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Title: Refining the site conceptual model at a former uranium mill site in Riverton, Wyoming, USA

Abstract

Milling activities at a former uranium mill site near Riverton, Wyoming, USA, contaminated the shallow groundwater beneath and downgradient of the site. Although the mill operated for <6 years (1958-1963), its impact remains an environmental liability. Groundwater modeling predicted that contaminant concentrations were declining steadily, which confirmed the conceptual site model (CSM). However, local flooding in 2010 mobilized contaminants that migrated downgradient from the Riverton site and resulted in a dramatic increase in groundwater contaminant concentrations. This observation indicated that the original CSM was inadequate to explain site conditions and needed to be refined. In response to the new observations after the flood, a collaborative investigation to better understand site conditions and processes commenced. This investigation included installing 103 boreholes to collect soil and groundwater samples, sampling and analysis of evaporite minerals along the bank of the Little Wind River, an analysis of evaportranspiration in the shallow aquifer, and sampling naturally organic-rich sediments near groundwater discharge areas. The enhanced characterization revealed that the existing CSM did not account for high uranium concentrations in groundwater remaining on the former mill site and groundwater plume stagnation near the Little Wind River. Observations from the flood and subsequent investigations indicate that additional characterizationmore » is still needed to continue refining the CSM and determine the viability of the natural flushing compliance strategy. Additional sampling, analysis, and testing of soil and groundwater are necessary to investigate secondary contaminant sources, mobilization of contaminants during floods, geochemical processes, contaminant plume stagnation, distribution of evaporite minerals and organic-rich sediments, and mechanisms and rates of contaminant transfer from soil to groundwater. Future data collection will be used to continually revise the CSM and evaluate the compliance strategy at the site.« less

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
US Department of Energy Office of Legacy Management, Frand Junction, CO (United States)
Sponsoring Org.:
USDOE Office of Legacy Management (LM), Office of Field Operations
OSTI Identifier:
1494370
Alternate Identifier(s):
OSTI ID: 1262342
Grant/Contract Number:  
LM0000415
Resource Type:
Published Article
Journal Name:
Environmental Earth Sciences
Additional Journal Information:
Journal Name: Environmental Earth Sciences Journal Volume: 74 Journal Issue: 10; Journal ID: ISSN 1866-6280
Publisher:
Springer Science + Business Media
Country of Publication:
Germany
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; conceptual site models, uranium, unsaturated zone, groundwater contamination, river flooding, evaporite mineral deposits

Citation Formats

Dam, William L., Campbell, Sam, Johnson, Raymond H., Looney, Brian B., Denham, Miles E., Eddy-Dilek, Carol A., and Babits, Steven J. Refining the site conceptual model at a former uranium mill site in Riverton, Wyoming, USA. Germany: N. p., 2015. Web. doi:10.1007/s12665-015-4706-y.
Dam, William L., Campbell, Sam, Johnson, Raymond H., Looney, Brian B., Denham, Miles E., Eddy-Dilek, Carol A., & Babits, Steven J. Refining the site conceptual model at a former uranium mill site in Riverton, Wyoming, USA. Germany. https://doi.org/10.1007/s12665-015-4706-y
Dam, William L., Campbell, Sam, Johnson, Raymond H., Looney, Brian B., Denham, Miles E., Eddy-Dilek, Carol A., and Babits, Steven J. Tue . "Refining the site conceptual model at a former uranium mill site in Riverton, Wyoming, USA". Germany. https://doi.org/10.1007/s12665-015-4706-y.
@article{osti_1494370,
title = {Refining the site conceptual model at a former uranium mill site in Riverton, Wyoming, USA},
author = {Dam, William L. and Campbell, Sam and Johnson, Raymond H. and Looney, Brian B. and Denham, Miles E. and Eddy-Dilek, Carol A. and Babits, Steven J.},
abstractNote = {Milling activities at a former uranium mill site near Riverton, Wyoming, USA, contaminated the shallow groundwater beneath and downgradient of the site. Although the mill operated for <6 years (1958-1963), its impact remains an environmental liability. Groundwater modeling predicted that contaminant concentrations were declining steadily, which confirmed the conceptual site model (CSM). However, local flooding in 2010 mobilized contaminants that migrated downgradient from the Riverton site and resulted in a dramatic increase in groundwater contaminant concentrations. This observation indicated that the original CSM was inadequate to explain site conditions and needed to be refined. In response to the new observations after the flood, a collaborative investigation to better understand site conditions and processes commenced. This investigation included installing 103 boreholes to collect soil and groundwater samples, sampling and analysis of evaporite minerals along the bank of the Little Wind River, an analysis of evaportranspiration in the shallow aquifer, and sampling naturally organic-rich sediments near groundwater discharge areas. The enhanced characterization revealed that the existing CSM did not account for high uranium concentrations in groundwater remaining on the former mill site and groundwater plume stagnation near the Little Wind River. Observations from the flood and subsequent investigations indicate that additional characterization is still needed to continue refining the CSM and determine the viability of the natural flushing compliance strategy. Additional sampling, analysis, and testing of soil and groundwater are necessary to investigate secondary contaminant sources, mobilization of contaminants during floods, geochemical processes, contaminant plume stagnation, distribution of evaporite minerals and organic-rich sediments, and mechanisms and rates of contaminant transfer from soil to groundwater. Future data collection will be used to continually revise the CSM and evaluate the compliance strategy at the site.},
doi = {10.1007/s12665-015-4706-y},
journal = {Environmental Earth Sciences},
number = 10,
volume = 74,
place = {Germany},
year = {Tue Jul 07 00:00:00 EDT 2015},
month = {Tue Jul 07 00:00:00 EDT 2015}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
https://doi.org/10.1007/s12665-015-4706-y

Citation Metrics:
Cited by: 25 works
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Works referenced in this record:

Groundwater contamination from an inactive uranium mill tailings pile: 1. Application of a chemical mixing model
journal, November 1984

  • White, A. F.; Delany, J. M.; Narasimhan, T. N.
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Groundwater contamination from an inactive uranium mill tailings pile: 2. Application of a dynamic mixing model
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Geochemical, mineralogical and microbiological characteristics of sediment from a naturally reduced zone in a uranium-contaminated aquifer
journal, August 2012


Works referencing / citing this record:

Improving soil quality for higher grain yields in Chinese wheat and maize production
journal, January 2020

  • Pan, Junxiao; Shang, Yiwei; Zhang, Wen Jie
  • Land Degradation & Development, Vol. 31, Issue 9
  • DOI: 10.1002/ldr.3515