Abstract

 The operation of a manufactured gas plant at a coastal location resulted in the generation of coal tar and cyanide bearing waste in the terrestrial and marine portions of the site. Coal tar-related compounds and cyanide have been detected and measured in ground water and surface water samples.
  A passive in-situ ground water treatment system installed as part of a remedial action for the terrestrial portion of the site has abated the migration of NAPL to the beach and inter-tidal zone, reduces concentrations of dissolved phase low molecular weight organic compounds to comply with Massachusetts regulatory standards, and elevates the groundwater pH from the range of 3-4 to 5-7. The system does not currently treat the cyanide in groundwater. Residual contamination, including NAPL and purifier box waste, exists in the beach fill and tidal flat sediments located down-gradient from the treatment system.
  The objective of this study was to assess the aqueous transport of residual contamination located within the beach area to the near shore sediments and surface waters. Groundwater wells installed in the tidal flat sediment were tested for PAHs, cyanide, and selected metals. Seeps located near the toe of the beach, near-shore surface water, and sediments were also sampled and analyzed.
  This presentation will examine the potential migration of cyanide in groundwater, seeps, and surface water. Total and available cyanide were analyzed using the low-level analytical methods, OIA-1678 and OIA-1677, respectively. The results from the first round of sampling found total cyanide concentrations in unfiltered water samples ranged from 35 to 428 ppb in groundwater, 30 to 155 ppb in seeps, and at or near the detection limit (0.3 ppb) in seawater. A comparison of the total and available cyanide concentrations including the results of samples collected from wells located down-gradient from the treatment system will be discussed.