Hydrochemistry and hydrogeologic conditions within the Hanford Site upper basalt confined aquifer system

Spane, F.A.; Webber, William D.

doi:10.2172/111944

Cited by 32 publications

(63 citation statements)

References 16 publications

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“…It is most likely that fire-burned areas are relatively small compared to the whole basin area, and the recharge rate may vary over space with the shift in climate as reported in other Oregon watersheds in a semi-arid climate [4]. Historic mean basin recharge is 42 cm/year, within range of previous studies of 2.0 to 36.0 cm/year [21,69]. After forest cover reduction, mean recharge decreases by 1.9 cm in RCP 4.5 and decreases 6.71 cm in RCP 8.5 in comparison to historic conditions.…”

Section: Potential Basin Recharge and Base-flowsupporting

confidence: 58%

Watershed Response to Climate Change and Fire-Burns in the Upper Umatilla River Basin, USA

Yazzie

Chang

2017

Climate

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This study analyzed watershed response to climate change and forest fire impacts in the upper Umatilla River Basin (URB), Oregon, using the precipitation runoff modeling system. Ten global climate models using Coupled Intercomparison Project Phase 5 experiments with Representative Concentration Pathways (RCP) 4.5 and 8.5 were used to simulate the effects of climate and fire-burns on runoff behavior throughout the 21st century. We observed the center timing (CT) of flow, seasonal flows, snow water equivalent (SWE) and basin recharge. In the upper URB, hydrologic regime shifts from a snow-rain-dominated to rain-dominated basin. Ensemble mean CT occurs 27 days earlier in RCP 4.5 and 33 days earlier in RCP 8.5, in comparison to historic conditions (1980s) by the end of the 21st century. After forest cover reduction in the 2080s, CT occurs 35 days earlier in RCP 4.5 and 29 days earlier in RCP 8.5. The difference in mean CT after fire-burns may be due to projected changes in the individual climate model. Winter flow is projected to decline after forest cover reduction in the 2080s by 85% and 72% in RCP 4.5 and RCP 8.5, in comparison to 98% change in ensemble mean winter flows in the 2080s before forest cover reduction. The ratio of ensemble mean snow water equivalent to precipitation substantially decreases by 81% and 91% in the 2050s and 2080s before forest cover reduction and a decrease of 90% in RCP 4.5 and 99% in RCP 8.5 in the 2080s after fire-burns. Mean basin recharge is 10% and 14% lower in the 2080s before fire-burns and after fire-burns, and it decreases by 13% in RCP 4.5 and decreases 22% in RCP 8.5 in the 2080s in comparison to historical conditions. Mixed results for recharge after forest cover reduction suggest that an increase may be due to the size of burned areas, decreased canopy interception and less evaporation occurring at the watershed surface, increasing the potential for infiltration. The effects of fire on the watershed system are strongly indicated by a significant increase in winter seasonal flows and a slight reduction in summer flows. Findings from this study may improve adaptive management of water resources, flood control and the effects of fire on a watershed system.

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Section: Potential Basin Recharge and Base-flowsupporting

confidence: 58%

Watershed Response to Climate Change and Fire-Burns in the Upper Umatilla River Basin, USA

Yazzie

Chang

2017

Climate

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“…Previous investigations focusing more specifically on Gable Gap include surface geologic mapping (Fecht 1978;Myers et al 1979), subsurface geophysical investigations (Holmes and Mitchell 1981;Ault 1981, Repasky et al 2009, and aquifer intercommunication studies between the unconfined aquifer and the Rattlesnake Ridge interbed (Strait and Moore 1982;Graham et al 1984;Jensen 1987;Spane and Webber 1995). All these previous studies established the foundation for the conceptual hydrogeologic model presented in this report.…”

Section: Introductionmentioning

confidence: 73%

“…This is an area for potential comingling of groundwater from unconfined and confined aquifers. The potential for aquifer intercommunication within this erosional window has long been recognized (Strait and Moore 1982;Graham et al 1984;Jensen 1987;Spane and Webber 1995). However, vertical head differences measured between the confined and unconfined aquifers suggests that any local groundwater contamination will not travel far within interbeds of the Ellensburg Formation.…”

Section: Hydrologymentioning

confidence: 98%

“…However, vertical head differences measured between the confined and unconfined aquifers suggests that any local groundwater contamination will not travel far within interbeds of the Ellensburg Formation. While groundwater may be locally driven into the upperbasalt confined aquifer system due to previous water-table mounding conditions within the Gable Gap area, this groundwater will likely discharge back into the overlying unconfined aquifer due to the reversal in vertical hydraulic head conditions (Graham et al 1984;Jensen 1987;Spane and Webber 1995). Figure 7.2 shows the elevation of the water table in the study area; also shown is the stratigraphic unit in contact with the top of the unconfined aquifer.…”

Section: Hydrologymentioning

confidence: 99%

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Hydrogeologic Model for the Gable Gap Area, Hanford Site

Bjornstad¹,

Thorne²,

Williams³

et al. 2010

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“…Numerous reports on Hanford Site geology and hydrogeology have been published. Reports relevant to the 100 Areas include the following publications and references therein: Delaney et al (1991), Hartman (2000), Horton et al (2001Horton et al ( , 2002, Lindberg (1995), Lindsey (1995), Peterson et al (1996b), Reidel and Chamness (2007), Spane and Webber (1995), and Thorne et al (1993). A general stratigraphy of the site is shown in Figure 1.3.…”

Section: Geologic Setting and Sediment Mineralogymentioning

confidence: 99%

Geochemical Characterization of Chromate Contamination in the 100 Area Vadose Zone at the Hanford Site

Dresel¹,

Qafoku²,

McKinley³

et al. 2008

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The major objectives of this study were to 1) determine the leaching characteristics of hexavalent chromium [Cr(VI)] from contaminated sediments collected from 100 Area spill sites; 2) elucidate possible Cr(VI) mineral and/or chemical associations that may be responsible for Cr(VI) retention in the Hanford Site 100 Areas through the use of macroscopic leaching studies, and microscale characterization of contaminated sediments; and 3) provide information to construct a conceptual model of Cr(VI) geochemistry in the Hanford 100 Area vadose zone that can be used for developing options for environmental remediation.In addressing these objectives, additional benefits accrued were as follows: 1) a more complete understanding of Cr(VI) entrained in the vadose zone that can be utilized in modeling potential Cr(VI) source terms; and 2) accelerating the 100 Area Columbia River Corridor cleanup by providing valuable information to develop remedial action based on a fundamental understanding of Cr(VI) vadose zone geochemistry.A series of column experiments were conducted with contaminated and uncontaminated sediments to study Cr(VI) desorption patterns in aged and freshly contaminated sediments; evaluate the transport characteristics of dichromate liquid retrieved from old pipelines in the 100 Area; and estimate the effect of strongly reducing liquid on the reduction and transport of Cr(VI). Column experiments used the <2-mm fraction of the sediment samples and simulated Hanford Site groundwater solution. Periodic stop-flow events were applied to evaluate the change in elemental concentration during time periods of no flow and greater fluid residence time. The results were fit using a two-site, one-dimensional reactive transport model. Sediments were characterized for the spatial and mineralogical associations of the contamination using an array of microscale techniques including X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, X-ray microprobe, and X-ray absorption near-edge structure.The following are conclusions and implications:1. Results from column experiments indicated that most of the contaminant chromium traveled quickly through the sediments and appeared as Cr(VI) in the effluents. However, the fine-grained surface coatings on sediment clasts acted as a porous but restricted medium that was accessible to chromate by diffusion from migrating chromate-laden water.2. The Cr(VI) concentration remained above the drinking water standard of 100 μg/L for many pore volumes. However, the significance of this for groundwater concentrations would depend on the mass flux of recharge to the water table.iii iv 3. Adsorption of Cr(VI) to sediments from spiked Cr(VI) solution was low; calculated retardation coefficients were close to one. During desorption experiments, sediment-dependent tailing was observed.4. Results from column experiments conducted with a strong reductant, such as calcium polysulfide solutions, to characterize and measure solution and sediment r...

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Hydrochemistry and hydrogeologic conditions within the Hanford Site upper basalt confined aquifer system

Cited by 32 publications

References 16 publications

Watershed Response to Climate Change and Fire-Burns in the Upper Umatilla River Basin, USA

Watershed Response to Climate Change and Fire-Burns in the Upper Umatilla River Basin, USA

Hydrogeologic Model for the Gable Gap Area, Hanford Site

Geochemical Characterization of Chromate Contamination in the 100 Area Vadose Zone at the Hanford Site

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