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Title: Origin of elevated water levels encountered in Pahute Mesa emplacement boreholes: Preliminary investigations

Abstract

The presence of standing water well above the predicted water table in emplacement boreholes on Pahute Mesa has been a recurring phenomenon at the Nevada Test Site (NTS). If these levels represent naturally perched aquifers, they may indicate a radionuclide migration hazard. In any case, they can pose engineering problems in the performance of underground nuclear tests. The origin of these elevated waters is uncertain. Large volumes of water are introduced during emplacement drilling, providing ample source for artificially perched water, yet elevated water levels can remain constant for years, suggesting a natural origin instead. In an effort to address the issue of unexpected standing water in emplacement boreholes, three different sites were investigated in Area 19 on Pahute Mesa by Desert Research Institute (DRI) staff from 1990-93. These sites were U-19az, U-19ba, and U-19bh. As of this writing, U-19bh remains available for access; however, nuclear tests were conducted at the former two locations subsequent to this investigations. The experiments are discussed in chronological order. Taken together, the experiments indicate that standing water in Pahute Mesa emplacement holes originates from the drainage of small-volume naturally perched zones. In the final study, the fluids used during drilling of the bottom 100more » m of emplacement borehole U-19bh were labeled with a chemical tracer. After hole completion, water level rose in the borehole, while tracer concentration decreased. In fact, total mass of tracer in the borehole remained constant, while water levels rose. After water levels stabilized in this hole, no change in tracer mass was observed over two years, indicating that no movement of water out of the borehole is taking place (as at U- 19ba). Continued labeling tests of standing water are recommended to confirm the conclusions made here, and to establish their validity throughout Pahute Mesa.« less

Authors:
; ; ;
Publication Date:
Research Org.:
Nevada Univ., Reno, NV (United States). Desert Research Inst.
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
10164133
Report Number(s):
DOE/NV/10845-43
ON: DE94015055; TRN: 94:007308
DOE Contract Number:  
AC08-90NV10845
Resource Type:
Technical Report
Resource Relation:
Other Information: DN: Publication No. 45123; PBD: Nov 1993
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; NEVADA TEST SITE; HYDROLOGY; GROUND WATER; HYDRAULICS; WELLS; 540250; SITE RESOURCE AND USE STUDIES

Citation Formats

Brikowski, T, Chapman, J, Lyles, B, and Hokett, S. Origin of elevated water levels encountered in Pahute Mesa emplacement boreholes: Preliminary investigations. United States: N. p., 1993. Web. doi:10.2172/10164133.
Brikowski, T, Chapman, J, Lyles, B, & Hokett, S. Origin of elevated water levels encountered in Pahute Mesa emplacement boreholes: Preliminary investigations. United States. https://doi.org/10.2172/10164133
Brikowski, T, Chapman, J, Lyles, B, and Hokett, S. 1993. "Origin of elevated water levels encountered in Pahute Mesa emplacement boreholes: Preliminary investigations". United States. https://doi.org/10.2172/10164133. https://www.osti.gov/servlets/purl/10164133.
@article{osti_10164133,
title = {Origin of elevated water levels encountered in Pahute Mesa emplacement boreholes: Preliminary investigations},
author = {Brikowski, T and Chapman, J and Lyles, B and Hokett, S},
abstractNote = {The presence of standing water well above the predicted water table in emplacement boreholes on Pahute Mesa has been a recurring phenomenon at the Nevada Test Site (NTS). If these levels represent naturally perched aquifers, they may indicate a radionuclide migration hazard. In any case, they can pose engineering problems in the performance of underground nuclear tests. The origin of these elevated waters is uncertain. Large volumes of water are introduced during emplacement drilling, providing ample source for artificially perched water, yet elevated water levels can remain constant for years, suggesting a natural origin instead. In an effort to address the issue of unexpected standing water in emplacement boreholes, three different sites were investigated in Area 19 on Pahute Mesa by Desert Research Institute (DRI) staff from 1990-93. These sites were U-19az, U-19ba, and U-19bh. As of this writing, U-19bh remains available for access; however, nuclear tests were conducted at the former two locations subsequent to this investigations. The experiments are discussed in chronological order. Taken together, the experiments indicate that standing water in Pahute Mesa emplacement holes originates from the drainage of small-volume naturally perched zones. In the final study, the fluids used during drilling of the bottom 100 m of emplacement borehole U-19bh were labeled with a chemical tracer. After hole completion, water level rose in the borehole, while tracer concentration decreased. In fact, total mass of tracer in the borehole remained constant, while water levels rose. After water levels stabilized in this hole, no change in tracer mass was observed over two years, indicating that no movement of water out of the borehole is taking place (as at U- 19ba). Continued labeling tests of standing water are recommended to confirm the conclusions made here, and to establish their validity throughout Pahute Mesa.},
doi = {10.2172/10164133},
url = {https://www.osti.gov/biblio/10164133}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Nov 01 00:00:00 EST 1993},
month = {Mon Nov 01 00:00:00 EST 1993}
}