Fig. 6. Time series data of the average NO₃ concentrations observed from the shallow wells fit with Eq. [1]. Nitrate concentrations increase in Phase 1, decrease in Phase 2, and reach and maintain a steady value in Phase 3. The jagged lines are the 50% confidence limit and the red area indicates a period of time where 50% of the well samples tested above the 10 mg L^-1 level.