2017-01-13_REPORT - M1977004 - Laserfiche WebLink

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Homestake 2016 Geotechnical Observations Pitch Reclamation Project Indian Creek and Tie Camp Waste Rock Dumps Homestake Pitch Reclamation Project 2016 Geotechnical Observations Indian and Tie Camp Rock Dumps 1. Indian Creek Rock Dump "10800" Level Site Description: Identical to that of past reports for 1996 through 2015. 2016 Observations: The 2016 observations were the same as reported for this area over the past 19 years when this area was regraded to provide improved surface drainage. Visual inspection of the area in 2016 revealed no evidence of settling or slumping of the rock dump material and the drainage channels are functioning as designed. The drainage on the western side of the upper portion of the Indian Rock Dump, just above the sericite stockpile, where the rock dump intersects native ground, had undergone minor erosion_ In 2012, a low gradient diversion ditch, oriented roughly perpendicular to the main channel, was excavated allowing water from the channel to be diverted and dispersed at lower velocities. Boulders were placed above the steep section of the channel and rip -rap was placed below the boulders. The boulders and rip -rap function as energy dissipaters, such that flow velocities are reduced and sediment retention is enhanced. Observations in 2016 indicate that this repair appears to have corrected the erosion issue. The area will be visually inspected after snow melt and heavy precipitation events. "10780 —10650" Level Site Description: Identical to that of past reports for 1996 through 2015. 2016 Observations: The 2016 observations in this area were like past observations. Visual inspection of the area revealed no evidence of settling or slumping of the rock dump material. The drainage channels are functioning as designed. "10650 -- 10600" Level Site Description: Identical to that of past reports for 1996 through 2015. 2016 Observations: In 2016, like previous years, the water elevation in Piezometer IC10630 rose by 6.95 feet from April through June, and then dropped back to its normal range by the end of August. As noted in previous reports, in October 2001, an obstruction was removed from Piezometer IC 10600, allowing it to be used for the collection of water level data. The rise in the phreatic surface in this piezometer reflects the difference in snow pack from year to year, but has always fallen back to its normal range by the end of summer. If the area receives heavy summer rain, the phreatic surface takes longer to fall back. For example, between 2007 and 2011, the water level increased between 6.5 to 12.5 feet in May through June, which is indicative of heavier snow pack and increased summer rainfall. In 2016, the water level increased by 5.5 feet from May through June, and then fell back to its normal level by July. During the same period in 2014, the water level elevation rose by 11.8 feet. Homestake Pitch Reclamation Project Page 2 2016 Annual Geotechnical Report December 31, 2016 M-1977-004HR 2016 AnnualGeotechnicalReportTexl Final.doe