Near‐Surface Disposal Performance Assessment: Modeling Monthly Precipitation and Temperature in Various Climate Environments

Abstract

A more stable and extensive analysis of climate is necessary to simulate long-term impacts associated with climate change. The exponential dispersion model (EDM) family of distributions, a popular choice when characterizing precipitation levels and temperature in different climate environments, is being considered for its applicability to near-surface disposal performance assessments. In this study, the EDM family is examined to determine if there is a preferred distributional form within the family for these parameters using data from two sites whose climate environments are quite different. One site is in a semiarid environment and the other is in a humid environment. In addition, the merits of selecting a different distributional form to represent INTRODUCTIONThe US Department of Energy (US DOE) is responsible for the cleanup of nuclear waste at former nuclear weapons sites across the United States. Cleanup activities include the containment of radioactive and hazardous chemical waste materials in near-surface disposal facilities, such as landfills, trenches, and vaults (US EPA, 1989). With the abundance of sites across the United States and the variability in operational management at each site, the US DOE introduced DOE Order 435.1, Radioactive Waste Management, in 1999 to assess the performance of these facilities. While the order requires uncertainty analyses, it may be unclear to users with respect to whether these requirements address important long-term features associated with climate (Ho et al., 2001 entire United States may be impacted by a changing climate, the extent to which certain effects are prevalent should be determined on a regional basis. Therefore, any approach to understanding how long-term features will affect environmental performance must be performed at a regional level using numerical models that assess the design integrity and performance of disposal facilities. Since these models require temperature and precipitation inputs, they are directly impacted by climate change. Traditional approaches to evaluating near surface facility performance neglect the effects of increases in average temperatures or the occurrence of more frequent and extreme weather conditions (Ho et al., 2001). Typically, records are examined from earliest records to the present. Common weather patterns are identified, as well as extreme occurrences (e.g., wettest year). These extreme events are taken to be a worst-case scenario and are used as "design year" conditions. A disadvantage of using solely historical data is that the lengths of recorded time periods are typically small relative to the forecast period. In addition, worst-case scenarios are developed based on precipitation, ignoring extreme-temperature episodes, such as hotter than normal months. Research has 100Remediation DOI: 10.1002/rem c⃝ 2013 Wiley Periodicals, Inc. REMEDIATION Autumn 2013Exhibit 3. Monthly precipitation distribution for Monticello, Utahshown that near-surface disposal facility cover systems rely on plants to remove water from the s...

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