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Site Characterization Process
The Department of Energy's (DOE) 1988 Site Characterization Plan for
Yucca Mountain established the initial basis for the many engineering and
scientific investigations of the site. It has been conducting site
characterization to gather enough information about the Yucca Mountain
site to evaluate the waste isolation capabilities. In 1991, the State of
Nevada granted the DOE the permits necessary to proceed with certain site
characterization activities. These activities included the excavation of
test pits and trenches, drilling bore holes, and monitoring ground
water.
In September 1994, the DOE began excavation of the exploratory studies
facility using a tunnel boring machine. The initial design called for a
continuous tunnel 7.6 meters (25 feet) in diameter. The tunnel was
completed in April 1997. The tunnel begins at the North Portal and extends
to the northwest approximately 2000 meters (1.24 miles). The tunnel then
transitions into an approximately 60 degree turn to the south. The section
from the North Portal to the 60 degree turn is known as the "North Ramp".
The turn from the "North Ramp" leads to a main tunnel, at a depth of 300
meters (984 feet) below the surface. The main tunnel has a north-south
alignment and extends south approximately 3000 meters (1.86 miles). The
main tunnel ends in a 90 degree turn. From this turn the tunnel travels
east about 1300 meters (0.8 miles) and emerges at the South Portal. The
tunnel machine has bored through a series of geologic features including a
structural feature known as the Bow Ridge Fault. Within the tunnel are
seven testing alcoves and four test niches that are being used to
investigate the hydrologic, hydrochemical, and thermo-mechanical
properties of the rocks underlying Yucca Mountain.
In December 1997, the DOE began excavation of a smaller exploratory
tunnel (5.5 meters/18 feet) across the main tunnel. This smaller tunnel is
known as the "east-west" or "cross" drift and runs almost perpendicular to
the North Ramp. The "cross" drift begins to the west of the Bow Ridge
Fault, and crosses over and above the north-south main tunnel. It is about
2600 meters (1.6 miles) in length and ends near the Solitario Canyon
Fault. The "cross" drift will also contain instrumentation for scientific
tests and should provide additional data on the sub-surface geology of
Yucca Mountain to the west of the main tunnel. The layout of both the Exploratory
Studies Facility and the Cross Drift can be
viewed. |