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• • • SECTION 5.0 RESULTS • • decreasing for two of the three piezometers (TG-1 and TG-2)in the original test grove and • monitoring well KP-1R.Piezometer TG-3 has a less determinate trend,with the concentra- • tions gradually rising since 2007,but below the concentrations detected in the late 1990s. Nitrate trends in deep monitoring well KP-6D have varied over the years,but showed a • steady decrease from 2007 to the present.Although nitrate concentrations have varied • upward and downward among sampling events,the overall trend in the original poplar test grove has been downward.Nitrate concentrations in shallow groundwater in the original • test grove in 2011 were generally consistent with results from the 2010 annual sampling • event. • The nonparametric Mann-Kendall statistical trend test was used to verify trends indicated • by the regression analysis on Figure 5-5.The Mann-Kendall statistic was calculated in • accordance with methods detailed in Rank Correlation Methods (Kendall and Gibbons,1990) and Statistical Methods for Environmental Pollution Monitoring(Gilbert,1987).Using ground- • water data collected from 2000 through 2011,the Mann-Kendall test concluded that there is • a statistically significant downward trend in nitrate concentrations in monitoring • well KP-1R and piezometers TG-1 and TG-2.The significance level used was 0.05.The calculated probability of a downward trend is 100 percent for well KPAR and piezometer • TG-1 and 99.9 percent for piezometer TG-2.The calculated probability of a decreasing trend • of nitrate concentrations in well KP-6D is 95.3 percent.The Mann-Kendall test results for data collected from 2000 through 2011 indicate that there is not enough evidence to support • a statistically significant trend in piezometer TG-3 (58.2 percent probability of a decreasing • trend). • Regression analyses performed on the nitrate concentration data for the three original • monitoring wells (KP-2,KP-3,and KP-4) are shown on Figure 5-7.The Mann-Kendall statistical trend test was used to verify trends indicated by the regression analyses on • Figure 5-7.Using groundwater data collected from 2000 through 2011,the Mann-Kendall • test concluded that there is a statistically significant downward trend in nitrate concen- • trations in monitoring well KP-4 and a statistically significant upward trend in monitoring well KP-3.The significance level used was 0.05.The calculated probability of a downward • trend was 100 percent for monitoring well KP-4, and the calculated probability of an • upward trend was 100 percent for monitoring well KP-3. Monitoring well KP-4 nitrate concentrations have steadily decreased from 94 mg/L in 1996 to 2.6 mg/L in August 2011. • The Mann-Kendall test results for data collected from 2000 through 2011 indicated that there • is not enough evidence to support a statistically significant trend in Monitoring Well KP-2 (78.3 percent probability of a decreasing trend). • Ammonia • The ammonia concentrations from grab groundwater samples collected in July 2011 during the Former Bagging Plant Investigation and the August 2011 annual groundwater monitor- ing event are presented on Figure 5-5. The highest concentration of ammonia detected • during the August 2011 annual groundwater sampling event,23 mg/L,was detected in a • duplicate sample from monitoring well KP-2,adjacent to the planting area north of the warehouse.Ammonia concentrations have fluctuated in Monitoring Well KP-2,but have • shown a general decreasing trend from the maximum historical ammonia concentration of • 124 mg/L in this well. During recent monitoring events,the maximum ammonia concen- tration detected at the site was in a sample from piezometer TG-2,in the original poplar test • • 56 RDD/112370001(CAH5003.00CX) • �.mazsiianronoo • • •