Hydrogeologic characteristics of the surficial aquifer in northwest Hillsborough County, Florida ( FGS: Information circular 86 )

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

DIVISION OF INTERIOR RESOURCES
Robert 0. Vernon, Director

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

Information Circular No. 86

HYDROGEOLOGIC CHARACTERISTICS OF THE SURFICIAL
AQUIFER IN NORTHWEST HILLSBOROUGH COUNTY, FLORIDA

By
William C. Sinclair

Prepared by the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with the
BUREAU OF GEOLOGY
DIVISION OF INTERIOR RESOURCES
FLORIDA DEPARTMENT OF NATURAL RESOURCES
and
SOUTHWEST FLORIDA WATER MANAGEMENT DISTRICT

TALLAHASSEE, FLORIDA
1974

DEPARTMENT
OF
NATURAL RESOURCES

REUBIN O'D. ASKEW
Governor

RICHARD (DICK) STONE
Secretary of State

THOMAS D. O'MALLEY
Treasurer

FLOYD T. CHRISTIAN
Commissioner of Education

ROBERT L. SHEVIN
Attorney General

FRED 0. DICKINSON, JR.
Comptroller

DOYLE CONNER
Commissioner of Agriculture

HARMON W. SHIELDS
Executive Director

LETTER OF TRANSMITTAL

Bureau of Geology
Tallahassee
February 12, 1974

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

Dear Governor Askew:

The Bureau of Geology of the Division of Interior Resources is publishing
as its Information Circular No. 86 a report prepared by William C. Sinclair of the
U. S. Geological Survey entitled, "Hydrogeologic Characteristics of the Surficial
Aquifer in Northwest Hillsborough County, Florida".

Considerable information is available on the hydrogeologic properties of
the Floridan aquifer of Northwest Hillsborough County, but little is known
about these properties in the overlying surficial aquifer. This report provides a
detailed evaluation of the storage of water in these surficial deposits and its
movement into the Floridan aquifer.

Respectfully yours,

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

Completed manuscript received
January 11, 1974
Printed for the Florida Department of Natural Resources
Division of Interior Resources
Bureau of Geology
by Ambrose the Printer
Jacksonville, Florida

Tallahassee
1974
iv

CONTENTS

Page
Abstract ............................................. 1
introduction .......................................... 1
Geographic setting ...... ........ ............... ......... 2
Test drilling ........................ .. ................ 3
Sampling methods ....................................... 5
Laboratory analyses ...................................... 5
Particle-size analyses ................................. 6
Hydraulic conductivity ................................. 6
Specific yield ..................................... 7
Clay and mineral identification ........................... 7
Lithology ........................................... 7
Natural-gamma logs ...................................... 8
Geohydrology .......................................... 9
Limestone ........................................ 9
Clay .... .. .... ... .... .. .. .... ... .... .. .. .. 10
Sand and clay ...................................... 11
Sandy clay ...................... .. ............ 11
Clayey sand .................................... 11
Sand and clay laminae .............................. 12
Sand .. .. .... .. .... ... .... ... ... ..... .. ..... 12
Hydrologic system ....................................... 13
Sum mary ........................................... 16
References cited ........................................ 19

ILLUSTRATIONS

Figure
I. Map of Northwest Hillsborough County, and adjoining counties showing
location of test sites and contours on the potentiometric surfaces of the
surficial and Floridan aquifers . . . . . . .

Page

4

TABLES

Table
1.
2.
3.
4.

Relationships of soil, terrain, geology, and hydrology at 59 test sites . .
Results of laboratory tests of 67 samples from 24 sites . . . .
Clay-mineral identification for selected samples . . . . .
Logs showing lithology, gamma radiation, and generalized geohydrology of
surficial deposits at sites tested in northwest Hillsborough County . .

Page
20
23
26

28

HYDROGEOLOGIC CHARACTERISTICS OF THE SURFICIAL
AQUIFER IN NORTHWEST HILLSBOROUGH COUNTY, FLORIDA

By
William C. Sinclair

ABSTRACT

Fifty-nine holes were angered to the top of the limestone Floridan
Aquifer. Lithologic and gamma logs of the holes were used in conjunction with
laboratory analyses of samples to define the hydrogeology of the unconsolidated
deposits of the surficial aquifer overlying the limestone. The surficial aquifer is
comprised of an upper fine sand unit which averages about 15 feet thick and a
lower sequence of sandy clay and clayey sand layers which average about 25 feet
thick. Median grain size, specific yield, and vertical permeability of the surficial
aquifer decrease downward. The coefficient of vertical permeability of the sand
is about 100 gallons per day per square foot, but the coefficient of vertical
permeability of the lower sand and clayey sand is much lower ranging from 0.01
to 0.1 gallon per day per square foot.

A confining layer of dense clay underlies the surficial aquifer separating it
from the Floridan Aquifer below. The coefficient of vertical permeability of the
clay is about 0.001 gallon per day per square foot. Although this clay is
discontinuous, it averages 4 feet thick throughout 'the area and is apparently a
weathering product of the underlying limestone. The limestone surface is
irregular and its average depth is 45 feet below land surface.

The potentiometric surface in the surficial aquifer stands an average of 10
feet above that in the Floridan. Leakage from the surficial aquifer to the
Floridan occurs through the confining layer as well as through perforations in
the confining layer. Estimates of leakage to the Floridan Aquifer based on
vertical permeability calculated at each test site varied widely from place to
place. A regional estimate, based on the average coefficient of vertical
permeability, is about 140,000 gallons per day per square mile.

INTRODUCTION

Heavy withdrawal of ground water from the Floridan Aquifer in northwest
Hillsborough and northeast Pinellas Counties, Florida, has lowered the water
table in the overlying surficial aquifer. The effects of the pumpage were anlayzed
by Stewart (1968), and his analysis led the Southwest Florida Water
Management District to request the U. S. Geological Survey to investigate the
feasibility of artificially recharging the Floridan Aquifer in the area.

BUREAU OF GEOLOGY

Considerable information is available on the hydraulic and hydrogeologic
properties of the Floridan Aquifer in this area but little has been known about
these properties in the overlying surficial aquifer. A principal aim of this
investigation is to provide a detailed evaluation of the role of the surficial
deposits in the storage of rain falling upon the land surface and its movement
into the Floridan Aquifer.

The investigation began in December 1968. This report, the first from the
investigation, documents the results of test drilling undertaken to define the
hydrologic characteristics of the unconsolidated deposits. These deposits
comprise both the sands of the surficial aquifer, which is the water-table aquifer
in the area, and the clay confining bed that retards movement of water between
this aquifer and the Floridan Aquifer below. The report is limited to description
of the methods used and interpretation of data derived from the test drilling.

GEOGRAPHIC SETTING

Northwest Hillsborough County is a flat to slightly undulating sandy plain.
Its altitude is about 50 feet in the eastern part of the area of investigation; the
regional slope westward toward and into the Gulf of Mexico, is about 4 feet per
mile.

The plain is perforated by sinkholes -- circular depressions typical of
karst erosion that bottom as much as 15 to 20 feet below land surface. These
small circular depressions, locally called cypress heads or cypress domes, are one
of the most characteristic vegetative and geomorphic features of the gulf coastal
lowlands. These features result from local subsidence of the land surface due to
sapping of the surficial material into solution openings forming in the underlying
limestone. Sinkholes are prevalent throughout the area in all stages of formation
ranging from freshly collapsed pits a few feet in diameter to large lakes and
swamps with irregular shorelines and bottoms composites of many
coalescent sinkholes. The sinks permit local hydraulic connection between the
surficial water-table aquifer and the Floridan Aquifer and are an important
avenue of natural recharge to the Floridan Aquifer in this area.

Most of the natural surface drainage of the area is poorly developed. The
myriad sinkhole swamps and lakes that dot the sandy plains fill when rainfall is
heavy, then spill one into another as the water moves generally southwestward.
Only a small part of the rainfall runs off and percolation to both aquifers is also
slight. By far, the greatest part of rainfall in the area is lost by evaporation and
transpiration.

BUREAU OF GEOLOGY

Considerable information is available on the hydraulic and hydrogeologic
properties of the Floridan Aquifer in this area but little has been known about
these properties in the overlying surficial aquifer. A principal aim of this
investigation is to provide a detailed evaluation of the role of the surficial
deposits in the storage of rain falling upon the land surface and its movement
into the Floridan Aquifer.

The investigation began in December 1968. This report, the first from the
investigation, documents the results of test drilling undertaken to define the
hydrologic characteristics of the unconsolidated deposits. These deposits
comprise both the sands of the surficial aquifer, which is the water-table aquifer
in the area, and the clay confining bed that retards movement of water between
this aquifer and the Floridan Aquifer below. The report is limited to description
of the methods used and interpretation of data derived from the test drilling.

GEOGRAPHIC SETTING

Northwest Hillsborough County is a flat to slightly undulating sandy plain.
Its altitude is about 50 feet in the eastern part of the area of investigation; the
regional slope westward toward and into the Gulf of Mexico, is about 4 feet per
mile.

The plain is perforated by sinkholes -- circular depressions typical of
karst erosion that bottom as much as 15 to 20 feet below land surface. These
small circular depressions, locally called cypress heads or cypress domes, are one
of the most characteristic vegetative and geomorphic features of the gulf coastal
lowlands. These features result from local subsidence of the land surface due to
sapping of the surficial material into solution openings forming in the underlying
limestone. Sinkholes are prevalent throughout the area in all stages of formation
ranging from freshly collapsed pits a few feet in diameter to large lakes and
swamps with irregular shorelines and bottoms composites of many
coalescent sinkholes. The sinks permit local hydraulic connection between the
surficial water-table aquifer and the Floridan Aquifer and are an important
avenue of natural recharge to the Floridan Aquifer in this area.

Most of the natural surface drainage of the area is poorly developed. The
myriad sinkhole swamps and lakes that dot the sandy plains fill when rainfall is
heavy, then spill one into another as the water moves generally southwestward.
Only a small part of the rainfall runs off and percolation to both aquifers is also
slight. By far, the greatest part of rainfall in the area is lost by evaporation and
transpiration.

INFORMATION CIRCULAR NO. 86

TEST DRILLING

Sites were selected for test drilling on the basis of many criteria. Broad
geographical coverage seemed desirable to determine the variability of the
surficial deposits within the area. Test holes were drilled one-half mile to 1 mile
apart from east of the Section 21 well field to the Cosme well field, and at about
1-mile intervals both north and south of the Section 21 field (fig. 1). Within this
geographical framework, sites were selected on different soils and landforms to
determine whether soil and terrain might give some indication of the lithology of
underlying deposits. Table 1 lists several geologic and hydrologic factors at each
site, for comparison. The "Soil Survey, Hillsborough County" (Dept.
Agriculture, 1968) was used as authority for the soil type (table 1) at the test
sites.

Much of the test drilling was concentrated within the 1-square-mile area of
the Section 21 well field where the effects of pumping from the Floridan
Aquifer on water levels in lakes and in wells tapping the surficial aquifer are
most severe. Test holes were augered in Starvation Lake (site 31) where a
12-foot decline in stage had exposed much of the bottom. A hole was also
augered near Jackson Lake (site 23) just west of Starvation Lake. In Jackson
Lake the stage did not seem to be fluctuating greatly. Test holes were augered in
the center of a well-defined sinkhole marsh (site 40), and in a well-defined
sinkhole swamp (sites 32-35). Several wells were also augered in a flatwoods area
where incipient sinkholes are developing (sites 26-28) and in soil types not
previously augered. In all, 59 wells were drilled and sampled using the power
auger and one (site 60) was sampled at land surface by hand.

Where possible, wells were augered on Hillsborough County Road
Department rights-of-way. The upper few feet there is generally artificial fill so
the first sample was usually taken from 5 feet below land surface. The
cooperation of the Hillsborough County Engineer's Office, the city of St.
Petersburg Water Department, and the many private citizens who allowed access
to their property is gratefully acknowledged.

Test sites where wells were drilled and sampled during this study are
numbered in sequence. At each site a well was installed using 2-inch plastic
casing with a screen set in the topmost part of the Floridan Aquifer. At most
sites a shallow well was also installed with the screen set in the surficial aquifer
just below the water table. Thus, measurements can be made of the
potentiometric surface of each aquifer.

-',6

Ill I'

INFORMATION CIRCULAR NO. 86

SAMPLING METHODS

The test holes were augered with a truck-mounted power rig. The auger
flights are 5 feet long, 8 inches in diameter, and are formed around a 3-inch
diameter steel tube. A plug seals the bottom of the central tube during augering.
This plug is held in place by 5-foot sections of steel rod. The steel rod is added
to the string, along with additional auger flights, as the hole is deepened. When
the auger bit reaches the desired sampling depth, the drill is stopped and the rods
are pulled out. The sampler is then lowered through the auger and pushed or
driven into the undisturbed material below the auger bit, cutting a cylindrical
sample the diameter of the tube.

The sampler used is called a split spoon and is made of two half tubes that
fit together to form a cylinder and are held together by a threaded coupling at
the top and a threaded, case-hardened, cylindrical cutting shoe at the bottom.
Three aluminum tubes 6 inches long and 1 inches in diameter fit snugly into it.
When the sample is retrieved, the split spoon is opened. The aluminum tubes are
sealed at each end with plastic caps and labeled. The ends of the tubes are sealed
in wax to prevent loss of moisture and disturbance of the sample before it
reaches the laboratory.

Sampling unconsolidated material through a hollow-stem auger is superior
to sampling by other methods because uncontaminated samples can be obtained
at any desired depth in a relatively undisturbed condition. Most samples of clay
and laminated clay and sand show the extent of disturbance by drag folds in the
bedding planes at the cylinder walls. The clay is soft, and undisturbed samples
were usually collected without difficulty. Because massive sand has little
cohesion, undisturbed samples are nearly impossible to obtain from below the
water table. The sand is homogeneous and the amount of disturbance is difficult
to determine.

Samples were usually taken at 5-foot intervals. Test holes at sites 35, 37,
40, and 44 were sampled continuously from land surface to limestone. The
lithologic logs of these test holes indicate that samples collected every 5 feet
would prove adequate for the needs of this study when augmented by gamma
logs.

LABORATORY ANALYSES

Sixty-nine samples from 25 of the test holes were analyzed by the
Geological Survey's laboratory in Denver for certain physical and hydrologic
parameters.

BUREAU OF GEOLOGY

PARTICLE-SIZE ANALYSES

In unconsolidated, granular material, the hydraulic conductivity is largely
a function of the size and shape of the component grains and their degree of
sorting. The median diameter is the particle size that is larger than 50 percent of
the sample and smaller than the other 50 percent. The median diameter of the
samples tested ranged from 0.002 mm (millimeter) for dense clay to 0.22 mm
for sand and mixtures of sand and clay (table 2). The average of all the median
diameters was 0.14 mm, and for the samples without an appreciable silt and clay
fraction, 0.17 mm. These sizes are in the fine sand range (0.125 to 0.25 mm) of
the Wentworth classification (Twenhofel and Tyler, 1941, p. 46-48, and
Wentworth, 1922). Sand particles of medium size (0.25 to 0.5 mm) rarely
constituted more than 2 or 3 percent of the samples except for sample 23-351/
which contained 16.8 percent. That fraction within the coarse sand size (0.5 to
1.0 mm) was less than 1 percent of any sample.

The sorting coefficient listed in table 2 is a measure of the degree of
sorting in a sample. It is sometimes called the geometrical quartile deviation
(Trask, 1932, p. 70-72). It is represented by the expression (Q3/Ql) in which
Q3 is the particle diameter that is larger than 75 percent of the sample, and Qi is
the particle diameter that is larger than 25 percent of the sample. A sorting
coefficient less than 2.5 (Krumbein and Pettijohn, 1938, p. 232) indicates a well
sorted material. Most of the sorting coefficients listed in table 2 are less than 2.5,
indicating that most of the samples are well sorted.

HYDRAULIC CONDUCTIVITY

Hydraulic conductivity is the capacity of a material to transmit water.
Hydraulic conductivity is reported in table 2 as the rate of flow, in cubic feet per
day, through a cross-sectional area of 1 square foot, under a hydraulic gradient
of 1 foot per foot, at the prevailing kinematic viscosity in units of feet per day.
This terminology is suggested for use in reports of the Geological Survey by
Lohman, and others, (1972). The coefficient of permeability is also reported in
Meinzer Units, the former standard of the Geological Survey gallons per day
per square foot, under a hydraulic gradient of 1 foot per foot at a temperature
of 600 F.

Hydraulic conductivity of 36 samples was determined in the laboratory
using either constant-head or variable-head permeameters. The conductivity of

11 Sample numbers are a composite of the site number and sample depth. For example,
sample 23-35 is from a test well at site 23 and from a depth of 35 feet.

INFORMATION CIRCULAR NO. 86

one clay sample was determined by a consolidation test. Because most of the
tests were made on undisturbed material in the collection tube, the data cited in
table 2 represent vertical permeability.

SPECIFIC YIELD

The specific yield of a material was defined by Meinzer (1923, p. 28) as
"the ratio of (1) the volume of water which, after being saturated, it will yield
by gravity to (2) its own volume". In applying laboratory results to field
problems specific yield is commonly taken as a measure of the capacity of a
water-table aquifer to store water.

The specific yields listed in table 2 were determined as the
centrifuge-moisture equivalent. This equivalent is the moisture content of a
sample after it has been saturated with water and then subjected for 1 hour to a
force 1,000 times that of gravity. Such specific yields represent extreme degrees
of dewatering and are higher than specific yields of the same materials under
field conditions.

Specific yields decrease with increasing silt and clay content. Average
specific yield for the sand sample is 34.6 percent for clayey sand, 28.9 percent;
and for sandy clay, 19.1 percent. The specific yields of 11 samples of laminated
sand and clay range from 22.4 to 37.4 percent. This variation reflects a wide
range in clay content and degree of sorting within this unit. Specific yields
determined for three samples of clay average 10.4 percent. The specific yield of
another clay sample is 53.6 percent. This sample is a black, organic fluid clay
found in solution openings in the upper part of the Floridan Aquifer.

CLAY MINERAL IDENTIFICATION

Ten samples of clay were submitted to the laboratory for identification.
The identifications, listed in table 3, show mixed-layered illite-montmorillonite,
with illite generally predominant.

LITHOLOGY

The lithologic descriptions of the samples in table 4 were made at the test
site. Observations were made of the properties that affect the hydrology of the
sediments particle size, shape, sorting, clay content, and stratification. Color
was also noted as an aid to interpretation of the environment of deposition; the
degree of weathering; the presence of organic matter; and other pertinent factors
significant to the geohydrology.

INFORMATION CIRCULAR NO. 86

one clay sample was determined by a consolidation test. Because most of the
tests were made on undisturbed material in the collection tube, the data cited in
table 2 represent vertical permeability.

SPECIFIC YIELD

The specific yield of a material was defined by Meinzer (1923, p. 28) as
"the ratio of (1) the volume of water which, after being saturated, it will yield
by gravity to (2) its own volume". In applying laboratory results to field
problems specific yield is commonly taken as a measure of the capacity of a
water-table aquifer to store water.

The specific yields listed in table 2 were determined as the
centrifuge-moisture equivalent. This equivalent is the moisture content of a
sample after it has been saturated with water and then subjected for 1 hour to a
force 1,000 times that of gravity. Such specific yields represent extreme degrees
of dewatering and are higher than specific yields of the same materials under
field conditions.

Specific yields decrease with increasing silt and clay content. Average
specific yield for the sand sample is 34.6 percent for clayey sand, 28.9 percent;
and for sandy clay, 19.1 percent. The specific yields of 11 samples of laminated
sand and clay range from 22.4 to 37.4 percent. This variation reflects a wide
range in clay content and degree of sorting within this unit. Specific yields
determined for three samples of clay average 10.4 percent. The specific yield of
another clay sample is 53.6 percent. This sample is a black, organic fluid clay
found in solution openings in the upper part of the Floridan Aquifer.

CLAY MINERAL IDENTIFICATION

Ten samples of clay were submitted to the laboratory for identification.
The identifications, listed in table 3, show mixed-layered illite-montmorillonite,
with illite generally predominant.

LITHOLOGY

The lithologic descriptions of the samples in table 4 were made at the test
site. Observations were made of the properties that affect the hydrology of the
sediments particle size, shape, sorting, clay content, and stratification. Color
was also noted as an aid to interpretation of the environment of deposition; the
degree of weathering; the presence of organic matter; and other pertinent factors
significant to the geohydrology.

BUREAU OF GEOLOGY

NATURAL GAMMA LOGS

Natural gamma logs are useful in hydrologic studies as an aid in
determining the type of materials penetrated by cased wells. The interpretation
of gamma logs is qualitative because the instrument used for logging gamma
radiation was not calibrated to a standard radiation source. Methods and results
obtained in a given geohydrologic environment may not be applicable beyond
that environment. -The trace of gamma radiation obtained from logging of each
test hole is shown in table 4. Extensive use of gamma logs was made in this study
to extend interpretations of the geohydrologic properties of the surficial
deposits obtained from studies of the samples.

All the logs were made with the probe traveling up the casing at 20 feet
per minute. Pulse-averaging time was 8 seconds and full-scale deflection 100
counts per time constant. Thus, qualitative interpretation and correlation
between each well logged was possible.

The natural radioactivity of material such as quartz sand and pure
limestone is negligible. Most clay minerals are moderately radioactive. Thus, an
increase in radioactivity may indicate an increase in the clay content of the
material. This relationship is significant in a hydrologic study where the
permeability of an aquifer may be controlled by clay content.

On the basis of samples collected at 5-foot intervals, the upper 15 to 20
feet of material in each well drilled was logged as sand or clayey sand. Minor
fluctuations in the gamma traces indicate that in many of the test wells the
material logged may have laminae of clayey material not noted in the samples.

The lithologic log for the test hole at site 35 is one of the more detailed in
this report. The well was sampled continuously from land surface to limestone,
and the gamma log agrees very closely with the lithologic log. This gamma log
illustrates their usefulness in refining the lithologic logs for those wells sampled
at 5-foot intervals. Where the gamma log was used to pick the boundary between
units, the midpoint on the curve between minimum and maximum was taken as
the contact.

Gamma radiation of the dense clay immediately overlying the limestone is
very high. This clay is probably a weathering product of the underlying
limestone and the very high gamma radiation may be due to enrichment of the
clay with a concentration of secondary phosphate and uranium-rich minerals as
described by Carr and Alverson (1959, p. 54, 67).

INFORMATION CIRCULAR NO. 86

Phosphate and uranium analyses were not made during the current
investigation but sample 37-36 (table 3) contains 2-3 percent of potash feldspar.
Potassium-40 is a common source of high gamma radiation in feldspars and in
clays formed by their decomposition.

At site 40, a thick section of peat and organically-rich clay was penetrated,
and at site 21 about 20 feet of dense clay was countered. The gamma logs for
both sites show that neither the peat nor the clays have appreciable
radioactivity. No explanation is apparent for these anomalous logs but they
indicate that the gamma log alone is not always a reliable indicator of lithology.

GEOHYDROLOGY

Laboratory analyses and field observations were used to determine the
hydrologic characteristics of the material underlying the area of investigation.
The material is divided into four major geohydrologic units: (1) limestone; (2)
clay; (3) sand and clay; and (4) sand. The geohydrologic units are listed in table
4.

LIMESTONE

The Tampa Limestone is the consolidated bedrock immediately underlying
the surficial deposits throughout the area studied, and is the upper unit of the
Floridan Aquifer. The limestone is gray or light tan to white, usually sandy,
fossiliferous in places and commonly contains clay lenses and cavities. The
limestone is dense and hard; especially where sandy, but may be soft at places
where badly weathered. Commonly, the upper surface of the limestone is case
hardened by impregnation with silicon dioxide.

Cavities in the upper few feet of the limestone were penetrated by the
auger at several sites. These cavities were commonly filled with a black clay. The
black color indicates an organic origin; a sapropel, or gyttja, which may have
flowed into the cavernous limestone through connection with swampy sinkholes.
This clay is extremely soft and fluid as though it were not part of the aquifer
structure. Sample 23-40 (table 2); which seems typical of this clay, had a specific
yield- of 53.6 percent, suggesting that it may have been intruded into its present
position under artesian pressure.

Permeameter tests, made on two samples of limestone indicated
coefficients of permeability of 0.1 and 15 gpd per ft2. The actual range in
permeability of the limestone is much greater because of variations in lithology,
the degree of weathering, and because most movement of water through
limestone is principally along enlarged bedding planes and joints. Tests of wells

BUREAU OF GEOLOGY

in the Tampa Limestone indicate that the coefficient of permeability of the
limestone in the test area is about 1,000 gpd per ft2.

CLAY

A dense, plastic clay overlies the Tampa Limestone throughout the area
and is often interbedded with thin layers of limestone in the upper part of the
Floridan Aquifer. The clay is generally green or greenish-gray, is streaked or
mottled with gray and black, and contains sand. The sand fraction in the 6
samples analyzed averaged 44 percent, and ranged from 22 percent to 64
percent.

The clay may be calcareous in places, particularly near the limestone
contact. Clay, as described above, was penetrated in 47 of the 59 test holes.
Where present, it is as much as 20 feet thick and averages about 4 feet.

The laboratory analyses of the clay minerals are similar to those obtained
by Cart and Alverson (1959, p. 32) for clay minerals in west-central Florida.
Carr and Alverson also show (1959, p. 52-53, fig. 14) with sand-clay ratios of the
clay and unweathered limestone that the clay is a residuum of the underlying
Tampa Limestone. They postulate 5 to 10 feet of original limestone for each
foot of residual clay.

Other evidence that indicates the clay is a weathered residuum of the
Tampa Limestone is (1) the presence of distorted and crenulated bedding planes
in the clay resulting from slumping and collapse of underlying material; (2) the
occurrence of fresh chert; and (3) the clay's high gamma radiation.

Carr and Alverson (1959) attribute the high gamma radiation to
uranium-rich minerals concentrated by dissolution of the Tampa Limestone and
possibly by leaching of these minerals from the younger Hawthorn and Bone
Valley Formations. Although the Hawthorn and Bone Valley Formations were
not identified in the test drilling, they probably once overlay the Tampa
Limestone in this area as they do the Tampa Limestone in much of west-central
Florida.

Samples collected at any depth expand somewhat when the overburden
load is removed. The result is that the porosity and permeability, as determined
in the laboratory, generally seem to be higher than expected for the material in
place. This is particularly true of samples of plastic clay. Consolidation tests,
although time consuming and expensive, yield values of permeability which more
closely represent natural conditions because this test permits adjustment for the
overburden load. Clay sample 17-65, selected as typical by comparing several

INFORMATION CIRCULAR NO. 86

differential thermal analyses, was subjected to a consolidation test and the
coefficient of vertical permeability, adjusted for an overburden load of 60 psi
(pounds per square inch), was about 0.001 gpd per ft2.

Permeability will vary within the clay because of differences in the sand
content, the degree of compaction and the structure as well as many other
factors. However, these variations are minor. Therefore, the coefficient of
permeability obtained from the consolidation test, 0.001 gpd per ft2, is
considered representative of the vertical permeability of the clay layer in the
area.

SAND AND CLAY

A sequence of sand and clay layers lies unconformably on the eroded
surface of the weathered clay residuum or the limestone where the clay is
absent. The mottles and crenulations which are common in the dense clay are
absent in the laminated sand and clay. Stratification in this unit is apparently
undisturbed, indicating that deposition occurred after that period of weathering
of the Tampa Limestone represented by the dense clay.

The hydrologic characteristics of this unit vary greatly with the clay
content of the material and with the degree of stratification. Vertical and lateral
changes in composition are abrupt within the section.

Material comprising the sand and clay unit has been subdivided, for better
definition of hydrologic properties, into three geohydrologic subunits: sandy
clay, clayey sand, and sand and clay laminae.

SANDY CLAY

The term sandy clay is used to define material in which clay fills the
interstices between sand grains. The proportion of clay is not high enough to
give the material a plastic cohesiveness characteristic of the underlying residual
clay. In four samples of this unit tested by the laboratory, the silt-clay fraction
ranged from 24.3 to 42.9 percent. The coefficients of vertical permeability of
these samples ranged from 0.0013 to 0.16 gpd per ft2. For this study, a value of
0.01 gpd per ft2 was taken as a reasonable average coefficient of vertical
permeability of the material logged as sandy clay.

CLAYEY SAND

Clayey sand is the term used to describe that part of the laminated
sequence which is chiefly sand but contains sufficient clay to have a significant

BUREAU OF GEOLOGY

effect on its permeability. The clay appears to be evenly dispersed throughout
the material. Silt and clay content of 10 samples of the clayey sand ranged from
8.2 to 25.4 percent and averaged 14.6 percent. The coefficient of vertical
permeability of 6 samples whose clay content ranged from 12.2 to 20.0 percent
ranged from 0.021 to 9.8 gpd per ft2. A value of 1 gpd per ft2 is a reasonable
average for the clayey sand throughout the area.

SAND AND CLAY LAMINAE

The term sand and clay laminae is used to define material that is
predominantly sand or clayey sand but is banded with distinct layers of sandy
clay or clay. Individual layers of clay are as much as 1 centimeter thick. The silt
and clay content of the six samples for which the coefficient of vertical
permeability was also determined ranged from 10.7 to 19.4 percent. The vertical
coefficient of permeability of these samples ranged from 0.0069 to 0.49 gpd per
ft2, and 0.01 gpd per ft2 is a reasonable average.

The silt and clay content of the sand and clay laminae at site 60 is
somewhat less than at other sites and ranges from 7.0 to 9.1 percent.
Coefficients of horizontal permeability of the samples from site 60 ranged from
8.3 to 29 gpd per ft2; with one anomalous value of 120 gpd per ft2. Even
excluding the anomalous value, the average for the horizontal permeabilities is
more than 16 times greater than that of the average vertical permeability of the
other sand and clay subunits.

The low vertical permeability of the subunit is caused by stratification.
Although silt and clay comprise a small fraction of the total sample, their
concentration in horizontal layers greatly retards vertical movement of water
through the unit. The thin layers of dense clay have more effect on the vertical
permeability than would a larger amount of clay evenly dispersed through the
sand.

SAND

The uppermost deposit underlying the study area is a clean well-sorted,
fine to very fine quartz sand. The sand has no apparent bedding and is
noncohesive except for a zone of cementation which occurs at places near the
surface. The sand ranges from 0 to 35 feet in thickness and averages about 16
feet. It is absent at only one site. The sand is commonly white to light tan or
buff colored near the surface where it often contains a mixture of organic matter
and silt.

INFORMATION CIRCULAR NO. 86

The clay content of the massive sand unit seems to increase gradually with
depth. This clay may have been reworked by wave action on the underlying
laminated sand and clay unit thus obscuring the contact. It is also possible that
the sand may be a near-shore faces of the underlying unit.

The lithologic descriptions of the sand in table 4 were verified by
laboratory analyses. Particle-size analyses of 19 samples show that the silt and
clay fraction ranges from 0.2 to 6.8 percent. All the samples are within the fine
sand classification of Wentworth (median diameter 0.125 to 0.25 mm). The
average of the median grain size for all samples was 0.17 mm. The coefficient of
vertical permeability of five samples ranged from 2.7 where the silt clay content
was 4.7 percent to 98 gpd per ft2 where the silt clay content was 0.9 percent.
An aquifer test made in the surficial aquifer indicates that the horizontal
coefficient of permeability of this sand is about 100 gpd/ft2. That value is
considered a reasonable average for the unit.

HYDROLOGIC SYSTEM

In northwest Hillsborough County surficial sand of relatively high
permeability and large storage capacity is underlain by layers of sand and clay of
less permeability and storage capacity. Underlying these units is a relatively
impermeable clay which overlies the permeable limestone of the Floridan
Aquifer and is the most important factor in retarding the downward movement
of water from the surficial aquifer to the Floridan Aquifer.

A common method of calculating the composite coefficient of vertical
permeability of a section is by the equation (modified from DeWiest, 1965, p.
231):

Pv = M
ml/Pi + m2/P2 + - mn/Pn

where Pv is the composite coefficient of vertical permeability for all
confining layers,
M is the total thickness of all confining layers,
m is the thickness of each confining layer,
p is the coefficient of permeability of the confining layers as
described in the preceding sections.

For example, well 23 in table 4 is shown to penetrate 4 feet of clay, 8 feet
of sandy clay, 16 feet of sand and clay laminae, and 11 feet of sand. The clay
and sandy clay are considered to be confining layers because of their low
coefficients of permeability; 0.001 and 0.01 gpd per ft2. Although the vertical

BUREAU OF GEOLOGY

permeability of the sand and clay laminae is also low, this subunit is considered a
part of the aquifer along with the 11 feet of sand, because of the high horizontal
permeability. Substituting the values from the log of well 23 into the equation: :

Pv = 4+8
4/0.001 + 8/0.01

= 12
4800

= 0.0025 gpd per ft2

The clay, with a coefficient of permeability of 0.001 gpd per ft2, is the
dominant factor in the equation controlling the composite vertical permeability
of the surficial deposits.

The values of composite coefficients of vertical permeability divided by
the confining layer thickness are listed in table I where they are called leakage
factors. These range from 0.3 x 10-4 to 33.0 x 10-4 and average 4.9 x 10-4
gpd/ft3.

Estimates of leakage from the surficial aquifer through the confining bed
to the Floridan Aquifer may be made by multiplying the leakage factor by the
difference in head in the two aquifers. For example: assuming a head difference
of 10 feet and using the average factor given above, than 10 ft x .00049 gpd/ft3
= .0049 gpd/ft2. Leakage over I square mile, under these conditions would be
about 140,000 gallons per day.

Inter-aquifer leakage is commonly estimated from aquifer test data. Cherry
and others (1970, p. 60) report a leakage factor of 1.5 x 10-3 on the basis of a
long-term aquifer test on a well in the Section 21 well field. This leakage factor
is an order of magnitude larger than 4.9 x 10-4 the average of the values
calculated from the well logs throughout the area. Data collected from the test
drilling are biased by the location of the test sites (relatively few were drilled in
sinkholes, swamps, and lake bottoms) just as aquifer-test data are biased by the
location of the pumped well. In the absence of an infinite number of test sites or
aquifer tests, the true value of regional leakage can only be approached by
judicious interpretation of the available data.

Variations in the composite vertical permeability are large within short
distances because of the variations in the thickness of the dense clay layer.
Variations in clay thickness may result from local variations in the rate of
dissolution of the underlying limestone which, in turn, may be due to local

INFORMATION CIRCULAR NO. 86

variations in limestone lithology. Variations in the topography of the limestone
surface just before the onset of karst erosion represented by the'clay may also
affect the thickness of the clay layer. The clay may have been subject to
subaerial erosion prior to the deposition of the sand and clay unit and to
removal by subsidence into active sinkholes.

Study of the logs in table 4 indicates that at least three generations of
sinkholes exist; relict, established, and incipient. Sinkholes apparently developed
in the surface of the Tampa Limestone before deposition of the sand and clay
unit. Sites 17 and 44, for example, are flatwood areas with no surface indication
of sinkhole development. The logs of the wells drilled at sites 17 and 44 (table 4)
indicate a swampy environment at depth. These deposits are overlain by the sand
and clay and the sand. The limestone surface in these wells was found 35 and 20
feet lower than the limestone surface encountered at the nearest adjacent test
sites. The sinkholes penetrated by these wells are relict.

Well 40 was drilled within a circular marsh an established sinkhole of
at least 50-years duration, judging from the size of the cypress trees. Well 40
penetrated more than 60 feet of black clay and peat and had not reached
limestone at 107 feet below land surface. Nearby wells penetrate limestone at 45
feet on the average.

The appearance of incipient sinkholes, some only a few feet in diameter,
attest to the stopping of surficial sediments into newly developing solution
cavities in the limestone. Many of the incipient sinks have developed surface
expression since the beginning of this study in 1968.

Although natural recharge occurs more rapidly through perforations in the
confining layer than where the clay is intact, sinkholes occupy a small
percentage of the total area and leakage through the clay confining layer,
although slower, probably constitutes the major part of natural recharge to the
Floridan Aquifer in the area. '

Variations in thickness of clay.and in depth to the limestone surface are so
great over such short distances that very close spacing of test holes would be
necessary to delineate any pattern. No relations were discovered among surface
terrain, vegetation or soil type and the types of materials penetrated in test wells
which might aid in predicting the nature of these materials from surface
expressions in places where there are no test wells. Circular depressions, swamps,
and lakes are presumed to represent sinkholes which perforate the clay layer and
permit hydraulic connection between the aquifers. Many of these features may
be underlain by plugged sinkholes and, conversely, active sinks may exist that
have not yet developed any surface expression.

BUREAU OF GEOLOGY

The contours on the potentiometric surfaces of the surficial aquifer and
the upper part of the Floridan Aquifer (fig. 1) show the difference in water level
between the two. The potentiometric surface of the surficial aquifer is rarely
more than 10 feet below land surface and is commonly less than 5 feet.
Contours on the potentiometric surface of the surficial aquifer generally reflect
the configuration of the land topography. The contours slope gently from an
altitude of about 60 feet in the northeastern part of the area southwestward
toward Tampa Bay and the gulf.

The potentiometric surface in the upper part of the Floridan Aquifer in
this area stands 5 to 10 feet lower than that of the surficial aquifer (the water
table) under natural conditions. The artesian head is a function of the altitude of
the water table, the resistance to vertical movement of water from the surficial
aquifer through the confining layer to the Floridan Aquifer, and the resistance
to horizontal movement of water through the Floridan Aquifer.

Near the Section 21 well field where data are sufficient to define both
potentiometric surfaces in detail, a depression in the water table overlies the
cone of depression in the Floridan Aquifer. The latter depression is due to
pumpage from the Floridan Aquifer and the former to leakage induced by the
increased head difference between the two aquifers.

The minor depression in the water table southeast of the well field may be
due to the absence of the confining layer in this area and a consequent high rate
of leakage to the Floridan Aquifer. The logs of test wells in this area show that
the limestone is at a shallow depth and is overlain directly by the surficial
aquifer.

Just east of the well field, Lakes Charles, Saddleback, and Round are
artificially maintained at stages between 50 and 55 feet by pumpage from the
Floridan Aquifer. Seepage from the lakes maintains the potentiometric surface
of the surficial aquifer at a relatively high level in this area even though
considerable leakage to the Floridan Aquifer is also taking place. The effects of
this leakage on the potentiometric surface of the Floridan Aquifer are not
obvious because of the relatively high permeability of the limestone.

SUMMARY

Northwest Hillsborough County is underlain by a surficial sand
(water-table) aquifer that has a large capacity to store water. The sand becomes
less permeable with depth and grades downward through a sequence of sand and
clay layers. Although the sand and clay is an important part of the surficial
aquifer, the vertical permeability of the lower unit is low because of the

INFORMATION CIRCULAR NO. 86 17

horizontal laminae of clayey sand and sandy clay. A dense, plastic clay underlies
the sand and clay unit throughout most of the area. The clay, a weathering
product of the underlying limestone, forms a confining layer because of its
extremely low permeability and is the most important factor in retarding the
downward movement of water from the surficial to the Floridan Aquifer.

Lithologic logs based on auger samples taken at 5-foot intervals in
combination with natural-gamma logs adequately defined the components of the
surficial aquifer system and the confining bed.

Laboratory tests of the size, sorting, permeability and storage capacity of
samples of sediments of the surficial aquifer and confining bed were useful in
estimating field values for the various geohydrologic units. The values of vertical
coefficient of permeability thus calculated vary widely but are useful in making
regional estimates of infiltration capacity or in calculating the rate of recharge to
the Floridan Aquifer from the overlying surficial aquifer.

18 BUREAU OF GEOLOGY

INFORMATION CIRCULAR NO. 86 19

REFERENCES CITED

Carr, W.J., and Alverson, D.C.,
1959 Stratigraphy of middle Tertiary rocks in part of west-central Florida: U. S.
GeoL Survey Bull. 1092, 111 p.

DeWiest, R. J. M.
1965 Geohydrology; New York, John Wiley and Sons, Inc., 366 p.

Krumbein, W. C., and Pettijohn, F. J.
1938 Manual of sedimentary petrography: New York, Appleton-Century-Crofts,
Inc. 549 p.

Lohman, S. W., and others
1972 Definitions of selected ground-water terms revisions and conceptual
refinements: U. S. Geol. Survey Water-Supply Paper 1988, 21 p.

Meinzer, 0. E.
1923 Outline of ground-water hydrology, with definitions: U. S. Geol. Survey
Water-Supply Paper 494, 71 p.

Stewart, J. W.
1968 Hydrologic effects of pumping from the Floridan Aquifer in northwest
Hillsborough, Northeast Pinellas, and southwest Pasco Counties, Florida: U. S.
Geol. Survey open-file rept., 241 p.

Trask, P. D.
1932 Origin and environment of source sediments of petroleum: Houston, Tex.,
Gulf Publishing Co. 323 p.

Twenhofel, W. H. and Tyler, S. A.
1941 Methods of study of sediments: New York, McGraw-Hill Book Co., 183 p.

Wentworth, C. K.
1922 A scale of grade and class terms for elastic sediments: Jour. Geology, v. 30,
377-392.

U. S. Department of Agriculture
1958 Soil Survey, Hillsborough County, Florida: U. S. Dept. Agriculture Report,
Series 1950, no. 3, 68 p.

20 BUREAU OF GEOLOGY

table 1. Relationship of soil, terrain, geology and hydrology at 59 test sites
(gpd per ft-3: gallons per day per square foot per foot)

Altitude (feet), Clay
Land Top ofz- thickness
surface limestone (feet) .

Leakage
factor 5 .
gpd per ft xlO"

Altitude of
p6tentiometric
surface
(feet)
Floridan Surficial
Aquifer aquifer

Leon
Blanton
Leon
Blanton
Leon

6
7
8
9
10

Leon
Leon
Ona
Ona
Leon

Leon
Leon
Leon
Leon
Ona

Leon
Leon
Ona
Leon
Leon

16
17
T78
19
20

,Test sites shown
Negative numeral

flat, lakeshore
upland, interlake
flat, interlake
slope, lakeshore
extensive flatland

flat,
flat,
flat,
flat,
flat,

interlake
interlake
interlake
interlake
interlake

low drainageway
flat, interlake
flat, interlake
flat, interlake
flat, interlake

extensive flatland
extensive flatland
extensive flatland
flat, interlake
flat, interlake

on figure 1.

is distance in feet below sea level.

Test,
site
number-

Terrain

Soil
type

Date
of
measurement

14
0
2
5
4.5

44.4
47.9
47.7
48.3
64.4

50.6
52.5
51.4
50.1
56.1

57
56.3
58.3
57.7
54.5

60
61.3
58.6
56.9
56.9

-19
-20
-19
- 2
29

- 4
- 1
6
-10
- 6

17
5
8
- 2
9

19
-19
16
5
19

0.7
33.
2.9
2.0
2.2

10.0
1.3
3.3
0.9
1.4

5.0
1.7
1.7
1.2
1.5

5.0
0.3
11.0
1.4
3.3

33.32
40.40
27.14

59.36

35.46

35.53
37.73

49.5
34.4
52.02
31.66
36.87

50.7
52.06
49.78
27.43
28.76

41.39

39.58
35.10
59.99

49.23
44.21
49.95
47.30
51.33

54.0
..--
53.00
52.91
51.4

55.7
58.60
56.75

50.74
50.74

12-12-71

11-05-71

05-18-71

11-05-69
05-18-71
11-05-69
11-05-69
05-18-71

05-16-70
05-16-70
05-27-71
05-16-70
05-16-70

05-16-70
05-18-71
09-05-69
05-16-70
05-16-70

Table 1, Relationship of soil, terrain, geology and hydrology at 59 test astes (cont.
(gpd per rt gallons per day per square foot per toot)

Altitude Ltet) Clay
Land Top of- thickness
surface limestone (feet)

leakage
fact 10
gpd per ft xlO"0

'Altitude of
potentiometric
surface
(feet)
Floridan Surficial
Aquifer aquifer

DaCe
of
measurement

One
Leon
Leon
Leon
Rutledge

Ona
Ona
One
Leon
Ona

Lake
bottom
Ona
One
Ona
Ona

extensive flatland
flat, interlake
flat, interlake
flat, interlake
flat, lakeshore

flat,
flat,
flat,
flat,
flat,

incipient
incipient
incipient
incipient
incipient

a inks
sinks
sinks
sinks
sinks

shallow between
deeps
flat, interlake
flat, interlake
flat, interlake
flat, interlake

36 Swamp sinkhole swamp
37 Ona flat, interlake
J8 Ona flat, interlake
39 Ona flat, interlake
40 Swamp sinkhole marsh

53 3 20
56.4 11 5
55.2 14 4
56.2 14 2
53.0 8 3

56.1 8
56.3 8
58.3 19
59.0 20
59.4 7

50.4 3

56.0 16
56.0 20
56.0 6
55.1 13

52.5
56
55.1
55.8
53.1

10

-10
13
below
-54

4.5
7+
17
0

0.5
2.0
2.1
5.0
3.3

0.7
2.5
10.0
3.3
10.0

43.28
20.16
27.99
28.96
38.59

33.09
33.62
43.90
47.99
29.23

50.62
50.28
49.62
48.54

46.94
47.26
48.30
51.17
50.25

05-27-71
05-16-70
05-16-70
05-16-70
05-16-70

05-16-70
05-16-70
05-16-70
05-16-70
05-16-70
05-16-70

25.87 44.18 05-27-71

1.8
1.4
0.5
13
-

21
22
23
24
25

26
27
28
29
30

31

32
33
34
35

45.23
44.92
44.58
43.97

43.63
-ft."
44.21
44.37
44.24

05-16-70
05-16-70
05-16-70
05-16-70

05-16-70
--- f
05-16-70
05-16-70
05-16-70

Teot

number

'Soil
type

Terrain

25.58
25.39
25.19
26.00

26.02

25.60
25.49
,---

_____

Table 1. Relationship of soil, terrain, geology and hydrology at 59 test sites (cont.)
(gpd per ft3: gallons per day per square foot per foot)

Altitude (feet)E. Clay Leakage
Land Top of- thickness factor
surface limestone (feet) gpd per ft xlO"4

Altitude of
potentiometric
surface
(feet)
Floridan Surficial
Aquifer aquifer

Leon flat, incipient
sinks
Blanton upland, interlake
Ona extensive flatland
Leon flat, interlake
Leon flat, interlake

Blanton
Leon
Leon
Leon

Leon
Leon
Leon
Leon
Blanton

Leon
Leon
Blanton
Leon

upland, interlake
flat, interlake
extensive flatland
extensive flatland
flat, lakeshore

flat, interlake
extensive flatland
flat, interlake
flat, interlake
flat, interlake

flat, interlake
flat, interlake
upland, interlake
flat, interlake

59.0 15

51.9 30
60 -15
59.8 9
57.1 9

58.5
55.8
60
60.7
68.0

64.4
66.8
64.5
66.0
61.8

59.3
55.6
56
56

14.0

20
1.5
1.2
2.5

2.5
1.1
10
2.3
1.4

2.0
2.8
4.0
3.3
3.3

1.4
2.5
33.0
20.0

27
15.:
25
18
13

9
20
22
16
22

14
25
11
21

29.14 47.53 05-16-70

47.84
41.1
34.90
24.23

29.88
13.30
53.4
52.19
60.60

52.25
55.00
52.21
51.15
52.25

47.46
46.72
40.2
47.4

47.89
57.6

48.87

43.72
46.74
52.4
58.26
63.18

60.55
61.73
61.26
61.31
57.25

51.78
47.97
49.5
50.5

05-16-70
05-16-70
05-16-70
05-16-70

05-27-70
05-16-70
05-16-70
11-04-69
05-16-70

05-27-70
05-18-71
05-16-70
05-16-70
05-16-70

05-16-70
05-16-70
05-16-70
05-16-70

Test
site
number

Soil
type

Terrain

41

42
43
44
45

Date
of
measurement

w

Table 2, Resauts of laboratory analyses of 66 samples of sedilmntary depogstt
from test well at 24 sites

Hydraulic conductivity ft day" cubic feet per day per square foot.
of permeability gpd/ft gallons per day per square foot.

Coefficient

Sample depth!
(ft)

Hydraulic
Lithology conductivity
(ft day" )

Specific yield
(percent)

5
5
5
5
4.5

55.5
5
29.5
5
20
40
5
30
40
65
74.5
5

23

(See footnotes

10
15
20
25
30
35
40
44.5
at end

Sand
do
do
do
Clayey sand

Clay
Sandy clay
do
Sand
Clayey sand
Clay
Sand
Sandy clay
Sand & clay
Clay
do
Sand

Sand
Clayey sand
do
Sand and clay
do
Sand
Clay
Limestone
of table.)

Test
sinumber
number

0.36

,Median
diameter
(m)

porting
coefficient

2.7

.0015

.0030

.032
.0067
.0015
.0037

8.2
.042
.29
.029
.097
4.9

.097

.0002
-u

.0004

.0043
.0009
.0002
.0005

1.1
.0056
.0394
.0039
.0013
.66

.013

- m
35.7
36.5
40.7

16.4
30.3
11.8
36.0
--i

31.8
21.8

35.6

33.7

21.9
22.4

53.6
m--

0.19
.19
.18
.18
.18

:"I;
.16
.13
.16
.12
.11
.15
.15
.09
.074
.045
.17
m--
0.13
.17
.098
.20
.19
---
m--

---
1.4
3.6
1.3
1.4
8.9
1.2
5.4
1.4
13.
9.6
1.3

Table 2. Results of laboratory analyses of 66 samples of sedimentary deposits
from test wells at 24 sites (cont'd.)

Hydraulic conductivity: ft day'l, cubic
gallons per day per square foot

Sample depth
(ft)

Hydraulic
Lithology conductivity
(ft day"1)

.0003
.0016

Clay
do

feet per day per

Permeabi ity
(gpd/ft )

square foot. Permeability: gpd/ft2

Specific yield
(percent)

.0024
.012

Sand
do
Clayey sand
Sand and clay
Sandy clay
Clayey sand
Sand and clay
Clay

.021
---,

...

Clayey sand 0.11
Sand and clay ---
do ---
do ---
Clayey sand 1.3
Sandy clay .0098

Sand 13
do 1.7
Clayey sand .46
Sand and clay .066
do .052
Clayey sand .0028

Test
site
number

Median
diameter
(Nm)

Sorting
coefficient

.088
.002

5
10
15
25
29.5
35
40
44.5
b10.6
b18.4
b20
b24.5
b30
33.3

5
10
15
20
25
30

---

.16

0.82

9.8
.073

98
12
3.4
.49
.39
.021

27.1
40.3
41.7
37.4
22.9
36.4

6.1

27.3
35.4
34.1
35.9
15.4
19.8

37.6
33.6

20.2

.22
.19
.17
.21
.095
0.088
.22
.023

.13
.17
.15
.092
.092
.18

.15
.14
.110
.13
.14
.13

1.2
1.1
1.4
1.4
2.8
1.3
1.4
7.9

1.4
1.4
1.4
1.2
1.2
2.0

1.3
1.2
1.5
1.4
1.4
1.4

__

Table 2, Results of laboratory analyses of 66 samples of sedimentary deposits
from test wells at 24 .ttes (cont'i,)

Hydraulic conductivity: ft day" cubic feet per day
gallons per day per square foot

Sample depth

Hydraulic
Lithology conductivity
(ft day"1)

Permeability
(8pd/ft2)

per square foot,

Specific yield
(percent)

Permeability; gpd/ft2

Median
diameter
(mm)

Sorting
coefficient

Clayey sand ---
Sand --.
Clay 0.0028
Limestone 2.1
Sand and clay ---

Clay .0007
Sand ---
Sand and clay .0052

Sand ---
do
do
do
do --

Sand
do
do
do
do
do

and clay 1.1
2.3
16.
2.1
1.6
3.9

..i

0.021
16

.0052

.039

8.2
17
120
16
12
29

25.8
28.6

8.7
30.2

35.4
35.6
38.8
36.1

26.2
27.4
26.0
26.7
26.8
28.4

0.18
.17
.12

.094

.15
.17

1.4
1.3
14

1.4

1.2
1.4

.16 1.3

0.13
.14
.16
.13
.14
.13

aSample depth is feet below land surface to top of 6-inch sample.
Vertical samples in slotted tube for determination of horizontal permeability.
cHorizontal samples in plain tube for comparison with vertical samples in slotted tube.
Site 60 is not an auger hole. Samples are from the bottom of an excavation about 10 feet
below land surface.

Test
itber
number

35.5
40
45
47.5
20

d60-1
60-2
60-3
60-4
60-5
60-6

bo
b0
c .25
b 0
c 25
b :5

INFORMATION CIRCULAR NO. 86 27

Table 3. Clay-mineral identification for selected samples

Sample depth
Test site (feet) Description
Differential Thermal Analysis
5 35 Illite. Mixed-layered clay (illite and
montmorillonite) small amount; quartz,
small amount; organic material, small
amount; CaCO3, none.

17 65 Illite, Mixed-layer clay (illite and
montmorillonite) small amount; quartz,
large amount; organic material, moderate
amount; CaCO3 none.

23 40 Illite, small amount; organic material,
large amount; CaCO3, very large amount,
75 percent.

26 38 Mainly mixed-layered clays, composed of
illite and montmorillonite. Illite
predominant.

26 45 Mainly mixed-layered clays composed
of illite and montmorillonite. Illite
predominant.

31 44.5 Illite. Mixed-layered clay (illite and
montmorillonite), small amount; quartz,
small amount; organic material, small
amount; CaCO3, none.

50 20 Illite. Quartz, small amount; organic,
large amount;CQaC03, none.

50 54 Illite. Mixed-layered clay (illite and
montmorillonite), small amount; quartz,
fair amount; organic material, fair
amount; CaCO3, none.

28 BUREAU OF GEOLOGY

Table 3. Clay-mineral identification of selected samples (cont.)

Sample depth
Test site (feet) Description

X-ray Diffraction

37 36 Sample contains about 35 percent quartz,
2-3 percent feldspar, and the remainder
clay minerals. The clay mineral is mont-
morillonite with a small amount of illite
mixed layering. The basal spacing is
indicative of Ca-montmorillonite.

46 30 Sample contains about 30 percent quartz
and the remainder clay minerals. Clay
minerals consist primarily of a random-
mixed-layer illite-montmorillonite in
which the montmorillonite layers are the
most abundant. The peaks are poorly de-
fined, but d spacings greater than 15
indicate the presence of some regular
mixed layering. On heating to 3000C,
the clay mineral collapses to 10.4,
which indicates some interlayering.

INFORMATION CIRCULAR NO. 86

TABLE 4
Logs showing lithology, gamma radiation, and generalized
geohydrology of surficial deposits at sites tested
in northwest Hillsborough County

Increased radiation

Geohydrol9gic
unitE

Thickness
(feet)

eIsd

- 5 nd, fine-grained, sub-rounded to sub-angular. Sand
-0 and, as above, but slightly clayey, dark brown Sand 18
-15 and, as above. Sand
-20 d, as above, but with layers of dark clayey Sand and clay 4
sand
- Sand, rare coarse grains of white material, and Clayey sand 27
.30 clay balls.
Sand, as above.

Sand, runny.

14

Limestone, white, sandy. Traces of green and black Limestone at 63 ft.
clay on auger.

Site 1

Sample
depth
(feet)

&2 o
"A

Snoa

& 5'
^*5

c33

0*S
ss 0'
0 5
I3
0e?

-65

Site 2
Sample
fela

-5 a/Sand, very fine-grained, well rounded clear
quartz.
10 Sand, as above but slightly silty with black
rootlets.
Sand, as at 5 ft.
1 Sand, as above but with broken layers of dense
-20 black-brown clay.
25 Sand, with layers of clay, as above.
-30 Sand, as at 5 ft but runny; clayey.
-35 Sand, as above

45 Sand, very fine to medium-grained, with brown
clay.

r55
-60
-65
-68

Sand, light brown, clayey.
Sand and clay layers, light brown.
Clay, sandy, with limestone chips.
Limestone.

Geohydrologic
unit

Thickness
(feet)

Sand

Sand and clay

Clayey sand

Sand and clay 5
Sandy clay 3
Limestone at 68 ft.

Increased radiation
ON--k

as above but with streaks of 1
massive, runny.

a aove. Slightly more clay.

Sand, clayey as above.
Sand and clay and shell
Clay, light green, sandy. -4:
Sand, slightly clayey, with clay
Clay, light green, sandy.
Clay, li ht lers of
Limestoe, gray, sandy, hard.

Geohydrologic
unit

Thickness
(feet)

Clear Sand 15
content.

eight Clayey sand 15

Sand 5

Clayey sand 5

Limestone at 67 ft.

Site 3
Sample
depth
(feet)

Sand,
tan
Sand,

Sand,

Geohydrologic
unit

Sand, very fine-grained, well-rounded clear quartz.
Slightly clayey.
Sand, as above, but black from organic material.
Sand, as at 5 ft. but dark brown.
Sand, as above, but with streaks of clay.
Sand, brown, clayey.
Sand, brown, clayey.
Sand, as above, with clay streaks and chips of charcoal
to 5 mm.
Sand and clay, light brown with streaks of black clay.
Clay and sandy clay laminae. Dark brown with pieces of
white chalky chert.
Clay, green, plastic. Weathered limestone at 50 ft.
Limestone.

Sand

Sand and clay

Clayey sand

Sand and clay
Clay
Limestone at 50

Site 4
Sample
depth
(feet)

Thickness
(feet)

- Isd
- 5
- 10
- 15
- 20
- 25
. 30
- 35
- 40
- 45
- 48
" 50
- 54

"*4
0

0

5
ft.

Ge
Increased radiation

Sand, very fine-grained, sub-angular clear quartz
9 with dark brown stain. Very slightly clayey.
and, as above but with black stain.
San s above.

Ls above but with more clay.
; _yey as above.

-'Limestone at 35.5'.
Limestone, white, sandy.

ohydrologic
unit

Sand

Clayey sand

Thickness
(feet)

20

11

Clay 4.5
Limestone at 35.5 ft.

Site 5
Sample
depth
(feet)

- 5

- 10
- 15
- 20
- 25
- 30
- 35
- 40

Site 6
Sample Geohydrologic Thickenss
depth Increased radiation unit (feet)
(feet)

.lasd ,
-5 a Sand, brown, fine-grained, slightly silty, organic.

-1 Sand, as above. Sand 20
-15 and, as above with rootlets. z
-20 nd, tan, clayey.
Clayey sand 12
-25 San ey as above.
-30 Sand, clayey s above.
-33 Sand, with clay stre Sand and clay 13
-38 Sand, as above with more clay. 0
-40 Sand and clay, as above. 0o
-45 Clay, sandy. Dark gray-black drusy chert. Sandy clay 10
-50 Clay, dark gray with yellow streaks, sandy.
-55, Limestone, sandy. Weathered light gray and Limestone at 55 ft.
cream. Fine drusy pyrite in small vugs.

Site 7
Sample Geohydrologic Thickness
depth Increased radiation unit (feet)
(feet)

- 8 nd, dark brown, very fine-grained, silty. Sand 15
-10 .and, as above but darker brown.
-15 Sand and clay laminae, light brown. o
-20 nd and clay, as above but more clay. Sand 16
-25 Sand and c ove. 0
-30 Sand and cla a above.
-32 Sandvry d. well rounded, clear Sand 4
J-3' Sand, as above.
-40 tnd and clay laminae, light gray. clay 10
-43 San i-114
:45 Sand and clay. C-y in d-e' W-plastic, black
C47 land asc, shades of green with streaks of
-53 white sand. Contortions in laminae may be due Clay 8
to collapse. m a
Limestone, white, with brown chert. Limestone at 53 ft.

Site 8
Sample Geohydrologic Thickness
depth Increased radiation unit (feet)
(feet ) Alb. M

lsd
5 /Sand, gray, very fine-grained, slightly clayey.
l -1 Sand, as above. Sand 17
Sand, tan, very fine-grained, clayey.
20 Sand, clayey.

grayish-brown, more clayey. Clayey sand 25
-30 clayey, as above.
-35 San lightly clayey, light tan. oc
-40 Sand, very j n
42 Clay, blue, plastic. 3
45 Limestone, hard, weathered, white with nodules
of gray. Limestone at 45 ft.

Increased radiation
-DO

Geohydrologic
unit

d
_ 5 Sand very fine-grained, rounded to sub-rou
clear quartz.
S1 Sand, light brown, fine-grained to silty, p
sorted, slightly clayey. Occasional dar!
grains.
. 20 Sand and clay, layers, clean white sand, br
clay.

- 30 Sand, c aye
- 35 Clay, sand ough, grayish brown.
- 40 San ite, fine-grained to silty. Poorly
sorte unded to sub-angular.

-59 Clay, black.
- 60 Limestof 1 e.

nded Sand
poorly
k

own

Clayey sand
Sandy clay

28

2
5

Sand

Sandy clay 10

Clay 10
Limestone tf_60 fn

Site 9
Sample
depth
(feet)

Thickness
(feet)

Site 10
Sample G
depth Increased radiation
(feet)

-lsd
_ 5 a very fine-grained, brown.
S10 Sa as above, dark brown
15 Sand, as ove.
- 17 Sand a y dark brown. Clay nodules and thin
-0 s of ense dark clay.
2 San cay, as above.
25 Sand, c light brown.
25 Clay, sand .
30 Sand, very fine. 'ned. Occasional clay balls.
35 Sand, very ine-grained, tan.

-40 Sand, clayey very runny.
-45 Sand, less clay, unn
-.50 Clay, variegated yellow-gray, sandy.

-55 Malay gray with stringers of green, plastic,
chips of limestone at base.
60 Clay, as above but with more coarse pieces of
-62 limestone.
Limestone, gray.

eohydrologic Thic
unit (fc

Sand ]

Sand and clay 1

Sandy clay
Sand and clay

Sand

Clayey sand
Sandy clay 1

Clay

Limestone at 62 ft.

cness
bet)

h-4
0

0
z

0

00
ON

Increased radiation
-IN-

Geohydrologic.
unit

]- d.cla ey, grayish-tan, tough, with rootlets
a s or marl.
Sand, very rained, rounded to sub-rounded,
some clay, lig tan, occasional dark grains.
Sand, as above but w lightly more clay, gray.
Sand, very fine-grained, sub. unded clear
auartz. Very slightly claye.
.Sand, as above but with more gray q .
-/Clay, light green, ough plastic.
Sand, light gray, very ine-grained, rounded to
sub-rounded, s8a y clayey.
Limestone, whi e, sandy, crumbly.

Sandy clay

Clayey sand

Sandy clay

Thickness
(feet)

8

Limestone at 40 ft.

Site 11
Sample
depth
(feet)

lsd
5
10
15
20
25
30
35
-40
-44

Site 12
Sample Geohydrologic Thickness
depth Increased radiation unit (feet)
(feet)

lsd
5 light gray, clayey. Clayey sand 6
S10T Sand, very fine-grained, rounded to sub-rounded, Sand 14 q
clear quartz, slightly clayey. 0
15 Sand, as above but no clay. Z
20 d clay laminae.
- 25 San ay, as above but with more clay. Sand and clay 6
- 30 ay, greenish-brown, sandy.
- 35 S d, light brown, clayey. Clayey sand 19 Z
-40 Sand, claye ,
- 45 Sand, cla; Cla
- 47 Clay, sandy --- Clay 6

- 55 Limestone, gray, sandy, with dark layers of Limestone at 51 ft.
sand and siliceous cement.

Geohydrologic
unit

Increased radiation

-5 -Sand, brown, very fine-grained. Sand
10 Sand, as above but darker brown, with organic silt.
12 d, as above.
S~ .5 ft but slightly silty. Clay
20 San ht brown, very fine-grained, slightly silty. Sand

30 Clay, light gray, sa Sandy clay
33 Sand, gray, aminae. Sand and clay
36 Sand, light br very fine-grained, silty. Sand
40 Sand, runny. Clayey sand
45 C very soft. Tools dropped ne. Cla

50 Limestone, Atb wik, dense. Limestone at 50

16

2 0

7 9

2
3
10
3

ft.

Limestone, white, medium hard, amorphous.

Site 13
Sample
depth
(feet)

Thickness
(feet)

-59

Increased radiation
----

Geohydrologic Thickness
unit (feet)

" Sand, very fine-grained, sub-rounded to sub-angular
clear quartz brown. Slightly clayey.
d, as above but with black stain from silt.
Sa as above. Sand
Sand, as above but clayey, with streaks of clean white Clayey san
sand.
nd, white, very fine-grained, rounded clear quartz. Sand
Sand an laminae light brown. Sand and c
Clay dy. Sandy clay
very fine-grained, sub-rounded, runny. Sand

Clay, gray, soupy, d shells to 1 mm and chert, Clay
grayish-white, to 3 cm.
Clay, sandy, soupy as above. --3__-- clay
Limestone, gray, sandy, hard. Limestone

d

lay

5

10
15
20
25
- 30
- 35
-40

- 47

- 55
- 60

Site 14
Sample
depth
(feet)

at 60 ft.

Geohydrologic
Increased radiation unit

Saia, dark brown, very fine-grained, with some
organic material.
Sand, chocolate brown, as above.
Sand, as above but with less organic material.
d5Md white, clayey.
Clay, gray, sandy (very fine-grained).

hite-gray, sandy (very fine-grained).
,TTr- wti13. X' fine-grained, clayey.

Clay, very soft; sampler ded from 40 to 42'.
Limestone, light gray, very hard.

Sand

Sandy clay

Clayey sand
Sandy clay

Clay
Limestone at

Site 15
Sample
depth
(feet)

Thickness
(feet)

-lsd&
- 5
-10
-15
-.20
25
-27
-30
-35
.40
42
-45

5
45 ft.

Site 16
Sample
depth
(feet)

Geohydrologic
unit

Increased radiation

Thickness
(feet)

lsd
Sand light brown, very fine-grained sub-rounded
clear quartz, slightly clayey,
Sand, as above but dark brown. Sand 17
15 Sand, as.above but with mottles of slightly clayier
a 5nsand
- 20 San i above but with streaks of sandy clay. Sand and clay 5
- 25 tan, very fine-grained. Sub-rounded, clear
^t tly clayey.
- 30 Sand, ligAt layey. Clayey sand 17
- 35 Sand, clayey as above.
- 40 a/Clay, brown and gray layers, plastic with some sand 5
and chert. _._.
- 45 Limestone, white-gray, dens q1 some saad, crystals of Limestone at 44 ft.
" 47 calcite.
Limestone.

Site 17
Sample Geohydrologic Thickness
depth Increased radiation unit (feet)
(feet) -

ad
-5 Sand, very fine-grained, sub-rounded to rounded, clear
quartz, with slight black silt.
10 nd, as above, but with slight brown silt.
15 as above, runny. Sand 15
20 as at 5 ft but with slightly more clay and layers
ray sandy clay.
25 d, light tan, very fine-grained, sub-rounded, runny,
a/ -tt some cla. .
30 Cla brown, san y (very fine-grained, sub-rounded). Clayey sand 25
35 Sand light tan, very fine-grained, sub-rounded, runny
-40 -'Sand, as above, w n clay. Clay 3 0
45 Clay, black, plastic, w an y c ay. Sand and clay 20 <
50 Clay, black, with drusy p and black fibrous material.
Sandy.
55 Clay, dark y, sandy, with layers of pure black clay. Sandy clay 4
60 Sand, gray, v rained, sub-rounded, slightly
b/ clayey. Very soft; sampler Clay 4
- 65 Clay, green, plastic, some sand. Sandy clay 5

- 75 a/ Clay, green and black layers and mottles. Plastic, sandy. ay 4
80 Limestone, white-gray, dense, hard. <4 =Limestone at 80 ft.

Geohydrologic
Increased radiation unit

lsd
5 nd, light brown, very fine-grained, sub-angular to
Ssub-rounded, and dark brown clay.
10 very fine-grained, sub-rounded, with black silt.
15 Sand, 'ite, very fine and occasional medium-grained.
Sub-roun to rounded.
- 20 Sand, as above t with greenish-brown clay.
- 25 Clay, greenish-brown, sa
- 30 Sand, white, very fine-gra d. Sub-rounded, clear
quartz with gray clay.
- 35 Clay, gray, with layers of s
-40 ,Sand, gray, clayey.
_ 45 Limestone, white and light tan, sandy, dense, hard.

Site 18
Sample
depth
(feet)

Sand 1E

Clayey sand 10
Sandy clay 5
Clayey sand 5
Sandy clay 4

Limestone at 42 ft.

p0
Z

0

0

Thickness
(feet)

' n l, ,

Site 19
Sample Geohydrologic Thickness
depth Increased radiation unit (feet)
(feet) -

sd
5 brown, very fine-grained, sub-angular to sub-
ro d.
10 Sand, as ae. Sand 20
15 San ite. Fine-grained, slight clay.
20 Sand, above but with more clay.
- 25 Clay, brown, an ey sand. Alternate layers. M
- 30 Clay, gray, with streaks of w Sand and clay 15
- 35 Sand an laminae, gray.
- 40 Sand, fine-grained, some clay. Clayey sand 10
- 45 Sand, as above u r ca .--
- 50 Clay, green and gray etas and mottles, plastic, some n _ay- 7
sand. --
- 55 Limestonq gray, san3y, with sandy green clay. Soft. Limestone at 52 ft
- 58

Site 20
Sample Geohydrologic Thickness
depth Increased radiation unit (feet)
(feet)

hd-
5 nd, tan, very fine-grained. Occasional mottlings
f chocolate brown clay.
10
15 Sand 17

-20 Sand, tan, v fine-grained, with brown clay. Clayey sand 18
25
_30 Sand, as ye, but with slightly less clay.
-35 Sand, tan, very ne-gra C Z
40 Limestone, light ray n, with oatterd .and.. !LIU..LLa 38 ft.
45 Clay, greenish-gray, ve- sQandy.
- 50 Limestone.
_ 54 ?"

Site 21
Sample
depth
(feet)

Geohydrologic
Increased radiation unit
---- No

Thickness
(feet)

- 5 San n, very fine-grained, sub-rounded to rounded.
10 nd, as above, but with slight gray clay. Sand ]
15 nd white, very fine-grained, sub-rounded to rounded.
_20 Sand, as above, with some gray clay.
25 Clayey sand ]
30 Sand, as a nd grayish-tan clay layers.
-35 Sand light gra nd Clay
clayey. -k--
-40 Clay, light green, i some sand and fine pyrite.
45 ove, but with mottles of black clay. Clay (?) 1
50 Clay, as e. Very hard, dry, breaks into blocks.
_55 Clay, as above, ot hard. Limestone at 56 ft.
-60 Limestone.

Site 22
Sample Geohydrologic Thickness
depth Increased radiation unit (feet)
(feet
0
do
S5 -- U b-Lrown, very fine-grained, sub-rounded to Sand 5
rounded, ear quartz.
-10 Sand, as abe but with some clay- gray with brownish z
mottlin f higher clay content.
-15 Sand, as ve, but with less clay. Clayey sand 15
-20 Sand and clay 1 brownish-gray.
'25 >
-30 Sand and c as above but runny. Sand and clay 20 Z
35
g ~1~. ~------ .__
-40 Clay, greenish-gray, la eying sand content. Clay 5
45 Limestone, ,W a a-yye-rs of sandy green clay. Limestone at 45 ft.
-48

Geohydrologic
Increased radiation unit

d
5 Woa
-10 a/Sand, e fine to fine-grained, sub-rounded.
15 a/Sand, as above, th layers of clay.
_20 /Sand, as above, cl runny.
-25 a/Sand and clay laminae.
-30 I/Sand, white, very fine-grainedA wi se
/ of gray clay.---- --
-35 -Sa "ne-grained sub-rounded, slightly cla;
-40 a/b/Clay, black, very soft,-pcc, some chert. Limestone,
a/ very soft.
-45 -Limestone, light gray, crumbly, some sand.

Sand

Sand and clay 18

Site 23
Sample
depth
(feet)

Thickness
(feet)

Limestone 43 ft

Site 24
Sample Geohydrologic Thickness
depth Increased radiation unit (feet)
(feet) %-

asd
S5 very fine-grained. well-rounded, well sorted Sand 5 >
clear tz.
10 Sand, as ab but with clay layers. 0
-15 Sand and clay 15 0
-20 Sand, with streaks of clean sand.
-25 Sand, li gray, clayey.
-30 Sand, as above, but s more clayey. Clayey sand 20
-35
-40 Clay, br "ud emn with layers of sandy clay. Clay 2
.45 Limestone, ray, sandy. Gastropod 1 cm across. Lt.
-50 Limestone, gray, sandy, with chi].n .
53 Dark gray sandy clay at 50' wv th shards of chert.

Site 25
Sample Geohydrologic Thickness
depth Increased radiation unit (feet)
(feet)

l d and, dark brown, fine-grained, silty, roots.
S- fine-grained, sub-rounded clear quartz. Slightly Sand 16
o 1n as aove, bar pan from 6.5' to 12'.
and, as above, but more indurated.
-15 Sa fine to very fine-grained, sub-rounded clear
quartz.
-20 Sand, brown, c Clayey sand 9 0
-25 Sand, 1 rown, fine to-very fine-grained, sub-rounded Sand 5
a- r quartz. Runny.
-30 San layey. Clayey sand 5 0
_35 Sand, tan, ined, sub-rounded clear quartz. Sand 7

.44 Clay, green, en Clay 3
~45 Limestone, sandy, w- i.fd. Limestone at 45 ft.
49

Site 26

Sample,
depth
(feet)

Sand, fine-grained, sub-rounded clear quartz
slightly silty (black) with many rootlets and
huus.
Sanus, as above but more silt (brown). No humus.
Sand, as above but with chips of brown,clayey,
indurated sand.
Sand, asat 1 ft.but with layers and mottles of
brown clayey sand.
Sand and clay laminae.
Sand, fine to very fine-grained, sub-rounded
clear quartz with matrix of brown clay.
Clay, sandy, grades downward into dense green
clay at 34.
b/ Clay, greenish-gray, dense. With streaks of
sand.
b/ Clay, as above.
Limestone, hard.

Geohydrologic Thickness

unit

Sand

(feet)

Sand and clay 15

Clayey sand

Clay

lsd
1
5
-10
15
20
25

-33
-38 a

_45 a/
-48
.51

Limestone at 48 ft.

Site 27
Sample Geohydrologic Thickness
depth Increased radiation unit (feet)
(feet) ....
lad

Sand, clayey. Clayey sand 20
-15 nd, brown, clayey.

-20 Sand, to very fine-grained, sub-rounded clear quartz.
Wit years of clayey sand.
25 Sand, ey as above, clay content increases downward. Sand and clay 24

- 45 Clay, green{-h I",nanz sandy, with chert frame nts. Clay 4
-48 Limestone, hard. Limestone at 48 ft.
- 53

Geohydrologic
unit

Increased radiation

-lsd
5 rnd, light brown, very fine-grained, rounded, slightly
clayey.
- 10 s above but with layers of dark brown.
- 15 Sand, as ft but with layers of blocky, chocolate
brown ay and stringers of clean white sand.
- 20 Clay, sandy, ough.
- 25 Sand ay laminae, light gray.
-30 Sand fine-grained, rounded, with laminae of
light tan. an
- 35 Sand, tan, very fine-graine f grayishbrown
Sandy clay. -
- 40 Clay, alternate brown (tou h a i uid), sandy.
-43 Limestone, gray with green mottles, sandy, hard.

Sand

Sand and clay 26

Clay 1
Limestone at 39 ft.

Site 28
Sample
depth
(feet)

Thickness
(feet)

Site 29
Sample Geohydrologic Thickness
depth Increased radiation unit (feet)
(feet)

-ad
- 5 d, very fine to fine-grained, sub-rounded clear quartz Sand 16
and tan clay.
-10 nd, white, very fine to fine-grained, sub-rounded clear 0
--15 rtz.
- 17 Sand, as ab but with greenish clay. Clayey sand 3
-20 Sand, as 10'.
- 25 Sand, as ove but with greenish clay. 0
- 30 Sand and clay laminae. Sand and clay 17

-35 Sand, and gray clay. Clay 3
- 39 Limestone, light gray, sandy, very hard. Limestone at 39 ft.

Site 30
Sample Geohydrologic Thickness
depth Increased radiation unit (feet)
(feet)

-lsd 0
4 Ssd, brown, fine to very fine-grained, rounded clear Sand 4
S5 a-quartz.
Sand, as above, but clayey. Clayey sand 10
10 and, clayey as above but indurated. 0
- 15 Sand and clay laminae, light and dark brown, very hard Z
20Ylyers.
20
SSand and clay 37
30
- 35 Sand an alternate layers of clean sand and sandy 0
clay, 5 t thick.
- 40 Clay, sandy, soft, wit of bluish-white chert
to 2 cm.

- 52 Limestone, sandy, very hard. Clay 1.
-54 Limestone. Limestone at 52 ft.

Site 31
Sample Geohydrologic Thickness
depth Increased radiation unit (feet)
(feet)

a/Sand, very fine-grained, sub-angular to sub-rounded Sand 15
a I/ clear quartz.
-1 Sand, as above, but slightly clayey, runny.
15 as above, but more clayey.
20 Sand, clayey as very runny.
S25 a/Sand and brown.
Sand and clay 27 0
-30 --Clay, light brown, tough.
-35 a/Sand, clayey.
40 -/Sand dlay laminae.
45 a-'Clay, green, plastic san ack clay, soft plastic Clay 5
with chete---
50 Limestone, soft, sandy, with mollusc shell. M Liestone at 47 ft.

- 59 Limestone.

Site 32
Sample Geohydrologic Thickness
depth Increased radiation unit (feet)
(feet) ---Z
0
1 d
L Sand, light tan, very fine-grained, occasional medium-
grained. Well rounded clear quartz, slightly clayey. 0
- Sand, as above, but brown. Sand 15
-15 and, as at 5' but with streaks of brown sandy clay.
20
2 > Sand and clay 21
- 25 Clay, tan, san ayers.
_ 30 Sand, ey as at 15'
35 Cla y-t h plastic, sandy, wit streaks of sand. o0
_ 39 Clay, green s grades downward into limestone. Clay 4
- 40 Li eight gray, ha~n1 Fsure tilled with calcite. Limestone at 40 ft.

- 48 Limestone, soft, slightly sandy, clay streaks.

Site 33
Sample Geohydrologic Thickness
depth Increased radiation unit (feet)
(feet) .-

-1
- S Sand, tan, very fine-grained, well-rounded, clear quartz. Sand 10
Slightly silty.
I10 Sand, dark brown, clayey.
0
S15 Sand, as at 5' but with streaks of dark brown clay.
20 a ark brownish-gray, dense, plastic. Sand and clay 21
25 S some clay. t
30 Sad r fine to medum g r n, ,om ay
35 Sand, clayey, ru Clay
- 38 Limestone, light gray -tyuff, very tnin-bedded, occasional Limestone at 36 ft.
/sand grains.
41 Cavity (?3, half foot of very soft drilling.-"

48 Limestone.

Geohydrologic
unit

Increased radiation

Ilsf and, tan, very fine to fine-grained.

-5
10 a as above, but slightly clayey.
- 15 Sa as above, but with very fine-grained clay balls,
k brown.
- 20 Sand, a above, but with more clay balls.
1 Sand and ay laminae.
- 30 Sand, very sli htly clayey.

Sand

Sand and clay

Clay, 1r -h 1. h laers .of soft non- Clay
calcareous white material. GradeS 4dnward into sandy
clay withhgt l.AC. Wit"h
Clay, dark gray, plastic, bi .
Limestone at 50
Clay, green plastic y sandy.
Limestone, light gray, sa
Limestone, as above.

- 62 Limestone.

Site 34
Sample
depth
(feet)

Thickness
(feet)

- 35
- 40

- 55

ft.

Site 35
Sample
depth
(feet)

Geohydrologic
Increased radiation unit

Sand, tan, very fine-grained, well-rounded clear quartz.
Slightly silty.

Sand, as above, but with organic mottles.
5 Sand, light brown with streaks of iron-stained cemented Sand
grains. Very fine-grained, well-rounded, slightly silty.
. Sand, as above, but with no streaks.
Sand, as above, but with clay mottles.
Sand, as above, but with streaks of organic material.
.5 Sand, very fine-grained, with thin clay streaks.
Sand, as above.
Sand, very fine-grained, clayey, runny.

Clay y, sandy, plastic.
Sa clayey; streaks of varying clay content.
Sand, layey, massive. Clayey san

.5 San clayey, more clay than above.
.5 Sand, ey, with layers of sandy clay.
Sand, v fine-grained, slightly clayey, soupy.

Clay, green-gray with occasional play of p C------
Sandy plastic, vugs of drusy, white kaolinite (?)
Clay, alternate sureas of green and brown, plastic, slick,
some sand.
Clay, softer than above, slightly more sand. Clay

d

Thickness
(feet)

23
24
26

29
31
32

37
38
40

18

5

Site 35 contain
Sample
depth
(feet)
.40

F42

ied

Increased radiation
------m
Clay, dark.gray, much chert in plates and angular pieces
to 2 cm. Black with gray rime.
Limestone, light gray, very hard.

Geohydrologic

unit

Thickness
(feet)

Limestone at 42 ft.

Limestone, soft, with 1

ayers of plastic green clay.

Limestone with clay streaks; hard and soft layers.

L 69

Geohydrologic
Increased radiation unit

lsd
-) 5

-113

Organic soil; swamp.

Sand, brown, very fine-grained.

4 4 Clay, sandy, massive, gray.
-Clay, more sandy than above.

- 3 Sand, clayey.
- 38 Clay, dark gray, ,s k
- 42.5 Limestonelightgray, Veyh.
48 Clay. -

- 55 Li tone.

67 Limestone.

with grains and plates of chert.

Clayey sand
Sand

Sandy clay

Clayey sand
Clay

Limestone at 42.5 ft.

Site 36
Sample
depth
(feet)

Thickness
(feet)

13
11

10 I

4 0
4.5 C

Site 37
Sample
depth
(feet)

Increased radiation

Sand, very fine to fine-grained, sub-angular clear quartz.
Slight black silt.

Saa as above, but with slight pinkish tinge.
San 6.a above, but with very slight clay.
n yIayey
Sand, clayey with mottles of clean sand.
Sand, very fine to fine-grained sub-angular, with laminae
of sandy clay and clayey sand.

Sand

Clayey sand

Sand and clay
and clay, as above but with more clay.

'Sand, clayey, very runny.

- Sand, clayey.
=!Clay, sandy.
Clay, brown, sandy.
Clay, green, plastic.
-/Clay.

Clayey sand

Clay

Geohydrologic
unit

Thickness
(feet)

' 30

- 36.5

11

02
1
P4

0
0

13

00
9 as

_ _

Site 38
Sample Geohydrologic Thickness
depth Increased radiation unit (feet)
(feet) .g

ad
Sand. very fine-grained. well rounded clear quartz.
10 Sand, as above, but with black silt; indurated. w
15 Sand, as above, but slightly less indurated. Sand 35
Sand, dark brown, slightly indurated, silty.
0
-30 ad very fine-grained, occasional medium-grained,
iv clayey, runny. 0
- 35 Sand, runny.
- 40 Sand, gray, clayey. Sandy clay 13
- 45 Clay: nd .
50 Clay, black, p dy.
55 Clay, black, plastic, wit ert grains and pieces to 1 cm. Clay 17
Streaks of sand att ssn-.
60 Clay, greenish-blac plastic, sandy, very soft.

Limestone at 65 ft.
- 74 Limestone.,

Site 39
Sample
depth
(feet)

Increased radiation
--===-=

7-Asd
X5' Sand, light gray, very fine-grained, well rounded.
10 Sand', as above, but light brown.
-1 Sand, as at 5 ft., but yellow-brown.

-20 Sand, as at ut with chunks of gray sandy clay.
-25 Sand above, but with sand balls cemented by black,
W&4--cement.
-30 Sand, as a 5 ft. runny.
-35 Sand, medium-grained clear quar lay.
-40 Clay, sandy, dense.
.45 Limestone, grayishwtt, dense, sandy.

Geohydrologic Thickness
unit (feet)

I

Sand

Clayey sand

Limestone at 43 ft.

Limestone.

Site 40
Sample
depth Increased radiation
(feet)
-led

1 Sand, gray, fine-grained to slightly sil well-rounded clear quartz;
1.5 rootlets.
Sand, as above., but brown.
2.5 Sand, as above, but with less silt.
3 Sand, brown, very fine-grained to slight ilt.
4 Sand, as above, bu asional medium-grain.
4.5 Sand, as above ut with chips of black cemented sand. 0
- 5 Sand, .
- 5.5 San tan, very fine to fine-grained.
6 San as above, but clean whitish-tan.
- 7 Sand, as ve, but with well-cemented black streaks.

- 8.5 Sand, white, fi rained to slight silt, sub-angular clear quartz.
- 9 Sand, as above but h streaks of black, silty sand.
- 9.5 Sand, as at 8.5 ft
- 10 Sand, as at 8.5 ft. but with clay mottles.

_ 11.5 Sand, as above, bu more clayey.
- 12 Sand, as at 8.5', but gray.

Site 40 continued
Sample
depth
(feet)

13.5 Sand, c:
14 Sand, f:

15 Sand, a,
16 Sand, c

- 17.5

- 18.5
.19

- 20

Increased radiation

layey with layers oN-4
ine-grained to slight

s above, but gray.
layey with mottles of

lack and brown clayey sand.
*it, sub-angular clear quartz.

Sand, dark gray, clayey.
Sand, clayey.
Sand and clayey s

Sand, ;lack, clayey.

r

-

Site 40 continued

Sample Increased radiation
depth
(feet)
-29.5 Sand, gray, sub-angular clear quartz with mottles of b

-33 Sand, clean white with dense brown clay layers. Roqtj

Site 40 continued

Sample
depth,
(feet)

-39.5
-40
-40.5
..41

Increased radiation
----^--m

Clay, black, plastic, sandy, with bits of organic material (Charcoal?)
Sand, clean white quartz, and black, plastic, sandy clay in layers.
Clay, black, blocky, plastic, with occasional clean sand grain.
Peat, fibrous brown roots and organic material.

Sand, fine-grained to slightly clayey, sub-angular clear quartz, and black clay.
Clay, black, and fibrous organic material.

Clay, sandy, organic.

Clay, black, blocky, organic material.

-48.5

-50.5

Site 40 continued

Increased radiation

Peat, fibrous

material with silty clay.

Sample
depth
(feet)

-60

-64

w~

49

Site 40 continued

Sample
depth Increased radiation
(feet)

-70

0

0

-75 0
0"

80
^ ---J
( sA

-85

Site 40 continued
--4

Sample
depth Increased radiation
(feet)

-85

-90 0

0

-95

-10 End ga a log at 98'.
107 Sand, black, silty, with organic material.

Geohydrologic
Increased radiation unit
-.----4-de

sd Sand, fine to very fine-gr ined, well rounded clear
quartz with slight black silt.
- Sand, clayey.
1- 10 Sand, with brown resinous clay matrix.
- nd, as above and layers of indurated clayey sand.
- 20 Sand, g clayey, and layers of tough sandy clay.
25 S gray, clayey.
- 30 Sand, a bove with clayey sand streaks.
- 35 Clay, sandy, and layers of c ayey band.

- 40 Clay, green, dense, sandy, very soft.
- 6 Limestone, weahered.
49 Limes one War.
- 49 Limestone.

Sand

Clayey sand

Sand and clay

Limestone at 44 ft.

Site 41

Sample
depth
(feet)

Thickness
(feet)

54
00

Site 42
Sample Geohydrologic Thickness
depth Increased radiation unit (feet)
(fe e t ) -- ^

Sand, dark brown stain, fine-grained sub-rounded to Sand 3
S4 sub-angular clear quartz.
d, as above, but clayey. Clayey sand 1
-10 Sand, 2' but clean white. Sand 13
-15 Sand, runny.
20 Sand, with gray clay and streaks of dar gray 5 o
23 Limestone, weathered, mottled with green clay. e- ~ma r at 22 ft.
- 25 Limestone, very hard, siliceous layers banded with weathered, ----
- 29 soft layers of white limestone. One well-rounded pebble
I2 of gray, pitted phosphate.

Site 43
Sample Geohydrologic Thickness
depth Increased radiation unit (feet)
(feet)

L 5 a fine-grained, sub-rounded clear quartz.
S10 Sand, as e, but with slight brown clay.
SSand 15
15 Sand ne-grained to silt, poorly sorted, rounded to
s b-roun ed, with layers of brown clayey sand.
- 20 Sand, above, but with less clay.
- 25 Clay, gray si sandy, tough. Sand and clay 19
- 30 Sand, clayey.
- 35 C lay.- Clay 3
- 40 Clay, green, sandy, 1tou1 oylI., liF.
- 45 0
- 47 Clay, but with no chert.
SSandy clay 38 0
- 55 Clay, sandy, and with light gree clay layers.

. 65 Clay, as above, but wi ite chert.

- 5 Limestone, grayish-white, sandy. Limestone at 75 ft.

Site 44
00
Sample Geohydrologic Thickness
depth Increased radiation unit (feet)
(feet)
-lad
- -- Sand, gray, very fine-grained, rounded to sub-
F rounded clear quartz with slight black silt.
- 3 Sand, light yellowish-brown. Sand 9
- 5 Sand, dark br wn, very fine-grained, rounded to
ub-rou dea clar uartz slightly clayey.
- J n as above, but ore clayey.
- 7.5 San as at 5 ft. but with very slight clay.
- 9 Sand, brown, very fine-grained, round to
sub-roun clear quartz with some clay.
- 10.5 Sand, more yey than above. Rootlets.
- 12 Sand, te, and layers of light brown, Clayey sand 11
- 13.5 San ght an, as at 9' but with less clay.
- 15 nd, clayey, runny. 0
- 16.5 Sand, clayey.
- 18.5 S d', clayey, with layers of sandy clay.
- 20 San d clay laminae.

- 23 Sand, white, very Mrained, round to sub-rounded
- 2,4 clear quartz slightly cay..
- 245 Sand and clay laminae, as at 20
25.5 Clay, greenish-gray sandy. Sand and clay 13
" 27 Sand white, with yellow-brown reaks, slightly
-28.5 Sand, eligt brown, with some clay and rs of clayey
-30 Sang ana above but with more clay.

Site 44 continued
Sample Geohydrologic Thickness
depth Increased radiation unit (feet)
(feet) _

-32 Sand, white, very fine-grained, slightly clayey.
-33.5 Clay, dark gray, dense, some sand.-
-35 Clay, black, slightly sandy.
Cl=1a 7
C i
39.5 Cl ar gray. 0
-41Ld, white, very fine-grained, round to sub-rounded,
ghtly clayey, with layers of dark-gray clay. Sand and clay 5
-44 Sand, white, and black clay in layers.
-45.5 Clay, black, sandy. z
-47 Clay, black, dense, with str ks of clean white snad
and yellow-brown rootlets. oo
-48.5 Clay, black, with more whi sand and black woody 0
material, and rare pl es of chert.

Sandy clay 10

_55.5 Clay, blacl and sand in laminations.

Geohydrologic
unit

Increased radiation
i ---- 1^

Thickness
(feet)

Sand and cl laminae with rootlets.
Sand and cliy laminae, more sand.
Clay, ack, dense, and shells.

Site 44
Sample
depth
(feet)

-55.5
-57
-58.5
-60

-62.5
-64
-65.5
-67
-69

Shd and clay laminae, gray, few shells.
Sand and clay and broken shell, gray.
Limestone, gray, hard, sandy.

Sand and clay

Limestone at 69 ft.

continued

clay and shell fragments.
:kay laminae, more clay.

Sand
Sand

Geohydrologic
unit

Increased radiation

ad
S /Sand, light brown, very fine-grained, rounded clear
S quartz.
10 San above, but with slight black silt.
- 15 -/Sand and clay nae, black and brown, partly indurated.
- 20 a/Sand, very fine.- Lned to slightly clayey, layers and
a/ mottles of colate-brown clay.
- 25 Clay and 1 of clean white sand.
- 30 2/Sand, clayey.
35 a/Sand, clayey as above, runny.
- 40
a!
-45 s-Clay, laminations of lLeT>-acd lack plastic clay with
48 Limes 9ne, mo ea graZ ad-wlity ard.
52

Sand

Sand and clay

Clayey sand

18

14

Clay

Limestone at 48 ft.

Site 45
Sample
depth
(feet)

Thickness
(feet)

00
I

Site 46
Sample Geohydrologic Thickness
depth Increased radiation unit (feet)
(feet)

5 Sand light brown, very fine to fine-grained, sub-angular Sand 10
clear quartz, with slight silt in streaks.
10 sad,-L& above, but white with occasional streaks, light
brown s 0
15 Sand, as at 5 ft. u w ht grayish-brown clay.
- 20 Sand, as above but cla Clayey sand 17
- 25 Sand, very fine to fine-graine tiiIlar tn sub-
/ roun uartz, slightly clayey. ay 4
30 -Clay, eenish-tan, plastic, sand Limestone at 31 ft.
35 Limestone, white-,sd with layers of green plastic
clay alternatin 6o 45'.
40 Limey clay, greenish-tan mottled plastic clay with ayers
and mottles of gray limestone.
45 Limestone and clay layers.

Geohydrologic
unit

Increased radiation
ON--

Thickness
(feet)

d
- 5 tan, very fine-grained to silt, rounded to sub-
rounde uartz.
- 10 Sand, slight c.ay.
- 15 Sand, above, but with streaks of white sand. Sand 3C
- 20 Sand, ght brown, very fine-grained to silt, rounded
-25 o sub-,ngular, slight clay.
- 25 nd, as aove, but wi h very slight clay.
- 30 Sand, as a ove, Sandy clay 2
- 35 Clay gown, sandy, with small pieces of white Clay 9
chert 17
40 nish-brown. very prp climy. JLimestone at'41 ft.
41 limestone, very hard, cherty.
- 44

Site 47
Sample
depth
(feet)

Sand, fine-grained to slight clay, sub-rounded to sub-
angular clear quartz.

Sand, clean white, as above but without clay.
Sand, as at 5 ft. but with brownish-gray clay.

Sand, with gray clay.
Clay, green, plastic sandy.
Limestone, creamy white, sand, soft greenish-black clay
streaks.

Geohydrologic
unit

Sand

Thickness
(feet)

20

Clayey sand 14
Clay 1
Limestone at 35 ft.

Core of contact shows:
Clay, 10 20% sand at 34.5 ft.
Clay, 10 20% sand with limestone streaks.
Sandy limestone or calcareous sand.
Limestone, 10 20% sand with streaks of black clay at 35.0 ft.

Site 48
Sample
depth
(feet)

-lsd
S5
10
15
20
25
30
- 34
- 35
- 39

Geohydrologic
unit

Sand, light tan, very fine-grained to slight clay, sub-
rounded clear quartz.
Sand, as above, but whitish.
Sand, as above, but with brown clay, runny.
Sand and clay layers, brown, very runny.

Sand, tan, very fine-grained to slight clay, sub-
rounded clear quartz.
Clay, greenish-tan, plastic, sandy.
Limestone, hard, dense, sandy.

Sand 15

Sand and clay 2C

Clayey sand 5
Clay 3
Limestone at 43 ft.

Site 49
Sample
depth
(feet)

Thickness
(feet)

-lsd
5
10
- 15
- 20
- 25
- 30
- 35
- 40
- 45
- 49

0
0
I

z

00
00

Site 50
Sample Geohydrologic Thickness
depth Increased radiation unit (feet)
(feet)
-sd

5 Sand, light tan, very fine-grained, well-sorted, sub. Sand 12
rounded.
- 10 d as above, but with dark stain.
15 Sand, n stain, clayey.
20 -a/bSand lay. Streaks of brown sandy clay and white sand.Sand and clay 8
0
25 Sa light brown, clayey,. runny. Clayey sand 10
30 Sand, s ay poor sample.
35 Clay, greenish-tan, a oughh. Sandy clay 20

40 Sand, clayey.

-55 b/Clay, greenish-gray, plastic, sandy, with chips of Clay 5
limestone at 55.5'.
60 Limestone, cream, cheesy-soft, with soft gray clay, sandy, Limestone at 55 ft.
with occasional chert chips.

Site 51
Sample
depth
(feet)

Geohydrologic
Increased radiation unit

lsd
- a/Sand, very fine-grained, rounded, well-sorted clear Sand
auartz.
10 Sand, as above, and gray clay laminae.
15
21 Sand as above becomes dense black clay at 21'. Sand and clay
25 ay, gray, dense, becomes white sand at 25'.
30 nd, very fine-grained, well-sorted, rounded, clear Sand
rtz.
35 Sand, a ve, and gray clay laminae.
40 Sand, as at 30', an y.
42 Sand, as above, but w more clay. Sand and clay
45 Sand and clay laminae.
- 50 a/- Sand nand'Lln m ae. as above; streaks of clean sand and Clay
green or gray clay. __-
- 55 Limesnj----_. ___Limestone at 55

Thickness
(feet)

ft.

Limestone.

- 63

Site 52
Sample Geohydrologic Thickness
depth Increased radiation unit (feet)
(feet) ----

- 5 San v rained, rounded, clear quartz, slightly Sand 5
- 10 .d a with more gray clay. C
510
- 20 Sand, clayey. Clayey sand 27
0

- 32 Sand, bove, but more clay.
- 35
S37 Sa e as above, but with slightly less clay.
40 Sand and clay, Sand and clay 6
- 45 Clay, greenish, with gray-black mottles, san y. 6
50 Clay, black, sticky, very soft. Claj4`- 3
-52 Limestone, light gray, sandy. Limestone at 47 ft.

Geohydrologic
Increased radiation unit
No- k

light tan, very fine to fine-grained, rounded
cleda artz.
Sand, as ove, and light gray clay.

Sand, clayey, br sh-gray.
Sand, clayey, as ab but with lenses of clean white
sand.
Clay, li h sand and sandy streaks.
Sand, wi light greenish-tan clay.
Clay, greenish-gray, plastic, sandy, and with streaks of
sandy clay.
Limestone, whitish-gray, hard, sandy.

Sand

Clayey sand

Sandy clay

Clayey sand

Clay
Limestone at

Site 53
Sample
depth
(feet)

Thickness
(feet)

lsd
5

-10
- 15
- 20
22
25
- 30
- 35
- 40
_45

20

5

10

2
41.5 ft.

Site 54
Sample Geohydrologic Thickness
depth Increased radiation unit (feet)
(feet)

lsd
- 5 Sand, light gray, very fine to fine-grained, slightly
clayey.
10 Sand, as above, but stained dark brown.
Sand, as at 5', mottled tan and gray. Sand 35
-2
25 Sand, as above, but even tan; no mottling.
S30 and, as above, but with even less clay.
35 Sa d clayey, runny.
- 40 Sand, as a ov less clay. Runny sand. Clayey sand 12
Clay 3
-50 Limestone, gr sandy. Limestone at 50aft.

- 60 Limestone.

	Title Page
	Department of Natural Resources...
	Transmittal letter
	Abstract and introduction
	Geographic setting
	Test drilling
	Sampling methods and laboratory...
	Lithology
	Natural -- Gamma logs
	Geohydrology
	Hydrologic system
	Summary
	References
	Tables

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