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1 04 March 1996 AGE-NC Project No 95-0144 Page 7 of 18 ' 54 ANALYTICAL RESULTS OF WATER SAMPLES TPH-g was detected in MW-1 at a concentration of 170µg11 (parts per billion, ppb) BTE&X were also detected in the sample from MW-1 No other petroleum hydrocarbons were detected in any of the samples collected on 8 February 1996 Analytical results are summarized on Tables 4 and 5 The laboratory report (MAI, ID 461427 - 61435) and chain-of-custody form are included in Appendix D 6.0. REMEDrATiON OF HYDROCARBON-IMPACTED SOIL , 61 SOIL V APOR EXTRAC,FION Soil vapor extraction (SVE) is a well-accepted method of treatment that has been used successfidly at numerous sites with an excellent rate of success The method i& most effective on volatile hydrocarbons in permeable soil ' 611 PRINCIPLES ' For most SVE systems, a vacuum blower is used to volatilize hydrocarbons and draw the vapors into extraction wells installed and screened within the contaminant plume The vapors are drawn from the ' wells and treated in one of several possible treatment units (carbon canisters, internal combustion . engines, thermal oxidizers, and catalytic oxidizers) Air injection wells may be installed outside the contaminant plume to increase air flow,to the extraction unit iIn an internal-combustion system, vapors are drawn into a carburetor system of the engine and mixed , with air before undergoing combustion Exhaust gasses (oxides of carbon and hydrogen) are further broken down in a catalytic converter before being emitted to the atmosphere These systems require supplemental fuel, such as propane or natural gas, which can become increasingly expensive as vapor r concentrations decrease below levels normally required for combustion Typically, internal combustion engines work eflectrvely where in-situ hydrocarbon concentrations approach the 40,000 pp my required for peak performance of the engine As concentrations decrease below 20,000 ppmv, supplemental fuel requirements become burdensome Another disadvantage of these systems is the ' noise generated by the engine, however, this can be mitigated by placing the unit inside an enclosure, such as a building In a carbon-canister system, hydrocarbon vapors are 'routed through; activated carbon filters, where adsorptro,n of the hydrocarbons takes place, removing them from the vapor stream These systems work best for low concentrations of hydrocarbons, but become expensive when high concentrations of hydrocarbon vapors necessitate frequent canister replacement and disposal of spent carbon l