Section 742.225  Demonstration of Compliance with Soil and Groundwater Remediation Objectives

Compliance with soil and groundwater remediation objectives is achieved if each sample result does not exceed that respective remediation objective unless a person elects to proceed under subsections (c), (d) and (e).

a)         Compliance with groundwater remediation objectives developed under Subparts D through F and H through I shall be demonstrated by comparing the contaminant concentrations of discrete samples at each sample point to the applicable groundwater remediation objective.   Sample points shall be determined by the program under which remediation is performed.

b)         Unless the person elects to composite samples or average sampling results as provided in subsections (c) and (d), compliance with soil remediation objectives developed under Subparts D through G and I shall be demonstrated by comparing the contaminant concentrations of discrete samples to the applicable soil remediation objective.

1)         Except as provided in subsections (c) and (d), compositing of samples is not allowed.

2)         Except as provided in subsections (c) and (d), averaging of sample results is not allowed.

3)         Notwithstanding subsections (c) and (d), compositing of samples and averaging of sample results is not allowed for the construction worker population.

4)         The number of sampling points required to demonstrate compliance is determined by the requirements applicable to the program under which remediation is performed.

c)         If a person chooses to composite soil samples or average soil sample results to demonstrate compliance relative to the soil component of the groundwater ingestion exposure route, the following requirements apply:

1)         A minimum of two sampling locations for every 0.5 acre of contaminated area is required, with discrete samples at each sample location obtained at every two feet of depth, beginning at six inches below the ground surface for surface contamination and at the upper limit of contamination for subsurface contamination and continuing through the zone of contamination.  Alternatively, a sampling method may be approved by the Agency based on an appropriately designed site-specific evaluation.  Samples obtained at or below the water table shall not be used in compositing or averaging.

2)         For contaminants of concern other than volatile chemicals:

A)        Discrete samples from the same boring may be composited; or

B)        Discrete sample results from the same boring may be averaged.

3)         For volatile chemicals:

A)        Compositing of samples is not allowed.

B)        Discrete sample results from the same boring may be averaged.

4)         Composite samples may not be averaged.  An arithmetic average may be calculated for discrete samples collected at every two feet of depth through the zone of contamination as specified in subsection (c)(1).

d)         If a person chooses to composite soil samples or average soil sample results to demonstrate compliance relative to the outdoor inhalation exposure route or ingestion exposure route, the following requirements apply:

1)         A person shall submit a sampling plan for Agency approval, based upon a site-specific evaluation;

2)         For volatile chemicals, compositing of samples is not allowed;

3)         All samples shall be collected within the contaminated area;

4)         Composite samples may not be averaged.  Procedures specified in "Calculating Upper Confidence Limits for Exposure Point Concentrations at Hazardous Waste Sites", USEPA Office of Emergency and Remedial Response, OSWER 9285.6-10 (December 2002), as incorporated by reference in Section 742.210, or an alternative procedure approved by the Agency, shall be used to determine sample averages.

e)         When averaging under this Section, if no more than 15% of sample results are reported as "non-detect", "no contamination", "below detection limits", or similar terms, such results shall be included in the averaging calculations as one-half the reported analytical detection limit for the contaminant.  However, when performing a test for normal or lognormal distribution for the purpose of calculating a 95% Upper Confidence Limit of the mean for a contaminant, a person may substitute for each non-detect value a randomly generated value between, but not including, zero and the reported analytical detection limit.  If more than 15% of sample results are "non-detect", procedures specified in "Guidance for Data Quality Assessment, Practical Methods for Data Analysis, EPA QA/G-9, QA00 Update", EPA/600/R-96/084 (July 2000), as incorporated by reference in Section 742.210, or an alternative procedure approved by the Agency shall be used to address the non-detect values, or another statistically valid procedure approved by the Agency may be used to determine an average.

f)         All soil samples collected after August 15, 2001 shall be reported on a dry weight basis for the purpose of demonstrating compliance, with the exception of the TCLP and SPLP and the property pH.

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