2013-03-06_REPORT - C1982057 - Laserfiche WebLink

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In the Probable Hydrological Consequences (PHC, Tab 17) section of the Seneca II -W Mine PAP, predictions were made as to the expected TDS increases to be observed at various monitoring wells. The following table outlines these predictions along with this year's observed average values (annual average for bedrock wells, May- September average for alluvial wells). Well Predicted TDS values (mg /l WHAL7 -2 1299 WOV14 4365 WOV17 4295 WOV25 none WW14 2630 WW17 3002 WW25 none * indicates value above prediction This year's average TDS (mg /1) 1290 4870* 5920* 1430 5040* 810 2870 For Wadge Overburden Well WOV14, a value of 4385 mg /l was predicted, while a value of 4870 mg /l was observed this year. At this well, pre - mining (prior to November 1992 for the north area) water level (i.e., depth to water) values ranged from 65 to 90 feet deep. The water level this year, 9.80 feet, indicates that additional strata are being saturated, which may explain the elevated TDS value. For Well Wadge Overburden WOV17, a value of 4295 mg- /1 was predicted, while a value of 5920 mg /l was observed in this year. The predicted value for Well WOV17 was predicated on a 5.5% increase of the pre -- mining (prior to August 1990 for the central area) value of 4072 mg /l, which is an average of several,overburden wells. However, Well WOV17 exhibited a pre - mining TDS average value of 8043 mg /1, while the next highest TDS Wadge overburden well (WOV15) had a baseline TDS average of 3741 mg /l. Well WOV17 also exhibited a high degree of baseline TDS variability (min. = 6860, max. = 8586 mg /1). The TDS value in this year, 5920 mg /l, was below the PHC prediction using the average baseline value (8043 + 5.3% = 8485 mg /1) , and is also below a 5.5% increase of the maximum baseline TDS value (8586 + 5.5% = 9058 mg /1) . In 2008, 2009 and 2011, 8