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' Geological rechmics t4 Page 6 Groundwater Monitoring Report Project No.425.2 February 22,2005 3.0 FINDINGS AND DISCUSSION ' The laboratory analytical data generated during the November 03, 2004 groundwater- monitoring event indicates that MTBE and/or TPH-G and BTEX constituents have been detected in monitoring wells: MW-1, MW-2, MW-3, MW-4, MW-5, MW-8, and MW-201. ' The results of the November 2004 event are comparable with the results from previous monitoring events. The following observations are made: ' • The horizontal groundwater bearing calculated from the Zone A wells, is currently towards the northeast. • The bearing calculated from the Zone B wells is to the northwest. ' • Vertical groundwater gradients were positive in the Zone A /Zone B and Zone B /Zone D well pairs. • 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. ' • Contamination in monitoring well MW-5 fluctuates seasonally. The average TPH-G concentrations per season have increased over the past three years. • For the sixteenth consecutive event, well MW-102 did not contain contaminant concentrations above the laboratory reporting limits. • Two domestic wells were sampled and found non-detect for this monitoring event. • Dissolved Oxygen measurements are on the low to moderate end of the scale, ranging ' between 0.04 and 2.45 ppm (Table 9). • Oxidation-Reduction Potential (ORP) measurements are mostly negative values (Table 9). 4.0 CONCLUSIONS AND RECOMMENDATIONS Conclusions ' 1. Zone A groundwater historically flows in a northerly direction. 2. Zone B groundwater shows a northwesterly flow over the last four monitoring events. 3. The dominance of upward vertical now of groundwater may be the primary reason ' contaminants have not impacted the drinking water aquifer. 4. Petroleum hydrocarbon concentrations in the groundwater at the site fluctuate with each monitoring event. The residual contamination in soil, up gradient of MW-2, remains a ' significant source of impact to the groundwater plume. 5. Contamination has been detected in MW-201 (Zone Q. This is an indication of site- specific vertical movement of plume into the deeper zones. 6. Generally the soil and groundwater testing data suggests that the contaminants are spreading laterally, but not vertically to any extent. 1