2014-11-17_PERMIT FILE - C1982056 (2)

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Wolf Creek Reserve Groundwater Investigation Work Plan March 6, 2014 Site water Levela: and ".Fleid`. Param tees °t ; _ `: , .1)V ter . aiity' 1 9 F`r+�u6ri�y- „” P6riad3o # "1e4t�+�;; gtileia'syr .. Fie, �.... Phi l a,o`R6card 95M001 Annual 1995 -2012 Bi- annual 1995 -2012 97012TC Deactivated 1997 -2002 Deactivated 1997 -2002 97013TC Annual 1998-2013 Bi- annual 1998-2013 FBR -2 -E Annual 1995-2013 Bi- annual 1995-2013 Fish Creek Sandstone 91 M001 Semi - annually (WL o 1992-2013 Annual 1992 -2002 91 M004 Semi -annu lly (WL o 1992-2013 Annual 1992 -2002 Ashley Semi - annually 1996-2013 Annual 1996-2013 Water Levels Dewatering activities for mining of the Wadge Seam have removed groundwater from the Wadge overburden and lowered potentiometric surface elevations in the Wadge Overburden, starting in the mid- to late - 1990s. The declines were not uniform, nor did they occur at all locations. Of the three overburden monitoring wells closest to the Wolf Creek Reserve, Well 008 -77 -58 to the east has remained relatively steady since its installation in 1979, Well 93M001 to the south declined continuously from 1995 to 2002 but has since remained steady, and Well 91 M006 to the west has exhibited declines since its installation in 1991. The two other monitored overburden wells, 006- 82 -74C and 009 -79 -4, have maintained relatively steady water levels since a recovery period in the early to mid- 1980s. Water levels in the overlying Twentymile Sandstone show mining - related water level responses. Water levels in Well 97013TM north of the Wolf Creek Reserve have shown an overall decline since 2001, with an interim period of relatively stable water levels. Water levels in Well 006 - BRDH -7 south of the Wolf Creek Reserve rose between 1986 and 2000 and have since declined by about 20 feet. Water levels in Well FBR -2 east of the Wolf Creek Reserve were steady from its installation in 1995 until 2002, when nearby mining may have caused a decline of about 190 feet between 2002 and 2005. Since 2005, the water level in FBR -2 has recovered about 120 feet. Water levels in the Trout Creek Sandstone are monitored in three wells southwest, one well east, and one well north of the Wolf Creek Reserve area. Water levels in the southwestern wells appear to have been affected by pumping for potable water supply more than directly by mining activities. Water levels in Well 001 -83 -106 (the facility water supply well) and Well 001 -83 -107 began to decline in the late 1980s and early 1990s, respectively, as mine personnel water use increased. Water levels in Well 95M001 declined from the well's installation in 1994 until they appeared to stabilize in 2002, and again declined in 2007 through 2012. The declines may have been influenced by the underground mining operation, although the water supply well is updip and upgradient of well 95M001. Water levels in Well 97013TC north of the Wolf Creek Reserve were stable until declines began in 2002, stabilized in 2004 through 2010, and have since declined as the area was mined through. Well FBR -2 -E along the eastern permit boundary exhibited consistent water levels until early 1999, dropped about 50 feet, and immediately stabilized, with consistent water levels at the lower depth to date. The reason for the drop was not apparent, although many historical boreholes and some faulting exist in the general vicinity. No significant inflows from the Trout Creek formation into the mine workings have been encountered to explain water level changes or to suggest that dewatering of the formation is directly attributable to mining activities. TETRA TECH