High-Resolution Stratigraphy, Geophysics, and Rock Core Testing to Optimize a Bioremediation Remedy

The implementation of a bioremediation remedy for a bedrock contaminant plume is a significant undertaking both in terms of effort and cost and technical complexity. To ensure the success of the remedy, it is vital that the design is appropriate for the geologic conditions encountered at the Site. Several approaches were utilized to develop a high-resolution conceptual model of the injection zone and better characterize the remediation target zones via methods such as borehole optical and acoustic televiewers, caliper, natural gamma, heat-pulse flow meter, bedrock topography, tracer studies, short-term pumping tests, straddle-packer testing, pilot bioremediation injection analysis, rock core analysis and 3D visualization.

The high resolution study area is at the head of a 5,000-foot commingled VOC plume in bedrock, located in the Newark Basin of northern New Jersey, which ultimately discharges to surface water. The design basis for the bioremediation injections was a high-resolution mapping of the fracture network, which includes shallow-dipping bedding plane partings as well as steeply-dipping tectonic fractures, and the intersections of both. Detailed 3D hydraulic conductivity data was collected from discrete fracture zones in part from multiple fluorescent tracer studies. This evaluation was important to customizing the emulsified vegetable oil (EVO) product into suitable droplet sizes tailored to specific fracture zones. We used custom droplet sizes to address the variable groundwater velocities (<1 to >10 fpd) and vertical extent (>200 feet deep) in the residual source area fracture network.

After injection of over 32,000 liters of EVO we further evaluated the fracture network by visualizing hydraulic responses as well as changes in performance monitoring parameters in six successive sampling and analysis episodes. With a more comprehensive understanding of the fracture network and contaminant concentrations within the open fractures and the rock matrix, there is a higher probability of implementing a successful remedial injection design.