ARAPUNI LEAK

Wanganui Chronicle, Volume 75, Issue 190, 13 August 1932, Page 8

ARAPUNI LEAK

MYSTERY DEEPENS THE SEARCH CONTINUED i . AIR PASSAGE DISCOVERED [ Per Press Association.] , WELLINGTON, Aug. 12. > The search for the headrace leakage at Arapuni is continuing. Boring • operations are still in progress in the ■ bed of the headrace above the cut-off • wall, and it has been discovered that i compressed air passes between two i bore holes, suggesting the possibility ■ of a water path. Stops were imine i diately taken to block up the sus- ’ peeled pathway by means of concrete ' grouting. The Engineer in Chief of the Public Works Department (Mr. F. W. Furkert) stated this afternoon, that be was advised that the men on the -job had been able to get very little grouting into the country, showing that it was not at all open. Although compressed air had been forced in in small quantities, they had not succeeded in getting water through, adding to the mystery of the leakage. Mr. Furkert said that boring operations were now being conducted some thirty or forty feet below the surface. 1 Excellent progress is being made ( with the construction of the coffer dam r which is being installed to enable the ’. subsidence in the lining of the headrace inside the cut-off wall to bo re- > paired. I The concrete mixture being used in the grouting process is of the consis- ' tency of milk, and is being forced down the bores under a pressure of 501 b. to the square inch. This is vastly higher pressure than that exercised by any water that might trickle underground, representing, in fact, pressure exerted by a column of water 120 ft. e high. At such pressure, the concrete grouting, after reaching the bottom of the bore, which penetrates to. a depth of 80ft. from the surface of the ground, is forced into every nook and cranny, and if a fissure exists grouting has been known to travel along it for well over 100 ft., filling it completely and solidifying into a substance of extraordinary strength and hardness. Grouting under i these conditions has a wonderful searching effect, blocking up every crevice in a surprisingly large area of country.