Date of Award:

5-1999

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Watershed Sciences

Committee Chair(s)

James P. Dobrowolski

Committee

James P. Dobrowolski

Committee

Frederick B. Pierson Jr.

Committee

Gail S. Bingham

Abstract

Production of low-level radioactive waste (LLRW) has created a need for safe storage facilities. These facilities must be capable of isolating radioactive waste and preventing contamination from physical or biological intrusion until the waste material is isotopically stable. At the present time, managers of the Idaho National Engineering and Environmental Laboratory (INEEL) have a substantial database characterizing rainfall events and the subsequent impact on integrity of shallow land burial sites used for storage of LLRW. Little information has been gathered describing the processes of snow accumulation/ablation and the resulting impact on storage facilities. This study examines snowmelt runoff, infiltration, and erosion occurring at the INEEL and the potential hazard created against shallow-land burial facilities.

Snowmelt runoff, infiltration, and erosion were measured during extreme snowmelt events produced by simulated rainfall in order to re-create a "worst case" situation for snowmelt erosion. Rainfall simulations were conducted on soils that were unfrozen, continually frozen, or diurnally frozen, and covered by natural snow or simulated snow, or were without snow cover. Diurnally frozen soils without snow cover produced significantly more interrill erosion (μ = 7870 kg/ha) than frozen or unfrozen soils. Results indicate that shallow land burial caps at the INEEL would be most susceptible to erosion immediately following snowmelt when soils are saturated and experiencing freeze/thaw cycles.

Ambient levels of snow accumulation/ablation and subsequent runoff, infiltration, and erosion were measured on nine simulated waste burial trench caps (SWBTC) maintaining three surface cover treatments. Data collected from SWBTC plots during 1994-97 were utilized to test the SNTHERM89 and SHAW (Simultaneous Heat and Water) models to determine their ability to accurately estimate the processes of snowmelt, runoff, and infiltration as they occur in sagebrush-steppe ecosystems. SNTHERM89 could not successfully operate during periods of rapid snowmelt and transient, shallow snowcovers. SHAW accurately estimated soil freeze/thaw cycles, snow accumulation/ablation patterns, and snowmelt infiltration producing r2 values of 0.84 and 0.91 and a mean difference < 0.045 m3/m3, respectively. The results from this study indicate the ability of the SHAW model to accurately characterize transient shallow snow covers found at the INEEL and indicate potential for management applications.

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