Overview
Sun. Mar. 2.
My 31st visit to Mangahao Hydro-electric Works. A recent invite from Mr. E.S. Lancaster resulted to-day in another excursion to Mangahao. Soon after 7.am Mr. Lancaster arrived in his car, left Mrs. L. to spend the day with Maud, + he, Mr. F.J. Ramsey (accountant to Horowhenua Power Board) who also came along, + I set out at 7.11am for the works. Reached Mangatangi Ford at 7.57 + leaving the car here proceeded on foot via road + the spur route over Te Paki Ridge. Left road at 8.12 + reached timber tram saddle at 8.52. The weather was fine but a little cloudy
[page break]
with a smoke haze in distance but during the afternoon the sky + atmosphere both became clear. Descended to Arapete 9.7. The quarry in the Tokomaru gorge below the dam-site was deserted to-day but during the last three months a good deal of material has been removed, presumably to the rock-crushing plant. From the top of the western end of the dam-trnech we could see that considerable progress has been made with the concrete dam-wall which has now been carried up to a height of some 15ft above the level of the tramline crossing the eastern wing of the dam-trench + has at this stage a more even crest-line than on my last visit (Dec.10th). At the moment concrete is being poured into the boxing at the western end, immediately beneath the elevated “concrete platform”. The dam-wall at present ends rather abruptly at the tramline mentioned above, + the higher-level rock-“steps” forming the bottom of the eastern wing of the dam-trench have not yet been built upon through the seepage-pipes of coarse rubble have been cemented in position. The tramline mentioned is the one leading from the quarry to the crushing plant, + it being necessary to retain the
[page break]
use of this, wooden boxing has been built on it to form an aperture through the dam in every way similar to that replacing the flume, viz. hour-glass shaped. 1/2pl. photo (1) Tokomaru Dam-wall in course of construction, also “concrete platform”, +c, from top of western end of dam-trench. 1/2pl. (2) part of back-slope of dam with flume aperture from left bank of Tokomaru R.[iver] immediately below dam-site. 1/2pl. (3) of dam-wall from NE. 1/2pl. (4) of dam-wall from top of estern end of dam-trench. The face of the Tokomaru dam-wall presents a slightly convese[?] face upstream, a form which doubtless gives additional strength, + on this face a projecting shaft-like construction of concrete has been built to take a sluice-gate which will be used to close the 12-inch flushing pipe that pierces the base of the dam. A short section of the wooden flume, extending from the auxiliary dam to the upstream opening of the “flume” aperture, is still in postion. 1/4pl. photo (5) of wooden boxing of “tramline” aperture looking north. {no good) We left Arapete at 9.57 + proceeded up Tokomaru R. to Tunnel No1. Entered tunnel at 10.9 + traversed it in 25 minutes. The eastern hald of this tunnel is not yet lined but since my
[page break]
last visit the concrete floor has been put in. At Mangahao River which we reached at 10.34 there was abundant evidence of the passage of the big flood of 17th ult. [of last month] The appearance of the river-bed had again been altered by the deposition of large quantities of detritus + the main channel of water is now undercutting the right bank between the pier suspension bridge + the Gorge. Much drift-wood has been left stranded but only a small amount compared with the immense quantities carried past the works at the height of the flood. The flood waters, it would seem, rose on this occasion to a height of 24ft. above normal river level + flooded the engine-room, repairshops +c on the left bank at foot of jig tramline to a depth of 4ft. Allowed quantity of water also flowed through Tunnel No1. At the pier suspension bridge the floors of the adjacent buildings were under water + the bridge itself was endangered, the water rising to the level of the flooring so that great masses of drift-timber accumulated against the structure + it was reckoned that if the flood had maintained its maximum for another hour the whole would have been swept away. Fortunately however the
[page break]
waters fell rapidly before this occurred, though minor damage was done to the side-railings by huge floating trees. The principle damage to the constructional works occurred at No1 Gorge itself: the small suspension bridge spanning the head of the gorge was swept clean away + the water-pipes supplying the camp severed; the rest of the flume was wrecked; the massive Diversion Dam (12yds wide) of cemented boulders on a crib-structure of heavy logs was breached by the raging torrent; [Here Adkin indicates that the * section below should be inserted]
* [This is incorrect. The Diversion Dam was cut through by manual labor to divert the river back through the gorge while the By-pass Tunnel is being sealed up to enable the “Stoney Sluice Sate” to be placed in the sate shaft.]
and detritus + driftwood swept on + into the concrete foundations of the big dam without however any serious harm being done to the concrete work itself. The enormous force exerted by the flood was shown by the manner in which one of the lines of steel sheet piling of the downstream cofferdam was bent as a whole into nearly a right angle. At the inlet of Tunnel No1 preparations are now being made for the sinking of a shaft to house a sluice-gate + an elaborate log-screen of vertical reinforced concrete bars set closely-spaced in horizontal bands of the same material is under construction. We preceded via the pier suspension bridge across which electric locomotive trains of shingle-loaded trucks were running at high speed, + ascended
[page break]
to the men’s cookhouse taking en route 1/4pl.[ate] photo (7) of the log-screen as seen across river at entrance of Tunnel No1. From the cookhouse I took 1/2pl. (8) a general view of the Mangahao river-bed, No1 Gorge +c showing effects of flood. Mr Lancaster obtained boiling water from the cook + brewed tea + we lunched alongside the uppermost tramline above the high-level terrace. The clouds dissipated + the rest of the day was beautifully clear. Descended to head of No1 Gorge: 1/4pl. (9) of masonry facing consisting of courses of boulders set in cement, now being built up to form the surface of the glacis of the filling on the eastern side of the upstream wing-wall. 1/2pl. (10) of the breached Diversion Dam with gang of men clearing away the debris. Met Mr J.A. Johnston, resident engineer + Mr Hudson, assistant ditto, + was introduced to young Mr. Phillips-Turner who was with the former. In place of the elevator “mast” hitherto used to lift the concrete “skip” to the top of the shutes, a tower (“Hoist Tower”) of lattised timber construction is now being erected + this rises to a height of 130 feet above its base, completely dwarfing the tall crane alongside. In the gorge-bottom the massive concrete blocks forming the base of the dam are,
[page break]
as a result of the flood, submerged, but further concrete construction [four crossed-out words] in the shape of lateral portions of the dam-wall has been built up during the last three months, that against the right wall of the gorge being by far the larger, measuring [missing word] ft by [missing word] ft + 44ft in height. The backslope of the dam-wall is now defined, the new massive block of concrete against the right wall of the gorge showing it well. The completion of the new elevator “tower” will enable the core wall in the high-level terrace to be proceeded with – this is the next work to be done but the dam in No1 Gorge will also be gone on with, the lateral portions first, a gap being left in the middle to let flood-water through until the Control Shaft + Sluice-gate of the By-pass Tunnel are concreted + put in position respectively. 1/4pl. photo (11) of the downstream cofferdam showing the steel sheet piling bent by flood. Left my companions here + crossed over to left bank of gorge. 1/4pl. (12) of gorge + river-bed above showing dam in course of construction +c. from a fine point of vantage on left bank, viz. the upper track at a spot above the lower part of the gorge, + from same place took 1/2pl. (13) of elevator “tower”, crane, dam foundations,
[page break]
upstream wing-wall etc. From the small foot-bridge on the same track where it crosses the western end of the damn-trench, I took 1/2pl. (14) looking along line of dam towards high-level terrace. The bar of gravel at the foot of the gorge on which the punt has been stranded for some months past was swept away by the flood + the punt is now beached on the right bank of river. 1/4pl. panoramic view (15) + (16) of camp, constructional apparatus + works, +c on high-level terrace from lower part of zig-zag track leading up to Service Road. 1/2pl. (17) of Diversion Dam with men clearing away debris in breach from left bank near bottom of jig tramline, + finally another general view of No1 Gorge +c (duplicate of No8) from men's cookhouse, the light being more favorable than earlier in the day. Of feature of today, it being a Sunday, was the very large number of visitors to the works – elderly men + women, girls + youths, children + even babies. Many of the girls were beautifully dressed + some of them + young fellows donned bathing suits + had a fine bathe in a splendid pool upstream from the pier suspension bridge. One of the visitors was a Mr. Standew[?] of Auckld [Auckland], a friend of Mr. L., who made himself very agreeable
[page break]
– he was accompanied by a large party who appeared to be touring the North Id in two or more cars. At Mr Johnston's invitation we partook of pm tea at the staff cookhouse + at 1:42pm. re-entered No1 Tunnel en route for home. Traversed tunnel in 23 minutes – left Arapete at 2.28 – reached timber tram saddle at 2:45. Here we had a long spell, chatting in the sunshine, scanning the ranges which were now clear through Mr. L’s binoculars. Descended to Tokomaru Valley Road 3.38 + proceeded to Powerhouse in car. Stopped here + inspected – the outer shell of the building + most of the roof is now complete, but the interior is still full of debris from the enormous amount of wooden scaffolding. Left Powerhouse 4.45 + reached Woodside at 5:30 – a very fine outing.