West Highway 6 & Highway 281 Superfund Site, Hastings, Nebraska


HGL executed a multiphase Remedial Investigation (RI)/Feasibility Study (FS) at a facility that had manufactured cast iron piston rings. The main production building housed four degreasing units where the piston rings were cleaned with chlorinated solvents before plating. These operations resulted in volatile organic compound (VOC) and metals contamination in on- and off-site soil and groundwater, and a groundwater treatment system installed as an interim remedy had not maintained hydraulic control of the plume or reduced contaminant mass.

HGL’s extensive RI included groundwater sampling and a hydrogeological investigation, surface and subsurface soil sampling, air dispersion modeling of stack emissions, subslab soil vapor sampling to evaluate the vapor intrusion pathway, and concrete chip sampling to determine potential risks to workers in the building. HGL used direct-push technology to advance soil cores to bedrock at 240 feet below ground surface to determine the nature and extent of VOC and chromium contamination in soil and groundwater. The lithology in the borings was characterized using downhole geophysics, and a membrane interface probe was used to determine total VOCs and aquifer conductivity over depth. Subsurface soil samples were collected from varying depth intervals and analyzed in an on-site laboratory to facilitate decision-making in the field. Point-source groundwater samples also were collected and analyzed in the on-site laboratory. Permanent monitoring wells were installed and screened based on the results of groundwater and soil profiling. HGL also conducted human health and ecological risk assessments as part of the RI. Based on the findings of the RI, HGL completed an FS to evaluate potential cleanup alternatives

Project Highlights
Used the Triad approach for systematic project planning, dynamic work strategies, and innovative rapid sampling and analytical technologies.
Developed an accurate conceptual site model, which was used to identify data gaps so that additional data collection efforts could be targeted to support the quantification of risk posed by the site and lead to an effective site cleanup strategy.
Conducted on-site sample analysis in a mobile lab that allowed for rapid field decision-making on sample locations and depths as new data was obtained.
Determined from the RI that the groundwater contaminant plume extended 2.4 miles off site and was co-mingled with the plume of an adjacent Superfund site, which caused the treatment plant being designed for the adjacent site to be expanded to treat the co-mingled portion of the plume.