Preliminary Estimates of Specific Discharge and TransportVelocities near Borehole NC-EWDP-24PB

Freifeld, Barry ; Doughty, Christine ; Finsterle, Stefan

Lawrence Berkeley National Laboratory

关键词: Flow Rate;    54;    Sensitivity;    Radioisotopes;    Tuff;   

DOI  :  10.2172/901046
RP-ID  :  LBNL--60740
RP-ID  :  DE-AC02-05CH11231
RP-ID  :  901046

美国|英语

来源: UNT Digital Library

【 摘 要 】

This report summarizes fluid electrical conductivity (FEC)and thermal logging data collected in Borehole NC-EWDP-24PB, locatedapproximately 15 km south of the proposed repository at Yucca Mountain.Preliminary analyses of a small fraction of the FEC and temperature dataindicate that relatively large, localized fluid fluxes are likely toexist at this location. The implication that considerable flow is inducedby small gradients, and that flow is highly localized, is significant forthe estimation of groundwater transport velocities and radionuclidetravel times. The sensitivity of the data to potential perturbationsduring testing (i.e., internal wellbore flow in the case of FEC data, andbuoyancy effects in the case of thermal logging data) make it difficultto conclusively derive fluid fluxes and transport velocities without adetailed analysis of all data and processes involved. Such acomprehensive analysis has not yet been performed. However, thepreliminary results suggest that the ambient component of the estimatedflow rates is significant and on the order of liters per minute, yieldinggroundwater transport velocities in the range of kilometers per year. Oneparticular zone in the Bullfrog tuff exhibits estimated velocities on theorder of 10 km/yr. Given that the preliminary estimates of ambient flowrates and transport velocities are relatively high, and considering thepotential impact of high rates and velocities on saturated-zone flow andtransport behavior, we recommend that a comprehensive analysis of all theavailable data be performed. Moreover, additional data sets at otherlocations should be collected to examine whether the current data set isrepresentative of the regional flow system near YuccaMountain.