2006-02-15_REVISION - M1983141 (2)

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07/11/1996 10:37 303-24.04 MINERALS 8 GE.G~iY PAGE 03 b. Partial vsrsns full replacement. The operator her assumed that only partial failure of the bulkhead seals would occur. However, given the apparent lack o! ampirioal data oa the long term performance o! this typo of bulkhud seal, sad the trmeadous preeaures acting on the seals (the Lmerieaa Tunnel real is partioular), it would ram prudent to iaolude costs' for ooa~lete recoaetruation o! the bulkhead seals, inoluding astablishiag colfar dear sad/or water divrriaar, 1001 loan building sad bracing, sad placing dabri^ sareeas sad limestone. 11s I recall, soae o! the periodic •blowouts^ of the 1-rgo Tunnel is Idaho Bpriags were quite spectacular sad aptly demonstrated the sffeats of the tremendous forcer generated by release of water that had built up is the tassel. euah lorce^ would ream to ba capable of completely destroying the bulkhead(s). 2. Titaael rehabilitation aoatr. ]lithough I do sot have say ialormatioa is our Durango ofEiae filer showing bow far Eras the surface the scale are located is the uadergrouad workings, it would ^eem prudent to iaciude costs for possible tuaasi rehabilitation work that may be accessary to ensure safe sad efficient aeoess baok lato the rorkinga by a contractor to re- iastall bulkhead rule. The condition o! the tassels may Lava deteriorated (rock falls, sludge/sediment/debris deposition oa tassel !loos) to soma natant over time after the tassels have bees closed, flooded, sad no longer maiataiaed. 1-dditionaliy, there may be coma specific ltBfL requiresteat^ associated with re-opeaiag the tassel that may result is additional sorts to a Division hired contractor. I! electrical power is nsceeaary~ sad aaaaot be provided with portable generators due to possible 7f8H~ rsstriatioaa, there may be additional cost^ aseoaiated with providing electrical power to the iaetallatloa sites. 3. lteplacassnt of upper seals. l-lthough I do sot have all of the dasiga sad iastallatioa iaformatioa for the seals is the Durango Olfiae files, I know there were additional bulkheads (i do sot know how many) installed behind the main seals. It would ram reasonable to assume that failure of the main bulkhead may result in part frog failure of the upper seal(s) which would cause additional pressure to b• exerted on the lowermost seal, causing it to !ail. If this wire to occur, the upper realm would probably seed to be replaoad is order to maintain the integrity of the satire sealing systm ss originally designed. The cost of replaeiag the upper meal(s) would involve both the direct bulkhead re-iastallatioa costs plus additional cots for further tassel rehabilitation, hoist refurbiahlag or rsplaceaeat, sad possible rxpaasion/aztrasion of the ventilation syitam. 4. ~dditiaaal camtraetor costa. 6inee thin work is fairly specialised, it is doubtful that qualified contractors would be located near the project rite. This would lik.ly result lsi hlghar mobilisation/demobilisation coats which do not appear to have bare laaluded is the operator's estimate. additionally, since it it assumed that the surlaae lacilitie^ will have bees partially or