Terrace Geochemistry at the Shiprock, New Mexico, Disposal Site - 17232
- Navarro Research and Engineering, Inc., 2597 Legacy Way, Grand Junction, Colorado 81503 (United States)
- US Department of Energy Office of Legacy Management, 2597 Legacy Way, Grand Junction, Colorado 81503 (United States)
The objective of this investigation was to identify and differentiate potential non-mill-related water inputs to a shallow terrace groundwater system through the use of aqueous chemical and isotopic tracers at a former uranium- and vanadium-ore processing facility. Terrace groundwater in the vicinity of the Shiprock, New Mexico, site is hypothesized to be largely anthropogenic because natural rates of recharge in the terrace are likely insufficient to sustain a continuous water table in the terrace alluvial system, as observed in several analogue terrace locations east of the site and in response to post-mill dewatering efforts across the site. The terrace is composed of alluvial sand and gravel and weathered and unweathered Mancos Shale. Terrace groundwater exists and flows in the alluvium and to a much less extent in the Mancos Shale. Historical data established that in both the terrace and flood plain below the terrace, mill-derived uranium and sulfate is found primarily in the alluvium and the upper portion of the weathered Mancos Shale. Groundwater extraction is being conducted in the vicinity of former mill operations and in washes and seeps to de-water the formation and remove contamination, thus eliminating these exposure pathways and minimizing movement to the flood plain. However, past and present contribution of non-mill anthropogenic water sources may be hindering the dewatering effort, resulting in reduced remedy effectiveness. Groundwater source signatures can be determined based on chemical and isotopic ratios and are used to help identify and delineate both mill and non-mill water contributions. Aqueous chemical and isotopic tracers, such as {sup 234}U/{sup 238}U activity ratios and uranium concentrations, δ{sup 34}S{sub sulfate} and sulfate concentrations, tritium concentrations, and δ{sup 2}H{sub water} and δ{sup 18}O{sub water} are being used in this Phase I study. The aqueous chemical and isotopic analysis has identified areas on the terrace where groundwater is derived from mill-related activities and areas where the groundwater is associated with non-mill activities. A separate field effort of Phase II work will follow, including investigating additional locations for these isotopes and examination of δ{sup 18}O{sub sulfate}, δ{sup 34}S{sub sulfate}, and chloro-fluorocarbon signatures. (authors)
- Research Organization:
- WM Symposia, Inc., PO Box 27646, 85285-7646 Tempe, AZ (United States)
- OSTI ID:
- 22794615
- Report Number(s):
- INIS-US-19-WM-17232; TRN: US19V0294038834
- Resource Relation:
- Conference: WM2017 Conference: 43. Annual Waste Management Symposium, Phoenix, AZ (United States), 5-9 Mar 2017; Other Information: Country of input: France; 12 refs.; available online at: http://archive.wmsym.org/2017/index.html
- Country of Publication:
- United States
- Language:
- English
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