Project Challenge/Solution:
The FFP Travel Mart Site (Site) in Oklahoma City had two documented LNAPL releases in 1990 resulting in a persistent LNAPL plume. Regional geological crosssections showed faulting around the Site, but it was unknown the extent of how these structures were impacting the transport of contaminants. The project team was tasked with characterizing and remediating the free product and related dissolved-phase plume with a remedial concentration goal of 1 ppm or less of benzene.
The problem:
Previous remedial efforts at the Site included a free product recovery system, enhanced fluid recovery via high vacuum event, and surfactant injections – but these did not sufficiently reduce measured free product in wells across the Site.
An updated conceptual site model (CSM) with a firm understanding of fault zones throughout the Site was essential for informing future remedial design. Aestus’ specialty electrical resistivity subsurface scanning technology, GeoTrax Survey™, was leveraged to provide ultra-high data density across the Site to infill data gaps, map fracture zones and contaminant distribution, and inform critical zones for further investigation.
Left graphic shows where free product (red) and 1ppm concentrations of benzene (yellow) were prior to scanning. Right graphic shows updated plumes with mapped fracture zones as a result of the imaging and targeted drilling locations (wells with pink labels).
Solution:
Through collaboration and application of Aestus’ Electrical Hydrogeology™ process and use of 3D visualization software, an updated CSM was created with integrated GeoTrax Survey™ data, geology, groundwater analytical data, PID measurements, boring logs, and confirmation drilling results targeted from the electrical resistivity images.
Outcome:
This robust, updated CSM allowed extraction wells to be targeted in the delineated fracture zones for an increased radius of influence (i.e., 40 feet), with a total of 152 gallons of free product and an associated 2,914 equivalent gallons of free product vapor removed from the Site via high vacuum extraction events (a higher removal volume per well than seen in the high vacuum extraction event 11 years prior).
One survey image, FFP-02, that informed the mapped fractures and the strong, electrically resistive anomaly (red/black located ~80 feet along the image) that was targeted by well CD-02 and found to have free product upgradient from the known source zone along a main fracture.