Illinois Administrative Code › Title 35 - ENVIRONMENTAL PROTECTION › Part 742 - TIERED APPROACH TO CORRECTIVE ACTION OBJECTIVES › Subpart G - TIER 2 SOIL AND SOIL GAS EVALUATION › Section 742.715 - RBCA Soil Equations

Current through Register Vol. 48, No. 28, July 12, 2024
a) This
				Section presents the RBCA model and describes the equations and parameters used
				to develop Tier 2 soil remediation objectives.
b) Ingestion, Outdoor Inhalation, and Dermal
				Contact
1) The two sets of equations in
				subsections (b)(2) and (b)(3) shall be used to generate Tier 2 soil remediation
				objectives for the combined ingestion, outdoor inhalation, and dermal contact
				with soil exposure routes.
2)
				Combined Exposure Routes of Soil Ingestion, Outdoor Inhalation of Vapors and
				Particulates, and Dermal Contact with Soil
A)
				Equations R1 and R2 form the basis for deriving Tier 2 remediation objectives
				for the set of equations that evaluates the combined exposure routes of soil
				ingestion, outdoor inhalation of vapors and particulates, and dermal contact
				with soil using the RBCA approach. Equation R1 is used to calculate soil
				remediation objectives for carcinogenic contaminants. Equation R2 is used to
				calculate soil remediation objectives for noncarcinogenic contaminants. Soil
				remediation objectives for the outdoor inhalation exposure route from
				subsurface soils must also be calculated in accordance with the procedures
				outlined in subsection (b)(3) of this Section and compared to the values
				generated from Equations R1 or R2. The smaller value (i.e., R1 and R2 compared
				to R7 and R8, respectively) from these calculations is the Tier 2 soil
				remediation objective for the combined exposure routes of soil ingestion,
				outdoor inhalation, and dermal contact with soil.
B) In Equation R1, numerical values are
				calculated for two parameters:
i) The
				volatilization factor for surficial soils (VFss) using
				Equations R3 and R4; and
ii) The
				volatilization factor for surficial soils regarding particulates
				(VFp) using Equation R5.
C) VFss uses Equations
				R3 and R4 to derive a numerical value. Equation R3 requires the use of Equation
				R6. Both equations must be used to calculate the VFss.
				The lowest calculated value from these equations must be substituted into
				Equation R1.
D) The remaining
				parameters in Equation R1 have either default values listed in Appendix C,
				Table D or toxicological-specific information (i.e.,
				SFo, SFi), which can be obtained
				by following the guidelines in OSWER Directive 9285.7 -53, as incorporated by
				reference in Section
				742.210
				or requested from the program under which the remediation is being
				performed.
E) For Equation R2, the
				parameters VFss and VFp are
				calculated. The remaining parameters in Equation R2 have either default values
				listed in Appendix C, Table D or toxicological-specific information (i.e.,
				RfDo, RfDi), which can be
				obtained by following the guidelines in OSWER Directive 9285.7-53, as
				incorporated by reference in Section
				742.210
				or requested from the program under which the remediation is being
				performed.
F) For chemicals other
				than inorganics which do not have default values for the dermal absorption
				factor (RAFd) in Appendix C, Table D a dermal absorption
				factor of 0.5 shall be used for Equations R1 and R2. For inorganics, dermal
				absorption may be disregarded (i.e., RAFd =
				0).
3) Outdoor
				Inhalation Exposure Route from Subsurface Soils (soil below one meter)
A) Equations R7 and R8 form the basis for
				deriving Tier 2 remediation objectives for the outdoor inhalation exposure
				route from subsurface soils using the RBCA approach. Equation R7 is used to
				calculate soil remediation objectives for carcinogenic contaminants. Equation
				R8 is used to calculate soil remediation objectives for noncarcinogenic
				contaminants.
B) For Equation R7,
				the carcinogenic risk-based screening level for air
				(RBSLair) and the volatilization factor for soils below
				one meter to ambient air (VFsamb) have numerical values
				that are calculated using Equations R9 and R11, respectively. Both equations
				rely on input parameters from a variety of sources.
C) The noncarcinogenic risk-based screening
				level for air (RBSLair) and the volatilization factor
				for soils below one meter to ambient air (VFsamb) in
				Equation R8 have numerical values that can be calculated using Equations R10
				and R11, respectively.