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Groundwater Quality Monitoring - 152 East 11 th Street, Tracy Page 5 of the wells installed for both the 152 and 153 East 11th Street properties are compiled in 4D Table 4 ) Interpretation of Results The geotechnical and geochemical data from the investigations reported herein and data from available records of previous investigations conducted on the 152 and 153 East 11th Street properties have been synthesized and used as the basis for an interpretation of the extent to which the subsurface has been affected by hydrocarbons released at the 152 East Street site This interpretation is presented in the form of the plan view on Figure 2 The groundwater-table contours shown on Figure 2 reflect the data gathered on February 25th 1994 Compared to conditions when depths to groundwater were last measured on October 13th 1993, the water table has risen some 0 6 to 0 9 feet However, the direction of groundwater flow remains to the northwest and its gradient (approximately 0 004 ft /ft ) is similar to that observed previously These results confirm earlier observations that seasonal changes in groundwater conditions at the site are small The analyses of the groundwater samples recovered on February 25th support earlier interpretations of the distribution of hydrocarbons in the subsurface that are shown on Figure 2 Analysis of groundwater from sampled wells around the perimeter of the plume confirm that these areas remain unaffected by detectable traces of hydrocarbon fuel components It is important to understand that the interpretations shown on Figures 2 are not intended to precisely define the exact boundaries of hydrocarbon fuel components affecting the subsurface Specifically, they should not be used for reaching a conclusion as to whether or not groundwater affected by hydrocarbons that may have been released into the subsurface on the 152 E 11th Street site has, or has not, coalesced with fuel components released into the subsurface on the Beacon Station site However, when taken together with the previously available data, the geotechnical, geochemical and hydrological data reported herein support an interpretation that gasoline that leaked from underground tanks, or the associated piping, that were on the 152 East 11th Street property has moved downgradient from the point where those tanks and piping were formerly located toward the East 11th Street frontage of the site and has probably migrated some distance northward under the street Concentrations of hydrocarbons in the sample revered from interior well NAV-4 on February 25th 1994 are somewhat elevated compared to those measured in the sample recovered from that well on October 13th 1993 (Ref Table 4) The concentration of Total Petroleum Hydrocarbons quantified as gasoline was 1,800ug/Liter on February 25th 1994 compared to 570pg/Liter on October 13th 1993 and there were corresponding changes in the measured concentrations of the other analytes These changes are .� interpreted to be due to groundwater rising into a zone of contaminated soil that was