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Title: Evaluation of Deep Vadose Zone Contaminant Flux into Groundwater: Approach and Case Study

Abstract

For sites with a contaminant source located in the vadose zone, the nature and extent of groundwater contaminant plumes are a function of the contaminant flux from the vadose zone to groundwater. Especially for thick vadose zones, transport may be relatively slow making it difficult to directly measure contaminant flux. An integrated assessment approach, supported by site characterization and monitoring data, is presented to explain current vadose zone contaminant distributions and to estimate future contaminant flux to groundwater in support of remediation decisions. The U.S. Department of Energy Hanford Site (WA, USA) SX Tank Farm was used as a case study because of a large existing contaminant inventory in its deep vadose zone, the presence of a limited-extent groundwater plume, and the relatively large amount of available data for the site. A predictive quantitative analysis was applied to refine a baseline conceptual model through the completion of a series of targeted simulations. The analysis revealed that site recharge is the most important flux-controlling process for future contaminant flux. Tank leak characteristics and subsurface heterogeneities appear to have a limited effect on long-term contaminant flux into groundwater. The occurrence of the current technetium-99 groundwater plume was explained by taking into accountmore » a considerable historical water-line leak adjacent to one of the tanks. The analysis further indicates that the vast majority of technetium-99 is expected to migrate into the groundwater during the next century. The approach provides a template for use in evaluating contaminant flux to groundwater using existing site data and has elements that are relevant to other disposal sites with a thick vadose zone.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1254579
Report Number(s):
PNNL-SA-117617
Journal ID: ISSN 0169-7722; 830403000
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Journal of Contaminant Hydrology
Additional Journal Information:
Journal Volume: 189; Journal ID: ISSN 0169-7722
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
Vadose zone; Numerical modeling; Contaminant transport

Citation Formats

Oostrom, Martinus, Truex, Michael J., Last, George V., Strickland, Christopher E., and Tartakovsky, Guzel D. Evaluation of Deep Vadose Zone Contaminant Flux into Groundwater: Approach and Case Study. United States: N. p., 2016. Web. doi:10.1016/j.jconhyd.2016.03.002.
Oostrom, Martinus, Truex, Michael J., Last, George V., Strickland, Christopher E., & Tartakovsky, Guzel D. Evaluation of Deep Vadose Zone Contaminant Flux into Groundwater: Approach and Case Study. United States. https://doi.org/10.1016/j.jconhyd.2016.03.002
Oostrom, Martinus, Truex, Michael J., Last, George V., Strickland, Christopher E., and Tartakovsky, Guzel D. 2016. "Evaluation of Deep Vadose Zone Contaminant Flux into Groundwater: Approach and Case Study". United States. https://doi.org/10.1016/j.jconhyd.2016.03.002.
@article{osti_1254579,
title = {Evaluation of Deep Vadose Zone Contaminant Flux into Groundwater: Approach and Case Study},
author = {Oostrom, Martinus and Truex, Michael J. and Last, George V. and Strickland, Christopher E. and Tartakovsky, Guzel D.},
abstractNote = {For sites with a contaminant source located in the vadose zone, the nature and extent of groundwater contaminant plumes are a function of the contaminant flux from the vadose zone to groundwater. Especially for thick vadose zones, transport may be relatively slow making it difficult to directly measure contaminant flux. An integrated assessment approach, supported by site characterization and monitoring data, is presented to explain current vadose zone contaminant distributions and to estimate future contaminant flux to groundwater in support of remediation decisions. The U.S. Department of Energy Hanford Site (WA, USA) SX Tank Farm was used as a case study because of a large existing contaminant inventory in its deep vadose zone, the presence of a limited-extent groundwater plume, and the relatively large amount of available data for the site. A predictive quantitative analysis was applied to refine a baseline conceptual model through the completion of a series of targeted simulations. The analysis revealed that site recharge is the most important flux-controlling process for future contaminant flux. Tank leak characteristics and subsurface heterogeneities appear to have a limited effect on long-term contaminant flux into groundwater. The occurrence of the current technetium-99 groundwater plume was explained by taking into account a considerable historical water-line leak adjacent to one of the tanks. The analysis further indicates that the vast majority of technetium-99 is expected to migrate into the groundwater during the next century. The approach provides a template for use in evaluating contaminant flux to groundwater using existing site data and has elements that are relevant to other disposal sites with a thick vadose zone.},
doi = {10.1016/j.jconhyd.2016.03.002},
url = {https://www.osti.gov/biblio/1254579}, journal = {Journal of Contaminant Hydrology},
issn = {0169-7722},
number = ,
volume = 189,
place = {United States},
year = {Wed Mar 09 00:00:00 EST 2016},
month = {Wed Mar 09 00:00:00 EST 2016}
}