Section 40.0953 - Exposures to be Considered in Imminent Hazard EvaluationsThe focus of an Imminent Hazard Evaluation shall be on actual or likely exposures to Human and Environmental Receptors under current site conditions, considering the current use(s) of the disposal site and the surrounding environment, and considering an appropriate short period of time.
(1) The short period of time considered in the evaluation shall be five years, unless site circumstances indicate that a shorter time period is appropriate. The specific time period shall be selected in consideration of the nature of the hazard under investigation and the projected time until a Comprehensive Response Action could be completed, in order to determine the need for an Immediate Response Action.(2) For the evaluation of soil-related exposures, the levels of oil and/or hazardous material at the ground surface or within 12 inches of the ground surface shall be considered in the development of the Exposure Point Concentrations.(3) For the evaluation of drinking water exposures, the levels of oil and/or hazardous material in the groundwater or surface water which serves as the source of the drinking water shall be considered in the development of the Exposure Point Concentrations.(4) Hot Spots shall be the primary, but not exclusive, focus of an Imminent Hazard Evaluation, provided that they are located in areas of actual or likely human exposure under current site conditions.(5) If a small subset of oil and/or hazardous material are likely to dominate the risk estimates based upon their concentration and toxicity, then the Imminent Hazard Evaluation may be limited to those chemicals.(6) As indicated by the site conditions, the Imminent Hazard Evaluation shall consider acute, subchronic and/or chronic exposures to the oil and/or hazardous material. The Exposure Point Concentrations shall be developed to reflect the type of exposure being evaluated. The use of upper percentile or maximum concentrations may be appropriate for certain evaluations, and shall be considered as described at 310 CMR 40.0926.(7) The Imminent Hazard Evaluation shall be conducted in a manner which results in conservative estimates of potential exposures.(8) The documentation of the Imminent Hazard Evaluation shall clearly identify and explain the basis for exposure parameters chosen for the Risk Characterization.Amended by Mass Register Issue 1503, eff. 3/1/2024.Amended by Mass Register Issue S1516, eff. 3/1/2024.