FRACTURE TRACE MAPPING

OF THE ELDRIDGE-WILDE WELL FIELD,

PINELLAS COUNTY, FLORIDA

by D.M. Diodato

U.S. GEOLOGICAL SURVEY 

Open-File Report 99-235

Reston, Virginia 

1999
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY 

Charles G. Groat, Director

Acknowledgments

Ann Tihansky of the USGS generously provided field support, data, and helpful discussion and commentary. Robert Evans, GIS Analyst, Mapping and GIS section, Southwest Florida Water Management District, was most generous and helpful in sharing his equipment and his considerable expertise and insights 

regarding fracture traces in the study area. Charles Brown and Jurate Landwehr of the USGS were very 

helpful in sharing their considerable expertise and insights regarding application of nonparametric statistical methods.

The use of firm, trade, and brand names in this report is for identification purposes only 

and does not constitute endorsement by the U.S. Geological Survey.

For additional information write to: Copies of this report can be purchased from:

David M. Diodato U.S. Geological Survey

U.S. Geological Survey Information Services

Water Resources Division Box 25286

431 National Center Federal Center

Reston, VA 20192 Denver, CO 80225
CONTENTS

ABSTRACT..................................................................................................................... 1

INTRODUCTION ............................................................................................................ 1

HYDROGEOLOGIC SETTING ....................................................................................... 2

FRACTURE-TRACE MAPPING PRINCIPLES ............................................................... 3

PHOTOLINEAR MAPPING METHODOLOGY ............................................................... 5

MAPPED FRACTURE TRACES AND PHOTOLINEARS ............................................... 6

INFLUENCE OF FRACTURE TRACE LOCATION ON WELL YIELD ............................ 9

APPLICATION TO FIELD HYDROGEOLOGIC INVESTIGATIONS ............................. 10

SUMMARY AND CONCLUSIONS ................................................................................ 12

REFERENCES ............................................................................................................. 13

APPENDIX A. MAPPED PHOTOGRAPHS ................................................................ A-1

ILLUSTRATIONS

1. Map showing approximate locations of production and monitoring wells

(shown in blue) in the study area at the Eldridge-Wilde well field. ............................. 2

2. Approximate potentiometric surface of the Upper Florida Aquifer (Meyer, 1989)....... 4

3. Map showing projected locations of the mapped photolinears at the

Eldridge-Wilde well field. Only the photolinear near well 109 has been verified in the 

field to be a fracture trace. .......................................................................................... 7

4. Sinkhole near well 109 which developed recently before the March 1999 field visit.. 8

5. Rose diagram showing frequency (percent) of mapped photolinear orientations....... 8

6. Boxplot of well yields from non-fracture trace and fracture trace wells..................... 10

7. Photograph GS-SWFM 4-54 with mapped photolinears and fracture traces. ......... A-1

8. Photograph GS-SWFM 4-55 with mapped photolinears and fracture traces. ......... A-2

9. Photograph GS-SWFM 4-56 with mapped photolinears and fracture traces. ......... A-3

10. Photograph GS-SWFM 4-57 with mapped photolinears and fracture traces. ....... A-4

TABLES

1. Generalized hydrostratigraphy in the study region (modified from Tihansky and 

others, 1996). ............................................................................................................. 3

2. Photographs used in the photolinear analysis at Eldridge-Wilde Well Field,

Pinellas County, Florida. ............................................................................................. 6

3. List of factors which may influence the distribution of porosity and

permeability at the Eldridge-Wilde well field. ............................................................ 12
ABSTRACT

A photolinear analysis of the Eldridge-Wilde well field, Pinellas County, 

Florida, was conducted to identify zones of fracture concentration. Photolinear fracture traces and lineaments correspond to vertical zones of fracture concentration. Forty-three photolinears, ranging in length from 269 

meters to 2.53 kilometers were mapped on four aerial photographs. The 

dominant azimuthal orientation of the photolinears is in the range of 041 ° to 

050°.

The relation between well yield and well location relative to fracture trace 

location was investigated. Of the forty-eight production wells in the field 

study area for which specific yield data were available, seven are located 

on mapped fracture traces, one of which is on a fracture trace intersection. 

Boxplots of specific yields of wells "on" and "off" fracture traces show that 

the median productivity of the "on" group, 308 gallons per minute per foot 

of drawdown, is almost twice that of the "off" group, 160 gallons per minute 

per foot of drawdown. However, nonparametric statistical analysis could 

not reject the null hypothesis that both samples were from the same statistical population.

Application of this photolinear analysis to any subsequent water supply 

investigations would require supplementary inquiries, including field checking of the mapped photolinears and test drilling. In the course of the investigation, a list of sixteen hydrogeologic variables that can influence porosity 

and permeability at the Eldridge-Wilde well field was developed.

INTRODUCTION

Although many fracture traces have been 

mapped in West-Central Florida, to the 

best of the author's knowledge no rigorous 

quantitative demonstration of the relation 

between fracture zone and well yield has 

been published for the Upper Floridan 

aquifer. Water wells located on zones of 

enhanced fracture concentration in other 

areas of the United States have been 

shown to have significantly larger yields 

than similar wells not located on such 

zones (Siddiqui and Parizek, 1971). Photolinear mapping was conducted to investigate the relation between well yield and 

fracture trace location in the Upper Floridan aquifer at the Eldridge-Wilde well 

field.

The Eldridge-Wilde well field is located in 

sections 1,2, 11, and 12, Township 27 S, 

Range 16 E on the U.S. Geological Survey 

(USGS) topographic quadrangle of Elfers, 

Florida, near the intersection of Pinellas, 

Pasco and Hillsborough counties on Florida's western coast (fig. 1). Maximum 

relief in the quadrangle is less than 20 

meters. Most of this relief is due to the 

presence of paleodunes west of the study 

area. The area of investigation encompassed approximately 11 square kilometers. The well field is one of several that 

supplies water to west-central Florida. 

The geologic setting of the well field is 

dominated by thick, areally-extensive limestone with some dolomite. Karst features 

are pervasive and many sinkholes occur in 

the study area.
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Figure 1. Map showing location of production and monitoring wells (shown in 

blue) in the study area at the Eldridge-Wilde well field, based on a 21 June 1999 

global positioning system survey. See figure 2 for location within state of Florida. 

(Topographic map is not rectified to the well coordinates and is for reference only.)

HYDROGEOLOGIC SETTING

The wells in the Eldridge-Wilde well field 

produce water primarily from the Tertiary 

Upper Floridan Aquifer. The hydrostratigraphy of the Tertiary and Quaternary rocks 

in the study region is summarized in 

Table 1.

A map of the regional potentiometric surface of the Upper Floridan Aquifer in May 

1980 was published by Meyer (1989). 

That map shows the approximate location 

of a prominent ground-water divide running down the central axis of the Florida 

Peninsula. Although the data synthesized 

on the map are not recent, the configuration of the potentiometric surface on a 

regional scale does not change apprecia-
Table 1: Generalized hydrostratigraphy in the study region (modifled from Tihansky and 

others, 1996)

System Series Hydrostratigraphic 

Unit Generalized Lithology

Quaternary Pleistocene

Pliocene

Miocene

Surficial Aquifer 

System

Intermediate Confining 

Unit

Oligocene

Eocene

Upper Floridan 

Aquifer

Fine to very fine sand, shelly in places, infrequent 

clay beds.

Fine-grained carbonate,

variably dolomitic (Arcadia Formation)

Sandy wackestone (Tampa Member)

Fine- to medium-grained limestone with trace organics and variable dolomite and clay (Suwanee Limestone)

Chalky, fine- to very fine-grained limestone, changing with depth to medium to coarse-grained biogenic 

limestone, variable dolomite (Ocala Limestone)

bly with time (M.L Merritt, USGS, oral 

comm., 1999). The stippled area indicates 

potable water.

The local geology consists of a karstic carbonate rock sequence with considerable 

heterogeneity with respect to dolomite 

content and the presence or absence of 

karst conduits, shelly beds, and clayey 

zones. As is typical of karst hydrogeologic 

settings, the thickness of the sedimentary 

overburden varies considerably but is up 

to 30 m in places. The sediments are 

dominated by sand, but also include claydominated and shelly zones on top of the 

carbonate rock sequence. Cypress 

swamps dot the landscape, and peat 

deposits are present in some of these 

swamps. Although topographic relief is 

negligible, the northern portion of the 

study area can be classified as "upland" 

based on the occurrence of relatively 

hydrophobic pine and palmetto, whereas 

the southern portion can be classified as 

"lowland" based on the scarcity of those

plant types and the dominance of hydrophyllic cypress trees.

FRACTURE-TRACE MAPPING 

PRINCIPLES

Photolinear analysis is a type of remote 

sensing analysis wherein investigators 

map linear features ("photolinears") 

observable on aerial photographs or other 

remotely-sensed images. The use of photolinears for ground-water well siting was 

pioneered by Lattman and Parizek (1964). 

For linear features of geologic origin, lineaments are defined as those photolinear 

features greater than one mile in length, 

whereas fracture traces are the same type 

of feature having a total length of less than 

one mile. The width of these zones of 

fracture concentration can vary from a few 

to tens of meters. In general, longer lineaments tend to have wider surface expressions of the zone of fracture concentration 

and wider zones of fracture concentration 

at greater depths. Because the fracture
Kilometers 

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WATER STANDARDS

POTENTIOMETRIC CONTOUR-Shows altitude al 

which water level of Upper Flondan aquifer would 

have stood in tightly cased wells (May 1980) Dashed 

where approximately located. Hachures indicate 

depression. Contour interval 10 feet Datum is sea level

FLOW UNE--Shows general direction of ground-water 

movement.

Figure 2. Map showing approximate potentiometric surface of the Upper Florida 

Aquifer in May 1980 (Meyer, 1989). Inset: Location of the study area at the 

intersection of Pinellas, Hillsborough, and Pasco counties near Tampa Bay is shown 

in red.
trace is the surface expression of the vertical zone of fracture concentration, Parizek 

has suggested that "fracture zone trace" 

might be a more appropriate descriptive 

term (Parizek and Diodato, 1995).

The potential geologic origins of lineaments and fracture traces are discussed in 

Lattman (1958) and Lattman and Parizek 

(1964). Lineaments and fracture traces 

can be evidence of zones of permeability 

contrast relative to the neighboring rock 

mass. In the case in which they are zones 

of enhanced permeability, they may preferentially conduct groundwater. Alternatively, where weathering in zones of 

fracture concentration in relatively permeable parent rocks leads to formation of 

clays in situ, reduced permeability may 

result. In that case, zones of fracture concentration create impediments to groundwater flow. Zones of fracture concentration in soluble rocks such as carbonates 

and evaporites can lead to enhanced dissolution of these rocks due to accelerated 

chemical and physical weathering. In the 

case of rocks prone to karstification, White 

(1999) has determined that the development of karst conduits begins when fracture apertures reach about 1 centimeter.

Because of the narrowness of fracture 

traces, application of fracture-trace mapping to siting of ground-water wells 

requires substantial care and accuracy 

(Lattman and Parizek, 1964; Parizek and 

Diodato, 1995). In some geologic settings, errors in well siting as small as a 

meter can result in well yields far below 

their potential maximum. Accordingly, 

great care is required in the transfer of 

mapped photolinears from aerial photographs to base maps or orthorectified photographs. Where field orientation is 

ambiguous or difficult, the use of the global positioning system satellites to locate

digitally-orthorectified fracture traces may 

prove to be of great benefit to the field 

hydrogeologist.

The detection of lineaments and fracture 

traces is based on a variety of criteria 

including, but not limited to, soil tonal variation, tree height-alignment, topographic 

relief or offset, and stream-segment alignment. In well-drained areas, fractures can 

result in a lightening of soil tones as a 

result of enhanced water movement and 

leaching of organic materials and minerals. In poorly-drained areas, relatively 

dark fracture traces may be the result of 

increased soil moisture content. In carbonate rocks where karstification occurs, 

the alignment of sinkholes can be diagnostic. In the Eld ridge-Wilde well field, 

sinkholes are so ubiquitous that they cannot be used as diagnostic indicators. 

However, the occurrence of sinkholes 

along mapped fracture traces and at fracture trace intersections is taken as supplemental independent evidence of the 

occurrence of a zone of enhanced permeability.

PHOTOLINEAR MAPPING 

METHODOLOGY

The photolinear analysis described here 

was based on the photographs identified 

in Table 2. The photographs are at a scale 

of 1:20697 (Aerial Photography Summary 

Record System, 1996).

Following a site inspection, the analysis

was conducted as follows.

1. First, large photolinears clearly 

observable without stereoscopic 

views or magnification were delimited on the photos with pairs of 

symbols ">" and "<" marking their 

termini. In some cases, a 7x magnifying lupe was used to check that
Table 2: Photographs used in the photolinear analysis at Eldridge-Wilde well field, 

Pinellas County, Florida

Series 

GS-SWFM 

GS-SWFM 

GS-SWFM 

GS-SWFM

Number 

4-54 

4-55 

4-56 

4-57

Date

12 December 1971 

12 December 1971 

12 December 1971 

12 December 1971

the features were not remnants of 

old roads or other non-geologic 

activity, or to search more closely 

for termini.

2. Second, photolinears observable 

using oblique views were marked 

with " " at their termini. The 

oblique analysis was accomplished 

by placing the photographs on a 

stiff board and rotating through 360 

degrees at close viewing range and 

high viewing angle

3. Third, photolinears observable with 

the aid of a mirror stereoscope at 

either 1x or 3x magnification were 

marked with "I" at their termini.

Because relief in the study area is negligible, viewing the photographs under a mirror stereoscope did not significantly aid in 

the detection of fracture traces.

When the photolinear mapping was completed, the mapped features were transferred to the USGS Elfers topographic 

quadrangle 1:24000-scale base map 

using a Bausch & Lomb zoom transfer 

scope. The zoom-transfer scope optically 

corrects for flight-line parallax, allowing 

rectification of small areas of the images to 

the base maps. Confidence in the exact 

placement of the photolinears on 

basemaps was reduced because the 

entire photograph could not be rectified

simultaneously. Furthermore, it was not 

always possible to rectify the entire extent 

of regions containing long photolinears 

simultaneously.

Potentially misleading linear features -- 

those not related to fractures or fracture 

zones -- clearly observable on aerial photographs in the study area included jeep 

trails, animal paths, drainage ditches, 

areas of citrus tree and other agricultural 

cultivation, and recent and historical fence 

lines. In addition, it was reported that 

paleohurricane tracks have been documented to leave long-lasting linear scars 

on the landscape in this region (R. Evans, 

Southwest Florida Water Management 

District, oral comm., 1999), although none 

of these were recognized in this analysis.

MAPPED FRACTURE TRACES AND 

PHOTOLINEARS

A total of forty-three unique photolinears 

were mapped on the four photographs 

listed in Table 2. (Those photographs are 

included in Appendix A.) Figure three 

shows those fracture traces and photolinears mapped within the study area, as 

projected using the Bausch & Lomb zoom 

transfer scope onto the USGS Elfers topographic quadrangle. Two of the photolinears were mapped in whole or in part on 

two photographs. Four of the forty-three
Figure 3. Map showing projected locations of the mapped photolinears at the EldridgeWilde well field. Only the photolinear near well 109 has been verified in the field to be a 

fracture trace.

photolinears were outside of the study 

area.

The length of the forty-three photolinears 

ranged from 269 m to 2.53 km, with an 

average length of 1.09 km. The dominant 

azimuthal orientation of the photolinears is 

in the range of 041° to 050° (fig. 5). A secondary orthogonal peak in the range of 

331 ° to 340° is most likely a structural conjugate set of fractures.

More confidence is placed on linears 

detected on more than one photograph 

and/or mapped by more than one method. 

In two cases, photolinears were mapped
Figure 4. Sinkhole near well 109 which developed recently before the March 1999 

field visit. This well is on the edge of a mapped fracture trace. Note the break in 

topographic slope in front of the cluster of tall trees to the right of the well house.

Figure 5. Rose diagram showing frequency (percent) of mapped photolinear 

orientations. Azimuthal orientation is shown from zero to 90 degrees.
on two photographs. However, the extent 

of those mapped photolinears was not 

identical.

The angle of the sun, both at the time of 

photography and at the time of analysis, 

can influence which linears are discernible 

on which photograph. Further inspection 

of the photographs in different light 

revealed one fracture trace extending substantially beyond the originally mapped 

length. This extension, nearly doubling 

the length of the mapped photolinear, 

extended outside of the study area and 

was not included in this analysis. More 

fracture traces and lineaments can be 

identified on these photographs by 

inspecting them under different lighting 

conditions.

Although field verification is a critical component of fracture trace analysis, the location of only one of the fracture traces 

mapped in this study has been field-verified. Wells 102, 103,113, 116, 117, 5N, 

and N1S lie on mapped but not field-verified fracture traces. In fig. 6, a new sinkhole in alignment with older sinkholes was 

observed in the field near well 109. This is 

independent evidence of the existence of 

the mapped fracture trace at this location. 

Well 109 is adjacent to a field-verified fracture trace. Wells 101 and 122 lie on visible fracture traces that were not mapped.

INFLUENCE OF FRACTURE TRACE 

LOCATION ON WELL YIELD

None of the wells in the Eldridge-Wilde 

well field were represented to the author 

as having been located on the basis of 

fracture-trace mapping. Despite this, 

some wells appear to have been located 

on fracture traces purely by chance. For 

the purpose of analysis, wells were classified as either "off" a fracture trace or "on" a

fracture trace. A well was defined as 

being "on" a fracture trace if it was within 

±1 millimeter of that trace on the aerial 

photograph (approximately 20 m on the 

ground). A total of seven wells were found 

to have been drilled on fracture traces, 

forty-one other wells were classified as "off."

Acknowledging that (1) not all fracture 

traces that exist were mapped, and (2) 

only one of the fracture traces was field 

verified, it is nonetheless of interest to test 

for the significance of zones of fracture 

concentration on ground-water well yield 

in the Upper Floridan Aquifer at the Eldridge-Wilde well field. To this end, exploratory and non-parametric statistical 

analysis of well yield versus fracture trace 

location were conducted.

Specific yield data for forty-eight production wells in the Eldridge-Wilde well field 

were available from five different engineering studies (Black, Crow and Eidness, 

1970; Gee and Jenson Engineers-Architects-Planners, 1981 a, 1981b, 1983; Nettles and Vandor, 1985). For many wells, 

the multiple values reported in the studies 

often differed owing to well development, 

redrilling, and other unknown factors. 

Because of that variability, the largest 

reported specific yield was arbitrarily used 

for all wells. Furthermore, no correction 

was made for well bore diameter, which 

ranged from 12 to 16 inches, or for length 

of open well interval. Because of the small 

number of samples (wells in the data set), 

further subsetting by those factors or by 

production interval or horizon was not pursued.

Figure six is a boxplot comparing yields 

from wells not located on fracture traces 

with those of wells that are located on fracture traces. The whiskers extend to the
600 -

E 500 -

o.

CD

£ 400 -|

I 300

O 200 'o

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Off On

Fracture Trace Well Location

Figure 6. Boxplot of well yields from non-fracture trace and fracture trace wells. 

Specific capacity is in units of gallons per minute per foot of drawdown. Central 

lines are median values, asterisks are outliers.

limits of the quartiles of the data sets, the

box limits indicate the 95th-percentile confidence interval, and the lines in the boxes 

show the median values of the sample 

population. The median specific yield of 

wells on fracture traces (308 gallons per 

minute per foot of drawdown (gpm/ft)) was 

nearly twice that of wells not located on 

fracture traces (160 gpm/ft). The outliers, 

shown in the plot as asterisks, represent 

wells 101 and 122. Although no fracture 

traces were initially mapped in the vicinity 

of these wells, further examination of the 

photographs in different lighting conditions 

reveals proximal photolinears that are 

most likely the surface expressions of 

zones of fracture concentration. Productivity data for well N1S was not available, 

and it was not included in the "on" data 

set.

The Kruskal-Wallis test is a nonparametric 

test that can indicate whether multiple 

samples come from populations having 

the same statistical distribution and central

value (Davis, 1986). Non parametric tests 

are preferred in this case because they do 

not assume an underlying statistical distribution of the data. The null hypothesis 

posed to the Kruskal-Wallis test was that 

the samples came from the same population. The Kruskal-Wallis test statistic, H, 

was 1.54 for the one degree of freedom 

test, so that the null hypothesis could not 

be rejected.

APPLICATION TO FIELD 

HYDROGEOLOGIC INVESTIGATIONS

Successful application of the mapped photolinears to hydrogeologic investigations at 

the Eldrige-Wilde well field will require 

awareness on the part of the investigator 

of the issues outlined in this paper. 

Because of likely inaccuracies introduced 

in the rectification of photolinears onto the 

topographic base map, because the locations of features on USGS topographic 

quadrangles may be in error by as much 

as 13 m (G. Desmond, USGS, oral comm.,

10
1999), and because of other subsequent 

distortions in scanning and printing, no 

well siting should be based on fig. 3. 

Instead, wells can be reliably located by 

field-verification of fracture traces mapped 

on the photographs included in Appendix 

A, along with all relevant supplemental 

information available to the field hydrogeologist.

Parizek (1978, 1985, 1988a, 1988b) has 

identified several dozen natural geologic 

and hydrogeologic factors as variables 

that can influence the development of 

porosity and permeability, the dynamics of 

ground-water flow, and the stability of 

engineering projects in carbonate, gypsum, and evaporite rock settings. Heterogeneity in the distribution of permeability 

and porosity can influence the flow of 

ground water and the transport of solutes. In this study, sixteen variables of 

that type that are confirmed or are likely to 

exist in the Floridan Aquifer at the Eldridge-Wilde well field were identified. 

Those variables, listed in Table 3, are 

based on field observations and background information pertain ing to the hydrogeology of the region. The controls in 

Table 3 are variables that have different 

spatial extents; furthermore not all of them 

may have surficial expression. Any hydrogeological investigations at the site should 

include the consideration of the factors 

listed in Table 3.

To take full advantage of photolinear analysis of fracture traces, further supplemental information and interpretation is 

required. First, the locations of fracture 

traces identified on photographs must be 

field checked and verified. Other desirable supplemental information includes, in 

part: detailed lithologic and hydrologic 

stratigraphy at the site scale, aquifer 

stress test data with drawdowns from two

or more monitoring wells, and local- and 

site-scale potentiometric surface data. 

Aquifer stress tests with drawdown data at 

multiple, orthogonally-positioned monitoring wells can be used to measure anisotropy of the permeability tensor. The 

average permeability tensor in the field 

may be found to be aligned with the orientation of the fracture traces shown in fig. 4. 

Further, multivariate nonparametric statistical analysis of all wells in the field with 

classification according to: (a) productivity,

(b) proximity to fracture trace or lineament,

(c) proximity to intersection of two or more 

fracture traces or lineaments, and possibly

(d) solute concentration may be fruitful. 

Multivariate analysis can be used to determine the relative influence of a large number of hydrogeologic parameters on well 

production (Siddiqui and Parizek, 1971), 

and potentially the relation of well water 

chemistry to zones of fracture concentration. Other statistical methods, such as 

principal components analysis, may also 

prove fruitful.

In addition to those activities, it is worthwhile to seek correlation with fracture 

traces mapped by other investigators. 

The delineation of fracture traces by multiple investigators gives greater confidence 

in the existence of the mapped features.

Finally, correlation of the results of fracture-trace mapping with geophysical 

investigations may prove fruitful. Previous 

researchers have investigated the relation 

between photolinear analysis and geophysical survey results with regard to identification of hydrogeologic features. Spratt 

(1996) found that some geophysical methods were able to image mapped fracture 

traces and others were not. Successful 

detection of fracture zones by geophysical 

methods requires experimental design 

consideration of the likely scales and

11
Table 3: Factors that may influence the distribution of porosity and permeability at the 

Eldridge-Wilde well field

Zones of fracture concentration

Zones of biogenic limestone

Sandy zones

Shelly zones

Bedding planes

Location of karst conduits

Location of karst sinkholes

Location of paleowater tables

Location of paleokarst conduits

Location of paleofluvial channels

Location of paleodune deposits

Zones of chalky chemical limestone

Zones of dolomite

Clay-rich zones - will reduce permeability

Zones of paleolacustrine deposits - will reduce permeability

Coincidence of two or more of the above factors

extents at which they will be detectable for 

the various methods of geophysical investigation.

SUMMARY AND CONCLUSIONS

Forty-three unique photolinears were 

mapped in the vicinity of the EldridgeWilde well field, Pinellas County, Florida. 

One photolinear was positively identified in 

the field to be a fracture trace. More photolinears can be mapped in the study area 

by examination of the photographs under 

different lighting conditions.

Specific yield data were available for fortyeight wells in the study area. The median 

specific yield of wells located on fracture 

traces was 308 gpm/ft, compared with 160 

gpm/ft for wells not located on fracture 

traces. The higher median specific yield of 

the "on" group as compared to the "off" 

group suggests that the yield of new production wells in the Upper Floridan can be 

increased by locating the wells directly on 

fracture traces, optimally at fracture trace 

intersections.

In the course of the investigation, a list of 

sixteen hydrogeologic variables that can 

influence porosity and permeability at the 

Eldridge-Wilde well field was developed. 

Water supply development can be optimized by considering each of the elements in the list and identifying spatial 

zones where one or more of them may 

contribute to enhanced porosity and permeability in the Eldridge-Wilde well field.

12
REFERENCES

Aerial Photography Summary Record System, 

1996, Aerial Photography Summary 

Record System CD-ROM, May 1996. U.S. 

Geological Survey, National Mapping Division. Available from U.S. Geological Survey, ESIC, 507 National Center, 12201 

Sunrise Valley Drive, Reston, VA 20192.

Black, Crow and Eidness, Inc, 1970, Water 

Resources Investigations for the Pinellas 

County Water System, Pinellas County, 

Florida, Engineering Report Project No. 

272-69-51.

Gee and Jenson Engineers-Architects-Planners, 1981 a, Eldridge-Wilde Wellfield Modification Program Phase I for Pinellas 

County Water System, 35 p.

__, 1981b, Eldridge-Wilde Wellfield Modification Program Phase II for Pinellas County 

Water System, 11 p. 

., 1983, Eldridge-Wilde Wellfield Modification Program Phase III for Pinellas County 

Water System, 20 p.

Nettles and Vandor, 1985, Eldridge-Wilde 

Wellfield Modification Program Phases 4 

and 5, 22 p.

Davis, J.C., 1986. Statistics and Data Analysis 

in Geology, Second Ed., John Wiley & 

Sons, New York., 646 p.

Lattman, L.H., 1958, Technique of mapping 

geologic fracture traces and lineaments on 

aerial photographs, Photogrammetric 

Eng., v. 24, p. 568.

Lattman, L.H., and R.R. Parizek, 1964, Relationship between fracture traces and the 

occurrence of ground water in carbonate 

rocks: Journal of Hydrology, v. 2, p. 73.

Meyer, F.W., 1989, Hydrogeology, groundwater movement, and subsurface storage 

in the Floridan aquifer system in southern 

Florida: U.S. Geological Survey Professional Paper 1403-G, 59 p.

Parizek, R.R., 1978, Lecture Notes, Symposium on Engineering Geology in Karst Terranes. International Association of 

Engineering Geologists, Hershey, PA.

__, 1985,1988a, Lecture Notes, Special Topics on Fracture Flow. U.S. Geological Survey Training Branch, Denver, CO.

__, 1988b, The hydrogeologic framework of 

karst - Geologic controls on porosity and 

permeability development, in Engineering 

Geology of Karst Terranes, J. Quintan, ed. 

Florida Sinkhole Research Institute and the 

College of Extended Studies, U. of Central 

Florida, Orlando, FL, Feb 1-5,1988.

Parizek, R.R. and D.M. Diodato, 1995, Fracture Trace and Lineament Analyses and 

Hydrogeological Investigations, Combat 

Maneuver Training Center Hohenfels, 

Hohenfels, Germany, R.R. Parizek and 

Associates, State College, PA 16803 and 

Center for Environmental Restoration Systems, Energy Systems Division, Argonne 

National Laboratory, Argonne, IL 60439.

Renken, R., 1999, Hydrogeologic, hydrologic, 

hydrochemical characterization and 

assessment of the Upper Floridan aquifer 

system for purposes of Aquifer Storage and 

Recovery in South Florida, U.S. Geological 

Survey Place-based Research proposal, 

54 p.

Siddiqui, S.H., and R.R. Parizek, 1971, Hydrogeologic factors influencing well yields in 

folded and faulted carbonate rocks in Central Pennsylvania, Water Resources 

Research: v. 7, no. 5, p. 1295-1312.

Spratt, J. G., 1996, Application of surface geophysical methods to delineate fracture 

zones associated with photolinear features 

in West-Central Florida, SAGEEP 96, proceedings.

Tihansky, A.B., Arthur, J.D., and DeWitt, D.W., 

1996, Sublake geologic structure from 

high-resolution seismic-reflection data from 

four sinkhole lakes in the Lake Wales 

Ridge, central Florida: U.S. Geological Survey Open-File Report 96-224, 72 p.

White, W.B., 1999, Groundwaterflow in karst 

aquifers: in Delleur, J.W., ed., The Handbook of Groundwater Engineering, CRC 

Press, Boca Raton, FL, p.18-1 18-36.

13
APPENDIX A. PHOTOGRAPHS WITH MAPPED PHOTOLINEARS IN THE VICINITY 

OF THE ELDRIDGE-WILDE WELL FIELD

Figure 7. Photograph GS-SWFM 4-54. Image has been scanned at 500 dpi optical and scaled 

to 0.66 of original size.

A-l
Figure 8. Photograph GS-SWFM 4-55. Image has been scanned at 500 dpi optical and scaled 

to 0.66 of original size.

A-2
Figure 9. Photograph GS-SWFM 4-56. Image has been scanned at 500 dpi optical and scaled 

to 0.66 of original size.

A-3
Figure 10. Photograph GS-SWFM 4-57. Image has been scanned at 500 dpi optical and scaled 

to 0.66 of original size.

A-4