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-M --' '-M15, V R-gusAl.MGM WEN '�Nlvli� <br /> MIN <br /> W <br /> 2.0 SITE SETTING <br /> g The project site is situated on level terrain comprised of <br /> Quaternary-Recent alluvial sediments. Near surface <br /> -4 materials in the area consist of intercalated sands, silts, <br /> clays, and gravels. As is typical of alluvial environments, <br /> I higher permeability zones representing former stream <br /> channels occur as sinuous or lenticular features. <br /> The site is• located within the Eastern San Joaquin <br /> Groundwater Basin. Tho basin is drained by the <br /> northwesterly glowing ,San Joaquin River located <br /> `-0 approximately one mile south of the site. Depth to <br /> groundwater as measured in the on-site monitoring well is <br /> approximately 33 feet below grade. Regional groundwater <br /> flow is southwesterly ;San Joaquin County Flood Control, <br /> � > Spring 1589) although localized reversals in gradient can <br /> result from groundwater extraction. <br /> rs,y <br /> 3.0 INVESTIGATION PROCEDURES <br /> The past tank removal investigations have been completed in <br /> + three phases including 1) excavation and sampling of the <br /> former diesel tank pit 2) drilling and soil groundwater <br /> I CA sampling of a groundwater monitoring well adjacent to the <br /> waste oil tank and 3) drilling and soil sampling of an angle <br /> boring beneath the on-site building adjacent to the waste <br /> oil tank. <br /> nr,e✓l <br /> 3.1 Phase 1 <br /> To remove the remaining diesel contaminated soils from the <br /> west and of they middle diesel tank pit WaterWork proposed to <br /> re-excavate the Fest wall. On December 16, 1989 re- <br /> excavation of the west tank wall and floor of the middle <br /> diesel tank pit was conducted with Haden Knoll of SJCEHD <br /> present. The excavation was extended laterally over an <br /> APPROXIMATELY 10,0 by 10.0 foot area and vertically to <br /> depths ranging from 2.0 to 16.0 feet below grade. Due to <br /> the proximity of the public sidewalk, lateral excavation to <br /> the west was limited. Soils consisted of medium stiff to <br /> stiff lean clays and elastic silts. Slight diesel fuel <br /> f_ odors were detected in -the excavated material and west <br /> excavation wall. <br /> One floor and two wall confirmation samples were collected <br /> with the excavator bucket. The wall samples were collected <br /> at a depth of 2.0 and 6.0 feet below grade and the floor <br /> sample was collected at a depth of 16.0 feet. The samples <br /> were collected under the direction of Harlen Knoll sicEHD. <br /> In addition, a composite sample of the excavated material <br /> was collected for analysis. The samples were analyzed by <br /> B.C. Laboratories, a State certified laboratory, for <br /> benzene, toluene, ethylbenzene, and xylenes (BTEX) by <br /> 2 <br /> -- <br />