Questions and Answers
Yes, if the source was documented to contain hazardous substances.
Sampling location (depth, position in stream, etc.), grain size, sampling date, etc.
Yes, because the background samples are placed between the suspected source and any alternative sources, which may exist further upstream. Thus, in judging whether the release sample is significantly elevated above background, the background measurement will already account for the contribution of any alternative sources. This allows the scorer to isolate the impact of the suspected source in attributing it to any contamination.
Do the two background samples still adequately address attribution?
No, because the background samples are no longer placed between the suspected source and the alternative source. Thus, in judging whether the release sample is significantly elevated above background, the background measurement will not account for any possible contribution of the alternative source. This prevents the scorer from isolating the impact of the suspected source in attributing it to any contamination.
No. An attribution sample located between the two sources is needed because it is not possible to determine ground water flow from two points. Because of possible subterranean obstructions, the flow depicted on this graphic may only be a component vector of the actual flow.
information documenting that a substance attributable to the site has been
entering the media of concern (Direct Observation); or
- The detection in the media of one or more hazardous substances attributable to the site with concentrations significantly above background levels. The "significant increase" has to be at least partially attributable to the site.
Because the maximum value for potential to release is 500 and an observed release is assigned a factor value of 550, potential to release will always have a lower score. Also, because actually contaminated (Level I or II) targets cannot be evaluated without an observed release, the target values will also be significantly lower.
If the background is non-detect, any release sample above the detection limit qualifies as a significant increase above background. If the substance is detected in the background sample, the release sample concentration must be at least three times greater than the background level.
Attribution samples may be needed when there is a possible alternative source of the same hazardous substance being examined at the site.