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[I f Second Quarter 2005 Groundwater Monrtonng Report Eckert Cold Storage,Manteca,California August 12,2005 Page 3 • Table 1 —Groundwater Elevation Data (July 8, 2005) Monitoring Screened Interval(bgs) TOC Elevation Depth to Water Groundwater Well Elevation MW-1 13 -28 3809 1825 1984 MW-2 15-30 3790 1809 1981 MW-3 15 -30 3831 1846 1985 MW-4 12-27 3784 1806 1978 MW-5 14-34 4122 21 33 1989 MW-6 13 -33 3765 17 88 197 MW-7 13 -33 3822 1833 1989 MW-8 17-37 3776 1 18 11 1 1965 'TGC 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 to feet Historically, the groundwater gradient direction at the site has been variable but generally to the northwest Last quarter (March 9, 2005), the groundwater gradient direction (northwest) was consistent with the predominant histonc gradient direction This represented a shift back from the two previous quarterly monitonng events which indicated a northerly flow (December 2004) and a northeasterly flow (September 2004) The current gradient direction (west on July 8, 2005) is not consistent with recent historic gradient directions The current gradient magnitude (0 0011 ft/ft), however, indicates a very gentle water table slope The current flow direction, therefore, may not be significant relative to transport of site groundwater contamination LABORATORY ANALYTICAL RESULTS The groundwater samples collected on July 8, 2005, from monitoring 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 monitonng event, historic 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 9, 2005 indicated higher contaminant concentrations (but with a decreasing trend in contaminant concentrations) The current results indicate that the trend is continuing — contaminant concentrations have returned to very low levels Conversely, prior to the December 2004 monitoring event, historic 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 9, 2005 indicated lower contaminant concentrations relative to the historic results The current results indicate that contaminants in MW-8 have increased back to the relatively higher concentrations consistent with samples from the well collected pnor to December 2004 Historic groundwater monitoring data are included in Attachment C Laboratory certificates of analyses and the chain-of-custody documentation for the samples are included in Attachment D The samples were analyzed by Argon Laboratones of Ceres, California r i CONDOR