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, I ,Ili <br />xm,n,.m,s IV <br />^s gym.-a.m .m..�ylpz,ix.-r: rer°r�« <br />, <br />� �n +irlmnli <br />I <br />••�' �F �ilmiiilltil <br />i I <br />lllii <br />I <br />Page 4 <br />I <br />i I ii <br />; I <br />Ms Margaret Lagono <br />dl <br />' <br />March 23, 1995y <br />' <br />, s HOP, W� li{I' JI' <br />,n <br />The extracted groundwater would be treated through a granular activated carbon <br />(GAC) adsorption system and discharged Organic compounds have an affinity for <br />adsorption to the GAC Reinjection of water into the aquifer or discharge into the s <br />"ki";'" ; ;s <br />tsanitary sewer would require permits It has been our experience with the City of <br />Stockton that they do not readily allow discharge of even treated water into their <br />I I, <br />sewers <br />' <br />fl <br />Groundwater extraction and treatment is an effective technology for plume <br />control, but it is neither an efficient or effective method of remediation This <br />I j,l <br />' <br />system does not effectively remediate dissolved phase gasoline compounds <br />adsorbed in the soil matrix that may be present at the site Even though some of <br />the contaminant is typically removed from groundwater through advection, <br />I i <br />pockets of adsorbed gasoline that remain the soil/groundwater system can serve as <br />" <br />a long-term source that slowly diffuses Additionally, inorganic treatment may be <br />' required to limit potential hydroxide or carbonate scale that may form on piping or <br />„ <br />equipment Inorganic treatment could be a costly investment requiring intensive <br />and frequent operation and maintenance <br />The estimated costs to implement a full scale groundwater extraction and <br />treatment system is approximately $400,000 00 This cost includes the installation <br />IIIr1 <br />1 of extraction wells and equipment, and operation and maintenance of this system <br />for a period of about 7 years Therefore, extraction and treatment is not considered <br />i <br />a viable alternative to clean up impacted groundwater to regulatory required levels <br />,U „Ili <br />I <br />In -Situ Bioremediation <br />1.5 114' <br />I, fill <br />In-situ bioremediation involves the introduction of oxygen (as hydrogen peroxide) <br />and nutrients to the groundwater to stimulate indigenous organisms and degrade <br />' target contaminants Naturally occurring organisms that thrive on gasoline <br />constituents have been previously identified in the site groundwater <br />_ <br />Oxygen and nutrients would be introduced in infection wells or in an infiltration <br />gallery located upgradient to the area of gasoline impact The concentrations and <br />nl, a igui AI <br />dosage rates of these nutrients would be calculated based on pilot studies and <br />IIII II II i <br />bench tests that would have to be performed Nutrients would be fed to the <br />infection wells utilizing a chemical metering system that is controlled to shut down <br />IIII <br />should a malfunction occur An infiltration gallery would be backfilled with pea <br />gravel to allow percolation of the nutrients to the subsurface The gallery would be <br />it <br />designed based on infiltration tests conducted at the facility <br />P I <br />I Ih <br />' <br />I I N i <br />