|Research and Development Laboratory|
Location: New Jersey
Regulatory Program: Industrial Site Recovery Act (ISRA)
Duration: February 2000 to Present
Summary: Complex, multi-media investigation and remediation project; soil removal adjacent to buildings and electrical utilities in two areas; innovative groundwater trace-metals characterization and chloroform source assessments; cost-effective and very practical remedy for remediation of soil and groundwater impacts at abandoned septic system location.
Following a property transfer in late 1995, this telecommunications industry client initiated activities necessary for regulatory closure of this research and development laboratory site, under New Jersey’s Industrial Site Recovery Act (ISRA). Initial activities performed by the client included signing a Remediation Agreement and submitting Preliminary Assessment (PA) Reports for this and five other ISRA-subject sites. Since early 1996, Mr. Peterson has provided all project management and technical consulting services in connection with one of the project sites and Princeton Geoscience has served as the project consultant since its formation in February 2000.
Site characterization activities included developing, implementing, managing and reporting for work activities, during ISRA Site Investigation (SI) and, Remedial Investigation (RI) phases of work. The PA Report identified 28 potential Areas of Concern at the site. Sampling and other evaluation required during the SI focused on 19 of these areas, including decommissioned septic systems, underground chemical wastewater piping, sumps, underground storage tanks, stormwater sewers, a detention basin, and transformers.
Based on the SI results, Princeton Geoscience performed an RI to evaluate the extent of contamination at four areas, and to evaluate hydrogeologic conditions and groundwater quality across the site. Hydrogeologic investigations required consideration of several Coastal Plain geologic formations, multiple areas of aquifer recharge, complex flow conditions, and groundwater discharge into two wetland areas. Naturally elevated concentrations of several trace metals were associated with minerals of the aquifer matrix, which necessitated development of specialized sampling and statistical evaluation procedures to obtain representative characterization of natural vs. facility-related groundwater impacts. A well search and water supply survey and a Baseline Ecological Evaluation were conducted in conjunction with contaminant fate and transport analysis, to assess potential impact to receptors.
Based on the completed SI and RI, No Further Action status was obtained for 26 of the 28 Areas of Concern identified during the PA. Active remediation was required in four areas, including:
· An area of PCB-contaminated soil adjacent to an active transformer
· An area of pesticide-contaminated soil in a landscape bedding area which was identified during sampling along delivery lines leading to a septic system
· Groundwater impacted by nitrate, ammonia and trace levels of chlorinated organic compounds near a decommissioned septic system leachfield
· Groundwater impacted by chloroform downgradient of a parking lot and concrete walkway
Soil Remedial Actions
Princeton Geoscience designed and managed implementation of removal actions to address the PCB- and pesticide-impacted soils at the transformer and landscape bedding areas. Challenges included performing excavation work safely in immediate proximity to the main facility building and in an area of active, high-voltage electrical units and subsurface utilities, and ensuring effective containment of excavated soil and prevention of dust transport of contaminants at this occupied facility. A total of 450 tons of non-hazardous waste soil were excavated and transported offsite for recycling at a mine reclamation site in eastern Pennsylvania. The excavation and restoration was completed over three weekends, allowing facility activities to proceed without interruption during the work week.
Groundwater Remedial Actions
Abandoned Septic System Area
Bench-scale treatability and field pilot studies were completed to evaluate the feasibility of implementing enhanced, in-situ bioremediation for nitrate, ammonia and chlorinated organic compounds in groundwater near the abandoned septic system leachfield. Based on the positive results of these innovative studies, a full-scale remedy was considered which incorporated two separate treatment zones (permeable reactive barriers) along the groundwater flowpath. In the leachfield area, oxygen-releasing compounds were to be injected to establish a nitrification enhancement zone, where sorbed ammonium would be converted under aerobic conditions to nitrate, a more mobile nitrogen compound. Downgradient of the leachfield, oxygen scavenging compounds and a carbon source material would be injected to create a denitrification enhancement zone, where nitrate formed in the leachfield area would be “cut off” by anaerobic denitrification processes. The anaerobic conditions and available carbon source would also facilitate reductive dehalogenation of the chlorinated organic compounds found at low concentrations near the leachfield. Excavation and conventional pump and treat alternatives were also considered, but were ruled out due to their cost and partial effectiveness.
In 2004, the New Jersey Ground Water Quality Standard (GWQS) for ammonia was increased by a factor of six, to 3.0 mg/L. In light of this development, Princeton Geoscience determined that a simpler remedy based on potable water discharge to the former leachfield piping might be appropriate. Field pilot testing over a 90-day period indicated this approach reduced nitrate and ammonia concentrations to below the GWQS, with only limited rebound following the cessation of the potable water discharge. We attributed the contaminant concentration reductions to dilution, flushing, and geochemical and microbial changes coincident with the potable water discharge. Based on these findings, potable water discharge has been proposed as a source reduction remedy for the abandoned leachfield area, in conjunction with monitored natural attenuation for downgradient plume areas.
Chloroform Plume Area
The source of the chloroform in site groundwater was initially unclear, because the plume appeared to originate in a relatively undisturbed, wooded area of the site, away from any known or likely past chemical releases. To define the extent and source of the chloroform concentrations in groundwater, Princeton Geoscience conducted a detailed delineation program using direct-push (i.e., Geoprobe®) groundwater sampling techniques and in-field analyses by an NJDEP-certified mobile laboratory. This effort showed that the plume in fact originates in a wooded and grass-covered area traversed by a concrete sidewalk and stairway at the downgradient edge of a paved parking lot. Potential sources such as leakage along sanitary sewer lines or water lines were ruled out, based on locations of these utilities and the distribution of chloroform in groundwater. Since their construction in the mid-1980s, the parking lot and concrete walkway have been treated with salt for snow and ice removal. Runoff of deicing meltwater to adjacent organic topsoil takes place in this area.
Based on a literature search and review of site conditions, Princeton Geoscience identified alternate mechanisms which explain the chloroform occurrence. Specifically, we concluded that natural in-situ halogenation of soil organic matter, augmented by influxes of low pH, chloride-containing runoff associated with the deicing salt applications, caused enhanced formation of chloroform in the soil zone, leading to the observed groundwater impact. This finding is novel, because although halogenation of soil organic matter via both biological and abiotic processes has been associated with natural chloride deposition in precipitation, chloride-enhancement by road salt has not been considered previously. Princeton Geoscience developed and is in the process of obtaining a United States patent for a simple remedial process to treat primary and residual sources of chlorinated VOC impacts resulting from salt-enhanced in-situ halogenation of soil organic matter. We anticipate the process will be utilized to remediate chloroform impacts at the site.
Institutional controls will also be required as a component of the ISRA site remediation. These will include development of a Classification Exception Area for groundwater contamination and filing of a Deed Notice. NJDEP is currently reviewing the Remedial Action Selection Report and Remedial Action Workplan for the two areas of groundwater impact. Upon receipt of NJDEP’s comments on the documents, final design of the remedies will be completed, followed by implementation of the remedies and institutional controls.