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n Second Quarter.2002 Quarterly Groundwater Monitoring Report Eckert Cold Storage,Manteca,California Page 2 Nature of contamination: BTEX, Range in concentrations: TPH-G, Benzene(p.g/L) <0.5-2,000 TPH-D TPH-G (mg/L) X0.05--15 Oxygenates TPH-D (mg/L) <0.05---0.46 /Additives MTBE (µg/L) X0.5-32 TAME (µg/L) X0.5-82 1,2-DCA( /L2 <0.5-15 FIELD OBSERVATIONS No sheen or separate phase petroleum was noted in the wells, but a strong petroleum odor was noted in MW-1 and moderate petroleum odors were noted in well MW-3 and MW-8. Field observation sheets are included in Attachment B. GROUNDWATER ELEVATIONS The average groundwater elevation was approximately 2.2 feet Iower on June 26, 2002 than the previous sampling event conducted on February 27, 2002. The groundwater elevation contours (Figure 3, Attachment A) estimated with the depth to water measurements indicate the groundwater gradient was generally towards the west on June 26, 2002. Historical groundwater data collected by WHF indicates a highly variable gradient at the site. Review by Condor of historical groundwater gradient infonnation provided by WHF indicates there are potential inconsistencies in the data and possibly components of the interpretation of those data, especially related to MW-5 measurements. However, Condor agrees that the general historical groundwater gradient is predominantly towards the northwest at the site. The highly variable gradient at the site may be related to • domestic/supply well pumping both on site and off site. At times in the past, the water table slope has been very flat(very gentle groundwater gradient). When this occurs, any slight variability in groundwater measurements and the tolerance for error for the water level measurement devices can result in apparent groundwater elevation contours that are not particularly coherent. Therefore, when the water table at the site is relatively flat, it may be more representative to depict the groundwater gradient with a three-point construction using groundwater elevation data from three site monitor wells that circumscribe the site, allowing triangulation of the contaminant plume, including the contaminant source area. Consistent with this, Figure 4, Attachment A shows the groundwater gradient direction and magnitude using monitor wells MW-3, MW-4, and MW-6. On June 26, 2002 the groundwater gradient was 0.0011 ft./ft. towards the northwest, as shown. Groundwater elevation data for June 26,2002 are presented in Table 1, below. Table 1 -Groundwater Elevation Data(.Tune 26,2002) Monitoring Screened Interval(bgs) TOC Elevation Depth To Water Groundwater Well Elevation MW-1 13 -28 38.09 18.68 19.41 MW-2 15 -30 37.90 18.51 19.39 MW-3 15 -30 38.31 18.91 19.40 MW-4 12-27 37.84 18.56 19.28 MW-5 14-34 41.22 21.72 19.50 MW-6 13 -33 37.65 18.27 19.38 MW-7 i 3 -33 38.22 18.78 19.44 MW-8 17-37 37.76 1 18.52 1 19.24 '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 SS datum. All measurements are in feet. 1 Ltf CONDOR