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Mr. George Lockwood September 7, 2004 Page 3 through May 2004. The discussion presented on Pages 4 through 8 of the Status Report is still valid considering this supplemental information. Future quarterly and annual reports are to address this topic and are to include a calculated flow gradient and a discussion of flow direction. Comment 5: Figures 4 and 5 show areas where nitrogen was added in surplus over the estimated annual crop uptake. The surplus may have contributed to nitrogen percolating into groundwater. Nitrogen percolation to groundwater appears to be the explanation for Figures C3 and C9 contained in Appendix C indicating a nitrogen anomaly in the same area. The report does not fully explain the anomaly presence. Instead, Conclusion 9 states no significant impact from the treatment plant operations on groundwater. Also, the no impact conclusion is presented without any presentation, evaluation, or discussion to support excluding Specific Conductivity and Total Coliform Organisms from the groundwater quality analysis. Therefore, water quality has not been completely evaluated and the no impact conclusion is offered without considering half of the data. City Response: Surplus nitrogen over estimated crop uptake was added to some fields in 2001 and 2002 and this may have contributed to nitrate percolating into the groundwater. A discussion of how and why that occurred was discussed in the Status Report on Pages 9 through 13. Potential ways to avoid this in the future were also presented in the Status Report. The City has been evaluating and implementing various improvements to its reuse facility management practices. Since the submittal of the Status Report, some effort has been made toward gaining an understanding of the uncharacteristically high nitrate levels observed in WSM4. Several of the recommendations included in the Report have been implemented. One such recommendation is the temporary monitoring of the nitrate levels in the City's storage ponds. The nitrate (as N) concentrations of the water in the ponds have been recorded for June 2003 through May 2004. See tabular summary enclosed. The concentrations have ranged from a low of Non-Detect to a high of 7.3 mg/L. However, the City also tested the samples for ammonia concentrations. The ammonia levels have ranged from Non-Detect to 48 mg/L. The City is considering options for evaluating the impact of the ammonia concentrations on the nitrate levels in the groundwater. The intent of Conclusion 9 was to state that based on the nitrate information collected and evaluated, it appeared that City operations had not had a significant impact on downgradient water quality. It does appear that water quality beneath limited portions of City property has been impacted, but the data did not clearly demonstrate that the City alone has impacted the downgradient water quality. This issue will be discussed further later in this letter. The City has evaluated the Specific Conductivity and Total Coliform Organisms data. Those evaluations will be discussed later in this letter. LLOCKW OOD_NPDESPERMIT.DOC