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Preliminary Endangerment Assessment Page 9 <br /> Former Haley's Flying Service <br /> GPE Project 474.2 <br /> analyzed, total number of detections, range of detection limits, and range of concentrations <br /> detected <br /> Not all chemicals detected at a site warrant a quantitative evaluation. In many cases, <br /> chemicals are detected at so low a concentration as to pose a negligible risk and may be <br /> eliminated from further consideration. On the other hand, it can not be assumed that <br /> chemicals that were tested for, but not detected, are altogether absent. For the purposes of <br /> this PEA, it is assumed that a chemical detected in any sample is present in all samples at a <br /> concentration of '/2 the SQL. This is considered an acceptable approach to evaluating <br /> chemicals that may be present at less than detectable concentrations (U.S. EPA, 1989). In <br /> this case, one sample (B-6) was diluted by a factor of 10 to 1 prior to the analytical testing. <br /> Text Table 2-Groundwater Sample Characterization Table <br /> Chemical No. of No. of Range of Range of Reported <br /> Spls Detects SQL(µg/L) Concentrations(µg/L) <br /> Method 8081E <br /> Endosulfan I 6 1 0.01-0.1 <0.01-1.2 <br /> Endosulfan II 6 2 0.02-0.2 <0.02-0.84 <br /> Endosulfan sulphate 6 1 2 0.05-0.5 <0.05-2.3 <br /> Endrin 6 1 0.01-0.1 <0.01-1.0 <br /> Toxaphene 6 2 0.05-0.5 <0.05-22 <br /> Note: No.of Samples does not include QA Samples or water well sample <br /> All of these chemicals are identified as chemicals of potential concern with respect to <br /> groundwater. Based on these sample results, and in view of the concerns regarding cross- <br /> contamination in the two groundwater samples collected for the original PEA, the pesticides <br /> DDT, DDD, and DDE are no longer considered to be COPCs with regard to the groundwater. <br /> 2937 Veneman Avenue,Suite B240 Geo-Phase Environmental Inc. Phone: (209)569-0293 <br /> Modesto,Ca 95356 Fax: (209)569-0295 <br />