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On 24 February 1993 , GeoAudit visited the site to sample the three <br /> on-site monitoring wells. The depth to groundwater was measured in <br /> each well. An oily substance was observed in monitoring well MW-1 <br /> during bailing, and it was determined that an interface meter <br /> should be obtained to determine the thickness of this layer prior <br /> to sample collection. <br /> On 5 March 1993 , GeoAudit returned to the site with an interface <br /> meter. The oily substance was determined to be a film, and not <br /> significant for depth to groundwater measurements. The depth to <br /> groundwater was then measured in each well, the three wells were <br /> purged and samples were collected. The results of this sampling <br /> event are in the April 1993 Quarterly Groundwater Monitoring <br /> Report. <br /> 2.5 Groundwater Depth and Gradient <br /> The depth to groundwater was approximately 8 1/2 to 10 feet in each <br /> well. The groundwater gradient was determined to be 0 . 0050 ft/ft <br /> oriented N 160 W on 24 February 1993 and 0. 0022 ft/ft oriented N 80 <br /> W on 5 March 1993. This is consistent with previous groundwater <br /> determinations and regional trends. <br />• 2 . 6 Laboratory Results <br /> Laboratory analyses of the samples collected on 5 March 1993 showed <br /> TPH as gasoline and diesel in MW #1 at levels of 4 , 000 gg/L (parts <br /> per billion, ppb) and 1, 800 ppb respectively. BTE&X were detected <br /> in monitoring well MW-1 at levels of 6. 1 ppb, 4 . 1 ppb, 29 ppb and <br /> 450 ppb, respectively; No hydrocarbon contamination was detected <br /> 1n monitoring well MW-2 and only toluene (0. 32 ppb) was detected in <br /> monitoring well MW-3 . <br /> 3. 0 SCOPE OF WORK <br /> To further define the extent of down-gradient groundwater <br /> contamination, GeoAudit will install an additional groundwater <br /> monitoring well to the north of monitoring well MW-1 (see Figure <br /> 2) . <br /> Some of the stockpiled soil that was placed back into the <br /> excavation was contaminated and is a probable source of continuing <br /> contamination to groundwater. This soil should be removed from the <br /> excavation. However, the soil imported to backfill the excavation <br /> from 7 feet below grade to the surface was clean and may be used as <br /> backfill material. In addition, the original excavation did not <br /> reach the limits of soil contamination to the north of the tanks. <br /> The water purged from the January 1990 excavation was released at <br /> the site of the former excavation. While this water was reportedly <br /> not contaminated, it had the potential to leach additional <br /> contamination into the groundwater. <br /> 2 <br />