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    Jacksonville's water, by Gilbert W. Leve
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        Copyright
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STATE OF FLORIDA
STATE BOARD OF CONSERVATION
DIVISION OF GEOLOGY



FLORIDA GEOLOGICAL SURVEY
Robert O. Vernon, Director





LEAFLET NO. 6




JACKSONVILLE'S WATER



By
Gilbert W. Leve, Geologist










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


TALLAHASSEE
1965



























































iA.






JACKSONVILLE'S WATER


By
Gilbert W. Leve

Water is the life blood of Jacksonville--
millions of gallons are used each day. Because
water of good quality abounds in Jacksonville,
little anxiety normally is expressed as to its
adequacy and quality. However, Jacksonville is
a burgeoning metropolis, and municipal and in-
dustrial demands for water are increasing stead-
ily. These demands have made officials more
and more concerned about the future water
supplies in the area.

WHAT IS THE SOURCE OF JACKSONVILLE'S
WATER?

Jacksonville straddles the St. Johns River
,and is nearly surrounded by its numerous tribu-
taries. However, as scenic and ample as these
streams appear, they cannot easily furnish
Jacksonville its drinking water. The Atlantic
Dcean is only 15 miles away and the St. Johns
River and.its tributaries are close to mean sea
level. Salty water from the ocean, pushed by
'ides, migrates up these streams and causes
them to be almost as salty as the ocean. For
this reason, practically all of the water used
at this time in Jacksonville comes from wells
Lhat tap drinkable water in the rocks below the
surface of the ground. Fortunately, water in
cne ground is ample to supply the needs of all
of the people and industry in the area at the
present time.
Ground water, the water in the rocks that
underlie the land surface, occurs throughout
northeastern Florida. Some rocks such as clay,
silt, and hard dolomite are tight and very little
water moves through them to wells. Other rocks
such as sand, shell beds, and limestone are
porous and water fills the void spaces similar
-o the way water fills a sponge. Porous rocks






ho. 6
which are capable of yielding water to wells
are called "aquifers". The principal aquifers
underlying the area are shown in figure 1.
The Floridan aquifer underlies Jacksonville
and vicinity and is the principal source of
drinking and industrial water.







~LL I- -




Figure 1. Block diagram showing aquifers in the
vicinity of Jacksonville and recharge to the artesian
aquifer.

What Aquifers Are In Jacksonville?

Jacksonville and vicinity are supplied water
mainly from three aquifers: (1) sand beds that
blanket the surface of the ground; (2) thin lime-
stone and shell beds between 50 and 150 feet
deep; and (3) thick limestone beas below 300
to 600 feet deep. The surficial sand beds are
called a water table aquifer. Here the water
level is free to rise and fall. Wells drilled into
the water table aquifer must be pumped to
bring water to the surface. The thin limestone
and shell beds form an artesian aquifer because
nonporous beds overlie the aquifer and confine
the water under pressure. However, the lime-
stone and shell beds are locally connected to
the water table aquifer and water in these beds
rises to about the height of the top of the water
table aquifer. The deeper, thick, limestone
aquifer is also an artesian aquifer because an
extensive tight clay bed overlies the aquifer
and confines the water under pressure. When








a well is drilled through the confining bed into
the limestone, water will rise in the well. In
most of Jacksonville, the water will flow at the
surface. In a few areas where the land surface
is relatively high or where the artesian pres-
sure has been lowered by many discharging
wells, the wells will not flow but water in them
will rise to within a few feet of the land sur-
face.
The water table aquifer and the thin lime-
tone and shell aquifer are replenished by local
rainfall that seeps into the ground and gradually
,ercolates downward to the aquifers. The deep
artesian aquifer is replenished as far away as
:0 and more miles in northcentral Florida.
here the limestone beds are at or near the
and surface. Water enters the limestone through
nany lakes and sinkholes in this area and
noves slowly toward the ocean. En route, part
Af the water is intercepted by the many dis-
-harging wells in Jacksonville and other parts
>f northeastern Florida.

[OW MUCH WATER IS AVAILABLE FROM EACH
AQUIFER-HOW GOOD IS IT?

Surficial Sand Beds.-In most places the
water table aquifer in the surficial sand beds
yield from 10 to 15 gallons per minute. These
yields are controlled more by the manner in
which the wells are constructed and the sizes
of pumps than by the availability of water. The
type of well commonly used in the surficial
sand beds is shown in figure 2. Commonly, the
surficial sand beds are tapped by "surface
wells" which consist of %-inch to 2-inch dia-
meter casing and a sand point. The sand point
at the bottom of the casing is driven or jetted
to between 10 and 30 feet below the surface so
that the well screen is below the water table.
A shallow well pump is installed on the well
to lift the water to the surface.
Water from this aquifer generally is high
in iron which stains plumbing fixtures and
painted surfaces. In addition, this aquifer at







2 Surface well 4' "Rock" well


Sea level .:- .. Suficrio .. Sond : -. ;
Well screen
Nonporous Beds
100 -


200-


U 300- Nonporous < Beds


- 400-

0U
o 500


600
Artesi on quifer
]0 1 I I I I I I
700 -



Figure 2. Diagram showing water wells in three
aquifers in the Jacksonville area.
some places may be subject to contamination
from nearby septic tanks, leaky sewerage pipes,
and polluted bodies of surface water. There-
fore, water from this aquifer is the least desir-
able source of water for drinking and domestic
use although it is used for lawn sprinkling
systems and air conditioning.
Limestone And Shell Beds Between 50
And 150 Feet Deep.-These relatively thin lime-
stone and shell beds are present in most parts
of the Jacksonville area. In some areas they are
absent or too thin to supply usable quantities of
water to wells. However, in many parts of
Jacksonville and vicinity, they are thick enough
to yield 15 to 20 gallons per minute to wells and
in some locations as much as 80 gallons per
minute. In addition to the thickness of the aqui-
fer, the construction of the wells and the sizes
of the pumps control the yield of water (fig. 2).
A typical "rock well" tapping the limestone


12'Artesion well








and shell aquifers is constructed by driving or
jetting 2 to 4-inch casing to the top of the lime-
stone or shell bed and then drilling an open
hole from a few inches to about 20 feet into
the aquifer. A shallow well pump or jet pump is
installed on the well to lift the water to the
surface and distribute it to water lines or a
pressure tank.
Water from this aquifer is generally of good
quality for drinking and domestic supplies. In
fact, as shown in table 1, water from these shal-
low limestone and shell beds is generally softer
and contains less dissolved mineral matter than
water from either the surficial sand beds or the
underlying artesian aquifer--the principal source
of water in the area.

Table 1. --Chemical quality of water from typical wells
in each of the aquifers in the Jacksonville area.-!
(Chemical components in parts per million.)
Surficial Thin limestone Artesian
sand and shell aquifer
Total dissolved solids 324 159 515
Total hardness, as CaCO3 264 124 318
Calcium (Ca) 86 34 72
Magnesium (Mg) 12 9 34
Bicarbonates (HCO3) 317 151 158
Sulfates (SO4) 0 10 140
Chlorides (Cl) 23 11 3
Iron (Fe) 2.2 --- 0.42
Color (Pt-Co scale) 80 5 5
pH 6.9 7.1 7.5
Fluorides (F) 0.0 0.05 0.8
Hydrogen sulfide (HZS) None None Present
Depth (feet) 40-50 99 900
1/Analysis from: Some physical and chemical characteristics of
selected Florida waters; 1960, Florida State Board of Health,
Division of Water Supply.

The Deep Artesian Aquifer.-Wells that will
yield large quantities of water from the deep
artesian aquifer can be drilled anywhere in the
Jacksonville area. (See fig. 2.) This is because
the artesian aquifer underlies all of northeast






05'


200-300 ft
Z300-400ft.
B400-500ft. f,
e_ 500 -600 ft.
4E_ 600-700 ft

- !











30




l-









0 :


. J
-""Kl


t^n


C L A Y
or-

.,:


82 00 55I 50 40
1 11 1TI I I I 17


;w
.~:
" ';


rii -:
C~f~. --..-~-- ~TYa~e~r(


COUN


Figure 3. Depth to he artesian aquifer
in the I area.


-1
-1



1
. -1
"',

_.


-v


-11


I
I r-



a_






Florida and because the aquifer is everywhere
composed of highly porous, water-filled rock.
Essentially all of the larger wells in the area
are drilled into this aquifer. The top of the
aquifer--a soft, white limestone--is from 300
to nearly 600 feet below sea level in Duval
County as shown by the color patterns on figure
3. The deepest water wells in Jacksonville
have penetrated about 1,000 feet into the lime-
stone and have not reached the bottom of the
aquifer.
The amount of water that can be obtained
from the artesian wells depends on well dia-
meter, depth of penetration into the aquifer, and
artesian pressure and water transmitting cha-
racter of the aquifer at the well site. Depending
on location and well construction, artesian
wells may flow naturally at rates from about
500 gallons per minute to as much as 6,000
gallons per minute as shown in table 2. All
of these wells will yield greater quantities of
water with the use of large capacity centrifugal
or deep-well turbine pumps. The artesian wells
are constructed by driving or inserting 2 to 20-
inch diameter casing to the top of the limestone
and then drilling an open hole from a few feet
to several hundred feet into the aquifer.
The water from the deep artesian aquifer
is quite hard. It retards the cleaning action of
soaps and detergents and forms a precipitate
or scale on plumbing fixtures, boiler pipes and
utensils when it is heated. The hardness can
be easily removed by heating or by inexpensive
commercial softeners. The water also contains
hydrogen sulfide gas which has an offensive
"rotten egg" odor and a corrosive effect on
plumbing. The gas can be removed from the
water by simple aeration by natural loss to the
atmosphere in an open tank or pool or in a
commercial aeration system.

HOW IS THE WATER USED?

Water from the surficial sand bed and the





Table 2. Characteristics of aquifers in Jacksonville and vicinity.


Common depths (feet Principal quality
Aquifer Usual well construction below land surface) Common yield (gpm) characteristics Principal uses


Surficial "Surface well": to 2-inch diameter casing and 10 to 30 10 to 15 (pumped) High in iron and sub- Lawn sprinkling systems,
sand beds a sand point; driven or Jetted so that the well ject to pollution air conditioning
screen is below the water table


Limestone "Rock well": 2 to 4-inch diameter casing, dri- 50 to 150 15 to 20 (pumped) Some Soft; low in dissolved Rural domestic supplies,
and shell yen or jetted to the top of the aquifer and then 4-inch diameter wells mineral content lawn sprinkling systems,
beds drilled without casing from a few inches to 20 may yield as much as heating and cooling
feet into the aquifer 80 gpm (pumped)


Artesian "Artesian well": 2 to 20-inch diameter casing, 500 to 1,000 2 to 6-inch diameter Good quality, hard; Principal source of
aquifer driven or inserted to the top of the aquifer wells=500 (natural flow) hydrogen sulfide gas water in the Jacksonvilla
(300 -600 feet) then drilled without casing from area. Municipal, commer.
a few feet to several hundred feet into the 8 to 12-inch diameter cial, industrial, and
aquifer wells=l, 000 to 2,000 private supplies.
(natural flow)

12 to 20-inch diameter
wells=, 000 to 6,000
(natural flow)






thin limestone and shell beds is used to irrigate
lawns, supply air conditioning systems, and
to supply rural homes in areas not serviced by
municipal or private water utilities. However,
the amount of water from these shallow, rela-
tively thin water table aquifers is not sufficient
to supply all of the people and industry in the
area. Most of the water in the Jacksonville area
is from the deep artesian aquifer.
The City of Jacksonville has 46 municipal
wells drilled into the deep artesian aquifer.
These wells supply slightly more than 38 million
gallons of water per day for domestic, commer-
cial, and industrial use. Privately owned water
utility wells supply an additional 15 to 20
million gallons per day. Also, many industries,
commercial buildings and private homes have
private wells. The large industries, such as
paper manufacturing, may use as much as 20
million gallons per day; smaller commercial
establishments and industries such as dairies,
laundries, and food processing plants may use
as much as 5 million gallons per day. Various
business buildings and private homes have
wells that supply a few gallons to as much as
about 100,000 gallons per day for drinking,
heating, cooling, lawn sprinkling systems,
domestic use, and swimming pools.

ARE SUPPLIES ADEQUATE FOR
THE FUTURE?

At present and for the immediate future,
there is more than adequate water to supply all
of the people and industry in the Jacksonville
area. However, the population is increasing
rapidly and new industry is moving into the
Jacksonville area. This growth creates a demand
for more and more water. Artesian pressures
are declining continuously and wells that once
produced sufficient water by natural flow must
now be pumped to meet this growing demand for
water. If the decline in artesian pressure be-
comes excessive, the artesian aquifer may be-






come contaminated by intrusion of salty water
from salt-water zones in the deeper part of the
artesian aquifer, from the ocean, or from both.
Such intrusions have already happened in some
areas in eastern Florida and southern Georgia
where ground water conditions are similar to
those in Jacksonville and vicinity. Perhaps
the greatest threat to future water supplies in
the Jacksonville area is not a shortage of water
but salt-water intrusion. However, proper con-
servation measures and careful planning in the
development and use of water, based upon
scientific information, can retard or prevent
salt-water contamination. Adequate supplies
of fresh water for the Jacksonville area can
thus be assured for many years to come.

WHAT ABOUT EMERGENCY
WATER SUPPLIES?

Two hydrologic factors place Jacksonville
in a favorable position with respect to water
supply in the event the water systems are threa-
tened as a result of accidental or other radio-
active fallout or a local emergency such as a
hurricane. First, water in the artesian aquifer
is not susceptible to immediate contamination.
Second, the artesian wells flow and water can
be obtained without power.
Water taken directly from an artesian well
will be safe to drink during or after a fallout.
Surface water, shallow ground water, or water
from distribution lines may be exposed to radio-
active fallout, but the water that comes directly
from the artesian aquifer is protected by 300
to 600 feet of overlying rock and would not be
contaminated for many, many years. Because
most of the artesian wells in the Jacksonville
area flow above land surface, this water would
be available even during a power failure when
the pumps were disabled. Water could be ob-
tained at the well head by simply opening an
outlet valve, tap, or by removing any obstruc-
tion that prevents the well from flowing. The
many hundreds of artesian wells scattered







throughout the Jacksonville area could serve
as sources of emergency water supply. Artesian
wells located close to or inside fallout shelters
could supply adequate amounts of good watei
to large numbers of people for a long period ol
time.

WHERE CAN MORE INFORMATION BE
OBTAINED ON WATER?

Publications and specific information
about water in the Jacksonville area can be
obtained on request from a number of State
and Federal agencies. Both the Florida Geo-
logical Survey and the U.S. Geological Survey
conduct comprehensive investigations of watei
supplies in the Jacksonville area. Information
on these investigations may be obtained by
writing to the Florida Geological Survey and
the U.S. Geological Survey, Tallahassee, Fla-
rida, and Ocala, Florida.










FLRD GEOLOSk ( IC SUfRiW


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