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Title: Influence of Clastic Dikes on Vertical Migration of Contaminants at the Hanford Site

Abstract

Clastic dikes are subvertical sedimentary features that cut through horizontally layered sediments, and they are common at the Hanford Site. Because of their cross-cutting relationship with the surrounding matrix, they have been proposed as potential fast paths from former contaminant discharge sites at the surface to the water table. However, little was known of the detailed hydrogeologic properties of the dikes and detailed modeling of flow and transport through the dikes had not been performed. We excavated a 2 m wide clastic dike at the Hanford Site and characterized it using an air minipermeameter, infrared imagery, and grain size analyses. Field injection experiments were also used to characterize the system. The resulting data were used to prepare a detailed numerical model of the clastic dike and surrounding matrix for a portion of the excavation. Unsaturated flow and transport through the system were modeled for several recharge rates. The highly heterogeneous nature of the system led to complex behavior, with the relative flux rates in the matrix and clastic dike being highly dependent on the recharge rates that were imposed on the system. The study suggests that the potential role of clastic dikes in vertical transport at the Hanford Site wouldmore » depend on the leakage rate, and that areas of contaminant deposition formed at high flow rates might become isolated at low flow rates, and vice-versa. The results may also help explain the occurrence of complex breakthrough patterns of contaminants at the water table.« less

Authors:
; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
922178
Report Number(s):
PNNL-SA-54224
KP1301020; TRN: US0800983
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Vadose Zone Journal, 6(4):959-970
Additional Journal Information:
Journal Volume: 6; Journal Issue: 4
Country of Publication:
United States
Language:
English
Subject:
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; 58 GEOSCIENCES; HANFORD RESERVATION; GEOLOGIC STRUCTURES; EXCAVATION; ENVIRONMENTAL TRANSPORT; FLOW RATE; GEOLOGIC MODELS; FLOW MODELS; POLLUTANTS; clastic dikes; geostatistics; vadose zone modeling; Hanford Site

Citation Formats

Murray, Christopher J, Ward, Andy L, and Wilson, John. Influence of Clastic Dikes on Vertical Migration of Contaminants at the Hanford Site. United States: N. p., 2007. Web. doi:10.2136/vzj2007.0004.
Murray, Christopher J, Ward, Andy L, & Wilson, John. Influence of Clastic Dikes on Vertical Migration of Contaminants at the Hanford Site. United States. https://doi.org/10.2136/vzj2007.0004
Murray, Christopher J, Ward, Andy L, and Wilson, John. 2007. "Influence of Clastic Dikes on Vertical Migration of Contaminants at the Hanford Site". United States. https://doi.org/10.2136/vzj2007.0004.
@article{osti_922178,
title = {Influence of Clastic Dikes on Vertical Migration of Contaminants at the Hanford Site},
author = {Murray, Christopher J and Ward, Andy L and Wilson, John},
abstractNote = {Clastic dikes are subvertical sedimentary features that cut through horizontally layered sediments, and they are common at the Hanford Site. Because of their cross-cutting relationship with the surrounding matrix, they have been proposed as potential fast paths from former contaminant discharge sites at the surface to the water table. However, little was known of the detailed hydrogeologic properties of the dikes and detailed modeling of flow and transport through the dikes had not been performed. We excavated a 2 m wide clastic dike at the Hanford Site and characterized it using an air minipermeameter, infrared imagery, and grain size analyses. Field injection experiments were also used to characterize the system. The resulting data were used to prepare a detailed numerical model of the clastic dike and surrounding matrix for a portion of the excavation. Unsaturated flow and transport through the system were modeled for several recharge rates. The highly heterogeneous nature of the system led to complex behavior, with the relative flux rates in the matrix and clastic dike being highly dependent on the recharge rates that were imposed on the system. The study suggests that the potential role of clastic dikes in vertical transport at the Hanford Site would depend on the leakage rate, and that areas of contaminant deposition formed at high flow rates might become isolated at low flow rates, and vice-versa. The results may also help explain the occurrence of complex breakthrough patterns of contaminants at the water table.},
doi = {10.2136/vzj2007.0004},
url = {https://www.osti.gov/biblio/922178}, journal = {Vadose Zone Journal, 6(4):959-970},
number = 4,
volume = 6,
place = {United States},
year = {Tue Nov 20 00:00:00 EST 2007},
month = {Tue Nov 20 00:00:00 EST 2007}
}