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Plans and Practices for Groundwater Protection at the Los Alamos National Laboratory: Final Report Color Plates

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Plans and Practices for Groundwater Protection at the Los Alamos National Laboratory: Final Report PLATE 1 Satellite photograph of the Los Alamos area of the Española Basin. Green indicates areas of greater vegetation in this false-color image. For orientation, the lines running approximately west to east below Los Alamos indicate the location of the representative cross section shown in Color Plate 2. SOURCE: Donathan Krier, LANL

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Plans and Practices for Groundwater Protection at the Los Alamos National Laboratory: Final Report PLATE 2 Representative geological cross section of the LANL site. Note that the representative canyon cuts from the Sierra de Los Valles and surface water flows toward the Rio Grande. Alluvial material is erosional sediment, including gravels, sands, silts, and clays, that is deposited by surface water. The materials are eroded from higher elevations in the watershed. SOURCE: Donathan Krier, LANL.

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Plans and Practices for Groundwater Protection at the Los Alamos National Laboratory: Final Report PLATE 3 Location of the key liquid waste outfalls on the LANL site. This map includes the outfalls that LANL believes to be sources of contamination that has been detected in site groundwater. In addition, the map shows regions where LANL’s site characterization work indicates relatively fast travel times downward through the vadose zone, based largely on the detections of contamination in groundwater. All except two of these “historic” outfalls have been closed; see Table 3.1. The Radioactive Liquid Waste Treatment Facility discharges wastes from Outfall 051 into Mortandad Canyon, and a power plant and sanitary waste facility discharge wastes from Outfall 001 into Sandia Canyon. Discharges from these two facilities and other currently operating facilities meet NPDES and DOE requirements. SOURCE: Donathan Krier, LANL.

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Plans and Practices for Groundwater Protection at the Los Alamos National Laboratory: Final Report PLATE 4 Location of the key material disposal areas (MDAs) on the LANL site. These nine areas contain sufficiently large inventories of solid wastes that they may pose future threats to groundwater; see Table 3.2. Most are located on mesa tops that are normally dry. Some are relatively near fast vadose zone pathways identified by LANL. Thus far in LANL’s groundwater protection program solid waste disposal areas have received relatively less attention than liquid outfalls. SOURCE: Donathan Krier, LANL.

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Plans and Practices for Groundwater Protection at the Los Alamos National Laboratory: Final Report PLATES 5a,b Illustrative plots of plutonium data from site sampling. Plot A shows plutonium detected in surface soils ratioed to a chosen reference value of 0.054 pCi/g. Plot B shows the most recent plutonium analyses of regional groundwater ratioed to a chosen reference value of 0.03 pCi/L. The reference value of 0.054 pCi/g in soil is an upper tolerance limit used by LANL (Ryti et al., 1998). The reference value of 0.03 pCi/L is the average background value for plutonium detected in sediments in the Rio Grande from Graf (1994). Note: the plot will look different for different reference values chosen. All analytical values at or below the MDL (non-detects, shown in gray) are shown to illustrate where samples were collected but no plutonium was detected. Blue values show measured concentrations at or below the reference value, interpreted in these plots to be below or near atmospheric fallout levels. Red values show where plutonium was detected. Most of the plutonium is located in the shallow surface soils within the canyons. There is one analysis of plutonium in the regional groundwater that is a J value, which means a detection was reported, but the level is too low to be reported with a high degree of confidence; see Sidebar 5.2. Two duplicate analyses were subsequently analyzed and both were non-detect values. Therefore, this J-value should be interpreted with caution and serves to demonstrate the difficulty of interpreting data that are near the analytical limits of detection. See discussion in Chapter 5. These plots are for illustrative purposes only. SOURCE: Risk Assessment Corporation.

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Plans and Practices for Groundwater Protection at the Los Alamos National Laboratory: Final Report PLATE 6a,b Illustrative plots of tritium data from site sampling. Plot A shows tritium detected in shallow alluvial groundwater ratioed to a chosen reference value of 50 pCi/L. Plot B shows the tritium analyses in the top of the regional groundwater ratioed to a chosen reference value of 2 pCi/L. The reference value of 50 pCi/L in the alluvial groundwater was taken as a reasonable background atmospheric fallout level (LANL, 2006b). The reference value of 2 pCi/L is the average background value for tritium detected for regional groundwaters as a result of atmospheric fallout (LANL, 2006b). Note, the plot will look different for different reference values chosen. All analytical values at or below the MDL (non-detects, shown in gray) are shown to illustrate where samples were collected but no tritium was detected. Blue values show measured concentrations at or below the reference value, interpreted in these plots to be below or near atmospheric fallout levels. Red values show where tritium was detected. Tritium has been detected in both the shallow alluvial groundwater and the regional aquifer. These plots are for illustrative purposes only. SOURCE: Risk Assessment Corporation.

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Plans and Practices for Groundwater Protection at the Los Alamos National Laboratory: Final Report PLATE 7 Conceptual model of hydrogeology and contaminant transport in Mortandad Canyon. Mortandad Canyon is located above the Mortandad watershed, which is shown on Color Plates 9 and 10. LANL considers this canyon to be a significant source of groundwater contamination. Much scientific effort has been focused on understanding the hydrogeology of wet canyons, as discussed in Chapter 4. SOURCE: Donathan Krier, LANL.

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Plans and Practices for Groundwater Protection at the Los Alamos National Laboratory: Final Report PLATE 8 Occurrences of perched water beneath the LANL site. Small zones of intermediate-depth groundwater are referred to as “perched” because they occur in the unsaturated zone above the more laterally extensive and productive regional aquifer. This west-to-east cross section shows the variety of occurrences of perched water found beneath the area of the site between the lines indicated on Color Plate 1. Contaminants have been found in perched water, and it is believed that the hydrogeology associated with perching can redirect contaminant transport laterally between watersheds, as discussed in Chapter 4. SOURCE: Donathan Krier, LANL.

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Plans and Practices for Groundwater Protection at the Los Alamos National Laboratory: Final Report PLATE 9 Well and borehole emplacements at LANL in about 1997. Most wells are water supply wells, which reach the regional aquifer. These wells supply water to Los Alamos County, the Pueblo de San Ildefonso, and to the LANL site. Wells in the Buckman well field, east of the Rio Grande (on the right margin of the figure), supply water to the city of Santa Fe. Relatively few wells or boreholes had been emplaced for site characterization or monitoring. This map, as well as Color Plate 10, shows the seven watersheds or groups of watersheds on which LANL’s interm plans for site monitoring are based. SOURCE: Broxton, 2006.

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Plans and Practices for Groundwater Protection at the Los Alamos National Laboratory: Final Report PLATE 10 Wells and boreholes in 2005 after completion of the Hydrogeologic Workplan. Under the workplan 25 wells (designated R) were drilled into the regional aquifer. Most of these wells provided sampling points (screens) at more than one depth. About 22 new intermediate-depth boreholes and wells were drilled to sample groundwater perched above the regional aquifer. The original intent of this work was to improve LANL’s knowledge of the site’s hydrogeology in order to begin planning a groundwater monitoring network. Extending the use of the R-wells for groundwater monitoring has been controversal, as discussed in Chapter 5. Well R-35 was installed in 2007 near the end of this study. SOURCE: Broxton, 2006.