Fears about Wheao geology ‘passed on’

Press, 11 March 1983, Page 3

Fears about Wheao geology ‘passed on’

PA Rotorua D.S.I.R. fears about the geological suitability of the Wheao area for the hydro scheme were passed to the consultants, Murray-North Partners, Ltd, the Committee of Inquiry investigating the Wheao canal collapse heard yesterday. The Commission for the Environment had passed to the Rotorua Area Electricity Authority D.S.I.R. concerns about the use of brown ash lining for the canal. The D.S.I.R. warned Mur-ray-North that brown ash was a “tricky material” for engineering work. D.S.IK scientists had differing views from Murray-North geological consultants on the acceptability of brown ash. The Nature Conservation Council had also expressed grave concern about the scheme’s feasibility because of erosion factors. For the Commission for the Environment, an assisant commissioner, Mr J. T. Gilbert, said in submissions that

in preparing an appraisal of the Wheao scheme in 1977 the commission had sought evidence from the D.S.I.R. Soil Division. He presented a letter from a D.S.I.R. scientist, Dr W. A. Pullar, to Murray-North in 1976 which said, “If brown ash dries out, cracks will form and these will not close up upon rewetting. Thus, for sealing purposes brown ash has the wrong kind of mineral — allophane.” Dr Pullar said brown ash was a “tricky material for engineering work.” In a further letter presented with the commission’s evidence the director of the D.S.I.R. Soil Bureau, Mr R. B. Miller, wrote to the directorgeneral of the D.S.I.R. in 1977 expressing concern about Murray-North’s confidence in brown ash. He said that: a D.S.I.R. scientist, Dr R. D. Northey, had examined the scheme and his principal query was “the apparent confidence of their (Murray-North’s) engineering geologist that the

brown ash will prove suitable. “I have some considerable reservations, because of ■its low density, low strength and irreversible shrinkage characteristics that it can maintain an intact lining. In its submission, the commission expressed concern that there was no recognisable process for evaluating the safety aspect of small hydro schemes, nor any apparent guidelines for a system of surveillance and monitoring during the commissioning and long working life of such projects. The Nature Conservation Council said that a scheme similar to the Wheao scheme had been dropped after advice from the council and the Bay .of Plenty Catchment Commission concerning erosion, The council said that in 1976 it had told the Rotorua Area Electricity Authority of its objection to the Wheao scheme, because of geological and oth’er factors. Earlier report, page 5