Geophysical investigation and evaluation of the hydrologic significance of fractures in a tertiary carbonate aquifer

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Geophysical investigation and evaluation of the hydrologic significance of fractures in a tertiary carbonate aquifer

Material Information

Title:
Geophysical investigation and evaluation of the hydrologic significance of fractures in a tertiary carbonate aquifer
Creator:
Spratt, James G.
Place of Publication:
Tampa, Florida
Publisher:
University of South Florida
Publication Date:
Language:
English
Physical Description:
xiii, 115 leaves : ill. ; 29 cm.

Subjects

Subjects / Keywords:
Groundwater flow -- Florida -- Hillsborough County ( lcsh )
Floridan Aquifer ( lcsh )
Dissertations, Academic -- Geology -- Masters -- USF ( FTS )

Notes

General Note:
Thesis (M.S.)--University of South Florida, 1993. Includes bibliographical references (leaves 84-87).

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Source Institution:
University of South Florida
Holding Location:
Universtity of South Florida
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All applicable rights reserved by the source institution and holding location.
Resource Identifier:
029494565 ( ALEPH )
29155407 ( OCLC )
F51-00106 ( USFLDC DOI )
f51.106 ( USFLDC Handle )

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Book

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GEOPHYSICAL INVESTIGATION AND EVALUATION OF THE HYDROLOGIC SIGNIFICANCE OF FRACTURES IN A TERTIARY CARBONATE AQUIFER by James G. Spratt A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in the Department of Geology in the University of South Florida May 1993 Dr. Mark T. Stewart

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Graduate Council University of South Florida Tampa, Florida CERTIFICATE OF APPROVAL Master's Thesis Th i s is to certify that the Master's Thesis of James G. Spratt with a major in Geology has been approved by the Examining Committee on March 26, 1993 as satisfactory for the Thesis requirement for the Master of Science degree. Thesis Committee : Major Professor: Dr. M T. Stewart Member : Dr. H. L. Vacher Member : Dr. A. Hine

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TABLE OF CONTENTS List of Tables . . . . . . . . . . . . . . . . . . . . . 1v List of Figures . . . . . . . . . . . . . . . . . . . . . v Abstract . . . . . . . . . . . . . . . . . . . . . . . xi Introduction . . . . . . . . . . . . . . . . . . . . . . 1 Background . . . . . . . . . . . . . . . . . . . 1 Purpose ....... ................................... 3 Objectives . . . . . . . . . . . . . . . . . . . . 4 Photolinear Selection . . . . . . . . . . . . . . . . . 4 Site Location . . . . . . . . . . . . . . . . . . . 5 Geology ......................................... 5 Hydrogeology . . . . . . . . . . . . . . . . . . . 8 Methods .............................................. 10 Aerial Photograph Analysis .............................. 10 Geophysical Methods . . . . . . . . . . . . . . . . 10 Horizontal-Loop Electromagnetics (HLEM) ................. 12 Very Low Frequency Electromagnetics (VLF) . . . . . . . . 13 Horizontal-Electrical Profiling (HEP) ..................... 15 Seismic Reflection ................................. 16 Microgravity . . . . . . . . . . . . . . . . . . 17 Self Potential . . . . . . . . . . . . . . . . . . 19 Ground-Penetrating Radar ............................ 20 Evaluation of the Groundwater System ....................... 21 Pumping-Test Data ................................ 21 Groundwater Flow Model . . . . . . . . . . . . . . 23 11

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Results ............................. .................. 25 Aerial Photograph Analysis ........... . . ............... 25 Geophysical Methods . . . . . . . . . . . . . . . . 27 Horizontal-Loop Electromagnetics (HLEM) ................. 27 Very Low Frequency Electromagnetics (VLF) . . . . . . . . 29 Horizontal-Electrical Profiling (HEP) ........... ..... ..... 32 Seismic Reflection . . . . . . . . . . . . . . . . 35 Microgravity . . . . . . . . . . . . . . . . . . 36 Self Potential . . . . . . . . . . . . . . . . . . 39 Ground-Penetrating Radar ................. . . ....... 39 Evaluation of the Groundwater System .......... ............ 41 Pumping-Test Data ................................ 41 Anisotropy . . . . . . . . . . . . . . . . . . 49 Numerical Model ........ . ................ . . . 49 Di sc u ss ion .................. .... ...... ............... 54 Con c lusion .... . ....... .... .... .... . . . . ......... 81 R e fer e nces . . . . . . . . . . . . . . . . . . . . . . 84 App e ndices ........ ............................. . ... 88 Appendix 1 HLEM data . . . . . . . . . . . . . . . 89 Appendix 2 VLF data . . . . . . . . . . . . . . . 98 Appendix 3 Appendix 4 Appendix 5 Appendix 6 Direct Current Resistivity data ............. . 101 Self Potential data ........................ 103 Gravity data . . . . . . . . . . . . . . 106 Pumping Test data .................. ...... 107 iii

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LIST OF TABLES Table 1 Well construction summary . . . ..................... 22 Table 2 Summary of pumping-test results for Pemberton Creek . . . . . 48 lV

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Figure 1 Fig ure 2 Fig ure 3 Figure 4 Fig ure 5 F i g ur e 6 F i gure 7 F i g ure 8 Fig ure 9 F i g ur e 10 LIST OF FIGURES Location map of study areas. . . . . . . . . . . . 6 Generalized stratigraphic cross section of the Pemberton Creek area adapted from Wolansky and Corral (1985). . . . . 7 Pemberton Creek site map showing location of photolinears, geophysical tr a verses, and monitor wells . . . . . . . . 11 Subgrid of numerical model showing area near pumping well. . . 24 A 1:20 000 aerial photograph of the Pemberton Creek s i te Photolinears are indicated with arrows. . . . . . . . . 26 Terrain conductivity across T2, T4, and TS using vertical dipoles, 20-meter coil separation and a three-meter s tation i nterval Photolinears are ind i cated w i th arrows . . . . 2 8 VLF tilt-angle data obtained across T2, T4 and TS using a six m ete r station interval Photolinears are indicated with arrows. . . . . . . . . . . . . . . . . 30 Pseudo condu c ti v ity sections across T2, T4, and TS produced u s ing the McNeill filter (1991). Photolinears are ind i cated with arrows. . . . . . . . . . . . . 3 3 Appar e nt r es i s tivity measured across T2 T4, and TS using a W enne r array, an "a" spacing of 30 meters, and a ten me ter station interval. Photolinears are indicated with arrows. ................................ 3 4 Optimum-of f set seismi creflection profile across T2. Photolinears are ind i cated with arrows. . . . . . . . . 3 7 v

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Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 Figure 18 LIST OF FIGURES (Continued) Bouguer residual-gravity profile across T2 using a five meter station interval. Photolinears are indicated with arrows. .................. . . ............ 38 Self-potential profile across T2 using a three-meter station interval Photolinears are indicated with arrows . ......................... . ....... 38 A segment of the GPR profile across T2 showing one of two high-amplitude reflectors that are approximately 60 meters wide and six meters deep. ........ .......... 40 A segment of the GPR profile across T2 showing a high amplitude reflector that is approximately 20 meters wide and 9 meters deep. . . . . . . . . . . . . . 42 A segment of the GPR profile across T2 showing a parabolic reflector at 500 meters and a shallow high-amplitude reflector at 520 meters. . . . . . . . . . 43 Plot of corrected drawdown for the A von Park monitor well at Pemberton Creek, Florida, overlain on the Theis type-curve for early-time and late-time. . . . . . . 44 Plot of corrected drawdown for the Ocala monitor well at Pemberton Creek, Florida, overlain on the Theis type-curve for early-time and late-time. ............... 45 Plot of corrected drawdown for the Tampa 22 monitor well at Pemberton Creek, Florida, overlain on the Theis type-curve for early-time and late-time. . . . . . . 46 Vl

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Figure 19 Figure 20 Figure 21 Figure 22 Figure 23 Figure 24 LIST OF FIGURES (Continued) Plot of corrected drawdown for the Tampa 23 monitor well at Pemberton Creek, Florida, overlain on the Theis type-curve for early-time and late-time. ............ 47 Scenario 1 Contour map showing the shape of the cone of depression after seven days of pumping with homogeneous isotropic conditions. Drawdown is greatest at the pumping well, APTPW, and decreases away from the well. Contours of drawdown are dimensionless . . . . . . . . 50 Scenario 2 Contour map showing the shape of the cone of depression after seven days of pumping with photolinears modeled as high-transmissivity zones. Drawdown is greatest at the pumping well, APTPW, and decreases away from the well Contours of drawdown are dimen s ionless . . . . . . . . . . . . . . . . 51 Scenario 3 Contour map showing the shape of the cone of depression after seven days of pumping with photolinears modeled as low transmissivity zones Drawdown is greatest at the pumping well, APTPW, and decreases away from the well. Contours of drawdown are dimensionless. . . . . 52 Interpreted geologic model for Pemberton Creek, Florida developed using geophysical data obtained across T2. . . . . 55 Interpretation of terrain conductivity across photolinears at Pemberton Creek, Florida (McNeill, 1991) (a) Profile data show a zone of multiple clay-filled fractures and an M-shaped anomaly associated with PL-2. (b) Contour map of conductivity shows highs flanking a low associated with the photolinears. . . ............ ..... 56 vii

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Figure 25 Figure 26 Figure 27 Figur e 28 Figure 29 Figure 30 Figur e 31 LIST OF FIGURES (Continued) Terrain conductivity across T2 using 20-meter and 40meter coil separations. ........................ ... 58 Predicted EM34 response across several geologic targets (after McNeill, 1980). .......................... 58 Theoretical VLF tilt-angle (in-phase) response across two vertical sheet like conductors adapted from Geonics (1979) . ........... ................... . . 60 Interpretation of VLF tilt-angle data across photolinears at Pemberton Creek, Florida (after McNeill, 1991). (a) Profile data show a large anomaly associated with PL-2 and a zone of multiple clay-filled fractures. (b) Estimated fracture locations based on VLF tilt-angle data. ...................................... 61 Interpretation of pseudo-conductivity sections across photolinears at Pemberton Creek, Florida. Photolinears are indicated with arrows . . . . . . . . . . . . . 63 Interpretation of apparent resistivity profiles across photolinears at Pemberton Creek, Florida A Wenner array with an "a" spacing of 30 meters was used Photolinears are indicated with arrows. . . . . . . . . 63 Optimum-offset seismic-reflection section at Pemberton Creek, Florida, across T2 showing a chaotic-reflection zone associated with PL 2 and a zone of strong reflectors associated with PL 1. Photolinears are indicated with arrows. .......................... ....... 65 viii

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Figure 32 Figure 33 Figure 34 Figure 35 Figure 36 Figure 37 LIST OF FIGURES (Continued) Lithologic log of the Suwannee monitor well at Pemberton Creek, Florida, adapted from SDI (1991). ........... ... 67 Interpretation of Bouguer residual-gravity profile at Pemberton Creek, Florida, across T2 showing clayfilled fractures corresponding to gravity lows and limestone pinnacles corresponding to gravity highs. Photolinears are indicated with arrows. . . . . . . . . . . . . 68 Interpretation of self-potential data across T2 showing a strong negative streaming potential associated with the photolinear-related fracture zone. Photolinears are indicated with arrows. . . . . . . . . . . . . . 70 Interpretation of GPR profile at Pemberton Creek, Florida across T2 showing correlation between high-amplitude reflectors and local sand-rich resistivity highs. . . . . . . 72 Plot of drawdown for observation wells at Pemberton Creek, Florida, showing an anomalous linear draw down for T-23 which is believed to be in the fracture zone. Note the similar drawdown response in the other wells especially in late-time .......................... 74 The shape of the cone of depression after seven days of pumping with the photolinears modeled as high-transmissivity zones. The major axis of anisotropy is parallel to the photolinears with an anisotropy ratio (Tzz/Tnn) of approximately 2:1. Drawdown is greatest at the pumping well, APTPW, and decreases away from the well. Contours of drawdown are dimensionless. . . . . . . . 77 1X

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Figure 38 Figure 39 LIST OF FIGURES (Continued) The shape of the cone of depression after seven days of pumping with the photolinears modeled as low-transmissivity zones. The major axis of anisotropy is perpendicular to the photolinears with an anisotropy ratio (Tzz/Tnn) of approximately 2:1. Drawdown is greatest at the pumping well, APTPW, and decreases away from the well. Contours of drawdown are dimensionless . . . . . . . . . . . . . . . . 78 Comparison of the anisotropic response observed in the field with the modeled responses. . . . . . . . . . . 79 X

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GEOPHYSICAL INVESTIGATION AND EVALUATION OF THE HYDROLOGIC SIGNIFICANCE OF FRACTURES IN A TERTIARY CARBONATE AQUIFER by James G. Spratt An Abstract A thesis submitted in partial fulfillment of the requirem e nts for the degree of Master of Science in the Department of Geology in the University of South Florida May 1993 Major Professor : Dr. Mark T. Stewart xi

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An integrated geophysical and hydrologic study of two photolinears in west central Florida suggests that they are part of a large-scale fracture zone in the Floridan Aquifer. Geophysical techniques used in this study include horizontal-loop electromagnetics (HLEM), very low frequency electromagnetics (VLF), direct-current resistivity, seismic reflection, self potential, microgravity, and ground-penetrating radar. The geophysical data reveal a fracture zone that appears to be more than 700 m wide and consists of a central, 100 m wide, sand-filled, bedrock low flanked by zones of dense, recrystallized-limestone pinnacles and clay-filled fractures. The clay-filled fractures appear to be 40 m to 50 m wide and are parallel to the observed photolinear trend. Closely-spaced HLEM data, obtained using vertical dipoles and a 20-m coil separation, and VLF tilt-angle data were successfully used to locate geophysical anomalies associated with photolinears. Horizontal-electrical-profiling (HEP) data correlate well with the results of the electromagnetic methods. The "optimum-offset" seismic-reflection technique accurately delineates the large-scale fracture zone; however, small-scale resolution was insufficient for detailed stratigraphic interpretation. Self-potential data show a large, negative-streaming potential associated with the center of the fracture zone. xii

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Analysis of drawdown data from three observation wells during a seven day, 11,700 m3 / day pumping test in the Floridan Aquifer yield average, late-time transmissivity and storativity values of 3,300 m2/day and 2 x 1o-3 respectively. Evaluation of the test data using an anisotropic analytical model indicates a late-time anisotropy ratio of about 6:1 with the apparent major axis of anisotropy roughly perpendicular to the photolinears. Comparison of the field data and hypotheticalmodeling results suggests that the photolinear-related fractures at Pemberton Creek are not hydrologically significant relative to the pumping test and that structural or lithologic controls not associated with the photolinears are responsible for the observed, nonTheis drawdown response. These controls may include cavernous porosity within the A von Park Formation or a fracture trend not evaluated in this study. Abstract approved: xiii Dr. Mark T. Stewart Chairman Department of Geology Date of Approval

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1 INTRODUCTION Background Aerial photography and satellite imagery have been analyzed to detect linear features on the Earth's surface for several decades. Blanchet (1957) observes that linear features occur worldwide in four principal directions: WNW, NNW, NNE, and ENE. Blanchet postulates that the linear features are fractures induced by crustal flexing caused by Earth tides. Earth tides are believed to be caused by the gravitational influences of the Sun and Moon and changes in radial acceleration of the Earth. Although the exact mechanisms which cause the systematic, worldwide fracturing are still not clearly defined, the fractures are of great interest to hydrogeology, petroleum exploration, and geotechnical engineering Lattman and Parizek (1964) define a fracture trace as a natural, linear feature that is less than one mile long and is the surface expression of a vertical fracture zone. Fracture traces are characterized by tonal variations in soils and vegetation, topographic depressions, and other similar linear or aligned features. For the purposes of this study, photolinears or fracture traces are considered to be linear features which can be recognized on an aerial photograph, regardless of length, and which require verification

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2 by surface geophysics or other field data to determine their geologic significance. Previous research in west-central Florida by Moore and Stewart (1983) and Stewart and Wood (1991) shows that photolinears correlate well with geologically significant features in the Floridan Aquifer. Seismic refraction, direct -current resistivity, gravity, and electromagnetic terrain-conductivity methods were used to evaluate the geophysical response of photolinears. Moore and Stewart (1983) use seismic and resistivity methods and show a sagging and thickening of the overburden over fracture traces Stewart and Wood (1991) observe characteristic M-shaped gravity signatures across two photolinears. The gravity response is interpreted as a central zone of lower density in the fracture zone flanked by zones of higher-density, recrystallized limestone Most studies of photolinears focus on locating fracture traces by analysis of aerial photography and assume these features are zones of increased hydraulic conductivity. While this approach is valid in Paleozoic carbonates and igneous or metamorphic terrains, the dual-porosity nature and high bulk porosity of the Floridan Aquifer may complicate the hydrologic response of fractures associated with photolinears. An investigation west of Ocala, Florida, shows fracture traces in the Floridan Aquifer are discontinuous and hydraulically heterogeneous (GeoTrans, 1988) Hydraulic testing by GeoTrans suggests well response is more sensitive to the orientation and extent of the fracture than to the hydraulic conductivity of the fracture. If the controlling factor for groundwater movement in the Floridan Aquifer is the bulk matrix porosity, then analytical pumping-test solutions based on Theis (1935) are valid. However, if fractures

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3 exert significant control on the velocity or direction of groundwater flow, as suggested by GeoTrans (1988), pumping-test solutions based on the assumption of homogeneous and isotropic conditions may yield inaccurate results. Purpose The purpose of this research is to investigate the geophysical characteristics and hydrologic significance of photolinear features associated with fracture zones in the Floridan Aquifer, a dual-porosity, Tertiary carbonate aquifer. The geophysical methods used in this study include horizontal-loop electromagnetic (IaEM), terrain conductivity (Geonics EM-34-3), very low frequency (VLF), electromagnetic tilt-angle profiling ( Geonics EM -16), horizontal-electrical profiling (HEP), seismic reflection, micro gravity profiling, self-potential profiling, and ground-penetrating radar (GPR) Geophysical data and existing lithologic data are incorporated in the development of a geologic and hydrologic model of the fracture zone. Schreuder and Davis, Inc. of Tampa, Florida (SDI) was retained by West Coast Regional Water Supply Authority (WCRWSA) as the technical consultant for the aquifer performance test at Pemberton Creek. The pumping test and observation well network were designed to evaluate the potential for future groundwater development in the eastern portion of Hillsborough County, Florida. The author participated in the field data collection effort and independently interpreted the drawdown data in an attempt to evaluate the hydrologic significance of two photolinears observed at Pemberton Creek.

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4 A hypothetical model was constructed usmg the U.S. Geological Survey's modular, three-dimensional, fmite-difference, groundwater flow model, MODFLOW (McDonald and Harbaugh, 1988) to evaluate the hydrologic significance of the photolinear-related fracture zone. Model output from hypothetical fracture and nonfracture scenarios are compared to evaluate the effect the fractures have on the system Simulated well test data are compared to the field data to determine if the theoretical models describe the field response. Objectives 1. Locate and classify photolinear features based on their strength and linear continuity 2. Employ surface geophysical methods to verify the geologic significance of the photolinears 3. Use the geophysical data to infer the geologic character and lateral extent of the photolinear-related fracture zone. 4 Compare the drawdown response observed in the field during a seven-day pumping test to the response predicted by the hypothetical, numerical model. 5. Utilize geophysical, lithologic, hydraulic, and numerical modeling data to evaluate the hydrologic influence of the photolinear-related fracture zone. Photolinear Selection Multiple surface-geophysical techniques were employed to evaluate a total of four photolinears at two sites in southwest-central Florida, Crystal River Quarry No. 2 and

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5 Pemberton Creek. Geophysical responses obtained across one photolinear at Pemberton Creek and electromagnetic signatures obtained at Crystal River Quarry (Stewart and Wood, 1991) did not indicate associated geologic structure Geophysical signatures obtained across two photolinears located at Pemberton Creek indicate the presence of a large-scale fracture zone. The presentation and discussion of data collected in this study are limited to the two photolinears at Pemberton Creek. Site Location The Pemberton Creek site is located in theSE 1/4, Section 20, Township 28S, Range 21E of Hillsborough County (Figure 1). The study area is approximately 10 km west of Plant City and due east of Tampa along Interstate 4. The property is used as a pasture for cattle grazing, and total relief across the site is less than 2 m. Pemberton Creek lies in the Polk Upland physiographic province (White, 1970). Geology The Floridan Aquifer system is the principal aquifer at the study site. The Upper Floridan is composed of a thick sequence of Eocene to Miocene carbonates: A von Park Limestone, Ocala Limestone, Suwannee Limestone and Tampa Limestone (Miller, 1986). Well logs obtained at the Pemberton Creek site by Menke (1961) and Schreuder & Davis, Inc. (1991) indicate that approximately 15 m to 20 m of Pliocene to Holocene Deposits and the Hawthorn Formation overlie the Tampa Limestone (Figure 2).

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FLORIDA Crystal N 0 STUDY AREAS kilometers 15 30 Figure 1 Location map of study areas. 6 CITRUS HERNANDO PASCO j I __ jl I I I I I ----------J ---

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SERIES elevation (meters) 30 Sand UNIT 7 &+t: su,ficia l A4'wter:r'411: .. +-::..!-' -=-=-=-=-=Hawthorn -=-=-=-=-============ F o rmation :==== ====== : SemiC onfining' Un i t Figure 2 Generalized stratigraphic cross section of the Pemberton Creek area adapted from Wolansky and Corral (1985)

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8 The Tampa Limestone is a micritic, moldic, sandy limestone that locally contains phosphate and chert The Suwannee Limestone is very similar to the Tampa except that it contains no sand or phosphate (Miller 1986). Underlying the Suwannee Limestone are the Ocala and Avon Park Limestones, respectively The Ocala Limestone and Avon Park Limestone are composed of limestones and dolostones. The upper Ocala consists of a porous coquina bound by a matrix of micritic limestone while the lower Ocala is mainly a fine grained, semi-indurated, micritic limestone (Miller, 1986). The Avon Park Limestone can be highly fossiliferous in places and does contain some dolomitic layers (Bengtsson et al 1986). Hydrogeology The surficial aquifer consists of the undifferentiated sands and sandy clays wh i ch overlie the Hawthorn Formation. The thickness of the surficial aquifer is variable due to intermittent clay and peat lenses Clay content generally increases with depth (Bengtsson et al., 1986) The Hawthorn Formation acts as a confining unit, but is breached in numerous places by sinkholes. Sinkhole development is common due to irregularities in the confining unit caused by the karstified surface of the Tampa Formation (Bengtsson et al., 1986). Sinkholes are often sand filled and are the principal source of recharge for the Floridan Aquifer in this region (Menke, 1961). The Tampa, Suwannee, Ocala, and Avon Park Limestones are well connected hydraulically as a result of numerous solution

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9 openings along fractures or faults (Menke, 1961). The Floridan Aquifer is highly productive due to the reactivation of paleokarstic features (Stringfield et al 1979). Transmissivity values at the Pemberton Creek site range from a low of 450 m2/day to a high of 2, 700 m2/day (Menke 1961) In east central Hillsborough County wells completed in the Tampa and Suwannee Formations yield approximately 1 m3/minute and wells completed in the Ocala and Avon Park yield about 4m3/minute (Bengtsson et al., 1986).

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10 METHODS Aerial Photograph Analysis Aerial photograph analysis was performed using 1:20,000 black and white photographs of the Pemberton Creek area Photolinear features were identified and located in the field for evaluation with surface geophysical methods. The principal photolinear identification was performed by Dr. Mark Stewart from the University of South Florida. The author and Mr. Robert Evans, from the Southwest Florida Wat e r Management District (SWFWMD), independently evaluated the Pemberton Creek ae ri al photographs and identified photolinears The three photographic interpretations were compared and the photolinears were classified based on strength and linear continuity. Geophysical Methods Geophysical data at Pemberton Creek were collected along traverses o ri ented perpendicular to photolinears PL-1 and PL-2. The photolinears are parallel approximately 125 m apart, and trend N 500 E (Figure 3). Geophysical traverses 2, 4, and 5 (!'2, T4, and T5) are oriented N 40 W, share a common x-axis based on T5 and cross PL-2 and PL-1 at 235 m and 350m, respectively.

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.... BOOm ' T-2 ', T-5 Photolinear 1/ -N/ / Photolinear Y / 0 50 100 Meters Legend Obs ervation Well Produ c tion Well / Note: Geophysical survey lines T2, T4, and T5 s har e common X-ax i s based on T5 / / / / APMW 0 APTPW -g 0 QG .., 11 c: u. 0 I I I I I I .., I I g I I I I I I I I I I Gau Figure 3 Pemberton Creek site map showing location of photolinears geophysical traverses, and monitor wells.

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12 Geophysical data were collected from July 1990 to March 1991. Data were collected with a Geonics EM-34-3 terrain-conductivity meter (HLBM), Geonics EM-16 VLF tilt-angle meter (VLF), ABEM Terrarneter SAS 300C resistivity meter, Worden Master gravity meter #1022, and a Bison 7000 seismograph. A 120-Mhz antenna and a GSSI SIR-3 system was used for the first ground-penetrating radar (GPR) survey, and a 100-Mhz antenna and a GSSI SIR-10 system for the second survey. Self-potential readings were obtained using two Gisco porous-pot electrodes and a milli-voltmeter. Horizontal-Loop Electromagnetics (HLEM) The horizontal-loop electromagnetic (HLEM) or Slingram method uses a fixed transmitter-receiver separation, and the coils are configured to detect the vertical magnetic component. The HLEM instrument is relatively insensitive to near-surface conductivity variations and produces a characteristic M-shaped response over a narrow (less than 0.5 x the coil separation), vertical, conductive target. The width of influence of an anomaly caused by a small, vertical, conductive structure is twice the coil separation. HLEM instruments can detect conductors at a depth approximately half the coil separation. Telford et al. (1990) provide a detailed explanation of the theory and operation procedures for the HLEM method. The Geonics EM-34-3 was used as a Slingram device to detect lateral conductivity variations associated with photolinears. The EM-34-3 produces a time-varying primary magnetic field that induces eddy currents in the ground. The eddy currents produce a

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13 secondary magnetic field in the subsurface materials The sum of the primary and secondary magnetic fields is detected by the receiver (McNeill, 1980) Since the primary magnetic field is known, the secondary magnetic field can be readily determined Within the operational limits of the EM-34-3, as described by the low-induction-number theory, there is a linear, proportional relationship between the ratio of the quadrature component of the secondary field and the in phase component of the primary magnetic field and terrain conductivity (McNeill, 1980). This linearly proportional relationship allows bulk terrain-conductivity values to be measured directly in the field. The effective exploration depth of the EM-34-3 with vertical dipoles and a 20-m or 40-m coil separation is 30m and 60 m, respectively. McNeill (1980) explains the theory and operational use of the EM-34-3. The EM-34-3 was used to survey approximately 1,900 m along three traverses at Pemberton Creek (T2, T4, T5). Surveys were conducted using vertical dipoles, a 20m coil separation, and a three-meter station interval. Additionally, one of the traverses (T2) was surveyed with vertical dipoles, a coil separation of 40 m, and a three meter station interval. Very Low Frequency Electromagnetics (VLF) Very low frequency (VLF) radio waves produced by powerful military transmitters can be used to evaluate geophysical properties of near-surface materials. VLF radio waves are used for long-range naval communications, and can be detected at

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14 distances in excess of 10,000 km due to the reflection of the signal off of the ionosphere (McNeill and Labson, 1991). Broadcast frequencies of the VLF transmitters are 17-25 KHz. The VLF method of geophysical prospecting can be employed as a tilt-meter that detects lateral changes in conductivity or as a resistivity instrument that measures field apparent resistivity. Wright (1988) and McNeill and Labson (1991) provide detailed explanations of the theory and geophysical applications of the VLF method. The VLF field consists of an electrical component and a primary magnetic component (Wright, 1988). At distances greater than 800 Km from the transmitter, the primary magnetic field is horizontal (Stewart and Bretnall, 1986). Lateral conductivity variations in the vicinity of a conductive structure create a secondary, vertical magnetic component in the VLF field. The secondary, vertical magnetic field forces the local magnetic field to vary from the horizontal position on either side of the conductive structure. The VLF receiver records the total magnetic field tilt over a conductor as a "crossover" response. The VLF crossover occurs as the tilt-angle values increase approaching the conductor then decrease and cross the zero tilt-angle line above the conductor. McNeill (1991) suggests that the VLF crossover response is caused by galvanic current flow that alters the local magnetic field by concentrating the electrical current in the subsurface conductive structure The VLF tilt-meter can be strongly influenced by shallow conductivity variations because of the galvanic-current flow phenomenon. The electrical skin depth in the subsurface materials determines the exploration depth of the

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15 VLF method. Stewart and Bretnall (1986) approximate the skin depth by the following equation: where; a = 3.6..fp o = skin depth (m) p = terrain resistivity (ohm-m) (1) The Geonics EM -16 was used in the tiltmeter configuration for this study. The EM-16 is a VLF receiver capable of detecting two frequencies, and measuring the in phase (real) and quadrature (imaginary) components of the secondary magnetic field. Three traverses totaling approximately 1,900 m were surveyed at Pemberton Creek using the EM16. The Annapolis, Maryland, VLF transmitter (NAA, 21.4 KHz) was used in this study, and a six-meter station interval was maintained for all surveys. Horizontal-Electrical Profiling (REP) Horizontal-electrical profiling (HEP) is a direct-current resistivity technique that detects lateral resistivity variations. Depth of investigation varies with the resistiv i ty profile and the current electrode separation. An electric current is introduced into the earth through two electrodes, and the potential difference created is measured with a second pair of electrodes. Profiling is accomplished by measuring the resistance at a station and then moving the entire electrode array to the next station to repeat the process. The apparent resistivity, a weighted average of the resistivities from all

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16 subsurface units within the zone of measurement, can be determined when the geometric arrangement of the electrodes, the resistance measured in the field, and the inter electrode spacing are known (Vingoe, 1972) Detailed explanations of the theory and procedures for direct-current resistivity methods are provided by Van Nostrand and Cook (1966) and Dobrin and Savit (1988). A Wenner array a four-electrode configuration, w i th a constant inter-electrode spacing of 30 m was used in this study The inter-electrode spacing or "a" spacing determines the effective exploration depth (EED). Approximately 70% of the measured resistivity response is contributed by materials above the EED (Stewart and Stedje, 1990). The 30-m "a" spacing used in this study has an EED of about 20m. An ABEM Terrameter SAS 300C was used to survey approximately 1,900 m along three traverses at Pemberton Creek. A station interval of 10 m was maintained throughout all surveys Seismic Reflection Seismic-reflection methods involve timing the propagation of near-surface, acoustic energy from the acoustic source to an array of receiving geophones. A seismic wave encountering a boundary between materials with contrasting velocities is reflected and travels in a nearly vertical path from the source to the receiver at the surface The location of reflecting interfaces can be estimated from the analysis of the travel times, velocity information, and wave paths Dobrin and Savit (1988) provide a detailed explanation of the theory and application of seismic methods

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17 The "optimum-offset" technique (Hunter et al., 1982a) is a shallow, highfrequency, seismic-reflection method developed primarily to map the bedrock-overburden interface. The optimum-offset technique is the simplest seismic-reflection method The optimum offset allows reflectors to be seen on the seismic record with minimum interference from surface, direct, and refracted waves. Each channel is shot individually with a constant source-receiver separation that is maintained throughout the survey. The principal advantage of this reflection method is the simplicity of processing the field data. The optimum-offset, shallow-reflection technique was used to conduct a survey along a 500 m section ofT2. A Bison 7000 seismograph and 100-Hz geophones, spaced at 4 m intervals, were used to record the field data. A walkaway test was conducted in the field to determine an optimum offset of 15 m. The seismic source consisted of a 12pound sledge and a steel plate. Microgravity Micro gravity is a potential field method that measures the change in the earth's gravitational field, and is able to determine lateral variations in the density of geologic materials between measuring stations. The gravity solution is non-unique and must be constrained by additional geologic or geophysical information Gravity methods have been employed successfully in metals exploration (Parasnis, 1966) and cavity detection (Negmann, 1977). Gravity has also been used to determine aquifer geometry and estimate total porosity (Eaton and Watkin, 1970).

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18 Microgravity is a gravity method that requires accuracy, precision, and instrument sensitivity in the uGal range (Butler, 1980). The procedures for a microgravity survey are identical to the gravity method described by Parasnis (1966). In this study, microgravity was used to determine if lateral density variations associated with photolinears in the Floridan Aquifer (Stewart and Wood, 1991) could be detected at Pemberton Creek. A 300m section ofT 2 at Pemberton Creek was surveyed using a Worden Master gravity meter capable of reading to the nearest 0 01-0.02 mGal. Gravity measurements were taken every 5 m along the traverse at stations with surveyed elevations determined to + 0.0015 m. Base stations were occupied every 30-60 minutes to determine total drift. A latitude correction was applied using a base latitude of 28". A Bouguer density of 2.0 g/cm3 was used for data reduction. Because total relief at Pemberton Creek is less than 2 m, terrain corrections were not applied. Total drift, latitude, free air, and Bouguer corrections were applied to determine the Bouguer anomaly. The regional gravity gradient was determined visually from the data plot, and the resultant Bouguer residual gravity was calculated. At Crystal River Quarry No. 2 limestone samples were collected from the Ocala Limestone. Samples were taken in the vicinity of the fracture trace studied by Stewart and Wood (1991). Samples were collected from recrystaiJized limestone associated with the fracture trace and from unaltered limestone located away from the fracture trace. The specific gravity (density) of the limestone samples was determined using laboratory

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19 determined values of mass and volume. Self Potential Naturally-occurring electrical potentials in earth materials can be measured by the self potential (SP) method. SP surveys that measure the voltage resulting from the electrochemical interaction between conductive mineral deposits and groundwater have been used in mineral exploration to locate sulfide deposits (Sato and Mooney, 1960). Corwin and Hoover (1979) suggest that voltages generated from thermoelectric and electrokinetic processes may be responsible for SP anomalies observed in geothermal areas. The thermoelectric effect is caused by differential heating of the earth by a subsurface heat source. A streaming potential (electrokinetic effect) is created when a fluid, such as groundwater, moves through a porous medium (Corwin and Hoover, 1979). Streaming potential varies with lithology, groundwater flow, water-table elevation, and soil-moisture content. The SP method was employed in this study to detect fluid streaming potentials associated with photolinears. A 500 m section of T2 was surveyed using the SP method. A milli-voltmeter and Gisco porous pots containing copper sulfate were used to obtain SP readings in millivolts. A fixed electrode was positioned approximately 150 m from the traverse, while the roving electrode was moved from station to station. A three-meter station interval was maintained throughout the survey.

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20 GroundPenetrating Radar Ground-penetrating radar (GPR) transmits very high-frequency electromagnetic energy (80 Mhz-1,000 Mhz) into the earth to obtain lithologic information. Some of the transmitted pulse is reflected back to the receiving antenna after striking a strong subsurface contrast in the dielectric constant. Below the water table the bulk dielectric constant is controlled by moisture content or porosity. The GPR field record is similar to a continuous marine, seismic-reflection record except that electrical, rather than acoustical properties determine the amplitude of the reflected energy. Signal attenuation by conductive materials can greatly limit the depth of penetration of the GPR method. In general, the best GPR results are obtained in coarse, dry, resistive materials such as clean quartz sand Low frequency antennas (80-120 Mhz) have greater penetration capabilities, while high-frequency antennas (300-500 Mhz) provide the best resolution. Two GPR surveys were conducted to determine lateral continu i ty of subsurface units across photolinears at Pemberton Creek. The initial GPR survey was conducted using a 120-Mhz antenna and a GSSI SIR-3 transmitter. An additional survey using a 100 Mhz antenna and a SIR-10 transmitter was performed because the d e pth of penetration of the frrst survey was unsatisfactory. Both surveys used a sled mounted GPR system that was towed by a truck along the traverse at a rate of about 3 km/hr.

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21 Evaluation of the Groundwater System Pumping-Test Data The Pemberton Creek pumping test began at 8:00AM, December 11, 1990, and continued for seven days. The A von Park test production well (APTPW) discharge rate was approximately 11,700 m3/day. Drawdown data from four Floridan wells, Tampa 22 (T-22), Tampa 23 (T 23) the Ocala monitor well (OMW) and the Avon Park monitor well (APMW) were recorded and analyzed (Table 1). Schreuder and Davis Inc. applied corrections to drawdown data from T-22, OMW, and APMW to account for regional groundwater trends and adjustments to the discharge rate at the start of the pumping test. These data corrections result in calculated transmissivity values approximately 10%-15% less than the uncorrected data Field drawdown data from the four Floridan observation wells were matched to the theoretical Theis type curve for both early-time and late-time (Theis, 1935). The match-point values were substituted into the non-equilibrium equation to determine transmissivity and storativity at the Pemberton Creek site. Partial-penetration corrections were calculated for Kh/Kv ratios of 1 : 1 and 10:1 using a BASIC program by Walton (1987, PTI). In both cases the Floridan Aquifer was estimated to be 300 m thick at Pemberton Creek (Bengtsson et al., 1986). An analytical model using calculated latetimeT and S values was used to evaluate horizontal anisotropy (Papadopulos, 1965)

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TABLE 1 Well construction summary Open Interval Distance to below ground Pumping well Depth surface Well Number (meters) (meters) (meters) A von Park monitor well (APMW) 120 244 172-244 Ocala monitor well (OMW) 122 137 76-137 Tampa 22 (T-22) 183 244 94-244 Tampa 23 (T-23) 435 48* 24-48* Originally drilled to a depth of 78 m. Due to blockage or collapse this well is only open to 48m. 22

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23 Groundwater Flow Model A hypothetical model was constructed using the United States Geological Survey's modular, three-dimensional, finite-difference, groundwater flow model, MODFLOW (McDonald and Harbaugh, 1984). The model consists of a single layer using 59 columns and 59 rows with variable grid dimensions Constant-head boundaries are set 40,000 m from the pumping well to eliminate the influence of boundary conditions on the predicted response. The area of interest includes the geometric arrangement of the Floridan wells and photolinears found at Pemberton Creek (Figure 4). The average late-time transmissivity and storativity values, calculated from the curve matching procedure for the four Floridan observation wells, are used in the model. The discharge rate for the pumping well in the model is 11, 700 m3/day. Three hypothetical MODFLOW scenarios were constructed to evaluate the effect fracture zones associated with photolinears have on aquifer response to pumping The hypothetical aquifer responses were compared to the aquifer response observed in the field. Scenario 1 simulates ideal Theis conditions. Scenarios 2 and 3 are identical to 1 except that the photolinears are assigned a transmissivity two orders of magnitude higher and two orders of magnitude lower than the matrix, respectively.

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0 a: 18 20 22 24 26 28 30 32 COLUMN 24 26 28 30 T-22 APTPW PL-1 PL-2 LOCATION Row 20 Column 1 3-47 LOCATION Row 23 Co lumn 1 5-45 32 (!) APMW 0 50 100 Meters Legen d (!)Observation W ell Pr od u c t ion Well Figure 4 Subgrid of numerical model showing area near pumping well. 24

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25 RESULTS Aerial Photograph Analysis Photolinear 1 (PL 1) displays a stronger photographic expression than Photolinear 2 (PL 2). PL 1 is visible as a dark, vegetative tonal pattern which trends N 50 E (Figure 5). The photolinear is approximately 2,900 m long and 50 m wide. PL 1 is not readily visible in the field, but it can be recognized as a slight topographic high. This photolinear was identified on the aerial photograph by two of the three investigators. Photolinear 2 (PL 2) is visible as a dark, vegetative tonal pattern and is parallel to PL 1 (Figure 5). The photolinear is 1,700 m long and 50 m wide. In the field, PL 2 is seen as a slight linear swale with approximately 1.5 m of total relief. In some areas along the photolinear, linear sinkholes with peaty soil are visible. In other areas there is no visible sinkhole development. This feature was identified on the aerial photograph by all of the investigators. The two photolinears evaluated at Pemberton Creek trend N 50 o E and are consistent with published photolinear patterns. Menke (1961) observes that photolinear features in Hillsborough County, Florida trend N 40 W, N 40 E, N 13o E, and

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26 Figure 5 A 1 : 20,000 aerial photograph of the Pemberton Creek site Photolinears are indicated with arrows

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27 N 70 E. Photolinears in Hillsborough County correspond with the worldwide fracture patterns observed by Blanchet (1957). Methods Horizontal-Loop Electromagnetics (HLEM) EM-34-3 data were obtained along profiles T2, T4 and T5 using the Slingram configuration (vertical dipoles) and a 20-m coil separation. Data were also obtained along profile T2 using a 40-m coil separation and vertical dipoles. Field terrain conductivity values are plotted versus common axes for profiles T2 (Figure 6a), T4 (Figure 6b), T5 (Figure 6c) In general, profiles T2, T4, and T5 show a central, terrain-conductivity low located at approximately 250 m flanked by relative conductivity highs. The 20-m data obtained along T2 characterizes the flanking conductivity high as a zone of alternating local conductivity highs (75 m, 125 m, 160 m, 200 m, 340 m, 380 m, 430 m, 475 m, 520 m, and 560 m) and lows (360m, 410 m, 450 m, 500 m, and 540 m). The large scale central conductivity low is characterized by a decrease in overall terrain conductivity. Profile T5 exhibits the same pattern in terrain conductivity as T2, but the range of conductivity values is not as large. Data collected along profile T4 exhibit the large-scale conductivity trend; however, only one flanking conductivity high is visible The 40-m data obtained along T2 indicate a similar trend of a central conductivity low

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a) T2 40 I I I I I I I 30 I I I -E. 20 en E 10 -40; me er 0 0 200 400. 600 800 Meters b)T4 40 PL-1 I 30 -E. 20 en E 10 0 0 200 400 600 800 Meters c) TS 40 I I 30 -E. 20 en E 10 0 200 -400 Meter s 600 800 28 Figure 6 Terrain conductivity across T2, T4, and T5 using vertical dipoles, 20-meter coil separation and a three-meter station interval. Photolinears are indicated with arrows.

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29 and flanking conductivity highs as the other profiles, except for the presence of an anomalous polarity reversal zone located at 175 m. The general conductivity low observed along all profiles roughly corresponds to the location of PL-2 at 235 m. The beginning of an area of overall high terrain conductivity at about 350 m to 375 m along profiles T2 and T5, and at 325 m along profile T4, roughly corresponds to the location of PL-1 at 350 m. Terrain-conductivity values from profiles T2, T4, and T5 range from 6-38 mS/m and 0-23 mS/m for the 20-m and 40-m coil separations, respectively. Very Low Frequency Electromagnetics (VLF) VLF tilt-angle data values obtained along profiles T2, T4, and T5 range from +20 to -20. Tilt-angle values are plotted versus common axes for profiles T2 (Figure 7a), T4 (Figure 7b), and T5 (Figure 7c) A large-amplitude crossover at 255 m along profiles T2 and T5 roughly corresponds to the location of PL-2 at 235m. The large crossover consists of a zone of negative tilt-angle values centered at 200 m, and flanking zones of positive tilt-angle values from 125 m to 175 m to the southwest and 250 m to 400 m to the northeast. PL-1 is located at 350 m in the northwest limb of the large-scale crossover. All three segments of the large-scale crossover show excellent correlation between profiles T2 and T5. A large tilt-angle crossover located at about 130m along profile T2 is not present

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a)T2 0 c)TS 20 10 rn 0 0) tb 0-10 -20 -30 0 200 PL-2 t 200 400 Meters 400 Meters 30 600 BOO I I : i I I i i I 600 BOO Figure 7 VLF tilt-angle data obtained across 1'2, T4, and T5 using a six-meter station interval. Photolinears are indicated with arrows

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31 in data from profile T5 or T4. The zone of positive tilt-angle values from 225 m to 400 m along profile T4 corresponds to one flanking zone of positive tilt-angle values seen along profiles T2 and T5. A zone of multiple, small-scale tilt-angle reversals occurs along profiles T2 and T5 between 400 m to 650 m Small-scale tilt-angle reversals along profile T2 result in actual crossovers at 425 m, 444 m, 462 m, 495 m, 520 m, and 640 m. Along profile T5, tilt-angle reversals occur mainly in the positive value range and only two actual crossovers at 565 m and 650 mare visible. Profile T4 data do not show a similar tilt angle reversal pattern, but a negative tilt-angle zone from 400 m to 550 m follows the general tend of decreasing tilt-angle values observed along profiles T2 and T5 Tilt-angle (in-phase) data were processed using the McNeill filter (McNeill, verbal communication, 1990). The McNeill ftlter is a continuous-sum filter that produces a pseudo-conductivity section: zj = (ZH + aJ, where; zj is filtered data value, a = is field tilt-angle value, n = j+1, j = number of filtered data. (Example; if j = 1, Z1 = at + at j = 2, Zz. = Z1 + a:z)

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32 The McNeill filter acts as a low-pass filter that strongly smooths small-scale variations of the in-phase component, and makes large-scale variations more visible. The shape of the pseudo-conductivity curve produced by the McNeill filter indicates the relative conductivity of the features encountered along the profile. Pseudo-conductivity sections are plotted versus common axes for profiles T2 (Figure 8a), T4 (Figure 8b) and T5 (Figure 8c). Filtered data values obtained along profiles T2, T4, and T5 range from +2000 to -280. Pseudo-conductivity sections for profiles T2 and T5 show a prominent resistive feature centered at 250 m which is flanked by two conductive limbs. Filtered data from profile T4 indicate a similar pattern, but the resistive feature is offset by 25 m and only one conductive limb is visible. Pseudo-conductivity sections for profiles T2, T4, and T5 show similar conductivity trends across their respective lengths. Horizontal-Electrical Pronling (HEP) HEP data were obtained along profiles T2, T4, and TS using a Wenner array and an inter-electrode spacing of 30 m. HEP data are plotted versus common axes for profiles T2 (Figure 9a), T4 (Figure 9b), and T5 (Figure 9c). A zone of elevated apparent resistivity approximately 50-100 ohm-m higher than average is visible along profiles T2, T4 and T5 between 200 m and 300 m. The

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a)T 2 b ) T4 c ) TS 3 0 0 i P L -2 200 I t I 100 I I "' I QJ 0 l!:! t>O QJ 0 -100 -20 0 -300 0 2 0 0 0 200 300 2 0 0 100 -200 PL1 t 400 Met e r s 4 0 0 Me t e r s PL1 600 B O O 600 Boo 0 200 400 Meter s 600 BOO 33 Figure 8 Pseudo-conductivity sections across T2 T4, and T5 produced us ing the McNeill filter ( 1991) Photolinears are ind i cated with arrows

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a) T 2 250 2 0 0 tl E 150 E 100 .c 0 50 0 0 b ) T4 250 200 ., ... 150 u E E 100 .c 0 50 0 0 c ) TS 250 200 ., ... u 150 Q) E E .c 0 100 5 0 0 0 200 400 Meters I PL 2 i P L1 I I I I I I I I I I I I i i I I I I I I I I I I I I I I 200 400 Met e r s 1 P L2 PL-1 i 200 400 Met ers 34 600 eoo 600 eoo 600 eoo Figure 9 Apparent resistivity measured across T2, T4, and T5 using a Wenner array, an a spacing of 30 meters, and a ten-meter station interval. Photolinears are indicated w ith arrows.

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35 resistivity high is about 100 m wide, is flanked by relative resistivity lows along profiles T2 and T5, and roughly corresponds to the location of PL-2 at 235 m Only one resistivity low is visible along profile T4. Within the relative resistivity high, a local resistivity low centered at 250 m is present along profiles T2 and T5. A broad resistivity low is visible along profile T2, from 310m to 400 m. HEP data obtained along profile T5 also indicate a relative resistivity low from approximately 310m to 370m. The relative resistivity low observed in the HEP data collected along profiles T2 and T5 corresponds to the location ofPL-1 at 350m. Along profile T4, the location of PL-1 marks the beginning of a resistivity low that exhibits little station-to station variability in apparent resistivity HEP data obtained along profiles T2, from 400 m to 590 m, and T5, from 370 m to 510 m, show a zone with station-to-station apparent resistivity variability as great as 80-100 ohm-m The zone of variable resistivity correlates well between both profiles. HEP data suggest the cause of the station-to-station variability is local, with electrical heterogeneities ranging from 10 m to 30 m in width. HEP data obtained from 350 m to 510 m along profile T4 are anomalous in that total station-to-station variability in apparent resistivity is less than 15 ohm-m. Seismic Reflection An unprocessed, optimum-offset, seismic-reflection section was obtained at

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36 Pemberton Creek along profile T2 from 52 m to 560 m. A 95-Hz high-pass filter was applied to the data as they were recorded in the field The seismic section shows two chaotic-reflection zones at approximately 255m and 435 m. The chaotic-reflection zone at 255m roughly corresponds with the location of PL-2 (Figure 10) A strong reflector centered at 350 m coincides with PL-1. Coherent reflectors are visible on the section at approximately 30-32 msec, 42 msec, and a strongly undulating reflector at about 60 msec can be traced across the section. A small-amplitude signal at 48 msec is consistent across the seismic section Microgravity Bouguer residual gravity data (Figure 11) obtained along profile T2 show two gravity lows, approximately -0.04 mGals below background, located at 375m and 510 m The 40 m wide, central-gravity low is flanked by two relative-gravity highs present from 275 m to 355 m and 415 m to 485 m. Both relative, residual-gravity highs are about 70 m wide. The southernmost gravity high ranges from 0.01 to 0.04 Mgals above background and the northernmost high ranges from 0.02 to 0.06 Mgals above background. Laboratory-determined, specific gravity values for samples of the Ocala Limestone collected at Crystal River quarry No. 2 confirm the density contrast suggested by Stewart and Wood (1990) between unaltered limestone and the recrysta11ized limestone associated with the fracture trace. The calculated density of unaltered Ocala Limestone ranged from

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48 92 140 188 tPL-2 236 284 332 368 416 464 512 560 .I 0 -------------20 -------------40 ------------60 -----------80 1\J'i.N 14\'MMll /'It Ulll/111 \\mN..41f411 )\ 100 Figure 10 Optimum offset seismic-reflection profile across T2 Photolinears are indicated with arrows ------120 ------140 a ,.-... 8 1;/l n -(,.) -....)

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.. 0.06 0.06 0.04 0.02 PL-2 PL1 E -o.o2 -o.04 -o.06 0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 600 Meters 38 Figure 11 Bouguer residual-gravity profile across T2 using a five-meter station interval. Photolinears are indicated with arrows. 20 0 0 > E -20 -40 PL-2 PL-1 0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 600 Meters Figure 12 Self-potential profile across T2 using a three-meter station interval. Photolinears are indicated with arrows.

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39 1.8-2.0 g/cm3 Samples of recrystallized Ocala Limestone ranged from 2 5-2 7 g/cm3 SelfPotential Self potential (SP) data obtained along profile T2 show a central, large-scale, negative anomaly at 270 m that is flanked by relative highs (Figure 12). The location of the negative SP anomaly roughly corresponds to PL 2 at 235 m Station-to-station variability of SP read i ngs appears to be greater between 300m to 550 m than from 75 m to 250 m. A strong negative anomaly is present at the beginning of the profile. Ground-Penetrating Radar At Pemberton Creek a GPR survey using a 120-Mhz antenna was conducted along profiles T2 T4 and T5. Results from the 120-Mhz survey indicate that a laterally continuous reflector is present at a depth of approximately 0.6 m to 2.4 m along all proflles Due to strong signal attenuation the GPR receiver was able to detect only the shallow reflector; therefore, these data are not presented. A GPR survey was conducted from 80 m to 560 m along proflle T2 using a 100Mhz antenna. This survey shows that a shallow reflector is present along the entire record at approximately 1 m below ground surface. Two nearly identical, high amplitude reflectors approximately 60 m wide and 6 m deep are located at 100m to 155m and 180m to 240m (Figure 13 shows one of these features). A strong, high -

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250 ,......_ u Cl) c ....... Cl) E e: 'i) > E-< 9 10 '""' "' .... '-" .c a C1) 0 < 0 .... 0. 0. < 100 Meters 120 40 Figure 13 A segment of the GPR profile across T2 showing one of two high-amplitude reflectors that are approximately 60 meters wide and six meters deep.

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41 amplitude reflector approximately 20m wide and 9 m deep is located at 290m (Figure 14). At 500 m along profile 1'2, the 100-Mhz GPR record shows a parabolic reflector at approximately 3 m below the surface (Figure 15). A shallow, high-amplitude reflector located at 520 m is about 30 m wide and ranges from 2-9 m deep. Evaluation of the Groundwater System Pumping-Test Data Field drawdown curves for APMW (Figure 16), OMW (Figure 17) T-22 (Figure 18), and T-23 (Figure 19) were compared to the theoretical Theis curve, and aquifer parameters were calculated for both early-time and late-time (Table 2). Partial penetration corrections were evaluated and were not required for the drawdown data Early-time transmissivity values calculated for all wells, except T-23, range from 1.8 to 2 5 times larger than the late-time values. The early-time transmissivity value for T-23 is an order of magnitude greater than the late-time value. The late-time transmissivity values for all wells are within 20% of each other and storativity values for all wells, except T-23, increase with time. The average values of late-time transmissivity and storativity for APMW, OMW, and T-22 are 3,300 m2/day and 2 x 10-3, respectively. Maximum drawdown in the Floridan wells range from 2.26 m in the pumping well (APTPW) to 0.94 min T-23.

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42 Meters 260 280 300 50 2 3 100 4 5 50 6 7 200 8 9 250 10 ,..... ,..... u Cl) Cl) c:: Q) '--" 6 I!) E .c t= a. v Cl) > 0 < e 0. 0. < Figure 14 A segment of the GPR proftle across T2 showing a high-amplitude reflector that is approximately 20 meters wide and 9 meters deep.

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43 Meters 480 500 520 540 0 2 3 4 5 6 7 8 9 250 10 ........ ....--u Q.l (/) .... ..!!:. Q.l c: 0 ....... ::E Q.l E ....... ..c: E= 0. u Q.l > 0 Q.l 8 0. 0.
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e .._. "0 E Q 10 0.1 O.Ql ---r T TTTTTTT I T -A early-time B late-time r-W(u)= 1 1 U = 1 1 -s= 0.10 m 0.27m t= 0.17 min. 1.9 m in. -B ..; y I 't A r;:,. /\. v I I /i I J 1 / I 0.1 ... -..... ,..... ..,.,.,. ii""""' Theis Type Curve 10 100 1000 1 0000 Time (minutes) Figure 16 Plot of corrected drawdown for the Avon Park monitor well at Pemberton Creek, Florida, overlain on the Theis type-curve for early-time and late-time

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5 '-' "C cu L.. Q IO 0.1 0.01 0.1 \latch Point Coordinates A early-time B l ate-time W(u) = I I U= I I S= 0.17m t= 1.7 min. 10 100 1000 1 0000 Time ( minutes) Figure 17 Plot of corrected drawdown for the Ocala monitor well at Pemberton Creek, Florida, overlain on the Theis type-curve for early-time and late-time.

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e '-' 0 1 co ... Q 10 0 1 0 .01 T T'T"TTTT T = -A early-time B late-time -W(u) = I l n= I I S= O.I3m 0 30m t= 0.7 min 3.0min. -B l
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e .._, ... Q 10 0 1 0 .01 0 1 :'\lall'h Point Coordinates A early-time B late-time 1 1 U= 1 1 S= 0 05m 0 24m t= 20min. 105 min 10 100 1000 10000 Time (minutes) Figure 19 Plot of corrected drawdown for the Tampa 23 monitor well at Pemberton Creek, Florida, overlain on the Theis type-curve for early-time and late-time. -....l

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48 TABLE 2 Summary of pumping-test results for Pemberton Creek Well Transmissivity Storativity (m2/day) early late early late A von Park monitor well (APMW) 9,300 3,400 4 X 10-4 1 X 10"3 Ocala monitor well (OMW) 5,500 3,400 2 X 10"3 3 X 10"3 Tampa 22 (T-22) 5,000 3,100 3 X 104 8 X 1Q-4 Tampa 23 (T-23) 19,000 3,900 6 X 10 "3 6 X 10"3

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49 Field drawdown curves for APMW, OMW, and T-22 show similar curve shapes,but the curves show a variation in early-time storativity. The field curve for T-23 shows a nearly linear drawdown for approximately 1,000, minutes then approaches the general shape of the drawdown curves from the other wells. Anisotropy Aquifer parameters calculated from the late-time Theis-curve match values for APMW, OMW, and T-22 were used to estimate apparent horizontal anisotropy (Papadopulos, 1965) The calculated anisotropy ratio is 6:1 and the direction of the major axis of anisotropy is N 24 W. The direction of the major axis of anisotropy is 16 from the perpendicular to the observed photolinears, which trend N 500 E. Numerical Model MODFLOW output head data simulating seven days of pumping, were used to construct hydraulic-head contour maps for Scenarios 1 (Figure 20), Scenario 2 (Figure 21), and Scenario 3 (Figure 22). Contour lines used in the maps are dimensionless and draw down decreases with increasing distance from the pumping well (APTPW). Comparisons of all model scenarios show that equipotential lines close to APTPW (early time) do not appear to be influenced by varying the transmissivity of the photolinears. Drawdown is symmetrical with respect to the X axis in all cases. A drawdown ellipse

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33780 r----"7'"""----------r---------..,.....-------, 33280 T-23 32780 3278 0 0 Scale 100 Meters 33280 3378 0 200 50 Figure 20 Scenario 1 Contour map showing the shape of the cone of depression after seven days of pumping with homogeneous isotropic conditions Drawdown is greatest at the pumping well APTPW and decreases away from the well. Countours of drawdown are dimensionless

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33780 .--------------.---------------., 33280 Matrix T = 3300 m2/ day Photolinear T = 330,000 m2/ day 32780 L..____ ..;:,_ ______ __. _______ "'--------' 51 32780 33280 33780 0 Scale 100 Meters 200 Figure 21 Scenario 2 Contour map showing the shape of the cone of depression after seven days of pumping with the photolinears modeled as high transmissivity wnes Drawdown is greatest at the pumping well APTPW, and decreases away from the well. Countours of drawdown are dimensionless

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52 33780 .--------------.----------------, 33280 Photolinear T = 33 m2/day 32780 32780 33280 33780 Scale 0 100 200 Meters Figure 22 Scenario 3 Contour map showing the shape of the cone of depression after seven days of pumping with the photolinears modeled as low transmissivity zones Drawdown is greatest at the pumping well, APTPW, and decreases away from the well. Countours of drawdown are dimensionless

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53 showing unequal drawdown with respect to the Y -axis forms during late-time in Scenarios 2 and 3. Total drawdown is least for Scenario 2, intermediate for Scenario 1 and greatest for Scenario 3.

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54 DISCUSSION The geologic model developed using the results of the integrated geophysical study suggests that a fracture zone is associated with the two observed photolinears. The fracture zone appears to consist of a central, karstic, bedrock low flanked by dense, recrystallized, bedrock highs that contain multiple limestone pinnacles and clay-filled fractures (Figure 23). Clay-filled fractures appear to be limited to the dense, recrystallized bedrock highs and display a consistent trend parallel to the observed photolinears. These photolinears correspond to the central bedrock low (PL-2) and one flanking recrystallized limb (PL-1) of the fracture zone. The geologic model suggested by this study is consistent with the M-shaped gravity anomaly associated with lateral variations in density across photolinears in the Floridan Aquifer observed by Stewart and Wood (1991). The HLEM (EM-34-3) data obtained across the photolinears indicate an M-shaped response with a central conductivity low flanked by general conductivity highs (Figure 24). The general conductivity highs are interpreted as areas where conductive deposits are present. General conductivity highs are characterized by alternating terrain conductivity highs and lows and VLF tilt-angle inflection points The geophysical responses obtained across the general conductivity highs suggest multiple clay-filled

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-5 0. a) Q "0 e c 0 30m Ground Surface 400 600 :: :-: -:._: .... ;:". : : : ... : ? Tampa/Suwannee Limestones Figure 23 Interpreted geologic model for Pemberton Creek Florida, developed using geophys i cal data obtained across T2. 800

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40 30 e en zo e 10 -TS -T2 PL-2 T4 PL-1 Clay-Filled Fracture I 0 0 200 400 0 50 100 Meters Legend --Conductivity Contours mS/m '\BOOm 'T-5 Meters Tampa IS 600 800 56 Figure 24 Interpretation of terrain conductivity across photolinears at Pemberton Creek, Florida (McNeill, 1991). (a) Profile data show a zone of multiple clay-filled fractures and an M-shaped anomaly associated with PL-2. (b) Contour map of conductivity shows highs flanking a low associated with the photolinears.

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57 fractures and limestone pinnacles. The interpretation of HLEM and VLF data in this study is consistent with results obtained by Yager and Kappel (1987) which show that conductivity highs and VLF crossovers correspond to clay-filled fractures in the Lockport Dolomite. PL-1 corresponds to a general conductivity high and is interpreted as a general bedrock high with conductive clays. In contrast, PL2 corresponds to a general conductivity low which is interpreted as a sand-filled fracture zone. Conductive, clay rich deposits appear to be absent at the general conductivity low Lithologic logs from Pemberton Creek (USGS, 1961; SDI 1991) indicate that the Tampa Limestone begins at a depth of 15-18 m; therefore, the principal control on the HLEM response appears to be the variation in overburden thickness associated with karstification of the underlying limestone. The Slingram instrument is insensitive to surface conductivity variations, and the effective exploration depth (EED) is 1.5 times the coil separation (McNeill, 1980). The depth of maximum response (DMR) for the EM-34 3 in the Slingram configuration is approximately 8 m and 16m for 20-m and 40m coil separations, respectively Comparison of HLEM data obtained across profile T2 using coil separations of 20 m and 40 m show decreasing conductivity w i th increased BED and DMR (Figure 25). The observed conductivity decrease between the 20 m and 40-m d a ta is interpreted as a decrease in the proportion of clay and an increase in the proportion of limestone contributing to the total instrument response. A hypothetical model illustrates the relationship between terrain-conductivity data obtained using a EM-34 3 in the Slingram configuration with coil separations of

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4 0 30 s 00 20 s 10 -20meter --40 m eter PL-2 ..,_.Cla y Filled Fracture 0 0 20 0 400 600 800 m e t ers 58 Figure 25 Terrain conductivity across T2 using 20-meter and 40-meter coil separations 5 ,..-.. lil ""' s 10 .c c. Q 1 5 2 0 Ground Surface . .. ... . d : s : : : m : ; :, fY/W!iN_!\ l _;._ i -!i _ m_; .. . ------------------..... ... . -------------------..... .... ... ----------.. .. ::.:. .. :.} .. : .. : :.:.:>:.:: .. / : : .. ============= ========= Case 1 Sand Filled Fracture Case2 Bedrock High C ase3 Clay Filled Fracture Case4 B a ckground Coil Seperation 20m 40m 2 0m 40m 20m 40m 20m 40m Oa (mS/ m ) 8 9 9 10 23 17 17 13 F i gure 26 Predicted EM-34 response across several geologic targets (after McNeill, 1980)

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59 20 m and 40 m (Figure 26). Comparison of a sand-filled fracture (case 1) with a limestone high (case 2) suggests that these features show similar terrain conductivities for both coil separations. A conductive unit in the overburden (cases 3 and 4) results in an overall increased terrain conductivity. Increased thickness of the conductive unit such as a clay-filled bedrock fracture (case 3) results in a terrain conductivity higher than background conditions (case 4). In all cases, the depth and thickness of the conductive unit is the primary control on the terrain conductivity. The terrain-conductivity method, like all electrical methods, is susceptible to the problem of equivalence and requires additional information to constrain the geologic interpretation The theoretical VLF tilt-angle response predicted across several adjacent, thin, vertical-sheet conductors (McNeill, 1991) approximates the observed field response at Pemberton Creek (Figure 27). Theoretical models indicate that several adjacent conductors can alter the VLF response associated with each conductor. Interference from adjacent conductors shifts the entire VLF response above or below the zero tilt-angle line and the inflection points in the resultant VLF response locate the conductive targets (MeN eill, 1991). At Pemberton Creek, the conductive geologic targets that cause the observed VLF tilt-angle response are interpreted as clay-filled fractures in the underlying limestone. The fractures exhibit a consistent trend parallel to the observed photolinears and appear limited to the general conductivity highs (Figure 28). The results of the resistivity survey at Pemberton Creek indicate an average resistivity of 100 ohm-m. Using equation 1, the

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+ Center of Slope of In phase Data Indicates Location of Target 60 Figure 27 Theoretical VLF tilt-angle (in-phase) response across two vertical, sheet-like conductors adapted from Geonics (1979).

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-Ts 20 10 -10 -20 -30 0 200 -T2 PL-2 r -T4 Zone of Multiple Clay Filled Fractures 400 Meters Tampal5 600 0 50 1 00 Meters Legend ----Fracture 61 800 Figure 28 Interpretation of VLF tilt-angle data across photolinears at Pemberton Creek, Florida (after McNeill, 1991). (a) Profile data show a large anomaly associated with PL-2 and a zone of multiple clay-filled fractures. (b) Estimated fracture locations based on VLF tilt-angle data.

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62 EED for the VLF instrument at Pemberton Creek is estimated to be 36 m Excellent correlation between the HLEM data and VLF data indicate that near-surface conductors do not adversely affect the VLF response. Pseudo-conductivity sections produced from filtered VLF tilt-angle data (McNeill, 1990) reduce variability caused by small-scale lithologic variations and clearly show a large-scale anomaly associated with the observed photolinears (Figure 29). The shape of the filtered VLF plot indicates the relative conductivity of the target. The central low on all profiles roughly corresponds to the location of PL-1. The location of PL-2 corresponds to a general conductivity high on all profiles. Pseudo-conductivity sections based on tilt-angle data greatly improve the large-scale interpretation of the Pemberton Creek data. The rapid profiling capabilities of the VLF method coupled with the application of the McNeill filter (1990) to tilt-angle data result in a rapid, accurate, and cost-effective reconnaissance technique for locating large-scale geologic features associated with photolinears. The problem of equivalence, potential susceptibility to near-surface conductors, and possible cultural interferences require an integrated geophysical program to constrain the VLF interpretation. Horizontal-electrical-profiling (HEP) data obtained using a Wenner array and an inter-electrode spacing of 30 m successfully located the lateral variations in resistivity associated with the photolinears. The HEP results correlate well with results of the

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300 250 100 -100 -200 TS Relative Conductor PL-2 I I / 0 200 T2 --T4 63 PL-1 Relative Conductor /---I / / --t--/ 400 600 800 Meters Figure 29 Interpretation of pseudo-conductivity sections across photolinears at Pemberton Creek, Florida. Photolinears are indicated with arrows. TS T2 --T4 250 PL-2 PL1 Clay Filled Fr acture 200 <11 ... ./'Limesto n e Pinnacle Cl.l Cl.l 150 5 5 .c 0 100 50 Sand Filled Fracture 0 200 400 600 800 Meters Figure 30 Interpretation of apparent resistivity profiles across photolinears at Pemberton Creek, Florida. A Wenner array with an "a" spacing of 30 meters was used. Photolinears are indicated with arrows

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64 HLEM and VLF surveys. The length of the Wenner array used at Pemberton Creek was 90 m, which results in an EED of abount 20 m. The inter-electrode separation was selected on the basis of borehole data that indicate a bedrock depth of 15-18 m (SDI, 1991; and USGS, 1961). The general resistivity high (Figure 30) is interpreted as the center of the large-scale fracture zone where conductive clays are absent. The resistivity high is approximately 100 m wide with apparent resistivities 80-100 ohm-m above flanking relative-resistivity lows. These lows are believed to be the result of the presence of clays along the recrystallized flanks of the fracture zone The recrystallized flanks show multiple, local resistivity highs and lows that are interpreted as alternating limestone pinnacles and clay-filled fractures. The interpretation of the HEP data at Pemberton Creek is consistent with previous work done in karst terrain (Van Nostrand and Cook, 1966). The optimum offset seismic-reflection data collected at Pemberton Creek show a seismic anomaly associated with the observed photolinears (Figure 31). A chaotic reflection zone located at 255 m is associated with the center of the large-scale fracture (PL-2). A zone of strong reflectors corresponds to a recrystallized limb of the structure (PL-1). Interpretation of the seismic reflection data requires the estimation of seismic velocities for geologic materials at Pemberton Creek. Assuming a velocity of 300 m/ s

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0 5 .-... 30 e '-" -= .... c. Q Lime s tone Chaotic 48 92 140 188 tPL-2 236 284 fL-1 332 368 416 464 512 560 0 -------------20 -------------40 Airwave ------60 ...., Top of a Limestone .-... 3 -----80 Cll f') '-" 100 -----140 Figure 31 Optimum offset seismic-reflection section at Pemberton Creek, Florida, across T2 showing a chaotic reflection zone associated with PL 2 and a zone of strong reflectors associated with PL 1. Photolinears are indicated with arrows.

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66 for the unconsolidated surface materials (Haeni, 1986) and using a travel time of 32 msec, the depth to the first reflector at station 48 m is estimated at 5 m. The first reflector is believed to be the water table Based on the assumption that all materials below the water table are a soft limestone, a velocity of 1700 mJ s (Dobrin and Savit, 1988) is used to calculate the distance between reflectors. The second prominent reflector occurs at approximately 60 msec. The distance between these reflectors is estimated at 23m by using a two-way travel time of28 msec and a velocity of 1700 m/s. Therefore, the total depth to the second reflector is approximately 28 m. The seismic interpretation correlates well with lithologic logs from the Suwannee monitor well, located 10 m east of station 48 m, which show the top of the Suwannee Limestone at 30 m below ground surface (Figure 32). The depth to the top of the Suwannee reflector appears to vary by as much as 21 m between stations 220 m and 364 m. Microgravity data obtained across a section of the general conductivity high show a lateral variation in density that is interpreted as a clay-filled fracture in the limestone bedrock. A residual-gravity low approximately 0.4 mGals lower than background is located at 375 m along profile T2. The residual-gravity low corresponds to a local terrain-conductivity high suggesting a clay-filled fracture in the bedrock (Figure 33) The interpretation of a residual-gravity low as a clay-filled fracture is consistent with results obtained by Butler (1980) at Medford Cave, Florida. Laboratory-determined densities of unaltered and recrysta11i zed limestone samples collected at CRQ ranged from 1.8-2.0 g/cm3 and 2.5-2. 7 g/cm3 respectively. A density

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Approximate Stratigraphic Depth Unit (m, bls) Well Undifferentiated Deposits and Hawthorn Formation Tampa Lim es tone ----------30 Suwannee Limestone Ocala Group 60 90 120 8"Dia. Steel Casing Open Hole L-.....J Total Depth 67 Figure 32 Lithologic log of the Suwannee monitor well at Pemberton Creek, Florida, adapted from SDI (1991).

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0.08 0.06 0 .04 0.02 23 cu "" 0 e -0.02 -0.04 -0.06 -0.08 0 200 t Limestone Pinnacle 400 meters Bouguer Residual Gravity (a) 600 20 meter c oil s with vertical dipoles 40 30 Vl 20 e 10 Clay Filled Fracture Limestone Pinnacle 68 800 0 0 200 400 meters Terrain Conductivity (b) 600 800 Figure 33 Interpretation of Bouguer residual-gravity profile at Pemberton Creek, Florida, across T2 showing clay-filled fractures corresponding to gravity lows. Photolinears are indicated with arrows

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69 of 2. 7 g/cm3 for calcite and an initial porosity of 40% yields a saturated limestone density of 2 0 g/cm3 A decrease in porosity from 40% to 10% is required to obtain a saturated limestone density of 2 5 g/cm3 The large density contrast observed in this study is probably due to the limited number and the small size of the samples tested. The porosity decrease observed on a field-scale study of photolinears may be less extreme. Microgravity data from Pemberton Creek and laboratory-determined densities of samples collected at CRQ are consistent with lateral variations in density associated with photolinears as found by Stewart and Wood (1991). The authors suggest that a bulk density decrease at the center of the fracture and an increase adjacent to the fracture due recrystallization is responsible for the M-shaped gravity anomaly obtained across the fracture trace at CRQ. A negative streaming potential as great as 40 millivolts is visible at the center of the large-scale fracture zone (Figure 34) Corwin (1986) defines streaming potentials as electrical voltages generated by the flow of fluid through a porous medium. Bogoslovsky and Ogilvy (1969) evaluate leakage from reservoirs using streaming potentials and find that negative streaming potentials are generally associated with sinks. Consequently, the large-scale negative potential observed at Pemberton Creek is interpreted as the downward flow of groundwater in a sand pipe associated with the large-scale fracture zone The strong negative potential located at about 60 m along T2 may be associated with a streaming potential or may be due to an electrochemical response caused by the steel cas ing in well Tampa 15. Self-potential data were rapidly obtained and assisted in

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ll 0 > e 20 0 20 -40 0 I I I 200 PL-2 PL-1 l l Streaming Potential 400 600 Meters Figure 34 Interpretation of self-potential data across T2 showing strong negative streaming potential associated with the photolinear-related fracture zone Photolinears are indicated with arrows. 800 z

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71 the overall geologic interpretation, but the problem of equivalence requires that this technique be used in an integrated geophysical program. Ground-penetrating radar was not effective for locating geologic fractures associated with the photolinears at Pemberton Creek. The results of the GPR survey using the 100-Mhz antenna were superior to the results obtained with the 120-Mhz antenna. Results of the HLEM and resistivity surveys indicate the overburden materials at Pemberton Creek are moderately conductive and suggest the poor penetration depth obtained in both GPR surveys is caused by the attenuation of the GPR signal due to a conductive subsurface. The GPR record reveals several reflection-free wnes that generally correspond to conductivity highs. Therefore, the reflection-free zones are interpreted as clay-rich areas where signal attenuation is high. The high-amplitude reflectors (Figure 35a, A, B, C, and D) correlate well with resistivity highs (Figure 35b) suggesting these reflectors may be sand-rich areas Analysis of drawdown data from a seven-day, 11,700 m3/day, aquifer test in the Floridan Aquifer yield average, late-time transmissivity and storativity values of 3,300 m2/day and 2 x IQ-3 respectively Estimates of aquifer parameters in this study correlate well with previous studies. Wolansk:y and Corral (1985) estimate transmissivity and storativity values at Pemberton Creek to be 3450 m2/day and 1.5 x 10-3 respectively. Corrections for local groundwater trends were applied to the drawdown data from observation wells T-22, OMW, and APMW. These corrections result in transmissivity values 10-15% less than the transmissivity values obtained with the uncorrected data.

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72 0 ,-...
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73 Observation well T 23 is located a considerable distance from the background monitoring station and corrections were not applied to the drawdown data, resulting in a transmissivity value slightly higher than the other wells. Calculated early-time transmissivity values for APMW, OMW, and T-22 are 2-2.5 times larger than the late-time values The early-time transmissivity value for T-23 is approximately an order of magnitude greater than the late-time value. Early-time and late time storativity values are the same order of magnitude for all wells except APWM. Storativity values for APMW increase from an early-time match of 4 x 10"' to a late-time match of 1 x 10-3 The dual-porosity theory (Barenblatt et al., 1960) states that an aquifer consists of two media: fractures and matrix blocks. The aquifer matrix is characterized by low transmissivity and high storage capacity. In contrast, the fractures exhibit high transmissivity and low storage capacity. Elevated early-time transmissivity values in all wells may represent the response of a doubly-porous aquifer. The early-time response represents the dewatering of small-scale, highly transmissive heterogeneities caused by well-developed solution porosity or fractures. The late-time response represents the greater storage capacity and lower bulk transmissivity of the aquifer matrix and the effect of vertical leakage. The data from a seven day pumping test at Pemberton Creek exhibit an apparent anisotropic drawdown response. The APMW and OMW are about 120 m from the pumping well (APTPW) and show similar drawdown curves after 150 minutes (Figure 36). The drawdown measured at T-22, which is 183m from the APTPW is similar to

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e ....... a: f 10 Vertical effect' "" -'!! .-. .. v t<' APMW"' va-., .,. I? T-23 JJ Itt" LA I,.! v .X v [,.a' v v /I\ 1/ v.: ..><'! OMW 0.1 7' Linear drawdown 7 / 1/ 1 II 7 !.X' 4-II v v t---T-22I I lr I 0.01 0.1 10 100 1000 10000 Time (m inutes) Figure 36 Plot of drawdown for observation wells at Pemberton Creek, Florida, showing an anomalous linear drawdown for T 23 which is believed to be in the fracture zone Note the similar drawdown response in the other wells especially in late-time.

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75 the drawdown at APMW and is actually greater than drawdown observed at OMW. Analysis of late-time drawdown data with an anisotropic analytical model indicates an anisotropy ratio of 6 : 1 (Papadopulos, 1965) The major axis of anisotropy trends approximately N 24 W and is nearly perpendicular to the N 50 E strike of the photolinears. Due to an anomalous straight-line drawdown response during the first 1000 minutes, an accurate early-time match with the Theis curve was difficult to achieve for T-23 (Figure 36). The rate of drawdown during the fust 1000 minutes is greater than that predicted by the theoretical Theis curve. A straight line on a log log plot suggests the Theis solution is not appropriate and may indicate linear flow to a fracture rather than radial flow (Jenkins and Prentice, 1982). The drawdown response observed in T-23 suggests the well may be located in a fracture. T-23 is located between PL-1 and PL-2 and may be in recrystallized limestone adjacent to the bedrock low The late-time response at T-23 correlates well with the other observation wells and suggests the fracture believed to be responsible for the anomalous drawdown response is small relative to the volume of the aquifer tested. The average late-time values for transmissivity (3,300 m2/day) and storativity (2 x 1o-3 ) were used to construct a single-layer, groundwater flow model. The aquifer response predicted by the model for ideal Theis conditions was compared to the response predicted with the photolinears represented as high-transmissivity zones (330,000 m2/day) and as low-transmissivity zones (33m2/day)

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76 Analysis of the predicted aquifer response with the photolinears represented as high-transmissivity zones shows the apparent major axis of anisotropy is parallel to the fracture trend and the anisotropy ratio is approximately 2:1 (Figure 37) Moore (1980) evaluates aquifer anisotropy associated with a fracture zone at Cross Bar Ranch and finds the major axis of anisotropy is parallel to the fracture trend with an anisotropy ratio of approximately 2:1. Modeling results suggest that an apparent anisotropic aquifer response similar to the response observed in the field data may be obtained by representing the photolinears as zones of low transmissivity (Figure 38). The hypothetical aquifer response obtained with the photolinears as low-transmissivity zones is consistent with the observed field response in that both indicate an apparent major axis of anisotropy approximately perpendicular to the photolinears. Numerical modeling results show that the appli c ation of an anisotropic analytical model to a heterogeneous, isotropic aquifer may res ult in misinterpreting increased drawdown due to a barrier boundary as an anisotropic response. Comparing the trend of the major axis of anisotropy predicted by the model to the response observed in the field suggests that the field response may be due to structural or lithologic variations that are undefined by the existing data (Figure 39). Lithologic variations within the A von Park Limestone that are unrelated to the observed photolinears or a vertical fracture not visible as a photolinear, may be responsible for the apparent anisotropic aquifer response The major axis of anisotropy obtained from the field data trends N 24 W which is close to an observed fracture strike in

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3378 0 33280 Matrix T = 3300 m2/ day Photolinear T = 330 000 m2/ day 3 2780 L-____ ::..,_ ______ -l.,_ ______ .....c:.. ____ __J 327 8 0 0 Scale 100 Meters 33280 3 3780 200 77 Figure 37 The shape of the cone of depression after seven days of pumping with the photolinears modeled as high-transmissivity zones The major axis of anisotropy is parallel to the photolinears with an anisotropy ratio (Tzz/Tnn) of approximately 2 : 1. Drawdown is greatest at the pumping well APTPW and decreases away from the well Contours of drawdown are dimensionless

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78 33780 33280 Photolinear T = 33 m2/day 32780 32780 33280 33780 0 Scale 100 Meters 200 Figure 38 The shape of the cone of depression after seven days of pumping with the photolinears modeled as low-transmissivity zones. The major axis of anisotropy is perpendicular to the photolinears with an anisotropy ratio (Tzz/Tnn) of approximately 2: 1. Drawdown is greatest at the pumping well, APTPW, and decreases away from the well. Contours of drawdown are dimesionless.

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------N-o----o Legend T-22 OMW F ield res ponse Nume rical response with PL1 and PL2 as low-transmi ss ivity zones N um erical resp o nse wit h PL-1 and PL-2 as high-transmiss i vity zo nes APMW Tzz/Tnn N24 W 6 : 1 N40W 2: 1 N50E 2:1 79 Figure 39 Comparison of the anisotropic drawdown response observed in the field w ith the model-predicted anisotropic drawdown responses.

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80 Hillsborough County of N 400 W (Menke, 1961). Additionally, the Avon Park Limestone, which is the production zone for the Pemberton Creek pumping test, contains highly transmissive dolomites (Stringfield, 1966) that could cause an anisotropic drawdown response that is unrelated to the photolinears. In the Floridan Aquifer, low porosity recrystallized limestone associated with photolinear-related fractures may result in low-transmissivity zones. The hydrologic effect of the low-transmissivity recrystallized limestone is expected to be similar to a barrier boundary. Drawdown data from the Floridan observation wells at Pemberton Creek do not indicate the presence of a barrier boundary. A transmissivity contrast of two orders of magnitude was required in the model to obtain a major axis of anisotropy perpendicular to the photolinear, yet the magnitude of the predicted anisotropy ratio of 2: 1 is still considerably smaller than the ratio obtained with the field data of 6: 1. The combination of the absence of an observed barrier boundary in the drawdown data and the magnitude of the anisotropy ratio observed in the field suggest that the fractures associated with the photolinears at Pemberton Creek are not hydrologically significant relative to the pumping test.

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81 CONCLUSION An integrated geophysical and hydrogeologic study of two photolinears in southwest-central Florida suggest that they are part of a large-scale fracture zone in the Floridan Aquifer. The fracture zone appears to be greater than 700 m wide and consists of a 100 m wide, sand-filled bedrock low flanked by zones of dense, recrystallized limestone approximately 300-400 m wide. The recrystallired zones are bedrock highs comprised of limestone pinnacles and clay-filled fractures. The clay-filled fractures appear to be 40-50 m wide and are parallel to the observed photolinear trend. Geophysical responses obtained at the center of the large-scale fracture zone show a chaotic-reflection zone suggestive of a karstified bedrock low a general conductivity low and resistivity high which appear to be due to the absence of conductive overburden deposits, and a negative steaming potential that is interpreted as a downward flow of groundwat e r through the sand column in the fracture zone. Geophysical responses across the dense flanks indicate a general conductivity high and resistivity low associated with clays of the Hawthorn Formation and a zone of strong reflectors due to the presence of recrystallized limestone. Local geophysical response across the flanks show alternating conductivity highs and lows caused by clay filled fractures and limestone pinnacles. Closely-spaced terrain conductivity (EM 34 3) and very low frequency (VLF) tilt-

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82 angle measurements are rapid and accurate techniques for locating geophysical anomalies associated with photolinears. EM-34-3 data obtained using vertical dipoles and a 20-m coil separation correlate well with the VLF tilt-angle data (EM-16), and provide excellent resolution VLF tilt-angle data processed with the McNeill filter greatly improve the large-scale geologic interpretation Horizontal-electrical-profiling (HEP) data correlate well with the results of the electromagnetic methods, but required more time and personnel. The optimum-offset, seismic-reflection technique accurately delineated the large scale fracture, but small-scale resolution was insufficient for detailed stratigraphic interpretation. The use of self-potential and microgravity techniques were limited in this study; however, both methods provided useful data that assisted in the overall geologic interpretation. Ground-penetrating radar was not effective due to the high conductivity of the survey area. Geophysical responses obtained in this study are consistent with previous work performed in karst terrains. Van Nostrand and Cook (1966) obtain resistivity lows across clay-filled depressions in limestone bedrock. Butler (1980) observes microgravity and resistivity lows across clay-filled fractures in the Floridan Aquifer Moore and Stewart (1981) fmd a thickening of conductive overburden across photolinears in west-central Florida. Yager and Kappel (1987) show conductivity highs and VLF crossovers correspond to clay-filled fractures in the Lockport dolomite. Stewart and Wood (1991) suggest characteristic M -shaped gravity anomalies obtained across fracture zones in Florida are associated with a zone of lower bulk density flanked by more dense, recrystallized limestone

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83 Analysis of drawdown data from three observation wells during a seven-day, 11,700 m3 I day pumping test in the Floridan Aquifer yield average, late-time transmissivity and storativity values of 3,300 m2/day and 2 x 10 -3 respectively. Evaluation of the test data using an anisotropic analytical model (Papadopulos, 1965) indicates a late-time anisotropy ratio of 6 : 1 with the apparent major axis of anisotropy roughly perpendicular to the photolinears. Comparison of the field data and hypothetical modeling results suggests that the photolinear-related fractures at Pemberton Creek are not hydrologically significant relative to the pumping test and that structural or lithologic controls not associated with the photolinears are responsible for the observed drawdown response These controls may include cavernous porosity within the A von Park Formation (Stringfield, 1966) or a fracture trend not evaluated in this study (Menke, 1961). Future studies of photolinears in southwest-central Florida should use high density electromagnetic surveys as rapid reconnaissance techniques, and high-resolution, shallow, seismic reflection, or vertical-electric-sounding techniques to provide detailed stratigraphic information A distributed-parameter model that accounts for lateral and vertical variations in transmissivity within the Floridan Aquifer may be more appropriate for future evaluations of photolinears The geometry of the monitoring-well network and the placement of the pumping well in the geologic structure associated with the photolinear are critical for a definitive evaluation of the hydrologic significance of these features in the Floridan Aquifer.

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84 REFERENCES Barenblatt, G.B., Zheltov, I.P., Kochina, LN., 1960, Basic concepts in the theory of seepage of homogeneous liquids in fissured rocks, Jour. of Applied Mathematics and Mechanics, 24(5), p. 1286-1303. Bengtsson, T.O. Downing, Jr., H.C., Geurin K., J.S., 1986, The hydrologic effects from intense groundwater pumpage in east-central Hillsborough County, SWFWMD, Brooksville, Florida, 33 p. Blanchet, P .H., 1957, Development of Fracture Analysis as an exploration method, Am. Assoc. Petroleum Geologists Bull., Vol. 41, p 1748-1759. Bogoslovsky, V.A., and Ogilvy, A.A., 1969, Natural potential anomalies as a quantitative index of the rate of seepage from water reservoirs, Geophysical Prospecting, Vol. 18, p. 261-268. Bulter, D.K., 1980, Microgravity techniques for geotechnical applications, U.S. Army Engineer Waterways Experiment Station, Misc. Paper GL-80-13, 121 p. Corwin, R .F., and Hoover, D.B., 1979, The self-potential method in geothermal exploration, Geophysics, Vol. 44, p. 226-245 Corwin, R.F., 1986, Electrical resistivity and self-potential monitoring for ground water contamination, Proc. of surface and borehole geophysical methods and groundwater instrumentation, p. 203-214. Dobrin, M.B and Savit, C.H., 1988, Geophysical Prospecting, McGraw-Hill, N.Y., N.Y., 867 p. Eaton, G.P. and Watkins, J.S., 1970, The use of seismic refraction and gravity methods in hydrogeological investigations; Geol. Survey Canada, Economic Geol. Report 26, p. 544-568. Geonics Ltd., 1979, EM-16 and EM-16R Operating Manuals, Geonics Ltd., Mississauga, Canada, 37 p.

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GeoTrans, 1988, Northern district model project fracture zone delineation, Geotrans, project No. 55.3, Herndon, Virgina, 16p. Gilboy, A B., 1985, Hydrogeology of the Southwest Florida Water Management District, SWFWMD, Brooksville, Florida, 18 p. Hantush, M.S., 1964, Hydraulics of wells, In: Advances in hydroscience (V.T. Chow, editor), Vol. I, p. 281-432, Academic Press, New York and London. 85 Hunter, J A., Bums, R.A., Good, R L MacAulay, H.A., and Gagne, R.M., 1982a, Optimum field technical for bedrock reflection mapping with multichannel engineering seismograph, In: Current Research, Pt. B, Geol. Survey. Can., Paper 82-lB, p. 125-129. Jenkins, D.N., and Prentice, J.K 1982, Theory for aquifer test analysis in fractured rocks under linear (nonradial) flow conditions, Ground Water, Vol. 20, p. 12-21. Lattman, L.H., and Parizek, R.R., 1964, Relationship between fracture traces and the occurrence of groundwater in carbonate rocks, Jour. Hydro!., Vol. 2, p. 73-91. McDonald, M.G., and Harbaugh, A.W., 1988, A Modular three-dimensional, finite-difference ground water flow model, Techniques of Water-Resources Investigation 06-A1, USGS, 576 p. McNeill, J.D., 1980, Electromagnetic terrain conductivity measurement at low induction numbers, Technical Note-6, Geonics Ltd., Mississaugu, Canada, 15 p. McNeill, J.D., 1990, Personal communication. McNeill, J.D 1991, Advances in electromagnetic methods for groundwater studies, Geoexploration, Vol. 27, p. 65-80. McNeill, J.D., and Labson, V.F., 1991, Geological mapping using VLF radio waves, In: Electromagnetic Methods in Applied Geophysics, Investigations in Geophysics, No. 3 (M.N Nabighian, editor), Society of Exploration Geophysicists, Tulsa, Oklahoma, p. 521-640. Menke, C.G., Meredith, E.W., and Wetterhall, W.S., 1961, Water resources of Hillsborough County, Florida, Fla Geol. Survey RI-25, 91 p.

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Miller, J.A., 1986, Hydrogeologic Framework of the Floridan Aquifer System in Florida and in parts of Georgia, Alabama, and South Carolina, USGS Prof. Paper 1403-B. 91 p. Moore, D.L. and Stewart, M T., 1983, Geophysical signatures of fracture traces in a karst aquifer (Florida, USA), Jour. of Hydrol., Vol. 61, p. 325-340. Moore, D.M., 1980, Anisotropic analysis of a pumping test at Cross Bar Ranch Wellfield, unpublished report, SWFWMD, Brooksville, Florida, 7 p Negmann, R 1967, La gravimetric de haute precision-application aux recherches de cavities, Geophysical Prospecting, Vol. 15, p. 116-134. Papadopulos, I.S., 1965, Nonsteady flow to a well in a infinite anisotropic aquifer, Int. Assoc. Sci. Hydrol., Roches Fissures, proceedings Dubrovinik Symposium, p 21-31. Parasris, D.S., 1966, Mining geophysics, Elsevier Publ., Amsterdam, 356 p. Sato, M., and Mooney, H.M., 1960, The electrochemical mechanism of sulfide self potentials, Geophysics 25, p. 226-49. Schreuder and Davis, Inc., 1991, Pemberton Creek site well construction and aquifer testing, West Coast Regional Water Supply Authority, Clearwater, Florida, 63 p. Stewart, M.T., and Bretnall, R., 1986, Interpretation of VLF resistivity data for ground water contamination surveys, Groundwater Monitoring Review, Winter, p. 71-75. Stewart, M.T., and Stedje, D., 1990, Geophysical investigation of cypress domes, West Central Florida, SWFWMD, Brooksville, Florida, 103 p. Stewart, M.T., and Wood, J., 1991, Geologic and geophysical character of fracture zones in a tertiary carbonate aquifer, Florida, In: Geotechnical and Environmental Geophysics, Vol. 2, (S. Ward editor), Society of Exploration Geophysicists, Tulsa, Oklahoma, p. 235-243. Stringfield V.T., 1966, Artesian water in tertiary limestone in southeastern states, USGS Prof. Paper 517, 226 p. 86 Stringfield, V.T. Rapp, J.R., and Anders, R.B., 1979, Effect of Karst and geologic structure on the circulation of water and permeability in carbonate aquifers, Jour of Hydrol., Vol. 43, p. 313-332

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Telford W.M., Geldart, L.P., and Sheriff R.E., 1990, Applied Geophysics, Cambridge Univ. Press, N Y., N.Y ., 770 p. Theis C V., 1935, The relation between the lowering of the piezometric surface and the rate and duration of discharge of a well using ground-water storage Am. Geophys. Union Trans 16th Ann. Mtg pt. 2, p. 519 524. Van Nostrand, R.G., and Cook, K .L., 1966, Interpretation of resistivity data, USGS, Prof. Paper No 499, 310 p Vingoe, P. 1972, Geophysical memorandum S/72, ABEM Geophysics, Bromma, Sweden, 16 p Walton, W.C., 1987, Groundwater pumping tests ; des i gn and analysis Lewis Pub p.201. White W A. 1970, The geomorphology of the Florida Peninsula Fla. Geol. Survey Bull. No. 51, 164 p. Wolansky, R.M., and Corral, Jr., M.A., 1985 Aquifer tests in West-Central Florida, 1952-72, USGS Water-Resources Investigations Report, 84 4044, 127 p. Wright J L. 1988, VLF interpretation manual EDA Instruments Englewood Colorado 148 p. 87 Yag er, R M and Kappel, W.M., 1987 Detection and characterization of fractures and their relation to groundwater movement in the Lockport Dolomite Niagara County New York In: Pollution, risk assessment, and remediation in groundwater systems (R M Khanbilvardi and J. Fillos editors) p. 149-195.

PAGE 102

88 APPENDICES

PAGE 103

Appendix 1 : HLEM data Pemberton Creek 20 meter horizontal coils note: all distances normalized to T5 .. ...... : .. .... ....... .. .... c : : m8"s: .. :.:... .. : ... .; :.l.!_j _.: .. :.:.:i_. .. . :. : .. Ill : rileters' \ 111 1/1 0 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 48 51 54 57 60 63 66 69 72 75 78 81 84 87 90 93 96 99 101 104 107 110 113 116 119 122 125 128 131 22 21 20 21. 5 20.5 22 18.5 21. 5 19 19 20 19 17 16 17. 5 18 18. 5 19 19 20 21 18 19 17 17. 5 18 16. 5 17 17 16 14 5 17 5 18 18 19 19 19 19 18. 5 18. 5 16 0 3 6 9 13 16 16 12.5 19 12 22 13 25 13 28 15 31 15 34 15. 5 37 17 40 16 5 43 15 46 15 49 14 5 52 14 5 55 16 5 58 15 61 14 64 15 67 15 70 15 73 15 0 89

PAGE 104

Appendix 1: (continued) Pemberton Creek 20 meter horizontal coils note: all distances normalized to T5 134 16.5 76 16 3 137 15 79 1 6 5 6 140 15. 5 82 16.5 9 12 143 17 85 18. 5 12 9 146 16 88 18 15 10. 5 149 17 91 17 152 17. 5 94 16 155 19. 5 97 12. 5 158 19 100 8 161 19. 5 103 8 164 19. 5 106 6 167 18 109 6 170 18. 5 112 9 173 18 115 10. 5 176 17 118 13 179 15 121 14 182 12. 5 124 9 185 10 127 9 188 9 130 10.5 191 9 133 11 194 10 136 12. 5 197 13 139 13 200 15 142 10.5 203 15 145 12 206 15 148 10. 5 209 14 151 12 212 13 154 11 215 11.5 157 10 218 9 160 8 221 10 163 8 224 10 166 8 227 9 5 169 7 230 10 172 7 233 10 175 8 236 10.5 178 8 239 11 181 6 5 242 10.5 184 7 245 10 187 6 248 10.5 190 6 251 10.5 193 6 254 10 196 6 257 10.5 199 6 260 11 202 7 263 11 .5 205 7 266 10. 5 208 7 5 18 21 24 27 30 33 36 39 42 45 48 51 54 57 60 63 66 69 72 75 78 81 84 87 90 93 96 99 102 105 108 111 114 117 120 123 126 129 132 135 10. 5 10 10.5 7 10 10 10 10 10 9.5 9 5 10 11 5 10 10.5 11 10 11 11 12 11 9 5 11. 5 9 9 5 8.5 9 8 7.5 8.5 9 8 5 9 11 10. 5 11 11 11 12 13 90

PAGE 105

Appendix 1: (continued) ::Actual Pemberton Creek 20 meter horizontal coils note: all distances normalized toTS Actual. < Actual .. T4 .... >T?H .::: t : Station< . Sttltion < .. Conductivity < metfirs nisirneter meters ( 269 10. 5 211 9 138 14 272 9.5 214 9 141 15 5 275 8 217 9.5 144 15 5 278 8.5 220 10 147 15 281 7 223 11 150 19 284 8 226 11 153 13.5 287 8 229 12 156 11. 5 290 8 232 13 159 11 293 9 235 14 162 11 296 10 238 15 165 10 299 11 241 16 168 11 302 12 244 16 171 12 305 11 247 16 174 13 308 11 250 15 177 15 311 11. 5 253 14 5 180 16.5 314 11 256 14 183 18 317 12 259 14 5 186 20 320 12.5 262 15.5 189 22 323 13 265 19 192 21 326 13 268 19 195 21 329 12 5 271 22 198 22 332 13.5 274 23 201 22 335 15.5 277 24.5 204 20 5 338 15 280 23 207 18 341 16 283 27 210 18 344 16 286 26 213 17.5 347 16.5 289 24.5 216 17 350 16.5 292 25 219 16.5 353 17 295 22 222 17 356 16.5 298 21.5 225 15 5 359 15.5 301 23 228 15.5 362 17 304 24 231 16 365 15.5 307 27 234 17 368 16 310 28 237 19 371 18 313 30 240 22 374 21 316 32 243 13 377 22 319 32 246 24 380 22.5 322 30 249 23 383 23 325 28 252 21 386 22 328 26 255 1 7 389 21 331 26 258 15 392 24 334 28 261 14 395 22 337 24 264 14 398 21. 5 340 24 267 19 401 22 343 22 270 20 91

PAGE 106

Appendix 1: (continued) Actual :Station .meters 404 407 410 413 416 419 422 425 428 431 434 437 440 443 446 449 452 455 458 461 464 467 470 473 476 479 482 485 488 491 494 497 500 503 506 509 512 515 518 521 524 527 530 533 536 Pemberton Creek 20 meter horizontal coils note: all distances normalized to T5 .. =Ts .. cohtiuctivity 'mS/meier 21 18 19 5 18 21.5 19 22.5 21 23. 5 23 25.5 23 25 25 23 19.5 20 20 20.5 22.5 25 26 26 25 25 25 25.5 26 26 27 22. 5 24.5 25 24 28 25 25.5 29 28 27 30 26 28 26 29 ==Actuat ==T2 :::=Actual =staiioh ,: istalion = meters ,:: mS/meter = meters 346 20 273 349 20 276 352 22 279 355 25 282 358 28 285 361 29 288 364 30 291 367 30 294 370 31 297 373 30 300 376 26 303 379 382 385 388 391 394 397 400 403 406 409 412 415 418 421 424 427 430 433 436 439 442 445 448 451 454 457 460 463 466 469 472 475 478 26 24 22 21 20 24 22 26 29 32 37 36 37 34 28 28 26 22 19 18 16 20 22 24 30 34 36 37 37 35 32 26 23 18 306 309 312 315 318 321 324 327 330 333 336 339 342 345 348 351 354 357 360 363 366 369 372 375 378 381 384 387 390 393 396 399 402 405 T4 Conductivity mS/meter 24 23 24.5 22 25.5 20 22 22 21 22 19.5 18 19 16.5 18 17 18 18 19 22 18 22 20 20 19. 5 14 18 14 18 15 16 16 18 16 17 20 20 19 16 18 17 15 15 14 92

PAGE 107

Appendix 1 : (continued) ,.Actual ,-.meters 539 542 545 548 551 554 557 560 563 566 569 572 575 578 581 584 587 590 5 9 3 5 9 6 599 602 605 60 8 611 614 617 620 6 2 3 626 629 632 635 638 641 644 647 650 653 6 5 6 65 9 662 665 668 671 Pemberton Creek 20 meter horizontal coils note: all distances normalized to T5 .,,_>,--.,_-.:TS _, :Actual -,, ___ ,,. ,,,_T2 -. _. -,.:,::Actual T4 ) Station -::;conductivitY Station __ ,_ Conductivity \ hiet9 i s ,. mS/meter > ::mS/ineter meters mS/mete r 28 481 15 408 16 28 484 13 411 15 26 487 16 414 14 26 490 17 417 16 25 493 22 420 17 22 496 24 423 15 22 499 26 426 15 22 502 28 42Q 15 22 5 505 26 432 14 24 5 508 24 435 16 24 5 511 21 438 15 27 514 21 441 18 24 517 22 444 17 24 520 21 447 16 24 523 19 450 18 23 526 20 453 16 19 529 18.5 456 18 21 532 16.5 459 17 17. 5 535 1 8 462 16 18.5 538 18 465 17 20 541 19.5 468 17 22 544 19.5 471 17 24 547 18 474 16 23 550 18.5 4n 18 25 553 17 5 480 16 23 556 17 483 16 22 5 559 14 486 18 20 562 17 5 489 18 19. 5 565 1 6 492 18 19 568 21 495 18 18 57 1 15 5 498 18 18. 5 574 17 5 501 18 21 5n 18 -1 9 5 580 16 --21 583 18 -23 586 17.5 -23 589 16 5 --22 592 16 5 -23 595 16 -20 598 14 5 -20 601 14 --18. 5 604 14 --16 607 13 -1 5 610 14 --16 613 17 -93

PAGE 108

Appendix 1: (continued) (-Actual .. /:Station .. meters 674 677 680 683 686 689 692 695 698 701 704 707 710 713 716 719 722 725 728 731 734 737 740 743 746 749 752 755 758 761 764 767 Pemberton Creek 20 meter horizontal coils note: all distances normalized to T5 14 5 616 15 14 619 17 16 622 18 15 625 17 5 16 628 19 20 631 18 22 634 19 23 637 18 22 640 19 21 643 19 646 19 649 19 652 18 655 18 658 18 661 17 664 18 667 17. 5 670 15 673 19. 5 676 19 679 19 682 17. 5 685 18 688 19.5 691 17 694 17 697 17.5 700 17 703 16 706 16 709 16.5 T4 Conductivity I mS/meter 94

PAGE 109

Appendix 1: (continued) Pemberton Creek 40 meter horizontal coils note: all distances normalized toTS
PAGE 110

Appendix 1: (continued) Pemberton Creek 40 meter horizontal coils note: all distances normalized toTS ::Nomalized ... Nomalized :: Actual =T2-.. ::>-station } station .... :\ : .. Station .!conductivity .. .. -, .. -.: meters-:::= .. mS/me ier .=meters :: meters 361 302 16 499 440 10 364 305 12 502 443 11 367 308 14 505 446 16 370 311 12 508 449 18 373 314 12.5 511 452 20 376 317 18 514 455 18 379 320 15 517 458 20 382 323 15 5 520 461 19 385 326 15 523 464 22 388 329 16 526 467 18 391 332 13 529 470 16 394 335 10 532 473 14 397 338 10 535 476 16 400 341 11 538 479 10 403 344 10 541 482 11 406 347 13 544 485 14 409 350 12 547 488 10 412 353 15 550 491 10 415 356 14 553 494 10 418 359 16 556 497 10 421 362 16 559 500 12 424 365 18 562 503 13 427 368 18 565 506 14 430 371 18 568 509 13 433 374 17 571 512 14 436 377 18 574 5 1 5 14 439 380 16 577 518 12 442 383 15 580 521 12 445 386 11 583 524 12 448 389 1 1 586 527 12.5 451 392 14 589 530 11.5 454 395 14 592 533 12 5 457 398 15 595 536 13 5 460 401 15 598 539 12 463 404 18 601 542 14 466 407 17 604 545 14 469 410 18 607 548 13.5 4 7 2 413 17 610 551 17 475 416 18 613 5 54 17 478 419 16 616 557 16 481 422 14 619 560 18 484 425 12 622 563 16 487 4 2 8 9 625 566 17 5 490 431 10 628 569 17 493 434 9 631 572 20 5 4 9 6 437 10 634 575 16 96

PAGE 111

Appendix 1: (continued) Pemberton Creek -40 meter horizontal coils note: all distances normalized to T5 : Nomalized ::-;.: Actual:. Nomalized .. . .... : ... :T2 ':; ... :.: . :o ... .o:Actual ::station iSfation COfidi.Jc_ tivity:."' :::Station : / Station ponductivitY meters ,. ... \:meter s .. :: mS.Lmeter meters = mS/meter ..'meters 637 578 16 709 650 10 640 581 15 712 653 10 643 584 14 715 656 9 646 587 14 5 718 659 8 649 590 14 721 662 12. 5 652 593 14 724 665 10 655 596 13. 5 727 668 11 658 599 12 5 730 671 9 661 602 13.5 733 674 11 664 605 13 736 677 10.5 667 608 12.5 739 680 9 670 611 11 742 683 13 673 614 11 745 686 11.5 676 617 12 5 748 689 12. 5 679 620 15. 5 751 692 10 682 623 12 754 695 12 685 626 12 5 757 698 12. 5 688 629 12 760 701 11 691 632 14 763 704 12 694 635 14 5 7 66 707 12. 5 697 638 12 769 710 12. 5 700 641 11 772 713 11 703 644 12 775 716 11 706 647 11. 5 778 719 11 97

PAGE 112

Appendix 2: VLF data :.ActuOII. ::. 'station' meters 0 6 12 18 24 30 36 42 48 54 60 66 72 78 84 90 96 102 108 114 120 126 132 138 144 150 156 162 168 174 180 186 192 198 204 210 216 222 228 234 240 246 252 258 264 270 Pemberton Creek VLF Tilt Angle Data note: all distances normalized toTS :: :Actua l T2 :.:Actual :: station : :station ':dearees ' :meters -2 -1 0 -0. 5 1 1.5 3 2 0 -18 2 5 6 -14 1.5 12 -14 1 18 18 1 24 -20 0.5 30 -19.5 0 36 -16 0 42 -16 -1. 5 48 -14. 5 -1 54 -11. 5 0 5 60 -7 0 66 -5. 5 0 5 72 -2 0 0 78 4 6 -1 84 6 5 12 -2 90 8 5 18 -2 96 9.5 24 -1.5 102 6 30 -1.5 108 3 36 -1 114 -4.5 42 -5 120 -6. 5 48 -8.5 126 -15 54 -13 132 -18 60 -17. 5 138 -19 66 -18. 5 144 -20 72 -17 150 -18 78 -15 156 -13. 5 84 -13 162 -12. 5 90 -11 168 -6. 5 96 -8 174 -4 102 -6. 5 180 1 108 -3 1 86 2 5 114 1 5 192 3 5 120 0 198 8 126 2 204 10 132 5 210 14 138 98 T4 Tilt angle dearees -3. 5 -3. 5 -2. 5 1 5 0 0 1 0 5 -1 -0. 5 -1 0 5 0 0 5 1 5 6 5 7 8 5 6 5 6 7 7 7 5 9 5

PAGE 113

Appendix 2: (continued) Pemberton Creek VLF Tilt Angle Data note: all distances normalized to T5 H' : / T S:. : .. } /' Actual <'. ... 'J"2 .. . .. Actual ... m .. _8 ters. . ..' .... _.' .. : .. .,. .. Station : : 'Tilt ari9te : \ station meters:):\ .decrees : meters 276 5 216 16. 5 144 282 4 222 16 150 288 3 5 228 17 156 294 2 5 234 17.5 162 300 3 240 19 168 306 4 5 246 17 174 312 6 252 14. 5 180 318 9 258 10 186 324 10 264 10 192 330 10. 5 270 10 198 336 12. 5 276 9 5 204 342 13. 5 282 10 210 348 14 288 12. 5 216 354 14 294 9 222 360 11.5 300 7 5 228 366 9 306 3 234 372 7 5 312 4 240 378 4 5 318 2 5 246 384 4 5 324 3 5 252 390 3 5 330 3 258 396 4 336 3 5 264 402 4 342 1 270 408 3 348 1 276 414 2 354 0 282 420 1 360 -0. 5 288 426 2 5 366 2 294 432 2 372 1 5 300 438 3 5 378 3 306 444 5 384 -1 312 450 4 390 1 318 456 3 396 0 5 324 462 1 5 402 -2 330 468 2 408 -1 336 474 3 414 4 342 480 4 5 420 4 348 486 4 5 426 3 354 492 6 432 2 360 498 5 438 -1. 5 366 504 3 5 444 3 5 372 510 3 5 450 -4. 5 378 516 3 5 456 -2 384 522 3 462 0 390 528 3 5 468 1 5 396 534 5 5 474 1 402 540 4 480 -2 408 546 4 486 -4 414 T4 Tilt.: angle dearees 10 11 11 10. 5 10 6 5 4 4 5 4 5 4 3 5 5.5 6 4 3 3 5 6 7 5 5 5 6 5 3 5 0 5 0 5 1 5 -1. 5 1 5 2 5 -2 4 5 -2 -2 -2 -2 -2 -2. 5 -2. 5 -2 -3 -3 -3. 5 -2 2 5 -1.5 0 5 0 99

PAGE 114

Appendix 2: (continued) Pemberton Creek VLF Tilt Angle Data note: all distances normalized to T5 100

PAGE 115

Appendix 3: Direct-Current Resistivity data Pemberton Creek DC resistivity Wenner array a=30m note: all distances are normalized to T5 101 i::;i!iil: ::. I :.:::::: .. :.;.: ... : olim? meters i .. 50 59. 0 60 60 9 0 70 57.7 10 80 60.3 20 90 66.5 30 100 73. 3 40 110 76.7 50 65.6 120 67.5 60 127.6 130 79.4 70 93. 9 0 140 65. 2 80 114.2 10 150 62.0 90 122.0 20 160 69.9 100 95.2 30 170 76.2 110 66. 5 40 180 74. 5 120 86.0 50 167.6 190 156.8 130 125.2 60 68.4 200 122.3 140 165.5 70 118.8 210 141.6 150 179.6 80 64. 1 220 170.8 160 179.1 90 142. 1 230 122.7 170 175.5 100 101.4 240 106.7 180 186.4 110 127. 2 250 100.3 190 144. 8 120 107.1 260 104. 6 200 208.5 130 107. 1 270 141.0 210 188. 3 140 83. 3 280 172.3 220 191 1 150 73.3 290 137.0 230 186.2 160 95.4 300 120 8 240 157 6 170 72. 2 310 114.0 250 99.0 180 39.2 320 115 5 260 76.0 190 78.4 330 84. 4 270 65.4 200 81.1 340 110.1 280 60.9 210 63.3 350 109.0 290 64.5 220 58.6 360 91. 0 300 71.6 230 57. 9 370 82. 7 310 68.2 240 57.9 380 161.2 320 66. 2 250 59. 0 390 93. 9 330 70.9 260 50. 5 400 95.2 340 86.0 270 44. 7 410 164.0 350 142.1 280 49.2 420 83.5 360 78.8 290 53. 9

PAGE 116

Appendix 3: (continued) Pemberton Creek DC resistivity Wenner array a=30m note: all distances are normalized to T5
PAGE 117

Appendix 4: Self-Potential data Pemberton Creek SelfPotential Distances normalized to TS 60 0 177 117 63 3 -40.5 180 120 66 6 -13 183 123 69 9 2 186 126 72 12 5 189 129 75 15 0 5 192 132 78 18 2 195 135 81 21 7 198 138 84 87 90 93 96 99 102 105 108 111 114 117 120 123 126 129 132 135 138 141 144 147 150 153 156 159 162 165 168 171 174 24 27 30 33 36 39 42 45 48 51 54 57 60 63 66 69 72 75 78 81 84 87 90 93 96 99 102 105 108 111 114 -1 1 3 -3. 5 -3 -1. 5 1 13 11. 5 16. 5 17. 5 29 5 26.5 29 26 17. 5 13. 5 12 16 14. 5 16 5 16 9 5 12. 5 9 5 12.5 15 5 3.5 5 -14.5 -4. 5 201 204 207 210 213 216 219 222 225 228 231 234 237 240 243 246 249 252 255 258 261 264 267 270 273 276 279 282 285 288 291 141 144 147 150 153 156 159 162 165 168 171 174 177 180 183 186 189 192 195 198 201 204 207 210 213 216 219 222 225 228 231 mVolts 2 3.5 7.5 13 1 -3 -17 -10.5 -12.5 25. 5 -3 -13.5 -11. 5 -8. 5 -16 -12 -20 -21.5 -18.5 -18.5 -18 -20.5 -25 -17.5 -24 -33.5 9 -21 -28.5 -25 -19 -15.5 -17.5 -26.5 -29. 5 -41 -43 -35 -26. 5 103

PAGE 118

Appendix 4: (continued) Pemberton Creek Self-Potential Distances normalized to TS actual 1 . .:\.,: ::.. :actual :.. :.[:: i2'stiilcih .. :. ::::: ': i.:. :.::): : ::. .:;r2:,;taiioo :8taiior. ::.: ::meter$: .. .:. ... .. : .. .:-::!ili:ltiOO:t ::-: . ::\meters 294 234 -14.5 411 351 297 237 -17. 5 414 354 300 240 -14.5 417 357 303 243 3 5 420 360 306 246 -17 423 363 309 249 -13. 5 426 366 312 252 -9.5 429 369 315 255 -33. 5 432 372 318 258 -6. 5 435 375 321 261 -10 438 378 324 264 -2. 5 441 381 327 267 7 444 384 330 333 336 339 342 345 348 351 354 357 360 363 366 369 372 375 378 381 384 387 390 393 396 399 402 405 408 270 273 276 279 282 285 288 291 294 297 300 303 306 309 312 315 318 321 324 327 330 333 336 339 342 345 348 5 5 -3. 5 -7. 5 -3. 5 -5. 5 16 -8.5 -3.5 -7.5 -23. 5 -4. 5 -8. 5 5 9 -6 -13. 5 -30. 5 -30. 5 3 -15 -12. 5 2 -3 4 5 -20 5.5 -5.5 447 450 453 456 459 462 465 468 471 474 477 480 483 486 489 492 495 498 501 504 507 510 513 516 519 522 525 387 390 393 396 399 402 405 408 411 414 417 420 423 426 429 432 435 438 441 444 447 450 453 456 459 462 465 mVolts -6.5 -7.5 -6.5 8 -13 -1.5 -3.5 -1 1 -6 -16. 5 8 5 9 13 11 -8.5 6 7.5 7 0 0 5 -11.5 -13. 5 -12.5 -4. 5 2 5 8 2 13 6 4.5 12. 5 0 3.5 7 8 14. 5 10 11 104

PAGE 119

Appendix 4: (continued) Pemberton Creek SelfPotential Distances normalized to T5 528 468 531 471 534 474 18 5 537 477 5.5 540 480 10 543 483 9 546 486 14 549 489 11.5 552 492 13 5 555 495 -0.5 558 498 105

PAGE 120

Appendix 5: Gravity data W! e !I r 1 tl ,AAaa j I i. + a if! 111 it' II I! 106 ,, .. ................. -..................................... .................... .. t 3 : t : 8!!111 f!;ttfll i It I I I I I j i j

PAGE 121

107 Appendix 6: Pumping-Test data AVON PARK MONITOR WELL Corrected Drawdown Client: WCRWSA Location: Pemberton Creek (S20!f28S/R21 E) Date : 11-Dec-1990 to 18-Dec-1990 Open Interval: -565 to -800 (ft BLS*) Elapsed Corrected Water Time Level Drawdown (minutes) (feet) 0.27 0 09 0.33 0 23 0.50 0.40 0.67 0 26 0 .83 0.51 1 00 0 47 1.17 0.48 1 .33 0 62 1.50 0 53 1.67 0 57 1.83 0.67 2 .00 0.62 2.17 0 67 2.33 0 72 2 50 0 68 2.67 0 73 2 .83 0 77 3 00 0 74 3.17 0 .81 3.33 0.80 3.50 0.81 3.67 0.85 3.85 0 85 4.00 0.86 4.17 0.88 4 .33 0.89 4.50 0 .91 4.67 0.92 4.83 0 93 5 00 0 95 5.17 0 96 5 33 0 97 5.50 0 .98 5 67 0 99 5.83 1 .01 6.00 1 02 6.17 1 02 6.33 1 04 Pumped Well and Distance : APTPW 392ft Pump On: 8 :00AM 11-Dec-1990 Pump Off: 8 :00AM 18-Dec-1990 Avg Pumping Rate: 2150 gpm Measurement Method: Stevens Type F Elapsed Corrected Water Time Level Drawdown (minutes) (feet) 6 .50 1 .05 6 .67 1.06 6.83 1.07 7 00 1 08 7 .17 1 .09 7 33 1 .10 7 50 1 .11 7 83 1 .13 8 00 1 14 8 .17 1 15 8.33 1 16 8 .50 1.17 8 67 1 17 8 .83 1.18 9 00 1.19 9.17 1 .21 9 .33 1.22 9 50 1 22 9 .67 1.22 9 83 1 .23 10 .00 1 24 10 .50 1 27 11. 00 1.29 11.50 1.32 12. 00 1 33 12.50 1.35 13. 00 1.37 13. 50 1 .40 14. 00 1.42 14. 50 1.43 15 00 1 .45 16. 00 1 .49 17. 00 1 .52 18 .00 1 56 19 .00 1 .59 20 00 1 .62 21.00 1 .65 22 00 1 68

PAGE 122

Appendix 6: (continued) Elapsed Time (minutes) 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 42 44 46 48 50 52 56 58 60 65 70 75 80 85 90 95 100 105 110 115 120 130 140 153 160 170 180 AVON PARK MONITOR WELL Corrected Drawdown (continued) Corrected Water Level Drawdown (feet) 1 .72 1 .75 1 .76 1.79 1 .82 1 .84 1.87 1 .90 1 .92 1 .94 1 .96 1 .98 2 .01 2 .02 2 .05 2 .06 2 .09 2.11 2 .14 2 .17 2 .21 2 25 2 28 2 .31 2 .37 2 .40 2.43 2.50 2 .56 2 .61 2.68 2 .72 2 77 2 .82 2 .87 2 .91 2 95 2 99 3 .03 3 10 3 18 3 26 3 .31 3 .36 3 .42 108 Elapsed Corrected Water nme Leve l Drawdown (minutes) (feet) 210 3 .58 240 3 .72 270 3 .83 300 3.94 330 4.06 360 4 .14 390 4.20 417 4 .37 560 4.94 672 5 .16 787 5.39 902 5 .52 1052 5 .62 1140 5 6 7 1260 5 .73 1380 5 .77 1570 5.83 1744 5 .87 1928 5.87 2 105 5.97 2289 6 .05 2466 6 .08 2651 6.05 2825 6 .08 2905 6 .09 3066 6 11 3242 6 .09 3430 6.19 3613 6.33 3810 6 .36 3966 6 .34 4146 6 .27 4335 6.28 4515 6 .35 4680 6.34 4832 6 .35 4912 6.38 4954 6 .40 5041 6 .42 5100 6 .43 5186 6 .45 5280 6 .47 5406 6 .48 5585 6 .53 5768 6 .55

PAGE 123

Appendix 6: (continued) AVON PARK MONITOR WELL Corrected Drawdown (continued) Elapsed Corrected Water Time Level Drawdown lminutesl (feet) 5768 6.72 5946 6.76 6122 6 .83 6313 6.96 6477 6 .96 6679 6.99 6849 6 .91 7024 6.81 7203 6.81 7382 6.85 7565 6.87 7732 7.05 7916 7.03 8106 7.06 8287 6.96 8470 6 .82 8646 6.77 8818 6.78 8997 6.76 9187 6.92 9369 6.95 9546 6.99 9725 6.96 9910 6.85 10080 6.83 109

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Appendix 6 : (continued) OCALA MONITOR WELL Corrected Drawdown Client: WCRWSA Location : Pemberton Creek {S20{T28S/R21 E) Date : 11-Dec-1990 to 18-Dec-1990 Open Interval : 250 to -450 {ft BLS*) Elapsed Corrected Water Time Level Drawdown (mi nutes) (feet) 1 0 08 2 0 15 3 0 28 4 0 38 5 0 46 6 0 .54 7 0 59 8 0 65 9 0 70 10 0 75 11 0 80 12 0 .84 13 0 88 14 0 .92 15 0.96 16 0 98 17 1 .02 18 1 06 19 1 09 20 1 .11 21 1 15 22 1. 18 23 1 20 24 1 .23 25 1 26 26 1 28 27 1 30 28 1 33 29 1 35 30 1 37 35 1 48 40 1 58 45 1 67 50 1 75 55 1 83 60 1 90 70 2 .03 80 2.15 Pumped Well and D istance: APTPW 399ft Pump On: 8 :00AM 11-Dec-1990 Pump Off: 8 :00AM 18-Dec-1990 Avg Pumping Rate : 2150 gpm Measurement Method: Stevens Type F Elapsed Corrected Water Time Level Drawdown (minutes) jfeet t 90 2 .23 100 2 .31 110 2 .41 120 2 .49 130 2.56 140 2.64 151 2 .71 160 2.76 170 2.81 180 2 .87 210 3 .02 240 3 15 270 3 .27 300 3 .39 330 3 .48 360 3 .57 390 3 .64 400 3 .67 430 3 .76 574 4 .22 662 4 .43 772 4 .68 922 4 .84 1042 4 .96 1150 5 .05 1272 5.09 1390 5 .13 1579 5 1 7 1753 5.19 1955 5 .26 2120 5 .33 2311 5 .39 2488 5.42 2660 5 .43 2841 5 .45 2913 5 .46 3070 5 .47 3245 5 .45 110

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Appendix 6: (continued) OCALA MONITOR WELL Corrected Drawdown (continued) Elapsed Corrected Water Time Level Drawdown (minutes) (feet) 3441 5 .52 3627 5.67 3801 5 .72 3982 5 .69 4161 5.63 4344 5 .65 4521 5 .70 4710 5 .75 4871 5.78 5159 5.85 5228 5.87 5420 5 91 5604 5.95 5781 6.00 5959 6 .04 6138 6.08 6330 6 .13 6513 6.13 6668 6 .15 6856 6.10 7027 6 .01 7214 6.00 7394 6 .03 7576 6.03 7745 6 .18 7929 6.18 8126 6.19 8303 6 .11 8487 5 99 8649 5 95 8820 5 .94 9003 5 .91 9190 6 .03 9372 6 07 9562 6.11 9740 6 08 9924 5 99 10080 5 96 111

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Appendix 6 : (continued) TAMPA-22 WELL Corrected Drawdown Client: WCRWSA Location : Pemberton Creek (S20/T28S/R21 E) Date : 11-Dec-1990 to 18-Dec-1990 Open Interval: -310 to -800 (ft BLS*) Elapsed Corrected Water Time Level Drawdown lminutes) (feet) 0 5 0.06 1 0 0.18 1 5 0 26 2 0 0 33 2 5 0 43 3 0 0 48 3 5 0.55 4 0 0.59 4 5 0 64 5 0 0 68 5 5 0 73 6 0 o n 6 5 0 .81 7 0 0 84 7.5 0 88 8 0 0 92 8.5 0.95 9.0 0.97 9.5 0 99 10 0 1 04 13.0 1 18 14. 0 1 .21 15.0 1 26 16.0 1 29 17 0 1 34 18.0 1 36 18.5 1.38 19.0 1 40 20 0 1 .44 21.5 1 48 22.0 1.49 23.0 1.53 24.0 1.56 25.0 1 58 26.0 1.62 27 0 1.64 28.0 1 66 29.0 1.69 Pumped Well and Distance : APTPW, 600ft Pump On : 8 :00AM 11-0ec-1990 Pump Off : 8:00AM 18-Dec-1990 Avg Pumping Rate : 2150 gpm Measurement Method : Stevens Type F Elapsed Corrected Water Time Level Drawdown (minutes) (feetl 30 1 .71 35 1 .83 36 1 85 40 1.94 45 2 .03 50 2 .11 55 2 .19 60 2 27 75 2 46 85 2 57 95 2 67 105 2 76 115 2 85 125 2 .92 135 3 00 145 3 .06 155 3 .13 165 3 19 175 3 25 185 3 .29 215 3 45 245 3 59 275 3 .71. 305 3 8 2 33 5 3 .92 365 4 .01 395 4.08 420 4 .20 515 4 .58 565 4 .68 668 4 .92 78 2 5.15 906 5 35 1023 5.41 1143 5 .46 12 6 6 5 52 138 5 5 54 1573 5 60 112

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Appendix 6: (continued) Elapsed Time (minutes) 1748 1931 2108 2292 2472 2645 2828 2921 3073 3248 3432 3615 3798 3971 4148 4350 4526 4703 4862 5044 5215 5409 5588 5771 5949 6127 6318 6499 6664 6863 7032 7205 7384 7567 7734 7918 8112 TAMPA-22 WELL Corrected Drawdown (continued) Corrected Water Elapsed Level Drawdown Time (feet) (minutes) 5.63 8209 5 69 8473 5 79 8651 5 .87 8821 5 .88 9004 5.89 9193 5.91 9376 5.93 9549 5 .92 9728 5.91 9912 6 .03 10080 6 .17 6.20 6 .18 6 .11 6 .13 6 .18 6 .16 6 .20 6.25 6.30 6 .35 6.40 6.45 6 .50 6 .55 6.60 6.60 6 .63 6 .54 6.45 6.44 6 .46 6 .47 6 .65 6.64 6 .63 113 Corrected Water Level Drawdown (feet)_ 6 .55 6.41 6 .35 6 .39 6 .34 6.49 6.53 6 .56 6 .51 6 .43 6 .42

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Appendix 6 : (continued) Elapsed Time (minutes) 0 2 17 4 6 8 10 .33 12 14 16 18 20 22 24 26 28 30. 33 35 40. 50 45 50 55 61 70. 50 81. 50 92 102 112 122 130 151 50 1 60 170 180 190 213 243 273 TAMPA-23 WELL Unco r rected Drawdown Uncorrected Elapsed Drawdown Time (feet) (minutes) 0 1586 0 .00 1758 0 .01 1934 0 .01 2115 0 .02 2298 0 .03 2479 0 .03 2640 0 .03 2833 0 .04 2924 0.04 3078 0.05 3253 0 06 3436 0.06 3621 0 .06 3793 0 07 3993 0.07 4148 0.08 4357 0 09 4530 0.10 4705 0 .11 4865 0 .12 5048 0.13 5220 0 15 5413 0.17 5593 0 19 5775 0.21 5955 0 23 6131 0 26 6322 0.28 6504 0 .32 6698 0.34 6871 0 36 7038 0.38 7208 0 .39 7388 0 45 7572 0 .51 7738 0 56 7923 114 Unc orrec ted Draw down (feet) 1 .89 1.94 2.01 2.13 2.20 2 23 2.23 2 27 2.29 2 .31 2.27 2.36 2 46 2.51 2.52 2.51 2 .53 2 56 2 57 2 .75 3 23 3 48 3 43 3.31 3.21 3.15 3.06 3.06 3.13 3 .14 3 .11 3.05 3 .03 3.04 3.01 3.08 3 .14

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Appendix 6 : (continued) Elapsed Time {minutes) 302 333 364 394 426 540 672 787 910 1031 1137 1258 1379 TAMPA-23 WELL Un c orrected Drawdown Uncorrected Elapsed Drawdown Time (feet) (minutes) 0 .61 8118 0 66 8297 0 .71 8478 0 76 8657 0 .81 8824 1 .01 9008 1 .22 9198 1 37 9381 1 48 9554 1 53 9732 1 .63 9917 1 68 10080 1.76 115 Uncorrected Drawdown {feet) 3 16 3.13 3.05 3 .01 2 .98 2 .93 3 .02 3 .12 3 .17 3 16 3 09 3.07


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