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1 <br /> Total petroleum hydrocarbons as gasoline (TPHg), benzene, toluene, ethylbenzene and total xylenes <br /> (BTEX) are the primary residual constituents in the soil and groundwater beneath the Site. <br /> ' Historical soil data show that the distribution of petroleum hydrocarbon soil impacts is primarily <br /> located between 30 and 50 feet, depths typically below the recent historical groundwater surface. <br /> Soil Vapor Extraction (SVE) pilot testing performed by Geocon confirmed the absence of vadose <br /> ' zone impacts at the Site. <br /> The lateral distribution of the dissolved petroleum hydrocarbons in groundwater is limited to within <br /> ' no greater than 175 feet downgradient of the former onsite USTs as supported by the absence of <br /> TPHg in monitoring wells MW-5 and MW-6 over the past 8 years. The greatest dissolved <br /> concentrations remain onsite in the area of the former USTs in the vicinity of wells MW-1 and <br /> ' GWX-1 with order of magnitude lower concentrations in cross-gradient wells MW-2 and MW-3. <br /> Vertically, the distribution of dissolved petroleum hydrocarbons is limited to the shallow and <br /> intermediate zone (the same sand lens). Additional information including cumulative historical <br /> groundwater analytical data tables, well construction details, groundwater gradient maps and <br /> ' geologic cross-sections and conceptual site models showing the approximate lateral and vertical <br /> distribution of the dissolved petroleum hydrocarbons in the groundwater beneath the Site are <br /> included in the attached CAP. <br /> ' H: Project Proposal <br /> The proposed groundwater remediation system will consist of an H2O Engineering ozone-sparge <br /> ' system(ozone system) Model No. OSU20-52 [3.8 cubic feet per minute (cfm), 110 volts, 30 amps], <br /> Schedule 80 poly-vinyl chloride (PVC) conveyance piping, Teflon'M tubing and 17 ozone-sparge <br /> wells. <br /> ' Seventeen ozone-sparge wells are proposed to be installed in the vicinity of the former USTs. Nine <br /> sparge points will be set at approximately 40 feet, and eight sparge points will be set at <br /> ' approximately 50 feet. The 40- and 50-foot-deep wells will be at alternate locations to optimize the <br /> vertical and lateral influence of the ozone. Geocon assumed a 10-foot-radius of ozone injection <br /> influence based on the Site lithology and AS pilot testing results. <br /> ' The ozone system cabinet will be mounted on a concrete pad and enclosed within the existing <br /> fenced former treatment compound.A lean-to or canopy with a sloped roof will be installed over the <br /> cabinet to provide weather protection. Each sparge point will be connected to the ozone system <br /> ' manifold by 3/8-inch-diameter Teflon"' tubing. The tubing will be routed to each injection point <br /> through an outer 1-inch-diameter Schedule 80 PVC conduit. <br /> ' The ozone system will be initially programmed to cycle ozone injection between the 17 sparge <br /> points approximately four times per day for 20 minutes per point. Each injection cycle will be <br /> followed by a 30-minute rest period. Following start-up, the number of cycles and cycle length for <br /> ' any individual injection point may be modified depending on the overall system performance. <br /> I: List of Interested Parties <br /> Owner: California State Controller's Office <br /> Unclaimed Property Division <br /> 10600 White Rock Road <br /> Rancho Cordova, CA 95670 <br /> ' Attn.: Mr. Dale Mauch <br /> (916)464-6088 <br /> 1 <br /> 1 <br />