Laserfiche WebLink
1 <br /> PRAFT <br /> 39 System Maintenance <br /> The VES unit will be maintained weekly. Routine maintenance should represent the only <br /> periods of"down time" for the unit. About twice monthly (assuming 24-hour operation) the <br /> unit will be shut down for routine maintenance procedures such as lubrication, oil changing <br /> and system adjustments. <br /> 4.0 IN-SITU AIR SPARGING <br /> 4.1 Principles <br /> In-situ airsparging (IAS) utilizes air injection beneath the water table to volatilize dissolved <br /> hydrocarbons in groundwater and force hydrocarbon vapors into the vadose zone, where <br /> they can be withdrawn by vapor extraction systems. IAS is commonly conducted concurrently <br /> with vapor extraction. <br /> IAS induces the transfer of hydrocarbons from the water to air by creating a strong <br /> concentration gradient from groundwater to air. The vapor extraction wells are surrounded <br /> by specifically designed air injection wells that are screened only within the saturated zone. <br /> ' Blowers connected to the injection wells force air under pressure into the saturated zone <br /> producing air bubbles that strip dissolved contaminants from the groundwater and rise to <br /> the air-water interface.Upon reaching the unsaturated zone, the vaporized hydrocarbons are <br /> drawn into the extraction wells. <br /> Injection wells are screened within the saturated zone, and normally have short screened <br /> F , intervals (less than 5 feet). Since most of the air escapes from the upper part of the interval <br />'t where head pressure is the least, little is gained by increasing the length of the screen <br /> interval. <br /> The radius of influence of a sparging well is dependent on site geology, the depth of the <br /> sparging well, and the depth of the screened interval. Relatively large radii can be attained <br /> in homogeneous sandy aquifers, like that at the Art & Artists site. <br /> According to Hinchee (1994), "the two mechanisms by which IAS works are volatilization <br /> ' and biodegredation. Volatilization evaporates and then extracts the contaminant. <br /> Biodegradation typically is stimulated by the introduction of oxygen." More information on <br /> ' air sparging is contained in the PAR. <br /> 4.2 Proposed Sparging System <br /> The proposed air sparging system will be composed of a blower and two sparging wells.The <br /> low-pressure blower will provide between 3 and 10 psi of air to each sparging well. The <br /> proposed blower will be an EG&G Rotron EN 404 Explosion-Proof Regenerative Blower <br /> ,son FRP/7.%4,47 <br />