Laserfiche WebLink
treatment or disposal facility. On-site soil treatment is usually by aeration <br /> or bioremediation. Advantages of this method is that it is the fastest and <br /> most effective method in treating contaminated soil, and removes <br /> contaminated soil which could act as a source for groundwater <br /> contamination. The disadvantages of this method are that (a) it would <br /> require the closure of the on-site business for an extended period of time, <br /> (b) it may require the removal of soil surrounding the UST and fuel <br /> dispensing system (possibly endangering the integrity of these systems), <br /> (c) it may cause significant nuisance odors, and possibly unhealthy <br /> hydrocarbon concentrations in the air in the site vicinity, (d) it does n o t <br /> directly remediate contaminated groundwater beneath the site, and (e) is <br /> very expensive at properties where USTs are still in service. <br /> Given the disadvantages of this method, this method is not seen as a <br /> viable remediation alternative for the site at this time. <br /> 2.2 Air Snargt and Soil VapQr Extraction <br /> Soil vapor extraction remediation entails the removal of hydrocarbons <br /> from the ground in-situ. These vapors are removed -through vapor <br /> extraction wells placed in contaminated areas. The vapors are removed <br /> through wells by a vacuum source and abated by one of several methods <br /> such as an internal combustion (IQ engine, a thermal oxidizer or carbon <br /> absorption. <br /> Vapor extraction technology is often used in conjunction with air <br /> sparging. Air sparging is the injection of air beneath the water table, <br /> generally at the bottom of an unconfined aquifer. Air bubbles rise <br /> through the saturated zone volatilizing hydrocarbons and forcing the <br /> hydrocarbons into the vadose (unsaturated) zone. The hydrocarbons are <br /> then subsequently removed from the vadose zone using soil vapor <br /> extraction. The addition of air through air sparging may also stimulate <br /> bioremediation. <br /> However, the vapor extraction feasibility test at the site showed that it <br /> would not be possible to achieve sufficient flow for vapor extraction to be <br /> a feasible remediation alternative. The clayey content of the soil beneath <br /> the site will not permit effective remediation at the site using this <br /> remediation alternative. Although the aquifer was able to receive air <br /> during the air sparging test, conventional air sparging remediation <br /> requires the removal of hydrocarbons from the vadose zone with soil <br /> vapor extraction once they have volatilized from the saturated zone. <br /> 574 West Grant Line Road CAF — January 2002 <br /> -17- <br />