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k CONESTOGA-ROVERS &ASSOCIATES groundwater samples. Cambria concluded that there may have been mixing of shallow impacted groundwater with deeper zone groundwater during drilling and/or sampling activities, which caused the TPHd and MTBE detections at depth in this boring. The results of this investigation are documented in Cambria's June 24,2003 Site Investigation Report. Dispenser and Piping Upgrade 2004: During March 2004, Shell performed upgrade activities of their under-dispenser containment equipment. On March 12, 2004, Cambria performed soil sampling activities at each of the six dispensers locations (Figure 3). Cambria collected eight soil samples (D-1 through D-8) from beneath the product dispensers at depths ranging from 3 to 4 fbg. The results of this investigation are documented in Cambria's August 3, 2004 Product Dispenser and Piping Replacement Report. Groundwater Monitoring and Sampling. The three existing groundwater monitoring wells have been monitored and sampled quarterly since they were installed. The groundwater flow direction beneath this site has been consistently toward the northeast with a typical gradient of approximately 0.003. Historical groundwater monitoring data and the most recent groundwater contour map are included as Attachment A. SITE CONDITIONS Soil Types: The predominant soil type beneath the site is fine grained soils(silt and clay). There is a coarse-grained layer (sand) at approximately 15 fbg beneath the site that appears to be laterally continuous across most of the site. An additional coarse-grained layer was encountered at approximately 75 fbg in boring CPT-1. Boring logs are included in Attachment B, and a geologic cross section is included as Figure 4. Table 1 summarizes available soil boring and well construction details. Hydrogeology: Measured depths to groundwater in the site wells have ranged historically from 4.7 to 18.5 fbg, and groundwater elevations have ranged historically from 8.6 feet above to 2.3 feet below msl. The groundwater flow direction is typically toward the northeast with the groundwater gradient averaging 0.003. Groundwater depth and elevation data, and the most recent groundwater contour map are included in Attachment A. Hydrocarbon Distribution in Soil: Available historical soil sampling results are summarized in Table 2. Soil sample locations are shown on Figures 2 and 3. According to Delta's November 28, 1990 report, all soils containing gasoline constituents were removed to the depth of the water 0813 4 -- - - Worldwide Engineering.Environmental.Construction,and IT Services