Mathematical models of water and chemical movement in soils are being used as decision aids for defining ground-water protection practices for Superfund sites. Numerous transport models exist for predicting movement and degradation of hazardous chemical through soils. Many of these require extensive input parameters which include uncertainty due to soil variability and unknown future weather. The impact of uncertain model parameters upon the model output is not known. Model users need an understanding of this impact so they can measure the appropriate parameters for the site and incorporate the model prediction uncertainty into their decisions. The report summarizes research findings which address the sensitivity and uncertainty of model output due to uncertain input parameters. The objective of the research was to determine the sensitivity and uncertainty of travel time, concentration, mass loading and pulse width of contaminants at the water table due to uncertainty in soil properties such as organic carbon content, bulk density, water content, and hydraulic conductivity. Chemical properties, such as organic carbon partition coefficient and degradation half-life, were also examined. The four models selected for this analysis were RITZ, VIP, CMLS and HYDRUS.

"Funded wholly or in part by the ... under cooperative agreement # CR-818709 with the Oklahoma Agricultural Experiment Station, Oklahoma State University, Stillwater, Oklahoma"--T.p. verso. Shipping list no.: 94-0168-P. "March 1994." Includes bibliographical references (p. 184-186). "EPA/600/R-93/184."