquifer causes the
water to be acidic and therefore corrosive. Most industries and munici-
palities in the western part of the Florida Panhandle treat the water
from this aquifer to reduce its corrosiveness in order to protect water
pipes, water heaters, and other metallic objects with which the water
comes into contact.

WATER IN THE SAND-AND-GRAVEL AQUIFER
Water in the sand-and-gravel aquifer is not only abundant but also
extraordinarily soft and relatively unmineralized. The availability of a
water supply of such excellent quality is the prime reason that major
industries, such as the Chemstrand Corp. and St. Regis Paper Co., have
chosen to locate in this part of the State. The Columbia National Corp.
extracts zirconium from minerals mined at Starke, Florida, and trans-
ports the ore 345 miles to its processing plant in Santa Rosa County in
order to utilize ground water in the area.
Dissolved solids. The dissolved-solids content of water from the sand-
and-gravel aquifer in this area generally is extremely low, ranging from
15 to 40 ppm. However, water from this aquifer in some localities may
contain as much as 300 ppm of dissolved solids.
Hardness. Water from the sand-and-gravel aquifer is exceptionally
soft, generally containing 4 to 30 ppm of calcium and magnesium car-
bonates. In places, water from deeper parts of this aquifer may be
considerably harder, containing as much as 150 ppm of these carbonates.
Chloride. The chloride content of water from the sand-and-gravel
aquifer generally ranges from 2 to 30 ppm except where salty water has
not been completely flushed from the aquifer or where lateral encroach-
ment from salt-water bodies has occurred.
Fluoride. The water from the sand-and-gravel aquifer usually con-
tains less than 0.2 ppm fluoride.
Iron. The iron content of water from the sand-and-gravel aquifer
ranges from 0.06 to 4.9 ppm, although it is usually less than 0.25 ppm.
Dissolved gases. Water from the sand-and-gravel aquifer contains
enough carbon dioxide to make the water acidic. Some water from this
aquifer contains hydrogen sulfide in solution.

WATER IN THE FLORIDAN AQUIFER
'The upper limestone of the Floridan aquifer is of more economic
importance to the area than the lower limestone as a source of fresh
water, for both present and future use. Few, if any, wells in the area







REPORT OF INVESTIGATIONS No. 29


DItamn water trom the lower limestone, whereas the upper limestone is
the principal aquifer for wells in the eastern part of the area.
UPPER LIMESTONE OF THE FLORIDAN AQUIFER
Water in the upper limestone of the Floridan aquifer is suitable for
most uses in the eastern two-thirds of the area. However, increasing
concentrations of dissolved solids, chloride, and fluoride in the western
third of the area makes the water unsuitable for most purposes.
Dissolved solids. In the western part of the Florida Panhandle, the
dissolved-solids content of water from the upper limestone ranges from
92 ppm at De Funiak Springs to 3,960 pp.m at Pensacola Beach. As shown
in figure 9, dissolved-solids content increases in a southwesterly direction
across the area. In the region between De Funiak Springs, Crestview,
Holley, Fort Walton Beach, and Freeport, water from the upper lime-
stone contains less than 500 ppm of dissolved solids. The dissolved-solids
content increases toward Point Washington and in a small area in Fort
Walton Beach, as well as southward and westward from Holley. At
Pensacola, Gulf Breeze, and Pensacola Beach, the dissolved-solids con-
tent of water from the upper limestone exceeds 1,000 ppm (fig. 9).
Hardness. Figure 10 shows that the hardness of water from the upper
limestone ranges from 24 to 146 ppm across the area. The hardest water
occurs in the area between Crestview and Destin (including Niceville
and Valparaiso) and around Point Washington. Moderately hard water
(hardness range from 60-120 ppm) from the upper limestone is found
at Pensacola, Gulf Breeze, Crestview, De Funiak Springs, and Freeport.
Soft water (hardness range 0-60 ppm) is found at Fort Walton Beach,
Destin, Navarre, and Holley.
The dissolved-solids content of the water from the upper limestone
increases in a southwesterly direction within the area (fig. 9). It would
be reasonable to expect the water to become increasingly harder in this
direction also, for the hardness of ground water in limestone usually
increases as the dissolved-solids content increases. This actually happens
in the area between De Funiak Springs and Niceville and around Point
Washington. However, from Niceville to Fort Walton Beach the hardness
decreases rather abruptly; and at Pensacola and Pensacola Beach, where
the water is highly mineralized, it is only moderately hard.
A possible explanation for this decrease of hardness may be natural
softening of the water by ion exchange between the water and clay
minerals, as considerable clay occurs in the upper limestone of the
Floridan aquifer. Glauconite, an ion-exchange mineral commonly found
in marine sediments, also has been noted in many well cuttings from this
area. Carlston (1942, p. 16) suggests that the increase in bicarbonate





FLORIDA GEOLOGICAL 'SURVEY


content of water from northern Alabama is ,caused by carbon dioxide
reacting with calcium and magnesium carboniates in the sediments. The
calcium and magnesium ions that were taken into solution by this reac-
tion are exchanged for sodium ions on glauconite and on clay minerals.
Such a process would explain the softening of the water and the increase
in sodium and bicarbonate ion contents.
A less important process that may tend to reduce thei hardness of the
water is indirectly a result of the dip of the upper limestone. In general,
where the top of the upper limestone is more than 400 feet below sea
level, the water in it is softer than farther updip. The temperature of the
ground water down to a depth of about 50 feet is usually about the same
as the average annual temperature of the air, which at Pensacola is
about 680F. Below a depth of 50 feet the temperature of ground water
increases steadily downward for a considerable distance. In the western
Florida Panhandle the temperature of ground water increases about
IVF for each 50 to 80 feet of depth. Thus, the temperature of water in
the upper limestone of the Floridan aquifer increases in a southwesterly
direction as the aquifer gets deeper. In the areas where the water is
relatively soft, its temperature is at least 750F. As water becomes warmer
the amount of carbon dioxide gas that it can hold in solution decreases.
The less carbon dioxide in the water, the smaller the amount of calcium
and magnesium carbonate that can remain in solution. Therefore, as the
temperature of the water increases, these carbonates tend to precipitate
out of solution, leaving the water softer.
Chloride. The chloride content of water from the upper limestone of
the Floridan aquifer ranges from 2 to more than 2,000 ppm. Figure 11
shows how the chloride content varies in the area. The chloride con-
centration is very low between Crestview, De Funiak Springs, and Nice-
ville, and increases in a southwesterly direction. The 250-ppm contour
crosses Fairpoint Peninsula west of Navarre and crosses Santa Rosa
Island near the Santa Rosa-Okaloosa County line. Except in a small area
at Fort Walton Beach and another south of Point Washington, the
chloride content of water east of this contour meets the U.S. Public
Health Service recommended standards for a public supply. West of the
250-ppm contour much of the water from the upper limestone is too
salty for a public supply.
This study revealed evidence of incipient salt-water encroachment in
the upper limestone of the Floridan aquifer in a small area at Fort
Walton Beach. During 1948, the chloride content of water from the well
at the Fort Walton Beach Elementary School was determined at three
different times to be 70, 68, and 72 ppm. On October 7, 1960, the






UNITED STATES DEPARTMENT OF THE INTERIOR
GEOLOGICAL SURVEY


FLORIDA BOARD OF CONSERVATION
DIVISION OF GEOLOF GY


DV8 OF. G. o "
17 I .


8 '00


87*15' 8700' 86045' 86030' 8615'

E X P L A N AT I O N


Less than 500 ppm
Water suitable for
municipal supplies


*450
Well
Number is dissolved solids in

LI I
500-1000 ppm
Water suitable for some
purposes
Contour interval variable


ppm


More than 1000 ppm
Water too highly mineralized
for most purposes


se t::ken from Army Mop
c topographic Map
I 250,000


Figure 9. Western Florida gulf coast showing the dissolved-solids content of water from the upper limestone of the Floridan aquifer.


30045'

















30,301


I '' "~4 11 -~ _I IL -- L P-~rr _bb ~


1 It







UNITED STATES DEPARTMENT OF THE INTERIOR
GEOLOGICAL SURVEY


FLORIDA BOARD OF CONSERVATION
DiVIcSINiM r>F G:'FnI ncV


87,15' 8700d


E X P L A N A T I O N
*24
Well
Number is hardness in ppm

IEI
61-120 ppm
Moderately hard


30045'















30030'


121-200 ppm
Hard


Hardness expressed as CaCo3
Contour interval, 20 ppm


:-ce taken from Army Map
-'r e topographic Map
I 250,000


Figure 10. Western Florida gulf coast showing hardness of water from the upper limestone of the Floridan aquifer.


0-60 ppm
Soft






REPORT OF INVESTIGATIONS No. 29


chloride content was 262 ppm, and about 2 weeks later it was 290 ppm.
This is an increase of more than 200 ppm in the last 12 years. Salt-
water encroachment may be a result of the drastic lowering of the water
level in this well (fig. 7). Before much water was withdrawn from the
upper limestone, the artesian pressure head in the upper limestone prob-
ably was about the same as in the lower limestone. Extensive pumping
of water from the upper limestone has doubtless reduced the artesian
pressure head considerably below that in the lower limestone. This differ-
ence in head would cause the water in the lower limestone to move
upward, under the higher artesian pressure. Salt water from, the lower
limestone probably is moving upward through about 60 feet of the
Bucatunna Clay Member (fig. 3) into the upper limestone. This upward
encroachment may have been facilitated by the presence of old wells
that penetrated the Bucatunna Clay Member and were later plugged
or partially plugged. Salt water may have moved upward through part
of the borehole.
As the water level in the upper limestone at Fort Walton Beach is
below sea level most of the time, salt water from the Gulf of Mexico or
Choctawhatchee Bay would have the potential head to percolate down-
ward to this limestone. However, the possibility that this has happened
seems remote, because a bed of clay about 300 feet thick overlies the
limestone and-would greatly retard the movement of water from! above
into the aquifer. In contrast, the clay bed below the upper limestone
is relatively thin and, moreover, is perforated by open-hole sections of
several old wells; this situation, coupled with the fact that water in
the lower limestone has a higher head than water in the upper lime-
stone, makes intrusion of salt water from below much more likely.
Furthermore, no appreciable increase in the chloride content has been
noted in water from wells closer to the gulf or the bay than the high-
chloride well at the elementary school.
The implications of the data collected at the school well in Fort
Walton Beach warrant continued measurement of the water level and
the initiation of a periodic sampling program to keep a check on the
chloride content. In addition, the chloride content of water from nearby
wells, especially the city wells, should be checked periodically to deter-
mine any significant change in the salinity of the water.
Fluoride. The fluoride content of water from the upper limestone of
the Floridan aquifer ranges from 0.0 ppm in the vicinity of Niceville to
6.5 ppm at Pensacola Beach. Figure 12 indicates that the fluoride con-
tent of water from this aquifer increases in a southwesterly direction
across the area. Patterns on the map indicate areas in which the fluoride





24 FLORIDA GEOLOGICAL SURVEY

content of the water (from 0.5 to 1.5 ppm) would reduce tooth decay
among children drinking the water (Black and Brown, 1951, p. 15).
An area of beneficial fluoride content lies between Destin and Holley,
and another south of Point Washington. An area in which the fluoride
content (more than 1.5 ppm) of water from the upper limestone is so
high that it might cause mottling of children's teeth also is shown on
figure 12 (Black and Brown, 1951, p. 15). This area includes Fairpoint
Peninsula west of Navarre and the western part of Santa Rosa Island.
It is interesting to note that the fluoride content of water from- a test well
at Pensacola Beach (6.5 ppm) was almost twice as high as that from any
other well in Florida known to the writers (excluding ground water con-
taminated by industrial wastes). In the area between Niceville, Crest-
view, and De Funiak Springs the fluoride content of water from the
upper limestone is less than 0.5 ppm and probably would have little or
no effect on children's teeth (Dean, 1943, p. 1173).
There are several possible sources of this fluoride. Certain minerals
common in marine sediments contain fluoride. Among these are glau-
conite, phosphate, and muscovite, which have been noted in well samples
in West Florida. The mica (muscovite) is especially abundant. According
to Hem (1959, p. 112), "Cederstrom (1945) attributes fluoride in ground
waters of the Virginia coastal plain to solution of micas which contain
fluoride." Another possible source, mentioned by LaMoreaux (1948, p.
32-34) is sea water that has not been completely flushed from the aquifer.
Fluoride is a normal, although minor, constituent of sea water. In West
Florida, the fluoride content of water from the upper limestone gener-
ally increases with increasing depth of the aquifer. LaMoreaux noted a
similar correlation in certain marine sands of southern Alabama. He also
observed a relation between high-fluoride content of ground water and
marine glauconitic sands. Some of the.fluoride may be derived from the
clay beds located within the aquifer.
Iron. The concentration of iron in water from the upper limestone
of the Floridan aquifer ranges from 0.0 to 5.0 ppm.
Dissolved gases. Most waters from the Floridan aquifer within the
study area contain hydrogen sulfide gas in solution.
LOWER LIMESTONE OF THE FLORIDAN AQUIFER
Unfortunately, no water samples could be obtained from the lower
limestone of the Floridan aquifer. However, electric-log resistivities indi-
cate that most of the water in this limestone is salty. The upper part of the
lower limestone possibly contains fresh water north and east of Fort
Walton Beach (updip), but until samples of the water can be analyzed,
this possibility can be only speculative.







UNITED STATES DEPARTMENT OF THE INTERIOR
GEOLOGICAL SURVEY


3C45'


30o30'


FLORIDA BOARD OF CONSERVATION
DIVISION OF GFOL OGY


Chloride content in

--500 -


ppm


Contour interval variable


less than 250 ppm
Water suitable for
municipal supplies


E X P L A N AT I O N
o64
Well
Number is chloride content in


250-1000 ppm
Water suitable for some
manufacturing and
irrigation uses


ppm


more than 1000 ppm
Water too salty for
most uses


Base taken from Army Map
Service topographic
I: 250,000


Figure 11. Western Florida gulf coast showing chloride content of water from the upper limestone of the Floridan aquifer.


___~_~ I L --1 --- c I-


--


~~ -~ ----~~'








UNITED STATES DEPARTMENT OF THE INTERIOR
GEOLOGICAL SURVEY


FLORIDA BOARD OF CONSERVATION
DIVISION OF GEOLOGY


8715' 87000'


Less than 0.5 ppm
Fluoride content too low
to have any appreciable
effect on children's teeth


E X P L A N AT ION

LII
0.5 to 1.5 ppm
Fluoride content beneficial
to children's teeth


Contour interval, 0.5 ppm


More than 1.5 ppm
Fluoride content
injurious to children's
teeth


3Bse taken from Army Map
Service topographic Map
I: 250,000


Figure 12. Western Florida gulf coast showing fluoride content of water from the upper limestone of the Floridan aquifer.


86045'


300435'

















3C-30,


86030'


86 15'


30045'

















3n-030,


I I ~ I ~ L I ~ ~C~s~CI ,,


I I I ~-- I ~ 1 l- Ir~ e -arl ,- ~~s ae ~s -.1 L-






REPORT OF INVESTIGATIONS No. 29


SUMMARY AND CONCLUSIONS
Three aquifers separated by clay aquicludes underlie the area dis-
cussed in this paper. The sand-and-gravel aquifer at the surface contains
soft, relatively unmineralized water and supplies most of the wells in
the western half of the area. The deeper lying upper limestone of the
Floridan aquifer contains water that is more mineralized and supplies
most of the wells in the eastern half of the area. Most of the lower lime-
stone of the Floridan aquifer is too salty for use.
Maps showing hardness, dissolved solids, chloride, and fluoride in
water from the upper limestone indicate that this water is suitable for
most uses in the eastern two-thirds of the area. The concentrations of
the mineral constituents increase in a southwesterly direction, making
the water unsuitable for most purposes in the western third of the area.
The hardest water occurs in the eastern part of the area and the water
becomes softer in a southwesterly direction.
A decline in head in the upper limestone at Fort Walton Beach has
amounted to about 82 feet since 1986. Apparently, this caused salt water
from the lower limestone to move upward through the Bucatunna Clay
Member into the upper limestone. Clay in the upper limestone of the
Floridan aquifer has played a significant role in the production of large
drawdowns by decreasing both the permeability and the effective poros-
ity of the aquifer. It has also effectively softened the water in the aquifer
by ion exchange.










REPORT OF INVESTIGATIONS No. 29


REFERENCES

Barraclough, J. T. (see Musgrove, R. H.)


Black, A. P.
1951


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


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


Carlston, C. W.
1942


Fluoride in the ground water of the Cretaceous area of Alabama:
Alabama Geol. Survey Bull. 52.


Cederstrom, D. J.
1945 Geology and ground-water resources of the Coastal Plain in south-
eastern Virginia: Virginia Geol. Survey Bull. 63.
Clark, W. E. (see Heath, R. C.)


Collins, W. D.
1928


(and Howard, C. S.) Chemical character of waters of Florida:
U. S, Geol, Survey Water-Supply Paper 596-G.


Cooke, C. Wythe
1945 Geology of Florida: Florida Geol. Survey Bull. 29.

Cooper, H. H., Jr. (see Jacob, C. E.)

Dean, H. Trendley
1943 Domestic water and dental caries: Am. Water Works Assoc. Jour.,
v. 35, no. 9, p. 1161-1183.

Gunter, Herman (see Sellards, E. H.)


Heath, R. C.
1951



Hem, J. D.
1959


(and Clark, W. E.) Potential yield of ground water on the Fair
Point Peninsula, Santa Rosa County, Florida: Florida Geol. Survey
Rept. Inv. 7.


Study and interpretation of the chemical characteristics of natural
water: U. S. Geol. Survey Water-Supply Paper 1473.


Howard, C. S. (see Collins, W. D.)

Jacob, C. E.
1940 (and Cooper H. H., Jr.) Report on the ground-water resources of the
Pensacola area in Escambia County, Florida, with a section on the
geology by S. A. Stubbs: U.S. Geol. Survey open-file report.

LaMoreaux, P.E.
1948 Fluoride in the ground water of the Tertiary area of Alabama:
Alabama Geol. Survey Bull. 59.






FLORIDA GEOLOGICAL SURVEY


Marsh, O.T. (also see Musgrove, R.H.)
1962 Relation of Bucatunna Clay Member (Byram Formation, Oligocene)
to geology and ground water of westernmost Florida: Geol. Soc.
America Bull., v. 73, p. 243-251.
Matson, G.C.
1913 (and Sanford, Samuel) Geology and ground waters of Florida:
U.S. Geol. Survey Water-Supply Paper 319.
Musgrove, R.H.
1961 (and Barraclough, J.T., and Marsh, O.T.) Interim report on the
water resources of Escambia and Santa Rosa counties,. Florida:
Florida Geol. Survey Inf. Circ. 30.
Sanford, Samuel (see Matson, G.C.)


Sellards, E.H.
1912


(and Gunter, Herman) The water supply of west-central and west
Florida: Florida CGeol. Survey 4th Ann. Rept., p. 81-155.


Stubbs, S.A. (see Jacob, C.E.)
US. Public Health Service
1946 Drinking water standards: Public Health Rcepts., v. 61, no. 11,
p. 371-384.










FLRD GEOLIOWC( ICA SURflViEWY~


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