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5 y� OHS Greiner Woodward Clyde Ms. Carol Oz Page 2 San Joaquin County -Public Health Services Environmental Health Division July 18, 2000 To assess the lateral and vertical extent of soil contamination and the presence or absence of groundwater contamination, URSGWC installed four soil borings as shown on Figure 1. The borings were drilled with 5.5- inch outside diameter(OD)hollow stem augers to a total depth of approximately 58 feet bgs. Groundwater was encountered in the borings at approximately 56 feet bgs. Copies of the soil boring logs are included as Attachment I. Soil samples were collected using a California-modified split spoon sampler at 5-foot intervals beginning at 5 feet bgs. A portion of each soil sample was retained for field screening analysis. Based on field screening observations, two soil samples from each boring were submitted to Curtis & Tompkins, Limited (Curtis & Tompkins),a California State Certified Laboratory,for analysis of TPH-G by EPA method 8015 modified and BTEX,MTBE,TBA,DIPE,ETB,and TAME by EPA method 8260. The previous analytical results reporting MTBE at 25 feet bgs was rationale for selecting the sample from each boring at 25 feet bgs. A groundwater grab sample was collected from each boring by lowering a dedicated bailer slowly through the open augers to the water and allowing it to fill while causing a minimum of agitation to the water column. Groundwater samples were carefully transferred to precleaned, laboratory-provided sample containers. Once collected,the sample bottles were labeled with the time and date of collection,project and sample identification codes, the sampler's initials, the type of analysis to be performed, and the preservative used, if any. The groundwater samples were submitted for analysis of TPH-G by EPA Method 8015 modified,and BTEX,MTBE, TBA,DIPE,ETB, and TAME by EPA Method 8260. Soil cuttings generated during the drilling activities were placed in labeled 55-gallon Department of Transportation(DOT)-approved steel drums pending disposal. The equipment used in the drilling of the borings was thoroughly cleaned using a high temperature, high pressure steam cleaner before commencing work and between each boring. The waste water generated during the equipment cleaning was stored in labeled 55-gallon DOT-approved steel drums pending disposal. Each of the soil borings was abandoned by tremieing a cement grout mixture from the base of the boring to the surface. The grout was monitored for settling and more was added as necessary. Analytical Results A total of eight soil samples,two from each soil boring,were selected for analysis. Analytical results for each of the eight samples were non-detect for TPH-G,BTEX,TBA,DIPE,ETB,TAME,and MTBE. The analytical results for the soil samples collected from the soil borings are summarized in Table 1. A copy of the analytical reports is included as Attachment II. The analytical results for the groundwater samples were non-detect for TPH-G, BTEX, TBA, DIPE, ETB, TAME, and MTBE. The results are summarized in Table 2 and a copy of the analytical report is included as Attachment II. I:114214103_Stockton11071500.wpd