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1 e r <br /> 1 <br /> 14 November 1995 <br /> AGE-NC Project No 95-0121 , <br />' Page 7 of 20, <br /> 1 <br /> I <br /> 1 a I r I <br />' to 0 91 inches in VW-2, approximately 30 feet away, during the same time span No measurable <br /> vacuum was observed at MW-4, approximately 85 feet from EW-1 <br />' The vacuum apphed at EW-1 and the induced vacuums at VW-1 and-VW-2 were graphed verses t ' <br /> = distance on a semi-loganthmic scale(see Figure 4) However, a clear correlation of induced vacuum <br /> verses distance was not observed Vacuum data is included in Table 4 <br /> 55 ANALYTICAL RESULTS OF VAPOR SAMPLES <br /> Hydrocarbon concentrations in the well effluent stream were measured at regular intervals PID field <br /> measurements ranged from 342 ppm to 1,023-ppm Laboratory analysis of the four vapor samples <br />' collected indicated TPH concentrations in the extracted vapors ranging from 6,600 µg/1 (4 10) to <br /> k 24,000 µg/1 (2 00) Converting these values to parts per million volume (ppmv), concentrations <br />' ranged from 1,848 ppmv to 6,720 ppmv The analytical results are summarized to Table 5 The <br /> laboratory report and chain-of-custody form are included in Appendix E Equations for conversion <br /> ofµg/1 to ppmv are included to Appendix F <br /> I <br /> 6.0. REMEDIATION OF HYDROCARBON-IMPACTED SOIL <br /> 61 SOIL VAPOR EXTRACTION <br />' Soil vapor extraction (SVE) is a well-accepted method of treatment that has been used successfully <br /> at numerous sites,with an excellent rate of success The method is most effective on volatile <br /> hydrocarbons in permeable soil ' <br /> I I <br /> K <br /> i611 PRINCIPLES ; <br /> For most SVE systems, a vacuum blower is used to volatilize hydrocarbons and draw the vapors into <br /> extraction wells installed and screened withiri the contaminant plume The vapors,are drawn from the <br /> I wells and treated in one of several possible treatment units (carbon canisters, internal combustion <br /> engines;thermal oxidizers, and catalytic oxidizers) Air infection wells may be installed outside the <br /> contaminant'plume to increase air flow to the extraction unit , <br /> I , I <br /> In an internal-combustion system,vapors are drawn into a carburetor system of the engine and mixed <br /> with air before undergoing combustion Exhaust gasses(oxidesof carbon'and hydrogen) are further <br /> broken down in a catalytic converter before being emitted to the atmosphere These,systems require <br /> . supplemental fuel, such as propane or natural gas;winch can become increasingly expensive as vapor <br /> ' x 1 <br /> s <br /> 1 r <br /> 4 <br /> I <br /> 1 1 I I <br />