Regional Evaluation of the Hydrogeologic Framework, Hydraulic Properties, and Chemical Characteristics of the Intermediate Aquifer System Underlying Southern West-Central Florida

By Lari A. Knochenmus

Prepared in cooperation with the Southwest Florida Water Management District

Scientific Investigations Report 2006-5013

U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior Dirk Kempthorne, Secretary U.S. Geological Survey P. Patrick Leahy, Acting Director

U.S. Geological Survey, Reston, Virginia: 2006

For product and ordering information: World Wide Web: http://www.usgs.gov/pubprod Telephone: 1-888-ASK-USGS For more information on the USGS--the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment: World Wide Web: http://www.usgs.gov Telephone: 1-888-ASK-USGS

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report.

Suggested citation: Knochenmus, L.A., 2006, Regional Evaluation of the Hydrogeologic Framework, Hydraulic Properties, and Chemical Characteristics of the Intermediate Aquifer System Underlying Southern West-Central Florida: U.S. Geological Survey Scientific Investigations Report 2006-5013, 52 p. iii

Contents

Abstract...... 1 Introduction...... 2 Purpose and Scope...... 3 Description of the Study Area...... 3 Hydrologic Data Sources...... 3 Acknowledgments...... 4 Definitions and Terms...... 5 Geologic Framework...... 6 Depositional History...... 6 Stratigraphy...... 7 Hydrogeologic Framework...... 10 Evolution of Hydrogeologic Unit Nomenclature...... 11 Properties of the Aquifers Overlying and Underlying the Intermediate Aquifer System...... 11 Intermediate Aquifer System...... 13 Permeable Units...... 15 Zone 1...... 15 Zone 2...... 15 Zone 3...... 20 Confining Units...... 22 Clay Beds...... 22 Leakance Across Confining Units...... 23 Hydraulic Head Differences...... 26 Regional Evaluation of the Intermediate Aquifer System...... 31 Summary...... 35 Selected References...... 37 List of ROMP Reports...... 38 Appendix 1A-B. (A) Major ion data and (B) Pie charts showing major ion composition of water samples from wells at selected Regional Observation and Monitoring-well Program (ROMP) sites, 2001...... 41-48 Appendix 2A-B. Water levels in and differences among zones and adjacent aquifers at selected Regional Observation and Monitoring-well Program (ROMP) sites, (A) April 2001 and (B) October 2001...... 49-52 iv

Figures

1-2. Maps showing: 1. Location of the study area, selected Regional Observation and Monitor-well Program (ROMP) sites, and lines of sections in southern west-central Florida...... 2 2. Physiography of the study area in southern west-central Florida...... 4 3. Graph showing representative Stiff diagram...... 5 4. Chart showing series, past and present stratigraphic unit nomenclature, and hydrogeologic units...... 6 5. Maps showing the early Miocene to Pliocene sediment patterns in Florida...... 7 6. Sections showing stratigraphy, aquifer, and open-hole intervals of wells at selected Regional Observation and Monitoring-well Program sites ...... 8-9 7. Chart showing hydrogeologic units in this study compared with those in previous reports...... 12 8. Sections showing stratigraphy, aquifer, open-hole interval, clay beds, and potential flow direction at selected Regional Observation and Monitoring-well Program sites...... 16-17 9-11. Maps showing Regional Observation and Monitor-well Program well locations, transmissivity values, and Stiff diagrams for: 9. Zone 1...... 19 10. Zone 2...... 20 11. Zone 3...... 21 12-17. Maps showing: 12. Percentage of clay in the Hawthorn Group sediments...... 22 13. Leakance values, in foot per day per foot, shown on sections and maps at selected Regional Observation and Monitor-well Program sites...... 24-25 14. Recharge and discharge areas and magnitude of water-level differences between the surficial aquifer system and the Upper Floridan aquifer during the wet and dry seasons, 2001...... 26 15. Water-level differences during the wet and dry seasons, 2001...... 27-28 16. Flow potential category and representative water-level hydrographs...... 29 17. Distribution of water types in Zones 1, 2, and 3...... 31 18. Graph showing boxplots of transmissivity...... 32 19. Maps showing permeability subregions and transmissivity ranges in Zones 1, 2, and 3...... 34-35

Tables

1. Regional Observation and Monitoring-well Program well identification, site characteristics, construction information, and zone specification...... 13-14 2. Transmissivity values for the intermediate aquifer system...... 18 3. Leakance values at selected Regional Observation and Monitor-well Programs sites...... 23 

Conversion Factors and Datums

Multiply By To obtain square mile (mi2) 2.590 square kilometer foot per day (ft/d) 0.3048 meter per day foot squared per day (ft2/d) 0.09290 meter squared per day foot per day per foot [(ft/d)/ft] 1.00 meter per day per meter inch per year per foot [(in/yr)/ft] 83.33 millimeter per year per meter

*Transmissivity: The standard unit for transmissivity is cubic foot per day per square foot times foot of aquifer thickness [(ft3/d)/ft2]ft. In this report, the mathematically reduced form, foot squared per day (ft2/d), is used for convenience. Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 (NGVD 29). Altitude, as used in this report, refers to distance above the vertical datum.

Acronyms and Additional Abbreviations

FGS Florida Geological Survey IQR interquartile range > greater than > greater than or equal to < less than LPZ lower permeable zone ROMP Regional Observation and Monitoring-well Program SWFWMD Southwest Florida Water Management District SWUCA Southern Water Use Caution Area TR SWFWMD ROMP transect wells UPZ upper permeable zone USGS U.S. Geological Survey

Regional Evaluation of the Hydrogeologic Framework, Hydraulic Properties, and Chemical Characteristics of the Intermediate Aquifer System Underlying Southern West-Central Florida

By Lari A. Knochenmus

Abstract to < 20 percent (southern part) of the study area. Zone 2, the only regionally extensive zone, is characterized by moderately Three major aquifer systems—the surficial aquifer low permeability. Zone 3 is found in about 50 percent of the system, the intermediate aquifer system, and the Floridan study area, has the highest transmissivities, and generally is in aquifer system—are recognized in the approximately 5,100- good hydraulic connection with the underlying Upper Floridan square-mile southern west-central Florida study area. The aquifer. In parts of the study area, particularly in southwestern principal source of freshwater for all uses is ground water Hillsborough County and southeastern De Soto and Charlotte supplied from the three aquifer systems. Ground water from Counties, Zone 3 likely is contiguous with and part of the the intermediate aquifer system is considered only moderately Upper Floridan aquifer. abundant compared to the Upper Floridan aquifer, but it is an Transmissivity of the intermediate aquifer system ranges important source of water where the Upper Floridan aquifer over five orders of magnitude from about 1 to more than 2 contains water too mineralized for most uses. In the study 40,000 feet squared per day (ft /d), but rarely exceeds 10,000 2 area, the potential ground-water resources of the intermediate ft /d. The overall transmissivity of the intermediate aquifer aquifer system were evaluated by regionally assessing the system is substantially lower (2 to 3 orders of magnitude) than vertical and lateral distribution of hydrogeologic, hydraulic, the underlying Upper Floridan aquifer. Transmissivity varies and chemical characteristics. vertically among the zones within the intermediate aquifer Although the intermediate aquifer system is considered system; Zone 2 has the lowest median transmissivity (700 ft2/d), a single entity, it is composed of multiple water-bearing zones Zone 1 has a moderate median transmissivity (2,250 ft2/d), separated by confining units. Deposition of a complex assem- and Zone 3 has the highest median transmissivity (3,400 ft2/d). blage of carbonate and siliciclastic sediments during the late Additionally, the transmissivity varies geographically (from Oligocene to early Pliocene time resulted in discontinuities site to site) within a zone. Specifically, a region of relatively that are reflected in transitional and abrupt contacts between low transmissivity (< 100 ft2/d) throughout the vertical extent facies. Discontinuous facies produce water-bearing zones that of the intermediate aquifer system is present in the central part may be locally well-connected or culminate abruptly. Changes of the study area. This low transmissivity region is encom- in the depositional environment created the multilayered inter- passed by a larger region of moderately low transmissivity mediate aquifer system that contains as many as three zones (< 1,000 ft2/d) that covers a large part of the study area. of enhanced water-bearing capacity. The water-bearing zones Clay beds and fine-grained carbonates form the confining consist of indurated limestone and dolostone and in some units between the water-bearing zones and are characterized places unindurated sand, gravel, and shell beds, and these by low leakance. Leakance through the intermediate aquifer zones are designated, in descending order, as Zone 1, Zone 2, system confining units ranges over 4 orders of magnitude from and Zone 3. Zone 1 is thinnest (< 80 feet thick) and is limited 4.2x10-7 to 6.0x10-3 foot per day per foot [(ft/d)/ft]. Despite  Regional Evaluation of the Hydrogeologic Framework....West-Central Florida

the large range, the geometric mean and median leakances of aquifers. Heads differences between Zone 1 and the surficial individual confining units are within the same order of magni- aquifer system range from -1 (downward) to 3 (upward) feet, tude, 10-5 (ft/d)/ft, which is 2 orders of magnitude less than the and heads are nearly the same (< 1 foot) between Zone 3 median leakance of the semiconfining unit within the Upper and the Upper Floridan aquifer in much of the study area. In Floridan aquifer. contrast, head differences across the upper and lower groups Major ion concentrations in water from the intermediate of confining units of the intermediate aquifer system range aquifer system, and throughout the ground-water flow system, from -48 to 14 feet and from -119 to 24 feet, respectively. generally increase with depth. The chemical composition of These head differences among the zones indicate some degree water in the intermediate aquifer system is more varied than of hydraulic separation between zones within the intermediate the adjacent aquifers. This variation is related to the different aquifer system. types of minerals forming the aquifer matrix, and complex mixing with waters from adjacent aquifers. The dominant water type throughout the intermediate aquifer system is mixed-cation bicarbonate, typically with nearly equal concen- Introduction trations of calcium and magnesium ions. At the southern extent of the study area, sodium-chloride type water is present The southern half of the Southwest Florida Water throughout the intermediate aquifer system. Calcium-magne- Management District, encompassing a 5,100-square-mile sium sulfate type water is present along the coastal margin area, includes all or parts of Hillsborough, Polk, Manatee, from Tampa Bay to southern Sarasota County in Zone 3 and in Hardee, Highlands, Sarasota, De Soto, and Charlotte Counties two Zone 2 wells in west-central Sarasota County. and is designated the Southern Water Use Caution Area Differences in hydraulic head generally are greater (SWUCA; Southwest Florida Water Management District, between adjacent zones within the intermediate aquifer system 2004) (fig. 1). This area was designated a water-use caution than between the intermediate aquifer system and adjacent area in 1992 when it was recognized that steadily increasing

82°30’ 82° 81°30’

28° 58 HILLSBOROUGH 59 57 57x POLK A 49 CL-2 9-1 B 45 9-2 CL-3 48 50 Tampa 40 Gulf of Me Bay C' 43x HIGHLANDS 8-1 39 MANATEE HARDEE 27°30’ xico 31 7-2 7-1 33 32 30 7-4 C 25 28 SA-1 22 23 26 35 28x SARASOTA D' AREA 6-1 DE SOTO 20 SHOWN 5-3 19 17 15 18 16 D 19x 5-1 5-2 9.5 14 13 16.5 9 12 EXPLANATION 4-1 4-2 27° 10 AA' LINES OF SECTION— 3-3 11 5 Figure 1. Location Shown in figures 6 A' 3-1 GLADES of the study area, and 8 CHARLOTTE 1-2 STUDY AREA selected Regional 26 ROMP SITE LOCATION— BOUNDARY Observation and And number B' Monitor-well Program Charlotte 0 10 20 MILES Harbor LEE (ROMP) sites, and lines HENDRY of sections in southern 0 10 20 KILOMETERS west-central Florida. Base from U.S. Geological Survey digital data, 1:2,000,000, 1972 Albers Equal-Area Conic projection Standard Parallels 29°30’ and 45°30’, central meridian -83°00’ Introduction  ground-water withdrawals in response to growing demands and discharge areas of the aquifer system and degree of from public supply, agriculture, mining, power generation, and hydraulic connection. The primary source of data analyzed recreational uses resulted in declines in aquifer heads causing and presented in this report is from the SWFWMD Regional saltwater intrusion in coastal areas, lowered lake levels in the Observation and Monitor-well Program (ROMP). Additional upland areas, and reduced base flow in selected river reaches data were compiled from USGS, SWFWMD, Florida (Southwest Florida Water Management District, 2004; Beach Geological Survey (FGS), and consulting reports. and Chan, 2003). The principal source of freshwater for all uses is ground water supplied from three aquifers; the surfi- cial aquifer system, the intermediate aquifer system, and the Description of the Study Area Upper Floridan aquifer. In general, ground-water availability The regional topography alternates between well-drained is low to moderate, moderate, and abundant from these three ridges and poorly drained lowlands. Ridges, the dominant aquifers, respectively (Torres and others, 2001). Ground-water landform, are remnant shoreline features (marine scarps) availability is geographically limited by the quantity or quality found throughout the State (Schmidt, 1997). The landforms of water in each aquifer. In the coastal and southern parts of the SWUCA, the Upper Floridan aquifer contains water too result from depositional and erosional processes (Scott, 1992): mineralized for most uses so ground water from the surficial altitudes range from about 0 to 250 feet (ft) above the National aquifer system and intermediate aquifer system is in greater Geodetic Vertical Datum of 1929 (NGVD 1929), and most demand (Knochenmus and Bowman, 1998; Torres and others, of the study area is a relatively flat plain (Carr and Alverson, 2001). 1959). The intermediate aquifer system is an important source of The physiographic features in the study area include the water in Sarasota and Charlotte Counties, and a potential but Central Highlands, Polk Upland, De Soto Plain, Southern limited source of water in most of the SWUCA. Well yields Gulf Coastal Lowlands, and Gulf Barrier Chain (fig. 2; White, are generally much less in the intermediate aquifer system 1970). These features result from the reworking of geologic than from the Upper Floridan aquifer (Duerr and others, units by wind, ground water, and surface water over geologic 1988). To successfully and efficiently manage the ground- time (Parker and others, 1955; Scott, 1992). The Central water resources of the intermediate aquifer system throughout Highlands physiographic region includes the Winter Haven, the SWUCA, an investigation was initiated in 1999 by the Gordonville, Lakeland, Lake Henry, and Lake Wales Ridges U.S. Geological Survey (USGS) in cooperation with the (shaded dark blue in fig. 2). The Central Highlands region Southwest Florida Water Management District (SWFWMD) is an internally drained area of rapid recharge, and is prone to evaluate the available hydrologic data and assess the extent to cover-collapse sinkhole development (Brooks, 1981). and interconnectedness of the intermediate aquifer system Land-surface altitudes range between 100 and 130 ft in the regionally. The study area excludes the northernmost extent of Polk Upland, which is a poorly drained plateau containing the SWUCA, where the intermediate aquifer is absent. flatwoods, wetlands, and lakes (White, 1970; Brooks, 1981). Land-surface altitudes range from 30 to 100 ft in the De Soto Plain, which is a broad, gently sloping plain containing wet Purpose and Scope prairie, cypress swamps, and flatwoods drained by streams and sloughs (Brooks, 1981). Land-surface altitudes are < 20 ft This report provides an evaluation of the relation between in the Southern Gulf Coastal Lowlands, which is bounded on the geologic and hydrogeologic framework, the occurrence the west by the Gulf of Mexico. The Southern Gulf Coastal of permeable and confining units, the vertical and lateral Lowlands is a ground-water discharge area that is dominated hydraulic properties, chemical characteristics, and the varia- by wet prairie and flatwoods vegetation, and includes the tions in the potential vertical flow direction and water-level barrier beaches, barrier islands, spits, and overwash fans of changes among units within the intermediate aquifer system. recent origin (Brooks, 1981; Schmidt, 1997). Although the report focuses on the characteristics of the intermediate aquifer system, hydrologic data were evaluated from the overlying surficial aquifer system and underlying Upper Floridan aquifer to assess the interactions between Hydrologic Data Sources the intermediate aquifer system and adjacent aquifers. A brief discussion of the adjacent aquifers is included in this The primary sources of geologic, hydrologic, and report. Specifically, this report presents: (1) stratigraphic chemical data were observation wells at ROMP sites; compli- cross sections emphasizing the locations of clay beds and mentary data were compiled from USGS and SWFWMD showing the lateral continuity of geologic and hydrogeologic databases and reports. SWFWMD and FGS delineated the units; (2) the spatial distribution of the hydraulic properties geologic framework, including lithologic descriptions and within the permeable and confining units in the intermediate stratigraphic boundaries, using wire-line cores and cuttings aquifer system; (3) the spatial distribution of water-quality retrieved during test-well drilling. SWFWMD personnel iden- types; and (4) water-level differences that define the recharge tified permeable zones and confining units based on changes  Regional Evaluation of the Hydrogeologic Framework....West-Central Florida

82°30’ 82° 81°30’ Northern Gulf Western Valley Lakeland Ridge Winter Haven 28° Coastal Lake Osceola Plain Lowlands Ridge Gordonville W Ridge ales Ridge Lake

Henr Bombing

y Ridge

Polk Upland Range Tampa Gulf Barrier Chain Bay Ridge

Intraridge 27°30’

Gulf of Me V alley Okeechobee Plain Southern Gulf Coastal Lowlands xico Desoto Plain

EXPLANATION

Incline 27° STUDY AREA BOUNDARY

Note: Ridges (shown in dark blue) Gulf Barrier Chain

compose the Central Highlands. Caloosahatchee

Charlotte 0 10 20 MILES Harbor Caloosahatchee Valley Immokalee Rise 0 10 20 KILOMETERS

Base from U.S. Geological Survey digital data, 1:2,000,000, 1972 Albers Equal-Area Conic projection Standard Parallels 29°30’ and 45°30’, central meridian -83°00’

Figure 2. Physiography of the study area in southern west-central Florida (modified from White, 1970). in the visual porosity, specific capacity, ground-water level, The water-quality characteristics of the aquifers were and water-quality characteristics observed during test-well evaluated using major-ion data provided by SWFWMD. Data drilling. Subsequent to test-well drilling, multiple observation were collected in 2001 from selected observation wells at wells were constructed, each of which was open to the most ROMP sites, and were used to characterize water types and to permeable strata within the surficial aquifer system, interme- illustrate the spatial distribution of ionic species. diate aquifer system, and Upper Floridan aquifer. SWFWMD, USGS, and private consulting companies Acknowledgments have conducted numerous aquifer tests at the ROMP sites. The author recognizes and is extremely grateful for the In 2000, SWFWMD recompiled and published the aquifer- invaluable support of the cooperating agency, the Southwest test results. Most of the published transmissivity values were Florida Water Management District. The author thanks the estimated using analytical techniques. In a concurrent USGS Resource Data Section of SWFWMD who provided the study, the hydraulic characteristics, including transmissivity detailed hydrogeologic and water-quality data interpreted in and leakance, at selected ROMP sites were re-analyzed using this report. The hydrogeologic data are contained in ROMP numerical techniques (Yobbi and Halford, 2006). reports listed separately in the selected references section of Continuous water-level data from observation wells this report. Dave DeWitt graciously provided water-quality at ROMP sites were compiled from USGS and SWFWMD data. The continuous water-level data collected by SWFWMD databases during 2000-2002. Water-level hydrographs were were provided by the Hydrologic Data Section. The author compared to determine the range in annual fluctuation, also thanks Ron Basso and Mike Beach of the Hydrologic seasonal variation, and response to hydrologic stress. USGS Evaluation Section of SWFWMD for their insightful and chal- personnel collected periodic water-level data to verify the lenging debate as to the nature and extent of the intermediate accuracy of the continuous water-level data. aquifer system in west-central Florida. Hydrologic Data Sources 

Definitions and Terms observations from smallest to largest and then selecting the data point that has an equal number of observations The clay beds shown on cross sections and the clay both above and below it. percentages shown on maps are distinct units that were noted • Interquartile range (IQR) measures the range of the as clay on lithologic logs. Clay percentages represent the ratio central 50 percent of the data. The IQR is defined of the clay thickness to the total thickness of the Hawthorn as the 75th (upper quartile) percentile minus the 25th Group. Entries on lithologic logs that included a clay compo- (lower quartile) percentile, and is not influenced at all nent, but did not list clay as the primary component, were not by the 25 percent of the data on either end of the range. used to calculate the thicknesses. An example of a lithologic unit excluded from the thickness calculation is a unit described Water types are defined by their predominant cation and as clayey sand. anion concentrations, expressed in milliequivalents per liter. An aquifer is a formation, group of formations, or part of For water to have a single cation/anion pair type, the cation a formation in the zone of saturation that is permeable enough and anion concentrations must exceed 50 percent of the total to transmit usable quantities of water (Peek, 1958). cation/anion concentration. Water samples containing cation A permeable unit is an identifiable horizon of enhanced and anion concentrations not exceeding 50 percent are defined water-bearing capacity (Basso, 2002). Permeability is highly as mixed-ion type waters (Hem, 1985). The water types used variable, thus, ranges of transmissivity, in feet squared per day in this report are: (ft2/d) are used to qualitatively define the relative permeability • Mixed-cation bicarbonate: no dominant cation species, within the intermediate aquifer system: commonly containing equal concentrations of calcium • semiconfining unit: < 0.1 ft2/d. and magnesium with bicarbonate as the dominant • low permeability unit: > 1 and < 100 ft2/d anion • moderately low permeability unit: > 100 and • Calcium-magnesium sulfate: typically containing < 1,000 ft2/d about equal concentrations of calcium and magnesium • moderate permeability unit: > 1,000 and < 10,000 ft2/d with sulfate as the dominant anion • moderately high permeability unit: > 10,000 and • Sodium chloride: both a single cation and anion species < 100,000 ft2/d are dominant Zone numbers used in this report are equivalent to PZ • Mixed-ion: neither a dominant cation nor anion species, numbers used in reports by SWFWMD. Zone 1 is equivalent and ion combinations are highly variable to PZ1, Zone 2 is equivalent to PZ2, and Zone 3 is equivalent Major ion data, in milliequivalents per liter, were to PZ3. analyzed using a graphical method originated by Stiff (1951). Boxplots, a graphical display for summarizing data, Stiff diagrams have three parallel horizontal axes, bisected by a illustrate the symmetry of a data set and provide a visual “zero” vertical axis. The cation (sodium, calcium, and magne- summary of the median, spread (interquartile range or box sium) and anion (chloride, bicarbonate, and sulfate) data are size), skewness (relative size of box halves), and presence of plotted to the left and right of the vertical axis, respectively. extreme values (outside and far-out values). The distance (or Plotting of the data results in a six-sided polygon; the size and length of the line) to the last observation (largest and smallest) shape indicate the relative concentration and composition of that is within 1.5 times the interquartile range is defined as the the water sample (fig. 3). whisker length (Helsel and Hirsch, 1992). The statistical terms used to summarize the hydraulic data include the mean, geometric mean, median, and interquartile range. The definitions of the statistical terms are from Helsel Milliequivalents per Liter and Hirsch (1992). Cations Anions • Mean is the average value within the sampled data set and is computed as the sum of the samples (observa- tions) divided by the sample size. Sodium + Potassium Chloride • Geometric mean is the mean of the logarithms, trans- formed back to their original units. It is commonly Calcium Bicarbonate reported for positively skewed data sets. For positively skewed data sets, the geometric mean is usually quite Magnesium Sulfate close to the median. • Median, or 50th percentile, is the central value of the distribution when the data are ranked in order of magnitude, and is computed by first ranking the Figure 3. Representative Stiff diagram.  Regional Evaluation of the Hydrogeologic Framework....West-Central Florida

Geologic Framework Depositional History

The geologic framework presented in this report is a During the late Oliocene to early Pliocene, when the departure from the framework presented in reports published Hawthorn Group was deposited, frequent sea-level fluctua- before 1988. The stratigraphic names used in this report are tions spread a complex lithologic assemblage across the based upon the geologic definitions of Scott (1988) that are Florida Platform. In the study area, carbonates and siliciclastic used by the FGS. Changes in nomenclature resulted from sediments were deposited concurrently, with the sediment type the re-interpretation and refinement of the ages, names, varying geographically in the study area in relation to varia- and hierarchy of the stratigraphic units in Florida. Figure 4 tions in the altitude of the sea-level stand (Randazzo, 1997). shows the correlation between past and present stratigraphic Geographically, more carbonate sediments were deposited in nomenclature used in the study area. The chart illustrates the the southern and southwestern parts of the study area whereas revisions in the ages, names, and hierarchy of units described siliciclastic sediments were deposited in the northern and in published reports up to Ryder (1985), and after the redefini- eastern parts. In general, enhanced zones of permeability tion of the Hawthorn Group by Scott (1988). Earlier reports are found in the carbonate units within the Hawthorn Group. had the Tampa Limestone and Hawthorn Formation of equal Carbonates also are more susceptible to post-depositional stratigraphic status and had the Bone Valley Formation as part alteration such as dissolution and fracturing than siliciclastics, of the undifferentiated deposits. The current definition places which can further increase permeability. Siliciclastic sedi- all three of these units in the Hawthorn Group. ments such as well-sorted or coarse-grained sands may also produce water. Confining units are domi- Past Present nantly fine-grained siliciclastics like clays, Series Stratigraphic Stratigraphic Hydrogeologic and clay-size carbonates (mudstones) that Unit Unit Unit hydraulically separate water-bearing zones 2 Ryder, 1985 Scott, 1988 SEGS , 1986 within the intermediate aquifer system. Surficial Sand, In the study area, the synchronous Holocene Undifferentiated Terrace Sand, deposition of carbonate and siliciclastic Pleistocene Surface Deposits, Surficial Phosphorite sediments produced the highly heteroge- Caloosahatchee, Aquifer neous Hawthorn Group, with both grada- and Tamiami System tional (transitional) and abrupt contacts Undifferentiated Formations between facies (Missimer, 2002). Siliciclastic Pliocene 1 Deposits carbonate sediments were deposited during Bone Valley Member early Miocene time, with the siliciclastic Peace content increasing eastward in the study area Hawthorn River Intermediate (fig. 5a). Siliciclastic sediments containing Formation Formation Aquifer interbedded carbonate units were depos- ited during middle Miocene time (fig. 5b). Miocene System Arcadia Phosphate deposits were reworked and silici- Tampa Formation clastic sedimentation was dominant in the Limestone study area during late Miocene time (fig. 5c). a During Pliocene time, carbonate sedimenta-

Hawthorn Group r mp Ta Intermediate tion resumed along the Gulf Coast margin Membe Confining south of Charlotte Harbor; contemporane- Nocatee Member Unit ously, siliciclastic sedimentation dominated Oligocene Suwannee the area between Tampa Bay and Charlotte Limestone Harbor. In the western half of the peninsula Suwannee north of Tampa Bay, a hiatus in deposition Limestone occurred (fig. 5d).

Upper Ocala Ocala Floridan Limestone Limestone Aquifer Eocene

Avon Park Avon Park Figure 4. Chart showing series, past and Formation Formation present stratigraphic unit nomenclature, and hydrogeologic units. 1 2 Includes Caloosahatchee SEGS, Southeastern Marl, Bone Valley Formation, Geological Society and Tamiami Formation Geologic Framework 

SILICICLASTIC CARBONATES SILICICLASTIC CARBONATES SILICICLASTICS WITH INTERBEDDED SILICICLASTICS SILICICLASTICS AND CARBONATES

SILICICLASTICS DECREASE

SILICICLASTICS SILICICLASTIC CARBONATES WITH CARBONATES

SILICICLASTICS INCREASE SILICICLASTICS INCREASE

CARBONATES SILICICLASTIC WITH MINOR CARBONATES SILICICLASTICS

(A) Early Miocene Sediment Pattern (B) Middle Miocene Sediment Pattern

SILICICLASTICS SILICICLASTICS LOCAL REWORKING OF SEDIMENTS WITH MINOR DEPOSITION NO DEPOSITION?

NO DEPOSITION

REWORKING SILICICLASTICS OF PHOSPHATE DEPOSITS

SILICICLASTICS SILICICLASTICS WITH AREAS OF CARBONATE DEPOSITION CARBONATES ? (C) Late Miocene Sediment Pattern (D) Pliocene Sediment Pattern

EXPLANATION MAP EXTENT—Shown in figure 1.

Figure 5. Early Miocene to Pliocene sediment patterns in Florida (modified from Scott, 1997).

Stratigraphy (1) the stratigraphic units dip to the south, (2) the Suwannee Limestone and Hawthorn Group thin and are absent, in places, To illustrate the occurrence and distribution of strati- at the eastern extent of the study area, and (3) the undiffer- graphic units in the study area, a series of stratigraphic entiated surface deposits thicken substantially at the eastern sections were prepared. The thickness and depth of the extent of the study area. The stratigraphic units of interest are stratigraphic units of interest vary in the study area (fig. 6; briefly described below and summarize geologic descriptions lines of section shown in fig. 1). General trends include presented by Scott (1988, 1997) and Randazzo (1997).  Regional Evaluation of the Hydrogeologic Framework....West-Central Florida

NORTH SOUTH A A' 200 200 TR9-2 TR8-1 TR7-2 SA-1 TR6-1 20 TR5-1 TR4-1 TR3-3 0 0

-500 -500

TUM OF 1929, IN FEET

-1,000 -1,000

-1,500 -1,500 B B' 200 48 32 25 35 9.5 10 TR1-2 200

TIONAL GEODETIC VERTICAL DA 0 0

-500 -500

-1,000 -1,000

DEPTH ABOVE AND BELOW THE NA

-1,500 -1,500 30:1 VERTICAL EXAGGERATION EXPLANATION

SURFICIAL AQUIFER SYSTEM UPPER FLORIDAN AQUIFER Undifferentiated Surface Deposits Suwannee Limestone INTERMEDIATE AQUIFER SYSTEM Ocala Limestone (Hawthorn Group) Avon Park Formation Peace River Formation OPEN-HOLE—Interval of wells at Regional Tampa Member of the Arcadia Formation Observation and Monitor-well Program sites. Nocatee Member of the Arcadia Formation BASE OF SECTION Undifferentiated Arcadia Formation

Figure 6. Stratigraphy, aquifer, and open-hole intervals of wells at selected Regional Observation and Monitor-well Program (ROMP) sites. The lines of section are shown in figure 1. Geologic Framework 

WEST EAST C C' 200 TR7-1 TR7-4 33 32 31 30 43XX 200 TR7-2 0 0

-500 -500

TUM OF 1929, IN FEET

-1,000 -1,000

-1,500 -1,500

200 D D' 200 20 TR5-2 19 19x 18 17 16 15 28X TIONAL GEODETIC VERTICAL DA 0 0

-500 -500

-1,000 -1,000

DEPTH ABOVE AND BELOW THE NA

-1,500 -1,500 30:1 VERTICAL EXAGGERATION

Figure 6. (Continued) Stratigraphy, aquifer, and open-hole intervals of wells at selected Regional Observation and Monitor-well Program (ROMP) sites. The lines of section are shown in figure 1.

The Avon Park Formation, Ocala Limestone, and The Ocala Limestone ranges in thickness from 75 to 300 ft, Suwannee Limestone were deposited in open-marine or the texture ranges from packstones to mudstones, and the restricted marine environments during middle Eocene through fossil diversity is high. late Oligocene time (Randazzo, 1997). The Avon Park The Suwannee Limestone is similar in composi- Formation is primarily composed of poorly to well-indurated tion and texture to the Ocala Limestone, particularly in the fossiliferous limestone that has been pervasively dolomitized southwestern part of the study area, obscuring the boundary in places. The Avon Park Formation generally is thicker than between the units. The Suwannee Limestone is composed of either the Suwannee or Ocala Limestones. The depositional interbedded, sand-size limestone grains and calcareous mud. texture ranges from wackestones to mudstones, and fossil Near the base of the unit, the limestone may be dolomitized; diversity is low. near the top of the unit, quartz sand beds are present in parts of The Ocala Limestone contains two distinct lithologic the study area. The Suwannee Limestone ranges in thickness units; the lower unit is composed of partially dolomitized from 0 to 500 ft; the limestone texture ranges from packstone limestone and interbedded sucrosic dolostone, and the upper to mudstone and is distinguishable from the Hawthorn Group unit is composed of soft, poorly indurated, porous limestone. by the lack of phosphate. 10 Regional Evaluation of the Hydrogeologic Framework....West-Central Florida

The Hawthorn Group was deposited during late areas, a chert and phosphate rubble zone delineates the forma- Oligocene through early Pliocene time, which was character- tion boundary (Scott, 1988). The Peace River Formation is ized by a gradual shift from carbonate to siliciclastic deposi- composed of > 66 percent siliciclastics with minor carbonate tion (Scott, 1997). Complicating the general lithologic shift sedimentation—the carbonate content increases with depth. were recurring cyclic episodes of transgressive/regressive sedi- Phosphate minerals and magnesium-rich clay beds are common. mentation resulting in a heterogeneous mixture of shell, clay, The Peace River Formation generally is thin (< 50 ft thick) silt, sand, and carbonate facies. Additionally, the Hawthorn except in central Charlotte County where the unit is more than Group contains phosphorite (phosphate mineral), palygorskite 250 ft thick. The Peace River Formation is absent in parts and sepiolite clays (magnesium-rich clays), and dolomitized of Hillsborough, Pinellas, Manatee, De Soto, and Sarasota limestone (magnesium-rich carbonates). Phosphate concen- Counties. The Peace River Formation has one named member— trations range from trace amounts to about 50 percent. The the Bone Valley Member. The Bone Valley Member was not thickness of the Hawthorn Group ranges from 50 to 850 ft; the identified on lithologic logs from ROMP sites in the study area texture ranges from grainstones to mudstones. and consequently is not delineated on stratigraphic sections. The Hawthorn Group includes two formations—the basal The stratigraphic units deposited during the Pliocene to Arcadia Formation contains predominantly carbonate sedi- Holocene are designated the “undifferentiated surface deposits” ments, and the overlying Peace River Formation contains a in the study area. The undifferentiated surface deposits gener- greater abundance of siliciclastic sediments. Generally, in the ally are < 50 ft thick, except at the eastern extent of the study study area, the Arcadia Formation is substantially thicker than area where the deposits are thicker than 200 ft. The undifferen- the Peace River Formation (fig. 6). tiated surface deposits locally contain the Tamiami Formation The Arcadia Formation, as described by Scott (1988), is and as many as three distinct lithologic units: (1) the Plio- more than 300 ft thick south of Hillsborough and Polk Counties Pleistocene shell beds, shelly, sandy, or silty marl, marl, and and west of Highlands County. The unit thickens to more than sandy limestone; (2) the Pleistocene yellow to orange quartz 700 ft in Charlotte County (southern extent of study area) and sand with interbedded clay and shell; and (3) the Holocene thins to < 50 ft at the northern and eastern extent of the study fine-grained quartz sand (Torres and others, 2001). In the study area. The Arcadia Formation contains two named members— area, the Tamiami Formation is absent or thin (Jon Arthur, the Tampa and the Nocatee Members. Where the Tampa and Florida Geological Survey, oral commun., 2000), and consists Nocatee Members cannot be identified, the Arcadia Formation predominately of siliciclastic sediments (Missimer, 2002). is designated as the undifferentiated Arcadia Formation. The dominant lithology of the Arcadia Formation is dolomitic limestone containing varying amounts of quartz sand, clay, and phosphate grains. Beds of quartz sand, silt, and clay recur Hydrogeologic Framework throughout the section. The phosphate content ranges from trace amounts to 25 percent, and averages 10 percent. The The stratigraphic units of varying permeability described texture ranges from mudstone to wackestone. above form three major hydrogeologic units—the surficial The Nocatee Member of the Arcadia Formation is a aquifer system, the intermediate aquifer system, and the predominantly siliciclastic unit, containing an interbedded Floridan aquifer system (figs. 4 and 6). The Floridan aquifer sequence of quartz sand, clay, and carbonate facies. Clay system consists of the Upper and Lower Floridan aquifers sepa- beds are common. The limestone texture is wackestone. The rated by the middle confining unit. The Lower Floridan aquifer unit ranges in thickness from 0 to 200 ft, is absent west of the contains highly mineralized water in west-central Florida. Only Myakka River in central Sarasota County, and is thickest in the Upper Floridan aquifer is described herein. In general, the southeastern De Soto County. aquifer systems are delineated along stratigraphic boundaries; The Tampa Member of the Arcadia Formation is however, near the northwestern and southern geographical composed primarily of limestone with minor amounts of extent of the study area, hydrogeologic units cross the strati- dolostone, sand, and clay (Scott, 1988). The Tampa Member graphic boundaries. In general (1) the surficial aquifer system is thickest (as much as 300 ft) along the coastal margin of is equivalent to the undifferentiated surface deposits; (2) the the Gulf of Mexico and is absent east of the Peace River in intermediate aquifer system is equivalent to the Hawthorn Polk and Hardee Counties. Sand and clay beds are present Group; and (3) the Upper Floridan aquifer is equivalent to the sporadically within the section and are more common in the carbonate sediments that form the Avon Park Formation, Ocala updip areas. Phosphate content is lower (< 3 percent) than in Limestone, and Suwannee Limestone. The top of the Upper other stratigraphic units in the Hawthorn Group and is the Floridan aquifer generally corresponds to the upper surface of distinguishing characteristic identifying the Tampa Member. the Suwannee Limestone where it is present. Where carbonate The texture ranges from mudstone to packstone, but the most units within the lower Hawthorn Group are contiguous with common texture is wackestone. the Suwannee Limestone, the top of the aquifer is above the The Peace River Formation overlies the Arcadia Suwannee Limestone. Where the Suwannee is absent (as in Formation. The stratigraphic boundary between the Arcadia parts of Highlands County), the top of the aquifer coincides and Peace River Formations is disconformable—in some with the Ocala Limestone. Hydrogeologic Framework 11

Evolution of Hydrogeologic Unit Properties of the Aquifers Overlying and Nomenclature Underlying the Intermediate Aquifer System

Multiple permeable units within the aquifers have Properties of the aquifers adjacent to the intermediate long been recognized and documented in published reports aquifer system, the overlying surficial aquifer system and (Bishop, 1956; Peek, 1958; Menke and others, 1961; Stewart, underlying Upper Floridan aquifer, are briefly described 1966; Sproul and others, 1972; Sutcliffe, 1975; Joyner and herein because ground water exchanged among the aquifers Sutcliffe, 1976; Wilson, 1977; Brown, 1983). These early varies in source, quality, and quantity. The quality of the water, reports emphasized the hydrology of the Upper Floridan the degree of interconnection, and potential for interaquifer aquifer, and while permeable units above the top of the Upper leakage are important for gaining a complete understanding of Floridan aquifer were identified, neither a regional delinea- the intermediate aquifer system. tion nor hydrologic evaluation of these zones was the prin- Ground-water flow is not regionally extensive within cipal subject of these reports (Wolansky, 1983). Beginning the surficial aquifer system. In most of the study area, the in the mid-1980s, the permeable units within the strata that water-producing capacity of the surficial aquifer system is lie between the overlying surficial aquifer system and under- limited by the saturated thickness (generally < 50 ft) and by lying Upper Floridan aquifer were collectively included in the degree of sediment sorting. The surficial aquifer system is the intermediate aquifer system (Wolansky, 1983; Duerr and used locally as a water supply in areas where the sand deposits Wolansky, 1986; Duerr and others, 1988). The intermediate thicken substantially beneath the Lake Wales Ridge, where aquifer system was defined as an upper confining unit, a group the undifferentiated deposits are composed of predominantly of as many as three permeable units, and a lower confining shell and sand beds of moderate water-producing capacity, unit (Duerr and others, 1988). The hydrogeologic unit nomen- or where deeper aquifers are highly mineralized (Torres and clature used in published reports included stratigraphic names, others, 2001). Sand and shell beds thicken in coastal Manatee, lithologic names, numbers, and general hierarchy such as Sarasota, and Charlotte Counties, and encircling Charlotte “upper” or “lower.” Recent reports use zone numbers (PZ1, Harbor (Vacher and others, 1992; Torres and others, 2001). PZ2, and PZ3) to designate the permeable units identified in The surficial aquifer system is used for public water supply in the intermediate aquifer system (Barr, 1996; Torres and others, southwestern Sarasota and coastal Charlotte Counties where 2001; Basso, 2002; Beach and Chan, 2003). Figure 7 shows deeper aquifers are highly mineralized. The hydraulic conduc- the published hydrogeologic unit designation, geographical tivity of the surficial aquifer system varies from 1 to 1,490 extent of the investigation, and equivalent zone number used feet per day (ft/d), with a mean of 62, median of 27, and upper herein. and lower quartiles of 13 and 51 ft/d, respectively (Beach and In this report, hydrogeologic unit Zone 1 is equiva- Chan, 2003). A single water type (calcium-bicarbonate) char- lent to the “sandstone aquifer” (Sproul and others, 1972; acterizes the surficial aquifer system at the eight ROMP sites Reese, 2000), “artesian zone 1” (Sutcliffe, 1975; Joyner in the study area (app. 1A-B). and Sutcliffe, 1976), and is included in the “Tamiami-upper The Upper Floridan aquifer is a confined aquifer Hawthorn aquifer” (Wolansky, 1983; Duerr and Wolansky, throughout the study area. The top of the aquifer dips to the 1986). Hydrogeologic unit Zone 2 is equivalent to the “upper south from about NGVD 1929 in central Polk County to Hawthorn aquifer” (Sproul and others, 1972), “Tamiami-upper > 1,000 ft below NGVD 1929 in southern Charlotte County, Hawthorn aquifer” (Brown, 1983; Wolansky, 1983; Duerr and whereas thickness varies from about 1,000 to more than Wolansky, 1986), “artesian zone 2” (Sutcliffe, 1975; Joyner 1,400 ft. In the study area, the Upper Floridan aquifer consists and Sutcliffe, 1976), “mid-Hawthorn aquifer” (Reese, 2000), of three hydrogeologic units—the moderately permeable pack- “uppermost artesian zone” (Stewart, 1966), “phosphorite unit” stone unit of the Suwannee Limestone (UPZ); the semicon- (Wilson, 1977), “shallow artesian aquifer” (Menke and others, fining mudstone unit of the Ocala Limestone, and the highly 1961), and “permeable bed” (Peek, 1958). Hydrogeologic permeable fractured crystalline dolostone in the Avon Park unit Zone 3 is equivalent to the “lower Hawthorn-upper Formation (LPZ) (Basso, 2002; Beach and Chan, 2003). The Tampa aquifer” (Wolansky, 1983; Duerr and Wolansky, 1986), transmissivity of the Upper Floridan aquifer generally exceeds 2 “artesian zone 3” (Sutcliffe, 1975; Joyner and Sutcliffe, 1976), 10,000 and can be > 1,000,000 ft /d (Southwest Florida Water “secondary artesian aquifer” (Stewart, 1966), and “upper unit Management District, 2000). Transmissivities of the Suwannee 2 of the Floridan aquifer” (Wilson, 1977). Near the southeastern Limestone range from 1,400 to 290,000 ft /d; with a mean of and northwestern extent of the study area, units previously 17,000, median of 15,000, and lower and upper quartiles of 2 called the “lower Hawthorn aquifer” and “Tampa producing 7,800 and 37,000 ft /d, respectively (Beach and Chan, 2003). zone,” respectively, are included in the Upper Floridan aquifer Transmissivities of the Avon Park Formation range from 2 (Menke and others, 1961; Sproul and others, 1972; Brown 4,900 to 1,600,000 ft /d, with a mean of 110,000, median of 1983; Reese, 2000). 100,000, and lower and upper quartiles of 54,000 and 260,000 ft2/d, respectively (Southwest Florida Water Management District, 2000; Beach and Chan, 2003). 1 

HIGHLANDS HILLSBOROUGH POLK HARDEE AND MANATEE THIS CENTRAL GREATER SOUTH- Regional Evaluation of the Hydrogeologic Framework....West-Central Florida COUNTY COUNTY COUNTY DE SOTO COUNTY REPORT SARASOTA AND SARASOTA AND WESTERN COUNTY CHARLOTTE CHARLOTTE FLORIDA COUNTY COUNTY

Surficial Water Table Nonartesian Surficial Surficial Surficial Surficial Water Table Water Table

Intermediate Lower Tamiami Zone 1 Confining Zone 1 Sandstone Unit Venice Clay Venice Clay Uppermost PhosphoriteUnit Upper Unit Tamiami-Upper Water- Shallow Artesian Zone 2 Hawthorn Zone 2 bearing Mid-Hawthorn Artesian Lower Unit units Upper Unit Secondary Floridan Tampa Zone 3 Lower Hawthorn- Artesian Sand and Producing Zone 3 Lower Hawthorn Zone Upper Tampa

Clay Unit Intermediate Aquifer System Producing Zone

Tampa- Suwannee Suwannee Producing Limestone Zone Upper Zone 4 Permeable Zone

Suwannee- Principal Lower Unit Ocala Upper Floridan Floridan Floridan Artesian Floridan Producing Ocala Semi- Ocala Semi- Floridan Zone Confining Unit Confining Unit

Upper Floridan Aquifer

Floridan Aquifer System

Artesian Aquifer System

Avon Park Zone 5 Avon Park Formation Producing Lower Zone Permeable Sutcliffe, 1975; Joyner and Zone Sutcliffe, 1976; Bishop, 1956; Barr, 1996; Barcelo and Wolansky, 1983 Knochenmus others,1990; Menke and Peek, 1958; Duerr and and Bowman, Middle Confining Yobbi, 1996 others, 1961 Stewart, 1966 Wilson, 1977 Brown, 1983 Wolansky, 1986 1998 Unit, Reese, 2000 Unnamed confining or semi-confining unit.

Figure 7. Hydrogeologic units in this study compared with those in previous reports. Intermediate Aquifer System 13

The concentration of major ions is generally higher in The intermediate aquifer system ranges in thickness from water from the Upper Floridan aquifer than from the inter- < 100 ft in southern Hillsborough and central Polk County mediate aquifer system in the study area (app. 1A-B). The to more than 800 ft in southern Charlotte County (Duerr chemical composition of water in the Upper Floridan aquifer and others, 1988), (table 1). The number of permeable units evolves along regional flow paths from mixed-cation bicar- increases as the intermediate aquifer system thickens. The bonate to calcium-magnesium sulfate to sodium-chloride type permeable units are of limited vertical extent and are present water (Plummer, 1977; Sacks and Tihansky, 1996). Half of at variable depths (fig. 8). Within the intermediate aquifer the samples from the Upper Floridan aquifer in the study area system, there is considerable hydraulic and chemical vari- contain calcium-magnesium sulfate type water. Mixed-ion ability among the three vertically stratified water-bearing type water is present at ROMP sites in coastal Hillsborough zones. County and at selected ROMP sites (13, 14, and 16.5) in Variations in hydraulic and chemical properties of perme- southeastern De Soto and southwestern Highlands Counties. able units reflect the original texture and composition of sedi- ments and post-depositional processes such as dolomitization, Intermediate Aquifer System recrystallization, fracturing, and dissolution (Knochenmus and Bowman, 1998; Torres and others, 2001). The reported The intermediate aquifer system generally is coincident transmissivities of water-bearing zones in the intermediate with the Hawthorn Group and underlies most of the study area. aquifer system vary over 5 orders of magnitude, from about 1 The heterogeneous lithologic composition of the Hawthorn to more than 40,000 ft2/d. This wide range is because perme- Group results in a hydrogeologic unit that is best characterized able units are (1) thin, (2) absent in places where clay beds as thin permeable units in a predominantly fine-grained clayey dominate, and (3) vary with lithology and solution develop- matrix. As a single entity, the intermediate aquifer system ment within the carbonate sediments rather than with thick- is characterized as a system with substantially lower perme- ness (Wolansky, 1983; Knochenmus and Bowman, 1998; ability than the underlying Upper Floridan aquifer, and is often Southwest Florida Water Management District, 2000; Basso, classified as a confining or semiconfining unit (Basso, 2002). 2002). Transmissivity values are listed by zone in table 2.

Table 1. Regional Observation Monitioring-well Program (ROMP) well indentification, site characteristics, construction information, and zone specification.

[USGS site ID, base ID and does not include the 2-digit sequence number assigned to each well. FGS, Florida Geological Survey; LSD, land surface datum, in feet above NGVD29; thickness, total thickness of the Hawthorn Group; casing, casing depth below NGVD29; depth, well depth below NGVD29; zone 3*, well open to zone 3 and the Upper Floridan aquifer; %, percent; *, Venice clay present; x, zone at site; -- absent; ND, no data]

ROMP Thick- Venice name USGS Site ID FGS ID LSD ness Clay % Clay Zone 1 Casing Depth Zone 2 Casing Depth Zone 3 Casing Depth Zone 3* Casing Depth

5 2656440814833 16913 40 642 43 * ------x -90 -190 x -410 -560 9 2704320820857 17056 25 518 23 -- x -15 -40 x -97 -140 x -169 -295 9.5 2707370820251 17597 38 420 12 -- x -23 -39 ------x -167 -293 10 2701520820028 12684 9 583 0 ------x -101 -201 x -294 -479 11 2658370815611 30013 13 ND ND ------x -207 -332 ------12 2702250814433 16578 41 667 13 -- x -16 -69 x -239 -368 x -464 -664 13 2704180813658 17392 60 492 20 ------x -222 -357 x -450 -532 14 2708580812111 17001 145 282 61 ------x -315 -376 ------15 2712320813922 15801 79 365 75 ------x -181 -251 ------16 2711150814627 50001 60 564 17 ------x -45 -176 x -240 -280 16.5 2703400815302 18116 40 535 34 * x -16 -50 ------x -307 -421 17 2710260815836 15303 25 413 10 ------x -75 -135 x -175 -215 x -370 -445 18 2711370820748 14383 40 420 9 * ------19x 2710210821516 14717 31 385 6 -- x -49 -90 x -177 -190 ------19 2709590822030 14787 20 375 19 ------x -67 -185 ------20 2711370822845 17087 15 472 19 * ------x -60 -110 x -235 -355 22 2718130822013 16783 35 339 42 * ------x -60 -90 x -195 -255 23 2719060821124 14382 60 505 13 * ------x -115 -190 x -244 -314 25 2721590820025 17608 85 361 19 ------x -20 -60 ------x -215 -591 26 2717570814930 14878 75 500 48 ------x -65 -105 x -180 -355 1 Regional Evaluation of the Hydrogeologic Framework....West-Central Florida

Table 1. (Continued) Regional Observation Monitioring-well Program (ROMP) well indentification, site characteristics, construction information, and zone specification.

[USGS site ID, base ID and does not include the 2-digit sequence number assigned to each well. FGS, Florida Geological Survey; LSD, land surface datum, in feet above NGVD29; thickness, total thickness of the Hawthorn Group; casing, casing depth below NGVD29; depth, well depth below NGVD29; zone 3*, well open to zone 3 and the Upper Floridan aquifer; %, percent; *, Venice clay present; x, zone at site; -- absent; ND, no data]

ROMP Thick- Venice name USGS Site ID FGS ID LSD ness Clay % Clay Zone 1 Casing Depth Zone 2 Casing Depth Zone 3 Casing Depth Zone 3* Casing Depth

28 2722070812604 17000 84 191 ND ------x -286 -346 ------28x 2715590812023 17418 105 ------30 2727280814747 15648 67 330 42 ------x 12 -113 x -213 -249 31 2727140815459 13514 78 396 33 ------x -52 -272 32 2728140820348 16257 104 454 53 ------33 2727280821530 16784 74 441 19 ------x -21 -89 x -330 -676 33a 2727280821530 16784 74 441 19 ------x -141 -216 ------35 2717050820221 18117 65 530 24 ------x -55 -124 x -165 -295 39 2735210821505 16740 125 466 28 ------x -5 -80 ------40 2738510820315 30003 140 375 53 ------x 64 -40 ------43X 2736160812848 14884 148 ND ND ------45 2745470814709 14385 122 285 41 ------x 12 -70 48 2744270820837 14386 102 197 53 ------x 57 41 ------x -113 -439 49 2745460821514 14888 130 330 43 ------x -100 -160 50 2742400822127 13517 50 260 0 ------x -150 -512 57 2754110813720 14883 128 85 70 ------x 33 -12 ------57x 2753480813357 16309 197 54 ND ------x 6 -12 ------58 2755070813537 16307 142 ------59 2753140815142 12640 119 140 35 ------x 69 5 ------59a 2753140815142 12640 119 140 35 ------x -3 -23 ------TR1-2 2650260815854 15289 24 847 27 ------x -195 -231 x -496 -576 TR3-1 2656380821307 15332 7 574 11 * x -48 -68 x -133 -153 x -243 -263 TR3-1a 2656380821307 15332 7 574 11 * ------x -373 -393 TR3-3 2655310821948 15683 6 650 16 * ------x -149 -169 x -364 -404 TR4-1 2703260822627 17488 5 620 7 * x -25 -107 x -116 -219 x -262 -627 TR4-2 2702400822357 14871 15 437 7 * ------x -445 -460 TR5-1 2708080822705 15168 12 465 13 * x -28 -47 ------x -263 -277 TR5-2 2709190822342 15636 15 490 15 * ------x -85 -105 x -230 -250 TR5-2a 2709190822342 15636 15 490 15 * ------x -345 -385 un- TR5-3 2709350822411 15 ND ND ------x -48 -125 ------known TR6-1 2716010823305 14882 5 491 13 * ------x -295 -310 TR7-1 2725100823457 15166 10 404 27 * ------x -310 -330 TR7-2 2726120823301 17057 19 420 11 * ------x -41 -86 x -338 -446 TR7-2a 2726120823301 17057 19 420 11 * ------x -181 -271 ------TR7-4 2725390822920 16303 17 499 29 * ------x -196 -251 x -363 -483 TR8-1 2734580823247 15826 15 376 39 ------x -85 -145 ------TR9-1 2744210822754 13515 4 214 0 ------x -120 -284 TR9-2 2745540822338 16618 13 220 4 ------x -105 -135 CL-2 2745220813039 15938 82 235 17 ------x -248 -264 ------CL-3 2745450813425 16306 123 130 ND ------x -74 -148 ------SA-1 2720490823245 17452 13 468 26 ------x -315 -375

aMore than 1 well in a zone at a ROMP site. Intermediate Aquifer System 15

The chemical composition of water in aquifers is Zone 1 is composed of discontinuous limestone, dolos- controlled by the mineralogy and solubility of aquifer material, tone, sand, gravel, and shell beds located in the unconsolidated the time of residence in the aquifer, and mixing of water from sediments within the Peace River Formation and uppermost adjacent aquifers with differing compositions. The chemical Arcadia Formation in areas of the SWUCA, where it is present composition of water is highly variable in the intermediate (Torres and others, 2001; Basso, 2002). Zone 1 is < 80 ft thick aquifer system because of the greater variety of minerals (Beach and Chan, 2003). Zone 1 is > 50 ft thick in central composing the intermediate aquifer system, and mixtures with Charlotte County (Barr, 1996), and found at depths ranging water from the underlying Upper Floridan aquifer and over- from 55 to 148 ft below land surface (Sutcliffe, 1975). In the lying surficial aquifer system. Differences in composition result study area, the Zone 1 wells found at eight ROMP sites are from the abundance of clay, phosphorite, and dolomite in the completed above the Venice Clay at depths of < 150 ft (fig. intermediate aquifer system (Sacks and Tihansky, 1996). Four 9a). South of the study area in Lee County, Zone 1 is 50 to 100 ground-water quality types (water types), defined in terms of ft thick at depths ranging from 60 to more than 170 ft below cation and anion concentrations, are present in the intermediate land surface (Wedderburn and others, 1982; Reese, 2000). aquifer system in the study area—mixed-cation bicarbonate, Transmissivity values are reported for 14 sites in Zone 1 calcium-magnesium sulfate, sodium chloride, and mixed ion. in the study area, and range from about 50 to 8,700 ft2/d The water-quality data are listed and the major ion compositions (fig. 9b; table 2). The mean, geometric mean, median, lower, are exhibited as pie charts in appendixes 1A and 1B. and upper quartile values are about 3,300, 1,600, 2,200, 1,100, and 5,500 ft2/d, respectively. The most common transmissivi- Permeable Units ties are in the moderate permeability range, in the thousands of feet squared per day The wells at the ROMP sites were constructed to pene- Multiple water types with relatively low ionic concentra- trate the most permeable strata in the underlying aquifers. tions are present in Zone 1 (fig. 9c). The ionic composition Identification of horizons of enhanced permeability was based and concentration of water samples in Zone 1 are indicated predominantly on visual inspection of rock cores, and was by the shape and size of the Stiff diagrams. Mixed-cation corroborated by water-level and water-quality changes and bicarbonate type water is present in southern De Soto County specific-capacity data collected during test drilling. Permeable (ROMP sites 9.5, 16.5 and 12). Sodium-chloride type water units were assigned zone numbers based on a naming conven- is present in southern Sarasota County (ROMP sites TR4-1 tion begun by Sutcliffe (1975), furthered by Barr (1996), and and 9). Mixed-ion type water is present at ROMP site 19x in currently used in reports published by SWFWMD. In this central Sarasota County. A water sample with anomalously report, the vertically stratified permeable units in the interme- high ionic concentration was collected from the well at the diate aquifer system are designated (in descending order) as ROMP TR4-1 site. This site is located in southern Sarasota Zone 1, Zone 2, and Zone 3 (table 1). County on a spit surrounded by the Gulf of Mexico. The Zone 1 ionic composition and concentration indicate that this zone is hydraulically connected to the Gulf of Mexico and has been The uppermost permeable unit (Zone 1) of the inter- locally inundated by seawater (De Haven and Jones, 1996; mediate aquifer system has been described in the southern fig. 9c; and app. 1A-B). and southwestern parts of the study area, underlying all of Sarasota, Charlotte, and Lee Counties, and parts of Manatee and De Soto Counties (fig. 9). Zone 1 generally is found Zone 2 above the confining unit called the Venice Clay, which is The middle permeable unit of the intermediate aquifer found in southern Manatee County, throughout Sarasota system (Zone 2) is composed of dolomite and limestone units County, in eastern Charlotte County, and in western De Soto County (Sutcliffe, 1975; Wedderburn and others, 1982; Barr, within the upper Arcadia Formation (Torres and others, 2001; 1996; Reese, 2000). Zone 1 is best recognized and mapped Basso, 2002). Zone 2 generally is above the Tampa Member in southern Sarasota and coastal Charlotte Counties (Joyner and is hydraulically separated from adjacent zones by clay and Sutcliffe, 1976; Sutcliffe and Thompson, 1983; Barr, beds (Beach and Chan, 2003). Zone 2 is present over most 1996; Basso, 2002). Zone 1 is used for irrigation in the eastern of the study area, south of southern Hillsborough County part of Charlotte County, underlies central Sarasota, and and central Polk County (Basso, 2002) and west of central extends into northern Lee County (Sutcliffe, 1975). Zone 1 Highlands County (fig. 10a). At the northern and eastern also has been described at ROMP sites 9, 12, and 17, located extent of Zone 2, permeable units are discontinuous, but the in eastern Sarasota, southern De Soto, and western De Soto unit also is locally present in low-lying areas west of the Counties, respectively (Torres and others, 2001). Compared to Lake Wales Ridge in Highlands County (Bishop, 1956) and recent studies by SWFWMD (Basso, 2002; Beach and Chan, in Hillsborough County (Menke and others, 1961). In the 2003), this study delineates a larger extent for Zone 1 that is study area, Zone 2 wells are found at 38 ROMP sites (fig. 10a; consistent with the extent delineated in earlier studies. table 1). 1  North South 200 200 A A’ Regional Evaluation of the Hydrogeologic Framework....West-Central Florida TR9-2 TR8-1 TR7-2 SA-1 TR6-1 20 TR5-1 TR4-1 TR3-3 0 0 1 1 2 2 3 2 2 2 2 -300 3 -300 3 3 3 3 3 3

TUM OF 1929, IN FEET 4 EXPLANATION -600 -600 SURFICIAL AQUIFER SYSTEM INTERMEDIATE AQUIFER SYSTEM Peace River Formation Tampa Member (Arcadia Formation) -900 -900 Nocatee Member (Arcadia Formation) North South Undifferentiated Arcadia Formation B B’ 200 200 UPPER FLORIDAN AQUIFER

TIONAL GEODETIC VERTICAL DA 48 32 25 35 9.5 10 TR1-2 2 OPEN-HOLE INTERVAL — number 2 corresponds to zone numbers in the 0 0 Intermadiate Aquifer System, asterisk 2 1 indicates open to more than one zone 2 CLAY BED INTERVAL 2 POTENTIAL FLOW DIRECTION 2 3* 3 3 45:1 Vertical Exaggeration -300 -300

3* 3

3

DEPTH ABOVE AND BELOW THE NA -600 -600

-900 -900

Figure 8. Stratigraphy, aquifer, open-hole interval, clay beds, and potential flow direction at selected Regional Observation and Monitor-well Program sites. (Locations of sections shown on figure 1.) West East C C’ 200 200 TR7-1 TR7-4 33 32 31 30 43XX

TR7-2 0 0 2 2 2

2 3 2 2 3 3 TUM OF 1929, IN FEET -300 -300

3 3

3*

-600 -600

West East

TIONAL GEODETIC VERTICAL DA 200 D D’ 200

20 TR5-2 19 19x 18 17 16 15 28X

0 0 1 2 2 2 2 2 2 3 2 3 3 3 -300 -300 Intermediate Aquifer System 3 3*

DEPTH ABOVE AND BELOW THE NA

-600 -600

Figure 8. (Continued) Stratigraphy, aquifer, open-hole interval, clay beds, and potential flow direction at selected Regional Observation and Monitor-well Program sites. (Locations of sections shown on figure 1.)

1 7 1 Regional Evaluation of the Hydrogeologic Framework....West-Central Florida

Table 2. Transmissivity values for the intermediate aquifer system.

[All values in feet squared per day; --, indicates absent; SWFWMD, Southwest Florida Water Management District]

ROMP data only Non-ROMP data from SWFWMD (2000)

Well name Zone 1 Zone 2 Zone 3 Well IDa Zone 1 Well IDa Zone 2 Well IDa Zone 3

ROMP 5 -- 1,400 3,000 40 1,100 1 700 5 600 ROMP 9 50 200 700 43 1,100 3 200 9 400 ROMP 9.5 -- -- 9,900 51 3,000 4 700 14 13,000 ROMP 12 5,600 1,200 43,000 51 3,800 6 2,600 15 200 ROMP 13 -- 300 800 51 1,500 7a 300 19 200 ROMP 14 -- 30 -- 52 1,300 7b 300 21 10,000 ROMP 16.5 600 -- 4,900 53 5,500 8 300 23 400 ROMP 17 -- b20 b60 55 7,800 10 1,400 25 5,800 ROMP 18 -- 2,100 -- 55 5,500 11 5,000 28 2,000 ROMP 20 -- 1,800 1,700 61 8,700 17 200 32 13,000 ROMP 22 -- -- 100 20 8,800 35 8,000 ROMP 23 -- b3,600 b60 27 700 39 13,000 ROMP 25 -- 1 -- 32 5,300 40 15,000 ROMP 28 -- 200 -- 33 1,200 44 15,000 ROMP 30 -- b100 -- 36 2,700 46 5,600 ROMP 33 -- b100 b20 40 800 50 2,900 ROMP 35 -- c3 c200 41 500 55 8,200 ROMP TR4-1 100 1,300 3,800 42 700 56 15,000 ROMP TR5-2 -- 5,000 10,000 43 800 57 5,300 ROMP TR7-4 -- -- 2,700 43 500 58 6,800 45 400 59 3,000 46 300 48 700 49 200 57 4,200 60 1,000 61 2,400

Transmissivity statistics for all wells Zones Mean Geometric mean Median Lower quartile Upper quartile

Zone 1 3,261 1,629 2,250 1,100 5,500 Zone 2 1,401 520 700 200 1,800 Zone 3 6,232 2,090 3,400 500 9,950 All zones 3,551 1,058 1,300 300 5,000

aData from SWFWMD (2000); cells without footnotes are from this source. bData from Stephanie Hertz, SWFWMD, written commun. (2001). cData from J.J. LaRoche, ROMP 35 Final Report (2004). Intermediate Aquifer System 19

(A) Romp wells open to Zone 1 (C) Stiff diagrams for Zone 1 82°30’ 82° 81°30’ 82°30’ 82° 81°30’ 28° 28° EXPLANATION Hillsborough Polk MILLIEQUIVALENTS PER LITER 40 0 40

Highlands Manatee Hardee 27°30’ 27°30’

Sarasota De Soto 9.5 TR5-1 19x 9 16.5 12 TR4-1 27° 27° Reduced 500%  TR3-1 Charlotte Glades

Lee Hendry

Note: numbers shown on the map (A) refer to the ROMP site number, 0 10 20 MILES corresponding well information given in table 1. 0 10 20 KILOMETERS

(B) Transmissivity values for Zone 1 82°30’ 82° 81°30’ 28° EXPLANATION LOCATION AND TRANSMISSIVITY VALUE, ft2 /d less than 100 100 to 999 27°30’ 1,000 to 9,999

3,800 3,000 1,100 1,500

1,100 600 50 100 Figure 9. Regional Observation and Monitor-well 27° 1,300 5,600 5,500 Program well locations, transmissivity values, and Stiff 5,500 8,700 diagrams in Zone 1. 7,800

Base from U.S. Geological Survey digital data, 1:2,000,000, 1972 Albers Equal-Area Conic projection Standard Parallels 29°30’ and 45°30’, central meridian -83°00’

The thickness of Zone 2 ranges from < 20 to about 200 ft, Transmissivity values for Zone 2 are reported for 43 wells and typically is < 100 ft in the study area (Duerr and Wolansky, in the study area and range from 1 to 8,800 ft2/d (fig. 10b) 1986; Barr, 1996; Knochenmus and Bowman, 1998; Beach (Southwest Florida Water Management District, 2000; Beach and Chan, 2003). In Lee County, south of the study area, and Chan, 2003). The mean, geometric mean, median, lower, Zone 2 rarely is thicker than 80 ft and it terminates near the and upper quartile values are about 1,400, 520, 700, 200, and southern county line (Reese, 2000). Depths below land surface 1,800 ft2/d, respectively. The most frequently reported trans- to Zone 2 generally increase to the south from about 25 ft missivities (more than 50 percent) are in the low permeability (northern sites) to more than 200 ft (southern sites). Depths of range, in the hundreds of feet squared per day. wells open to this zone are 30 to 75 ft in central Polk County Multiple water types are present in Zone 2 (app. 1A-B). (Stewart, 1966), average 40 and 65 ft in Hardee and northern The ionic composition and concentration of water samples in De Soto Counties, respectively (Wilson, 1977), and range from Zone 2, indicated by the shape and size of the Stiff diagrams, about 25 to more than 200 ft in Manatee County (Peek, 1958), are shown in figure 10c. Mixed-cation bicarbonate type from 90 to 280 ft in Sarasota County (Duerr and Wolansky, water is present at two-thirds of the ROMP sites, has rela- 1986; Knochenmus and Bowman, 1998), and from 120 to tively low ionic concentrations, and is located everywhere 360 ft in Charlotte County (Sutcliffe, 1975). but in southern and coastal Sarasota County and Charlotte 20 Regional Evaluation of the Hydrogeologic Framework....West-Central Florida

(A) Romp wells open to Zone 2 (C) Stiff diagrams for Zone 2 82°30’ 82° 81°30’ 82°30’ 82° 81°30’ 28° 28° EXPLANATION 57 Hillsborough 59 57x MILLIEQUIVALENTS PER LITER Polk 40 0 40 48 CL-3 CL-2 40 TR8-1 39 Highlands Manatee Hardee 27°30’ 27°30’ TR7-4 30 TR7-2 33 25 28 22 23 26 TR5-3 35 19 19x 15 20 17 16 14 Sarasota De Soto 13 9 TR4-1 TR5-2 10 12 27° TR3-3 TR3-1 27° 11 5 Glades Charlotte TR1-2 Lee Hendry

Note: numbers shown on the map (A) refer to the ROMP site number, 0 10 20 MILES corresponding well information given in table 1. 0 10 20 KILOMETERS

(B) Transmissivity values for Zone 2 82°30’ 82° 81°30’ 28° 700 EXPLANATION 200 700 2,600 1,400 LOCATION AND 300 5,000 TRANSMISSIVITY 300 300 VALUE, ft2 /d 200 less than 100 8,800 100 to 999 1,000 to 9,999 27°30’ 100 100 700 1 5,000 3,600 200 1,200 3 1,800 2,100 5,300 2,700 20 30 800 700 200 300 500 400 1,200 Figure 10. Regional Observation and Monitor-well 1,300 200 27° 700 300 1,400 Program well locations, transmissivity values, and Stiff 4,200 diagrams in Zone 2. 1,000 2,400

Base from U.S. Geological Survey digital data, 1:2,000,000, 1972 Albers Equal-Area Conic projection Standard Parallels 29°30’ and 45°30’, central meridian -83°00’

County. Calcium-magnesium sulfate type water is present at Zone 3 is present over a smaller part of the study area two coastal sites in Sarasota County (ROMP 20 and TR 5-2). than Zone 2, and is present south of Hillsborough and Polk Sodium chloride type water is present in southern Sarasota Counties (Basso, 2002), west of Highlands County, and County and Charlotte County (ROMP sites TR1-2, TR3-1, north of west-central Charlotte County (fig. 11a). At five TR3-3, 5, 9, 10, and 11). Mixed-ion type water is present at sites (ROMP TR4-2, 25, 33, 48, and 50), wells are open ROMP TR7-2 site in coastal Manatee County. to both Zone 3 of the intermediate aquifer system and the Zone 3 Suwannee Limestone of the Upper Floridan aquifer. Zone 3 is up to 300 ft thick and typically is > 100 ft thick (Barr, The third and lowermost permeable unit of the inter- mediate aquifer system (Zone 3) is composed of limestone 1996; Knochenmus and Bowman, 1998; Beach and Chan, and varying amounts of dolostone and siliciclastics sedi- 2003). Depths below land surface of wells open to Zone 3 ments within the Tampa or Nocatee Members of the Arcadia generally increase to the south from about 150 ft (northern Formation (Torres and others, 2001; Basso, 2002). Where the sites) to over 600 ft (southern sites). Zone 3 is hydraulically named members of the Arcadia Formation are absent, Zone 3 connected to the Upper Floridan aquifer at the northwestern is present in the lower undifferentiated Arcadia Formation. and southern extent of the study area (Sutcliffe, 1975; Reese, Intermediate Aquifer System 1

(A) Romp wells open to Zone 3 (C) Stiff diagrams for Zone 3 82°30’ 82° 81°30’ 82°30’ 82° 81°30’ 28° 28° Hillsborough EXPLANATION Polk EXPLANATION MILLIEQUIVALENTS PER LITER TR9-2 49 45 WELL OPEN TO 40 0 40 TR9-1 50 48 ZONE 3 AND THE UPPER FLORIDAN AQUIFER Manatee Hardee 27°30’ TR7-2 31 30 27°30’ TR7-4 33 TR7-1 25 SA-1 22 23 35 26 TR6-1 Sarasota De Soto 20 17 TR5-2 9.5 16 Highlands TR5-1 16.5 13 9 TR4-1 10 12 27° TR4-2 27° TR3-1 5 TR3-3 Charlotte Glades TR1-2

Lee Hendry

Note: numbers shown on the map (A) refer to the ROMP site number, 0 10 20 MILES corresponding well information given in table 1. 0 10 20 KILOMETERS

(B) Transmissivity values for Zone 3 82°30’ 82° 81°30’ 28° 600 400 13,000 200 EXPLANATION 200 LOCATION AND TRANSMISSIVITY 10,000 400 VALUE, ft2 /d 27°30’ 20 less than 100 2,700 5,800 100 to 999 2,000 1,000 to 9,999 10,000 TO 99,999 100 60 200 1,700 13,000 10,000 60 9,900 2,900 8,000 13,000 43,000 3,800 5,600 4,900 800 Figure 11. Regional Observation and Monitor-well 15,000 700 27° 15,000 6,800 Program well locations, transmissivity values, and Stiff 15,000 8,200 5,300 3,000 3,000 diagrams in Zone 3.

Base from U.S. Geological Survey digital data, 1:2,000,000, 1972 Albers Equal-Area Conic projection Standard Parallels 29°30’ and 45°30’, central meridian -83°00’

2000; Basso, 2002). Depth below land surface of wells open transmissivities are in the moderate permeability range, in to this zone ranges from 130 to 300 ft in Hardee County, from the thousands of feet squared per day, however, nearly equal 130 to 400 ft in De Soto County (Wilson, 1977), from 280 to numbers of reported transmissivities are in the hundreds and 440 ft in Sarasota County, and from 350 to 400 ft in Charlotte tens of thousands of feet squared per day. County (Sutcliffe, 1975; Knochenmus and Bowman, 1998; Multiple water types also are present in Zone 3 at selected Reese, 2000). ROMP sites (fig. 11c). The water types are about equally split Transmissivity values for Zone 3 are reported for 36 sites among mixed-cation bicarbonate, calcium-magnesium sulfate, in the study area, and range from 20 to 43,000 ft2/d (Southwest and sodium chloride. The ionic composition and concentration Florida Water Management District, 2000; Beach and Chan, of water samples are indicated by the shape and size of the 2003). Of the three permeable zones in the intermediate Stiff diagrams. Mixed-cation bicarbonate type water is present aquifer system, only Zone 3 has values exceeding 10,000 at seven inland ROMP sites (9.5, 13, 16, 17, 30, 31, 45, and ft2/d (fig. 11b). The mean, geometric mean, median, lower, 49) located in south central Hillsborough, Polk, Hardee, and and upper quartile values are about 6,200, 2,100, 3,400, 500, most of De Soto Counties. Calcium-magnesium sulfate type and 9,900 ft2/d, respectively. The most frequently reported water is present at nine coastal Manatee and Sarasota County  Regional Evaluation of the Hydrogeologic Framework....West-Central Florida

ROMP sites (TR 4-1, 4-2, 5-1, 5-2, 6-1, 7-2, 7-4, SA-1, Clay Beds and 20). Sodium chloride type water is present at eight ROMP The degree of hydraulic connection between permeable sites (TR1-2, TR3-1, TR3-3, 5, 9, 10, and 12) in Charlotte and zones is related to the presence and thickness of clay beds southern De Soto Counties. Mixed-ion type water is present at within the Hawthorn Group. Clay beds, described in litho- three ROMP sites (TR9-2, 22, and 30) in coastal Hillsborough, logic logs, make up 0 to 75 percent of the sediments in the eastern Sarasota, and central Hardee Counties. Hawthorn Group; the clay content generally increases to the north and east (fig. 12). At about 70 percent of the ROMP sites, the clay beds in the Hawthorn Group make up < 25 Confining Units percent of the lithology; however, even at small percentages, clays lower the permeability. The clay beds are heteroge- In most of the study area, confining units restrict, to neously distributed both laterally and vertically and range in varying degrees, the vertical movement of water between thickness from about 2 ft (stringer) to more than 100 ft (fig. 8). permeable units. The confining units consist of sandy and silty Clay beds that are distributed throughout the Hawthorn clays as well as mudstones and dolosilts that hydraulically Group tend to lower the overall permeability, resulting in a separate the permeable units within the intermediate aquifer hydrogeologic unit that is best described as a confining or system, and isolate the intermediate aquifer system from the semiconfining unit separating the overlying surficial aquifer adjacent aquifers. Although the confining units impede the system and underlying Upper Floridan aquifer. In general, the movement of water between zones, the units are leaky and clay content is lowest in the Tampa Member, and higher in the water moves across them depending on hydraulic head differ- Peace River Formation, the Nocatee Member, and undifferen- ences and the relative permeability of the units. tiated Arcadia Formation.

82°30’ 82° 81°30’

28°

70 35 A B 4 A 43 41 53 17 B C Tampa Gulf of Me Bay 39 28

27°30’ 53 xico A A 33 42 11 29 19 19 26 C 24 42 13 48

17 75 9 0 5 10 15 MILES 19 15 19 6 10 61 13 12 0 5 10 15 KILOMETERS A 20 7 23 34 13 7 0 A 27° EXPLANATION 43 AREAS OF CLAY PERCENTAGE 16 11 A Less than 20 percent STUDY AREA 27 B 20 to 40 percent BOUNDARY C Greater than 40 percent Charlotte 42 SITE LOCATION AND CLAY Harbor PERCENTAGE

Base from U.S. Geological Survey digital data, 1:2,000,000, 1972 Albers Equal-Area Conic projection Standard Parallels 29°30’ and 45°30’, central meridian -83°00’

Figure 12. Percentage of clay in the Hawthorn Group sediments. Intermediate Aquifer System 

Leakance Across Confining Units 4.3x10-7 to 6.0x10-3 (ft/d)/ft, (Yobbi and Halford, 2006) (table 3). Leakance of confining units ranges from 4.6x10-5 to In general, confining units have low hydraulic conduc- 1.1x10-4 (ft/d)/ft for the units separating the surficial aquifer tivity and transmit water at a very slow rate. Over a large area system from Zone 1; 7.1x10-6 to 2.9x10-4 (ft/d)/ft for the units of contact and sufficient time, however, confining units can separating Zone 1 from Zone 2; 1.3x10-6 to 1.1x10-3 (ft/d)/ft contribute substantially to the recharge of aquifers (De Weist, for the units separating Zone 2 from Zone 3, and 1.1x10-6 1965). Leakance is the hydraulic property that quantifies the -3 potential for confining units to transmit water vertically from to 6.0x10 (ft/d)/ft for the units separating Zone 3 from the an underlying or overlying aquifer (Wolansky and Corral, Upper Floridan aquifer (table 3). The spatial and vertical 1985). In the study area, leakance was estimated between adja- distribution of leakance for each confining unit evaluated in cent aquifers and zones at 12 ROMP sites. Leakance values of the study area is shown in figure 13. No apparent pattern, such the confining units within the intermediate aquifer system that as increasing/decreasing with depth or location, is observed in were determined, numerically spans 4 orders of magnitude— the vertical distribution of leakance (fig. 13a).

Table 3. Leakance values at selected Regional Observation and Monitor-well Program (ROMP) sites.

[All values in foot per day per foot]

ROMP Upper confining Upper-middle Lower-middle Middle Lower Ocala semiconfining a b c d e name unit confining unit confining unit confining unit confining unit unitf

5 2.4x10-5 SAS–2 1.6x10-5 Zone 2–3 4.2x10-3 Zone 3–UFA 1.5x10-3 UPZ–LPZ 9 1.4x10-4 SAS–1 1.7x10-5 Zone 1–2 2.0x10-5 Zone 2–3 1.7x10-4 Zone 3–UFA 1.6x10-2 UPZ–LPZ 12 4.6x10-5 SAS–1 2.9x10-4 Zone 1–2 1.1x10-3 Zone 2–3 6.0x10-3 Zone 3–UFA 9.7x10-3 UPZ–LPZ 13 2.2x10-6 SAS–2 1.3x10-6 Zone 2–3 9.8x10-6 Zone 3–UFA 2.0x10-3 UPZ–LPZ 14 5.8x10-7 SAS–2 4.3x10-7 Zone 2–UFA 7.8x10-3 UPZ–LPZ 20 1.3x10-5 SAS–2 4.4x10-6 Zone 2–3 8.9x10-5 Zone 3–UFA 1.0x10-3 UPZ–LPZ 22 1.5x10-5 SAS–2 3.2x10-5 Zone 2–3 8.5x10-4 Zone 3–UFA 1.7x10-2 UPZ–LPZ 25 1.1x10-5 SAS–2 8.1x10-6 Zone 2–UFA 9.6x10-4 UPZ–LPZ 28 7.9x10-4 SAS–2 2.2x10-5 Zone 2–UFA 3.7x10-3 UPZ–LPZ g 39 1.0x10-5 SAS–2 2.4x10-5 Zone 2–2 7.8x10-7 Zone 2–UFA 7.7x10-5 UPZ–LPZ TR4-1 1.1x10-4 SAS–1 7.1x10-6 Zone 1–2 6.5x10-5 Zone 2–3 6.3x10-4 Zone 3–UFA 6.0x10-3 UPZ–LPZ TR9-2 2.9x10-6 SAS–3 1.1x10-6 Zone 3–UFA 7.6x10-4 UPZ–LPZ

Upper grouph Lower groupi Ocalaf

Mean 9.9x10-5 1.1x10-4 5.5x10-3 Geometric Mean 2.0x10-5 1.2x10-5 2.6x10-3 Median 1.5x10-5 1.8x10-5 2.8x10-3 Minimum 5.8x10-7 4.3x10-7 7.7x10-5 Maximum 7.9x10-4 1.1x10-3 1.7x10-2

aUpper confining unit separates the surficial aquifer system (SAS) and the uppermost Zone (1 or 2) in the intermediate aquifer system. bUpper-middle confining unit separates Zone 1 from Zone 2. cLower-middle confining unit separates Zone 2 and Zone 3. dMiddle confining unit separates Zone 1 or Zone 2 from Zone 3. eLower confining unit separates lowermost Zone (2 or 3) from the upper permeable zone of the Upper Floridan aquifer (UFA). fOcala semiconfining unit separates the upper (UPZ) and lower permeable zones (LPZ) of the Upper Floridan aquifer. gZone 2 to 2 confining unit separates zones both designated 2. hUpper group includes all confining units above Zone 2. iLower group includes all confining units below Zone 2.  Regional Evaluation of the Hydrogeologic Framework....West-Central Florida

(A) Leakance, in foot per day per foot across confining units separating permeable units A A’ TR9-2 39 25 5 0 -6 -5 -5 2.9x10 1.0x10 -5 1.1x10 2.4x10 -6 -7 200 1.1x10 7.8x10 8.1x10-6 1.6x10-5 400

-4 600 7.6x10 4.2x10-3 800 9.6x10-4

1,000 -3 EXPLANATION -5 1.5x10 1,200 7.7x10 SURFICIAL AQUIFER SYSTEM

1,400 ZONE 1

1,600 ZONE 2 ZONE 3

1,800 SUWANNEE (UPPER B B’ PERMEABLE ZONE) 20 22 25 28 AVON PARK (LOWER 0 -5 -5 PERMEABLE ZONE) 1.3x10 1.5x10 1.1x10-5 -6 -5 200 4.4x10 3.2x10 8.1x10-6 7.9x10-4 8.5x10-4 400 -5 8.9x10 2.2x10-5 600

ACE, IN FEET 800 -4 3.7x10-3 1.7x10-2 9.6x10 -3 1,000 1.0x10

1,200

1,400

1,600

1,800

DEPTH BELOW LAND SURF C C’ TR4-1 9 12 13 14 0 -4 1.4x10-4 -5 1.1x10 -5 4.6x10 7.1x10-6 1.7x10 -5 -4 -6 -5 2.0x10 200 6.5x10 2.9x10 2.2x10 -7 -4 5.8x10 400 1.7x10 -3 -6 1.1x10 1.3x10 -6 -7 600 6.3x10-4 9.8x10 4.3x10 6.0x10-3 800 7.8x10-3 -2 1,000 6.0x10-3 1.6x10 9.7x10-3 2.0x10-3

1,200

1,400

1,600

1,800

Figure 13. Leakance values, in foot per day per foot, shown on sections and maps at selected Regional Observation and Monitor-well Program sites. Intermediate Aquifer System 

(B) Leakance across the upper group of confining units–(above Zone 2) 82°30’ 82° 81°30’ EXPLANATION 28° CC’ LINES OF SECTION—Shown in figure 13A. LOCATION AND LEAKANCE 4.6x10-5 A -6 -4 VALUE—In foot per day per Tampa 2.9x10 2.9x10 foot. Pairs of numbers indicate Bay two confining units, value for shallower unit shown in red. -5 Gulf 1.0x10

o 27°30’ f Me xico 1.1x10-5 B’ 1.5x10-5 7.9x10-4

1.3x10-5 -7 -4 B -4 1.4x10 5.8x10 C’ 1.1x10 -5 -5 -6 1.7x10 4.6x10 7.1x10 2.9x10-4 2.2x10-6 27° C -5 A’ 2.4x10 STUDY AREA BOUNDARY 0 10 20 MILES Charlotte 0 10 20 KILOMETERS Harbor

(C) Leakance across the lower group of confining units–(below Zone 2) 82°30’ 82° 81°30’ EXPLANATION 28° -6 LOCATION AND LEAKANCE 1.3x10-6 VALUE—In foot per day per 9.8x10 foot. Pairs of numbers indicate two confining units, value for Tampa -6 shallower unit shown in red. Bay 1.1x10

Gulf 7.8x10-7 o 27°30’ f Me

xico -5 8.1x10-6 2.2x10 3.2x10-5 8.5x10-4 -6 4.4x10 -7 -5 4.3x10 8.9x10 2.0x10-5 1.7x10-4 -3 1.3x10-6 1.1x10-3 -6 -5 6.0x10 9.8x10 6.5x10 27° 6.3x10-4 -5 1.6x10-3 4.2x10 STUDY AREA BOUNDARY 0 10 20 MILES Charlotte 0 10 20 KILOMETERS Harbor

Base from U.S. Geological Survey digital data, 1:2,000,000, 1972 Albers Equal-Area Conic projection Standard Parallels 29°30’ and 45°30’, central meridian -83°00’

Figure 13. (Continued) Leakance values, in foot per day per foot, shown on sections and maps at selected Regional Observation and Monitor-well Program sites.  Regional Evaluation of the Hydrogeologic Framework....West-Central Florida

The apparent randomness of the leakance values is Hydraulic Head Differences due in part to the limited geographical extent of Zone 1, and overall good hydraulic connection between Zone 3 Differences between hydraulic heads of aquifers in the and the Upper Floridan aquifer. Zone 2, however, typi- study area were used to characterize recharge and discharge cally is hydraulically separated from the adjacent aquifers; areas, to illustrate the magnitude and direction of vertical therefore it was deemed appropriate to evaluate leakance flow, and to qualitatively assess the degree of interconnection in terms of an upper and lower group of confining units. between permeable units. The magnitude of the head differ- The upper group includes any and all intermediate aquifer ences at a particular site reflects the degree of confinement system confining units above Zone 2; the lower group between the aquifers and zones, and is related to the lithologic includes any and all intermediate aquifer system confining composition and thickness of the confining units. Thicker and units below Zone 2, multiple leakance values listed for a hydraulically tighter confining units typically result in greater site indicate the presence of more than one confining unit head differences and reduced hydraulic connection between within the upper or lower group (figs. 13b,c). Leakance zones. Small differences indicate good hydraulic connection values for the upper group range from 5.8x10-7 to 7.9x10-4 and larger differences indicate greater hydraulic separation. (ft/d)/ft and values for the lower group range from 4.3x10-7 Head differences between permeable units create the potential to 1.1x10-3 (ft/d)/ft. The mean, geometric mean, and median for vertical ground-water flow across confining units (Wilson, values for the upper group are 9.9x10-5, 2.0x10-5, and 1977). In 2001, head differences varied from as much as 1.5x10-5 (ft/d)/ft; and for the lower group are 1.1x10-4, 1.2x10-5, -153 ft (downward head difference) in the recharge area to and 1.8x10-5 (ft/d)/ft, respectively (table 3). Despite the large more than 30 ft (upward head difference) in the discharge area overall range in leakance, the most frequent values for both (fig. 14; app. 2A (April) and app. 2B (October)). The transi- groups of confining units within the intermediate aquifer tion from recharge to discharge conditions is abrupt, and is system are about the same order of magnitude (10-5), which delineated by a hinge line, a boundary line separating recharge is about 2 orders of magnitude lower than the semiconfining areas from discharge areas (Freeze and Cherry, 1979). The unit (Ocala) separating the upper permeable zone (UPZ; hinge line divides De Soto County, passes through east central Suwannee Limestone) from the lower permeable zone (LPZ; Sarasota County, and parallels the coast in Sarasota, Manatee, Avon Park Formation) in the Upper Floridan aquifer (table 3; and Hillsborough Counties (fig. 14). The hinge line moved fig. 13a). slightly south in Sarasota County between the dry and wet

82°30’ 82° 81°30’ EXPLANATION 28° Polk Hinge Line-DRY Hillsborough -20/-15 RECHARGE NM/-2 Hinge Line-WET AREA -4/1 -153/-126 -4/1 LOCATION AND WATER-LEVEL -8/2 -84/-60 -53/-33 -48/-33 DIFFERENCE— In feet, dry season/wet season. NM Tampa -46/-30 -129/-95 indicates not measured. Gulf Bay 4/7 Highlands Positive number indicates water levels increase with o -132/-116 Hardee f Me Manatee depth. Negative number 27°30’ xico -54/-31 -42/-16 indicates water levels -2/2 -73/-60 -97/-70 decrease with depth 1/7 -18/-8 8/9 -24/-13 -46/-35 -74/-52 -31/-24 NM/-25 De Soto -23/-18 -2/4 -18/-14 7/9 -4/2 24/28 -28/-24 NM/18 3/7 -91/-89 Sarasota 9/13 NM/8 -10/-9 22/24 23/27 10/10 10/14 27° DISCHARGE 13/17 AREA 25/25 30/32 Charlotte Glades 23/24 STUDY AREA BOUNDARY Charlotte 0 10 20 MILES Harbor 0 10 20 KILOMETERS Lee Hendry

Base from U.S. Geological Survey digital data, 1:2,000,000, 1972 Albers Equal-Area Conic projection Standard Parallels 29°30’ and 45°30’, central meridian -83°00’

Figure 14. Recharge and discharge areas and magnitude of water-level differences between the surficial aquifer system and the Upper Floridan aquifer during the wet and dry seasons, 2001. Intermediate Aquifer System  seasons in 2001. Water-level differences and potential flow Because of the absence of Zones 1 and 3 in parts of the directions between zones in wells that are located close to the study area, differences in hydraulic head across the interme- hinge line alternate seasonally between discharge and recharge diate aquifer system were evaluated by separating the confining conditions. units into an upper and lower group of units. Differences in Hydraulic heads differ among zones within the interme- hydraulic head across the upper group of units were defined by diate aquifer system and between these zones and adjacent water-level differences between the surficial aquifer system and aquifers. Generally, head differences are greater across the Zone 2 during 2001. Differences in hydraulic head across the intermediate aquifer system than between the intermediate lower group of units were defined by water-level differences aquifer system and adjacent aquifers. In the small part of the between Zone 2 and the Upper Floridan aquifer during 2001. study area where Zone 1 is found, head differences between Water-level differences between the surficial aquifer system and Zone 2 ranged from about -48 to 14 ft, and water-level differ- Zone 1 and the surficial aquifer system range from -1 to 3 ft. ences between Zone 2 and the Upper Floridan aquifer ranged Additionally, heads are nearly the same (< 1 ft) between Zone 3 from -119 to 24 ft (fig. 15). In the discharge area (Charlotte, and the Upper Floridan aquifer, except in coastal Charlotte most of Sarasota, and coastal Manatee and Hillsborough and Sarasota Counties where the differences range from 2 to Counties), upward head differences between Zone 2 and the 10 ft (ROMP sites TR3-1, TR3-3, TR4-1, TR5-1, TR5-2, 20, Upper Floridan aquifer are greatest. With a few exceptions, and SA-1) and inland sites where differences range from < -1 downward head differences between the surficial aquifer system to -5 ft (ROMP sites 9.5, 17, 30, 31, 45, and 49) (app. 2A-B). and Zone 2 are greatest in the recharge area. Total head differences between the surficial aquifer system Water levels in aquifers in southwest Florida follow a and the Upper Floridan aquifer range from -153 to 30 ft, and natural cyclic pattern of seasonal fluctuation, typically rising head differences between the intermediate aquifer system and during the summer wet season (when the rate of recharge adjacent aquifers are within plus or minus 5 ft. Therefore, the exceeds the rate of discharge) and falling to the lowest levels large remainder of these differences in head is found between in the spring dry season (when the rate of discharge exceeds adjacent zones within the intermediate aquifer system. the rate of recharge). The magnitude of fluctuation in water

(A) Water-level difference between the surficial aquifer system and Zone 2 of the intermediate aquifer system. 82°30’ 82° 81°30’ EXPLANATION 28° -5/0 -6/-4 LOCATION AND WATER-LEVEL Hillsborough DIFFERENCE— In feet, dry season/wet Polk season. NM indicates not measured. -5/0 Positive number indicates water levels Tampa -1/-1 -48/-33 increase with depth. Negative number Bay indicates water levels decrease with depth -10/-8 NOTE: Values of -0 indicate that the Gulf of Me -42/-41 Highlands difference was less than 0 but not greater 1/4 Hardee Manatee than -0.5 feet. 27°30’ -30/-14 -2/-0 -2/4 xico -45/-37 -40/-30 -15/-8 -35/-34 NM/-6 -32/-25 -19/-10 De Soto NM/0 10/13 -28/-24 -27/-30 -13/-10 -3/2 -18/-13 -5/-2 10/14 -10/-11 Sarasota 10/14 2/2 12/14 27° 10/12 -10/-4 Glades 10/11 Charlotte STUDY AREA -1/1 BOUNDARY 0 10 20 MILES Charlotte 0 10 20 KILOMETERS Harbor Lee Hendry

Base from U.S. Geological Survey digital data, 1:2,000,000, 1972 Albers Equal-Area Conic projection Standard Parallels 29°30’ and 45°30’, central meridian -83°00’

Figure 15. Water-level differences during the wet and dry seasons, 2001.  Regional Evaluation of the Hydrogeologic Framework....West-Central Florida

(B) Water-level difference between Zone 2 of the intermediate aquifer system and the Upper Floridan aquifer. 82°30’ 82° 81°30’ EXPLANATION 28° -14/-11 0/1 Hillsborough -25/-10 LOCATION AND WATER-LEVEL DIFFERENCE— In feet, dry season/wet Polk season. NM indicates not measured. 0/1 Positive number indicates water levels Tampa -83/-58 Bay -0/-0 increase with depth. Negative number -119/-86 indicates water levels decrease with depth Gulf of 3/3 Highlands NOTE: Values of -0 indicate that the -90/-75 Hardee Manatee difference was less than 0 but not greater 27°30’ than -0.5 feet. M -12/-2 e 1/2 3/2 xico -28/-22 -34/-23 -3/-1 -5/-2 1/1 -12/-1 NM/-19 De Soto 20/18 14/15 -64/-59 -1/0 1/-1 0/-0 15/18 8/9 Sarasota 13/13 0/2 20/22 0/0 27° 15/14 23/20 Glades 20/21 Charlotte STUDY AREA 24/23 BOUNDARY 0 10 20 MILES Charlotte 0 10 20 KILOMETERS Harbor Lee Hendry Base from U.S. Geological Survey digital data, 1:2,000,000, 1972 Albers Equal-Area Conic projection Standard Parallels 29°30’ and 45°30’, central meridian -83°00’

Figure 15. (Continued) Water-level differences during the wet and dry seasons, 2001.

levels can vary greatly from season to season and from year to Changes in the potential vertical flow direction were year in response to varying climatic conditions. Additionally, observed at 14 ROMP sites in the study area (fig. 16a). Under the magnitude and timing of seasonal water-level fluctuations ambient (nonpumping) conditions, 13 of the 14 sites are in the may vary in different aquifers in the same geographic area, discharge area and heads increase with depth. Under stressed depending on the sources of recharge to and discharge from the (pumping) conditions, changes in the vertical head distribu- aquifers and the hydraulic properties of each (Taylor and Alley, tion range in duration from less than a day (temporary), to 2001). Water levels in wells at most of the ROMP sites also are short-term (seasonal), to long-term (year-round). Changes may affected by nearby pumping. The withdrawal of ground water affect the entire ground-water system or only certain zones at by pumping is the most important human activity that alters the a site. Ground-water development is primarily from the upper volume of water in storage, the rate of discharge from aquifers, intermediate aquifer system (Zones 1 and/or 2) in the southern and the direction of flow both horizontally and vertically (Taylor part of the study area, coincident with the occurrence of poor and Alley, 2001). Declines in ground-water levels can alter the quality water in the deeper zones (Sutcliffe, 1975). potential flow direction among zones within the intermediate Potential vertical ground-water flow patterns, based on aquifer system and between the intermediate aquifer system and water-level differences in cluster wells, can be grouped into five adjacent aquifers. Temporary changes in vertical flow direc- categories: (1) decreasing water levels with depth (downward tion likely result from localized heavy but short-lived pumping flow potential); (2) increasing water levels with depth (upward conditions; whereas widespread, long-term ground-water flow potential); (3) water levels that are lower in the upper inter- pumping can lead to persistent ground-water level declines and mediate aquifer system (Zones 1 or 2) than in adjacent aquifers gradient changes, creating new recharge areas within the aquifer (both upward and downward flow potential); (4) unstressed system (Galloway and others, 1999). Ranges in the annual water levels that increase with depth (upward flow potential) but water-level fluctuation, seasonal variations, and cumulative under temporary stressed conditions water levels are lowered in effects of short-term and long-term hydrologic stresses in the the upper intermediate aquifer system (upward and downward aquifers throughout the study area are exhibited on hydrographs flow potential); and (5) water levels that alternate seasonally of water levels from nested wells (fig. 16). between increasing water levels with depth during the wet season and decreasing water levels with depth during the dry season (upward and downward flow potential throughout the entire ground-water flow system) (fig. 16a). Intermediate Aquifer System 

(A) 40 82°30’ 82° 81°30’ (C) Category 2 Suwannee Limestone 28° STUDY AREA BOUNDARY 30 Polk Zone 3 Hillsborough ROMP TR3-1 Tampa Bay 20 Gulf 22 Highlands Zone 2 Hardee o Manatee 27°30’ f Me 10 Surficial Aquifer System xico Zone 1

19x 0 Sarasota De Soto 9 60 27° (D) Category 3 ROMP 5 TR3-1 5 Zone 3 0 5 10 15 MILES Charlotte Glades 50

0 5 10 15 KILOMETERS Charlotte Harbor Lee Hendry Avon Park Formation

TUM OF 1929, IN FEET Suwannee Limestone Base from U.S. Geological Survey digital data, 1:2,000,000, 1972 40 Albers Equal-Area Conic projection Standard Parallels 29°30’ and 45°30’, central meridian -83°00’ Surficial Aquifer System EXPLANATION 30 Zone 2 LOCATION AND VERTICAL FLOW CATEGORY Category 1- downward flow direction Category 2- upward flow direction 20 Category 3- mixed flow direction, lowest in zones 1 or 2

GEODETIC VERTICAL DA 50 Category 4- mixed flow direction, temporarily lowest in zones 1 or 2 (E) Category 4 ROMP 9 Category 5- alternating flow direction Avon Park Formation

Single well at site, category undetermined TIONAL 40

Suwannee Limestone Zone 3 30 TIONAL 50 Zone 2 (B) Category 1 ROMP 22 40 20 Zone 1 30 Surficial Aquifer System Surficial Aquifer System

TUM OF 1929, IN FEET 20 10 Zone 2 TER LEVELS ABOVE THE NA

WA 45 10 Avon Park Formation (F) Category 5 ROMP 19x Zone 3 0 Suwannee Limestone Suwannee Limestone 35 Zone 1 -10 Zone 2 TER LEVELS ABOVE AND BELOW THE NA M J J A S O N D J F M A M J J A S O N D J F M A

GEODETIC VERTICAL DA 2000 2001 2002

WA

25

Surficial Aquifer System

15 M J J A S O N D J F M A M J J A S O N D J F M A 2000 2001 2002

Figure 16. Flow potential category and representative water-level hydrographs. 30 Regional Evaluation of the Hydrogeologic Framework....West-Central Florida

The ROMP 22 site is an example of the first category, than in the surficial aquifer system. At this site, water levels where water levels decrease with well penetration depth are about 20 ft higher in the Suwannee and Avon Park wells (fig. 16b; table 1). Water-level differences among wells vary than in the surficial aquifer system well (fig. 16e). This 20-ft seasonally in that differences are typically lower during the water-level difference essentially occurs within the inter- late summer (lower recharge potential) and higher during the mediate aquifer system, with nearly equivalent differences late spring (higher recharge potential). A persistent water-level between the Zones 3 and 2 wells, and between the Zones 2 and difference of about 2 ft is observed within the Upper Floridan 1 wells (about 10 ft, respectively). During pumping periods, aquifer, between the Suwannee and Avon Park wells, but no however, water levels in the Zone 2 well may temporarily measurable difference is observed between the Suwannee and decline below the levels in the Zone 1 well and occasionally Zone 3 wells. Zone 2 is hydraulically separated from the surfi- below levels in the surficial aquifer system as well. Thus, cial aquifer system, and the water-level difference between the during momentary pumping periods in 2000-2002, there wells in these two zones is as much as 20 ft. During unstressed was the potential for both upward and downward flow from periods (wet season), heads are nearly identical within zones adjacent zones (Zones 1 and 3) and aquifers (surficial aquifer of the intermediate aquifer. During stressed periods (dry system and Upper Floridan aquifer) into Zone 2. season), however, heads are about 10 ft lower in Zone 3 than The ROMP 19X site is an example of the fifth category, in Zone 2. where both upward and downward flow potential occurs. The ROMP TR3-1 site is an example of the second Water levels increase with well penetration depth by the end category, where water levels increase with well penetration of wet season (September and October), decrease with well depth (fig. 16c). Head differences at this site are smaller penetration depth by the end of the dry season (April and between the intermediate aquifer system and adjacent aquifers May), and are mixed during the rest of the year (fig. 16f). (2 ft or less) compared to head differences between zones The mixed gradients result from the timing of seasonal within the intermediate aquifer system (10 ft between Zones water-level fluctuations (maximums and minimums) among 1 and 2, and 15 ft between Zones 2 and 3). In May and June, the aquifers. Annually, water-level differences between the water levels are about the same in Zone 1 and surficial aquifer system wells. Water-level fluctuations are similar in all of the wells penetrating the Upper Floridan aquifer and the surficial wells, so differences and potentials for upward flow are about aquifer system vary from -4 to 3 ft. Most of the time, water the same throughout the year. levels are nearly the same in the surficial aquifer system and The ROMP 5 site is an example of the third category, Zone 1 wells. During the winter (January and February), water where water levels are lowest year-round in the Zone 2 well levels are nearly the same throughout the intermediate aquifer (about 20 ft lower than levels in the Suwannee, Avon Park, and system, in the surficial aquifer system, and occasionally in the Zone 3 wells) (fig. 16d). Water levels are the same in Suwannee, Upper Floridan aquifer. Avon Park, and Zone 3 wells. Water-level differences between In general, the magnitude of the water-level differences the Zone 2 and surficial aquifer system wells annually fluctuate, among wells at a particular site reflects the degree of confine- ranging from 3 to 10 ft and averaging about 5 ft. Thus, during ment between the aquifers and zones, and is related to the 2000-2002, there was the potential for both upward and down- lithologic composition and thickness of the confining units. ward flow from adjacent aquifers into Zone 2. Thicker and hydraulically tighter confining units typically The ROMP 9 site is an example of the fourth category, result in greater water-level differences and reduced hydraulic an area where the potential for upward flow exists during connection between zones. Small differences indicate good unstressed conditions, but during stress conditions, water hydraulic connection and larger differences indicate greater levels are temporarily lower in the intermediate aquifer system hydraulic separation. Regional Evaluation of the Intermediate Aquifer System 1

Regional Evaluation of the Comparison of the chemical composition of water among the zones indicates the lack of a distinct geochemical Intermediate Aquifer System signature that characterizes individual zones. In contrast, the geographic distribution of water types in all zones is similar A regional evaluation of the chemical characteristics, (fig. 17). Sodium chloride type water is present in the south- hydraulic properties, head gradients, and water-level responses ernmost part of the study area in all zones, with the likely is presented below. Comparisons among zones, particularly source of sodium and chloride from relict saltwater from past the distribution of the hydraulic properties and chemical char- marine inundations during periods of high sea level stand that acteristics, indicate that the study area can be separated into has not been flushed from the aquifers (DeHaven and Jones, interrelated subgroups (subregions with similar characteristics) 1996). Calcium-magnesium sulfate type water is present along regardless of the intermediate aquifer system zone. the coastal margin from Tampa Bay to southern Sarasota

(A) WATER TYPES ZONE 1 82°30’ 82° 81°30’ EXPLANATION 28° SODIUM CHLORIDE WATER TYPE CALCIUM-MAGNESIUM SULFATE WATER TYPE MIXED-CATION BICARBONATE WATER TYPE 27°30’ LOCATION OF WELLS WITH MIXED-ION WATER TYPE LOCATION OF WELLS

 0 10 20 MILES

27° 0 10 20 KILOMETERS

(B) WATER TYPES ZONE 2 (C) WATER TYPES ZONE 3 82°30’ 82° 81°30’ 82°30’ 82° 81°30’ 28° 28°

27°30’ 27°30’

27° 27° 

Base from U.S. Geological Survey digital data, 1:2,000,000, 1972 Albers Equal-Area Conic projection Standard Parallels 29°30’ and 45°30’, central meridian -83°00’

Figure 17. Distribution of water types in Zones 1, 2, and 3.  Regional Evaluation of the Hydrogeologic Framework....West-Central Florida

County, with the likely source of magnesium and sulfate from data available from 93 wells. Of the 93 wells, 15 percent (14 upwelling of sulfate-rich waters from the Upper Floridan wells), 45 percent (43 wells), and 39 percent (36 wells) were aquifer (Sacks and Tihansky, 1996). Mixed-cation bicarbonate open to Zones 1, 2, and 3, respectively (fig. 18). The data sets type water is present in the inland areas, and is the predomi- are similar in the following ways; each of the boxplots shows nant water type within the intermediate aquifer system, with (1) a median line that is closer to the lower quartile than the the likely source of magnesium and calcium from the dolo- upper, indicating a greater number of low values, and (2) the mitic aquifer matrix. The overall permeability in the intermediate aquifer taller top box halves and significantly longer upper whiskers system is best characterized as low to moderately low. indicate a right-skewed distribution (fig. 18). Right-skewed Comparisons of the hydraulic characteristics among the zones distributions are the most commonly occurring shape for were made using standard boxplots of the transmissivity water-resources data (Helsel and Hirsch, 1992).

Y

15,000 3 values

3 values

10,000

, IN FEET SQUARED PER DA 5,000

0

TRANSMISSIVITY All Zones Zone 1 Zone 2 Zone 3 EXPLANATION OUTSIDE VALUES—Values between 1.5 and 3 times greater than the IQR; “far-out” values greater than 3 times the IQR;1 far-out value of transmissivity in Zone 3 data set, value not shown LARGEST VALUE WITHIN 1.5 TIMES THE INTERQUARTILE RANGE (IQR) AND IS NOT THE MAXIMUM VALUE 75th PERCENTILE MEDIAN (50th)

IQR 25th PERCENTILE VALUE WITHIN 1.5 TIMES THE IQR AND IS THE MINIMUM OR MAXIMUM VALUE

Figure 18. Box plots of transmissivity. Regional Evaluation of the Intermediate Aquifer System 

The statistically defined differences among the zones can are highest near the coast in southwestern Sarasota County, be seen in the variations in the median values and interquartile and moderate transmissivities predominate in the coastal and ranges. Zone 2 is the least transmissive with the lowest median southern parts of the study area (fig. 19c). value, which is less than half the Zone 1 value. The median More noticeable than variations within zones, however, is transmissivity for Zone 3 is highest, with a value twice as large the geographical distribution of transmissivity resulting from as the value for Zone 1 and more than four times the value for the lithologic variability and differences in the depositional Zone 2. The spread of the data is smallest for Zone 2, medium environment in the study area. More carbonate sediments for Zone 1, and largest for Zone 3. Zone 2 has a single outside where deposited in the southern and southwestern parts of value of transmissivity (value between 1.5 and 3 times the the study area where transmissivity is higher, whereas silici- interquartile range) and Zone 3 has a single far-out value of clastic sediments were deposited throughout the rest of the transmissivity (value beyond 3 times the interquartile range). study area where transmissivity is lower. Specifically, a region When all zones are combined, there are seven transmissivity of relatively low transmissivity (< 100 ft2/d) throughout the outliers (six outside values and one far-out value). vertical extent of the intermediate aquifer system is present The permeability distribution within each zone was in the central part of the study area encompassed by a larger mapped, creating permeability subregions that were defined region of moderately low permeability (< 1,000 ft2/d) that using ranges of transmissivity (fig. 19). Zone 1 underlies the covers a large part of the study area. Therefore, permeability smallest part of the study area and is present in southwestern subregions based on ranges of transmissivity can be defined Manatee and De Soto Counties and most of Sarasota and geographically for the intermediate aquifer system regardless Charlotte Counties (fig. 19a). Transmissivities are between of zone. 1,000 and 10,000 ft2/d, except at three isolated sites. Data are Water-level differences reflect the degree of confinement lacking for almost half of the area; where data are available, between aquifers and zones, well location with respect to the Zone 1 is characterized as moderately permeable (fig. 19a). regional ground-water flow system (recharge/discharge), and Of the three zones, Zone 2 underlies the largest part of ground-water withdrawals. Thicker and hydraulically tighter the study area. More than half of the study area has trans- confining units typically result in greater head differences missivities in Zone 2 that are moderately low, ranging from 100 to < 1,000 ft2/d. Three regions within Zone 2 have and reduced hydraulic connection between zones. Markedly transmissivities between 1,000 and 10,000 ft2/d and are thinner or absent confining units result in nonexistent or characterized as moderately permeable (blue areas in fig. 19b). small water-level differences and indicate good hydraulic A larger region that has moderately low permeability sepa- connection. The following water-level characteristics were rates these three smaller regions. A region of low permeability noted in the study area. Water-level differences are equiva- (transmissivity ranging from 1 to < 100 ft2/d) is located in the lent or nearly so between surficial aquifer system and Zone 1 central part of the study area. wells, and between Zone 3 and Upper Floridan aquifer wells. Zone 3 underlies the southern half of Manatee County, Water levels in Zone 2 wells typically are distinct from south central Polk County, all of Sarasota County and most of levels measured in adjacent zones at a site. The recharge area Hardee, De Soto, and Charlotte Counties. In eastern De Soto, (decreasing water levels with well penetration depth) encom- southeastern Charlotte, western Hillsborough, and north- passes more than 70 percent of the study area. Water levels western Manatee Counties, the carbonate strata of the lower alternate seasonally between increasing and decreasing water Arcadia Formation and the Suwannee Limestone are contig- levels with depth along the hinge line separating the discharge uous and Zone 3 is included in the Upper Floridan aquifer and recharge areas. Ground-water withdrawals from Zones 1 rather than the intermediate aquifer system (Reese, 2000; and 2 in the southern part of the study area have lowered levels Basso, 2002). The permeability of Zone 3 in the intermediate in these zones, causing recharge to the intermediate aquifer aquifer system ranges from low to moderately high; lowest system from both the surficial aquifer system and the Upper transmissivities are present in the central part, transmissivities Floridan aquifer.  Regional Evaluation of the Hydrogeologic Framework....West-Central Florida

(A) ZONE 1 82°30’ 82° 81°30’ EXPLANATION 28° 58 Hillsborough Polk NO DATA 57 59 57x LOW PERMEABILITY —Transmissivity is less than 100 CL-2 Tampa9-1 9-2 49 feet squared per day 45 CL-3 Bay 50 48 MODERATELY LOW PERMEABILITY 40 —Transmissivity is greater than 43x 100 and less than 1,000 feet Gulf Highlands 8-1 39 Hardee squared per day o Manatee 27°30’ f Me MODERATE PERMEABILITY 7-2 32 31 30 —Transmissivity is greater than xico 7-4 33 7-1 25 28 1,000 and less than 10,000 feet SA-1 squared per day 23 26 22 35 28x MODERATELY HIGHPERMEABILITY 6-1 De Soto 20 15 —Transmissivity is greater than 5-3 17 10,000 and less than 100,000 feet 19 18 16 14 5-1 5-2 19x squared per day 9.5 16.5 13 Sarasota 9 12 14 ROMP SITE LOCATION AND 4-1 4-2 10 27° NUMBER 3-1 11 5 3-3 Glades Charlotte STUDY AREA 1-2 BOUNDARY 0 10 20 MILES Charlotte 0 10 20 KILOMETERS Harbor Lee Hendry

(B) ZONE 2 82°30’ 82° 81°30’

28° 58 Hillsborough 57 59 57x Polk CL-2 9-1 9-2 49 45 Tampa CL-3 Bay 50 48 40 43x Gulf 8-1 Highlands 39 Hardee o Manatee 27°30’ f Me 32 7-1 7-2 31 30 xico 7-4 33 25 28 SA-1 22 23 26 35 28x 6-1 De Soto 20 15 5-3 19 19x 18 17 16 9.5 5-1 5-2 13 14 Sarasota 9 16.5 12 4-1 4-2 27° 10 3-3 11 5 3-1 Glades Charlotte STUDY AREA 1-2 BOUNDARY 0 10 20 MILES Charlotte 0 10 20 KILOMETERS Harbor Lee Hendry

Base from U.S. Geological Survey digital data, 1:2,000,000, 1972 Albers Equal-Area Conic projection Standard Parallels 29°30’ and 45°30’, central meridian -83°00’

Figure 19. Permeability subregions and transmissivity ranges in Zones 1, 2, and 3. Summary 

(C) ZONE 3 82°30’ 82° 81°30’

28° 58 Hillsborough Polk 59 57 57x

9-2 49 CL-2 Tampa9-1 45 48 CL-3 Bay 50 40 43x Gulf 8-1 39 Highlands Hardee o Manatee 27°30’ f Me 32 7-2 31 30 xico 7-1 7-4 33 25 28 SA-1 23 26 22 35 28x De Soto 6-1 20 15 17 5-3 19 18 16 19x 14 5-1 5-2 9.5 13 Sarasota 9 16.5 12 4-1 4-2 27° 10 3-3 11 5 3-1 Glades Charlotte STUDY AREA 1-2 BOUNDARY 0 10 20 MILES Charlotte 0 10 20 KILOMETERS Harbor Lee Hendry

Base from U.S. Geological Survey digital data, 1:2,000,000, 1972 Albers Equal-Area Conic projection Standard Parallels 29°30’ and 45°30’, central meridian -83°00’

Figure 19. (Continued) Permeability subregions and transmissivity ranges in Zones 1, 2, and 3.

Summary The lithologic composition of the Hawthorn Group, especially the presence of clay beds, controls lateral and vertical ground-water flow and influences the hydraulic Whereas the intermediate aquifer system is considered connectivity between water-bearing zones in the intermediate a single entity that generally coincides with the Hawthorn aquifer system. The zones are designated, in descending order, Group stratigraphic unit, it is composed of multiple water- Zone 1, Zone 2, and Zone 3. Zone 1 is thinnest (< 80 ft thick) bearing zones separated by confining units. Deposition of a and limited to the southern part (< 20 percent) of the study complex assemblage of carbonate and siliciclastic sediments area. Zone 2 is the found throughout most of the study area but during the late Oligocene to early Pliocene time resulted in has moderately low transmissivity. Zone 3 is found south of discontinuities that are reflected in transitional and abrupt central Manatee and southern Polk County (about 50 percent contacts between facies. Discontinuous facies produce water- of the study area), has the highest transmissivities, and gener- bearing zones that may be locally well-connected or culminate ally is in good hydraulic connection with the underlying Upper abruptly. Changes in the depositional environment created a Floridan aquifer. In parts of the study area, particularly in multilayered system with as many as three zones of enhanced southwestern Hillsborough County and southeastern De Soto water-bearing capacity. At the extremities of the study area, and Charlotte Counties, the carbonates that compose Zone 3 the Hawthorn Group is missing or composed of fine grain are contiguous with the Upper Floridan aquifer and function as sediments that lack permeable units. In parts of the study area a single hydrogeologic unit. where the Hawthorn Group lacks permeable units, it behaves Transmissivity of the intermediate aquifer system ranges hydraulically as a confining unit rather than an aquifer system over 5 orders of magnitude, from about 1 to more than 40,000 and is often referred to as the intermediate confining unit. ft2/d, but rarely exceeds 10,000 ft2/d. The overall transmissivity  Regional Evaluation of the Hydrogeologic Framework....West-Central Florida of the intermediate aquifer system is substantially lower (2 to There is no apparent pattern in the leakance data for the 3 orders of magnitude) than the underlying Upper Floridan intermediate aquifer system, such as increasing or decreasing aquifer. Transmissivity varies vertically among the zones leakance with depth or location. within the intermediate aquifer system and geographically Concentrations of major ions generally increase with (from site to site) within a zone. Both the median value and depth both in the intermediate aquifer system and throughout interquartile range of transmissivity values are statistically the ground-water flow system. The chemical composition different among the zones, and samples are not normally of water in zones of the intermediate aquifer system lacks a distributed. All transmissivity values are skewed to the right distinct geochemical signature characterizing an individual towards higher transmissivity values. Zone 2 has the lowest zone, and overall is more varied than the adjacent aquifers. median transmissivity (700 ft2/d) and the smallest interquar- This variation is related to the types of minerals forming the tile range, Zone 1 has a moderate median transmissivity aquifer matrix, and complex mixing of waters from adjacent (2,250 ft2/d) and interquartile range, and Zone 3 has the highest aquifers. The dominant water type throughout the intermediate median transmissivity (3,400 ft2/d) and interquartile range. aquifer system is mixed-cation bicarbonate, typically with More noticeable than variations within zones, however, nearly equal concentrations of calcium and magnesium ions. is the geographical distribution of transmissivity resulting The mixed-cation bicarbonate type water is the most prevalent from the lithologic variability and differences in the deposi- type in the intermediate aquifer system. Sodium chloride type tional environment in the study area. Permeability subregions water is present in the southernmost part of the study area based on ranges of transmissivity can be defined geographi- in all zones. The source of the sodium and chloride is relict seawater emplaced during past marine inundations that has not cally for the intermediate aquifer system regardless of zone. been flushed from the aquifers. Calcium-magnesium sulfate Specifically, throughout the vertical extent of the intermediate type water is present along the coastal margin from Tampa aquifer system the highest permeability (thousands to tens of Bay to southern Sarasota County in Zone 3 and at two Zone thousands feet squared per day) is present in the southwestern 2 wells in west-central Sarasota County. The source of the part of the study area corresponding to areas with greater magnesium and sulfate is upwelling from the Upper Floridan carbonate deposition. A region of relatively low transmissivity aquifer. (< 100 ft2/d) is present in the central part of the study area Differences in hydraulic head generally are greater encompassed by a larger region of moderately low perme- between adjacent zones within the intermediate aquifer system ability (< 1,000 ft2/d) that covers a large part of the study area. than between the adjacent aquifers. Heads differences between Areas of lower transmissivity correspond to greater silici- Zone 1 and the surficial aquifer system range from -1 to 3 ft, clastic deposition. and heads are nearly the same (< 1 ft) between Zone 3 and Clay beds and fine-grained carbonates form the confining the Upper Floridan aquifer except at seven sites in coastal units separating the water-bearing zones, influence the Charlotte and Sarasota Counties and six inland sites. Whereas hydraulic connectivity, and control the vertical exchange head differences across the upper (between the surficial of water between aquifers and zones. The potential for the aquifer system and Zone 2) and lower (between Zone 2 and vertical flow of water across confining units is defined as the Upper Floridan aquifer) groups of confining unit of the leakance. Leakance through the intermediate aquifer system intermediate aquifer system range from -48 to 14 ft and from confining units ranges over 4 orders of magnitude from -119 to 24 ft, respectively. Larger head differences indicate 4.2x10-7 to 6.0x10-3 (ft/d)/ft. Despite the large range, the hydraulic separation of zones within the intermediate aquifer geometric mean and median leakance are within the same compared to between the intermediate aquifer system and order of magnitude, 10-5 (ft/d)/ft, and 2 orders of magnitude adjacent aquifers. less than the median leakance of the semiconfining unit within In general, the overall permeability of the intermediate the Upper Floridan aquifer. The geometric mean and median aquifer system is low relative to the Upper Floridan aquifer, values of leakance are within the same order of magnitude permeability and water-quality contrasts can be defined (10-5) for both the upper and lower groups of confining units, geographically regardless of zone, and Zone 2 is the most which is about 2 orders of magnitude lower than the leakance hydraulically isolated and spatially extensive water-bearing of the semiconfining unit within the Upper Floridan aquifer. unit in the study area. Selected References 

Selected References Helsel, D.R., and Hirsch, R.M., 1992, Statistical methods in water resources: Studies in Environmental Science: Amster- Reports for the Regional Observation and Monitor-Well dam, Elsevier Science, v. 49, 522 p. Program (ROMP) sites are listed separately at the end of this Hem, J.D., 1985, Study and interpretation of the chemical section. characteristics of natural waters: U.S. Geological Survey Barcelo, M.D., Slonena, D.L., Camp, S.C., and Watson, J.D., Water-Supply Paper 2254, 263 p. 1990, Ridge II, A hydrogeologic investigation of the Lake Hutchinson, C.B., 1978, Appraisal of shallow ground-water Wales Ridge: Report in the files of the Southwest Florida resources and management alternatives in the Upper Peace Water Management District in Brooksville, Fla., 121 p. and eastern Alafia River basins, Florida: U.S. Geological Barr, G.L., 1996, Hydrogeology of the surficial and interme- Survey Water-Resources Investigations Report 77-124, 57 p. diate aquifer systems in Sarasota and adjacent Counties, Joyner, B.F., and Sutcliffe, Horace, Jr., 1976, Water resources Florida: U.S. Geological Survey Water-Resources Investiga- of Myakka River basin area, southwest Florida: U.S. tions Report 96-4063, 81 p. Geological Survey Water-Resources Investigations Report Basso, R.J., Jr., 2002, Hydrostratigraphic zones within the 76-58, 87 p. Eastern Tampa Bay Water Use Caution Area: Report in the Knochenmus, L.A., and Bowman, Geronia, 1998, Transmis- files of the Southwest Florida Water Management District in sivity and water quality of water-producing zones in the Brooksville, Fla., variable pagination. intermediate aquifer system, Sarasota County, Florida: U.S. Beach, Michael, and Chan, Doreen, 2003, Southern district Geological Survey Water-Resources Investigations Report ground-water flow model, version 1.0: Report in the files 98-4091, 27 p. of the Southwest Florida Water Management District in Menke, C.G., Meredith, E.W., and Wetterhall, W.S., 1961, Brooksville, Fla., variable pagination. Water resources of Hillsborough County, Florida: Tallahas- Bishop, E.W., 1956, Geology and ground-water resources of see, Florida Geological Survey Report of Investigations 25, Highlands County, Florida: Tallahassee, Florida Geological 101 p. Survey Report of Investigations 15, 115 p. Missimer, T.M., 2002, Late Oligocene to Pliocene evolution Brooks, H.K., 1981, Guide to the physiographic divisions of of the central part of the South Florida Platform: Mixing of Florida—Map and descriptive text: Prepared for the Florida siliciclastics and carbonate sediments: Tallahassee, Florida Cooperative Extension Service, 10 p., 1 sheet. Geological Survey Bulletin 65, 184 p. Brown, D.P., 1983, Water resources of Manatee County, Parker, G.G., Ferguson, G.E., Love, S.K., and others, 1955, Florida: U.S. Geological Survey Water-Resources Investiga- Water resources of southeastern Florida: U.S. Geological tions Report 81-74, 112 p. Survey Water-Supply Paper 1255, 965 p. Carr, W.J., and Alverson, D.C., 1959, Stratigraphy of middle Peek, H.M., 1958, Ground-water resource of Manatee County, Tertiary rocks in part of west-central Florida: U.S. Geologi- Florida: Tallahassee, Florida Geological Survey Report of cal Survey Bulletin 1092, 111 p. Investigations 18, 99 p. De Haven, E.C., and Jones, G.W., 1996, Origin of chlorides Plummer, L.N., 1977, Defining reactions and mass transfer in in Floridan aquifer ground water in the Southern Water-Use part of the Floridan aquifer: Water Resources Research, v. Caution Area: Report in the files of the Southwest Florida 13, no. 5, p. 801-812. Water Management District in Brooksville, Fla., 26 p. Randazzo, A.F., 1997, The sedimentary platform of Florida: De Wiest, R.J.M., 1965, Geohydrology: New York, John Mesozoic to Cenozoic, in Randazzo, A.F., and Jones, D.S., Wiley, 366 p. eds., The Geology of Florida: Gainesville, University Press Duerr, A.D., Hunn, J.M., Lewelling, B.R., and Trommer J.T., of Florida, chap. 4, p. 39-56. 1988, Geohydrology and 1985 water withdrawals of the Reese, R.S., 2000, Hydrogeology and the distribution of salin- aquifer systems in southwest Florida, with emphasis on the ity in the Floridan aquifer system, southwestern, Florida: intermediate aquifer system: U.S. Geological Survey Water- U.S. Geological Survey Water-Resources Investigations Resources Investigations Report 87-4259, 115 p. Report 98-4253, 86 p. Duerr, A.D., and Wolansky, R.M., 1986, Hydrogeology of Ryder, P.D., 1985, Hydrology of the Floridan aquifer system the surficial and intermediate aquifers of central Sarasota in west-central Florida: U.S. Geological Survey Profes- County, Florida: U.S. Geological Survey Water-Resources sional Paper 1403-F, 63 p. Investigations Report 86-4068, 48 p. Sacks, L.A., and Tihansky, A.B., 1996, Geochemical and Freeze, R.A., and Cherry, J.A., 1979, Groundwater: Engle- isotopic composition of ground water, with emphsis on wood Cliffs, N.J., Prentice-Hall, 604 p. sources of sulfate, in the Upper Floridan aquifer and inter- Galloway, D.L., Jones, D.R., Ingebritsen, W.E., eds., 1999, mediate aquifer system in southwest Florida: U.S. Geologi- Land subsidence in the United States: U.S. Geological cal Survey Water-Resources Investigations Report 96-4146, Survey Circular 1182, 177 p. 67 p.  Regional Evaluation of the Hydrogeologic Framework....West-Central Florida

Schmerge, D.L., 2001, Distribution and origin of salinity in Torres, A.E., Sacks, L.A., Yobbi, D.K., Knochenmus, L.A., the surficial and intermediate aquifer systems, southwestern and Katz, B.G., 2001, Hydrogeologic framework and Florida: U.S. Geological Survey Water-Resources Investiga- geochemistry of the intermediate aquifer system in parts of tions Report 01-4159, 41 p. Charlotte, De Soto, and Sarasota Counties, Florida: U.S. Schmidt, Walter, 1997, Geomorphology and physiography of Geological Survey Water-Resources Investigations Report 01-4015, 74 p. Florida, in Randazzo, A.F., and Jones, D.S., eds., The Geol- Vacher, H.L., Jones, G.W., and Stebenisky, R.J., 1992, ogy of Florida: Gainesville, University Press of Florida, Heterogeneity of the surficial aquifer system in west-central chap. 1, p. 1-12. Florida: Tallahassee, Florida Geological Survey Special Scott, T.M., 1997, Miocene to Holocene history of Florida, Publication 36, p. 93-99. in Randazzo, A.F., and Jones, D.S., eds., The Geology of Wedderburn, L.A., Knapp, M.S., Waltz, D.P., and Burns, Florida: Gainesville, University Press of Florida, chap. 5, W.S., 1982, Hydrogeologic reconnaissance of Lee County, p. 57-67. Florida: Brooksville, South Florida Water Management Scott, T.M., 1988, The lithostratigraphy of the Hawthorn District Technical Publication 82-1, 192 p. Group (Miocene) of Florida: Tallahassee, Florida Geologi- White, W.A., 1970, The geomorphology of the Florida Penin- cal Survey Bulletin 59, 148 p. sula: Tallahassee, Florida Geological Survey Geological Scott, T.M., 1992, A geological overview of Florida: Tallahas- Bulletin 51, 164 p. Wilson, W.E., 1977, Ground-water resources of De Soto and see, Florida Geological Survey Open-File Report 50, 76 p. Hardee Counties, Florida: Tallahassee, Florida Geological Southeastern Geological Society, 1986, Hydrogeologic units Survey Report of Investigations 83, 102 p. of Florida: Florida Bureau of Geology Special Publication Wolansky, R.M., 1983, Hydrogeology of the Sarasota-Port 28, 9 p. Charlotte area, Florida: U.S. Geological Survey Water- Southwest Florida Water Management District, 2000, Aqui- Resources Investigations Report 82-4089, 48 p. fer characteristics within the Southwest Florida Water Wolansky, R.M., and Corral, M.A., Jr., 1985, Aquifer tests Management District: Report 99-1, Report in the files of the in west-central Florida, 1952-76: U.S. Geological Survey Southwest Florida Water Management District in Brooks- Water-Resources Investigations Report 84-4044, 127 p. ville, Fla., 123 p. Yobbi, D.K., 1996, Analysis and simulation of ground-water Southwest Florida Water Management District, 2004, South- flow in Lake Wales Ridge and adjacent areas of central Florida: U.S. Geological Survey Water-Resources Investiga- ern Water Use Caution Area recovery strategy: Revised tions Report 94-4254, 82 p. draft in the files of the Southwest Florida Water Manage- Yobbi, D.K., and Halford, K.J., 2006, Numerical simulation of ment District in Brooksville, Fla., variable pagination. aquifer tests, west-central Florida: U.S. Geological Survey Sproul, C.R., Boggess, D.H., and Woodard, H.J., 1972, Saline Scientific Investigations Report 2005-5201, 85 p. water intrusion from deep artesian sources in the McGregor Isles area of Lee County, Florida: Tallahassee, Florida Bureau of Geology Information Circular 75, 30 p. Stewart, H.G., Jr., 1966, Ground-water resources of Polk ROMP Reports County: Tallahassee, Florida Geological Survey Report of Clayton, J.M., 1994, ROMP 39 (Oak Knoll), Final report of Investigations 44, 170 p. drilling and testing activities, Manatee County, Florida: Stiff, H.A., Jr., 1951, The interpretation of chemical water Brooksville, Southwest Florida Water Management District, analysis by means of patterns: Journal of Petroleum Tech- Regional Observation and Monitor Well-Program, 23 p., nology, v. 3, no. 10, p. 15-17. and apps. Sutcliffe, Horace, Jr., 1975, Appraisal of the water resources Clayton, J.M., 1998, ROMP 14 Hicoria, Monitor well site, of Charlotte County, Florida: Tallahassee, Florida Geologi- Highlands County, Florida, Final report, drilling and testing; cal Survey Report of Investigations 78, 53 p. Brooksville, Southwest Florida Water Management District, Regional Observation and Monitor Well-Program, 47 p., Sutcliffe, Horace, Jr., and Thompson, T.H., 1983, Occurrence and apps. and use of ground water in the Venice-Englewood area, Clayton, J.M., 1999, ROMP 12 Prairie Creek—Final report, Sarasota and Charlotte Counties, Florida: U.S. Geological drilling and testing program, Southern District Water Survey Open-File Report 82-700, 59 p. Resource Assessment Project, DeSoto County, Florida: Taylor, C.J., and Alley, W.M., 2001, Ground-water-level moni- Brooksville, Southwest Florida Water Management District, toring and the importance of long-term water-level data: Regional Observation and Monitor Well-Program, 57 p., U.S. Geological Survey Circular 1217, 68 p. and apps. ROMP Reports 

Decker, J.L., 1990, Executive summary, ROMP TR9-2 Apollo Gates, M.T., 1999, ROMP 13 Tippen Bay, Monitor well site, Beach, WRAP #1, Hillsborough County: Brooksville, DeSoto County, Florida, Phase three, Aquifer performance Southwest Florida Water Management District, Regional testing: Brooksville, Southwest Florida Water Management Observation and Monitor Well-Program, 27 p., and apps. District, Regional Observation and Monitor Well-Program, Decker, J.L., 1989, Executive summary, ROMP 49 Balm Park, 13 p., and apps. Hillsborough County: Brooksville, Southwest Florida Water Gates, M.T., 1998, ROMP 25 Lily, Monitor well sites, Hardee Management District, Regional Observation and Monitor County, Florida, Phase one, Core drilling and testing: Well Program, 36 p., and apps. Brooksville, Southwest Florida Water Management District, DeWitt, D.J., 1992, Executive summary addendum, ROMP Regional Observation and Monitor Well-Program, 13 p., TR 8-1 Rubonia, WRAP #2, Statement of completed work: and apps. Brooksville, Southwest Florida Water Management District, Gates, M.T., 1999, ROMP 25 Lily, monitor well site, Hardee Regional Observation and Monitor Well-Program, 26 p., County, Florida, Phase two, Exploratory drilling and moni- and apps. tor well construction: Brooksville, Southwest Florida Water DeWitt, D.J., 1995, ROMP TR-AB-1 Big Bend, drilling and Management District, Regional Observation and Monitor testing report, salt-water interface monitor well site, Hill- Well-Program, 14 p., and apps. sborough County, Florida: Brooksville, Southwest Florida Gates, M.T., 2000, ROMP 25 Lily monitor well site, Hardee Water Management District, Regional Observation and County, Florida, Phase three, Aquifer performance testing: Monitor Well-Program, 17 p., and apps. Brooksville, Southwest Florida Water Management District, DeWitt, D.J., 1997, ROMP 20 Osprey, Monitor well site, Regional Observation and Monitor Well-Program, 11 p., Sarasota County, Florida, Open File Report, Exploratory and apps. drilling and testing: Brooksville, Southwest Florida Water Gates, M.T., 2000, ROMP 9.5 IAS, monitor well site, DeSoto Management District, Regional Observation and Monitor County, Florida, Phase two, Monitor well construction and Well-Program, 26 p., and apps. aquifer performance testing: Brooksville, Southwest Florida DeWitt, D.J., 1998, ROMP 28 Kuhlman, Drilling and testing Water Management District, Regional Observation and report, Highlands County, Florida: Brooksville, Southwest Monitor Well-Program, 14 p., and apps. Florida Water Management District, Regional Observation Gates, M.T., 2001, Hydrogeology of the ROMP 16.5, Fort and Monitor Well-Program, 43 p., and apps. Ogden, Monitor well site, DeSoto County, Florida, Phase Gates, M.T., 1997, ROMP 13 Tippen Bay, Monitor well site, one, Core drilling and testing: Brooksville, Southwest DeSoto County, Florida, Vol. 1, Core drilling and testing: Florida Water Management District, Regional Observation Brooksville, Southwest Florida Water Management District, and Monitor Well-Program, 17 p., and apps. Regional Observation and Monitor Well-Program, 11 p., Gates, M.T., 2001, Hydrogeology of the ROMP 16.5, Fort and apps. Ogden, Monitor well site, DeSoto County, Florida, Phase Gates, M.T., 1997, ROMP 5 Cecil Webb, Monitor well site, two, Deep exploratory drilling and monitor well construc- Charlotte County, Florida, Vol. 1, Core drilling and testing: tion: Brooksville, Southwest Florida Water Management Brooksville, Southwest Florida Water Management District, District, Regional Observation and Monitor Well-Program, Regional Observation and Monitor Well-Program, 14 p., 25 p., and apps. and apps. Gates, M.T., 2003, Hydrogeology of the ROMP 16.5, Fort Gates, M.T., 1997, ROMP 5 Cecil Webb, Monitor well site, Ogden, Monitor well site, DeSoto County, Florida, Phase Charlotte County, Florida, Vol. 2, Exploratory drilling and three, Aquifer performance testing: Brooksville, Southwest testing: Brooksville, Southwest Florida Water Management Florida Water Management District, Regional Observation District, Regional Observation and Monitor Well-Program, and Monitor Well-Program, 17 p., and apps. 15 p., and apps. Geohydrologic Data Section, 1991-1993, ROMP 22 Utopia, Gates, M.T., 1997, ROMP 5 Cecil Webb, Monitor well Supplementary data appendix H, Drillers daily logs: site, Charlotte County, Florida, Vol. 3 & 4, Monitor well Brooksville, Southwest Florida Water Management District, construction and aquifer performance testing: Brooksville, Regional Observation and Monitor Well-Program. Southwest Florida Water Management District, Regional Geohydrologic Data Section, 1995, Drilling and testing report Observation and Monitor Well-Program, 11 p., and apps. ROMP 22 Utopia: Brooksville, Southwest Florida Water Gates, M.T., 1998, ROMP 13 Tippen Bay, Monitor well site, Management District, Regional Observation and Monitor DeSoto County, Florida, Phase two, Exploratory drilling Well-Program, 17 p., and apps. and monitor well construction: Brooksville, Southwest LaRoche, J.J., 2004, ROMP 35 West DeSoto, Final report, Florida Water Management District, Regional Observation Exploratory coring, monitor-well construction, and aquifer and Monitor Well-Program, 16 p., and apps. performance testing, DeSoto County, Florida: Brooksville, Southwest Florida Water Management District, Regional Observation and Monitor-well Program, 44 p., and apps. 40 Regional Evaluation of the Hydrogeologic Framework....West-Central Florida

Lee, R.A., 1998, ROMP TR SA-1 Payne Terminal, Drilling Rappuhn, D.H., Gates, M.T., McQuown, S.G., 1994, ROMP and testing report, Saltwater interface monitor wellsite, TR-AB-3 Bullfrog Creek, Drilling and testing report: Sarasota County, Florida: Brooksville, Southwest Florida Brooksville, Saltwater interface monitor well, Hillsborough Water Management District, Regional Observation and County, Florida, Southwest Florida Water Management Monitor-well Program, 12 p., and apps. District, Regional Observation and Monitor Well-Program, Lee, R.A., 1999, ROMP TR SA-3 Sarasota, Drilling and 13 p., and apps. testing report, Saltwater interface monitor wellsite, Sarasota Thompson, D.L., 1997, ROMP 9 Northport, Drilling and test- County: Brooksville, Florida, Southwest Florida Water ing report, Sarasota County, Florida: Brooksville, Southwest Management District, Regional Observation and Monitor Florida Water Management District, Regional Observation Well-Program, 10 p., and apps. and Monitor Well-Program, 26 p., and apps. Rappuhn, D.H., 1992, Executive Summary—ROMP 33/ Thompson, D.L., 2000, Hydrogeology of the ROMP TR 4-1, WRAP #6, Waterbury/Kibler Agricultural Corporation Caspersen Beach well site, Sarasota County, Florida: property: Brooksville Southwest Florida Water Management Brooksville, Southwest Florida Water Management District, District, Regional Observation and Monitor Well-Program, Regional Observation and Monitor Well-Program, 41 p., 42 p., and apps. and apps. Rappuhn, D.H., 1995, ROMP TR7-2 Oneco monitor well site, Manatee County, Florida, Final report, drilling and testing: Brooksville, Southwest Florida Water Management District, Regional Observation and Monitor Well-Program, 45 p., and apps.