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operation costs can increase dramatically as hydrocarbon concentrations in soil decrease <br /> Therefore,we recommend a "phased" approach After an initial six month period, or when <br /> the efficiency of the unit has significantly declined, an evaluation of the IC-based unit will <br /> be made The evaluation will be made using PID data, soil samples, vapor samples and <br /> supplemental fuel costs After the data has been analyzed, a decision will be made to either <br /> continue with the IC-engine or install a different unit on the property, such as catalytic <br /> ' oxidizer, thermal oxidizer or carbon canister <br /> However, it must be noted that these alternate units tend not to operate as efficiently when <br /> ' high concentrations of hydrocarbons are being extracted Therefore, initially, we do <br /> recommend an IC-based engine because of the high hydrocarbon concentration in the soil <br /> ' at the site <br /> 4.8 Confirmation Borings <br /> ' When the initial six-month peiiod has been completed, or efficiency of the unit has declined, <br /> one or two soil boi Ings will be di filled within the projected contanimation plume to <br /> ' determine the concentration (if any) of hydrocarbon remaining in the impacted soil If <br /> significant impacted soil remains, we recommend drilling one or two soil borings each 6- <br /> months to evaluate the remediation progress The locations of future soil borings will be <br /> submitted in Quarterly Repoi is <br /> The borings will be dulled with a truck-mounted, hollow stern auger drill rig The borings <br /> will be drilled into groundwater (approximately 25 to 30 feet) Soil samples will be collected <br /> at five-foot intervals using a split-spoon sampler The sampler will be loaded N%ith three <br /> clean, 2 by 6-inch brass sleeves Samples will be screened ill the field using a PID <br /> S p P <br /> Selected samples will be trains oited under chain-of-custody to a state-ceitified laboratory <br /> for analysis The samples will be analyzed for TPH as gasoline and BTE&X ill accordance <br /> ' with approved EPA methods These analyses NNill be used for eventual site-closure <br /> deter inination <br /> ' 4.9 System Maintenance <br /> The SVE unit will be maintained weekly Routine maintenance should represent the only <br /> periods of"down time" for the unit About tierce monthly (assuming 24-hour operation) the <br /> unit will be strut down for routine maintenance procedures such as lubrication, oil changing <br /> ' and system adjustments <br /> 1 <br /> Qeob�+I AIJ'l S-1 Inc <br /> ' CHAPIN FU13 9566_94 U 105&02 2 <br />