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GEOMATRIX Ms. Donna Heran, REHS, Director San Joaquin County Public Health Services Environmental Health Division October 31, 2000 Page 2 shallow groundwater sample in the former UST area for MtBE analysis. The PHS/EHD approved the work plan in a letter dated August 22, 2000, and requested that additional soil samples be collected from 20 feet bgs to the groundwater table. These groundwater and soil samples were submitted to a laboratory for chemical analysis. The results of the field investigation are discussed in the following sections. SHALLOW GROUNDWATER AND SOIL SAMPLING Field activities were performed on August 21, 2000. Field activities were coordinated by a Geomatrix project geologist under the direction of a Geomatrix senior engineer registered in the State of California. Field activities were performed in accordance with the health and safety plan prepared for the site. A permit for the soil boring was obtained from the PHSIEHD prior to the initiation of the field activities, and a PHSIEHD representative provided the required site inspections during the field activities. Underground Service Alert was contacted prior to field activities to provide utility clearance. A soil boring was advanced to groundwater at a location just west and outside of the former UST excavation area (Figure 2). Drilling services were provided by Spectrum Exploration, Inc., of Stockton, California. The soil boring was advanced to a depth 65.5 feet bgs using the hollow-stem auger method. Soil samples were collected in approximately 5-foot depth intervals from the ground surface to 60 feet bgs. Groundwater was encountered at 64 feet bgs, and soil samples were not collected past the groundwater table. Soil samples were collected for lithologic logging and field screening using a photoionization device. Lithologic logging was performed using visual/manual procedures in accordance with the Unified Soil Classification System described in the American Society for Testing and Materials Method D 2488-90. The lithologic log is included in Attachment A. Soil samples collected from 20, 30, 40, 50, and 60 feet bgs were submitted to the laboratory for chemical analysis. Soil samples retained for chemical analysis were removed from the sampler, sealed with Teflon sheeting and plastic caps, labeled, and placed into an ice-cooled chest for delivery to the laboratory using chain-of-custody procedures. After reaching the groundwater table, a HydroPunch sampler was driven approximately 3 feet into the undisturbed water-bearing zone at a depth of approximately 68 feet bgs. The HydroPunch sampler was retracted approximately 1.5 feet to expose the screen for collecting a groundwater sample. The groundwater sample was collected using a disposable bailer and decanted into laboratory-supplied containers. The groundwater sample was sealed, labeled, and placed immediately into an ice-cooled chest for delivery to the laboratory using chain-of- custody procedures. I:TROJECTN6508.0001document16508-06.doc