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' Fox River Paper Compano • September 30, 2004 Addendum to 2003 Annual Groundwater-Monitoring Report Page 2 of 5 Five-Year Report (Five-Year Report, page 9, Figure 16). In other words, groundwater quality under the site is either stable or improving in 75% of all wells. For the semiperched aquifer alone, water quality is stable or improving in over 80% of monitoring wells. Those monitoring wells that have increasing trends for TDS are located near the City of Ripon's sewage-treatment pond (OB-24 and OB-25) or near the northern property boundary (OB-1, OB-2, and OB-26), and their increasing TDS trends may not be related to FR's effluent disposal. 2003 Groundwater-Monitoring Summary COC (specific conductance,TDS, sulfate, and chloride) results from the first through fourth quarters of 2003 were averaged for each monitoring well and the results were evaluated to determine which monitoring wells were in compliance with water quality maximum contaminant levels (MCLS) set forth in CCR Title 27 and the Regional Board's Water Quality Control Plan For the Sacramento River and San Joaquin River Basins (Basin Plan). Results of the evaluations are presented on Figures 12 through 15. Specific Conductance Wells OB-20, TH-5, TH-6, TH-10, and M-20-D were below the primary water-quality MCL of 700 µmhos/cm. Wells OB-17, OB-27, TH-3, and TH-8 were below the secondary water-quality MCL of 900 µmhos/cm. All other monitoring wells completed in the semiperched, upper, and intermediate aquifers exceeded the secondary water- quality MCLs for specific conductance (Figure 12). In your July 26, 2004, letter, you specifically requested an explanation for an EC spike which occurred in monitoring well TH-8. Specifically"...monitoring well TH-8 shows a significantly increasing trend in EC from the 3rd quarter sampling event (787 µmhos/cm) as compared to 4th quarter event (1,060 µmhos/cm). An explanation of this spike in EC should be included in the evaluation." Previously, EC spikes have occurred in well TH-8 during the first-quarter 2000 (1,640 µmhos/cm), the first-quarter 2002 (1,520 µmhos/cm), and the current fourth-quarter 2003. Upon analysis of the historic data for well TH-8 and for adjacent well TH-7,EC spikes in well TH-8 correlate with anomalous EC decreases in well TH-7. This suggests that the samples for wells TH-7 and TH-8 occasionally have been switched during past sampling events. The trend for EC in TH-7 (upper aquifer) is decreasing while the trend for TH-8 (intermediate aquifer) is increasing. Total Dissolved Solids Wells OB-17, OB-20,TH-5,TH-6, and TH-10 were below the primary water-quality MCL of 450 mg/L. All other monitoring wells completed in the semiperched, upper, and intermediate aquifers exceeded the secondary water-quality MCL of 500 mg/L for TDS (Figure 13). 003287.00, Task 9 Lawrence&Associates \\Powervault2\shared\Clients\FoxRiver\QuarterlyMonitoring\2003\Addendum to 2003 Annual Report.doc