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_�' • i October 17, 2000 Page 3 • Monitoring Well Installation. Four deep groundwater monitoring wells (MW-5 through MW-8) will be installed at the general locations shown on Figure 2 The proposed wells will be installed to a total depth of approximately 80 feet bgs and will be constructed with 10-foot screen intervals Anticipated depth to water is approximately 30 feet bgs Because petroleum hydrocarbon concentrations at the water table are relatively low to non-detectable, conductor casing is not proposed for the deeper wells All work will be done in accordance with stipulations of permits obtained from the SJCPHS/EHD • Soil Selection and Analysis. Soil samples will be collected every five vertical feet in the borings Selected soil samples will be submitted to a California State- certified laboratory and analyzed for the presence of total petroleum hydrocarbons quantified as gasoline (TPH-g), benzene, toluene, ethylbenzene, and total xylenes (BTEX), and methyl tertiary-butyl ether (MtBE) by EPA Methods 8015 Modified and 8020 The highest MtBE detection from each boring will be confirmed by EPA Method 8260 No additional oxygenate analysis of soil samples will be conducted based upon non-detection of DIPS, ETBE, TAME and TBA an over-excavation soil samples at depths of 11 and 13 feet bgs Sampling and analytical methods are presented an Attachment B • Groundwater Analysis. Groundwater samples will be submitted to a California State-certified laboratory for analysis Groundwater samples will be analyzed for the presence of TPH-g, BTEX, and for five oxygenates (MtBE, DIVE, ETBE, TAME and TBA), 1,2-DCA, and EDB using EPA Methods 8015 Modified, 8020 and 8260, respectively • Well Surveying. Upon completion of well construction, the wells will be surveyed by a licensed surveyor for location and elevation relative to mean sea level Groundwater gradient will be interpreted utilizing wellhead elevations and depths to water • Report. A report will be prepared after completion of fieldwork The report will include the following 1) boring logs, 2) boring and well location map, 3) groundwater contour map, 4) soil/groundwater analytical results, 5) chain-of- custody hain-ofcustody documentation, and 6) summary of findings SCHEDULE IT is prepared to initiate fieldwork following approval of this work plan and the issuance of necessary permits by the SJCPHS/EHD and receipt of the encroachment permit from the City of Stockton A report documenting the findings of the investigation is anticipated to be submitted approximately 8 to 10 weeks after commencement of fieldwork NIranefpllProjects\Projects1911101111A101021911011 wp doc