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From April 12 to April 15, 2004 an ATC geologist supervised the advancement of MW10a to approximately 75 feet bgs, MW10b to approximately 95 feet bgs and MW6c and MW10c to ' approximately 110 feet bgs. Gregg Drilling, California License C57 485165, advanced the borings utilizing a limited access hollow stem auger drill rig. A site plan with soil boring ' r locations is shown on Figure 2. l Soil samples were collected from MW6c, MW7c, MW8, MW9b, MW9c, MW10b, and MW10c ' at five-foot intervals in stainless steel sampling tubes. The cored samples and drill cuttings were characterized for soil type, moisture content, and visual evidence of petroleum hydrocarbons. A photo-ionization detector (PID) was used as a field-screening device for the detection of ' petroleum hydrocarbon vapors in drill cuttings and cored samples. A field geologist logged drill cuttings and soil samples utilizing the Unified Soil Classification System. Descriptions of soil types encountered and sample collection intervals are included on the well logs contained in ' Appendix A. Soil� pP borings MW6c, MW7c, MW8, MW9c, MW9b, MW9c, MW 10a, MW10b, and MW10c were completed as groundwater monitoring wells. ' 222 Soil Sample Analyses Selected soil samples were kept on ice and delivered under chain-of-custody documentation to State-certified Argon Laboratories Inc. (Environmental Laboratory Accreditation Program Cert. No. 2359) in Ceres, California for chemical analysis. Selected soil samples were analyzed by Argon Laboratories for total petroleum hydrocarbons as gasoline (TPHg) and total petroleum hydrocarbon as diesel TPHd b EPA Method { ) Y 80158; benzene, toluene, ethylbenzene, and xylenes (BTEX) by EPA Method 8021B; and methyl tert butyl ether (MTBE), t-butanol (TBA), tertiary amyl methyl ether (TAME), ethyl tertiary butyl ether (ETBE), di-isopropyl ether (DIPE), 1,2-dichloroethane (1,2-DCA), and ethyl dibromide (EDB) by EPA Method 8260B. The analytical results for soil samples are summarized in Table 1. Laboratory data sheets and chain- of-custody documentation are included in Appendix B. ' 2.3Ground _ water Monitoring Well Construction Soil borings MW6c, MW7c, MW8, MW9a, MW9b, MW9c, MW10a, MW10b, and MW10c were completed as groundwater monitoring wells to assess potential hydrocarbon impact to groundwater beneath the site, to further assess the extent of potential hydrocarbon impact to the J southeast of the site, and to provide measurement points for the determination of groundwater flow direction and hydraulic gradient. The wells were surveyed to NAD83 and NGVD29 benchmarks for position and elevation. Survey results are summarized in Table 2 and referenced in Table 3. The surveyors report is contained in Appendix C. Each well was constructed with 2-inch PVC casing to depths ranging from 75 feet bgs in the A zone wells, 95 feet bgs in the B zone wells, and to 110 feet bgs in the C zone wells. The screened interval of each A zone screen was positioned from approximately 5 feet above to 15 feet below the encountered water table to allow for seasonal water level fluctuations. The screen SAFnviromenta1126823-JamarVeportslsum.doc 3