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Mr. John Trinkle 2 - 3 October 2008 <br /> chlorobenzene, 1,4-dichlorobenzene, and diuron at-concentrations that exceed water quality <br /> �.• objectives, as shown in Table 2. The constituents 1,3-dichlorobenzene, 2,4-D;and d icamba <br /> were'also detected, but at concentrations sign>ficantiy below the applicable water quality <br /> objectives. <br /> Table 2. Detected Grab Groundwater Sample Results and Wafter Quality Objectives <br /> Plumber of Detected Water Quality Basis for Water <br /> Constituent Detections Concentration Range Objective .Quality Objective <br /> CaAforhla Dept. Of <br /> Pesttaide Regulation <br /> 1,3-dichlorobenzene 1 11 ug1L 600 ug/L Notification Level for <br /> driiikiig water <br /> 1,24cNorokienzene 2 32—40 ug/L 24 ug/L Odor Threshold <br /> California Primary <br /> 1.4-dichlorobenzene 2 6.6—22 ug/L 5 ug/L Maximum Contaminarit <br /> Level . <br /> USEPA; Office of <br /> diuron Pesticide Programs 1 30 ug/L 2 ug/L Cancer Potency.Factor <br /> as a drinking water level <br /> 2,4-D 3 2,7--23 U. 70 u9/L Califomia Public Health <br /> Goal for.Drinking Water <br /> USEPA, Office of <br /> Dicamba 1 0.7 ug/L 4,000 uglL Pesticide Programs <br /> Drinking Water Health <br /> Advisory-non-cancer <br /> In:our I May 2008 letter concurring With the Site investigation Work Plan,.Regional Water <br /> Board staff requested analyses for carbamatelurea.compounds, including diuron. The <br /> analytical laboratory only-analyzed fordiuron, not other carbamatelurea compounds. When <br /> Trinkle &. Boys obtains groundwater sm m <br /> samples froonitoring wells, these.samples should be <br /> analyzed for the carbamatelurea shite sof compounds. <br /> One of the;.scenarios we discussed in our 7 Febntary 2008 meeting included the scenario that <br /> we find today: the eastern portion is.-suitable for.development,.'but the operations area is not. <br /> As we discussed in that meeting, the Remedial.Action:Plan for this site could include a remedy <br /> for groundwater in the operations area and no action necessary.on the eastern portion of the <br /> site. <br /> Next Steps <br /> Trinkle and.Boys should install three monitoring wells in the.operations areas to confirm the <br /> findingwof the.grab groundwater investigation. On occasion, water samples obtained from <br /> groundwater monitoring wells show lower do:nc nfttions than.those obtained from grab <br /> groundwater sanip16s. <br /> ( As Regional Water Board staff requested in its 1 .July 2008 letter,TrtnW-&Boys needs to <br /> either locate the motMitoring wells that--were identitW in 1991, or demonstrate.that there are no <br />