2015-04-17_REPORT - M1977004 (2)

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Pitch Reclamation Project Colorado Mined Land Reclamation Board — 2014 Annual Reclamation Report located where the workings once day - lighted in the south wall of the North Pit. One possibility for the slow rise in water level in the vicinity of this piezometer is the continued collapse and compression of mine workings, disturbed bedrock, and material backfilled into the opened workings following mine activities, which has caused a decreased hydraulic conductivity and resulting head rise in this area. Therefore, water in the Pinnacle workings is not believed to be the cause of the slightly increasing water level in P -8 over the past seven years. Flow from the Chester Fault Zone into the North Pit Lake is measured at CFS and CFS -2, which are springs located on the south wall of the North Pit (Figure 3). The flow from CFS has been measured since fall 1999 and has ranged from 0.1 to 7.2 gpm. The flow from CFS -2 has been measured since fall 2002 and has a similar range from 0.4 to 4.4 gpm. Review of the flow measurements reveals that there is no apparent increase in the flow rate from these springs into the North Pit Lake. i Pinnacle Adit Flow The flow rate from the Pinnacle adit at PP -01 has been monitored since November 1993. The flow from the adit generally consists of a seasonal pattern of high flows during the short period of spring melt in late May or early June and stable flows of less than 10 gallons per minute (gpm) throughout the year. The spike in flows observed at PP -01 each spring are likely a result of snowmelt and runoff from surrounding sources originating between the Pinnacle plug and the' PP -01 monitoring point. Once the snowmelt period is over, the flow rate at PP -01 decreases and stabilizes at normal levels. { The adit discharge is a direct reflection to the snow pack each year. This is shown clearly on the hydrograph of the Pinnacle adit flow at PP -01 provided as Figure 5. In 2014, the snow pack was higher than the normal range compared to 2012 when the snow pack was significantly reduced and there was little pike in adit discharge. The peak flow in 2014 was 57 gpm in June compared to 20 gpm in 2013, 6.0 gpm in 2012 and 28.5 gpm in 2011 and 22.6 gpm in 2010. Dissolved radium 226 and total uranium have been I monitored at PP -01 since March 1994. After construction of the Pinnacle adit plug in September 1995, both the dissolved radium 226 and total uranium concentrations have stabilized at reduced concentrations. A graph of the radium and uranium concentrations at PP -01 is provided as Figure 6. During 2014, total uranium and dissolved radium 226 levels remained at the reduced concentrations observed over the preceding twenty -year period. 4.4 Sediment Control Embankment The safety and efficiency of the sediment embankment is monitored with a network of surface and subsurface systems. There are five permanent survey monuments where any physical movement of the embankment can be measured and nine piezometers have been installed to monitor the phreatic surface within the embankment. Five of the nine piezometers were installed during the initial construction in 1980, and four of the piezometers were completed in the core of the embankment in 2001. The 2014 monument survey was performed on July 30 and results indicate the amount of vertical movement is minimal and within the range of survey instrument error. No significant vertical displacement has occurred since the initial settlement following construction. The pond level was maintained at 9,884 ft amsl during 2014, except during the May reading, when the pond elevation had reached 9888 ft amsl.for four weeks in June. This was below the clay blanket repair top elevation of 9,885.5 ft. As a result, the water levels in the piezometers showed little response to water stored in the impoundment in 2014. 1 Because piezometer P4 is in close proximity to the seepage area noted in 2000, it is monitored closely. From 2005 to 2009 the water level in P4 was not falling back as rapidly as the other piezometers. It was noted that when the probe was pulled out of both P4 and P5 it was covered with silt. The silt build up had Pitch 2014 Reclamation Report 16April2015_Cw.Docx 1 1 25