AL001 - Pneumatic Fracturing, Feroxsm

NASA Marshall Space Flight Center - Huntsville, Alabama

Project Summary

The Feroxsm 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 Feroxsm treatment zones: a 3000-sq. ft Source Area Treatment Zone and a 450-foot long by 60-foot wide Downgradient Treatment Zone. The construction plan is shown on the next page. 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 the source of 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 is found primarily in a "rubble zone" consisting of a heterogeneous aggregate of clay, sand and small to large gravel-sized cherts. The 5-7 foot rubble zone was overlain by approximately 30 feet of a clayey residuum and underlain by limestone bedrock.

Through a total of 29 open boreholes, more than 11,000 pounds of Feroxsm powder in the form of a slurry were 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 feet away from the injection point. Under pressures of 90 to 115 psi, the Feroxsm slurry was intermixed within the rubble zone by fluidizing the formation sandwiched between the two confining layers.

Outcome

Based on field observation and pressure monitoring, the injection process was a success in effectively dispersing the Feroxsm powder into the targeted zones. A data summary table on the following page shows the baseline and post-injection analytical results.

View the results of the baseline and post-injection groundwater sampling events (140kb)
 
During the Feroxsm injection at the site, pressure influence and hydraulic connection were observed in another borehole more than 80 feet from the injection point.

As-built layout of the Feroxsm reactive zones. The discharge pond was the likely source of TCE in the groundwater.



As-built layout of the Feroxsm reactive zones. The discharge pond was the likely source of TCE in the groundwater.


The attached table shows the results of the baseline and post-injection groundwater sampling events. Baseline data were 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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