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ug11- We believe this is a result of the air sparging The wells side gradient and downgradient of the sparging well are BM-1, BM-5 and BM-8 There oxygen levels this quarter were 3 2 mg1L_, whereas their oxygen levels last quarter were 1 8, 2 8 and 2 5 respectively Well BM-9 is in the path of contamination from the ARCO station and BM-7 is directly downgradient of well BM-9 Wells BM-3 and BM-6 are located in the path of previous gradients and the contamination could have come from the ARCO station MtBE was detected in BM-1, BM-2, BM-3, MW-4 and MW-5 BM 1 is located in the old tank pit and BM-3 is located upgradient of the old tank pit TBA tertiary Butanol was found in wells BM-3 and perhaps in BM4, this product can be a byproduct of MtBE when it is bioremediated It is also an oxygenate We believe this MtBE is related to gasoline coming from the ARCO station Dissolved oxygen levels were recorded this quarter at this site The levels were Imeasured 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 The readings of dissolved oxygen are between 2 6 at well BM-12 and 3 6 at well BM-11 The levels appear to be stabilizing across the site IAs requested in the EHD letter dated January 10, 2000, a plot of the wells and the old and new piping runs of the dispenser lines is shown in Figure 8 I0 VAPOR EXTRACTION SYSTEM The site has been under remediation since July 1997 A total of 43,441 pounds of l gasoline has been removed since the beginning of this project The vapor extraction system (VES) had been shut down since February 1999 because no BTEX chemical was being recovered We drilled vapor extraction well VW-7 and found soil contamination in this well This well is used as a vapor extraction well and it assists in controlling the air sparging well located between BM-1 and BM-5 The VES was started up along with sparging January 12, 2000, although Table 5 shows some testing activity was performed in September and December 1999 iThe testing indicated that there was no water mound formed by the sparging air during December, however, a mound was found during the sampling of February 2000 This mound is about 0 25 feet high and extends between wells BM-4 and BM-8 in the easterly direction and between BM-1 and BM-6 in the northerly direction The mound can be seen in Figure 1 and a profile of the top of the water table between wells BM-9 and BM-11 can be seen in Figure 6 and a 3 dimensional plot in Figure 7 The mound is causing some of the contamination in the old tank area to flow towards BM- 8, BM-5 and BM-2 However, we believe the oxygen supplied to the groundwater is . beneficial, since it has increased the aerobic activity in the old tank area as noted by the reduction of contamination in the water from well BM-1