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Acknowledgements and production
ENVIRONMENTAL GEOLOGY AND HYDROLOGY
." '... .
.i *;: St
.. . ..
) 11o0oY Library
plorida Bureau o Ge3 Lrar
903 33' C
I .-. --' 3304
FGS TAMPA AREA
STATE OF FLORIDA
DEPARTMENT OF NATURAL RESOURCES
Harmon Shields, Executive Director
DIVISION OF INTERIOR RESOURCES
Robert O. Vernon, Director
BUREAU OF GEOLOGY
C. W. Hendry, Jr., Chief
SPECIAL PUBLICATION NO. 19
o0 aa (eotloE~-ral Survey
903 West Tennessee Street
T Ialhas Ee Florida 32304
ENVIRONMENTAL GEOLOGY AND HYDROLOGY
TAMPA AREA, FLORIDA
by Alexandra P. Wright
Prepared by the
BUREAU OF GEOLOGY
DIVISION OF INTERIOR RESOURCES
FLORIDA DEPARTMENT OF NATURAL RESOURCES
ACKNOWLEDGEMENTS AND PRODUCTION
PREFACE,Charles W. Hendry, Jr. ...... ........................ v
Transportation, Carleton J. Ryffel, A. P.
Topographic Maps ...........
Topography of the Tampa Area . .
Topography and Land Use Planning ..
Water Cycle . . . . . . .
Rainfall and Evapotranspiration . .
Drainage . . . . . . . .
Water Quality . . . . . . .
Lakes . . . . . . . . .
Streams . . . . . . . .
Hillsborough River . . . . . .
Water Table and Swamps . . . .
Floridan Aquifer and Springs . . .
Water Use ...............
Geologic History . . . . . .
General Geology . . . . . .
Structure . .. .. ......... .
MINERAL RESOURCES, E. C.Pirkle, W. H. Yoho, Fredric L.Pirkle, A.P. Wright
Phosphate . . . . . . . . . . . . . . . . . .
Sand . . . . . . . . . . . . . . . . . . .
Clay .. . . . . . . . . . . . . . . . .... . .
Lim estone . . . . . . . . . . . . . . . . . .
Cerhent, Oyster Shells and Peat ........................
Concluding Remarks ..............................
Foundations, A.. Wright, James F. Orofino ....
Sands ........... ..... .. ....
Sand Suitability as a Foundation Material . . .
Clays . . . . . . . . . . . .
Organics . . . . . . . . . . .
Potential Collapse . . . . . . . . .
Soil Associations . . . . . . . . .
Soil Relationships in Urban Planning . . . .
Primary Energy Sources, W. B. Simonds . . .
Electric Energy, W. B. Simonds ..........
Energy of the Future, W. B. Simonds . . . .
Oil and Gas, W. R. Oglesby . . . . . ...
Current Land Use .. ..............
Future Land Use ..................
Transportation Planning and Geology . . . .
Geologic Factors Affecting Construction . . .
Geologic Factors and Sanitary Landfills . . .
. . . . . . . . . . ...... 43
Geology and Urban Planning .
Gratitude is expressed to Dr. Robert O. Vernon,
Director of the Division of Interior Resources, Mr.
Charles W. Hendry, Jr., Chief of the Bureau of
Geology and Mr. Steve R. Windham, Assistant
Bureau Chief, for making this publication possible.
Appreciation is expressed to the staff of the
Bureau of Geology for encouragement throughout
the project and assistance in reviewing the text.
Special thanks are due J. W. Yon, Jr. who gave
generously of his time to assist in the preparation of
Sincere thanks are extended to Dr. Joseph S.
Rosenshein, Subdistrict Chief of the U.S. Geological
Survey's Tampa office and to his staff for generously
providing data and helpful suggestions for the Water
Resources chapter. Assistance from Mr. Gerald
Parker, Chief Hydrologist, and other staff members of
Southwest Florida Water Management District and
from staff members of the Tallahassee District U.S.
Geological Survey office is also gratefully acknow-
ledged. Mr. Samuel R. Lockwood, past Superin-
tendent of the City of Tampa Water Department also
provided invaluable data.
Special thanks is expressed to James F. Orofino,
Orofino and Company whose extensive assistance
made possible the Engineering Geology chapter of the
Appreciation is also due William B. Forney, past
District Conservationist, Soil Conservation Service
who kindly gave of his time to assist with the soils
sections of the study.
Gratitude is expressed to the following people for
assisting in the preparation and review of the Mineral
Resources chapter: T. Walter Herbert, Bobby J.
Timmons, J. S. Weaver, Thomas J. Patterson, Bruce
Congleton, Allen C. Edgar, L. B. Carnes, James L.
Eades, Walter W. Rowe, and Edward Medard. The
Department of Physical Science and the Department
of Geology, University of Florida and the Florida
Phosphate Council are also acknowledged. Sincere
appreciation is expressed to Xiomara Ortiz for typing
and lay-out of materials.
Sincere appreciation is extended to Timothy
Varney, past Environmental Planner, Hillsborough
County Planning Commission. William Ockunzzi and
other staff members of the Tampa Bay Regional
Planning Council provided much useful information
with regard to land use. Thanks are expressed to both
planning agencies for extending encouragement and
sincere interest during the study.
Thanks are also due the following people for
providing vital information and assistance with
various parts of the study; Peter McPhee, Division of
Recreation and Parks, Thomas Griepentrog, Depart-
ment of Transportation, Dr. Daniel P. Spangler,
University of South Florida, H. J. Woodard, Bureau
of Water Resources, S. Melodie Oleson, Southwest
Florida Water Management District, Robert W.
Johnson and Bishop Beville, Soil Conservation Ser-
vice, and Philip Linn, Hillsborough County Planning
Genuine thanks are extended to the many people
too numerous to mention who have taken an interest
in the project and cooperated throughout the
preparation and production of this publication.
-chapter title pages
Typing and Type Setting
Alexandra P. Wright
Carleton J. Ryffel
Juanita D. Woodard
Donald F. Tucker
Simmie L. Murphy
Stephen J. Wharton
D. E. Beatty
Robert M. Grill
Dorothy P. Janson
Philip R. Shaw
Dorothy P. Janson
Anne M. Prytyka
Stephen J. Wharton
"Environmental geology. The collection, analysis,
and application of geologic data and principles to
problems created by human occupancy and use of the
physical environment, including the maximization of
a rapidly shrinking living space and resource base to
the needs of man, the minimization of the deleterious
effects of man's interaction with the Earth, and the
accommodation of the exponentially increasing
human population to the finite resources and terrain
of the Earth. It involves studies of hydrogeology,
topography, engineering geology, and economic geo-
logy, and is concerned with Earth processes, Earth
resources, and engineering properties of Earth materi-
als. It involves problems concerned with construction
of buildings and transportation facilities, installation
of utility facilities, safe disposal of solid and liquid
waste products, development and management of
water resources, evaluation and mapping of rock and
mineral resources, and overall long-range physical
planning and development of the most efficient and
beneficial use of the land." So states the Glossary of
Geology, published by the American Geological
Institute, and to this end this publication is pre-
To accommodate the exponentially increasing
human population to the finite resources and terrain
of the earth has become the foremost responsibility
of government officials, planners and technical
researchers within the last two decades. In the not
too distant past, it seemed we had inexhaustible
supplies of clean air, potable water, energy and other
mineral resources, but such excesses are no longer
assured. We have entered the era of shortages and
recycling which has resulted in the reestablishment of
priorities and the sequential uses of our resources in
order to insure our survival.
This publication is presented not as the answer to
any of the monumental problems facing those with
the responsibility of planning for the future, but as a
tool to help those with such responsibilities.
Charles W. Hendry, Jr.
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Although Tampa's first incorporation occurred in
1849 with a population of 185, Tampa officially
became a city after a second incorporation in 1855.
Since that time Tampa and its surrounding suburbs
have experienced a population explosion. To put
Tampa's growth into perspective, the following table
provides a summary of census facts:
Population figures alone have little environmental
significance. The statistic that probably relates most
directly to the physical setting is population density,
or the number of people per acre of land. Based on
1970 census data, figure one shows population
densities within the Tampa area.
Obviously, the individual requires a certain
minimal space for life, work and leisure and it seems
reasonable to assume that creature discomfort and
environmental damage can result from overcrowding.
Establishing an optimum space requirement for the
individual is an interdisciplinary problem and no
reliable estimate can be given here.
Attention can be paid, however, to future growth
patterns and specific areas in which accelerated
population increases are anticipated. For this
purpose, the graphs below exhibit population
projections through the year 2000 for the fourteen
areas outlined on figure one. These graphs indicate
that the population of some areas will increase by
many times during the next 30 years. It is these areas
which are prime candidates for the environmental
damages that have historically accompanied
Prudent planning must keep pace with
development in these areas and such planning must be
based on thorough knowledge of both physical and
biological environ. It is the job of scientific agencies
to provide planners with such information if
environmental crises are to be avoided as more and
more people populate the Tampa area.
0 -o -20 ..X)..
* I .AREA11 (2.5 x
- 1970 '5 '80 '85 '90 '95 2000
POPULATION PROJECTIONS BY CENSUS AREA
(SOURCE: TAMPA BAY REGIONAL PLANNING COUNCIL)
(1.3X) Number of times by which the population will increase.
1970 '75 80 '85 '90 '95 2O00~
'80 '85 '9b '45 20000
Recreational facilities are a significant asset to any
area in both the intangible enjoyment they provide
and the role they play in the local economy. Due to
the great influx of tourists to the area as well as the
accelerated resident population increases, Tampa's
recreational demands are especially high. In fact,
according to the Division of Recreation and Parks,
current and projected demands for recreational
facilities in the Tampa region1 are the highest in the
Fortunately, the area is endowed with many
natural resources which are the crux of outdoor
recreation. Geologic features frequently provide the
focal point for recreational facilities in the Tampa
area. Springs, for example, are a main attraction of
many local parks. Another example of a unique
natural feature can be found in Hillsborough River
State Park where the occurrence of a rock outcrop in
the river provides a scenic stretch of rapids. A
primary natural asset of the Tampa Bay area is the
Bay itself. Although the Bay has not been as
significant a recreational resource as it might have
been, several proposed recreation sites are located on
000 2000 P
LAND ACREAGE NEEDED FOR
CAMPING, BEACH, HIKING
TRAILS, NATURE STUDY,
O SALT AND FRESH WATER
SURFACE ACREAGE NEEDED
FOR BOATING, FISHING,
SWIMMING, WATER SKIING
The map shows existing and proposed recreational
facilities within the Tampa area. The status of
proposed facilities varies from the "drawing board
stage" to "development near completion". Tampa's
current and projected recreational demands are great,
and the proposed recreation areas will not meet all of
the needs. The task of the recreation planner,
however, is simplified by the fact that any site
distinguished by its natural or historical elements has
potential for recreational development. The
important point is that the creation of a list of
potential recreational lands and acquisition of those
lands should be done now. This is necessary for two
reasons: the rising costs of real estate, and the need to
preserve the lands' natural resource assets until such
time as the sites can be developed for recreation. The
fact that demands for water related recreation are
greatest further emphasizes the necessity of properly
managing the regional water resources.
includes Hillsborough, Pinellas, Pasco, Polk, Manatee,
Hardee, DeSoto, Sarasota and Highlands counties.
RECREATIONAL NEEDS OF THE TAMPA AREA CONTRASTED WITH THOSE OF
THE MIAMI AREA (DATA SOURCE; DIVISION OF RECREATION AND PARKS, 1971)
PASCO COUNTY OLK CO
-- -- -. -..------ .------ -- ----------- 7
-I / LOWER HILLSBOROUGH RIVER /
7 RESERVOIR PARK /
I K 'LAKEPARK BLACKWATER CREE
T M P TAP SAY-.7' RIVER92
,UPPERTK .r w PLANT CITY I
aOLD T A M P A
S TAMPA SEDDON
BAY j / PLEASANT GROVEON
\ !\) RESERVOIR PARK
EXISTING and PROPOSED RECREATIONAL LTHASPRI*
FACILITIES in HILLSBOROUGH COUNTY ALLARIVER I- PARK-
TREAMPA BAY REGIONAL PL NG COUNCIL
/ MAN"" NTEE COU N
r '~ ' '~ ~ MANATEE ~ - - COU'NTY - - - - --
Historically, transportation in the Tampa area has
been vitally linked with the expanding population of
the area. The existence of the natural estuary (ideally
suited for the development of a port), played an
important role in the location and subsequent growth
of the City of Tampa.
Tampa channel was initially dredged in the late
1800's, and has since been deepened several times to
accommodate larger ships and cargo. The port was first
used for shipping cattle to Cuba in the 1800's. Later,
with the discovery of phosphate in the area, a
prosperous future for the port was assured. Currently,
phosphate is the leading product shipped from Port
Tampa, and many area residents depend directly or
indirectly on the port for their livlihood.
Whereas the port is a key to the economy of the
Tampa area, the supporting role of the railroads for
carrying goods to the port cannot be ignored. Like
the shipping industry, the rail industry was initiated
in Tampa during the late 1800's. In 1883, the railroad
stretched eastward toward Plant City and by 1885 it
was linked with the north. With the expansion and
diversification of industry in the area, rail trade
continued to grow.
A benchmark in transportation history was the
completion of Gandy Bridge in 1924, then the
world's longest auto toll bridge. Today's impressive
network of highways reflects local and regional
growth patterns in the Tampa area. Tampa is served
by U. S., state and interstate highways.
The airline industry was born in 1914 in the
Tampa area when Tony Janus made the first regularly
scheduled flights from St. Petersburg to Tampa in an
airboat. Tampa's new International Airport is a
monument to the spectacular growth of air travel.
Tampa's transportation facilities are an important
asset to the area. They provide convenience to
residents, in addition to facilitating the flow of
tourists to the area. Many transportation planning
studies, now underway, incorporate environmental
considerations to insure that future development of
transportation facilities will have minimal
< 5000 Vehicles
-- 15000-50000 Vehicles
In 1971, Port Tampa handled over thirty six
million tons of cargo. This is the largest tonnage
handled by any port in Florida. Further, the port
ranks eighth in the nation in total tonnage handled,
and fourth in export tonnage. With the proposed
deepening of the channel, the projected tonnage may
reach sixty million tons by 1985, and one hundred
million tons by the year 2000.
At the present time, the U. S. Geological Survey
and the Tampa Port Authority have undertaken an
estuarine hydrology and environmental study of
Tampa Bay, to insure the wisest environmental and
commercial management of the Bay. The present
status and the fate of Tampa Bay have long been
subjects of heated controversy. The comprehensive
Bay study will provide a plethora of data including:
--the quality of Bay waters and sediments
--the quality of inflow to the Bay
--characteristics of bottom and sub-bottom
Among the most sophisticated estuarine
investigations ever undertaken, the Tampa Bay study
will entail development of a computer model which
will provide accurate predictions of changes in the
Bay environment so that improvements in the ship
channel can be planned and designed to minimize
The deepening project is necessary to
accommodate the larger new ships which the
phosphate industry (the largest user of port facilities)
will be using. The dredging operation will increase the
channel depth to forty-seven feet. The actual desired
depth is forty-three feet, but two foot allowances
must be made for error and for slumping of the
sediment after dredging is completed. It is expected
that fifty million cubic yards of sediment will be
removed under the supervision of the Army Corps of
Engineers, which is the agency responsible for
maintenance of the channels. Some sediments
removed from the Bay will be used for construction
purposes. The remainder will be used in spoil areas.
... . .i, *. -.I . .
The new Tampa International Airport has been
designated an intercontinental facility and jet
terminal by the Federal Aviation Authority, and its
runways and terminal complex are designed to
accommodate all commercial aircraft including the
747 and SST. Currently, ten major scheduled airlines
operate from Tampa International. Completed in
1971, the airport features four levels: baggage claim,
ticketing, transfer (landside-airside shuttle), and
parking. The multi-level concept and radial design
minimize walking distance from automobile to
aircraft seat and maximize efficiency.
The remainder of the airports in the area (exclusive
of Macdill) are for private use. They offer flight
schools, aircraft sales, service and leasing, or some
combination of these.
Hillsborough County is served by interstate
highways 4 and 75. On completion, 1-75 will enable
driving from Tampa to Saulte Ste. Marie, Michigan on
the Canadian border. Interstate 4 provides easy access
to Florida's east coast, and in Daytona Beach it
connects with 1-95 which runs along the entire
eastern coast of the United States.
With regard to rail transportation, the Tampa area
is served by Seaboard Coastline, the eighth largest
railroad in the nation. Seaboard is primarily a carrier
of phosphate, and to a lesser degree, citrus products
and passengers. Seaboard is also a feeder line to
junctions where goods are transferred to other
railroads and carried to more distant destinations.
Photo by R.C. Reichenbaugh
Topography (or the shape of the land surface) is of
great significance to virtually every aspect of land use
planning. The relationship of relief to geography and
physiography, location and thickness of mineral
resources, drainage patterns, climatology, vegetative
patterns, occurrence of natural disasters, soil
development, physical aesthetics, etc. points up the
value of a familiarity with the topography of the
study area. The shape of the land, portrayed by
contour lines (lines of equal elevation), is the
distinctive feature exhibited on topographic maps,
however, a wealth of information about the area is
also shown on the maps.
The Tampa area encompasses all, or portions of
sixteen quadrangle maps, each showing an area of 7.5
minutes latitude by 7.5 minutes longitude. The scale
on these maps is 1:24,000 that is, one inch on the
map equals 24,000 inches or 2000 feet on the
ground. The contours are imaginary lines following
the land surface at a constant elevation above sea
level. The contour interval (given at the bottom of
each map) is the vertical difference in elevation
between adjacent contours on the map. In flat areas
such as Tampa, the contour interval is generally small
so that contour lines are not far apart.
Several characteristics of contour lines are
1) Contour lines never cross or intersect one
another, nor do they split.
2) Every contour line closes on itself either within
or beyond the limits of the map.
3) The closer the spacing of contour lines, the
steeper the slope.
4) Contour lines curve upstream, but cross the
stream at right angles to its course.
Topographic maps are ideal for pinpointing exact
locations, as they are referenced to latitude-longitude,
and contain a sectional gridwork within each
township. Township is given on the sides of each
map, and range on the top and bottom. Each of the
36 sections within a township represents one square
mile, and each section number is shown in red on the
Color coding and numerous map symbols indicate
a variety of physical and cultural features. Black is
used for man-made features (roads, buildings, etc.),
blue for water, brown for contour lines, mines, etc.,
green for vegetative cover, and red for urban areas,
section lines, etc. In addition, lavender is used on
photorevised maps to show new features.
Cross sections (as shown in the diagram) can easily
be constructed from topographic maps and are useful
in representing cross country relief or slope of the
Topographic maps covering the Tampa area are
available through the U. S. Geological Survey in
Washington, D. C.
VERTICAL EXAGGERATION X40
INTERIOR-GEOLOGICAL SURVEY W SHINGTON,D.C -1970-NS
0.3 MI. TO U.S.92 82922
TAMPA (CH.) 6.9 MI.
Heavy duty........... Light duty.........
Medium duty........ -- Unimproved dirt =...
0 Interstate Route U.S. Route 0 State Route
SULPHUR SPRINGS, FLA.
AMS 4540 IIISW-SERIES V847
1 2 0 1 MILE
1000" 0 1000 2000 3000 4000 5000 6000 7000 FEET
1 .5 0 1 KILOMETER
CONTOUR INTERVAL 5 FEET
DATUM IS MEAN SEA LEVEL
TOPOGRAPHY OF THE TAMPA AREA
The index map on this page shows the boundaries
of the sixteen 7.5 minute topographic quadrangles
which encompass the Tampa area. Seven of them
have been photorevised. Space does not permit
reproduction of each quadrangle, however, the
Tampa, Gandy Bridge, and Sulphur Springs quads are
discussed on subsequent pages.
The simplified contour map presented here
portrays the general topography of the Tampa area.
The interbay peninsula, and the coastal strip (which
ranges from about 1 to 3 miles wide) are
characterized by elevations rarely exceeding 20 feet
above sea level. Low relief extends inland for some
distance from the mouths of the river channels. The
area gradually slopes upward to the north and east.
Highest elevations are found within the Polk Upland
(see Physiography Section) in the eastern part of the
0 2 3 4
DEPARTMENT OF THE INTERIOR
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SULPHUR SPRINGS QUADRANGLE
FLORI DA-HLLSBOROUH SCOC
7S MINUTE SERIES (TOPOGRAPHIC)
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SULPHUR SPRINGS, FLA
.... v 41 ...
Sulphur Springs Quadrangle
The southern half of this quadrangle is highly
urbanized. Physically, two distinctive regions are
evident a lake region and a swamp region. The
western part of the map exhibits a preponderance of
lakes, whereas the eastern half contains almost none.
The elevations of most lakes are printed on the map
within the surface area of the lake.
The northeastern quarter of the map is covered by
wooded swamp, which accounts for the lack of
development in that area. With the continued growth
of the University of South Florida community, it is
conceivable that urbanization may push its way
toward the swamps as developers attempt to
overcome the limitations of this hitherto low-priority
Another interesting feature of the map is the
cluster of sinkholes near 109th Street and Florida
Avenue. These appear as series of concentric circular
contour lines with hachure marks indicating a drop
rather than a rise in elevation. The blue symbol for
water appears in the center of the sinkholes on the
original map, but cannot be seen on this
J- 1 I .
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DEPARTMENT OF THE INTERIOR
r, '^. ,
The Gandy Bridge quadrangle e.t.oh.
the western half of the ,nieit.'
peninsula. Much "made-land" anfi rmai
alterations of the coast are evidenced by
the artificial shape of the shoreline. in
the northwest corner of the map, the
mangrove symbol appears prominently
along the coast.
GANDY BRIDGE QUADRANGLE
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B A Y
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75 MINUTE SERIES (TOPOGRAPHiC)
,lIrrc~lt ;e ?n'de Tar'pa L s'crngl ,s
urb.nied' r IMarn ,T-,C e .iexr. ding
ino ins6 Bav .' rchracl r'-ed u r isri.it
crc nes \ia:; ;icaure: .*i tr. tEa..
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Cuiur oni v~n com lanl i lrir IIlrl
----- --- - -
Nioro IWsea :
3ANDY BRIDGE, FLA
MARIANNA LOWLANDS PHYSIOGRAPHY
The Tampa area lies within the major physiographic subdivision known as the
GEORGIA -Gulf Coastal Plain and in general exhibits little variation in physiography.
S AHAE "\ VL- The terrain is flat and low-lying, reflecting the relatively low relief of the
C NORTHERN ZONE bedrock. In the eastern part of the area, the land surface becomes gently rolling
S-k with smoothly rounded hills and shallow depressions.
L4" regions. These regions have been discussed in detail by White (1970).
Q ISULA ZONE Notable physiographic features within the area are related to the marine origin
STAMPA 1 of the region. Traces of ancient stands of sea level are found in parts of the study
1 r area where the landscape has not been greatly altered by fluvial processes.
._, GULF COASTAL LOWLANDS
The western part of the Lowlands is very swampy and many lakes are present.
Sokeecobee Relict marine features, such as bars, barrier islands, etc., formed during ancient
stands of sea level are found in the Gulf Coastal Lowlands. The area is largely
SOUTHERN ZONE covered by somewhat poorly drained sands with an organic pan and is
MIAMI characterized by flat topography and swamps. Sinkholes are scattered in the
northwest area and will be discussed in greater detail later.
Each of the Pleistocene glacial stages was followed by an interglacial stage
during which the ice melted and the seas encroached on the land. Each encroachment reached successively lower
levels and consequently the remnants of interglacial shorelines can still be identified on land. These remnants provide
clues to paleogeography. The Pamlico shoreline represents an advance of the sea to an elevation of about 25 feet
above present sea level. From the configuration of the Pamlico shoreline in the Tampa area, it can be deduced that
this area was occupied by a large and more open estuary during late Pleistocene time. Several islands also existed,
primarily in the area of what is now Pinellas County. Relict sand dunes are found in the Temple Terrace area.
The extent of the Pamlico shoreline is shown on the map. This is the only Pleistocene shoreline that is well
preserved in the Tampa area.
THE CENTRAL HIGHLANDS
The Central Highlands comprise a number of upland areas within mid-peninsular Florida. Among these is the Polk
Uplands which is of considerably less elevation and local relief than many of the other Upland features. The general
Central Highlands also encompasses several lowlands including the Western Valley. These lowland and highland
features can be attributed to differential erosion which reduced unprotected soluble areas to lower elevations,
leaving residual remnants of former regional upland areas.
The Hillsborough River Valley: The Hillsborough River Valley trends northeast-southwest through the central
portion of the area and represents the southern end of the Western Valley which includes both the Hillsborough and
Withlacoochee Rivers. There is evidence that the Western Valley may have once held only one long stream.
Periodically, the Withlacoochee overflows into the Hillsborough River via a topographic saddle.
The Hillsborough River Valley has gently sloping to flat relief and is dissected by the Hillsborough River and its
numerous tributaries. The size of Hillsborough Bay into which the river flows, coupled with the fact that a
Pleistocene shoreline can be traced part way up the river valley suggests that the Hillsborough River has existed for
some time. The river's broad, swampy flood plain is also indicative of an older river. Although well drained, deep
sands cover much of the area, portions of the River Valley are swampy, and relatively few lakes are present.
The Polk Upland: The eastern part of the study area encompasses a small portion of the Polk Upland. This area is
topographically higher than the surrounding Coastal and River Valley lowlands and attains elevations of 100 to 130
feet. The terrain is gently rolling and bounded on the west by a scarp whose slope steepens toward the Hillsborough
River. The area is covered by well drained sands which are mixed with phosphatic material in places.
0 I 2 3 MILES
TOPOGRAPHY AND LAND USE PLANNING
Because of the detail and accuracy of topographic
maps and the relevancy of topography to land use,
planners can utilize topographic maps for myriad
purposes. Some examples are given below:
Locating and Evaluating Mineral Resources
Valuable mineral deposits are often associated with
physiographic features (arches, relict beach dunes,
etc.) that are revealed on topographic maps. In
addition, if the elevation of the top of an economic
mineral deposit has been mapped, this map can be
superimposed on a topographic map of the area and
the land surface elevation minus the deposit elevation
is equal to -the thickness of overburden that will have
to be removed prior to mining.
Selecting Industrial and Residential Sites
Topographic maps provide information that is
useful in selecting industrial and residential sites.
Topographic maps can be used as base maps for
showing utility lines, access roads and waterways,
zoning boundaries, potential water supply and the
present industrial-residential pattern of the
Planning Recreation Areas
Topographic maps are ideal for locating areas with
unique physical attributes that may be suitable as
recreation areas. Potential hiking and canoe trails can
be sketched on topographic maps, then evaluated in
the field. Lack of urbanization is often a primary
criteria for recreation areas, and undeveloped land
can be spotted at a glance on topographic maps.
Defining and Evaluating Water Resources
Topographic maps serve as a tool for planning
watersheds, recharge areas, well fields, surface water
supply sources, flood control structures, reservoirs,
etc. Indeed their applications to hydrology are almost
limitless. The map illustrates how surface drainage
patterns and drainage basin boundaries can be
delineated on a topographic map. Such flow nets are
used in planning flood control and drainage projects
and in correlating climatological conditions with
surface water flow.
Incorporating Physical Aesthetics in the Regional Plan
In many areas there is an aesthetic quality to the
"lay of the land". Creative planners can sometimes
capitalize on inherent physical appearances by
emphasizing the natural landscape in the land use
plan. Topographic maps can be a starting point from
which a land use design that is harmonious with
natural features can be developed.
"o .. .. ..~ . _.--' i ~ ,,_
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s.. ..*~ '.^ --- *^ ...- ; .;-: -. .,7 :
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,,~ ~ ~ -L< I_----^:---
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FLOW NET SKETCH DRAWN FROM
CITRUS PARK QUADRANGLE
r DRA~INAGE DIVIDES
One of the consequences of urbanization is an
increasing demand upon available water resources for
public supply, recreation, industry and other
As the competition for water intensifies, hydrology
becomes a more prominent aspect of planning, and
sound and equitable water management becomes a
necessity. The hydrologic cycle is a fundamental
concept in understanding, planning for and managing
Fresh water on land is derived from ocean water
evaporated by the sun's heat. Evaporated water in
vapor form is transported by convective air currents
through the atmosphere to inland areas, where part of
the vapor condenses and precipitates.
Rain that reaches the land returns either to the
ocean by gravity flow or to the atmosphere by
evaporation from land, water and plant surfaces.
Before the basic cycle is completed, however, much
interchange of water may take place between lakes,
swamps, streams and the ground. Time required for a
'water particle to complete the cycle may vary from
an instant to many years, depending on the path it
Once rain reaches the land surface its path depends
on the terrain. Two important characteristics are the
slope of the land surface and the permeability of the
surficial and underlying materials.
Steep slopes and low permeabilities promote the
runoff of rainfall to streams or to lakes, swamps, and
sinkholes which may or may not connect to streams
leading to the ocean.
Gentle slopes and high permeabilities promote the
infiltration of rainfall into the ground. Much of the
water that infiltrates is stored in a soil zone, serving
to supply water for vegetation, but part of it moves
down to the water table, ultimately to emerge at
some lower level, usually in areas that contain or
adjoin streams, lakes and swamps.
In Hillsborough County water may also move
downward into the Floridan aquifer, which underlies
the water table aquifer and is generally separated
from it by a layer of relatively impermeable material
called a confining bed. Sinks in the bottoms of some
streams and lakes may connect directly with the
Floridan aquifer. Water in the Floridan aquifer
eventually emerges as springflow in streams, lakes,
swamps, or the ocean.
Recharge to and discharge from the Floridan
aquifer are dependent on the relative position of the
waters involved and the fact that water always moves
from higher to lower elevations. Because water in the
Floridan aquifer is confined, its potential elevation is
represented by an imaginary surface, called the
potentiometric surface, which is determined by the
level at which water freely stands in tightly cased
wells that penetrate the aquifer. Given the necessary
openings in the confining bed, water can move into
the Floridan aquifer from water bodies which stand
above the potentiometric surface; conversely, the
Floridan aquifer can discharge water into water
bodies whose levels stand below the potentiometric
It is evident that all components of the hydrologic
system are interrelated to form a delicate balance,
and when one component of the system fluctuates,
other components fluctuate similarly. This can be
illustrated by the relationship between streamflow,
lake and well levels. These levels respond to both
natural and artificial alterations in the quantity of
water within the system. Projects involving water
withdrawal, addition, or diversion should be
evaluated in terms of possible effects on the entire
GULF of MEXICO
PRECIPITATION AND EVAPOTRANSPIRATION
1900 1910 1920 1930 L940
YEARLY PRECIPITATION, IN INCHES,
AT TAMPA, FLORIDA
Replenishment of lakes, streams, and aquifers in
the Tampa area is largely dependent on precipitation.
Normal annual precipitation at Tampa is 51.57
inches, however, total yearly precipitation fluctuates
widely. The lowest yearly total recorded was 28.89
inches in 1956, and the highest recorded was 76.57
inches in 1959.
Monthly variations in precipitation are important
to farmers, construction companies, homeowners,
etc. Two wet seasons are defined by the graph of
monthly precipitation in Tampa: a pronounced one
during the summer, and lesser one early in spring.
Most rainfall occurs between June and September as a
result of thunder storms, tropical depressions or
hurricanes. During these months, outdoor activity is
often restricted by frequent showers, and local
flooding may occur.
Lack of precipitation in late spring may bring
about regional drought which causes the vegetation to
experience moisture stress. At this time, there are
critical demands on water resources for irrigation and
sprinkling, and restrictive measures are sometimes
Whereas precipitation is the primary source of
replenishment of the water resources in the area, the
amount of water that actually enters the hydrologic
system is sharply reduced by evapotranspiration (ET).
Potential monthly ET can be calculated on the
basis of mean monthly temperatures and sunlight
duration. During months when precipitation exceeds
the potential ET value, all potential ET can take
place. If the precipitation is less than the potential
ET, actual ET consumes all precipitation plus some of
the moisture stored in the soil, and the actual ET is
less than the potential ET. This leaves a moisture
During rainy months there may be a moisture
surplus. This is equal to the precipitation that remains
after all potential ET has taken place and the soil
moisture retention has been restored to full capacity
(about 4 inches per foot in the Tampa area). Each
month when there is a moisture surplus, about half of
the accumulated excess water leaves the area as
It is easy to see that evapotranspiration takes a
heavy toll on precipitation, and the "leftovers" must
be carefully managed. Although drainage is essential
to optimum land use in many locations within the
Tampa area, the consequences of drought can be
lessened by retaining as much excess water in the area
as is feasible.
MAXIMUM, MINIMUM, AND MEAN MONTHLY PRECIPITATION, 1952- 1971
WATER BUDGET-TAMPA, FL., 1971
(methodology from Thornwaite & Mather, 1957)
J F M A M J J A S O N D TOTAL
.86 4.25 .54 1.80 4.09 2.54 7.74 7.46 10.16 4.70 1.40 .79 46.33
.99 1.44 1.41 2.63 4.47 6.02 6.45 6.18 5.07 4.28 1.97 2.21 43.12
1.34 2.42 4.33 3.92 6.45 6.18 5.07 4.28 1.94 1.86 40.22
0 0 .07 .21 .14 2.10
0 0 0 0 .03 .35 2.90
0 0 0 0 0 1.28 5.09 .42 0 0 9.47
I- - I:. -I I I T I- i T I .
- '.l I F NFALL
On one hand, the Tampa area is facing
ever-increasing demands for water, which are difficult
to meet with present supply sources...
A critical need exists to retain water on or
below the land surface.
On the other hand, many acres of valuable land are
flood prone and many additional acres are swampy
and unusable throughout most of the year...
A critical need exists to dispose of, or provide
facilities for the disposal of excess water.
The polarity of these problems provides the
greatest challenge to water management efforts.
Ideally, projects which deal with one problem can
be planned so as not to intensify the other; or water
management can be directed toward alleviating, in
part, both problems simultaneously.
Water management projects in the Tampa area are
currently underway by the U. S. Army Corps of
Engineers and the Soil Conservation Service.
UPPER TAMPA BAY WATERSHED
Soil Conservation Service
The watershed includes about 103 square miles in
which the two principal problems are flood damage
and drainage. The objectives of the SCS watershed
project are 1) to protect improved pasturelands,
citrus groves and other agricultural developments
from flood water damage (2) to provide drainage
outlets, and 3) to conserve water during the dry
..-----DIRECTION OF SURFACE FLOW
-----DIRECTION OF GROUND WATER FLOW
These objectives will be accomplished by land
treatment measures, channel construction and
improvement and installation of channel control
The average annual cost of the project ($160,000)
compared to the average annual benefits ($212,340)
places the benefit: cost ratio at 1.33 to 1.
The main objective 6f SCS is to improve
agricultural land, however, when lowlying areas are
drained, they become suitable for other land uses
which may have higher economic priority.
Consequently, as land values increase the ownership
and use of the land may gradually change.
Although SCS proposes to retain much of the
drainage and flood water, evapotranspiration losses
will be high, as all retention areas will be above
ground. If the excess water could be rapidly
recharged to the Floridan aquifer, more could be
conserved and the raised potentiometric surface
would reduce the threat of salt water encroachment.
(One of the SCS structures can be seen in the soil
portion of this study.)
FOUR RIVER BASINS PROJECT
U. S. Army Corps of Engineers
The objective of the total project is to deal with
the following items: flood control, major drainage,
navigation, recreational boating, water conservation,
pollution abatement, and salt water intrusion. Several
works of improvements are slated for the
Hillsborough River. Of special importance to the
Tampa area are the lower Hillsborough River
"Detention Area" (discussed previously) and the
Tampa Bypass Canal.
The Canal, when completed, will lead south from
the Lower Hillsborough Reservoir and pass east of
urban Tampa. During time of flood, it will divert
water from the Hillsborough River directly to the
bay. It is designed to give urban Tampa maximum
protection from floods including one so severe, its
likelihood of occurrence is once in about 200 years.
The benefit: cost ratio of the entire Four River
Basins project is estimated at about 1.5 to 1.
Sections of the Canal have been excavated below
the top of the Floridan aquifer and below the level of
the potentiometric surface. Here, newly made springs
are discharging into the canal and the potentiometric
surface is being lowered. It is hoped that an adequate
number of control structures will be installed to raise
the water levels in the Canal and thereby prevent a
large decline in the potentiometric surface, excessive
drainage from the aquifer, and salt water
encroachment. (A view of the Canal can be seen in
the Geology section of this study.)
A variety of chemical and biological constituents
are present in water sources in varying amounts, and
the quality of any water sample reflects many factors,
1) source of the sample
2) season during which the sample was taken
3) time of sampling
4) specific location and depth of the sample
5) nature of soils, rocks and vegetation that the
water has contacted
6) kind and amount of matter that has been
introduced to the water source by man.
Water quality standards have been established for
public water supply, shellfish harvesting, recreation,
agriculture, industry, navigation and utility. In
addition, quality standards have been set for specific
water uses such as production of carbonated
beverages, pulp, canned foods, etc. These standards
necessitate the following considerations in planning:
-- is the existing quality of the available water
source suitable for a given use, or will extensive
treatment be necessary?
Since all water "used" is actually "borrowed" and
will eventually be returned to the environment in
some form, a second consideration is important:
-- will the use add detrimental constituents to
the water in such quantity that treatment will
be necessary before the water can be returned
to the environment?
Discharge of noxious liquid effluents is only one
means of fowling a water body. Alteration of the land
surface or landscape may also have detrimental
effects on water quality. For example, removing
vegetation from a construction site may accelerate
erosion and increase turbidity in a nearby stream or
Detriment to the water resources may not be
readily evident after a project has been completed,
but it may be avoided if the possibility is considered
during the planning phase of the project.
SOURCE & SIGNIFICANCE OF CHEMICAL CONSTITUENTS IN WATER
Constituent or property
Bicarbonate (HCO3) and Car-
Calcium (Ca) and Magnesium (Mg)'
Dissolved solids (TDS)
Sodium (Na) & Potassium (k)
Specific conductance (Kx 106)
Source or Cause
Produced by reaction of atmospheric CO2 with water.
Dissolved from carbonate rocks such as limestone and
Dissolved from most soils and rocks, especially limestone,
dolomite, and gypsum. Magnesium is present in large
quantities in seawater.
Dissolved from rocks and soils. Present in sewage and
abundant in ancient, and industrial brines and seawater.
Chief mineral constituents dissolved from rocks and soils.
Dissolved in small quantities from most rocks and soils.
Enters many water from fluoridation of municipal supplies.
Decaying organic matter, sewage, fertilizers, and nitrates in
Dissolved from many rocks and soils. Some from fertilizers,
detergents, domestic and industrial wastes.
Dissolved from most rocks and soils, usually in small amounts
from 1-30 mg/I.
Dissolved from most rocks and soils. Found in ancient brines,
seawater, industrial brines, and sewage.
Measure of the'ability of water to conduct electrical current.
Dissolved from rocks and soils containing gypsum, iron
sulfides, and other sulfur compounds. Usually present in
sewage, mine waters and some industrial waters.
Significance. Maximum tolerable concentration for public
water supply is shown in parentheses.
HCO3 and CO3 produce alkalinity. In combination with
calcium and magnesium, cause carbonate hardness.
Cause most of the hardness and scaleforming properties of
water; consumes soap.
About 300 mg/I in combination with sodium gives salty taste
to water. Increases the corrosiveness of water. (250 mg/I).
Water containing more than 1,000 mg/1 of dissolved solids are
unsuitable for many purposes (500 mg/1).
Fluoride in drinking water can reduce tooth decay but may
cause mottling of teeth depending on concentration and
other factors (1.4 to 1.6 mg/l depending on air temperature).
Concentrations much greater than the local average may
suggest pollution. Nitrate encourages growth of algae and
other organisms which produce undesirable tastes and odors.
Phosphates stimulate the growth of algae. Excessive amounts
may indicate pollution from phosphate mining or domestic
Forms hard scale in pipes and boilers. Inhibits deterioration
of zeolite-type water softeners.
Large amounts, in combination with chloride, give a salty
taste. High sodium content may limit the use of water for
Specific conductance is directly proportional to dissolved
mineral content of water. Can also be related to individual
constituents in water.
Sulfate in water containing calcium forms hard scale in
steam boilers. In large amounts, sulfate in combination with
other ions gives bitter taste to water (250 mg/l).
= 250 mr9/
WATER QUALITY IN THE TAMPA AREA SHOWING
RELATIVE PROPORTIONS OF TOTAL DISSOLVED
SOLIDS AND CHEMICAL CONSTITUENTS OF
TOTAL DISSOLVED SOLIDS.
(Data from: U.S.G.S. Provisional records)
SODIUM PLUS POTASSIUM (Na + K)
CHLORIDE, FLUORIDE & NITRATE
(CI, F and NO3)
Modified: M. E. Beard, 1969, The Florida District Water Quality Laboratory:
The Tampa area is dotted with numerous lakes
which are especially abundant north of the city (see
map). Here, lakes are concentrated on a low sandy
ridge which is 20 to 40 feet higher than adjacent
poorly drained swamplands.
Some lakes occupy depressions that intersect the
shallow water table. Water levels in these lakes
respond to changes in water table elevation. Other
lakes occupy partly filled sinkholes or cavities
connected to the Floridan artesian aquifer, and
fluctuate with the potentiometric surface. A third
lake type is found in depressions lined with relatively
impermeable material perched above the water table.
Although water levels in all lakes are affected by
rainfall and evaporation, perched lakes depend almost
entirely on rainfall to maintain their levels. It is
doubtful that perched lakes in the Tampa area would
have any permanence, as such lakes in the Tampa
climate would soon be filled with vegetation.
Underground movement of water to or from a lake
depends on the relationship between lake level,
water-table level, potentiometric surface, and the
nature of the deposits underlying the lake. J. W.
Stewart (1968, p. 118) has found that the decline in
levels of some lakes near the well fields in northwest
Hillsborough County was in part due to the
cumulative effects of well pumpage. In order to
prevent large fluctuation in water level, control
structures have been installed at many lakes in the
LAKE LEVEL CONTROLLED BY:
-SOUTHWEST FLORIDA WATER C
I MANAGEMENT DISTRICT STRUCTURE
*HILLSBOROUGH COUNTY STRUCTU
0 I 2 3 4 MILES
DISTRIBUTION OF LAKES IN THE TAMPA AREA
(INFORMATION FROM S.W. FLA.WATER MANAGEMENT DISTRICT)
; Frto P ----------------
White Trot j
--....---- ---- I
HYDROGRAPHS OF SELECTED LAKES IN THE TAMPA AREA
The chemical quality of lake water is an important
factor in the continued use of lakes in the area.
Although the quality of lake water is generally good,
the total dissolved solids in several of the larger, more
urbanized lakes in the area are increasing with time.
Conductance and turbidity of several local lakes are
shown in the graph.
A decrease in the quality of lake water may reflect
either the direct addition of contaminants to the lake
water such as by surface drainage or indirect addition
by seepage. Lands with high animal populations,
septic tank fields, or receiving high pesticide
applications may indirectly contribute contaminants
to a nearby lake.
Eutrophication is another factor which threatens
lakes. This is the enrichment of water with nutrients
that promote excessive plant and animal growth.
Eutrophication accompanies the natural aging process
of a lake, but may be greatly hastened by the
activities of man. Study is essential to determine
which lakes are under accelerated enrichment before
any corrective measures can be employed.
During the developments of subdivisions, dredging
of lake bottoms is sometimes undertaken to increase
the size or depth of a lake and provide fill material to
adjacent property. Such projects have the potential to
disturb the ecology of the lake basin, change the
drainage area, remove impermeable material from the
lake bottom with consequent altering of lake level
characteristics, and render the lake highly turbid.
Extremely fine particles suspended in lake water may
not settle for many years.
In some areas, new man-made lakes have been
created. It is clear that a thorough investigation of the
geology and hydrology of the area must precede such
a project. With careful planning, some borrow pits
may be reclaimed and converted to lakes bordered by
Lakes in the Tampa area are utilized largely for
recreation and residential focal points. Property
values usually increase with proximity to a lake.
Continued recreational and residential benefits hinge
on maintaining adequate chemical quality, and
reasonable water level fluctuations. Some range of
fluctuation in lake level is conducive to the health of
Some of the potential lake problems which should
be considered in developing and managing lakes and
adjoining property are:
1) lakefront flooding
2) abnormal recessions in lake levels
3) sedimentation caused by stripping nearby
terrain (a special threat during the
4) contamination from:
a) septic tanks
b) outboard motor oil
c) storm runoff from urban areas
d) runoff from agricultural or
A lake planning and management model is
presented on this page.
Influent Tributary Streams n I_
-- -- ;
Runoff-Overland Flow and
Interflow i I
Runoff--Storm Drainage System 0
Discharge to Streams
Treatment Cost of
S system Water Quality
From: U.S.G.S.Circular 601-G, Real Estate Lakes,D.A.Rickert and A.M.Spieker
SCHEMATIC DIAGRAM OF A BASIC LAKE PLANNING AND MANAGEMENT MODEL.
Typical circular collapse structure.
(photograph by J.W. Stewart)
"To improve lake quality three major
things must be accomplished:
1. The nutrients must be reduced in the
lake and future sources of input reduced or
2. A significant zone of rooted aquatic
vegetation must be maintained.
3. The lake must be allowed to fluctuate
in a manner similar to the historical natural
fluctuation of the lake."
Southwest Florida Water Management
District Hydroscope, Vol. 3, No. 11.
Shoreline of Lake Thonotosassa (photo by R.C. Reichenbaugh)
WATER QUALITY AT SELECTED LAKES, 1970 AND 1971
TURBIDITY SPECIFIC CONDUCTANCE
JACKSON TURBIDITY UNITS
(FROM USGS PROVISIONAL RECORDS)
Excluding the Hillsborough River, which will be
treated separately, there are four major streams
within the Tampa area which discharge into Tampa
Bay. Streamflow is highly variable seasonally as well
as annually due to climatological conditions.
Water in the four streams is generally not of the
highest quality because of the addition of urban
wastes to streams within the Tampa area and
contamination from upstream sources which may be
outside the County. The ultimate recipient for all
streamflow from the area, Tampa Bay, receives
328,400 pounds of suspended solids per year from
sewage treatment plants alone. Some important
points, regarding streams, that should be land use
planning considerations include:
-- Any development which alters the
topography will likely alter the drainage
pattern in the area.
Any emplacement of contaminants in a
stream may endanger the downstream uses of
-- The lower the flow in a stream, the greater
the chances for salty bay water to move
Two consequences of the movement of bay water
inland during low flow are: mineralization of the
stream itself, and seepage of brackish water into the
Competent and effective drainage basin
management is mandatory if the effects of drought,
flood and pollution are to be minimized and stream
channel aesthetics maintained.
Land use planning for riverfront areas must be,
prudent. An assessment should be made of present
riverfront land use, and existing physical, chemical,
and biological conditions of the stream. In addition,
an order of priorities (or a downstream order) for use
of the water and waterfront lands should be
Stream channel segments may be designated as:
--sites for historic monuments or archaeological sites,
--sites for scenic or aesthetic natural areas,
--sites for water supply plants, dams, bridges, canals,
--low or high density residential sites;
' SWEETWATER CREEK
1961 62 63 64 65 66 67 68 69 70
MEAN STREAMFLOW AT GAGING STATIONS 1/61 9/70
Period of Record
Flow at Mouth2
Maximum -.. Minimum Flow
CHEMICAL QUALITY3 (Samples taken at gage)
- ....... .,
F .. ..: W .'
80 7.6 25 4/26/71
17 7.9 0.21 5/22/70
23 7.3 0.13 5/13/71
24 6.6 0.94 5/9/70
Gaging station locations shown on may on preceding page.
Discharge at gage times basin factor (ratio of total drainage area to area
above gage) plus any springflow downstream from gage
Pollution Loads discharged
To Tampa Bay (Ibs/day)
Date Sewage Plants
Sampled Discharging to Stream
NH4 + NO2
Discharge from treatment plants (Ibs./days)
BOD SUSPENDED SOLIDS
4 385 580
3From U.S.G.S. provisional water quality data
4Residue at 180 C
5 Orthophosphates as PO4
_ ~ ~ __I
4 4i, ...
.. . ..
The Hillsborough River rises in the Green Swamp
area south of the Withlacoochee River. Crystal
Springs, Sulphur Springs and numerous small springs
feed the river. The channel is about 54 miles long and
flows through Polk, Pasco and Hillsborough Counties.
Tampa has acquired the majority of its water
supply from the Hillsborough River since the mid
twenties. The water treatment plant, located at the
dam near twenty-second Street, has a capacity of 60
million gallons a day (mgd). The "firm flow" of the
river is estimated to be 50 mgd. During 1971,
pumpage averaged 49 mgd (see figure 1).
In 1964, the Tampa water supply was augmented
by flow from Sulphur Springs. During periods of low
flow in the river, 20 mgd have been diverted from the
Spring to the Reservoir. Currently, the firm available
supply of the Hillsborough Reservoir does not meet
the water needs of the City, and plans for
development of well fields are being implemented.
The quality of water from the Hillsborough River
is not ideal. High values are obtained for turbidity,
settleable solids, color, odor, and taste. Treatment by
the city water plant includes flocculation,
sedimentation, filtration, chlorination, algae control,
coagulation, stabilization, clarification, pH control,
and taste and odor control.
A notable problem in water quality is the presence
of a disturbing number of coliform bacteria1 (figure
2). Only one of 13 samples taken from the swimming
area of the Hillsborough River State Park between
January 14 and July 27, 1971 by the Hillsborough
County Health Department was found to have less
than 1000 bacteria per 100 milliliters (ml) (the upper
limit for public water supply, according to state law).
2400 bacteria per 100 ml were found in water
samples collected from the stream from the dam
upstream to the Polk County line. The effluent of dt
least six sewage treatment plants finds its way to the
Hillsborough River--four of these plants are in Polk
Another problem is the presence of water
hyacinths, which at times cover Tamps's entire water
supply reservoir. Hyacinths are treated with a
chemical herbicide (2-4 D) and sink to the bottom of
the Reservoir or are discharged downstream. The
hyacinths are a hindrance to recreational uses of the
river. Also when they are discharged to Tampa Bay
and decompose, each acre of hyacinths can
contribute 200 pounds of nitrogen and 26 pounds of
phosphate (Florida State Board of Health. 19fiB.
tSource-intestinal tract of warm blooded animals;
significance-general indicator of pollution.
Total drainage basin area
Average discharge at gage/period of record
Estimated average flow at mouth
Total dissolved solids (mg/I)
Sewage plants discharging to stream
POLLUTIONAL LOADS discharged TO BAY
Total filterable residue
NH4 + NO2 + N03
690 square miles
*428 mgd/32 years
*none/ 11-30 to 12-2-45
(Data from U.S.G.S. water quality records)
6 (4 in Polk County)
*these figures do not include water diverted for use by the City of Tampa
DISCHARGE (MGD) I
FIG. I DISCHARGE OF HILLSBOROUGH RIVER E PUMPAGE FROM
RIVER BY CITY OF TAMPA WATER DEPARTMENT.
FIGURE 2. COLIFORM CONTENT AT PLANT INTAKE CITY WATER WORKS AT HILLSBOROUGH RIVER DAM
Much of the land adjacent to the Hillsborough
River is being acquired for construction of the Lower
Hillsborough River Flood Detention area in
Hillsborough County and the Upper Hillsborough
River Flood Detention area in Pasco and Polk
Counties. These areas will be set aside for temporarily
detaining flood waters during extreme high flow
The multi-use concept will be employed in the
Lower Hillsborough River Detention area. Much of
the area is still in a wilderness state and lends itself to
recreation and conservation. Exclusive of the primary
purposes of the reservoir (prevention of flood damage
and improvement of ground water levels), land-use
plans for the reservoir area include:
1) development of a well field in the western
2) establishment of a high intensity day use
recreation area to be leased to local agencies,
The University of South Florida, and
3) incorporation of a portion of the reservoir in
the existing program of Hillsborough River
4) leasing of lands to the Florida Game and
Fresh Water Fish Commission for
management purposes and limited hunting.
In addition, over seventeen miles of the river
channel in Hillsborough and Pasco Counties has bedn
proposed for designation as a scenic river and canoe
trail by the Florida Division of Recreation and Parks.
This means that the natural environment of this
segment of the river will be preserved for public
The Hillsborough River is a tri-county resource.
Regional planning is obviously the basis for successful
maintenance and management of the river channel.
PARKIS SUPENDD'TEM ORAI
PENDNG JINT EST Y TH
_-w 0NO ULCHATAN
DIVSIN O RCRETI(Ak,?PA
AMPA LOWER HILLSBOROUGH
RESERVOIR-WELL FIELD -
STATE OWNED PARKLANDS
HIGH INTENSITY DAY USE AREA
PROPERTY TO BE INCORPORATED IN
HILLSBOROUGH RIVER STATE PARK
I- WILDLIFE MANAGEMENT and
SLake I CONTROLLED HUNTING
LOWER HILLSBOROUGH RIVER RESERVOIR
Sou e S.W.Flordo ManagementDistrict
SCENES AT HILLSBOROUGH RIVER STATE PARK
The sandy surface deposits in Hillsborough County
generally contain water. The upper surface of the
saturated zone is the water table. Water table
contours generally follow topographic contours with
the water surface lying a few feet below land surface.
The level of the water table fluctuates primarily in
response to rainfall, which is the principal source of
recharge to the shallow aquifer.
Discharge of water from the aquifer is by seepage
into lakes and streams, drainage from canals and
ditches, evapotranspiration, pumpage from wells, and
natural drainage from springs.
In some places, the water-table aquifer is
hydraulically connected to the underlying artesian
aquifer. The primary uses of the shallow aquifer are:
1) as a source of recharge to the Floridan
2) as a source of water for lawn irrigation.
Wells can be driven or drilled into the water table
aquifer easily and inexpensively, but because the
water produced is small in quantity and of poor
quality, it is not useful as a source of public supply.
Since the water table lies so close to land surface, the
shallow aquifer is suspectible to pollution.
Pollution of the shallow aquifer should be carefully
avoided in areas where it rapidly recharges the
Floridan aquifer, perhaps our most valuable water
--I 0-5' I
O 10' 5' TA 1MPA
DEPTH BELOW LAND SURFACE,
IN FEET,OF SHALLOW WATER TABLE
(Stewart and Hanan, Map Series 39,1970)
0 1 2 3 4MILES
WAT -.-.-.. .."""- -- : ... ... ..- -:-:- --.":::""
-....... sA- ND :-. - REC H A RG E -
..-..LA-FL'O-RLDAN AQUIFER ----
... -- --_ ------_-- -- . . ... ." ".".". ." ." ." ".".".". . " "."."." " "."-;- -"-"".".
The type and abundance of native vegetation
present in an area is in part dependent on the position
of the water table with respect to land surface.
Where the water table is above land surface, lakes
or swamps occur. Swamps, cypress domes or
bayheads represent a distinct ecosystem in which the
flora and fauna are specifically adapted to the
environment. Development in low-lying wetlands is
preceded by drainage, filling, or both.
Since the swampland biota is dependent on the
presence of excessive water, drainage or filling results
in a relatively barren landscape.
Another limitation of swamps for development is
the character of the subsurface material. Many
swamps are underlain by thick organic or peaty
deposits which form unstable foundation conditions
for many types of construction. In addition,
low-lying areas are generally flood prone.
Despite the limiting factors, many swamplands
have been successfully developed for a variety of land
uses. Prior to developing swamplands, the potential
destruction of a unique habitat should be considered.
WATER LEVEL IN WATER TABLE WELL NEAR
TAMPA, AND ACCUMULATED PRECIPITATION
MINUS ACCUMULATED EVAPOTRANSPIRATION
J FM A M J
J A S O ND
'.r '. ,y
I.? 7* r
-' ~aIv'~ Li, Vd'4,.L --
Unique swampland biota (photo by J. W. Stewart)
A flourishing swamp (photo by J. W. Stewart)
I j 1
The Floridan aquifer is the principle source of
ground water in the state. It includes the Lake City,
Avon Park and Ocala Limestones (Eocene age),
Suwannee Limestone (Oligocene), Tampa limestone
and parts of the Hawthorn Formation (Miocene). It is
exposed at the surface in some areas and underlies
several hundred feet of sediments in others.
In the Tampa area, the top of the Tampa
limestone can be considered the top of the Floridan
aquifer. The aquifer is artesian, and in some places
wells that penetrate it flow. An aquifer is artesian
when it is confined by an impermeable layer and the
water in the aquifer is under sufficient hydrostatic
pressure to cause it to rise above the base of the
confining bed in wells.
The level to which water will rise in wells
penetrating the artesian aquifer is called the
potentiometric surface. When the potentiometric
surface is above land surface, the well is said to be
Water in the Floridan aquifer moves into
Hillsborough County from adjacent counties and
most fresh water discharge from the aquifer occurs
inland of Tampa Bay. Currently, the Floridan aquifer
produces a large quantity of good quality water from
wells in the Tampa area, however, decline in water
quality and/or severe reduction of water stored in the
aquifer can result from improper land use or
Recharge or "replenishment" of water to the
aquifer takes place where the confining layer is thin
or absent and rain water can infiltrate permeable
surficial deposits and percolate into the aquifer itself.
Recharge occurs also as leakage through the confining
layer wherever the altitude of the water table exceeds
the altitude of the potentiometric surface of the
Floridan aquifer. Recharge areas should be identified
and land maintained as "open space". In addition,
recharge in these areas can be accelerated by artificial
means. When development occurs in recharge areas,
the wastes associated with urbanization have ready
access to the aquifer and can damage water quality.
Likewise, pavement (the ever-present foundation of
urbanization) prevents water from infiltrating the soil
and greatly reduces the recharge potential of an area.
Recharge can also take place through sinkholes
that breach the confining layer. Great damage to the
quality of water in the aquifer can result when
sinkholes are used as dumps or waste basins.
Another threat to the aquifer in any coastal area is
salt-water encroachment. At depth saline water
underlies the fresh water in the aquifer. Theoretically,
the depth below sea level to the top of this salt water
is forty times the height of the potentiometric surface
above sea level. Or, for every foot that the
potentiometric surface is lowered, salt water moves
forty feet upward in the aquifer.
During the twenties, public supply wells for the
City of Tampa were abandoned due to ever increasing
salinity in the water. This is the result of drilling wells
too close to the coast, too deep, or overpumping
Salt-water encroachment can also take place when
canals are dredged inland from the coast. If the
aquifer is exposed by the excavation, the
potentiometric surface would be lowered as fresh
water was drained to the ocean. During periods of
low water levels and high tides, salt water inl the
canals can move inland and contaminate the aquifer.
Construction of dams or water level control
structures near the coast can reduce potential salt
water encroachment in such canals by maintaining a
higher fresh water level.
LAND SURFACE -
-- MEANSEA LEVELn
SALT WATER ENCROACHMENT
Water table springs generally occur where the
permeable material in the water table is exposed or
crops out in a ditch or along the side of a steeply
sloping bank. Artesian springs are found where the
limestone aquifer lies at or near land surface and the
potentiometric surface is higher than land surface.
There are five large springs in the Tampa area and
these have been studied by the U. S. Geological
Survey. In addition, there are innumerable small
springs in the area that have been flowing for years.
Springs can be used to supplement water supply
and are a valuable asset to recreation areas. Continued
use of springs for these purposes is dependent on
maintenance of water quality through wise
management of recharge areas which supply the
Scenic Lithia Springs, a popular recreation area.
Wells and a storage tank in a northwest Hillsborough County well field. These wells pump
large amounts of potable water from the Floridan aquifer.
Water in Hillsborough County is mainly used for
irrigation, industry, and public supply. In 1970,
about 69 mgd was used for irrigation and 56 mgd for
industry. Most of this water was self-supplied. Twelve
of the major public supply systems are shown on
figure 1. Their combined pumpage for 1971 (or 1970,
as indicated on the map) was 33,933 million gallons
or 93 mgd. About a third of this water was removed
from Northwest Hillsborough County for use in
There is a vast quantity of fresh water within the
Tampa Bay region, however, only a portion of it can
be withdrawn from the hydrologic system without
creating serious environmental repercussions
(declining lake levels, parched vegetation, etc.)
G. G. Parker (1972) states that "If we can capture
for our consumptive use more than one-third of
runoff, we will be fortunate indeed." For the Tampa
Bay region (Hillsborough, Pinellas, Pasco, and
Manatee counties), Parker estimates one-third of the
runoff to be on the order of 254 billion gallons per
year or. 695.4 mgd. Projected water needs for the
Tampa Bay region are illustrated on this page. The
figures are based on population projections in
"Florida Land and Water Resources, Southwest
Florida, 1966", and the assumption that 300 and 500
gpcd represent reasonable minimum and maximum
figures for regional needs. Although the picture
apparently looks grim (interpolation indicates that
water demand will equal water supply in 1973 at the
500 gpcd rate of withdrawal or 1987 at the 300 gpcd
rate), two factors should be borne in mind as the
illustration is examined: 1) The figures are based on
the assumption that the water withdrawn is
permanently consumed. They do not take into
account the fact that much water that is withdrawn is
re-cycled or at some time returned to the hydrologic
cycle and therefore, much is not permanently
consumed. 2) As time goes by, greater sophistication
in water management will improve the outlook.
A water use projection for Hillsborough County is
also shown on this page. This graph applies Parker's
per capital water use rates (300 and 500 gallons/day)
to the population projections for Hillsborough
County published by the Hillsborough County
Planning Commission in April, 1972.
-*j Ci r^ i
* I '..
Water stage recorder at Hillsborough River dam. (photo by W. M. Woodham)
ri i i
From GG Parker,SWFWMD
1970 1975 1980 1985 1990
FIGURE 3. WATER USE PROJECTIONS -
O AT 300 GALLONS PER CAPITAL PER DAY (GPCD)
O- AT 500 GPCD
The water problems of Hillsborough County have
been widely publicized. Much of the problem can be
attributed to the inadequacy of the facilities rather
than the sources.
Governmental agencies and private consulting firms
have submitted innumerable recommendations for
remedial actions to alleviate the City's and County's
water problems. Some of the measures suggested
1) establish flood retention reservoirs
2) develop the Lower Hillsborough River
Reservoir well field immediately
3) establish control structures on dams and
streams to reduce salt-water encroachment
4) supplement the water supply by pumping
water from sinkholes
5) investigate the possibility of acquiring
springs in neighboring counties
6) create recharge facilities for rapid replen-
ishment of water to the aquifer
7) reduce waste of water by plugging
abandoned flowing wells, and encouraging
re-use of water by industry and agriculture
8) treat and re-cycle waste waters
Many of these plans are now being implemented.
The seriousness of the water situation and the
suggested courses of action highlight the role that
hydrology must play in land use planning.
Hillsborough River dam. (photo by W. M. Woodham)
WATER USE FACTS
Number of industries in Hillsborough
Number of electrical power plants' 3
Population served by public supply2 370,000
Population served by ground water2 65,000
Population served by surface water2 305,000
Number of acres irrigated2 47,000
Saline water (self-supplied)2
Used by industry 86
Used for thermoelectric power 1899
Cost of water1
From Hillsborough River $92.74/million gallons
From Lower Hillsborough
Reservoir Well Field $31.71/million gallons
SI .) IN HI
"Those of us who work in the water management
field know that some of the multimillion dollar
public works projects that we are now constructing
could have been prevented if the citizens had simply
not been allowed to construct their houses, businesses
and developments on land that is often flooded by
the stream, creek, river or lake that it abuts. Yet, day
after day, we see more and more marginal and
submarginal land being developed and sold -- often
times to unwary buyers -- who after the first normal
rainy season or two, come to us and demand flood
control. We believe that much of their anquish and
heartache -- and lots of public works money -- could
be saved if the construction process included a
requirement for full knowledge of the historic or
predictable water conditions at that site so the
proposed construction could be accommodated to
the conditions, or be prevented altogether."
Southwest Florida WaterManagement District
Everyone is aware of the loss of life and property
often associated with floods, but unfortunately, not
everyone is aware of the flooding potential of the
area in which they reside.
Many flood prone areas have already been
developed, and others are in the path of urban
expansion. Now is the time to strengthen controls on
flood prone land and provide 1) a zoning
classification which would prevent development in
these areas, and/or 2) guidelines for construction in
flood prone areas where development is allowed.
Additional drainage projects could provide even
more widespread flood protection, but such projects
are costly and may tend to diminish regional water
Results of Hurricane Agnes, June, 1972. (photo by Bill Wood)
[ -c_----,-- --. ...
... .. . :.: .
.-..., -,- -
._"_~ ; ;.
- -- - .
: ,i ""-. -'-
sC. ~b L_1_",, ~. .F~-l
1000 0 1000 2000 3000 4000 5000 6000 7000 FEET
The large map presented here was constructed by compiling and reducing all
the 1:24000 scale flood prone quadrangle maps of the Tampa area which were
completed by the U.S. Geological Survey. The detail above shows a small area at
the actual scale of the 1:24000 maps. The following explanation appears at the
base of each quadrangle map of flood-prone areas, and is quoted verbatim:
The purpose of the flood-prone area maps is to show to administrators, planners, and
engineers concerned with future land developments those areas that are occasionally
flooded. The U.S. Geological Survey was requested by the 89th Congress to prepare these
maps as expressed in House Document 465. The flood-prone areas have been delineated
by the Geological Survey on the basis of readily available information.
Flood-prone area maps were delineated for those areas that meet the following criteria:
(1) Urban areas where the upstream drainage area exceeds 25 square miles, (2) rural areas
in humid regions where the upstream drainage area exceeds 100 square miles, and (3) rural
areas in semiarid regions where the upstream drainage area exceeds 250 square miles.
This map indicates only areas that may be occasionally flooded, and provides no infor-
mation on the frequency, depth, duration, and other details of flooding. Larger areas than
those shown on the map may be inundated by less frequent floods.
Flood-hazard reports provide the detailed flood information that is needed for economic
studies, for formulating zoning regulations, and for setting design criteria to minimize
future flood losses. When detailed information, such as that contained in the flood-hazard
reports, is required, contact the U.S. Army, Corps of Engineers; the U.S. Geological Survey;
or the Tennessee Valley Authority in the areas of their jurisdiction.
. . .
- - -
______________ ..-, - -.
Depending on the depth, temperature, and
circulation of the water, varying assemblages of
organisms flourished and their skeletal remains make
up much of the sedimentary sequence. The physical
characteristics of the rocks and the fossils they
contain enable the geologist to reconstruct a picture
of the ancient geography and environment.
During Paleocene and Eocene time, the Tampa area
was covered by open ocean in which layers of
limestone were deposited. Intermittently, the seas
regressed and the limestone was subjected to
weathering. As sea level fluctuated, the local
environment changed and limestones with slightly
different physical characteristics and dissimilar fossils
were deposited in succession. At the close of Eocene
time, the seas retreated from the Tampa area and did
not return until later in Oligocene time.
The nature of local late Oligocene sediments
indicates that they were laid down in a warm, quiet,
shallow sea in which mollusks and micro-organisms
flourished. The limestones are relatively pure and of
economic value in those parts of the state where they
are available to surface mining.
The geology of Florida is reflected in the
topography of the state, the nature and occurrence of
water resources, the character of soils, and the type
and extent of valuable minerals. As all of these are
important factors in land use planning, the planner
should be knowledgeable about what lies blow the
Beneath the Tampa area, there are several thousand
feet of carbonate rocks (chiefly limestones) which
were deposited during Cenozoic time. These rocks
overlie sandstones, shales and igneous rocks of
Mesozoic and Paleozoic age.
The thick carbonate sediments were deposited in
the warm, shallow seas that covered all of peninsular
Florida at one time or another during the Cenozoic
era. Accumulation of these sediments was
accompanied by subsidence of the land surface with
numerous transgressions and regressions of the sea.
When sea level was low the emerged land areas were
exposed to erosion; consequently, the rock record is
-i - C -~
~- --.T-~L- .-
-r; -.-~J-L-:~ ~ ',
Photo by R.C. Reichenbaugh
From: Bulletin 29, Florida Geological Survey
-~-,- - 'are
Throughout Miocene time, more and more rocks
eroding from the highlands north of Florida were
washed southward and deposited in the Tampa area.
Due to the great distance of transport, these minerals
were abraded and broken into sand and clay size
particles. Considerable quartz sand is found in the last
consistent limestone deposit of the area. The Miocene
and Oligocene limestones of the Tampa area are
generally permeable and yield substantial quantities
of water to wells.
During late Miocene time, sand and limy,
phosphatic clays were deposited in the very shallow,
sometimes stagnant seas, estuaries and swamps of the
Tampa area. As the shoreline migrated, islands,
lagoons and lakes developed in various, locations.
Marine, fresh water and land fossils have been found
in Miocene deposits around Tampa.
Pliocene sediments similar to late Miocene
sediments, are scanty and difficult to differentiate
from late Miocene sediment in the vicinity of Tampa.
In eastern Hillsborough County, sands and clays
containing abundant phosphate nodules are presumed
to be Pliocene in age and may have been weathered
from older deposits. In Polk County, these
phosphate-bearing sediments are mined extensively.
Throughout Pleistocene time, the alternate
formation and melting of glaciers caused sea level to
move back and forth over the Tampa area and seas
washed quartz sand over Tampa and much of the
state several times. These fluctuations left behind
terraces which are still evident today and record
ancient sea level stands. The mantle of quartz sand
covering the area served as parent material of many of
the soils which later developed. In areas where the
sands are thick and pure, they are of economic value.
Well developed stream channels in Tampa, and
relict dunes on the campus of the University of South
Florida reflect the effect that wind and water had on
the sandy deposits. Gradually, a landscape with
abundant vegetation developed.
Throughout the Cenozoic history of Tampa,
deposits accumulated essentially as horizontal
blankets of sediment which dip slightly to the
southwest. This is reflected in the gently sloping land
surface, and pronounced local relief can largely be
attributed to recent fluvial processes and
underground solution activity.
GEOLOGIC TIME SCALE
ERA PERIOD EPOCH APPROXIMATE
5000 YEARS B.P. *
2 MILLION YEARS B.P.
.12 MILLION YEARS B.P.
25 MILLION YEARS B.P.
38 MILLION YEARS B.P.
.55 MILLION YEARS B.P.
65 MILLION YEARS B.P.
225 MILLION YEARS B.P.
600 MILLION YEARS B.P.
* Before Present
Tampa By-pass Canal
ARTIST'S RECONSTRUCTION OF HOW THE TAMPA
AREA MAY HAVE APPEARED DURING TERTIARY TIME
The thick carbonate rock sequence underlying the
Tampa area has been divided into lithologically
similar, mappable units or formations. These
formations are generally bounded above and below
by ancient erosion surfaces.
Formations can be mapped on the basis of rock
exposures at land surface (outcrops), and from
samples retrieved during the drilling of water wells or
An examination of the surface geology in the
Tampa area reveals that rocks of Tampa age outcrop
in several locations along the banks of the
Hillsborough River and can be seen in other stream
channels, sinkholes, roadcuts, etc. Ballast Point was
considered a classic locality for studying Tampa
sediments during the late 1800's and early 1900's,
but now the exposures are limited and inaccessible at
The Hawthorn Formation, which occurs east of
Tampa, can also be studied in a number of exposures.
Much of the Tampa area is covered by a veneer of
Pleistocene and Recent sandy deposits. In the map,
these deposits have been stripped away to reveal what
lies directly beneath them.
Because each formation has distinct physical
attributes, mapping and cross-sections of these units
provide some key to the depth and extent of
economically valuable deposits, highly productive
water bearing zones, and zones susceptible to
subsurface solution which could manifest on the land
surface as sinkholes.
(Modified from Carr and Alverson, 1959)
Florida Bureau of Geology drilling rig
Crystal River Formation (Eocene)
The Crystal River Formation is a granular, white to
tan limestone which, in part, is largely made up of
fossil fragments cemented by a calcareous matrix,
giving it the appearance of coquina rock. Due to its
porosity, some portions have been washed out and
filled with clay. Masses of chert also occur within the
The limestone was studied and named in a quarry
in Citrus County. Here, and in adjacent counties
where it lies near the surface, the formation's overall
purity and uniform texture make it economical to
mine. In the Tampa area, the Crystal River is
generally deeply buried and of no economic
importance at present.
Suwannee Limestone (Oligocene)
In general, the Suwannee Limestone is a pure, very
fossiliferous limestone of variable hardness. It
contains a minor amount of fine quartz sand
cemented among the abundant fossil fragments and
imprints. The formation was named for exposures
that occur along the Suwannee River. Much of the
Suwannee Limestone has been altered by ground
water since its deposition. This accounts for some of
the differences in texture, hardness and porosity
within the formation.
The base of the Suwannee Limestone in the Tampa
area is marked locally by clay lenses. Some core
samples from Tampa reveal the presence of peat in
varying amounts in the lower portion of the
The Suwannee, like the Crystal River Formation, is
mined for crushed stone in counties north of the
Tampa area where it occurs near the surface. In the
Tampa area, the Suwannee is a principal source of
water to many supply wells.
Tampa Stage (Miocene)
In the Tampa area, rocks of Tampa age are soft,
white, impure limestones averaging between about 40
and 160 feet in thickness. It can be seen from both
the map and cross-section that the Tampa limestone
is absent in the northeast portion of the study area.
In some localities, the upper portion of the deposit is
composed of calcareous sands and clays grading
downward into unconsolidated or loosely cemented
lime mud. Chert layers and silicified fossils are also
common to the upper portion of the deposit. In a few
locations, phosphate nodules or pebbles occur within
the Tampa limestone. The base of this unit is
frequently marked by beds of clay and clayey sand.
Although the sediments are generally not as
fossiliferous as the underlying Suwannee Limestone,
there are zones within the Tampa that are
consequently highly porous. This is because the fossil
fragments are generally coarse grained and irregularly
shaped and thus do not pack together as tightly as the
finer calcium carbonate grains. Most of the Tampa
limestone is very sandy and crumbly. Due to the sand
content of the rock and the occurrence of lenses of
clay and sand within the limestone, the formation is
not quarried for crushed stone. The Tampa limestone
is valuable, however, as a source of water and yields
large quantities to many wells in the Tampa area. The
loose cementation and high porosity of portions of
the Tampa limestone make it susceptible to
weathering and dissolution by ground and surface
waters. Many solution cavities, sinkholes and collapse
structures occur in the formation, especially where it
lies near the surface.
Hawthorn Formation (Miocene)
This formation exhibits a great variation in
composition and physical properties. In general, the
formation in the Tampa area consists of an upper
sand unit, a phosphatic clay unit, and a lower
limestone unit. These layers occur in varying
thicknesses and tend to interfinger. In most of the
Tampa area, the formation is absent, and where it
does occur, frequently only one or two of the units
are present. Maximum thickness of the formation in
Hillsborough County is about 250 feet. Fossils are
rare in Hawthorn deposits. The formation thickens to
the east and becomes a significant deposit in Polk
County, where it is overlain by the Bone Valley
Formation, which is thought to be residual material
from the weathering of the upper parts of the
Hawthorn Formation. It is this residuum that
contains the rich concentrations of phosphate so
extensively mined in Polk County.
In the Tampa area, the clays of the Hawthorn
Formation, along with clays in the upper part of the
Tampa Limestone, make up the impermeable
confining layers overlying the limestones of the
Undifferentiated Plio-Pleistocene and Recent Deposits
These deposits cover most of the Tampa area and
vary from a few inches to many feet thick. They are
predominantly fine grained quartz sands which
contain varying amounts of organic material. Some of
these deposits are of economic value and are
discussed further in the Mineral Resources section.
GEOLOGIC CROSS SECTION showing SOUTHWESTERLY DIP
OF STRATA in the TAMPA AREA
G E 0 R G I A
Sinkholes exhibit varying characteristics in the
Tampa area and are difficult to classify. There are
two basic sink hole types: 1. Collapse sinks produced
by collapse of the limestone roof above an
underground void. 2. Solution (funnel) sinks
developed slowly downward by dissolution beneath a
soil mantle without rupture of the rock in which they
Collapse sinks are normally steep sided, rocky and
abruptly descending. Formation of collapse sinks is
unpredictable and often instantaneous, thus they
constitute the greater threat to land development.
Solution sinks may be funnel-shaped depressions
broadly open upward, or pan or bowl-shaped. They
develop slowly and are usually heralded by the
formation of a radial fracture pattern in the soil or
even in concrete or asphalt overlying them. Though
their formation may not have the devastating effect
of a collapse sink, their occurrence can equally limit
Sinkholes in the Tampa area may be of either type,
or some variety and are commonly formed in an
environment with the following physical
1) occurrence of permeable limestones in
which a cavity system has been developed
through dissolution by ground water
2) these limestones are generally overlain by a
relatively thin layer of unconsolidated
3) overlying sediments are usually well drained
4) a water table higher than the potentiometric
surface of the artesian aquifer
Overlying sediments may slowly ravel or wash
downward, filling in the cavity system and resulting
in a structural sag reflected at the surface; or, the
cavity system may continually enlarge until the
cavern roofs are too thin to bear the weight of the
overburden, resulting in catastrophic collapse.
Two activities which tend to increase the
likelihood of sinkhole occurrence are dewatering the
aquifer and increasing stresses on the land surface.
When the potentiometric surface is lowered,
dewatered cavities in the limestone provide less
support to overburden layers. Similarly, the added
weight of buildings or fill material may exceed the
strength of underlying cavernous limestones.
G U L F
M E X I C 0
This large portion of the State represents the area
where the piezometric surface is at or above land
surface and/or the plastic overburden is in excess of
100 feet thick. It appears to be the least probable
area for sinkhole development.
This area is the portion of the State characterized by
stable prehistoric sinkholes, usually flat bottomed,
steep sided, both dry and containing water.
Modifications in geology and hydrology may activate
I This portion of the State is characterized by
limestones at or very near the surface. The density of
sinkholes in this area is high, however, the intensity
of surface collapse is moderate due to the lack of
overburden. Exploration by drilling and geophysical
methods for near-surface cavities can be realistically
This portion of the State has moderate overburden
overlying cavernous limestones and appreciable water
use. These areas have histories of steep-walled, wider
sinkhole collapse but require more detailed study. A
thick overburden or high water table present within
these areas lessen the probability of sinks occurring.
C E A
D A D E
Sinkholes in the Tampa area may or may not be
filled with water. Sinkhole lakes are characteristically
circular and deep. Unless sinkholes have been filled
with impermeable material, they are directly
connected to the Floridan aquifer and provide a rapid
means of recharge. Such direct recharge is not
conducive to the removal of contaminants from water
by filtration or chemical reaction. It is therefore
essential to safeguard the quality of water entering
Sinkholes in the Tampa area generally occur in a
wide northwest-southeast trending band. There is a
concentration of them in the northwest area, but
their apparent predominance here is partially due to
more detailed mapping in this section (see map).
Although existing sinkholes can be mapped,
predicting specific areas of potential collapse is
difficult. No particular pattern to the cavity system in
limestones has been discovered.
The most widely used method for detecting
sub-surface cavities is drilling bore holes. This
approach has the obvious disadvantage of producing
little data for the amount of effort expended. Other
new procedures have been used experimentally in an
attempt to identify sub-surface cavities, but the
results are not foolproof.
One method utilizes airborne remote sensing
devices. Computer processed imagery obtained from
flights over a test area reveals thermal and apparent
moisture-stressed vegetative patterns that may be
associated with sub-surface cavities.
Additional data collection and refinement of
techniques are necessary before the effectiveness of
this method can be evaluated.
Another experimental method of identifying
sub-surface cavities is gravity mapping. A gravity
meter records, on the land surface, local differences
in gravity which, after correction factors have been
applied, are directly related to differences in density
of the underlying rocks. Areas underlain by cavernous
limestones produce lower gravity readings than areas
underlain by limestones containing fewer voids.
Gravity surveying as a means of detecting subsurface
voids has certain limitations. The smaller the cavity
and the more deeply it is buried, the less detectable it
is by gravity methods. A cavity with a diameter equal
to or greater than its depth of burial is readily
detectable because the gravity anomaly is great. Small
gravity anomalies can be produced by a variety of
subsurface conditions and therefore may or may not
be indicative of small and/or deeply buried subsurface
DATA OBTAINED FROM TOPOGRAPHIC MAPS AND J.W. STEWART, 1970, MAP SERIES 39.
DATA OBTAINED FROM SOUTHWEST FLORIDA WATER MANAGEMENT DISTRICT AERIAL
PHOTOGRAPHS.1:200 SCALE WITH ONE FOOT CONTOUR INTERVALS AND J.W.STEWART,1970.MAP SERIES 39.
AREAS IN WHICH SUBSURFACE CAVITIES OR RELICT KARST FEATURES HAVE BEEN /
ENCOUNTERED IN DRILLING. Data from OROF4NO and Co. /
Victor Stringfield (U.S.G.S.) examines sinkhole
near Lake Magdalene. (photo by J.W. Stewart)
0 1 2 3 4 MILES
I 1 1 c LE
The map presented on this page shows the top of
the first consistent limestone. The data is referenced
to mean sea level, therefore the contours reflect the
actual topography of the bedrock surface. Knowledge
of this bedrock surface is important in understanding
surface features which are often genetically related to
the underlying rock.
The complexity of the contours is due, in part, to
post-depositional alteration of the rock. This could
include shifting and settling, differential compaction
of the limestone strata at some time after deposition,
erosion of the rock surface between depositional
cycles, and solution weathering of the limestone by
The contours, however, do reveal something about
ancient paleogeography. For example, the minus ten
foot contour line (shown as a bold line on the map),
can be considered an approximation of an ancient
shoreline that occurred here some million years ago
when sea level was ten feet lower than it is now, and
before surficial sands and clays were deposited. At
this time, the Tampa area had a broader estuary, a
smaller interbay peninsula and Old Tampa Bay
extended further inland. In a broad sense, the
topography of the present land surface in the Tampa
area reflects bedrock topography.
The bedrock underlying the area generally strikes
or trends in a northwest-southeast direction. The rock
surface dips gently downward toward the bay in a
southwesterly direction with a slope on the order of
0.1% or about 5 feet per mile. The dip of the beds is
perhaps better illustrated on the cross section (found
on another page in this section).
0 1 2 3 4MILES
Two of the more severe problems associated with
urbanization are proper waste disposal and adequate
water supplies during periods of water shortage.
Recent investigations indicate that in some areas
there are possibilities for simultaneous alleviation of
both problems by utilizing the technique of deep well
injection. Successful application of this technique
hinges on a good knowledge of subsurface strati-
graphy and hydrology.
The method of deep well injection involves
injecting treated wastewaters and/or storm runoff
into subsurface permeable zones that do not other-
wise lend themselves to water supply or mineral
production. Many factors, however, must be carefully
evaluated before such a project can commence.
Further, according to Garcia-Bengochea, et. al.(1973,
p. 5-6), Underground disposal of wastewater by wells
" . can be achieved successfully if five general
requirements are fulfilled. These are:
1. There is a stratum or strata (aquifer) which can
accept the waste.
2. The hydraulic and structural characteristics of
the aquifer will not be changed significantly by
the disposal of the waste.
3. The disposal of such waste will not impair the
present or future use of the water in such
4. The disposal of such waste will not impair the
present or future use of the water in adjoining
aquifer or surface-water supplies.
5. The installation is designed properly, with
consideration of the physical, chemical, and
biological characteristics of the waste and the
hydrogeological characteristics of the receiving
aquifer and confining strata."
"Present hydrological knowledge indicates that the
treated fresh water effluent should not readily mix
with the saline waters of the aquifer but would create
a large fresh water bubble in storage at the top of the
aquifer which could be partially recovered at a later
date for low quality uses (irrigation) or for further
specific treatment and reuse." (Garcia-Bengochea, et.
al., 1973, p. 4-5)
Deep well injection is being carried on in several
areas in Florida and additional sites are being
evaluated. Several sites currently under investigation
are within the geological realm of the Tampa area.
These include a site to the east of the Tampa area in
Mulberry and several sites in Pinellas County.
According to Wilson, Rosenshein and Hunn (1973,
p. 1, abstract), an injection well in Mulberry was
completed in 1972 at a chemical plant which
produces a liquid waste from phosphate processing
that has a high chloride content and high acidity (pH
generally less than 2). This effluent is injected into
several permeable zones penetrated by the well
between 4040 and 4984 feet deep. Tests performed
at the Mulberry well provided not only information
about the characteristics of the injection zones, but
also suggested additional evaluative techniques that
might be employed at other sites.
Mr. H. J. Woodard, Geologist with the Department
of Natural Resources, is supervising a pilot hole in St.
Petersburg which is a cooperative effort by the
Division of Interior Resources and the City of St.
Petersburg. The project is to study the feasibility of
injecting excess surface water into a saline aquifer and
recovering it for subsequent use.
According to Garcia-Bengochea, et. al., 1973, p.
27, the objectives of the project are to determine:
1. the characteristics of the deep underground
formation at that site;
2. the quality of the deep ground water;
3. the injection rate capacity and associated
increase in pressure;
4. ratio of the amount of fresh water that could
be subsequently recovered to the amount
5. quality of the recovered water.
According to H. J. Woodard, as of July, 1973, the
pilot hole is completed to a depth of 3500 feet. One
injection test was performed at a depth of about 850
feet, and two additional tests are slated for zones that
appear promising. One shallower, less saline zone may
be suitable for stormwater disposal, and a second
deeper zone (greater than 3000 feet deep) may be
found satisfactory to receive secondarily treated
GEOLOGY AND URBAN PLANNING
:TE iL O'R PLASTIC)
(from: R. O. Vernon, 1970, p. 4)
The deep well injection technique has the poten-
tial to provide some relief to the waste disposal and
water shortage problems of urban centers such as the
Tampa Bay area. At present, the need to continue
basic geologic and hydrologic data collection cannot
be over-emphasized. If deep, permeable zones could
be identified and mapped, and their geohydrologic
properties and stratigraphic relationships studied,
determination of the feasibility of subsurface storage
of waste in this area could be greatly facilitated.
Deep well injection studies serve to further
illustrate the integral role that geology plays in many
phases of urban planning.
DISPOSAL of TREATED WASTES
PLUG FOR WATER LEVEL MEASUREMENTS
WASTE ----- VALVE
. .. .:::. :::::::::
During 1970 mineral resources valued at slightly
more than 20 million dollars were produced from
Hillsborough County, giving it a rank of third among
all Florida counties, as shown in Table 1. The figures,
however, do not give insight into the impact on
Tampa of massive phosphate operations and the
mining of construction sands in adjacent Polk
County, nor of the quarrying of limestone in Sumter
and Hernando counties and the extraction of clay in
Citrus County. Practically every aspect of our modern
way of life depends in some way on mineral
resources. Mineral resources are necessary for building
homes, constructing and maintaining roads and
highways, manufacturing automobiles and planes, and
for producing food crops to feed the people of the
world. No one can question that our society depends
upon mineral resources. Furthermore no one can
question that mineral resources are finite; they are
exhaustible. If they are not mined where they occur,
they are lost to society.
In recent years it has become evident that mining,
especially of mineral resources near the land surface,
can result in extensive environmental damage. Air
may be polluted. Stream life may be partially or
totally destroyed. Land may be left in a state no
longer useful. However, it also has been shown that
with planning and controls, mining can take place
with minimal environmental damage. The necessity of
mining and the necessity to minimize environmental
damage and reclaim mined-out land has led some
investigators to emphasize the need for leadership in
undertaking mineral evaluation studies on large land
areas prior to development. Then, when socially
necessary mining operations have been completed,
leadership is again appropriate for reclaiming the land
mined. The need for planning is most pressing in areas
of rapid population growth.
Mineral resources in the general vicinity of Tampa
include phosphate, sand, clay, limestone, cement,
oyster shells and peat. These products will be
Value of Mineral Production in Florida for Leading Counties
Value Minerals Produced in
(Thousands) Order of Value
G EO R G I A
---- --- NASSA
I HAMLTON --i '- / F'
----- / 2 iBAKER D..V. AL
-. SUWANNEE COLUMBIA
TAYLO I UNION/ I
LAFAYETTE '- CLA
O GILCHRIST ALACHUA
DIXIE ~ PUTNAM
Polk $140,598 Phosphate rock, sand and
Dade 35,184 Cement, limestbne, sand and
1970 Hillsborough 20,041 Cement, phosphate rock, sand
and gravel, oyster shell,
Broward 11,930 Limestone, sand and gravel
Marion 2,562 Limestone, fuller's earth,
sand and gravel, phosphate
Polk 137,696 Phosphate rock, sand and
Dade 33,953 Cement, limestone, sand and
1969 Hillsborough 22,555 Cement, phosphate rock,
oyster shell, sand and
Broward 11,187 Limestone, sand and gravel
Sumter 3,741 Limestone, lime, peat
'Data from Bureau of Mines Minerals Year Books, 1969 and 1970.
A TL ANTIC
of 7\ '--. ---
CITRUS i L A K E
MEXICO ---- SUMTER
----- I L
'-- F .. .. .. ..._ .. -1
CREST OF OCALA UPLIFT 11
SSARAASOTA DE SOTO
AREAS THAT INCLUDE PEBBLE |
PHOSPHATE DEPOSITS _L .. .. .
S F ..F -HA-I OTTE
Although phosphate is used in the manufacture of
a wide variety of products, including well-known
detergents, water softeners and metal polishes, most
phosphate is used in the manufacture of fertilizers.
The importance of fertilizers in feeding the people of
the world would be difficult to exaggerate, and
Florida has long been a world leader in supplying
phosphate. It is evident, therefore, that the needs of
the world, not Florida alone, must measure the
impact of Florida's phosphate.
HIGHLANDS S LC-
-\ i ..----.
FIGURE 1. PEBBLE PHOSPHATE DEPOSITS OF FLORIDA. THE CREST OFTHEOCACALARCH-fS-
INDICATED BY A HEAVY DARK LINE. MODIFIED FROM PIRKLE ET AL.(1967, FIG. I, 238).
Location and Regional Significance of
Pebble Phosphate Deposits
By far the greatest production of phosphate rock
in Florida is of the type called "pebble phosphate."
The deposits consist of phosphate particles mixed
with varying amounts of quartz sand and clay. The
phosphate particles usually range from colloidal size
to pebbles an inch or more in diameter. Figure 1
shows locations of known pebble phosphate deposits
on the Florida peninsula. An examination of the
figure reveals that the deposits occur along the flanks
or fringes of the Ocala Uplift, an upwarped area
cresting in eastern Citrus and Levy counties along the
western side of the peninsula. Knowledge of this
relationship has been useful in exploration programs.
Some phosphate rock is produced from Hamilton
County in the northern part of the peninsula (Fig. 1),
but most of Florida's phosphate rock is mined east of
Tampa from the large area known as the "Bone
Valley District." During 1970 phosphatic sediments
produced from the Bone Valley District had a value
of approximately 150 million dollars and accounted
for almost three-fourths of our domestic needs and
one-third of the world's needs. Most of the rock in
one form or another is shipped through the port of
Tampa. In fact, phosphate is responsible for nearly 50
per cent of the tonnage entering and leaving this
important port. Obviously the mining of phosphate
rock has an enormous influence on the economy of
the Tampa area and the State of Florida (Table 2).
The Bone Valley phosphate field of central Florida
is shown on Figure 2. The northern part of the region
contains the highest grade phosphate rock and has
been mined most extensively. If mining continues it
must spread into the southern part of the area.
Production of marketable
rock (short tons)
State ad valorem taxes
Polk County ad valorem
State sales taxes
Expenditures for raw
Nature of Sediments in the Bone Valley District
Three types of sediments are encountered in the
phosphate mines (Fig. 3). From the land surface
downward these materials are: (1) loose quartz sands
and clayey sands (top soil and sand overburden),
(2) phosphate beds of the Bone Valley Formation
(leached zone and ore zone or matrix), and (3) bed-
rock (limestone) or bedclay of the Hawthorn Forma-
tion. The mixture of phosphate particles, sand and
clay of the Bone Valley Formation is the material
mined for its phosphate content. Data illustrating
various characteristics of the overburden sediments,
the phosphate beds, and the underlying bedrock or
bedclay are given in Table 3. These data are of
samples collected from a test hole drilled on the
Lakeland Ridge between the towns of Bartow and
$ 59,000,000 $ 59,061,293 $ 59,093,035 $ 68,848,000 $ 69,000,000
30,500,000* 29,300,000* 29,900,000* 33,000,000* 31,900,000*
(*Includes N.C. production-U.S. Bureau of Mines)
$ 5,215,968 $ 5996,090 $ 5,882,553 $ 5,856,154 $ 6,326,018
$ 3,619,312 $ 4,635,566 $ 4,577,014 $ 4,627,404 $ 4,583,587
$ 3,135,273 $ 3,129,152 $ 2,836,648 $ 2,385,727 $ 2,112,112
$ 30,000,000 $ 22,189,867 $ 18,227,300 $ 35,420,585 $ 56,827,650
$174,764,731 $161,192,084 $181,658,064 $175,487,087 $175,086,157
The overburden of top soil and loose to slightly
hardened quartz sand and clayey sand (Fig. 3) ranges
in thickness from a few feet to more than 50 feet
JSpls. A through H, Table 3), and typically from 5 to
25 feet. Some investigators believe these surface sands
___ P A S C 0_ t _1
H I LLS B 00 R
I MP A
s. sor. ._.MYAK.ACIT
Si r ,I\ L _ i e R "
S 5 S A R A S A 0 TA D E S 0 T 0
Sr C'H AR LOTT E
FIG.2 BONE VALLEY PHOSPHATE DISTRICT OF FLORIDA. THE
DISTRICT IS DIVIDED INTO A HIGH-GRADE NORTHERN
PART AND A LOW-GRADE SOUTHERN PART.
(Mop furnished by Mr Joe Weaver of Wayne Thomas, Inc.)
were deposited under marine conditions as seas
encroached and retreated from the area during
Pleistocene time. Other workers consider the quartz
sand blanket to represent a simple insoluble residue
accumulated on-site from the weathering of underly-
*Data furnished by the Florida Phosphate Council. Five-year comparison.
Figure 3. Typical section in central Florida Phosphate
district. Modified from Fountain and Zellers,
Fig. 2, 1972.
FLORIDA PHOSPHATE INDUSTRY*
Channel T-i., .. '..n:o Grace G" 'i' Hole
SW '.-.ri, 4. 4, T '.'.' R ..' E., i il- County, Florida
'.. ;,..* : -. ... 4 Miles West of Bartow
. face Sands and .i'. ..i ::. T l- ,; of the T.:-r,- .1,' ., District
-.. ,;- Quartz
S, '"- 7
(- -'. mesh) Soluble
in % in %
in % in %
..:. ,-, - -. and Clayey .'"
Phosphate Beds of the Bone Valley Formation:
Phosphate beds (Fig. 3) beneath the surface sands
consist of varying mixtures of phosphate particles,
quartz sand and clay (Spls. I and J, Table 3). The
phosphate particles, often referred to as phosphorite,
range in color from white or cream to dark gray or
black and assay from less than 65 per cent to as much
as 80 per cent bone phosphate of lime (BPL) or
tricalcium phosphate, Ca3 (P04)2. The unweathered
phosphate mineral is apatite, more specifically car-
bonate-fluorapatite. In the upper parts of the
phosphate beds, where the sediments are more
subject to weathering processes, much of this apatite
changes to various aluminum phosphate minerals,
partly through reactions with surrounding sediments.
This upper zone containing the aluminum phosphate
minerals is called the aluminum phosphate zone or,
locally, the leached zone (Fig. 3). Its thickness
usually is between 5 and 10 feet. During mining this
upper zone normally is stripped off and discarded as
The "matrix" or commercial zone of the phos-
phate beds (Fig. 3) occurs beneath the upper
weathered aluminum phosphate zone. Its average
district-wide composition according to Altschuler et
al. (1964, p. 25) has the following range:
Apatite (carbonate-fluorapatite) . 35-40 per cent
Clay (montmorillonite) ........ 20-25 per cent
Quartz sand and some chert ..... 25-40 per cent
This lower zone may be more than 50 feet in
thickness, but commonly is between 10 and 20 feet,
with an average for the district of approximately 15
Hawthorn Bedrock or Bedclay:
The commercial phosphate beds or matrix rests
either on bedclay or on bedrock (Fig. 3). The bedclay
is a phosphatic, impure clay, sandy clay or clayey
sand and the bedrock is a pale yellow, impure,
phosphatic limestone (Spls. K and L, Table 3).
Neither bedclay nor bedrock carries sufficient phos-
phate content to be commercial. Characteristics of
the overburden sands, the phosphate beds and the
underlying bedclay or bedrock are summarized on
Terrace sands -
Nearly pure quortz sand
( ,o b ie
phosphate .. .. -"| ii ,
some cloy but no opite
z nodule- a' F.* -
(Lower part generally
-, ", , ,-
APPROXIMATE MI E
K : ... 10.24 63.19 6
L 17. 7.:.'- 74..- 3.64 .08
i... ,. from et al. ( !' Table 11, p. 253)
FIG 4 STRATIGRAPHIC RELATIONS, LOCAL TERMINOLOGY AND MINERAL COMPOSITION
OF THE OVERBURDEN SANDS, THE LEACHED ZONE AND MATRIX OF THE
PHOSPHATE BEDS, AND THE UNDERLYING BEDCLAY AND BEDROCK.
MODIFIED FROM CATHCART et ol (1953, Fig., p.82).
UC%.K ri uN ArKV IM~tMItK L --UItl,
History of Mining
Pebble phosphate was originally discovered in the
Bone Valley District along the Peace River in 1881 by
Captain J. Francis LeBaron of the Army Engineers
(Davidson, 1892), and mining of the river-pebble
deposits began in 1888. In 1891 production from
land-pebble deposits was initiated as mining activities
began to shift from the irregularly distributed
deposits of river beds and flood plains to the more
continuous ores beneath the surface sands of the
region. Since this early beginning, approximately
97,000 acres of phosphate land have been mined. It is
estimated that today an average of 6,500 tons of
marketable product are produced from each acre of
phosphate land mined. In the early days, however, a
large volume of the smaller phosphate particles that
are removed today could not be extracted from the
sediments. In fact, in recent years some of the waste
from these earlier operations has been remained to
recover the small phosphate particles.
Mining and Land Reclamation
Difficult environmental problems result from any
mining operation in which the top layers of the earth
are removed to reach a valuable mineral product, or
in which the top layers of the earth are stripped off as
the valuable mineral product. This type of mining,
called strip mining, is practiced in the Bone Valley
District. Overburden sands and clayey sands are
removed by giant, electric-powered draglines to
uncover the valuable phosphate beds (Fig. 5). The
phosphate beds in turn are removed by draglines, one
of which can pick up as much as 49 cubic yards of
sediments at a time. The phosphatic sediments are
dumped by the draglines into sumps where the ore is
mixed with water and then pumped to recovery
During the early days of mining, no thought was
given to restoring the mined-out land to useful
purposes. An area, after mining, was left turned
up-side-down with man-made ridges and hills com-
posed mostly of sand and clayey sand interspersed
with low areas and filled sludge ponds or settling
ponds which take many years to dry sufficiently to
permit any type of beneficial use. With changing
times it has become evident that such valuable land
cannot be left in an unreclaimed, unuseable state. In
1961 the mining companies agreed among themselves
to restore to useful conditions as much of the
mined-out land as they could afford. Since that
agreement the Florida phosphate industry has re-
claimed an average of approximately 1,500 to 2,000
acres of mined-out land each year. Additional
incentives to reclaim land stem from the mineral
severance tax law passed by the Florida Legislature in
1971. Furthermore, Polk, Manatee and Sarasota
counties have zoning ordinances requiring a certain
amount of phosphate land reclamation.
Nearly all of the phosphate companies have
reclaimed significant land areas. Some of the projects
are tabulated on Table 4. Current projects include
Lakeland Skyview Mobile Home area and golf course,
Sanlan Ranch Campgrounds, and simultaneous min-
ing and reclamation on Lake Parker in Lakeland.
However, major reclamation problems exist. These
problems are complex and to the present are largely
unsolved. A clay-water slurry (slime) is produced in
the processing of the phosphate rock. This slurry
dries very slowly and after standing for many years
still has a volume nearly 6 times greater than the
original clay volume. In fact the volume is about
twice as great as the original volume of the matrix
mined. Slightly more than two-thirds of the land
mined must be used as settling areas for these slimes.
Therefore a substantial amount of the mined-out land
is not readily available for reclamation. Much study
has been directed toward this problem of the slimes
with encouraging results (Timberlake, 1969). Un-
doubtedly such studies will continue to demand a
high priority until the slime problem is solved.
Examples of Land Reclamation Activities
of Various Phosphate Companies*
Example Company Description of Project
1 IMC Southwest Bartow-100 acres-A tract adjoining IMC's Bartow offices. Mined 1965-66. Residential
2 IMC U.S. 17 strip-135 acres-South of Bartow. Right-of-way for anticipated four-lane road. Good for
3 IMC West Mulberry-31 acres-2,500 ft. frontage on Fla. 60. Sold to out-of-state industrial firm.
4 IMC Noralyn recovery plant site-20 acres-office, lab, on reclaimed land.
5 IMC Mulberry area-1,000 acres-North, south and south east of Mulberry; all acreage fronting on a
highway. One part recreational, another agricultural, rest of reclaimed area for residential or
6 (Armour) West Bartow Elementary School-Dedicated in May, 1966; Deeded to city in 1960.
7 (Armour) Clark Property--170 acres-Swampland prior to mining. A real estate subdivision after reclamation.
8 (Cyanamid) Saddle Creek Park-740 acres-Originally a swamp; land has been donated to people of Polk County
for recreational area. Swimming, fishing, picnicing, and other activities. East of Lakeland.
9 (Cyanamid) Orange Park, north of Lakeland-2,224 acres reclaimed-mining and simultaneous reclamation.
Reclamation completed within a month after mining.
10 (Cyanamid) 315 acres-east of Lakeland-donated to Florida Audubon Society as a wildlife sanctuary. Largest
reserve owned by society in state.
(Mobil) Peace River Park-donated to city of Bartow (east of city limits) as recreational area.
12 (Mobil) Christina Park-1,100 acres-Large area south of Lakeland. Sold to private interests for housing
13 (Cyanamid) Pleasant Grove Fish Management area, east of Tampa-1,160 acres-Under supervision of Fla. Game
and Fresh Water Fish Commission.
14 (IMC) Bartow Civic Center-10 acres-1966, land was donated to city for civic center.
15 (Cyanamid) Sydney-1,613 acres reclaimed-15 miles east of Tampa. Sold portion of reclaimed land for 18-hole
16 (W.R. Grace) Sylvester Shores-Fashionable residential subdivision built on reclaimed land in southeast Lakeland.
Mined in 1955. Reclaimed in 1960.
17 (W.R. Grace) North Mulberry area-367 acres fronting on SR 37 and Carter Road. Potential commercial and
residential property. 2,600 ft. reclaimed on SR 37.
18 (W.R. Grace) East Mulberry area-1 55 acres with 4,400 ft. on SR 60. Potential commercial property.
*Data furnished by the Florida Phosphate Council and phosphate companies.
Figure 5. Mining with giant dragline.
Pollution Control and Water Conservation
The phosphate producers also have been con-
cerned with problems of air and water pollution.
During the past 10 years more than 40 million dollars
have been spent by the phosphate companies to
install equipment to reduce emissions to the air of
fluorides, sulfur dioxide, and dust. Furthermore, an
amount in excess of 30 million dollars has been spent
during the same period of time for water quality
control, with phosphorus and nitrogen discharges
receiving much attention. In addition, millions of
dollars have been spent to install and operate water
conservation systems. The magnitude of the efforts
expended toward the control of air and water
pollution and for the conservation of water is
suggested by the vast expenditures directed toward
these ends. Expenditures. for the past 5 years are
summarized on Table 5.
Substantial progress has been realized. The recircu-
lation of water is much above the national industry
average. Airborne fluoride emissions were reduced
about 90 per cent during the period from 1959 to
1966. Likewise discharges of phosphorus and nitro-
gen into local streams have been reduced almost 90
per cent during recent years.
At one time or another, interest has been
expressed in the presence of various materials in the
phosphatic sediments of the Bone Valley District or
in the tailings left after the processing of phosphate
rock. For example, more than one-third of the
phosphate values mined can not be extracted profit-
ably and must be discarded with waste materials.
Therefore the waste contains a relatively high per
cent of unclaimed phosphate. Also, the phosphatic
sediments of the district contain minor amounts of
uranium. With such tremendous volumes of phos-
phate rock being mined, the minute amount of
uranium in individual phosphatic particles adds up to
an impressive quantity of uranium handled in the
mining operations. During World War II, studies were
made on extracting the uranium from the phosphatic
sediments and several plants were constructed in
which small amounts of uranium were recovered on a
Furthermore, the Bone Valley sediments contain
traces of heavy minerals such as ilmenite, rutile,
zircon and monazite. Rutile and ilmenite are import-
ant source materials for titanium which has many
uses such as a whitener in paper and cloth, a white
paint pigment, and a source for titanium metal.
Zircon is used in molds in making castings and as a
source of zirconium metal. Monazite is a source of
rare elements. Also the phosphate rock contains 3 to
4 per cent fluorine, and the district has interest as a
possible source of vast quantities of this element.
Partly as a result of pressure from air pollution laws
and as a result of a shortage of the principal mineral
source of fluorine, plants to recover fluorine from
phosphate rock have been planned for the Bone
Valley District, and some have become realities.
Investigations indicate that phosphate rock may
eventually become a significant source of aluminum
fluoride, according to some estimates by the mid-
EXPENDITURES FOR AIR AND WATER POLLUTION CONTROLS
AND FOR WATER CONSERVATION PRACTICES*
Item 1971 1970 1969 1968 1967
Expenditures to install air pollution controls
Expenditures to install water pollution controls
Expenditures to install water conservation
Expenditures to operate air pollution
Expenditures to operate water pollution
Expenditures to operate water conservation
*Data furnished by the Florida Phosphate Council.
$5,532,090 $2,850,370 $1,925,330 $5,173,066 $9,079869
$3,353,867 $2,136,658 $2,544,587 $2,832,692 $4,822,825
$2,528,070 $ 892,400 $1,276,970 $ 729,575 $3,530,218
$4,591,511 $4,111,540 $4,365,305 $3,981,000 $4,040,120
$3,354,340 $3,000,902 $5,592,750 $4,830,500 $5,569,370
$2,623,739 $2,035,770 $2,417,492 $2,530,900
Interesting Elements and Minerals
The costs of homes, buildings, roads and highways
reflect the availability and quality of such common
construction sands as concrete sand, plaster sand and
mortar sand. All commercially useful sands contain
grains of various sizes (diameters). Concrete sand is a
clean, relatively coarse sand graded to contain grain
sizes within specific ranges (Table 6). Plaster and
mortar sands are finer than concrete sand, but like
concrete sand, must be clean and graded to specifica-
tions (Table 7).
Because much of the surface of Florida is covered
with a blanket of quartz sand it might seem that
concrete sand could be produced at almost any site.
Nothing could be farther from the truth. The median
diameters of surface sands collected along east-west
traverses crossing the Florida peninsula are given on
Figure 6. From this figure it can be seen that the
coarsest surface sands in peninsular Florida occur
near the center of the peninsula, trend in a nearly
north-south direction, and coincide with the general
area of Trail Ridge and the Lake Wales Ridge. A
comparison of the median diameter (Md) of the
surface sands (Fig. 6) with the median diameters (Md)
of concrete sand (Table 6) shows that most surface
sands collected along the traverses are too fine to
serve as a source for quality concrete sand.
In order to obtain large quantities of concrete sand
in the peninsula it has been found necessary to
extract coarse sands from sediments occurring
beneath the surface sands. These underlying coarse
sands are present only in the area of the Lake Wales
Ridge (Fig. 7). There sand is mined from the
Citronelle Formation which locally contains con-
centrations of very coarse sand grains, quartz gran-
ules, and small quartzite pebbles. These localized
concentrations of coarse sediments are the materials
from which construction sands are produced.
At some localities the surface sands must be
removed as overburden before mining the deeper,
coarser sands; in other areas, however, surface sands
can be mined with the underlying Citronelle sedi-
ments. In either case open pit mining methods are
used, utilizing dragliries in those pits which are dry,
and dredges with barge-mounted pumps in those pits
which are partly water-filled. Sand removed from the
pits is washed and sized by screens to meet required
specifications of concrete and plaster sands and then
shipped by truck or rail to the market area.
Because transportation is a major cost factor in the
sand and gravel industry, various population centers
in the peninsula receive their construction sand from
pits in that part of the Lake Wales Ridge area closest
by road or rail. For example, Jacksonville receives its
quality construction sands from mines in Clay and
Putnam counties in the northern part of the ridge
area. Orlando receives its coarse construction sands
from mines in Lake and Polk counties. The Tampa
area receives a major part of its quality construction
sand from the Lake Wales Ridge area in Polk County.
However, some production for the Tampa market has
come from other localities, such as sites on the
Lakeland Ridge southwest of Bartow (Fig. 7).
A. S o.... ..... .
Figure 7. Areaof Citronelle sediments as mapped byCooke(1945). The Citronelle sediments are the major source
materials of quality construction sands in the Florida peninsula. These sediments also contain kaolin clay.
Screen Analyses by Weight of Finished Concrete Sands Collected
at Major Producing Mines within the Area of the
Lake Wales Ridge
State Road Site Site Site
Sieve Specifications A B C
Size % Cumulative Putnam County Lake County Polk County
4 0- 5 0.00 0.00 0.0
8 0- 15 3.2 1.2 1.0
16 3- 35 12.6 10.8 13.2
30 30- 75 39.3 39.7 50.4
50 65- 95 69.9 81.1 73.0
100 95-100 94.5 99.5 93.6
Grading of Sands for Masonary and Mortar Uses*
FM* 221 232 231 199
Md.** .47 .52 .60 .39
*Sum of cumulative values for samples. Expression of coarseness.
*Median diameter (mm).
each screen by weight
8 95 to 100
16 60 to 100
30 35 to 70
50 15 to 35
100 0to 15
*Recommendations of the American Society for
""' -? )
-. r- h
*; '" ) "' 1 "' , ,'- .,
A.. . ... T) ;) '
s'' ' 'i ' ' ,
@ 1 @.12 &@ C232 -
(' 0' 7 0-
'' I/ .
METERS OF THE QUARTZ SAND COLLECTED AT THAT LOCALITY.
2. Grain Size The glass sand shall conform to the
following requirements with respect to grain size:
A Specialty Sand
Glass sand, an important specialty sand, is pro-
duced in both Polk and Hillsborough counties. The
glass sand from Polk County is mined in the Lake
Wales Ridge area near Davenport where the sands are
separated from the same sediments from which
concrete and plaster sands are produced. Special
processing, including flotation to remove heavy
minerals and other impurities, is required to obtain a
high quality product.
The glass sand from Hillsborough County is
presently produced from surface sands in the Plant
City area. Parts of this deposit contain a very
high-grade glass sand which in its natural state meets
high quality requirements, both texturally and chem-
ically. There are very few natural deposits of glass
sand anywhere that meet the quality of these Plant
City sands for manufacturing glass. Prior to 1970
flotation was not used in processing the sand. Since
that date, however, flotation has been used to remove
heavy minerals and other impurities to ensure a
Glass sands must be of very high purity; even a
fraction of a percentage of some impurities, such as
iron, will color the glass produced. Table 8 illustrates
the allowable percentages of certain of the more
common impurities found in sand deposits. Further-
more glass sand must have a uniform grade-size
distribution of sand particles with most of the grains
having diameters falling within a range of approxi-
mately 0.840 to 0.149 mm (-20 mesh to + 100 mesh).
Glass manufacturers differ somewhat in the details
of their specifications for glass sands. Requirements
quoted by one major manufacturer for a high-grade
glass sand are given below.
1. Chemical Composition The glass sand shall be
composed of the following oxides in the following
percentages by weight as determined by analysis
based on ignited samples.
not less than 98.500
not more than 0.500
not more than 0.035
not more than 0.200
percent remaining on 16 mesh screen
percent remaining on 30 mesh screen
percent remaining on 60 mesh screen
percent remaining on 120 mesh screen
percent passing through 120 mesh screen
Some of the glass sands in Hillsborough County
and similar deposits in Manatee County in their
natural state regularly approach these specifications
for high purity glass sand. Analyses of a sample of
Plant City sand as taken from the ground are given on
The value of the deposits near Plant City as a glass
sand was recognized in 1961 (Pirkle et al., 1963, p.
Specifications for Chemical Composition of Glass Sands
Percentage composition based on ignited samples
SiOZ A1203 Fe203
Minimum Maximum Maximum
First quality, optical glass
Second quality, flint-glass
containers and tableware
Third quality, flint-glass
Fourth quality, sheet glass
rolled and polished plate
Fifth quality, sheet glass,
rolled and polished plate
Sixth quality, green glass
containers and window
Seventh quality, green
Eighth quality, amber
Ninth quality, amber
128). Since that time studies have been undertaken to
locate additional deposits. During one study the
following procedure for locating deposits of the
Plant City type was followed by the authors. At the
outset, all areas of St. Luci sands were plotted from
soil maps onto topographic maps of Hillsborough and
Manatee counties. Field checks of these areas were
then made to determine which of the regions of St.
Luci sands support a true scrub vegetation. Holes
were drilled in the sands supporting a true scrub
growth, and the sands taken from the holes were
analyzed for texture (sand size), heavy mineral
content and iron content. From the analyses it was
found that the sand in many of the regions is too fine
for glass purposes. However, sands from some areas
were found to be of the same quality as the Plant
City deposits. The final result of the study was the
location of new resources of glass sand of the Plant
City type. It must be added, however, that this
procedure for locating glass sands will not work in
other parts of Florida. Different methods of explora-
tion must be devised for other areas.
99.8 0.1 0.02 0.1
98.5 0.5 0.035 0.2
95.0 4.0 0.035 0.5
98.5 0.5 0.06 0.5
95.0 4.0 0.06 0.5
98.0 0.5 0.3 0.5
95.0 4.0 0.3 0.5
98.0 0.5 1.0 0.5
95.0 4.0 1.0 0.5
*Taken from Fettke (1926, p. 400).
Plant City Glass Sand
Accumulative percent retained on mesh Heavy
Site 12 16 20 30 50 60 100 140 Minerals Fe203
in % in %
Plant City 0.0 Tr. 0.4 3.6 41.3 58.3 87.0 93.9 0.154 0.016
Sand mine at Plant City.
Among the most interesting Florida clays from the
commercial viewpoint are kaolinitic clays for ceramic
purposes, fuller's earth clays for their adsorbent
properties, and bloating clays for their use in making
lighweight aggregate. None of these clays is currently
mined in Hillsborough County. However all are mined
in the Florida peninsula and are a part of the mineral
environment of Tampa.
Kaolinitic Clays of the Citronelle Formation
The north-south trending Lake Wales Ridge area
which divides the Florida peninsula into an eastern
and western part (Fig. 7) is underlain by Citronelle
sands that contain varying amounts of kaolinitic clay.
These, usually assigned a late Miocene or Pliocene
age, are the materials previously discussed as the
source sediments for quality construction sands of
the peninsula. The kaolinitic clay occurs disseminated
throughout the sands, usually constituting from 2 or
3 per cent to as much as 25 per cent of the beds.
The kaolinite of the Citronelle Formation is a high
quality ceramic clay. It has been mined at one time or
another in Clay, Lake and Putnam counties, the
production from Putnam County being continuous
since 1892. In addition to its value as a ceramic clay,
the kaolinite of the Citronelle Formation may have
potential as a future source of aluminum. Citronelle
clays are not present in Hillsborough County, but
they do occur in the eastern, central and northern
parts of adjacent Polk County.
Fuller's Earth Clays of the Hawthorn Formation
The Hawthorn Formation contains fuller's earth
clays, utilized for their adsorbent properties. The
dominant clay minerals are montmorillonite and
attapulgite. Extensive mining of the clays is carried
out in Gadsden County northwest of Tallahassee and
in southwestern Georgia. The production of the
adsorbent clays closest to the Tampa area is at Lowell
in Marion County. Clay from that site is shipped to
the Tampa market for use as an adsorbent cat litter,
as a pesticide carrier, and as an inter-caking agent for
fertilizers. Although Hawthorne sediments are present
in the subsurface of Hillsborough County, no
extensive occurrences of fuller's earth type clays
suitable for mining have been reported.
Some clays will expand or bloat when heated,
often taking on the appearance of a burned, porous
or cellular cinder rock. The expanded or bloated
material is relatively light and if sufficiently strong is
ideal as a lightweight aggregate for use in the
production of concrete and concrete products.
Clays Along the St. Johns River:
The only site from which bloating clays currently
are mined in Florida is near Russell just west of the
St. Johns River in Clay County. However, there are
other occurrences of similar clays known to be
present along the St. Johns. These clay bodies
apparently are confined to the general vicinity of the
Deposits of Clayey Sediments in West-Central
Within the past few years massive bodies of clayey
sediments possibly useful as a bloating clay have been
found in northern Pinellas County (west and south-
west of Lake Tarpon) and in the vicinity of Telegraph
Swamp in Charlotte County. These clays have been
drilled and studied by members of the Florida Bureau
of Geology, the Geology Department of the Universi-
ty of Florida, and the United States Bureau of Mines
Laboratories (Wahl and Timmons, 1972). Figure 8 is
a fence diagram showing the stratigraphic position of
the clay body near Lake Tarpon. Wahl and Timmons
(1972, p. 109) report that the large clay deposit
probably is Miocene in age, consists of montmorillo-
nite type clays, has an average thickness of 25 to 35
feet, and is overlain by unconsolidated Pleistocene
sands. The clays have good bloating characteristics
across an acceptable temperature range and develop a
good cellular structure with a fairly thick and
apparently tough wall structure. However the deposit
is in an area of rapid population growth and mining
may not be feasible. In regard to this problem Wahl
and Timmons (1972, p. 112) state:
"It is possible that development of the Pinellas
County deposit to its maximum potential might
already be prohibited by urbanization, for the
Pinellas-Hillsborough County area is one of the fastest
growing regions in the state at the present time. It is,
indeed, imperative that other similar deposits
throughout the state be located and their potential
for development be realized so that land-use planning
and resource development can be coordinated."
In light ot these comments by Wahl and Timmons
it is of interest to note that extensive deposits of
clayey sediments that may have potential as a base
material for the manufacture of lightweight aggregate
are present in a number of other counties in
west-central peninsular Florida, including Pasco, Polk
and Hillsborough. In evaluating these clayey sedi-
ments a number of economic factors must be
considered. Obviously the overburden covering the
clay deposits should be as thin as possible so that the
cost involved in its removal is not substantial. Also,
the moisture content of the clay should be low. Every
bit of moisture present is significant in that it
increases processing costs. It is desirable that the clay
be a natural bloating clay; however, coal or fuel oil
can be used to make the clay bloat if the melting
range of the clay is over a sufficient temperature
span. In addition to these factors, transportation
costs and problems related to the environment and to
the restoration of mined-out land must be given
FIGURE 8: FENCE DIAGRAM CONSTRUCTED FROM FIVE DRILL HOLES IN
PINELLAS COUNTY WITH INSERT MAP SHOWING LOCATION
OF DRILLED AREA. MODIFIED FROM WAHL AND TIMMONS
(1972, FIG. 5).
There are different methods that could be used in
attempting to locate and pinpoint deposits of these
clays. To illustrate, Figure 9 shows a section through
Pasco, Sumter and Lake counties. From this section it
is clearly seen that the Ocala Arch crests beneath
Sumter County (holes 3, 4 and 5). The near-surface
sediments on the flanks of the arch are shown to be
sandy clay (yellow color with dashes and dots). These
sandy clays flanking the crest area of the Ocala Arch
grade away from the arch into sediments containing
less clay (yellow color). Clearly the sediments closest
to the crest area are the highest in clay content and
should be considered as broad targets for possible
Figure 10 is a map of the same general area showing
the depth to the top of the Floridan aquifer (usually
limestone). By combining information from this
figure with information from Figure 9 the target areas
for the clays flanking the Ocala Uplift can be further
localized. That area colored dark yellow on Figure 10
marks the crest area of the uplift. Limestone is within
10 feet of the land surface and a thick deposit of clay
would not likely be present over the limestone.
Beneath the area colored light yellow the limestone is
at a depth of 10 to 25 feet. Again the closeness of the
limestone to the land surface would tend to preclude
the presence of a massive deposit of thick, clayey
materials between the land surface and the limestone,
although the occurrence of a potential clay body
could not definitely be ruled out. Throughout the
area colored yellow-green the limestone is from 25 to
50 feet below the land surface. This depth to the
I Surfiial sand Ha.w.horn formto .n(sand uni) ..othorn forml.an(phosphor.te unit)
Loose, mossive quart sound Prtly Gray to brown, clyey, fine-groined quartz Gray brown, cayey quor sond ond
Recent wind deposit, portly resdual sand intersltioal secondary phosphlot phosphrte, /, ne-grtned quartz send;
phosphorte nodules are as large as pebi
T 2 Tampa limston (clay unt) Tampa limestone (phosphorite unit) Suwannae I mestone
Greenish-gray o brown, sandy (very fine White to brown, oncretonary, cloy-sized Slightly sandy hmestone
grained) cloy. opotte and clay
a Ocoa limestone lo"
Almosture hmslone DADE CITY AREA tro'
Hard-rock phosphate mine
S Hard-rock phosphale mine
D 0-10  75-100
S10-25 1 100-200
[ r25-50 Greaterthan 200
Figure 10. Green Swamp and surrounding areas showing
thickness of sediments over the Floridan aquifer.
(Reproduced from R. Pride et al. 1966, Fig. 3)
limestone should be sufficient for clay occurrences
and for clay mining. Thus on the basis of the work of
Pride, Meyer and Cherry (1966) the yellow-green area
on Figure 10 of this report should be considered as
areas in which clays of interest for their bloating
qualities may be present.
Additional information of significance in speculat-
ing on the possible occurrences of bloating clays is
given in the work of Ketner and McGreevy (1959,
Plates 3 and 4). Information from their plates has
been selected and reproduced here as Figure 11. This
figure shows subsurface sediments along a line from
Brooksville southeastward through Dade City into
Polk County. In this section the materials marked by
1OC 3 4 5
dashes are designated by Ketner and McGreevy as the
clay unit of the Tampa Formation. In Pasco County
this clay unit is shown to be near the land surface
along the flanks of the Brooksville Ridge as indicated
by holes 5 and 9 on Figure 11. Therefore another
broad target area for possible clay deposits would be
along the flanks of the Brooksville Ridge where
clayey sediments are not covered by thick overburden
sands. Obviously these published reports by the
Florida Bureau of Geology and the United States
Geological Survey can be used as starting points in
planning for exploration programs directed toward
the recognition of potential clay resources in the
general area of Tampa.
I 3 It\ mL C3
Figurell. SECTION FROM BROOKSVILLE SOUTHEASTWARD THROUGH THE
BROOKSVILLE RIDGE. NOTE CLAY UNIT OF TAMPA FORMATION
IS CLOSE TO THE LAND SURFACE ALONG THE FLANKS OF THE
BROOKSVILLE RIDGE (HOLES 5 AND 9).
Modified from Ketner and McGreevy (1959, Plates 3 and 4).
I 0 ,5 4 MILES
POLK CO. L....
Sketch Map Showing Location of Cross-Section
Figure 9. SECTION THROUGH PARTS OF PASCO, SUMTER AND
LAKE COUNTIES. THE CREST OF THE OCALA ARCH
IS IN THE VICINITY OF SUMTER COUNTY NEAR
CORE HOLE NO.4. NOTE THE CLAY CONTENT OF SEDI-
MENTS IS HIGHEST AROUND THE FLANKS OF THIS
ARCH (YELLOW COLOR WITH DASHES). MODIFIED
FROM PRIDE ET AL. (1966, FIG.8).
deposits(clayey sand on
left side graded into sandy
cloy on right side)
S| Crystal Rivet Formation
W-- Inglis Formation
Avon Park Limestone
SFault, arrows indicate
61 direction of movement
LIMESTONE Uses of Limstone
Centers of Limestone Production
During 1970 slightly more than 40 million tons of
crushed limestone valued at 55.2 million dollars were
produced in Florida from 90 quarries in 23 counties
(Table 10). The producing areas can be grouped into
two major centers of limestone production, one north
of Tampa in the area of the Ocala Uplift (Fig. 12),
and the other in the southeastern part of the
peninsula in Dade and Broward counties. All of the
Florida peninsula can be supplied with limestone
products from these two centers.
Of most direct interest to Tampa is the center in
the Ocala Uplift area. There limestones arched
upward from depth are now exposed or covered by
only a thin veneer of overburden sediments. They are
accessible for mining by open pit methods and may
be removed with draglines, power shovels, front end
loaders and bulldozers.
Florida: Crushed limestone sold or used by producers, by counties
(Thousand short tons and thousand dollars)
Collier . ...... .......
M arion ...............
M onroe ...............
Palm Beach ............
Sum ter ...............
W Witheld to avoid
data; included wil
1,744 $ 1,335
O MINE SITES
disclosing individual company confidential
SIncludes Charlotte, Citrus, Lee, St. Lucie, Suwannee, Taylor,
and Palm Beach counties.
2 Data may not add to totals shown because of independent
*Bureau of Mines Minerals Yearbook, 1970.
Figure 12. Center of limestone production north of Tampa.
The crest of the Ocala Uplift is indicated by a
heavy black line. Areas in which active limestone
quarries are present are shown in color. Note
their correlation with the area of uplift.
Limestone mined in Florida is used principally as a
roadbase, as concrete aggregate, and in the manu-
facture of cement and lime (Table 11). The loose,
granular "Ocala Lime Rock," mined extensively
within the Ocala Uplift area in many counties
including Alachua, Marion, Levy and Sumter, is used
as a roadbase material and in the manufacture of
lime. A crystalline limestone called "Brooksville
stone," mined primarily in Hernando County, is
marketed as a concrete aggregate, although some is
used for railroad ballast and for agricultural purposes.
During the past, much of the limestone used in
making cement for the Tampa market came from
mines in Citrus and Hernando counties. Now,
however, limestone sediments are being imported
from the Bahamas for the Tampa cement market.
Some carbonate rocks have a relatively high
content of magnesium. These rocks, often called
dolomites or dolomitic limestones, are used mainly as
fertilizer filler and for soil improvement. They are
mined north of Tampa in some parts of the uplift
area and south of Tampa in Manatee and Sarasota
Florida: Crushed limestone sold or used by producers, by uses
(Thousand short tons and thousand dollars)
Use Quantity Value
Concrete aggregate ............ . 9,824 $16,302
Dense graded roadbase stone . ...... 15,232 20,398
Other roadstone .............. 2,820 4,214
Unspecified aggregate and roadstone . 2,866 2,788
Agricultural purposes ........... 375 1,353
Fill ................. ..... ... 3,373 2,651
Railroad ballast ... ........... .. 120 165
Other uses3 .................. 5,600 7,306
Total4 .................... 40,210 55,176
Other roadstone includes bituminous aggregate, macadam
aggregate, and surface-treatment aggregate.
2Data include stone used in poultry grit.
Includes asphalt filler, cement, chemical stone, other filler,
lime, stone sand.
4Data may not add to totals shown because of independent
*Bureau of Mines Minerals Yearbook, 1970.
Like many other low unit-value mineral resources,
limestone deposits must have natural purity and be
easily accessible for mining in order to be economic-
ally important. Although the Tampa area is underlain
by vast quantities of limestone, the thickness of
overburden coupled with the impure nature of the
limestone renders the sediment throughout most of
the area insignificant as economic deposits. However,
about 10 miles northwest of Lakeland there is a large
region in which limestone is close to the land surface
(Fig. 10, yellow-green color). That area, partly
in Hillsborough County, has potential as a source
Florida's reserves of limestone are monumental.
Reves (1962, p. 7) states that in the northern half of
the peninsula alone, the amount of limestone which
has less than 15 feet of overburden, if mined to a
depth of 40 feet, would approach 4.2 trillion tons. A
vast amount is a very high calcium limestone, ranging
from a minimum of 95 per cent calcium carbonate to
as much as 99.8 per cent calcium carbonate.
Furthermore there is a great deal of dolomitic
limestone. For example, Vernon (1951, p. 218)
reports more than 100 square miles underlain by
dolomitic limestone in Citrus and Levy counties
alone. Other occurrences of dolomitic limestone are
known in Florida, including deposits along the Gulf
Coast in Dixie, Taylor, Jefferson and Wakulla
counties (Reves, 1962, p. 12) and in Pasco, Hernan-
do, Suwannee, Manatee and Sarasota counties (Max-
well, 1970, p. 26).
Potential Deposits of Crystalline Limestone
Recently Yon and Hendry (1972) investigated the
occurrences of crystalline limestone in Hernando and
Pasco counties. Limestone products from these
counties, just north of Tampa, would have a marked
impact on the Tampa market. Yon and Hendry
determined that crystalline limestone suitable for
concrete aggregate is associated with an elongated
subsurface high extending from Pasco County north-
westward into Hernando County (Figs. 13 and 14).
They interpreted the buried "ridge" of limestone as a
possible carbonate bank built during Oligocene time
in a warm shallow sea.
The highs and lows of the upper surface of this
buried limestone "ridge" conform in general with the
highs and lows of the land surface. To prospect in
that area for limestone suitable for aggregate, one
may superimpose contour maps of land surfaces onto
Yon and Hendry's contour map of the upper surface
of the limestone high (Fig. 13). The crystalline
limestone should be close to the land surface at those
sites where the two sets of contour lines show nearly
the same elevations (Yon and Hendry, 1972, p. 40).
These correlations brought out by Yon and Hendry
constitute a vivid illustration of the significance of
basic geological studies in pointing to occurrences of
accessible mineral resources.
:L ..J oe -
^-^ A ,. ^-^ ^ ^ss^...~4-
Figure 13. CONTOURS DRAWN on the TOP of the SUWANNEE LIMESTONE in
HERNANDO and PASCO COUNTIES. A HIGH, ELONGATED AREA
JUST WEST of DADE CITY is CLEARLY SHOWN. ITS TREND is
NORTHWEST-SOUTHEAST. (FROM YON and HENDRY,1972, Fig.5,p.12)
Figure 14. AREA of POTENTIAL LIMESTONE AGGREGATE in
HERNANDO and PASCO COUNTIES is SHOWN in
COLOR. THIS AREA CORRESPONDS to the HIGH on
FIGURE 13. (FROM YON and HENDRY, 1972, Fig.16,p.39.)
Limestone mine in Sumter County.
CEMENT,OYSTER SHELL,& PEAT
Cement itself is not a mineral but normally is
considered a mineral resource. The raw materials
needed in its production are lime or limestone and
minor amounts of silica, alumina, and iron oxides. In
manufacturing portland cement the raw materials are
crushed, then proportioned under strict chemical
controls, ground to a powder or slurry and fed.into
an inclined rotary kiln. The powdered material moves
under gravity from the upper toward the lower end of
the rotating kiln where intense heat is produced. The
heat fuses the powdered charge to a glassy clinker
composed of calcium silicates and aluminates. The
clinker is then mixed with a small amount of gypsum,
which later helps regulate setting time, and the mass
is ground to a fine powder. This powder is portland
The limestone used in producing portland cement
must not contain more than 3 per cent magnesia. This
is a stringent requirement that eliminates many
potential limestone sources. Part of the small
amounts of silica, iron oxides, and alumina needed
may be present in the limestone as impurities.
Additional amounts usually are added by introducing
clays or other materials containing these substances.
Staurolite from the heavy mineral operations near
Starke has been used to some extent in Florida as a
source of iron and aluminum.
Factors important in establishing a cement plant
include the availability and quality of deposits of
limestone and the other raw materials. In addition, a
satisfactory source of fuel for the rotary kilns must
be considered. Most important, however, is the
location of the market area. The plant should be
established as close as possible to major population
centers to reduce costs of transportation.
At present there are four plants producing cement
in Florida. Three are in the Dade County or Miami
area and one is in the Hillsborough County or Tampa
area. The Tampa plant, with an annual capacity of 6
million barrels of cement, is by far the largest in the
state. Nevertheless, a cement shortage exists in the
Tampa region and cement is being imported into the
area. One of the new sources is Honduras in Central
Approximately 87 per cent of the cement pro-
duced in Florida during 1970 went to building
material dealers, concrete products manufacturers,
and ready-mix concrete manufacturers (Minerals
Yearbook, 1970). Much of the remainder was used by
highway contractors and government agencies.
Limestone for the cement plant in the Tampa area
was mined for years at sites in Citrus and Hernando
counties. Now limestone sediment aragonitee) is being
dredged near Bimini in the Bahamas and shipped to
the Tampa plant. The clay needed to furnish small
amounts of iron oxides and alumina is mined in
Citrus County. Soon, however, clay for the Tampa
operation will be mined from a new pit to be opened
in Hernando County.
The quantity of raw materials consumed in the
production of cement at the Tampa site is enormous.
Dust from the clinker burning process makes for a
significant problem which currently is of a crisis
nature at the Tampa plant. A new cement plant is in
the planning stage for Manatee County just south of
Hillsborough County. This will reportedly be a
pollution-free plant, but resistance to its construction
is already substantial.
If a population center is to thrive it must have
cement and other construction materials, and it must
be able to obtain them at a reasonable cost. Raw
materials necessary for the production of cement are
available to the Tampa region. However, as illustrated
by the Tampa plant, cement manufacturing can be
plagued by pollution problems. The need for cement,
when considered with problems associated with its
production, serves as a striking illustration of the
need for informed leadership in planning for the
economical and popularly acceptable manufacture of
a product necessary for a thriving and expanding
Scenes at cement plant in Tampa
For years oyster shells have been dredged from
Tampa and Hillsborough Bays, with an estimated
tonnage of slightly more than one-half million cubic
yards now being produced annually. The sites of
current dredging operations are shown on Figure 15.
Most of the oyster shells are used for road base
materials, the city of Tampa being among the largest
of the consumers. According to Mr. E. Medard of Bay
Dredging and Construction Company (personal com-
munication), the shell layer being mined in the bay
ranges in thickness from 2 to 20 feet, approximately,
and is overlain by 4 to 15 feet of overburden. The
amount of reserves is unknown.
Dredging of these shells in the bay area has been
the subject of much concern during recent months.
The problems include possible destruction of marine
life and biological resources and possible adverse
effects on local water quality. Again there is
insufficient data to evaluate all aspects of these
concerns intelligently and effectively, and clear-cut
recommendations or decisions cannot be drawn with
comfort and conviction. To illustrate the dilemma,
late last year when the Florida Cabinet considered
requests for renewal of permits to continue dredging
operations for oyster shells in Tampa and Hills-
borough Bays, it was faced with different opinions
from different individuals, institutions, and state
agencies. The consensus was that further study was
During 1970 peat was produced in Florida from 8
plants in 6 different counties including Hillsborough.
Total production from the entire state amounted to
approximately 46,000 tons valued at slightly more
than 300,000 dollars (Minerals Yearbook, 1970).
Most of the peat is used for improving the physical
character of soil. The production in Hillsborough
County is largely for local needs and comes from sites
near Mango. Davis (1946) has made a thorough study
of Florida's peat deposits. That work can be
consulted for discussions of the various kinds of peat
and mucks, their distribution, origins and character-
This brief discussion of mineral resources of the
Tampa area touches upon interesting and crucial
environmental and land-use problems. Some of the
problems can not be evaded and will become more
and more pressing with time. They are both
philosophical and practical. It is evident that among
the most significant needs for understanding any of
the problems are reliable, basic data. These data can
not be accumulated in a few days or in a few months;
their accumulation takes years. A strong case can be
built that one of our most severe deficiencies in
preparing for the land-use and environmental
problems that face us today has been our lack of
support for those studies and for the work of those
agencies which supply basic data. Where and when
plans and decisions can be based by competent
leadership upon reliable data, socially beneficial
solutions to these challenging problems will be more
Mountain of oyster shells at Bay Dredging and Construction Co.
--aog cI -
Engineering geology may be defined as: "The
application of the geological sciences to engineering
practice for the purpose of assuring that the geologic
factors affecting the location, design, construction,
operation, and maintenance of engineering works are
recognized and adequately provided for"'. As such,
engineering geology is concerned with the physical
characteristics of earth materials and deals with
quantitative data obtained from testing the suitability
of those materials for specific uses or roles.
In the Tampa area, construction planning perhaps
most frequently demonstrates the simultaneous use
of engineering and geological concepts. Likewise, soils
studies incorporate engineering and geological prin-
ciples. This phase of the report will deal with the use
of engineering geology techniques applied to con-
struction planning and the study of soils.
In planning the construction of any building, of
primary consideration is the character of the earth
materials upon which the building will rest. Various
physical properties of these materials determine how
much weight they can bear and, in turn, how a given
building must be supported.
Three factors are involved in the selection of an
appropriate foundation design:
1. The nature and competency (strength and com-
pressibility) of the subsurface materials.
Incompentent (weak and/or compressible) subsur-
face materials may necessitate special site prepara-
tion prior to construction and/or a complex
2. The size and type of building.
The size of the building is important in that small,
light buildings such as residences obviously require
less support than heavy multi-story structures; and
likewise low-rise structures, such as shopping
malls, generally require less support than heavy
high-rise buildings. The type of building con-
struction, such as steel, concrete, masonry or
wood, determines the building's adaptability and
tolerance to settlement and its effects.
The cost of constructing a feasible foundation
system should be in balanced proportion to the
cost or value of the structure itself.
All three factors must be weighed in determining
the suitability of a site for construction. It may also
be pointed out that the same three factors listed
above also determine the scope and extent of the
subsurface investigation and study which is required
for a building site.
The thickness and character of surficial soil
deposits and the depth to rock often are of prime
importance in the selection of a building site and
development of construction plans. Probably the
most accurate statement that can be made about the
surficial soil deposits and the depth to the rock
surface in the Tampa area is that they are character-
ized by their inconsistency. The thickness and extent
of the cohesionless and cohesive soils-that is, the
sands and clays-can vary greatly, even among the
borings made at one site. In addition, soils intermedi-
ate in nature between the noncohesive sands and the
cohesive clays, such as sandy clays and clayey sands
are quite common. In some instances, sands grade
slowly downward into clayey sands and then sandy
clays and then relatively pure clays. In other
instances, clayey lenses are found within the sands;
and sand lenses within the clays. Consequently,
accurate mapping of the thickness of the cohesive and
non-cohesive soils in the Tampa area is very difficult.
In addition to the areal extent and thickness of the
cohesionless sands and cohesive clayey soils; the
strength and compressibility of these soils is a vital
parameter. Standard penetration tests provide some
indication of both the relative strength and relative
compressibility of soil deposits. The specific pro-
cedures for performing this test and obtaining soils
samples is comprehensively presented in American
Society for Testing and Materials specification D
1586. In general, this procedure involves driving a 2
inch split spoon sampler 18 inches into the soil by
means of the energy imparted by a 140 pound drop
hammer falling 30 inches. The number of blows
required to drive the sampler the last foot into the
soil is the standard penetration resistance, commonly
called the 'blow count'. Other supplemental invest-
igative procedures, such as the auger borings or cone
penetrometer borings are sometimes used to obtain
additional information regarding the nature of the
surficial soil deposits; but the standard penetration
test is the most widely used method of determining
and evaluating the nature of the subsurface condi-
tions. However, it should be noted that the data
obtained from this procedure is rather limited and
more qualitative than quantitative in nature. More
specific and quantitative information regarding shear
strength and compressibility of soils is generally
obtained by laboratory testing of undisturbed soil
samples. Sometimes field load tests are necessitated
because of the nature and geology of the soil
Subsurface conditions which limit the suitability
of a site for construction can generally be overcome
by the use of certain site preparation techniques or
special foundation design, or both. Before subsurface
problems and their solutions can be discussed, some
pertinent terms need defining:
Shallow Foundation Systems
This type of foundation bears at a very shallow
depth and imparts the foundation loads to the
shallow subsoils. There are a number of types of
shallow foundations, all of which are used to spread
the superimposed loads over a sufficient area so that
the safe bearing capacity of the foundation soils are
not exceeded. The type that is best suited for a
particular site depends upon the subsurface condi-
tions. The following are the three major types of
shallow foundation systems listed in the order of least
costly to most costly.
Individual or Continuous Foundations-Individual
spread footings are utilized to support columns;
whereas continuous spread footings are used to
support load carrying walls. These are normally the
least costly type of foundation systems and are
utilized where good subsurface conditions exist.
Strap Foundations-This type of foundation is
utilized to support a row of two or more columns.
The foundation strap is structurally designed with
sufficient stiffness and rigidity to function as a single
unit. This type of foundation system is used where
somewhat poor subsurface conditions exist and when
it is desirable to reduce subsurface stresses and
minimize potential settlement between columns.
Mat Foundations-A mat or raft foundation, com-
monly called the floating foundation, encompasses
the entire base of the structure and spreads the
building load over the entire building area. The main
functions of such a foundation system are to reduce
subsurface stresses in compressible soils, bridge weak
zones or possible subsurface cavities, and reduce total
and differential settlement. This is generally the most
costly of the various types of shallow foundation
Deep Foundation Systems
Piles or caissons are the most common type of
deep foundations. Their purpose is to transfer a load
which cannot be supported at a shallow depth to a
greater depth where adequate support is available.
Caissons are rarely used in the Tampa area because of
installation difficulties imposed by the general geo-
logy of the area; whereas timber, steel and/or
concrete piling are commonly used. Because of the
variable and unreliable nature of the clayey subsoils,
the piling are usually end-bearing on the limestone
bedrock. The cost of piling can vary widely,
depending upon their length and capacity.
This generally refers to the pumping of sand-
cement mixtures or chemical grouts into weak porous
permeable zones and/or underground cavities or
networks of cavities in order to strengthen and
stabilize the subsurface strata. This procedure, al-
though not commonly used, is frequently necessi-
tated in certain areas within the Tampa area because
of the geological conditions. The cost of this type of
site preparation work is extremely variable and can be
Individual spread footing
Piles or Caissons
Foundation problems common to the Tampa area
can be dealt with in a variety of ways depending on
the severity of the problem and the nature of the
structure. Four fundamentally undesirable site condi-
tions include: loose sands, compressible clay, organic
materials, and sinkholes.
Structures built on loose sands may settle and
crack if the sands densify or compress. Densification
can result from the imposed load, changes in ground
water levels, or from vibration of the ground due to
traffic, sonic booms, machinery, etc.
In order to prevent settlement, three alternatives
are possible: 1) loose sands can be removed and
replaced, 2) pilings can be utilized for support, or
3) the sands can be densified.
Even for high rise buildings, excavation of loose
sands for foundations rarely exceeds depths of ten
feet. With deeper excavations, costs are higher, and
the water table becomes a problem. If the entire
ground floor area of a building must be excavated,
every foot of material removed results in a significant
increase in cost. Following removal of loose sands,
the site is back filled and properly compacted.
In-place densification of loose sand is usually the
least expensive means of adequately preparing the site
for buildings. The older method of densifying loose
cohesionless soils was to excavate it, replace it in thin
layers and compact it. However, modern compaction
equipment and techniques now make possible the
densification or appreciable thicknesses of sand
without excavation. If surface deposits of loose
cohesionless soils are only moderately thick, the use
of large heavy vibratory compaction equipment
usually will adequately densify the soils; whereas if
the loose sands are either very thick or buried, a
process called "Vibroflotation"1 can be utilized. This
latter system utilizes water and vibration to compact
the sand. All methods of in-place densification are
reasonable in cost.
In the Tampa area, pure quartz sands and sands
with minor amounts of silt, clay, and organic material
generally range from a few inches to more than 30
feet thick. The sands tend to thin toward the Bay.
The meandering contour lines on the map partially
reflect the effects of stream channel development and
the erosion of sands by streams. The reaches of the
river channels exhibit thinner sand than adjacent
SAND SUITABILITY AS A
The map presented here incorporates both thick-
ness and compressibility of the relatively pure surface
sands and outlines the areas or problem sands and
satisfactory sands. It must be borne in mind that the
map has been compiled from data currently available
and is thus generalized. Close spacing of "good" and
"poor" sands bears witness to the local variability of
It can be seen from the map that thick loose sands
are especially prevalent in the Temple Terrace-
University of South Florida area and around Bran-
don. Firm sands are fairly well scattered but appear
to be concentrated in the downtown and interbay
With regard to site suitability for construction, this
map illustrates one of the many aspects which must
be considered, and it will be utilized as an overlay in
the Land Use section of the report.
Good: Firm sands five feet or greater in thickness
have been encountered in these areas. These sands are
capable of supporting many types of structures with
no pre-construction site preparation.
Variable: These areas have been found to contain
varying thicknesses of sand that exhibits eradic
compressibility. Because of their unpredictable nature
pre-construction treatment for the sands may be
Moderate: This includes areas in which sands are
predominantly firm but contain compressible lenses
and areas in which less than five feet of loose sand lies
at the surface and is underlain by more than five feet
of firm sand. Depending upon the type of con-
struction proposed, very little treatment may be
necessary to render these sands suitable to provide
adequate foundation support.
Poor: Included are areas in which sands are 10 feet
or greater in thickness and are predominantly loose,
but contain lenses of firm sand. Also, included are
totally loose sands five to ten feet thick. These two
conditions have been grouped as "poor" because
some preconstruction site preparation would proba-
bly be required but may not be as extensive as in the
areas labeled "very poor".
Very Poor: This includes areas in which loose
sands ten feet or greater in thickness have been
encountered, areas in which firm sands less than five
feet thick are underlain by loose sand greater than
five feet thick, and areas in which sands containing
organic deposits have been found. All of these
conditions would likely necessitate treatment prior to
It should be noted that sands less than five feet
thick have been omitted from consideration in this
map. When very thin sands are encountered, the
material underlying them is generally of equal or
greater importance in foundation planning. These
areas will be brought to light in the discussion of
I 2 3 4 5 MILES
S I I
The presence of clays at or near the surface
presents a problem to many types of construction.
This is due to the low shear strength of many clays as
well as their compressibility. To compound the
problem, compressibility and shear strength of the
clays in the Tampa area are very variable and
inconsistent. Furthermore, clays or cohesive soils
cannot normally be mechanically improved.
One method of treatment is to remove the weak,
compressible, cohesive soils and replace them with
properly compacted competent materials. Unfortun-
ately, this is only feasible when they lie at or near the
surface; which in the Tampa area they rarely do.
Where they are deeply buried, the soils overlying
them may be sufficiently thick and competent to
adequately support a structure. However, when the
weak clays are shallow, they generally necessitate
some special attention in foundation design. If the
underlying limestone is also shallow, piling can be
used to transfer the foundation loads through the
weaker compressible clays to bedrock. However, since
piling is an expensive means of supporting small
structures, shallow weak clays can be a bigger
stumbling block to small construction projects than
to large ones.
The map on this page shows the areas in which
firm clays have been found underlying surface sands,
and areas in which soft clays or clays containing soft
lenses have been encountered beneath the sands. In
addition, areas are shown in which clay occurs only as
thin lenses within the sand or mixed with sand as a
minor constituent. Like the map illustrating sand
conditions this map is generalized on the basis of the
network of known values. The thickness and com-
pressibility of clay and cohesive soils varies as much
as if not more than the sands. It is virtually
impossible to predict the conditions that will occur at
a specific site without performing a subsurface
investigation at the site.
On the map, soft clays have been shown according
to thickness ranges (less than five feet, five feet to ten
feet, and greater than ten feet). If the soft clays are of
significance to a particular construction project, then
the greater their thickness, the more of a problem
they become. No attempt has been made however, to
categorize the clays according to the severity of the
problem they may cause. Whether or not the clays
will be a problem at all, largely depends on their
depth and thickness, and thickness and competency
of the overlying soils, the magnitude of the building
loads to be imparted and the structure tolerance to
This map will be used in the Land Use section in
combination with other maps to indicate land
suitability for construction.
Areas in which soft clays greater than ten feet
thick are found to occur. This includes soft clays with
interspersed lenses, clays containing peat layers and
karst areas with greater than ten feet of clay.
Areas in which five to ten feet of soft clay have
Areas in which soft clays less than five feet thick
Areas in which clays occur only as thin lenses
within the sand, or as a minor faction mixed with
Areas in which firm clays containing no soft lenses
occur. These clays are of varying thickness.
Deposits of organic soils, including peat and muck
are undesirable for almost all construction. Like
clays, they cannot be mechanically improved and in
most cases, must be removed and replaced with
Since areas where organic deposits occur are
generally swampy or lowlying, such sites have other
disadvantages imposed by the high ground water
table. Many swampy areas, however, have been
excavated, filled and compacted to provide accept-
able building sites.
The map shows areas which are designated as
marshes or swamps on the topographic maps of the
Tampa area. In many instances, these swamps were
filled after the topographic maps were compiled but
all of the areas designated on the map can be
expected to contain organic deposits. While these
areas need not be eliminated from consideration as
potential building sites, it should be realized that
their surficial deposits may limit land use or impose
additional expense for pre-construction site prepara-
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DISTRIBUTION OF WETLANDS IN THE TAMPA AREA
S WOODED MARSH
Areas underlain by cavernous limestones present
special foundation problems especially for heavier
buildings. Stronger foundations for high rise
structures are a necessity in such areas and inexpen-
sive spread foundations are usually not adequate. If
the problem is not severe, strap foundation (which is
the next least expensive) may be adequate, but in
many cases more costly mat foundations must be
used. A pile foundation is not generally a satisfactory
alternative; since when sinks develop, slumping of
sediments creates lateral pressure which may cause
standard piling to fail.
Other steps which may be taken in order to
minimize the potential risk of loss of foundation
support include proper site drainage and design of the
structure to minimize the net increase in stress on the
subsurface deposits. Stress increases can be minimized
by placing a basement beneath a structure and in this
way the total weight of the building may not be
substantially greater than the weight of the soils
excavated for the basement.
A last resort in dealing with the problem of
collapse is subsurface grouting. However, this is very
expensive and the amount of grouting required is
unpredictable. When grouting is undertaken, the final
cost and success of the effort is unknown.
An alternative action, though not necessarily a
solution to the problem is to move the location of the
building to a different position on the site where
cavities in the limestone have not been encountered
in the subsurface investigation.
It is difficult to assess the risk involved in
constructing in an area of potential collapse. Al-
though imminent risk of collapse can be minimized
by site treatment and careful foundation design, there
is still a potential risk of loss of foundation support
due to cavities which may not have been revealed by
the subsurface investigation.
"The final decision as to the type of foundation
system to utilize will be dependent upon the owner's
willingness to incur certain costs and assume certain
risks. These must be balanced against one another in
view of the type structure, intended use and
consequence of problems which might develop if the
risk becomes a reality."1
Areas in which collapses have occurred in the past
are shown on a map in the Geology section of the
report with the discussion of sinkholes.
DEPTH TO ROCK
A map showing the position of the rock surface
relative to mean sea level is presented in the Geology
section. Whereas that map is prerequisite to under-
standing subsurface relationships, the matter of
concern in construction planning is the depth to rock
measured from land surface as illustrated on this
page. The contour lines reflect not only variations in
the bedrock surface, but also variations in local
topography. This map can also be considered a map
of the thickness of surficial deposits and is a useful
tool in construction planning. When the surficial
deposits are incompetent as a support material, it is
vital to know how deeply buried the rock surface is
so that a decision can be made as to whether it would
be more economical to improve the surficial deposits
or to utilize piling for support.
This map is an important component of land
suitability for construction as presented in the Land
Use section of the report.
SJames F. Orofino, Orofino and Company, (Personal
4 S MILES
Soils are an integral aspect of both geology and
land use planning. The mantle of sand deposited in
Hillsborough County during Pleistocene time is the
parent material for many of the soils which developed
in the area. Drainage, climate, vegetation, and
topography have also played roles in the formation of
local soil types.
The Soil Conservation Service (S.C.S.) has identi-
fied and mapped the soils of Hillsborough County on
the basis of their characteristics as determined in the
field and lab. These include color, texture, structure,
consistence, depth of soil over bedrock or compact
layers, steepness of slope, degree of erosion, nature of
underlying parent material, acidity or alkalinity of
the soil, etc. The soil layer studied and described by
the S.C.S. ranges from 40 inches to 72 inches thick.
On the basis of observed analytically determined
characteristics, soils are classified into phases, types
and series. "The soil type is the basic classification
unit. A soil type may consist of several phases. Types
that resemble each other in most of their characteris-
tics are grouped into soil series."'
Detailed maps of soil phases in the Tampa area are
presented in the Hillsborough County Soil Survey. In
addition, a County map showing soil associations is
included and a revised map is presented in the
Supplement to the Soil Survey. Part of this map is
reproduced here and the major characteristics of each
association are given.
Soils that occur together in a regular pattern in the
landscape have been grouped into soil associations.
The individual soils within each association may or
may not have similar properties and interpretations.
POMELLO-ST. LUCIE ASSOCIATION: Areas
dominated by nearly level to gently sloping, nearly
white, excessively to somewhat poorly drained,
strongly acid, deep sands. The native vegetation
consists of scrub oak, slash pine, saw palmetto and
sand pine. Soils in this association are low in organic
matter and fertility and are very drought, hence
they're poorly suited to cultivated crops and citrus.
LAKELAND-ARREDONDO ASSOCIATION: Areas
dominated by nearly level to gently sloping, well to r
somewhat excessively drained, slightly to very strong-
ly acid, deep, brownish colored phosphatic and non
phosphatic sands. The native vegetation consists
primarily of turkey oak, pine, shrubs, grasses, and a
few palmettos. The soils in this association are low in
organic matter content and fertility and have a low
available water capacity.
BLANTON-LEON ASSOCIATION: Areas dominated
by nearly level to gently sloping, moderately well
drained, deep sands. Native vegetation includes pine,
oaks, grasses and palmettos. The soils have low
organic matter content, low natural fertility, and low
available water capacity.
LEON-PLUMMER ASSOCIATION: Areas dominated
by nearly level, very strongly acid, deep, somewhat
poorly drained sands with an organic stained sub-
surface layer. The native vegetation includes slash
pine, saw palmetto, runner oak, gallberry, woody
shrubs, and various grasses. The soils are low in
organic matter content, natural fertility and available
ONA-SCRANTON-LEON ASSOCIATION: Areas
dominated by nearly level to gently sloping, some-
what poorly drained, strongly acid, deep sands on
broad, low flatland. The natural vegetation consists
of pine, turkey oak, live oak, saw palmetto, woody
shrubs, and grasses. Most soils in this association have
moderately high to high organic matter content, and
are moderately low in natural fertility.
TION: Areas dominated by nearly level, somewhat
poorly drained, sandy soil with loamy to clayey
subsoils. The native vegetation is pine, cabbage
palmetto trees, saw palmetto, runner oak, woody
shrubs, and grasses. The soils have low organic matter
content, and low to moderate natural fertility and
available water capacity.
RUTLEDGE-FRESH WATER SWAMP-PLUMMER
ASSOCIATION: Areas dominated by nearly level,
very poorly drained, deep, strongly acid to medium
acid sands in low wetland. Native vegetation is mainly
water-tolerant grasses and sedges, pickerelweed and
St. Johnswort, with cypress, bay, gum and occasional
pine trees in swampy areas. Soils have low to high
organic matter content and low fertility. Wetness is
an outstanding limitation for many uses of these soils.
BRIGHTON-TERRA CEIA ASSOCIATION: Areas
dominated by nearly level, very poorly drained,
shallow to moderately deep, acid to neutral organic
soils in marshes and swamps. Native vegetation
consists of sawgrass and various other sedges and
grasses. Organic soils in this association are high in
nitrogen but low in all other plant nutrients.
Excessive wetness is characteristic.
FRESH WATER SWAMP: Areas dominated by nearly
level, very poorly drained mineral and organic soils in
stream bottoms and swamps. Native vegetation
consists of hardwoods, cypress, bay, cabbage, palmet-
to, pines, shrubs, vines, ferns, and grasses.
SALT WATER SWAMPS AND MARSHES: Areas
dominated by nearly level, very poorly drained, saline
soils lying adjacent to and affected by salt water tidal
action. Native vegetation includes salt-tolerant grasses
and mangrove trees.
MINE PITS AND DUMPS: Areas dominated by larg,
open pebble phosphate mines and adjacent spoil
ISoil survey, Hillsborough County, Florida, 1958, p. 58.
0 I 2 3 MILES
i I ,1I I
Soil data can be utilized in a variety of projects
which are of concern to local and regional planners.
In addition, the S.C.S. can provide technical assist-
ance on water management, soil erosion and stabili-
zation, agronomy, biology, etc.
"One of the most talked about concepts in recent
years is the idea of spreading the effluent from
municipal sewage treatment plants on the land to
eliminate the discharge of the effluent into surface
waters in the state."' Soil properties and plant
relationships play a vital role in land renovation of
waste water. The cation exchange capacity of the
soils (especially clayey soils) is a most important soil
property. This soil property along with plant nutri-
ent removal and denitrifying bacteria can very effec-
tively remove certain constituents of waste water.
"Any design of a system for land spreading of waste
materials must consider the soil system and its
relation to the local landscape, which includes the
stratigraphy, geomorphology, and hydrology of the
area under consideration."2
The local Soil and Water Conservation District has
expended a good deal of effort toward solving
drainage problems in the Tampa area. Although much
of this effort has involved agricultural lands, the
drainage principles have been applied to urban lands
as well. For example, shortly after the completion of
Tampa Stadium, it was found that the parking area
became flooded and unusable after rains. Using the
standard soil survey in conjunction with field
investigations, the S.C.S., working through the Hills-
borough Soil and Water Conservation District, de-
signed a subsurface drainage system for the parking
areas, and the flooding problem was eliminated.
Soils data can and should be used along with
geologic and hydrologic data as an input source for
1 Livingston, J. B., Land Renovation of Waste Water, p. 1
from: Workshop Proceedings-Use and Interpretations of Soil
Surveys and Engineering Principles of Water Management,
1972, Soil Conservation Service.
SDaniels, R. B., Water Movement in Soils, p. 7, from
Workshop Proceedings-Use and Interpretations of Soil
Surveys and Engineering Principles of Water Management,
1972, Soil Conservation Service.
n URBAN PLANNING
Soil Conservation Service control structure in northwest
Tampa Stadium parking area after installation of the
subsurface drainage system.
Shallow excavation showing a soil profile.
Many land uses are essentially "surface" uses and
consequently, soil characteristics are the most import-
ant geohydrologic consideration in planning. The land
use most vitally linked with soils is agriculture or
agronomy. Land areas in which the soils are
particularly productive warrant consideration for
designation as agricultural lands. The S.C.S. has
compiled detailed information on the productivity of
various soils with regard to assorted crops.
Other land uses in which surficial materials (soils)
are of primary concern include recreational areas,
highway and airport sites, cemeteries, golf courses,
single story buildings, etc.
Shown on this page is Table 5 from the
Supplement to the Soil Survey: Hillsborough County,
Florida. This lists the degree of limitations, restric-
tions and hazards for various land uses by soil
Two factors should be borne in mind when this
table is examined:
1) This generalized table is derived from more
detailed S.C.S. tables and maps. Final evaluation of a
specific site for a proposed use must be supported by
detailed on-site investigations.
2) The limitations listed in the table are based on
the characteristics of only the top 40-72 inches of
The Rating System
None to slight: Soils have properties favorable for a particular
use. Limitations are so minor that they can be overcome
easily. Good performance and low maintenance can be
expected from these soils.
Moderate: Soils have properties moderately favorable for a
particular use. Limitations can be overcome or modified
with planning, design, or special maintenance.
Severe: Soils have one or more properties unfavorable for a
particular use. Limitations are difficult and costly to
modify or overcome, requiring major soil reclamation,
special design, or intense maintenance.
Very severe: Soils have one or more properties so unfavorable
for a particular use that overcoming their limitations is
very difficult and costly. Reclamation is extreme, re-
quiring the soil material to be removed, replaced or
The rating provided for each association is for the
predominant soil in the association. Other soils in the
association may have different ratings. These ratings are
actually measures of "degree" or "intensity" of soil
limitations, restrictions, or hazards for a certain use. Most
soils are suitable for all uses if provisions can be made to
overcome or eliminate the problems.
NAME OF ASSOCIATION
WITH COMPONENT SOILS AND
PERCENT OF EACH
ST. LUCIE 24
RUTLEGE-FRESH WATER SWAMP-
FRESH WATER SWAMP 24
TERRA CEIA 30
FRESH WATER SWAMP
SALT WATER SWAMPS & MARSHES
MINES, PITS AND DUMPS
HIGHWAYS, DIRT ROADS
AIRPORTS, UNPAVED STREETS
STREETS, PAVED AND PARKING
ROADS AND AREAS
MODERATE MODERATE MODERATE
WT WT, FL TRAF, WT, FL,
WT, FL, PBV
WT. FL, PBV
SEVERE SEVERE MODERATE MODERATE
TRAF, PROD PROD, AWC WT WT, PROD, AWC
MODERATE MODERATE MODERATE
WT, AWC WT, FL WT, FL,
MODERATE MODERATE MODERATE MODERATE SEVERE
WT, FL TRAF, WT, FL WT, TRAF, FL WT, FL WT, FL
SEVERE MODERATE MODERATE SEVERE
TRAF, WT, FL WT, TRAF WT WT, FL
WT, SH-SW WT, TRAF
TSC, WT, FL
FL, WT, TSC
TRAF, WT, FL
FL, WT, TSC
(VARIABLE) (VARIABLE) (VARIABLE)
MODERATE MODERATE SEVERE
WT,TRAF WT WT, FL
TRAF, WT, FL
FL, WT, TRAF
TRAF, WT, FL
WT, FL, TRAF,
(VARIABLE) (VARIABLE) (VARIABLE) (VARIABLE)
ABBREVIATIONS: WT-WATER TABLE, TRAF-TRAFFICABILITY, FL-FLOOD HAZARD, AWC-AVAILABLE WATER CAPACITY, PROD-PRODUCTIVITY, PBV-PRESUMPTIVE
BEARING VALUE, SL-SLOPE, TSC-TRAFFIC SUPPORTING CAPACITY, PERM-PERMEABILITY, ORG-ORGANIC
DEGREES OF LIMITATIONS, RESTRICTIONS AND HAZARDS FOR SELECTED USES BY SOIL ASSOCIATIONS, HILLSBOROUGH COUNTY, FLORIDA
(MODIFIED FROM SOIL CONSERVATION SERVICE, 1969, TABLE 5)
PRIMARY ENERGY SOURCES
For purposes of this energy discussion, the Tampa
Bay Area will be assumed to include Hillsborough,
Pinellas, Pasco, Polk and Manatee Counties.
Adequate supplies of primary energy sources, at
reasonable costs, are essential to modern living.
Without such supplies every facet of our way of life is
handicapped. Growth of industry and of population
is dependent upon the relative cost of such supplies.
Historically and right up to the end of 1972, the
area is 100% deficit in internal primary energy
supplies. All primary energy used in the area, both
directly and through conversion to secondary energy
(electricity), is imported. Most is "domestic",
imported from other parts of the United States, some
is foreign, imported from other countries.
This complete dependence upon imports may
change in the future. It is now suspected that there
may be petroleum deposits in the area. It is known
that uranium (the fuel source of nuclear power
plants) exists in connection with the phosphate
deposits in the eastern portion of the area. Develop-
ment of this resource may become economically
feasible in the future. More detailed discussion of
these possible future energy sources will be found in
other sections of this report.
Primary energy is imported to the area in the
forms of liquid petroleum products, natural gas and
Table "A" lists the various primary energy sources
brought into the area during 1971 and illustrates the
growth for 12 months ending October 31, 1972. For
ease in comparing utilization value, tons of coal and
MCF (million cubic feet) of gas have been converted
to "equivalent barrels" of oil.
Some indeterminate portion of the liquid products
brought into the area is exported to other parts of
Florida by truck, rail and pipeline. There appear to be
no available statistics covering these movements but a
guess is that they may amount to 15-20% of the
quantities shown in the table.
63 Million Bbls.
In addition to the quantities shown in the table,
7,957,000 barrels of residual oil were brought into
Port Manatee in 1972, all of which was barged up the
coast to Florida Power Corporation's plant at Crystal
River. All of this residual was of foreign origin.
Liquid petroleum products are, with very minor
exceptions, brought in by water through the Port of
Tampa (including Weedon Island in St. Petersburg)
and Port Manatee. All of the crude oil, most of the
residual fuel and minor amounts of the jet fuel and
diesel oil are used as power plant fuel in the
generation of electricity. The balance of the residual
is used in industrial heating and for fueling ships in
the port, while the uses of the other products are
Most of the residual is of foreign origin, mostly
from Venezuela and the Dutch West Indies. (Starting
in 1973 there will be substantial imports of residual
from the Virgin Islands). All of the crude oil is
imported from Libya. The balance of the liquid
petroleum products is of domestic origin, principally
from the refineries along the Texas and Louisiana
coasts of the Gulf of Mexico.
Jet Fuel & Kerosene
Diesel Fuel (No. 2)
Residual (No. 6)
Coal (equiv. bbls)
Gas (equiv. bbls)
As an approximation, the cost of transportation of
petroleum products and of coal, in large quantities by
ocean vessel, is about 1/30 of the cost of moving the
same quantity overland by truck. Specifically, at this
writing, a barrel of residual oil moves 2,000 miles
from the refinery in Venezuela to the Port of Tampa
for about 30 cents. It costs over 50 cents more to
then move the same barrel 100 miles by truck from
Tampa. There are no more than three other ports in
Peninsular Florida which can handle ships as large as
can be handled in Tampa Bay. And none of these
have as extensive oil handling and terminal facilities
as does the Port of Tampa (including Port Manatee).
The net result is that the Tampa Bay Area can offer
fuel using industries all grades of petroleum products,
from more suppliers, and at lower costs than can
almost any other area in Florida or for that matter, in
the entire southeast.
(Assume 3.639 bbls/ton)
77,952,000 (Equivalent bbls.)
(Assume 6.32 MCF/bbl.)
11,396,000 (Almost exclusively No. 6 and crude)
Note: Basic data from reports issued by the Tampa Port Authority.
Primary Energy Sources Received in Tampa Bay Area
(Barrels of 42 U.S. Gallons)
12 Months Ending
Natural gas is brought into the area by the pipeline
system of the Florida Gas Transmission Company
which extends from southern Texas around the Gulf
into Florida. Most of the gas handled by the pipeline
originates in Texas and Louisiana. Relatively small
amounts are now being picked up from the new oil
fields in northwest Florida.
Approximately 45% of the gas the pipeline brings
into the area is used in generation of electricity.
Another 30% is sold directly to large industrial users,
with the balance being sold to 8 retail gas distributor
systems for resale for residential, commercial and
small industrial use.
The pipeline facilities of the Florida Gas Trans-
mission Company and of the retail distribution
systems supplied by it have expanded and kept pace
with the demand for gas in the area. In spite of the
nationwide shortage of natural gas, there has been
very little curtailment, or interruption, of gas supply
to industrial users, and none at all to commercial and
residential users. However, at least until the nation-
wide gas supply picture improves, Florida Gas is
accepting no new large industrial customers but to
date there has been no restriction placed on serving
new residential, commercial and small industrial
All of the coal brought into the area is used by
Tampa Electric Company for generation of electrici-
ty. This coal originates in strip mines in Western
Kentucky and Southern Illinois and is moved in river
barges down the Ohio and Mississippi Rivers to a
transship facility below New Orleans. At this point it
is reloaded into ocean going barges, holding over
20,000 tons each, for the Gulf of Mexico crossing to
the Tampa Electric docks where it is unloaded by
fast, automatic machines. The barges return loaded
with phosphate rock, an operation which substantial-
ly reduces the transportation cost of the coal.
FLORIDA GAS TRANSMISSION LINES
The entire State of Florida is blanketed by a
network of high voltage transmission lines which
interconnect the load areas with 35 power plants of
four investor owned power systems, four major
municipally owned systems, several smaller municipal
systems and. one small federally owned plant.
Additionally, the transmission network is intercon-
nected at several points to the north and west with
the country's overall network.
Various portions of the Florida network are
owned by the individual power supplying systems.
However, it is completely interconnected and
operated substantially as though it were all under one
ownership. This results in a high degree of service
reliability, with every electrical load area being served
by multiple sources. With rare exceptions, power
plant and transmission failures do not cause inter-
ruption of electrical service anywhere in the state.
The accompanying map shows the portion of this
transmission network within the Tampa Bay Area as
of January 1, 1972, with most of the circuits
operating below 115,000 volts omitted for clarity.
Also not shown are some 50 of the small substations
where power is stepped down to lower voltages for
distribution to ultimate users and many of the
industrial substations where power is delivered to
large users at transmission voltages.
The Tampa Bay Area is served by three investor
owned and one municipally owned electric utility
systems. Hillsborough County, the eastern portion of
Polk County, and minor portions of Pinellas and
Pasco Counties are served by Tampa Electric Com-
pany. Florida Power Corporation serves, with minor
exceptions, Pinellas, Pasco and the west portion of
Polk County. Manatee County is served by Florida
Power and Light Company. The City of Lakeland and
some adjacent territory is served by the Lakeland
Department of Electric and Water Utilities. Electric
power distribution in some portions of the area is by
municipally owned distribution systems and Rural
Electric Cooperatives, all of whom purchase their
power wholesale from one or another of the
There are power plants at eight locations within
the area, as detailed in Table 1, with a total capability
of 2975 MW. The interconnected transmission net-
work enables any part of the area to be served irn case
of need from any of the 35 power plants in the state
which have a total capability of over 14000 MW.
That the electric utilities serving the area are
keeping abreast of needs is shown by the fact that
generating capability within the area has doubled
since 1965 and that additional capability now under
construction or definitely planned, will, in the next
four years, more than double the present capability.
Depending on the type of generating unit and the
economics of a particular situation, these power
plants burn a variety of fuels-all brought into the
area through the Port of Tampa (except natural gas,
which is pipelined in). Table II shows the total
amount of each fuel used and the percentage this
represents of the total brought into the area. In
summary 29% of the total primary energy sources,
coal, oil and gas, brought into the Tampa Bay Area
are converted by the utilities into electric inprrn,
Total Equiv. Bbls.
Tampa Bay Area
Power Plant Fuel Use
(1,337,185 equiv. bbl.)
(12,189,646 equiv. bbl.)
% of Total Shipped into Area
Note: Data supplied by the utilities.
Tampa Bay Area Power Plants (1/1/73)
No. Generating Units
1972 Net Output
Type Fuel (Millions of KWH)
FLORIDA POWER CORP.
TAMPA ELECTRIC CO.
CITY OF LAKELAND
Plant No. 3
Plant No. 3
D ..... ....
.......... Steam Turbines
........... Gas Turbines
.. ............. Diesel
. .Residual (No. 6) Oil
......... Crude Oil
.. Light Oil distillatee)
....... Natural Gas
Note: Data supplied by the utilities
Greek owned tanker "Demosthenes V" discharging 140,000 barrels of Venezuelan residual oil at
Florida Power Corp, Weedon Island, St. Petersburg. (photo courtesy of Florida Power Corp.)
Preliminary figures indicate that during 1972 the
electric utilities supplies over 15 billion KWH of
electric energy, broken down as follows:
Millions of KWH
% of Total
Typical Electric Bills
January 1, 1971
'Approximately 50% of industrial use was in the
phosphate mining and processing industries.
2Includes street lighting and other municipal uses,
sales for resale, company's own use, etc.
0 E z
E 0 E
C = E E2
ES So E BO
(fl N 2 ,r ^ 1
Rates for electric service in the Tampa Bay Area
are generally closely in line with National and Florida
average rates, and far below the highest rates in the
"lower 48" states. These highest rates are generally
found in the New England and New York City areas.
Rates lower than charged in the Tampa Bay Area are
generally found in areas abundantly supplied with
hydro-energy, with its zero fuel costs, or in areas
within coal or gas fields where there is little or no
transportation component in the utilities fuel costs.
Table III lists rates in effect on January 1, 1971.
As the direct result of spiralling fuel costs, general
inflation and the high costs of meeting environmental
demands, most of the country's electric utilities have
been forced to increase rates during the intervening
Therefore the actual rate figures given in the table
are no longer applicable. However, there would be no
important change in the relative positions of the
various areas listed.
Highest in 48 States
(cities of 50,000
or more) 12.78 27.66 43.07
National Average 7.84 19.24 28.45
Florida Average 7.39 19.51 30.65
Tampa Bay Area Avge. 8.03 19.50 32.68
Tampa Bay Area
Highest 8.13 19.73 36.18
Tampa Bay Area
Lowest 6.93 19.27 29.19
Sources: Federal Power Commission Publication
"Typical Electric Bills", December, 1971.
1Approximately 50% of industrial use
was in the phosphate mining and
2Includes street lighting and other
municipal uses, sales for resale,
company's own use, etc.
USE OF ELECTRICITY
*MILLION KILOWATT HOURS
ENERGY OF THE FUTURE
Modern man needs sources of energy to support
his way of life. Such sources are needed to provide
light, heat and cooling of his buildings; to move his
automobiles, airplanes, trains, trucks, ships; to power
his shops, factories and mines and for countless other
uses. Without adequate supplies of energy, civilization
and life would end.
For the United States, 97% of the energy used
comes from the three fossil fuels, coal, oil and gas.
Hydro-electric and nuclear energy supply the remain-
ing 3%. About 26% of the fossil fuels are converted
into electricity, the balance is used directly. The
figures for the rest of the world are not greatly
different, except that in some areas wood and other
organic materials contribute to the energy supply in a
The fossil fuels represent a finite resource-once
used they can not be replaced. Therefore there must
inevitably come a day when there are no more fossil
fuels to support a civilization. Opinions vary as to
when this day will come but the best estimates
indicate that by the end of this century supplies of
natural gas will be substantially exhausted, liquid
petroleum supplies may last through the middle of
the next century, coal will probably last 300 to 500
In the intervening years we can expect constantly
increasing costs, coupled with spasmodic but in-
creasingly severe shortages. The local shortages of
natural gas and heating oil during the winter of
1972-73 were an insignificant illustration of what will
become commonplace if substitute sources of energy
are not developed.
To date there appear to be two such substitutes
which have reasonable hopes of being developed into
practical sources of energy-nuclear power and solar
Nuclear power is furthest along, having been
developed to the point where it is (early 1973)
contributing 2% or 3% of the nation's total energy
needs, all of this in the form of electric energy.
Present indications are that by 1985, nuclear will be
contributing between 11% and 15% of the country's
Florida's two largest utilities have been among the
leaders in the nuclear field. In January 1973 they had
one large nuclear generating unit operating, three in
various stages of construction and one more in the
advanced planning stage. All of Florida's utilities are
studying the need for, and feasibility of additional
None of the nuclear units now definitely planned
for Florida will be in the Tampa Bay Area. However,
the area will probably see such units in the future
since there are locations in the area which meet the
rather stringent siting requirements for such generat-
The current commercial types of nuclear generat-
ing units consume uranium as a fuel, much as a fossil
unit consumes coal, oil or gas. Uranium, like the fossil
fuels, is a finite resource. As available supplies are
used up, the price increases.
It is known that there are fairly large amounts of
uranium ore in connection with the phosphate
deposits in the eastern portion of the Tampa Bay
Area. It is currently estimated that this ore is
recoverable at costs of around $15 per pound of
refined U30s. The current market price of U308 is
less than $8 per pound and industry sources estimate
that it will be the late 1900's before market
conditions will make recovery of Florida's uranium
ore economically feasible. (See W. R. Oglesby's article
on this subject, Page 48, Tallahassee Area study
published by the Bureau of Geology in 1972.)
U.S. ENERGY SOURCE
PROJECTED TO 1985
There are four major processing steps involved in
converting the U308 to actual nuclear plant fuel.
Special requirements make it most unlikely that
Florida would ever be an attractive location for plants
involved in the first two of these steps, conversion of
the powder U308 into the gaseous UF6, and
enrichment of this gas by increasing its contained
percentage of the isotope U235 .
However, the remaining steps, conversion of the
gaseous, enriched UF6 to the powder UO2, pelletiz-
ing this powder, and assembling the pellets into
reactor fuel assemblies are exactly the type of
industries which Florida likes and which like Florida.
They are light, clean, high precision industries,
requiring good supplies of highly skilled labor and
abundant resources of engineering and scientific
manpower. Given an adequate local market for their
output, which should exist by the early 1980's, it
should be possible to attract this industry to Florida.
Going back now to the statement that uranium is a
finite resource, it is evident that, like the fossil fuels,
there must come a day when it is exhausted. Before
that day comes, perhaps early in the next century,
another type of energy source must have been
brought to commercial practicality.
Uranium oxide could be produced from 'wet process' phosphate plants.
Photo courtesy of the Florida Phosphate Council 79
01 AND GAS
The "breeder reactor" which actually can produce
more fuel than it consumes, has been proven in the
laboratory stage. Funded jointly by the electric
utility industry and the Federal Government, the first
"demonstration" plant, using the breeder process, is
now in the engineering stage. Because of the problems
involved in converting a laboratory process to a
practical commercial power plant, many in areas of
new and unknown technology, it is expected that it
will be the mid 1980's before the first commercial
breeder plant will be operational, at a total develop-
mental cost of well over one billion dollars.
But, if the "breeder" or some equivalent process is
not available by early in the next century, civilization
as we know it must come to an end!
Solar energy research has been sadly neglected,
perhaps because it does not have the glamor of
nuclear and other advanced scientific development.
The work which has been done in this field, largely at
the University of Florida leads us to believe that if a
small fraction of the money and scientific man hours
which are going into nuclear development were put
into solar development, then we would have the
means to capture enough of the limitless solar energy
to supply all of the energy needs of the world as long
as it exists. And Florida, because of its unique
climate, should be the center of such research.
SrANTA OSA OKALOO5A WALTON JACKSON G E O R G I A
ASHINGTON_ GTD -DN -- -.
GADSDEN M/ HAMILTON
v CALHOUN / MADISON
fl \u --~ TAYLOR I FYTT
GULF --- -A.N \ LAFAYETTE
EASTERN MARGIN OF F ilxE
MISSISSIPPI SALT BASIN o E
Scale In Miles
There.is no oil or gas production within the Tampa
Area, and no immediate prospects for such produc-
tion. Hillsborough County, and the six counties
surrounding it within a 50-mile radius, have had 41
oil tests drilled therein between 1900 and 1973.
However, only 12 of these tests have been drilled
within the past 30 years, since the discovery of
Sunniland Field, in Collier County. Sunniland marked
the entry of Florida into the ranks of oil producing
states, and we now rank 12th out of 32 states which
have petroleum production.
Many of the earlier wells in the Tampa area were
not adequate to test the potential pay zones. In short,
these seven counties remain in the Twilight Zone, as
far as their petroleum prospects are concerned; they
are possible but not probable areas from which oil or
gas may be recovered some day. The preceding
statement is made in light of the following considera-
1. The known producing trend in south Florida
extends along the northeastern portion of the
Shelf associated with the South Florida Basin.
2. The known producing trend in northwest
Florida extends along the eastern margin of the
Mississippi Interior Salt Basin.
3. The Tampa Area is not located in a basin but
rather on the central Florida platform, a
structurally positive area. There is no particular
reason to believe adequate petroleum source
beds exist on or in conjunction with this central
The lack of oil production in the vicinity of
Tampa does not signify that the availability of
gasoline or fuel oil is less here than in other
metropolitan areas. Austin, the capital of Texas,
experienced a dozen critical periods of petroleum
shortage during 1972. The City of San Antonio,
Texas, was threatened by a blackout when the
municipal electric power system could not obtain
natural gas to operate in the spring of 1973. No
power shortages due to lack of fuel were reported in
the Tampa area. Tampa, like the rest of Florida, but
unlike Texas and most of the United States has no
liquid petroleum products pipe lines; and hence has
complete flexibility of its sources of supply. Tampa is
one of four deep sea ports in the Gulf Coast of the
U.S. and is open to the fuel markets of the world. On
the other hand, most of the inland cities of the
United States are served' by product pipe lines which
are inflexible. If the input supply of such pipe lines is
curtailed, the output at the distribution point is
Although there is no pipe line supply of petroleum
to Tampa, the city is served by the natural gas line of
Florida Gas Transmission Company. Natural gas for
domestic use is no real problem; the supply of natural
gas for generating electricity is, unfortunately, in-
adequate here as in other cities. This is not due to
lack of capacity of the pipe line. Its carrying capacity
could be increased by the simple expedient of
increased compressor capacity along the line. There is
a real shortage of natural gas at the sources of supply.
Company officials of Florida Gas recently have
announced an intention to convert one of the parallel
lines in their gas transmission system to a products
pipe line. If this is done, Tampa as well as other areas
of Florida served by the Florida Gas Company will
enjoy lower transmission costs of fuel overland and
reduced trucking on the highways. However, users of
this fuel may find they have traded a flexible
seaborne supply open to world markets for a rigid
source controlled by the supply available at the input
points to the pipeline.
LINE of SECTION
Crude oil produced in Florida is from two widely
separated basins which are: The Mississippi Interior
Salt Basin and the South Florida Basin, shown on
Page 80. Production occurs below 11,000 feet in the
South Florida Basin and below 15,000 feet in the
Florida portion of the Mississippi Salt Basin.
The production from Jurassic age strata in Jay,
Blackjack Creek and Mt. Carmel Fields occurs in the
Norphlet Sand, which immediately overlies the
Louann Salt, and in the Smackover Limestone which
overlies the Norphlet Sand. These three fields will
produce about 100,000 barrels of oil and
100,000,000 cubic feet of gas per day, when fully
developed, about 20% more than their current
The Sunniland Limestone of lower Cretaceous age
supplies the balance of crude oil production from six
fields centering around Immokalee, Collier County,
Florida. The combined daily production from these
fields is about 13,000 barrels of crude oil. No
commercial amount of gas is derived from these
Florida produces about 30,000,000 barrels of
crude oil annually and uses about 7 times this amount
of refined petroleum products. All of the crude
produced in Florida is exported to refineries in other
states and all its petroleum products are imported by
sea. Therefore, oil production in the state has no
more direct effect on Florida's petroleum products
supply than it has on other areas in the United States.
However in the case of gas, Jay Field produces about
a tenth of the supply carried for distribution by
Florida Gas Transmission pipe line to the Tampa area
and around the State. Gas is a desirable, clean, and
currently, low cost fuel. If enough of it is discovered
in the state, we could solve the environmental
problems connected with electric power generating
plants while the supply lasted.
30 YEARS TO
5 YEARS TO
THE U.S. ENERGY GAP 1970-1990
NEED FOR NEW
Source: SHELL OIL CO.
Ultimately, Florida, like the rest of the country,
will be forced to shift to an energy base other than
petroleum and natural gas, as the domestic supply
becomes exhausted. The international supply can
augment our own petroleum resources; but for
economic, security and political reasons it is nonsense
to suppose we could exist as a wholly dependent fuel
This is illustrated by a chart entitled "The U.S.
Energy Gap 1970-1990" from a publication by Shell
Oil Company shown in reproduction. The graph
shows total oil imports of about 2% million barrels
per day (B/D) in 1970, rising to 5% million B/D in
1975, and to 23% million B/D in 1990. If the true
cost of foreign oil in 1970 is taken at $1.00 per barrel
(considering that United States companies operating
abroad must pay foreign royalties and taxes, and that
shipping costs are paid to foreign nationals) our trade
deficit on oil was about $900,000,000. By 1975, this
cost may well double, as both oil prices, royalties,
and transport costs increase. Hence the 1975 deficit
estimated on oil imports is 4 billion dollars. These
costs will probably redouble by 1990, so that the
deficit on oil imports may attain 34 billion dollars.
These projections do not allow for dollar inflation
which the Organization of Petroleum Export
Countries insists must be adjusted with more dollars.
The chart indicates we will produce 10 million
barrels of oil per day in the U.S., and import 23%
million barrels by 1990. If this occurred, the Nation
would be dependent on foreign sources for the energy
necessary to our military and industrial survival, for
the two are interdependent. The obvious answer is
that the charted projection will not occur and that we
will not be using a total of 33% million barrels of
petroleum in 1990. Either we shall have adapted to
such alternate sources available by reduction of coal,
oil shales, and tar sands to petroleum liquids, or
perhaps shifted to a hydrogen energy base through
electrolysis of water in a related nuclear reactor
program furnishing electric power. A third course, to
reduce our total use of energy, will take place as the
cost of fuel increases relative to other items in the
gross national product.
*CRUDE OIL EQUIVALENT
^"^^ f^^ ^
CURRENT LAND USE
Although 86.5% of the land within the urban
limits of the City of Tampa is developed, only 15.1%
of the land within the Tampa area (as delineated by
the map) is developed. The following table shows the
percentage of land in the Tampa area that falls within
each land use category:
single family residences
retail and services
transportation and utilities
public and semi-public
recreation and open space
vacant and open range
Present land use largely reflects the "preference
development" practices of the past which were
essentially based on the location of certain natural
and cultural features and on economic considerations.
Certainly many examples of unwise land use within
the Tampa area could be identified, however, it is not
the purpose of this report to criticize the existing
conditions that cannot be significantly altered. It
should be pointed out that current land use patterns
do have a marked influence on the direction that
future development will take. As increasing know-
ledge about the area becomes available appropriate
legislation and zoning designations can serve to
channel development into patterns compatible with
(so-rcj. T-mp1a Da Regional Pla-:iing Co ,nil)
0 I 2 3 MILES
PROJECTION OF THE PERCENT INCREASE IN DEVELOPED LAND
BETWEEN 1972 AND 2000.
FUTURE LAND USE
Presented on this page is the Hillsborough County
Planning Commission's Provisional Plan of Develop-
ment through 1990. At the time of this writing, the
plan had not been finalized, and the copy shown here
is subject to revision. The plan is based on existing
major land use categories. Areas which are currently
urbanized represented the starting point for the
Preferred future expansion areas include those
areas into which urbanization anticipated by 1980
and by 1990 may best be channeled. It should be
pointed out that in both categories, two to three
times more land has been assigned for urbanization
than trends for future land consumption indicate is
needed. This extra allotment is to compensate for
portions of the designated land which may be found
undevelopable, and to allow for additional urbaniza-
tion that could not be foreseen at this time.
Around the fringes of the Tampa area, land is
slated to remain undeveloped or to be used as
agricultural land. According to the Planning Com-
mission, much of this land is developable, however, it
is not needed for current or projected land use
Substantial portions of land have been designated
as interim or permanent open area. Included in this
category are preservation and conservation areas or
those lands which should experience little or no
development. Riverine and swamp environments fall
into this category, and it is envisioned that recreation
will be the primary land use here. Also included are
Southwest Florida Water Management District's exist-
ing and proposed reservoir areas.
In preparing the Plan of Development the Planning
Commission has utilized a sequential approach.
Initially, environmental factors were evaluated and a
series of maps indicating land use suitabilities were
constructed largely on the basis of geohydrologic
considerations. These maps were used in conjunction
with socio-economic projections in order to establish
a basic pattern for growth.
In delineating specific urbanization patterns within
suitable areas, several planning concepts were utilized.
The concentric pattern of development (where
growth takes place around the perimeter of the
existing urban center) was used in combination with
the radiating plan (where urbanization expands along
highway routes) and the satellite cities concept
(discussed on the following page) to establish what is
hoped to be an equitable and environmentally
compatible plan of development.
With regard to specific land uses, several note-
worthy policies are employed by the Planning
Commission. Because of the need to de-centralize
traffic flow and diffuse pollution, planning of
concentrated industrial areas is avoided. In general
industrial parks help achieve the goal of diluting the
problems often associated with industry. With large
peripheral land areas and attractive planting, industri-
al parks can be a visually pleasing addition to the
landscape. Busch Gardens is a notable local example.
Transportation is another important consideration
in planning for the growing Tampa area. The Planning
Commission attempts to coordinate all phases of
transportation and to incorporate highway, port and
airport traffic into a single efficient network.
An additional effort of the Planning Commission is
to de-emphasize development in northwest Hills-
borough County in the area of the well fields.
The plan shown on this page reflects the environ-
mental awareness of the Planning Commission. As
new data becomes available and growth trends
change, the plan of development will be revised and
A future land use plan, by nature, constantly
evolves in response to changing regional needs and
increasing cognizance of local potentials. Both the
Hillsborough County Planning Commission and the
Tampa Bay Regional Planning Council are currently
involved in updating future land use plans for the
Tampa area. TBRPC prepared a preliminary plan for
1985 in 1968. A portion of that plan is presented on
the following page.
According to the Council,
"The preliminary plan provides for the alloca-
tion of the region's developable land resources
into patterns of use which will be required to
serve the future population."
Among the objectives of the plan are the following:
LAND DEVELOPMENT Encourage compatible
land use arrangements through purposeful site plan-
ning to provide compatible, compact and diversified
WATER SUPPLY Provide a guaranteed water
supply for the region through the investigation,
development and preservation of all possible sources
including watersheds, surface supplies, salt water
conversion, and aquifers.
WATER AND AIR POLLUTION Stop water and
air pollution through better public management and
control of wastes, location planning for polluting
industries, the formation of effective sanitary sewer
districts, the establishrant of on-site treatment of
industrial wastes, and the investigation of a regional
solid wastes disposal system.
SHORELINE DEVELOPMENT Discourage shore-
line development in conflict with existing develop-
ment, natural tidal flows and irreplaceable marine
OPEN SPACE/RECREATION Adopt a multi-use
open space program for the acquisition and develop-
ment of lands for recreation, conservation, cultural
and scenic uses thereby protecting this economic
resource which plays a major role in generating new
resident and tourist growth.
It is evident that the Council has a great concern
for the physical environment. In many instances the
Council relies heavily on available geohydrologic
information for making land use decisions. During the
planning process, many specific questions arise that
can best be answered by the geologist or hydrologist.
The answers to such questions are rarely readily
available and must be based on careful evaluation of
existing data. This illustrates the importance of
continuing basic geologic and hydrologic data collec-
tion programs and expanding these programs in areas
for which accelerated development is predicted.
In the Tampa area growth projections indicate that
areas peripheral to urban Tampa will experience the
greatest increase in development between now and
the year 2000. In conjunction with future develop-
ment, the Tampa Bay Regional Planning Council
believes that two new concepts in urban planning
might be applicable to the Tampa area. These are the
"new town" policy and the "satellite city" concept.
The "new town" policy involves designing small
self-sustaining cities outside the realm of existing
metropolitan areas. The "satellite cities" concept
entails encouraging development in existing suburbs
so that they could essentially function independently
but would in part be dependent on the urban center.
A major objective of the two concepts is to
deemphasize over development of urban areas. In
formulating plans for "new towns" and "satellite
cities", the Planning Council will be looking first at
Concern with environmental factors has also
prompted state legislation. Recently, the Florida
Land and Water Management Act was passed. The
purpose of the Act is to permit development without
destroying Florida's resources or environment and to
provide for the designation of areas of critical state
concern and development of regional impact.
In designating areas of critical state concern, the
state or the local government will set forth develop-
mental guidelines to insure preservation of historical
and archaeological resources, and guidelines for water
storage areas, significant marine resource areas and so
Development of regional impact is defined as any
development which, because of its character, mag-
nitude or location, would have a substantial effect
upon the health, safety or welfare of citizens of more
than one county. In evaluating regional impact
generated by development, such things as the degree
to which development would contribute to air, water
and noise pollution, number of new residents,
vehicular traffic and the likelihood of subsidiary
development are to be regarded in establishing
From: Tampa Bay Regional Planning Council,
1985 Preliminary Regional Plan.
Geology, engineering geology, and hydrology have
long been of eminent importance to transportation
planners. When new highway sites are designated,
on-site soil surveys and subsurface explorations are
carried out. The State Department of Transportation
maintains an Office of Materials and Research which
is charged with the responsibility of carrying out
The first phase of study is an office procedure that
entails gathering all available information on the soils
and geologic conditions in the project area. Aerial
photographs, Soil Conservation Service publications,
topographic maps and geologic maps and reports
published by the United States Geological Survey and
Florida Bureau of Geology are utilized as primary
After the evaluation of general site conditions, a
detailed field investigation follows which centers
around a comprehensive test boring program. Borings
are spaced according to site conditions and the
requirements of the given project. Vital phases of the
field exploration program are sample description and
testing. Among the soil and rock properties logged in
the field description are: color, principal and modify-
ing constituents, hardness, cementation, grading,
relative density, consistency, moisture content, par-
ticle shape, etc. Field tests frequently include
standard penetration tests, miniature vane shear tests,
etc. In addition, laboratory tests quantify various
properties of samples collected at the site. Some of
the common tests include the following:
C Silty or clayey sand
R Fine sand
P Peatand muck
H Man-made land
TRANSPORTATION PLANNING & GEOLOGY
Atterberg Limits & Indices
Grain Size Distribution
Unconfined Compression Test
Direct Shear Test
Triaxial Shear Test
Los Angeles Abrasion
Sodium Sulphate Test
Unconfined Compression Test
Triaxial Shear Test
Qualitative & Quantitative
1. discussions of the character and depth of soils
and/or rock encountered on-site
2. the nature and severity of the problems which
these materials might impose on the design or
performance of the roadway
3. treatments which might be undertaken to alleviate
the potential problems.
4. comments on slope erosion possibilities, occur-
rence of springs, swamps, seeps, and recommenda-
tions for borrow pit locations.
As with any engineering project, the transporta-
tion planning project that is most successful is the
one which is based on the larger and more detailed
array of basic data. The more that is known about an
area geologically (i.e., the more available basic data),
the fewer the problems, less the expense, and greater
the accuracy in transportation planning within that
The recent creation of the Remote Sensing Section
within the Topographic Office of the State Depart-
ment of Transportation is an excellent example of
current environmentally oriented thinking in trans-
portation planning. The topic of pilot study com-
pleted in 1970 by the Remote Sensing Section is the
proposed Tampa Bypass Corridor. The study area
(about 40 miles long and 4 miles wide) is shown in
the figure. The corridor study was based on aerial
photographic interpretation with the goal of the
project being to locate and identify physical and
cultural features within the corridor .. to a degree
of detail consistent with the information needs for
preliminary location and design, and within a time
frame . more realistic than that required by ground
mapping methods."1 The study includes five separate
photo-map series delineating the following: land use,
key features, property boundaries, drainage, and
engineering soils. Except for the property boundaries
series, mapping was based exclusively on air photo
The land use maps show 53 different land uses
within 12 basic categories. The key feature maps
emphasize areas of special land use such as gravel,
sand and clay extractive industries, outdoor museums
and monuments, etc., which require special considera-
tion during the planning phase. Property boundaries
maps show the limits of individually owned land.
Drainage maps outline existing drainage patterns at
the time of mapping. Soils maps provide an indication
of the engineering soil types within the corridor.
These can be roughly correlated with the AASHO
classification. A portion of one of the engineering
soils maps along with the soils classification is shown
on this page.
The use of remote sensing can greatly facilitate
transportation planning. The potential of multiple-
sensor techniques (including black and white pan-
chromatic, black and white infrared, color, and color
infrared photography; multi-band photography; and
thermal and multi-spectral line scan imagery for
indicating thermal properties, vegetative patterns,
solution activity, permeability, physiography and
potential borrow pits is being investigated. It is hoped
that airborne data collection can be implemented to
provide rapid, accurate, economical, and detailed
information for use by transportation planners.
1Remote Sensing Section, Topographic Office, State of Fla.
D.O.T., July, 1970, Tampa By-Pass Corridor Study, p. 1
1000 0 1000
Source: DEPARTMENT of TRANSPORTATION
ENGINEERING SOILS MAP
C~-~C~I I ,
GEOLOGIC FACTORS & CONSTRUCTION
In the Engineering Geology section of this study, a
detailed discussion of construction planning was
presented. Information from that section was
combined with information from the Water
Resources and Geology sections to produce this
overview of land suitability for construction.
I % t" *
The wetlands map was superimposed on
the flood prone area map which was superimposed on
the sinkholes and sinkhole-type lakes map which was superimposed on
the sand suitability for foundations map which was superimposed on
the depth to rock map.....
the clay conditions map which was superimposed on
LAND SUITABILITY FOR CONSTRUCTION
One unfavorable condition:
Flood prone and wetland areas
O sand poor for foundations
O clay poor for foundations
Areas of sinkhole occurence
Two unfavorable conditions:
Sfloodprone and wetland areas + poor sands
flood prone and wetland areas + poor clays
flood prone and wetland areas + sinks
O poor sands + poor clays
b poor sands + sinks
poor clays + sinks
Three unfavorable conditions:
Flood prone and wetland areas + poor sands + poor clays
flood prone and wetland areas + poor sands + sinks
flood prone and wetland areas + poor clays + sinks
poor sands + poor clays + sinks
* Four unfavorable conditions
Areas where rock lies near land surface
(suitable for seating piling for high rise structures)
GEOLOGIC FACTORS & SANITARY LANDFILLS
Solid waste disposal has become a topic of concern
in the Tampa area where population growth has
resulted in increasing production of waste and
decreasing undeveloped land areas suitable for waste
In the past, few controls were placed on solid
waste disposal, and site selection was based largely on
convenience. Gradually, damaging environmental
effects resulting from indiscriminate waste disposal
become apparent and the concept of the sanitary
landfill was introduced.
The American Society of Civil Engineers defines
a sanitary landfill as: "A method of disposing of
refuse on land without creating nuisances or hazards
to public health or safety, by utilizing the principles
of engineering to confine the refuse to the smallest
practical area, to reduce it to the smallest practical
volume, and to cover it with a layer of earth at the
conclusion of each day's operation, or at such more
frequent intervals as may be necessary."
Essentially, a sanitary landfill consists of a series of
trenches which, in the Tampa area are excavated to
dimensions on the order of 400 feet long, 80 feet
wide and 10 feet deep. Trash and garbage emptied
into the trenches are compacted, then covered daily
with a thin layer of earth in order to minimize odor,
fire hazard, insect and rodent problems, etc.
Waterborne pollutants are also a significant poten-
tial problem of sanitary landfills. Rains infiltrate the
refuse in a sanitary landfill and pick up dissolved
solids. Under certain conditions this "leachate" may
find its way to a local water supply. For this reason,
certain geohydrologic factors must be thoroughly
investigated prior to selection of a landfill site.
Hillsborough County sanitary landfill trench
(photo by J.W. Stewart)
Among other things, sanitary landfill sites should
be relatively "dry" in terms of both surface and
ground water conditions, and surficial sediments
should be clayey and relatively impermeable. Under
these conditions, flow of the leachate may be L
retarded and potential pollutants filtered and ab- *
The map presented on this page is based on 'P *
U.S.G.S.-F.B.G. Map Series 39 and on maps presented 0 l
earlier in this publication. Rating criteria are as
1. Type of unconsolidated material. Favorable:
clay, silty clay, clayey silt, and silt. Unfavorable: a
2. Thickness of unconsolidated materials. Favor- .
able: at least 25 feet. Unfavorable: less than 15 feet.
3. Site topography. Favorable: adequate drainage \
and not subject to flooding. Unfavorable: low
swampy areas; areas subject to flooding; sinkholes
and areas near sinkholes; along stream channels
hydraulically connected with Floridan aquifer. O L D
4. Ground-water levels. Nonartesian aquifer:
Favorable: greater than 15 feet below land surface.
Unfavorable: less than 5 feet below land surface. TA MPA
Artesian aquifer: Favorable: potentiometric surface
at least 5 feet above water table. Unfavorable:
potentiometric surface near or below the water table.
5. Character of limestone aquifer. Favorable:
dense, unfractured. Unfavorable: fractured and 1
6. Relation to public water supply wells. Favor-
able: at least several miles downgradient from large
pumping withdrawals. Unfavorable: adjacent to or
within the immediate cone of influence of large-scale
UNFAVORABLE FACTORS IN SELECTING
SANITARY LANDFILL SITES
Q0 1 flood prone and wetland aiea
O 2 high water table
Q 3 rock surface at shallow depth
4 areas of sinkhole occurence
1-+. 1+2 01+3 @1t4
0 23t2+ 02+3 @2+4 03+4
S1+2+3 0 1+2+4
7 1 + @1+3+4 @2+3+4
- -J 9!J%- ".- 0
Committee of 100 of the Greater Tampa Chamber of Commerce
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forum on geology of industrial minerals: Florida Bureau of Geology Spec. Pub. 17,
Yon, J. William
1972 (and Hendry, C. W., Jr.) Suwannee Limestone in Hernando and Pasco counties,
Florida: Florida Bureau of Geology, Bull. 54, part 1, pp. 1-42.
ENGINEERING GEOLOGY AND SOILS
Antil, J. M.
1967 (and Ryan, P.W.S.) Civil engineering construction: Angus and Robertson, Std,
Sydney, 631 p.
Hillsborough Soil and Water Conservation District
1972 Use and interpretations of soil surveys and engineering principles of water
management: (work shop).
Merritt, F. S.
1968 Standard Handbook for Civil Engineers: McGraw-Hill, Inc., ch. 7, 80 pp., and ch.
8, 94 pp.
U.S. Department of Agriculture, Soil Conservation Service
1958 Soil Survey: Hillsborough County, Florida: U.S. Government Printing Office,
Series 1950, No. 3, 68 p., 96 plates.
Florida Petroleum Council
1972 The Sun Below:
Garcia-Bengochea, J. I.
1970 Recharge of carbonaceous saline aquifer of South Florida with treated sanitary
wastewater: unpublished article, Artificial Groundwater Recharge Conference,
University of Reading, Berkshire, England (Sponsored by Water Research Assoc.,
Buckinghamshire, England, Sept. 21-24, 1970.)
National Petroleum Council
1972 U.S. Energy Outlook: A summary report, Dec. 1972.
Shell Oil Company
1973 The National Energy Outlook: March, 1973.
The Oil and Gas Journal
Weekly publication, Gulf Publishing Co.
Monthly publication, Gulf Publishing Co.
American Society of Civil Engineers
1959 Sanitary landfill: Manuals of Engineering Practice no. 39, New York, Am. Soc. of
Florida Department of Transportation
1970 Tampa by-pass corridor study: (Remote Sensing Section, Topographic Office) p. 1.
1971 Soils and foundations:
Florida Land and Water Management Act of 1972
1972 House Bill 629
Hillsborough County Planning Commission
1972 Hillsborough County, Florida population projections and environmental factors:
Leopold, L. B.
1971 (and Clarke, F. E., Hanshaw, B. B., Balsley, J. R.) A procedure of evaluating
environmental impact: U.S. Geol. Survey Circ. 645, 13 p.
McHarg, I. L.
1969 Design With Nature: Garden City, New York, Natural History Press, 197 p.
FLORIDA GEOLOGICAL SURVEY.
903 W. TENNESSEE STREET
TALLAHASSEE, FLORIDA 32304
3 9 '~1 0 5 4 5-
FLORIDA GEOLOGICAL SURVEY
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