Natural Degradation Helps NJ Site Achieve Unrestricted Closure

A former leaking underground storage tank dragged a New Jersey retail store owner into a long and costly cleanup obligation. 

Many years after removing the gasoline tank and the impacted soil, groundwater remained affected by benzene ranging between 10 and 280 ppb. Predictions for natural attenuation were approximately 10 – 12 years. 

With NJDEP groundwater standards for benzene set at a very low 1 ppb, many site owners across the state sit with their toes at the regulatory finish line waiting for natural attenuation to attain the benzene closure standard. And the idea of active remediation for such low-level impacts just doesn’t add up financially.

BSTI entered the project and proposed a short duration in-situ enhanced oxidation program to jump start and accelerate the natural degradation process. Over the course of three-monthly events, BSTI injected oxidation reagents into the subsurface soil and shallow groundwater.

Indicators such as pH, temperature, oxidation-reduction potential, and dissolved oxygen suggested that we were on the right track. We then backed away and let the process proceed without more expenditure by the client.

Two years after the injections, benzene concentrations in groundwater were below NJDEP standards. A subsequent year of confirmation sampling concluded that the site had met all regulatory obligations, providing for unconditional closure.

The result of BSTI’s plan is that the site owner now has a fully unencumbered property and saved over six years and $50,000 in estimated time and costs when compared to a natural degradation approach only. 

Under the right circumstances and if implemented well, short-term remedial measures that jump start natural processes can be a good operational and financial alternative to consider.