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I rr { , Completion of Initial Monitoring Wells �r On June 6, 1994, soil borings 4, 5, and 6 were drilled and completed as ground-water monitoring wells MW-4, MW-5, and MW-6. This sequence of well numbers was selected by the field geologist in order to avoid confusion regarding the previous Hydropunch'''numbers HP- 1, HP-2, and HP-3. All monitoring wells were drilled, sampled, and completed in order to determine the horizontal and vertical extent of soil and ground-water contamination and to allow for calculation of the ground-water flow direction and gradient. The monitoring well locations are depicted on the Site Sketch, Figure 2. W.W. Irvin, Inc. of Merced served as the environmental consultant while Woodward Drilling Company of Rio Vista drilled and completed the wells to a total depths of 30 feet. Collected soil samples were placed in an ice chest chilled to 4°C and dispatched to Sherwood Labs, Inc. of Hilmar using appropriate chain-of-custody procedures. Each sample collected to a depth of 20 feet was analyzed for the presence of Total Petroleum Hydrocarbons as gasoline (TPH-g) by modified EPA Method 801515030, Total Recoverable Petroleum Hydrocarbons as diesel (TRPH-d), and the volatile aromatics benzene, toluene, ethylbenzene, and total xylenes (BTEX) by EPA Method 8020. Detectable, primarily fractional BTEX analytes were detected only in soil samples collected from MW-6. The highest TPH-g result was 39 mg/Kg, revealed .:- in the sample collected from MW-6 at 15 feet bsg. TRPH-d results were nondetectable except for 8 mg/Kg of weathered diesel revealed in the sample collected from MW-5 at 5 feet. _ Ground-water samples collected from MW-4, MW-5, and MW-6 were received at Sherwood Labs on June 21, 1994. The analytical results revealed wholly nondetectable concentrations of TRPH-d analytes and nondetectable results for TPH-g and BTEX analytes in samples collected from wells MW-4 and MW-5. The results of the analysis of the sample collected from MW-6 indicated that the ground water underlying that vicinity was significantly impacted with TPH-g and BTEX analytes well above the Maximum Contamination Levels (MCLs) set by the California Department of Health Services (CDHS). Problem Assessment and Completions of MW-7 and MW-8 On July 3, 1995, W.W. Irwin, Inc. directed the drilling, logging, and sampling of HydropunchesTm HP-7, HP-8, HP-9, and HP-10. HP-7 and HP-8 were completed as monitoring wells MW-7 and MW-8 after ground-water samples collected for "rushed" analyses of gasoline and diesel analytes at Sherwood Labs in Hilmar were found nondetectable. The new monitoring wells were drilled, sampled, and completed in order to determine the horizontal and vertical E extent of soil and ground-water contamination. The new monitoring well locations are initially depicted on the Site Plan, Figure 2. W.W. Irvin, Inc. Project No. 33016.07 December 1995 3