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Atlantic Richfield Company(ARCO) S Harding Way,Stockton CA Jana 15,2002 ARCO Station #4932 16 E Har , depth of approximately 40 feet below ground surface (bgs) Based on previous assessment activities at the site, groundwater is anticipated to be encountered at approximately 30 feet bgs The groundwater wells will be screened from approximately 20-40 feet bgs • Deep Monitoring Well Installation. Three 2-inch diameter groundwater monitoring wells will be installed at the locations shown on Figure 2 The wells will be installed using a 8-inch diameter hollow-stem auger ng to a depth of approximately 77 feet below ground surface (bgs) and will be continuously cored from 50 to 77 feet Based on previous assessment activities at the site, impacted groundwater appears to extend to 77 feet bgs The groundwater wells will be screened from approximately 72 to 77 feet bgs, ideally in the silt/sand interval identified during the previous assessment Generalized cross-sections are included as Figures 3 and 4 • Permitting and Encroachment The applicable permits for well installation will be obtained from the San Joaquin County PHS/EHD prior to drilling Additionally, prior to installing the proposed offsite wells, appropriate encroachment permits from the City of Stockton will be secured • Soil Selection and Analysis. Soil samples will be collected at 5-foot intervals and will be sent under chain-of-custody procedures to a California iState-certified laboratory Selected soil samples will be analyzed for TPHg and TPHd using modified EPA Method 8015, and benzene, toluene, ethylbenzene, xylenes, and MtBE using EPA Method 8020 A minimum of three samples from each of the borings (including the samples collected at the capillary fringe and the deepest sample) will be sent to the lab for the above analysis Additionally,the samples collected from the capillary fringe will be the analyzed for fuel oxygenates MtBE, DIPE,TAME, EtBE,TBA, 1,2 DCA, and EDB by EPA Method 8250 • Monitoring Well Development and Sampling. After installation, the monitoring wells 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 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 and TPHd using modified EPA Method 8015, benzene, toluene, ethyl-benzene, xylenes, using EPA Method 8020, and fuel oxygenates TAME, DIPE,TBA, MtBE, ELBE, 1,2 DCA, and EDB by EPA Method 8260 • Well Surveying. Upon completion of well construction, the wells will be surveyed by a licensed surveyor to mean sea level Groundwater gradient will be interpreted utilizing wellhead elevations and depths to water REMEDIAL WELL INSTALLATION WKPLAN4932—1-11-02 doc