HILLSIDE SLIPPING

New Zealand Herald, Volume LXXVI, Issue 23405, 22 July 1939, Page 18

HILLSIDE SLIPPING

EANGITATA PEOBLEM THREAT TO DIVERSION RACE INSPECTION BY MR. SEMPLE LARGE PIPES TO BE INSTALLED [by telegraph—OWN correspondent] CHRISTCHURCH, Friday Slipping country on a stretch of one mile and a-half on the Surrey Hills has caused the abandonment of the building of the Rangitata diversion race on the affected section. The water will now be carried in huge pipes for 8000 ft. on, the downs below tho level of the race.

The diversion race, which will be 34 miles long-when completed, leaves the Rangitata River near Rocky Gorgo at thg entrance to the plains. Thence it passes over terraced country, turns norths and crosses the Hinds and Ashburton Rivers. The race will carry sufficient water for tho wholo Ashburton County, not only for [irrigation, but fork's took and domestic supplies. ,

When ho sa\r the.slip this week, the Minister of Public W6rks v the Hon. R. Semple, promptly authorised the abandonment of the race on tho hillside bench and the change of plans. On his first inspection of the hillside the 'Minister expressed his doubts as to its permanent safety, but it was not until a week ago that the hill began to move. The shifting "nature,;of the country became evident to the engineers when the bench was made and : the race partially' cut. For safety "reasons tlie course of the race will now be altered for one mile and a-half, although the slip has occurred in only one part.-The quality of the hillside further north suggests, that slips .are. a possibility there later. ' r j- ■

t'i The slip, which is on "the property of Mr. A. N. Grigg, M.P., is of 250,000 yards. The country is of clay, shinglo and pug. On its "first; day; of movement 'two and three-quarter acres ofthe Hillside began to creep down on the irrigation race, opening fissures at cross angles and at the top, parallel with the race. Hillside Moving The quarter of a million yards of hillside is now moving down 011 the race at the rate of lin. a day. The biggest fissures are Ift. wide and as deep as 6ft, With this terrific downward pressure the safety of the race, and indeed of the whole scheme, was er.dangered. However, engineering plans to alter the course of-the irrigation water and the... method of carrying have been rapidly*evolved. -From a safe distance beyond where the slip has occurred the '•water will drop,, down to the down country lOOyds. or so below the level of the abandoned race section. Under a 13ft. head, the water will bo carried through pipes; and forced up to the hillside race at a point beyond any danger of slips. i The pipes to be used:.will be the largest in the Southern Hemisphere/ They will have an inside diameter. of 12ft. and the shell, in which .probably lin. steel reinforcements,,will be used, will have a thickness of 10m. The pipes, which the department proposes to 'make at Surrey Hills, will have a weight of 23 tons for each 10ft. section antfwill be placed in a haunch for the mile and a-half stretch. • -• ; ; - No Delay to Scheme

r r "The"" alteration in -the* method of carrving - the water on this section of the Surrey Hills will not cause the of the diversion race to be delaved. The date for the diversion, of the "Rangitata River info the race is . set down for September, 1940, and two mdnths later the water will be available for irrigation. . In snow oin. deep, Mr. Semple made / a personal inspection this week of a number of phases of .development of the Ashburton-Lyndhurst irrigation scheme and the diversion race. JHe expressed his complete •. satisfaction with . the progress being made. ' ' ? "The earth-shifting figures are remarkablo for the middle of winter, he' said.. .'.'ln .the. last 20 working day? 245,000 yards of material have been moved by the batteries of machines, the quantity excavated- for * the diversion ra6e itself being 193,000 yards. ■ One-of-the' spectacular jobs inspected "bv the-Minister is the;, putting of the race in the high terrace, near/Mount Somers, on to which the water will be siphoned after being carried under the 'south'branch of 'the Ashburton River. For nearly half a mile a • drag-line exca- ' vator has dug down to a depth ot .tart. ThiS -cut is almost finished.

DOWNLANDS WATER BIG IRRIGATION SCHEME \ 880 MILES OF PIPES USE OF MODERN MACHINERY [by TELEGRAPH —OWN correspondent] ' CHRISTCHUKCH, Friday In 18 months from now the Downlands water supply scheme will be in operation. That estimate of the completion of one of the biggest watering schemes undertaken in New Zealand was given by engineers to the Minister of 'Public Works, the Hon. R. Semple, when ho .inspected the progress of the works. The intake. for the Downlands scheme 'is on the Tengawai River. The area to be served totals 154,000 acres, bounded on the nortli by the Kakahu River, on the? west by the high hills of the Levels and Mackenzie Counties, in the south by the Otaio River, and on the east by the sea. Work has been at full speed on the 6cheme for six months, and already 11 miles of the main pipe line —the pipes arc 13in. in diameter —hmve been laid. The country opened up to take the main pipes is mlich further ahead. Two mole drain plants arc placing the smaller pipes in the ground for a distance averaging one mile and arhalf

daily. 7lf the pipe-laying hacf been undertaken under the old methods of manual drain-cutting and pipe-laying, the work, it is estimated, would have taken, with the men we now employ, 3(3 times as long," said the Minister. "Apart from the hopelessness of tackling such a huge undertaking by the old methods of hand labour, tho cost would have been positively prohibitive."

Although each Ideal body concerned has yet to fix the rates it will charge for'supply, the engineers anticipate that the rate will. be approximately 8d an acre, a sum paid now in many cases for'stock water alone.

The magnitude of tho nchemo can be best pictured by the statement bv the f Minister,that,the piping, if placed in a straight/,i. line, ; would extend from to Chnstchui'ch, and from Wellington to ; Whangard.; : The total 'S tb 'M? f -^ a < r, -°u ÜB i sh& >> » 880 miles.Alms will distribute wator for domestic consumption and kock purposes over 4o4,;Qookacres,, and::meet the requirements of 4.000 persdns and 200.000 head., of stock. . : ._ , : ■ ... r .. ... . ... .. -