2017-01-13_REPORT - M1977004 - Laserfiche WebLink

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Homestake 2016 Geotechnical Observations Pitch Reclamation Project Indian and Tie Camp Rock Dumps "10725 - 1 0525" Level Site Description: Identical to that of past reports for 1996 through 2015. The minor overlap between this level and other bench designations reflects the original bench configuration. The total dump thickness at Piezometer IC10525 is approximately 229 feet at this location. 2016 Observations: Piezometers IC10600 and IC10525 bound this area and like Piezometer IC10600, the 2016 water level in Piezometer IC10525 rose by 7.9 fleet. This is approximately 1.1 feet lower that the rise in the phreatic surface measured in 2015 and 2014. In 2016, the water level in Piezometer IC10525 dropped back to its normal level by late summer compared with some previous years where heavier rainfall during the summer months prevented this piezometer from dropping completely to its January level. "10600 - 10400" Level Site Description: Identical to that of past reports for 1996 through 2015. 2016 Observations: Piezometer IC10440 represented this area of the rock dump until it became non-functional in 1996. Piezometer IC10525 is also considered representative of this area of the rock dump and was described in the previous section. "10400 -10370" Level Site Description: In 1997, the face of the permanent low-grade stockpile was reconstructed on the Indian Rock Dump. The purpose of the slope reconstruction was to reduce the potential for infiltration and promote more rapid runoff from the stockpile area. This reconstruction appears to have effectively reduced seepage in this area. 2016 Observations: In 2011, replacement Piezometer IC1037OR was completed approximately 67 feet west of the location of Piezometer IC10370. The piezometer was terminated at 208 feet below ground surface (bgs) and completed with an 8 -inch steel protective casing and set in concrete. Upon completion, a transducer was installed in Piezometer IC1037OR to assist in monitoring water levels. In 2012, the water level elevation in Piezometer IC10370R rose by 7,1 feet in the spring and fell back to an acceptable range by late summer. In 2013, the water level rose by 10.9 feet during the spring snow melt and lost approximately 5 feet of that gain by the end of the year. The increase in water level in 2013 compared with 2012 was attributable to heavier snow pack and higher summer precipitation in 2013. The same trends were observed in 2014, when the water level in Piezometer IC1037OR increased in elevation by 11.4 feet between January and June. In 2016, the phreatic surface rose 5.55 feet, which was like the 2015 observations. Piezometer IC10360, is also located in this bench had a water level increase of 8.75 feet in the spring_ This rise compared with a 6.52 and 7.68 feet rise in 2015 and 2014, respectively. This condition is like that of the other piezometers in the Indian Rock Dump, and reflects the seasonal snow pack in the area, "10300 -10100" Level Site Description: The Indian Rock Dump was regraded in 1994 following procedures approved in the February 1994 Technical Revision, During 1995, several minor, localized areas of slope instability were noted, corrected, and reported in the 1995 Annual Geotechnical Report. Homestake Pitch Reclamation Project Page 3 2016 Annual Geotechnical Report December 31, 2016 M-1977-004HR 2016 AnnualGeotechnicalReportText Flnal.doc