Source Identification Type
Any area meeting the HRS definition of "source" is a source and can be used in determining an HRS score. The only issue is whether the source is associated with the site (or release) under evaluation or whether it is associated with a different site. If the site consists solely of one source (and possibly plumes migrating from the source) the association of the source with the site is immediate. Otherwise, the issue is less straight-forward.
If other sources at the site have been identified, three considerations apply in determining whether a source is associated with a site:
- Commonality of origin with the site, e.g., the source
came to contain hazardous substances as a result of the same activities that
created the site or as a result of migration from other sources at the site
(except as specifically excluded in the definition of source);
- Commonality of location with the site, e.g., the source
is located on the same property as other sources at the site and within a
reasonable distance or the source physically overlaps with another source at
the site (e.g., a contaminated soil source extending over a landfill); and
- Commonality of risk with the site, e.g., the source together with the other sources at the site would pose a common risk to some individual or ecological receptor.
Unless the relationship is immediate, a rationale for associating a source with a site should be included in the HRS documentation record.
Once sources have been identified, they should be classified as one of the HRS source type categories.
Definitions for specific source types evaluated in the HRS can be found in the HRS Guidance Manual, Section 4.1.
Proper identification of Source Type is important because it has a significant impact on other HRS factors calculations (e.g., waste quantity).
Source types are not always easily defined. Professional judgement may be required. Documentation of the rationale underlying such judgement should be included in the HRS documentation record.
Sources are evaluated in the three migration pathways. In the Soil Exposure Pathway, areas of observed contamination are evaluated.
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