BURRINJUCK DAM

Wanganui Chronicle, Volume 83, Issue 56, 8 March 1939, Page 12

BURRINJUCK DAM

SOURCE OF DANGER ACTION FORTHWITH REPAIRS TO COST £1,850,000. SYDNEY, Jan. 20. The Burrinjuck dam, which irrigates Riverina in south-west New South Wales, has been revealed by the Premier (Mr. Stevens) to be a source of danger, and remedial measures to cost £1,850,000 will be started forthwith. Mr. Stevens made the announcement in releasing the report of engineering consultants who were engaged by the Government from various countries to examine the dam last year, when serious leaks and disintegration of concrete were discovered. He also disclosed that any abnormal flow of flood waters, such as in 1925, when the dam was overtopped, would have caused anxiety on the part of the Government's technical officers over the last year. The low level of water in the dam, however, had eased the strain on the whole structure. “In point of fact,” he said, “the abnormally dry season in the Riverina district, which has caused such widespread loss in the rural communities has, in a strangely fortuitous manner, helped the situation at the dam.” At present the dam is not provided with any drainage system, nor are there any inspection galleries within the structure. The absence of these facilities materially hampered the consultants in assessing the extent of internal deterioration which has taken place. They reported, however, that on the downstream surface there were considerable deposits of efflorescence having in parts a thickness of several inches, and, in view of the presence and magnitude of these deposits, there was no doubt that the process of disintegration of the concrete was in progress and had been going on for a long time.

The Remedial Measures. The proposals recommended by the consultants included the installation of a complete drainage system below the internal seal, with provision for inspection galleries through which the internal condition of tne structure could be adequately surveyed in the future. In dealing with the need for increasing the discharge under flood conditions, the report of the consultants set out that, when the dam was originally designed, provision was made for a maximum discharge capacity of 80,000 cusecs (cubic feet a i second). As a result, however, of floodings during construction, this provision was found to be quite inadequate, and subsequent amendments to the design were made to increase this discharge, first to 130,000 cusecs, and then to 160,000 cusecs. The original capacity of the dam was 745,600 acre feet, but this was reduced to 119,400 acre feet because of the fears when the dam was overtopped during the 1925 flood, and since that date the actual storage of the reservoir has been kept as closely as possible to a maximum of 626,200 cubic feet. The effect of the remedial measures recommended by th consultants will not only restore the storage lost since 1925 but will increase the total storage available in the future by a further 70,000 acre feet, bringing the total storage capacity up to 815,000 acre feet.