Plans and Practices for Groundwater Protection at the Los Alamos National Laboratory Final Report (2007) / Chapter Skim
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4 Pathways for Contaminant Transport
4 Pathways for Contaminant Transport
Pages 35-48
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From page 35... ...
In addition the Integrated Plan includes monitoring of water As summarized in Chapter 2 and described in this supply wells in Los Alamos County and in the City of Santa Fe (Section 2) ; chapter, LANL has developed a broad understanding monitoring of groundwater and surface water at locations within the Pueblo of the main features of the hydrogeologic environment de San Ildefonso (Section 3)
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From page 36... ...
5 Otowi-1 is indicated by O-1 near the upper right corner of Color Plates 9 2 The locations of these canyons are shown in Chapter 1, Figure 1.1, and and 10. Otowi-1 is one of the water supply wells for Los Alamos County several of the color plates following Chapter 2.
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From page 37... ...
However, disruptive events, such as the Cerro ments and transport both mobile and sorbing species. The Grande fire and its aftermath of severe stormwater runoff, contaminants in the canyons are subject to transport by storm can lead to significant mobilization and redistribution of flow toward the Rio Grande.
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From page 38... ...
LANL (2004b) describes investigations conducted in numerous springs, which are rare in the dry mesas or the Los Alamos and Pueblo canyons of surface water processes that eastern part of the plateau except where the regional aquifer transport contaminants across the site.
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From page 39... ...
PATHWAYS FOR CONTAMINANT TRANSPORT unsaturated hydraulic conductivity in the vadose zones of ponded water and the fractures are exposed at the surface, arid and semi-arid regions. However, there is evidence at fracture flow would be expected to occur.
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From page 40... ...
The recent discoveries of elevated chromium condownward percolation is slowed by a low-permeability centrations in wells R-28 in Mortandad Canyon and R-11 in barrier. Color Plate 8 illustrates the variety of perched water Sandia Canyon (LANL, 2006d)
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From page 41... ...
the Rio Grande. On the other hand, higher connectivity could Although mass balances are inherently difficult to perform for result in the contaminants spreading vertically and more highly heterogeneous media with preferential flowpaths, they likely entering the deep screened intervals of the regional can serve to test the validity of adopted conceptual models water supply wells.
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From page 42... ...
More generally, these boundaries to better incorporate regional flow and recharge LANL scientists have demonstrated that modeling and locations, which, in turn, better accommodate the simulation site characterization studies are important to selecting well of the aquifer system under the LANL site. Slightly earlier locations and sampling frequency as part of the design of an regional models used for water supply were developed by the effective monitoring system.
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From page 43... ...
Intermediate-perched groundwater -- localized satucan outweigh the uncertainty in parameters included in the rated zones within the vadose zone; and • model. Overlooking conceptual, non-modeled, uncertainties Regional groundwater -- the deep, laterally continucan lead to results that give an overly optimistic perception ous groundwater beneath the Pajarito Plateau.
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From page 44... ...
The alternative conceptual models might include differences In looking at the regional monitoring network, the in assumed transport pathways (i.e., alternative models of the committee found that the southern portion of LANL is one hydrogeology and geochemistry) , forcing conditions (e.g., area of the regional aquifer that is currently very sparsely input and boundary conditions)
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From page 45... ...
This current understanding can, and around the borehole. Modern geophysical methods can should, be improved to ensure groundwater protection in the at least supplement characterization and monitoring data coming decades and centuries.
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From page 46... ...
might remain near the top of the regional aquifer and Although LANL is using a numerically sophisticated most likely discharge in the springs near the Rio Grande. multiphase model for vadose and regional groundwater On the other hand, higher connectivity could result in modeling, it is not yet possible to predict with confidence the contaminants spreading vertically and more likely
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From page 47... ...
Recommendations: LANL should demonstrate better LANL's efforts to understand the role of geochemistry in use of its current understanding of contaminant transcontaminant migration have not kept pace with efforts port pathways in the design of its groundwater monitorto understand hydrology. The committee found a lack of ing program.
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