What is the appropriate measure for TPH in water samples to indicate a release?

The appropriate measure for Total Petroleum Hydrocarbons (TPH) in water samples to indicate a release is above 100 parts per billion (ppb). This threshold is significant as it represents a concentration level that is typically used to trigger regulatory attention or necessitate further investigation regarding potential contamination. Exceeding this limit suggests that there may be petroleum-related contaminants present in the water, which could be detrimental to both environmental and human health.

Monitoring for TPH concentrations at or above this level helps ensure that prompt action can be taken to assess the source and extent of the contamination, allowing for remedial measures to mitigate potential impacts. Therefore, the selection of 100 ppb as the defining measure reflects both environmental guidelines and public health concerns, making it a critical reference point in assessing petroleum leaks and their environmental implications.