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Risk-Based Closure Guide Draft

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Risk-Based Closure Guide Draft Risk-based Closure Guide July 1, 2021 Office of Land Quality Indiana Department of Environmental Management Disclaimer This Nonrule Policy Document (NPD) is being established by the Indiana Department of Environmental Management (IDEM) consistent with its authority under IC 13-14-1-11.5. It is intended solely as guidance and shall be used in conjunction with applicable rules or laws. It does not replace applicable rules or laws, and if it conflicts with these rules or laws, the rules or laws shall control. Pursuant to IC 13-14-1-11.5, this NPD will be available for public inspection for at least forty-five (45) days prior to presentation to the appropriate State Environmental Board, and may be put into effect by IDEM thirty (30) days afterward. If the NPD is presented to more than one board, it will be effective thirty (30) days after presentation to the last State Environmental Board. IDEM also will submit the NPD to the Indiana Register for publication. 2 Table of Contents 1 Introduction ..................................................................................................................................... 7 1.1 Applicability .............................................................................................................................. 8 1.2 Types of Closure ...................................................................................................................... 9 1.3 Process Overview .................................................................................................................... 10 2 Characterization.............................................................................................................................. 11 2.1 Task One: Identify Release Source(s) ..................................................................................... 15 2.1.1 Basis for Requirement ....................................................................................................... 15 2.1.2 Identifying Release Sources .............................................................................................. 16 2.1.3 How IDEM Will Evaluate Release Source Identifications .................................................. 17 2.2 Task Two: Determine the Nature of Release-related Chemicals............................................. 18 2.2.1 Basis for Requirement ....................................................................................................... 18 2.2.2 Sample Planning ............................................................................................................... 18 2.2.3 General Sampling Guidance ............................................................................................. 22 2.2.4 Sampling Soils ................................................................................................................... 22 2.2.5 Sampling Groundwater ...................................................................................................... 25 2.2.6 Sampling Vapor ................................................................................................................. 27 2.2.7 Sample Handling ............................................................................................................... 39 2.2.8 Sample Analysis ................................................................................................................ 39 2.2.9 Data Reporting .................................................................................................................. 39 2.2.10 Data Evaluation ................................................................................................................. 41 2.2.11 How IDEM Will Evaluate Nature Determinations .............................................................. 42 2.3 Task Three: Determine Extents of Release-related Chemicals ............................................... 43 2.3.1 Basis for Requirement ....................................................................................................... 43 2.3.2 Present Extents: Soil ......................................................................................................... 44 2.3.3 Likely Future Extents: Soil ................................................................................................. 45 2.3.4 Present Extents: Groundwater .......................................................................................... 46 2.3.5 Likely Future Extents: Groundwater .................................................................................. 48 2.3.6 Present Extents: Vapor ...................................................................................................... 52 2.3.7 Likely Future Extents: Vapor ............................................................................................. 56 2.3.8 Extents in Other Media ...................................................................................................... 56 2.3.9 How IDEM Will Evaluate Extents Determinations ............................................................. 57 3 Risk Evaluation ............................................................................................................................... 59 3.1 Task Four: Specify Decision Unit(s) and Their Use(s) ............................................................. 60 3.1.1 Basis for Requirement ....................................................................................................... 60 3.1.2 Specifying Decision Units .................................................................................................. 60 3.1.3 Decision Unit Use(s) .......................................................................................................... 61 3.1.4 How IDEM Will Evaluate Decision Unit and Future Use Specifications ............................ 62 3.2 Task Five: Determine Representative Concentration(s) .......................................................... 63 3.2.1 Basis for Requirement ....................................................................................................... 63 3 3.2.2 Determining Representative Concentrations ..................................................................... 63 3.2.3 How IDEM Will Evaluate Representative Concentration Determinations ......................... 69 3.3 Task Six: Specify Remediation Objectives .............................................................................. 70 3.3.1 Basis for Requirement ....................................................................................................... 70 3.3.2 Using Background Concentrations as Remediation Objectives ........................................ 70 3.3.3 Using IDEM’s Published Levels as Remediation Objectives ............................................ 71 3.3.4 Using Site-specific Levels as Remediation Objectives ..................................................... 76 3.3.5 Using Other Concentration-based Remediation Objectives .............................................. 77 3.3.6 Using Risk Levels as Remediation Objectives .................................................................. 78 3.3.7 How IDEM Will Evaluate Remediation Objective Specifications ....................................... 80 3.4 Task Seven: Determine Whether a Remedy is Necessary ...................................................... 81 3.4.1 Basis for Requirement ....................................................................................................... 81 3.4.2 Remedy Necessity Determinations: General Considerations ........................................... 81 3.4.3 Remedy Necessity Determinations: Lines of Evidence ..................................................... 84 3.4.4 Deciding Whether a Remedy is Necessary for Soil Exposure .......................................... 88 3.4.5 Deciding Whether a Remedy is Necessary for Leaching Potential ................................... 94 3.4.6 Deciding Whether a Remedy is Necessary for Groundwater Exposure ........................... 97 3.4.7 Deciding Whether a Remedy is Necessary for Vapor ....................................................... 102 3.4.8 Deciding Whether a Remedy is Necessary for Other Media ............................................. 105 3.4.9 Risk Characterization ........................................................................................................ 105 3.4.10 How IDEM Will Evaluate Remedy Necessity Determinations ........................................... 106 4 Remedies ........................................................................................................................................ 107 4.1 Task Eight: Select an Adequate Remedy ................................................................................ 108 4.1.1 Basis for Requirement ....................................................................................................... 108 4.1.2 Remedy Selection: General Considerations ..................................................................... 108 4.1.3 Remedy Selection: Statutory Requirements ..................................................................... 108 4.1.4 Remedy Selection: Active Remedies ................................................................................ 110 4.1.5 Remedy Selection: Engineered Exposure Controls .......................................................... 111 4.1.6 Remedy Selection: Institutional Controls ..........................................................................
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