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PROBLEM ASSESSMENT REPORT Moreland Court Shell 7700 Moreland Court, Stockton, California Delta Project No 40-88-146 Page 14 TABLE 7 Chemical Analyses of Soil Samples Collected From Soil Borings Drilled on August 1 and 2, 1990 (ppm) Sample Date Depth Ethyl- Total Number Collected LZ Benzene Toluene benzene Xylenes TPH Uada MW 1(30) 08/02/90 30 00073 00099 <0 005 <0 005 <10 34 MW 1(40) 08102/90 40 <0 005 <0 005 <0 005 <0 005 <10 74 SB9(40) 08/01/90 40 00068 00080 <0 005 <0 005 <10 69 SB9(70) 08/01/90 70 <0 005 <0 005 <0 005 <0005 <10 70 SB 10(10) 08/01/90 10 00066 00057 <0005 <0 005 <10 78 SB 10(30) 08/01/90 30 00063 00076 00058 <0005 <10 58 SB 10(40) 08101/90 40 <0005 <0005 <0005 <0 005 <10 84 a Concentrations in milligrams per kilogram (equivalent to ppm) i Concentrations of BTEX in samples collected from 10 to 40 feet below the surface ranged from 0 0057 to 0 0099 ppm Concentrations of TPH were less than the laboratory analytical method detection limit of 10 ppm for all soil samples submitted. Concentrations of BTEX to samples collected below 40 feet were Iess than the laboratory analytical method detection limits (<0 005 Qpm) Total lead concentrations ranged from 3 4 to 8 4 ppm An additional soil boring near soil sample location TS-2 was proposed in the Prehmvtary Report Attempts were made to advance this boring at seven locations. At each location, pea gravel beneath the concrete began to slump into the soil boring Therefore, we did not complete this soil boring due to the risk of undermining the concrete slab 3 4 Monitoring Well Information On August 1, 1990, two sots borings (SB-9 and SB-10) were advanced to 715 and 415 feet below grade, respectively During drilling activities,a wet silty sand to sand layer was encountered at 30 and 35 feet below grade within soil borings SB-9 and SB-10, respectively Both borings were left open overnight with the augers in place Aber leaving the boreholes open overnight, neither boring had accumulated water On k' August 2, 1990, another soil boring was advanced to a depth of 41.5 feet below grade and converted into a monitoring well screened between 25 and 40 feet The purpose of the monitoring well was to determine if a perched water table existed within the silty sand layer I