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+.. Work Plan for Refined Plume Definition and Management of Floating product-7500 W 11th A, Tracy, C4. Page 71 <br /> 9.4.3.6 System Operation and Maintenance <br /> The skimmer pump floating product extraction system is designed to operate automatically <br /> and, as noted above, has the ability to accommodate changing elevations of the groundwater <br /> table up to a maximum of 2 $. However, experience has shown that, in both the long and <br /> short term, such systems require frequent adjustment and maintenance for them to operate <br /> efficiently. The operation and vertical location of the skimmer pump system in the extraction <br /> wells will initially be checked at least weekly, and, as necessary, air regulator settings will be <br /> adjusted. It is hoped that after a period of approximately two months, it will be possible to <br /> �. reduce the frequency of routine inspection and manual system adjustment to once per month. <br /> During each weekly or monthly inspection, a qualified technician will inspect all of the <br /> equipment, check it for proper operation, check the lubricating oil level in the air compressor, <br /> ,. and, as necessary, clean or replace air filters. The technician will record the thickness of <br /> floating product in each extraction well and the total volume of liquid that has accumulated <br /> in the product holding tank. <br /> It is anticipated that, as time passes, during which the system has been in continuation, the <br /> skimmer pump system will reduce the thickness of floating product in the wells to a zero or <br /> .. insignificant thickness. However, for the reasons discussed in Sections 9.2 and 9.3, SJC is <br /> concerned that such an apparent indication that all floating product has been removed from <br /> the subsurface in the general area around Monitoring Well MW-7 may not reflect the actual <br /> *- conditions at even short distances from the extraction wells. To test for this false positive <br /> result, when no floating product is detected in the monitoring wells over a period of two <br /> months, the system will be completely shut down for periods between one and three months <br /> ^� before the thickness of floating product is again measured in each of the extraction wells. If <br /> floating product reappears, the system will be restarted and a new cycle of LNAPL extraction <br /> will be initiated. <br /> 9.4.3.7 System Shut Down <br /> When floating product no longer appears in the extraction wells for an extended period of <br /> time, samples of groundwater will be recovered from them on the same schedule as will <br /> prevail at that time for the general groundwater-quality monitoring program in place at the <br /> 7500 West Eleventh Street Site. When a sufficient record of groundwater quality in the <br /> extraction wells has been established (which will not be less than that obtained from four <br /> quarterly rounds of groundwater-quality monitoring), that data will be evaluated and, if <br /> appropriate, the extraction wells will be closed under the permit and oversight of the <br /> SJCEHD in the manner described in Section 10.0. At that time, subject to the approval of the <br /> SJCEHD, all of the surface equipment that supports the skimmer pump system will be <br /> removed from the site, the equipment enclosure fencing will be demolished, the dedicated <br /> power pole will be removed and the local transmission lines will be restored to original <br /> condition. <br /> sic <br />