In the summer of 2012, approximately 1,302 barrels (54,684 gallons) of gasoline were released as a result of a pipeline seam failure. The spill occurred in a rural area of the upper Midwest populated with a mix of farms and small residential subdivisions. The spill location geology consisted of a thin, 4-6 foot soil layer overlying a fractured dolomite limestone bedrock. There were over 200 potable wells within a one mile radius of the spill. The potable well sampling program initiated immediately after the release discovered hydrocarbon impacts to multiple residential wells located up to 1/3 of a mile from the release location. The client required immediate emergency response support to mitigate risk to the residents near the release and to remediate the spill.
Antea Group provided same day response and immediately started to complete delineation and removal of impacted soil, design interim soil and groundwater treatment systems and collect water well samples from over 200 nearby residences.Upon discovery of impacts to nearby potable wells Antea Group planned and staffed a comprehensive potable well sampling program that collected over 10,000 residential well samples over a 6 month period. Antea Group oversaw installation of carbon filtration point of entry water treatment systems in over 70 homes. Antea Group rapidly deployed interim remediation systems including soil vapor extraction, liquid product recovery, groundwater hydraulic control and vacuum truck recovery operations, while concurrently performing comprehensive site investigations and planning long term remedial efforts.Antea Group performed an extensive investigation of the site to identify and delineate impacted soil and groundwater in both the shallow surficial soil layers and the complex, fractured underlying bedrock. Significant hydrocarbon impacts were identified and delineated in both layers. The long term site remediation approach addressed the shallow soil and perched water impacts through 48 combination groundwater recovery and soil vapor extraction wells, and the deeper impacts through 5 deep wells to recover both LNAPL and impacted groundwater. The treatment system consisted of an approximately 500 SCFM soil vapor recovery system with catalytic oxidizer treatment of the recovered vapors and a groundwater treatment system capable of treating up to 50 gpm.
Antea Group’s rapid response to the release and recovery operations minimized impacts to groundwater and the local community. A team approach provided the needed technical expertise to deal with the complex fractured geology of the area and to engineer effective temporary systems while preparing for a more stable solution. At the same time, our broad network provided the required staff seven days a week throughout the extensive recovery effort and water supply sampling program.
The remediation system removed LNAPL from the site and provided hydraulic control of the dissolved phase hydrocarbon plume. After 2-years of system operation there was no longer any measurable LNAPL in any of the site wells and the dissolved plume had contracted such that it was largely contained to a relatively small area.
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