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SummaryAt the Hanford Site in southeastern Washington State, contaminated groundwater discharges to the Columbia River after passing through a zone of groundwater/river water interaction at the shoreline (i.e., the hyporheic zone). In the hyporheic zone, river water may infiltrate the riverbank during periods of high-river stage and mix with the approaching groundwater. Contaminants carried by groundwater may become diluted by the infiltrating river water, thus reducing concentrations at locations of exposure, such as riverbank springs and upwelling through the riverbed. There have been limited studies of contaminant concentrations, physical properties, or the extent of the hyporheic zone near the Hanford Site's 300 Area, yet this zone is a major interface for discharge of groundwater contamination into the Columbia River.The Remediation Task of the Remediation and Closure Science Project conducts research to meet several objectives concerning the discharge of groundwater contamination into the river at the 300 Area of the Hanford Site in Washington State. This report documents research conducted to meet these objectives by developing baseline data for future evaluation of remedial technologies, evaluating the effects of changing river stage on near-shore groundwater chemistry, improving estimates of contaminant flux to the river, providing estimates on the extent of contaminant discharge areas along the shoreline, and providing data to support computer models used to evaluate remedial alternatives. This report summarizes the activities conducted to date, and provides an overview of data collected through July 2006. Recent geologic investigations (funded through other U.S. Department of Energy [DOE] projects)have provided a more complete geologic interpretation of the 300 Area and a characterization of the vertical extent of uranium contamination. Extrapolation of this geologic interpretation into the hyporheic zone is possible, but little data are available to provide corroboration. Penetration testing was conducted along the shoreline to develop evidence to support the extrapolation of the mapping of the geologic facies. While this penetration testing provided evidence supporting the extrapolation of the most recent geologic interpretation, it also provided some higher-resolution detail on the shape of the layer that constrains contaminant movement. Information on this confining layer will provide a more-detailed estimate of the area of riverbed that has the potential to be impacted by uranium discharge to the river from groundwater transport.Water sampling in the hyporheic zone has provided results that illustrate the degree of mixing that occurs in the hyporheic zone. Uranium concentrations measured at individual sampling locations can vary by several orders of magnitude depending on the Columbia River and near-shore aquifer elevations. This report shows that the concentrations of all the measured constituents in water samples collected from the hyporheic zone vary according to the ratio of groundwater and C...

Dredging of the Columbia River navigation channel has raised concerns about dredging-related impacts on Dungeness crabs (Cancer magister). The overall objectives of this effort are to synthesize what is known about disposal effects on Dungeness crabs (Phase 1) and to offer approaches to quantify the effects, including approaches to gain a population-level perspective on any effects found in subsequent studies (Phase 2). This report documents Phase 1, which included 1) development of a conceptual model to integrate knowledge about crab biology and the physical processes occurring during disposal, 2) application of physics-based numerical modeling of the disposal event to understand the physical forces and processes to which a crab might be exposed during disposal, 3) conduct of a vulnerability analysis to identify the potential mechanisms by which crabs may be injured, and 4) recommendations of topics and approaches for future studies to assess the potential population-level effects of disposal on Dungeness crabs. The conceptual model first recognizes that disposal of dredged materials is a physically dynamic process with three aspects: 1) convective descent and bottom encounter, 2) dynamic collapse and spreading, and 3) mounding. Numerical modeling was used to assess the magnitude of the potentially relevant forces and extent of mounding in single disposal events. The modeling outcomes show that predicted impact pressure, shear stress, and mound depth are greatly reduced by discharge in deep water and somewhat reduced at longer discharge duration. The analysis of numerical modeling results and vulnerabilities indicate that the vulnerability of crabs to compression forces under any of the disposal scenarios is low. Modeling results and other information suggest that crabs may be vulnerable to injury from surge currents under some but not all disposal scenarios. For the shallow-water, short-duration disposal scenarios, the shear stress and surge currents estimated from the modeling and observed in the field at Palos Verdes appear to be sufficiently high to mobilize and transport bottom sediment and at least juvenile crabs. The surge currents estimated from modeling the deep water scenarios are not sufficient to mobilize sediment greater than 1 mm or juvenile crabs. The effects of such movement, if any, are not known and can be reduced by behavioral responses by crabs. There is evidence that burial by dredged materials can affect crab respiration and survival, but confounding factors in previous experiments preclude conclusions about thresholds and extent of effects. We recommend that future studies focus on burial effects during shallow water, short duration disposal scenarios and take into account the potential for behavioral responses to mitigate any effects.iii During disposal, the characteristics of the dredged materials (e.g., size distribution, cohesiveness), the water column (e.g., depth, stratification, currents), and the bottom (e.g., slope, grain-size distribution) interact to determine the characteristic...

ph: (865) 576-8401 fax: (865) 576-5728 email: reports@adonis.osti.gov Available to the public from the National Technical Information Service, U.S. Department of Commerce, 5285 Port Royal Rd., Springfield, VA 22161 ph: (800) 553-6847 fax: (703) 605-6900 email: orders@ntis.fedworld.gov online ordering: http://www.ntis.gov/ordering.htm Abstract The Heckathorn Superfund Site in Richmond, California, encompasses the property of the former United Heckathorn pesticide packaging plant and the adjacent waterway, Lauritzen Channel. The site was used from 1945 to 1966 by several operators to produce various agricultural chemicals. The site was placed on the National Priorities List of Superfund sites in 1990, which resulted in the removal of pesticide-contaminated soil from the upland portion of the site and dredging the marine portion of the site. Post-remediation marine monitoring and associated studies conducted through 2002 indicate that the contamination in the channel continues to pose a significant risk to biota and human health. This report documents continued marine monitoring and source investigation studies conducted in 2003. v

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