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S E C 0 R 4 Mr Mike Infurna April 7, 2003 Page 3 y diameter hollow-stem augers to a depth of approximately 25 feet bgs Upon completion of drilling, a 2-inch diameter groundwater monitoring well will be installed The well will be screened from approximately 5 feet bgs to 25 feet bgs depending on the depth at which groundwater is encountered • Sample Selection and Analysis Sod samples will be collected at 5-foot Intervals, and will be sent under chain-of-custody procedures to a California State-certified laboratory Selected sod samples will be analyzed for TPHg, BTEX compounds, and MtBE by EPA Method 8260B single run At a minimum, three sod samples in each boring will be analyzed for the above constituents ; • Monitoring Well Development and Sampling After Installation, the monitoring well will be developed by rigorously surging the well over the length of the screen Interval and by purging approximately 10 casing volumes of water After well development, groundwater samples tiA will be collected and sent under standard chain-of-custody procedures to a California State- certified laboratory The groundwater samples will be analyzed for TPHg, BTEX, and fuel oxygenates (MtBE, EtBE, DIPE, TAME, TBA, EDB, 1,2-DCA, and ethanol) by EPA Method 82606 • Well Surveying Upon completion of well construction, the well will be surveyed by a licensed surveyor to a local benchmark relative to mean sea level In order to comply with the State Geotracker requirements, the latitude and longitude location of the well will also be surveyed Groundwater gradient will be Interpreted utilizing wellhead elevations and depth- to-water measurements • Report A report will be prepared after completion of necessary fieldwork The report will Include the following items groundwater gradient map, groundwater dissolved petroleum hydrocarbon concentration maps, soil boring logs, soil analytical results, chain-of-custody documentation, and conclusions Field and laboratory procedures and a quality assurance plan are included in Attachment A. g Schedule s SECOR is prepared to initiate fieldwork within four to six weeks following approval of this work plan, Issuance of a monitoring well permit by the San Joaquin County Environmental Health Department, and Issuance of a encroachment permit by the City of Lathrop SECOR will prepare a report including soil boring logs, soil analytical results, and summarizing the investigation within four to eight weeks following completion of the assessment 11ConocoPhdhps\Tosoo Marketing112051Work Plans\WPLAN Off-Site Assmnt doe