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No, you can not use VPH or EPH data from groundwater samples in the DEQ spreadsheet to calculate site-specific risk-based concentrations. You can only use data that represent the composition of the product as it exists today. The best data for that purpose come from soil samples. Water samples will be enriched in the constituents that dissolve the most and depleted in the ones that dissolve the least. Even when using soil samples you should use relatively heavily contaminated samples.
The reason you must use data that represent the product is that models used in DEQ's TPH risk-based concentration spreadsheet are based on the assumption that you're starting out with product. The models calculate concentrations that are likely to end up in the air and water, and uses those concentrations to estimate risk-based concentrations.
VPH data from a groundwater sample would allow you to calculate risk from direct exposure to the water, such as from ingestion and/or dermal exposure. However, you'd have to do that manually by determining the risk (hazard quotient) for each component and then summing them to get the total risk (hazard index) from the entire product.
Mike PoulsenProject Manager503-229-6773
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