Laserfiche WebLink
TR-14 Revision <br /> Page 4 <br /> In addition, given the predicted neutral quality of the impounded <br /> water , the concrete mix design for durability (ie. Type V cement <br /> for sulfate resistance, pozzolan addition and low water :cement <br /> ratio) and the limestone PH buffering placed on the water side of <br /> the bulkhead Mr. Abel states, "It appears reasonable to anticipate <br /> a life for the American Tunnel Bulkhead exceeding 100 years" . This <br /> life expectancy should apply to all the bulkheads . <br /> As evidence of concrete longevity in the Sunnyside Mine, there is <br /> a concrete water door frame on I-Level. This frame was installed <br /> around 1931 when the Sunnyside Mine was sinking (mining down) on <br /> the Washington Vein and water was being pumped up the Washington <br /> Incline to dewater the workings below F-Level . This frame was <br /> submerged from around 1935 until around 1961 when these workings <br /> were inactive before the American Tunnel was connected to the <br /> Sunnyside Mine and drained the area. Even without the benefit of <br /> durability type construction as proposed in TR-14, this concrete is <br /> sound and in good shape. It is in excess of 50 years old with <br /> around 25 years of submerged conditions. <br /> Mr. Abel addresses likely failure modes for the bulkheads at the <br /> end of their functional life on p. 14-15 . The most likely failure <br /> mode is stated to be leakage causing chemical attack from the <br /> downstream face. In the case of the Brenneman bulkheads, <br /> inspection will not be possible. For this reason, twin bulkheads <br /> are to be installed to minimize the possibility of leakage. In <br /> addition, Mr . Abel ' s discussion related to the loss of bulkhead <br /> length for the American Tunnel and Terry Tunnel bulkheads apply to <br /> the Brenneman bulkheads . The F-Level Brenneman bulkheads could be <br /> reduced from 8 feet long to 5 . 8 feet and the B-Level bulkheads <br /> could be reduced from 3 feet long to 1 . 8 feet before approaching <br /> failure as plain concrete bulkheads. These reductions were <br /> calculated at the maximum possible design head. The predicted <br /> water pool elevation is in the neighborhood of 11 , 500 ' MSL <br /> elevation. If this occurs, both sets of Brenneman bulkheads will <br /> be dry bulkheads. If the water pool elevation does not exceed <br /> 11, 904' MSL elevation, there is no direct connection from the <br /> Brenneman bulkheads to surface and their failure would have no <br /> effect. If the mine pool elevation exceeds 11, 904' MSL elevation <br /> and the Brenneman bulkheads failed through seepage or the unlikely <br /> mode of structural failure, flow would increase from the Mogul No. <br /> 3 level portal . <br /> Bonding should not be an issue at the level of approval that this <br /> letter requests. If TR-14 is not approved in total , these <br /> bulkheads are inconsequential . <br />