ARCHIVED REPORTS XR0010714 - Laserfiche WebLink

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plume appears to be centered at well BM-3 as it has been in the past, since July 1998 ' We have had the tanks and piping of the tanks checked and there were no leaks found The fact that in well MW-3 minor amounts of TPH or BTEX chemicals were found in the water and MtBE being found in this well creates a problem The mole concentration of ' Benzene (I%), Toluene (111%), Ethyl benzene (2%) and mixed xylenes (11%) and MtBE (11%) in the average gasoline mixture has been calculated The solubility of Benzene (18 mg/L), Toluene (59 mg/L) Ethyl benzene (3 mg/L) Xylenes (19 mg/L) and MtBE (5200 ' mg/L) is known Because MtBE is very soluble and the BTEX chemicals are less soluble, we would expect the BTEX chemicals to be less concentrated than MtBE, however, they should also be present if the gasoline entered the water nearby The fact that none of the BTEX and TPH chemicals are present at levels as mentioned above indicates that the source of the MtBE is not entering the water near well BM-3, although Mr Nuel ' Henderson the Geologist for San Joaquin believes that MtBE can appear without gasoline, we do not believe this is true If the gasoline is captured by the vapor system the MtBE will also be captured We will be checking the tanks since there is no vapor ' extractor well near them The vapor extractor system is working and one of the extractor wells is located in the center of the pump islands The extractor system extracts vapor from about 40 feet in rdiameter around the well and this is in the area where the pumps are located Dissolved oxygen levels were recorded this quarter at this site The levels were measured with a calibrated YSI model 51 B meter by placing the sensor 5 feet below the surface of the water table after the bailing of the wells The measured levels are shown on Table 3A and showed in Figure 5 ' VAPOR EXTRACTION SYSTEM The system has been repaired and has been operating since .lune 21, 2002 A total of 44,442 59 pounds of gasoline has been removed since the beginning of this project See Table 5 Conclusions We will continue to monitor this site The next monitoring event will take place in October 2002 We will present a work plan to soil sparge around the tank area this quarter Attached is a Hazardous Waste Manifest showing the purged water has been properly disposed of • 2