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an oxygenate The presence of MtBE in wells BM-2, BM-3 and BM-4 seems to indicate <br /> I that MtBE has not leaked from the tanks to the groundwater at this station The levels of <br /> BM-3 fell from a high of 2000 ug/L in February 2000 to 27 ug/L at present Also a tank <br /> and line testing was performed on June 7, 2000 and no leaks were found We believe the <br /> air sparging will remove the MtBE and TBA from the water around wells BM-1 and BM-5 <br /> In the future all of the water at this site must pass through this area, therefore, all the <br /> MtBE will be removed with time <br /> Dissolved oxygen levels were recorded this quarter The levels were measured with a <br /> calibrated YSI model 51 B meter by placing the sensor 5 feet below the surface of the <br /> water table after the bailing of the wells The measured levels are shown on Table 3A and <br /> Figure 5 The readings of dissolved oxygen are between 0 5 at well BM-2 and 4 1 at well <br /> BM-12 Figure 5 indicates that natural attenuation is taking place in wells with <br /> contamination such as BM-2, BM-3, BM-7 BM-1, BM-5 and BM-8 The oxygen levels east <br /> of well BM-8 appear to be stabilizing <br /> As requested in the EHD letter dated January 10, 2000, a plot of the wells and the old and <br /> Inew piping runs of the dispenser lines is shown in Figure 7 <br /> A plot of the well mounding around BM-1, caused by air sparging is shown in Figure 8 This <br /> mound is about 0 2 feet high and is not considered an event which will cause unforeseen damage <br /> to the groundwater <br /> VAPOR EXTRACTION SYSTEM <br /> The site has been under remediation since July 1997 A total of 43,667 pounds of <br /> gasoline has been removed since the beginning of this project <br /> The vapor extraction system (VES) was shut down on April 13, 2000 because of a <br /> problem with the sparging system This system was repaired between June 28 and July <br /> 7, 2000 The system was started and found to be working properly <br /> Conclusions <br /> We will continue to monitor this site The next monitoring event will take place in October <br /> 2000 <br /> We will be implementing the approved work plan dated April 12, 2000 this quarter <br /> Yours truly, <br /> /John Cussen <br /> • <br /> RG� #6506 <br /> OF Cy.1F� <br /> I <br />