ARCHIVED REPORTS_XR0007882 - Laserfiche WebLink

Home Browse Search

NSA.. Working To Restore Nature Report on Vapor Extraction Test January 29, 1993 Coca-Cola Former Distribution Facility, Stockton, California 5400601 sample bags and labeled with the sample number, lob number, date, time, location, and sampler's name The samples were then placed on ice for transport to a State Certified laboratory A Chain of Custody Record accompanied all samples delivered to the laboratory LABORATORY METHODS Ten air samples were submitted with Chain of Custody Record to Sequoia Analytical, a State Certified laboratory in Redwood City, California Air samples were analyzed for TPHg and for the petroleum hydrocarbon constituents benzene, toluene, ethylbenzene, and total xylenes using EPA Methods 5030/8015/8020 Samples were analyzed on a 72 hour ' turnaround basis LABORATORY RESULTS Results of laboratory analyses of vapor samples are reported in Table 1 The Chain of Custody Record and laboratory analytical reports are included in Appendix C TPHg vapor concentrations ranged from a low of 33 milligrams per cubic meter (mg/m3) in the air sample from VEW-5 to a high of 19,000 mg/m3 in the sample from VEW-4 The average TPHg vapor concentration from all eight wells was 5,287 mg/m3 These are relatively low concentrations compared to other similar sites, and most likely this low concentration is due to the wide screen intervals (up to 60 feet) in the vapor wells and to moderate TPHg concentrations in the soil Benzene vapor concentrations ranged from 18 mg/m3 in VEW-5 ito 1,200 mg/m3 in VEW-3 After abatement by the IC engine, TPHg concentration was 320 mg/m3, and benzene was 46 mg/m3 This is an IC engine destruction efficiency of 97 5% for TPHg, and 84% for benzene The wells that contained the highest TPHg concentrations were VEW-3 which is located in ' the former tank pit, and VEW-4 which is about 20 feet north of the former tank pit In general, the wells with the lowest vapor concentrations are located farthest from the former tank pit After 120 minutes of operation, TPHg concentration decreased about 15% in ' VEW-3 However benzene increased, so that these fluctuations may be due in part to unsteady state conditions and laboratory methods standard deviation Comparing average vapor phase benzene concentration as a percent of TPHg average concentration for all wells, benzene generally comprised about 5% of the TPHg vapor This is a normal ratio of benzene to gasoline in soil vapors i r10