Laserfiche WebLink
and the device strips the vapors from groundwater. Thus,treatment occurs underground <br /> and no groundwater is pumped to the surface. The stripped vapors are piped to the <br /> surface for treatment,usually with GAC unless vapor concentrations are exceptionally <br /> high. The stripped groundwater is allowed to flow back down the well casing and annulus <br /> into the aquifer. A more detailed description of this method can be found at the following <br /> website: www.Artinwell.com. <br /> ATTRIBUTES OF THE TWO METHODS <br /> One of the advantages of evaluating these two contrasting methods is that they have quite <br /> different attributes. This simplifies the comparison of their cost-effectiveness. The <br /> advantages and disadvantages of both methods are listed in Table 1. <br /> One of the biggest advantages of groundwater extraction is that it is a well-established <br /> method with a proven track record of success.It has been utilized at thousands of sites <br /> across the U. S., and all regulatory agencies are familiar with it. However, specific <br /> characteristics of each site determine the degree of success and the cost-effectiveness of <br /> the method. The factors that limit its applicability are discussed in the next section. <br /> Another advantage of pump and treat systems is that they are relatively simple to install <br /> and maintain. They do not require highly intricate or unique equipment,equipment <br /> failures are relatively rare and easy to correct, and specialized skills or highly technical <br /> training are not required. This makes them quite flexible and adaptable, so that the system <br /> can be modified to meet changing conditions as the remedial operation proceeds. <br /> From a technical standpoint,a big advantage of pump and treat is that the withdrawal of <br /> groundwater causes a lowering of the water table in the vicinity of the pumping well. <br /> This creates a depression in the water table,and groundwater is thus induced to flow <br /> toward the pumping well under the force of gravity. As a result,contaminants are carried <br /> toward the extraction well and their tendency to spread outward from the contaminant <br /> source is reduced. Known as"plume control",this helps to prevent contaminant <br /> migration and reduce the time and expense needed to restore the site. <br /> One other advantage of the pump and treat method is worth noting.Although not as <br /> effective as larger diameter wells,the existing 2-inch diameter monitoring wells(VM-1 <br /> through VM4)could also be used for groundwater extraction. This would increase the <br /> cumulative pumping rate and likely speed up the remediation process to some extent. <br /> These wells are too small to be used in the in-well air stripping method. <br /> In-well air stripping has none of the attributes discussed above. It is a very new <br /> technology that is unfamiliar to most consultants and regulators, and it has a much shorter <br /> track record of success. It requires highly specialized technology that is apparently <br /> available from only one established vendor,and the design, installation, and monitoring <br /> of the system must be done by specialists trained in this method. Further,because it <br /> involves no groundwater extraction, its potential for plume control is limited,although in <br /> 2 <br />