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own <br /> FUGRO WEST, INC. JUL Q .5 1994 <br /> 1050 Melody Lane,Suite 160 <br /> ENVIRONMENTAL HEALTH Roseville,California 95678 <br /> PERMITISERVICES Tel: (916)782-2110 <br /> FAX: (916)786-7830 <br /> July 1, 1994 <br /> Ms. Mary Meays <br /> San Joaquin County Public Health Services 04& <br /> Environmental Health Division <br /> 445 N. San Joaquin Street <br /> P.O. Box 388 <br /> Stockton, California 95201-0388 <br /> Subject: Former Shell Service Station (WIC No. 204-7524-i5*09) <br /> 141 N. EI Dorado Ave. <br /> Stockton, California <br /> Dear Ms. Meays: <br /> Fugro West, Inc. (Fugro) is providing this correspondence in response to the letter, dated <br /> June 10, 1994, from San Joaquin County Public Health Services, Environmental Health <br /> Division (PHS/EHD), regarding the subject site. <br /> During the week of June 13, 1994, Fugro installed a groundwater oxygenation (GO) <br /> system at the site, as approved by PHS/EHD. Air diffusers were installed in wells MW-1, <br /> MW-2, MW-3, MW-4, RW-1, and RW-2. The GO system is designed to operate at <br /> considerably lower air flows than "air sparging". Air sparging systems use specially <br /> designed wells for injecting relatively large amounts of air (-10 cubic feet per minute per <br /> well) into soils below the water table at relatively high pressures. The GO system will <br /> diffuse small volumes of air (-0.15 cubic feet per minute per well) directly into existing <br /> monitoring wells. The small volumes of air diffused into the wells is intended to increase <br /> dissolved oxygen (DO) concentrations without causing mounding or migration of <br /> groundwater. <br /> During the field work, the vapor extraction system was upgraded by connecting wells <br /> MWA and MW-3. Additionally, a new groundwater discharge line was installed from the <br /> groundwater treatment system to the existing sewer lateral at the property line. <br /> The PHS/EHD letter expressed concern that"there will not be a down gradient unaffected <br /> well to monitor the migration of the plume. Additionally, there are no vapor extraction <br /> wells in the vicinity of these wells to capture migrating vapors." Per our telephone <br /> conversation on June 1, 1994, Fugro agreed with PHS/EHD to install the air diffusers in <br /> all the proposed wells. Fugro plans to operate the diffusers in wells MW-1, MW-2, and <br /> MW-3. Wells MW-4, RW-1, and RW-2 will not be used for groundwater oxygenation until <br /> the performance of the system has been evaluated. <br /> 93473011.MLT U.S. operating companies in California, Louisiana, Missouri, and Texas <br /> International operating companies in Australia, Belgium, Brunei, Canada, Germany, Hong Kong, Indonesia, Japan, <br /> Malaysia, The Netherlands, Saudi Arabia, Singapore, United Kingdom, and United Arab Emirates. <br />