Estimation of the release and migration of lead through soils and groundwater at the Hanford Site 218-E-12B Burial Ground. Volume 1, Final report

Abstract

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.