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1 WIA F Inc. Environmental and Engineering Group Post Office Box 427 Oakdale, CA 95361 Office: (249) 848-4280 Fax: (209) 848-4282 ' Jeffrey Wong, REHS February 7, 2001 LOP/Site Mitigation Unit N San Joaquin County PHS/EHD 304 East Weber Avenue, Third Floor Stockton, CA 95202 Re: Boyett Petroleum 419 S. Main Street ' Manteca, CA 95336 Dear Mr. Wong, ' On February 2, 2001, WIU, Inc., Environmental and Engineering Group of Oakdale, California, in conjunction with VBI In-Situ Testing of Sacramento, California, conducted two (2) Cone Penetrometer Technology(CPT) exploratory soil penetrations at Boyett Petroluem, located at 419 S. Main Street, in Manteca, California. The CPT penetrations were conducted prior to an installation of a deep monitoring well, which will have a short screen, and will be placed below the groundwater table, in order to define the extent of the oxygenate contamination below the groundwater table. CPT-1 was completed to a depth of 3' below ground level(bgl)when the cone met resistance and the penetrating was terminated. CPT-1 was then moved approximately 2' to the east. It was penetrated to a depth of 76' bgl when the cone encountered resistance and the penetration was completed at that depth. CPT-2 was penetrated approximately 21' feet northeast of MW-1, to a depth of 76.4', when the 1 cone again encountered resistance and the penetration was completed at that depth. In CPT-1, there exists a clay layer from 20' to 24.1'. From 50.2' to 57.6' there exists a clay layer ' and also cemented material. In CPT-2, there exists a clay layer from 23.8' to 26.4'. From 49.7' to 56.4' and also from 62.7' to 66.9', there exists clay along with cemented material. From 73.3' ' to 76.4' (bottom of penetration), there exists cemented material along with very dense soil. The cone was unable to penetrate below approximately 76' in both penetrations due to very dense material. ' WIC believes that based on the information from the CPT penetrations, there are significant aquacludes on the site, which are below the groundwater table, and would prevent the vertical �r miaratinn of nxvoenataa Thi-nrnnnePrl rlPPn wP11 ehniilrl not PxtPnd hPvnnr# ePrrnnrl an„arhids% --- ------ -- ---�o-------- ---- r--r---- ---r .--- ----------- -------- --� ..__..___ -..1_..__.-.._, which is approximately 7' thick in both wells. In.CPT-1, this layer exists between 50.2' to 57.6', �i and in CPT-2, this layer exists exists between 49.7' and 56.4'. The well should be drilled to 1