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arr f <br /> 2. FIELD INVESTIGATIONS <br /> 2.1 PRIOR INVES'T'IGATIONS <br /> Following a product line leak, three monitoring wells were <br /> installed in October 1986 by Groundwater Technology, Inc. water <br /> samples were collected at the time of installation and in March <br /> 1987. The res-alts are summarized in fable 1. <br /> 2.2 SOIL VAPOR CCNTAMINANT ASSESSMENT <br /> pn_19 N(,vember 1-987-,-. EA-collected and analyzed soil vapor samples <br /> from twelve soil locations and vapor headspace samples from three <br /> existing monitoring wells (Figure 5) . <br /> 2.2.1 SVCA Sarn lin <br /> Before each sample was rollerted, a vacuum pump Wis used to purge <br /> � . previously collected vapor from the probe to ensure that the <br /> sample was :lot contaminated. The vacuum pressure reading on the <br /> purging apparatus was recorded. This vacuum pressure is related <br /> to the soil's gas permeability and is useful in date. interpreta- <br /> tion. The samples were collected through a septum with a micro- <br /> syringe and injected into a Fhotovac 10S50 gas chromatograph for <br /> analysis. <br /> The Photovac 10550 is a portable, programmable, integrating has <br /> chro[natograp.i with a photoionizaticn detector (PID) . The PID is <br /> a nondestructive flow-through detector that uses high energy <br /> ultraviolet radiation as its ionization source. Vapor sample;; <br /> are injected into the gas chromatograph, separated on an <br /> analytical column, and sensed by the detector. The high energy <br /> radiation ionizes compounds, generating an energy increase in the <br /> detector :which appears as an electrical Signa]., measured in <br /> t. <br /> Volts; this is integrated across time by the instrument to give a <br /> value for the peak in Volt-seconds (V-sec) . The instrument is <br /> CHV18:81J 6 <br />