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19'J9 The deepest groundwater levels reported during this 12-year period were ' approximately 69 feet bgs in July 1991 This indicates a water elevation variation in the range of 34 feet Rising water levels since July 1991 has resulted in the monitoring well screens being submerged in several wells, as presented in Table 2 The screened intervals in wells DN4W- 1, DMW-2, and DMW-4 have been submerged since at least May 1994 The screen in DMW-4 has been submerged since at least May 1995, and DMW-5 has been submerged since at least January 1997 Monitoring wells DMW-6 and DMW-7 both have screened ' intervals that currently intersect the water table Variations in the direction of groundwater flow during the 12-year period are presented in Figure 3 Flow directions appear to have shifted from west in 1987 to the east in 1995, and are now generally in the direction of north-northeast to northeast 3.3 TPH-D in Groundwater 1 TPH-D groundwater results for samples collected on September 9, 1999 have been compiled with previous data in Table 3 Groundwater samples containing what appears to be weathered diesel were collected from wells D1vtW-6 (780 pg/1) and DMW-7 (660 ,ug/1), although no petroleum hydrocarbons exactly matching the labolatoiy diesel standard were reported in any samples collected in September 1999 As noted in Section 3 1, laboratory ' QC limits were exceeded, and the reported weathered diesel concentrations are considered estimated ' TPH as unknown hydrocarbons has also been reported in September 1999 samples collected at wells DMW-1 (1 10 Ng/1), DMW-2 (120 ,ug/1), DMW-3 (170 ,ug/1), and DMW-4 (120 ,ug/1) However, as noted in Section 3 1, sample DMW-3 was reanalyzed using method 8015M with Northwest Cleanup Results from this analysis suggest that the unknown hydrocarbon reported in these four samples is not weathered diesel or other recognizable petroleum product IReview of historical TPH-D data indicates that maximum TPH concentration reported since 1987 was from the most recent sampling event in September 1999 Prior to the installation ' of DMW-6 and DMW-7 in December 1998, the only other repotted TPH concentration was 180 pg/I at DMW-4 The weathered diesel reported as unknown hydrocarbon has been consistent) detected Y y dec ed during the four sampling events conducted at DMW-6 and DMW-7 since December 1998 DAMES&MOORE 6 1\AI P\REPORr1991 1_01 doc