HIGHWAY WASHOUT

Evening Post, Volume CXXXI, Issue 38, 14 February 1941, Page 8

HIGHWAY WASHOUT

GREAT DAMAGE DONE

BIG FILL EATEN OUT

ALL TRAFFIC STOPPED

Serious damage was done in the iXgahuuranga Gorge this morning as the result of a slip which, about 7 o'clock, fell from a sleep face near the Johnsonyiile end of the gorge, blocked an open section of the stream culvert, and diverted the full slorm flow on io the roadway. A quar- ! ter of a mile be)ow Ihe ■ big cut the rush of water attacked the edge of a 60-fcet-deep (ill, and within half an hour thousands of cubic yards of rock and metal were eaten out. Halfton rocks and the lighter filling were rushed downstream like so much silt. By 10 a.m. the outer half of the roadway (the downhill lane) had gone completely and the inner roadway was threatened. The road has been officially closed. The occurrence was extraordinary in that the slip, comparatively small, selected the one vital spot in that length of the gorge. When the new highway was built the" old stream was diverted over the greater part of its length to a new course altogether, in part open and in part through rock outcrops and under- fills, by culverts of large diameter designed for any storm flow. ONE VULNERABLE PoInT. The slip fell in a short length where j the stream emerges from one lengthof tunnel and runs behind a short concrete storm wall before going under- i ground again in a long culvert under: the big cut and the 60ft deep fill in which spoil from the cut was placed, j Heavy i*ain fell all night, and between i 6 and 7 a.m. there was a great.downpour. At 7 o'clock the slip came down. With the mouth of the second culvert blocked, the full flow poured over the storm wall guarding the length of open stream and down the road surface, all the way to the junction of the. Hutt Road, but within minutes only it got to work at the edge of the fill and rippad away at it fiercely. Rocks and lighter stuff disappeared in the rush, and the slope of the fill became a steadily receding vertical cliff. Most of the damage was done in the first twenty minutes of the overflow. After that the rain eased, but the stream still ran high, and the face of the fill still worked back, more thousands of1 yards going downstream, and threatening trouble by blocking the culverts nearer the Hutt Road. So great was the rush of water during the first overflow that some chains of footpath through the big cut. and therefore on solid rock foundation, were torn up in a matter of minutes only. Lower in the gorge, metal carried by the first overflow littered the roadway practically all the length of the gorge, but no damage was done to the lower road. surface. MEN AND PLANT ON THE JOB. The Public Works engineers arid emergency workers were quickly on the job. Rock-filled bags diverted the worst of the flow from the road edge and shifted the attack of the water towards the solid hill. The slip was difficult to work on, for the hillside above was still doubtful and the weight of water could have started a dangerous rush qnee the slip began to move. A drag line shovel was turned on to the foot of the slip, but conditions w°re most awkward while . 2 stream ran high. Many thousands of yards of spoil must be replaced and probably a good deal of walling work will have to be done before the outer lane of the gorge highway can be restored. The work may extend over some months. By midday the dragline workers had cleared enough of the toe of the slip j to allow the water to flow through the j culverts again., DETOUR SIGNS. The Automobile .Association (Wellington) has erected signs asking traffic to make a detour via Kharidallah and Ngaio. . (Pictures of the damage appear on page 5.)