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DRESDNER ROBIN performed RIR/RAR/RAW activities at the Hackettstown Maintenance Facility located between the eastbound and westbound lanes of Route 46 at the intersection of Drakestown Road in Washington Township, Morris County, New Jersey. The Remedial Investigation/Remedial Alternative Analyses (RI/RAA) entailed the characterization of soil and groundwater contamination related to a former leaking 4,000-gallon gasoline underground storage tank (UST) that resulted in free product in the vicinity of the UST excavation and dissolved phase groundwater contamination impacting a potable aquifer downgradient of the facility. The Remedial Investigation (RI) performed by DRESDNER ROBIN consisted of the advancement of soil borings; installation of monitoring wells; collection and analysis of soil and groundwater samples; aquifer characterization through the performance of slug tests and pump tests; residential well sampling; down-hole geophysical surveys; and fracture trace analyses.

The interim remedial approach, designed and implemented by DRESDNER ROBIN, involved the installation of an active free product recovery system at the source area and the installation, operation, and maintenance of a groundwater pump and treat system downgradient of the facility/source area. The free product recovery system consisted of a bladder pump, skimmer, compressor, and a holding tank. The pump and treat system consisted of four (4) groundwater extraction wells; bag filter filtration system; sequestering agent system; ultraviolet water purifier; polyethylene holding tank; air stripper feed pump; a low profile air stripper; air stripper discharge pump; two (2) air compressors, three (3) pneumatic pumps; one (1) submersible pump; and an electronic control system.

The remedial approach involved the installation of a soil vapor extraction (SVE) system with product recovery in conjunction with a dewatering system at the former UST location and the continual operation and maintenance of the groundwater pump and treat system downgradient of the facility/source area. Following remediation of the source area, DRESDNER ROBIN prepared a three-dimensional groundwater flow and solute transport model to assess the fate of the dissolved MTBE plume. The results of the model indicate that the use of Monitored Natural Attenuation (MNA) within a designated Classification Exception Area (CEA) could be utilized as a long term remedial approach for the dissolved phase contamination.