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URS Ms Lori Duncan Page 4 San Joaquin County Environmental Health Department March 25, 2004 On December 5, 2003, Woodward drilled SO-2 and installed deep single-completion monitoring well MW-12D approximately 5 feet from boring SO-1 MW-12D was constructed using 2-inch-inside- diameter (ID), schedule 40, flush-threaded polyvinyl chloride (PVC) well casing Five feet of 0 020- inch machine-slotted well screen were set in the depth interval from 75 5 to 80 5 feet bgs A Monterey No 3 silica sand filter pack was installed from the bottom of the boring to 2 5 feet above the well screen A 3-foot bentonite transition seal was placed above the sand pack Neat cement was used to seal the remaining annular space to the surface The surface was completed with an 8-inch flush- mounted well box, and a locking, water-tight well cap was placed on the well Well construction details are shown on the boring log in Attachment C Soil cuttings and wastewater generated during the drilling activities were placed in labeled 55-gallon US Department of Transportation (DOT)-approved steel drums and stored at ARCO Station No 2130 at 7906 North El Dorado Street in Stockton, pending characterization and disposal Subsurface Conditions The boring logs for boring SO-1 and well MW-12D (SO-2) are included in Attachment C A generalized geologic cross-section extending from the former ARCO station to MW-11M/D is presented as Figure 3 Boring SO-1 was logged from cuttings to a depth of approximately 55 feet bgs for the purpose of confirming the adjacent lithologic log for boring B-1 In SO-1, one soil sample was collected at 55 feet bgs for lithologic characterization, and then SO-1 was logged continuously from approximately 60 feet bgs to total depth The boring for MW-12D (SO-2) was not logged due to its proximity to SO-1 The subsurface at the site is composed of interbedded layers of sand, silt, and clay First water was encountered at approximately 20 feet bgs in borings SO-1 and SO-2 (MW-12D) The groundwater level stabilized at approximately 28 feet bgs in monitoring well MW-12D upon completion of drilling Monitoring Well Development and Sampling On December 15, 2003, Blaine Tech Services (BTS) of San Jose, California, developed the new deep groundwater monitoring well by rigorously surging over the length of the screen interval and by purging 10 casing volumes of water from MW-12D Development data sheets are included in Attachment D On December 23, 2003, BTS collected a groundwater sample from MW-12D as part of the fourth quarter 2003 groundwater monitoring program Surveying of welt MW-12D will be conducted after the proposed downgradient dual-completion monitoring well set is installed on the State of California property at 31 East Channel Street Installation is scheduled to occur in the second quarter of 2004 K 1WprocessV5 BP ARCO\044931Well Insta1114493 well installation reportO4 doe