Full-Scale Application of STAR (In Situ) to Treat Coal-Tar Impacted Soils

Former Industrial Site in New Jersey

The fill and alluvium units underneath a 37-acre site located in Newark, New Jersey, are contaminated with residual and free-phases of coal tar from the historic operations of a former industrial facility. The soil remedial objective is the removal of non-aqueous phase liquid (NAPL) to the extent practicable. A cost effect remediation strategy was developed for STAR based on results from Pre-Design Evaluation (PDE) studies.

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Image 1: Full-scale STAR System Deployed in the Field

Full Scale Design

PDEs were conducted to collect data regarding: 1) contaminant mass destruction rates; 2) radius of influence (ROI); 3) propagation rates; and 4) vapor emissions levels.

The application of STAR at full scale requires approximately 1500 surficial fill ignition points and 500 alluvium/sand aquifer ignition points. Rather than attempting to establish all ignition points simultaneously, STAR is being deployed in ‘leapfrogging cells’ that are made up of 20 ignition direct push points. Each cell is serviced by centralized equipment ‘nodes’ containing an air distribution and vapor collection/treatment system. After treatment is complete, the heaters are removed and deployed to another pre-installed cell, while the treated cell ignition wells are removed and installed in another location. Two parallel treatment systems are currently operating in this ‘leapfrog’ pattern.

Full Scale Implementation

System operation began in 2014 and is anticipated to continue through 2016. Data collected to date indicates that mass destruction rates from a single operating cell within the deep sand unit (6 ignition wells) are on the order of a ton of coal tar per day. Post-treatment soil concentrations are consistent with PDE results.

Conceptual Site Model of Contaminant Distribution

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Figure 1: A conceptual site model of contaminant distribution was developed from historic data, traditional borings and 585 TarGOST locations. PDEs were performed in both the shallow fill and alluvium/sand aquifer within and beneath a former lagoon. The deep sand PDE ignition point was located approximately 8 meters below ground surface (7 meters below the water table).

Pre-design Evaluation (PDE)

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Graph 1: Pre- and post-Total Petroleum Hydrocarbons (shallow fill) and Extractable Petroleum Hydrocarbons (alluvium/sand aquifer) soil concentrations by sample depth as determined during PDE activities. All post-PDE samples were collected from within combustion zones. Note that the depth (vertical) axis is a linear scale and the soil concentration (horizontal) axis is logarithmic.

Full Scale Design and Implementation

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Image 2a: Site schematic showing node and cell configurations.
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Image 2b: Treatment cells will be deployed and treated in a ‘leapfrog’ formation. While Cell 1 is being treated, Cell 2 will be installed and Cell 0 will be extracted to be installed as Cell 3.

Conclusions

  • PDEs determined treatment levels, cycle times and radius of influence
  • Full scale design approved by NJDEP
  • Field deployment has begun with operations to be completed in 2016

More Information

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