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.? Aa�n ti'^r�r��'•'` i d-1`a��'i+„�, il.���k"""'h^, m�� y�-xS � :.S ,�,s�{� Y-veA./,c,�+�..5-�4t: ,.,' '°w� q r S� �" �-e7�f. ° ^4i [ '-C+}. ,., y� w' '4 <br />¢roc <br /> Ir^ <br /> S513 91-1038 <br /> -thrifty Oil Company Station No. 172 Page 3 <br /> 7647 pacitie Avenue <br /> Stockton.California <br /> rocks yielding, saline waters tray underlie continental derived sedimentary rocks at depth. The <br /> basement in the region is composed of meta-sedimentary and meta-volcanic rocks and occurs at <br /> a depth of approximately 15,000 feet below the Stockton area. Structurally, the consolidated <br /> sediments have been folded into a west dipping homocline formed by the westward tilting of the <br /> Sierra Nevada structural block. <br /> 2,; Project History <br /> According to Thrifty Oil Company personnel, no previous environmental site assessments have <br /> been conducted at the site. Gasoline service stations have occupied the site for at feast the]as, <br /> 27 years. Inventory records and tank test results through 1989 indicate that no significant recent <br /> unauthorized releases have occurred. A work plan was prepared by Thrifty Oil Company in April, <br /> 1991, to assess the presence of petroleum range hydrocarbons in soil and possibly ground water <br /> at the site. The work plan was subsequently approved by the San Joaquin County Public Health <br /> Services, Environmental Health Division (S.EHD) who issued a permit for the work described. <br /> This report presents the findings of that assessment. <br /> 3.0 RESULTS AND FINDINGS <br /> The results of the field and laboratory irvcsti.gadons are summarized in the following sections. <br /> 3,1 Soil1'rnllie <br /> The soils encountered during drilling consisted of black, organic sandy clay to a depth of <br /> approximately 5 feet below site grade. Fine to medium grained, brown, silty sands were <br /> encountered from 5 to 10 feet. Fine to medium grained,poorly graded sands were encountered <br /> between 15 and 20 feet. fine to medium grained silty sandr,and 7.w plasticity sandy silts were <br /> encountered from 20 to 60 feet, Fine to medium grained, reddish-brown poorly graded sands <br /> _ were encountered at a depth of 60 feet,at which depth ground water was encountered and below <br /> which no additional soil samples were collected. <br /> SS11 LNVIitONMCN'l'AL CONSULTANTS,INC. <br />