university of florida - wuft...assessment included; 1) the installation of 14 monitoring wells, 2)...

University of Florida

Site Assessment Report forthe Former LandfillSite in Gainesville, Florida

September 2004

Final Report

Executive Summary Camp Dresser & McKee Inc. (CDM) was retained by the University of Florida (UF) to perform assessment investigations and prepare this Site Assessment Report (SAR) for the former landfill site in Gainesville, Florida. This SAR is being submitted in accordance with the Consent Order (OGC File No. 03-1825-C) entered into between UF and the Florida Department of Environmental Protection (FDEP). Investigations described in this SAR were performed in accordance with the Site Assessment Plan (SAP) submitted to the FDEP on December 18, 2003, and approved by the FDEP, with some modifications, on February 16, 2004.

The objectives of the Site Assessment for the former landfill are to define the lateral and vertical extents of contamination in groundwater, to evaluate and characterize the hydrogeology of the vicinity of the site, to assess and characterize the waste that has been placed in the landfill, and, to identify potential receptors of groundwater contamination. The objectives of the Site Assessment were achieved.

The former landfill site is located in Gainesville, Florida in the eastern one-half of Section 11, Township 10 South, Range 19 East, in Alachua County, Florida west of the intersection of Hull Road and S.W. 34th Street. The site is approximately 13.5 acres in area. The properties were acquired by the State of Florida in 1964 and 1972. The southeastern and western parts of the site were used between 1964 and 1968 for the disposal of University waste. After 1968, the site was used for the disposal of horticultural waste, soil and construction debris. Currently, UF is using the closed landfill as a student commuter parking lot (Park ‘N Ride).

Assessment investigations were initiated by CDM for UF in March 2004. The Site Assessment included; 1) the installation of 14 monitoring wells, 2) collection and analysis of groundwater samples from the 14 new monitoring wells, 21 existing monitoring wells, and seven (7) supply wells in the vicinity of the site, 3) soil and groundwater field screening investigations on the property immediately to the west and south of the UF property in the vicinity of well MW-1, 4) a ground penetrating radar survey of the site, 5) a Tier II landfill gas study of the site, and, 6) hydrogeologic investigations.

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Executive Summary University of Florida

The following conclusions are based on results of the Site Assessment:

There is no evidence that contamination associated with historical use of the UF site and adjacent properties has adversely impacted the quality of groundwater withdrawn from private supply wells not owned or operated by UF. Concentrations of all analytes in samples from private potable water supply wells (Kight, Lowe and Sheffield) and the Museum Walk irrigation well were below drinking water standards or background concentrations. Only the quality of groundwater in the Hilton irrigation well, which is located on UF property, has been adversely impacted.

Iron, manganese, and radionuclides (total alpha, total beta, radium 226, and radium 228) are present in concentrations that exceed drinking water standards in groundwater beneath the UF site and adjacent properties. These parameters are naturally-occurring and background concentrations also exceed drinking water standards. These compounds are not migrating from the UF site, but are mobilized from the soil as a result of changes in the groundwater chemistry because of percolation of rainwater through the disposal areas and areas where only a thin layer of confining sediments overlies the aquifer. Increased concentrations of iron, manganese, and radionuclides in the groundwater resulting from historical use of the site and adjacent properties are limited to the areas beneath and immediately adjacent to the former borrow pits.

1,4-Dioxane is also present in groundwater beneath the site and adjacent properties. The extent of 1,4-dioxane contamination in concentrations that exceed the Groundwater Cleanup Target Level (GCTL) established by the FDEP is limited to the areas beneath and immediately adjacent to former borrow pits. 1,4-Dioxane was not detected in any of the private supply wells that are not on UF property. This compound is an ingredient in many widely used products including shampoo, cosmetics, automotive coolants and solvents. 1,4-Dioxane is not naturally occurring and is an indicator of the extent of the effects on groundwater quality resulting from historical use of the UF site and adjacent properties as landfills.

The nature of the waste that was disposed of at the UF site is consistent with waste disposed of at municipal landfills. There is no indication that drums of chemical wastes were placed into the UF site.

Groundwater in the vicinity of the UF site moves from west to east. Contamination from properties to the west of the UF site is migrating onto the UF site.

Capping the unpaved part of the UF site is recommended to reduce percolation of rainfall through the former borrow pit in order to reduce the mobilization of iron, manganese and radionuclides from the soil. Capping this area will also reduce the


Executive Summary University of Florida

potential for additional quantities of 1,4-dioxane to be leached into the groundwater. Capping is a common method used to close landfills and reduce the potential for groundwater contamination. Relocation of the Hilton irrigation well is also recommended.


Contents

Executive Summary Section 1 Introduction

1.1 Authorization ............................................................................................................1-1 1.2 Objectives of the Site Assessment ..........................................................................1-1 1.3 Organization of Site Assessment Report...............................................................1-1 1.4 Background Information .........................................................................................1-2

1.4.1 Site Location and Description..................................................................1-2 1.4.2 Topography and Drainage.......................................................................1-2 1.4.3 Site History.................................................................................................1-5 1.4.4 Previous Investigations ............................................................................1-6

Section 2 Results of Investigation 2.1 Introduction...............................................................................................................2-1 2.2 Regional Geology and Hydrogeology...................................................................2-1

2.2.1 Introduction ...............................................................................................2-1 2.2.2 Physical Setting..........................................................................................2-2 2.2.3 Regional Geology ......................................................................................2-2 2.2.3.1 Introduction..................................................................................2-2 2.2.3.2 Undifferentiated Siliciclastic Sediments...................................2-2 2.2.3.3 Hawthorn Group.........................................................................2-4 2.2.3.4 Ocala Formation ..........................................................................2-4 2.2.3.5 Avon Park Formation .................................................................2-4 2.2.4 Regional Hydrogeology ...........................................................................2-5 2.2.4.1 Introduction..................................................................................2-5 2.2.4.2 Surficial Aquifer System.............................................................2-5

2.2.4.3 Intermediate Confining Unit/Intermediate Aquifer System ............................................................................2-6

2.2.4.4 Floridan Aquifer System ............................................................2-6 2.3 Site-Specific Geology/Hydrogeology....................................................................2-7 2.3.1 Site Geology and Hydrogeologic Units..................................................2-7 2.3.1.1 Introduction..................................................................................2-7 2.3.1.2 Undifferentiated Sediments/Surficial Aquifer System..........2-9

2.3.1.3 Hawthorn Group-Coosawahatchie Formation/ Intermediate Confining Unit .....................................................2-9

2.3.1.4 Ocala Limestone/Floridan Aquifer System ..........................2-14 2.3.1.5 Avon Park Formation ...............................................................2-14 2.3.2 Direction and Rate of Groundwater Movement .................................2-14 2.3.2.1 Direction of Groundwater Movement....................................2-14 2.3.2.2 Rate of Groundwater Movement ............................................2-17

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Table of Contents University of Florida

2.4 Groundwater Quality.............................................................................................2-19 2.4.1 Introduction .............................................................................................2-19 2.4.2 Surficial Aquifer System and Intermediate Confining Unit..............2-20 2.4.3 Floridan Aquifer System ........................................................................2-22 2.4.4 Private Wells ............................................................................................2-28 2.5 Sources of Contamination .....................................................................................2-34 2.5.1 Introduction .............................................................................................2-34 2.5.2 Assessment of Groundwater Contamination Near MW-1 ................2-35 2.5.3 Ground Penetrating Radar Study and Landfill Gas Study ...............2-41 2.5.3.1 Ground Penetrating Radar Study ...........................................2-41 2.5.3.2 Landfill Gas Study.....................................................................2-41

2.5.4 Results of Soil Sampling and Analyses and Mobilization of Naturally-Occurring Analytes...............................................................2-43 2.5.4.1 Analytical Results......................................................................2-43 2.5.4.2 Mobilization of Naturally-Occurring Constituents ..............2-46 2.5.4.3 Methodology and Data.............................................................2-47 2.5.4.4 Eh – pH Relationships for Iron................................................2-48 2.5.4.5 Eh – pH Relationships for Manganese ...................................2-50 2.5.4.6 Observed Eh, pH and Concentrations....................................2-50 2.5.4.7 Sample Results and Well Depth ..............................................2-54 2.5.4.8 Summary.....................................................................................2-59

Section 3 Methods of Investigation 3.1 Ground Penetrating Radar Survey.........................................................................3-1 3.2 Landfill Gas Study....................................................................................................3-1

3.2.1 Introduction ...............................................................................................3-1 3.2.2 Field Sampling Material and Equipment...............................................3-1 3.2.3 Field Sampling Procedures ......................................................................3-2 3.2.4 Laboratory Analysis Methods .................................................................3-5

3.3 Field Screening..........................................................................................................3-5 3.3.1 Introduction ...............................................................................................3-5 3.3.2 Soil Screening.............................................................................................3-5 3.3.3 Groundwater Screening ...........................................................................3-5 3.4 Monitoring Well Installation...................................................................................3-6 3.4.1 Intermediate Confining Unit Monitoring Wells ...................................3-6 3.4.2 Floridan Aquifer Monitoring Wells ........................................................3-6 3.4.3 Well Development and Completion .......................................................3-8 3.5 Groundwater Sampling and Analyses ..................................................................3-8 3.6 In-Situ Permeability Tests........................................................................................3-9 3.7 Soil Sampling and Analyses....................................................................................3-9 3.8 Management of Investigation Derived Waste......................................................3-9

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Table of Contents University of Florida

Section 4 Conclusions and Recommendations

4.1 Conclusions ...............................................................................................................4-1 4.1.1 Introduction.................................................................................................4-1 4.1.2 Extent of Contamination ..........................................................................4-1 4.1.3 Hydrogeology ............................................................................................4-2 4.1.4 Waste Characterization.............................................................................4-3 4.1.5 Potential Receptors....................................................................................4-4 4.2 Recommendations ....................................................................................................4-5

Section 5 References

Appendices Appendix A Copies of Aerial Photographs Appendix B Copy of the Brown & Cullen Permit Application Appendix C Drilling and Well Completion Logs for the Monitor Wells Appendix D Recovery-Versus-Time Graphs for the Slug Tests Appendix E Analytical Reports – Groundwater Samples Appendix F Analytical Reports – Direct Push Technology Samples Appendix G Copy of Report Prepared by Geohazards Appendix H Results of Analyses – Landfill Gas Samples Appendix I Analytical Reports – Soil Samples Appendix J Copy of the Profile and Manifest

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Figures

Figure 1-1 Location Map.................................................................................................. 1-3 Figure 1-2 Site Plan........................................................................................................... 1-4 Figure 2-1 Locations of Monitor Wells and Geologic Cross-Sections ....................... 2-8 Figure 2-2 Hydrogeologic Cross-Section A-A’ ........................................................... 2-12 Figure 2-3 Hydrogeologic Cross-Section B-B’ ............................................................ 2-13 Figure 2-4 Potentiometric Surface of the Floridan Aquifer System

(April 12, 2004) ............................................................................................. 2-15 Figure 2-5 Potentiometric Surface of the Floridan Aquifer System

(July 7, 2004) ................................................................................................. 2-16 Figure 2-6 Distribution of Iron in the Upper Part of the Floridan

Aquifer System............................................................................................. 2-26 Figure 2-7 Distribution of Manganese in the Upper Part of the Floridan

Aquifer System........................................................................................... 2-27 Figure 2-8 Distribution of Gross Alpha in the Upper Part of the

Floridan Aquifer System............................................................................. 2-29 Figure 2-9 Distribution of Radium 226 in the Upper Part of the

Floridan Aquifer System............................................................................. 2-30 Figure 2-10 Distribution of 1,4-Dioxanein in the Upper Part of the

Floridan Aquifer System........................................................................... 2-31 Figure 2-11 Locations of Private Supply Wells ............................................................ 2-32 Figure 2-12 Distribution of Benzene in Shallow Groundwater West

of the Former Alachua County Borrow Pit .............................................. 2-36 Figure 2-13 Distribution of Chlorobenzene in Shallow Groundwater

West of the Former Alachua County Borrow Pit .................................... 2-37 Figure 2-14 Ground Penetrating Radar Survey and Landfill Gas

Study Locations............................................................................................ 2-42 Figure 2-15 Fe – H20 – System at 24.00 C...................................................................... 2-44 Figure 2-16 Fe – H20 – System at 25.00 C...................................................................... 2-51 Figure 2-17 Mn – H20 – System at 25.00 C.................................................................... 2-52 Figure 2-18 Eh/pH Measurements – Fe (mg/L).......................................................... 2-53 Figure 2-19 Eh/pH Measurements – (Private Supply Wells) – Fe (mg/L) .............. 2-55 Figure 2-20 Eh/pH Measurements – Mn (mg/L)........................................................ 2-56 Figure 2-21 Eh/pH Measurements – (Private Supply Wells) – Mn (mg/L) ............ 2-57 Figure 2-22 Floridan vs. Shallow Wells ......................................................................... 2-58 Figure 2-23 Distribution of pH in the Upper Part of the Floridan

Aquifer System............................................................................................. 2-60 Figure 2-24 Distribution of Oxidation – Reduction Potential (ORP) in

Upper Part of Floridan Aquifer ................................................................. 2-61

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Tables

Table 2-1 Regional Stratigraphic/Hydrostratigraphic Correlation Chart ................................................................................................................ 2-3

Table 2-2 Intermediate Confining Unit and Floridan Aquifer Groundwater Elevation Data..................................................................... 2-10

Table 2-3 Floridan Aquifer Groundwater Elevation Data ...................................... 2-11 Table 2-4 Hydraulic Conductivity Values for the Intermediate

Confining Unit and Upper FAS from Slug Test Results ........................ 2-18 Table 2-5 Summary of Groundwater Analytical Results for Surficial and

Intermediate Confining Unit Wells – April 2004 .................................... 2-21 Table 2-6 Summary of Groundwater Analytical Results for

Floridan Aquifer System Wells – April and July 2004 ........................... 2-24 Table 2-7 Summary of Groundwater Analytical Results for Private Wells

April and July 2004...................................................................................... 2-33 Table 2-8 Summary of DPT Groundwater Analytical Results – April 2004......... 2-38 Table 2-9 Field Screening Log ..................................................................................... 2-39 Table 2-10 Summary of Analytical Results of Soil Samples ..................................... 2-45 Table 2-11 Summary of Groundwater Field Parameters Measurements

April and July 2004...................................................................................... 2-49 Table 3-1 Groundwater Monitor Well Construction Details .................................... 3-7 Table 3-2 Analytical Methods and Analytes............................................................. 3-10

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Section 1 Introduction 1.1 Authorization Camp Dresser & McKee Inc. (CDM) was retained by the University of Florida (UF) to perform assessment investigations and prepare this Site Assessment Report (SAR) for the former landfill site (also referred to as the site or UF site) in Gainesville, Florida. This SAR is being submitted in accordance with the Consent Order (OGC File No. 03-1825-C) entered into between UF and the Florida Department of Environmental Protection (FDEP). Investigations described in this SAR were performed in accordance with the Site Assessment Plan (SAP) submitted to the FDEP on December 18, 2003, and approved by the FDEP, with some modifications, on February 16, 2004.

1.2 Objectives of the Site Assessment Objectives of the Site Assessment are described in Exhibit B of the Consent Order. The specific objectives of the Site Assessment for the former landfill, discussed with representatives of the FDEP, are:

To define the lateral and vertical extents of contamination in groundwater;

To evaluate and characterize the hydrogeology in the vicinity of the site;

To assess and characterize the waste that has been placed of in the landfill, and;

To identify potentially impacted lands and structures of groundwater contamination.

1.3 Organization of Site Assessment Report This SAR was prepared in accordance with requirements described in Exhibit B of the Consent Order. Included in the SAR are:

Background information regarding the site including brief descriptions of the location, site, topography, drainage, history, previous investigations, and the Interim Remedial Action/Source Removal.

Results of the hydrogeological assessment of the site including the rate and direction of groundwater movement.

Results of assessment of the nature and extent of contamination including field screening of soil and groundwater samples, collection and laboratory analyses of soil samples, and collection and analyses of groundwater samples.

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Section 1 Introduction

Evaluation of the nature and extent of potential sources of contamination including field screening investigations, a ground penetrating radar survey, and landfill gas study.

Results of the evaluation of potential contamination migration pathways and receptors.

Methods of investigation.

Conclusions and recommendations.

1.4 Background Information 1.4.1 Site Location and Description The former landfill site is located in Gainesville, Florida in the eastern one-half of Section 11, Township 10 South, Range 19 East, in Alachua County, Florida west of the intersection of Hull Road and S.W. 34th Street. The site is approximately 13.5 acres in area. Figure 1-1 is a site location map. Figure 1-2 is an aerial photograph of the site and immediate vicinity taken in 2004.

Currently, UF is using the closed landfill as a student commuter parking lot (Park ‘N Ride). Land use south of the eastern approximately one-half of the site is a mixed residential community consisting of single-family residences and apartment buildings. To the east of the site on the south side of Hull Road is a hotel. An orthopedic and sports medicine clinic is currently being constructed just to east of the site and north of the hotel facility across Hull Road. The property to the north and west of the landfill and south of the western part of the site is undeveloped.

1.4.2 Topography and Drainage Topography in the vicinity of the site is characterized by gently rolling hills with elevations varying from approximately 60 to 80 feet National Geodetic Vertical Datum (NGVD), 1929. The site has little topographic relief with elevations varying from approximately 85 feet NGVD in the eastern part of the site to near 70 feet NGVD in the western part of the site.

With the exception of the southeastern part of the site, landscaped areas and a stormwater retention pond, the site is covered by pavement. Approximately six acres of the site is covered by asphalt or concrete pavement. Stormwater that falls on the paved areas is directed to drains and is conveyed to the stormwater retention pond. The stormwater retention pond is approximately two acres in area and is located in the north-central part of the site. Overflow from the retention ponds is conveyed to a drainage swale to the north of the retention ponds.


Section 1 Introduction Figure 1-1


Section 1 Introduction Figure 1-2


Section 1 Introduction

1.4.3 Site History The history of the site was evaluated using information provided by UF, reports of previous investigations performed by FDEP and ESE, and interpretation of historical aerial photographs. Aerial photographs taken in 1937, 1949, 1955, 1961, 1968, 1971, 1974, 1978, 1979, 1982, 1985, 1987, 1990, 1994, and 1999 were obtained from the UF library. Aerial photographs taken in 1964, 1971, 1975, 1978, 1982, 1985, 1987, 1990, 1991, 1994, and 1998 were obtained from the Florida Department of Transportation (FDOT). Copies of the aerial photographs are in Appendix A.

Evaluations of historical aerial photographs indicate that the site was cleared of vegetation by 1937. Aerial photographs taken in 1949 and 1955 indicate that the site may have been used as pasture. The aerial photograph taken in 1961 indicates that much of the eastern part of the site was likely being cultivated or being prepared for use as a borrow pit.

Information provided by UF indicates that the eastern part of the site, known as the “Murphree Property,” was acquired by the State of Florida and used by the UF Physical Plant Division as a sanitary landfill from 1964 to approximately 1968. According to information provided by UF, the Murphree property pit was approximately half full by the fall of 1966. The second borrow pit located to the west of the “Murphree Property” pit was leased from Alachua County and operated as a sanitary landfill from 1967 through early 1968. This property was acquired in 1972. Information regarding specific waste streams or quantities of waste disposed was not available.

The aerial photograph taken in 1964 shows that the former Alachua County property and the southern approximately 1/3 of the Murphree property have been excavated. The excavations appear to be dry. This is consistent with information provided by UF that indicates that the pits were between 10 and 15 feet deep. Aerial photographs were not available for the periods that the pits were used to dispose of sanitary waste.

Although information provided by UF indicates that disposal of sanitary waste ceased in 1968, considerable activity at the site is visible in aerial photographs taken in 1968, 1971, 1974, 1975 and 1978. Most of the activity appears to be taking place in the northern part of the Murphree property. A large excavated area is apparent on the property immediately south of the western part of the site (former Alachua County property) in the 1968 and 1971 aerial photographs. This area is not part of the site and access to this area appears to be from the south and not from the UF property. According to UF, this area was not used by UF either as a borrow pit or for disposal of waste. These areas appear to be filled in the 1974 and subsequent aerial photographs. The former Alachua County property appears to be unused in the 1975 aerial photograph. The site appears to be inactive in the aerial photograph taken in 1979.

What appears to be a trench, approximately 200 feet long and 30 feet wide, is visible on the aerial photograph taken in 1982. The trench is located in the approximate


Section 1 Introduction center of the Murphree property and appears to have water in the bottom. What appear to be piles of dirt/debris in the southern part of the Murphree property, adjacent to the northern boundary of the Murphree property, and on the Alachua County property are also visible. The trench is not visible in the 1985 aerial photograph. However, information contained in the ESE report completed in 1986, which documents work performed in 1985, indicates that the northern part of the Murphree property was an active borrow pit at the time of their investigation.

Use of the site to store/dispose of dirt/debris is apparent in the aerial photographs taken in 1987. Information contained in the Work Plan for the Environmental Contamination Assessment of the University of Florida Chemical Disposal Site prepared by Ecology and Environment, Inc. (E&E) for the Florida Department of Environmental Regulation dated August 1992, indicates that the western part of the site was being used in 1990 to store wastewater treatment plant (WTP) sludge and dirt. E&E also noted that the borrow pit in the northern part of the Murphree property was partially filled with WTP sludge. The central part of the borrow pit contained standing water. These features are visible in the aerial photographs taken in 1990 and 1991. Aerial photographs taken in 1994, 1998 and 1999 indicate excavation activities at the site ceased prior to 1994. Activity in the southern part of the Murphree property, piles of material on the northern part of the Murphree property and activity in the western part of the former Alachua County property are visible on the aerial photographs taken in 1998 and 1999.

Interpretations of historical aerial photographs are consistent with information provided by UF and results of geotechnical testing performed at the site. Results of geotechnical testing performed by Universal Engineering Sciences, Inc. (UES) in 1999, which are included in the permit application for the stormwater management system for the parking area that was prepared by Brown & Cullen, Inc., indicates that trash is present beneath the southern part of the Murphree property and the former Alachua County property and that fill material is present beneath the northern part of the Murphree property. A copy of the permit application is in Appendix B.

1.4.4 Previous Investigations Investigations to assess contamination of groundwater at the site were performed by ESE for UF and by the FDEP. Initial investigations were performed by ESE in 1985 at the request of UF and are documented in a report dated April 30, 1986, and entitled Groundwater Contamination Assessment for the University of Florida Landfill. Investigations performed by the FDEP were initiated in 1997 and are documented in a report entitled University of Florida Chemical Disposal Site Supplemental Work Plan, Gainesville, Alachua County, Florida dated February 1998 and in a report entitled University of Florida Chemical Disposal Site (SIS Report No. 2003-04) issued in September 2003.

Investigations performed by ESE included a limited electromagnetic (EM) survey, installation of six piezometers (No. 1 through No. 6), installation of three monitoring wells (MW-1, MW-2 and MW-3), and collection and analyses of groundwater


Section 1 Introduction samples. According to the ESE report, the EM survey was not effective in identifying any trends in groundwater quality.

Piezometers and monitoring wells installed by ESE varied in depth from 20 feet (No. 5) to 45 feet (No. 2). Based on lithologic data from boreholes and water level data, ESE concluded that the surficial aquifer was not present at the site and that groundwater in the intermediate aquifer moved to the northeast beneath the site.

Groundwater samples were collected from the three monitoring wells and piezometer No. 5 and analyzed for the 129 priority pollutants. Although a variety of organic compounds and metals were detected in the groundwater samples, including 15.6 ug/l of benzene in the sample from upgradient well MW-1, ESE concluded that groundwater at the site met the groundwater quality criteria that were applicable at the time and that there was no evidence of significant contamination at the site.

Pursuant to requests from the Northeast District of the FDEP, wells MW-1, MW-2 and MW-3 were monitored. Samples were collected and analyzed for volatile organic compounds (VOCs) and for radionuclides. Results of analyses confirmed the presence of volatile organic compounds in the samples from MW-1.

In 1992, a Work Plan for the Environmental Contamination Assessment of the University of Florida Chemical Disposal Site was prepared by Ecology and Environment, Inc. (E&E) for the Florida Department of Environmental Regulation. The plan apparently was not implemented.

A Preliminary Assessment Report dated October 1995 was prepared by the FDEP Site Screening Superfund Subsection. Information contained in this report indicates that, as a result of citizen complaints, the site was added to the CERCLIS list in July 1994. The Preliminary Assessment Report also concluded that any additional investigation of the site should be performed in accordance with the requirements of RCRA permit that was issued to UF.

In May 1996, the FDEP Site Investigation Section (SIS), at the request of the Northeast District of the FDEP, initiated an environmental assessment to determine the source and extent of volatile organic compounds (VOCs) detected in groundwater samples from monitor well MW-1 at the site. Results of the investigation are documented in a report entitled University of Florida Chemical Disposal Site Supplemental Work Plan, Gainesville, Alachua County, Florida dated February 1998.

The SIS installed six monitoring wells completed in the intermediate aquifer (DEP-1PZ, DEP-2S through DEP-6S), seven monitoring wells completed in the upper Floridan aquifer (DEP-1F through DEP-7F), and several piezometers. The new wells and piezometers were installed adjacent to UF property. Groundwater samples were collected from the new wells and piezometers, existing wells, and selected potable wells and analyzed for, as described in the report, a “full suite” of parameters.


Section 1 Introduction Based on results of this investigation, FDEP concluded that additional investigations were necessary to further evaluate the potential source of VOC contamination in the vicinity of MW-1 and to evaluate the potential for migration of contaminants downgradient of the disposal area. Plans for the additional investigations included the installation of additional monitoring wells and a passive soil-gas survey.

The soil-gas survey was completed in July 1999. Two additional shallow wells completed in the intermediate aquifer (DEP-9S and DEP-10S) and three additional wells completed in the upper Floridan aquifer (DEP-8F, DEP-9F, and DEP-10F) were installed in April 2003. Groundwater samples were collected from these new wells, existing wells except MW-3, and three potable/irrigation wells.

Results of this investigation were presented in the report issued in September 2003 and entitled University of Florida Chemical Disposal Site (SIS Report No. 2003-04). FDEP concluded that the operation of unlined landfills at the site adversely impacted groundwater in the intermediate and Floridan aquifers and that the source of the VOCs in the vicinity of well MW-1 is the former landfill, even though the former landfill is downgradient from MW-1. Iron, manganese, arsenic, and radionuclides in samples collected from the new downgradient wells were detected in concentrations that exceeded primary and secondary drinking water maximum contaminant levels. Results of the FDEP investigations also indicated that the direction of groundwater movement in the intermediate and upper Floridan aquifers is from west to east beneath the site.


Section 2 Results of Investigation 2.1 Introduction Assessment investigations were initiated by CDM for UF in March 2004. The initial phase of the site assessment included:

Installation of 9 of the 15 monitoring wells proposed in the SAP. Following discussions with the FDEP, shallow wells to be completed in the Intermediate Confining Unit (ICU) were not installed at several locations due to either the absence of saturated sediments or the presence of sediments with low hydraulic conductivity that would prohibit the discharge of groundwater to a well.

Collection and analysis of groundwater samples from the 9 new monitoring wells, 21 existing monitoring wells, and 6 supply wells in the vicinity of the site.

Performance of a soil and groundwater field screening investigation on the property immediately to the west of the UF property in the vicinity of well MW-1.

Performance of a ground penetrating radar survey of the site.

Performance of a Tier II landfill gas study of the site.

Measurements of water levels in all monitoring wells.

Performance of in-situ permeability tests at 6 monitoring well locations.

Based on results of the initial assessment investigations, and in accordance with the requirements of the Consent Order and SAP, additional assessment investigations were performed in July 2004. Four additional monitoring wells were installed in the upper Floridan aquifer and one deep Floridan Aquifer System (FAS) monitoring well was installed. Groundwater samples were collected from these wells, and one private supply well and analyzed. Four additional soil borings were completed and groundwater samples were also collected from the property immediately south of the former Alachua County borrow pit. Water level measurements in all wells completed in the upper Floridan aquifer were also measured.

Results of the investigations are described in the following paragraphs.

2.2 Regional Geology and Hydrogeology 2.2.1 Introduction The regional geology and hydrogeology were evaluated using information contained in the published reports prepared by the Florida Geological Survey (FGS) and the U.S. Geological Survey (USGS). The terminology applied to the regional and local hydrogeology conforms to that given in Vecchioli et al., (1986) and Miller (1986).

A 2-1

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Section 2 Results of Investigation

2.2.2 Physical Setting The Gainesville area occurs on a gentle hilly landscape within the Northern (proximal) and Central (mid-peninsular) geomorphic zones of White (1970). The boundary between these geomorphic zones is known as the Cody Scarp (Puri and Vernon, 1964), which also passes through other locations to the east (St. Augustine) and west into the panhandle area (Hoenstein and Lane 1991). The relatively high altitudes (for Florida) are caused by the location on the “Ocala Uplift” or Ocala Platform, which is a possible anticlinal structure (Puri and Vernon, 1964). The University of Florida campus lies along the southern extension of the Northern Highlands within the Northern Zone. This geomorphic feature is characterized as having moderate relief with gently sloping hills and incised streams (Hoenstein and Lane, 1991).

2.2.3 Regional Geology 2.2.3.1 Introduction Central Alachua County is an area influenced by geomorphic features, structure, and karst. The area has a veneer of predominantly siliciclastic sediments near surface overlying a deep section of Cenozoic and Mesozoic carbonate sediments (Hoenstein and Lane, 1991). This 3000-foot thick section of carbonates lies on a Paleozoic basement of quartzite and shale (Applin, 1951: Barnett, 1975). The geologic section of significance to this investigation occurs from the Holocene down to the Eocene. A generalized stratigraphic column is given to show both the stratigraphic units and the corresponding aquifers and confining beds (Table 2-1). The stratigraphic names of formations in the column conform to the latest geologic map of Florida (Scott et al., 2001) and the aquifer names conform to the terms accepted by the Southeastern Geological Society Committee on Hydrostratigraphic Nomenclature (Vecchioli et al., 1986).

2.2.3.2 Undifferentiated Siliciclastic Sediments A series of undifferentiated, predominantly siliciclastic sediments lies from land surface to the top of the underlying Hawthorn Group. These sediments were deposited either in the Pliocene or Pleistocene and were altered by erosion during the Holocene. The age of the unit is subject to debate because of the unknown age of corresponding marine terrace deposits and the ever-changing absolute time boundary between the Pliocene and Pleistocene. This unit ranges in thickness from 10 to 30 feet in the area in and around Gainesville (Macesich, 1988; Green et al., 1989; Hoenstein and Lane, 1991). The localized thickness of the unit is dependant on the depth of the erosional surface of the Ocala Limestone, which forms pinnacles and depressions, which cause either thinning or thickening of the overlying deposits. The unit typically is very heterogeneous with extreme variations in lithology from nearly pure quartz sand to pure clay and admixtures of these and other components, such as organics, phosphate, and chert. These sediments lie disconformably upon the underlying Hawthorn Group.

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Table 2-1

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2.2.3.3 Hawthorn Group Miocene-aged sediments within the Coosawhatchie Formation of the Hawthorn Group lie above the deeper carbonates of the Ocala Limestone along the eastern margin of the Ocala Platform (Scott, 1988). The thickness of this unit varies from zero to the southwest of Gainesville to nearly 80 feet to the east (Scott, 1988). However, in cores taken and analyzed by the Florida Geological Survey to the west (W-16199) and east (W-16203) of the University of Florida, the thickness of Coosawhatchie Formation sediment was only 5 to 10 feet (Green et al., 1989). Thicker sections of the formation may occur in depressions within the underlying Ocala Limestone. Descriptions of cores taken in the formation in the vicinity of Gainesville show the lithology of the Coosawhatchie Formation to be highly variable from a grayish-brown clay (rock color chart) with quartz, phosphate, and chert to a quartz sand with a clay matrix and various percentages of phosphate and chert (Scott, 1988; Green et al., 1989). There are some descriptions of beds of nearly pure quartz sand or sand mixed with chert “boulders or cobbles.” The clay percentage in the sediment matrix is nearly always above 15% (Green et al., 1989).

2.2.3.4 Ocala Formation The late Eocene-aged Ocala Limestone lies disconformably beneath the Coosawhatchie Formation. In the vicinity of Gainesville and throughout much of the Ocala Uplift area, the Oligocene section has been removed from the stratigraphic section by erosion and therefore, the Suwannee Limestone does not occur. There is considerable relief on the surface of the Ocala Limestone and it could be termed a mirco-karst or pinnacled surface (see Hoenstein and Lane, 1991, p. 31, photograph). This extreme relief causes infilling of the areas between pinnacles and hydraulic connection between the limestone and some horizontal beds of sand and chert nodules.

Lithologically, the Ocala Limestone is primarily a calcarenite or grainstone consisting of large foraminifera, small foraminifera mollusk fragments, echinoids, and bryozoans. It is slightly to well-cemented with a high degree of dissolution in many areas. The limestone has a generally white to very pale orange color (rock color chart). There are some areas in Florida, where parts of the formation are dolomitized. Silicified limestone or chert nodules commonly occur either at the surface of the limestone or within it. These chert nodules may have been formed during the Oligocene in the Suwannee Limestone and may be reworked as a lag deposit at the top of the formation or have been incorporated into the limestone in vertical karst features. The Ocala Limestone ranges from 200 to 300 feet in thickness in the Gainesville area. It does crop out at surface in areas in and near Gainesville.

2.2.3.5 Avon Park Formation The Avon Park Formation is a middle Eocene-aged unit that covers the entire Florida Platform. It contains both limestones and dolomites, which to a degree are fabric selective in occurrence. The sediments within the formation are generally tan or brown in color with quite variable degrees of induration and hardness. Large cavities

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do occur within the formation. There are a number of fossil types occurring within the limestones. These include foraminifera, mollusks, echninoids, calcareous algae, and plants. In deeper parts of the formation, molds and casts of evaporate minerals can occur and near the base of the formation gypsum and anhydrite cements can be present. The formation occurs at depths generally greater than 150 feet below surface in the Gainesville area (Hoenstein and Lane, 1991).

2.2.4 Regional Hydrogeology 2.2.4.1 Introduction There are three primary hydrogeologic units present beneath Alachua County and the Gainesville area. Based on the terminology of Vecchioli et al. (1986) and Miller (1986), these units are: 1) the Surficial Aquifer System, 2) the Intermediate Confining Unit /Intermediate Aquifer System, and 3) the Floridan Aquifer System. The hydrostratigraphy of these is presented in Table 2-1.

2.2.4.2 Surficial Aquifer System The Surficial Aquifer System (SAS) occurs within the veneer of Plio-Pleistocene siliciclastic sediments, where there is sufficient hydraulic conductivity to define it as an aquifer. The thickness of the aquifer is quite variable, but ranges from zero to 20 feet. Since the sediments comprising the aquifer have considerable heterogeneity, the aquifer has correspondingly considerable variation in hydraulic conductivity. There are areas in and near Gainesville where the sediments comprising the SAS do not have sufficient hydraulic conductivity to be termed an aquifer and in fact, are part of the Intermediate Confining Unit. Seasonally, the water level can drop in the SAS below the base of the aquifer as water drains into the underlying FAS as recharge. In the wet season, the head differential between the potentiometric surface of the SAS and that of the FAS can be up to 40 feet (Clark et al., 1964). This head differential can cause rapid draining of the SAS to the FAS in areas where the vertical connection is good and dry season continuous draining even in areas where the confinement is high. Therefore, parts of the SAS may be considered as an ephemeral or seasonal aquifer being water-bearing only during wet periods.

Recharge of the SAS occurs primarily from direct rainfall and in some cases horizontally from areas where the vertical hydraulic conductivity is sufficient to allow infiltration of rainfall. Where clayey soils occur at land surface, direct rainfall recharge cannot occur or where man-made impervious surfaces occur direct recharge also cannot occur. Since the vertical gradient between the SAS and the FAS is directed downward in the Gainesville area, no significant recharge to the aquifer occurs from the FAS. Water is discharged from the aquifer via evapotranspiration, vertical recharge to the FAS, horizontal discharge to drainage features, such as streams or ditches, and via the use of wells.

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2.2.4.3 Intermediate Confining Unit/Intermediate Aquifer System The Intermediate Confining Unit (ICU) exists between the SAS and FAS in the Gainesville area (Clark et al., 1964; Miller, 1986; Bush and Johnson, 1986; Macesich, 1988; Green et al., 1989; Scott et al., 2001). However, because the nature of the upper surface of the FAS, which is the pinnacle-karst surface of the Ocala Limestone, the degree of confinement is quite variable. Macesich (1988) defined the area of Gainesville to be within zone termed “confined, but perforated.” The confining sediments are clays, sandy clays, and clayey sands occurring within the Hawthorn Group and the overlying Plio-Pleistocene siliciclastics sediments. The thickness of the ICU ranges from zero to 80 feet.

Significant work has been done on the vertical rate of water movement across the ICU in the area in and around Gainesville. Bush and Johnson (1988) estimated that the leakance of the ICU was greater than 2.28 x 10-4 1/days. A series of hydraulic conductivity tests on the confining sediments were conducted by Green et al. (1989). The range in vertical hydraulic conductivities measured using the standing head measurement method on core samples was nearly zero (no flow in 21 days) to 1.5 feet/day. When the sand sample cores (3) and the pure clay cores (4) with no flow are eliminated, the average vertical hydraulic conductivity of the remaining 27 samples was 0.025 feet/day.

There are some thin beds of sand and chert cobbles within the ICU that have sufficient horizontal hydraulic conductivity to yield water. Although Hoenstein and Lane (1991) suggested that some IAS is present in the Gainesville area, there is no real evidence to support that claim. It is more likely that the yield of water from shallow wells tapping the IAS are really hydraulically connected to the FAS via horizontal beds of sand and chert in connection with limestone pinnacles of the Ocala Limestone. Clark et al. (1964, p. 112) contained a cross-section that showed limestones and sands within the ICU northeast of Gainesville but in the immediate area of Gainesville these units do not exist.

2.2.4.4 Floridan Aquifer System The FAS is the primary aquifer system used for water supply in the central Florida and Gainesville area (Clark et al., 1964; Miller, 1986; Bush and Johnson, 1986; Hoenstein and Lane, 1991). This regional aquifer system underlies the entire state of Florida as well as parts of South Carolina, Georgia, and South Carolina (Miller, 1986). The hydrostratigraphy of the FAS in the Gainesville area is shown in Table 2-1.

The top of the Ocala Limestone corresponds to the top of the FAS in the Gainesville area. The upper surface of the FAS is highly irregular because of the pinnacle-karst nature of the Ocala Limestone. This causes the FAS is be in direct hydraulic contact with some horizontally layered sands and chert deposits lying between pinnacles or other topographic highs.

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The FAS is one of the most productive aquifers in the world and has an estimated transmissivity in the Gainesville area of between 250,000 and 1,00,000 ft2/day with a corresponding thickness of about 1400 feet (Bush and Johnson, 1986). Based on the average thickness and the range in transmissivity values, the average hydraulic conductivity of the aquifer ranges between 179 and 714 feet/day. Since the aquifer lies within karstic formations, the hydraulic conductivity is not uniformly distributed and conduit flow is common in the area. Therefore, the rock matrix of geologic units, such as the Ocala Limestone, can be expected to have lower horizontal hydraulic conductivity values on the average.

Recharge to the FAS in the Gainesville area ranges from 5 to 10 inches per year, which is a very large range in values (Bush and Johnson, 1986). This large range in values is consistent with the variable thickness in the confining beds and the “confined-perforated” classification of the FAS in the Gainesville area by Macesich (1988). Also, the rate of recharge for the area was calculated in a pre-development state. With the considerable use of the FAS for water supply in the Gainesville area, the rate of recharge currently is higher than these older estimates. The enhanced rate of recharge likely causes the overlying SAS to drain more rapidly in dry periods, causing it not to be a reliable water supply and making it more ephemeral. Recharge to the FAS in the Gainesville area occurs by direct entry in sinkholes, by vertical leakage through the confining beds, by horizontal flow from topographic highs to the northeast, and by drainage of hydraulically connected beds within the ICU.

Flow through the FAS is the Gainesville area is affected by both topographic considerations and pumpage. The pre-development flow direction on a regional basis is generally from east to west with a southerly component (Bush and Johnson, 1986). Local topography, surface drainage to streams or wetlands, and centers of pumpage tend to locally control flow direction in the aquifer.

2.3 Site-Specific Geology/Hydrogeology 2.3.1 Site Geology and Hydrogeologic Units 2.3.1.1 Introduction The geology and hydrogeology of the site and immediate vicinity were evaluated using data from core samples. Sonic drilling was used to drill the boreholes during monitor well construction. Therefore, nearly continuous cores were collected from each well location. The cores were collected and described in detail to identify stratigraphic units, potential water bearing strata, and confining layers. Monitoring wells were installed and water levels measured. Aquifer hydraulic characteristics were evaluated using data from in-situ hydraulic conductivity measurement tests and water level data.

A total of 15 boreholes were drilled and 14 monitoring wells completed. The maximum depth drilled was 285 feet below land surface (bls) at monitor well MW-16FD. Locations of monitor wells are shown on Figure 2-1. The drilling and monitor

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Figure 2-1

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well completion logs for the monitor wells installed at the site are in Appendix C. Water level data are summarized in Table 2-2 and Table 2-3.

Evaluation of these data indicates that the site is underlain by undifferentiated sediments of Plio-Pleistocene age, the Coosawahatchie Formation of the Hawthorn Group, and the Ocala Limestone. The data also indicate that the upper part of the FAS is the only aquifer that underlies the entire site and immediate vicinity. The SAS is ephemeral and the IAS really does not exist.

Two hydrogeologic cross-sections were constructed using data collected during monitor well installation and from water level measurements. The lines of cross-section are shown on Figure 2-1. Figure 2-2 is an east-west hydrogeologic cross section from MW-11F to MW-20F. Figure 2-3 is a north-south hydrogeologic cross section from MW-2F to MW-19F.

2.3.1.2 Undifferentiated Sediments/Surficial Aquifer System As indicated in the cross-sections and in the geologist logs, these sediments generally consisted of organic sand/silt and fine to medium grain sands of varying color. The total thickness of these sediments varied from 5 to 24 feet. If saturated, these sediments would form the surficial aquifer. Some of these sediments may have low hydraulic conductivities and may be part of the ICU. Groundwater was not present in any of the cores collected from this unit. Information contained in the SIS Report Number 2003-04 entitled University of Florida Chemical Disposal Site prepared by the FDEP Site Investigation Section (SIS) in September 2003 suggests that the SAS may be present west of the site in the vicinity of wells DEP-4PZ and DEP-4F.

2.3.1.3 Hawthorn Group-Coosawahatchie Formation/Intermediate Confining Unit

The sediments within this group were composed of clays, sandy clays, and clayey sands varying in color. Sands were typically fine to very fine grained. Clay and sandy clay strata were typically moderately stiff. Traces of phosphate were present in some of the strata. Chert rubble zones were penetrated at most locations. The total thickness of these sediments varied from 5 to 56 feet.

Based on the nature of the strata that comprise this unit and evaluation of water level data, the sediments of the Coosawahatchie Formation should not be considered an aquifer for the purposes of evaluating contamination associated with this site. At many locations, groundwater was not present in the sediments that comprise the Coosawahatchie Formation. These data indicate that water-bearing strata that are present within this formation are of limited areal extent and only bed-scale in thickness. Comparisons of water level data from nested wells completed in the upper FAS and overlying sediments, as shown in Table 2-2 and in Figure 2-2 and Figure 2-3, indicate that the water levels in saturated strata of the Coosawahatchie Formation are either the potentiometric surface of the FAS or water contained in sediments with low hydraulic conductivity.

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Table 2-2

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Table 2-3

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Figure 2-2

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Figure 2-3

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2.3.1.4 Ocala Limestone/Floridan Aquifer System Underlying the siliciclastic sediments of the Coosawahatchie Formation are carbonate sediments of the Ocala Limestone. Beneath the site and immediate vicinity, the Ocala Limestone consists of white to cream, pale brown-colored, fine to medium grained, poorly to moderately indurated, very fossiliferous limestone. The fossils present in the Ocala Limestone include abundant large and smaller foraminifers, echinoids, bryozoans and mollusks. At several locations, black, very soft, dark-colored clay was present within the upper 10 feet of the formation. Calcareous sand was noted at numerous locations prior to penetrating competent rock.

The depth to the top of the Ocala Formation varied from 11 feet below land surface (bls) at the location of well MW-20F to 80 feet bls at the location of well MW-12F. The variations in the thickness of the overlying sediments indicate that the surface of Ocala Limestone is an erosional surface characterized by pinnacles. At MW-16FD, the Ocala Limestone was fully penetrated. At this location, the Ocala Formation was 121 feet thick. The elevation of the contact between the base of the Ocala and the top of the Avon Park Formation is -62 feet NGVD.

The Ocala Limestone is the uppermost part of the FAS. The FAS is the only consistent water-bearing unit present beneath the entire site and vicinity.

2.3.1.5 Avon Park Formation The Avon Park Formation underlies the Ocala Limestone. At MW-16FD, the Avon Park was penetrated from 149 feet to 285 feet bls. The lithology of the Avon Park Formation at the location of MW-16FD consisted of well-indurated, dense pale brown to gray dolomitic limestone and dolomite with few fossils and interbedded layers of silty clay, clay, and sand. This formation is included in the FAS.

2.3.2 Direction and Rate of Groundwater Movement 2.3.2.1 Direction of Groundwater Movement A licensed professional surveyor and mapper determined measuring point elevations and locations of all wells. Water level elevations in all monitoring wells were collected and the data used to assess the direction and gradient of groundwater movement.

Following the completion and development of all monitor wells installed by CDM during Phase I installation, groundwater levels were measured in all existing monitor wells and piezometers on April 12, 2004. Water level data collected on April 12, 2004, are summarized in Table 2-2. Groundwater levels were measured in all wells completed in the FAS on July 7, 2004, after the installation of the additional monitoring wells. These data are summarized in Table 2-3.

Figure 2-4 is a contour map of the potentiometric surface of the FAS based on water level elevations measured on April 12, 2004. Figure 2-5 is a contour map of the potentiometric surface of the FAS based on water level elevations measured on July 7, 2004. Evaluation of the water level data indicates that the direction of groundwater

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Figure 2-4

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Figure 2-5

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movement in the upper FAS beneath the site and immediate vicinity is generally from west to east.

2.3.2.2 Rate of Groundwater Movement In-situ hydraulic conductivity tests (slug tests) were performed on three ICU wells (DEP-9S, MW-12S and MW-14S) and three FAS monitoring wells (MW-11F, MW-12F, and MW-16F). These wells were selected based on well construction information and their locations. Results of the in-situ tests were used to calculate hydraulic conductivity. These data were used with water level data and estimated effective porosity to estimate the rate of groundwater movement. The recovery-versus-time graphs for the slug tests are included in Appendix D.

Hydraulic conductivities were calculated using the Hvorslev (1951) method for partially penetrating wells. The calculations were performed using an in-house computer program. The calculated hydraulic conductivities are compiled in Table 2-4. The calculated hydraulic conductivities for the ICU varied from 0.3 ft/day to 166 ft/day. The value of 166 feet/day is anomalously high and is not considered valid. This result was determined using data from a “slug in” test. Based on evaluation of well construction and water level data, the high hydraulic conductivity value is attributed to an unsaturated sand pack absorbing displaced water during insertion of the slug. The calculated hydraulic conductivities for the FAS wells varied from 18 ft/day to 553 ft/day. All of these values are considered to be horizontal hydraulic conductivity values. Vertical hydraulic conductivity values for the ICU are typically two orders of magnitude lower than the horizontal values.

The rate of groundwater movement FAS was estimated using results of this investigation. Groundwater flow was calculated using the two-dimensional form of Darcy’s Law:

where,

V = K/ne * dh/dl

V = average linear velocity in ft/day

K = hydraulic conductivity in ft/day

ne = effective porosity in percent

dh/dl = hydraulic gradient

Based on results of the in-situ hydraulic conductivity tests, the average hydraulic conductivity value for the upper part of the FAS was calculated to be 192 feet/day. Water level data collected on April 12, 2004, was used to calculate the hydraulic gradient. The difference in water level elevations measured in wells DEP-4F (furthest upgradient) and MW-16F (furthest downgradient) was 1.12 feet. The distance between these wells is approximately 1,560 feet. Using these data, the resulting

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Table 2-4

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horizontal gradient is 0.0007. Based on these site-specific data and an effective porosity of 30%, the calculated rate of groundwater movement beneath the site is calculated to be 0.5ft/day.

2.4 Groundwater Quality 2.4.1 Introduction Objectives of the site assessment included assessment of the lateral and vertical extents of contamination in groundwater. These objectives were accomplished in two phases. The initial phase included the installation of 11 of the 15 monitoring wells proposed in the SAP. Wells MW-12S, MW-13S, MW-14S and MW-15S were completed in the ICU. Wells MW-11F, MW-12F, MW-13F, MW-14F, MW-15F, MW-16F and MW-17F were completed in the FAS. Wells MW-11S, MW-16S and MW-17S were not installed as planned. Following discussions with the FDEP, these proposed intermediate aquifer/confining zones were not installed due to the absence of groundwater in sediments that overly the FAS.

Groundwater samples were collected from the 11 new monitoring wells, 21 existing monitoring wells, and 6 supply wells in the vicinity of the site as part of the initial phase of the investigation. Groundwater samples were collected from all wells and analyzed for the following parameters:

Iron Manganese Arsenic Radionuclides (gross alpha and beta and radium 226 and 228) Ammonia (ammonium) Dissolved chlorides Nitrate Sodium Total dissolved solids (TDS) Total suspended solids (TSS) Color VOCs

Also, in accordance with FDEP requirements, all samples were also analyzed for analytes listed in Appendix II of 40 CFR 258. Field measurements of pH, specific conductance (SC), dissolved oxygen (DO), temperature, turbidity, and oxidation/reduction potential (ORP) were made on groundwater samples from all the wells. Filtered and unfiltered samples were collected from monitoring wells for analyses of metals and radionuclides. Only enough water to analyze for VOCs could be withdrawn from well DEP-1S. Although not included in either the suite of analytes proposed in the SAP or in Appendix II, groundwater samples were also analyzed for 1,4-dioxane. The presence of 1,4-dioxane was initially identified in samples collected as part of the assessment of

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the source of benzene in the vicinity of well MW-1. Upon notification of the possible presence of 1,4-dioxane, the UF requested that this analyte be included in the suite of analyses. 1,4-Dioxane is found in many products, including shampoos, cosmetics, automotive coolants, and solvents.

Based on results of the initial phase of the investigation, it was determined that additional investigations would be necessary to further define the lateral and vertical extents of contamination. Wells MW-18F, MW-19F, MW-20F and MW-21F were installed to further define the lateral extent of contamination in the upper part of the FAS. A deep FAS well, MW-16FD, was also installed to determine the vertical extent of contamination. The wells were installed and sampled in July 2004.

The concentration or activities of iron, manganese, arsenic and radionuclides in the sediments that comprise the ICU and the upper part of the FAS were also evaluated. Samples of the water-bearing strata at the locations of wells MW-5, MW-12F, MW-13F and MW-16F were collected and analyzed for these parameters to determine if these constituents are naturally-occurring in the groundwater.

Iron, manganese, arsenic, radionuclides, thallium, dieldrin, benzene, vinyl chloride, 1,4-dioxane, chlorides and total dissolved solids (TDS) were detected in concentrations or activities that exceeded the Groundwater Cleanup Target Levels (GCTLs) established in Table I of Chapter 62-777, F.A.C. The distributions of these analytes in the hydrogeologic units present at the site and in the immediate vicinity are discussed in the following paragraphs.

2.4.2 Surficial Aquifer System and Intermediate Confining Unit Groundwater samples were collected from 11 monitoring wells that are completed in the SAS and ICU. These wells are MW-1, DEP-1S, DEP-2S, DEP-3S, DEP-4S, DEP-9S, DEP-10S, MW-12S, and MW-14S. Of these wells, evaluation of available information indicates that only well DEP-4S is completed in the SAS. Locations of monitoring wells are shown on Figure 2-1. Groundwater samples were collected from all of these wells in April 2004. Analytical reports are in Appendix E. Table 2-5 is a summary of analytical results.

Based on well construction information included in reports prepared by the FDEP and water level data, piezometers and wells DEP-1PZ, DEP-4PZ, DEP-4S, DEP-6PZ and DEP-7PZ are completed in materials that are considered to be the SAS. All of these wells and piezometers contained no water with the exception of DEP-4PZ and DEP-4S. Therefore, groundwater samples were only collected from well DEP-4S.

Iron, manganese, thallium, radionuclides, vinyl chloride, benzene, 1,4-dioxane, chlorides, and total dissolved solids (TDS) were detected in concentrations or activities that

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Table 2-5

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exceeded the GCTLs in samples from wells completed in the ICU. The highest concentrations of these analytes were detected in wells DEP-9S, DEP-10S and MW-12S.

The highest activities or concentrations of radionuclides, benzene (12 ug/l), 1,4-dioxane (3,500 ug/l), chlorides (470 mg/l), and TDS (770 mg/l) were detected in the sample from well DEP-9S. In addition to these analytes, the concentration of manganese exceeded the GCTL in the sample from FEP-9S. This well is located in the southeastern part of the Murphree property borrow pit.

The highest concentrations of manganese (0.60 mg/l total), vinyl chloride (1.4 ug/l) and thallium (0.009 mg/l) were detected in the sample from well DEP-10S. In addition to these analytes, the concentration of iron exceeded the GCTLs in the sample from DEP-10S. This well is located immediately at the northeast corner of the former Murphree property borrow pit.

The highest concentration of iron was detected in the sample from MW-12S (58 mg/l total). In addition to iron, the concentration of manganese and the activities of radionuclides (alpha +radium 226 and radium 226 + radium 228) exceeded the GCTLs in the sample from this well. This well is located near the southeastern corner of the former Alachua County borrow pit.

Concentrations of iron also exceeded the GCTL in samples collected from wells MW-1, DEP-3S, and MW-14S. Concentrations of manganese exceeded the GCTL in samples from well MW-14S. Activities of radionuclides exceeded the GCTLs in samples from wells MW-1, DEP-2S, and DEP-3S. The concentrations of 1,4-dioxane exceeded the GCTL in samples from wells MW-1. The concentrations of benzene exceeded the GCTL only in the samples from MW-1.

Because the water-bearing strata in the ICU are of limited lateral extent, the distributions of these analytes in the ICU are not presented graphically. Evaluation of the hydrogeologic data indicates that the ICU does not contain water-bearing strata at most locations along the boundary of the site and east (downgradient) of the site. Therefore, it is unlikely that contaminants are migrating laterally for any significant distance via water-bearing strata in the ICU.

2.4.3 Floridan Aquifer System Groundwater samples were collected from 24 monitoring wells that are completed in the FAS. These wells are MW-1F, DEP-2F, MW-2, MW-2F, DEP-3F, DEP-4F, DEP-5F, DEP-6F, DEP-7F, DEP-8F, DEP-9F, DEP-10F, MW-11F, MW-12F, MW-13F, MW-14F, MW-15F, MW-16F, MW-17F, MW-18F, MW-19F, MW-20F, MW-21F, and MW-16FD. Locations of monitoring wells are shown on Figure 2-1.

Groundwater samples were collected from wells MW-1F, DEP-2F, MW-2, MW-2F, DEP-3F, DEP-4F, DEP-5F, DEP-6F, DEP-7F, DEP-8F, DEP-9F, DEP-10F, MW-11F, MW-12F, MW-13F, MW-14F, MW-15F, MW-16F, and MW-17F in April 2004 as part of the

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initial investigation. Analytical reports are in Appendix E. Table 2-6 is a summary of analytical results.

Concentrations or activities of iron, manganese, arsenic, nickel, radionuclides, 1,4-dioxane, dimethoate, ammonia and TDS were detected in concentrations that exceed the GCTLs in the FAS wells. Because concentrations of analytes exceeded GCTLs in samples collected from wells installed along the boundary of the site, in upgradient well DEP-2F, and in downgradient well MW-16F, additional investigations were performed to further define the lateral extent of contamination to the west, south, and east of the site. Wells MW-18F, MW-19F, MW-20F, and MW-21F were installed at locations shown on Figure 2-1 and sampled in July 2004. Analytical reports are in Appendix D. Analytical results are included in Table 2-6. Concentrations of all analytes in the samples collected from wells MW-18F, MW-19F, MW-20F, and MW-21F were below the GCTLs.

Concentrations of arsenic, nickel, dimethoate, TDS and ammonia that exceeded GCTLs were localized. The concentrations of arsenic (0.12 mg/l) and nickel (0.12 mg/l) exceeded the GCTLs only in the sample from MW-16F. The concentration of dimethoate (0.30 ug/l) exceeded the GCTL only in the sample from MW-2F. The GCTL for TDS was only exceeded in the sample from MW-1F (560 mg/l) and in the sample from MW-16F (770 mg/l). Only the concentration of ammonia in the sample from well MW-13F exceeded the GCTL.

Iron, manganese, radionuclides and 1,4-dioxane were detected in samples from several wells in concentrations or activities that exceeded GCTLs. The distribution of iron in the upper part of the FAS is shown on Figure 2-6. The highest concentrations are in the vicinity of well MW-16F (39 mg/l). Evaluation of these data indicates that the distribution of iron in concentrations that exceed the GCTL of 0.3 mg/l has been defined to the west (off-site), south (off-site), and east of the site. Evaluation of these data with respect to the direction of groundwater movement, locations of waste disposal areas, results of analyses of samples from private wells, and the distribution of other analytes indicates that the concentrations of iron in samples collected from wells MW-14F, MW-2F, and MW-15F are consistent with background concentrations in the vicinity of the site and may not be solely attributed to waste disposal activities. Background concentrations and potential causes for exceedances of the GCTLs for iron and other analytes are discussed in Section 2.4.

The distribution of manganese in the upper part of the FAS is shown on Figure 2-7. The highest concentrations are in the vicinity of well MW-13F (0.75 mg/l). Evaluation of these data indicates that the distribution of manganese in concentrations that exceed the GCTL of 0.05 mg/l has been defined to the northwest, west (off-site), south (off-site), and east of the site. Evaluation of these data with respect to the direction of groundwater movement, locations of waste disposal areas, results of analyses of samples from private wells, and the distribution of other analytes indicates that the concentration of manganese in the sample collected from well MW-15F may not be

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Table 2-6

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Table 2-6

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Figure 2-6

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Figure 2-7

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associated with waste disposal activities. Background concentrations and potential causes for exceedances of the GCTLs for iron and other analytes are discussed in Section 2.4.

The distributions of alpha and radium 226 radionuclides are shown on Figure 2-8 and Figure 2-9, respectively. The activities of these radionuclides were contoured because the concentrations were generally higher than those of beta and radium 228. The highest activities are in the vicinity of well MW-13F (16.2 pCi/l alpha and 6.69 radium 226).

The distribution of 1,4-dioxane in the upper part of the FAS is shown on Figure 2-10. The highest concentrations are in the vicinity of well MW-11F (210 ug/l) and well DEP-9F (210 ug/l). Evaluation of these data indicates that the extent of 1,4-dioxane in concentrations that exceed the GCTL of 5 ug/l has been defined in all directions.

The distributions of iron, manganese, and 1,4-dioxane in concentrations that exceed the GCTLs are very similar. Evaluation of the distributions of iron and manganese indicates that iron and manganese are moving from the vicinities of the western boundary of the former Alachua County borrow pit and from the former Murphree property borrow pit towards the east. Evaluation of the distributions of radionuclides and 1,4-dioxane indicate that these analytes are also moving from the vicinities of the western boundary of the former Alachua County borrow pit and from the former Murphree property borrow pit towards the east. In addition, these analytes also appear to migrating from the area to the south of the former Alachua County borrow pit. These data also indicate that the concentrations of these analytes decrease to below the GCTLs and/or background concentrations within 500 feet of the boundary of the site. The direction of movement of all of these analytes is consistent with the direction of groundwater movement.

2.4.4 Private Wells Groundwater samples were collected from 7 private supply wells in the vicinity of the site. Locations are shown on Figure 2-11. The Knight well (1) and the Lowe well (2) were identified as potable wells by the Alachua County Environmental Protection Department (ACEPD) and the Alachua County Health Department (ACHD). The Sheffield well (3) may also be used for potable water. Four irrigation wells, Hilton (4), IFAS (5), Museum Walk (6) and Immunogenetics (7) are within ¼-mile of the site. Groundwater samples were collected from all of these wells except the Lowe well in April 2004. The Lowe well could not be sampled at that time because the residence was vacant and the power was turned off. Arrangements were made by UF to have the power turned on at the Lowe property and a sample was collected in July 2004. Copies of analytical reports are in Appendix E. Analytical results are summarized in Table 2-7.

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Figure 2-8

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Figure 2-9

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Figure 2-10

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Figure 2-11

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Table 2-7

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Concentrations or activities of all analytes were below the GCTLs in the sample from the Sheffield well. Only the concentration of iron (1.6 mg/l) exceeded the GCTL in the sample from the Knight well. Concentrations of iron (0.68 mg/l) and manganese (0.17 mg/l) exceeded the GCTLs in the sample from the Lowe well. The Knight and Lowe wells are across the flow paths in the FAS from the western part of the site.

Concentrations of iron (3.0 mg/l) and manganese (0.053 mg/l) exceeded the GCTLs in the sample from the Immunogenetics irrigation well. Concentrations or activities of all analytes were below the GCTLs in the samples from the IFAS and Museum Walk irrigation wells. The Museum Walk irrigation well is less than 1000 feet from the southeast corner of the former Murphree property borrow pit. The IFAS and Immunogenetics irrigation wells are nearly 2000 feet from the site.

Concentrations of iron (0.83 mg/l) and 1,4-dioxane (31 ug/l) exceeded the GCTLs in the sample from the Hilton irrigation well. The Hilton irrigation well is less than 100 feet from the eastern boundary of the former Murphree property borrow pit. According to the drilling company that installed the well, it is cased to 173 bls and is completed with open hole construction to a depth of 210 feet bls.

Based on this information, well MW-16FD was installed adjacent to MW-16F in July 2004 to define the vertical extent of contamination. Well MW-16FD is completed at a depth of 285 bls. A groundwater sample was collected from MW-16FD in July 2004. A copy of the analytical report is in Appendix E and the results are summarized in Table 2-6. These data and results of analyses of the sample from the Hilton irrigation well indicate that the vertical extent of contamination in concentrations that exceed the GCTLs or background concentrations is between 210 and 285 feet bls in the area immediately downgradient of the site.

2.5 Sources of Contamination 2.5.1 Introduction Objectives of the site assessment included investigations of potential sources of contamination. These evaluations included investigations to identify the source of contamination of groundwater in the vicinity of well MW-1, a ground penetrating radar and Tier II landfill gas study to evaluate the extent and nature of waste on the former Alachua County and Murphree properties, and collection and analyses of soil samples from water-bearing strata to evaluate the potential for naturally-occurring constituents in the groundwater. Results of these investigations were evaluated with respect to results of groundwater quality investigations and information regarding the history of the site and immediate vicinity.

2.5.2 Assessment of Groundwater Contamination Near MW-1 Well MW-1 is located approximately 125 feet west (upgradient) from the southwestern corner of the former Alachua County borrow pit. Concentrations of benzene in groundwater samples collected from this well exceed the GCTL. The initial investigation to evaluate the source of benzene in this area was conducted in

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April 2004. This investigation consisted of the collection and field screening of soil and groundwater samples from 19 locations (DPT-1 through DPT-19). Locations are shown on Figure 2-12 and Figure 2-13. Samples were collected using direct push technology (DPT). Soil/refuse samples were screened in the field using an OVA. Soil samples collected from beneath the refuse and groundwater samples were analyzed for VOCs using a mobile laboratory. Analytical reports are in Appendix F. Based on these results and results of other investigations performed as part of the site assessment, four additional borings (DPT-J1, DPT-J2, DPT-J3, and DPT-J4) were completed adjacent to the south of the southwest corner of the former Alachua County borrow pit. The locations of these samples are shown on Figure 2-12 and Figure 2-13. Three (3) groundwater samples and one soil sample were collected from these locations and analyzed for VOCs and I,4-dioxane. Analytical reports are in Appendix F and results are summarized in Table 2-8. Results of field screening of soil samples are summarized in Table 2-9.

Evaluation of soil/refuse samples indicates that fill material consisting of soil and refuse is present to depths of up to 19 feet bls. The refuse contained in the samples consisted mainly of charred wood, bricks, plastic, glass, and metal. Results of field screening indicate that the soil/refuse contained organic vapors in concentrations of up to 4,260 parts per million (ppm). Most of the organic vapors were determined to be methane. No VOCs were detected in the soil samples that were collected from beneath the base of the refuse and analyzed by the mobile laboratory.

Benzene, chloroform, 1,2-dichloroethane, and isopropylbenzene were detected in groundwater samples in concentrations that exceeded GCTLs. The concentrations of ispopropylbenzene in samples from DPT-5 (1.8 ug/l), DPT-12 (1.1 ug/l), and DPT-16 (1.6 ug/l) exceeded the GCTL of 0.8 ug/l. The concentration of chloroform in the sample from DPT-5 (6.3 ug/l) slightly exceeded the GCTL of 5.7 ug/l. The concentration of 1,2-dichloroethane in the sample from DPT-18 (3.6 ug/l) slightly exceeded the GCTL of 3.0 ug/l.

The concentrations of benzene in samples from DPT-1, DPT-2, DPT-3, DPT-4, DPT-5, DPT-7, DPT-10, DPT-11, DPT-12, DPT-14, DPT-18, and DPT-19 exceeded the GCTL. The distribution of benzene in the area immediately to the west and southwest of the former Alachua County borrow pit is shown on Figure 2-12. The extent of benzene contamination in shallow groundwater was determined except for the northern part of the study area. Rough terrain and dense vegetation prohibited investigation north of DPT-17 and DPT-19.

Chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, and/or 1,4 dichlorobenzene were detected in samples from all of the DPT sample locations. The

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Figure 2-12

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Figure 2-13

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Table 2-8

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Table 2-9

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Table 2-9

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distribution of chlorobenzene is shown on Figure 2-13. The distribution of chlorobenzene correlates with the distribution of benzene.

Evaluation of the results of this investigation indicates that source of the benzene is likely the degradation of chlorinated benzene compounds. Pathways for the reductive dechlorination of halogenated benzene rings is described by Rammand, et al. (1993) and in the University of Minnesota Biocatalysis/Biodegradation Database. The distribution of these compounds in the shallow groundwater indicates that this area was likely the source of these compounds. However, the absence of these compounds in the soil samples indicates that these compounds have leached from the soil/refuse and that the source is no longer active.

2.5.3 Ground Penetrating Radar Study and Landfill Gas Study 2.5.3.1 Ground Penetrating Radar Study A ground penetrating radar (GPR) study was performed to assess the lateral and vertical extents of waste disposal on the former Alachua County and Murphree properties. Geohazards, Inc. was subcontracted to perform the investigation. The investigation was performed April 26 through April 29, 2004. A copy of the report prepared by Geohazards is in Appendix G. DPT borings (GPR-1 through GPR-15) to field check the results of the GPR survey were performed concurrently with the GPR survey. DPT boring logs are also in Appendix G. Locations of the GPR transects and boring locations are shown on Figure 2-14.

The GPR survey was successful in identifying the lateral boundaries of the disposal of Class I waste. However, signal penetration below 6 to 8 feet bls was limited. Therefore, the depth of the base of the waste could not be determined using GPR. In addition, the presence of pavement limited the penetration of the signals.

Generally, the waste signature was characterized by reflectors that were irregular and discontinuous. There was no evidence of buried drums. The signature of undisturbed material and fill material was generally horizontal and continuous. Based on examination of samples from DPT borings, undisturbed material identified by GPR was either undisturbed material or fill material that contained large amounts of soil with some inert materials such as wood and construction debris. The approximate boundary of the Class I waste based on interpretation of the GPR data is also shown on Figure 2-14.

2.5.3.2 Landfill Gas Study A Tier II landfill gas study (LGS) was performed at the site to evaluate the nature of the waste disposed of at the site and to identify areas that are producing gas. The landfill gas samples were collected in accordance with the New Source Performance Standards for Municipal Solid Waste Landfills (NSPS) Tier 2 testing requirements in 40 CFR 60.754 (a) (3). The NSPS states that at least two samples must be collected per hectare of landfill surface for Tier 2 Non-Methanogenic Organic Compound (NMOC) sampling. Because the UF former landfill has approximately 15 acres (about 6 hectares) of existing surface requiring testing, 12 samples were taken. The sample

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Figure 2-14

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locations were spread out evenly across the former landfill area and are shown on Figure 2-14. The samples were also analyzed for carbon dioxide, oxygen, and nitrogen according to EPA Method 3C in Appendix A of 40 CFR 60. The NMOC sampling followed the procedures in 40 CFR 60.754 (a) (3) and Method 25C. Results of analyses are in Appendix H and are summarized on Figure 2-15.

By volume, landfill gas at a Class I facility typically contains 45% to 60% methane and 40% to 60% carbon dioxide. Landfill gas also includes small amounts of nitrogen, oxygen, ammonia, sulfides, hydrogen, carbon monoxide, and NMOCs.

Results of the analyses of the landfill gas samples indicates relative concentrations of gases in samples LFG-2 through LFG-5, LFG-8, LFG-10 and LFG-11 are consistent with gas generated by a Class I landfill. The relative concentrations of gases in samples LFG-1, LFG-6, LFG-7, LFG-9 and LFG-12 are not indicative of Class I waste.

As shown on Figure 2-14, samples that contained relative concentrations of gases that are associated with Class I waste are located in the west and southern portion of the site. Also as shown on Figure 2-14, this is consistent with results of the GPR survey, results of geotechnical investigations performed by Universal Engineering, and information provided by UF. Relative concentrations of gases in samples from LFG-5 and LFG-7 are also consistent with gas from Class I waste. However, results of the GPR survey and other information described above indicate that Class I waste is not present at these locations.

2.5.4 Results of Soil Sampling and Analyses and Mobilization of Naturally Occurring Analytes

2.5.4.1 Analytical Results In accordance with the approved SAP, samples of the aquifer matrix of the water- bearing strata at locations of 5 well nests were collected and analyzed for iron, manganese, arsenic and radionuclides (alpha, beta, radium 226 and radium 228). Samples were collected from a DPT boring adjacent to well MW-5 (30-40 feet bls) and from the cores collected during the drilling of wells MW-12S (27-33 feet bls), MW-12F 60-68 feet and 83-93 feet bls), MW-13F (37-47 feet bls), MW-14S (40-50 feet bls), MW-14F (73-83 feet bls), MW-15 F (45-55 feet bls), and MW-16F (52-62 feet bls). The objective of this element of the site assessment was to evaluate the potential for these analytes to be naturally occurring in the groundwater beneath and in the vicinity of the site. Analytical reports are in Appendix I. Results are summarized in Table 2-10.

Evaluation of the analytical results for the core samples verifies the presence of iron, manganese and radionuclides (gross alpha, gross beta, radium 226 and radium 228) in the solid aquifer material (water-bearing matrix). Although not directly comparable, the concentrations of iron, manganese, arsenic and radionuclides (alpha, beta, radium 226 and radium 228) in the aquifer matrix of the water-bearing strata (in terms of mg/kg) are orders of magnitude higher than the concentrations detected in groundwater samples (in terms of mg/L). The concentrations of iron in the aquifer matrix samples varied from 200 mg/kg in the sample from MW-12S (27-33) to

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Figure 2-15

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Table 2-10

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4,700 mg/kg in the sample from MW-12F (60-68). Concentrations of manganese varied from 0.41 mg/kg (MW-12S (27-33) to 37 mg/kg in the sample from MW-15F (45-55). Concentrations of arsenic varied from less than the detection limit in the samples from MW-12S (27-33), MW-14S (40-50), and MW-14F (73-83) to 4.6 mg/kg in sample from MW-12F (60-68).

Concentrations of radionuclides were also detected in concentrations that greatly exceeded the concentrations detected in groundwater samples. Concentrations of radionuclides were detected in all of the samples except the sample from MW-14F (73-83). The highest concentrations of alpha (94.5 pCi/g) and beta (68.4 pCi/g) were detected in the sample from MW-5 (30-31). The highest concentration of radium 226 (2.6 pCi/g) was detected in the sample from MW-13F (37-47). The highest concentration of radium 228 (0.093 pCi/g) was detected in the sample from MW-12F (83-93). However, the concentrations of radium 228 in the samples from MW-5 (30-31), MW-12S (27-33), MW-12F (60-68), MW-14S (40-50), MW-14F (73-83) were reported to be below detection limits varying from 0.125 pCi/g to 0.664 pCi/g.

2.5.4.2 Mobilization of Naturally-Occurring Constituents Background concentrations of iron, manganese, and radionuclides (total alpha, total beta, radium 226, and radium 228) are variable in the ICU and FAS in the vicinity of the site. Evaluation of analytical results from groundwater samples collected from upgradient FAS wells and private supply wells indicate that naturally-occurring concentrations of these analytes exceed the GCTLs. The concentration of iron in upgradient monitoring well DEP-4F was 0.93 mg/l and the concentration of iron in the Immunogenetics irrigation well was 3.0 mg/l. The concentration of manganese in the Lowe well was 0.17 mg/l. Activities of gross alpha and beta in the groundwater sample from the IFAS well were 7.99 and 8.59 pCi/L, respectively. The activity of radium 226 in the groundwater sample from the Lowe well was 1.44 pCi/l and the activity of radium 228 in the groundwater sample from the Lowe well was 2.59 pCi/l.

The natural presence of radionuclides in sediments and groundwater in Florida is well documented. Available information indicates that radionuclides are common in the groundwater in Alachua County. High concentrations of radon in an Alachua County well were attributed to phosphatic deposits that contain uranium (Crandal and Berndt, 1996). The mobility of uranium-series isotopes, including radium and alpha radionuclides, is influenced by pH and Eh (ORP) and that the mobility of the radionuclides is related to the stability of iron-hydroxy complexes and sulfate (Upchurch et al., 1991).

Analytical results, specifically those for iron and manganese, were further evaluated with respect to the pH and the oxidation-reduction potential of the groundwater as measured during the collection of groundwater samples. Although only iron and manganese were evaluated with respect to pH and Eh, this evaluation may also be applicable to the radionuclides (alpha, beta, radium 226 and radium 228) that are present in the groundwater in the vicinity of the site.

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In groundwater, the fate/transport and concentrations of metals is usually controlled by adsorption/desorption, dissolution/precipitation and oxidation/reduction processes. Iron and manganese concentrations in groundwater are mainly controlled by dissolution/precipitation processes. The major dissolution/precipitation processes effecting iron and manganese are oxidation/reduction reactions.

The controlling oxidation/reduction reactions and, therefore, the concentrations of iron and manganese in groundwater can best be evaluated using Eh – pH diagrams (oxidation/reduction or ORP – pH). These diagrams provide stability fields (areas of the Eh-pH diagram) for major metal species (dissolved and solid phases) at various temperatures, pressures and concentrations. The diagrams can then be used to evaluate reactions between the species at various oxidation/reduction and pH conditions.

Several precautions and assumptions must be stated when using Eh – pH relationships:

The calculations used assume equilibrium conditions. In many waters, equilibrium conditions may not be present because reactions may be slow (kinetically controlled). However in all cases, equilibrium calculations provide boundary conditions toward which the system must be proceeding.

Typically the calculations are based on thermodynamic data for crystalline mineral phases. In some cases amorphous solid phases are present which may not have measured thermodynamic data.

Oxidation/reduction potentials are difficult to measure in the field and may not be meaningful. Even when suitable conditions for measurement are obtained, the results are significant only for those chemicals whose behavior is electrochemically reversible at the electrode surface. Fortunately, at high iron concentrations, the oxidation/reduction potential is typically well controlled and the measurements are meaningful.

Even with these limitations, equilibrium considerations greatly aid attempts to understand observed and anticipated processes in natural waters. Partial equilibria are frequently approximated even though total equilibrium may not be reached. This allows prediction of significant processes and estimation of properties and reactions. Valuable insight is also gained even when differences are observed between theoretical computations and observations.

2.5.4.3 Methodology and Data Chemical data resulting from collection of groundwater samples in April and July 2004 in the vicinity of the University of Florida former landfill site were reviewed. All groundwater sample results with pH and oxidation/reduction (ORP) values were used in the evaluation (40 data points). All of these samples except one (DEP-1S) also had measured iron (39 values) and manganese (39 values) concentrations. Samples were collected from 11 shallow surficial/intermediate confining zone wells, 23

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Floridan wells and 6 private/irrigation wells. Field parameters determined during the collection of groundwater samples are summarized in Table 2-11.

Equilibrium calculations were performed using HSC Chemistry for Windows (Outokumpu Research, Version 5.1) and data taken from the PHREEQC database (Parkhurst, D.L., 1995, User's guide to PHREEQC--a Computer Program for Speciation, Reaction-Path, Advective-Transport, and Inverse Geochemical Calculations: U.S. Geological Survey Water-Resources Investigations Report 95-4227, 143 p.).

2.5.4.4 Eh – pH Relationships for Iron Using a temperature of 25 degrees Celsius (average temperature of the measured groundwater samples was 23.8 degrees) and an iron concentration of 47,000 µg/L (maximum concentration observed; equal to 8.4 x 10-4 molality), the Eh-pH diagram for the iron species was calculated (see Figure 2-15).

The blue dashed lines on Figure 2-15 provide the stability limits for water; therefore, any aqueous species must be within this area. Also shown are the major iron phases at various Eh (y axis) and pH (x axis) conditions. Dissolved phases are indicated as “aq” (aqueous) and solid phases are indicated by “s” (solid). This is a simplified diagram and contains only major species and phases (e.g, iron carbonate is not shown and may be present in high alkalinity waters). At typical Eh and pH conditions observed at the University of Florida former landfill, the concentration of dissolved iron will be controlled by the following oxidation/reduction reaction:

Fe2+ (aq) + 3OH- (aq) = Fe(OH)3 (s) + e-

The reaction as shown releases an electron (oxidation) and must be coupled with a reduction reaction (electron acceptor). This electron acceptor would typically be furnished by oxidized compounds in a landfill or its leachate. The reaction is a reversible, equilibrium reaction responding to changes in Eh and pH conditions. For example, a high concentration of dissolved ferrous (Fe2+) iron may exist at a pH of 6.5 and an Eh of -100 mv (-0.100 volts). An increase in the pH (to above about 7.0) would result in formation (precipitation) of the solid phase iron hydroxide (Fe(OH)3) and decrease in the concentration of dissolved iron (see Figure 2-15). That is, the “stability line” shown between Fe2+ and Fe(OH)3 has been crossed by the increase in pH. The same reaction will occur (precipitation of iron hydroxide) if the Eh is increased (to above about 0 mv) at a constant pH value of 6.5.

The reverse reaction (dissolution of iron hydroxide) can occur by a decrease in oxidation/reduction potential or pH (moving across the “stability line” from the Fe(OH)3 field to the Fe2+ field). Such a reaction is a reduction reaction (iron in the +3 oxidation state, ferric going to iron in the +2 oxidation state, ferrous) and requires an associated reducing agent (such as the reduced compounds typically found in landfill leachate). Such a reaction will result in an increase in dissolved ferrous iron (Fe2+) in the groundwater.

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Table 2-11

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Changes in iron concentrations will change the locations of the fields and “stability lines.” Some samples had nondetectable concentrations of iron (<37 µg/L). This value was used to generate an additional Eh-pH diagram (Figure 2-16) that was combined with the previous diagram. The “-04” signifies 8.4 x 10-4 molality (47,000 µg/L) and the “-07” signifies 6.6 x 10-7 molality (37 µg/L) for iron. As shown, the concentration of iron increases with a decrease in pH or Eh.

Typically, aquifer materials naturally contain iron as a coating on grains or discrete mineral phases. The iron may be contained in iron hydroxide, amorphous iron oxyhydroxides, hematite, magnetite or other iron containing compounds. Landfill leachate is typically much more reducing (lower oxidation/reduction potential) than normal groundwater. If landfill leachate enters groundwater, the resultant mixture is more reducing and will typically result in dissolution (reduction) of the natural iron compounds in the subsurface aquifer materials. This will result in an increase in dissolved iron concentrations in the groundwater. The Eh-pH diagram shows the solid phase as Fe(OH)3. Diagrams could also be generated for other iron minerals including hematite (Fe2O3). This diagram would be similar to the one shown. In reality, the Fe(OH)3 is probably an amorphous phase and the exact locations of the stability fields may change slightly.

2.5.4.5 Eh – pH Relationships for Manganese Using a temperature of 25 degrees Celsius (average temperature of the measured groundwater samples was 23.8 degrees) and a manganese concentration of 730 µg/L (maximum concentrations observed; equal to 1.3 x 10-5 molality), an Eh-pH diagram (Figure 2-17) was calculated:

Figure 2-17 is similar to the iron diagrams in that over the range of pH and Eh values observed at the Former landfill, the concentrations of dissolved manganese in the groundwater should be controlled by an oxidation/reduction reaction resulting in either dissolution or precipitation of a solid phase (MnOOH) and associated change in the dissolved phase (Mn2+) concentration. Similar to iron, decreases in either pH or oxidation/reduction potential (moving across the “stability line” from the MnOOH field to the Mn2+ field) can result in increase concentrations of dissolved manganese in the groundwater.

2.5.4.6 Observed Eh, pH and Concentrations If the above theoretical calculations and proposed control mechanisms are valid, the Eh, pH, and concentrations data from the landfill should fall along the “stability line” between the solid and aqueous phases (Fe(OH)3 and Fe2+, respectively, in the iron diagram). As shown on Figure 2-18, this “stability line” is reproduced for a relatively high iron concentration of 10,000 ug/L (1.79 x 10-4 molality, solid black line) and a nondetectable iron concentration of < 37 ug/L (6.6 x 10-7 molality, dashed black line). The Eh, pH and iron concentration for all data points except the private/irrigation wells are also shown on the diagram.

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Figure 2-16

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Figure 2-17

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Figure 2-18

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The actual data clearly reflect the previously discussed theoretical processes controlled by the Fe(OH)3/Fe2+ oxidation/reduction reaction. An exact match is not observed (e.g, the best fit line slope is slightly different than calculated) because the actual solid phase is probably amorphous iron hydroxide and field Eh values are typically variable. However as anticipated, low and nondetect concentrations (blue circles and red circles) are observed at higher Eh and pH conditions (all points are located in the Fe(OH)3 field to the upper right of the Fe(OH)3/Fe2+ dashed “stability line”). The highest concentrations (black diamonds) are observed at lower Eh and pH conditions (all points are located in the Fe2+ field to the lower left of the Fe(OH)3/Fe2+ solid “stability line”). Most other concentrations fall between the two “stability lines” shown on the figure. One data point does not match the theoretical conditions (orange square near a pH value of 4.7 and Eh of 240 mv). Theoretically, a higher concentration should be observed. However, Eh values for this point may be in error or an unknown solid phase may exist. The most likely explanation is the difficulty in measuring field Eh values in low pH waters.

Because definitive information concerning well depth and operations are not available, the 6 private/irrigation wells were evaluated separately and are shown on Figure 2-19. These wells typically have higher Eh and pH values and should, therefore, have lower iron concentrations. This is typically the case; however as shown, one yellow diamond (iron of 3 mg/L, pH of 6.98 and Eh of 93.6 mv) exists in the Fe(OH)3 field and should theoretically have a lower iron concentration.

Similar figures were constructed using the manganese data (see Figure 2-20 and Figure 2-21). The solid and dashed red lines represent the “stability lines” for the MnOOH/ Mn2+ fields at both the highest observed manganese concentration (730 µg/L) and the lowest observed concentrations (<1.4 µg/L). The solid and dashed black lines represent the Fe(OH)3/Fe2+ “stability lines” and are the same ones shown on Figure 2-18 and Figure 2-19.

In this case the data do not support the control of manganese concentrations by the theoretical MnOOH/Mn2+ oxidation/reduction reaction. Instead, the manganese concentrations appear to be controlled by the same Fe(OH)3/Fe2+ oxidation/reduction reaction. This result suggests that the most likely solid phase involved in controlling dissolved iron and manganese concentrations is an amorphous phase with general composition FexMn1-x(OH)3; this type of phase is known as a solid-solution phase or co-precipitate and typically forms when Mn substitutes for Fe in the usual amorphous Fe(OH)3. The iron concentrations both in the solid phase and dissolved phase are much higher than the manganese concentrations. Therefore, the Eh and pH observed concentrations more closely match the theoretical Fe(OH)3/Fe2+ oxidation/reduction reaction.

2.5.4.7 Sample Results and Well Depth Figure 2-22 is similar to the previous figures except the results are colored coded for SAS and ICU wells and wells completed in the FAS. Typically the FAS wells have higher pH values compared to ICU wells (yellow diamonds to the right and red

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Figure 2-19

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Figure 2-20

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Figure 2-21

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Figure 2-22

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squares to the left). However, as previously discussed, the Eh and pH conditions may be affected by recharge through former waste disposal areas.

2.5.4.8 Summary The concentrations of iron and manganese observed in groundwater in the vicinity of the University of Florida former landfill are caused by dissolution of natural iron containing compounds in the subsurface aquifer material. The dissolution results from the overall decrease in oxidation/reduction potential and pH values in the groundwater that occurs when more acidic and reducing water percolates through the unpaved waste disposal areas and ICU and mixes with the groundwater. Evaluation of the oxidation/reduction potential (Eh), pH and iron/manganese concentrations in the matrices of the water-bearing units and groundwater clearly demonstrates that the concentrations of iron and manganese are controlled by the Fe(OH)3/Fe2+ oxidation/reduction reaction. The distributions of pH and ORP in the upper part of the FAS are shown on Figure 2-23 and Figure 2-24.

The locations of the highest observed iron and manganese concentrations also confirm the process discussed previously. The highest measured iron concentrations in the shallow wells are at locations MW-12S, MW-DEP-9S and MW-DEP-10S (iron concentrations of 43, 47 and 39 mg/L, respectively). Waters is these wells have both the required lower Eh and pH conditions when compared to other shallow wells. These wells are located in the area of the former landfill with no cover (parking lots, buildings, etc.) where infiltration can move through the waste and generate leachate with lower Eh and pH conditions. Other shallow wells are in areas where no landfill waste existed or have limited infiltration due to parking lots.

The highest observed iron and manganese concentrations in the FAS wells (22, 23 and 39 mg/L iron at MW-13F, MW-DEP-9F and MW-16F, respectively) are located in the area directly below or downgradient of the shallow wells with the highest concentrations discussed above. The required lower pH and Eh conditions to support higher iron concentrations were measured in samples from these wells. If both conditions do not exist, the iron and manganese concentrations are not as high. Comparisons of the analytical results for aquifer matrix samples and groundwater samples also indicate that pH and Eh control the amount of these analytes in the groundwater as opposed to the amounts of these analytes in the aquifer matrix. For example, groundwater from well MW-16F has 39 mg/L iron (pH of 6.56 and Eh of -104.6 mv). A nearby well (MW-DEP-10F) has a similar Eh of -100.7 mv; however, the pH value is higher (7.57) resulting in a much lower iron concentration of 0.29 mg/L. Groundwater from well MW-13F has 22 mg/L (pH value of 6.53 and Eh of -63.6 mv). Nearby well MW-19F has a similar pH of 6.63; however, the Eh is much higher (84.3 mv) resulting in a nondetectable level of iron (< 0.037 mg/L). Also, the concentrations of iron in the aquifer matrix samples from MW-16F and MW-13F had much lower concentrations of iron and manganese than the aquifer matrix samples from MW-12F. These individual well results clearly indicate control by the Fe(OH)3/Fe2+ oxidation/reduction reaction.

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Figure 2-23

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Figure 2-24

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Section 3 Methods of Investigation 3.1 Ground Penetrating Radar Survey A comprehensive ground penetrating radar (GPR) investigation was performed by Geohazards, Inc. A Geophysical Survey Systems, Inc. (GSSI) SIR System 3000 radar was used. The system was equipped with a 100-megahertz transceiver antenna with a two-way travel time range of 125 nanoseconds was used.

Baseline studies were performed on UF property adjacent to the former landfill to establish background signal signatures for the radar. After establishing baseline signatures, a total of 82 GPR traverses were conducted along the established grid lines (Figure 2-14). The grid was established by a licensed professional surveyor and mapper (PSM). Control points for the grid system will be established at 200-foot intervals by a PSM. The grid covered the entire fenced area of the UF Park ‘N Ride site including the original configuration of borrow pits and stormwater retention areas.

Direct sampling of areas with demonstrated geophysical anomalies was conducted using direct push technology (DPT). Sixteen borings were completed at locations shown on Figure 2-14. Continuous cores were collected from land surface to depths of up to approximately 25 feet bls. Samples were retrieved from an acetate sleeve in the DPT drive point and described by the supervising geologist. Borings were terminated in undisturbed natural material.

3.2 Landfill Gas Study 3.2.1 Introduction As requested by the FDEP in their letter dated January 26, 2004, a landfill gas study was performed to further evaluate the nature and extent of the waste that was disposed of at the site. The landfill gas samples were collected in accordance with the New Source Performance Standards for Municipal Solid Waste Landfills (NSPS) Tier 2 testing requirements in 40 CFR 60.754 (a) (3). The NSPS states that at least two samples must be collected per hectare of landfill surface for Tier 2 NMOC sampling. Because the UF former landfill has approximately 15 acres (about 6 hectares) of existing surface requiring testing, 12 samples were taken (Figure 2-15).

3.2.2 Field Sampling Material and Equipment The following equipment was used to collect landfill gas samples and then analyzed in an EPA certified laboratory:

Sample Probe Driver (mobile track mounted Geo-probe)

Tritector (samples for methane as a percent of Lower Explosive Limit (LEL), O2

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O:\Beeson\UF\UF\SAR\Final SAR\Electronic\Text\UFSARSEC3F.doc

Section 3 Methods of Investigation

Interscan (samples for H2S)

Bentonite (For sealing sample probe holes)

Rotameter capable of measuring a sample flow rate of 500 ml/min or less

Landtec GEM-500 landfill gas analyzer, for field screening of sample methane, CO2, O2, and, by difference, nitrogen content

Explosion-proof purge pump, which is part of the Landtec GEM500.

Stainless-steel sampling valve for isolating the sampling train following the initial purge

0.25-inch outside diameter (OD) Teflon tubing and stainless-steel Swagelok fittings for sample train

Stopwatch

6-liter Summa canisters (one for each sample location), plus one canister that will be used for a field blank. These canisters were leak-checked in the laboratory prior to shipping to the site per Method 25C, Section 4.1. Since some samples had concentrations of carbon dioxide and methane together over 80 percent in the sample, the sample containers are not acceptable for shipping, per Department of Transportation (DOT) regulations. By adding helium to the canisters prior to shipping, the LEL of the gas mixture is lowered and acceptable for shipping. This is why a helium pad was added to the canisters prior to shipping.

Calibrated flow control valve, vacuum gauge, pressure gauge, and a particulate matter filter for each Summa canister

Labels for Summa canister samples

Chain of custody record for each sample

Portable barometer, thermometer, and field notebook to record ambient conditions

3.2.3 Field Sampling Procedures In accordance with Method 25C, the sampling was done for each location in the following steps:

1. Select sample location using site layout plan.

2. Check background levels of methane at/near the surface of landfill.

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3. Evaluate safety of location (methane level and slope/grade); if methane level is too high or the slope is unstable, move sample location to more suitable location.

4. Hand auger test areas were done to a depth of at least 1.0 meter into the waste to determine contents of waste and possible interference with nearby utilities.

5. Chose pilot probe location based on auger contents, then using the Geo-probe, a 2-inch diameter rod was penetrated into the ground surface. The rod was then lifted slightly out of the ground to expose a soil screen and expend the tip of the rod. The driving tip of the pilot probe rod was removed and at least 4 feet of 1/4-inch OD Teflon tubing was inserted into center of the 2-inch diameter rod. Using hydrated bentonite, the areas open to the atmosphere at the top of the rod and at the ground surface where the rod penetrated, were sealed.

6. The gas levels were checked by attaching the sampling tubing to the Landtec GEM-500 landfill gas analyzer to determine if gas levels would be acceptable for sampling. Since this was a modified Tier 2 sampling, which was to characterize the gas rather than specifically obtain methane content, the main parameter monitored closely was oxygen. If a sample location had less than 5 percent oxygen, then the location was sampled. If the oxygen content was more than 5 percent, the location was rejected. This reasoning was used because it ensured that with low oxygen, the sample was indeed coming from the gases within the landfill and not from the outside surrounding areas. The GEM-500 also analyzes for methane concentration, carbon dioxide concentration and oxygen concentration. If the methane and CO2 concentrations together are 80% or more, and the oxygen was at or near 0%, then the remainder, assumed to be primarily nitrogen, was at a concentration of 20% or less.

7. When the gas levels were acceptable (per step 6) then the sampling tubing was attached to the Interscan to test for hydrogen sulfide levels. If these levels are above 100 ppm then it was noted on the sample tag.

8. Connected the sampling train to the end of the sampling tubing.

9. The GEM-500 was connected to the sampling train to purge the sampling train and tubing for a minimum of 100 seconds. Oxygen levels were rechecked following Step 6 to ensure they are still acceptable.

10. The sampling tubing was watched continuously for a visible column of water or formation of water droplets inside the tubing. No water was visible during any of the sampling. However, if any water was visible in the tubing, it would have been disconnected and a new location selected.

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11. The GEM-500 was then disconnected and the sampling train was connected to the sample tank apparatus. The sample tank apparatus consisted of a stainless steel particulate filter and quick connect.

12. The sampling train was then connected to the Summa canister and all valves on the sampling train were closed.

13. The valve on the Summa canister was opened and the beginning reading on the vacuum gage was recorded. Due to the helium pad that was put into the canisters by the lab, the highest recorded vacuum prior to sampling was -20 inches of mercury (in. Hg)

14. The flow control valve was then opened and noted that there should be no flow. If there was flow, then it was assumed to be caused from faulty connections either on the summa canister apparatus or within the sampling train and the canister was rejected. If there was no flow, the sampling valve was opened and adjusted so that the flow of sample gas into the canister was below 500 ml/min (typically 300 to 400 ml/min). The sample was then timed from beginning to end.

15. When the vacuum gage was at about -3 inches Hg, the valve on the Summa canister was closed and the sample duration and ending vacuum reading were recorded in the field notebook. The summa canister was then disconnected from the sampling train.

16. The GEM-500 was then reconnected to the sampling train and the gas levels were re-checked following Step 6 to ensure that the gas levels were still acceptable. If the levels are not acceptable per Step 6, then the sample was rejected and a new sample location was selected.

17. The label on the canister was filled out and prepared for shipping to the laboratory.

18. The sample train assembly was disconnected from the sample probe.

19. The sample tubing was removed.

20. The Geo-probe 2-inch diameter rod was removed from the sampling hole and the pilot hole was backfilled with bentonite.

21. One field blank was also shipped to the laboratory for analysis. This is to ensure that no infiltrations occurred in the shipping of canisters to or from the site.

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3.2.4 Laboratory Analysis Methods The Summa canister samples were shipped to an EPA approved laboratory (Air Toxics LTD.) for analysis. Samples were analyzed for total non-methane organic compounds (NMOCs) by modified EPA Method 25C (GC/FID Triplicate Analysis) and for nitrogen, oxygen, carbon dioxide and methane by modified EPA Method 3C.

3.3 Field Screening 3.3.1 Introduction Soil and groundwater samples were collected using DPT from 23 locations immediately west and south of the former Alachua County borrow pit to assess the extent of contamination in soil and shallow groundwater. These data were used to evaluate the extent of VOC contamination in shallow groundwater and, if possible, identify the source of contamination in the vicinity of well MW-1. Soil and groundwater samples were collected from 19 locations immediately west of the former Alachua County borrow pit and screened in the field as described below. Groundwater samples collected from immediately south of the former Alachua County borrow pit were analyzed at a fixed laboratory. Locations of all field-screening locations to the west of the former Alachua County borrow pit were surveyed by a PSM. Locations of the four sampling sites immediately south of the former Alachua County borrow pit were identified using a hand-held Global Positioning System (GPS).

3.3.2 Soil Screening Continuous cores were collected at each field screening location using direct-push technology. Cores were collected from the land surface to as much as 6 feet below the top of undisturbed natural material. Samples were collected from depths of up to 25 feet bls. The soil samples were retrieved from an acetate sleeve in the DPT drive point.

After retrieval from the DPT drive point, each core sample was extracted for field screening. Field headspace analyses were performed on these soil samples using an organic vapor analyzer equipped with a flame ionization detector (FID). Selected soil samples were analyzed for VOCs at a mobile laboratory using EPA Method 8260.

3.3.3 Groundwater Screening Groundwater samples were collected from each of the direct-push borings. Groundwater grab samples were collected from the uppermost water-bearing stratum by advancing a well screen and retractable steel casing assembly (Geoprobe Screenpoint 16 water sampler or similar equipment). When the desired depth was reached, the sheath was retracted exposing the screened section to the groundwater. A groundwater sample was then collected using tubing with a check valve. The groundwater grab samples were analyzed for VOCs in a mobile laboratory (KB Laboratories, Inc.) using EPA Method 8260.

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3.4 Monitoring Well Installation 3.4.1 Intermediate Confining Unit Monitoring Wells Four monitoring wells (MW-12S, MW-13S, MW-14S and MW-15S) were completed in the Intermediate Confining Unit (ICU). Following discussions with representatives of the FDEP, confining unit monitoring wells were not installed at the locations of MW-11, MW-16, and MW-17 as proposed in the SAP. Water-bearing strata were not present in the strata that overly the Ocala Limestone at these locations.

A nominal 6-inch diameter borehole was drilled for each well using sonic drilling method. Nearly continuous cores were collected from each of the well locations. Cores were collected and described in detail to identify stratigraphic units, potential water-bearing strata, and confining layers. ICU monitoring wells varied in depth from 24 feet (MW-13S) to 51.5 feet bls (MW-14S).

ICU monitoring wells were constructed inside the drilling rods using Schedule 40 PVC with 0.010-inch machine slotted screens. The annular space opposite the screen and 2 feet above the top of the screen of each well was packed using size 20/30 sand. A bentonite seal at least 2 feet thick was placed above each filter pack. The remaining annular space was grouted from the bottom to the top with neat Portland cement grout. The monitoring wells were completed as flush-mounted wells with 2-foot by 2-foot concrete pads, bolt down manholes, and locking well caps. Construction diagrams for monitoring wells are included in the drilling and monitor well completion logs (Appendix B). Table 3-1 is a summary of well construction information.

3.4.2 Floridan Aquifer Monitoring Wells Eleven wells (MW-2F, MW-11F through MW-21F were completed in the Ocala Limestone which is the upper part of the Floridan Aquifer System (FAS). One well (MW-16FD), was completed in the Avon Park Formation.

Sonic drilling was used to drill the boreholes for the monitoring wells. Nearly continuous cores were collected from each of the proposed well locations. Surface casings, 8-inches in diameter, were installed for wells MW-12-F and MW-15F. Surface casings were not installed at the locations of the remaining Floridan aquifer wells, except for MW-14F, because of the absence of water-bearing strata overlying the Ocala Limestone. A surface casing was not installed for MW-14F because the presence of chert at a depth of approximately 36 feet bls prohibited advancement of the 12-inch diameter borehole. Boreholes for surface casings were 12 inches in diameter and were advanced using sonic drilling. The bottoms of the surface casings were set immediately above the top of the Ocala Limestone as determined from cores obtained from a pilot borehole.

A nominal 6-inch diameter borehole was advanced for each well using sonic drilling method. Wells installed in the Ocala Limestone varied in depth from 44.5 feet

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Table 3-1

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(MW-11F) to 93.5 feet (MW-12F). Well MW-16FD was completed in the Avon Park Limestone at a depth of 285 feet bls.

As with the ICU monitoring wells, wells installed in the FAS were constructed inside the drilling rods using Schedule 40 PVC with 0.010-inch machine slotted screens. The annular space opposite the screen and 2 feet above the top of the screen of each well was packed using size 20/30 sand. A bentonite seal at least 2-feet thick was placed above each filter pack. The remaining annular space was grouted from the bottom to the top with neat Portland cement grout. Bentonite and sand were added to the grout for well MW-16FD to minimize the risk of warping the casing due to the heat generated by the cement during the curing process. The monitoring wells were completed as flush-mounted wells with 2-foot by 2-foot concrete pads, bolt down manholes, and locking well caps. Construction diagrams for monitoring wells are included in the drilling and monitor well completion logs (Appendix B). Table 3-1 is a summary of well construction information.

3.4.3 Well Development and Completion All new monitoring wells were developed using submersible pumps. The depths to water, typically more than 25 feet bls, prohibited the use of centrifugal or peristaltic pumps. The wells were developed by pumping and surging until field parameters (pH, conductivity, and temperature) have stabilized and the water samples from the wells were free of fine-grained particles (i.e., sand and silt). Field determinations of pH, specific conductance, and temperature will be performed periodically during development. In addition, at twice the volume of water that was lost during drilling was removed during development.

Each well was completed with a locking cap and either an aboveground security cover surrounded by a concrete pad or a traffic-rated vault and manhole. Measuring points and locations of all new and existing monitoring wells were surveyed by Myers-Griffis & Associates, Inc. Measuring point elevations were surveyed to the nearest 0.01 foot ± and referenced to the North American Vertical Datum of 1988 (NAVD). The monitoring wells were located using the State of Florida North Zone Plane Coordinate System utilizing the 1983 adjustment.

3.5 Groundwater Sampling and Analyses Groundwater samples were collected from monitoring wells in accordance with procedures described in FDEP SOP FS 2200. Low-flow submersible pumps were used to purge the wells and collect the samples from the monitoring wells. Existing in-place pumps and plumbing were used to collect groundwater samples from private supply wells. Groundwater samples were collected and analyzed for iron, manganese, arsenic, radionuclides (gross alpha and beta and radium 226 and 228), ammonia, chlorides, nitrate, sodium, total dissolved solids (TDS), total suspended solids (TSS), color, and VOCs. In addition, as requested by the FDEP, samples were also analyzed for parameters specified in Appendix II of 40 CFR 258. Field

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measurements of pH, specific conductance (SC), dissolved oxygen (DO), temperature, and turbidity were measured during purging in accordance with FDEP SOPs FT 1100, FT 1200, FT 1400, FT 1500, and FT 1600. In addition, measurements of oxidation/reduction potential (ORP) were made on groundwater samples from all the wells. Filtered and unfiltered groundwater samples were collected from monitoring wells for analyses of metals and radionuclides.

Samples were placed in appropriate containers provided by the laboratory and delivered to STL Tampa for analyses. Documentation procedures described in FDEP SOP FD 5000 and FD 5100 were followed. Table 3-2 is a summary of analytical parameters and methods.

3.6 In-Situ Permeability Tests “Slug-in” and “slug-out” tests were performed on 6 monitoring wells. A solid PVC rod of known volume was used as the slug. Water levels were measured during the tests using a pressure transducer and recorded using a data logger. Hydraulic conductivity values were calculated using the Hvorslev (1951) method for partially-penetrating wells. Slugs, measuring tapes, and transducers were decontaminated prior to future use using procedures described in FDEP SOP FC 1000.

3.7 Soil Sampling and Analyses Samples of the matrix of the ICU and upper FAS (soil samples) were collected and analyzed for iron, manganese, arsenic, and radionuclides to evaluate the concentrations of these parameters that occur naturally in the aquifers. Soil samples for laboratory analyses were collected from the cores that were retrieved using the sonic drilling method. Samples were placed in appropriate containers provided by the laboratory and delivered to STL Tampa for analyses. Documentation procedures described in FDEP SOP FD 1100 were followed.

3.8 Management of Investigation Derived Waste Water recovered during drilling, development water and purge water from each well was contained and disposed of in the UF sanitary sewer system in accordance with approval from the FDEP. Drill cuttings/cores and used sampling equipment were collected in a roll-off box and disposed of at the Waste Management landfill in Okeechobee, Florida. A copy of the profile and manifest are in Appendix J.

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Section 4 Conclusions and Recommendations 4.1 Conclusions 4.1.1 Introduction Objectives of the Site Assessment are described in Exhibit B of the Consent Order. The specific objectives of the Site Assessment for the former landfill, discussed with representatives of the FDEP, are:

To define the lateral and vertical extents of contamination in groundwater;

To evaluate and characterize the hydrogeology of the vicinity of the site;

To assess and characterize the waste that has been disposed of in the landfill, and;

To identify potential receptors of groundwater contamination.

The Site Assessment was performed in accordance with the approved Site Assessment Plan (SAP) as modified pursuant to the FDEP letter dated February 16, 2004, and discussions with FDEP. The objectives of the Site Assessment were achieved. The following conclusions are based on results of the Site Assessment:

4.1.2 Extent of Contamination Iron, manganese, and radionuclides (gross alpha, gross beta, radium 226, and

radium 228) are naturally occurring in the sediments and groundwater in Alachua County and many other parts of Florida. Background concentrations of iron, manganese, and radionuclides (gross alpha, gross beta, radium 226, and radium 228) are variable in the ICU and FAS in the vicinity of the site. Evaluation of analytical results from groundwater samples collected from upgradient FAS wells and private supply wells indicate that naturally occurring concentrations of these analytes exceed the GCTLs. Evaluation of results of groundwater sampling and analyses indicate that background concentrations of iron may exceed 3.0 mg/l, background concentrations of manganese may exceed 0.17 mg/l, activities of gross alpha and gross beta may exceed 7.99 and 8.59 pCi/L, respectively, and that background concentrations of radium 226 and radium 228 may exceed 1.44 pCi/ and 2.59 pCi/l, respectively.

Iron, manganese, thallium, radionuclides, vinyl chloride, benzene, 1,4-dioxane, chlorides, and total dissolved solids (TDS) were detected in concentrations or activities that exceeded the GCTLs and/or background concentrations in samples from wells completed in the ICU. Groundwater quality data and hydrogeologic data indicate that contamination in concentrations of regulatory concern is not migrating from the former landfill via groundwater in the ICU.

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Iron, manganese, arsenic, nickel, radionuclides, 1,4-dioxane, dimethoate, ammonia and TDS were detected in concentrations or activities that exceed the GCTLs in samples collected from wells completed in the FAS. Evaluation of these analyte distributions indicates that arsenic, nickel, dimethoate, TDS, and ammonia are not migrating from the former landfill in concentrations of regulatory concern.

The nature and distribution of iron, manganese, and radionuclides at the site is consistent with the historical use of the borrow pits as landfills and the hydrogeology of the site and immediate vicinity. The distributions of these analytes in the upper part of the FAS correlates with the locations of buried waste and the thickness of the ICU. Concentrations or activities of these analytes are generally higher where the ICU is thin or has been at least partially removed as a result of borrow operations. These analytes are mobilized from the sediments by low pH and/or low eH water that percolates through the thin ICU sediments and/or the buried waste.

Concentrations or activities of iron, manganese and radionuclides in the FAS exceed background concentrations or activities within the boundaries of the site and downgradient no more than approximately 200 feet to the south of the former Murphree property borrow pit and 300 feet to the east of the site.

Concentrations 1,4-dioxane in the FAS exceed the GCTL within the boundaries of the UF site and downgradient approximately 200 feet to the south of the former Murphree property borrow pit and 350 feet to the east of the UF site (former Murphree property borrow pit). 1,4-Dioxane is found in many products, including shampoos, cosmetics, automotive coolants and solvents.

1,4-Dioxane, because of its distribution in the FAS and because it is not naturally occurring, is considered the marker for contamination associated with the former landfills and adjacent disposal areas.

Evaluation of analytical results of groundwater samples from the Hilton irrigation well (210 feet deep) and MW-16FD (285 feet deep) indicate that contamination in concentrations of regulatory concern (1,4-dioxane) extends to a depth of between 210 and 285 feet bls downgradient (east) of the site.

4.1.3 Hydrogeology Descriptions of cores indicate that the UF site and vicinity is underlain by

undifferentiated sediments of Plio-Pleistocene age, the Coosawahatchie Formation of the Hawthorn Group, and the Ocala Limestone.

The water level data indicate that the upper part of the FAS is the only aquifer that underlies the entire UF site and immediate vicinity.

In the vicinity of the site, the SAS is ephemeral.

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The IAS does not exist. Based on the nature of the strata that comprise this unit and evaluation of water level data, the sediments of the Coosawahatchie Formation should not be considered an aquifer for the purposes of evaluating contamination associated with this site. At many locations, groundwater was not present in the sediments that comprise the Coosawahatchie Formation. These data show that where water-bearing strata are present within this formation, they are of limited areal extent and only bed-scale in thickness. Therefore, these sediments are the ICU.

The depth to the top of the Ocala Formation and the FAS varied from 11 feet bls at the location of well MW-20F to 80 feet bls at the location of well MW-12F. The variations in the thickness of the overlying sediments suggest that the surface of Ocala Limestone is an erosional surface characterized by pinnacles.

Evaluation of the water level data indicates that the direction of groundwater movement in the upper part of the FAS beneath the site and immediate vicinity is generally from west to east. Based on results of the in-situ hydraulic conductivity tests, the average value for the upper part of the FAS is 192 feet/day. Based on these site-specific data and an effective porosity of 30%, the calculated rate of groundwater movement beneath the site is calculated to be 0.5ft/day.

4.1.4 Waste Characterization Historical information indicates that the former Alachua County borrow pit and the

former Murphree property borrow pit were used to dispose of sanitary waste generated by the UF. The remaining part of the site was used primarily to dispose of excavated soil and construction debris from UF construction projects. Ground penetrating radar (GPR) signatures for waste and soil were determined. Results of the GPR survey indicate that the distribution of Class I waste is consistent with the information regarding the history of the site. The GPR could not detect the base of the waste. No evidence of drums was visible on the GPR signatures. The approximate area of the Class I waste disposal area is approximately 7 acres.

Results of the Tier II landfill gas study indicate that the relative concentrations of methane and carbon dioxide being generated in the former Alachua County borrow pit and the former Murphree property borrow pit are typical of those generated by Class I sanitary waste. Evaluations of historical aerial photographs and results of soil and groundwater sampling indicate that the areas immediately to the south and west of the former Alachua County borrow pit were used to dispose of waste. The sources of the waste were not determined.

An investigation was performed to evaluate the source of benzene detected in groundwater samples collected from well MW-1 during previous investigations. Results of this investigation show that benzene is present in groundwater in the ICU in concentrations that exceed the GCTL to the west of the former Alachua County borrow pit. Evaluation of the results indicate that the benzene is likely

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from the degradation of chlorinated benzene (dichlorobenzene) and that the source is the area immediately to the west of the former Alachua County borrow pit.

1,4-Dioxane was initially identified in DPT groundwater samples collected from immediately west of the former Alachua County borrow pit. These data, and the distribution of 1,4-dioxane in the FAS indicate that the area to the west of the former Alachua County borrow pit and the former Murphree property borrow pit are or were sources of the 1,4-dioxane in the groundwater.

Evaluation of results indicates that neither benzene nor any other contaminants are migrating west from the UF site (former Alachua County borrow pit) toward MW-1. The data indicate that there is no lateral migration in the ICU and that contaminants are migrating from west to east in the FAS.

Volatile organics were not detected in soil samples collected from the area adjacent to the former Alachua County borrow pit. These data indicate that the source(s) of volatile organics is no longer active.

Evaluation of groundwater quality data and comparisons of results of analyses of groundwater samples collected from well DEP-7F indicate that the quality of groundwater has improved since the pavement was installed over the former Alachua County borrow pit in 2001. Well DEP-7F is immediately downgradient of the former Alachua County borrow pit. The concentrations of iron detected in groundwater samples collected by FDEP in 1997 and 2003 from well DEP-7F were 6.63 mg/l and 7.51 mg/l, respectively. The concentrations of manganese in these samples were 0.148 and 0.119 mg/l, respectively. The concentrations of iron and manganese in the groundwater samples collected in April 2004 were 1.9 mg/l and 0.48 mg/l, respectively. In addition, concentrations of arsenic, sodium, gross alpha and gross beta were much lower in the groundwater sample collected in 2004 than in the samples collected by FDEP in 2003.

Evaluations of the results of the Site Assessment show that contamination in concentrations that exceed GCTLs and/or background concentrations is associated with waste disposal areas that are west and south of the former Alachua County borrow pit and with the former Murphree property borrow pit.

4.1.5 Potential Receptors Seven (7) private supply wells were identified within approximately ¼-mile of the

site during the well inventory performed as part of the SAP. Three wells are used as a source of potable water (Knight, Lowe and Sheffield). Four wells are used for irrigation (Museum Walk, Hilton, IFAS and Immunogenetics).

Results of the Site Assessment indicate that only the quality of groundwater in the Hilton irrigation well has been affected by contamination associated with the former landfill. This well is the only private supply well that is directly downgradient from the UF site and is closest to the UF site.

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No evidence of contamination was present in groundwater samples collected from the Sheffield well. 1,4-Dioxane was not detected in the groundwater sample from this well. No analytes were detected in concentrations that exceed GCTLs in the sample from this well. This well is across the gradient (south) and approximately 650 feet from the southern boundary of the UF site (former Murphree property borrow pit).

No evidence of contamination was present in groundwater samples collected from the Knight well. 1,4-Dioxane was not detected in the groundwater sample from this well. Only the concentration of iron (1.6 mg/l) exceeded the GCTL. This concentration is below the background concentration (3.0 mg/l). Results of analyses of groundwater samples collected since 1988 by FDEP and the Alachua County Health Department also indicate that there have been no adverse affects on the quality of water withdrawn from this well that can be attributed to the UF site. This well is across the gradient (south) and approximately 300 feet from the southern boundary of the UF site (former Alachua County borrow pit).

No evidence of contamination was present in groundwater samples collected from the Lowe well. 1,4-Dioxane was not detected in the groundwater sample from this well. The concentrations of iron (0.68 mg/l) and manganese (0.17 mg/l) exceeded the GCTLs and are naturally occurring. This well is across the gradient (south) and approximately 750 feet from the southern boundary of the UF site (former Alachua County borrow pit) and approximately 450 feet south of the Knight well.

No evidence of contamination was present in samples collected from the Museum Walk, IFA or Immunogenetics irrigation wells. 1,4-Dioxane was not detected in the groundwater sample from any of these wells. The concentrations of iron in the groundwater samples from the Museum Walk and IFAS irrigation wells were below the GCTLs. The concentrations of iron (3.0 mg/l) and manganese (0.053 mg/l) in the groundwater sample collected from the Immunogenetics well exceeded the GCTLs. The Immunogenetics well is approximately 1,500 feet southeast of the southwest corner of the UF site and the IFAS irrigation well is approximately 900 feet northeast of the northeast of the northeast corner of the UF site. The Museum Walk irrigation well is across the gradient approximately 500 feet south of the southeast corner of the UF site and approximately 150 feet north of the Sheffield well.

4.2 Recommendations The following recommendations are based on results of the Site Assessment:

The former Murphree property borrow pit should be capped to prevent continued percolation of precipitation through the waste that has been placed in the former borrow pit. Capping is the most widely used measure to mitigate contamination associated with landfills.

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A groundwater monitoring program should be implemented to monitor expected improvements in groundwater quality associated with the capping of the former Murphree property borrow pit.

The Hilton irrigation well should be relocated along the southern or southeastern boundary of the property. The existing irrigation well should be considered for use as a monitoring well.

A 4-6


Section 5 References Applin, P. L. 1951. Preliminary report on buried pre-Mesozoic rocks in Florida and adjacent states: U. S. Geological Survey Circular 91,28 p. Barnett, R. S., 1975. Basement structure of Florida and its tectonic implications: Transactions of the Gulf Coast Association of Geological Societies, v. 25, 122-142.

Bush, P. W., and Johnson, R. H. 1988. Ground-water hydraulics, regional flow, and ground-water development of the Floridan Aquifer System in Florida and in parts of Georgia, South Carolina, and Alabama: U. S. Geological Survey Professional Paper 1403-C, 80 p. and 17 plates. Clark, W. E., Musgrove, R. H., Menke, C. G., and Cagle, J. W., Jr. 1964. Water resources of Alachua, Bradford, Clay, and Union counties, Florida: Florida Geological Survey Report of Investigations 35, 170 p. Crandall, C. A., and Berndt, M. P. 1996. Water Quality of Surficial Aquifers in the Georgia-Florida Coastal Plain: U.S. Geological Survey Water-Resources Investigation Report 95-4269. Department of Environmental Protection, Solid Waste Section, 2000. Florida Class III Lined Landfill Leachate Data Summary Report, 35 p. Ellis, L. B. M., Hou, B. K., Kang, W., and Wackett, L. P., 2003. The University of Minnesota Biocatalysis/Biodegradation Database: Post-Genomic Detamining: Nucleic Acids Research 262-265, Abstract, Full Text. Green, R., Duncan, J., Deal, T., Weinberg, J. M., and Rupert, F., 1989. Characterization of the sediments overlying the Floridan Aquifer System in Alachua County, Florida: Florida Geological Survey Open File Report 29, 114 p. Hoenstein, R. W., and Lane, E., 1991. Environmental geology and hydrogeology of the Gainesville area, Florida: Florida Geological Survey Special Publication No. 33, 70 p. HSC Chemistry for Windows, Version 5.1, 2004. Outokumpu Research, Finland. Macesich, M., 1988. Geologic interpretation of the aquifer pollution potential in Alachua County, Florida: Florida Geological Survey Open File Report 21, 26 p. Miller, J. A., 1986. Hydrogeologic framework of the Floridan Aquifer System in Florida, Alabama, and South Carolina: U. S. Geological Survey Professional Paper 1403-B, 91 p. and 33 plates.

A 5-1

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Section 5 References

Parkhurst, D. L., 1995. User’s guide to PHREEQC—a computer program for speciation, reaction-path, advective-transport, and inverse geochemical calculations: U.S. Geological Survey Water-Resources Investigations Report 95-4227, 143 p. Puri, H. S., and Vernon, R. O., 1964. Summary of the geology of Florida and a guidebook to the classic exposures: Florida Geological Survey Special Publication 5, 225 p. Reinhart, D. R., Grosh, C. J., 1997. Analysis of Florida MSW landfill leachate quality data: State University System of Florida, Florida Center for Solid and Hazardous Waste Management, Report 97-3. Scott, T. M., 1988. The lithostratigraphy of the Hawthorn Group (Miocene) of Florida: Florida Geological Survey Bulletin Number 59, 148 p. Scott, T. M., Campbell, K. M., Rupert, F. R., Arthur, J. D., Missimer, T. M., Lloyd, J. M., Yon, J. W., and Duncan, J. G., 2001. Geologic map of Florida: Florida Geological Survey Map Series 146, one sheet. Townsend, T. G., Jang, Y. C., Weber, W., 2000. Continued research into the characteristics of leachate from construction and demolition waste landfills: State University System of Florida, Florida Center for Solid and Hazardous Waste Management, Report 00-04. Upchurch, S. B., et al., 1991. Radiochemistry of Uranium – Series Isotopes in Groundwater: FIPR Publication #05-022-092. Vecchioli, J. et al., 1986. Hydrogeological units of Florida: Florida Geological Survey Special Publication Number 28, 8 p. White, W. A., 1970. The geomorphology of the Florida Peninsula: Florida Geological Survey Bulletin Number 31, 164 p.

A 5-2

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university of florida - wuft...assessment included; 1) the installation of 14 monitoring wells, 2)...

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