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Limited Groundwater Investigation 5 California. One groundwater grab sample was collected from each sampling location using direct push/dual tube sampling methods and a low volume peristaltic pump equipped with poly tubing. Ten probe holes were advanced to first groundwater at the Lathrop and French Camp facilities on May 7 and 8, 2001,respectively. Soil cores were collected by advancing a 2.7-inch diameter steel outer casing and 1.5 inch diameter stainless steel inner-sampling rod simultaneously through the subsurface. Soil samples were collected in a 3-foot long stainless steel sample barrel lined with stainless steel sleeves. One location was sampled continuously at each facility (LP-G1 and FC-G5) to determine depth to first groundwater and to obtain a general lithologic description. The XD-1 limited access drill rig was used at the Lathrop facility, but met with outer casing refusal in a hard pan layer at approximately 12 to 16 feet bgl at LP-G1. As a result, the outer casing of the sampling unit was unable to advance past the hard pan layer. Continuous core sampling activities stopped at approximately 15 feet bgl in LP-G1 due to refusal. The smaller diameter inner rod of the sampling unit was advanced past the outer casing to a total depth of 28 feet bgl in LP-G1, and a groundwater grab sample was collected. To complete sampling activities in the remaining four locations (LP-G2 through LP-G5), soil within the upper 10 feet was sampled for lithologic logging, and the inner rod was advanced to approximately 22 to 25 feet bgl to collect a groundwater grab sample. Similar drilling methods were used at the French Camp facility at the five sampling locations (FC-G1 through FC-G5),with the exception of the size of the drill rig. A more powerful rig (SD-1) was used at French Camp to minimize the potential for outer casing refusal. Sample location FC-G5 was continuously cored to a total depth of approximately 37 feet bgl to establish the depth to first groundwater at the French Camp facility. Soil from sample locations FC-G1 through FC-G4 was collected at depths of 10, 20, and 30 feet below grade for lithologic logging.At the French Camp Facility, groundwater was encountered at approximately 29 feet bgl. To expedite sampling activities, a groundwater grab sample was collected from each sample location at both facilities by installing temporary 0.75-inch PVC screen (pre-cleaned and wrapped in plastic with a 0.010-inch screen slot size) through the inner rods. The sampling unit (outer casing and inner rods) was then removed from the borehole and the temporary screened casing was left in place. Groundwater was collected from each temporary screen using an ISCO sampling devise (low volume peristaltic pump) and poly tubing. The groundwater samples were transferred directly to laboratory provided sample bottles through the tubing. Sample locations were backfilled by retraction grouting methods with a cement grout through the temporary PVC casing. Groundwater grab samples were submitted to Applied P and Ch Laboratory (APCL), located in Chino, California, and were analyzed for the following suite of parameters using USEPA SW-846 Test Methods (USEPA 1986): ■ Total and dissolved Cr using EPA Test Method 6010. ■ Dissolved Cr VI using EPA Test Method 7199. P:\wp\jobs\20587\LP FCGW.doc—DCN 1023W June 2001