Paul D. Thorne

Borehole Completion and Conceptual Hydrogeologic Model for the IFRC Well Field, 300 Area, Hanford Site

A tight cluster of 35 new wells was installed over a former waste site, the South Process Pond (316-1 waste site), in the Hanford Site 300 Area in summer 2008. This report documents the details of the drilling, sampling, and well construction for the new array and presents a summary of the site hydrogeology based on the results of drilling and preliminary geophysical logging.

Three-Dimensional Groundwater Models of the 300 Area at the Hanford Site, Washington State

Researchers at Pacific Northwest National Laboratory developed field-scale groundwater flow and transport simulations of the 300 Area to support the 300-FF-5 Operable Unit Phase III Feasibility Study. The 300 Area is located in the southeast portion of the U.S. Department of Energy’s Hanford Site in Washington State. Historical operations involving uranium fuel fabrication and research activities at the 300 Area have contaminated engineered liquid-waste disposal facilities, the underlying vadose zone, and the uppermost aquifer with uranium. The main objectives of this research were to develop numerical groundwater flow and transport models to help refine the site conceptual model, and to assist assessment of proposed alternative remediation technologies focused on the 300 Area uranium plume.

Groundwater Data Package for Hanford Assessments

This report presents data and interpreted information that supports the groundwater module of the System Assessment Capability (SAC) used in Hanford Assessments. The objective of the groundwater module is to predict movement of radioactive and chemical contaminants through the aquifer to the Columbia River or other potential discharge locations. This data package is being revised as part of the deliverables under the Characterization of Systems Project (#49139) aimed at providing documentation for assessments being conducted under the Hanford Assessments Project (#47042). Both of these projects are components of the Groundwater Remediation and Closure Assessments Projects, managed by the Management and Integration Project (#47043).

Uranium Contamination in the Subsurface Beneath the 300 Area, Hanford Site, Washington

This report provides a description of uranium contamination in the subsurface at the Hanford Sites 300 Area. The principal focus is a persistence plume in groundwater, which has not attenuated as predicted by earlier remedial investigations. Included in the report are chapters on current conditions, hydrogeologic framework, groundwater flow modeling, and geochemical considerations. The report is intended to describe what is known or inferred about the uranium contamination for the purpose of making remedial action decisions.

Results of Detailed Hydrologic Characterization Tests - Fiscal Year 2000

This report provides the results of detailed hydrologic characterization tests conducted within eleven Hanford Site wells during fiscal year 2000. Detailed characterization tests performed included groundwater-flow characterization; barometric response evaluation; slug tests; single-well tracer tests; constant-rate pumping tests; and in-well, vertical flow tests. Hydraulic property estimates obtained from the detailed hydrologic tests include transmissivity; hydraulic conductivity; specific yield; effective porosity; in-well, lateral flow velocity; aquifer-flow velocity; vertical distribution of hydraulic conductivity (within the well-screen section); and in-well, vertical flow velocity. In addition, local groundwater-flow characteristics (i.e., hydraulic gradient and flow direction) were determined for four sites where detailed well testing was performed.

Contaminants of Potential Concern in the 300-FF-5 Operable Unit: Expanded Annual Groundwater Report for Fiscal Year 2004

This report satisfies requirements in the Operations and Maintenance Plan for the 300-FF-5 Operable Unit (DOE/RL-95-73, Rev. 1) to provide detailed information, beyond that provided in the regular annual groundwater report (e.g., PNNL-15070), on groundwater conditions. The purpose is to characterize current conditions; provide a basis for changes to the monitoring schedules; and provide technical information to support the second 5-year review of the record-of-decision for the operable unit. Key topics include historical trends in the levels of various contaminants; updating the list of contaminants of potential concern; conceptual site models for uranium (300 Area) and tritium (618-11 waste site sub-region); performance of the interim actions under the current record-of-decision; and analysis of the applicability of Monitored Natural Attenuation as a remedial action alternative.

Analysis of the Hydrologic Response Associated With a Shutdown and Restart of the 200-ZP-1 Pump and Treat System

A number of programs have been implemented on the Hanford Site that utilize the pumping and treatment of contaminated groundwater as part of their remediation strategy. Often the treated water is reinjected into the aquifer at injection well sites. The implementation of remedial pump and treat systems, however, results in hydraulic pressure responses, both areally and vertically (i.e., with depth) within the pumped aquifer. The area within the aquifer affected by the pump and treat system (i.e., radius of influence) is commonly estimated based on detecting associated water-level responses within surrounding monitor wells. Natural external stresses, such as barometric pressure fluctuations, however, can have a discernible impact on well water-level measurements. These temporal barometric effects may significantly mask water-level responses within more distant wells that are only slightly affected (< 0.10 m) by the test system. External stress effects, therefore, can lead to erroneous indications of the radius of influence of the imposed pump and treat system remediation activities and can greatly diminish the ability to analyze the associated well responses for hydraulic property characterization. When these extraneous influences are significant, adjustments or removal of the barometric effects from the test-response record may be required for quantitative hydrologic assessment. This report examines possible hydrologic effects of pump and treat remediation actions and provides a detailed analysis of water-level measurements for selected 200-ZP-1 pump and treat system monitor wells during the recent Y2K shutdown (December 1999) and restart activity (January 2000). The general findings presented in this report have universal application for unconfined and confined aquifer systems.

Interim Report: 100-NR-2 Apatite Treatability Test: Low Concentration Calcium Citrate-Phosphate Solution Injection for In Situ Strontium-90 Immobilization

Following an evaluation of potential Sr-90 treatment technologies and their applicability under 100-NR-2 hydrogeologic conditions, U.S. Department of Energy, Fluor Hanford, Inc., Pacific Northwest National Laboratory, and the Washington Department of Ecology agreed that the long-term strategy for groundwater remediation at 100-N Area will include apatite sequestration as the primary treatment, followed by a secondary treatment if necessary (most likely phytoremediation). Since then, the agencies have worked together to agree on which apatite sequestration technology has the greatest chance of reducing Sr-90 flux to the river at a reasonable cost. In July 2005, aqueous injection, (i.e., the introduction of apatite-forming chemicals into the subsurface) was endorsed as the interim remedy and selected for field testing. Studies are in progress to assess the efficacy of in situ apatite formation by aqueous solution injection to address both the vadose zone and the shallow aquifer along the 300 ft of shoreline where Sr-90 concentrations are highest. This report describes the field testing of the shallow aquifer treatment.

Transient Inverse Calibration of Hanford Site-Wide Groundwater Model to Hanford Operational Impacts - 1943 to 1996

This report describes a new initiative to strengthen the technical defensibility of predictions made with the Hanford site-wide groundwater flow and transport model. The focus is on characterizing major uncertainties in the current model. PNNL will develop and implement a calibration approach and methodology that can be used to evaluate alternative conceptual models of the Hanford aquifer system. The calibration process will involve a three-dimensional transient inverse calibration of each numerical model to historical observations of hydraulic and water quality impacts to the unconfined aquifer system from Hanford operations since the mid-1940s.

Three-Dimensional Modeling of DNAPL in the Subsurface of the 216-Z-9 Trench at the Hanford Site

This work describes numerical modeling for simulating carbon tetrachloride flow and transport as outlined in two DOE reports for the 200-PW-1 Operable Unit and the 200-PW-1, 200-PW-3, and 200-PW-6 Operable Units. Simulations using the multifluid flow model STOMP were conducted to estimate how disposed dense nonaqueous phase liquid migrates in the vadose zone.