HRS rule, page 51646 section 5.0.1
5.0.1 General Considerations Evaluate the soil exposure pathway based on areas of observed contamination:
Consider observed contamination to be present at sampling locations where analytic evidence indicates that:
- A hazardous substance attributable to the site is present at a concentration significantly above background levels for the site (see Table 2-3 in section 2.3 for the criteria for determining analytical significance), and
- This hazadous substance, if not present at the surface, is covered by 2 feet or less of cover material (for example, soil).
Establish areas of observed contamination based on sampling locations at which there is observed contamination as follows:
- For all sources except contaminated soil, if observed contamination from the site is present at any sampling location within the source, consider that entire source to be an area of observed contamination.
- For contaminated soil, consider both the sampling location(s) with observed contamination from the site and the area lying between such location to be an area of observed contamination, unless available information indicates otherwise.
- If an area of observed contamination (or portion of such an area) is covered by a permanent, or otherwise maintained, essentially impenetrable material (for example, asphalt) that is not more than 2 feet thick, exclude that area (or portion of the are) in evaluating the soil exposure pathway.
- For an area of observed contamination, consider only those hazardous substances that meet the criteria for observed contamination for that area to be associated with that area in evaluating the soil exposure pathway.
If there is observed contamination, assign scores for the resident population threat and the nearby population threat, as specified in sections 5.1 and 5.2. If there is no observed contamination, assign the soil exposure pathway a score of 0.