2004-05-03_REPORT - M1977004 - Laserfiche WebLink

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Pitch Reclamation Project 2003 Annual Reclamation 4.3.2 Groundwater Levels April 29, 2004 Page 10 Seven piezometers were installed in the area of the Pinnacle Mine to monitor the piezometic surface within the workings area behind the adit plug. The piezometers are identified as P4 through P10. Piezometer P7 was installed as a replacement for P6, which was lost during plug grouting/construction. The locations of these piezometers are provided in Figure 3. All seven piezometers fluctuate seasonally with the highest levels in late May or early June. The water levels are sympathetic with snowmelt and large precipitation events and decrease to stable levels after these events. During 2003, the phreatic surfaces in all piezometers showed a comparatively normal spring cycle following the reduced level of fluctuation observed in spring 2002, probably attributable to the below average precipitation experienced in the region during 2002. In 2003, the seasonal low water levels observed in P-7 and P-10 have resumed the gradual upward trends that have been observed since 2000. Low water levels in these two wells in 2003 were slightly lower than, those observed in the preceding two-year period likely due to the drought conditions. A hydrograph of the piezometer water levels is provided in Figure 4. 4.3.3 Pinnacle Adit Flow The flow rate from the Pinnacle Adit at PP-01 has been monitored since November 1993. The flow from the adit remains in 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 measured peak flow in 2003 was 35.1 gpm on May 28, 2003. The average flow for 2003, excluding the peak flow of May 2003, was 7.4 gpm. A hydrograph of the Pinnacle Adit flow at PP-01 is provided in Figure 5. Water management practices employed at the Pitch site include storing additional water in the North Pit Lake during the spring thaw. This seasonal practice results in the elevation of the North Pit Lake water level rising by several feet during May and June. The purpose of this practice is to aid in control of total suspended solids in surface waters on the site, which may become elevated during the spring snow melt. The Pinnacle Adit discharge point PP-01 is located just down gradient of the North Pit Lake. As shown on Figure 5, the discharge at PP-01 increases every year in June. It is theorized that there is a hydrologic connection between the North Pit Lake at the higher water elevation and the Pinnacle Adit, causing increased flow at the PP-01 discharge point. snowmelt and runoff from other surrounding sources, originating between the Pinnacle plug and the PP-01 discharge point, may also contribute to the seasonal pattern. Once the snowmelt period is over, water is released from the North Pit Lake, the water level drops back to the original elevation range, and the discharge at PP-01 returns to 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 in Figure 6. During 2003, total uranium and dissolved radium 226 levels remained at the reduced concentrations observed over the preceding seven-year period. No elevated uranium levels, such as that observed in June 2001, were recorded in 2003.