WORK AT ARAPUNI.

New Zealand Herald, Volume LXIX, Issue 21131, 14 March 1932, Page 10

WORK AT ARAPUNI.

FILLING THE LAKE. OPERATIONS AT EASTER. EFFECT ON . RIVER LEVEL. FINAL STAGE OF RESTORATION. [from our own coruksvondent.'] HAMILTON, Sunday. The work of restoring th o Arapuni hydro-electrical scheme is so far advanced that commencement will be made to fill the dam on March 24, and electricity will again bo generated about- 12 days later. The actual time the filling process will occupy cannot be determined in advance. If heavy rain falls it will take less than 12 days, and if tho requirements of Hamilton make it necessary to keep the river level higher than is expected it will take longer. Advantage is being taken of the Easter season for tho change-over for several reasons. There will bo less demand for current during that period than is usually the case and demands on the river water for consumption and navigation purposes will bo at a minimum. When the dam was previously filled in December, 1927, a month was occupied in the process, but at that time the city of Auckland and the province were dependent on Horahora for electrical current, and sufficient water was passed through the tunnel at Arapuni to enable Horahora to continue operating. On this occasion Horahora will bo partially closed down and power for nearly all requirements will be supplied from the King's Wharf station in Auckland. Hamilton's Water Supply.

Tho effect of closing the gates in tho diversion tunnel on Hamilton, which draws its water supplies from the Waikato River, has been the subject of a report to tho Borough Council by the borough engineer, Mi;. R. Worley. He states that the Public Works Department is very anxious to fill the dam in tho shortest possible time and is desirous of cutting the discharge water down to the very minimum. The intake level of the Hamilton water supply is likely to be the dominating factor governing the operation, says Mr. Worley, and arrangements have been made for an operator to stand by at Arapuni during tho wholo period of the filling of tho lake in order to open tho diversion tunnel on receipt of advico should tho water level at Hamilton fall below tho level of tho intake.

Mr. Worley states that with only one pump in operation the intake level could be reduced further than would be possible if the two pumps were running. It would meet the wishes of the department if the lower level would serve Hamilton's purposes temporarily, and Mr. Worley suggests that these wishes can he complied with by prohibiting the use of garden hoses and by requesting the public to avoid any unnecessary usage of the water. If the water supply fails in Hamilton the new reservoir can be brought into use. Co-operation with Department.

It is expected that the level of the river will fall from "five to six feet, while tho Arapuni dam is being filled. The Borough Council has given Mr. Worley authority to do all he can to assist tho department and to watch the position during the timo tho Arapuni dam is being filled.

The Roose Shipping Company, Limited, has been advised of the effect (lie lowering of the river will have on navigation, and satisfactory arrangements have been made with it. It is probable that the company will have to cease operations for a few days. Other concerns that will be affected are the Horotiu Freezing Works and the railway services at Ngaruawahia, Huntly and Mercer. In each case water is drawn from the Waikato River, and special arrangements will have to be made for continuity of supply. Restoration Nearing Completion.

The restoration at Arapuni is now receiving ils final touches. The lining of the headrace with concrete tiles is now completed, and the work resembles a huge bath with a parquetry finish. A solid concrete floor has been provided in the overflow channel. Throughout its course I lie water will be confined to an artificially-made channel designed to cause a minimum of erosion.

The falls structure is a particularly attractive piece of work. Over it the water will fall in two steps. At the bottom of tho first step there is a cavity carved ill concrete and in tho cavity are placed a dozen immense concrete fins, which will break tho force of the water before it tumbles over tho second drop on to the concrete apron below from which it is emptied into tho Waiteto C hannel. Jhe falls structure is very heavily protected with its concrete floor and walls, and there should bo no repetition of tho erosion which previously occurred in that locality. A few men are still engaged putting the finishing touches to the base of tho falls structure, and in pressure grouting and painting the surface of the protection works. Screen at Headrace Entrance. A screen is being built at the entrance to thq headrace, and the floor of tho channel at this point is being given a vecner of concrete by the guniting process. Work on the second valve shaft at tho diversion tunnel is still occupying a number of men. The new valves, of course, cannot be installed until the existing ones are closed. in the [lower-house the installation ot Iho fourth generating plant is still in progress. Tho turbine is in position, and ihe generator is being assembled. Iho No 1 turbine, which gave some trouble after its installation, has been adjusted, but until the water is turned on, it cannot be tested. When the restoration work was at ns maximum, 800 men were employed. Ihe staff has now been reduced to 500, and in the next few weeks it will be necessary to dismiss a further 400 employees.