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Mr. Mike Miller June 3, 1996 Page 2 Project 20B02-001.010 to note that higher levels of VOCs (with the exception of the last quarter's results from MW -14) were detected in well 8106A 6 years ago. In 1989, 1990, and 1991, an extensive exploration program was conducted between the landfill and well 8106A (EMCON, April 1991). This program consisted of HydroPuncho sampling at 24 locations (SB -4 to SB -30). The locations of these sampling points in the first -encountered water -bearing zone are shown on Drawing 1. The results of this investigation indicated that the lateral extent of impact was detected only at locations SB -4 to SB -11, SB -18, SB -28, and SB -29. Since the remainder of the locations were free of VOCs, especially at locations SB -15 to SB -17, and SB -20 to SB -22, which were between well 8106A and the impacted sampling locations, ample evidence existed in 1991 to demonstrate that the VOCs in well 8106A were not from the landfill (see Drawing 1). In the summer of 1991, several monitoring wells were installed downgradient from the landfill to monitor the lateral and vertical extents of impact. Wells MW -6 and MW -7 were installed in the second -encountered water -bearing zone adjacent to the landfill at the location of the highest concentration of VOCs in the first -encountered water -bearing zone. Wells MW -10 and MW -11 were installed in the zone of impacted groundwater between the landfill and well 8106A. Wells MW -12 and MW -13 were installed between the zone of impacted groundwater and well 8106A. Low levels of VOCs in MW -13 were first detected in March 1994, with more consistent detections occurring after April 1995. Based on the indication that the plume of impacted groundwater had just reached MW -13, a new well (MW -14) was installed in the summer of 1995. The third and fourth quarter 1995 monitoring events at MW -14 did not indicate signs of landfill impact. However, the results of the first quarter 1996 monitoring event showed apparent signs of impact. As previously stated, the first quarter 1996 results confirm that well MW -14 contains VOCs. The question is, "are the VOCs in well MW -14 from the landfill or from another source, such as the one that apparently caused the impact at well 8106A in 1989?" If the VOCs were from an outwardly spreading plume from the landfill, we would expect the concentration levels to gradually build up in the well, as we have seen in MW -13. The extensive investigations conducted in 1989, 1990, and 1991 indicated two sources of VOCs in the vicinity of the landfill: a plume in the first -encountered water -bearing zone that had migrated approximately 1,000 feet to the north from the landfill, and a second isolated uninvestigated source detected by well 8106A. It is possible that this other isolated uninvestigated source could be the sole or partial contributor of the VOCs in well MW -14. A point could be made that the on-site extraction wells (EW -1 and EW -2) could have pulled VOCs from the well 8106A source to well MW -14. The extraction and treatment system has been operational for over a year; however, extraction well EW -1 has not been 100 percent operational throughout this entire time period. As of a few months ago, EW -1 SAC\N .\PJOvDBOZ\OB020011.OGS-96\pas:4