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06 August 2004 <br /> AGE-NC Project No. 04-1128 <br /> Page 2 of 6 <br /> L <br /> The Modesto, Riverbank and Turlock Lake Formations and overlying Recent alluvium are the <br /> L principal sources of domestic ground water in the 13,500-square mile San Joaquin Valley Ground <br /> Water Basin (Basin 5-22). The closest surface water is Mormon Slough, located just north of the <br /> property.Mormon Slough is intermittently dry,as most surface water is diverted to the north via the <br /> Stockton Diverting Channel. <br /> L 2.2. UNDERGROUND STORAGE TANK REMOVAL <br /> On 11 February 2003,one 12,000-gallon diesel USTassociated piping and dispenser were removed <br /> Lfrom the site. The UST was removed by Tank Specialists of California under permit from the San <br /> Joaquin County Environmental Health Department (SJCEHD). The approximate location of the <br /> r former UST is shown on Figure 2. <br /> L <br /> During the UST removal,twelve soil samples were collected from the site. Three soil samples were <br /> collected from the floor of the excavation(T1-W, T1-C and T1-E); one soil sample was collected <br /> beneath the dispenser island (D-1); and eight soil samples were collected from the excavated soil <br /> (SP-1 through SP-8). Total petroleum hydrocarbons quantified as diesel (TPH-d) and total xylene <br /> V was reported in sample D-1 (dispenser island) at 6,100 milligrams per kilogram(mg/kg) and 0.008 <br /> mg/kg,respectively.Total petroleum hydrocarbons quantified as gasoline(TPH-g),benzene,toluene, <br /> ethylbenzene and xylenes(BTEX)and methyl tertiary-butyl ether(MTBE)were not detected in any <br /> Lsamples collected beneath the UST or in the composited stockpiled soil samples. Analytical data <br /> from the samples collected during the UST removal are presented in Table 1. <br /> L <br /> 2.3. GROUND WATER DEPTH AND FLOW DIRECTION <br /> k <br /> Based on information obtained during drilling,ground water depth beneath the site is approximately <br /> 55 to 60 feet below surface grade (bsg). Once this depth is reached,water rises to a static depth of <br /> approximately 43 feet bsg.Based upon data obtained from nearby sites,the prevailing ground water <br /> flow direction in the vicinity of the site is estimated to be north-northeast. However, flow direction <br /> may vary both locally and seasonally. <br /> Ii <br /> 3.0. PROCEDURES <br /> L On 08 and 16 April 2004, soil borings B-1 ,and B-2 were advanced at the site as part of the <br /> assessment related to the former diesel dispenser. The.field work was conducted as outlined in the <br /> AGE-prepared Preliminary Site Assessment Work Plan, dated 04 February 2004 and approved by <br /> letter dated 13 February 2004. , <br /> r <br /> `++ Advanced GeoEnvironmental,Inc. <br /> i <br />