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From 2005 to 2008, the U.S. Geological Survey's Idaho National Laboratory (INL) Project office, in cooperation with the U.S. Department of Energy, collected water-quality samples from multiple water-bearing zones in the eastern Snake River Plain aquifer. Water samples were collected from six monitoring wells completed in about 350-700 feet of the upper part of the aquifer, and the samples were analyzed for major ions, selected trace elements, nutrients, selected radiochemical constituents, and selected stable isotopes. Each well was equipped with a multilevel monitoring system containing four to seven sampling ports that were each isolated by permanent packer systems. The sampling ports were installed in aquifer zones that were highly transmissive and that represented the water chemistry of the top four to five model layers of a steady-state and transient groundwater-flow model. The model's water chemistry and particle-tracking simulations are being used to better define movement of wastewater constituents in the aquifer. The results of the water chemistry analyses indicated that, in each of four separate wells, one zone of water differed markedly from the other zones in the well. In four wells, one zone to as many as five zones contained radiochemical constituents that originated from wastewater disposal at selected laboratory facilities. The multilevel sampling systems are defining the vertical distribution of wastewater constituents in the eastern Snake River Plain aquifer and the concentrations of wastewater constituents in deeper zones in wells Middle 2051, USGS 132, and USGS 103 support the concept of groundwater flow deepening in the southwestern part of the

For more information on the USGS-the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment-visit http://www.usgs.gov or call 1-888-ASK-USGS.For an overview of USGS information products, including maps, imagery, and publications, visit http://store.usgs.gov.Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner. Horizontal coordinate information is referenced to the North American Datum of 1927 (NAD 27).Altitude, as used in this report, refers to distance above the vertical datum. strontium-90, chlorine-36, iodine-129, plutonium-238, plutonium-239, -240 (undivided), americium-241, technetium-99, uranium-234, uranium-235, and uranium-238 were selected for the background study because they were either not analyzed in earlier studies or new data became available to give a more recent determination of background concentrations. Samples of water collected from wells and springs at and near the INL that were not believed to be influenced by wastewater disposal were used to identify background concentrations. Groundwater in the eastern Snake River Plain aquifer at and near the INL was divided into two major water types (western tributary and eastern regional) based on concentrations of lithium less than and greater than 5 micrograms per liter (µg/L). Median concentrations for each constituent were used to define the upper limit of background. Supplemental InformationThe upper limit of background concentrations for inorganic chemicals for western tributary water was 40.7 milligrams per liter (mg/L) for calcium, 15.3 mg/L for magnesium, 8.30 mg/L for sodium, 2.32 mg/L for potassium, 23.1 mg/L for silica, 11.8 mg/L for chloride, 21.4 mg/L for sulfate, 0.20 mg/L for fluoride, 176 mg/L for bicarbonate, 4.00 µg/L for chromium, and 0.655 mg/L for nitrate.The upper limit of background concentrations for inorganic chemicals for eastern regional water was 34.05 mg/L for calcium, 13.85 mg/L for magnesium, 14.85 mg/L for sodium, 3.22 mg/L for potassium, 31.0 mg/L for silica, 14.15 mg/L for chloride, 20.2 mg/L for sulfate, 0.4675 mg/L for fluoride, 165 mg/L for bicarbonate, 3.00 µg/L for chromium, and 0.995 mg/L for nitrate.The upper limit of background concentrations for radiochemical constituents for western tributary water was 34.15 ±2.35 picocuries per liter (pCi/L) for tritium, 0.00098 ±0.00006 pCi/L for chlorine-36, 0.000011 ±0.000005 pCi/L for iodine-129, <0.0000054 pCi/L for technetium-99, 0 pCi/L for strontium-90, plutonium-238, plutonium-239, -240 (undivided), and americium-241, 1.36 pCi/L with undetermined uncertainty for uranium-234, 0.025 ±0.001 pCi/L for uranium-235, and 0.541 ±0.001 pCi/L for uranium-238.The upper limit of background concentrations for radio...

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southwestern portion of the INEEL where, because of potential contaminants in this area, some of the most Questions of major importance for subsurface contaminant transintensive subsurface characterization efforts have been port at the Idaho National Engineering and Environmental Laboratory (INEEL) include (i) travel times to the aquifer, both average or done (Fig. 1). A major source of these contaminants is typical values and the range of values to be expected, and (ii) modes the INEEL facility known as the Subsurface Disposal of contaminant transport, especially sorption processes. The hydraulic Area (SDA) for radioactive and other hazardous waste. and geochemical framework within which these questions are ad-As a result, the SDA and its nearby surroundings are dressed is dominated by extreme heterogeneity in a vadose zone and the portion of the INEEL that has been most intensively aquifer consisting of interbedded basalts and sediments. Hydraulically, studied with respect to hydraulic and geochemical issues. major issues include diverse possible types of flow pathways, extreme This paper reflects this emphasis, though where possible anisotropy, preferential flow, combined vertical and horizontal flow, we have formulated generalizations to apply to most or and temporary saturation or perching. Geochemically, major issues all of the INEEL. This review is designed to complement include contaminant mobility as influenced by redox conditions, the that of Smith (2004). In terms of local-scale geologic concentration of organic and inorganic complexing solutes and other local variables, the interaction with infiltrating waters and with the framework, it picks up from Smith's presentation of teccontaminant source environment, and the aqueous speciation of con-tonics, volcanism, and basalt characteristics; it emphataminants such as actinides. Another major issue is the possibility of sizes relatively small-scale features and their role in colloid transport, which inverts some of the traditional concepts of transport processes. We cover basic issues of transportmobility, as sorbed contaminants on mobile colloids may be transrelevant characteristics as known mainly from investigaported with ease compared with contaminants that are not sorbed.tions since the 1950s by relatively standard techniques. With respect to the goal of minimizing aquifer concentrations of con-Much material in this paper derives from a 1999 taminants, some characteristics of the vadose zone are essentially USGS panel review of DOE-contractor investigations completely favorable. Examples include the great thickness (200 m) related to existing and potential contaminant transport of the vadose zone, and the presence of substantial quantities of fine (Rousseau et al., 2004). It follows the series of USGS sediments that can retard contaminant transport both hydraulically and chemically. Most characteristics, however, have both favorable Reports on the INEEL subsurface by Barraclough and and unfavorable aspects. For example, preferential flow, as promoted ...