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Mr. George Lockwood September 7, 2004 Page 6 frequency is recommended when existing Specific Conductivity and Total Coliform Organisms data has not been fully evaluated. City Response: The purpose for the temporary monthly water quality monitoring program, initiated in April 2003, was to increase the level of confidence in the quarterly monitoring program. The increased data has been helpful, as it has demonstrated for the most part that the water quality swings in the wells are factual. The information is being used to evaluate the potential for seasonal quality changes due to seasonal operational practices. See the enclosed Updated Time-Series of Groundwater Elevations and Nitrate (as N) Concentrations by Well. The City is actively evaluating its nitrogen loading and farming practices and implementing changes to improve results. As an example, the City is modifying its leasing contracts to maintain greater control of when the land is irrigated, when biosolids are applied, and when supplemental fertilizer is applied. The contracts now also require that both summer and winter crops be grown. The City has evaluated the Specific Conductivity and Total Coliform Organisms data. Those evaluations will be discussed later in this letter. 6. Ponds should be monitored for nitrates also. Comment: This should be standard practice. City Response: As discussed early in this letter, the City has implemented this recommendation from the Status Report. The duration of the monitoring is being discussed. Discussion of Evaluation of Specific Conductivity and Total Coliform Organisms and Overall Status of Monitoring Activities The City has evaluated Total Coliform Organisms, and they are not an issue. In 2003, of the 187 coliform samples collected from the monitoring wells and analyzed, only.three indicated coliform levels above 2.2 MPN/100 ml. The highest level was 8 MPN/100 ml. Thus far in 2004, 95 coliform samples have been collected and analyzed, and only five indicated coliform levels above 2.2 MPN/100 ml. The highest level was 5.1 MPN/100 ml. See the enclosed Tabular Presentation of Groundwater Quality Data by Well. As requested, the City has evaluated the Specific Conductivity (Electrical Conductivity (EC)) data collected from August 2001 through May 2004. See the enclosed Specific Conductivity (Electrical Conductivity) Contour Figures. The figure for the average values provides a good overview of the EC issue. Within City property, EC values are highest in the northwestern area around WSM15 and lowest in the center area around WSM3. EC values southwesterly of City property are the lowest in the region. EC values northeasterly and southeasterly of the property are also elevated. It is interesting to note that the lowest EC values within City property are immediately around WSM3 and to a lesser extent WSM4. This is puzzling because of the high nitrate levels found at WSM4. LLOCKWOOD_NPDESPERMIT.DOC