M&A designed and implemented a comprehensive field program to gather data for characterizing the site’s hydrogeology and the extent of VOC contamination in soil and groundwater. We supervised the installation of numerous soil borings and monitoring wells. We also led field efforts and analyzed data from depth-specific groundwater sampling and from geophysical, hydrophysical, and spinner flowmeter logging. These data were used to characterize the lithologic, hydraulic, and water quality profile at individual source areas and within the regional plume.

M&A designed and oversaw the construction and testing of three large-diameter extraction wells completed to depths exceeding 1,200 feet as part of the pump-and-treat remedy. To select favorable drilling sites for these wells, we evaluated hydrogeologic, water quality, and land ownership data and negotiated property access. We accomplished this challenging program in a populated metropolitan area, where purge water management and noise abatement were critical.

M&A developed or helped develop several models at the site (groundwater flow, particle tracking, solute-transport, and vadose zone) to achieve various remedial design objectives. The models were used to evaluate groundwater and contaminant movement within and between aquifers, assess plume capture and containment under a range of extraction regimes, and compare the effectiveness of remedial alternatives for remedy selection. The site-wide flow-and-transport model was updated and recalibrated in 2010 to assess remedy performance as part of at 5-year review process. Vadose zone models were used at the various source areas to assess the potential threat to groundwater from VOCs and identify the need for soil vapor extraction.

During the characterization and subsequent remedy-development process, M&A designed, constructed, and tested an extensive monitoring network at the site. We then developed a comprehensive monitoring program to track the occurrence and migration of VOCs and periodically verify our containment projections. Ongoing monitoring and reporting ensures that the remedial action objectives are met and that groundwater containing VOCs does not impact nearby wells.

M&A provided technical support for an alternate dispute-resolution process to allocate costs for the construction and long-term operation of the remediation program. We also developed cost-sharing approaches for ongoing pump-and-treatment activities and provided expert testimony related to an alleged loss of value for property overlying the zone of contamination.