THF HYDRAULIC WORKS. MR WILLIAMS'S REPORT. The work of rearranging and strengthening that portion of the Waipori I'alls hvdr.tulie works between the outlet of the tunnel and the power station has now been completed' under the supervision of Mr hj. J. Williams, civil and hvdra.ulic engineer. The work was placed in his hand's on August 31, 1913. alter the abnormal Hoods of that period, and since, that date no stoppage ot the works has been occasioned by any failure of the hydraulic works. Mr report on the work came before the Lh-e----tric Power ami Lighting Committee on Tuesday last, when it wiis decided to send copies of it to members ol the council. The report reads as follow* :
The work uiKlertaken was as under : (1) Insertion of expansion joints in pipe lines. (2) Additional anchorages. (oj New gates in penstocks and surge chain-, hers. (4) Additional control in main -conduit. (5) Reduction ot interna! stresses in main conduit. (6) Viaduct lor No. 3 pipe line.. (1) Conveying all foreign water directlv to the river.
Expansion Joints.—The number of expansion joints put in is eight—three in both No. 1 ami No. 2 line, and two in No. 3. They are. all of the same pattern, each having a draw of 3ft bin. The fixed portion of the pipe is securely anchored, while, tension rods have been provided to prevent the point pulling clear. Anchorages.--All angles and bends have now been securely anchored together with the fixed portion"of the line at expansion joints, as before referred to, while thrust blocks are provided for each line near the power station. Gates.—The llap valves at the head of ea-eh. pipe line kuvo been removed and direct-action gates substituted. These gates tun now he easily operated under all conditions, thereby' rendering them absolutely safe and reliable. The work of inserting these gates involved a large amount of labor, both in the design and construction, for it was essential to so arrange the work as to fit it with the existing structures. - Additional Control in Main Conduit.— The connection between the outlet to the. tunnel mid the penstock supplying No. 1 and No. 2 pipe lines is effected by a reinforced concrete main conduit. It will therefore be followed that in the event of tailure of the conduit No. 1 and No. 2 lines will become inoperative, but attire time of my taking over the work this also meant the total closing down of the works, for in order to turn the water out of the conduit it was necessary to dry the tunnel. This I have now obviated by placing a door in the conduit near the tunnel outlet, so that your aro now. in conjunction with the gates, enabled to work tiie pipe lines either separately or together. The door is what, is known as a "butterfly valve," working on a horizontal axis, and so geared that it is practically impossible to set up additional stresses by water hammer. Reduction of internal Stresses in Main Conduit. —ln the construction of the main conduit no provision was made for expansion and contraction, and considerable internal st r esses were thereby set tip. One of the- first works I put in" hand was the insertion of two expansion joints, and they have acted admirably, and as far ns 1 can sec have quite overcome the •difficulty. The conduit was < ompletely severed at these places, and a shield 18in wide was inserted and packed so as to allow the structure to move on the shield. An additional shield is on the work for use should it be required, and I am of opinion that this conduit requires -careful watching, and should any extensive movement be noticed the spare shield should immediately be used in a similar manner to the others. Viaduct for No. 3 Pipe Line.—The embankment built to carry No. 3 pipe line over Power House Creek was carried away by the July floods of last year, and as I funned the opinion that its existence was a. menace to the safety of the power house I decided to support the line over the creek on reinforced concrete columns. By this means the waterway was in no manner interfered with. Solid rock foundations were obtained, and the columns (five in number) varied' in height from 21ft to 32ft. The work was well carried out, and a permanent structure is assured. Conveying all Foreign Water Dire-ctly to the River.—The primary cause of the settlement on No. 1 and No. 2 pipe lines was the discharge of water, used for scouring the tunnel outlet, against the embankment. To avoid a recurrence of this trouble, and at the same time to make ample provision for scouring, a 9in diameter pipe has been laid from the tunnel outlet to the river, a. distance of 2.010 ft. At the same time all leakage was gathered into the depressions and led into the pipe. There is, therefore, no foreign water now running in this watershed, and the natural watercourses have only to carry off the natural drainage. This leaves the conditions such as were existing prior to any work in the vicinity, and consequently only doing such duty as designed by nature. The number of tracks cut on this watershed have the tendency to cause, the storm water to be more rapidly conveyed to the watercourses, and in times of heavy rain it will be essential to see that this water follows the course laid down. If not attended to the wafer will follow along the tracks until it increases to such a volume that, finding its way into the soft portions of the countryside, it will cause slips. With a little attention at such times, I am of opinion no further settlement will take place: but I would impress upon you the necessity of not further disturbing the country, and of cultivating as much growth on* it as possible. Cost of th.n Work. Tam unable to submit the total cost, of tiie work, for, with the exception nf 1 iv> viaduct, the cost of labor at Waipori has not been returned. The cost for material, etc., is set down as £1,459 7s. 3d. I have pleasure, now in handing over to yon the work, and am confident that yon will have no anxiety in regard to the stability of the hydraulic portion of the system. Everything that is possible t ) secure this end Ims been done, and with ordinary attention and intelligence on the 'part of your operatives no further trouble can arise.
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WAIPORI, Evening Star, Issue 15631, 23 October 1914
WAIPORI Evening Star, Issue 15631, 23 October 1914
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