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Evaluation of hydraulic characteristics of a deep artesian aquifer from natural water-level fluctuations, Miami, Florida...
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Title: Evaluation of hydraulic characteristics of a deep artesian aquifer from natural water-level fluctuations, Miami, Florida ( FGS: Report of investigations 75 )
Series Title: ( FGS: Report of investigations 75 )
Uncontrolled: Evaluation of hydraulic characteristics ..
Physical Description: vi, 32 p. : ill. ; 23 cm.
Language: English
Creator: Meyer, Frederick W
Geological Survey (U.S.)
Publisher: The Bureau
Place of Publication: Tallahassee
Publication Date: 1974
 Subjects
Subjects / Keywords: Aquifers -- Florida -- Miami   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by Frederick W. Meyer ; prepared by the United States Geological Survey in cooperation with the Bureau of Geology, Florida Department of Natural Resources, and with other city, county, state, and Federal agencies.
Bibliography: Bibliography: p. 31-32.
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Source Institution: University of Florida
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The author dedicated the work to the public domain by waiving all of his or her rights to the work worldwide under copyright law and all related or neighboring legal rights he or she had in the work, to the extent allowable by law.
Resource Identifier: aleph - 000127350
oclc - 01603991
notis - AAP3337
lccn - 75622508
System ID: UF00001262:00001

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STATE OF FLORIDA
DEPARTMENT OF NATURAL RESOURCES
Harmon Shields, Executive Director



DIVISION OF INTERIOR RESOURCES
Charles M. Sanders, Director



BUREAU OF GEOLOGY
Charles W. Hendry, Jr., Chief


Report of Investigations No. 75


EVALUATION OF HYDRAULIC
CHARACTERISTICS OF A DEEP ARTESIAN AQUIFER FROM
NATURAL WATER LEVEL FLUCTUATIONS,
MIAMI, FLORIDA




by
Frederick W. Meyer
U. S. Geological Survey


Prepared by the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with the
BUREAU OF GEOLOGY
FLORIDA DEPARTMENT OF NATURAL, RESOURCES
and with other
CITY, COUNTY, STATE, AND FEDERAL AGENCIES

Tallahassee, Florida


1974





DEPARTMENT
OF
NATURAL RESOURCES





REUBIN O'D. ASKEW
Governor


DOROTHY W. GLISSON
Secretary of State





THOMAS D. O'MALLEY
Treasurer





RALPH D. TURUNGTON
Commissioner of Education


ROBERT L. SHEVIN
Attorney General





FRED O. DICKINSON, JR.
Comptroller





DOYLE CONNER
Commissioner of Agriculture


HARMON W. SHIELDS
Executive Director







LETTER OF TRANSMITTAL


Bureau of Geology
Tallahassee
December 3, 1974


Honorable Reubin O'D. Askew, Chairman
Department of Natural Resources
Tallahassee, Florida

Dear Governor Askew:

We are pleased to make available the report "Evaluation of Hydrologic
Characteristics of a Deep Artesian Aquifer from Natural Water-Level
Fluctuations, Miami, Florida" by Frederick W. Meyer. The knowledge of the
hydrologic characteristics of aquifer systems is fundamental to defining the
vertical and horizontal controls on fluid movement; information which is needed
for assessing the environmental impact of subsurface waste storage. This
publication adds materially to this type of information and along with others to
follow will provide useful background information needed to evaluate deep
circulation patterns and the ultimate direction, rate of movement, and capacity
of the Boulder Zone to accept injected liquid waste.


Respectfully yours,




Charles W. Hendry, Jr., Chief
Bureau of Geology


















































Completed manuscript received
August 19, 1974
Printed for the
Florida Department of Natural Resources
Division of Interior Resources
Bureau of Geology

Tallahassee
1974



iv







CONTENTS

Page

Abstract .................................................. 1
Introduction ....................................................... 1
Purpose and scope ............................................... 2
Methods of investigation .................. ....................... 3
Acknowledgments ............................................... 3
Location and geohydrologic setting .................................. 4
Water-level fluctuations in the Boulder Zone ................................ 8
Long-term fluctuations ............................................ 9
Altitude of the water level ............................ ..... 12
Atmospheric effects ......................................... 13
Short-term fluctuations ........................................... 15
Atmospheric tide .......................................... 15
Earth and ocean tides ........................................ 16
Water-level fluctuations in the upper part of the Floridan aquifer ................ 20
Hydraulic characteristics of the Boulder Zone ............................... 21
Relation between aquifer characteristics and short-term water-level fluctuations 21
Hydraulic diffusivity .. .................... ...................... 22
Specific storage and hydraulic conductivity ............................ 23
Transmissivity and storage coefficient ................................ 27
Summary and conclusions ............................................. 28
References .......................................................... 31





















V







ILLUSTRATIONS

Figure Page

1. Map showing site location ....................................... 4

2. Sketch showing well construction ................................ 5

3. Generalized geohydrologic section from the Everglades to Bimini ......... 7

4. Hydrograph of water-level fluctuations in the Peninsula well, February 12 -
March 1, 1970; and November 25, 1970 February 12, 1971 ............ 10

5. Graphs comparing daily water-level fluctuations in the Peninsula well with
local barometric and sea-level fluctuations, December 1, 1970 February 18,
1971 ..................................................... 11

6. Graph comparing daily water-level fluctuations in the Peninsula well with
local barometric and sea-level fluctuations, February 12 28, 1970 ....... 14

7. Graph comparing semidiurnal water-level fluctuations in the Peninsula well
with local barometric and tidal fluctuations ......................... 16

8. Graphs comparing semidiurnal water-level fluctuations in the Boulder Zone
and overlying principal artesian zone of the Floridan aquifer with local
barometric fluctuations ......................................... 17

9. Graph showing earth-tide and ocean-tide components of well fluctuation ... 24



TABLES

Table Page

1. Estimated values of hydraulic conductivity and specific storage for
porosities ranging from 10 to 90 percent ........................... 26

2. Estimated values of transmissivity and storage coefficient for porosities
ranging from 10 to 90 percent ................................... 27






EVALUATION OF HYDRAULIC
CHARACTERISTICS OF A DEEP ARTESIAN AQUIFER
FROM NATURAL WATER- LEVEL FLUCTUATIONS,
MIAMI, FLORIDA

By
Frederick W. Meyer


ABSTRACT

Knowledge of the hydraulic characteristics of aquifer systems is
fundamental to defining the vertical and horizontal controls on fluid movement,
information which is needed for assessing the environmental impact of
subsurface waste storage. To meet this objective, natural water-level fluctuations
in the 2,947-foot deep Peninsula Utilities disposal well near Miami, Florida were
analyzed to obtain estimates of the hydraulic diffusivity, hydraulic conductivity,
specific storage, transmissivity, and the storage coefficient of the Boulder Zone.
The fluctuations are caused chiefly by oceanic and earth tides, and by changes in
atmospheric pressure. The oceanic tidal fluctuations probably result from
loading due to tides in Biscayne Bay.

Water from the well indicates that locally the water in the Boulder Zone is
chemically equivalent to sea water and has a temperature of 160C (60.80F). The
pressure head of the salt water in the Boulder Zone at the 2,947-foot depth
probably fluctuates at or near sea level. The quality and temperature of the
water, and with geologic considerations, suggest that the Boulder Zone crops out
in the Straits of Florida and that hydraulic connection exists between the
Boulder Zone and the Straits of Florida.

The hydraulic diffusivity of the Boulder Zone is estimated to be 2.1 x
1011 ft2/day. The hydraulic conductivity and specific storage are estimated to
be 2.1 x 10 ft/day and 1.0 x 10-6 per foot, respectively, based on an assumed
porosity of 50 percent and a 15-foot thickness of aquifer. The transmissivity and
storage coefficient are estimated to be 3.2 x 106 ft2/day and 1.5 x 10-5
respectively.

INTRODUCTION

As part of man's attempt to solve the increasing problem of liquid-waste
disposal and to alleviate the environmental deterioration of fresh and estuarine
waters, deep-well injection is being considered and evaluated. Southern Florida is
underlain at great depths by highly permeable carbonate aquifers and
interbedded fine-grained, less permeable strata. These hydrologic conditions may
be favorable to the successful use of deep disposal wells.






2 BUREAU OF GEOLOGY

Extensive cavern systems, some of which are indicated by zones of lost
circulation of drilling fluids, have been reported throughout southern Florida.
Zones of highly permeable dolomite and limestone collectively called the
Boulder Zone (Kohout, 1965 p. 256), contain relatively cold saline water at
depths of about 3,000 feet at the coast near Miami. The occurrence of
abnormally cold sea water at depth and high transmissivities within the Boulder
Zone suggest hydraulic connection with the Straits of Florida, 30 miles east of
Miami.

During 1969, a 2,947-foot disposal well was drilled near Miami at the
Peninsula Utilities (a subsidiary of General Waterworks Corporation) Snapper
Creek Park sewage treatment plant. Currently (1973), secondarily treated
effluent is injected down the well into cavernous limestone at a rate of 2 million
gallons per day.


Although data are available on the subsurface geology, water quality, and
injection rates (Garcia Bengochea, 1970; Vernon, 1970), no analyses have been
made to determine the hydraulic characteristics of the Boulder Zone. To
overcome this deficiency natural water-level fluctuations in the disposal well
were analyzed to obtain preliminary estimates of the Boulder Zone's
transmissivity and storage coefficient, and to determine the degree of hydraulic
separation with the overlying brackish and fresh-water zones and the degree of
hydraulic connection of the Boulder Zone with the Straits of Florida. This will
provide useful background information needed to evaluate deep circulation
patterns and the ultimate direction, rate of movement, and capacity of the
Boulder Zone to accept injected liquid waste. This preliminary analysis does not
eliminate the need for controlled pumping tests and additional exploratory
drilling.


PURPOSE AND SCOPE

The U. S. Geological Survey, as part of its research program to evaluate the
effects of underground waste disposal on the Nation's subsurface environment,
began the collection and analysis of water-level data from the Peninsula well
during 1970 and 1971.

The purposes of this investigation were (1) to determine the pressure head
of salt water in the Boulder Zone at the Peninsula well, (2) to identify the causes
and determine the magnitudes of the several types of water-level fluctuations in
the well, and (3) to determine the transmissivity and storage coefficient of the
Boulder Zone by an analysis of natural water-level fluctuations.






REPORT OF INVESTIGATIONS NO. 75 3

METHODS OF INVESTIGATION

A continuous record of water-level fluctuation in the Boulder Zone was
obtained at the Peninsula well during February 12 to March 1, 1970; and from
November 25, 1970 to February 12, 1971. Concurrent data on the tides in the
ocean at Miami Beach and in Biscayne Bay at Coconut Grove were obtained,
from stage stations operated by the National Ocean Survey and the U. S.
Geological Survey, respectively. Personnel of the Peninsula Utilities Company
determined the altitude of the land surface at the well. Barometric data were
obtained from the U. S. Weather Service at Miami International Airport, 7 miles
northeast of the well site.


Measurements of head in the principal artesian water-bearing zones that
overlie the Boulder Zone were obtained on February 10 and 11, 1971 by use of
a mercury manometer on the outlet to the annular space between the casings in
the well. Details of the well construction were described by Jose I.
Garcia Bengochea in an engineering report to General Waterworks Corporation
(1970).


The data were analyzed using methods described by Ferris (1951), Carr
and Van Der Kamp (1969), and Van Der Kamp (1972). Hilton H. Cooper and E.
P. Weeks, Geological Survey research scientists, suggested a method to separate
earth and oceanic tidal components of the observed semidiural water-level
fluctuations in the well, and a method to calculate hydraulic diffusivity (written
commun., 1973).



ACKNOWLEDGMENTS

The author expresses his appreciation to Clarence L. Reynolds,
Vice-President of the Southern Division of General Waterworks Corporation,
Coral Gables, Florida, and Jose I. Garcia-Bengochea, Vice President of Black,
Crow, and Eidsness Consulting Engineers, Gainesville, Florida, for their
cooperation in obtaining the necessary data, and to Hilton H. Cooper, Edwin P.
Weeks, Charles A. Appel, John E. Hull, and Howard Klein, colleagues in the U.
S. Geological Survey for assistance in collecting and analyzing the data.

This investigation was supported as part of the U. S. Geological Survey's
nationwide subsurface waste storage research program and as part of the
statewide cooperative water resources program.







BUREAU OF GEOLOGY


LOCATION AND GEOHYDROLOGIC SETTING

The Peninsula well is in Dade County, about 10 miles southwest of Miami
(fig. 1). It is 2,927 feet deep and is cased to 1,810 feet (fig. 2). The land surface
at the well is about 6 feet above msl (National Ocean Survey, mean sea-level
datum 1929).

The local water supply is obtained from the Biscayne aquifer, a highly
permeable limestone strata that underlies the area to a depth of about 100 feet.
Beneath the Biscayne aquifer is a 300-foot thick confining bed composed of
sand and clay, which confines the water in the underlying Floridan aquifer
system. The Floridan is about 1,500 feet thick and is composed of several


8 80eo"

1 B OO
MIAMI i ; BIMINI
DISPOSAL -
WELL =-
S 0

FLORIDA





,5 5 I
4J~


EXPLANATION
2400'-
LINE OF EQUAL WATER DEPTH,
IN FEET BELOW MEAN SEA LEVEL


Figure 1 Map showing site location.







REPORT OF INVESTIGATIONS NO. 75


hydraulically separate water-bearing zones (Meyer, 1971). The upper 600-foot
section is composed of limestone interbedded with calcareous clay and the lower
900-foot section (the principal water-bearing zone) is composed chiefly of highly
permeable dolomitic limestone. The head and the salinity of the ground water
increase with depth in the Floridan aquifer. Locally the head of the brackish
water in the principal artesian water-bearing zone stands 41 feet above msl.


CASINGS=


MINOR ARTESIAN
ZONES



MAJOR
I ARTESIAN
ZONES


1w



aI It
0
J LL
LL-


CONFINING
BEDS


SI I


BOULDER ZONE


20 10
I I
EXPLANATION:

. CEMENT

OPEN HOLE


0
INCHES


I 20
10 20


ADAPTED FROM
GARCIA-BENGOCHEA
1970, PLATE 4-2


Figure 2 Sketch showing well construction.


1000










2000










3000


1


I






BUREAU OF GEOLOGY


Chloride concentrations in the water from this zone range from 1,000 to 4,000
mg/1 (milligrams per liter).

A 1,000-foot thick confining bed composed of limestone interbedded with
dolomite underlies the principal artesian water-bearing zone. The permeability of
the bed varies with depth but generally is low in the vertical direction, according
to Vernon (1970, p. 10). Chloride concentrations of water in the confining bed
range from 4,000 to 18,000 mg/l; and the zone of transition between brackish
and saline water (sea-water) occurs between 1,800 and 2,000 feet below sea level
(Garcia-Bengochea, 1970).

The Boulder Zone, consisting of cavernous strata, is at the bottom of the
Peninsula well. The Bureau of Geology, Florida Department of Natural
Resources, designated the Boulder Zone as the most favorable place to inject
treated liquid wastes (Vernon, 1970, p. 31). According to the Department of
Natural Resources (Vernon, 1970, p. 23) the requisites for deep disposal are
"... that the wells terminate in zones of high transmissivities that are filled by
saline or unusable water. Such zones are located in the base or below the
Floridan aquifer and are reasonably separated from usable waters by dense
sediment with low or minimal vertical transmissivities". The terms salee
water" and "unusable water" need to be defined. Water containing more than
1,000 mg/l of dissolved solids is generally considered to be "saline" by the U. S.
Geological Survey. However, a criteria based on 15,000 mg/1 might be more
appropriate if the saline water can be economically used, that is, economically
converted to fresh water.


An extension of the subsurface geology from the Everglades eastward to
Bimini, in the Bahamas, suggests that the Boulder Zone crops out in the Straits
of Florida some 35 miles east of the well (fig. 3). Dredge hauls and seismic
profiles indicate the principal artesian water-bearing zone in the Floridan aquifer
system also crop out in the Straits of Florida (Malloy and Hurley, 1970, p.
1970). Malloy and Hurley (1970, p. 1947) indicate that karst features
(sinkholes) found on the east slope of the Straits may be kept free of sediment
by submarine flow from the Floridan aquifer.


Analysis of a water sample from the bottom of the well indicates that
locally the water in the Boulder Zone is chemically equivalent to sea water.
Temperature data obtained during drilling (Garcia-Bengochea, 1970, plate 4-2)
indicate that ground water becomes cooler with depth rather than warmer. The
thermal gradient in ground water seems to be closely related to the thermal
gradient in the ocean in the adjacent Straits of Florida (fig. 3).






REPORT OF INVESTIGATIONS NO. 75


NOT TO SCALE

Figure 3. Generalized geohydrologic section from the Everglades to Bimini.


A hypothesis that geothermal heating induces a cyclic flow of cold dense
sea water from the Straits of Florida inland through cavernous dolomitic
limestone was suggested by Kohout (1965 and 1967). Also, an inland flow of sea
water by dispersion-induced circulation may be indicated, as suggested by
Cooper and others (1964). In both cases such flow would require that the head
in the well in terms of an equivalent column of sea water (hence length and
density) would be lower than the sea.

Alternatively, Vernon (1970) and Garcia-Bengochea (1970) have suggested
that the temperature-gradient anomaly reflects the loss of heat from the aquifer
by conduction into the cold deep water of the Straits of Florida. Vernon (1970,
p. 13) states "Since no head exists at that depth, no flow and exchange of water





BUREAU OF GEOLOGY


with the ocean would be expected. Cooler temperatures are to be expected in
zones of large solutional caverns where larger volumes of water and increased
velocities of flow are present, when compared to zones of lower
transmnissivities."

To date (1973), the direction and amount of flow, if any, can only be
speculated upon because of the lack of definitive data on hydraulic gradients and
the horizontal extent and interconnection of the caverns. No pumping tests have
been made to determine the hydraulic characteristics of the Boulder Zone.
Therefore an analysis of natural water-level fluctuations nray provide useful
information on the hydraulic characteristics, including transmissivity of the
aquifer system and the extent of hydraulic connection with the adjacent Straits
of Florida.

WATER- LEVEL FLUCTUATIONS IN THE BOULDER ZONE

Fluctuations of the water level in the Peninsula well were continuously
recorded from February 12 to March 1, 1970, and from November 25, 1970 to
February 12, 1971. Long-term water-level fluctuations, lasting weeks or months,
were related chiefly to changes in the density of the water column in the well
due to dispersion of salt water and thermal conduction, to changes in
atmospheric (barometric) pressure, and, perhaps, to seasonal changes in tides.
Short-term cyclic fluctuations, lasting hours or days were related chiefly to
ocean and earth tides, and to atmospheric tide.

A summary of events before and after collection of water-level data
follows to help explain some of the variation in the water levels. Construction of
the Peninsula well began June 19, 1969, and ended December 15, 1969. The
well was drilled to a depth of 2,947 feet and contained 1,810 feet of 16-inch
steel casing. On December 16, 1969, the well was pumped at about 3,000 gpm
(gallons per minute) with compressed air to clear cuttings from the hole, and
caliper and fluid-velocity logs were obtained by the Florida Bureau of Geology.
On December 17, 1969, the well was pumped for about 2 hours at 3,000 gpm
and a water sample was collected for analysis by the U. S. Geological Survey.
The temperature of the sample was 16C (60.8F), and its chloride content was
19,300 mg/1. The water level in the well was 0.4 foot above msl 35 minutes
after pumping ceased. Subsequent measurements indicated a slow rise in the
water level.

From January 9 through January 29, 1970, fresh water from a nearby
canal was intermittently injected into the well at rates ranging from 1,000 to
4,000 gpm for testing. On February 6, 1970, cement bond, electric, and
gamma-ray logs were obtained. During February 12 through March 1, 1970,






REPORT OF INVESTIGATIONS NO. 75


records of water-level fluctuations were obtained by the U. S. Geological Survey.
On March 25, 1970, a repeat caliper log was obtained by the Florida Bureau of
Geology. On April 23, 1970, fluid conductivity, gamma ray, electric, and
temperature logs were obtained by the U. S. Geological Survey. During
November 25, 1970, through February 12, 1971, records of water levels were
obtained by the U. S. Geological Survey. On January 21, 1971, temperature and
casing-locator logs were obtained by the Florida Bureau of Geology. During
March through June 1971, the monitoring and injection systems were connected
to the well, and effluent from the treatment plant was intermittently injected
into the well for testing. On July 23, 1971, the system became operational, and
effluent flows of 2 to 3 mgd have been successfully injected into the well.

LONG TERM FLUCTUATIONS

The daily mean water level ranged from 6.8 to 7.1 feet above msl from
February 12 to March 1, 1970; from 3.4 to 3.9 feet above msl from November
25, 1970 to January 20, 1971; and between 5.6 and 5.9 feet above msl from
January 21 to February 12, 1971 (fig. 4).

In December 1969 the water level in the well was about 0.4 foot above msl
after the well had been pumped to obtain a water sample. An analysis of the
sample indicated that it was similar to sea water (chloride concentration of
19,300 mg/1).

In January 1970, during an injection test, a large amount of warm fresh
canal water was pumped into the well. After the test, the injected fresh water
was allowed to backflow into the canal. Flow ceased when the salinity of the
water column approached that of the Boulder Zone water. The water level in the
well from February 12 to March 1, 1970 was about 7 feet above msl (fig. 4).

However, on March 18, 1970, the chloride content of the water in the
upper 100 feet of the well was 18,000 mg/1, or about 1,300 mg/1 less that in
the Boulder Zone. A fluid-conductivity log obtained on April 23, 1970,
indicated that the salinity increased gradually with depth in the water column in
the well. Therefore the water level, in terms of the density of the Boulder Zone
water, was probably as much as 6 feet below the observed water level of
February 12 to March 1, 1970, or about 1 foot above msl. This compares with
0.4 foot above msl measured December 17, 1969, when the water in the well
was about the same density as the water in the Boulder Zone due to recent
pumping.

From March 1 to November 25, 1970, when daily records were not
available, the water level declined 3 feet, which, if the decline were steady,









PENINSULA UTILITIES WELL









AFTER LOGGING












BEFORE LOGGING


5 10 15 20
NOVEMBER


5 10 15 20
DECEMBER


5 10, 15 20 25
JANUARY


1970


5 10 15 20 25
FEBRUARY


1971


Figue 4 Hydrograph of water-level fluctuations in the Peninsula well, February
November 25, 1970 February 12, 1971.


12 March 1, 1970; and


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FEBRUARY
1970







REPORT OF INVESTIGATIONS NO. 75


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ow 34.
crm 34.
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I 5 10 15 20 25 31 5 10 15 20 25 31 5 10 15 20 2528


DECEMBER
1970


0 NEW MOON


JANUARY
1971
MOON PHASE
0 FULL MOON


FEBRUARY


.FIRST QUARTER ) SECOND QUARTER

Figure 5 Graphs comparing daily water-level fluctuations in the Peninsula well
with local barometric and sea-level fluctuations, December 1, 1970 -
February 28, 1971.


' BAROMETER I
U.S. WEATHER SERVICE
MIAMI
^^7^^AA,






BUREAU OF GEOLOGY


would have been at a rate of 0.012 foot per day. The decline was probably due
chiefly to the dispersion of salt water from the Boulder Zone into the upper part
of the water column in the well and to cooling of the water column. Hence, the
decline was caused by a gradual increase in the density of the water column.

From November 25, 1970, to January 20, 1971, the water level declined
from 3.9 to 3.4 feet, or an average rate of 0.008 foot per day. The recession was
probably related to the gradual increase in density, and in part to the seasonal
decline in sea level, as shown by the comparison with the ocean and bay
hydrographs in figure 5.

On January 21, 1971, after an electric log of the well was obtained by the
Florida Bureau of Geology, an unknown amount of relatively warm fresh water
was allowed to flow into the well while the logging cable was being rinsed. Upon
completion of the rinsing, the water level in the well stood at 5.7 ft above msl
(fig. 4) due to the addition of the less dense water to the top of the water
column.

The wide variation in water levels during these periods was apparently
caused by operationally induced changes in the density of the water column in
the well. Although declining, the water level was fluctuating naturally in
response to changes in atmospheric pressure and to tides (figs. 5 8).



ALTITUDE OF THE WATER LEVEL

Wide variations in the altitude of the water level in the well were indicated
by water-level measurements made on December 17, 1969 before injection of
fresh water into the well, and by continuous records of water-level fluctuations
during February 12 through March 1, 1970, and November 25, 1970, through
February 12, 1971, after injection of fresh water into the well (figs. 4 and 5). On
December 17, 1969, the water level was observed to be rising slowly from an
altitude of 0.4 foot above msl only 35 minutes after the well had been pumped
at about 3,000 gpm. The rise in water level could be related to the recovery of
the water level in the well after pumping, to changes in the density of the water
column, or to a combination of both. The cavernous nature of the aquifer
suggests that the water level would recover quickly; therefore, the slow rise in
the water level is, in the author's opinion, an indication of decreasing density in
the water column. The decrease in density could be caused by warming of the
water column in the well or by inflow of less saline.water into the water column
from strata exposed to the well between the bottom of the casing at 1,810 feet
and the cavern at 2,930 feet, or to a combination of both causes.






REPORT OF INVESTIGATIONS NO. 75


Therefore, the variations in the altitude of the water level in the well, as
shown in Figure 4, did not represent natural changes in pressure head of the salt
water in the Boulder Zone. Variations in the salinity of the water column
indicate that the water level, in terms of a well filled with water of the same
density as that in the Boulder Zone, probably fluctuates naturally at or near
present mean sea level.

Accurate pressure-head determinations are extremely important for
evaluating hydraulic gradients and deep circulation patterns. The true pressure
head can be measured by (1) installing a 2,930-foot liner inside the well with a
packer, (2) pumping the well until the temperature and salinity of the water
column in the liner are the same as that of the Boulder Zone water, (3) observing
the short-term recovery from pumping until the water level becomes more or less
static, and (4) correcting for changes in temperature. Also, the pressure head can
be accurately measured by installing a sensitive pressure transducer at the
bottom of the well.


ATMOSPHERIC EFFECTS

A comparison of the daily mean water level in the well with the daily
mean barometric pressure (expressed in feet of water) at Miami (fig. 5) indicates
that water-level fluctuations ranging from a day to several days duration were
chiefly caused by changes in atmospheric pressure. A comparison of barometric
fluctuations with sea-level fluctuations (fig. 5) indicates that the ocean-level also
fluctuated in response to changes in atmospheric pressure. However, the
atmospheric effect on the water level in the Peninsula well is shown more clearly
in Figure 6. The graphs indicate that decreasing atmospheric pressure caused the
water level in the well to rise and that increasing atmospheric pressure caused the
water level to decline.

The barometric efficiency (BE) of the Boulder Zone was estimated, by the
author, to be 0.70 by using the equation (Ferris and others, 1962, p. 85)



Sb
BE = .2w (1)



where Sw is the net change in the water level in the Peninsula well from
February 19 to 21, 1970, and Sb is the corresponding change in atmospheric
pressure, both expressed in feet of water.
















r.- Ld
0 :5--
21U3
W C






I-

Co


14 16 18 20 22 24 26 28

FEBRUARY 1970
EXPLANATION


0 FIRST QUARTER


0 FULL MOON


Figure 6 Graph comparing daily water-level fluctuations in the Peninsula well
with local barometric and sea-level fluctuations, February 12 28,
1970.


BUREAU OF GEOLOGY


UJ


rrO

W_



UJ
IL
CrO



L-
LU











01








Cr
i-


LLU





UL
bJ
LU








Un
z
UJ




LLU



LU


LU
LU

-J
-J
LU
HJ


1.0



0.5



0.0


-0.5'
12






REPORT OF INVESTIGATIONS NO. 75


SHORT TERM FLUCTUATIONS

Water levels in wells that tap coastal artesian aquifers often fluctuate
naturally in response to atmospheric, earth, and ocean tides (Bredehoeft, 1967;
Robinson and Bell, 1971). This response is usually due to the cyclic loading of
the aquifer, which is theoretically transmitted undiminished through the
overlying confining layer. Therefore, as the load on the confined water and
aquifer skeleton is increased, the water level in the well rises because of increased
pressure in the aquifer. The amplitude of the fluctuation in the well is dampened
because the aquifer, having some rigidity, supports part of the changing load,
and only the remainder of this change is reflected in the pressure of the water.


As previously stated, the water level in the Peninsula well is slightly higher
than the pressure head in the Boilder Zone, owing to operationally-caused
differences in the salinity and temperature, hence, the density of the water
column. However, short-term natural cyclic fluctuations of the water level, such
as tidal effects, are not significantly affected by this difference in density
because .the additions to and subtractions from the height of the water column
are made up of water from the Boulder Zone.



ATMOSPHERIC TIDE

Since the cyclic variations at atmospheric pressure are related to the sun's
transit they have a resonance period of 12 hours. The atmospheric pressure is
greatest at about 10:00 a.m. and 10:00 pnm. and least at about 4:00 a.m. and
4:00 p.m. The variations are primarily the result of the combined effects of the
sun's gravitational attraction and solar heating, with solar heating being the
major component. As previously shown in the section on long-term atmospheric
effects, the water level in an artesian well rises during declining atmospheric
pressure and declines during rising atmospheric pressure. Barometric fluctuations
in wells, therefore, have a semidiurnal component in which the minima occur at
about 10:00 a.m. and 10:00 pnm. and the maxima at about 4:00 a.m. and 4:00
p.m.


The effect of atmospheric tide on the water level in the Boulder Zone
appears to be minimal, according to figures 7 and 8. The water level seems to be
fluctuate chiefly in response to ocean tides. On the basis of a barometric
efficiency of 70 percent and the range of semidiurnal variations in barometric
pressure, the corresponding water-level fluctuations in the well is less than 0.05
foot.








BUREAU OF GEOLOGY


;n I I I I I I

S34 BAROMETER U.S. WEATHER SERVICE MIAMI


i I I I I I I I I I I I

PENINSULA WELL (BOULDER ZONE)




LL


8
FEBRUARY, 1971


Figure 7 Graph comparing semidirunal water-level fluctuations in the Peninsula
well with local barometric and tidal fluctuations.


EARTH AND OCEAN TIDES

The gravitational attraction of the moon and sun causes the ocean tides
and earth tides, or cyclic bulging up of the ocean and land. The periods of the
ocean and earth tides are both about 12.4 hours, but the effect of earth tide on
the level in wells that penetrate artesian aquifers is opposite to that of ocean tide
in that the water levels in these wells are low during the moon's transit. Details
of the effects of earth tides on well-aquifer systems are described in a report by
J. D. Bredehoeft (1967).










REPORT OF INVESTIGATIONS NO. 75


Earth tide, although relatively small, reinforces or diminishes the apparent
effect of oceanic tides on the water level in the well, depending upon the phase

relationship. Earth tides are alternately in and out of phase with the semidiurnal
atmospheric fluctuations in the well, augmenting them near the new and full

moon phases and counteracting them near first and third quarter phases.


w
z
0
N
Z

W
I-



CL







_j
LU
U

a-


-I


--I


I


0

13A371 V3S NV31AI
133J


n o0 on O in C

NT tO tO
3AOGV IJ31JVM JO 133_ 713A31 V3S NV31A 3A08V
*133A-


'.












ri













. 0
00
5 .








'h
'e4







BUREAU OF GEOLOGY


Daily water-level fluctuations in the Peninsula well are chiefly caused by
the semidiurnal lunar tide (fig. 7). The period of the lunar tides is 12.4 hours;
therefore, high and low tides arrive about 0.8 hour later each day. A comparison
of the water-level fluctuations in the well with the tidal fluctuations in Biscayne
Bay at Coconut Grove and in the ocean at Miami Beach shows that water-level
peaks and troughs seem to be related to the high and low tides. Diurnal
inequalities are indicated by unequal tides each day. Water-level fluctuations in
the well ranged from 0.2 to 0.4 foot, despite the fact that the well is about 6
miles inland from Biscayne Bay, the nearest body of tidal water.

The amplitude of the water-level fluctuations is only 10 to 20 percent that
of the oceanic tides, depending on the tides at the tidal station used for the
comparison. The amplitude of the fluctuations in the well seems to be about 17
percent of that in Biscayne Bay and about 13 percent of that in the ocean at
Miami Beach. These values, however, do not represent the true ratios, hence tidal
efficiency (TE), of the aquifer. According to Jacob (1950, p. 331 332), the
sum of the barometric and tidal efficiencies equals unity, that is

BE + TE = 1 (2)

The barometric efficiency was determined to be 0.70 (p. 28), therefore the tidal
efficiency would be 0.30, according to this relationship.

The comparison of the semidiurnal water-level fluctuations in the
Peninsula well with semidiurnal tides in Biscayne Bay at Coconut Grove (fig. 7)
indicated that water-level peaks and troughs led corresponding tides by about %
hour and 14 hours, respectively, or by an average of about 3/4 hour. Schneider
(1969) showed that tides in Biscayne Bay usually lagged ocean tides at Miami
Beach by more than 1 hour. On February 7, tides at Miami Beach (Miami Harbor
Entrance) led corresponding water-level fluctuations in the Peninsula well from
4 to I hour, or by an average of 40 minutes (from preliminary tide data, U. S.
Dept. of Commerce, August 1971).

Thus the well fluctuations led tide fluctuations everywhere in Biscayne
Bay, but lagged tides at Miami Beach. This relation is important with respect to
the area of aquifer loading and the degree of hydraulic interconnection of the
Boulder Zone with the Straits of Florida.

The relation between tides in the well and tides in Biscayne Bay suggested
that well tides were not related to loading in Biscayne Bay. However, an analysis
of the fluctuations by H. H. Cooper (written commun., March 15, 1973)
indicated that the anomaly was caused chiefly by the added effect of earth tide.
Therefore, the semidiurnal water-level fluctuation in the well was chiefly the







REPORT OF INVESTIGATIONS NO. 75


result of at least two out-of-phase components, namely earth tide and ocean
tide.

Semidiurnal atmospheric fluctuations, although small, are also out of
phase with the ocean tide and earth tide components and would therefore affect
the relation between tides in the well and tides in Biscayne Bay. However, by
selecting periods during which barometric changes were minimal this factor was
eliminated.

According to Cooper, the troughs of the earth tide component should
nearly coincide with the overhead transit of the moon, and the troughs of the
ocean tide component should lag the earth tide component both because ocean
tide is out of phase with earth tide and the velocity of the incoming ocean tide
component is reduced by the impedance of the aquifer. The water-level
fluctuation in the well would therefore be out of phase with each component,
resulting in water-level troughs that lag the troughs due to the earth tide
component and that precede the troughs due to the ocean tide component.

For convenience in the water-level analysis the semidiurnal fluctuation in
the well was assumed to be due chiefly to the sum of two out-of-phase
components, ocean tide and earth tide, and that the two components were
purely sinusoidal with a period of 12.4 hours (3600).

The times of the moon's transit, according to the Nautical Almanac
1970-71 (U. S. Naval Observatory, 1968 and 1969), were compared with
water-level troughs in the well during November 25 27, 1970 and February
5 -7, 1971, and the troughs seemed to lag the transits by 2% hours (72.50).
Water level troughs in the well were assumed to precede the arrival of low tide in
Biscayne Bay at Coconut Grove by about 3/4 hours (21.70) on the average. The
time required for the tidal effect to travel from the coastline to the well was
determined indirectly by an iterative process involving estimates of the hydraulic
diffusivity of the aquifer, as will be discussed later in the section dealing with the
aquifer characteristics. The value thus obtained was 1/3 hour (9.80).

The amplitudes of the ocean tide and earth tide components also were
determined indirectly by the iterative process involving estimates of the
hydraulic diffusivity of the aquifer and by trigonometric equations suggested by
Cooper.

The analysis of water-level fluctuations is expressed as:
Observed water-level fluctuation in the well =
fluctuation due to earth tide +
fluctuation due to ocean tide.






BUREAU OF GEOLOGY


The resultant equation for the harmonic analysis is

0.12 sin (i2t) = 0.065 sin (2t + 72.50) + 0.118 sin (2t + 31.50) (3)

where 12 = the angular frequency = 3600 = 360 degrees/hour
7 12.4

t = elapsed time with respect to an initial reference in hours.

S = period of fluctuation 12.4 hours.

The range of fluctuation in the well was 0.240 foot; the range of the earth
tide component was 0.130 foot; and the range of the ocean tide component was
0.236 foot. The components of equation 3 are plotted on figure 9.



WATER LEVEL FLUCTUATIONS IN THE UPPER PART OF
THE FLORIDAN AQUIFER

The pressure head in the principal artesian water-bearing zone of the
Floridan aquifer was measured at about 41 feet above msl by a mercury
manometer during February 10- 11, 1971. The pressure head representing the
composite pressures of artesian zones exposed to the annular space between
casings (between 545 and 1,678 feet) seemed to fluctuate slightly in response to
semidiurnal changes in atmospheric pressure (fig. 8). The difference between the
water level in the principal artesian zone and the water level in the Boulder Zone
is attributed by the author chiefly to the difference in fluid density.

The apparent lack of response of the pressure head in the Floridan to
ocean tide is due to the great disparity between hydraulic characteristics of the
principal artesian zone and those of the Boulder Zone. The difference in response
of the two aquifer systems coupled with geologic considerations, suggests the
following: (1) the Boulder Zone and the principal artesian zone of the Floridan
aquifer may function as hydraulically separate systems, (2) a hydraulic
interconnection may exist between both the Boulder Zone and the Straits of
Florida, (3) a hydraulic interconnection may exist between the principal artesian
zone of the Floridan aquifer and the Straits of Florida, (4) permeabilities in the
horizontal direction exceed permeabilities in the vertical direction by an
appreciable amount, and (5) the transmissivity of the Boulder Zone is much
greater than the transmissivity of the principal artesian zone of the Floridan
aquifer.






REPORT OF INVESTIGATIONS NO. 75


HYDRAULIC CHARACTERISTICS OF THE BOULDER ZONE

RELATION BETWEEN AQUIFER CHARACTERISTICS AND
SHORT TERM CYCLIC WATER- LEVEL FLUCTUATIONS

The hydraulic characteristics of an aquifer can be determined from
short-term natural water-level fluctuations in a well. Ferris (1951) described a
method that related cyclic sinusoidall) water-level fluctuations in wells and
nearby surface-water bodies to hydraulic diffusivity (the ratio of transmissivity
to storage coefficient T/S, or, equivalently, the ratio of hydraulic conductivity
to specific storage K/Ss of an aquifer). The method assumes that the aquifer is
homogeneous, of uniform thickness, and of great areal extent. Furthermore, the
aquifer is assumed to be bounded along a straight line on one side by a
surface-water body. Within the aquifer, water storage is assumed to change
instantaneously with and at a rate proportional to the change in head. Tidal
fluctuations are, therefore, transmitted horizontally through the aquifer from
the surface water-aquifer contact. The fluctuation decreases exponentially with
time and distance from the source.

Carr and Van Der Kamp (1969) modified the method to permit the
determination of hydraulic conductivity and specific storage for a confined
aquifer underlying the ocean. Tidal fluctuations in inland wells are induced by
the inland migration through the aquifer of the pressure waves produced by the
cyclic loading of the ocean. Fluctuations of water levels in the inland wells are
less than those of the pressure head in the part of the aquifer beneath the sea,
owing to the energy losses that accompany the to-and-fro movement of water in
the aquifer. Later Van Der Kamp (1972) showed that the tidal efficiency at the
coastline would be about one-half the loading efficiency; and that the loading
efficiency is essentially the tidal efficiency expressed in equation 2.

The dampening of a oceanic tidal fluctuation in an artesian aquifer during
transit from the shoreline to an inland well (Ferris, 1962, p. 133, equation 63)
can be written

-x N/7rS/
IrT

hw =hoe (4)


when hw = Fluctuation in the well at distance x from the shoreline


fluctuation in the aquifer at the shoreline (x = 0)


ho =






BUREAU OF GEOLOGY


T = transmissivity

S = storage coefficient

r = period of fluctuation


The time required for a given oceanic tidal fluctuation to travel through an
artesian aquifer from the shoreline to an inland well (Ferris, 1962, p. 134,
equation 67) can be written

xx/TS
t 1 (5)
2 rrT

where t1 = the time lag at distance x from the shoreline.


HYDRAULIC DIFFUSIVITY

Hydraulic diffusivity is defined as the conductivity of the aquifer when the
unit volume of water moving is that involved in changing the head a unit amount
in a unit volume of aquifer (Lohman, 1972, p. 8). As stated earlier it is
essentially the ratio of transmissivity (T) to the storage coefficient (S) or the
ratio of hydraulic conductivity (K) to specific storage (Ss).

Hydraulic diffusivity = T = K/Ss (6)


Equations 4 and 5, the stage-ratio and time-lag equations of Ferris, were
rearranged and solved for diffusivity (T/S):

TS = K = x2 r (7)
s 7 (In ho )2



TS =K S x2 T (8)
S 4 r t2


The hydraulic diffusivity of the Boulder Zone was computed by a method
using equations 7 and 8, trigonometric equations suggested by Cooper to
separate ocean-tide and earth-tide components of the water-level fluctuations in







REPORT OF INVESTIGATIONS NO. 75


the Peninsula well, and the relation between tidal effects at the shoreline and
tidal efficiency that was proposed by Van Der Kamp (1972).

On the basis of Van Der Kamp's theory of tidal efficiency at the shoreline,
the tidal fluctuation (ho) in the Boulder Zone at the shoreline was calculated
from tidal fluctuations in Biscayne Bay at Coconut Grove during November
25 27, 1970 and February 5 8, 1971. The tidal fluctuation in Biscayne Bay at
Coconut Grove was 1.86 feet on the average; therefore, the fluctuation in a well
tapping the Boulder Zone at the shoreline (ho) would be 0.28 foot on the
premise that the tidal efficiency at the shoreline is about half the loading
efficiency (0.30).

The distance (x) from the shoreline to the Peninsula well is 6 miles. The
analysis of water-level fluctuations in the well and tide fluctuations at Coconut
Grove indicated that the ocean tide component lagged the well component by
3/4 hour (21.7) in addition to the time required for the tidal fluctuation to
travel from the shoreline through the aquifer to the well, which is equivalent to
t1 in equation 5.

By assuming values of t1 it was possible to calculate phase and amplitude
relationships and approximate diffusivity values using the time-lag and
stage-ratio equations. The substitution or iterative process continued until a
diffusivity value was obtained that satisfied both equations and the
phase-amplitude relationship in figure 9. The results of the iterative process
yielded a diffusivity of 2.1 x 1011 ft2/day.


SPECIFIC STORAGE AND HYDRAULIC CONDUCTIVITY

The specific storage, Ss is the volume of water released from or taken into
storage per unit volume of aquifer per unit change in head. Hydraulic
conductivity, K, is the volume of water that will move in a unit time under a
unit hydraulic gradient through a unit area of aquifer measured at right angles to
the direction of flow.

The specific storage was calculated for porosities ranging from 10 to 90
percent by the following equation (Bredehoeft, 1967, p. 3083; Carr and Van Der
Kamp, 1969, p. 1023):


S, = 0 f 7 (9)
BE





TIME, HOURS
0 I 2 3 4 5 6 7 8 9 10 II 12
0.2 -A OBSERVED FLUCTUATION IN WELL, RANGE EQUALS 0.240 FOOT
B EARTH TIDE COMPONENT, RANGE EQUALS 0.130 FOOT
C OCEAN TIDE COMPONENT, RANGE EQUALS 0.236 FOOT


240
41T/3


300


0




360 DEGREES
2T7 RADIANS


PHASE ANGLE


Figure 9 Graph showing earth-tide and ocean-tide components of well fluctuation.


-0.I



-0.2


60

T/3


120


180







REPORT OF INVESTIGATIONS NO. 75


where 0 = porosity

3 = compressibility of water (2.23 x 10-8 ft2/lb at 600F)

7 = specific weight of water (64 lbs/ft3 for salt water)

BE = Barometric efficiency (0.70)

therefore

Ss = 0 (2.23 x 10"8) (64) ft2 lb
7.0 x 10-1 lb ft3

0 (2.04 x 10-6) ft-1;


Based on the relationships in equation 6, the hydraulic conductivity was
calculated for porosities ranging from 10 to 90 percent by the following
equation:

K = hydraulic diffusivity x Ss, (10)

substituting

K = (2.1 x 1011) (2.04 x 10-6) 0 ft2 1
day ft

4.28 x105 0 ft/day

The results of the computations are shown in table 1. The values of K and
Ss vary widely, depending upon the porosity. Generally, the connected porosity
of very permeable limestone aquifers, like the Biscayne aquifer, which is about
100 feet thick, ranges from 20 to 30 percent. The caliper-flowmeter log of the
Peninsula well showed that the main water-bearing zone occurs between 2,930
and 2,945 feet. The porosity of the 15-foot zone is probably higher than that of
the Biscayne aquifer.

In the author's opinion a reasonable estimate of porosity for the 15-foot
thick zone is 50 percent. The specific storage and hydraulic conductivity values
corresponding to a 50 percent porosity (table 1) are 1.0 x 10-6 ft1 and 2.1 x
105 ft per day, respectively. If, on the other hand, the thickness of the
water-bearing zone is greater than 15 feet one would expect a lesser value for
porosity.





BUREAU OF GEOLOGY


TABLE 1
Estimated values of hydraulic conductivity and specific storage
for porosities ranging from 10 to 50 percent.

0 percent porosity

Ss specific storage, ft1

K hydraulic conductivity, ft day-1


0 K Ss
10 4.3 x 104 2.0 x 10-7
20 8.6 x 104 4.1 x 10-7
30 1.3 x 105 6.1 x 10-7
40 1.7 x 105 8.2 x 10-7
50 2.1 x 105 1.0 x 106
60 2.6 x 105 1.2 x 106
70 3.0 x 105 1.4 x 10'6
80 3.4 x 105 1.6 x 10-6
90 3.9 x 105 1.8 x 10-6



A method suggested by Bredehoeft (1967, p. 3083), was also used to
estimate specific storage and porosity. The method assumes that Poisson's ratio
for the aquifer is known. The specific storage was calculated to be 1.4 x 10-7
ft based on the assumption that the earth tide component (0.13 ft) at the well
is equal to the change in head produced by the tidal dilitation at the earth's
surface (At) and on other assumptions used by Bredehoeft (1967, eq. 25). The
porosity of the aquifer was calculated to be 7 percent using equation 9; and the
hydraulic conductivity was calculated to be 3.0 x 10 ft/day1 using equation
10.


A comparison of values of K and Ss for 50 percent porosity (table 1) with
the values derived by the Bredehoeft method suggests that a 15-foot thick
aquifer with 50 percent porosity is hydraulically equivalent to a 105-foot thick
aquifer with 7 percent porosity. Therefore it is conceivable that the true values of
hydraulic conductivity and specific storage for the aquifer could range between
those for 7 percent porosity and 50 percent porosity, depending upon the
thickness of the permeable zone. In the author's opinion, the physical situation
supports the values for a 15-foot thick aquifer.





REPORT OF INVESTIGATIONS NO. 75


TRANSMISSIVITY AND STORAGE COEFFICIENT

The transmissivity (T) and the storage coefficient (S) of the aquifer, or
zone, are related respectively to the hydraulic conductivity (K) and the specific
storage (Ss) by the equations


T=mK

S = mS


(11)

(12)


where m is thickness. These equations assume that K and Ss are uniform.
Computed values of T and S for porosities ranging from 10 to 90 percent are
presented in table 2.


TABLE 2
Estimated values of transmissivity and storage coefficient for
porosities ranging from 10 to 90 percent.

0 percent porosity

T transmissivity, ft2 day-1

S storage coefficient, dimensionless


6.4 x 105
1.3 x 106
1.9 x 106
2.6 x 106
3.2 x 106
3.9 x 106
4.5 x 106
5.1 x 106
5.8 x 106


S1

3.1 x 10-6
6.1 x 10-6
9.2 x 106
1.2 x 10-5
1.5 x 10-5
1.8 x 10-5
2.1 x 10-5
2.4 x 10-5
2.8 x 10-5


Based on a 15-foot thickness of aquifer.


The caliper flowmeter log of the Peninsula well showed that the
cavernous water-bearing zone extends in depth from 2,930 to about 2,945 feet,
a thickness of 15 feet. If the porosity is assumed to be about 50 percent, then
the transmissivity and storage coefficient would be 3.2 x 106 ft2 per day and 1.5
x 10-5, respectively. The same values of T and S would apply for a 105-foot





BUREAU OF GEOLOGY


thick water-bearing zone with a 7 percent porosity a hydraulic conductivity of
30 x 104 ft/day, and a specific storage of 1.4 x 10 per foot.

Lohman (1972, p. 52) suggests that storage coefficient can be estimated
by multiplying the aquifer thickness in feet times 10-6 ft- The value for a
15-foot thick aquifer would be 1.5 x 10-5 which is equivalent to that computed
on the basis of the hydraulic diffusivity (2.1 x 1011 ft2 day1) and a 15-foot
thick water-bearing zone with a 50 percent porosity. Based on a specific capacity
test during the early stage of well development, J. I. Garcia-Bengochea (oral
common., November, 1971) estimated that the transmissivity was about 1.6 x
I05 ft2/day, which compares reasonably well with the author's estimate of 3.2 x
106 f2[day.

According to data from oil test wells in southeast Florida, cavernous zones
might extend in depth from about 2,900 feet to perhaps 3,500 feet. The
hydraulic characteristics (T and S) for the 15-foot water-bearing zone are, in the
author's opinion, representative of the geologic conditions at the Peninsular well,
but the same values could apply to a thicker zone with lower porosity. The
estimates herein will be improved upon as more reliable data are obtained from
pumping tests.


SUMMARY AND CONCLUSIONS

The natural water-level fluctuations in the 2,947-foot-deep Peninsula
Utilities disposal well open to the Boulder Zone, near Miami, Florida, are caused
largely by atmospheric fluctuations, earth tides, and ocean tides. The water level
ranged from 7.1 to 3.4 feet above mean sea level as a result of
operationally-caused variations in the density of the water column. The pressure
head of the Boulder Zone at the 2,947-foot depth in terms of equivalent
sea-water density fluctuates at or near present sea level.

Semidiurnal natural fluctuations in the well are caused chiefly by loading
due to earth tides and tides in Biscayne Bay. The tidal efficiency of the Boulder
Zone is about 30 percent, and the barometric efficiency is about 70 percent. An
analysis of cyclic water-level fluctuations in the well suggests that the earth-tide
and ocean-tide components are about 104 degrees out of phase. The range of
fluctuation in the well was 0.24 foot; the component due to ocean tide was
0.236 foot; and the component due to earth tide was 0.130 foot. The amplitude
and phase relationships are apparently responsible for tides in Biscayne Bay
lagging corresponding tides in the well tides by 3/4 hour. The geology, water
quality, and temperature gradient suggest a hydraulic connection between the
Boulder Zone and the Straits of Florida about 35 miles to the east of Miami'.





REPORT OF INVESTIGATIONS NO. 75


The effect of tidal loading on the principal artesian water-bearing zone of
the Floridan aquifer was not apparent in measurements of pressure head at the
well, although this aquifer also underlies Biscayne Bay and crops out in the
Florida Straits. The difference in response of the two aquifer systems to tides at
the Peninsula well suggests that they function as hydraulically separate systems
(although evidence is inconclusive), that horizontal permeabilities significantly
-exceed vertical permeabilities, and that the transmissivity of the Boulder Zone is
much greater than the transmissivity of the principal artesian water-bearing zone
of the Floridan aquifer.

The hydraulic diffusivity of the Boulder Zone was computed to be 2.1 x
1011 ft2/day. The hydraulic conductivity and specific storage of the 15-foot
permeable zone are estimated to be 2.1 x 105ft/day and 1.0 x 10-7 per ft,
respectively, based on an assumed porosity of 50 percent. The transmissivity and
storage coefficient of the Boulder Zone are estimated to be 3.2 x 106 ft/day
and 1.5 x 105, respectively. Pumping tests and precise water-level and density
data are needed to determine deep circulation patterns accurately and the
ultimate direction and rate of movement of injected fluids.





30 BUREAU OF GEOLOGY





REPORT OF- INVESTIGATIONS NO. 75 31

REFERENCES

Bredehoeft, J. D.
1967 Response of well-aquifer systems to earth-tides. Jour. Geophys. Research, v. 72,
no. 12, p. 3075-3087.

Carr, P. A., and Van Der Kamp, G. S.
1969 Determining Aquifer Characteristics by the Tidal Method: Water Resources
Research v. 5, no. 5, p. 1023-1031.

Cooper, H. H., Kohout, F. A., Henry, H. R., and Glover, R. E.
1964 Sea water in coastal aquifers: U. S. Geol. Survey Water-Supply Paper 1613-C.

Defant, Albert
1958 Ebb and flow: Ann Arbor, Michigan, University of Michigan Press, Ann Arbor
Science Series.

Ferris, J. G.
1951 Cyclic fluctuations of water levels as a basis for determining aquifer
transmissibility: Internat. Union Geodesy and Geophysics, Assoc. Sci.
Hydrology Assemb., Brussels, 1951, V. 2, p. 148-155; pub. in U. S. Geol. Survey
Water Supply Papers 1536 E p. 132-135, 1962; and 1536 I, p. 305-318, 1963.

Garcia-Bengochea, J. I.
1970 Engineering report on drilling and testing of deep disposal well for Peninsula
Utilities Corporation, Coral Gables, Florida: Black, Crow, and Eidsness, Inc.
Gainesville, Fla., Mimeographed report on Project No. 498-70-53, February
1970, 102 p.

Institute of Marine Science
1962 A report of data obtained in Florida Straits and off the west coast of Florida,
January June 1962: Marine Laboratorys University of Miami, mimeographed
report of Cruise G 6215 to U. S. Office of Naval Research under Contract No.
840(01).

Jacob, C. E.
1940 On the flow of water in an elastic artesian aquifer: Am. Geophys. Union Trans.
pt. 2, p. 574-586.

1950 Flow of ground water, in Engineering Hydraulics, edited by H. Rouse: New
York, John Wiley and Sons, p. 321-386.

Kohout, F. A.
1965 A hypothesis concerning cyclic flow of salt water related to geothermal heating
in the Floridan aquifer: New York Acad. Sci. Trans. ser. II, v. 28, no. 2, p.
249-271.

1967 Ground-water flow and the geothermal regime of the Floridian Plateau: Gulf
Coast Assoc. Geol. Soc. Trans. v. XVII, p. 335-354.

Lohman, S. W.
1972 Ground-water hydraulics: U. S. Geol Survey Prof. Paper 708.






32 BUREAU OF GEOLOGY

Lahman, S.W. and others
1972 Definitions of selected ground-water terms-revisions.-,:and.. conceptual
refinements: U. S. GeoL Survey Water Supply Paper 1988.

MalIoy, R. J., and Hurley, R. J.
1970 Geomorphology and geologic structure: Straits of Florida: GeoL Soc. America
BuI, v. 81, p. 1947-1972.

Meyer, F. W.
1971 Saline artesian water as a supplement: Am. Water Works Assoc. Jour. v. 63, no.
2, February 1971, p. 65-71.

Robinson, E. S. and Bell, R. T.
1971 Tides in confined well-aquifer systems: Jour. Geophys. Research, v. 76, no. 8, p.
1857-1869 (corrections v. 76, no. 26).

Schneider, JJ.
1969 Tidal relations in the South Biscayne Bay area, Dade County, Florida: U. S.
Geol Survey open-file rept, 16 p.

Van Der Kamp, G. S.
1972 Tidal fluctuations in a confined aquifer extending under the sea: Internat. Geol.
Congress, Section 11, p. 101-106.

Vernon, R- O0
1970 The beneficial uses of zones of high transmissivities in the Florida subsurface for
water storage and waste disposal: Florida Bureau Geol. Inf. Circ. No. 70.

U. S- Department of Commerce
1969 Tide tables east coast of North and South America, 1970: Washington, D.C.,
Coast and Geodetic Survey.

1970 Tide tables east coast of North and South America, 1971:. Washington, D.C.,
Coast and Geodetic Survey.

U. S- Naval Observatory
1968 The NauticalAlmanac 1970: Washington, D. C., U. S. Dept. of Navy.

1969 The NauticalAlmanac, 1971: Washington, D.C., U. S. Dept. of Navy.










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