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473

The five sampling points to the right of the pile can be joined to define an area of observed contamination. Do not join this area to the area of the pile. Rather, rely on the two samples near the pile to define the perimeter.

Do not join the area from wind deposition to the area of deposition by runoff unless you can present evidence that the area of wind deposition extends into the runoff area.

Ask EPA to review this illustration and answer

Can surface water sediment samples be considered soil samples in the soil exposure pathway?

Yes, in those cases where the sampling point is "periodically out of water" (HRS Guidance Manual, page 381). Examples are samples from the intertidal zone, samples from wetland areas that are not perennially inundated, samples from intermittent stream beds in arid and semi-arid areas, and samples from the portion of streambeds that are inundated during high-water events but are periodically dry.

EPA Please Review

This may be valuable to remember when contamination is carried as sediments through people's back yards. Sampling in the non-perennial portion of the streambed can document observed contamination.

What observations should be recorded at the site inspection?

What part of the area of observed contamination is covered? Is the cover permanent? Maintained? Essentially impenetrable?

What if the asphalt cover is cracked and pitted?

Document the situation and do not delete the sub-area because it fails to meet the criteria for cover given above.

Can a tank which is shown by sampling to contain a hazardous substance be considered to be an area of observed contamination?

First, what does the tank contain? An excluded substance such as petroleum? Feedstock, process chemicals, or product are also generally excluded from evaluation as CERCLA releases unless they have been leaked or abandoned.

There is no guidance on whether the tank constitutes a "permanent, or otherwise maintained, essentially impenetrable material." Document the condition of the tank and request guidance from EPA.

Guess how many target points result from a household of 4 people subject to Level I concentrations.

That's right, 90 points. The same as for a contaminated well or inake supplying 4 people and contaminated at Level I. 50 points for the MEI risk called resident individual (or nearest well, or nearest intake), and 10 points for each person exposed to Level I concentrations.

Remember the 50 points for Level I and 45 points for Level II? How many points for potential?

Trick question like "Simon says." No points because the resident population threat does not evaluate potential targets. That's done in the nearby population threat.

What about wetlands and species associated with wetlands?

Wetlands and species associated with wetlands are scored in the surface water and the air pathways but not in the soil exposure pathway where consideration is limited to terrestrial sensitive environments.

 

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