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Mr'. Tinj Smith <br /> County of Los Angeles %..0 <br /> Department of Public Works <br /> October 19, 2009 <br /> Page 2 <br /> This area includes three islands, each containin <br /> petroleum product and three product line runs exgtending beneath the dispensers.three dispensers for h �sD e. and diesel <br /> activities the dispensers were removed and product piping was exposed. <br /> ring upgrade <br /> > p p pp, g P <br /> Flying J contracted the services of Nichols Consulting Engineers, Chtd. (NCE) to mobilize to the <br /> site to observe soil conditions and to collect soil samples from beneath seven of the nine dispenser <br /> locations and along product line runs for the RV islands. A total of 15 soil samples were submitted <br /> to a State of California certified laboratory for analysis of total petroleum hydrocarbons (TPH), <br /> gasoline and diesel range organics, and fuel oxygenates using the EPA Test Methods 8015 and <br /> 826013, respectively.- Results of these analyses indicated 1 of the 15 samples analyzed contained <br /> TPH-diesel range organics at a concentration of 240 milligrams per kilogram, <br /> rThe sample was <br /> collected from approximately 1 to 2 feet beneath the diesel dispenser located on the south'side'of <br /> the center RV island. No other constituents were detected in any of the samples analyzed. <br /> In response to these findings, San Joaquin County issued a correspondence dated September 15, <br /> 2009 requesting "a work plan to investigate the lateral and vertical extent of the soil and <br /> groundwater contamination at your site...." This work plan is being provided pursuant to this <br /> request. <br /> Area Geology <br /> The subject site lies within the Central or Great Valley of California.' The Great Valley is an <br /> elongated lowland located between the Sierra Nevada on the east and the Coast Ranges on the west. <br /> The southern portion of the Great Valley drained by the San Joaquin River is referred to as the San <br /> Joaquin Valley and the northern portion drained by the Sacramento River is referred to as the <br /> Sacramento Valley. Rocks of the Great Valley consist of sedimentary deposits ranging in age from <br /> late Mesozoic through Holocene (Recent).' <br /> Unconsolidated continental deposits constitute the primary source of groundwater in the Great <br /> Valley' The continental deposits consist primarily of alluvium; however, some areas consist of <br /> permeable lake bed sediments. <br /> 4 Norris, Robert M. and Robert W. Webb, 1990. Geology of California, 2nd edition, John Wiley & Sons, Inc., USA, <br /> 541 pages. <br /> 2 Norris, Robert M. and Robert W. Webb, 1990. Geology of California, 2nd edition, John Wiley & Sons, Inc., USA, <br /> 541 pages. <br /> Geologic Map of California, Compilation by Charles W.Jennings, California Division of Mines and Geology, 1977. <br /> Davis, G. H.,J. H. Green, F. H. Olmstead, and D.W. Brown, 1959. Ground-Water Conditions and Storage Capacity <br /> in the San Joaquin Valley,California, United States Geological Survey Water-Supply Paper 1469. <br /> 3 F. H.Olmstead and G.H. Davis, 1961. Ground-Water Conditions and Storage Capacity in the Sacramento Valley, <br /> California, United States Geological Survey Water-Supply Paper 1497. <br />