For sites with TPH levels greater than 10,000 ppm, what is the separation requirement between PCS and groundwater?

For sites with total petroleum hydrocarbon (TPH) levels exceeding 10,000 ppm, a separation requirement of 10 feet between petroleum-contaminated soils (PCS) and groundwater is mandated. This regulation is put in place to ensure that the contamination from the hydrocarbons does not migrate into the groundwater, which can pose significant risks to drinking water supplies and the surrounding ecosystem.

The larger separation distance is designed to provide an additional safety margin for preventing groundwater contamination, especially in areas where the contaminants may be particularly concentrated. The goal is to mitigate the environmental impact and protect public health by maintaining a barrier that minimizes the potential for leaching or migration of pollutants into the groundwater system.

This regulation reflects an understanding of how hydrocarbon compounds can behave in the environment and the necessity for stringent measures in cases of high contamination levels.