Government Quarries
6.71. Operation of the newly-completed quarry at Diamond Hill and the newly-mechanized quarry at Mount Butler continued during the year. Demand was largely for bitumen-coated material, which varies little from year to year and attempts were made to encourage the use of Government produced aggregates also.
6.72. A new asphalt mixing plant was installed at Mount Butler, and despite some commissioning defects, was working well by the end of the year. The bitumen-coated material produced by this plant, and by the new and reconditioned plants at Diamond Hill, is of high quality and close laboratory control ensures that high standards are regularly maintained.
6.73. Dust suppression equipment was installed at Mount Butler during the year, causing an immediate marked reduction in visible dust. Although invisible dust levels were still too high at first, satisfactory performance was achieved by the end of the year. Similar equipment has been ordered for Diamond Hill.
Private Quarries
6.74. Private quarries operating on Government Contracts experienced a satisfactory increase in demand as a result of increased constructional activity after several years of difficult trading conditions. Four contract quarries were in operation at the beginning of the year, another commenced operation during the year, and preparations for two further quarry contracts were made. Increased use of Government-produced aggregates on Government projects appeared desirable as a means of reducing the pressure on the private sector.
6.75. Increased demand made continued operation of short-term permit quarries profitable and stimulated resistance to closure, but applications to re-open old permit quarries were refused and agreement was reached on closure dates in 1971 for most of the remaining permit quarries.
Laboratories
6.76. The main materials testing laboratory at North Point assumed responsibility for the branch laboratory at Farm Road and the two quarry laboratories, enabling some useful rationalization to be effected. Demand for laboratory services continued to increase, straining available resources.
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