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Page 1 of 1 <br /> v .I <br /> Vicki McCartney [EH] <br /> From: Nuel Henderson [EH] <br /> Sent: Tuesday, April 30, 2013 1:38 PM <br /> To: 'Barton, Jim@Waterboards' <br /> Cc: Vicki McCartney [EH] <br /> Subject: 2494 Fremont Street MW S-1 Data <br /> Attachments: MWS-1 Data.xls <br /> Jim, <br /> Attached is the data set and graph I made of TPHg and benzene concentrations in the only problem well <br /> on the site: S-1. You can see that periodically the TPHg concentrations spike up for no apparent reason; <br /> benzene spikes have less magnitude other than the recent spike to 5900 ppb. The overall trend of both <br /> analytes is downward, albeit very slowly. There appears to be a very general correlation between DTW <br /> and contaminant concentrations, but this does not appear to be causing the spikes. I doubt that CRA can <br /> give a satisfactory explanation for the spikes, but I don't see them as indicating a significant change in the <br /> overall trend. <br /> MW S-1 is in the vicinity of soil sample ST4 (5'), collected at the west end of the northern dispenser <br /> island. Considerable soil contamination was encountered at depth in the area and ST4 may represent the <br /> tip of the iceberg of the soil plume. ST4 is the only soil sample collected at 5 feet bsg or less among some <br /> 26 such samples, that does not pass the LTCP Table 1 criteria for commercial sites direct contact <br /> (benzene = 9.2 mg/kg, ethylbenzene= 110 mg/kg); it does pass for utility workers. <br /> Nuel <br /> 4/30/2013 <br />