ARCHIVED REPORTS XR0011423 - Laserfiche WebLink

Home Browse Search

Geologic:d!Techlacs 1AC. Page 6 Groundwater Monitoring Report Project No. 425.2 March 21, 2005 The results of the November 2004 event are comparable with the results from previous P ' monitoring events. The following observations are made: The horizontal groundwater bearing calculated from the Zone A wells, is currently towards the north. ' * 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 / Zane D well pairs. ' • TPH-G concentrations in MW-l continue to fluctuate within levels usually observed for the site. The concentration of TPH-G, Benzene, Ethyl Benzene, and total Xylenes in MW-1 measured during the January 2005 event were in the highest range recorded at the ' site in ten years. • Contamination in monitoring well MW-5 fluctuates seasonally. 0 For the seventeenth 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 0.03 and 2.13 ppm (Table 9). • Oxidation-Reduction Potential (ORP) is found negative only in MW-2 (Table 9). 4.0 CONCLUSIONS AND RECOMMENDATIONS Conclusions ' l. Zone A groundwater historically flows in a northerly direction. 2. Zone B groundwater shows a northwesterly flow over the last five monitoring events. 3. The dominance of upward vertical flow 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. Generally the soil and groundwater testing data suggests that the contaminants are spreading laterally, but not vertically to any extent. ' 6. The two domestic wells sampled remain non-detect for all analyzed constituents, indicating that the drinking water aquifer has not been impacted. ' Recommendations The following recommendations are made. ' 1. Continue quarterly groundwater monitoring events.