SITE INFORMATION AND CORRESPONDENCE

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• _ • 29 February 2000 . Mr. W.T. Nickerson - 2 - in the well furthest away(MW-12). There does not appear to be a corresponding fluctuation in constituent concentrations in these upgradient wells. The largest fluctuations of consitutuent concentrations in groundwater occur in MW-8, which is approximately 130 feet west of the northern former disposal pond. During low flows in the canal, MW-8 is downgradient from the northern disposal pond, and during high flows, it is sidegradient. During high flows, constituent concentrations in MW-8 are comparable to concentrations in the upgradient well. Concentrations of most constituents in the two downgradient wells closest to the northern former disposal pond(MW-8 and MW-6) are highest during periods of low groundwater elevations. In contrast, the monitoring well directly adjacent to the northern former pond(MW-2) contains its highest concentrations during periods of high groundwater elevations. The peak concentrations of nitrate, dibromochloromethane, chloroform, and ethylene dibromide in downgradient wells MW-8 and MW-6 are greater than the peak concentrations in MW-2 at the disposal pond. This suggests that the center of mass of these constituents originating beneath the northern disposal pond is migrating downgradient. In contrast, concentrations of 1,2,3-trichloropropane, 1,2-dichloropropane, and dibromochloropropane are greatest in MW-2, suggesting that these constituents travel more slowly than the others. Report Details The The constituent concentration graphs and hydrographs present information dating back to 1993. a rate of data in the graphs suggest that concentrations declined after the ponds were capped, and suggest constituent movement. Trends in the data will be more easily identified if you will incorporate a few manipulations to the data and graphs. Since there appears to be a relationship between groundwater elevations and constituent concentrations, it will help to see this if the hydrograph can be visually correlated with the constituent concentration time graphs. Three examples of how to accomplish this are: 1. All the graphs can be produced at the same horizontal scale, so that the reader can overlay the hydrograph onto the concentration graphs. 2. The hydrograph data can be incorporated into each concentration graph by using independent vertical axes. 3. The hyrdrograph can be reproduced as a separate graph on the same page at the same horizontal scale as the concentration graphs. These graphs should also indicate dates of significant physical events, specifically, when the ponds were capped.