Section 40.0904 - Site Information Required for Risk CharacterizationAn adequate characterization of the disposal site is a prerequisite to the characterization of risk of harm to health, safety, public welfare and the environment, although the appropriate type and amount of information required to complete a Risk Characterization will depend on the unique characteristics of a release and/or disposal site. Particular attention shall be paid to the following site assessment parameters:
(1)Physical Characteristics The physical characteristics of the disposal site including, but not limited to, the topography, geology, hydrogeology, and surface characteristics shall be evaluated as warranted by release and site conditions and described in sufficient detail to support the Risk Characterization.(2)Extent of Release The documentation of the Risk Characterization shall contain a description of the source and extent of the release of the oil and/or hazardous material including, where appropriate: (a) the horizontal and vertical extent and concentrations of oil and/or hazardous material in all evaluated media;(b) background concentrations of oil and/or hazardous material in all evaluated media; and(c) all existing or potential Migration Pathways including, but not limited to: soil, groundwater, soil gas, surface water, air, sediment and the food web. The potential for oil and/or hazardous material migration along preferential pathways such as utility lines or corridors must be evaluated, where applicable. Concentrations of oil and hazardous material in the sediment and/or surface water must be measured in any of the following circumstances to determine whether such material at or from the site has been or is being transported in a manner that would result in surface water or sediment concentrations of potential ecological significance, unless the need for such measurements is obviated by a technical justification consistent with 310 CMR 40.0193: 1. Hazardous materials at or from the site, excluding VOCs, are present in groundwater within 200 feet of a surface water body;2. Hazardous materials at or from the site, excluding VOCs, are present in the groundwater at concentrations higher than the GW-3 standard(s) within 500 feet of a surface water body;3. Nonaqueous Phase Liquid (NAPL) at or from the site is present within 200 feet of a surface water body;4. Historical evidence indicates past discharge or dumping of oil or hazardous material from the site to the surface water body, unless such discharges were permitted;5. Evidence indicates current or past runoff of oil or hazardous material from or with site soil into the surface water body; and6. Site-specific conditions indicate that oil or hazardous material from the site may reasonably be expected to be present in the sediment or surface water at concentrations of potential ecological significance.(3)Characterization of the Oil and/or Hazardous Material. The documentation of the Risk Characterization shall describe the oil and/or hazardous material at the disposal site including, without limitation and where appropriate: (a) type, volume, composition, nature, physical, chemical and toxicological characteristics; and(b) environmental fate and transport characteristics, including mobility, stability, volatility, ability and opportunity for bioaccumulation, and persistence in the environment.(4)Soil Sampling Approach for Risk Characterization. Data used to estimate Exposure Point Concentrations for chronic and subchronic human direct contact exposures to soil (other than for screening evaluations) may be obtained using either discrete or incremental sample collection procedures. The choice of sampling approach (judgmental or systematic) must support conservative estimates of exposure considering the site history and the Conceptual Site Model and shall be consistent with the following: (a) a judgmental sampling approach is appropriate for characterizing the soil Exposure Point Concentration, pursuant to 310 CMR 40.0926, where the contamination has originated from a known source or sources; there is evidence that the contamination is limited to a defined area; the area with the highest concentrations within the Exposure Point can be clearly identified; and there is no evidence, including site history, that the soil has been significantly redistributed since the release;(b) except as provided in 310 CMR 40.0904(4)(c), a systematic sampling approach is required for characterizing the soil Exposure Point Concentrations where the soil contamination has not been attributed to a known source; the contamination may not be limited to a defined area; it is not possible to identify the area with the highest concentration within the Exposure Point; or the soil may have been significantly redistributed since the release; and(c) notwithstanding 310 CMR 40.0904(4)(b), a judgmental sampling approach may be supported where specific circumstances support a technical justification that judgmental sampling provides a conservative estimate of exposure.(5)Sediment Sampling Approach for Risk Characterization. The choice of sampling approach (judgmental or systematic) shall consider the site history, the Conceptual Site Model, the type, size and depth of the water body in question, the hydrologic regime, the depositional patterns and the Receptors of Concern. Where systematic sampling is employed, these characteristics shall also be considered when determining whether systematic grid sampling or systematic transect sampling is appropriate.Amended by Mass Register Issue 1503, eff. 3/1/2024.Amended by Mass Register Issue S1516, eff. 3/1/2024.