Illinois Administrative Code › Title 35 - ENVIRONMENTAL PROTECTION › Part 742 - TIERED APPROACH TO CORRECTIVE ACTION OBJECTIVES › Subpart F - TIER 2 GENERAL EVALUATION › Section 742.610 - Chemical and Site Properties

Current through Register Vol. 48, No. 28, July 12, 2024
a)
				Physical and Chemical Properties of Contaminants
Tier 2 evaluations require information on the physical and
				  chemical properties of the contaminants of concern. The physical and chemical
				  properties used in a Tier 2 evaluation are contained in Appendix C, Table E. If
				  the site has contaminants not included in this table, a person may request the
				  Agency to provide the applicable physical and chemical input values or may
				  propose input values under Subpart I. If a person proposes to apply values
				  other than those in Appendix C, Table E, or those provided by the Agency, the
				  evaluation shall be considered under Tier 3.
b) Soil and Groundwater Parameters
1) A Tier 2 evaluation requires examination
				of soil and groundwater parameters. The parameters that may be varied, and the
				conditions under which these parameters are determined as part of Tier 2, are
				summarized in Appendix C, Tables B, D, and M. If a person proposes to vary
				site-specific parameters outside of the framework of these tables, the
				evaluation shall be considered under Tier 3.
2) To determine site-specific physical soil
				parameters, a minimum of one boring per 0.5 acre of contamination shall be
				collected. This boring must be deep enough to allow the collection of the
				required field measurements. The site-specific physical soil parameters must be
				determined from the portion of the boring representing the stratigraphic units
				being evaluated. For example, if evaluating the soil component of the
				groundwater ingestion exposure route, two samples from the boring will be
				required:
A) A sample of the predominant soil
				type for the vadose zone; and
B) A
				sample of the predominant soil type for the saturated zone.
3) A site-specific SSL dilution
				factor (used in developing soil remediation objectives based upon the
				protection of groundwater) may be determined by substituting site information
				in Equation S22 in Appendix C, Table A. To make this demonstration, a minimum
				of three monitoring wells shall be used to determine the hydraulic gradient. As
				an alternative, the default dilution factor value listed in Appendix C, Table B
				may be used. If monitoring wells are used to determine the hydraulic gradient,
				the soil taken from the borings shall be visually inspected to ensure there are
				no significant differences in the stratigraphy. If there are similar soil types
				in the field, one boring shall be used to determine the site-specific physical
				soil parameters. If there are significant differences, all of the borings shall
				be evaluated before determining the site-specific physical soil parameters for
				the site.
4) Not all of the
				parameters identified in Appendix C, Tables B, D, and M need to be determined
				on a site-specific basis. A person may choose to collect partial site-specific
				information and use default values as listed in Appendix C, Tables B, D, and M
				for the rest of the parameters.