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URS • Ms Lori Duncan Page 4 San Joaquin County Environmental Health Department February 4, 2003 Altamont, California, where it was disposed of as non-hazardous waste Stockpiled soil laboratory analytical reports are included as Attachment D Subsurface Conditions Soil samples collected during the drilling of MW-11M/D indicate that sandy silt and sandy clay were present from the ground surface to 42 feet bgs A fine to medium-grained silty sand was encountered from 42 to 56 feet bgs A dark blue-gray silty clay was observed in the bottom of the boring from 56 to 56 5 feet bgs The boring log for this well is included in Attachment B A generalized geologic cross-section extending from the former ARCO Station to MW-11M/D is presented as Figure 3 Groundwater was encountered at approximately 20 feet bgs in the boring and stabilized at approximately 20 feet bgs in the monitoring wells During the fourth quarter 2002 groundwater monitoring event, depth to groundwater at the site ranged from 13 35 feet bgs to 14 64 feet bgs Based on monitoring data collected on December 5, 2002, groundwater flow was to the east-northeast at 0 011 ft/ft A groundwater elevation • contour map is presented on Figure 4 Groundwater Monitoring Well, Development Sampling, and Surveying On December 3, 2002 Blaine Tech Services of San Jose, California developed the groundwater monitoring wells by rigorously surging over the length of the screen Interval and by purging 32 casing volumes of water from MW-11M and 82 casing volumes of water from MW-11D On December 5, 2002 Blaine Tech Services collected groundwater samples from the newly installed groundwater monitoring wells Groundwater samples were analyzed for TPHg and BTEX by EPA Method 8015/8021 and fuel oxygenates (including MtBE) and halogenated volatile organic compounds by EPA Method 8260B Attachment E presents detailed groundwater sampling and analysis procedures Results of groundwater samples from all existing monitoring wells will be presented in the Fourth Quarter 2002 Groundwater Monitoring Report On January 10, 2003 top of casing elevations and lateral positions for wells MW-11M/D were surveyed to mean sea level by Morrow Surveying of West Sacramento, California In addition, wells MW-1 and MW-5 were resurveyed on this date due to alterations made in the well casings Survey data are included as Attachment F Groundwater Analytical Data Analytical data from groundwater samples collected from the newly installed monitoring wells MW-11M/D • reported MtBE at 55 ppb In MW-11M and at 2 2 ppb in MW-11D Total xylenes were detected in MW-11D at 1 1 ppb No other gasoline related compounds were reported in the newly installed wells K 1J5 BP ARC01044931Regulatory Coaespondence14493 WIR doc