G., Harris, S. T., and Phelan, J. M., 2004, Assessing groundwater
perching horizons using synthetic, ground, and airborne TDEM data
at the Pantex Plant, Texas, in Proceedings, Symposium on
the Application of Geophysics to Engineering and Environmental Problems:
Environmental and Engineering Geophysical Society, p. 874-889 (CD-ROM).
in Word format]
the Integrity of the Ogallala Fine-Grained Zone Using Airborne Geophysics
At the U.S.
Department of Energy's Pantex Plant near Amarillo, Texas, recharging
groundwater encounters a perching fine-grained zone (FGZ) above
the main Ogallala (High Plains) aquifer, which is a critical source
of agricultural, municipal, and industrial water. In March, airborne
geophysical surveys were conducted to measure the magnitude and
variation of apparent electrical conductivity of the subsurface
to help assess the extent and integrity of the FGZ. We obtained
time-domain electromagnetic induction data along flight lines totaling
1,243 km in length within four survey blocks located north, east,
south, and west of the main Pantex Plant.
results include the observation that the conductivity structure
beneath surveyed playa basins differs from that outside the basins.
In particular, playas have high higher apparent electrical conductivities
than do interplaya areas at shallow depths, and lower apparent conductivities
at equivalent deeper depths. This observation is consistent with
the dissolution-induced subsidence model of playa formation, where
the shallow, more conductive material represents lacustrine basin
fill with high clay content and the deeper, less conductive material
may represent deposits disturbed by subsidence. These data will
be integrated with available geological and hydrological data from
survey area wells and borings to establish the relationship between
stratigraphic and hydrologic characteristics and measured apparent
more infomation, please contact Jeff Paine, principal investigator.