Illinois Administrative Code › Title 35 - ENVIRONMENTAL PROTECTION › Part 742 - TIERED APPROACH TO CORRECTIVE ACTION OBJECTIVES › Subpart A - INTRODUCTION › Section 742.110 - Overview of Tiered Approach

Current through Register Vol. 48, No. 28, July 12, 2024
a)
				This Part presents an approach for developing remediation objectives (see
				Appendix A, Illustrations A and B) that include an option for exclusion of
				pathways from further consideration, use of area background concentrations as
				remediation objectives and three tiers for selecting applicable remediation
				objectives. An understanding of human exposure routes is necessary to properly
				conduct an evaluation under this approach. In some cases, applicable human
				exposure routes can be excluded from further consideration prior to any tier
				evaluation. Selecting which tier or combination of tiers to be used to develop
				remediation objectives is dependent on the site-specific conditions and
				remediation goals. Tier 1 evaluations and Tier 2 evaluations are not
				prerequisites to conducting Tier 3 evaluations.
b) A Tier 1 evaluation compares the
				concentration of contaminants detected at a site to the corresponding
				remediation objectives for residential and industrial/ commercial properties
				contained in Appendix B, Tables A, B, C, D, E, G, H and I. To complete a Tier 1
				evaluation, the extent and concentrations of the contaminants of concern, the
				groundwater class, the land use classification, human exposure routes at the
				site, and, if appropriate, soil pH, must be known. If remediation objectives
				are developed based on industrial/commercial property use, then institutional
				controls under Subpart J are required. For the indoor inhalation exposure
				route, institutional controls under Subpart J are required to use remediation
				objectives in Appendix B, Table H or Table I.
c) A Tier 2 evaluation uses the risk based
				equations from the Soil Screening Level (SSL) model, Risk Based Corrective
				Action (RBCA) model and modified Johnson and Ettinger (J&E) model documents
				listed in Appendix C, Tables A, C and L, respectively. In addition to the
				information that is required for a Tier 1 evaluation, site-specific information
				is used to calculate Tier 2 remediation objectives. As in Tier 1, Tier 2
				evaluates residential and industrial/commercial properties only. If remediation
				objectives are developed based on industrial/commercial property use, then
				institutional controls under Subpart J are required. For the indoor inhalation
				exposure route, institutional controls under Subpart J are required to develop
				remediation objectives pursuant to Appendix C, Table L.
d) A Tier 3 evaluation allows alternative
				parameters and factors, not available under a Tier 1 or Tier 2 evaluation, to
				be considered when developing remediation objectives. Remediation objectives
				developed for conservation and agricultural properties can only be developed
				under Tier 3.
e) Remediation
				objectives may be developed using area background concentrations or any of the
				three tiers if the evaluation is conducted in accordance with applicable
				requirements in Subparts D through I. When contaminant concentrations do not
				exceed remediation objectives developed under one of the tiers or area
				background procedures under Subpart D, further evaluation under any of the
				other tiers is not required.