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David Wang, P.E. , Chief <br /> Page 8 <br /> March 6, 1991 <br /> Recommendation: Data should be presented to support the <br /> statement. <br /> 5. Page 4-23 , Plume 1 <br /> The report states "Concentrations measured in Well 418C <br /> had increased for a time (in late 1988) but now appear to <br /> be declining again. " <br /> Recommendations: The report should specify what is meant <br /> by "now" . The report should also clarify if the decline <br /> can be attributed to operation of extraction Well C-3 <br /> which is mentioned on Pages 4-23 and 7-10. <br /> 6. Page 4-24 , Plume 2 <br /> The report states "VOC concentrations in Well 422A have <br /> not varied significantly for several years. <br /> Concentrations found in Well 422B have been somewhat <br /> erratic, with the latest data showing a decreasing trend. <br /> Concentrations measured in Well Cluster 441 and Well 408A <br /> have been consistently at or below detection limit <br /> (BDL) . 11 <br /> Recommendation: Data should be presented to support <br /> these statements. Reference to Figure 6. 1-26, page 6-56, <br /> indicates increasing, relatively low concentrations of <br /> TCE in both 441A and 441B. The other graph on Page 6-56 <br /> appears to be mislabeled. <br /> B. Chapter 5, Hydrogeological Assessment <br /> 7 . On Page 5-8 the report states "Prior to December 1990, <br /> water levels were obtained by hand. . . . " Apparently water <br /> levels have been obtained and recorded via an automated <br /> system since that time. <br /> Recommendations: This system should result in data <br /> suitable for determining monthly ground water flow <br /> directions. Monthly water level elevations should be <br /> contoured for each water bearing zone. The resulting <br /> plots should be submitted quarterly for review. <br />