Technical Evaluation of the Interaction of Groundwater With the Columbia River at the Department of Energy Hanford Site 100-D Area

Abstract

EXECUTIVE SUMMARY BACKGROUND AND OBJECTIVESGroundwater beneath much of Hanford's 100 Areas is contaminated with hexavalent chromium (Cr+ 6 ) as a consequence of treating reactor cooling water to prevent corrosion. The Cr+ 6 is thought to have infiltrated the subsurface through disposal of reactor cooling water in ponds or through spills in areas where Cr+ 6 solutions were mixed. Several treatment systems are in place as interim remedial actions to remove Cr+ 6 from the groundwater. These systems don't capture groundwater that has already passed down-gradient from or outside ofthe system's influence, which is the focus of this report. Some of this impacted groundwater is currently discharging to the Columbia River and some will continue to discharge in the future until sources are depleted or remediated.Cr+6 is highly mobile and toxic to aquatic organisms, including benthic and hyporheic-zone aquatic life residing on and in the river bed, as well as salmon eggs and alevin in redds and river spawning beds. Of concern is the fate of Cr+6 as it discharges to areas within the channel of the river, because sensitive species inhabit the river and its associated transition zone. The aquatic standard for Cr+ 6 is 11 ug/l under the current Record of Decision (ROD) for Interim Action.In April 2008, an expert panel of scientists was convened to provide observations and suggestions intended to improve the current understanding of groundwater-surface water interactions in the 100 Areas (primarily focusing on 100-D Area), and to identify what additional analyses or approaches may provide critical information needed to design and implement effective remediation systems that will minimize impacts to river aquatic systems. The panel was asked to evaluate the likely mechanisms that control the locations, timing, and quantity of contaminated groundwater that enters the riverbed and suggest how current data sets and interpretations and possibly new data sets and interpretations would facilitate remediation of Cr+ 6 -impacted groundwater and reduce negative impacts to the river aquatic system. In this context, they were tasked to:• evaluate past and current conceptual models of the interaction of local near-bank groundwater with the Columbia River;• evaluate past and current data collection methods, data analysis techniques, assumptions, and groundwater transport and mixing mechanisms;Evaluate the current monitoring network;• evaluate the role played by modeling; and,• recommend additional research to fill existing data gaps.The expert panel's report is organized as follows:• The Conceptual Model Framework• Data Acquisition, Network Design, and Data Analysis In the report, the panel provides observations and suggestions that are intended to enhance understanding of how the interaction of site groundwater and the Columbia River could influence remedial technology selection, design, operation, and evaluation. The panel is aware that extensive data sets, field investigations and analyses have already been completed at the 100 Area sites...

Evaluation of mercury stabilization mechanisms by sulfurized biochars determined using X-ray absorption spectroscopy

“…CPS is a low-cost (~$0.32 L -1 [69]) reagent approved for use for contaminated site remediation (including Superfund sites) in the US [70]. After impregnation of CPS in the biochar, stabilization of Hg is enhanced, potentially decreasing the environmental impact of Hg.…”