At 1:30 pm today, Tuesday February 21, 2012, the Indiana Department of Environmental Management (IDEM) intends to present its Remediation Closure Guide and Remediation Program Guide to the Indiana Solid Waste Management Board. This will mark the final step in the two-year process undertaken by IDEM, with private industry input, to overhaul their subsurface environmental investigation and remediation Non-Rule Policy guidance.
The soon to be replaced Risk Integrated System of Closure, or RISC program, has been in effect since February 2001 and has provided default cleanup levels for soil and groundwater in both residential and commercial/industrial scenarios in cookbook fashion. Groundwater levels were established largely on health-based levels deemed safe for human consumption in residential and industrial exposure scenarios. Soil levels were established primarily on the most conservative of direct contact, ingestion or migration to groundwater pathways, the latter of which was typically selected as default.
The RISC Residential Default Closure Levels (RDCLs) and the Industrial Default Closure Levels (IDCLs) have provided distinguishable targets for site screening activities and the development of remedial action objectives over the past decade or so. By matching the desired land use with the corresponding soil and groundwater RDCL or IDCL presented in the RISC program, the amount of cleanup work necessary at individual sites was fairly evident in RISC default approach.
With the arrival of the Remediation Closure Guide tomorrow, February 22, 2012, the process by which many property owners evaluate the level of risk associated with impacts at their site has changed fundamentally. While groundwater screening levels remain intact (with appropriate updates based on recently updated toxicological information from EPA), the soil to groundwater migration pathway has been eliminated from consideration as a driver for establishing soil screening levels for volatile organic compounds; replaced instead with a series of “Rules of Thumb”. Direct measurement of the soil to groundwater leaching pathway can also be conducted on a site-specific basis via the synthetic precipitation leaching procedure (SPLP).
It appears that the intended purpose of the new Remediation Closure Guide is to provide a less rigid approach to assessing and cleaning up environmental remediation sites in light of intended future land use, real-world risk caused by impacts and the tolerability of land use restrictions in support of site closure. While the Remediation Closure Guide still provides guidance for site investigations and cleanups in the same cookbook style as its RISC predecessor, the recipe seems considerably more complex.
Check for the latest developments on this topic, including the incorporation of vapor intrusion assessment guidelines, in the Announcements section of the EnviroForensics Homepage.