7-SECOND SEMIANNUAL REPORT 2024 - DAVIS.pdf

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Attached to: 25B-143 GROUNDWATER SAMPLING AND ANALYSIS
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Issued by: Marion County, Florida

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Second Semi-Annual 2024 Groundwater Monitoring Report Davis Closed Landfill Marion County, Florida Site ID#: ERIC_11047

Marion County Solid Waste Department 5601 S.E. 66th Street Ocala, Florida 34480

3922 Coconut Palm Drive, Suite 102 Tampa, FL 33619

813-621-0080

09219274.26 | January 28, 2025

Second Semi-Annual 2024 Groundwater Monitoring Report Davis Closed Landfill Marion County, Florida Site ID#: ERIC_11047

Marion County Solid Waste Department 5601 S.E. 66th Street Ocala, Florida 34480

09219274.26 | January 28, 2025

3922 Coconut Palm Drive, Suite 102 Tampa, FL 33619 813-621-0080

Whitney L. Rodriguez, P.E.

Project Manager FL License No. 82430

Fauve Herron, E.I.

Staff Professional

Whitney L. Rodriguez, P.E. State of Florida, Professional Engineer, License No. 82430.

This item has been digitally signed and sealed by Whitney L. Rodriguez, P.E. on the date indicated here.

Printed copies of this document are not considered signed and sealed and the signature must be verified on any electronic copies.

Davis LF – Second Semi-Annual 2024 Report www.scsengineers.com i

Table of Contents

Section Page

Introduction Site Background

November 2024 Groundwater Sampling Event Groundwater Flow Assessment

Level B Groundwater Flow Zone Level C Groundwater Flow Zone Level D Groundwater Flow Zone Level E Groundwater Flow Zone Level F Groundwater Flow Zone Level G Groundwater Flow Zone

Groundwater Analytical Results and Evaluation QA/QC Evaluation Groundwater Analytical Results

Level B Monitoring Well Groundwater Sampling Results Level C Monitoring Well Groundwater Sampling Results Level D Monitoring Well Groundwater Sampling Results Level E Monitoring Well Groundwater Sampling Results Level F Monitoring Well Groundwater Sampling Results Level G Monitoring Well Groundwater Sampling Results

Reductive Dechlorination Evaluation Findings and Recommendations

Figures

Figure 1. Site Vicinity Map Figure 2. Site Map Figure 3. Level "B" - Surficial Aquifer Potentiometric Map - November 2024 Figure 4. Level "C" - Floridan Aquifer Potentiometric Map - November 2024 Figure 5. Level "D" - Floridan Aquifer Potentiometric Map - November 2024 Figure 6. Level "E" - Floridan Aquifer Potentiometric Map - November 2024 Figure 7. Level "F" - Floridan Aquifer Potentiometric Map - November 2024 Figure 8. Level "C" - 1,1-Dichloroethene Contamination Extent Map - November 2024 Figure 9. Level "C" - 1,1-Dichloroethane Contamination Extent Map - November 2024 Figure 10. Level "C" - 1,2-Dichloroethane Contamination Extent Map - November 2024 Figure 11. Level "C" - Benzene Contamination Extent Map - November 2024 Figure 12. Level "C" - Vinyl Chloride Contamination Extent Map - November 2024 Figure 13. Level "D" - 1,1-Dichloroethene Contamination Extent Map - November 2024 Figure 14. Level "D" - 1,1-Dichloroethane Contamination Extent Map - November 2024 Figure 15. Level "D" - Vinyl Chloride Contamination Extent Map - November 2024 Figure 16. Level "E" - 1,1-Dichloroethene Contamination Extent Map - November 2024 http://www.scsengineers.com/ ii

Figure 17. Level "E" - 1,2-Dichloroethane Contamination Extent Map - November 2024 Figure 18. Level "E" - Vinyl Chloride Contamination Extent Map - November 2024 Figure 19. Level "F" - 1,1-Dichloroethene Contamination Extent Map - November 2024 Figure 20. Level "F" - 1,2-Dichloroethane Contamination Extent Map - November 2024 Figure 21. Level "F" - Benzene Contamination Extent Map - November 2024 Figure 22. Level "F" - Vinyl Chloride Contamination Extent Map - November 2024 Figure 23. Level "G" - 1,1-Dichloroethene Contamination Extent Map - November 2024

Tables

Table 1. Summary of Monitoring Well Construction Details Table 2. Groundwater Elevation Measurements – November 18, 2024 Table 3. Summary of Groundwater Analytical Results – July 2016 through November 2024 Table 4. Groundwater Geochemical Parameters of Impacted Wells – November 2024

Appendices

Appendix A FDEP Correspondence dated September 13, 2024 Appendix B Groundwater Sampling Logs, Calibration Logs, and Depth to Water Level Measurements Appendix C Laboratory Analytical Report Appendix D Mann-Kendall Spreadsheets

INTRODUCTION

SCS Engineers (SCS), on behalf of Marion County (the County), prepared this Second Semi-Annual 2024 Groundwater Monitoring Report for the Davis Closed Landfill (Site) [Site ID#: ERIC_11047] located at the intersection of SE 128th Place Road and SE 115th Avenue in Belleview, Florida (Figure 1). The groundwater sampling event was conducted according to Rule 62-780.690 and following the Florida Department of Environmental Protection (FDEP) approved semi-annual groundwater monitoring program. The most recent FDEP correspondence dated September 13, 2024, is included in Appendix A.

The purpose of the groundwater monitoring program is to monitor volatile organic compound (VOC) concentrations in the surficial and Floridan aquifer flow zones (B, C, D, E, F, and G) beneath the Site (Figure 2). Current monitoring data is evaluated with historical monitoring data to develop and track VOC concentration trends and evaluate contaminant plume stability. This report includes a brief Site background, field methodology employed for data collection, results of recent groundwater sample analyses, findings, and recommendations.

SITE BACKGROUND

The County and its consultants have been conducting groundwater assessment and remedial actions at the Site since 1993 in response to requirements outlined in Consent Order #87-0445. To date, substantial assessment activities and remedial actions have been performed at the Site, and related documentation has been submitted to the FDEP.

Between November and December 2015, SCS completed the supplemental vertical and horizontal delineation of groundwater impacts. Based on those results, SCS recommended the initiation of a Site-wide, semi-annual groundwater monitoring program. SCS presented the results of this investigation to the FDEP in the Site Assessment Report Addendum III, dated January 14, 2016. The FDEP approved the semi-annual groundwater monitoring plan in correspondence dated June 16, 2016. In correspondence dated September 27, 2017, the FDEP concurred with SCS’s recommendations to install three additional Level F monitoring wells and repair DMW-105F to incorporate these wells into the Site monitoring program.

Semi-annual monitoring has been conducted at the Site since 2016. Since the First Semi-Annual 2020 Groundwater Monitoring Report, SCS has recommended discontinuing sampling at select monitoring wells and reducing monitoring frequency to annual at other wells in the semi-annual groundwater monitoring plan. Below is a summary of monitoring wells approved to be reduced or discontinued by FDEP.

• Approved discontinuing sampling monitoring wells (September 17, 2020, correspondence): DMW-10B, DMW-33B, DMW-60B, DMW-50C, DMW-65C, DMW-78C, and DMW-84E.

• Approved reducing sampling frequency to annual at monitoring wells (September 17, 2020, correspondence): DMW-2RB, DMW-15RC, DMW-16C, DMW-19D, DMW-32D, DMW-83D, DMW-46E, DMW-90E, and DMW-109E. The annual sampling event is completed in May of each year.

• Approved reducing sampling frequency to annual at monitoring wells (May 17, 2023, correspondence): DMW-6B, DMW-25C, DMW-76C, DMW-87C, DMW-67D, DMW-81D, and

DMW-64ER.

• Approved discontinuing sampling monitoring wells (August 25, 2023, correspondence):

DMW-15RC, DMW-26D, DMW-32D, and DMW-90E.

• Approved discontinuing sampling monitoring well (February 15, 2024, correspondence):

DMW-2RB.

• Approved reducing sampling frequency to annual at monitoring well (February 15, 2024, correspondence): DMW-11B.

• Approved discontinuing sampling monitoring wells (September 13, 2024, correspondence): DMW-44C, DMW-93C, and DMW-83D.

Additionally, during the November 2023 sampling event, monitoring wells DMW-79D and DMW-80C were not located and presumed destroyed. Depth to groundwater measurements were previously collected from these wells as part of the semi-annual groundwater monitoring program; however, they were not sampled as part of the monitoring program. Monitoring wells DMW-83D and DMW-82C are located side-gradient of DMW-79D and DMW-80C, respectively, and are used to collect groundwater elevation data in this area of the Site. Therefore, DMW-79D and DMW-80C do not need to be re-installed. FDEP concurred that monitoring wells DMW-80C and DMW-79D do not have to be re-installed in correspondence dated September 13, 2024.

NOVEMBER 2024 GROUNDWATER SAMPLING EVENT

Aqua Pure Water & Sewage Service, LLC (Aqua Pure) personnel completed the groundwater sampling activities from November 18 through 21, 2024. Before initiating groundwater sampling procedures, field personnel collected depth-to-groundwater measurements from the monitoring well network. Monitoring well construction details are provided in Table 1. Depth to water measurements and corresponding groundwater elevations are provided in Table 2. Aqua Pure personnel calibrated the multi-parameter and turbidity meters in general accordance with FDEP protocols in preparation for the sampling event.

Once equipment calibration was complete, each monitoring well was purged using a decontaminated submersible pump generally following FDEP Groundwater Sampling Standard Operating Procedure (SOP) FS 2200. Groundwater field parameter measurements, including specific conductance, pH, temperature, turbidity, dissolved oxygen (DO), and oxidation-reduction potential (ORP) were recorded on sampling logs following FDEP SOPs. Following field parameter stabilization, groundwater samples were placed in laboratory-supplied containers. Following sample collection, the containers were appropriately identified, placed in an iced cooler, and transported to Pace Analytical Services, LLC located in Ormond Beach, Florida, for analysis of VOCs by U.S. Environmental Protection Agency (EPA) Method 8260. Appropriate chain of custody forms accompanied the samples. Groundwater sampling and equipment calibration logs are provided in Appendix B.

The following FDEP-approved monitoring wells were sampled:

• C Zone: DMW-20C, DMW-21C, DMW-30C, DMW-42C, and DMW-101C;

• D Zone: DMW-43D, DMW-45D, DMW-51D, DMW-55D, DMW-59D, DMW-61D, DMW-62D, DMW-63D, DMW-73D, DMW-75D, DMW-77D, DMW-88D, DMW-102D, DMW-103D, and

DMW-108D;

• E Zone: DMW-54E, DMW-71E, DMW-89E, DMW-91E, DMW-92E, and DMW-111E;

• F Zone: DMW-85F, DMW-86F, DMW-105F, DMW-106F, DMW-110F, DMW-112F, DMW- 113F, and DMW-114F; and

• G Zone: DMW-107G.

GROUNDWATER FLOW ASSESSMENT

The groundwater gradient was evaluated by collecting depth-to-groundwater measurements and top-of-casing elevation measurements from the existing monitoring well network at the Site. With this information, potentiometric maps for Levels B, C, D, E, and F were prepared using the corresponding groundwater elevation measurements collected on November 18, 2024 (Table 2).

LEVEL B GROUNDWATER FLOW ZONE

Figure 3 shows the potentiometric surface of the surficial aquifer at the Site. Groundwater elevation measurements from the Level B monitoring well network ranged from 53.84 feet (ft) referenced to the National Geodetic Vertical Datum (NGVD) to 67.18 ft NGVD (Table 2). Water level data indicated that groundwater highs are located near monitoring wells DMW-47B and DMW-48B, with hydraulic gradients indicating the overall groundwater flow direction is primarily toward the west-northwest.

The November 2024 interpreted groundwater gradients in the Level B flow zone wells are consistent with historical findings.

LEVEL C GROUNDWATER FLOW ZONE

Figure 4 shows the potentiometric surface of the Upper portion of the Ocala Group at the Site.

Groundwater elevation measurements from the Level C monitoring well network ranged from 51.94 ft NGVD to 64.43 ft NGVD (Table 2). Water level data indicated that a groundwater high is located near monitoring wells DMW-40C and DMW-57C, and from this area, the groundwater appears to flow radially but predominantly toward the north-northwest. The November 2024 interpreted groundwater gradients in the Level C flow zone wells are consistent with historical findings.

LEVEL D GROUNDWATER FLOW ZONE

Figure 5 shows the potentiometric surface of the middle portion of the Ocala Group at the Site.

Groundwater elevation measurements from the Level D monitoring well network ranged from 52.09 ft NGVD to 62.33 ft NGVD (Table 2). Water level data indicated that groundwater highs are located near monitoring wells DMW-59D, DMW-61D, and DMW-66D. From these areas, groundwater appears to flow radially outward. The data suggests that subsurface relic karst features affect the Level D groundwater flow pattern more significantly than the other flow zones. The November 2024 interpreted groundwater gradients in the Level D flow zone wells are consistent with historical findings.

LEVEL E GROUNDWATER FLOW ZONE

Figure 6 shows the potentiometric surface for wells screened within the lower middle portion of the Ocala Group. Groundwater elevation measurements from the Level E monitoring well network ranged from 52.63 ft NGVD to 54.24 ft NGVD. Hydraulic gradients in the Level E flow zone indicated the overall groundwater flow is primarily toward the west-southwest. The November 2024 interpreted groundwater gradients in the Level E flow zone wells are consistent with historical findings.

LEVEL F GROUNDWATER FLOW ZONE

Figure 7 shows the potentiometric surface for wells screened within the middle lower portion of the Ocala Group. Groundwater elevation measurements from the Level F monitoring well network ranged from 52.66 ft NGVD to 60.98 ft NGVD. Potentiometric water level data indicated that a groundwater high is located near monitoring well DMW-86F. Hydraulic gradients in Level F flow zone wells indicated the overall groundwater flow is radially away from monitoring well DMW-86F. The November 2024 interpreted groundwater gradients in the Level F flow zone wells are consistent with historical findings.

LEVEL G GROUNDWATER FLOW ZONE

Given that only one monitoring well (DMW-107G) has been installed within the Level G Zone, a potentiometric map was not created.

GROUNDWATER ANALYTICAL RESULTS AND EVALUATION

QA/QC EVALUATION

Quality assurance/quality control (QA/QC) samples, including trip blanks, were collected during the November 2024 semi-annual sampling event. Trip blanks were provided by the laboratory in the sample coolers and remained in the coolers through the return delivery to the laboratory. The temperature measured from the coolers upon delivery to the laboratory indicated the samples were received within the acceptable temperature range in the sample coolers.

Based on laboratory QC reported for the collected groundwater samples analyzed by EPA Method 8260:

• Samples were received in good condition and analyzed within the established hold times for each analyte;

• The trip blank sample had an estimated (“I” qualified) detection of methylene chloride;

however, methylene chloride was not detected above the laboratory method detection limit (MDL) in the groundwater samples and methylene chloride is a common laboratory contaminant;

• The method blanks for the samples were below the MDL; and

• The laboratory control samples (LCS) were generally within limits. Results for analytes outside limits for LCS had no detections. Select analytes were outside limits for matrix spike samples; however, they were accepted based on LCS recoveries.

The laboratory analytical report is included in Appendix C. Based on the QA/QC results, the data set is of adequate quality to meet the sampling and reporting objectives of this project.

GROUNDWATER ANALYTICAL RESULTS

A total of 39 samples were collected for analysis. Analytical results were compared to the Groundwater Cleanup Target Levels (GCTLs) provided in Chapter 62-777, Florida Administrative Code. Groundwater analytical results are presented in Table 3. The laboratory analytical report is included in Appendix C.

VOCs with concentrations exceeding the GCTLs during the November 2024 sampling event include:

• Benzene

• 1,1-Dichloroethene (1,1-DCE)

• 1,1-Dichloroethane (1,1-DCA)

• 1,2-Dichloroethane (1,2-DCA)

• Vinyl chloride (VC)

These exceedances are shown in bold text in Table 3 and their distribution is presented in Figures 8 through 23. Further discussion is provided below.

Level B Monitoring Well Groundwater Sampling Results Level B monitoring wells were not sampled as part of the November 2024 semi-annual sampling event.

Level C Monitoring Well Groundwater Sampling Results Figures 8 through 12 show the distribution of 1,1-DCE, 1,1-DCA, 1,2-DCA, benzene, and VC concentrations across the Level C zone. A discussion of the November 2024 groundwater sampling results for the Level C wells is provided below:

• 1,1-DCE was detected at concentrations above the GCTL of 7 micrograms per liter (µg/L) at monitoring wells DMW-21C, DMW-30C, and DMW-42C, as shown in Figure 8.

• 1,1-DCA was detected at a concentration above the GCTL of 70 µg/L at monitoring well DMW-21C as shown in Figure 9.

• 1,2-DCA was detected at a concentration above the GCTL of 3 µg/L at monitoring well DMW-21C as shown in Figure 10.

• Benzene was detected at a concentration above the GCTL of 1 µg/L at monitoring well DMW-21C as shown in Figure 11.

• VC, a degradation product of 1,1-DCE, was detected at a concentration above the GCTL of 1 µg/L at monitoring well DMW-21C as shown in Figure 12.

As shown in Figure 9, 1,1-DCE is the most prevalent contaminant in the Level C flow zone. It extends across the northern boundary of the landfill. The 1,1-DCE plume appears stable, with little to no horizontal movement over time. 1,1-DCE concentrations at well locations in Level C remained stable or decreased. Analytical results indicate that 1,1-DCE appears to be degrading to VC and the conditions are conducive for VC degradation in the Level C flow zone, as demonstrated by VC not being detected above the MDL in downgradient monitoring wells. A Mann-Kendall trend analysis of contaminants of concern (COCs) in groundwater from Level C is provided in Appendix D.

Level D Monitoring Well Groundwater Sampling Results Figures 13 through 15 show the distribution of the 1,1-DCE, 1,1-DCA, and VC concentrations across Level D, as these constituents were detected at concentrations above their respective GCTLs. A discussion of the November 2024 groundwater sampling results for the Level D wells is provided below:

• 1,1-DCE was detected at concentrations above the GCTL of 7 µg/L at monitoring wells DMW-43D, DMW-45D, DMW-55D, DMW-63D, DMW-73D, DMW-75D, and DMW-88D. The highest concentrations were detected at monitoring wells DMW-45D and DMW-75D. As shown in Figure 13, 1,1-DCE extends along the northern and eastern edges of the landfill and extends off Site east of the landfill.

• 1,1-DCA was detected at a concentration above the GCTL of 70 µg/L at monitoring well DMW-75D as shown in Figure 14.

• VC was detected at concentrations above the GCTL of 1 µg/L at monitoring wells DMW- 61D, DMW-62D, DMW-88D, and DMW-108D (Figure 15).

SCS compared the November 2024 analytical results with historical data for the Level D wells and 1,1-DCE concentrations at well locations generally remained stable or decreased, except at DMW- 55D, DMW-63D, and DMW-73D. Analytical results indicate that 1,1-DCE appears to degrade to VC.

Monitoring well DMW-61D only had VC exceedances of the GCTL. However, VC concentrations are decreasing and the lateral extent within Level D has been stable over the recent sampling events.

Additionally, DMW-43D, DMW-62D, and DMW-73D are located downgradient of DMW-61D. 1,1-DCE concentrations in DMW-62D have been below the GCTL during the sampling period (2016 to November 2024) so this well could serve as a downgradient point of compliance well to the impacts observed at DMW-43D and DMW-73D. VC concentrations in DMW-43D and DMW-73D have been below the GCTL during the sampling period (2016 to November 2024) so these wells could serve as downgradient point of compliance wells to the impacts observed at DMW-61D.

A Mann-Kendall trend analysis of COCs in groundwater from Level D is provided in Appendix D.

Level E Monitoring Well Groundwater Sampling Results Figures 16 through 18 show the distribution of the 1,1-DCE, 1,2-DCA, and VC concentrations across Level E groundwater, as these constituents were detected at concentrations exceeding their respective GCTLs. A discussion of the November 2024 groundwater sampling results for the Level E wells is provided below:

• 1,1-DCE was detected at concentrations above the GCTL of 7 µg/L at monitoring wells DMW-54E and DMW-71E, as shown in Figure 16.

• 1,2-DCA was detected at a concentration above the GCTL of 3 µg/L at monitoring well DMW-71E, as shown in Figure 17.

• VC was detected at concentrations above the GCTL of 1 µg/L at monitoring wells DMW- 54E, DMW-71E, and DMW-111E as shown in Figure 18.

The plume extents for 1,1-DCE and VC in the Level E flow zone generally appear stable compared to historical data. VC concentrations are increasing at DMW-54E and DMW-71E, which is indicative of degradation. This demonstrates that 1,1-DCE continues to degrade to VC. A Mann-Kendall trend analysis of COCs in groundwater from Level E is provided in Appendix D.

Level F Monitoring Well Groundwater Sampling Results Figures 19 through 22 show the distribution of the 1,1-DCE, 1,2-DCA, benzene, and VC concentrations across Level F. A discussion of the November 2024 groundwater sampling results for the Level F wells is provided below:

• 1,1-DCE was detected at concentrations above the GCTL of 7 µg/L at monitoring wells DMW-85F and DMW-86F. The 1,1-DCE plume extends from northeast to southwest along the eastern edge of the landfill as shown in Figure 19.

• 1,2-DCA was detected at a concentration above the GCTL of 3 µg/L at monitoring well DMW-86F, as shown in Figure 20.

• Benzene was detected at a concentration above the GCTL of 1 µg/L at monitoring well DMW-86F, as shown in Figure 21.

• VC was detected at concentrations above the GCTL of 1 µg/L at monitoring wells DMW- 86F, DMW-110F, DMW-112F, and DMW-114F, as shown in Figure 22.

A comparison of the November 2024 results with historical data indicated the 1,1-DCE concentrations in the Level F monitoring wells remained stable or decreased and VC concentrations remained stable, except at DMW-86F and DMW-112F. The lateral extents of the 1,1-DCE and VC plumes in Level F have been stable over the recent sampling events. A Mann-Kendall trend analysis of COCs in groundwater from Level F is provided in Appendix D.

Level G Monitoring Well Groundwater Sampling Results Only 1,1-DCE was detected at a concentration above the GCTL of 7 µg/L at monitoring well DMW- 107G (Figure 23). The concentration increased from May 2024 (5.5 µg/L) to November 2024 (8.9 µg/L) at DMW-107G. A comparison of the November 2024 results with historical data shows an overall decreasing trend in the 1,1-DCE concentrations at monitoring well DMW-107G. A Mann- Kendall trend analysis of COCs in groundwater from Level G is provided in Appendix D.

REDUCTIVE DECHLORINATION EVALUATION

Field measurements were recorded in samples from the monitoring well network to evaluate whether geochemical conditions are suitable for microbial activity that would support reductive dechlorination and the contribution this makes to the natural attenuation of chlorinated VOCs (CVOCs) at the Site.

This evaluation only focused on wells with groundwater samples exhibiting CVOC concentrations above the GCTLs. Field measurements included temperature in degrees Celsius (°C), pH (standard units; SU), ORP in millivolts (mV), and DO in milligrams per liter (mg/L). Field measurements are provided in Table 4 and summarized for each groundwater zone as shown in the table below.

Groundwater Zone

Temperature (°C) pH

(SU)

Average ORP (mV)

Average

(mg/L)

Conducive for Reductive

Dechlorination

C 25.0 – 26.0 6.77 – 8.36 +24.00 1.84 Varies Spatially

D 24.0 – 25.6 6.41 – 9.36 -20.50 0.96 Varies Spatially

E 23.8 – 24.8 7.17 – 7.72 -119.67 0.13 Yes

F 23.6 – 24.6 5.80 – 7.77 -104.40 0.12 Varies Spatially

G 24.2 7.40 -138.00 0.04 Yes

Conditions conducive to reductive dechlorination include the following:

• pH values between 6 and 8 SU

• ORP values less than 0 mV indicate reductive dechlorination is possible, and ORP values less than -100 mV indicate reductive dechlorination is likely to occur

• DO concentrations less than 0.5 mg/L

As seen in the above table, conditions for reductive dechlorination are generally favorable in groundwater within zones C through G. In addition, 1,1-DCE is typically generated from reductive dechlorination of higher-order chlorinated compounds such as tetrachloroethene (PCE) and trichloroethene (TCE), both of which are commonly used solvents. Microbial dechlorination of PCE and TCE typically proceeds rapidly under reducing conditions; however, this process often stalls at 1,1-DCE. The degradation rate of 1,1-DCE to VC is typically slower, so concentrations of 1,1-DCE either increase or stabilize. This can be misunderstood to indicate that microbial degradation is not occurring; however, the presence of VC confirms that 1,1-DCE is degrading. VC further breaks down to ethane, and ultimately to carbon dioxide and water; however, the dechlorination path for VC is more efficient in the presence of oxygen. There is an active pathway for VC to break down under reducing conditions; however, it is slower. Thus, under reducing conditions both 1,1-DCE and VC are typically found, and concentrations remain relatively stable, while under aerobic conditions 1,1-DCE is detected without VC because VC degrades relatively more quickly.

FINDINGS AND RECOMMENDATIONS

Results of laboratory analyses from the second semi-annual groundwater monitoring event of 2024 indicated CVOC concentrations across the Site are relatively stable, with only a few exceptions.

Groundwater geochemistry data collected in the field continue to indicate favorable conditions supporting reductive dechlorination in the various depths monitored; however, these conditions varied spatially.

The presence of 1,1-DCA, 1,2-DCA, 1,1-DCE, and VC in groundwater suggests that natural microbial degradation of CVOCs is occurring. The persistence of these specific compounds also suggests the primary degradation pathway is anaerobic. VC is most effectively broken down in the presence of oxygen and tends to persist in groundwater where anaerobic conditions predominate; however, the VC groundwater plume appears stable without measurable migration.

Groundwater elevation data indicated the groundwater flow direction at the Site is generally to the west except in the Level D and F flow zones where groundwater flow is radial.

SCS recommends continued semi-annual groundwater sampling until the groundwater data indicates plume stability across the six flow regimes. CVOC concentrations across the Site remain stable in most groundwater monitoring wells.

A review of the historical data, groundwater flow direction in each zone, and/or Mann-Kendall trend analysis indicating that groundwater in the vicinity of the following monitoring well has decreasing CVOC concentration trends lead to the following recommendations by SCS. SCS recommends that sampling of this well be discontinued moving forward:

• Level D monitoring well: Monitoring well DMW-61D only had VC exceedances of the GCTL.

However, VC concentrations are decreasing and the lateral extent within Level D has been stable over the recent sampling events. Additionally, DMW-43D, DMW-62D, and DMW-73D are located downgradient of DMW-61D. 1,1-DCE concentrations in DMW-62D have been below the GCTL during the sampling period (2016 to November 2024) so this well could serve as a downgradient point of compliance well to the impacts observed at DMW-43D and DMW-73D. VC concentrations in DMW-43D and DMW-73D have been below the GCTL during the sampling period (2016 to November 2024) so these wells could serve as downgradient point of compliance wells to the impacts observed at DMW- 61D.

Figures

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FIGURE 1

SITE VICINITY MAP

DAVIS CLOSED LANDFILL

MARION COUNTY, FL

Tampa, FL January 2025

Legend

Property Boundary

±0 250 500 Feet file:C:/Users/4455aba/OneDrive

EDED

@A @A

@A@A

@A @A

@A@A

@A @A

@A @A @A

@A @A

@A@A

DMW-9A

DMW-57C

DMW-66D

DMW-72E

DMW-85F

DMW-87C

DMW-88D

DMW-79D

DMW-80C

DMW-76C

DMW-77D

DMW-90E

DMW-56A

DMW-60B

DMW-74C

DMW-75D

DMW-84E

DMW-44C

DMW-45D

DMW-58E

DMW-42C

DMW-43D

DMW-35C

DMW-48B

DMW-33B

DMW-55D

DMW-30C

DMW-51D

DMW-23B

DMW-61D

DMW-71E

DMW-86F

DMW-21C

DMW-32D

DMW-54E

DMW-110F

DMW-10B

DMW-17C

DMW-19D

DMW-89E

DMW-108D

DMW-112F

DMW-101C

DMW-102D

DMW-12RA

DMW-22B

DMW-62D

DMW-40C

DMW-41D

DMW-68E

DMW-6B

DMW-5A

DMW-4A

DMW-3A

DMW-93C

DMW-91E

DMW-83D

DMW-82C

DMW-81D

DMW-78C

DMW-67D

DMW-65C

DMW-63D

DMW-59D

DMW-53C

DMW-34C

DMW-47B

DMW-46E

DMW-37C

DMW-36B

DMW-26D

DMW-25C

DMW-24A

DMW-20CDMW-18B

DMW-16C

DMW-11B

DMW-2RB DMW-114F

DMW-113F

DMW-111E

DMW-109E

DMW-106F

DMW-105F

DMW-104F

DMW-103D

DMW-15RC

DMW-39D

DMW-64ER

DMW-107G

DMW-49B

DMW-50C

DMW-73D

DMW-92E

D oc um en t P at h:

:\U se rs \4

5a ba \O ne D riv e

C S

E ng in ee rs \G

\D av is

_L an df ill

\M X

D \P

R O

\P R

O .a pr x

FIGURE 2

SITE MAP

DAVIS CLOSED LANDFILL

MARION COUNTY, FL

Tampa, FL January 2025 ±0 175 350 Feet

Legend

Monitoring Wells

ED Not Clustered

@A Clustered

@A Destroyed

Property Boundary

@A @A

DMW-3B

58.78

DMW-2RB

60.54

DMW-6B

54.36 DMW-10B

61.94

DMW-11B

53.84

DMW-18B

61.28

DMW-23B

63.50

DMW-33B

63.93

DMW-36B

65.34

DMW-47B

67.18

DMW-48B

65.78

DMW-49B/C

63.93

DMW-60B

64.79

DMW-22B

61.09

65.0

64.0

63.0

62.0

56.0

55.0

54.0

66.0

64.0

1 .0

D oc um en t P at h:

:\U se rs \4

5a ba \O ne D riv e

C S

E ng in ee rs \G

\D av is

_L an df ill

\M X

D \P

R O

\P R

O .a pr x

Tampa, FL January 2025 ±0 175 350 Feet

50.0 Groundwater Elevation (Feet NGVD)

Legend

@A Active Monitoring Wells

Approximate Groundwater Elevation Contour (Feet NGVD)

Approximate Groundwater Flow Direction

Property Boundary

FIGURE 3

LEVEL "B"

SURFICIAL AQUIFER POTENTIOMETRIC MAP

NOVEMBER 2024

DAVIS CLOSED LANDFILL

MARION COUNTY, FL

Note: NGVD = National Geodetic Vertical Datum

@A @A

DMW-80C

DMW-16C

57.96

DMW-17C

53.64

DMW-20C

53.70

DMW-21C

54.52

DMW-25C

56.92

DMW-30C

57.35

DMW-34C

59.60

DMW-35C

59.79

DMW-37C

56.06

DMW-40C

64.32

DMW-42C

57.65

DMW-44C

58.13

DMW-50C

60.04

DMW-53C

60.11

DMW-57C

64.43

DMW-65C

62.02

DMW-74C

61.71

DMW-76C

60.21

DMW-78C

62.64

DMW-82C

54.04

DMW-87C

53.40

DMW-93C

54.00

DMW-101C

51.94

DMW-15RC

61.03

57.0

56.0

5.0

60.0

53.0

52.0

59.0

58.0

D oc um en t P at h:

:\U se rs \4

5a ba \O ne D riv e

C S

E ng in ee rs \G

\D av is

_L an df ill

\M X

D \P

R O

\P R

O .a pr x

Tampa, FL January 2025 ±0 175 350 Feet

50.0 Groundwater Elevation (Feet NGVD)

Legend

@A Active Monitoring Wells

@A Destroyed Monitoring Wells

Approximate Groundwater Elevation Contour (Feet NGVD)

Approximate Groundwater Flow Direction

Property Boundary

FIGURE 4

LEVEL "C"

FLORIDAN AQUIFER POTENTIOMETRIC MAP

NOVEMBER 2024

DAVIS CLOSED LANDFILL

MARION COUNTY, FL

Note: NGVD = National Geodetic Vertical Datum; NA= Not Available

@A@A

DMW-79D

DMW-19D

53.71

DMW-32D

53.83

DMW-39D

53.90

DMW-41D

55.36

DMW-43D

54.15

DMW-45D

54.38

DMW-51D

53.93

DMW-55D

54.03

DMW-59D

60.13

DMW-62D

53.85

DMW-63D

53.55

DMW-67D

59.13

DMW-73D

54.21

DMW-77D

56.04

DMW-81D

54.14

DMW-83D

54.04

DMW-88D

53.46

DMW-102D

52.09

DMW-108D

53.88

DMW-26D

54.16

DMW-61D

62.33

DMW-66D

59.94

DMW-75D

57.26

DMW-103D

53.58

57.0

56.0

59.058.0

54.0

0. 0

D oc um en t P at h:

:\U se rs \4

5a ba \O ne D riv e

C S

E ng in ee rs \G

\D av is

_L an df ill

\M X

D \P

R O

\P R

O .a pr x

Tampa, FL January 2025 ±0 175 350 Feet

50.0 Groundwater Elevation (Feet NGVD)

Legend

@A Active Monitoring Wells

@A Destroyed Monitoring Wells

Approximate Groundwater Elevation Contour (Feet NGVD)

Approximate Groundwater Flow Direction

Property Boundary

FIGURE 5

LEVEL "D"

FLORIDAN AQUIFER POTENTIOMETRIC MAP

NOVEMBER 2024

DAVIS CLOSED LANDFILL

MARION COUNTY, FL

Note: NGVD = National Geodetic Vertical Datum; NA= Not Available

DMW-46E

54.15

DMW-54E

53.84

DMW-58E

54.19

DMW-64ER

52.71

DMW-84E

54.14

DMW-89E

53.73

DMW-90E

54.19

DMW-91E

53.89

DMW-109E

54.24

DMW-111E

52.63

DMW-68E

54.14

DMW-71E

54.14

DMW-72E

54.20

DMW-92E

54.18

54.0

53.0

D oc um en t P at h:

:\U se rs \4

5a ba \O ne D riv e

C S

E ng in ee rs \G

\D av is

_L an df ill

\M X

D \P

R O

\P R

O .a pr x

Tampa, FL January 2025 ±0 175 350 Feet

50.0 Groundwater Elevation (Feet NGVD)

Legend

@A Active Monitoring Wells

Approximate Groundwater Elevation Contour (Feet NGVD)

Approximate Groundwater Flow Direction

Property Boundary

FIGURE 6

LEVEL "E"

FLORIDAN AQUIFER POTENTIOMETRIC MAP

NOVEMBER 2024

DAVIS CLOSED LANDFILL

MARION COUNTY, FL

DMW-85F

54.12

DMW-86F

60.98

DMW-104F

53.06

DMW-105F

53.16

DMW-106F

53.11

DMW-112F

52.66

DMW-113F

52.88

DMW-114F

53.19

DMW-110F

54.03

58.0

56.0

55.0

54.0

59 .0

D oc um en t P at h:

:\U se rs \4

5a ba \O ne D riv e

C S

E ng in ee rs \G

\D av is

_L an df ill

\M X

D \P

R O

\P R

O .a pr x

Tampa, FL January 2025 ±0 175 350 Feet

50.0 Groundwater Elevation (Feet NGVD)

Legend

@A Active Monitoring Wells

Approximate Groundwater Elevation Contour (Feet NGVD)

Approximate Groundwater Flow Direction

Property Boundary

FIGURE 7

LEVEL "F"

FLORIDAN AQUIFER POTENTIOMETRIC MAP

NOVEMBER 2024

DAVIS CLOSED LANDFILL

MARION COUNTY, FL

@A @A

DMW-20C

0.60 I

DMW-21C

DMW-30C

43.8

DMW-42C

46.3

DMW-101C

0.59 U

DMW-16C

DMW-17C

DMW-25C

DMW-34C

DMW-35C

DMW-37C

DMW-40C

DMW-44C

DMW-50C

DMW-53C

DMW-57C

DMW-65C

DMW-74C

DMW-76C

DMW-78C

DMW-80C

DMW-82C

DMW-87C

DMW-93C

DMW-15RC

D oc um en t P at h:

:\U se rs \4

5a ba \O ne D riv e

C S

E ng in ee rs \G

\D av is

_L an df ill

\M X

D \P

R O

\P R

O .a pr x

FIGURE 8

LEVEL "C"

1,1-DICHLOROETHENE CONTAMINATION EXTENT MAP

NOVEMBER 2024

DAVIS CLOSED LANDFILL

MARION COUNTY, FL

Tampa, FL January 2025 ±0 175 350 Feet

Notes:

U = Compound was analyzed for but not detected above the laboratory method detection limit (MDL) I = The reported value is between the laboratory MDL and the laboratory practical quantitation limit μg/L = micrograms per liter NS = Not sampled

7.0 1,1-Dichloroethene Concentration (μg/L)

Legend

Property Boundary

@A Active Monitoring Wells

@A Destroyed Monitoring Wells

Approximate 1,1-Dichloroethene Groundwater Cleanup Target Level (7 µg/L) Iso-contour

@A @A

DMW-20C

0.34 U

DMW-21C

DMW-30C

6.5

DMW-42C

7.2

DMW-101C

0.34 U

DMW-15RC

DMW-16C

DMW-17C

DMW-25C

DMW-34C

DMW-35C

DMW-37C

DMW-40C

DMW-44C

DMW-50C

DMW-53C

DMW-57C

DMW-65C

DMW-74C

DMW-76C

DMW-78C

DMW-80C

DMW-82C

DMW-87C

DMW-93C

D oc um en t P at h:

:\U se rs \4

5a ba \O ne D riv e

C S

E ng in ee rs \G

\D av is

_L an df ill

\M X

D \P

R O

\P R

O .a pr x

FIGURE 9

LEVEL "C"

1,1-DICHLOROETHANE CONTAMINATION EXTENT MAP

NOVEMBER 2024

DAVIS CLOSED LANDFILL

MARION COUNTY, FL

Tampa, FL January 2025 ±0 175 350 Feet

Notes:

Legend

Property Boundary

@A Active Monitoring Wells

@A Destroyed Monitoring Wells

70.0 1,1-Dichloroethane Concentration (μg/L)

Approximate 1,1-Dichloroethane Groundwater Cleanup Target Level (70 µg/L) Iso-contour

@A @A

DMW-20C

0.27 U

DMW-21C

3.5

DMW-30C

0.27 U

DMW-42C

0.27 U

DMW-101C

0.27 U

DMW-15RC

DMW-16C

DMW-17C

DMW-25C

DMW-34C

DMW-35C

DMW-37C

DMW-40C

DMW-44C

DMW-50C

DMW-53C

DMW-57C

DMW-65C

DMW-74C

DMW-76C

DMW-78C

DMW-80C

DMW-82C

DMW-87C

DMW-93C

D oc um en t P at h:

:\U se rs \4

5a ba \O ne D riv e

C S

E ng in ee rs \G

\D av is

_L an df ill

\M X

D \P

R O

\P R

O .a pr x

FIGURE 10

LEVEL "C"

1,2-DICHLOROETHANE CONTAMINATION EXTENT MAP

NOVEMBER 2024

DAVIS CLOSED LANDFILL

MARION COUNTY, FL

Tampa, FL January 2025 ±0 175 350 Feet

Notes:

3.0 1,2-Dichloroethane Concentration (μg/L)

Legend

Property Boundary

@A Active Monitoring Wells

@A Destroyed Monitoring Wells

Approximate 1,2-Dichloroethane Groundwater Cleanup Target Level (3 µg/L) Iso-contour

@A @A

DMW-20C

0.30 U

DMW-21C

5.6

DMW-30C

0.30 U

DMW-42C

0.41 I

DMW-101C

0.30 U

DMW-15RC

DMW-16C

DMW-17C

DMW-25C

DMW-34C

DMW-35C

DMW-37C

DMW-40C

DMW-44C

DMW-50C

DMW-53C

DMW-57C

DMW-65C

DMW-74C

DMW-76C

DMW-78C

DMW-80C

DMW-82C

DMW-87C

DMW-93C

D oc um en t P at h:

:\U se rs \4

5a ba \O ne D riv e

C S

E ng in ee rs \G

\D av is

_L an df ill

\M X

D \P

R O

\P R

O .a pr x

FIGURE 11

LEVEL "C"

BENZENE CONTAMINATION EXTENT MAP

NOVEMBER 2024

DAVIS CLOSED LANDFILL

MARION COUNTY, FL

Tampa, FL January 2025 ±0 175 350 Feet

Notes:

1.0 Benzene Concentration (μg/L)

Legend

Property Boundary

@A Active Monitoring Wells

@A Destroyed Monitoring Wells

Approximate Benzene Groundwater Cleanup Target Level (1 µg/L) Iso-contour

@A @A

DMW-20C

0.39 U

DMW-21C

11.1

DMW-30C

0.39 U

DMW-42C

0.55 I

DMW-101C

0.39 U

DMW-15RC

DMW-16C

DMW-17C

DMW-25C

DMW-34C

DMW-35C

DMW-37C

DMW-40C

DMW-44C

DMW-50C

DMW-53C

DMW-57C

DMW-65C

DMW-74C

DMW-76C

DMW-78C

DMW-80C

DMW-82C

DMW-87C

DMW-93C

D oc um en t P at h:

:\U se rs \4

5a ba \O ne D riv e

C S

E ng in ee rs \G

\D av is

_L an df ill

\M X

D \P

R O

\P R

O .a pr x

FIGURE 12

LEVEL "C"

VINYL CHLORIDE CONTAMINATION EXTENT MAP

NOVEMBER 2024

DAVIS CLOSED LANDFILL

MARION COUNTY, FL

Tampa, FL January 2025 ±0 175 350 Feet

Notes:

1.0 Vinyl Chloride Concentration (μg/L)

Legend

Property Boundary

@A Active Monitoring Wells

@A Destroyed Monitoring Wells

Approximate Vinyl Chloride Groundwater Cleanup Target Level (1 µg/L) Iso-contour (dashed where inferred)

@A@A

DMW-43D

22.3

DMW-45D

DMW-51D

0.62 I

DMW-55D

62.6

DMW-59D

0.59 U

DMW-61D

4.5

DMW-63D

13.2

DMW-73D

20.9

DMW-77D

0.94 I

DMW-88D

14.2

DMW-102D

0.59 U

DMW-103D

0.59 U

DMW-108D

0.59 U

DMW-19D

DMW-32D

DMW-39D

DMW-41D

DMW-67D

DMW-79D

DMW-81D

DMW-83D

DMW-62D

1.7

DMW-75D

DMW-66D

DMW-26D

D oc um en t P at h:

:\U se rs \4

5a ba \O ne D riv e

C S

E ng in ee rs \G

\D av is

_L an df ill

\M X

D \P

R O

\P R

O .a pr x

FIGURE 13

LEVEL "D"

1,1-DICHLOROETHENE CONTAMINATION EXTENT MAP

NOVEMBER 2024

DAVIS CLOSED LANDFILL

MARION COUNTY, FL

Tampa, FL January 2025 ±0 175 350 Feet

Notes:

7.0 1,1-Dichloroethene Concentration (μg/L)

Legend

Property Boundary

@A Active Monitoring Wells

@A Destroyed Monitoring Wells

Approximate 1,1-Dichloroethene Groundwater Cleanup Target

@A@A

DMW-43D

3.0

DMW-45D

23.8

DMW-51D

0.34 U

DMW-55D

23.1

DMW-59D

0.34 U

DMW-61D

33.8

DMW-62D

8.4

DMW-63D

1.5

DMW-73D

2.8

DMW-75D

95.8

DMW-77D

0.34 U

DMW-88D

6.6

DMW-102D

0.34 U

DMW-103D

0.34 U

DMW-108D

1.6

DMW-19D

DMW-26D

DMW-32D

DMW-39D

DMW-41D

DMW-66D

DMW-67D

DMW-79D

DMW-81D

DMW-83D

D oc um en t P at h:

:\U se rs \4

5a ba \O ne D riv e

C S

E ng in ee rs \G

\D av is

_L an df ill

\M X

D \P

R O

\P R

O .a pr x

FIGURE 14

LEVEL "D"

1,1-DICHLOROETHANE CONTAMINATION EXTENT MAP

NOVEMBER 2024

DAVIS CLOSED LANDFILL

MARION COUNTY, FL

Tampa, FL January 2025 ±0 175 350 Feet

Notes:

Legend

Property Boundary

@A Active Monitoring Wells

@A Destroyed Monitoring Wells

70.0 1,1-Dichloroethane Concentration (μg/L)

Approximate 1,1-Dichloroethane Groundwater Cleanup Target Level (70 µg/L) Iso-contour

@A@A

DMW-43D

0.39 U

DMW-45D

0.39 U

DMW-51D

0.39 U

DMW-55D

0.39 U

DMW-59D

0.39 U

DMW-61D

15.1

DMW-62D

43.4

DMW-63D

0.39 U

DMW-73D

0.39 U

DMW-75D

1.0

DMW-77D

0.39 U

DMW-88D

13.8

DMW-102D

0.39 U

DMW-103D

0.39 U

DMW-108D

14.2

DMW-19D

DMW-26D

DMW-32D

DMW-39D

DMW-41D

DMW-66D

DMW-67D

DMW-79D

DMW-81D

DMW-83D

D oc um en t P at h:

:\U se rs \4

5a ba \O ne D riv e

C S

E ng in ee rs \G

\D av is

_L an df ill

\M X

D \P

R O

\P R

O .a pr x

FIGURE 15

LEVEL "D"

VINYL CHLORIDE CONTAMINATION EXTENT MAP

NOVEMBER 2024

DAVIS CLOSED LANDFILL

MARION COUNTY, FL

Tampa, FL January 2025 ±0 175 350 Feet

Notes:

1.0 Vinyl Chloride Concentration (μg/L)

Legend

Property Boundary

@A Active Monitoring Wells

@A Destroyed Monitoring Wells

Approximate Vinyl Chloride Groundwater Cleanup Target Level (1 µg/L) Iso-contour

DMW-54E

14.6

DMW-89E

1.4

DMW-91E

0.99 I

DMW-111E

0.59 U

DMW-46E

DMW-58E

DMW-64ER

DMW-84E

DMW-90E

DMW-109E

DMW-71E

14.4

DMW-92E

4.2

DMW-68E

DMW-72E

D oc um en t P at h:

:\U se rs \4

5a ba \O ne D riv e

C S

E ng in ee rs \G

\D av is

_L an df ill

\M X

D \P

R O

\P R

O .a pr x

FIGURE 16

LEVEL "E"

1,1-DICHLOROETHENE CONTAMINATION EXTENT MAP

NOVEMBER 2024

DAVIS CLOSED LANDFILL

MARION COUNTY, FL

Tampa, FL January 2025 ±0 175 350 Feet

Notes:

7.0 1,1-Dichloroethene Concentration (μg/L)

Legend

Property Boundary

@A Active Monitoring Wells

Approximate 1,1-Dichloroethene Groundwater Cleanup Target

DMW-54E

0.27 U

DMW-71E

5.1

DMW-89E

0.27 U

DMW-91E

0.27 U

DMW-92E

0.27 U

DMW-111E

0.27 U

DMW-46E

DMW-58E

DMW-64ER

DMW-68E

DMW-72E

DMW-84E

DMW-90E

DMW-109E

D oc um en t P at h:

:\U se rs \4

5a ba \O ne D riv e

C S

E ng in ee rs \G

\D av is

_L an df ill

\M X

D \P

R O

\P R

O .a pr x

FIGURE 17

LEVEL "E"

1,2-DICHLOROETHANE CONTAMINATION EXTENT MAP

NOVEMBER 2024

DAVIS CLOSED LANDFILL

MARION COUNTY, FL

Tampa, FL January 2025 ±0 175 350 Feet

Notes:

3.0 1,2-Dichloroethane Concentration (μg/L)

Legend

Property Boundary

@A Active Monitoring Wells

Approximate 1,2-Dichloroethane Groundwater Cleanup Target

DMW-54E

20.8

DMW-71E

45.5

DMW-89E

0.39 U

DMW-91E

0.39 U

DMW-92E

0.39 U

DMW-111E

1.5

DMW-46E

DMW-58E

DMW-64ER

DMW-68E

DMW-72E

DMW-84E

DMW-90E

DMW-109E

D oc um en t P at h:

:\U se rs \4

5a ba \O ne D riv e

C S

E ng in ee rs \G

\D av is

_L an df ill

\M X

D \P

R O

\P R

O .a pr x

FIGURE 18

LEVEL "E"

VINYL CHLORIDE CONTAMINATION EXTENT MAP

NOVEMBER 2024

DAVIS CLOSED LANDFILL

MARION COUNTY, FL

Tampa, FL January 2025 ±0 175 350 Feet

Notes:

1.0 Vinyl Chloride Concentration (μg/L)

Legend

Property Boundary

@A Active Monitoring Wells

Approximate Vinyl Chloride Groundwater Cleanup Target Level (1 µg/L) Iso-contour

DMW-85F

DMW-105F

0.59 U

DMW-106F

0.59 U

DMW-112F

0.59 U

DMW-113F

0.59 U

DMW-114F

1.9

DMW-104F

DMW-110F

1.5

DMW-86F

16.9

D oc um en t P at h:

:\U se rs \4

5a ba \O ne D riv e

C S

E ng in ee rs \G

\D av is

_L an df ill

\M X

D \P

R O

\P R

O .a pr x

FIGURE 19

LEVEL "F"

1,1-DICHLOROETHENE CONTAMINATION EXTENT MAP

NOVEMBER 2024

DAVIS CLOSED LANDFILL

MARION COUNTY, FL

Tampa, FL January 2025 ±0 175 350 Feet

Notes:

7.0 1,1-Dichloroethene Concentration (μg/L)

Legend

Property Boundary

@A Active Monitoring Wells

Approximate 1,1-Dichloroethene Groundwater Cleanup Target

DMW-85F

0.27 U

DMW-86F

7.6

DMW-105F

0.27 U

DMW-106F

0.27 U

DMW-110F

0.27 U

DMW-112F

0.27 U

DMW-113F

0.27 U

DMW-114F

0.27 U

DMW-104F

D oc um en t P at h:

:\U se rs \4

5a ba \O ne D riv e

C S

E ng in ee rs \G

\D av is

_L an df ill

\M X

D \P

R O

\P R

O .a pr x

FIGURE 20

LEVEL "F"

1,2-DICHLOROETHANE CONTAMINATION EXTENT MAP

NOVEMBER 2024

DAVIS CLOSED LANDFILL

MARION COUNTY, FL

Tampa, FL January 2025 ±0 175 350 Feet

Notes:

3.0 1,2-Dichloroethane Concentration (μg/L)

Legend

Property Boundary

@A Active Monitoring Wells

Approximate 1,2-Dichloroethane Groundwater Cleanup Target

DMW-85F

0.92 I

DMW-86F

1.5

DMW-105F

0.30 U

DMW-106F

0.30 U

DMW-110F

0.30 U

DMW-112F

0.30 U

DMW-113F

0.30 U

DMW-114F

0.30 U

DMW-104F

D oc um en t P at h:

:\U se rs \4

5a ba \O ne D riv e

C S

E ng in ee rs \G

\D av is

_L an df ill

\M X

D \P

R O

\P R

O .a pr x

FIGURE 21

LEVEL "F"

BENZENE CONTAMINATION EXTENT MAP

NOVEMBER 2024

DAVIS CLOSED LANDFILL

MARION COUNTY, FL

Tampa, FL January 2025 ±0 175 350 Feet

Notes:

1.0 Benzene Concentration (μg/L)

Legend

Property Boundary

@A Active Monitoring Wells

Approximate Benzene Groundwater Cleanup Target Level (1 µg/L) Iso-contour

DMW-85F

0.63 I

DMW-86F

96.3

DMW-105F

0.39 U

DMW-106F

0.39 U

DMW-110F

8.3

DMW-112F

18.6

DMW-113F

0.39 U

DMW-114F

2.2

DMW-104F

D oc um en t P at h:

:\U se rs \4

5a ba \O ne D riv e

C S

E ng in ee rs \G

\D av is

_L an df ill

\M X

D \P

R O

\P R

O .a pr x

FIGURE 22

LEVEL "F"

VINYL CHLORIDE CONTAMINATION EXTENT MAP

NOVEMBER 2024

DAVIS CLOSED LANDFILL

MARION COUNTY, FL

Tampa, FL January 2025 ±0 175 350 Feet

Notes:

1.0 Vinyl Chloride Concentration (μg/L)

Legend

Property Boundary

@A Active Monitoring Wells

Approximate Vinyl Chloride Groundwater Cleanup Target Level (1 µg/L) Iso-contour

DMW-107G

8.9

D oc um en t P at h:

:\U se rs \4

5a ba \O ne D riv e

C S

E ng in ee rs \G

\D av is

_L an df ill

\M X

D \P

R O

\P R

O .a pr x

FIGURE 23

LEVEL "G"

1,1-DICHLOROETHENE CONTAMINATION EXTENT MAP

NOVEMBER 2024

DAVIS CLOSED LANDFILL

MARION COUNTY, FL

Tampa, FL January 2025 ±0 175 350 Feet

Notes:

7.0 1,1-Dichloroethene Concentration (μg/L)

Legend

Property Boundary

@A Active Monitoring Wells

Approximate 1,1-Dichloroethene Groundwater Cleanup Target

Tables

Table 1. Summary of Monitoring Well Construction Details Davis Closed Landfill, Marion County, Florida

Top Bottom Top Bottom DMW-2R B 667632.78 1708253.94 S 2/6/2002 2" PVC 97.51 93.66 63.00 66.90 3.85 15 0.01 48.0 63.0 45.61 30.61 NR DMW-3 A 666855.41 1708854.59 S 7/15/1985 2" PVC 107.76 105.09 71.20 73.90 2.67 20 0.01 51.2 71.2 53.86 33.86 NR DMW-4 A 666857.40 1708313.24 S 6/15/1992 2" PVC 112.26 109.12 49.00 52.10 3.14 10 0.01 39.0 49.0 70.16 60.16 20/30 DMW-5 A 667697.52 1709153.33 S 6/12/1992 2" PVC 94.99 94.10 55.00 48.90 -0.22 20 0.01 35.0 55.0 66.09 46.09 20/30 Flush-mount well - TOCE bls DMW-6 B 666796.32 1709546.82 S 6/28/1993 2" PVC 97.61 95.10 64.10 66.60 2.51 10 0.01 54.1 64.1 41.01 31.01 20/30 DMW-7** --- --- --- --- 6/30/1993 2" PVC 97.16 97.60 60.40 60.00 -0.44 10 0.01 50.4 60.4 47.16 37.16 20/30 Abandoned 9/5/1996; flush cover DMW-8** --- --- --- --- 1/26/1999 2" PVC 79.45 76.40 23.00 26.10 3.05 15 0.01 08.0 23.0 68.35 53.35 30/45 Abandoned DMW-9 A 668132.14 1708817.74 S 6/29/1993 2" PVC 99.83 97.10 44.50 47.20 2.74 10 0.01 34.5 44.5 62.63 52.63 20/30 DMW-10 B 667292.15 1709331.00 S 9/5/1996 2" PVC 96.75 96.80 56.00 56.50 0.52 10 0.01 44.0 54.0 50.25 40.25 30/45 Well has 2' silt trap w/ 0.5' PVC tip; replaced DMW-7 DMW-11 B 666698.86 1709639.60 S 9/6/1996 2" PVC 93.83 93.50 59.80 59.60 -0.17 10 0.01 47.3 57.3 44.23 34.23 30/45 Well has 2' silt trap w/ 0.5' PVC tip; flush-mount well - TOCE bls DMW-12R A 667558.02 1708261.07 S 1/17/2002 2" PVC 100.84 97.43 46.60 50.00 3.40 15 0.01 31.6 46.6 65.84 50.84 20/30 DMW-13** --- --- --- --- 1/26/1999 2" PVC 94.27 94.60 40.00 39.70 -0.33 15 0.01 25.0 40.0 69.57 54.57 20/30 Abandoned DMW-14** --- --- --- --- 1/27/1999 2" PVC 93.50 93.80 40.00 39.70 0.30 15 0.01 25.0 40.0 68.80 53.80 20/30 Abandoned DMW-15R C 667708.28 1708255.07 F 1/16/2002 2" PVC 101.06 98.65 86.00 88.90 2.90 15 0.01 71.0 86.0 27.16 12.16 30/45 DMW-16 C 666856.76 1708823.28 F* 2/1/1999 2" PVC 107.62 104.70 103.00 105.90 2.92 10 0.01 93.0 103.0 11.72 1.72 30/45 DMW-17 C 667304.41 1709326.05 F 2/3/1999 2" PVC 96.67 97.20 89.00 89.20 0.18 10 0.01 79.0 89.0 17.47 7.47 30/45 DMW-18 B 667296.18 1709705.85 S 1/18/2002 2" PVC 92.04 89.06 51.80 54.80 2.95 15 0.01 36.8 51.8 52.24 37.24 30/45 DMW-19 D 667297.97 1709334.97 F…

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