northspur

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The North Spur Stabilization Plan in 1999 SNC Final Feasibility Study : 2 e) North Spur Stabilization It is recommended that the north spur be stabilized by: - lowering the groundwater table in the downstream part of the spur by the installation of additional pumpwells in the line of pumpwells installed in 1982, with the final pumpwell spacing selected based on the existing subsurface conditions and the performance of the existing pumpwell system; - provision of toe relief drains and a major drainage trench for further lowering of the water table; - provision of downstream erosion protection and downstream stabilizing fill in selected areas to improve local toe stability and eliminate potential for retrogressive failures due to presence of sensitive marine clays in the Upper Clay unit; - local top cutting of the spur and unloading of portions of the high, steep downstream side slopes to improve local stability; and - provision of erosion protection and a stabilizing upstream berm to prevent raveling of the upstream slopes from reservoir wave action and eliminate the potential for sliding in the unlikely (but possible) event of rapid drawdown during future project operation. 38
WHY ARE GLACIO–MARINE CLAYS SO DANGEROUS ? Glacio-marine clays (also called “Quick Clays”) have very peculiar properties. Most importantly, it only takes a small disturbance to turn them suddenly from a solid to a liquid. 39
Page 1 and 2: The North Spur Quick Clay Instabili
Page 3 and 4: NOTE ON SOURCES The following prese
Page 5 and 6: Overhead view of North Spur showing
Page 7 and 8: What is the North Spur ? The North
Page 9 and 10: • The previous slide shows on the
Page 11 and 12: Overhead view of North Spur showing
Page 13 and 14: Nalcor Depiction of the Muskrat Fal
Page 15 and 16: In February 1978, a large landslide
Page 17 and 18: General Overview of Muskrat Falls i
Page 19 and 20: 1988 - 10 years after the 1978 Nort
Page 21 and 22: View in 2007 showing line of pumpin
Page 23 and 24: The SNC - AGRA Final Muskrat Falls
Page 25 and 26: Unfortunately the critical Jacques
Page 27 and 28: 1979 Hydro Contour map of the North
Page 29 and 30: GLACIO-MARINE CLAY: Source of the N
Page 32 and 33: North Spur Soil Conditions As can b
Page 34 and 35: Borehole Results on the North Spur
Page 36 and 37: SNC- AGRA’s 1999 North Spur Plan:
Page 40 and 41: Clay on the downstream side of the
Page 42 and 43: “Quick Clay” conditions caused
Page 44 and 45: Nalcor’s Bank Stability Study of
Page 46 and 47: NRCan ‘s concerns came under four
Page 48 and 49: The Joint Review Panel (JRP) also a
Page 50 and 51: The 2008 SNC report filed by Nalcor
Page 52 and 53: The filling of the Muskrat Reservoi
Page 54 and 55: In February 2010, a major landslide
Page 56 and 57: View of February 2010 landslide are
Page 58 and 59: In August, 2010, Nalcor Energy, res
Page 60 and 61: On August 30, 2010, the JRP asked N
Page 62: The Norwegian Geotechnical Institut
Page 70 and 71: On March 9, 2011, the Joint Panel s
Page 72 and 73: Nalcor North Spur Technical Note On
Page 74 and 75: The Nalcor North Spur Technical Not
Page 76 and 77: Nalcor’s “Technical Note” sta
Page 78 and 79: On December 17, 2012 Nalcor sanctio
Page 80 and 81: SNC Lavalin seeks Package Leader -
Page 82 and 83: What is Nalcor/SNC Lavalin’s Nort
Page 84 and 85: How the 2013 North Spur Geotechnica
Page 86 and 87: And there may be an additional, and
Page 88 and 89:
Google Earth image of area upslope
Page 90 and 91:
NRCan slide on liquefaction 90
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