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r <br /> MEMORANDUM - - - - - - - - - -- - - - - <br /> Richmond, California <br /> October 21, 1994 <br /> Former Chevron Service <br /> Station No. 9-1918 <br /> 45 East Harding Way <br /> Stockton, California <br /> I <br /> Mr. S.L. Hunter <br /> San Ramon, CA <br /> The following comments concern my review of the remediation <br /> activity at former Chevron Service Station No. 9-1918, in Stockton, <br /> California. <br /> Observations <br /> 1) The site is the location of a former Chevron service station, <br /> which operated from 1953 to February 1988 . There are presently <br /> eleven monitor wells on-site (MW-1 to -11) , and three wells off--- <br /> site (MW-12 to -14) (see attached Site Map - Figure 1) . <br /> The station was closed in 1988, with the product and waste oil <br /> tanks removed at that time. Three additional product tanks (3000, <br /> 4000 and 500 gallon capacity) were later discovered and removed in <br /> 1988. Another 1000 gallon tank was discovered and removed in 1994 . <br /> 2) The site is underlain by an unconsolidated sedimentary sequence <br /> dominated by clayey silt, silty clay and sandy clay, with <br /> discontinuous fine sand layers of variable thickness. <br /> Depth to groundwater during the most recent monitoring event (July <br /> 8, 1994) was approximately 47 .5 to 49 feet BGL, with an apparent <br /> flow direction to the north/northeast. There has been an observed <br /> long term increase in depth to water from approximately 35 to 55 <br /> feet BGL, since initial monitoring began in November 1988 . All <br /> wells except MW-2R and MW-9 to -13 have been dry since mid-1989 . <br /> It should be noted that between October 1992 and July 1994, there <br /> has been a subsequent increase of the water table elevation of <br /> approximately 9 feet, as measured at MW-9 . <br /> 1 <br />