2012-02-21_REPORT - C1980001 (4)

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2.0 HYDROLOGIC MONITORING NETWORK The existing monitoring network is a modification of the network used during baseline monitoring. Continuous streamflow was historically collected from two sites (TR -a and TR -b) on Trout Creek from May through October. TR -a was located above the mine and TR -b was located below the Moffat area. Surface water quality samples were historically collected above and below the mine at TR -A and TR -D, respectively. Additional historic surface water sampling sites along Trout Creek were TR -B (located adjacent to the East Ridge area) and TR -C (located adjacent to the Moffat area). Surface water flow monitoring sites TR -a and TR -b and surface water quality monitoring sites TR -A, TR -B, TR -C and TR -D were discontinued September 2, 2009 in accordance with TR -48. All surface water sites had been removed from the monitoring network prior to 2011 (Plate 1). This report does not replicate data collected prior to 2011; therefore the Surface Water section has been removed. Ground water levels were historically collected from 10 wells (215W, 215L, 218W, 218L, M892S, M892L, TR -1.5, TR -3, TR -4 and WR -1). Ground water quality was historically collected from 5 wells (TR -1.5, TR -3, TR -4, WR -1 and TCS -1). Three wells were completed in the alluvium along Trout Creek (TR -1.5, TR -3 and TR -4) and one well was completed in the spoils (WR -1) located at the base of the West Ridge area. An additional water quality well was completed in the Trout Creek Sandstone (TCS -1) monitored downdip of mining activity. Additional ground water levels were collected from six wells (215W, 215L, 218W, 218L, M892S and M892L) located in the Moffat area. Monitoring wells 215W, 215L, 218W, 218L, M892S and M892L were discontinued September 21, 2007 in accordance with TR -47. Monitoring wells TR -1.5, TR -3, TR -4, WR -1 and TCS -1 were discontinued September 2, 2009 in accordance with TR -48. All ground water sites were removed from the monitoring network prior to 2011 (Plate 1). This report does not replicate data collected prior to 2011; therefore the Ground Water section has been removed. 2.1 CPDS Monitoring Monitoring of point discharge waters from sedimentation impoundments is accomplished under Colorado Department of Public Health and Environment (CDPHE) Colorado Permit Discharge System Permit (CPDS) CO- 0032638. Copies of required Discharge Monitoring Reports (DMR) are provided to the CDRMS under separate cover, and are included in this report by reference. All discharges during this reporting period were in compliance with effluent limits except for the following: DMP 007 exceeded the 30 -Day Average for Effluent Flow in May 2011. The Effluent Flow exceedance is attributed to run -off from an above average snowfall year, resulting in above average flow events. Natural Resources Conservation Service (NRCS) data for Site 709 at Rabbit Ears corroborates this assertion. The May 29, 2011 Accumulated Precipitation was 20 inches above, or 150% of, the 1971 to 2000 water year -to -date average. The May 29, 2011 Snow Water Equivalent was 25 inches above, or 267% of, the 1971 to 2000 water year -to -date average. Since the CDPS was renewed, with an effective date of July 1, 2007, there have been three 30- /y• V V Y VCENGINEERING Page 2