Tier 3 Evaluation Overview

Section 742 Section 742.900  Tier 3 Evaluation Overview a)         Tier 3 sets forth a flexible framework to develop remediation objectives outside of the requirements of Tiers 1 and 2.  Although Tier 1 and Tier 2 evaluations are not prerequisites to conduct Tier 3 evaluations, data from Tier 1 and Tier 2 can assist in developing remediation objectives under a Tier 3 evaluation. b)         The level of detail required to adequately characterize a site depends on the particular use of Tier 3.  Tier 3 can require additional investigative efforts beyond those described in Tier 2 to characterize the physical setting of the site.  However, in situations where remedial efforts have simply reached a physical obstruction additional investigation may not be necessary for a Tier 3 submittal. c)         Situations that can be considered for a Tier 3 evaluation include, but are not limited to: 1)         Modification of parameters not allowed under Tier 2; 2)         Use of models different from those used in Tier 2; 3)         Use of additional site data, such as results of indoor air sampling, to improve or confirm predictions of exposed receptors to contaminants of concern; 4)         Analysis of site-specific risks using formal risk assessment, probabilistic data analysis, and sophisticated fate and transport models (e.g., requesting a target hazard quotient greater than 1 or a target cancer risk greater than 1 in 1,000,000); 5)         Requests for site-specific remediation objectives because an assessment indicates further remediation is not practical; 6)         Incomplete human exposure pathways not excluded under Subpart C; 7)         Use of toxicological-specific information not available from the sources listed in Tier 2; 8)         Land uses which are substantially different from the assumed residential or industrial/commercial property uses of a site (e.g., a site will be used for recreation in the future and cannot be evaluated in Tier 1 or 2); 9)         Requests for site-specific remediation objectives that exceed Tier 1 groundwater remediation objectives so long as the following is demonstrated: A) To the extent practical, the exceedance of the groundwater quality standard has been minimized and beneficial use appropriate to the groundwater that was impacted has been returned; and B) Any threat to human health or the environment has been minimized [415 ILCS 5/58.5(d)(4)(A)]; and 10)         Use of building control technologies, other than those described in Subpart L, to prevent completion of the indoor inhalation exposure route. d)         For requests of a target cancer risk ranging between 1 in 1,000,000 and 1 in 10,000 at the point of human exposure or a target hazard quotient greater than 1 at the point of human exposure, the requirements of Section 742.915 shall be followed.  Requests for a target cancer risk exceeding 1 in 10,000 at the point of human exposure are not allowed. e)         Requests for approval of a Tier 3 evaluation must be submitted to the Agency for review under the specific program under which remediation is performed.  When reviewing a submittal under Tier 3, the Agency shall consider whether the interpretations and conclusions reached are supported by the information gathered [415 ILCS 58.7(e)(1)].  The Agency shall approve a Tier 3 evaluation if the person submits the information required under this Part and establishes through such information that public health is protected and that specified risks to human health and the environment have been minimized. f)         If contaminants of concern include polychlorinated biphenyls (PCBs), requests for approval of a Tier 3 evaluation must additionally address the applicability of 40 CFR 761.