Moisture Accumulation under Asphalt Cover at Radioactive Waste-Burial Site

Rofer, C.K.; Martinez, Bennie A.; Klein, M.; Bayhurst, Gregory K.; Triay, I.R.

doi:10.1061/(asce)1090-025x(1999)3:1(10)

Cited by 4 publications

(4 citation statements)

References 13 publications

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“…It was later found that the elevated asphalt pad unfavorably altered the naturally dry hydrologic characteristics of the site by inhibiting evapotranspiration and by damming surface water along its edge. At several times, the asphalt was found to be in disrepair, and estimates of leakage through the cracked asphalt pad ranged from 60 to 388 mm yr −1 (Table 1; LANL, 1992; Rofer et al, 1999).…”

Section: Vadose Zone Conceptual Models Of the Pajarito Plateaumentioning

confidence: 99%

Conceptual Models of Vadose Zone Flow and Transport beneath the Pajarito Plateau, Los Alamos, New Mexico

Birdsell

Newman

Broxton

et al. 2005

Vadose Zone Journal

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field observations. To best develop and test conceptual models, supporting data should be derived using a num-The Pajarito Plateau in northern New Mexico, on which the Los ber of observational techniques and include a variety Alamos National Laboratory is situated, is characterized by a thick of data types. vadose zone overlying the regional aquifer of the western Espanola Basin. In this study, conceptual models of vadose zone flow and Los Alamos National Laboratory (the Laboratory or transport processes are presented and then supported through the LANL; Fig. 1) has performed research and development interpretation of field data, including synthesis with numerical models. in nuclear weapons technologies and other national de-The conceptual models differentiate the rate of percolation by their fense activities for more than 60 yr, beginning with the location and surface hydrologic setting, including wet and dry canyons, Manhattan Project in the 1940s. During this time, Laboand wet, dry, and disturbed mesas. Net infiltration beneath wet canratory operations have been accompanied by both disyons is the highest, with rates on the order of a meter per year posal of and intentional or accidental releases of chemi-(100-1000 mm yr Ϫ1 ). Transport to the regional aquifer beneath the cal contaminants into the environment at a variety of wettest canyons is likely on the order of several years to several sites. Contaminants with possible negative impacts to decades, depending on the thicknesses of the various hydrostratigroundwater include high explosives, radionuclides, chemgraphic layers. Perched water is sometimes found beneath wetter canyons and is associated with near-surface alluvial systems and at ical solvents, and metals. Today, the Laboratory is reintermediate depths along low-permeability interfaces such as buried sponsible for ensuring that none of its past contaminant soils or unfractured regions of basalt flows. Percolation through the releases pose a threat to human health now or in the volcanic tuffs is generally considered to be via matrix-dominated flow, future, and to carry out remediation activities to clean whereas fracture flow may play a key role in contaminant transport up contaminated sites. One of the key potential risks is through densely welded tuffs or basalt units beneath wet canyons.groundwater contamination, possibly affecting drinking Infiltration beneath dry canyons and dry mesas is much slower (10 water quality in municipal or private wells. Contaminants mm yr Ϫ1 or less), yielding transport times to the aquifer of hundreds must travel through a thick vadose zone to reach the to several thousands of years. However, long-term surface disturregional aquifer. Therefore, a well-developed conceptual bances at mesa-top locations may alter infiltration rates such that model describing vadose zone flow and transport beneath at a local scale, the infiltration rates temporarily approach those of wetter canyons.

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Section: Vadose Zone Conceptual Models Of the Pajarito Plateaumentioning

confidence: 99%

Conceptual Models of Vadose Zone Flow and Transport beneath the Pajarito Plateau, Los Alamos, New Mexico

Birdsell

Newman

Broxton

et al. 2005

Vadose Zone Journal

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“…The occurrence of roads, asphalt paving, and structures overlying closed waste pits can be seen in Figure 7. Neeper et al (1996), Rofer et al (1997), and Levitt et al (2005) describe the effects of an asphalt cover over MDA AB at TA-49 at LANL. These studies conclude that the asphalt cover causes increased infiltration by all but eliminating ET, but allowing runoff and focused infiltration through cracks in the asphalt.…”

Section: Infiltrationmentioning

confidence: 99%

“…Condensation of water vapor beneath the asphalt may have also resulted in increased water contents. After asphalt cracks were sealed, new cracking was observed to occur in less than two years (Rofer et al, 1997). Many parts of Area G have been covered with asphalt and structures for decades, and their eventual removal will result in decreased water contents and infiltration fluxes in the future.…”

Section: Infiltrationmentioning

confidence: 99%

Moisture Monitoring at Area G, Technical Area 54, Los Alamos National Laboratory

Levitt¹,

Birdsell

Jennings³

et al. 2015

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“…It was suspected that the cracks and the collapsed area in the asphalt cover allowed focused infiltration of water into CH‐2. In 1976, the asphalt cap was repaired, but more cracks and standing water were again found in CH‐2 in 1979, 1980, and 1991 (LANL, 1992; Rofer et al, 1999). In 1994, two 46‐m‐deep boreholes (49‐2906 and 49‐2907) were drilled through the asphalt cover to evaluate the subsurface conditions below the depths of the shafts and to augment the existing moisture monitoring holes at MDA AB (LANL, 1992).…”

mentioning

confidence: 99%

Comparison of the Water Balance of an Asphalt Cover and an Evapotranspiration Cover at Technical Area 49 at the Los Alamos National Laboratory

Levitt

Hartmann

Kisiel

et al. 2005

Vadose Zone Journal

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test experiments were conducted is now referred to as Material Disposal Area (MDA) AB. The areas within Two different types of waste covers, an asphalt cap and an evapo-MDA AB where the underground experiments were transpiration (ET) cover, have been used to contain a contaminated site at Technical Area (TA) 49 at the Los Alamos National Laboratory conducted are referred to as Areas 1, 2, 2A, 2B, 3, and (LANL). In 1961, a 2.5-to 20-cm-thick asphalt cap and gravel and 4. These Areas are also referred to as Potential Release clay cover was constructed to isolate contamination of surface soils Sites (PRSs) (LANL, 1992; Levitt et al., 2003). Refer associated with subcritical hydronuclear safety experiments conducted to Fig. 1 for the location of TA-49 and LANL within at TA-49 between 1959 and 1961. The asphalt cap remained in place New Mexico, and refer to Fig. 2 for the locations of the for 37 yr until 1998 when it was replaced with an ET cover. Cracks Areas and PRSs within TA-49. and subsidence features in the asphalt cap were periodically filled During the drilling of a new test shaft in 1960, transduring that time. The thickness of the ET cover is 2.1 m at its center, uranic materials were encountered from an adjacent tapering to zero thickness at its edges. The ET cover is instrumented shaft, resulting in contamination of surface soils. The with three neutron logging access tubes, and four time domain reflecarea of contamination, within Area 2, was covered by tometry (TDR) probes, and covered by a galvanized steel mesh biointrusion layer. Soil moisture monitoring was conducted immediately Published in Vadose Zone Journal 4:789-797 (2005).

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Moisture Accumulation under Asphalt Cover at Radioactive Waste-Burial Site

Cited by 4 publications

References 13 publications

Conceptual Models of Vadose Zone Flow and Transport beneath the Pajarito Plateau, Los Alamos, New Mexico

Conceptual Models of Vadose Zone Flow and Transport beneath the Pajarito Plateau, Los Alamos, New Mexico

Moisture Monitoring at Area G, Technical Area 54, Los Alamos National Laboratory

Comparison of the Water Balance of an Asphalt Cover and an Evapotranspiration Cover at Technical Area 49 at the Los Alamos National Laboratory

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