Section 742.610  Chemical and Site Properties

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.

(Source:  Amended at 37 Ill. Reg. 7506, effective May 15, 2013)