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PNNR naphthanate, creosote, DEN, Hope and Lit). These data area presented in Attachment C, and were used for initial identification of chemical analytes expected to be present due to the wood preservative process. 3. Statistical Data Characterization According to USEPA's SW-846 Method (Chapter 9), the appropriate statistic to consider during waste classification is the upper confidence limit(UCL)on the mean analyte concentration in the waste sampled. Specifically, a significance level of 0.20 is used for the confidence interval (comprised of the lower and upper confidence limits; see Equation (6) in Table 9-1 of SW-846), and thus the upper confidence limit provides 90 percent confidence that the true mean concentration in the waste is no higher than the UCL. Determination of whether or not a waste is hazardous is decided as described in footnote (a) of Table 9-1 of the SW-846: "The contaminant of concern is not considered to be present in the waste at a hazardous level if the upper limit of the CI[confidence interval]is less than the applicable RT[regulatory threshold]. Otherwise, the opposite conclusion is reached." The appropriate calculation of a confidence interval for a data set depends on observed characteristics, in particular the data distribution (e.g., normal, gamma, lognormal), the presence of potential data outliers, and the presence of censored data (non-detects). Detailed discussion of UCL method selection and calculation is available in various USEPA guidance documents (e.g., 2015, 2009, 2006). The SW-846 method indicates that non-normal data sets may be normalized through the use of an appropriate data transformation if needed. GHD subjected the compiled waste characterization data (Attachment B)to a series of statistical procedures consistent with the SW-846 requirements focused on the following questions: i) Are UPRR's rail tie wastes non-hazardous on an overall basis? ii) How much do individual waste batches vary, and can a confidence interval on a "non-hazardous" classification be developed? Initial consideration was given to identifying chemical analytes present due to the wood treatment process. This was based on the analytical results for new rail ties treated with common preservatives. Table 3.1 (following text) summarizes the concentration ranges observed in untreated wood and compares the newly-treated wood ties to the control samples. Cases where an analyte was found to consistently be present at concentrations above controls in at least one of the treatment types (typically in at least half of the samples analyzed) are highlighted in yellow in Table 3.1. The following analytes were identified as being associated with the rail tie wood preservatives tested: a) Metals (arsenic, barium, cadmium, chromium, cobalt, copper, lead, molybdenum, nickel, silver, thallium and zinc) 11183843Pol lack-1.dou 3