Pore water chromium concentration at 100-H Reactor Area adjacent to fall chinook salmon spawning habitat of the Hanford Reach, Columbia River. Revision 1

Groundwater underlying the 100-H Reactor Area discharges into the Columbia River in the vicinity of fall chinook salmon (Onchorynchus tshawytscha) spawning habitat within the Hanford Reach. Hexavalent chromium is a contaminant of concern that is found in the groundwater. The contaminant is considered toxic to aquatic ecological receptors, as its concentrations exceed the US Environmental Protection Agency's chronic ambient water quality criteria (AWQC) of 11 μg/L. A methodology was designed and implemented to successfully obtain pore water samples from salmon spawning habitat located near the 100-H Reactor Area. Background data were obtained from three transacts, each containing two sample sites, upstream at Vemita Bar. Pore water was obtained from the substrate by divers from a depth of 46 cm (18 in.), which is deeper than the 10 to 40 cm (4 to 16 in.) substrate depth typically excavated by fall chinook salmon during spawning. Chromium was detected at levels above AWQC at three of 31 sample sites. One explanation for not detecting chromium at the remaining sites is that the interface between river water flowing within the substrate and groundwater upwelling into the substrate is below the 45 cm (18 in.) depth that was sampled. The potential impacts of contaminated groundwater discharge on the success of salmon spawning are uncertain