Hydrogeologic Investigations of Flow in Fractured Tuffs, Rainier Mesa, Nevada Test Site

Technical Report · Thu Mar 31 23:00:00 EST 1988

DOI:https://doi.org/10.2172/1466682· OSTI ID:1466682

Russell, Charles E. ^[1]; Hess, John W. ^[1]; Tyler, Scott W. ^[1]

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1. Desert Research Inst. (DRI), Las Vegas, NV (United States)

Rainier Mesa, a primary site for nuclear testing, is located in the north-central area of the Nevada Test Site and is composed of highly fractured and altered Tertiary tuffs. A hydrogeologic study was conducted within the mesa concentrating on several parameters: 1) the source of fracture water found there, 2) period of principal re­charge, 3) hydraulic residence time, 4) hydraulic response lag time, 5) total amount of recharge per year infiltrating into the U12n tunnel catchment basin, 6) extent of mix­ing between fracture systems, and 7) the effects of nuclear testing on localized ground-water chemistry and discharge. The data base consists of the precipitation record, discharge record of seeps, the gross chemistry and stable isotopic composition of these seeps, and two tracer studies conducted on the mesa surface. Results indicate that for Rainier Mesa: 1) ground water is of recent meteoric ori­gin, 2) the period of principal recharge is from late fall to early spring, 3) the period of hydrologic response is at least four months, 4) the total recharge through the U12n catchment basin is approximately 8% of the precipitation which falls on the mesa, and 5) travel time is estimated as greater than one year and less than six. It was also determined that the active fracture systems are poorly interconnected, and that the effects of nuclear testing increase discharge and the concentration of ionic species within fracture-seep water. The most likely mechanism through which these occur is the seismic P wave generated by a nuclear explosion. This flux of interstitial water increases discharge at the tunnel seeps and produces a concurrent increase in the TDS of the seep water. These observations reflect an environment which has been subjected to nuclear testing since 1957. Whether or not this is representative of the hydrogeologic regime which existed before nuclear testing, is unknown.

• Research Organization: Desert Research Inst. (DRI), Las Vegas, NV (United States); Nevada Univ., Reno, NV (United States)
• Sponsoring Organization: USDOE Office of Environmental Management (EM)
• DOE Contract Number: AC08-85NV10384
• OSTI ID: 1466682
• Report Number(s): DOE/NV/--10384-21; 45062
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
Rainier Mesa
Tertiary tuffs
U12n tunnel
fracture water
fractured-seep water
ground-water chemistry and discharge
hydraulic residence time
hydraulic response lag time
hydrogeologic
hydrologic
interstitial water
meteoric origin
precipitation
recharge
seeps
seismic P wave
stable isotopic composition
tracer studies