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precast concrete block-work in the contract. For the next contract, now being prepared, a mix of 1:9 will be used. With a 1:8 mix the density of the heavily vibrated concrete in the blocks averaged 154 lbs. per cub. ft.
151. For the contract of resurfacing the runways of the airport a small laboratory was set up on the site to control the grading of the granite aggregates and bitumen content of the bituminous macadam and asphalt turned out at the central mixing plant.
152. Further responsibilities were the examination of foundation conditions for new Government buildings and the examination of hundreds of boring samples from the harbour bed to ascertain the possibility of obtaining suitable sand for underwater foundations in dredged trenches and some millions of cubic yards of hydraulic reclamation fill for reclamations and possible airport extensions.
153. With an all-in annual cost of operation including wages, electric current and stores of $27,500 (£1,700), working with some $20,000 (£1,250) worth of equipment, the laboratory has proved itself a handsome investment. With the growing appreciation of the work of the laboratory an increasing number of applications have been received for tests for private interests. Such tests are now being done at a small charge.
154. In conjunction with the building of a new works depôt for the P.W.D. Works Office on the new North Point Reclamation and the rebuilding of the present pilot laboratory as a permanent institution on the same site, ways and means for the early establishment of stretching beds for the manufacture of prestressed concrete members are under consideration.
155. Miscellaneous works carried out during the year included the removal of a dangerous submerged reef obstructing a ferry berth, some 500 cub. yards of rock being removed by underwater drilling and blasting.
156. Investigation of submarine foundation conditions by borings were carried out for two large projects for 60 acres of reclamation and the construction of breakwaters for a possible new typhoon shelter some 65 acres in area.
157. A new light pier for passenger ferries and general use was commenced in February at Silver Mine Bay on the Island of Lantao. This pier, with a 130 feet long approach causeway and 150 feet long jetty of steel with timber decking was nearing completion by the end of the financial year.
158. Hydrostatic surveys of the Colony's natural reservoirs were undertaken to determine the reduction of capacity by silting.
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