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n t Third Quarter 2005 Groundwater Monitoring Report Eckert Cold Storage,Manteca,California October 26,2005 Page 3 • Table 1 --Groundwater Elevation Data (September 22, 2005) Monitoring Screened Interval(bgs) TOC Elevation] Depth to Water Groundwater Well Elevation MW-1 13 -28 3809 1860 1949 MW-2 15 -30 37 90 1837 1953 MW-3 15 -30 38 31 1881 1950 MW4 12-27 37 84 1852 1932 MW-5 14-34 41 22 2186 1936 MW-6 13 -33 3765 18 13 1952 MW-7 13 -33 3822 1866 1956 MW-8 17-37 3776 1828 1948 `TOC Elevation Elevations are measured from the top of the well casing and are referenced to NGS Benchmark HS4486,elevation 35 03 feet using NAVD 88 datum All measurements are in feet Histoncally, the groundwater gradient direction at the site has been variable but generally to the northwest Last quarter (July 8, 2005), the groundwater gradient direction (west) was not consistent with the groundwater gradient direction calculated during the previous two quarterly monitoring events (north in December 2004 and northeast in September 2004) The current gradient direction (northwest at a magnitude of 0 0014 ft/ft), however, is generally consistent with historic gradient directions . LABORATORY ANALYTICAL RESULTS The groundwater samples collected on September 22, 2005 from monitonng wells MW-5 and MW-8 were analyzed for benzene, toluene, ethyl benzene, and total xylenes (BTEX) by EPA Method 826013, total petroleum hydrocarbons quantified as gasoline (TPH-G) by EPA Method 8015M, and selected gasoline oxygenates/additives including methyl tertiary butyl ether (MTBE) by EPA Method 8260B The current analytical results are shown in Table 2, on the next page Prior to the December 2004 monitoring event, histonc laboratory analytical results of groundwater samples collected from MW-5 indicated generally very low contaminant concentrations Laboratory analytical results of samples collected from MW-5 in December 2004, January 2005, and March 2005 indicated higher contaminant concentrations (but with a decreasing trend in contaminant concentrations) Laboratory analytical results of groundwater samples collected from monitor well MW-5 during the previous (July 2005) monitoring event indicated that contaminant concentrations had returned to very low levels The current(September 2005) laboratory analytical results indicate that these very low levels have continued(see histonc groundwater monitoring data, Attachment C) Conversely, prior to the December 2004 monitonng event, histonc laboratory analytical results of groundwater samples collected from MW-8 indicated generally elevated contaminant concentrations Laboratory analytical results of samples collected from MW-8 in December 2004, January 2005, and March 2005 indicated lower contaminant concentrations relative to the historic results Laboratory analytical results from the previous (July 2005) monitoring event indicated that contaminants in MW-8 had increased back to the relatively higher concentrations consistent with samples from the well collected prior to December 2004 Current (September 2005) contaminant concentrations detected in MW-8, however, indicate that contaminant concentrations have returned to the low levels relative to historic results (see histonc groundwater monitonng data, Attachment C) �� CONDOR