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0 <br /> C,eologual rechmcs lnc Page 8 <br /> Feasibility Study&Investigation Work Plan <br /> Cardoza(Main St) <br /> Project No 662 2 <br /> April 19,2004 <br /> ' Groundwater Analyses <br /> Groundwater samples from the treatment system influent will be analyzed by a California <br /> State Certified Laboratory for <br /> • Benzene, toluene, ethylbenzene and xylene (BTEX)by EPA method 602 <br /> • Gasoline range petroleum hydrocarbons (TPH-Gas) by EPA method 5030/8015(m) <br /> t • Methyl tertiary butyl ether(MTBE)by EPA method 8260 <br /> The detection limits for these compounds are listed below A Chain of Custody will be <br /> ' completed for all samples collected and tracked to ensure sample integrity <br /> Detection Limits BTEX NIT.BE TPH-(j <br /> ' Water µg <br /> 5.0 DATA ANALYSIS <br /> The data analysis will allow for the determination of the proper construction f <br /> y p r • a vapor <br /> extraction system and groundwater treatment system for full remediation (if necessary) <br /> ' 5.1 Soil Vapor Extraction <br /> The vacuum response to vapor extraction will be measured using a Magnahelic differential <br /> pressure gauges by first attaching an airtight cap to the well top The cap has an orifice, <br /> which accepts the vacuum hose from the gauge The gauges will be checked and the values <br /> recorded on a floating schedule to be determined by vacuum development and stabilization <br /> ' during the process of the extraction test Initially, measurement readings will be taken <br /> every 30 to 60 minutes As vacuum stabilizes, readings will be taken every 4 to 8 hours If <br /> changes occur in site conditions, such as rain events, readings will be increased as needed to <br /> obtain high quality data <br /> GTI shall calculate the radius of influence by measuring vacuum pressure from the <br /> extraction well and rate of vacuum pressure drawdown in the existing wells MW-I through <br /> ' MW-3, and new wells MW-5 and MW-6 The pressure necessary for demonstrating <br /> vacuum influence is generally regarded as at least 0 1 inches of water ("How to Evaluate <br /> Alternative Cleanup Technologies for Underground Storage Tank Sates", USEPA, May, <br /> 1995) <br /> Volumetric Air Flow <br /> Two methods will be used to measure the volumetric airflow <br /> ' • Solomat 500e multifunctional instrument with a Pitot tube will be used to measure air <br /> speed inside a straight section of pipe The volumetric airflow is then calculated from <br /> the velocity and pipe cross sectional area <br /> ' • The second is by instrumentation provided by the remedial contractor and will be <br /> mounted on their dual phase equipment <br /> 5.2 Groundwater Extraction <br /> The data will be analyzed by constructing time-drawdown graphs The variables used in the <br /> common aquifer testing formula can be obtained from the graphs The exact equations that <br /> will be used and hence the corresponding graphs are not known at this time because it is <br />