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Third Quarter,2002 Quarterly Groundwater Monitoring Report Eckert Cold Storage,Manteca,California November 19,2002 Page 2 Summary of September 30, 2002 Quarterly Groundwater Monitoring Event Field Activi Number of monitor wells 8 Number of monitor wells sampled 7 Number of domestic wells 1 Number of domestic wells sampled 1 Date s)monitored and sampled 9/30/02 Site Ilydrology Average depth to groundwater below 20.70 ft bgsAverage increase(+)/decrease(---)in +1.71 feet monitor well measuring points depths to groundwater since last sam lin (deeper) Approximate groundwater flow direction West/ Northwest Groundwater Contamination Wells containing free product None Wells with petroleum hydrocarbon 3 odors noted Number of wells with concentrations 4 Number of wells with concentrations at 4 below MCLS for any reported or above MCLs for any reported contaminant contaminant Nature of contamination: BTEX, Range in concentrations: TPH-G, Benzene(µg/L) <0.5--1,400 Oxygenates Toluene(µg/L) <0.5—6.9 /Additives Ethyl Benzene (pg1L) <0.5—220 Total Xylenes(pg/L) <1.0—100 TPH-G(mg/L) <0.05—11 MTBE (pg/L) <0.5—10 1,2-DCA (Agj) <0.5—3.1 • FIELD OBSERVATIONS No separate phase petroleum was noted in the groundwater recovered from the wells, but a strong petroleum odor was noted in MW-1, MW-3, and MW-8 and a very slight "earthy" odor was noted in MW-7. A slight sheen was observed in the groundwater purged from MW-1. Field observation sheets are included in Attachment B. GROUNDWATER ELEVATIONS The average groundwater elevation was approximately 1.71 feet lower on September 30, 2002 than the previous sampling event conducted on June 26, 2002. The groundwater elevation contours (Figure 3, Attachment A) estimated from the depth to water measurements indicate the groundwater gradient was generally towards the west on September 30, 2002. Historical groundwater data collected by WHF, Inc. (previous consultant) indicates a highly variable gradient at the site. Review by Condor of historical groundwater gradient information 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-4, MW-6, and MW-7. On September 30, 2002 the y CONDOR