Science and Technology for Environmental Cleanup at Hanford (2001) / Chapter Skim
Currently Skimming:
6 Vadose Zone Technical Element
6 Vadose Zone Technical Element
Pages 79-99
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 79... ...
This chapter provides a brief review and assessment of the work supported under this technical element. The main sources of information used in this assessment are the Integration Project Roadmap (DOE 2000a)
|
From page 80... ...
Unsaturated zones are chemical and mechanical systems in disequilibrium in which fluids and solutes move in response to gradients in 2Neither diffusion theory nor advection theory alone accurately predicts gas transport near sources of contamination.
|
From page 81... ...
Vadose Zone Technical Element 81 free energy. Transport rates are approximately proportional to gradients in free energy, but the proportionalities are nonlinear functions of saturation (Figure 6.1~.
|
From page 82... ...
Field investigations of representative sites: This activity ncludes six projects to develop an improved understanding of contaminant distributions beneath selected tank farms and at 200 Area soil waste sites.3 3V\laste sites (e.g., tanks, ponds, cribs, trenches, landfills) in the 200 Area have been grouped based on waste inventories (DOE, 1997c)
|
From page 83... ...
3. Waste and sediment experiments and models: This activity includes six projects to obtain kinetic and thermodynamic data on key contaminants to determine first-order hydrochemical reactions controlling contaminant behavior in sediments beneath tank farms and at 200 Area soil waste sites.
|
From page 84... ...
EMSP Funding (thousand dollars) 1,600 Field investigations of representative sites 6 Transport 8 modeling Waste and 6 sediment experiments and models Vadose zone 4 transport field studies Advanced vadose zone charactenz ation Develop an improved understanding of contaminant distributions beneath selected tank farms and at 200 Area soil waste sites Obtain an improved understanding of fate and transport processes beneath selected tank farms and at 200 Area soil waste sites Obtain kinetic and thermodynamic data on key contaminants to determine first-order hydrochemical reactions controlling contaminant behavior in sediments beneath tank farms and at representative 200 Area soil waste sites Develop an improved understanding of water and solute movement, reactive transport, and migration pathways in vadose zone sediments in the 200 East Area and 200 West Area Use advanced characterization technologies to support the vadose zone transport field studies in Me 200 East Area and 200 West Area, and evaluate tools for monitoring contaminant plumes in the vadose zone beneath tank farms.
|
From page 85... ...
These projects are designed around field investigations at what the Integration Project calls "representative sites," that is, sites designed by the Integration Project to be broadly representative of the population of waste sites that exist in the 200 Area based on characteristics such as waste type and vadose zone geology. The scale of evaluation for most of the projects under this activity is the individual mineral, although studies of intact cores and homogenized core material will be undertaken to examine questions related to contaminant migration.
|
From page 86... ...
Three projects (VZ4, VZ-5, and VZ-6) are focused on developing conceptual models of the important processes controlling contaminant distributions beneath leaking single-shell tanks and soil waste sites in the 200 Area.
|
From page 87... ...
Are there other concerns, comments, or suggestions that should be considered by the Integration Project in executing the planned work? The committee is concerned about how the S&T program intends to set the data quality objectives for supporting sound management decisions.
|
From page 89... ...
, and one project (VZ-08) targets "high-priority' but unspecified 200 Area soil waste sites.
|
From page 90... ...
_ Debris flows; landsildes; channel shim; river meander cutoff; channelizaffon; diversion overdammir~ by humans Minor glac anon fluc~affon, very large landsildes; alluvial or colluvial valley filling; river meander development Technic uplift, subs dance; sea level dianges; gladaffon Hanford Site scale Sediment accumulation/ washout small bank failures; flood flow scour/deposldon Annual flow; seasonal meaophyle grow~/scour 0.1 1 10 100 1,000 K
|
From page 91... ...
The Integration Project has not provided an explicit link between the planned work and the issues to be addressecl, but the committee sees several such links. The planned work could help explain the cesium "anomaly' discovered in the deep vadose zone beneath one of the tank farms (Chapter 1~.
|
From page 92... ...
to develop an improved understanding of key geochemical phenomena in target waste sites by conducting kinetic and thermodynamic studies of contaminants of concern using uncontaminated and contaminated sediments to determine proximal chemical and hydrochemical reactions and (2) to use the data from the first goal in the development of numerical models for describing contaminant transport through unsaturated columns.
|
From page 93... ...
Are there other concerns, comments, or suggestions that should be considered by the Integration Project in executing the planned work? 93 As with the field investigation tasks, the problem remains of how to set the data quality objectives for supporting management decisions.
|
From page 94... ...
are identified prominently in the project descriptions given in Table 4-1 in the Integration Project Roadmap (DOE 2000a) , but aside from the high salt concentration reactive transport experiment, they do not seem to be a major consideration in the detailed work plans (DOE, 1999e, 20009~.
|
From page 95... ...
If these experiments can be used to establish an effective approach to characterize and simulate such large-scale heterogeneous nonlinear systems, this would be a major scientific contribution. Can the planned work have an impact on cleanup decisions at the Hanford Site?
|
From page 96... ...
Two involve field tests of characterization technologies for delineating moisture and contaminant plumes at the vadose zone field transport study sites in the 200 East Area and 200 West Area (VZ-25 and VZ-26~. The third project (VZ-27)
|
From page 97... ...
The advanced vadose zone characterization technical element appears to have been folded into the vadose zone transport field transport studies. Although the field study provides a valuable opportunity to test advanced characterization techniques, the magnitude of the S&T need would seem to warrant dedicated laboratory, theoretical, and field-based efforts beyond the immediate scope of the vadose zone transport field transport studies.
|
From page 98... ...
Moreover, the long period of time required to carry out vadose zone field experiments in dry environments such as Hanford is not considered adequately in the planning. One of the main "owners" of S&T results from the Vadose Zone Technical Element will be the SAC, which can use these results to develop more realistic models for contaminant transport in the vadose zone.
|
From page 99... ...
Vadose Zone Technical Element The committee therefore recommends that peer reviews be established specifically to provide continuing oversight of these field studies. This peer review should occur during all stages of the studies that is, from initial planning and design of the experiments through analysis and interpretation of results.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.