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a Fourth Quarter 2003 Groundwater Monitoring Report Eckert Cold Storage,Manteca,California January l3,2004 Page 2 • FIELD OBSERVATIONS On December 12, 2003, a Condor representative made field observations at four of the eight site monitor wells (MW-4, MW-5, MW-7, and MW-8). Field observations included sample odor, appearance (color, clarity, and presence of petroleum product sheen or phase in samples), and water quality field parameters. No sheen, product phase, or odor was noted in the field inspection samples collected from the four site monitor wells that were sampled during the 2003 annual monitoring event. Monitor well MW-5 appeared to have been damaged by a vehicle. The monument that houses monitor well MW-5 was damaged and the casing appeared to be broken just below ground surface. A bailer was able to fit down monitor well MW- 5 to purge and sample it, however, purge water from monitor well MW-5 carried an unusually high sediment load. Field observation sheets are included in Attachment B. GROUNDWATER ELEVATIONS All eight site monitor wells were measured for water level during this annual monitoring event. The average groundwater elevation was approximately 0.10 feet lower on December 12, 2003, than the previous sampling event conducted on September 2, 2003. The groundwater elevation contours (Figure 3, Attachment A) estimated from the depth to water measurements indicate the groundwater gradient was generally towards the northwest on December 12, 2003. 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 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. Consistent with this, Figure 4, Attachment A, shows the groundwater gradient direction and magnitude using monitor wells MW-3, MW4, and MW-6. On December 12, 2003, the groundwater gradient was 0.0020 ft./ft. towards the northwest, as shown. Groundwater elevation data for December 12, 2003 are presented in Table 1, below. Table 1 —Groundwater Elevation Data (December 12, 2003) Monitoring Screened Interval(bgs) TOC Elevation' Depth To Water Groundwater Well Elevation MW-1 13 —28 38.09 20.61 17.48 MW-2 15 -30 37.90 20.30 17.60 MW-3 15 -30 38.31 20.76 17.55 MW-4 12-27 37.84 20.56 17.28 MW-5 14-34 41.22 24.02* 17.20* MW-6 13 -33 37.65 20.10 17.55 MW-7 13 -33 38.22 20.65 17.57 MW-8 17- 37 1 37.76 20.24 17.52 'TOC Elevation:Elevations are measured from the top of the well casing and are referenced to MGs Benchmark HS4486,elevation 35.03 feet using NAVD 88 datum. All measurements are in feet. * Data is suspect due to damage casing s A i'a CONDOR