If the TPH-Dx is found to be non-detect, what is the requirement for PAHs?

The reasoning behind the requirement for PAHs when TPH-Dx is found to be non-detect is grounded in the regulatory framework and the practical considerations of testing for contaminants. When TPH-Dx (Total Petroleum Hydrocarbons-Droplet Extractable) returns a non-detect result, it indicates that there are no detectable levels of petroleum hydrocarbons present in the sample. In this case, it is understood that there is a lower likelihood of polycyclic aromatic hydrocarbons (PAHs) being present as well, since PAHs are a component typically associated with the presence of petroleum products.

Consequently, regulatory guidance often stipulates that if TPH-Dx is non-detect, testing for PAHs may be deemed unnecessary, leading to their elimination from subsequent testing requirements. This approach helps streamline the testing process and focus resources where contamination is more likely to exist, reducing both time and costs associated with unnecessary analyses. Therefore, under these specific circumstances, PAHs are not required to be tested.