USGS Groundwater Information: Branch of Geophysics
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C.B. Dawson, U.S. Geological
Survey, Storrs, CT
J.W. Lane, Jr., U.S. Geological Survey, Storrs, CT
Eric A. White, U.S. Geological Survey, Storrs, CT
Marcel Belaval, U.S. Geological Survey, Storrs, CT
The U.S. Geological Survey (USGS), in cooperation with United Technologies Corporation, used an integrated suite of borehole, surface, and water-borne geophysical methods near the site of the former Winthrop Landfill, Winthrop, Maine, to investigate the hydrogeology controlling the transport of leachate from the landfill to nearby Annabessacook Lake. During the fall of 2000 and summer of 2001, the USGS conducted borehole electromagnetic (EM) induction and gamma logging, and inductive terrain-conductivity, two-dimensional (2D) resistivity, continuous seismic reflection, and magnetic surveys.
The objectives of this integrated geophysical study were to provide constraints on the location and extent of the southern flow path(s) of contamination from the landfill to the lake; identify shoreline seep geophysical signatures; identify potentially hidden seeps in the lake; and determine depth to bedrock below Annabessacook Lake in the study area.
Interpretation of surface 2D resistivity, magnetic, and inductive terrain-conductivity
data and borehole EM logs delineates an electrically conductive anomaly consistent
with a leachate plume moving from the current landfill boundary southward through
the overburden to the shores of Annabessacook Lake. Surface and borehole geophysical
data collected south and southeast of the landfill indicate the presence of
discrete, shallow conductive anomalies at the southeastern edge of the landfill
and near the lakeshore. The conductive anomalies appear at increasing depths
closer to the lake. Magnetic anomalies offshore confirm the presence of iron-rich
landfill leachate discharging into the lake south of the landfill. High-resolution
swept-frequency seismic data used to map sediment and grain size distribution
in the lake sub-bottom along the shoreline identified sediment-infilled bedrock
may act as conduits for contaminant migration.
Final copy as submitted to Symposium on the Application of Geophysics to Engineering and Environmental Problems for publication as:Dawson, C.B., Lane, J.W., Jr., White, E.A., and Belaval, Marcel, Integrated geophysical characterization of the Winthrop Landfill southern flow path, Winthrop, Maine, in Symposium on the Application of Geophysics to Engineering and Environmental Problems, Las Vegas, Nevada, February 10-14, 2002, Proceedings: Denver, Colo., Environmental and Engineering Geophysical Society, CD-ROM, 22p.
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