Client: Large Retail Management Company
Project: Remedial System Design, Installation, Operation & Maintenance
Location: New Jersey
Description: Although the existing treatment system at the property had been in place and operational since May 1995, it did not appear to be effective in remediating the entire area of remaining soil impacts. Therefore, in accordance with a New Jersey Department of Environmental Protection (NJDEP) directive issued in January 2001, EWMA excavated hazardous soils which had contaminant levels as high as 30,000 parts-per-million (ppm), and modified the treatment system in order to remediate the remaining excavation periphery soil impacts that exceeded the NJDEP Soil Cleanup Criteria of 10,000 ppm for total organic contaminants, including total petroleum hydrocarbons (TPHC).
The modifications included the installation of vertical bio-venting wells and passive aeration vents between the bio-venting wells. The passive vents served to enhance the influx of nitrogen and oxygen from the ambient air to the subsurface soils as an aid to the bioremedial process. Additionally, the 200 pound capacity granulated activated charcoal (GAC) unit was replaced with a 400 pound capacity GAC unit.
From March 2001 through January 2004, the upgraded soil bio-venting system operated twenty-four hours per day, seven days per week, except during periods of routine maintenance. EWMA monitored the vacuum-based soil bio-venting system on a weekly basis for the first eight weeks and on a monthly basis thereafter, in accordance with both the approved Remedial Action Workplan and NJDEP monitoring requirements for soil venting systems. During each monthly monitoring event, vacuum readings were recorded from the bio-venting wells. Additionally, during periods of its operation, EWMA performed evaluations of the bio-venting system in order to focus maximum air flow within the remaining area of TPHC-impacted soils and optimize its performance.
The monthly monitoring data, which recorded as ppm of total volatile organic compounds (VOCs), represented the total degradation byproduct of No. 4 Fuel Oil that had volatilized due to bio-venting operations. EWMA determined that the average TPHC concentration remaining in the affected area was approximately 9,600 ppm. Consequently, remedial effectiveness soil sampling was proposed and approved by the NJDEP.
Following modification of the on-site treatment system through the installation of additional bio-venting points and passive aeration vents, influent concentrations continued to decrease. Following system adjustments performed during system operation, concentrations initially increased and then decreased substantially. Initial concentrations were approximately 5,000 ppm and reduced to less than 10 ppm over the last three years of system operation (following the system upgrade).
Based upon laboratory analytical results from soil samples collected in January 2003 and January 2004, compliance with TPHC and polynuclear aromatic hydrocarbons (PAHs) soil cleanup standards was achieved in all of the post-remedial sample locations at the required depth intervals. As a result of EWMA’s modifications to the treatment system and the subsequent effectiveness in addressing soil contamination issues (as indicated by compliant post-remedial soil sample results), the cleanup has been completed at the property and the NJDEP issued a No Further Action letter (NFA letter) for the property.