NGWA Event and Education Recordings Archive

We will present a case study for the combined groundwater remediation remedy of a 10-acre, $200 MM brownfield redevelopment project along the Hudson River waterfront in Yonkers, New York. The Site had multiple sources of historical contamination, including petroleum, historical fill, and coal tar from an off-site manufactured gas plant (MGP). Assessment of the Site occurred over a six-year period involving multiple parties and included traditional assessment techniques as well as TarGOST laser induced fluorescence technology to delineate the vertical and horizontal extent of coal tar contamination. The completed remediation was negotiated by a team of consultants and agencies while considering environmental exposure to the public, cost effectiveness, and feasibility. The Site remedy required a complex combination of remedial solutions including, in-situ soil solidification (ISS); auger column ISS; slurry wall; and injection of rigid foam along preferential utility pathways. In addition, traditional remedial methods were also utilized, including source removal by excavation and non-aqueous phase liquid (NAPL) recovery, bioremediation (e.g., oxygen release compound), sub-slab depressurization system, and site capping. Remedial efforts were complicated by a variety of factors including: an elevated, tidal water table in the floodplain; multiple geologic units; coal tar contamination at depth; poor soil quality/strength due to historical fill; deteriorated and aged municipal utilities and adjacent structures; nearby sensitive receptors including an adjacent food manufacturing facility; significant regulatory oversight; and redevelopment plans requiring construction in areas of residual contamination. The presentation will focus on the effect of remediation on groundwater quality, comparing pre- and post-remediation results in addition to discussing regulatory implications of baseline emerging contaminant sampling post-remediation.