Code of Massachusetts Regulations › 310 CMR - DEPARTMENT OF ENVIRONMENTAL PROTECTION › Title 310 CMR 40.0000 - Massachusetts Contingency Plan › Subpart I - RISK CHARACTERIZATION › Section 40.0924 - Identification of Exposure Points

Current through Register 1525, July 5, 2024
(1) All potential
				Exposure Points shall be identified and described in the documentation of the
				Risk Characterization after considering the site and receptor information
				described in
				310
				CMR 40.0904 through
				310
				CMR 40.0923.
(2) The identification of an Exposure Point
				shall be consistent with the type and method of Risk Characterization which is
				being performed.
(3) The Exposure
				Point(s) in all environmental media shall be identified for all current and
				reasonably foreseeable Site Activities and Uses.
(4) For comparisons to Applicable or Suitably
				Analogous Standards in Method 3, the Exposure Point shall be identified in a
				manner consistent with the applicable regulations.
(5) Consideration shall be given to the
				identification of Exposure Points which may be located at a distance from the
				original source of the release, particularly when the migration of oil and/or
				hazardous material may result in Exposure Points in addition to those
				identified under current site conditions.
(6)
Groundwater Exposure
				Points
.
(a) In Methods 1 and 2
				Risk Characterizations, the Exposure Point(s), for all groundwater categories,
				shall be the groundwater resource itself, as measured at each wellhead and/or
				nearest tap of a well screened within the horizontal and vertical distribution
				of the oil and/or hazardous material in the groundwater. Existing water supply
				wells and monitoring wells shall be used to represent current or potential
				groundwater Exposure Points.
(b) In
				Method 3 Risk Characterizations:
1. For
				comparisons to Applicable or Suitably Analogous Standards as described in
				310
				CMR 40.0993(3), the Exposure
				Point shall be identified in a manner consistent with the applicable
				regulations;
2. Except as provided
				in 310 CMR 40.0924(6)(c), in GW-1 groundwater areas, for the comparison to
				drinking water standards listed in
				310 CMR
				22.00:
Drinking Water
and for the
				calculation of current and/or potential exposure to the groundwater, the
				Exposure Point(s) shall be the groundwater resource itself, as measured at each
				wellhead and/or nearest tap of a well screened within the horizontal and
				vertical distribution of the oil and/or hazardous material in the groundwater.
				Existing water supply wells and monitoring wells shall be used to represent
				current or potential groundwater Exposure Points;
3. In areas where the groundwater is
				categorized as GW-3 only, groundwater Exposure Points shall be determined based
				on site-specific conditions, and potential current and future
				exposures.
(c) In GW-1
				areas that are designated GW-1 solely on the basis of being located within a
				Zone II or an Aquifer Protection District that overlays or is contiguous with a
				Zone II and where the relevant disposal site meets the criteria specified at
				310 CMR 40.0924(6)(c)3 through 8, the Exposure Point shall be the existing
				Public Water Supply well(s) for the evaluation of current and future drinking
				water exposures to petroleum hydrocarbons at or from the disposal site and the
				Exposure Point Concentration shall be identified pursuant to
				310
				CMR 40.0926(7)(e).
1. For the purposes of this provision, the
				term "petroleum hydrocarbons" shall mean the petroleum-derived constituents of
				crude or fuel oil, such as those constituents defined by the analytical methods
				for Total Petroleum Hydrocarbons, Volatile Petroleum Hydrocarbons, Extractable
				Petroleum Hydrocarbons, Benzene, Toluene, Ethylbenzene and Xylenes, but not
				including additives;
2. This
				Exposure Point is only applicable to petroleum hydrocarbons at or from the
				disposal site and shall be used in combination with Exposure Points identified
				for the evaluation of any other contaminants at or from the disposal site,
				including but not limited to additives;
3. A Phase II Report for the disposal site
				pursuant to
				310
				CMR 40.0830 has been submitted;
4. The disposal site is located at a distance
				greater than 1,000 feet from a Public Water Supply well;
5. It has been demonstrated that the
				requirements at
				310
				CMR 40.1003(5)(a) and (b)
				and 310 CMR 40.1003(7)(a)
				 have been met to address any NAPL
				present;
6. It has been
				demonstrated through adequate characterization of horizontal migration that
				groundwater petroleum hydrocarbon concentrations are:
a. not detected at or above analytical limits
				appropriate for a GW-1 area at the downgradient edge of the plume, at least
				1,000 feet from the Public Water Supply well(s); and
b. decreasing within the boundaries of the
				plume; demonstration of diminishing contaminant concentrations within the plume
				shall consider both the spatial and temporal distribution of the contamination
				and other measures indicative of biodegradation of the contaminants;
7. It has been demonstrated
				through adequate characterization of vertical migration that contamination has
				not entered bedrock, including through the submittal of a profile sectional map
				showing the following information:
a. known
				or inferred depth to bedrock;
b.
				depths to the top and bottom of the plume throughout the length of the plume;
				and
c. existing well screen depths
				in comparison to the plume.
8. It has been demonstrated that there is no
				potential Exposure Point Concentration in accordance with the criteria
				specified at
				310
				CMR 40.0926(7)(e).