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FEB 1, 6 196 1G:03 FROM CONOCO 713-293-3305 TO B12094640130 PAGE 002 <br /> Linda S.nompson �� <br /> Propw Manager <br /> Room Po-9038 <br /> 7131293-26W <br /> • RemediabonTeohnalagy , Conoco Inc <br /> Fax- 7131293-8305 P a Boz 2197 <br /> Houston.Tac 77252-2197 <br /> February s, 1996 <br /> Mr. Harlin Knoll <br /> San Joaquin County PHSIEHD <br /> P.0 Box 2049 <br /> Stockton, California 95201 <br /> i <br /> R8: Remediation System Shutdown <br /> Former Econo Gas Station <br /> 4325 past Washington Street <br /> Stockton, California <br /> Dear Mr. Knoll, <br /> As we discussed during our telephone convey ation this morning,the rernedratron system <br /> at the above referenced site will be shut down until further notice. The annual � <br /> groundwater monitoring will continue In addition, one of the two downgradient <br /> monitoring wells(MW-29 and MW-30)will be amplad quarterly,alternating from one wall <br /> to the other (see attached Groundwater Gradient Map). <br /> i <br /> Since the remediation system began operatio in August 1989, approximately 105,000 <br /> pounds (17.000 gallons) of gasoline have beremoved and treated. Concentrations of <br />• total petroleum hydrocarbons as gasolinic (Tind <br /> g) in the soil vapor have decreased from <br /> a high of 33,000 mg1m3 to approximately0 mg/m3 (see attached Summai;y of ,oar � <br /> Monitoring Analytical Results). Groundwaters contained no detectable concentrations <br /> of TPHg or benzene, toluene, ethylbanzene xylenes (BTEX) since May 1993 <br /> Groundwater elevations have fluctuated sign ficantly since assessment began in 1985. i <br /> Data indicate that groundwater was 45 to 50 feet below ground surface {bgs) in 1985 <br /> their dropped to 80 to 85 feet bgs in late 1992. 1995 data indicate that the groundwater <br /> level has risen to approximately 72 feet bgs. <br /> We will observe the quarterly groundwater d to for six to twelve months following the <br /> system►shutdown Pending the outcome of the anticipated regulatory changes, this site <br /> may be a candidate for closure If you have Any questions, please contact me at 1713) <br /> 293-2367 <br /> Sencsrely, <br /> Linda S. Thompson <br /> Project Manager <br />