The Upper Concentration Limits (UCLs) in Soil and Groundwater (310 CMR 40.0996(7)) are applicable when risk characterization or Method 3 is used to evaluate the potential risk of harm to health, public welfare and the environment. The Upper Concentration Limits (UCLs) are not used in risk characterization Methods 1 as sites meeting the Method 1 Standards meet the Upper Concentration Limits, by definition.
The categorization scheme devised to determine the "current and foreseeable use(s)" of the groundwater and soil (310 CMR 40.0933) describes why the Department is concerned about contamination in these media and related human and/or ecological impacts. Our ability to comprehensively describe (qualitatively or quantitatively) potential impacts is limited, however, particularly impacts which may only become evident in the future. The MCP defines areas of particular interest based upon human and ecological exposure potential and allows some flexibility to establish alternative cleanup requirements using risk assessment in Methods 2 and 3. The Upper Concentration Limits identify contamination which may pose a significant risk of harm to public welfare and the environment in the future, and to minimize the incremental contributions to anthropogenic background. The Department does not endorse the general degradation of groundwater or soil.
The revised MCP contains several features intended to provide protection to all groundwater and soil, including: (a) the requirement to meet the Response Action Performance Standard (RAPS) when characterizing a site (310 CMR 40.0191); (b) the requirement to eliminate all continuing sources of release to the environment (310 CMR 40.1003(5)); and (c) the list of Upper Concentration Limits applicable to all groundwater and soil as public welfare and environmental resource standards (310 CMR 40.0994(3) and 310 CMR 40.0995(5)).
A disposal site may qualify for a Class C Response Action Outcome (RAO), even if the concentrations of oil or hazardous material remaining at the disposal site exceed the Upper Concentration Limits. An exceedance of these standards is interpreted to indicate significant risk of harm to public welfare and/or environmental resources in the future, and thus a Class C RAO may be appropriate if, for current conditions, a condition of no significant risk of harm to health, safety, public welfare and the environment exists or has been achieved.
The UCLs are simply 10 fold multiples of the highest Method 1 exposure-related (S-1, S-2 or S-3 in soil and GW-1, GW-2 or GW-3 in groundwater) standard, capped at a maximum concentration. For soil, the UCL is capped at 10,000 ug/gram, or 1 %. For groundwater, the UCL is capped at 100,000 ug/L, or 0.01 %.
The Upper Concentration Limits in Soil are listed in Table 6 of the MCP: