HR: 1340h
AN: H43D-0523    [Abstracts]
TI: Impact of Extreme Events and Soil Hydraulic Conductivity on the Evolution of a Mesa-top Waste Repository Cover
AU: * Crowell, K J
EM: crowell@lanl.gov
AF: Earth and Environmental Sciences, Los Alamos National Laboratory, MS J495 PO Box 1663, Los Alamos, NM 87545
AU: Wilson, C J
EM: cjw@lanl.gov
AF: Earth and Environmental Sciences, Los Alamos National Laboratory, MS J495 PO Box 1663, Los Alamos, NM 87545
AU: Lane, L J
EM: ljlane2@msn.com
AF: Earth and Environmental Sciences, Los Alamos National Laboratory, MS J495 PO Box 1663, Los Alamos, NM 87545
AU: Newman, B D
EM: bnewman@lanl.gov
AF: Earth and Environmental Sciences, Los Alamos National Laboratory, MS J495 PO Box 1663, Los Alamos, NM 87545
AU: Schofield, T G
EM: tgs@lanl.gov
AF: Earth and Environmental Sciences, Los Alamos National Laboratory, MS J495 PO Box 1663, Los Alamos, NM 87545
AB: The Siberia model was used to optimize the design of a mesa-top waste repository cover at Los Alamos National Laboratory on the Pajarito Plateau in Northern New Mexico, USA. The cover was designed to meet criteria that the depth to waste from the cover surface would be greater than 1 meter after 1000 years of erosion. The model was run using two steady-state landscape forming events (2 and 5 year return periods) derived from a 20 year data set at the Santa Rita Experimental Watershed in Arizona, and hydraulic properties of two soils, loam and sandy loam. Although we were able to show that the final design cover met the performance criteria for both high and moderate erosion scenarios, concerns remained about the impact of extreme events. In addition, Hydrus simulations, based on saturated hydraulic conductivity (Ksat) measurements from cores of cover material comprised of crushed tuff and a bentonite admixture, suggested that surface runoff on the cover might be orders of magnitude higher than the landscape forming runoff events used for the Siberia simulations. The Siberia runoff events were based on Ksat values for loam and sandy loam soils with identical texture (% sand , silt and clay) to the engineered cover soil, but these values assume soil structure that may or may not develop in the engineered cover. This work summarizes the impacts of both 1) the timing and size of extreme events and 2) the impact of soil structure and Ksat, on long-term repository cover evolution.
DE: 1815 Erosion
DE: 1817 Extreme events
DE: 1824 Geomorphology: general (1625)
DE: 1862 Sediment transport (4558)
SC: Hydrology [H]
MN: Fall Meeting 2005