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PMR bond 4. Conclusions and Recommendations Based on the statistical analyses performed considering the analytical results for wooden rail tie waste samples, it is clearly evident that the UPRR's regular maintenance program rail ties meet the definition of non-hazardous waste under SW-846 methodology and California's Title 22 requirements. This is demonstrated by comparison of individual sample results and 90UCL of the sample population mean values to the respective regulatory threshold values (i.e., TTLCs for solids, STLC and TCLP limits for leachate, and fish bioassay LCso requirements). There are several data sets with isolated samples (from 1 to 5 samples out of over 2300 total)with concentrations that exceed the respective criteria, but as discussed above these are either clearly anomalous data (2,4-dinitrotoluene just above its criterion in 1 of 2080 samples) and/or represent non-leachable concentrations (for Endrin in 1 sample and pentachlorophenol in 5 samples)that do not exceed the related leaching limits in TCLP analysis. Additionally, none of these analytes are present in new rail tie samples at concentrations above those found in control samples and the applicable regulatory criteria. As such, it is not expected that the levels of wood preservatives used in the rail ties purchased by UPRR could cause hazardous waste conditions. The fish bioassay results show that a very small minority(1.4 percent)of the individual samples have LCso values below the limit of 500 mg/L. However, the population as a whole clearly meets the non-hazardous classification on average (represented by the 90LCL) and thus the maintenance program rail tie wastes do not need to be considered as California Hazardous waste under the Title 22 definition. In conclusion, based on the laboratory analysis of over 2000 wooden rail tie samples collected under UPRR's maintenance ties program, there is very strong evidence that this material is non-hazardous under RCRA and California's Title 22 definitions. The 90UCL values for all parameters regularly analyzed for in waste samples meet the TTLC, STLC and fish bioassay(considering the 90LCL) limits. It is noted that small number of individual samples (1.4 percent)fall into the California Hazardous classification based on the fish bioassay results, but the population average (90LCL of 738 mg/L) clearly meets the non-hazardous definition (i.e., LCso > 500 mg/L). In terms of the generation of future rail tie wastes no waste characterization sampling is necessary and the material should be considered non-hazardous under current RCRA and California definitions based on stability of the rail tie supply chain and the average concentrations (90UCL values)for tested parameters in UPRR's population of wooden rail tie maintenance program waste. This finding would need to be re-evaluated if changes to the hazardous waste criteria are made in the future. The present results are based on samples collected from UPRR's maintenance program rail tie wastes. If there are suspected other contaminants mixed into the waste stream beyond the treatment chemical used in tie manufacturing, for example if a hazardous chemical was released during a derailment in the area of the ties, waste characterization sampling and analysis is warranted prior to disposal. However, based on the Federal RCRA (SW-846) and California waste characterization requirements (i.e., comparing 95UCLs of mean contaminant concentrations to the applicable hazardous waste criteria), UPRRs wooden rail tie wastes generated from maintenance program activities are non-hazardous and should be disposed as such. 11183843Pol lack-1.dou 6