First Environment designed and implemented remedial technologies at a private, residential property in Far Hills, New Jersey. As a result of two leaking USTs, petroleum-related compounds including benzene toluene, ethylbenzene, and xylene (BTEX) were identified in the shallow aquifer and also in the bedrock aquifer beneath the property. We delineated the vertical and horizontal extent of contamination in both the shallow and bedrock aquifers, and completed a detailed analysis of possible remedial alternatives to remediate the groundwater plume.
Based on the results of this analysis, the project team determined that enhanced fluid recovery (EFR), followed by in-situ chemical oxidation (ISCO) using a groundwater re-circulation system with activated sodium persulfate amendments was the most appropriate technology for this site. We implemented the ISCO groundwater remediation work at the site following the completion of a pilot test.
Based on the results of the ISCO work and the findings that residual benzene contamination was still present in the bedrock aquifer, we designed and installed a dual phase extraction (DPE) system. The DPE system was the chosen remediation technology since it is widely accepted by NJDEP and is well suited for the site conditions. Site issues that presented challenges included: operating the DPE system on a residential property, noise level constraints, and overall aesthetics of the remediation equipment. In order to minimize these impacts to the property owner, we worked with the remediation trailer vendor to house all of the pumping and remediation equipment in an insulated and well-ventilated trailer. To protect the local site aesthetics, we built a wooden stockade fence/enclosure around the entire system to hide the trailer from a nearby county road.
In addition, due to the long term operation of the DPE system, we had to properly winterize the entire trailer and associated piping and also had to obtain the necessary regulatory permits from NJDEP to address treated air emissions and treated groundwater discharge to the on-site Moggy Brook.
The DPE system has now been in operation for more than eight months and will continue to operate into the spring of 2016. We check and monitor the remediation equipment twice a week and perform weekly effluent sampling of the groundwater discharge to comply with the current NJDEP Discharge to Surface Water (DSW) Permit. Both air emissions and groundwater contaminants removed from the two on-site extraction wells are treated using granular activated carbon. We also prepare and submit Monthly Discharge Monitoring Reports to NJDEP in compliance with the DSW permit.
Based on a comprehensive review of the current site conditions, potential residential receptors, and groundwater contaminant trends with the benzene concentrations, First Environment has recommended to the client that a Classification Exception Area (CEA) be established for the property and monitored natural attenuation be implemented as the selected remedial approach for the site. It was apparent that an overall decreasing trend in contaminant concentrations was occurring and no potential receptors were at risk. We therefore deemed the “no action” alternative most appropriate for the site.
Future project work tasks will include the preparation of a detailed Remedial Action Report (RAR) detailing the trend in benzene concentrations along with a Remedial Action Permit Application for groundwater, which will establish the CEA at the site.