Abstract: Detection
of a Clay Aquiclude by Means of Surface Electrical Resistivity
DAO, THANH, C. and ROBERT M. NEGRINI
A clay aquiclude has
been detected under a Kern County landfill based on an electric log from
a nearby well. Landfill expansion may depend on the continuity of the aquiclude
under the proposed area of expansion. In this study we investigate the
feasibility of using surface electrical resistivity
as a cost-effective
method to determine the extent of the clay aquiclude.
The Schlumberger arrangement
was used for three soundings. From these soundings, apparent
resistivity
vs. electrode spacing plots were constructed which are crude estimates
of true
resistivity
vs. depth. Two of these lines were characterized by
a high signal to noise ratio. Subtle relative dips to lower
resistivity
,
10-40 ohm-meters in magnitude, are observed in both lines at electrode
spacings of 60-250 meters. This reproducible feature may be attributable
to the low
resistivity
clay aquiclude.
Computer modeling demonstrated
that the relative resistivity
values and the corresponding electrode spacing
of the aforementioned subtle dips are consistent with the synthetic data
modeled with a 25 to 35 feet thick low
resistivity
unit. This unit has
the same depth as the clay aquiclude shown by the electric log. We conclude
that the surface electrical
resistivity
method is feasible as a means of
investigation at this site.
Search and Discovery Article #90945©1997 AAPG Pacific Section Meeting, Bakersfield, California