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uncertain but possibly southward in five of six monitoring events Initially, the water table was within the 2"d Riverbank aquifer,but by July 1995 it had risen into the 1st Riverbank aquifer Three new wells were installed in late 1996, and were screened within the 1st Riverbank aquifer Data from the three wells in the 2"d Riverbank were combined with data from the three wells in the 1St Riverbank, and groundwater flow appeared to be bi-directional to both the north and south through 1997 One additional well (GT-10) was installed in early 1999, and the screened interval was within the Modesto aquifer From March through June 1999, the water table was within the Modesto aquifer, and wells in the Modesto, I't Riverbank, and 2"d Riverbank were used to contour the piezometric surface Eastward and northwestward groundwater flow directions were mapped In the third and fourth quarters of 1999, the water table dropped below the base of the Modesto aquifer Groundwater flow directions were either uncertain or possibly eastward during this time The water table again rose into the Modesto aquifer in the first and second quarters of 2000 In the first quarter, groundwater flow appeared to be northward, but in the second quarter it appeared to be southeastward Since the middle of 2000, the water table has remained within the I" Riverbank aquifer Ten groundwater elevation maps were constructed prior to the November 2004 monitoring event Except for quarter (January 2003), eastward or southeastward flow directions have been dominant The northward flow direction mapped in November 2004 (Figure 10) is therefore a departure fiom the previous maps However,the southward flow depicted for the 3`d Riverbank aquifer is relatively consistent with the previous ten maps, but the westward flow depicted for the 2nd Riverbank aquifer is strongly at odds with most other maps The only other time that a generally westward or northwestward flow direction was mapped occurred in June 1999, when the water table was unusually elevated and was within the Modesto aquifer In sum, groundwater flow at the site has varied considerably over time, appears to be different in different aquifers, and is still rather poorly understood. Additional wells and monitoring events will be needed to sort out this unusually complicated situation 3.5 Analytical Results In this section, soil and groundwater analytical results are discussed in sequence from youngest (Modesto Channel) to oldest (3rd Riverbank Channel) All samples were analyzed for Total Petroleum Hydrocarbons in the gasoline and diesel ranges, volatile aromatic hydrocarbons (BTEX), and MTBE by EPA methods 8015 and 8020 The water samples from the newly installed wells were also analyzed for gasoline oxygenates by EPA method 8260 The laboratory reports are in Appendixes B and D 3 5.1 Modesto Channel A few soil samples were collected from the Modesto Formation, but only two were contaminated No hydrocarbons were detected in the samples collected at 42 5 feet in GT-13, 60 feet in GT-14 8