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06/27/2003 09:47 2098325y" WRIGHT ENVIRONMENfrAL PAGE 05 <br /> Page 4 <br /> Trust ofMmy Gardella. <br /> June 20,,2003 <br /> S9i15 . <br /> An excavation;may be considered in localized areas of suspected residual relatively shall('1w soil <br /> conta ts.w However soil vapor extraction (SVE) could cast effectively target the exciwation <br /> backfill and the 15-30 foot zone fi nmediately below the former tank pit with the bea*rst soil <br /> co;ntarnkution. The SVE well would be placed in the vickdty of MW-2 and within the €bmcr <br /> tank pit. Well and SVE equ.ipmeat design requires a. review of site stratigmaphy, prepU:lora.of <br /> geologic dross sections and an understanding of the relative permeability's of the soil straUl at the <br /> target depths. Lead dentes required in obtanwS permits to const ud end operate from Owe San. <br /> Joaquin County Air Pollution Control District (SJAPCD) will detamrrime the tiny required to <br /> deploy the SVE*,stemxn. <br /> wud Water <br /> The emphasis for source area interim cleanup would be in the aquifer at fine 35-50 foot zone(that <br /> is the area of current monitoring well slotted interval)where a lie residual count pr'=nce <br /> is located (Wel)! MW-2 currently shows the mst elevated dissolved concentration). ftivious <br /> discussions suggested the use of ozone bubblers to initially address this largest contmninant <br /> problem Tbo su=ssfnl use of ozone spanr&g regress effectively delivering the ozone to the <br /> dissolved phase hydrocarbons. The feasibility and system design depend on am uaderst aIng of <br /> the site stratigraphy, the hydrogeology, the potential for cba weling and the extern# of dissolved <br /> phage contawhv6on. Dissolved phase concentrations and mass affect the dosage an t: time <br /> required fur cleanup. Where the stratigraphy is suitable, ozone bubblers deliver ozoznc io the <br /> eft area and have been a cost effective approach to degrading contamim s rektively <br /> quic*- <br /> A detailed evaluation of the geologic cross smtions, ground water con entiratiins ar:d other site <br /> data may m d"e that other technologies such, as oxygen releasing compounds (ORCs) an n2Ore <br /> suitable for this site. Should these other techoologi be huliaded Wr*t will revieyv the <br /> atter native technology with the PHS EHD before mYmakiung a decision. Hovmver, Wright propipses a <br /> wmmptual approach using ozone technology and possibly us4 one of the existixxtr monitoring <br /> wells to deliver the ozone into the coatamimnated aquifer. <br /> Pap 4 of 6 <br />