Studies of the geothermal aspect-of the Bridge area of
the Raft River basin in south-central Idaho (fig. 1) by the
U.S. Geological Survey began in 1972 when Young and Mitchell
(1973) made a geochemical and geologic reconnaissance of
selected thermal waters in Idaho. The Bridge area had been
designated the Frazier known geothermal resource area
(Frazier KGRA) by the U.S. Geological Survey (Godwin and
others-, 1971) . Since 1972, several units of the Geological
Survey have studied the area to provide data for the U.S.
Energy Research and Development Administration, which proposes to ascertain whether the geothermal resource can be
developed for power generation and other uses. The studies
include geologic mapping, geophysical surveys, water sampling, test drilling, and studies of all available drill-
hole data. A list of reports already prepared on the area
is included with this report.
Core drilling of five holes began in August 1974 and
was completed in March 1975. These holes are referred to as
intermediate-depth core holes, principally because in the
spring of 1974, 35 auger holes 25 to 98 feet (7.6 to 30
meters) were completed in the area (Crosthwaite, 1974), and
the Aerojet Nuclear Company, under the auspices of the U.S.
Energy Research and Development Administration, was planning
some deep drilling 4,000 to 6,000 feet (1,200 to 1,800
meters) (fig. 1). The purpose of the core drilling was to
provide information to test geophysical interpretations of
the subsurface structure and lithology and to provide hydrologic and geologic data on the shallow part of the geothermal
system. Samples of the core were made available to several
divisions and branches of the Geological Survey and to
people and agencies outside the Survey. This report presents the basic data from the core holes that had been
collected to September 1, 1975, and includes lithologic and
geophysical well logs, chemical analyses of water (table 1),
and laboratory analyses of cores (table 2) that were completed as of the above date. The data were collected by the
Idaho District office, Hydrologic Laboratory, Borehole
Geophysics Research Project, and Drilling, Sampling, and
Testing Section, all of the Water Resources Division, and
the Branch of Central Environmental Geology of the Geologic
Divison.
