Laserfiche WebLink
a <br />Letter to Anne Beierle -2- October 2, 1996 <br />haulage tunnel inflows are derived from sources located in the 1000 feet <br />of tunnel west of the bulkhead location. Is this the case? How will <br />tunnel inflows west of the bulkhead location be managed? Are the 200-300 <br />gpm tunnel inflows diffuse, or are they from a few specific primary <br />locations? <br />4. The cost for water treatment provided in the TR-006 submittal are <br />based on a projection of 600 gpm inflow to the treatment system. The mine <br />currently produces water at a rate of 1000 gpm, and CMC projects that this <br />rate may increase to 1500 gpm as lower working are developed. Although <br />it is logical to assume that water generation will decrease upon flooding <br />of the workings to the 8100' level, the amount by which inflows will <br />decrease has not been adequately evaluated or modelled to justify CMC's <br />600 gpm projection. Unless this inflow rate can be better justified, it <br />is the Division's opinion that the amount of bond required for water <br />treatment should based on the current and established inflow rate of 1000 <br />gpm. <br />5. In Section 2.3.2 of the TR-006 submittal it is stated that it will <br />take a minimum of 9 years for the mine pool to reach the tunnel portal <br />elevation of 8948', therefore, it is expected to take a minimum of 4 years <br />for the mine pool to reach the 8100' level when pumping and treatment <br />would again be required. The estimate of 4 years to flood the workings <br />up to the 8100' level assumes that the rate of elevation gain of the mine <br />pool is linear between 7500' and 8948' of elevation. Would not, in fact, <br />the rate of elevation gain for the mine pool by relatively rapid between <br />7500' and 7700', then slower above 7700' where there is a greater <br />proportion of mine voids? And would not the effect of rapid mine pool <br />rise over the first 200' potentially result in a mine pool rise to the <br />8100' level in significantly less than 4 years? <br />6. As stated in item #1 above, a design for the proposed haulage tunnel <br />bulkhead is not needed at this time. However, a few basic details need <br />to be clarified so that bulkhead installation costs can be estimated. <br />(a) It is stated in Section 2.3.1 of the TR-006 submittal that the <br />design pressure for the haulage tunnel bulkhead is 350 psi assuming <br />worst case flooding to the elevation of the Henderson Mine glory <br />hole. The Division's evaluation of design pressure at the bulkhead <br />is as follows: <br />Red Mountain Elevation <br />West Portal Elevation <br />Bulkhead Elevation <br />Head @ bulkhead <br />Pressure @ Bulkhead <br />12,315' <br />8948' <br />8918' (plug is 1000' inby of <br />portal @ 3$ down <br />grade) <br />12,315' - 8918' = 3397' <br />3397' x .4331 psi/ft. = 1471 psi <br />Unless CMC can better justify use of a different pressure head, it <br />