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1 <br /> CONCLUSIONS AND RECOMMENDATIONS <br /> . Conclusions <br />' The following conclusions may be made from the data collected during the four quarters of monitoring in <br /> 2005,as well as the overall historical data for the site <br /> • Groundwater elevations have declined by approximately 13 feet to—31 feet MSL since reaching a <br /> high of approximately—18 feet MSL in May 2000 <br /> • The groundwater gradient in 2005 ranged from 0 001 to 0 004 feet per foot to the north-northeast, <br /> which is generally consistent with the average groundwater gradient at the site <br /> TPH has not been reported in any of the samples since June 2004, and has been reported only <br /> sporadically since approximately December 2001 <br /> • 1,2-DCA was reported for four wells during 2005 at concentrations ranging from 20 to 36 µg/L <br /> The highest concentration was observed in the sample collected from DMW-9 In June PCE was <br /> reported only to the samples collected from DMW-9, at a maximum concentration of 4 2 µg/L <br /> • The trend of concentrations of 1,2-DCA is downward for all wells with the exception of DMW-9 <br /> The period of record for DMW-9 is short, and the data are variable within that period More data <br /> is needed to fully assess the trend in DMW-9 The lack of detections of 1,2-DCA in DMW-8 <br /> compared to the shallower well DMW-9 suggests a lack of vertical migration for that constituent <br /> Recommendations <br /> Based on the sporadic low detections of TPH, the low concentrations of 1,2-DCA, and the generally <br /> declining trend in 1,2-DCA concentrations after eight quarters of sampling from monitoring wells DMW- <br /> 8 and DMW-9, the site appears to be nearing conditions acceptable for closure It is recommended that <br /> closure status or the need for active remediation be decided upon based on quarterly data collected during <br /> the remainder of 2006 <br /> If you have any questions or need additional information, please do not hesitate to call me at <br /> (916)679-2293 <br /> Sincerely, <br /> URS Corporation Americas <br /> Anthony gMindlina R G <br />' Project Geohydrologlst <br /> Attachments <br /> r <br /> r <br /> rD IQ4051REVIEW PACKAGE12005 GROUNDWATER MONITORING REPORT-TEXT DOC <br /> r <br />