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r • <br /> Geological Audit Services, Inc. <br /> �- 1803 W March Lane, Suite A•Stockton, CA 95207• (209) 956-0264• FAX (209) 956-0700 <br /> w� <br /> • 10 March 1992 <br /> (GeoAudit CV 43C4-1. 1) <br /> ] = _��'z <br /> 73 <br /> Ms. Margaret Lagorio, REHS LH , <br /> Public Health Services - San Joaquin County MAR 1 3 9992 <br /> Environmental Health Division LWIRONMEE I-AL HEALTr) <br /> P.O. Box 2009 PERM 11 <br /> / � �`, USStockton, California 95201 <br /> Subject: Progress Report No. 2 for Vacuum Extraction Proaect at <br /> Genova Bakery - <br /> 749 North Sierra Nevada Stockton, California <br /> Dear Ms. Lagorio <br /> In accordance with the request of our client, the Estate of Angelo <br /> Rolleri, we have prepared this report to update you on the progress <br /> of the mitigation pro]ect up to 15 February 1992 at the referenced <br /> address. <br /> The vacuum extraction at the referenced addressed has been in <br /> operation since 15 August 1991. In the last 4 months, the vacuum <br /> extraction system has been operating practically 24-hours/day, <br /> . extracting an average of 60 cubic feet per minute (cfm) of vapor <br /> from the well. As of 14 February 1992 , the vacuum extraction unit <br /> is in operation for approximately 3 , 500 hours. <br /> Organic vapor (OV) concentrations are measured on weekly basis at <br /> the inlet, pre-catalyzer outlet and post-catalyzer with a photo- <br /> ionization detector (PID: Thermo Environmental 580A, 10 . 0 eV lamp <br /> energy, calibrated to isobutylene) . The recovered OV concentrations <br /> from the well prior to combustion (y-axis) are plotted versus time <br /> (x-axis) on Figure 1. During organic vapor readings, fluctuations <br /> were noted in the concentration of hydrocarbon vapors. For <br /> recording purposes, however, the highest levels were consistently <br /> recorded. <br /> A destruction rate of greater than 90% has been achieved throughout <br /> the entire operational period. Organic vapor records demonstrated <br /> an initial increase followed by an overall decline. Currently, the <br /> average OV readings in the last 5 monitoring periods is 1, 000 ppm <br /> as zsobutylene, representing approximately 45 % of the (average) <br /> highest readings of 2 , 200 ppm. These data indicate an on-going <br /> venting progress. <br /> Upon further decrease of OV to approximately 50 ppm as isobutylene, <br /> or 500 ppm as hexane, additional vapor extraction from MW--1 is <br /> planned. The contamination at this well is assumed to be restricted <br /> to the perforated casing and this well design allows an effective <br />. venting from this well. Hydrocarbon laden vapor from this well is <br /> expected to increase the concentration of OV. <br /> Environmental Seances • Hydrogeology•Geotechnical Seances <br />