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Indiana Department of Environmental Management Releases Final Remediation Guidance


On March 22, 2012, the Indiana Department of Environmental Management (IDEM) released final versions of the long-anticipated revisions to the agency’s risk-based remediation site investigation and closure guidance.  The revised guidance consists of the Remediation Closure Guide (RCG) which includes significant revisions to the procedures for the investigation, remedy selection and risk-based closure of contaminated sites managed under various IDEM remediation programs and the separate Remediation Program Guide (RPG) which provides general information and program-specific administrative information regarding processes and procedures IDEM will use in its remedial programs as well as standard forms and reporting information to be used when submitting information to IDEM.  The RCG and RPG will replace IDEM’s Risk Integrated System of Closure (RISC) Technical Guide (RISC Tech Guide) and RISC User’s Guide currently being used as guidance for IDEM’s site remediation programs. 

The RCG and RPG contain significant changes to IDEM’s approach to risk-based site investigation and closure and generally provide increased flexibility to responsible parties in addressing contaminated property.  The following is a summary of some important changes to IDEM’s site investigation and closure procedures effected by the RCG and RPG.

Conceptual Site Model Development

The RCG focuses on the development of a Conceptual Site Model (CSM) to guide contaminated site investigations and closures.  According to the RCG, CSM development is intended to facilitate site understanding and help organize site activities.  While the RISC Tech Guide includes guidance regarding the development of CSMs, the RCG places greater emphasis on the importance of CSM development and the related site characterization activities which form the basis of all subsequent decisions regarding remedy selection and risk-based closure.  The RCG requires parties conducting site investigations and risk-based closures to develop a CSM through the collection of pre-sampling information similar to information gathered during the performance of a Phase I Environmental Site Assessment, collection of sampling data, analysis of groundwater plume behavior, consideration of and sampling (if necessary) related to vapor intrusion, and the consideration of and sampling (if necessary) related to background contaminant levels and off-site contaminant sources.

By emphasizing the development of a CSM, the RCG encourages parties undertaking the investigation and risk-based closure of contaminated properties to focus on site-specific exposure pathways and to avoid the investigation of exposure pathways that do not warrant investigation based on a rigorous risk analysis.  The RCG’s focus on CSM development also provides a more flexible approach to site investigation and characterization than the RISC Tech Guide which involved a more prescriptive approach and required initial site investigations to be conducted in the same manner for all sites regardless of exposure pathways.  Because the RISC Tech Guide’s investigation process did not account for site-specific factors, site investigation under the new guidance may result in reduced or eliminated expenses.  The RCG approach to site investigation and CSM development allows for greater flexibility and promotes the use of professional technical judgment by both IDEM and environmental professionals.

Incorporation of the Requirements of House Enrolled Act (HEA) 1162

The RCG incorporates provisions consistent with the requirements set forth under HEA 1162.  HEA 1162 was enacted by the Indiana General Assembly in 2009 in order to provide a clearer statutory directive to IDEM that remedial activities be driven by risk-based remedies and that IDEM recognize institutional controls that limit or eliminate exposure pathways in making closure determinations.  The components of HEA 1162 incorporated directly into the RCG include:

  • The statutory definition of environmental restrictive covenant (ERC), specific guidance regarding how IDEM’s review of ERCs is limited to determining whether the ERC meets the statutory definition and whether the use restrictions are appropriate, how ERCs must be recorded and how ERCs may be modified or terminated;
  • The statutory definition of environmental restrictive ordinance (ERO), specific guidance regarding how IDEM is required to consider and evaluate proposals to rely on EROs as part of a risk-based closure, and notification of IDEM regarding the passage, amendment or repeal of an ERO;
  • The consideration of land use remediation objectives when requiring determinations of the nature and extent of contamination; and
  • The incorporation of an express acknowledgment that remediation site closure may be obtained with ongoing obligations related to active remediation systems and maintenance of engineering and/or institutional controls.

Site Delineation

The RCG introduces several concepts related to site delineation that are not provided for under the RISC Tech Guide.  Although site delineation remains an iterative process typically conducted through step-out sampling procedures, the RCG allows for on-site delineation to be limited to only that delineation necessary to evaluate all potential exposure pathways identified in the CSM and demonstrate that contaminants do not leave the site’s Exposure Control Area (ECA) at concentrations exceeding residential remedial objectives.  An ECA is defined under the RCG as “an area over which a remedy reduces exposure to an acceptable level.  An exposure control area can be, but often is not, the same as an area of property control, it may involve multiple properties and multiple owners.”  RCG at 197.

With regard to soil delineation, the RCG further specifies that vertical delineation of soil is only required “as far as necessary for development of the CSM and evaluation of exposure scenarios, and to provide any information needed for other purposes, such as remedial design.”  Id at 40.  With regard to vertical delineation of ground water, the “vertical delineation of ground water contamination below the first water bearing unit may or may not be necessary, depending on potential contaminant and site characteristics.”  Id. 

The RCG’s approach to delineation differs from the more rigid RISC Tech Guide which requires horizontal and vertical delineation of contamination to residential closure levels regardless of the existence of exposure routes and migration pathways.  In addition, the RISC Tech Guide does not provide for the ECA concept.  The RISC Tech Guide typically requires that contamination extending beyond a site’s boundaries to an off-site area be delineated and remediated to below applicable residential closure levels.  The RCG’s ECA concept allows for a responsible party to make a demonstration, based on lines of evidence (LOEs), that delineation to residential remedial objectives is not necessary even where contamination extends off-site or beyond the ECA.  Through the use of the ECA concept and consideration of LOEs, the RCG incorporates a significantly more site-specific and flexible approach to site investigation than that prescribed by the RISC Tech Guide.

To view a complete PDF of the March/April 2012 issue of the Environmental Letter, click HERE.

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