2012-04-19_REPORT - M1977004 (2)

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Pitch Reclamation Project Colorado Mined Land Reclamation Board — 2011 Annual Reclamation Report early June and stable flows of less than 10 gallons per minute (gpm) throughout the year. The measured peak flow for the 2011 season was 28.5 gpm on June 15, 2011. This was consistent with the peak discharge in 2009 of 29.2 gpm and 22.6 gpm in 2010 and consistent with higher snow packs at the site since 2005. A hydrograph of the Pinnacle Adit flow at PP -01 is provided as Figure 5. 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. 4.3.4 Radium and Uranium Concentrations at PP -01 Dissolved radium 226 and total uranium have been 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 2011, total uranium and dissolved radium 226 levels remained at the reduced concentrations observed over the preceding fifteen -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 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 2011 monument survey was performed on September 24 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. In 2011, the highest water level in the pond of 9890.0 amsl occurred on June1 and dropped back down to the 9884.0 elevation by June 27 and remained at the level through the rest of the year. As a result, the water levels in the piezometers showed little response to water stored in the impoundment in 2011. In 2011, the water level in Piezometer P1 in the upstream face of the embankment rose by 12.90 feet compared with 15.45 feet in 2009 when the pond level reached 9891.0 amsl. In response to the higher water levels in the pond since 2005, the maximum water level in Piezometer P3 increased from 9863.56 to 9866.02ft. amsl, representing a rise of 2.46 feet. The water level in P3 increased by 3.61 feet in mid June and dropped back to the normal ranged by the end of summer. In contrast, from 2004 through 2010, the maximum water level in Piezometer P4 decreased from 9831.1 to 9829.3 ft. amsl, a drop of 1.8 feet. In 2011, the water level in P4 increased by 1.52 feet. Because P4 is in close proximity to the seepage area noted in 2000, it is monitored closely. Over the previous five years it was observed that 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 the P4 and P5 they were covered with silt. The silt build up didn't allow the pipes to drain sufficiently to show the phreatic surface in the embankment. In an attempt to remedy the problem, in July 2009 both piezometers P4 and P5 were flushed with high - pressure water in an attempt to minimize the silt and other debris that had built up in the standpipes. The high pressure flushing resulted in the water levels in both piezometers falling back to normal levels within a few days in 2009, with the average water level in P4 dropping by more than 3 feet. Piezometer P5 also fell back rapidly after being flushed. In 2010, the maximum water elevation in P5 was 2.46 feet, below the maximum elevation of 6.7 feet in 2009. The 2011 maximum water levels in the embankment piezometers P6, P8 and P9 also decreased from levels over the past four years. Only P6 Pitch 2011 Reclamation Finalreport 19Apr12.Doc 15