AL001 – Pneumatic Fracturing, Ferox™
NASA Marshall Space Flight Center – Huntsville, Alabama
The Ferox™ process was applied under this project at an active federal government facility located in northern Alabama. The remedial action was implemented under the CERCLA program targeting a former waste holding pond. The project scope included the installation of two Ferox™ treatment zones: a 3000-sq. ft. Source Area Treatment Zone and a 450-ft. long by 60-ft. wide Downgradient Treatment Zone. The construction plan is shown in the figure below. The primary contaminant, TCE, was detected at concentrations as high as 72 mg/liter in the groundwater within the Source Area Treatment Zone. The objective of the technology implementation was to actively remove TCE within the source area and rely on a passive downgradient barrier zone to intercept the more dilute portions of the plume. Contamination at the site was found primarily in a “rubble zone” consisting of a heterogeneous aggregate of clay, sand and small to large gravel-sized cherts. The 5-7 ft. rubble zone was overlain by approximately 30 ft. of a clayey residuum and underlain by limestone bedrock.
Figure 1: During the Ferox™ injection at the site, pressure influence and hydraulic connection were observed in another borehole more than 80 feet from the injection point.
Through a total of 29 open boreholes, more than 11,000 lbs. of Ferox™ powder in the form of a slurry was injected into the formation during the 4-week project utilizing a pressurized nitrogen gas based delivery system in conjunction with Pneumatic Fracturing. During the injections, pressure influence was observed as far as 80 ft. away from the injection point. Under pressures of 90-115 psi, the Ferox™ slurry was intermixed within the rubble zone by fluidizing the formation sandwiched between the two confining layers.
Based on field observation and pressure monitoring, the injection process was a success in effectively dispersing the Ferox™ powder into the targeted zones. A data summary table in the link below shows the baseline and post-injection analytical results.
View the results of the baseline and post-injection groundwater sampling events here.
Figure 2: Marshall Space Flight Center Construction Plan in Huntsville, AL | As-built layout of the Ferox™ reactive zones. The discharge pond was the likely source of TCE in the groundwater.
This table shows the results of the baseline and post-injection groundwater sampling events. Baseline data was represented by the results of the July 11, 2000 sampling event. Note the decrease in the TCE concentrations and the corresponding increase in cis-1,2-DCE, and chloride levels in source area wells.
This is indicative of effective dechlorination of the TCE. Two years after the injection took place, the TCE concentrations have been significantly reduced by as high as 90% in the “hottest” well. A second injection or “polishing phase” will further remove the remaining TCE.
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