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i • • <br /> TABLE 2 <br /> ANALYTICAL DATA GROUND WATER <br /> Port of Stockton Former UST Site No 3 , San Joaquin County <br /> 1 Results reported in µg/1 (Parts per billion=ppb) <br /> Well Date TPH-g Benzene Toluene Ethylbenzene XylenesMTBE <br /> Number Sampled EPA 8015-m EPA 8260 EPA 8260 EPA 8260 EPA 8260 EPA 8260 <br /> 1 MW3-1 07/09/99 610 18 302 236 791 N D <br /> 10/22/99 2,750 270 120 49 390 N D <br /> MW3-2 07/09/99 640 119 296 219 666 N D <br /> 10/22/99 4,100 49 270 50 320 ND <br /> MW3-3 j 07/09/99 8,420 113 2,506 886 1,772 ND <br /> 10/22/99 7,220 207 680 221 1 1,360 ND <br /> 1 Reporting Limits 1 50 pg/1 0 5 pgn <br /> IIID Analyte not detected at reporting Ivttsis listed m laboratory report <br /> 1 MCis mµg/1 as follows benzene=l,toluene-150,ethylbenzene=700,xylenes-1750 <br /> SUMMARY OF FINDINGS <br /> On October 22, 1999, field personnel sounded and sampled the Port's former UST Site No 3 <br /> monitoring wells MW3-1 through MW3-3 At that time, the local direction of groundwater flow was <br />�! calculated at approximately N40°W along a gradient of 0 024 feet/foot (equivalent to 24 feet of dip per <br /> 1000 feet of horizontal distance) The average depth-to-water on October 22 was 1136 feet below the <br /> casing-tops of the three project monitoring wells <br />' Groundwater samples were collected from the monitoring wells on October 22, 1999 and analyzed for <br /> Total Petroleum Hydrocarbons as gasoline (TPH-g) by EPA Modified Method 8015, volatile <br /> 1 aromatics benzene,toluene, ethylbenzene, and total xylenes (BTEX), as well as MTBE constituents by <br /> EPA Method 8260 No gasoline as free product was observed in any well <br />' Concentrations of BTEX have decreased significantly in all of the wells For MW3-1, benzene <br /> concentrations in groundwater dropped from 18 µg/1 on July 9, 1999 to 2 70 µg/1 on October 22, <br /> 1999 Toluene concentrations in groundwater were decreased from 302 µg11 on July 9, 1999 to <br /> 120 µg/1 on October 22, 1999 Ethylbenzene concentrations in groundwater plummeted two <br /> orders of magnitude from 236 µg11 on July 9, 1999 to 49 µg/1 on October 22, 1999 Xylene also <br /> exhibited a decrease from 791 µg/1 on July 9, 1999 to 390 µg/1 on October 22, 1999 The same <br />' decreasing trend was observed for BTEX concentrations in MW3-2 and MW3-3 The samples <br /> collected from MW3-1 and MW3-2 exhibited an increase in TPHg from 610 and 640 to 2,750 and <br /> 4,100 µg/1 respectively However, samples from MW3-3 showed decreased levels of TPHg from <br /> 1 8,420 to 7,220 gg/1 <br /> MTBE compounds were also analyzed from all well samples and results were again "not detected" <br /> 1 (ND) on both July 9, and October 22, 1999 MTBE has not been detected in any soil or groundwater <br /> samples collected at this site Therefore it is recommended that MTBE be eliminated from future <br /> sampling requirements <br /> ust srte3 gtr2 99 doc 5 <br />