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ERI 205513 QS1 Unocal Service Station 5886, Stockton, Cab OMM August 21, 1997 <br /> SAt the request of Tosco, ERI submitted the addendum to our work plan (dated July 14, 1997) for the <br /> subject site by the requested date The addendum addressed the directive for a full dimensional <br /> definition and investigation of soil and groundwater beneath and in the vicinity of the site and <br /> submittal of a Soil and Water Investigation report <br /> Tosco also performed a well survey to identify registered wells within a 114 mile radius of the site <br /> The purpose of this survey is to identify wells that may provide conduits for potential vertical <br /> migration of dissolved hydrocarbons and oxygenate compounds and provide information regarding <br /> sensitive receptors in the area The data indicates ten documented wells are located within a 114-mile <br /> of the site, seven of these wells are Cathodic protection wells and three are water supply wells (i e <br /> irrigation) The closest water supply well is approximately 1,000 feet northeast of the site in the <br /> generally upgradient direction of interpreted groundwater flow <br /> ONGOING WORK <br /> Based upon previous work completed at the site and in accordance with the correspondence and <br /> request from the San Joaquin PHSIEHD, Tosco completed the following <br /> • Performed a tightness test to evaluate the integrity of the existing fuel distribution system <br /> The results indicate the system passed within allowable tolerances The results and data are <br /> attached <br /> The following work is being performed <br /> • • MPDS Services Inc of Concord, California will implement the third quarter 1997 monitoring <br /> and sampling event on September 2, 1997 The results of the quarterly monitoring and <br /> sampling event will be submitted along with the upcoming quarterly summary report <br /> • ERI and Tosco are pursuing off-site access agreements with the owners of properties directly <br /> across March Lane (south) and adjacent to the western Tosco property boundary to allow off <br /> site use of cone penetrometer ERI will forward the assessor's parcel numbers (A P N ) to <br /> Tosco personal in the near future to allow Tosco personal to obtain an acceptable access <br /> agreement with the appropriate parties <br /> • ERI is performing an underground utility search to identify locations and orientations of utility <br /> trenches such as sewer lines by gathering appropriate maps depicting locations and depths of <br /> pertinent utilities from local agencies This will enable ERI to evaluate whether these <br /> facilities may provide conduits for the potential lateral off-site migration of dissolved <br /> hydrocarbons and oxygenate compounds Based upon these data and historic groundwater <br /> flow direction (towards the west-southwest), ERI will submit proposed locations to advance a <br /> cone penetrometer (CP) into underlying soil to San Joaquin County PHS/EHD for review and <br /> approval <br />