Investigation and Remediation of Aquifer Contamination Projects
Assessment and LNAPL Recovery from a Buried Valley Aquifer, Canton, Ohio: This project involved a hydrogeologic site investigation in which over 1.5 million gallons of free-phase gasoline were identified in the subsurface at a refinery in Canton. Dissolved petroleum hydrocarbon constituents were first detected in the refinery water supply; and subsequent investigation identified the presence and extent of two principal free- and dissolved-phase plumes. Over 100 test borings, 90 monitoring wells, and nine recovery wells were installed. Product recovery systems at the site included a cut-off trench with a dual-pumping system (water pump and hydrocarbon skimmer), passive down-well product-only systems, as well as other active dual-pumping installations. Over 600,000 gallons of free product have been recovered and the Site is now performing monitored natural attenuation as the principle preferred remedy.
Lafayette, Indiana: Pumping from a municipal water-supply well located adjacent to a golf course was halted after TCE was detected in raw water at concentrations that exceeded the USEPA MCL of 5 ug/L for drinking water. Eagon & Associates performed an investigation consisting of depth-oriented direct-push sampling and an electromagnetic survey to identify the source and delineate the contaminant plume. Pumping was resumed at the affected supply well in order to capture the plume and prevent TCE from migrating to the other wells in the well field. TCE concentrations increased between 1999 and 2004, leveled off, and began to decrease by 2005. An interceptor well was subsequently installed to withdraw water from the center of the plume; and water was pumped to an air stripper to remove the TCE from the water before it was discharged. TCE concentrations at the water-supply well steadily decreased to below 5 ug/L.
Delineation and Recovery of Hydrocarbon Products at Cross Lanes, West Virginia: This project involved problem definition, design of a system to remediate the problem, and supervision of the clean-up contractor for the U.S. Environmental Protection Agency. Twelve test borings with monitoring wells and six exploration pits were installed. Gasoline from old tank leaks at a service station was found to be migrating in a very shallow perched zone of saturation and seeping at the surface in a small ravine. Strong product odors and potentially hazardous concentrations were a concern. Very slow seepage rates due to the low permeability of subsurface materials made rapid recovery difficult. Two recovery sumps were installed near the source and about 3,000 gallons of gasoline were removed during a period of about six months. A passive French drain system which discharged through an oil-water separator was installed and operated for about two years to handle the slow seepage problem downgradient of the source area.
Delineation and Recovery of Free-Phase Hydrocarbon at a Steel Mill, Whitting, Indiana: A steel mill near Chicago was built mostly on slag material deposited adjacent to Lake Michigan, and No. 6 fuel oil was found floating on the water table in the slag. The oil was seeping into the lake, and when the water table was high, oil was seeping through the sub-basement floor of the slab mill and fires were occurring due to high temperatures at the soaking pits. Several monitoring wells were installed under extremely difficult drilling conditions to define the extent of the released fuel oil. A dewatering well was installed to control fluid levels under the slab mill to eliminate the safety hazard. Because of the viscosity of the oil, recovery operations were difficult; even measuring the product thickness in wells was problematic. Through mutual efforts with Oil Recovery Systems, Inc., a heated probe was developed to measure the oil-water interface and control probes were designed in order to successfully operate recovery wells. A prototype well was installed and plans for full scale remedial operations were developed.
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