UE-25 ONC#1 and UE-25 NRG-4 BOREHOLES

To investigate uncertainties in how water moves from the land surface to the water table and how it moves in the water table, Nye County drilled and conducted extensive tests at borehole UE-25 ONC#1 (drilled in December, 1995).  Nye County installed and monitored pressure and temperature instruments in boreholes UE-25 ONC#1 and UE-25 NRG-4.  The data collected from these instruments was used to evaluate the long-term pneumatic conditions at strategic depths in the subsurface.

Nye County collected gas samples from the vadose zone in UE-25 ONC#1 to establish background conditions and to evaluate changes in the chemical composition of the gases. Changes in the chemical compositions of the gases in the vadose zone with time may be used to evaluate the impact of the Exploratory Shaft Facility (ESF) construction and obtain transport properties of the rock mass at the site.

Nye County analyses have indicated that one or more packers seated directly against the rock wall in the unsaturated portion of borehole UE-25 ONC#1 may not have functioned as intended.  These analyses suggest that preferential pathways may exist in the unsaturated rock wall immediately adjacent to the 1-meter long packers, thereby allowing "short circuiting" of air between depth intervals previously thought to be isolated by these packers.  It has not been possible to conclusively determine which of the 14 unsaturated zone packers may have been "short circuiting", nor has it been possible to determine when this problem began.  This potential "short circuiting" could introduce significant error into air pressure data, and possibly some error into temperature data, collected from 7 pressure/temperature probes located between unsaturated zone packers in UE-25 ONC#1.  An explanation of these potential problems will be attached to all Nye County reports that contain unsaturated zone air pressure and temperature data from this borehole.

Water elevation and temperature data collected from the UE-25 ONC#1 borehole (April 1995 through March 2001) and UE-25 NRG-4 borehole (March 1995 through December 1998) are available for download as Excel spreadsheet files (.xls).

ESF TUNNEL AND ECRB DRIFT MONITORING DATA

Nye County installed instruments to measure temperature, pressure, humidity and wind speed within the Exploratory Shaft Facility (ESF) tunnel and Enhanced Characterization of the Repository Block (ECRB) drift.   These measurements were used to characterize the air being used to ventilate the tunnel which could potentially impact the performance of the repository.

Pressure, temperature, and relative humidity data collected behind the ESF Tunnel Boring Machine (August 1995 through April 1997) are available for download as Excel spreadsheet files.