2017-04-14_REPORT - M1977004 - Laserfiche WebLink

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Pitch Reclamation Project Colorado Mined Land Reclamation Board—2016 Annual Reclamation Report each spring are a result of snowmelt and runoff, likely from sources originating between the Pinnacle plug and the PP-01 monitoring point. To some extent, the magnitude of the observed flow is correlated with the extent of snow pack;for example,the peak was especially low in 2012 and 2013 following a particularly dry period in early 2012, which exhibited minimal spring snow pack. Spring peak flows increased in 2014 through the present. However, note that the precise magnitude of the spring peak flow is not necessarily reflective of the maximum flow, since high-flow conditions occur over a short period, and the timing of the flow measurements doesn't necessarily coincide exactly with peak flow. Once the snowmelt period is over, the flow rate at PP-01 decreases and stabilizes at normal levels. 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 (Figure 8). During 2016, total uranium and dissolved radium 226 levels remained at the reduced concentrations observed over the preceding twenty- year period. 4.4 Sediment Control Pond Embankment In 1980, an approximately 80 ft high earthen embankment was constructed below the confluence of Indian and Tie Camp drainages to allow settlement of suspended solids from surface water prior to its release to Indian Creek. The safety and efficiency of the Sediment Control Pond 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 2016 monument survey was performed on August 30 and results indicate the amount of vertical movement is minimal,within historic levels, and within the range of survey instrument error. There was no significant vertical displacement in any of the monuments located on the crest of the embankment in 2016. Piezometer water levels in 2016 increased in some piezometers and decreased in others compared to 2015. Due to lighter than normal snow pack the past two years,the pond water level was maintained below the 9885.5 elevation repair except for three weeks in May of 2016. The results were noted in slight water level increases in most piezometers for a short period in 2016. The outlet pipe on the embankment was monitoring closely in 2016 to assure it is flowing freely. The monuments will be surveyed again in late summer or early fall of 2017 and the piezometers will be monitored monthly or more often if it is necessary to store water above the 9885.5 ft amsl level.All piezometers will be inspected for silt build up in 2017 and pressure flushed as necessary to eliminate a buildup of silt. Because piezometer PZ-4 is in close proximity to the seepage area noted in 2000, it is monitored closely. From 2005 to 2009 the water level in PZ-4 was not falling back as rapidly as the other piezometers. It was noted that when the probe was pulled out of both PZ-4 and PZ-5 it was covered with silt. The silt build up had not allowed the pipes to drain sufficiently to accurately reflect the phreatic surface in the embankment. In July 2009 both piezometers PZ-4 and PZ-5 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 over the past two years, with the average water level in PZ-4 dropping by more than 4 ft. In 2015, the water level rise in P4 was small due to the water level in the pond being kept below the elevation of the repair. In 2016,the water in the pond increased to 9888 ft amsl elevation for approximately a couple of weeks in May due to snow melt with little rise in the water level in PZ-4. The flushing of PZ-7 and PZ-8 in late 2015, along with clearing of the drain line in 2009 continued to keep water levels low in the downstream and toe section of the embankment. In 2016, with precipitation the lowest in the past three years, the piezometer levels were down relative to 2015 and 2014. In 2014, the 22