The Daily Alaska empire., 1932-09-28
AL ASKAlP JUNEAU. STORY IS TOLD.
 BY MINE STAFF.
P. R. Bradley Says Outlook Points to 5000 Tons
 Daily from Depth
(Continueu rom Page Che,

Fl NAOutAAfbSAf AAVAAA a346St \$SlCJ 'tft. apart vertically, and in con. \ fcrmance with this arrangement the 1,O00-ft. level will be made the
 first main hau1age level. The us- ual intermediate levels will h< |tdriven for access, service, and con-
 venience, but ore will be trammed
 to the main shaft on the even
 thousand foot levels only.
 For stoping, the shrinkage meth
 od will be used, and stopped will
 be started simultaneously from sev-
 eral levels in the block between the 1,000-ft. level and Gold Creek Etunnel. Broken ore will be passed
 to the main haulage level either from stope to stope or through transfers. Dimensions of the stopes
 and of the pillars have not been
 finally decided upon, but, from what is now known, stopes 50 ft, Hong by 50 ft. wide, with Soft, Epillars intervening, would seem to meet requirements best. The bot tom of the first stope will be at Ia point about 50 it. above the 1 ], ,00O- it. level, and the top of the upper stope in this block will be 100 it. below the Gold Creek tun- mel level, leaving that level protect ed by a sheet pillar 100 it. thick. Ore to be broken in the stopes will therefore be much less than so per cent of the total volume,
 but eventually, the pillars will be blasted and the entire mass allow
 ed to cave along with the lower
 grade hanging-wall areas There after, operations will be quite sim
 liar to the present methods used
 in mining the ore, above Gold
 Creek tunnel level By following
 this program, ore remaining in the
 pillars will eventually be mined
 and delivered to the shaft at a cost less than that for mining ore
 in the shrinkage stopes. <, Much study was given to the hauling of ore to the main shaft, Handling of ore at the shaft, and the transfer of ore at the top of the shaft for transport to the mill. To obtain the cheapest stop ing costs. rock should be handled in large pieces, but if these pieces are too large, additional expense is incurred in tramming and trans ferring at the shaft. Gazing yer sus skip hoisSing was considered, but shaft of sufficient diinen- sions to handle 1o-ton ore cars, standard mine equipment, was deemed altogether too large and Underground crushing in connection with skip floistins was also given Consideration, and rejected because of the expense in volved. I 2 The aforesaid subjects were view ed in terms of Alaska Juneau ex- perience in handling large pieces of ere through ore. passes, through chutes, into cars, and to the mill. This experience has perhaps been uriqle, and has resulted in the | development of equipment and a system of handling that are son1e- what out of the ordinary. Rock is delivered to the ore pass through grizzlies, with bars spaced at 27 in. on centers. chdte-ga equip ment developed at the. mine worked out so satisfactorily that decis- lon was made to use standard skip -hoisting methods, and to rely | on locally developed methods for | large material, thus Saw ing the expense of an underground ! installation.
 "Main-hoist design and specifi cations are being studied, but no details have as yet been develbped to the point where they would provide material of interest for publication. f .g s,se s
 'sAll plans and cost estimates for mining deep-level ores in the Alas ka a-Juneau mine have been made | after a close study of mining prac- bices, costs. and experience at the Alaska Treadwell mine, on Doug las Island. The two properties[ are similar in general aspects. but preseiat1day Alaska Juneau methods nave many advantages over the Alaska Treadwen operations, which,, ceased fifteen tears ego. A de- 'cription of. the differences thct affect costs, capacities, and output, iollows:
 At Alaska Treadwell the haul E lge levels were spaced l5o 1t. apart mo each level was a separate min ng operation. At Alaska. Juneau; ne haulage levels will be spaced 1000 1t apart, with intefmedfate evels tor service only. In Alaska fieadwell shrinkage stopes, drill ng was with two-men piston drills: ne ore was bulltozed -or s3edgedl n the stepes down to "a spermissa- ne size for, passing through load. | ng cnuoes into lh-ton cars. Thess ars were dumped at the shaft sta, l. lon on flat grizzlies spaced at 12 D. where the ore was again lsiedg- ; q q yo 2 size that would facilitate |anonng into and out of skips. Att Ilaska Juneau the drilling will ba q l014e 5hu r,,os3a,-, 1-o- "