Engineers disagree on ski-field road

Press, 4 March 1980, Page 3

Engineers disagree on ski-field road

The No. 3 Planning Tri-i bunal has been asked to ig-| nore warnings about the safety risks of building an access road to the proposed ski-field in The Remarkables, near Queenstown. A civil engineer (Dr R. O. Davis) told the tribunal that a commissioned report on the feasibility of building a road to the Rastus Burn skifield was “oversimplified” and “foggy.” Dr Davis said- that the analysis written by Dr J. R. Chivers, a consultant engineer, and presented to the tribunal last month, was “incorrect, inappropriate, and simplistic, and as such should have no bearing on the possible development of the Rastus Burn ski-field.” Dr Davis was giving evidence at a resumed hearing of the Remarkables Protection Committee appeal against a decision by the Lake County Council to allow the Mount Cook Group, Ltd, to develop a skifield in the Alpine basin. The tribunal was Mr P. R. Skelton S.M. (chairman), and Messrs R. T. Calvert, G. W. Ensor, and G. J. Broker. Dr Davis said that the best way to determine the stability of the site was to examine carefully existing roads in similar geological terrain. , , Mr Chivers had _ argued that to be sure of soil stability, samples had to be taken from the exact area or from

identical soil. He had analysed the soil and found that the proposed 45-degree angle method of cutting into the mountain would make the land unstable. Dr Davis said he thought a theoretical analysis of “cut and fill batters” (angled cuts into the mountain), was a “fruitless task.” Varied depths of soil on the mountain, combined with changing slope angles made a complete analysis of the proposed road impractical. Mr Chivers had treated the soil as if it had no cohesion, Dr Davis said. He was surprised at Mr Chivers’s conclusion because he had visually confirmed that the soil was cohesive. Mr Chivers had ignored the cohesive strength of the silt forming the slope. There was also disagreement about the maximum angle of a slope for safety. Dr Davis said that the steepest existing slope he had measured was 37 degrees. The slope was safe and his assumption was conservative, he said. Mr Chivers said that any slope greater than 34 degrees would be unsafe for roadbuilding. . In cross-examination by Mr G. S. Tuohy for the appellants, Dr Davis admitted that his analysis was based on an ideal so _far__from

being identical to the soil on the proposed road that he might regret his conclusions. But he said that analysis 1 samples of the exact soil i would not safely represent the strength of the collu-. vium because it was impossible to get an undisturbed : sample. ; Mr D. H. Bell, a lecturer . in engineering geology, told I the tribunal that after study- • ing the area on foot, he was ■ satisfied that the best post sible route had been chosen > for the road. He said that the design 1 plans were realistic for road - construction in the geologi--5 cal area, and he agreed with ; Dr Davis that both the con--1 suitant for Mount Cook (Mr : I. D. Stewart) and Mr Chi- - vers were wrong in suggest- - ing that cut slopes would t degrade above an angle of 34 degrees. “This shows a lack of - understanding of the theor retical and practical bases of slope stability in schist col- » luvium, and as such renders ; many of their criticisms in--7 valid,” said Mr Bell. > He said the proposed road could be built to acceptable environmental standards, but 7in .restricted sections . of 1 steep'"slopes, fhe road might, r have to be reduced to 6 metres wide. r The hearing will continue - today and a decision is exi pected either on Thursday 1 afternoon oij Friday morn-