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Limited Groundwater Investigation 7 3.5 Equipment Decontamination and Waste Containment Non-disposable field sampling equipment was decontaminated between samples using a high- pressure wash steam cleaner. Decontamination fluids and soil cuttings were containerized in labeled Department of Transportation (DOT)-approved 55-gallon drums, and were handled by MonierLifetile facility personnel for disposal. 3.6 Sampling Location Survey The ten probe holes were surveyed by Morrow Surveying (a California licensed surveyor located in West Sacramento, California) on May 9,2001,using an established benchmark. The northing, easting, and ground surface elevations were measured for each sampling location. The vertical survey for each location was measured to 0.01 foot relative to mean sea level (msl) using a vertical datum of NAVD 88. The horizontal reference was measured to the California State Plan Zone 3 Coordinate System using NAD 83 (1986). A summary of the survey data is included in Appendix A with the boring logs. 4.0 SUMMARY OF ANALYTICAL RESULTS This section presents the results of the shallow groundwater grab samples. 4.1 Lathrop Facility Groundwater Samples Two of the five groundwater grab samples (LP-G2-Water and LP-G4-Water) collected at the Lathrop facility contained dissolved Cr VI at concentrations of 10 µg/L and 2.0 µg/L, respectively. Groundwater from the remaining three sample locations (LP-G1,LP-G3, and LP-G5) were reported as not detected (<0.2 µg/L) for dissolved Cr VI. Total and dissolved Cr was detected in all the groundwater samples collected at Lathrop. The total Cr concentrations ranged between 55 µg/L to 2100 µg/L,with the dissolved Cr concentrations ranged between an estimated concentration of 2.3 J µg/L to 16 µg/L. The highest total and dissolved Cr concentrations were detected in the duplicate ground water sample collected from LP-G1 (LP-G6). Additionally, Cr VI was not detected at this location. A summary of these data is included in Table 1. 4.2 French Camp Facility Groundwater Samples Groundwater grab samples collected from all five sampling locations (FC-G1 through FC-G5) at the French Camp facility contained dissolved Cr VI at concentrations ranging between an estimated 0.3 J µg/L to 16 µg/L,with the highest Cr VI concentration reported at sample location FC-G4. Similar to Lathrop, total and dissolved Cr was detected in all the groundwater samples collected at the French Camp Facility. The total Cr concentrations ranged between an estimated concentration of 28 µg/L to 1700 µg/L, with the dissolved Cr concentrations ranging between an estimated concentration of 1.8 J µg/L to 54 µg/L. In this case the highest total and dissolved Cr concentrations were found at the same sample location (FC-G4) as the highest detected Cr VI concentration. A summary of these data is included in Table 1. P:\wp\jobs\20587\LP FCGVF.doc—DCN 102300 June 2001