SUPERINTENDENT'S ANNUAL REPORT FOR YEAR ENDED 31st DEC., 1911.
Waihi, 20th February, 1912.
The Chairman and Directors,
Waihi Gold Mining Company, Limited, London.
I beg to submit my Report on the operations of the Company for the year ended 31st December, 1911.
Work has been pushed forward at the Hora Hora Rapids.
The greater part of the water channel has been excavated. The Head Gates are completed and all the concrete foundations for the Power House are finished ready for the machinery which is now arriving.
H. P. BARRY, Superintendent.
REPORT on the HORA HORA HYDRO ELECTRIC WORKS
For the Year ended 31st December, 1911.
Waihi, 19th February', 1912.
The Chairman and Directors,
WAIHI GOLD MINING COMPANY, LIMITED, LONDON.
Excavation and Construction works at Hora Hora have been pushed forward during the year. Particulars of the work are given in the Engineer's Report herewith.
Where the Transmission Line will cross the Te Aroha Ranges, a bullock track has been formed from both sides up to the summit to enable the necessary materials to be hauled on to the ground.
The Surveyors have been laying out the best route for the line, some points yet having to be finally settled.
The line from Hora Hora to Waikino will consist of three wires of solid hard drawn copper No. 0, S.W.G., 0.324 " diameter, weighing 1,678 lbs. per mile. Over the Ranges, however, in this section there will be best hard drawn bronze trolley wire, 0.459" diameter weighing 3,366 lbs. per mile. From Waikino to the Mine the wires will be 37/13 S.W.G. bare hard copper cable (stranded) weighing 5,104 lbs. per mile.
Telephone wires of hard drawn bronze wire, 100 lbs. per mile, will be carried right through.
The transmission wires will be carried on steel towers spaced about 500 feet. Over the Ranges there will be more uneven spans owing to the very rough nature of the ground, and the towers will be built accordingly.
The towers are now arriving and will be transported to their sites and erection commenced in a few weeks' time.
The Transformers are being made by Siemens Bros. and are now ready for testing.
Every endeavour is being made to get all the heavy material up to the Power Station during the Summer as the roads could not stand the traffic in winter. We are finding the work very heavy on the traction engines, as the sand smothers them and cuts up the bearings and gear wheels terribly.
H. P. BARRY.
ENGINEERS REPORT—HORA HORA HYDRO ELECTRIC WORKS.
Hora Hora Rapids,
February 7th, 1912.
H. P. Barry, esq.,
I have the honour to report as follows upon the progress of the works Hora Hora for the year 1911.
EXCAVATION FOR POWER HOUSE FOUNDATIONS AND HEAD AND TAIL RACE CUTTINGS.
The nature of the strata to be cut through was about 50 feet of Pumice sand gravel and river drift overlying a boulder bed from 10 to 20 feet thick, below this is the country rock, a volcanic tufa varying very much in hardness, but on the whole easily worked.
The rock is outcropping along the Waikato River bank in the central part of the Head Race, but dips away at the intake and also at the Tail Race.
The foundations of the Power House and Head Gates are upon the rock, as is also the bottom of the Head Race for a greater part of its length. Wherever the rock is not found the race has its bottom in the boulder bed.
It will therefore be apparent that the whole of the sands and gravels had to be removed, and a greater part of the boulder bed, while the rock cutting reached a maximum depth of 18 feet at one place.
It was decided that the sands and gravels should be sluiced away, and a dam and flume were constructed to bring water for this purpose from the Pokai stream a distance of about ¼ mile, at such an elevation as to give a head of about 5 feet above the highest point of the boulder bed.
This water is also used to supply electric power for winches, cranes, and other services upon the works.
The material of the boulder bed is quite unsuitable for sluicing, consisting as it does of gravel and boulders cemented together with clay and iron oxide so as to be almost impervious to water. Nor can this material be worked by any kind of mechanical excavator, the boulders being of large size, some of them many tons in weight. It has had therefore to be worked with picks, and the large boulders drilled and blasted, the spoil being moved with horse trucks of two-yards capacity.
This is the most expensive material with which we have to deal. The relative costs for removing the sands, boulder bed and rock, being :—
Sands per cubic yard ... 1d.
Boulder bed „ „ ... 18d
Rock „ „ ... 12d
(For breaking, loading, hauling, and tipping the material, actual cost at Hora Hora.)
Construction Work.— The excavations for the Power House foundations having been completed on June 4th, at a depth of 16 feet below Tail Water Level in the Waikato River and 78 feet below the surface, the first concrete forming the floor of the Draught Tube Chambers for Turbines* was deposited on the following day, and construction work has gone on uninterruptedly since that date.
The material used for the Power House has been entirely concrete, plain and reinforced. Those parts subject to tension have been reinforced, and about 50 tons of steel have been used for this purpose.
The more massive parts of the foundation have not required reinforcement.
The total quantity of concrete deposited for the year has been 6,400 cubic yards, which represents about 9,600 cubic yards of material put through the mixer, a shrinkage of about one-third of the whole volume measured loose occurring in the wetting and depositing of the concrete.
Timber for the forms was procured in the early part of the year before the roads got bad, and a stock of about 200,000 feet super, was stacked on the ground ready for use.
2,000 tons of cement also were brought in and stored in three large sheds specially built to keep it in good order through the winter. This cement is of entirely local manufacture, the two Companies of Auckland supplying it in approximately equal quantities. It was sent by rail to Tirau Railway Station and carted from there to Hora Hora by waggon, a distance of about 12 miles. A good deal of trouble was experienced in forwarding, carting and storing this large quantity of perishable material. A part of this was delivered during November and December, 1910.
Office Note.—Some interesting remarks re experience gained in the life of Turbines are contained in Mr. Frasers Report, pages 69 and 70.
Aggregate.—A splendid deposit of clean shingle was found occupying the Tail Race adjoining the Power House and consisting of two principal seams, one containing a good deal more sand than the other. By varying the proportions of material taken from each of these seams almost any required mixture could be made.
The concrete used in the Power House consisted of two qualities.
Where a perfectly watertight concrete was required the mixture was—1 cement, 2 sand, and 4 stone, by weight, or approximately 5 of sand and stone to 1 of cement by measure. Where perfect watertightness was not required the mixture used was 1—3—6, or approximately 7 of sand and stone to 1 of cement by measure ; both these mixtures have proved very satisfactory, and the strength and hardness of the concrete is all that can be desired.
A large number of the hard and heavy boulders from the boulder bed were broken up and used in the larger of the concrete walls, especially where great weight was a matter of importance, thereby improving the wall and saving expense.
Head Gates.—The concrete apron on which the concrete piers for the head gates stand was put in during the month of June, and the piers themselves constructed in the following month. The steel work for the superstructure continued to arrive during the next couple of months, and during October was being erected. The gates were completed and the skin plates rivetted on before the Christmas holidays. These gates are now all complete and ready to be used when required. The steel work of the gates was well made and fitted and no trouble was experienced in putting it together.
Power House Construction.—The floor of the Draught Tube Chambers was begun on June 5th, and completed about a week later. Timbering was commenced for the division walls between units, and the archways carrying the Main Power House floor. As this averages more than 5 feet thick, the centreing for the arches had to be made correspondingly heavy, and about 125,000 feet super, of timber was used for this purpose.
The forms for the walls and centreing for arches were completed on August 1st, and concreting again commenced on the following day and continued day and nigh until the 21st August, when the turbine floor level was reached.
Timbering for the foundation blocks of the generators and other machines in the generating room was then begun. This was completed on 29th August, and the concrete deposited during the following week. Timbering for the turbine chamber walls, including retaining walls, extending two chains along each side of the head race, and also main division wall between the generators and turbines, all to a height of 20 feet above the floor of the head race was then put in and concrete deposited during November. All these walls are reinforced.
A reinforced concrete gangway was also constructed along the face of the plant fronting the river to give access to the stop log grooves of draught tube chambers and another heavier reinforced gangway along the head race front of the turbine chambers to give access to the strainers and stop logs at that side of the plant. These gangways were found to be cheaper than steel girders and wooden floors, and are more in keeping with the general substantial character of the plant.
The floor of the generator room and the walls for a height of 7 feet are made impervious to water so as to exclude the most exceptional floods.
The generators are in fact in a large concrete tank with sides 7 feet high, all the openings for windows and doors being above this level.
This finishes all the foundation work at the Power House and the great bulk of the concrete work. There remains to be done, the switch room, such of the side walls of the generator room as are of concrete and more than 20 feet high, and one or two smaller items to complete the Power House, including 132 feet along each side of the head race.
This part of the construction work is well advanced, and we are now quite ready for the steel work of the turbine gates, the superstructure of which also carries one rail for the traveller over the turbines. This has not yet come to hand although it is shortly expected, but no further progress can be made with this part of the plant until it arrives, as no commencement can be made to place any of the machinery in position until the overhead travelling cranes are erected.
The only other concrete work carried out during the year is the construction of a dam across the Pokai Creek on the East side of the Head Race, thereby diverting the stream outside the Head Gates, where it will have its permanent course; the dam forms part of the side wall of the Head Race.
Draught Tubes (Turbine).—A commencement has been made in rivetting up the Draught Tubes of the Turbines. The plates reached Hora Hora in good order, and are being put together in the draught tube chambers directly under the positions they are to occupy permanently. The ironwork has been well made, and the plates are going together without trouble.
The electric service plant for the purpose of driving winches, pumps, cranes, etc., on the works consists of two Westinghouse Direct Current generators of 30 h.p., each driven by a Turbine, using Pokai Creek water with a head of about 30 feet.
This power has been very satisfactory and convenient, and has been constantly in use since it was put in.
Machinery from London.—It was decided that the Hinuera Railway Station, distant 10½ miles from Hora Hora, was the best place to send the machinery from Auckland, and a gantry and siding were built there to handle the heavy weights expeditiously. Two traction engines were provided for the haulage. All the bridges and considerable culverts on the road were strengthened, and a contract let on the River Road for re-grading, widening and metalling the worst parts of it at a cost of £175, the Mata Mata County Council not contributing anything to this work.
Unfortunately, the Spring proved very wet, and the Hinuera Road being unmetalled for a great part of its length became impassable after a few hours rain and considerable delay was experienced from this cause. With good weather, however, I think the road will carry the traffic very well.
The new bridge over the Waikato River, subsidised by the Waihi Company to the amount of £450, was completed during the year. We can now close the approach to the old bridge and cut our Head Race through it; the County road being diverted to the new bridge. We are still keeping the old road open, as it is convenient to us in many ways; and it forms a bar across our Head Race, preventing the water getting to the Power Station in case of any very heavy flood.
As the Summer and Autumn were very dry, and the Waikato exceptionally low, another measurement of the flow of the river was made, with the result that the water going past Hora Hora was 6,316.9 cubic feet per second, as against about 9,000 last year, the quantity required for the plant being 4,500 cubic feet per second. I am informed that the river was lower this season than for many years, and that the flow measured may be looked upon as a minimum.
The permanent Staff have worked zealously and well, and must get credit for the satisfactory progress of the works.