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In GeoAudit ' s experience, the cost of bioremediation compares <br /> favorably to the estimated costs for vapor extraction. Very little <br /> maintenance is required; therefore operating costs are minimal . <br /> From economic concerns alone, bioremediation is often the most <br /> attractive method, though each site must be considered on a site•- <br /> specific basis. <br /> 5.2 Groundwater Remediation <br /> GeoAudit has considered two alternative methods of groundwater <br /> remediation at the site. Pumping and treatment of groundwater was <br /> proposed in the PAR submitted by PES Environmental and was <br /> subsequently endorsed by GeoAudit in the January 1992 FRP. <br /> Bioremediation provides an alternative to pumping. The following <br />' sections briefly discuss the theory, feasibility, cost and <br /> estimated time of completion for each method. <br /> 5.2 . 1 Pump and Treat <br /> IThere are several variations of this technique, but all involve <br /> extraction of contaminated groundwater from the aquifer for <br /> M treatment above ground. To extract the contaminated water a <br /> pneumatic pump system is usually employed. The pump system is <br /> controlled automatically to maintain capture characteristics in the <br /> aquifer and to assure process requirements are maintained. <br /> A typical method of treatment of extracted water is carbon <br /> filtration, but many other methods are available. The treated water <br /> is usually discharged to a storm drain or sanitary sewer system. A <br /> waste discharge permit is usually required. <br /> The cost of any pump and treat method can be high, especially when <br /> a productive aquifer is involved. Equipment and set-up costs can be <br /> in the neighborhood of $50, 000 to $150, 000 or more. Tests, <br /> monitoring, extraction well installation and maintenance can push <br /> the price of remediation to over $1, 000, 000. <br /> The key objection to employing pump and treat technology is that <br /> the method is usually not very effective, and remedial objectives <br /> are rarely met. <br /> I5.2 . 2 Bioremediation <br /> The same biological processes come into play for in-situ <br /> bioremediation of groundwater as for soil treatment. Existing <br /> I monitoring wells can be used to inoculate bacteria . Additional <br /> nutrients may not be needed. Additionally, the bacteria have the <br /> ability to migrate in the groundwater with the contamination plume. <br /> At a site in Ukiah, California (silty sand soil type) both <br /> groundwater and soil contamination was present. Since the soil was <br /> 9 <br />