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OUAMERLY OM" WATER lrlON R111NG MICW <br /> 6131 PaGflc Avenue Stockton Calffomla <br /> Weekly and twice monthly hand-bailing of floating liquid hydrocarbons, from monitoring <br /> well MW-3, has been conducted from February 1991, to the present Measured <br /> thicknesses of liquid hydrocarbons in MW-3 are summarized in Table 1 Liquids removed <br /> from the three wells are temporarily stored on site in 55-gallon drums The liquids are <br /> disposed of through Crosby & Overton, Inc , of Oakland, California, on a quarterly bass <br /> A 45-day vapor extraction pilot test is scheduled for the site, beginning <br /> November 27, 1991, and continuing through mid-January 1992 During the test, <br /> hydrocarbon vapors will be drawn from the subsurface, via vapor extraction wells VE-1 <br /> and VE-2, and the horizontal slotted piping run installed beneath the former product lines, <br /> and burned using a portable internal combustion engine The purpose of the pilot test <br /> will be to determine efficiency parameters (i e , hydrocarbon vapor yield, combustion <br /> efficiency, etc ) that may be expected during possible subsequent vapor extraction at the <br />' site <br /> Sufficient data does not exist at the present time to estimate "zero lines" for petroleum <br /> hydrocarbons in groundwater beneath the site Data obtained during subsurface <br /> investigations, VST removal, quarterly groundwater monitoring, and pilot testing <br /> performed at the site will be used to form recommendations for further investigation <br /> and/or remediation alternatives <br /> 4.0 GROUNDWATER MONITORING <br /> I4.1 Groundwater <br /> Depth-to-liquid measurements, collected since the three wells were installed, including the <br /> most recent measurements on October 8, 1991, are summarized in Table 1 The <br /> measurements were made according to the Aegis standard operating procedures (SOP) <br /> included in Appendix A All depth-to-liquid measurements were recorded to the nearest <br /> 0 01 foot and were referenced to wellhead (top of casing) elevations Wellhead elevations <br /> were surveyed by a licensed surveyor and referenced to a temporary benchmark with an <br /> assumed elevation of 100 feet above mean sea level <br /> Depth-to-liquid measurements collected on October 8, 1991, indicatedroundwat r a <br /> g e t <br /> 57 18 feet below surface in MW-1, 56 83 feet in MW-2, and 58 93 feet in MW-3 Floating <br /> hydrocarbons were observed in MW-3 at a 1 f]R_fnnt thirknecc TF,o rlezn�su+h� t <br /> .+.+ �e w uvw., <br /> groundwater in MW-3 was corrected for hydrocarbon suppression according to the <br /> formula noted in Table 1 <br /> I <br /> 90-020E RPT -2- <br />