SURVEY OF DAMAGE

Taranaki Daily News, 5 March 1935, Page 9

SURVEY OF DAMAGE

NEW PLYMOUTH’S LOSSES

STATEMENT TO BOROUGH COUNCIL

HYDRO WORKS SUFFER HEAVILY.

EXPENSIVE PROTECTION WORK.

Comprehensive reports of the damage to New Plymouth borough property done by the recent floods were submitted to the meeting of the borough council last night by the council’s engineers. Apparently the damage to the Mangorei power station was the most extensive and it is thought that an expenditure of £3OOO or more may be necessary to effect permanent repairs and protect the station against damage in future floods. Until exact estimates for the .major construction and reconstruction work are to hand, the council will not be able to authorise procedure with the work.

Mr. Clarke stated that he had accompanied the electric light committee and electrical engineer on a visit of inspection of the flood damage at the Mangorei power station on Monday. Apart from the washing away of a portion,of the tail race and bridge over the tail race, no damage of any consequence was caused at the power station. As a result of the flood, however, the Waiwakaiho River immediately above the power station had changed its course and had already scoured away approximately one and three-quarter acres of land from Mr. King’s property. Owing to the configuration and weak nature of the river banks where the scour had taken place, there seemed no doubt that the river, if not checked, would continue to scour until it completely altered its course to a position immediately in front of the power station.

DANGER IN DELAY.

If allowed to take its course unchecked and this did happen the council would be faced with considerable expense in protecting the new river banks for many chains of its length above and below the power station. Moreover, the danger of large stone jambs raising the tailwater level of the power station, and thereby causing the reduction of efficiency of the turbines, must be prevented. With the river flowing past the power station this \vould be a constant danger, and might ultimately necessitate expenditure running into many thousands of pounds. He was satisfied that, for the reasons mentioned and for many other reasons less important, the council should not spare expense in endeavouring to keep the river in its normal course. With this idea in view, he was, with as little delay as possible, carrying out the necessary surveys and investigations and hoped to be able to report further to the council at an early date. As an approximate guide in the meantime, he would estimate the necessary expenditure at £2OOO.

As the scour was on Mr. King’s land, and as the necessary protective works would require to be carried out on and over his land, his permission Should be obtained in the meantime. Flood waters rose above the intake chamber and washed away the small shelter shed which housed the telephone, and bent one valve operating the spindle, stated the electrical engineer, Mr. W. H. Huggett. Large quantities of boulders of all sizes had been deposited towards the front of the screens, forming a bar and deflecting much of the river water away from the intake and causing it to flow down the river. This would be removed as soon as possible and would be used to form a low weir to tap the whole of the river into the intake during low river periods. BLOCKED WITH BOULDERS. . No. 2 intake, was now completely blocked with large boulders and shingle. The eastern wall of the race from the intake gates and for a distance of approximately 50 feet became undermined and had fallen out towards the river. Part qf it, together with the supporting bank, had been swept away. As the intake and race were now. of little value, he suggested that they be left in the meantime.

At the low head dam at Mangamahoe the flood waters rose to about two feet above the overflow and had scoured out the back of the dam approximately four feet wide and three feet deep across the greater portion of the base. This he proposed to fill in with concrete. Rock and shingle was handy for the job. Slight interruptions to the electricity service in areas were caused by poles at river crossings being washed out. At the crossing between the Smart Road and Mangorei Road, seven poles were washed out, allowing the lines to fall to the ground; two poles at the crossing near Rimu Street and at two other river crossings in the Okato district had been similarly damaged. Workmen had been concentrating on restoring the service temporarily and permanent structures in the chape of H poles would be used at the longer span crossings. The interruptions to the supply, generally, were of short duration, owing to the fact that five main, lines left the power station traversing three different routes and were so arranged that most parts of the system could be fed' over either route after certain sections had been isolated.

With-the breaking of the culvert tinder the main road near Kent Road at’the Mangamahoe dam the great amount of water released into the lake caused it to rise rapidly. The flow over the spillway was up to approximately four feet and sufficiently high to overflow the race and scour the filling from the western side for a distance of about 20 feet. The large flow of water down the race also scoured the bank back to the timbering and apron at the end of the race. This would be closely watched, but appeared quite safe and was being fenced. ■ - The gates at the intake had been closed when the river started to rise, but the flood waters from the Mangamahoe kept the lake overflowing and the large quantity of water released by the road break swept across the lake and over the spillway without in any way damaging the dam, although the sudden rise must have considerably increased the pressure. Examination of the damage caused to works under the control of the engineer’s department by the recent floods revealed . little serious ■ damage, said a further, report by Mr. Clarke. The most serious damage was that caused by the washing away of the bridge over the Henui stream, carrying the 12-inch water main. Two sewer pipe crossings over the Henui stream were damaged, and one was leaking badly. Minor slips and washouts occurred over most of the borough. Early on the morning of the flood all members of the council’s staff were organised to deal with the damage, and additional staff and lorries were engaged. A special effort was made to expedite the repair of the water pipe bridge over the Henui stream, and the staff had this main again in commission at 7 o’clock on the day of the flood. Anything not repaired the same evening and considered dangerous was adequately lighted. By Saturday evening very little "emained to be done to complete the repairs to the more serious damage to the streets. The leak in the sewer pipe over the Henui stream had been repaired and the bridge itself was being repaired. The footbridge over the Henui stream in the East End reserve adjacent to the croquet greens had been completely washed away and he would

like the council’s direction as to the erection of a new bridge. The electrical engineer was instructed to submit for consideration at a later meeting a schedule showing particulars of damage caused by the recent flood to consumers’ electrical apparatus and the cost of reconditioning it. Consideration of the reports of flood damage to the electrical system were deferred for consideration at a special meeting of the committee. In the meantime, the borough engineer was instructed to submit a further report and estimates in regard to the protection of the power house. The Taranaki County Council will be requested to provide an adequate waterway when repairing the washout on Junction Road at the Kokako stream and so remove the possibility of a. future washout causing damage to the electrical headworks and waterworks.