RESTORING ARAPUNI.

New Zealand Herald, Volume LXVII, Issue 20619, 18 July 1930, Page 10

RESTORING ARAPUNI.

REPORT BY GEOLOGISTS.

REFERENCE TO ENGINEERS.

PROPOSALS TO BE DRAFTED. SUBMISSION TO SWEDISH EXPERT. [BY TELEGRAPH. —SPECIAL REPORTER.] WELLINGTON. Thursday. Tlio full text of the geological report on tho fracture of the rock at the Arapuni spillway was tabled in the House of Representatives to-day hy the Minister of Public Works, Hon. W. B. Taverner. At the conclusion of their report the geologists say: "The evidence does not clearly show that the purely geological factors, as detailed in the report, were im port ant in causing the era ck. Possibly they were sufficient, in combination with the definitely known engineering shesses, to rupture the rock, already weakened bv the erosion of the channel forming the headrace and bv the engineering excavations.

"The cause of the fracture must tie definitely ascertained so that remedial measures may be taken. We suggest that the strata beneath the power-house tie explored to a depth of 100 ft,. or more, by shafts or by bores of large enough diameter to yield a continuous core, and that the different rock layers be geologically examined and tested for their strength and clastic properties." The Minister explained that apart from the suggestions made in the report r.n investigation was actively in progress on tho water content and clastic content of tho various materials in the neighbourhood of the dam and power-house. "Already," he said, "there has been obtained information which indicates that tho material has about one-tenth the elasticity of concrete and a value which agrees with the conjecture that, after the initial crack in tho forebay had been formed, tho block between the forebay and tho gorge bent over as a result of hydrostatic force. "The present investigations are aimed at an estimation of the behaviour of tho pumice breccia and rhyolite under different degrees of moisture content. One possibility suggesting itself is that water seeping into the rhyolite and breccia caused volume alterations, which possibly resulted in the original crack. This and other investigations are being actively pursued with a view to ascertaining more definitely the original cause of the disturbance. "I have submitted the geological report to my departmental engineers, und I have asked them now to supply me with a report, based on the geological position, indicating what steps they consider should be taken from an engineering point of view to deal with the trouble that has occurred. This engineering report will be submitted by me to Professor Hornell, the expert from overseas, who has been appointed by the Government to investigate the Arapuin scheme, in order that he may advise on the steps suggested by the department." The full text of the report appears on pago 13.