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Indiana Department of Environmental Management

IDEM > Environmental Cleanup > Risk-based Closure > Risk-based Closure: Frequently Asked Questions Risk-based Closure: Frequently Asked Questions

Table of Contents

General

  1. IDEM guidance references an out of date U.S. EPA guidance document. Does IDEM request contractors to follow the referenced guidance or a newer version?
  2. Has Indiana adopted the Remediation Closure Guide by rule? Or is it still simply guidance?

Sample Collection/Analysis

  1. For RCRA unit closure risk assessments, what guidance do you provide to evaluate hot spots?

Screening Levels

  1. When will IDEM update its screening levels table?
  2. How does IDEM calculate its screening levels?
  3. Is it possible to get either a spreadsheet or database file of IDEM’s default closure and/or screening levels?
  4. Are IDEM's screening levels approved by U.S. EPA?

General

  1. IDEM guidance references an out of date U.S. EPA guidance document. Does IDEM request contractors to follow the referenced guidance or a newer version?
    • The most recent version is acceptable.
  2. Has Indiana adopted the Remediation Closure Guide by rule? Or is it still simply guidance?
    • The Remediation Closure Guide is a non-rule Policy Document and has not been adopted by rule. If the Remediation Closure Guide conflicts with a statute or rule, the statute or rule controls.

Sample Collection/Analysis

  1. For RCRA unit closure risk assessments, what guidance do you provide to evaluate hot spots?
    • Hot spots can be evaluated in a number of ways:
      1. You can establish a simple grid system over the source area and randomly sample within the grid. The results can be averaged using the UCL calculation contained in the Remediation Closure Guide.
      2. Another option (for the migration to groundwater pathway) is to calculate weighted averages using multiple sampling intervals within each boring. There are 2 options here:
        1. divide the vertical column into equal increments, sample each increment and average the results, or
        2. divide the vertical column into increments based upon stratigraphy, and calculate a length-weighted mean for the boring.

Screening Levels

  1. When will IDEM update its screening levels table?
    • IDEM intends to update its screening levels table every January.
  2. How does IDEM calculate its screening levels?
    • IDEM derives its screening levels from the U.S. Environmental Protection Agency's Regional Screening Level (RSL) Table. IDEM's screening levels are often different from those found in the RSL Table. Appendix A of the Remediation Closure Guide describes the specific procedures that IDEM uses to derive its screening levels.
  3. Is it possible to get either a spreadsheet or database file of IDEM’s default closure and/or screening levels?
  4. Are IDEM's screening levels approved by U.S. EPA?
    • No. U.S. EPA has neither approved nor disapproved of IDEM's screening levels.

For More Information

If you have questions regarding risk-based closure, please see the Contact about Risk webpage.