Current through Register 1531, September 27, 2024
An 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; and
6. 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.
