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Gee(ogkalTecknlcslac Page 5 Groundwater Monitoring Report ` Project No.425.2 August 6,2004 • MW-3, MW-6, MW-7, MW-2X, MW-102, MW-105, MW-107, MW-202 and all sampled domestic wells were non-detect above laboratory reporting limits for all analyzed constituents. ` • MW-1, MW-4, MW-101 and MW-201 showed low levels of TPH-G and BTEX constituents. L • MW-2 showed high concentrations of TPH-G and BTEX constituents during this monitoring event and also in the historical data. The monitoring wells: MW-2X (42- 50 ft bsg), MW-102 (55-60 ft bgs), and MW-202 (70-85 ft bgs) do not show any contamination. This indicates that contamination did not move to the deeper zones of water near MW-2(the place of highest contamination). • MW-5 showed moderate levels of TPH-G and BTEX constituents. • Total Xylene(0.4µg/L),and TPH-G(172µg/L)have been detected in MW-106. • During this monitoring event, MW-8 shows the contamination from TPH-G and BTEX constituents, but the historical data from MW-8 shows that there was not any contamination. It is not clear if the contaminated plume reached MW-8 or the contamination is a sampling error,the next monitoring event will clarify this point. 3.0 FINDINGS AND DISCUSSION The laboratory analytical data generated during the April 27, 2004 groundwater-monitoring event indicates that TPH-G and BTEX constituents have been detected in monitoring wells: MW-1,MW-2, MW-4,MW-5,MW-8,MW-106 and MW-201. The results of the April 2004 event are comparable with the results from previous monitoring events. The following observations are made: • The horizontal groundwater gradient, calculated from the water table wells, is currently towards the north. .. • The gradient calculated from the intermediate wells is to the northeast. • Vertical groundwater gradients were positive in the shallow/intermediate well pairs and positive in the intermediate/deep well pans. y • TPH-G concentrations in MW-1 continue to fluctuate within levels usually observed for the site. The concentration of TPH-G in MW-1 measured during the April 2004 event were the lowest recorded at the site in three years. See Figure 7 for a graph of Benzene ` and TPH-G versus time (MW-1) and Figure 8 for a contour map showing the distribution of TPH-G at the site. • Contaminant concentrations in well MW-4 exhibit a historically static trend. • Contamination in monitoring well MW-5 fluctuates seasonally but exhibits an overall increasing trend. This quarter shows the highest concentrations of TPH-G in MW-5 to i. date. • For the fourteenth consecutive event, well MW-102 did not contain contaminant concentrations above the laboratory reporting limits.