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11 August 1999 K. <br /> AGE-NC Project No. 95-0109 <br /> Page 9•o f 10 ; <br /> were previously detected in soil samples collected near each of the current sample locations. <br />' Significant decreases-in hydrocarbons were observed in 23 of the 26 samples analyzed, , H <br /> relative to samples:previously collected nearby. ; <br /> r The mass of petroleum hydrocarbons.in soil was estimated to be approximately 3,550 gallon ' <br /> in October 1993 and 315 gallons in February 1999, a reduction of approximately 90 percent. <br />' - Ground water elevation increased at the site during the first quarter of 1999.and-&creasEd <br /> during the second quarter of 1999. Ground water flow direction continues to be toward.the <br /> south-southwest at the site. A slight,ground,water mound was again detected near MW=9. A <br /> groundwater depression was detected west of MW-14 during the July.1999 monitoring. <br /> • Hydrocarbori concentrations decreased'in ground water samples from six wells and increased <br />' . in samples,from eight wells between the December 1998 and March 1999 sampling,events. <br /> Hydrocarbon concentrations increased.in four wells and decreased'ih two wells between the <br /> March and June 1.999 sampling,events.. <br />' The concentration'of hydrocarbons detected in MW-8 were higher.than during previous <br /> - sampling events. Hydrocarbons detected in the remaining wells were'within historical.levels. <br />�. • TBA was detected-in the ground water sample from one:,well during ,the March 1999- <br /> sampling <br /> 999sampling event and one well during the June sampling event. Other oxygenates were not <br />' detected at,the site. <br /> Overall, concentrations of dissolved oxygen remained stable between the December 1998, <br /> March'1999 and June']999sarilpling-events. <br /> • <br /> Only low,general microbiological activity.was,detected at the site during the March 1999 <br /> sampling event. Selective subpopulatioris.were not detected. <br /> 5.0. RECOMMENDATIONS <br /> Based upon data collected from'-the site;.AGE recommends: .` ' <br /> • -A-meeting`be:scheduled with the CVRWQCB and,the PHS-EHD to ex"amine'the'site for <br /> possible closure. Any further requirements for site closure should be determined,at-this,time.• <br />' - •" if appropriate, based upon the+meeting with the CVRWQCB -and PHS-EHD; a Closure <br /> Summary Report'should,be prepared... <br />' •' Quarterly ground water.monitoring 'should be'suspended.,pending results of the above <br /> 'described meeting. <br /> Advanced GeoEnvironmcntal,Inc. <br />