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r— <br /> report on the RFS site: "Because personnel are secure in believing that no <br /> surface water leaves the property, little attention is paid to incidental <br /> spillage. Therefore, stormwater from this area may contain significant <br /> concentrations of plant nutrients." See Footnote 2 of the report by The <br /> Source Group, dated May 31, 2006, and titled Evaluation of Potential Nitrate <br /> Sources near City of Ripon Well #12. It is also consistent with the marked <br /> seasonal increases in nitrate concentrations, to approximately 900 ppm, in <br /> the RFS water supply well. See Figure 2 of the above-referenced report. <br /> 3. It should also be noted that there are a number of uncertainties associated <br /> with the current dataset, including the following: <br /> a. The accuracy of concentration results from well RMW-3S is <br /> questionable. The analytical results from two laboratories vary by <br /> approximately 100 percent (McCampbell result was 440 ppm while <br /> Excelchem result was 898 ppm). <br /> b. The direction of groundwater flow is not clear from the data presented <br /> in the RFS off-site monitoring report dated April 26, 2007. It appears <br /> possible that the top-of-casing elevation for the new well RMW-IS-R is <br /> incorrect. <br /> C. The direction of groundwater flow and, therefore, the direction of <br /> contaminant migration in the vicinity of the RFS site, appear to vary <br /> over time. While water elevation data from past RFS reports may <br /> indicate a northwesterly groundwater flow direction at times, the data <br /> presented in the RFS off-site monitoring reports dated December 14, <br /> 2006 and February 28, 2007 are consistent with a flow direction in the <br /> shallow water-bearing zone that is west-southwest. Given this flow <br /> direction, any contamination present at RMW-3S would not impact <br /> the RFS site and RFS contamination present in the vicinity of the <br /> Batch Mixer would migrate toward City Well 12. <br /> In summary, while RFS may have developed data revealing that there is a regional <br /> nitrate problem, that does not eliminate the need to investigate (1) RFS' contribution to <br /> that problem, and (2) on-site contamination caused by past actions. The City believes that <br /> the following actions should be taken by RFS to properly evaluate the contamination: <br /> 1. All wells that will provide useful information regarding the source of nitrate <br /> groundwater contamination in the vicinity of City Well 12 and the RFS site <br /> should be sampled and gauged simultaneously so that a complete picture of <br /> the nitrate concentration distribution and migration direction(s) can be <br /> developed. These wells should include all on-site and off-site monitoring <br /> wells associated with the RFS site investigation and monitoring, the RFS <br /> water supply well, City Well 12, and the water supply wells previously <br /> sampled by The Source Group as part of the City's investigation (report by <br />