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u t1 very low concentrations of degraded petroleum hydrocarbons were observed in the sample The laboratory noted that the results did not match the gasoline standard The very low concentrations of only Ethylbenzene and Xylene support the interpretation of highly degraded fuel The previously observed dissolved contaminant concentrations were more elevated in the reconnaissance groundwater sample at B-3 than that the monitoring well MW-1 The discrepancy is attributed to the sampling from an open borehole, where drilling muck and water is mixed The drilling action may have the effect to release immobile absorbed contaminants in the capillary fringe region, causing more elevated concentrations in the reconnaissance groundwater samples. In our opinion, the MW-1 monitoring well data are interpreted to more accurately represent the mobile contaminant concentrations Conclusions and Recommendations Wight installed one groundwater monitoring well in Grantlme Road, adjacent to the previous Bonng B-3 The sample from this well shows very low degraded dissolved concentrations of TPHG, Ethylbenzene and Xylenes The laboratory noted that the TPHG did not match the laboratory standard A plot of groundwater flow was made from the two sites dust to north (Gemelos and Cheaper Gas), which shows a north-northeasterly flow direction under a low flow gradient Wright recommends that well MW-1 continue to be monitored at quarterly intervals for the next quarter Limitations This report has been prepared specifically for the City of Tracy, for Tracy Auto Stereo site on Grantline Road in Tracy, CA and was done according to State and local agency suggested guidance documents for these investigations The interpretations, conclusions and recommendations made herein are based on the data and analysis for the soil and water samples collected at the boring locations noted and should be reviewed in the context of this report and other site reports Wright Environmental Services, Inc is not responsible for errors in laboratory analysis and reporting, nor for information not available during the course of the study, and no warranty or guarantee is expressed or implied therein If you have any questions, please call Sincerely, /�S pQF��R 11 Wright Environmental Services, Inc. Cc N° 1252 CERTIFIED John Lynch Christopher M Palmer s� CEGLCGIST President HG 246, CEG 1262T� i Attachments: Figure 1 Monitoring Well Location Map and Groundwater Contour Map, November 8, 2000 Figure 2 Geologic Cross Section Figure 3 Dissolved Contaminant Map, September 21, 2000 Page 5