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E <br />• <br />• <br />Three wells monitor the Sage Creek alluvium. Well WSAL12, located on <br />Sage Creek adjacent to Surface Water Site SW-S2-FG4 (WSSF3), is <br />downstream of all mine discharges on Sage Creek. TDS values at this well <br />had been increasing since it was drilled in 1990. Well WSAL13 is located <br />below NPDES 009 on the northern Sage Creek tributary (this NPDES site, <br />constructed in 1991, started flowing for the first time ever in 1996). <br />There is often not enough water to sample in this well, but there was <br />enough this May. This well displays a decreasing TDS trend. Well WSAL14 <br />exists on the southern Sage Creek tributary below NPDES 015 (constructed <br />in August 1999, first flow February, 2000). Monitoring was resumed at <br />this well in may 1998 after being discontinued in October 1995. It <br />displays a decreasing TDS trend. <br />In the Probable Hydrologic Consequences section (PHC, Tab 17) of the <br />Seneca II-W PAP, predictions were made for the May-September average TDS <br />values at various alluvial wells. In the 006 Gulch alluvium at Well <br />WHAL10, a value of 3394 mg11 was predicted, while a value of 3040 mg/l <br />was observed this year. In the Sage Creek alluvium at Well WSAL12, a <br />value of 972 mg/1 was predicted, while a value of 635 mg/1 was observed <br />this year. <br />The May-September average TDS value measured this year in the Hubberson <br />Gulch alluvium at Well WHAL7-2 was 1483 mg/1, while the predicted value <br />was 1299 mg/1. The value observed was determined gravimetrically (i.e., <br />dry a water sample and weigh the residue). According to Hem (1989, pg. <br />157), it is not uncommon for water high in calcium and sulfate <br />concentrations to yield a residue after drying an hour at 180°C that <br />exceeds the computed dissolved solids by several hundred milligrams per <br />liter" and also, "In many instances, especially if the concentration is <br />greater than 1000 mg/l, the calculated dissolved-solids value may be <br />preferable to the residue-on-evaporation value". The calculated <br />dissolved solids value is determined by adding up all the concentrations <br />for all of the various dissolved constituents. For May-September 2008, <br />the calculated TDS average value is 1383 mg/1. However, as previously <br />5