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all three maps that the main flow direction was to the east This is not significantly different from • the southeast flow direction that was mapped in the second quarter 3.3 Analytical Results--Groundwater The laboratory results are shown in Table 3 The number of wells in which diesel-range hydrocarbons were detected declined from 15 in the second quarter of 2005 to 12 in the third quarter Only one of eight wells screened in the 2nd Riverbank Aquifer had detectable TPH-d concentrations this quarter, down from six wells in the second quarter Diesel was present dust above the detection limit in two wells (GT-12B and GT-14B) in the 3`d Riverbank Aquifer in the second quarter, but both were below the detection limit this quarter On the other hand, the three wells that detected no TPH-d in the second quarter (GT-13B, GT-15B, and GT-18B) all detected it - 0�� this quarter Hence, there was a net increase of one well-in-this ,aquifer this quarter In the 1St "m�t Riverbank Aquifer, the number of wells in which TPH-d was detected increased from seven to �� ij eight tvtr�) d"I , Alb There were no sharp increases or decreases in concentration this quarter The slight changes that were detected are within historical ranges and are typical of the small variations that are seen on a quarterly basis at most sites In the Second Quarter 2005 Report we noted that it was slightly surprising that the highest concentration in the 1st Riverbank.Aquifer was detected in GT-16A, which is relatively far from the former UST facility This is still the most impacted well in this aquifer, but the concentration declined by 15% this quarter Perhaps related to that decline is an increase in concentrations in GT- 6, GT-20, and GT-21, which (respectively) are located to the southeast, east, and northeast of GT- 16 and are downgradient of this well Downgradient diffusion of hydrocarbons could explain both a decrease in an upgradrent well (GT-16) and an increase in downgradient wells Comparison of Figure 6 from the Second Quarter Report to Figure 17 from this report seems to support that possibility, because the perimeter of the plume has expanded outward while the core of the plume appears to have narrowed and become more elongate, and the maximum concentration may have dropped below 1,000 ppb In that same report we also observed that the dissolved-phase plume in the 2nd and 3`d Riverbank Aquifers appeared to be elongated, or"stretched', in a north-south direction toward G-1 (the former Gillies domestic well), and suggested that this could be due to the influence of pumping of that well Based on that suggestion, we predicted that because the domestic well has now been destroyed and can no longer affect the plume, concentrations in GT-12A and GT-12B (located close to G-1) might decline for the rest of the year So far, the results support this suggestion, concentrations declined from 108 ppb to <50 ppb in GT-12A and from 59 5 ppb to <50 ppb in GT- 12B Figure 18 maps the extent of TPH-d in the 2"d Riverbank, and comparison of this figure to Figure 7 in the Second Quarter Report reveals that the plume is now considerably smaller and fewer wells are impacted 1t,also demonstrates that the plume is not stretched in a north-south direction, because none of the wells that are located to the north or south of the former UST cavity are impacted at this time In the 3rd Riverbank the plume may still be somewhat elongate north- south, although the number of impacted wells is limited to three and the plume could be contoured differently with the limited data(Figure 19) 5