PENSACOLA,
FLORIDA, AREA

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UNITED STATES DEPARTMENT OF THE INTERIOR
CECIL D. ANDRUS, Secretary

GEOLOGICAL SURVEY
H. William Menard, Director



























TEXT PREPARED IN COOPERATION WITH THE
CITY OF PENSACOLA







U.S. GEOLOGICAL SURVEY
Water-Resources Investigations
Open-File Report 79-89

Revised by Henry 'Tapp, Jr., U.S. Geological Survey
from Florida Department of Natural Resources, Bureau
of Geology, 1965 Leaflet No. 3 by R. H. Musgrove, J. T.
Barraclough, and R. G. Grantham, U.S. Geological Sur-
vey.







WATER IN THE PENSACOLA, FLORIDA, AREA
The Pensacola area is endowed with a vital and
bountiful natural resource-WATER. Available in large
quantities, it is easily obtained, is remarkably soft, and
contains very small amounts of dissolved minerals. The
quality of much of this water is far better than that
required for public supply and for many industries.


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Industry, shipping, and recreation . there's plenty of water for all.

Tb explain the occurrence of this water we must look
back into the geologic history of the area. For millions of
years part of the gulf coastal area has been sinking very
slowly. This lowered area has been covered to depths of
300 to 1,000 feet with sand, gravel, and clay brought
in by streams. The sand and gravel beds form a vast,
highly productive water-bearing formation, or aquifer,
that supplies almost all the wells and part of the
streamflow in the area. This surface sand-and-gravel
aquifer is replenished with water by a bountiful
rainfall-about 62 inches annually. That portion of the
rainwater that seeps underground to replenish the
aquifer remains almost pure because the sand and
gravel are composed of quartz, a silica mineral that is
not very soluble in water.

Beneath the sand-and-gravel aquifer are two thick
strata of limestone that make up the extensive Floridan
aquifer. They, too, contain large amounts of water, but
for several reasons very little water is used from these


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GEOLOGIC


SECTION ALONG THE GULF COAST


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VERTICAL SCALE GREATLY EXAGGERATED


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Sea
Level


1000


2000


3000








limestones in Escambia County: they are deeper than
the sand-and-gravel aquifer, the water contains more
dissolved minerals, and, in the area around Pensacola,
they contain saltwater. The lower limestone is being
used for disposal of industrial wastes in Escambia and
Santa Rosa Counties. The natural formation water in
the lower limestone is salty in the southern parts of the
two counties.



S / EVAPOTRANSPIRATION
S.. ~M / Mgol/d






UNDERGROUND FLOW
00 Mgal/d






WATER BUDGET
ESCAMBIA AND SANTA ROSA COUNTIES


The Pensacola area receives freshwater from three
sources-rain falling directly on the area, streams flow-
ing in from adjacent areas, and flow through the under-
ground system. Escambia and Santa Rosa Counties re-
ceive each year on the average 62 inches of rain, which
amounts to 5 billion gallons of water per day. Streams
bring in 61/2 billion gallons per day from adjacent areas.
About 0.1 billion gallons of ground water flow into the
Pensacola area each day through the limestone strata
that are fed by rain falling on the northern parts of


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2 9 mI base ol__
N --E-- -MR PR M JUE -19UL1 70 records


MIl FEB MAR APR M A UdE MY Au6 SUOVoNe


MONTHLY RAINFALL AT PENSACOLA







Escambia and Santa Rosa Counties and on southern
Alabama. The sand-and-gravel aquifer, recharged by
local rainfall, supplies most of the ground water being
used.
ALABAMA

SAlNT& FsA I

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":,, iai 5rrv rD
V %O Fi.:l.rda
AVERAGE FLOW


MINIMUM FLOW -' '" I

0 5000 -- 0
M gl /d -
SLF oF MEXICO


8500 Mgal/d FLOWS INTO BAYS FROM FOUR MAJOR
RIVERS

Of the 5 billion gallons of water per day, on the
average, that falls as rain on Escambia and Santa Rosa
Counties, about 3 billion is returned to the atmosphere
through the processes of evaporation and transpiration
(water given off by plants and trees). Two billion gallons
of this rainwater enters the streams as overland flow or
as seepage from the ground and runs off into the es-
tuaries. Streams receive about two-thirds of their flow
from the ground, resulting in stable flows even during
dry seasons. Only a small part of the rainwater leaves
the area as underground flow.

Although huge quantities of water are used every
day, vast amounts remain untapped. Most of the 101
million gallons of fresh ground water used each day in
Escambia and Santa Rosa Counties is taken from the
sand-and-gravel aquifer in the southern half of the area.
Water from streams also is used for cooling and some
wastes are discharged into the rivers. Even with this
large use, additional water is available. Pensacola, as do
other communities, derives its water supply from wells
developed in the sand-and-gravel aquifer.

In the northern half of the area only a compara-
tively small quantity of water is used. Almost all of this
comes from wells, but much of the billion gallons of clear,
soft water that flow from the small tributary streams
each day could also be used.











W ESCAMBIA COUNTY
PUMPAGE
S50- SANTA ROSA
Z COUNTY PUMPAGE

a-
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z 40 -




o 30
z
0
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C
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20
z



_ 10





INDUSTRY CITY RURAL MILITARY
SUPPLIES AND
IRRIGATION


GROUND-WATER PUMPAGE BY VARIOUS CLASSES
OF WATER USERS IN ESCAMBIA AND SANTA ROSA
COUNTIES, 1975


Most of Pensacola's public-supply wells can pump 2000 gallons per minute.


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930 1940 1950 1960 1970 1980


POPULATION TRENDS AND WATER PUMPED FOR
PUBLIC SUPPLY IN PENSACOLA AND
ESCAMBIA COUNTY


Gaging a stream.


Population of Escamblo County
- Water pumped by Pensocola
Population of Pensacola
Water pumped by other utilities
in Escombia County F
i' x


--1


200




150 I
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3




0
50 a
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WATER QUALITY
MILLIGRAMS PER LITER
MAXIMUM
ALLOWABLE 0 200 400 600 o00o ooc

TEXTILES


PAPER, KRAFT


PAPER. FINE


WOOD CHEMICALS

DRINKING WATER
AVAILABLE ] DISSOLVED SOLIDS
HARDNESS
SURFACE WATER


GROUND WATER


MAXIMUM ALLOWABLE CONCENTRATIONS OF DISSOLVED
SOLIDS AND HARDNESS IN WATER FOR VARIOUS USES
COMPARED TO CONCENTRATIONS IN THE AVAILABLE
WATER

Are there any problems associated with developing
and using this supply of water? There certainly are.
Excessive withdrawals of ground water can dry up
streams, consume what could be a renewable resource,
induce saltwater encroachment, and, under certain con-
ditions, cause land subsidence and flooding. Unwise
handling of wastes or industrial products can contami-
nate both ground water and streams. Works of man
frequently have detrimental effects on our water re-
sources.

For the immediate future in the Pensacola area, the
dangers of excessive withdrawals of ground water are
confined to small areas of concentrated pumping. Exces-
sive pumping in isolated areas has lowered the level of

GROUND WATER
ALABAMA
.--..-- 1 Large quantities
ECM- R available
E SCAOMB ANTA A Small to moderate
SCOMA I SANTA ROS
COUNTY COUNTY z --quantities available
Sf l1 Areas of
O concentrated use
U) (Water available to wells
N A W from the sand-and-gravel
< /&. / aquifer







THICKNESS OF SANC-,NiD-GRAVEL AQUIFER
ALABAMA
," <250 feet
"-' / JTA ROSA I 250-500 feet
o c OuNT' I i -



N. P r .





GULF 00

fresh ground water and allowed salty water to replace it.
This is saltwater intrusion; the saltwater is difficult to
remove, but once it occurs it can be controlled by proper
management. There is no evidence of significant ad-
vance of saltwater into the aquifer around Pensacola in
recent years.

Industrial wastes and drainage from landfills,
leaky sewers, and septic tanks may seep underground
and contaminate water wells and streams. Storm runoff
carries a variety of pollutants and also sediment from
new construction sites into surface bodies of water. One
municipal well was abandoned in Pensacola because
part of the sand-and-gravel aquifer was contaminated
by industrial waste. Many years are required for an
aquifer to recover from contamination. It also may take
many years of diligent effort and large sums of money to
clean up a stream, bayou, or bay after it has received
excessive wastes.

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Streams and bayous in the ensacola area are vulnerable to pollution by storm runoff

Streams and bayous in the Fensacola area are vulnerable to pollution by storm runoff.







HOW IS THE WATER RESOURCE MEASURED?

A community must know many things about the
water resource in order to plan orderly industrial and
urban expansion. For example, they must know the
answers to: What are the sources of water? How much is
available? How does the supply fluctuate? What is the
quality of the water? What are the effects of use on
quantity and quality? Ib answer questions of this sort
and the many other questions pertaining to water re-
sources, there must be a planned program of water-
resources investigations. In the Pensacola area, several
studies have been made as part of such a program.

A general study of the water resources of Escambia
and Santa Rosa Counties was completed in 1962 by the
U.S. Geological Survey with financial cooperation from
the Florida Bureau of Geology, the city of Pensacola,
Escambia County, and Santa Rosa County. The U.S.
Geological Survey has been conducting a more detailed
study of the hydrology of the sand-and-gravel aquifer in
southern Escambia County in cooperation with the city
of Pensacola from 1970 to the present (1979). In addition,
the Survey has long-term cooperative agreements with
Escambia County, Florida Department of Environmen-
tal Regulation, the Florida Department of T'ansporta-
tion, and the Northwest Florida Water Management
District to gage and sample streams and measure water
levels in wells, and with the Florida Department of
Environmental Regulation to monitor the effects of
deep-well waste injection.
For the long term, the limit to the quantity of water
available to the Pensacola area depends on the adverse
effects on the environment that can be tolerated and the
price, in dollars, that people in the area are willing to
pay for additional supplies. Hydrologic studies can pre-
dict the effects on the system of withdrawing water from
various sources, and thus make informed choices possi-
ble.

Mapping and measuring water-bearing formations:
We can only imagine the confusion that would exist if
there were no maps or plans of Pensacola's waterworks
showing the source of water and the location and size of
the underground pipe system. Community life might go
smoothly until a break in a line occurred or an expansion
of this system was necessary to take care of a population
increase. At that time many questions would have to be
answered before progress could be made, some of which
are: Where are the pipes? Are they large enough to allow











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Otto Reichmann, Jr., of Pensacola has measured water levels in observation wells for
the U.S. Geological Survey since 1942.

for the expansion? How long has the system been here?
Do the pipes leak? Where does the water come from and
in what amounts? Difficult as these questions are to
answer, those concerned with a natural water-resource
system that serves a complex industrial society are
many times more difficult. The earth structure that
serves both as a storage reservoir and as a distribution
system is mapped by piecing together information from
many sources. The services of experienced hydrologists,
geologists, engineers, and chemists are necessary to
identify and measure the extent and water-bearing
characteristics of the materials that make up the earth.
Much geologic information is obtained from wells.
Existing wells must be studied and tested, test wells
drilled and logged, drill cuttings examined, water sam-
ples analyzed chemically, and water levels measured.
Much information is gained by observing the reaction of
ground-water levels to rainfall and to pumping. When a


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'NATIONAL WEATHER STA

-NORMAL -4 --WET--l-4 DRY--WET"- NORMAL-4-WET-+-NORMAL4--- DRY--*
-w 00 Trend 6Mean val

Sequels 59
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L_ 40
3zw 20












20
0
20







1940 1945 1950 1955 1960 1965


ANNUAL RAINFALL AND FLUCTUATIONS
IN GROUND-WATER LEVELS NEAR PENSACOLA, 1940-1976










well is pumped the water level underground lowers to

form a depression, similar in shape to a cone, but with

the point down. The rate and amount of this lowering

while the well is being pumped at a measured rate and

the rate at which the water level recovers after pumping

ceases are measures of the ability of the formation to

transmit and store water.

Water-level fluctuations in a well not only tend to

parallel fluctuations in rainfall, but may also show the

effects of people's use of water or changes in the envi-

ronment. For example, a long-term decline that does not

coincide with a decline in precipitation may be caused by

an increase in the quantity of water being pumped in the

surrounding area. Urbanization, with its associated

construction, paving, and drainage, tends to reduce

ground-water recharge, and thus may also cause a long-

term decline in water levels.


C-
" 20


0 10
Oo


I I I
2 4 6 8
DISCHARGE, IN THOUSANDS OF
CUBIC FEET PER SECOND
STAGE-DISCHARGE CURVE


5 10 25 50
RECURRENCE INTERVAL, IN YEARS
FLOOD-FREQUENCY'CURVE


40
30 -
ZL.
20
20u









1200


B NW
1200
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0 B00 5



2000
o 2 40040

2 0 00\00 30 0,g,0 00 2 -


TRENDS IN STREAMFLOW

THE BEHAVIOR OF A STREAM
(PERDIDO RIVER AT BARRINEAU PARK, FLORIDA)


20
YEARS
CURVES


15


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The behavior of a stream: Certain physical aspects
of a stream must be measured at least several times over
a period of years in order to determine how much water
it carries, how its water level fluctuates, and the quality
of its water. The stage of a stream, or the height of its
water surface above an established datum, is changing
continually. It is either rising or falling. Continuous
stage measurements over a period of time, together with
discharge measurements at various stages, are used to
calculate a continuous record of the stream's discharge
for that period. Stage and discharge measurements are
also used in calculating the frequency of floods and the
duration of various rates of discharge. Recurrence inter-
val graphs are used to show the average interval of time
within which a hydrologic event of given magnitude,
such as a flood or low-flow period, will be equalled or
exceeded once.

The U.S. Geological Survey, in cooperation with
State and local agencies, maintains several long-term
gaging stations on rivers and creeks in the Pensacola
area. Short-term records are available for other streams.
Variations in mineral concentration of water: To
determine the seasonal variations in the chemical qual-
ity of surface water, samples of the water are taken daily
or sometimes at less frequent intervals for analysis. To
determine the chemical quality of ground water, several
wells must be sampled, but often only one sample need
be collected from each well for analysis. Maps showing
the mineral concentration of the water in an aquifer
may be prepared from these analyses. In areas of sus-
pected contamination, ground water must be analyzed
repeatedly to determine changes in mineral concentra-
tion.








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Pensacola's Water Production Technician Tommy Stevens testing a water sample at a
city well.








Although ground water in the Pensacola area con-
tains a much lower concentration of dissolved mineral
matter than most ground water throughout the world,
there are problems of high iron concentration, corro-
siveness, and, in places, the water is contaminated or
is in danger of being contaminated.




IRON CONCENTRATIONS IN GROUND WATER



ent LAreas in southern Escambia
County in which water from wells
in the sand-and-grovel aquifer
\ generally contains less than 300
B ( micrograms per liter of iron

SACOLA







CARBON DIOXIDE CONCENTRATIONS IN GROUND WATER

Carbon dioxide concentrations in
Sweater from wells in the sand-and-
C eonment grovel aquifer in southern Escambia
County

t <20 milligrams per liter
( L 20-80 milligrams per liter
P NSACOLA
Zir >80 milligrams per liter






NITRATE (as N) CONCENTRATIONS IN GROUND WATER

I Nitrate (as N) concentrations in
Water from wells in the sand-and-
Stonment grovel aquifer in southern Escombia
County

S i2 a
M >5 milligrams per liter









Some of the iron in ground water originates from
the corrosion of well casing, and some is naturally
present. Detailed sampling of water from wells in
the southern part of Escambia County shows that
the ground water in some areas is free of excessive
iron. High concentrations of carbon dioxide are as-
sociated with corrosiveness. Ground water in the south-
western part of Escambia County was found to have
especially high concentrations of carbon dioxide. Al-
though nitrate is an indicator of contamination by hu-
man, animal, or industrial wastes, it is not a dependable
one-it may occur naturally. Nitrate is generally absent
or is low in water from rural areas in southern Escambia
County; rarely does it exceed the limit of 10 milligrams
per liter as nitrogen recommended by the Florida De-
partment of Environmental Regulation for drinking
water. In rural areas, water may be contaminated from
septic tanks or livestock Jperations.

AVAILABILITY OF ADDITIONAL INFORMATION
Additional information on the water resources of
the Pensacola area is contained in the following reports
by personnel of the U.S. Geological Survey:
Availability of Ground Water for Public-Water Supply
in Central Southern Escambia County, Florida, In-
terim Report, July 1972: U.S. Geol. Surv. open-file
rept., by Henry Trapp, Jr.

Availability of Ground Water for Public-Water Supply
in the Pensacola Area, Florida, Interim Report,
June 1971: U.S. Geol. Surv. open-file rept., by
Henry Trapp, Jr.

Geology of Escambia and Santa Rosa Counties, Western
Florida Panhandle: Fla. Geol. Surv. Bull. No. 46, by
O.T. Marsh.

Hydrology of the Sand-and-Gravel Aquifer in Central
and Southern Escambia County, Florida, Prelimi-
nary report-November 1973: U.S. Geol Surv.,
Open-File Rept. FL-74-027, by Henry Trapp, Jr.
Monitoring Regional Effects of Pressure Injection of
Industrial Wastewater in a Limestone Aquifer:
Ground Water, v. 13, no. 2, p. 197-208, by G.L.
Faulkner and C.A. Pascale. (Reprints available
through U.S. Geol. Surv., Tallahassee.)







Water Resources Data for Florida, Water Year 1975,
Vol. 1, Northern Florida: U.S. Geol. Surv. Water
Data Rept. FL-751-1, by U.S. Geol. Surv.

Water Resources of Escambia and Santa Rosa Coun-
ties, Florida: Fla. Geol. Surv. Rept. of Inv. No. 40,
by R.H. Musgrove, J.T. Barraclough, and R.G.
Grantham.
Water Resources Records of Escambia and Santa Rosa
Counties, Florida: Fla. Geol. Surv. Inf. Circ. No. 50,
by R.H. Musgrove, J.T. Barraclough, and R.G.
Grantham.




These reports are available in many libraries and
the following office:
U.S. Geological Survey
325 John Knox Rd., Suite F-240
Tallahassee, FL 32303



































For use of those readers who may prefer to use
metric (SI) units rather than inch-pound units, the con-
version factors for the terms used in this report are listed
below:


Multiply
inch-pound unit
inch
foot
cubic foot per second
gallon per minute

millions of gallons
billions of gallons
million gallon
per day (Mgal/d)
billion gallon
per day (Bgal/d)


Ib obtain
By metric (SI) unit
millimeter
25.4 meter
.3048 cubic meter per second
.0282 cubic meter
.00006309 per second
cubic meter
3,785 cubic meter
3,785,000
cubic meter per second
.04301
43.01 cubic meter per second
























As the Nation's principal conservation agency, the
Department of the Interior has responsibility for most of
our nationally owned public lands and natural re-
sources. This includes fostering the wisest use of our
land and water resources, protecting our fish and
wildlife, preserving the environmental and cultural val-
ues of our national parks and historical places, and
providing for the enjoyment of life through outdoor rec-
reation. The Department assesses our energy and min-
eral resources and works to assure that their develop-
ment is in the best interests of all our people. The
Department also has a major responsibility for American
Indian reservation communities and for people who live
in Island Territories under U.S. administration.

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