Final Report
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FINAL REPORT Using Advanced Analysis Approaches to Complete Long-Term Evaluations of Natural Attenuation Processes on the Remediation of Dissolved Chlorinated Solvent Contamination SERDP Project ER-1348 OCTOBER 2008 J. Steven Brauner Douglas C. Downey Ross Miller Parsons Infrastructure and Technology Group TABLE OF CONTENTS Page EXECUTIVE SUMMARY ....................................................................................................... xiv 1.0 INTRODUCTION ........................................................................................................... 1-1 1.1 STUDY OBJECTIVES ........................................................................................ 1-2 1.2 LIMITATIONS ON PROJECT SCOPE .............................................................. 1-3 1.3 DOCUMENT ORGANIZATION ....................................................................... 1-3 2.0 BACKGROUND AND TECHNICAL APPROACH ...................................................... 2-1 2.1 MNA ASSESSMENT AT CAH-IMPACTED SITES: CURRENT STATE-OF-PRACTICE ...................................................................................... 2-1 2.1.1 Existing Regulatory Guidance on MNA Evaluation Requirements ........ 2-1 2.1.2 Previous Investigations of CAH Plume Dynamics and MNA Sustainability............................................................................................ 2-2 2.1.3 Summary of Current Understanding of MNA Processes for CAHs ........ 2-4 2.1.4 Critiques of the Current State-of-Practice ................................................ 2-6 2.2 PROCESS FOR EVALUATING MNA SUSTAINABILITY AT CAH- IMPACTED SITES ............................................................................................. 2-6 2.2.1 Protectiveness and CAH Plume Stability ................................................ 2-7 2.2.2 Estimating Remediation Timeframe ...................................................... 2-10 2.2.3 Evaluation and Prediction of MNA Sustainability ................................ 2-11 3.0 ADVANCED METHODS FOR ASSESSMENT OF MONITORED NATURAL ATTENUATION-BASED REMEDIES .......................................................................... 3-1 3.1 EVALUATING PROTECTIVENESS AND CHLORINATED SOLVENT PLUME STABILITY .......................................................................................... 3-2 3.1.1 Concentration-Based Metrics ................................................................... 3-2 3.1.2 Mass-Based Metrics ................................................................................. 3-3 3.2 ESTIMATING REMEDIATION TIMEFRAMES .............................................. 3-4 3.2.1 Conceptual Models of CAH Sources ....................................................... 3-5 3.2.2 Overview of Modeling Techniques ......................................................... 3-5 3.2.2.1 Mechanistic Modeling of CAH Sources ................................ 3-5 3.2.2.2 Empirical Modeling of CAH Sources .................................... 3-7 3.2.3 Description of Approach ........................................................................ 3-10 4.0 CASE STUDY REVIEWS AND EXAMPLES .............................................................. 4-1 4.1 EVALUATION OF PLUME STABILITY ......................................................... 4-1 4.1.1 Case Study: Site FTA-2, Tinker Air Force Base, Oklahoma ................... 4-3 4.1.1.1 Site Overview and Summary of Available Data .................... 4-3 4.1.1.2 Summary of Historic Plume Stability Assessment ................ 4-8 4.1.1.3 Results of Current Concentration-based Stability Analysis.................................................................................. 4-8 i TABLE OF CONTENTS (continued) Page 4.1.1.4 Results of Current Mass-based Stability Analysis ............... 4-13 4.1.1.5 Plume Stability Analysis Summary ..................................... 4-19 4.1.1.6 Recommendations ................................................................ 4-19 4.1.2 Case Study: LF-06, Columbus Air Force Base, Mississippi ................. 4-20 4.1.2.1 Site Overview and Summary of Available Data .................. 4-20 4.1.2.2 Summary of Historic Plume Stability Assessments ............. 4-24 4.1.2.3 Results of Current Concentration-based Stability Analysis................................................................................ 4-29 4.1.2.4 Results of Current Mass-based Stability Analysis ............... 4-37 4.1.2.5 Plume Stability Analysis Summary ..................................... 4-38 4.1.2.6 Recommendations ................................................................ 4-38 4.1.3 Case Study: SS-45, England Air Force Base, Louisiana ....................... 4-39 4.1.3.1 Site Overview and Summary of Available Data .................. 4-39 4.1.3.2 Summary of Historic Plume Stability Assessments ............. 4-46 4.1.3.3 Results of Current Concentration-based Stability Analysis................................................................................ 4-52 4.1.3.4 Results of Current Mass-based Stability Analysis ............... 4-64 4.1.3.5 Plume Stability Analysis Summary ..................................... 4-75 4.1.3.6 Recommendations ................................................................ 4-75 4.1.4 Facility 1381, Cape Canaveral Air Station, Florida ............................... 4-77 4.1.4.1 Site Overview and Summary of Available Data .................. 4-77 4.1.4.2 Summary of Historic Plume Stability Assessments ............. 4-84 4.1.4.3 Results of Current Concentration-based Stability Analysis................................................................................ 4-87 4.1.4.4 Results of Current Mass-based Stability Analysis ............... 4-94 4.1.4.5 Plume Stability Analysis Summary ................................... 4-102 4.1.4.6 Recommendations .............................................................. 4-103 4.1.5 Case Study: Site FPTA-2, Brooks City-Base, Texas ........................... 4-103 4.1.5.1 Site Overview and Summary of Available Data ................ 4-103 4.1.5.2 Summary of Historic Plume Stability Assessment ............ 4-109 4.1.5.3 Results of Concentration-Based Stability Analysis ........... 4-112 4.1.5.4 Results of Current Mass-based Stability Analysis ............. 4-122 4.1.5.5 Plume Stability Analysis Summary ................................... 4-130 4.1.5.6 Recommendations .............................................................. 4-131 4.2 ESTIMATES OF REMEDIATION TIMEFRAME ........................................ 4-132 4.2.1 Review of Source Models Used in Previous Modeling Efforts ........... 4-132 4.2.2 Comparison of Predicted and Measured Source Area Concentrations ..................................................................................... 4-134 4.2.2.1 Case Study: Operable Unit 1, Altus AFB, Oklahoma ....... 4-134 4.2.2.2 Case Study: Facility 1381, Cape Canaveral AFS, Florida ................................................................................ 4-137 4.2.2.3 Case Study: Site FTA-2, Tinker AFB, Oklahoma ............. 4-140 ii TABLE OF CONTENTS (continued) Page 4.2.2.4 Summary of Remediation Timeframe Case Study Results ................................................................................ 4-143 5.0 SUMMARY AND RECOMMENDATIONS.................................................................. 5-1 5.1 PLUME STABILITY ASSESSMENTS .............................................................. 5-1 5.2 REMEDIATION TIMEFRAME ESTIMATES .................................................. 5-8 5.3 EVAULATION AND PREDICTION OF MNA SUSTAINABILITY ............. 5-10 6.0 REFERENCES ................................................................................................................ 6-1 APPENDIX A MATHEMATICAL DESCRIPTION OF METHODS FOR EVALUATING THE STABILITY OF CONTAMINANT PLUMES DISSOLVED IN GROUNDWATER APPENDIX B REVIEW OF CAH SOURCE DEPLETION PROCESSES AND SOURCE DECAY MODELS OFFERED IN SELECTED SOFTWARE PACKAGES APPENDIX C CASE STUDY DATA AND STATISTICAL ANALYSIS RESULTS APPENDIX D SELECTED FIGURES FROM PREVIOUS STUDIES AT CASE STUDY SITES APPENDIX E TECHNICAL REPORT: USING ADVANCED ANALYSIS APPROACHES TO COMPLETE LONG-TERM EVALUATIONS OF NATURAL ATTENUATION PROCESSES ON THE REMEDIATION OF DISSOLVED CHLORINATED SOLVENT CONTAMINATION iii This page left blank intentionally. LIST OF FIGURES Page Figure 2.1 Conceptual Framework for Assessing Appropriateness of MNA-Based Remedies at CAH-Impacted Sites. ...................................................................... 2-8 Figure 2.2 Schematic Representation of a Method for Estimating Duration of Organic Carbon/Electron Donor Control of Local Redox Conditions ............................ 2-13 Figure 3.1 Conceptual Model of Mechanisms Affecting DNAPL Migration and Dissolution ........................................................................................................... 3-6 Figure 4.1 Concentration of TCE in Upper USZ Groundwater August 1997 and April 1999 Site FTA-2, Tinker AFB, Oklahoma. ......................................................... 4-5 Figure 4.2 Concentration of cis-1,2-DCE in Upper USZ Groundwater August 1997 and April 1999 Site FTA-2, and Tinker AFB, Oklahoma. ......................................... 4-6 Figure 4.3 Statistical Trend Analysis Results, Site FTA-2, Tinker AFB, Oklahoma. ........ 4-11 Figure 4.4 Model Domain and Common Wells for Mass-Based Calculations Site FTA- 2, Tinker AFB, Oklahoma ................................................................................