Key Environmental, Inc.
Sampling OM&M
 
ROD Modification and Soils Stabilization
Investigation, Treatability Studies, Design, Construction, OM&M
Compaction
Project Activities
  • Subsurface Investigation to Determine the Location and Extent of NAPL
  • Remedy Selection and Regulatory Negotiations
  • Laboratory Treatability Study for the S/S Remedy
  • Oversight of Pilot-Scale Treatability Study for the S/S Remedy
  • Detailed Design
  • Construction Quality Assurance
  • As-Built Documentation / Reporting
  • Operations, Maintenance and Monitoring
KEY was instrumental in convincing the federal and state regulatory agencies that a soil stabilization (S/S) approach for managing potentially mobile and residual NAPL in the shallow groundwater regime was more effective than NAPL recovery, which was specified in the Record of Decision (ROD). The site was located adjacent to a navigable river and sensitive wetlands ecosystem. Therefore, an innovative slurry trenching and batch mixing procedure was designed and implemented that allowed excavation to approximately 14 feet below ground surface in saturated sands while being protective of the adjacent sensitive areas. Approximately 13,200 tons of soil was solidified using a Portland cement-based mix design. The resulting solidified mixture had an average permeability of 9 x 10-7 cm/sec and an average 28-day unconfined compressive strength (UCS) of 140 psi. Groundwater monitoring wells were installed between the soil treatment area and the adjacent wetlands and river, to ensure that NAPL remained immobile and dissolved constituents exhibited decreasing statistical trends. These data were also used to demonstrate that robust natural attenuation of the dissolved phase constituents is occurring at this location and the surrounding areas. Field & Technical Services (FTS) is currently the Operations, Maintenance and Monitoring contractor for the site, providing routine groundwater monitoring to support ongoing remedy evaluations.
Highlights
Implementation of the S/S remedy allowed KEY’s client to eliminate costly O&M associated with NAPL recovery and facilitate future waterfront development.
KEY and FTS met with the South Carolina Department of Environmental Control (SCDHEC) and USEPA and negotiated a reduction in frequency of monitoring and reporting.