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u <br /> ERI 205503 R02 Tosco 76 Service Station 5886,Stockton,California March 2,1999 <br /> analyzed within the mobile laboratory and subsequently stolen In response to further requests by <br /> Tosco and ERI personnel, Sequoia located hard copies of chromatograms (apparently in their <br /> warehouse) Sequoia estimated dissolved MTBE concentrations in groundwater samples, collected <br /> from Geoprobe'D equipment during UST replacement activities, ranged between c 5 0 micrograms per <br /> liter (uglL) to 1,300 ug/L (Attachment B) These data indicate dissolved MTBE was present in <br /> groundwater prior to installation and activation of the new underground fuel facilities <br /> Groundwater n <br /> Union Oil initiated quarterly groundwater monitoring and sampling at the site in December, 1996 <br /> Tosco has continued quarterly groundwater monitoring and sampling, and reports the data in the <br /> Quarterly Summary Reports The cumulative groundwater monitoring and sampling data are provided <br /> in Attachment C <br /> Encroachment Permit nAccess em <br /> During July and August 1997, an ERI representative contacted Mr Robert Brothers of the City to <br /> obtain an encroachment permit to drill within the City's March Lane right-of-way Mr Brothers <br /> informed ERI'S representative that improvements on March Lane had recently been completed and that <br /> the City would not authorize any work within this right-of-way <br /> In response to the City's moratorium on work within the March Lane right-of-way, ERI obtained <br /> information regarding the ownership of properties south and west of the subject site Based upon this <br /> information, Tosco successfully negotiated access agreements with the property owners of 2710 West <br /> March Lane (located directly south of the subject site) and 2800 West March Lane (located southwest <br /> of the subject site However, Tosco is still pursuing access agreements with the lessee of 2716 West <br /> March Lane (located south of the site) and with the property owner of 2727 West March Lane (located <br /> directly west of the site) <br /> Underground Utility Search <br /> During third quarter 1997, Tosco performed an underground utility search to identify locations and <br /> orientations of utility trenches and to evaluate whether these facilities may provide conduits for the <br /> potential lateral off-site migration of dissolved hydrocarbons and oxygenated compounds The results <br /> of this utility search indicated that utilities are primarily located within the March Lane right-of-way <br /> and are oriented east to west Lateral utility trench lines servicing specific sites are oriented <br /> perpendicular to the main utility lines The deepest utility trench, approximately 10 5 feet below <br /> ground surface (bgs) identified near this site appears to be a 21-inch sanitary sewer line located <br /> approximately 70 feet south of the southern property boundary of this site A file review indicated that <br /> this sewer line is a gravity drain system draining towards the west The locations of the underground <br /> utilities are shown on Plate 2 <br /> • 3 <br />