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Page 3 of 9 <br />The first 4 samples in Table 1 have tested hazardous for TCLP benzene, <br />and the last 4 samples are inconclusive. Based on this data, the <br />total <br />benzene concentrations in the last 4 samples cannot be assumed to be <br />nonhazardous and TCLP must be run on representative samples or the <br />waste <br />assumed hazardous. <br />In addition, we would like to clarify, that while we initially <br />approved <br />the addition of cement to stablize the slurry and to make it easier to <br />handle and remove, we were not clearly aware that sidewall and bottom <br />trench soils were also being added to the mixture. The addition of <br />the <br />soils from the trench sidewalls and bottom needs to cease. Once the <br />slurry waste is removed and dealt with, the insitu trench soils will <br />need to be sampled and excavated separately, depending on the results. <br />You may wish to evaluate your current method of cement stablization, <br />as <br />this may be creating larger and larger volumes of potentially <br />hazardous <br />waste. Again, the native soils cannot be added to the slurry to <br />stabilize or dilute it. On the other hand, any remaining slurry and <br />contaminated soil or water in the trench should be removed or treated <br />promptly to avoid continued leaching to shallow groundwater and <br />potentially to the river. <br />I also have some initial thoughts on the soil and groundwater <br />investigation, but a groundwater contour map is needed to more fully <br />evaluate. Given the river and whatever else may be going on here <br />(dewatering??), the hydrology is likely complex. Before you get too <br />far <br />down this road, we may wish to talk to make sure that samples are <br />being <br />collected from locations most likely to be impacted (immediately <br />downgradient, etc.). Also, on page 3 of your report, you state that <br />MW-1 has 2,700 mg/l benzene, while Table 3 shows this as ug/1. Please <br />clarify the proper units as I don't have the lab reports yet. <br />What info do you have on the spilled gasoline? Any additives? MSDS <br />sheets, etc. <br />These are my initial review comments and we can discuss further to <br />clarify, etc. Please contact me at your convenience at 303-692-3376. <br />Thank you. <br />Terry Bennett <br />CDPHE/HMWMD <br />6/9/2007