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��ax�; r� a.� ';:1"je9"'!•v+ vs :uy� _ Y %F.t� r..a�-- � as � -� � -p ',i°�...$' 3 T, a 3- PHASE,I-HY? Pl 11 LOGIC ASSM&MME fC 7910 Lower Sacramento Bead,Stockton,California Nita Project Na 404k%147 loge 6 Site Solis enol Gtoloav A total of six soil borings were drilled during August 1989 in order to characterize the subsurface geology and to evaluate the presence of petroleum constituents in soil$beneath the site. In order to evaluate the extent of petroleum constituents detected during tank removal in December 1988, soil and monitoring well borings were advanced in the vicinity of soil sampling locations where TPH had previously been detected. Soil boring SB-1 was advanced near pump island sampling Iocation T-3. Soil rTM boring SB-2 was located near pump island sample T-1. Soil boring SB-3 was advanced through the former tank excavation backfill, in the vicinity of tank samples T-5 and T-7. Monitoring well borings MW-1, MW-2, and MW-3 were located around the perimeter of the former tank excavation, to the southwest, i northeast,and northwest,respectively. Locations of the soil borings and mm• firing wells are shown in Figure 2. f Soil borings SB-1,SB-2,and SB-3 were advanced to depths ranging from 41.5 to S&S feet below ground p ! .. surfata The monitoring well borings were advanced to 68 feet below grade,. The borings were advanced x r�+ using 8-inch-diameter hollow-stem augers for soil borings,and 10-inch-diameter hollow-stem augers for monitoring well borings. Monitoring wells MW-1,MW-2,and MW-3 were drilled and installed on August r 11 and 13, 1989. Feld soil boring logs are presented in Appendix A. i Two cross-sections were generated to illustrate the subsurface geology. Figure 3 shows the surface trace of cross-sections A A' and B-B' which are presented in Figures 4 and S. Silty clays to clayey silts k ; i predominate bevmth'the site; A 17.5-foot-thick silty sand layer was encountered from 13.5 to 30 feet : below grade is soil boring SB-1 (Figure 4 A silty sand layer of equivalent thickness was encountered bi from 33 to 51 feet below grade in soil boring SB-3(Figure 5). Minor layers of sandy silt,silty sand,and .p sand are interbedded with the silty clay and clayey silt layers beneath the site. Clay,silty clay,and clayey 4. silt surround the backfill of the former tank excavation. &H CnernIstry Soil samples were collected at 5-foot depth intervals and screened with a portable photoionization detector (PID) for total organic vapors. Samples selected (based on PID readings) for chemical analysis were submitted to aCalifornia-certified laboratory for analysht of TPH,BTEX and total lead. The results of i l . these analyses are presented in Table 4. The certified laboratory reports forsoil boring samples are _. -- presented in Appendix B. l z d t