ARCHIVED REPORTS_XR0005707 CASE 2

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URS Mr Mike Infurna Page 3 San Joaquin County Environmental Health Department ARCO 6020 September 29, 2003 was 35 feet bgs, MW-12 was drilled to a depth of 37 5 feet, and MW-13D was drilled to 70 feet bgs First groundwater was encountered at approximately 25 feet bgs in each boring Soil samples were collected at 5-foot intervals with a modified California split-spoon sampler The soils were logged by a URS geologist according to the Unified Soil Classification System No hydrocarbon staining, odor,or photoionization detector(PID)readings were noted for any of the soil samples Soil boring logs are included as Attachment C Selected soil samples were retained for laboratory analysis from each soil boring The soil samples were sealed in 2-inch-diameter brass sleeves with Teflon squares and plastic end caps The samples were then labeled and placed on ice in a cooler, pending delivery to Sequoia Analytical Laboratories in Petaluma, California The soil samples were analyzed for TPHg,benzene,toluene,ethylbenzene,and xylenes(BTEX), and for fuel oxygenates and additives including MtBE,tert-butyl alcohol(TBA),di-isopropyl ether(DIPE), ethyl tert-butyl ether(ETBE),TAME, 1,2-dichloroethane(1,2-DCA),ethylene dibromide(EDB),and ethanol, by EPA Method 8260B All downhole sampling equipment was decontaminated between samples by washing in a non-phosphate detergent solution Rinsate water was contained in DOT-approved, 55-gallon drums and stored on site pending sampling results and subsequent disposal The monitoring wells were constructed using 2-inch-internal diameter (ID), schedule 40, flush-threaded polyvinyl chloride(PVC)well casing Twenty feet of 020-inch machine-slotted well screen was set from 15 to 35 feet bgs m MW-11 and MW-12 Five feet of 0 020-inch machine-slotted well screen was set from 65 to 70 feet bgs in well MW-13D A Monterey No 3 silica sand filter pack was installed from the bottom of the boring to 2 feet above the well screen A 2-foot bentonite seal was placed above the sand pack Bentonite- cement grout was used to sea]the remaining annular space to the surface The wells were completed with 8- inch flush-mounted well boxes,and locking,water-tight well caps Well construction details are shown on the boring log in Attachment C Field and laboratory procedures are presented in Attachment D Groundwater Monitoring Well Development, Sampling, and Surveying. On July 24, 2003, Blaine Tech Services of San Jose, California,developed the newly installed groundwater monitoring wells by rigorously surging over the length of the screen interval and by purging 10 casing volumes of water from each well Well development field sheets are included as Attachment E On July 28,2003,Blaine Tech Services collected groundwater samples from the site groundwater monitoring wells, including the three new wells Groundwater samples were analyzed for TPHg, BTEX, and fuel oxygenates by EPA Method 8260B Attachment E presents detailed groundwater sampling field sheets K IWprocessU5 BP ARCO\0602012003 Assessment16020 Assessment&SCM 2003 doc