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Geophysical Investigations of Contaminants at Anniston Army Depot and Fort Campbell

This case study delves into the geophysical methods employed at Anniston Army Depot and Fort Campbell to assess the presence and behavior of contaminants such as LNAPL and DNAPL within complex karst geology. It outlines the issues, goals, and methodologies applied, including seismic refraction, resistivity tomography, and downhole surveys, while addressing challenges posed by noise and complex geological structures. The study aims to refine geologic models, locate fracture zones, and provide critical information for effective remediation strategies to enhance environmental stewardship.

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Geophysical Investigations of Contaminants at Anniston Army Depot and Fort Campbell

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  1. GEOPHYSICSINCANTONMENT AREAS Seismic Case Studies: Anniston Army Depot Fort Campbell By: M.D. Thompson (ANL), W.A. Mandell (AEC) S.F. Miller (ANL), J.M. Cooper (ANL)

  2. Site Locations • ANAD FTC - Karst Geology - DNAPL and LNAPL Contaminants - Industrial Area & Active Airfield

  3. Overview • Issues Goals • Methodology • Case Studies • Anniston Army Depot (ANAD) • Campbell Army Airfield (CAAF) • Conclusions

  4. Concerns & Issues • LNAPL (fuels) & DNAPL (solvents) • Spiller, dumped, and are still in use. Where did they go and where did they come from? • Technical Feasibility • Once found, can they be remediated • Other Environmental Impacts • Land stewardship, land use • COSTS • Your’e taking bullets from my troops

  5. General Goals • Ideal Description of Karst • Reduce Drilling and Investigative Costs • Verification of Geotechnical Models

  6. Ideal Description of Karst • Fracture and Void Systems • Bedding Planes • Weathered Zones • Routes of Entry and Exit

  7. Geophysical Methods • Seismic Refraction • Top of “competent” bedrock • Top of epikarst? • Top of Saturated zone? • 2D Resistivity Tomography • Top of bedrock and epikarst • Bedrock fractures and cavities • EM Terrain-Conductivity • Clay-filled fracture systems • Downhole Surveys • Constrain surface models

  8. Refraction Method

  9. Refraction Targets • Bedrock Surface • Changes in Topography • Pinnacles, Depressions • Velocity Changes • Weak/Competent Zones • Fractured Intervals

  10. Refraction: Road Blocks • Noisy Environment • Sumps, Fans, Traffic • Difficult Medium • Road/Foundation Design • Low Signal Levels • Complex Geology

  11. Refraction: Solutions • Brute Force • High-energy Source • Survey Design • Source Location • Receiver-Ground Coupling • Target Parameters • Modify Instrumentation • Work Off Hours

  12. Anniston Army Depot Valley and Ridge Province Thrust Faulted Area Knox Group Dolomites

  13. ANAD: Geology • Knox Gp. Dolomites • Karst, Developed Void System • Structural Setting • Jacksonville Thrust Fault • Folded/Tilted Strata • Complex Geology • Fractured Rock

  14. ANAD: Problems • TCE and Chrome Contamination • Monitoring wells were set based on auger refusal • Heavily fractured rock • Groundwater controlled by geologic structure?

  15. ANAD: Refraction Surveys Data Acquired in the SIA Augment Existing Borings Bedrock Topography

  16. SE Boundary Profile

  17. ANAD: Refraction Surveys

  18. ANAD: Bedrock Surface

  19. ANAD: Bedrock Surface

  20. ANAD: Bedrock Velocity

  21. Fort Campbell: CAAF Views

  22. Fort Campbell

  23. Fort Campbell: Geology • St. Louis Limestone • Remnants of St. Genevieve • Cavity/Void Development • Structural Setting • Horizontal Strata • Minor Faulting • Karst System

  24. Fort Campbell: Objectives • Map the Bedrock Surface • Locate Fractures Zones • Refine the Geologic Framework • Provide Support Information

  25. Fort Campbell: Problems • Jet Fuels (JP-4) Spilled • Don’t know where fuel went! • Solvents in Sub-surface? • Carbonate Bedrock • Fractured & Cavernous Carbonate • Weathered Zone

  26. FTC: Conceptual Models

  27. Campbell Army Airfield

  28. FTC: Resistivity Profiles

  29. FTC: Resistivity Model

  30. FractureZones Resistivity Interpretation

  31. Resistivity Ground Truth

  32. CAAF: UFFS

  33. CAAF: Refraction Models

  34. CAAF: Bedrock Surface

  35. CAAF: Difference Map

  36. Conclusions • Map Bedrock Lows/Highs • Map Potential Weak Zones • Overcome Noisy Background

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