Overview
Sun. Dec. 12
My 6th visit to Mangahao. Clif + I walked down to Arapaepae Road and met the taxi (driven by Mr. McFarlane) and rest of party (Elsdon Clarke, Miss Cameron, Miss Jean Murray + Messrs Turner + Willowby) at 7.30 am. Reached the temporary power-house on banks of the Mangaore St[rea]m at 8.10, + left car at this point on account of open culvert across the road. The temporary power-house is now nearly completed with the machinery installed + a pipe-line evidently to
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conduct compressed air runs up the valley to the Mangatangi junction – a new ferro-concrete + wooden bridge has also been erected across the Mangaore + the excavations on the spur above for the future pipe-line of the hydro-electric scheme appear to be finished. Leaving the car to follow later, we proceeded on foot up the Tokomaru Valley Road, passed the “1st house” + took the spur track over the hill. ¼ pl[ate] photo (1) of party ascending track just above the road, Mangatangin valley-bottom below. Reached the timber train saddle at 9.45 + descended to the Main Camp. Proceeded along the service road. The car joined us again when we had gone about ½ mile past Main Camp. ¼ pl. photo (2) of car + party on log alongside road. We continued our walk, the car preceding us empty. Saw a new tramline leading down to the sawmill which is cutting the timber for the various buildings, bridges, scaffolding +c [etc] which will be required during the construction of the works. We also saw two small caterpillar tractors which are used for haulage along the service road. Mr. Joe Dunn + the two Webb brothers of Piaka Road, + on their first visit to
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Mangahao, joined us near Hilltop Camp. On reaching the top of the steep incline leading from the terminus of the service road down to the Mangahao we found the jig tramway installed, the descent being about 450 f[ee]t + the grade about 1 in 2. An excellent zig-zag track leads down to the river on the northern side of the tramline. W. Bird came along at this juncture + we discussed the structure of the No. 1 Gorge – to my surprise I found that he had come to the same conclusions as myself as to the structure of the gorge (see drawings made Jan. 11. 1920), but he believes the old filled gorge to be an earthquake crack + the present gorge to be the former locus of soft clayey [sic] material since washed away by the river – these ideas are of course quite erroneous. We descended the zig-zag and reached the Mangahao at 11.45. The changes on the vicinity of No. 1 Gorge are so great that the spot is almost unrecognisable: a small power-house has been erected at the foot of the jig tramway + a benched track runs past it to the tunnel site; a small suspension bridge now spans the upper end of the gorge + a good deal of the surrounding bush has been felled especially on
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the right bank on the face + flat top of the high level terrace. ¼ pl. photo (3) of No. 1 Gorge showing power-house + bridge, looking down stream from the future tunnel entrance. Crossed bridge and took ½ pl. photo (4) of the jig tramway from the right bank of the river. The party assembled on the river-bank just above the gorge and we partook of an excellent [sic], the hot tea being provided by a friendly workman. ¼ pl. photo (5) of party at lunch. Climbed to top of high-level terrace + took another ½ pl. photo (6) of jig tramline. A track for a tramline has been cleared along the top of the high-level terrace from the suspension bridge to a point opp[osite] the future tunnel entrance + it seems probable that another bridge is to be erected across the river at this spot to carry rock debris from the tunnel to the dam to be used in the concrete for that structure. On the top of the high-level terrace, on right bank alongside No. 1 Gorge, 5 or 6 pits are being sunk to test the ground for the foundations of the dam, + one of these is down 52 ft. + no sign of solid rock – this proves the correctness of my theory of an old detritus-filled gorge alongside the present one, the two being separated by a narrow
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wall of rock. This interesting but from an engineering point of view, unfortunate physiographic structure will mean the additional expense of perhaps £100,000 as the 25 f[oo]t base of the future dam must everywhere rest on solid rock + this is in the middle of the old filled gorge maybe 100 ft. below the surface of the high-level terrace. ½ pl. photo (8) of one of the test pits. The sinking of these, + they number at least half-a-dozen, costs £1 per ft. for 1st 20 ft., 25% to 30 ft., 30% to 40 ft., 35% to 50 ft. + £2 per ft. over 50 ft. ½ pl. photo (7) No. 1 Gorge looking down stream from high-level terrace opp. future tunnel entrance. ½ pl. photo (9) of No. 1 Gorge + new suspension bridge from river-bed with party on rocks on right. ¼ pl. photo (10) looking up Mangahao from just above gorge with W. Bird in foreground. ¼ pl. (11) suspension bridge from top of high-level terrace. We left the river at 3 pm + ascended zigzag + returned via service road. ½ pl. photo (12) of Hilltop Camp with car + party. Boarded car at Arapeti Bridge + drove home via Tokomaru Valley Road. ¼ pl. photo (13) of car at Hairpin Bend near “top house.” Passed lower camp at 5.10 + reached home at 6 pm.