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MW-5B, MW-9B and MW-10B, but decreased in well MW-3B between the March and June <br /> 2008 sampling events. Historically, the highest value of carbon tetrachloride recorded at the site <br /> was in May 2005 when a concentration of 1,700 µg/L was detected in MW-913. <br /> Chloroform was detected in all wells sampled in the June 2008 sampling events. Chloroform <br /> concentrations increased in wells MW-413, MW-5B, MW-913 and MW-10B, while decreasing in <br /> wells MW-313 and MW-4B between the March and June 2008. Historically, the highest value of <br /> chloroform found in groundwater at the site was 220 gg/L on November 2005 and March 2006 at <br /> MW-10B. <br /> There were also low levels (less than 15 gg/L) of 1,2-dichloroethane, 1,2-dichloropropane, <br /> tetrachloroethene, 1,2,3-trichloropropane, methylene chloride, benzene, toluene, and xylenes <br /> detected in groundwater samples this quarter. <br /> Additional monitoring requirements set forth in the new MRP require testing for various <br /> inorganic parameters. These inorganic parameters are: chloride and dissolved iron (See Tables 5 <br /> and 6 for inorganic monitoring results). <br /> Chloride was detected in the June samples in all three wells monitored with concentrations <br /> ranging from 94 mg/l (MW-1OB) to 120 mg/I (MW-I IB). During the June monitoring event six <br /> wells were analyzed for nitrate (as NO3) and concentrations ranged between 22 mg/1 and 46 <br /> mg/l,respectively. Dissolved iron was not detected in any of the wells sampled during this event. <br /> 1.1 Overview of Environmental Issues <br /> The French Camp Grain Elevator is an active grain storage and transfer facility located <br /> approximately five miles south of Stockton, California in San Joaquin County. The site <br /> encompasses roughly nine acres and includes improvements such as grain elevators, grain <br /> storage bins, seed storage, storage buildings, truck scales, and an office (see Figure 1). A septic <br /> system serves the bathrooms in the office area. There were two water supply wells (PW-1 and <br /> PW-2) at the facility; however, both were properly abandoned and closed per San Joaquin <br /> County regulations in April 2005. <br /> Prior to 1980, liquid fumigant containing carbon tetrachloride was stored and used at the site. <br /> The fumigant was reportedly stored in five-gallon containers and was used only sparingly at the <br /> site. Evidence of groundwater impact was discovered during an environmental site assessment <br /> conducted in 1999 in support of a pending property transaction (QST Environmental, 1999). In <br /> addition to a records search, this assessment involved two soil borings (SB-1 and SB-2), a <br /> borehole water sample, and a groundwater sample from a former on-site water well,PW-1. SB-1 <br /> was drilled at the reported storage location of carbon tetrachloride-bearing fumigant. Carbon <br /> tetrachloride and chloroform were not detected in any of the soil samples, although these <br /> compounds were detected in a borehole water sample and from the former on-site water well. <br /> MW-513, MW-913 and MW-1013, but decreased in well MW-313 between the March and June <br /> 2008 sampling events. Historically, the highest value of carbon tetrachloride recorded at the site <br /> was in May 2005 when a concentration of 1,700 µg/L was detected in MW-9B. <br /> 2 <br />