state of florida executive director division of …...jeremy a. craft, director florida geological...

FERENCE

REFFGSSP31c. 1

STATE OF FLORIDADEPARTMENT OF NATURAL RESOURCES

Tom Gardner, Executive Director

DIVISION OF RESOURCE MANAGEMENTJeremy A. Craft, Director

FlORIDA GEOLOGICAL SURVEYWalter Schmidt, State Geologist and Chiel

Published lor the

FLORIDA GEOLOGICAL SURVEY

Tallahassee1991

TABLE 1

CONVERSION FACTORS AND ABBREVIATIONS

This conversion table is for the convenience of readers who may prefer to use metric units insteadof the English units given in this report.

MULTIPLY

inch (in)foot (ft)mile (mi)gallon (gal)gallons (gal)gallons per minute (gal/min)gallons per minute per foot

I (gal/min) /ft]gallons per minute (gpm)cubic feet per second (cfs)pound avoirdupois (Ib)ton, short

BY

25.40,30481.6093.7850.0037850.063080.207

0.0022449

0.45360.9072

TO OBTAIN

millimeter (mm)meter (m)kilometer (km)liter (L)cubic meter (m')liter per second (LIs)iiler per second per

meter [ (Lls)/m]cubic feet per second (cfs)gallons per minute (gpm)ki logram (kg)megagram (Mg)

Chemical concentrations and water temperatures are given in metric units. Chemical concentration is given in milligrams per liter (mgIL) or micrograms per liter (ugIL). Milligrams per liter is a unitexpressing the concentration of chemical constituents in solution as weight (milligrams) of soluteper unit volume (liter) of water. One thousand micrograms per liter is equivaientto one milligram perliter. For concentrations less than 7,000 mg/L, the numerical value is the same as for concentrationsin parts per million.

Water temperature is given in degrees Celsius (QC), which can be converted to degrees Fahrenheit(OF) by the following equation:

Sea level: In this report, "sea level" refers to the National Geodetic Vertical Datum of 1929 (NGVDof 1929) - a geodetic datum derived from a general adjustment of the first·order level nets of boththe United States and Canada, formerly called "Mean Sea Level of 1929."

STATE OF FLORIDADEPARTMENT OF NATURAL RESOURCES

Tom Gardner, Executive Director

DIVISION OF RESOURCE MANAGEMENTJeremy A. Craft, Director

FLORIDA GEOLOGICAL SURVEYWalter Schmidt, State Geoiogist and Chief

SPECIAL PUBLICATION NO. 31

ENVIRONMENTAL GEOLOGY AND HYDROGEOLOGYOF THE

OCALA AREA, FLORIDA

ByEd Lane and Ronaid W. Hoenstine

Pubiished for the


Tailahassee1991

JIM SMITHSecretary 01 State

TOM GALLAGHERState Treasurer

BETTY CASTORCommissioner 01 Education

DEPARTMENTOF

NATURAL RESOURCES

LAWTON CHILESGovernor

TOM GARDNERExecutive Director

ii

BOB BUTTERWORTHAttorney General

GERALD LEWISState Comptroller

BOB CRAWFORDCommissioner 01 Agriculture

LETTER OF TRANSMITTAL

FLORIDA GEOLOGICAL SURVEYTallahassee

June 1991

Governor Lawton Chiles, ChairmanFlorida Department of Natural ResourcesTallahassee, Florida 32301

Dear Governor Chiles:

The Florida Geological Survey, Division of Resource Management, Department of NaturalResources, is publishing as Special Publication No. 31, Environmental Geology and Hydrogeologyof the Ocala Area, Florida, prepared by staff geologists Ed Lane and Ronald W. Hoenstine. This reportpresents data on the geology and hydrology of the Ocala area, which is one of the fastest growingurban areas in Florida. This report is timely because of the growth rate, and the information will beof significant use to local, county, and state planners, as well as to the private sector. The data willassist these groups to develop and implement long range plans to effectively manage this growth.

Respectfully,

Walter Schmidt, Ph.D.State Geologist and ChiefFlorida Geological Survey

iii

Printed for the

Florida Geological Survey

Tallahassee1991

ISSN 0085·0640

iv

CONTENTSPage

Acknowledgements viiIntroduction and purpose. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Location and transportation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Climate " . . . . .. . . . . . . . .. .. . . . . . .. . . . . . . . .. . . . . . . . .. . . . . .. . . . . . . . . 1Map Coverage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Well and locality numbering system. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Previous investigations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Geology....................... 4

Geomorphology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Geologic history. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Water Resources 16The Hydrologic cycle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Surface water. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Aquifers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Floridian aquifer system. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Intermediate aquifer system. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26Surficial aquifer system 26

Evolution of karst terrain 26Chemical weathering of carbonate rocks 26Karst in the Ocala area. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Water quality. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29Potentiometric surface 37Water usage ,................... 37Mineral resources. . . . . . .. . . . . . . . . . . . . . . .. .. . . .. . .. .. . . . . . . . .. . . . .. . . .. . . . .. . . .. . . . 46

Limestone 46Sand. . . . . . .. . . . . .. . . . . . . . .. . .. . . . . . . . . . . . . . .. . .. . . . . .. . .. . . . . . . . .. . . . . . . . . 49Undifferentiated resources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Land Use. . . . . . . . .. . . . . . . . .. . . . . . . . .. . . . . . . . .. . .. . . . . .. . .. . . . . .... . . . . . ... . . . . . . . 49Environmental hazards associated with karst. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60Solid waste disposal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65Summa~ 69References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

FIGURES

Figure 1Figure 2Figure 3Figure 4Figure 5Figure 6Figure 7Figure 8Figure 9Figure 10Figure 11Figure 12Figure 13Figure 14

Location map .Transportation map for Marion County .Average monthly air temperature at Ocala .Monthly rainfall distribution for Ocala .Annual rainfall for Ocala .Topographic map coverage of Marion County .Locality and well numbering system .Geomorphology of Ocala and Marion County .Terraces and shorelines of Ocala and Marion County .Stratigraphic column .Cross section location map .Cross sections A·A' and B-B' .Hydrologic cycle .Surface water of Marion County .

v

2356789

10121314151719

Figure 15

Figure 16Figure 17Figure 18Figure 19Figure 20

Figure 21Figure 22Figure 23Figure 24Figure 25Figure 26Figure 27Figure 28

Figure 29

Figure 30Figure 31Figure 32Figure 33Figure 34Figure 35Figure 36Figure 37Figure 38Figure 39Figure 40Figure 41

Figure 42

Figure 43

Figure 44

Figure 45Figure 46Figure 47Figure 48

Table 1Table 2Table 3

Table 4

Generalized cross-section showing hydrogeologicalfeatures common to the Ocala area 21Porosity and permeability of granular material . . . . . . . . . . . . . . . . . . 22Hydrostratigraphic correlation chart 24Drainage well in bottom of a sinkhole. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Evolution of karst landscape and underground drainage. . . . . . . . . . . . . . . . . . . . . 27Karst limestone surface exposed by a flood in Ocalain 1982 " . . . . . . . .. . . . . . . . . . . . . 30Solution pipes in Ocala limestone surface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31Topographic map of the Ocala area. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32Sinkholes in City of Ocala. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33Sinkhole in City of Ocala. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33Sinkhole in City of Ocala. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34Sinkhole in City of Ocala. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34Location of Ocala Very Intensely Studied Area (VISA) . . . . . . . . . . . . . . . . . . . . . . . 38Potentiometric surface maps of the upper Floridanaquifer system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 39-43Change in potentiometric surface of the upperFloridan aquifer system from September 1987 to May 1988 44Fresh ground and surface water withdrawals 45Mineral resources map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47Active limestone quarry near Ocala. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48General soil map of Ocala. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50Residential land use. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53Commercial land use 54Industrial land use. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55Agricultural land use. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56Governmental land use. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57Institutional land use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58Miscellaneous land use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59Drainage basin of the Oklawaha River with drainagebasins of Silver and Rainbow Springs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61Limestone fracture zone enlarged by dissolution ofOcala Group limestone. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62Flood waters recharging Floridan aquifer systemthrough sinkhole, 1982 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63Graphs showing relationships among rainfall, ground-water levels in the Floridan aquifer system anddischarge of Sliver Springs . . . . . . . . . . . . . . . . . . . . . . . . . . 64Finished cell of the Marion County landfill, 1989 66Newly opened cell at the Marion County landfill, 1989 67Leachate holding tank at the Marion County landfill, 1989 . . . . . . . . . . . . . . . . . . . 67Generalized cross section of new cells at the MarionCounty landfill, 1989 " . . . . . . . .. . . . . . . . .. . . . . . . . . . . . . . . . 68

TABLES

Conversion factors and abbreviations inside front coverWater quality for Silver Springs for 1946 and 1972 . . . .. . . . . . . . .. . . . . . . . .. . . . 20Specific parameters of a well used in DER's ground-water quality monitoring program at Ocala airport. . . . . . . . . . . . . . . . . . . . . . . . . . 35Screen analyses of sand samples. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

vi

ACKNOWLEDGEMENTS

The authors wish to thank the following people and organizations who gave freely of their timeand information. Their assistance provided a firm foundation for this study. Gary Maddox, Depart·ment of Environmental Regulation, who provided land use data and water quality data; EarlBlankenship, Solid Waste Administrator, Marion County Board of Commissioners, for informationon the Marion County landfill; Philip Cosson, Planner, City of Ocala, for statistical data for Ocala;Dennis G. Thompson, Planning Director, Division of Planning, Marion County Board of Commissioners,for statistical data on Marion County; the Economic Development Council of Ocala for business andeconomic information; and G. C. Phelps, U.S. Geological Survey, for information on the aquifer systemsin the Ocala area. In addition, the authors appreciate the efforts of Ken Campbell, Richard Johnson,Jim Jones, Ted Kiper, Jackie Lloyd, Frank Rupert, Walter Schmidt, Tom Scott, Steven Spencer, andBill Yon in reviewing this report.

vii


ENVIRONMENTAL GEOLOGY AND HYDROGEOLOGYOF THE

OCALA AREA, FLORIDA

ByEd Lane, P.G. #141 and Ronald W. Hoenstine, P.G. #57

INTRODUCTION AND PURPOSE

Florida is experiencing phenomenal populationgrowth. A significant part of this growth is occurring in the Ocala area, which is one of the fastestgrowing urban areas in the nation. Ocala, whichhad a 1987 population of 44,980, is projected tohave an annual growth rate of 4.64 percentthrough 1995 (Thompson, 1988). Rapid urbangrowth places unusual stresses on the environment due to the demands of energy, construction, transportation, water supplies, and wastedisposal. This report is designed to help localgovernments mitigate the impacts of society'spressures on the environment.

The principal objectives of this report are tointerpret and summarize available cultural information and scientific data. By integratingcultural, climatological, geological, and hydrological data the report will illustrate the importance that geology plays in land-use planning forthe Ocala urban area. Graphics are emphasizedas a means of presenting data in a format thatcan be readily used by the public, scientists,planners, water managers, and public policymakers.

LOCATION AND TRANSPORTATION

The City of Ocala is located in north-centralpeninsular Florida, approximately in the centerof Marion County (Figure 1). The air-mile circleson Figure 1 show that Ocala also lies aboutequidistant from both extremes of the state'sextent, from Pensacola In the western panhandleto Miami near the southern tip of the peninsula.

This central location makes Ocala a naturalhub of Marion County's transportation system(Figure 2). Several of the state's major roadspass near or through Ocala: Interstate 75, US 27,US 41, US 441, US 301, and State Highways 40and 475. A beltway encircling Ocala utilizingexisting and new roads is currently being

1

considered. CSX Transportation (formerly theSeaboard Coast Line Railroad) has severalroutes that branch out of Ocala. eventuallyconnecting to Gainesville, Jacksonville andpoints north, and south to Tampa, Orlando, andMiami. Several airlines have scheduled serviceto Ocala Municipal Airport.

CLIMATE

Ocala's location in north-central peninsularFlorida is refiected in its humid, sUbtropicalclimate. Its annual average temperature is71.1°F, varying from low averages of approximately 58°F in December and January to highaverages of about 82°F during July and August(Figure 3).

Rainfall distribution for Ocala is shown inFigures 4 and 5. Summer is the "wet" season,caused by an increase in thunderstorm activity(Figure 4). Figure 5 shows substantial fluctuations above and below annual average rainfall,with the widest extremes for the period occurringwithin two years of each other, in 1982 and 1984.The high rainfall of 1982 was due mainly to aseries of April thunderstorms that struck northcentral Florida from Marion County southwardto Brevard County. Hail the size of golf ballscovered the ground in many areas. On April 8,thunderstorms dropped up to 12 inches of rainover Marion County, and additional rains ofApril 9 produced storm totals up to 20 inches,causing flooding and 150 sinkholes, withheaviest damage in the Ocala area (NOAA, 1982).This incident is discussed in more detail in theEnvironmental Hazards section.

MAP COVERAGE

A total of 32 U.S. Geological Survey topographic maps are required to completely coverMarion County (Figure 6). These maps, whichwere used as base maps to plot field data, are7% minute quadrangles drawn at a scale of

FlORIDA GEOLOGICAL SURVEY

PENSACOLA

TALLAHASSEE

FGS260291

200 M\

JACKSONVILLE

o OCALA

o 25 50 MILES

.\ ' ab KILOMETERSSCALE

Figure 1. Location map for Marion County and the City of Ocala. Red circles indicate alr'mile distancesfrom Ocala.

2

\

~-N-

~0 2 4 t.lILES

I ii

i0 , 6 KILOMETERS

SCALE

k-EXPLANATION

@

""- Proposed Beltway

o Study Area

:x Ocalo MunicipalAirport \ ®~ Seaboard Coastline

Railroad

Romeo

IMortel

W

r I:x

@

~@

Dunnellon I @

4;::'~.4oC'ooC'-1

"'",-'S,,:..<S>....

FGS060291

Figure 2. Transportation map lor Marion County.

"

@>

Fort McCoy

@>

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@)!r-"tlc:til!::()

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1:24,000. All of the maps have 10-foot land elevation contour intervals. Also, the other U.S.Geological Survey maps of the State of Florida,at scales of 1:100,000, 1:250,000, and 1:500,000include Marion County. In addition, the FloridaDepartment of Transportation general highwaymap for Marion County was used in plottingroads and location descriptions. Other maps ofinterest covering Marion County and Ocalainclude the Florida Geological Survey's Environmental Geology Series: Gainesville (Knapp,1978), Orlando (Scott, 1978), Daytona Beach(Scott, 1979), and Tarpon Springs sheets (Deuerling and MacGill, 1981), all 1:250,000 scale. Amineral resources map of Marion County (Hoenstine et aI., 1988) is reproduced herein asFigure 31, at reduced scale.

WELL AND LOCALITY NUMBERING SYSTEM

The well and locality numbering system usedin this report is based on the location of the wellor locality, and uses the rectangular system ofsection, township and range for identification(Figure 7). The number consists of five parts.These are: 1) prefiX ietters designating L forlocality, W for well, and Mr for Marion County,2) the township, 3) the range, 4) the section, and5) the quarter/quarter location within the section.

The basic rectangle is the township, which is6 miles on a side and encompasses 36 squaremiles. It is consecutively measured by tiers bothnorth and south of the Florida Base Line, aneast-west line that passes through Tallahassee,as Township north or south. This basic rectangleis also consecutively measured both east andwest of the Principal Meridian, a north-south linethat passes through Tallahassee, as Range Eastor West. In recording the township and rangenumbers, the T is left off the township numbersand the R is left off the range numbers (e.g.,17S, 23E). Each township is divided equally into36 one-mile-square blocks called sections, andare numbered 1 through 36, as shown onFigure 7.

The sections are divided into quarters with thequarters labeled "a" through "d." In turn, eachof these one-quarter sections is divided intoquarters with these quarter/quarter squareslabeled "a" through "d" in the same manner. The"a" through "d" designation may be carried toany extent needed.

4

The location of well W-1762 on Figure 7 wouldbe in the center of the northwest quarter of thenorthwest quarter of Section 28, Township 17South, Range 23 East, Marion County.

PREVIOUS INVESTIGATIONS

A number of previous studies have beenpublished on the Ocala area. Many of theseinvestigations have focused on water resources,including Anderson and Faulkner (1973), whoconducted a study into the quantity and qualityof the surface water in Marion County. Rosenauet al. (1977) addressed in general terms thehydrogeology of Silver Springs and its tributaries;Miller (1986) published a comprehensive study ofthe hydrogeology of the Floridan aquifer system;and Marella (1988) reported on water use andtrends.

Other studies have been undertaken of a moregeneral nature. Knapp (1978) presented theenvironmental geology of the city of Ocaia andsurrounding area in a map format. Hoenstineet al. (1988) published a map that addressed themineral resources of Marion County. Thompson(1988) compil13d statistical data on popUlation,housing and transportation for Marion County.The Marion County Planning Department (1988)developed a future land use plan addressingmajor development, urban service, goals, objectives, and policies. The City of Ocala PlanningDepartment and the Ocala-Marion County Metropolitan Planning Organization (1988) prepared aCity of Ocala Statistical Profile, including dataon census, utilities, traffic, and other culturalparameters.

GEOLOGYGEOMORPHOLOGY

Marion County lies near the north edge of thecentral (mid-peninsular) physiographic zone ofWhite (1970). This zone is characterized by aseries of ridges and valleys trending approximately parallel to the Atlantic Coast. Within thisarea, these distinct ridges and valleys comprisegeomorphic subdivisions which are generallynamed for nearby towns or geographic areas(Figure 8).

SPECIAL PUBLICATION NO, 31

90

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I: D .. .. >- I: ::I I;Jl a. - > ColIII 1Il III a. 1lI ::l ::l 1Il " 0 •... Il. ::i c( ::i ... ... c( III 0 Z Q

Figure 3. Average monthly air temperature at Ocala for period of record 1951 ~1986(NOAA).

5


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Figure 4. Average monthly rainlall lor Ocala lor period 01 record 1951-1986,showing distribution 01 summer "wet" season and winter "dry" season (NOAA).

6

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en-0mn»r--0c:tllr-n»::!ozzp

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1990

-15.22

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Figure 5. Annual rainfall at Ocala for period of record 1951-1986, showing deviation above and below normalamount (NOAA).

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Figure 7. Locality and well numbering system.

9


o 2 .. hllLES

6 j' 6' KILOhlETERSCALE

FGS150291

Figure 8. Geomorphology of Ocala andMarion County (modified after White, 1970).

10

EXPLANATIONCENTRAL HIGHLANDS

0 CENTRAL VALLEY

0 MARION UPLAND

0 MOUNT DORA RIDGE

0 BROOKSVILLE RIDGE

0 FAIRFIELD HILLS

0 OCALA HILLS

• COTTON PLANT RIDGE

0 SUMTER UPLAND

0 MARTEL HILL

• WESTERN VALLEY

TSALA APOPKA PLAIN

• GULF COASTAL LOWLANDSDUNNELLON GAP

0 ST. JOHNS RIVER OFFSET


Four of these geomorphic subdivisions arepresent within the Ocala area. From north tosouth these include portions of the FairfieldHills, the Central Valley, the Sumter Upland andthe Ocala Hills.

The extreme southern portion of the FairfieldHills is present in the north·central part of thestudy area. Named for the community of Fairfield, this geomorphic feature forms an irregular15 by 20 mile area in northwest Marion Countyand is underlain by surface and near-surfaceclayey sands and sandy clays of the HawthornGroup. Within the Ocala area this feature haselevations ranging from 75 to 135 feet abovemean sea level (MSL). White (1970) considers theFairfield Hills to be remnants of a former uplandsurface.

The Central Valley occupies the northeastern,central, and a portion of the northwestern partof the study area. This geomorphic feature,which originates in Alachua County and extendsthrough east-central Marion County and LakeCounty into Orange County, is underlain in thenear-surface by sand with minor amounts of siltand clay. In contrast to the relatively high elevations associated with the Fairfield Hills, theCentral Valley ranges in elevation from approximately 50 to 75 feet above MSL in the studyarea.

The Sumter Upland, located south of the Fairfield Hills and the Ocala Hills, occupies thewestern third and southeastern part of the studyarea. This feature is characterized by sand andciayey sand hills having elevations ranging from70 to 150 feet above MSL. This region containsfew lakes or ponds.

The Ocala Hills comprise an elevated area inthe south-central and east-central part of thestudy area. Bounded on the north by the CentralValley and lying within the Sumter Upland, thisfeature is a nine-mile-Iong series of hilis trendingsouthwestward from Ocala. Composed primarilyof clayey sand, these hills have elevations thatrange from about 75 to 100 feet above MSL.White (1970) postulated an origin similar to theFairfield Hills.

Superimposed on the present day topographyof Marion County are a series of relict marine terraces (Figure 9). Formed during the PleistoceneEpoch, they reflect higher sea level stands.Healy (1975) recognized three marine terracesbased on elevation in this part of Marion County.

11

From highest (oldest) to lowest (youngest) theseinclude the Sunderland-Okefenokee Terrace (100to 170 feet above MSL), the Wicomico Terrace(70 to 100 feet above MSL), and the PenholowayTerrace (42 to 70 feet above MSL).

The higher Sunderland-Okefenokee Terracegenerally coincides with the Ocala Hills and Fairfield Hills_ The Wicomico Terrace is associatedwith the Central Valley and lower elevations ofthe Sumter Upland_ The Penholoway Terrace islocated in the northeastern part of the study areain the lower elevations of the Central Valley.Healy (1975) recognizes the higher CoharieTerrace (170 to 215 feet above MSL) and twolower terraces - the Talbot Terrace (25 to 42 feetabove MSL) and the Pamlico Terrace (8 to 25 feetabove MSL) as being present in Marion Countyoutside of the study area (Figure 9).

GEOLOGIC HISTORY

Located in north-central Florida, the studyarea is underlain by a thick sequence ofMesozoic and Cenozoic Era carbonate sedimentary rocks (limestone and dolomite) which aremantled by siliciclastic sediments composed ofquartz sand, silt, clayey sand and sand. Thecarbonate sequence is in turn underlain bymetamorphic basement rocks at a depth ofapproximately 4,200 feet below land surface. Anoil test well drilled in 1926 by the Ocaia OilCorporation eight miles southwest of Ocala(Florida Geological Survey (FGS) W-18, section10, Township 165, Range 20E) encountered aquartzite mica schist at a depth of 4,100 feetbelow land surface.

Much of the stratigraphy (the sequence oflayered rocks and their characteristics) ofwestern Marion County has been influenced bythe Ocala Platform. This structural feature,previously called the Ocala Uplift by Puri andVernon (1964), was described by them as "_ .. agentle anticlinal flexure about 230-miles longand 70-miles wide exposed near the surface inwest-central Florida." The influence of the OcalaPlatform in Marion County causes the OcalaGroup and Hawthorn Group sediments to occurat shallow depths in western Marion Countyrelative to their greater depths in eastern MarionCounty. Figure 10 is a generalized stratigraphiccolumn showing Middle Eocene and youngersediments present in the Ocala area.


o 2 .. MILES

6 '! '6' KILOMETERSSCALE

FGS140291

ooooo

EXPLANAliON

170'-215' COHARIE TERRACE

100'-170' SUNDERLAND TERRACE (COOKE, 1939)/OKEFENOKEE TERRACE (MACNEIL, 1950)

70'-100' WICOMICO TERRACE

42'-70' PENHOLOWAY TERRACE

25'-42' TALBOT TERRACE

10'-25' PAMLICO TERRACE

Figure 9. Terraces and shorelines of Ocala and Marion County(modified after Healy, 1975).

12


SYSTEM SERIES FORMATION

Holocene Undifferentiatedf------

QUATERNARY Sands and

Pleistocene Clays

Cypresshead

TERTIARY Pliocene Formation

Miocene Hawthorn Group

/ IIIOligocene ?rt /

EoceneOcala Group

Avon ParkFormation

Figure 10. Stratigraphic column.

13

"r-o:Dc»G)moroG)

(5»r-ooC:D<~• W-1165

'"X LMr-17S-22E-2oo

~ W-1762

• B'

• W-1766

\• W-892

IX LMr-14S-21E-14/23

B

W-937

• - I \ r-. ,:_I.".;'U"I I W-1146

.~.~ W-3889 A'

• •W-14315

~-N-

~

FGS280291

A

o 2 4 MILESI, I I

o 3 6 KILOMETERS

SCALE

X QUARRY

EXPLANATION

• WELL LOCATION

~

"

Figure 11. Cross section location map.

P\

UNDIFFERENTIATEDSANDS AND CLAYS

WMr-14S-20E-35bbW 937

UNDiFfERENTIATEDSANDS AND CLAYS

MSL

WMr-15S-26E-20obW-14315 I

CYPRESSHEADFORMATiON


WMr-15S-24E-15acW-3889

WMr-15S-23E-3W 1146WMr-15S-21E-12

lW-S679

1· \

'-

'7

MSL

40

20

0+0

100

FEET/METERS200,.... 60

TO 240'OCALA GROUP I UNDIFFERENTIATED

HAWTHORNGROUP UNDIFFERENTIATED

100

20

0+0

(J)

"mQ»r-

"c:tilr-o~ozz9'"~

TO 280'


MSL

1-/AVON PARK

FORMATION

B'

LMr-17S-22E-2ao,WMr-17$ 23E-2800W-1762 )

TO 178'

o 4 MILESI I I I rI I

o 6 KILOMETERS

SCALE

TO~ __ 1

LMr-15S-22E~30bc,WMr-16S-22E-28W-1161:;

HAWTHORN GROUPUNDIFFERENTIATED

Wmr 15S 21E-12W 5679 J


LMr-14S-21E-14

?---..t-----_. /TO US' 1

AVON PARKFORMATION

VERTICAL EXAGGERATION IS APPROXIMATELY 211 TIMES

MSL

BWMr-13S-21E 35W-892

WMr 13S-21 E 3cbW-1766 7

-20

40

FEET/METERS

200 I- 60

-100

~

(J1

OCALA GROUP UNDIFFERENTIATED TO 77'

OCALA GROUP UNDIFFERENTIATED 7---

-100J.- -20TO 305' TO 400'

_-17--./ TO 145'

AVON PARKFORMATION

/' TO 141'

AVON PARKFORMATION

FGS270291

Figure 12. Cross sections A·A' and B·B'.


The oldest rocks exposed in Florida are theAvon Park Formation. These rocks have nosurface occurrences in the study area. Theyform part of the Floridan aquifer system inMarion County and underlie the Ocala Grouplimestones.

The oldest rocks exposed in the study area arethe Ocala Group limestones. These rocks,referred to in this report as the "Ocala GroupUndifferentiated," were deposited approximately38 to 40 million years ago during the EoceneEpoch. Marine fossils associated with thesesediments, including foraminifera, mollusks,bryozoans, and echinoids, are abundant andindicate that deposition took place in a shallowmarine setting.

The Ocala Group limestone commonly occursas a soft, white, fossiliferous limestone. Theoccurrence of the distinctive foraminifera genusLepidocyclina is common to abundant and oftenused as a guide in identifying these sediments.Within the immediate Ocala area, it is variablein thickness ranging from less than 50 feet inFGS well W-1153 (section 30b, Township 15S,Range 23E) to a maximum observed thicknessof approximately 190 feet in FGS well W-892(Figures 11 and 12) (section 35, Township 13S,Range 21 E). Some variations in thickness are aresult of limestone removal through erosionalkarst processes, which are discussed in detaillater in this report.

The Hawthorn Group overlies the Ocala Grouplimestone in the Ocala area. These sediments,consisting of interbedded phosphatic clay, sand,dolomite, and limestone, are undifferentiated inthis report and are referred to in the crosssections as "Hawthorn Group Undifferentiated"(Figure 12). These diverse lithologic sedimentswere deposited during the Early and MiddleMiocene Epoch.

Common to lithologies within the HawthornGroup and an important lithologic guide to itsidentification is the presence of phosphategrains. This constituent, which may comprisegreater than eight percent of the sedimentsample, is generally disseminated throughoutsandy clays and very fine to medium, clayey,quartz sands and carbonates. The unconformableboundary between the Hawthorn Group and theunderlying Ocala Group is readily apparent. Thisdistinctive lithologic boundary presents a sharp

16

contrast between the common phosphatic sandpresent in the lower Hawthorn in the Ocala areaand the richly fossiliferous, white to creamcolored Ocala Group limestone.

The Hawthorn Group has an average thickness of approximately 20 to 30 feet throughoutthe study area. Exceptions to this occur due tothe presence of a number of paleosinks in Ocalalimestone in which Hawthorn Group and youngersediments have filled old, inactive sinkholes.One such occurrence is FGS W-3889 (section15dd, Township 15S, Range 24E) which penetrated 144 feet of Hawthorn Group sedimentsover the Ocala Group.

The Cypresshead Formation is present overmuch of the eastern half of Marion County eastof Ocala. This Pliocene-Pleistocene unit, whichoverlies the Hawthorn Group, has outcrops in theOcala National Forest and in southeasternMarion County. Lithologically, it consists of anorange to white, very fine to coarse clayey sandand some gravel. Highly variable in thickness,the Cypresshead Formation may reach over 100feet with even greater thicknesses encounteredin paleosinks.

Sands, silts, clayey sands, and clays, referredto in this report and cross sections as "Undifferentiated Sands and Clays," form a surfaceveneer over most of the study area. In general,they overlie the Cypresshead Formation ineastern Marion County and the Hawthorn Groupin the rest of the county. Exceptions occur inwestern Marion County where the HawthornGroup and Cypresshead Formation are missing,in which case these sediments directly overliethe Ocala Group limestone. Typically, thesePleistocene and Holocene age sediments consist of sand with a clay matrix and occasionaloccurrences of quartz pebbles. Figure 12 illustrates the variable thickness of these sediments.Undifferentiated sediments within the study areaare generally less than 10-feet thick.

WATER RESOURCESTHE HYDROLOGIC CYCLE

The hydrologic cycle describes the continuousmovement and interaction of water in all itsphases on, above, and below the earth's surface.Figure 13 shows the main phases of thehydrologic cycle in Florida.

FORMATION OF CLOUDS

C/)"'tImQ:J>r-"'tICOJr-o:J>-toZ

z9CN......

~ECHARGE BY

,IN,F1LTRATrON "t''/ ' "

. ,

"

PLANT

EVAPOTRANSPIRATION

~U~OffSU~fflo.C€.

SURFACESPRING

"

.:. ....,""'''''''~'.• ," I' ." I ; I I ~ • I : T'II I ~ I

',: ' "1' .,' I', t ,.t ,: \ 1'1,1 I't' I ;.11.:': ,':1: :.1 ',1::1'.1' I I,

,< 'I" '". 11 '1,11'" I: "1 I ',I, 'II .\ " , ,'I' I "I'"

" 1,\ "\>1 t I:' ,II I'-I· I··.· I . , I I'

EVAPORATION '" -'.',: RAIN' ',,","I' I' " II

EVAPORATION ",::: :;';,':,i \ \', '\ i; ~:,: II EVAPORATION,"; ,.\ I:' ,; . \ I,:,

FROM~,;-,,::::::',""i:1:/': FROM LAND" '" ' ' 'II' ," I, ,

SURFACE WATER ,,' -::1.;:1:1,,;, 'I

"II~:I,,~I\~I 1'1': II'

I I I I IJlt, I,:

~

SUBMARINE

SOLAR

ENERGY

•II

......"'-J

Figure 13, Hydrologic cycle, showing its main phases as they occur in Florida.


The hydrologic cycle is driven by the elementalforces of sunshine and gravity. Figure 13 showsthe paths water may take as it moves throughthe hydrologic cycle. Starting at the ocean, thesun's radiation heats the ocean's surface andevaporates fresh water, which is carried aloft byrising convection currents of air, eventuallyforming clouds of water vapor. The clouds droptheir moisture as rain, snow, or hall. Under usualatmospheric conditions some of the precipitationevaporates before it reaches the ground. Afterprecipitation reaches the ground, three thingscan happen to It: some will evaporate directlyfrom soil, plants, and free bodies of water, asevapotranspiration; some may infiltrate the soilor rocks; and some may run off across the landsurface. The runoff may contribute to normalsurface drainage in the form of streams or lakes,eventually returning to the ocean to begin thehydrologic cycle anew.

Water that finds its way underground, however,will have a more circuitous route before it returnsto the sea. Some water may percolate downwardto recharge ground-water aquifers, then movelaterally until being discharged to stream bedsor in surface or submarine springs. Some underground water may be taken up by plants andevapotranspired to the atmosphere; some maybe withdrawn by wells for human use. In theOcala area, two of the most Important paths arerecharge to the ground-water aquifers by infiltration and recharge through karst features.

SURFACE WATER

Marion County has a number of lakes, pondsand rivers which are primarily located around theperimeter of the county (Figure 14). In contrast,the Ocala area, which is located In west-centralMarion County, has only a few minor surfacewater bodies.

This surface water Is comprised of severallakes, in addition to both natural and man-madeponds. The lakes, which are small, generallyaverage between 5 and 20 acres In extent. Theponds are more numerous and are presentthroughout the area. Many of the ponds areman-made, established as retention ponds orresulting from mining activity. A number oflimestone quarries in the area have associatedwater bodies formed as a result of excavation

18

that has breached sediments of the Floridanaquifer system. These quarry ponds are relativelysmall, usually less than two acres in area. Atthese sites the water level represents the localpotentiometric surface of the Floridan aquifersystem. This Is the water level that water wouldrise In a lightly cased well that penetrates theaquifer.

One notable exception to this phenomenon isSilver Springs. This major spring, which islocated about six miles northeast of Ocala,forms the headwater of the Silver River, a majortributary of the Oklawaha River (Figure 14).

Silver Springs forms a large pool measuring250 feet In diameter at the head of the SilverRiver. Here, beneath a limestone ledge, the mainspring flow occurs at a depth of 30 feet from acavern mouth measuring five feet in height and135 feet in width (Rosenau et at., 1977).

Several smaller springs occur along the springrun out to a distance of 3,500 feet from the mainvent. Measurements of stream flow along theSilver River indicate that spring flow to the riveris concentrated within this 3,500 feet distance(Ferguson et aI., 1947). Investigations by the U.S.Geological Survey show that the spring flowoccurs through a system of fractures anddissolution channels In limestone and dolomiteof the Ocala Group (Rosenau et aI., 1977). Thisflow Is provided from recharge by local rainfallIn an area situated to the north, west and southof the springs measuring approximately 730square miles (Faulkner, 1973) (Figures 14 and 41).Discharge is highly variable and averages 820cubic feet per second (cfs). Measurementsranged from a maximum observed discharge of1,290 cfs recorded in October, 1960 to aminimum value of 539 cfs measured In May, 1957(Rosenau et aI., 1977).

Water clarity is usually excellent in the pooland along the run. Water temperature is relatively constant ranging from 23 to 24°C (73 and74°F) within a few feet of the surface (Rosenauet aI., 1977).

Analyses of water samples taken by the U.S.Geological Survey for the years 1946 and 1972are shown in Table 2. These results show thatthe majority of measured parameters Includingcalcium, magnesium and chlorides have remained relatively consistent over this period. Anexception to this is the nitrates (NO, as N) which


:>.-c.."0

(? ••• u..:'0:- c.. 0

01'".;:

'"::!:f 0 -0

~

'"t -~tl '";::~~

~ '"\',. ~ "~~V '"ll; ") . rf -cr> ~

\)Cl N "\;1 0 (/)9 t lO

"' 0 ..;~ (J) ~

'J f '"'fJ .'~u. '"~'C' .' 0 "6:,°""°",,,<> :.:" '"f} 1;;).<>r> If u::

0..

~ ~::l (J)

D .'f

.'.'

zof«z«.....Jl:LXW

....... . . . . .. . . . . .. . . . . .. . . . . .. . .. . .: :.:.' {,o

~>:.'.'."

19


Table 2. Water quality for Silver Springs for 1946 and 1972 (Rosenau et aI., 1977).Units are in milligrams per liter unless otherwise noted.

Date of Collection

Nitrite (NO, as N)Nitrate (NO, as N)Calcium (Ca)

Magnesium (Mg)Sodium (Na)Potassium (K)Silica (SiO,)Bicarbonate (HCO,)Carbonate (CO,)Sulfate (SO,)Chloride (CI)Fluoride (F)Nitrate (CO,)Dissolved solids

CalculatedResidue on evaporation at 180°C

Hardness as CaCO,Noncarbonate hardness as CaCO,Alkalinity as CaCO,Specific conductance

(micromhos/cm at 25°)pH (units)Color (platinum cobalt units)Temperature (0C)Turbidity (JTU)Biochemical oxygen demand

(BOD, 5·day)Total organic carbon (TOC)Organic nitrogen (N)Ammonium (NH, as N)Orthophosphate (PO, as P)Total phosphorus (P)Strontium (Sr)Arsenic (As)Cadmium (Cd)Chromium (Cr6

)

Cobalt (CO)Copper (Cu)Lead (Pb)

20

October 211946

0.2968

9.64.01.19.2

200o

347.8

.11.3

237210

4017.84

September 161972

0.002.6

68

9.34.3

.29.8

200o

398.00.2

24224621042

170

4208.1o

23.5o

.18.0

.37

.03

.14

.14500 ugll

o ugllo ugllo ugllo ugllo ugll2 ugll

urban runoff with contaminants

C/l

"mC'li>,...

"c00,...C'l

~ozzp

'"~... ...-

,.

..~- -

SILVERSPRINGS

,_L \r"t

~~

\•\

._.....1-.

Floridan aquifer

potentiometric surface

rechargethrough recharge by

open sinkhole infiltration

.-._-r.I

PUMPING

WELL

-}-

\ ......; I .... _ I

(.'....\---. r'--.., ~.- - ,me- •• ,., - ~ 'i!¥!! ' .. -"J I'" :~-_. - ---I , ,- '"\. ',;if' • I ,'-- M .\'.

.... I )',,' I'· .. , . -.!' '.' J_.~ ~ ~ - ........... ••. il',,,_ ~_""'l - ,"""""'" ,:,,~''''-r......,.. ,'" t 1.\ .. IJ (" t.\. je,..:).,.,,/'.... ~ ... , y .. f l '.' ..

" . '. ~ ... '.. '..' ._, '""",~,' .""··._::~h._-" ..' ,. , '",-'".'"•..CONTA MIN AN TS' , . :. ',' ,l./~'P!:";.,,,.J. .' ' " ,.... 1'\ < •.\ ,~ , .. ' , I .. , r 01;..Jq... ...... _-" r:.· I .~. • . -1·r .J. 1-:-t~-""'-~ .. '.' .. "' " , I ----1-·

-";"\". - ~ _[j -=~., I, ~~~ 1_ FLORIDAN AQUIFER SYSTEM\.,,-.. -; I _ , .. - J' <Ocala Group)

... ~.., ~ ! +......~ .....,

.'

kt-l,...,.

~~f-'. ' . SANDS I I and~ ..,-

DRAINAGEWELL

INSINKHOLE

-.-t~..

't .~._..'..I ...L .." ,

-- ~ ~

...J,..,',.

Jo, I

'1.f

'"~

Figure 15. Generalized cross·section showing hydrogeological features common to the Ocala area. Rechargeto the Floridan aquifer system can occur in several ways: (1) by infiltration from rain through thin, sandy soiior where limestone crops out at the surface; (2) through sinkholes that breach the confining units; or (3) by drainagewells. Drainage wells pose a threat to the aquifer due to contaminants in urban runoff, Discharge from the aquiferis by pumpage or at springs.


B

Figure 16. Porosity and permeability as shown by two examples of a well-sorted granular material,such as sand. In Figure A the porous and permeable sand is clean with open, interconnected voidsthat allow water to move freely. In Figure B the same well-sorted, porous sand is rendered impermeableto water flow due to the retarding effect of the interstitial material, such as clay (from Lane, 1986).

22


shows an increase. This may be attributed to theeffects of intensive agriculture practices, suchas fertilization and spraying, which are usedwithin the Silver Springs drainage basin.

AQUIFERS

Figure 15 illustrates several hydrogeologicalfeatures commonly encountered in Florida sediments and rocks. This figure particularly appliesto the local conditions in the Ocala area.

All ground water occupies the open spaces,or pores, that occur in many of the rocks of theearth's crust. Aquifers are defined as units ofrocks or sediments that yield water in sufficientquantities to be economically useful for society'sactivities.

Porosity and permeability are two fundamental characteristics of rocks or sediments thatcontrol the quantities of water that they canstore, transmit, or release. Porosity and permeability are intimately related. A porous medium,such as clean sand or gravel, has voids whichmay contain water, as shown in Figure 16.Permeability is a measure of a porous medium'sability to allow fluids to move through its pores.By definition, then, permeability implies that arock's pores are interconnected so fluids canmove through them. A clean sand, therefore, ispermeable; water can migrate through it (Figure16a). Porous rocks are not always permeable,however. A similar, well-sorted sand may haveIts interstices filled with clay, small grains oforganic matter, or some other fine-grainedmaterial, which effectively blocks the freepassage of water (Figure 16b). In this case, thesand would be classified as impermeable (if onlyvery small quantities of water could passthrough it).

Limestone, though usually thOught of as being"solid" rock, often has a granular texture andconsiderable porosity and permeability, eitherprimary (developed when the limestone wasdeposited) or secondary (developed after deposition). Ground-water flow through granular andporous limestone is, therefore, similar to flowthrough sand. This is an important concept tokeep in mind during the following discussions ofaquifers and chemical weathering of limestone.

Floridan Aquifer System

The Floridan aquifer system is the principalsource of water for the city of Ocala. Indeed, thisaquifer is the principal artesian aquifer inFlorida, Georgia, Alabama, and South Carolina(Miller, 1986). Figure 17 correlates the geologicformations that comprise the Floridan aquifersystem, which includes the Ocala Group and theAvon Park Formation.

In general, the Ocala Group limestone formsthe top of the Floridan aquifer system. This topoccurs at or near land surface throughout theOcala area, creating a matter of environmentalconcern. The industrial, commercial, andresidential growth in Ocala brings associatedenvironmental risks to the extremely fragileaquifer system. Because of the Floridan aquifersystem's near-surface occurrence in a highlykarstlc area, the potential exists for significantcontamination of this system from the flow ofsurface waters into the aquifer or from anaccidental spill (Phelps, 1989). Porous surfacesands and numerous sinkholes serve as excellentconduits for potential pollutants to enter theaquifer.

Recharge to the Floridan aquifer system inthis area occurs in the form of rainfall andground-water inflow from potentiometricallyhigher areas immediately to the north and south(Faulkner, 1973). In addition, recharge occurs viasinkholes, which are numerous throughout thearea, some of which have drainage wells installedto control urban runoff (Figures 15 and 18).Ground-water discharge in and around Ocalaoccurs primarily from Silver and RainbowSprings.

The water quality of the Floridan aquifersystem is considered excellent for publiC anddomestic consumption. The water is a hardcalcium bicarbonate type, commonly free 01bacteriological contamination. The mineralcontent usually increases with depth (Faulkner197~. '

Ocala's pUblic water supply is currentlyobtained from a well field consisting of five wellslocated in the northeastern part of the city(section 10bb, Township 15S, Range 22E). Thesewells are 24 inches in diameter, have casingdepths ranging from 86 feet to 140 feet below

23

N

"

HYDRO- GEOLOGIC UNIT SERIESSTRATIGRAPHIC UNIT

UNDIFFERENTIATED TERRACE POST-MIOCENEMARINE AND FLUVIAL DEPOSITSSURFICIAL AQUIFER

SYSTEM ------------INTERMEDIATE

AQUIFER SYSTEM HAWTHORN GROUP MIOCENEAND

INTERMEDIATECONFINING UNIT

OCALA GROUP

FLORIDAN AQUIFEREOCENE

SYSTEM AVON PARK FORMATION

FGS010291

Figure 17. Hydrostratigraphic correiation chart (Southeastern Geological Society, 1986).

..,ro:nc»Gl

2lroGl(')»r-ooc:n<~


Figure 18. City drainage well in bottom of a sinkhole connecting to the upper Floridanaquifer system. This type of well is used to control flooding by diverting urban runoffinto the cavernous limestone aquifer. Florida Geological Survey photograph.

25


land surface, and are drilled to depths rangingfrom 190 feet to 266 feet below land surface. Anolder abandoned well field is located near thecenter of the city. Wells in this field now serveas monitoring wells.

In addition to the Floridan aquifer system, twoother aquifer systems may be present. FGS welldata suggests that a surficial aquifer system andan intermediate aquifer system may havesporadic occurrences in the Ocala area, asdiscussed below.

Intermediate Aquifer System

An intermediate aquifer system may be presentin isolated pockets of relatively thick depositsof Hawthorn Group sediments. As cross sectionA·A' shows, Hawthorn Group thicknesses maybe as great as 130 feet (W-3889, Figure 12).Presently, there are no data indicating that eitherthe surficial or intermediate aquifer systems arebeing used as sources of water (Phelps, personalcommunication, 1989).

Surficial Aquifer System

When near-surface sand and clay lenses orbeds are arranged so that the units can retaininfiltrated water for a reasonable length of time,the sediments are included in a shallow aquifersystem (Southeastern Geological Society, 1986).A surficial aquifer system may be present inareas having appreciable thicknesses (on theorder of tens-of-feet) of undifferentiated sandand clay sediments.

EVOLUTION OF KARST TERRAIN

The evolution of any terrain into characteristiclandforms involves weathering and erosional oraccretionary processes: wind, water, frostheaving, slumping, or wave activity, to name afew. In most areas, the predominant weathering,erosional, and transporting agent is water, eitherfalling, flowing across the land, or circulatingthrough subsurface rocks.

26

Ocala lies in a karst terrain, an area characterized by undulating hill and swale topography,sinkholes, disappearing streams, springs, andcaves. The two things necessary to create karstare abundant in the area: limestone in theshallow subsurface and slightly acidic waters todissolve it.

CHEMICAL WEATHERINGOF CARBONATE ROCKS

The creation of karst involves the developmentof underground drainage systems (Figures 19a,19b, 19c, 19d). Most chemical erosion processesthat create karst take place unnoticed, underground, and imperceptibly slowly. Over time,perhaps after thousands of years, evidence ofthese persistent processes will occur as theformation of a sinkhole, a spring, ground subsidence, an influx of muddy water in a well, oras some other karst phenomenon that may interfere with society's activities.

Chemical weathering is the main erosive process that forms karst terrain, in an evolutionarysequence shown in Figures 19a, 19b, 19c, 19d.As rain falls, some nitrogen and carbon dioxidegases dissolve into it, forming a weak acidicsolution. When the water contacts decayingorganic matter in the soil, it can become evenmore acidic. When the water contacts limestone,its corrosive attack begins. All rocks andminerals are soluble in water to some extent, butlimestone is especially susceptible to dissolution by acidic water. Limestones, by nature, tendto be fractured, jointed, laminated, and to haveunits of differing texture, all characteristicswhich, from the standpoint of percolating groundwater, are potential zones of weakness. Thesezones of weakness in the limestone are avenuesof attack that, in time, the acidic waters willenlarge and extend. Given geologic time, conduits will form in the rock and allow water to flowrelatively unimpeded for long distances.

During the chemical process of dissolving thelimestone, the water takes into solution some ofthe minerals. The water containing the dissolvedminerals moves to some point of dischargewhich may be a spring, a stream bed, the oceanor a well.


A ..... ..;::;. -l

Figure 19a. Relatively young karst landscape showing underlying limestone beds and sandy over·burden with normal, integrated surface drainage. Solution features are just beginning to developin the limestone (after Lane, 1986).

Falling rain absorbs gases tobecome weakly acidic.

SPRINGS

Percolating ground water infiltrateslimestone, dissolving some andcarrying it away in solution.

-,-

INFILTRATING,ACIDIC GROUND

WATER

B

SOIL

sands, clays

LIMESTONE with joints, fractures,

'-""Vl~ bedding planes /'"--.........,.--.~+--

, i.,J--

Figure 19b. Detail of Figure 19a showing early stages of karst formation. Limestone is relativelycompetent and uneroded. Chemical weathering is just beginning, with lillie internal circulationof water through the limestone. Swales, forming incipient sinkholes act to concentrate recharge(alter Lane, 1986).

27


SWALLOW HOLE(disappearing stream)

HUMMOCKY TERRAIN

-..,- - ---J..... ,...>---!~t~1""""-.-

~":-.

CAVERNSDEVELOPING

ORIGINAL LAND

fSURFACE LOWERED

NATURAL BRIDGE

I'- r-S:K~~L~ _ _ _

I -_

C

Figure 19c. Advanced karst landscape. Original surface has been lowered by solution and ero·sion. Only major streams flow in surface channels and they may cease to flow in dry seasons.Swales and sinkholes capture most of the surface water and shunt it to the underground drainagesystem. Cavernous zones are well·developed in the limestone (alter Lane, 1986).

EXTENSIVESOLUTIONACTIVITY

SINKHOLE

CAVERNOUS UNDERWATERSPRING

D

Figure 19d. Detail of Figure 19c showing advanced stage of karst formation. limestone has well.developed interconnected passages that form an underground drainage system, which capturesmuch or all of prior surface drainage. Overburden has collapsed into cavities forming swales orsinkholes. Caves may form. Land surface has been lowered due to loss of sand into the limestone'svoids. Silver Spring is an example of a cavernous underwater spring (alter Lane, 1986).

28


Removal of the rock, with the continuingformation or enlargement of cavities, canultimately lead to the collapse of overlying rocksor sediments. If the collapse is sudden and complete, an open sinkhole will result, sometimesrevealing the cavity in the rock (Figures 20 and21). More often, though, debris or water coversthe entrance to subterranean drainage. Partialsubsidence of the overburden into cavities willform swales at the surface, producing hummocky, undulating topography. By this slow,persistent process of dissolution of limestoneand subsequent collapse of overburden, the landis worn down to form a karst terrain.

At some point in this process of dissolutionof underground rocks, any existing surfacedrainage system will begin to be transformedinto a dry or disappearing stream system.Continuing dissolution of the limestone willcreate more swales and sinkholes, which willdivert more of the surface water into the underground drainage. Eventually, all of the surfacedrainage may be diverted underground, leavingdry stream channels that flow only during floods,or disappearing streams that flow down swallowholes (sink holes in stream beds) and reappearat distant points to flow as springs or resurgentstreams.

KARST IN THE OCALA AREA

There are a variety of karst features in theOcala area. Figure 22 shows the extent to whichthe area's topography has been dissected bykarst features. Silver Springs is a spectacularexample of a cavernous spring, as shown inFigure 19d. It is the source of Silver River, anda major discharge point for water from theFloridan aquifer system, with flows ranging from539 to 1,290 cubic feet per second (834,000,000to 1,997,000,000 gallons per day) (Rosenau et aI.,1977). These quantities of water can dissolve andcarry away in solution as much as 541 tons oflimestone per day (Lane, 1986), which gives someidea of the erosive capacity of karst processes.

Sinkholes are common features in the Ocalaarea (Figures 23, 24, 25, 26). Sinclair and Stewart(1985) classify the sinkholes that occur in theOcala area as three types: solution, cover·collapse, and cover-subsidence. In their classification solution sinkholes occur in areas whereIimestone is exposed at land surface or is

29

covered by thin soil and permeable sand. Underthese conditions the land surface subsidesgradually. The topographic expression of thistype of sinkhole is usually a bowl-shaped depression that may have ponded water. The rolling,hill-and-swale topography of the Ocala area istypical. Cover-collapse sinkholes generally occursuddenly, in areas where limestone is near thesurface. Sinkhole walls tend to be near-vertical,exposing limestone in the round solution pipesthat lead to the underground drainage system(Figures 20 and 21). Cover-subsidence sinkholesoccur where the overburden is relatively permeable and poorly cohesive, which characterizesmuch of the soil in the Ocala area. In areas ofthick sand cover subsidence may be sudden orproceed ,slowly over many years, producingsinkholes only a few feet in diameter and depth.

WATER QUALITY

The Florida Department of EnvironmentalRegulation (DER) monitors a number of waterwells in Marion County which are part of thedepartment's statewide ground-water qualitymonitoring network. This network is made up ofwells placed in areas assumed to be unaffectedby man at the present time.

One of these wells is located west of the cityof Ocala, at the Ocala Airport (section 19b,Township 15S, Range 21 E). This six-inch well isdrilled to a depth of 90 feet below land surfaceinto the upper Floridan aquifer system. Table 3lists the specific parameters analyzed and theirrespective values for this well. All of the valuesare within established U.S. EnvironmentalProtection Agency (EPA) units for potable water.

In addition to the ambient network wells, DERand the St. Johns River Water Management District (SJRWMD) are in the process of establishinga Very Intense Study Area (VISA) network withinthe city of Ocala. This VISA is located in the eastcentral part of the study area (Figure 27) and isone of five initial VISAs to be established in thewater management district. In contrast to theambient wells, which are strategically placed tomonitor unaffected areas whose ground wateris not associated with degradation due to pollution sources, the VISA wells are intended tomonitor the impact of a potential or confirmedpollution source on local water quality (based onland-use activity).


Figure 20. Karst limestone surface exposed by a flash·flood in Ocala in 1982. Note ver·tical solution pipes. Florida Geological Survey photograph.

30


Figure 21. Close-up of solution pipes in Ocala limestone surface, in the same area asin Figure 20. Pipes are between one and two feet in diameter. Sinkholes and other karstsurface expressions can appear when such pipes become unplugged of their sediment·fill. Florida Geological Survey photograph.

31

<IJ.;::<IJ

'";::

<IJ

'"I-

R21E R22E R22E 'It23lE

o 1 IItLES I'''\''~''!'

KM

E::J OCALA

......... 110 Elevation, mil

~ D.pr"llo~

• Perennially' Wit

TOPOGRAPHICMAP

','I:',

"T1~

o::J:Jc»C)mo~oC)

o»~

00c:::J:J<m-<

Figure 22. Topographic map of the Ocala study area showing larger karst features. Hundreds of smaller sinkholesand depressions do not show at this scale. Contour interval is 25 feet with selected intermediate contours.


Figure 23. Sinkholes in City of Ocala formed during the flood of April 1982. FloridaGeological Survey photograph.

Figure 24. Sinkhole in City 01 Ocala formed during the flood of April 1982. FloridaGeological Survey photograph.

33


Figure 25. Sinkhole in City of Ocala formed during the flood of April 1982. FloridaGeological Survey photograph.

Figure 26. Sinkhole in City of Ocala formed during the flood of April 1982. FloridaGeological Survey photograph.

34


Table 3. Water quality analysis of Ocala Airport Ground-Waterquality monitor well (sec 19b, Township 15S, Range 21 E)

(Dept. of Environmental Regulation data, 1989)

PARAMETER

1, 1, 1 Trichloroethane1, 1,2 Trichloroethane1, 1 Dichloroethene1, 1 Dichloroethane1, 2 Dichloroethane1, 2 Dichlorobenzene1, 2 Dichloropropane1, 3 Dichlorobenzene1, 4 Dichlorobenzene1122 TetrachloroethaneArsenicBariumBicarbonateBromoformBromomethaneBromodichloromethaneC1,3 DichloropropeneCadmiumCalciumCarbonateCarbon TetrachlorideChloromethaneChlorideChloroethaneChlorobenzeneChloroformChromiumConductivityCopperDibromochloromethaneDichlorodifluoromethaneFluorideIronLeadMagnesiumManganeseMercuryMethylene ChlorideNitratepHPhosphatePotassiumSeleniumSilverSodium

35

AVERAGE

1.00001.00001.00001.00001.00001.00001.00001.00001.00001.0000

• 0.00200.0300

108.00001.00001.00001.00001.00000.0020

38.30000.10001.00001.00003.40001.00001.00001.00000.0120

230.00000.01301.00001.00000.04600.03000.02001.76000.00500.00001.00000.92407.40000.08100.21000.00200.00802.2000

UNITS'

ug/lugllugllugllug/lugllug/lug/lugllugllmg/lmg/lmg/lugllug/lugllug/lmg/lmg/lmgllug/lugllmg/lugllug/lug/lmg/l

umhos/cmmg/lug/lug/lmg/lmg/lmg/lmg/lmg/lmg/lug/lmg/ls.u.mg/lmg/lmg/lmg/lmg/l

PARAMETER

SulfateT1, 2 DichloroetheneT1,3 DichloropropeneTotal Dissolved SolidsTemperatureTetrachloroetheneTotal Organic CarbonTrichloroetheneTrichlorofluoromethaneVinyl ChlorideZinc2,4, 5-TP2,4-D2 Chloroethyl Vinyl Ether4,4'-DDD4,4'-DDE4, 4'-DDTAidrinBenzeneChlordaneDieldrinEndosulfan IEndrinEthyl BenzeneHeptachlorHeptachlor ExpoxideLaboratory pHMethoxychlorMirexParathionSulfideTolueneToxapheneg-BHCGross PCB's


AVERAGE

8.14001.00001.0000

157.000024.5000

1.000013.7000

1.00001.00001.00000.02000.00200.00501.00000.01000.00400.01000.00401.00000.01000.00200.01000.00101.00000.00300.08007.77000.01000.00100.01000.10001.00000.10000.00000.0100

UNITS'

mg/Iugllug/Img/l

degree Cugllmgllug/Iugllugllmg/Iugllug/Iug/Iugllugllugllugllug/lug/Iug/IugllugllugllugllugllS.u.ug/Iugllugllmgllugllugllugllugll

ugllmg/Is.u.

umhos/cm

= micrograms per liter= milligrams per liter= standard units= micromhos per centimeter

36


The Ocala VISA is placed in an area. designated as "mixed urban-light industrial"

covering approximately three square miles. ThisVISA will'have a number of wells installed tomonitor the local area's water quality. Waterquality from these wells will be compared to thatof nearby wells in the ambient ground-waterquality background network to determine if anydegradation is occurring as a result of land-useactivities within the VISA.

POTENTIOMETRIC SURFACE

Figures 28a-28e show the potentiometricsurface of the upper Floridan aquifer system forthe months of May and September for the years1978,1980,1982,1984,1986, and 1988(SJRWMDdata). The potentiometric surface is a measurement used by hydrogeologists to show the elevation or altitude (expressed in feet above meansea level) at which water level would stand intightly cased wells that penetrate the aquifer.

These contoured data show that Ocala andsurrounding areas have a potentiometric surfacethat varies in a narrow range from 40 to 47 feetabove MSL. A maximum value of 47 feet aboveMSL was recorded in September 1982 and aminimum value of 40 feet above MSL wasrecorded in May of 1988. This may be attributedto increased consumption of ground water thatSJRWMD records show occurred overthis periodof time.

The potentiometric surface appears to berelatively stable, having shown minimal variations over a period of time in which the City ofOcala has had significant growth. Figure 29lends support to this observation as the changein potentiometric surface experienced variationsfrom minus two feet to plus one foot in theperiod from September 1987 to May 1988, similarto seasonal fluctuations shown for prior years(Figures 28a, 28b, 28c, 28d, 28e). Approximatelyhalf of the study area experienced a sl ight risein the potentiometric surface, while a large partof the rest of Marion County had no observedchange.

37

WATER USAGE

Figure 30 shows the various water usagesfrom both ground and surface water withdrawalsin the SI. Johns River Water ManagementDistrict for 1986 (the latest year for which dataare available). These data clearly illustrate theimportance of the Floridan aquifer system, as itwas the source of more than 90 percent of theground water withdrawn in the district in 1986.

Thediagrams (Figure 30) show the dominanceof the agfJcllitural sector and to a lesser extentthe public water supply as users of ground water.Together, these two categories accounted for 73percent of the ground water withdrawnf-rom thedist(ict in 1986.

The a§ricultural sector is the largest user ofground water in Marion County. Within thiscategory irrigation accounts for the largestusage. The largest uses of water for irrigation arefield corn followed by improved pastures, golfcourse turf grass and sod. In the county waterwithdrawn for these purposes totaled 8.56million gallons/day from ground water and 2.10million gallons/day from surface water for theyear 1986. This wi.thdrawal has experiencedfluctuations over time showing a 28 percentdecline for the period 1975 to 1985 and a 22percent increase from 1985 to 1986. It should benoted that agricultural water usage is extremelysensitive to weather conditions and shows thegreatest seasonal variations in withdrawals.

The second largest user of ground water is thepublic water supply which accounts for 35 percent of the ground-water usage (Figure 30). TheFloridan aquifer system supplies 100 percent ofthe City of Ocala's public water supply and supplies more than 95 percent of the entire district'spublic water (SJRWMD data). Specifically, theCity of Ocala withdrew an average of 7.668million gallons of water per day for this purpose.This amount is included in the 10.91 milliongallons per day extracted from the Floridanaquifer system for all of Marion County in 1986.The public water supply usage in Marion CountyIncreased by 50 percent in the period from 1980to 1985.

."ro:rJ

o»G>moroG>n»r-ooc::rJ<~

OCALA CITY LIMITS

VISA AREA

wJ /~/

~N

wZ

"M 215

.6. M 213

M 2163RD ST. NE A

SILVER SPRINGS BLVD

FORT KING sf

M 214M 239

"M 211M 212Z-

<1 rM 086 . K'0Ml77~if:"~

M 210..:.1

~

~

M 243

"

wM 208 ~" I

M209 "-M 209

>-I;;'"

"-NM 205 w

"'~" wzi\!O~L

"<nn:

~ 110 M 217,.<n

IM ~05~ VISA area with monitor well

M 200

"ILVER SPRINGS IBLVD

'"M 244 z",I M 242" 1 I Iz

NW 10TH $I

FGS250291Figure 21. Location 01 Ocala Very Intense Study Area (VISA). (St. Johns River Water Management District data).

wen

Figure 28a. Potentiometric surface of the upper Floridan aquifer system in Marion County, May 1978 and September1978 (unpublished St. Johns River Water Management District data).

R 18 E R 19 E R 20 E R 21 E R 22 E R 23 E R 24 E R 25 E R 26 E

~~;'30 T 11 S

-N-

~ I~.--' 55~~!"/~ ~ I ./ ! ~r /1 .l I. L-,IT"f ";~.

T 12 S

0 2 4 MILES

b , ,3 ~ KILOMETERS

SCALE . I~~EXPLANAnON ~ ~"'~'/ \ '50.~~'l I. \ \ \1 "- \"- \, Iii'!. ~ T 13 S

50

• Well

~..--//May ~" ~-~ \ '-,'.

~-15~..,

• 30 ....~ .' -- '", '~~ 0

~ September ---~ ~ 40 -\1 T14S ::lJ45 . • " c

:r>ELEVATIONS IN fEET ABOVE MSL r '-I I r- I I \ \ I

I _________ r \ I if ( I G'lm0

-" I .....--1-' 40 II I \:1 .1 • r I -l !. 1 1 ~\ ~ 'rl." 15 S

....0 0• G'l

(5:r>....00C

•\ T 16 S

::lJ55

I<:m• I -<

50 1\

I" I h\

=' i.

•45 ~I

"55I. I. T 17 S• ••

FGS200291

Figure 28b. Potentiometric surface 01 the upper Floridan aquiler system in Marion County, May 1980 and September1980 (unpublished St. Johns River Water Management District data).


~~~ T 11 S

-N-

~ I•

I •--- T 12 SI _____ AI ~, ,1\--1 I I 1,1 I j I I ,OJ , I

0 2 4 MILESI

, ,,~ KILOMETERS0 3

SCALE I I

>~+~ 50 ~ \55 •

EXPLANAnON I • I \ 30~T 13 S•

• Well (J)

~May"tJ

40 m()

~ September T 14 S :;:.-ELEVATIONS IN FEET ABOVE M$L 40 "ll50

45 45-------

C

'''45 1 ttl

"'"!::

~ \/ ()

• • T 15 S »50 ::!

I"\ I 0

130 z~

70~

Z

60 / 50 40 955 • '"50

,T 16 S ~

! ,• :\

50 'f~ I!III-k-= -- \,• I• I

'l

-------

\• \.." I 50,1 \ I I / I I • I T 17 S45 ••

FGS190291~'

,

30

Figure 28c. Potentiometric surface of the upper Floridan aquifer system in Marion County, May 1982 and September1982 (unpublished St. Johns River Water Management District data).


~ ~~,f T 11 S

T la6~/\ L T 12 S

o 2 4 MILES 1/ f / ! \I "I 1/ I \

o ! ~ KILOMETERS 55 \\SCALE. 20 '-- . \

• - 55 ,,\ IU' ,• 50 ,,\ " f·~ _, T 1 3 S

EXPLANATION I I • 30 \\

• W.II W~\--· - 50 r: 40 • \" ;!!~ "ay 30 ~_______ September 0 T 14 S C

ELEVATIONS IN FEET ABOVE MSl 45 _ 45 "" 40......... 6

~ 50 \ I I I." I I"l~11 '~_0 __.'\"\ T 15 S I\ \ / ~'\. ---- r-!~ (J)50 45 c

:Xl

\ ! I T 16 S ;ii" . \ -<

50~ I" V \ \(" "\ \ I,

50-;- r \" 8 55 \ \ '

855\ "~I T 17 S",,- I ,,~ I I / / I \\

FGS180291

Figure 28d. Potentiometric surface of the upper Floridan aquifer system in Marion County, May 1984 and September1984 (unpublished SI. Johns River Water Management District data).

Figure 28e. Potentiometric surface of the upper Floridan aquifer system in Marion County, May 1986 and September1986 (unpublished St. Johns River Water Management District data).


! ~I T 11 S-H-

I ~ l ._-~\ -1 I J\ ,L T 12 S! I~

0 2 4 MILES

b !! '6' KILOMETERSSCALE , , ,. , , , . , ,

• v

,I~ I ~~EXPLANATION • I • T 13 S•• W.II

c:J • • • '1 "'T1+ CHANGE

0 r-0

c:J - CHANGE / T 14 S :!!c:r>e>m0

T 15 S r-• 1/ /1 •

I0

0 I I· e>• 0

:r>r-(J)../ I / __ +1 I J • I I I

/

I• c:

T 16 S::g

/. 0 <• m} -<

I I •• I • I I I I I I• • T 17 S

• "

Figure 29. Change in the potentiometric surface of the upper Floridan aquifer system from September 1987 toMay 1988 (unpublished St. Johns River Water Management District data).


St. Johns River Water Management District

GROUND WATER

Agricultural Irrigation403.33 Mgal/d

Commercial/Industrial self-supplied127,96 Mgal/d

38%

12%

Public supply366,52* Mgal/d

Domestic self-supplied82,33 Mgal/d

Power Generation4,71 Mgal/d - 0,5%

Miscellaneous66,25 Mgal/d

* includes 1.74 Mgal/d of saline ground water,

SURFACE WATER

Power Generation129,01 Mgal/d

Agricultural Irrigation214,64 Mgal/d

57%

Commercial/Industrial self-supplied20,50 Mgal/d

Public supply15.47 Mgal/d FGS240291

Figure 30. Fresh ground and surface water withdrawals by category, 1986, in the St. Johns River WaterManagement District (after Marella, 1988).

45


The commercial/industrial water use in MarionCounty (primarily in the study area) increasedfrom 0.3 to 2.6 million gallons/day between 1975and 1985. This amounts to a dramatic 780 percent increase, a strong indication of economicand population growth.

The total extraction of ground water from theunderlying aquifer systems in Marion County forall uses amounted to 33.36 million gallons/dayfor 1986. This total fresh water use in the county,excluding thermoelectric power generation,increased by 37 percent in the period from 1975to 1985 and eight percent from 1985 to 1986.

MINERAL RESOURCES

The following is a general discussion of theeconomic geology of the Ocala area. It is notintended to be a complete investigation leadingto immediate industrial development because,in many cases, the data represent informationon a single outcrop, pit or mine. However, wherethe data are favorable, they may indicate thatcertain areas might warrant further investigationand consideration in land-use planning. Figure31 is a mineral resource map designed to presentan overview of the major mineral commoditiesin and around Ocala (Hoenstine et aI., 1988).Factors such as thickness of overburden as wellas the quality and volume of the deposit willaffect the mining of the mineral commodity atany specific site. The following is a discussionof the limestone, sand, and more general undifferentiated resources present in the area.

LIMESTONE

Limestone deposits of considerable economicvalue are present in Marion County. Figure 31shows the distribution of the limestone depositsin Marion County. High calcium Ocala Grouplimestones lie at or near the surface throughoutmuch of west-central Marion County.

The Ocala Group limestones have been minedin Marion County for many years as indicated bythe numerous active and inactive quarriespresent throughout the county (Figure 31). As apoint of interest, Marion County has one of the

highest concentrations of limestone mines in thestate. These mines are generally confined to thewest-central part of the county. A number ofinactive mines are present in the north-centralportion of Ocala and one active mine is less thanone mile north of the study area (Figure 32).

All companies mining limestone in the countyemploy the open pit method for extracting therock. This method uses heavy equipment for theremoval of vegetation and overburden prior tomining a new quarry. The amount of overburdencan vary from a few inches to as much as 50 feet(Hoenstine et aI., 1988). For example, areas in thesouthwestern part of Marion County have thick

. deposits of overburden which may have potentialas a local source of fill. After clearing the areato be mined, shot holes are frequently drilled intothe rock and the quarry face is shattered byblasting. The shattered rock is then loaded bydragline or front-end loader into trucks andtransported to rock crushers for processing. Thisprocess involves size reduction and subsequentscreening to obtain the various rock size fractions (Campbell, 1986).

The Ocala Group limestones are presentlymined by a number of companies includingStavola Industries, Boutwell Construction,Monroe Mines, Ocala Bedrock, and RainbowMarion Mines. This limestone is fairly soft andis removed using bulldozers and front-endloaders. The depth of mining is dependent onavailable equipment. Currently, some companiesare mining limestone from a maximum depth of65 feet below the water table by dragline. Inmany instances, this results in a total minedsection of greater than 100-feet deep.

Limestone has a variety of uses, most ofwhich are dependent on the specific deposit'sphysical properties or chemical composition. InMarion County, the primary use of the commodityis for roadbase material with minor amountsused for agricultural lime and the processing ofglass sand.

Total production and resource estimates ofIimerock produced from the Ocala Group in thearea are not available. However, the widespreadoccurrence and thickness of the Ocala Grouplimestone suggest that these deposits can bemined for many years.

46

.'-"""0.. c.. <:..~ .""~••OII.~.ln"l.n Of' nJOt .. L "llO\lltCll

+ + : t +

.,••••#

~ CL. ...Y. TESTED DEPOSIT

C/'J"'tIm(')

:;r-"'tICOJr-(')~-l

oZ

zow...

-+-

~-N-

~.l"'-ltj1

.~ f

MARION COUNTYFLORIDA

19BB

MINERAL RESOURCES OF

+

'UlN"'" COUNlV

OCIAL

++

"

CL"'Y

H"'RD ROCK PHOSPH ...Te:IHIIlOII1C"L ..IHIHO I

L.IMITED POTENTI ... LIlO'IIOIL. 'ILL ITC. I

PE ...T

S"'ND

LIMESTONE

EXPLANATION

~:-..t-H-1

,"

f\

'\ CUY

~ U ....lOH.

~. 'IAT

~ ....HII

~1.'O"'"I1CIC 'HO"H ...n

;-

r~~

® MINE SITE ClHAClIV' I

1(' MINE SITE I ...ClIVI ,IT,QU ... III1VOII".IN.1

• MR-l S... MPL.ING LOC...TIONI.UTA.L.tl

D

•DDD

-+-

-+-

.j:l.-...J

Figure 31. Mineral resources map of Marion County (Hoenstine et aI., 1988).


Figure 32. Active limestone quarry in Ocala Group limestone, approximatelyone mile north of Ocala, T14S, R21 E, section 34. NQte karst conduit in centerof high wall. Florida Geological Survey photograph.

48


SAND

Sand covers much of the eastern third of theOcala area. In the topographically low region ofthe Central Valley, sand forms a surface veneerover limestone. Thicker sequences of clayeysand and sandy clay cap the upland and hillareas. Thicknesses typically vary from 40 to 60feet with a maximum thickness of 100 feet present to the east of Ocala in the vicinity of theOcala National Forest (Cathcart and Patterson,1983). These fine to coarse-grained sand depositsare extensive and can be observed in numerousborrow pits located in the Ocala National Forest.At present, two commercial and two county roaddepartment operations are located in MarionCounty. The Marion County Road Departmentmaintains two clayey sand pits, which arelocated to the southeast of Ocala, one nearCandler (section 26, Township 16S, Range 22E)and the other one at Celery Farm (section 27,Township 16S, Range 24E). One of the commercial operations is located in the southeasterncorner of the county (section 19, Township 17S,Range 26E) and the other near the town of Lynne(section 3, Township 15S, Range 24E) (Figure 31).

Figure 33 is modified from a United States SoilConservation Service (USSCS) map showing partof the USSCS (1979) soil survey of MarionCounty. This survey, which is based on a numberof soil samples taken to a depth of 80 inches,shows several major soil associations to bepresent in and around Ocala. These include theAstatula and Candler-Apopka soils (well drainedsandy soils), the Arredondo-Gainesville andKendrick-Hague-Zuber and Bluff-Martel soils(sandy to loamy soils), the Sparr-LochloosaTavares and Eureka-Paisley-Eaton and LyneePomona-Pompano soils (sandy, loamy to clayeysoils), and the Blichton-Flemington-Kanapahasoils (sandy, loamy and clayey soils).

This soil survey also provides data on thegeneral suitability of soils for use as construction materials. The SCS states that the Astatulaand Candler-Apopka soil associations, which arepresent in the southwestern quarter and theeastern half of the Ocala area, are good sourcesof sand (Figure 31).

Several sediment samples were collected inan area to the east and southeast of Ocala fortesting (Hoenstine et aI., 1988). These includedboth channel and individual spot samples and

49

were taken from selected existing pits (Figure 31).Laboratory procedures involved in analyzing

the samples consisted of drying then quarteringusing a riffle type sample splitter. One quarterwas then weighed and screened using a U.S.Standard Sieve Series. Data obtained are presented in Table 4 (Hoenstine et aI., 1988). Thisinformation can be useful in assessing theeconomic potential of these deposits.

Test results indicate that these sands may besuitable for concrete, brick masonry, sandcement riprap, sand-asphalt hot mix and as sandseal coat. Tests to determine suitability for glassmanufacturing were not made. However, ironoxide coatings on the sand grains probablyprecluge their use for this purpose. Data fromTable 3 represent only one particular set ofsamples and does not necessarily depict allmaterial in a given deposit.

UNDIFFERENTIATED RESOURCES

Much of the surface and near-surface sediments of the extreme eastern and south-centralportions of the study area are comprised ofclayey sands (referred to on Figure 31 as"Limited Potential"). This area coincides withmuch of the Ocala Hills geomorphic feature. Theheterogeneous nature of these sediments wouldtend to preclude their large scale economicmarketability. Locally, however, where costs arenot prohibitive and the need is present for usessuch as top soil or road fill, extraction is feasible.The possibility is very small that these undifferentiated sediments can be used for largescale economic or industrial appiications.

LAND USE

The University of Florida has developed a computerized data base to identify specific land usepatterns in Florida. These data are based on anumber of sources including municipal andcounty property taxes, assessments and platbooks. Presently, over 100 specific land useshave been defined, all of which have beengrouped by the Florida Department of Revenueunder one of seven general land use categories.These seven broad categories are residential,commercial, industrial, agricultural, governmental, institutional and miscellaneous.

2 MILESI

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SOIL ASSOCIATIONS

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MAINLY EXCESSIVELY DRAINED, NEARLY LEVEL TO STRONGLY SLOPING SOILS OF THEUPLANDS.

ASTATULA association: Nearly level to strongly sloping, excessively drained soiis, sandy to adepth of more than 80 inches.

CANDLER-APOPKA association: Nearly level to strongly sloping, excessively drained and welldrained sandy soils, some with thin sandy loam lamellae at a depth of 80 to 80 inches andothers loamy at a depth of 40 to 80 inches.

WELL DRAINED, NEARLY LEVEL TO SLOPING SOILS OF THE UPLANDS.

ARREDONDO-GAINESVILLE association: Nearly level to sloping, well drained soils, some sandyto a depth of more than 40 inches and loamy below and others sandy throughout.

KENDRICK-HAGUE-ZUBER association: Nearly level to sloping, well drained soils, sandy to adepth of less than 40 inches and loamy or clayey below.

SOMEWHAT POORLY DRAINED AND MODERATELY WELL DRAINED, NEARLY LEVEL TOSLOPING SOILS OF THE UPLANDS AND FLATWOODS.

SPARR-LOCHLooSA-TAVARES association: Nearly level to sloping, somewhat poorly drainedand moderately well drained soils, some sandy to a depth of 20 to more than 40 inches andloamy below and others sandy throughout.

POORLY DRAINED, NEARLY LEVEL SOILS OF THE FLATWOODS.

LYNNE-POMONA-POMPANO association: Nearly level, poorly drained soils, some sandy to adepth of 22 to 80 inches, weakly cemented within a depth of 30 inches, and loamy and clayeyin the lower layers and others sandy throughout.

POORLY DRAINED, NEARLY LEVEL TO STRONGLY SLOPING SOILS OF THE UPLANDS.

BLiCHTON-FLEMINGTON-KANAPAHA association: Nearly level to strongly sloping, poorlydrained soils, sandy to a depth of less than 20 to more than 40 inches and loamy or clayeybelow.

VERY POORLY DRAINED SOILS OF THE FLATWOODS AND FLOOD PLAINS.

BLUFF-MARTEL association: Nearly level, very poorly drained soils, some loamy and clayeythroughout and others loamy in the upper part and clayey within a depth of 20 inches.

Figure 33. General soil map of Ocala study area (after U.S. Soil Conservation Service Soil Surveyof Marion County, 1979).

50


Table 4. Screen analyses 01 sand samples in Marion County, Florida (Hoenstine et al., 1988).

LABORATORY TEST DATADEPOSITS SCREEN ANALYSIS

SIEVE NO. AND CUMULATIVE WEIGHT PERCENT RETAINED

SAMPLE NO. LOCATION METHOD OF SAMPLING 4 8 16 30 50 100 200-FINENESS

(T,RSEC.) MODULUS

MR-1 18S,24E,22ac CHANNEL - 1.070 1122 44.560 73.580 94.540 97.560 3.23

MR-2 17S,26E,5ba CHANNEL - 0.030 1520 10.480 28.960 79.460 94.770 2.15

MR-3 15S,24E,14da CHANNEL - - 1230 27.080 55.890 84.980 96.690 2.66

MR-4 15S,24E,3dc SPOT - 0.050 6.300' 35.100 56.580 88.050 99.700 2.86

MR-5a 11S,24E,28bd CHANNEL - 3.090 12.700 35.570 58.220 90.850 97.990 2.98

MR-5b 11S,24E,28bd CHANNEL - - 5.Q10 47.880 82.740 94.910 97.800 3.28

MR-6a 12S,24E,20ab CHANNEL - 2.080 14.680 42.520 39.080 82.030 94.900 2.95

MR-6b 12S,24E,20ab CHANNEL - 0.400 12.870 39.750 52.330 71910 95220 2.72

MR-6c 12S,24E,20ab CHANNEL - 0.220 3.760 12.030 27.150 76.150 95.540 2.15

*F1NENESS MODULUS: A MEANS OF EVALUATING SAND AND GRAVEL DEPOSITS WHICH CONSISTS OF SIEVING SAMPLES THROUGH A STANDARDIZEDseT OF SIEVES, ADDING THE CUMULATIVE WEIGHT PERCENTAGES OF THE INDIVIDUAL SCREENS, DIVIDING BY 100, AND COMPARING THE RESULTANTFINENESS MODULUS NUMBER TO VARIOUS SPECIFICATION REQUIREMENTS (BATES AND JACKSON, 1980).

51


Figures 34 through 40 are computer generated,color-coded illustrations that show either thenumber of parcels or the acreage within a section (640 acres) which are devoted to the statedland use. These numbers are based on percentages of the value in the section on the mapwhich contains the greatest numerical sum (inparcels of acreage as indicated) of that specificland use. For example, the section in MarionCounty which has the greatest number ofparcels for the residential land use, contains1,000 parcels (Figure 34). This section is shownon the map in the same color as the 81 to 100percent category. The other sections are shownin colors representing intervals from 1 to 100 percent, based on this 100 percent value of 1,000.

The residential category includes vacant residential, single family, mobile homes, condominiums and mUlti-family units. As Figure 34shows, this category is well represented in theOcala area with a number of the sections fallingin the 81 to 100 percent category. The densestresidential areas are located adjacent to thecentral part of the city. The lightest residentialdevelopment occurs in northwest Ocala. Aswould be expected, Ocala, which is the largestcity in Marion County, has the highest concentration of maximum residential values in thecounty. Residential housing units in Ocalatotaled 18,871 units, 21.18 percent of the total inMarion County in 1988 (Thompson, 1988).

The proximity of the Ocala Group limestoneto land surface in the western half of the studyarea is a cause for concern when planningresidential development. The presence of a thincover of undifferentiated sands and clays andHawthorn Group sediments overlying limestonebedrock in this area is a situation conducive tothe development of sinkholes and potentialstructural damage. In addition, the geology ofthis area permits easy access of potential contaminants to this limestone unit which is theupper part of the Floridan aquifer system. Extensive use of septic tanks and associated drainfields here has the potential for significantdegradation of ground-water quality.

Similarly, the surficial aquifer system presentin the thick deposits of Undifferentiated Sandsand Clays in the eastern half of the study areacould experience contamination by residentialdevelopments using drain fields and septictanks. Additionally, the use of pesticides and

52

fertilizers on residential lawns and gardenscould degrade water quality of both the Floridanaquifer system in the western half of the studyarea and the surficial aquifer system in theeastern half.

The commercial land use classification includes vacant commercial property, departmentstores, supermarkets, regional and communityshopping centers, professional servicesbuildings, service stations, parking lots,restaurants, motels, golf courses, and touristattractions. Except for the City of Ocala, thiscategory is lightly represented throughout thecounty (Figure 35). The localized commercial activity recorded in Ocala is in part a consequenceof tM city's rapid development and the diversityof. services associated with this growth.

Some commercial categories, such as servicestations and large parking lots associated withmalls and supermarkets, pose serious environmental threats to the fragile protection of theground water offered by the thin soil cover overthe limestone. Specifically, leaking or improperlyinstalled underground fuel storage tanks couldcause significant degradation of the limestoneaquifer. This is of special concern in the centralpart of Ocala where the highest concentrationof commercial activity occurs (Figure 35). Here,limestone is near to land surface and theassociated ground water is highly susceptible tocontamination. Also, runoff from improperlydesigned parking lots has the potential toinfiltrate surrounding unpaved sediments which,in eastern and central Ocala, form a thinpermeable cover over the Floridan aquifersystem.

Ocala's industrial complex is similar to thecommercial category in its diversity and concentration in the Ocala area (Figure 36). This activityincludes light manufacturing, heavy equipmentmanufacturing, warehousing, canneries, andlumber yards. The area's large mobile homemanufacturing plants are represented in thiscategory.

The concentration of industrial activity in central and west-central Ocala poses risks similarto those of commercial activities. The proximityof the aquifer to land surface in this area and itssusceptibility to contamination requires thateffective procedures involving the usage anddisposal of industrial chemicals must be implemented and strictly monitored.

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Figure 34. Residential land use, 1988. Number of parcels per section, 100% = 1,000 (from Hatchill, 1989).

R 23 E

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Figure 35. Commercial land use, 1988. Number of parcels per section, 100% = 200 (from Hatchitl, 1989).

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Figure 36. Industrial land use, 1988. Number of parcels per section, 100% = 100 (from Hatchitl, 1989).

(f) R 21 E R 22 E R 23 E

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Figure 37. Agricultural land use, 1988. Number of parcels per section, 100% =640 (from Hatchitt, 1989).

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Figure 38. Governmental land use, 1988. Number of parcels per section, 100% = 20 (from Hatchitl, 1989).

Figure 39. Institutional land use, 1988. Number of parcels per section, 100% = 20 (from Hatchitt, 1989).

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Figure 40. Miscellaneous land use, 1988. Number of parcels per section, 100% =640 (from Hatchitt, 1989).


Agriculture is an extremely important component of Marion County's economy. In addition tovegetables, fruit, field crops, and ornamentals,Marion County is nationally recognized for itsthoroughbred horse farms. Figure 37 shows thata significant percentage of the county is involvedin agriculture. In contrast, the City of Ocala hasa small amount of agricultural acreage. This maybe reduced in the future as continued growth anddevelopment in the city and the county willdoubtless expand in part at the expense ofagriculture.

Large scale use of pesticides, herbicides, andfertilizers by the agricultural sector is an everpresent threat to Ocala's ground-water supply.Concentrations of agriculture in the northeastern part of the study area is of particularconcern as the Floridan aquifer system occursalmost at land surface there, providingpollutants easy access to ground water.

As the county seat, Ocala has a number of cityand county government activities. These activities are part of the governmental category whichincludes municipal government facilities (countyand city), public colleges, hospitals and schools(Figure 38).

The institutional category is well representedin the Ocala area (Figure 39). It includeschurches, private schools and colleges, privatehospitals, clubs, convalescent homes andcultural organizations.

The miscellaneous category (Figure 40) is ageneral classification. It incorporates everythingnot covered by the above categories. Theseinclude such things as railroads, rivers, lakes,sewage disposal and rights-of-way of streets,roads, and ditches.

ENVIRONMENTAL HAZARDSASSOCIATED WITH KARST

The karst terrain of the study area createsspecial conditions that are responsible for mostof the area's environmental hazards, excludingsuch weather hazards as hurricanes. The priordiscussion of the evolution of the local karstterrain pointed out the most important aspect ofkarst - its underground drainage system. Karstand its intimate relationship to the area's water

resources dictates, to a large degree, the extentto which society's activities can stress theenvironment - and not create problems.

An adequate supply of fresh water is a keystone to a high standard of living, for publicwater supplies, for industrial demands, and foragricultural usage, such as irrigation farming.Because of karst there is very little surface wateravailable; consequently, most of the area's watersupplies are ground water from the Floridanaquifer system. Protection of the quality of thearea's ground water must be of paramount concern in any planning, development, or regulatorycontext. Special conditions associated withkarst hydrologic systems require special pre-

, caytions and considerations.The study area lies wholly within the drainage

basin of Silver Springs. Faulkner (1973) analyzedregional surface and ground-water levels todetermine the drainage basins of the OklawahaRiver, and Rainbow and Silver Springs (Figure 41).Note that the springs' drainage basins lie partlywithin and partly outsidethe Oklawaha River'ssurface drainage basin divide, which was drawnalong topographic highs. This anomalous situation is due to karst. The well developed underground drainage for the area provides rapidrecharge to the shallow sand aquifers or to thelimestone aquifer. Many of the sinkholes opendirectly into the limestone or they havepermeable sediment fill which allows infiltration.

This situation illustrates the uncertainties indealing with ground-water problems in karstterrain. Relative to the tiny pores in most sandy,unconsolidated sediments, the karstic porosityof the Floridan aquifer system's limestones aremegascopic, as shown in Figures 20,21, and 42.These cavernous openings in the limestonepermit conduit flow to occur, analogous to flowin a system of open pipes. Countless sinkholesin the area provide direct, almost instantaneous,recharge to the aquifer. Recharge, in this context, refers to water from any source, along withentrained contaminants, that enter the Floridanaquifer system. The ability of these avenues ofrecharge to accept practically limitless quantities of surface water was dramatically demonstrated during the flooding of parts of Ocala asa result of torrential rains in April 1982, whennearly 12 inches of rain fell in one day (Figure 43).

60


OKLAWAHA RNERBASIN EXTENDS TO SOUTH

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....... Oklawaha River drainage basin boundary2.870 square miles. •

EXPLANATION

Spring drainage area boundary

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igure 41. Drainage basin of the Oklawaha River with drainage basins of Silver and Rainbow SpringslUperimposed (modified after Faulkner, 1973).


Figure 42. Limestone Iracture zone enlarged by solution activity in Ocala Grouplimestone. The cavernous opening is aboutlour·leet high by two·leet wide; height01 photograph is about 20 leel. Location is the same as in Figure 32. FloridaGeological Survey photograph.

62


Figure 43. Flood waters recharging Floridan aquifer systemthrough a sinkhole that opened up as a result of the April 1982flood in Ocala. Ocala Group limestone is within two to three feetof surface here. Florida Geological Survey photograph.

63

52 .

'-lrI\ « WATER LEVEL IN A FLORIDAN AQUIFER WEllI-«135 FT. OEEP51 -I a

"I3.7 MI. S.E. 01 OCALA

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JAN J DEC J 0 J 0 J 0 J 0 J 0

1981 1982 1983 1984 1985 1986

Figure 44. Graphs showing relationships among rainfall, ground·water levels in the Floridan aquifer system anddischarge of Silver Springs. Note that all three graphs display very similar curves, which indicates a strong cause·effect relationship. Note the very short recharge lag·time (R) between major rainfall events and a rise in the waterlevel in the Floridan aquifer system well, usually only a few days_ The discharge lag-time (D) is longer and representsthe delays due to the water's travel through recharge, storage within the aquifer, and eventual discharge at SilverSprings; this can vary from a few days to a few weeks. Data from U.S. Geological Survey, Water Resources Data,1981-1986.


It is not difficult, therefore, to visualize howrapidly the cavernous porosity of the aquifer cantransmit recharge through the system, from apoint of entry, such as a sinkhole, to a point ofdischarge, such as a well or spring. Conduit flowwould prevail in many cases, with transit timesof only hours or days from point of entry to apoint of discharge that could be several. milesdistant. Figure 44 illustrates the two most Impor·tant characteristics of the Floridan aquifersystem's response to hydrologic events in theOcala area: (1) rapid recharge to the aquiferthrough karst features and thin soil cover overthe limestone, and (2) rapid transit of waterthrough the aquifer.

Up to a point, the natural workings of Ocala'shydrologic system can be considered favorableto society's activities. The area has plenty ofrain, which can be easily recharged to theaqUifer, providing large quantities of fresh waterin storage, which can be easily tapped by wells.However when society intrudes with some of Itsactivitie; which do not consider the workings ofthe karst'hydrology, the results can be environ·mental problems. Examples of society's stressesto the karst environment are: large expanses ofpavement and roofs, drainage wells for surfacerunoff, some types of agricultural and Industnalpractices, and landfills.

Paving and roofing remove large amounts ofland that would otherwise be diffuse rechargeareas thereby concentrating runoff and rechargeto sm~lIerareas. As urbanization continues, thishas the cumulative effect of concentratingsources of potential contaminants to the aqUifer.The use of drainage wells to alleviate surfacewater flooding problems also acts to concentrate potential contamination to the aquifer(Figure 18). In urban development plans there isa need to dedicate more green-belt open areasto offset the loss of recharge areas.

The over·application of fertil izers, pesticides,or the use of chemicals that are long-lived ornon-biodegradable, and the over-application ofirrigation water can create sources of contamination. New methods of irrigation, such astrickle delivery and root delivery, conserve largequantities of water while at the same timereducing the build-up of salts In the SOIl. .

Urban growth inevitably brings constructionand service industries, such as gas stations and

65

merchandisers, or manufacturing plants. Withvery few exceptions in the past, most of theseactivities have been implicated as sources ofpollution to surface or ground water. Beforeoperating permits or business licenses areissued, permitting authorities should require aninventory of materials to be handled, processedor dispensed, as well as a plan that adequatelyaddresses waste disposal practices at eachlocation.

SOLID WASTE DISPOSAL

Past and current practices of open dumpingand landfilling have been documented assources of ground-water pollution in Florida'skarst terrain (Hoenstine et aI., 1987). Recentregulatory and engineering approaches aredesigned to prevent contaminants from leavingthe landfills.

Managing solid waste is a monumental taskthat faces the nation. In many local areas it hasbecome a critical task, demanding short·termsolution. To avoid a garbage ,crisis in the'nearfuture it will be necessary to change the nation'sattitude towards solid waste disposal, and toindulge in careful planning b'ased on thosechanged attitudes. Instead of a "throwaway"society we must become a "recycle and conserve" society.

Realize that the United States generatesbetween 150-300 million tons of solid waste peryear, about 4 to 8 pounds per person per day.Florida generates more than 13 million tons ofsolid waste per year, about 7 pounds per personper day. At the Marion County landfill, southeastof Ocala, the daily input varies from 600-650 tonsper day - with peak inputs up to 1,000 tons perday (Earl Blankenship, Solid Waste Admini·strator, Marion County landfill, pers. comm.,1989). This means that, on the average, everyperson in Marion County generates from 6.5 to10.9 pounds of solid waste per day. In recentyears the disposal of these quantities of solidwaste has resulted in a mountain, literally,' beingcreated southeast of Ocala; this truncated pyramidal mountain currently has a 10·acre footprintand rises 90 to 100 feet above the surroundingflat countryside (Figure 45). Three additional,similar mountains will rise nearby before thelandfill reaches its planned capacity.


Figure 45. Finished cell of the Marion County landfill, view to north. FloridaGeological Survey photograph, February 1989.

66


Figure 46. Newly opened cell at the Marion County landlill, showing plastic liner on lelland background walls. The liner has been covered with sand on the other two walls lorprotection. Nole the leachate collection pipes on the lell and the 30,000 gallon holdingtank in the lell background. View to the south Irom the top olthe recently finished, oldercell, shown in Figure 45. Florida Geological Survey photograph, February 1989.

Figure 47. The 30,000 gallon leachate holding lank at the Marion Counly landfill, showing some 01 the pipes lhal conneclto lhose shown in Figure 46. Florida Geologicai Surveyphotograph, February 1989.

67

'"00

FINISHED, CLOSED CELL 7WALLS OF CELL MONITOR WELLS

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LEACHATE COLLECTION PIPES PLASTIC LINERON TOP OF LINER

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Figure 48. Generalized cross seclion of new cells at the Marion County landfill, 1989. Not to scale.


Some of the more obvious problems associ·ated with the disposal of such huge quantitiesof solid waste are: large expenditures by localgovernments to operate landfills; landfills arevery difficult to site in a safe environment; andthe available good sites are becoming harder tofind. One of the most important problems withsolid waste disposal is the potential for contaminating ground and surface water by biologicaland chemical constituents that leach out afterburial.

Federal and state regulatory agencies havemandated many requirements for operatinglandfills to protect the environment. Currentpolicy towards landfill design is to build facilitiesthat almost totally isolate the refuse from theenvironment. The first of the new cells at theMarion County landfill, which started operationin early 1989, incorporates much state-of-the-arttechnology to achieve this goal. Present andfuture cells have double linings of clay in thesub-floor, topped by a 100-mil-thick plastic linerthat extends up the sides of the cell (Figure 46),forming what is, in effect, a liquid-proof container in which the solid waste is placed; wateris excluded and leachate is contained. An extrameasure of protection is provided by a leachatecollection system, consisting of a series ofsuction pipes laid on top of the liner, andconnected to a 30,OOO-gallon, fiberglass holdingtank (Figure 47). Should it be necessary, collected leachate may be transported to an off-sitewaste-treatment facility. Figure 48 shows thesedesign features in the new cells.

The older landfill, however, was begun beforethe present standards and technology wereavailable for operating solid waste disposalfacilities. The Florida Department of Environmental Regulation requires all landfill operationsto maintain a system of ground-water monitoringwells around the facility, and to regularly sampleand test the aquifers, in order to detect anycontamination. As of the date of this report, nodeterioration of ground-water quality has beendetected.

69

SUMMARY

The data and information in this reportestablishes the intimate relationship amongclimate, geology, and hydrology of the Ocalaarea. There are demonstrated reasons for citizens, planners, and other governmental agenciesto have concerns with regards to past, and future,industrial, agricultural, and urban development.Protection of Ocala's ground-water resourcesmust be a top priority in planning, development,or regulatory context.

The carbonate rocks of the Floridan aquifersystem occur at or near land surface in the studyarea. Their high degree of karstification provideseasy, and rapid;· access to the aquifer by rainwater and any entrained contaminants. Urbanization increases the types and amounts ofcontaminants to the aquifer, as well as concentrating runoff so that the natural filtering actionof soil overburden is bypassed. Potential threatsto ground-water quality due to urbanization include improperly installed septic tanks and drainfields, leaking storage tanks for petroleum orother chemicals, runoff from paved areas, drainage wells, and improper landfilling practices.

Agriculture is a major part of the area'seconomy. Wide-spread use of chemicals toincrease yields poses a significant threat to theground water. Indiscriminant and over-applicationof irrigation water increases the possibility ofground-water contamination.


REFERENCES

Anderson, W., and Faulkner, G. L., 1973, Quantity and quality of surface water in Marion County,Florida: prepared by the U.S. Geological Survey in cooperation with the Southwest FloridaWater Management District and the Board of County Commissioners of Marion County,Florida, scale: 4 miles to 1 inch.

Campbell, K. M., 1986, Industrial minerals of Florida: Florida Geological Survey Information Circular102, 94 p.

Cathcart, J. B., and Patterson, S. H., 1983 Mineral resource potential of the Faries Prairie and BuckLake roadless areas, Marion County, Florida: U.S. Geological Survey Map SeriesMF-1519B.

City of Ocala Planning Department and the Ocala-Marion County Metropolitan Planning Organization,1988, City of Ocala Statistical Profile, 75 p.'

Deuerling, R. J., and MacGill, P. L., 1981, Environmental geology series, Tarpon Springs sheet: FloridaBureau of Geology Map Series 99, scale 1:250,000.

Faulkner, G. L., 1973, Geohydrology of the cross-Florida barge canal area with special reference tothe OCilla Vicinity: U.S. Geological Survey Water Resources Investigation 1-73, 117 p.

Ferguson, G. E., Ungham, G. w., Love, S. K. and Vernon, R. 0., 1947, Springs of Florida: FloridaGeological Survey Bulletin 31, 198 p.

Hatchitt, J., 1989, Florida summary mapping system (users guide), Armasi, Inc., 17 p.

Healy, H. G., 1975, Terraces and shorelines of Florida: Florida Bureau of Geology Map Series 71,scale 1:2,000,000.

Hoenstine, R. W., Lane, E., Rupert, F. R., Yon, J. W., Jr., and Spencer, S. M., 1988, Mineral Resources ofMarion County, Florida: Florida Geological Survey Map Series 117, scale: 2 miles to 1 inch.

____ , Lane, E., Spencer, S. M., and O'Carroll, T., 1987, A Landfill site in a karst environment,Madison County, Florida - a case study, in: Proceedings of the 2nd Multidisciplinary Conference on Sinkholes and the Environmental Impacts of Karst, Beck, B. F., and Wilson,W. L., eds.: Florida Sinkhole Research Institute, University of Central Florida, Orlando,Florida, p. 253·258.

Knapp, M. S., 1978, Environmental geology series, Gainesville sheet: Florida Bureau of Geology MapSeries 79, scale 1:250,000.

Lane, E., 1986, Karst In Florida: Florida Geological Survey Special Publication 29, 100 p.

Marella, R. L., 1988, Water withdrawals, use and trends in the SI. Johns River Water ManagementDistrict: SI. Johns River Water Management District Technical Publication 88·7, 131 p.

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Marion County Planning Department, 1988, Future land use element, Marion County ComprehensivePlan, March 1988 draft, 72 p.

Miller, J. A., 1986, Hydrogeologic framework of the Floridan aquifer system in Florida and in parts ofGeorgia, Alabama, and South Carolina: U.S. Geological Survey Professional Paper 1403-B,91 p.

NOAA (National Oceanic and Atmospheric Administration), 1982, Storm Data, v. 24, no. 4, 46 p.

NOAA (National Oceanic and Atmospheric Administration), 1981-1986, Climatological AnnualSummaries, Florida.

Phelps, G. C., 1989, Hydrogeology and effects of selected drainage wells and improved sinkholes onwater quality in the upper Floridan aquifer, Silver Springs Basin, Marion County, Florida:in Water Resources Activities in Florida, U.S. Geological,Survey Open File Report 89-227,p.68.

Puri, H. S., and Vernon, R. 0., 1964, Summary of the geology of Florida and a guidebook to the classicexposures: Florida Geological Survey Special Publication 5 (revised), 312 p.

Rosenau, J. C., Faulkner, G. L., Hendry, C. W., Jr., and Hull, R. W., 1977, Springs of Florida (revised):Florida Geological Survey Bulletin 31, 461 p.

Scott, T. M., 1978, Environmental geology series, Orlando sheet: Florida Bureau of Geology Map Series85, scale 1:250,000.

____ , 1979, Environmental geology series, Daytona Beach sheet, Florida Bureau of GeologyMap Series 93, scale 1:250,000.

Sinclair, W. C., and Stewart J. W., 1985, Sinkhole type, development and distribution in Florida: FloridaBureau of Geology Map Series 110, scale: 30 miles to 1 inch.

Southeastern Geological Society Ad Hoc Committee on Florida Hydrostratigraphic Unit Definition,1986: Florida Geological Survey Special Publication 28, 8 p.

Thompson, D., 1988, Marion County statistical overview: Marion County Department of CommunityDevelopment, 63 p.

U.S. Geological Survey, 1981-1986, Water Resources Data, Florida - Surface Water Records andGroundwater Records, vol. 1, Northeast Florida.

United States Soil Conservation Service, 1979, Soil survey of Marion County area, Florida: U.S.Department of Agriculture Soil Conservation Service in cooperation with University ofFlorida, Institute of Food and Agricultural Sciences, 148 p.

White, W. A., 1970, The geomorphology of the Florida peninsula: Florida Bureau of Geology Bulletin51,164 p.

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FLORiDA GEOLOGICAL SURVEY003 W. TENNESSEE STflEET

TAUAHASSEE, FLORIDA 323M-7700

Walter Schmidt, ChiefPeter M. Dobbins, Admin. Ass!.Jessie Hawkins, Custodian

Alice LibrarianSandie Ray, Admin. Sern,trli"l!

Vanessa Allred, Library Ass!.

GEOLOGICAL iNVESTIGATIONS SECTION

Thomas M. Scott, Senior Geologist/AdministratorJon Arthur, Petrologist Ted Kiper, {::artographerPaulette Bond, Geochemist Nancy LaPlace, Research Ass!.Dianne Brien, Research Ass!. Milena Mace~ich, Research Ass!.Ken Campbeli, Sedimentologist Mel Martinez, Research Ass!.Cindy Collier, Secretary Ted Maul, Research Ass!.Mitch Covington, Biostratigrapher Robert Mince, Research Ass!.Joel Duncan, Sed. Petrologist John Morrill, DrillerBob Fisher, Research Ass!. Larry Papetti, Research Ass!.Rick Green, Research Asst. Albert Phillips, Asst. DrillerMark Groszos, Research Asst. Frank Rupert, PaieontologistKent Hartong, Research Ass!. Frank Rush, Lab Tech.Jim Jones, Cartographer Tom Seal, ResearchClay Kelly, Research Asst.

MINERAL RESOURCE INVESTIGATIONSAND

ENVIRONMENTAL GEOLOGY SECTION

Jacqueline M. Lloyd, Senior Geologist/AdministratorEd Lane, Env. Geologist Ron Hoenstine, Env. Geologist

Steve Spencer, Economic Geologist

OIL AND GAS SECTION

L. David Curry, AdministratorScott Hoskins, Dis!. CoordinatorBarbara McKamey, SecretaryMarycarol Reily, GeologistKoren Taylor, Research Ass!.

Charles H. Tootle, Pet. Engineer

Brenda Brackin, SecretaryRobert Caughey, Disl. CoordinatorJoan Gruber, SecretaryDon Hargrove, Engineer


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state of florida executive director division of …...jeremy a. craft, director florida geological...

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