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PMMR bond 3.3 Semi-volatiles UPRR's rail tie waste samples were mainly subjected to semi-volatile organic compounds using TCLP (leachate) analyses, since with the exception of pentachlorophenol only TCLP limits exist for SVOCs (see Attachment A). Concentrations of semi-volatile organic chemical analytes were below hazardous waste criteria and/or detection limits in the over 2000 waste rail tie samples analyzed in virtually all cases. Five TTLC analyses (rail tie solids) had pentachlorophenol present above its limit of 17 mg/kg, but in all cases the leachable concentration (via TCLP)was well below its criterion (100 mg/L). Additionally, pentachlorophenol was not detected in any of the new rail tie samples analyzed (see Table 3.1). Therefore leachable pentachlorophenol concentrations in UPRR's waste rail ties, where detectable, represent non-hazardous conditions. One sample had a detectable concentration of 2,4-dinitrotoluene (0.39 mg/L in TCLP leachate; above its limit of 0.13 mg/L), which is an apparent anomaly amidst the other 2079 samples analyzed (all non-detects) and was not detected in any of the new rail tie samples analyzed. Based on the results of semi-volatile organic compounds in new rail ties and rail tie waste, representing over 2000 individual samples, it is clearly evident that UPRR's wooden rail tie wastes are not hazardous due to SVOC concentrations above any applicable hazardous waste criteria. 3.4 Fish bioassay results Fish bioassays were run on 2302 wooden rail tie waste samples following California regulations protocol. Of these, 32 samples (1.4 percent)were found to fail the limit of LC50 >500 mg/L. An LC50 value is the concentration causing 50 percent or greater mortality(Lethality) in the test organisms. In contrast to chemical concentration criteria where higher concentrations are more toxic, in the bioassay a lower LC50 value represents a more toxic waste extract. That is, less waste extract is needed to cause unacceptable (i.e. 50 percent) mortality. In contrast, a higher LCso indicates lower toxicity. Hence, the bioassay criterion for identifying non-hazardous waste is to have an LC50 greater than 500 mg/L). Consequently, instead of considering an upper limit on the mean concentration, a lower confidence limit (90LCL)was calculated for the fish bioassay results. The bioassay data are censored on both the lower end (having values where the result is given as LC50<250) and higher end (having results where the result is given as LC5o>750). To accommodate this, any censored data were assigned a value equal to the censoring limit (i.e., 250 or 750, as appropriate)for the purposes of statistical calculations. Additionally, the data were assumed to follow a normal distribution, although this assumption was difficult to assess due to the prevalence of censored data. The 90LCL value for the fish bioassay(LC50) results was 738 mg/L, indicating than the population mean of UPRR rail tie waste is expected to pass the regulatory limit of>500 mg/L. Additionally, given that 98.6 percent of the individual samples from UPRR's rail tie wastes passed the fish bioassay test it is clearly expected that the waste stream as a whole meets the fish bioassay requirements (i.e., an LC50 above—in compliance with—the limit). 11183843Pol lack-1.dou rJ