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rl First Quarter 2004 Groundwater Monitoring Report Eckert Cold Storage,Manteca,California April 8,2004 Page 2 . FIELD OBSERVATIONS On March 17, 2004, a Condor representative made field observations at two of the eight site monitoring wells (MW-4 and MW-8), and the site domestic well (DW-1). 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 or product phase was noted in the field inspection samples collected from the wells, but a slight petroleum odor was noted in the inspection sample collected from MW-8. GROUNDWATER ELEVATIONS All eight of the site monitoring wells were measured for water level during this quarterly monitoring event. The average groundwater elevation was approximately 1.11 feet higher on March 17, 2004, than the previous sampling event conducted on December 12, 2003. Historic groundwater data collected by WHF, Inc. (previous consultant) indicates a highly variable gradient at the site. Review by Condor of historic groundwater gradient information provided by WHF indicates that the general historic 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 monitoring wells. Consistent with this, the three-point solution using monitoring wells MW-3, MW-4, and MW-6 is shown in Figure 3, Attachment A. On March 17, 2004, the • groundwater gradient direction and magnitude was approximately 0.001 ft./ft. towards the north- northwest, consistent with historic groundwater gradient estimations. Groundwater elevation data for the March 17, 2004 monitoring event are presented in Table 1, below. Table 1 —Groundwater Elevation Data (March 17, 2004) Monitoring Screened Interval(bgs) TOC Elevation Depth To Water 'Groundwater Well Elevation MW-1 13 -28 38.09 19.48 18.61 MW-2 15 -30 37.90 19.28 18.62 MW-3 15 -30 38.31 19.72 18.59 MW-4 12-27 37.84 19.37 18.47 MW-5 14-34 41.22 22.65* 18.5.7* MW-6 13 -33 37.65 19.02 18.63 L:::MW-7 131 -33 38.22 19.55 18.67 MW-$ 17—37 37.76 19.32 18.44 '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. *Eckert indicated that they repaired MW-5 prior to the first quarter 2004 monitoring event,with no apparent change in elevation to the well measuring polo[. • 'I CONDOR