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San Joaquin/ARCO Meeting Minutes, March 30, 1993 Working To Restore Nature <br /> that during her site visit she noted subjective evidence (odor) of hydrocarbons <br /> in samples collected from the borings. She also questioned the data gathered <br /> from samples collected from the new tank cavity (excavation samples and <br /> boring samples), again stating that she noted subjective evidence of <br /> hydrocarbons in the samples. ARCO informed SJ that these areas fall within <br /> the vapor-extraction system's effective radius of influence and that verification <br /> would be performed in these areas by confirmation sampling following <br /> remediation. <br /> o SJ stated that based on other investigations conducted in the area, the ground- <br /> water elevation and flow direction beneath the site is approximately 70 ft bsg <br /> and likely trends to the southwest. <br /> o Linda stated that she observed brass sleeves containing soil sitting out, not <br /> being immediately placed in an iced cooler. She also indicated that the <br /> onsite geologist capped a sample sleeve with head space remaining in the <br /> sample. RESNA asked SJ to inform RESNA immediately if this is witnessed <br /> again; it is against RESNA's field procedures and staff geologist are well <br /> aware of the effects that headspace has on hydrocarbon concentrations in soil <br /> samples. <br /> ARCO SS No. 6100, South Patterson Pass, Tracy <br /> o Margaret Lagorio referenced the recently submitted status report which <br /> included the results of the last investigation. RESNA informed SJ that three <br /> additional vapor-extraction wells are to be installed across Patterson Pass on <br /> private property. <br /> o Margaret stated that the depth to ground water beneath the site is a primary <br /> concern. She has no records of first ground water in this region; the only <br /> information on the ground water is from the drillers log from the water supply <br /> well which states ground water was encountered at 100 ft bsg, and a boring <br /> log from RESNA which noted soil being slightly damp at 106 ft bsg. She said <br /> that she has previously asked that the depth to ground water be measured in <br /> the onsite water supply well but has not received the data yet. RESNA <br /> informed SJ that based on the construction details presented in the drillers <br /> log, the screened portion of the water supply well begins at approximately 420 <br /> ft bsg, and that the elevation of the water in the well casing will be that of the <br /> potentiometric surface in the screened portion of the aquifer (approx. 420 to <br /> 480 ft bsg). SJ believes that this information will provide some indication of <br /> 6 <br />