Table S.1. (contd) Technology Description State of Development Development Path Electrokinetic mobilization and recovery Application of an electric field in the soil induces contaminant mobilization through electromigration, electroosmosis, or electrophoresis. Particularly applicable to lowpermeability sediments. Method has been implemented in selected shallow vadose zone contaminant areas. Ability to deploy at depth and/or over large areas may be an issue. This area is not considered a high priority for R&D. Identify suitable chemical enhancements for particular applications if considering deployment on a site-specific basis. Hybrid electrokinetic delivery of treatment chemicals Mobilization of fluids to target areas by application of electric fields. Laboratory testing performed for reduction of chromate. Control of subsurface chemical conditions is critical. This area is a high priority for R&D applied to remedial design. Recommend further R&D for chemical fixation in low-permeability sediments and enhancement of other remediation systems. Hybrid electrokineticpermeable reductive barrier Electrical fields can enhance the reductive effectiveness of permeable barriers. Laboratory testing performed for reduction of chromate. Placement of electrodes and barriers in deep vadose zone may be problematic. May be useful in areas of low-permeability, high saturation sediments. This area is not considered a high priority for deep vadose zone R&D. Assess local geochemical and hydrological conditions when considering deployment on a site-specific basis. Enhanced Volatilization Volatilization by heating is limited to zero-valent mercury (Hg), organic mercury species, and potentially iodine-129. Hg(II) would have to be reduced to Hg(0) for volatilization. Conceptually simple but only laboratoryscale evaluations were found. This area is not considered a high priority for R&D. Assess local geochemical and hydrological conditions when considering deployment on a site-specific basis. viii Table S.1. (contd) Technology Description State of Development Development Path Enhanced Sorption Chemical manipulation of solution or solid surfaces to retard transport. Addition of materials to increase sorptive surfaces (altered mineralogy or particle size) or to alter aqueous speciation can retard chemical movement. Mature concept. Less fundamental information on desorption processes than for sorption. This area is not considered a high priority for R&D applied to remedial design. Fundamental research on desorption processes would be valuable. xiii Table S.1. (contd) Technology Description State of Development Development Path Hydraulic Control Caps and covers Caps and covers control infiltration and recharge, thus, reducing contaminant transport to the water table. Covers may be combined with other fixation technologies. Cap and cover technologies are well established but may need engineering for site-specific applications. This area is not considered a high priority for deep vadose zone R&D. Consider deployment on a site-specific basis. A...

This study was performed to evaluate the potential for transport of nickel radioisotopes from the Hanford Site 218-E-12B Burial Groundto the • surrounding surface-and groundwater. Burial of large metal components containing nickel-bearing alloys at this location may eventually result in release of elemental nickel and nickel radioisotopes (SgNi and S3Ni) to the subsurface environment, including groundwater aquifers that may be used for domestic and agricultural purposes in the future, and, ultimately, to the Columbia River. The rate at which nickel could be transported to downgradieqt locations dependson a complexset of factors, including climate, soil and groundwater chemistry, and the geologic and hydrologic configuration of the subsurface region between the burial ground and a potential receptor location. The .: geologic structure of the sedimentary formation in this area was investigated usingavailable published information, by observing the wallsof the excavated burialtrench,and by examining boreholecuttingstaken in the region. Physical,hydraulic, and geochemical properties of the sedimentary depositswere determined by laboratory analysisof samplestakenfrom the trenchwalls and a limitednumberof samplesfrom boreholecuttings. Releaseof nickel compounds to the subsurface environment was basedon eitherthe corrosion ratesof nickelalloysin the components or the solubility limitsfor the resulting nickelcorrosion productsin Hanfordgroundwater.The corrosion ratesfor nickelalloyswere takenfrom published literature, and the solubility of nickelcompounds was determined in laboratory studies. The groundwater transport analysis was conducted usinga one-dimensional screening modelwith a relatively conservative matrixof parameters obtained fromthe hydrogeologic and geochemical studies. The predicted peak concentrationsof nickelin the unconfined aquiferrangedfrom 1.g x 10"Isto 2.0 pCi/LSgNiand 3.1 x 10-4to 5.1 x 10-2mcj/L totalelemental nickel, .o depending on assumptions aboutthe numberof components buriedat the site, the climate,and the receptorlocation. The estimated transferof nickelto ." the ColumbiaRiverwas less than 1.3 x 107 pCi/yrfor 5SNiand 2.2 kg/yrfor lii EXECUTIVESUMMARY • An assessment was performed to evaluate release and transport of nickel from large metal components containing nickel-bearing alloys at the Hanford • Site 218-E-12B Burial Ground. The potential for ntckel within the components to enter groundwater under the burtal site was investigated by examining available data on the site's geology, geochemistry, and geohydrology to develop a conceptual model for release and transport of ntckel from the components. In addition, laboratory studies were performed to provide information needed for the model, but which was not available from existing databases. Estimates of future concentrations of ntckel radioisotopes (59Ni and 63N1) and total elemental ntckel in the unconfined aquifer and in the Columbla River were developed based on thts information. The geological strata underlying the burial ground form a ...

from the ROCSAN database (WHC Iggl). The wells used and the characterization data associatedwith each well are listed in Table A.I. Figure A.3 is a location map of the boreholes In the vicinityof the burial ground. Cross sections,located in Figure A.3, that show the interpretedsubsurface stratigraphybased on the data from these wells are presentedin Figures A.4 and A. 5. In addition to borehole studies, detailed observations were made and samples were collected from the excavated exposures of the 218-E-12B Burial Ground itself. A geologic map (Plate A.1) of the exposed burial ground wall was prepared and samples of the different lithologic types present were collected for a variety of laboratory analyses. These analyses include grain-size distribution, moisture content, porosity, permeability, bulk density, clay mineralogy, and bulk geochemistry. The analyzed samples are listed in Tables A.2 and A.3 and were collected from locations shown in Plate A.1 and Figures A.6 and A.7. Data from the completed analyses are provided in Appendix B (Parts 1-5). For comparison with outcrop samples, similar analyses were performed on selected samples of borehole cuttings obtained from two wells immediately adjacent to the 218-E-12B Burial Ground (299-E35-1 and 299-E34-7, Figure A.4). Completed analyses are reported in Appendix B (Parts 4-6). A.2.1.1 Columbia River Basalt Grouo The Columbia River Basalt Group is an assemblage of tholeiittc, continental flood basalt flows of Hiocene age. These flows cover much of the Columbia Plateau, which includes an area greater than 163,700 km z (63,000 mi2) tn Washington, Oregon, and Idaho, and have an estimated volume of about 174,000 Ion a (40,800 mta) (Tolan et al. 1989). Isotopic age deteminations indicate that basalt flows were erupted from approximately 17 to 6 million years before present (Ha). More than 98%of thts volume was erupted in a 2.5million-year period between 17 and 14.5 Ma (Reidel et al. 1989). The youngest basalt flows in the vicinity of the 218-E-12B Burial Ground belong to the Elephant Mountain Memberof the Saddle Hountains Basalt, which is about 8.5 Ha (HcKee et al. 1977).

The results of these tests were then used to predict the properties of similar formations in the deeper strata, and ultimately the travel time required for water to reach the unconfined aquifer. The chemistry of soil and groundwater also play an important role in predicting transport of lead from the burial site. The release rate of lead from the meta] components dependslargely uponthe oxidation rate of metallic lead, on the dissolution of secondaryminerals such as lead carbonates in water percolating through the soil, and on the total quantity of water percolating through the soil surrounding the components. After dissolution, transport of lead from the burial ground to the aquifer below is strongly influenced by the abiltty of surrounding soil to adsorb and retain it. The extent to which dissolved lead is adsorbedonto soil particles is a relatively complexfunctton of the water and soil chemistry, and of the properties of the lead species in solution. For this evaluation, sot1 samplesfrom the burial site were analyzed to detemine their chemical and mineralogical make-up, and the chemistry of groundwater tn the vicinity was available from data taken at onsite monitoring wells. The solubility of lead in Hanford soils and groundwater was predicted using the MINTEO computercode along with laboratory analytical data for groundwater chemistry at an onsite monitoring well. The model predictions were then comparedwith the results of laboratory studies tn which the solubility of lead in Hanford soil and groundwater systemswere determined empirically. The results of empirical laboratory experiments, in which lead solubility was determined to be approximately 236 /_g/L, was very close to the predicted solubility of 287 #g/L from the computer model. Becausepossible Interactions of lead with other metals in the components were of interest, the solubility of ntckel was also predicted, using the HINTEQcode, to be 16.6 mg/L. For the transport modeling, it was conservatively assumed that all water leaching from the burtal ground dissolved lead and nickel compounds up to the saturation limit. Twosolubi!ity estimates for lead, 300 and 550 /_g/L, were used in the transport modeling to represent a "best estimate" and a "conservative" case. Adsorption of lead onto soil from the burialsitewas beinginvestigated usingtwo methodologies.In batchadsorption tests,measuredquantities of vi ' _ Water F_GURE2.4. Water Tab]e Contours for the Steady-State 0.5 cm/yr Recharge Case (Graph sca]es in feet. Contour lines in feet above mean sea level.) 2.g U.S. Department of Energy. 1989. Decommisstonina of Eiaht Surplus Production Reactors at the Hanford Site. Richland, Washinqton, Draft Environmental Impact Statement. DOE/EIS-OIIgD, Washington, 9.C. U.S. Department of Energy (DOE). 1990a. Radioactive Waste Manaqement. DOE/RL5820.2A, Richland, Washington.