NEW CONSTRUCTION,
139. A contract for the construction of underwater foundations for some 4,000 lineal feet of sea wall to retain future reclamations at Kuntong Bay and at North Point, and a 1,500 ft. length of 100 ft. wide open nullah to drain the high ground behind the former bay was completed in December. In all, the contract called for 454,000 cub. yards of dredging for foundations, the dredging and dumping of 475,000 cub. yards of sand for foundations, 230,000 cub. yards of hydraulic sand fill and the quarrying and placing of 113,000 cub. yards of granite rubble. The works under the contract costing $5,613,000.00 (£350,750) were completed in the contract time of 26 months.
140. In each locality foundations were excavated by means of bucket dredgers to an average depth from -40' to -45' C.D. with a maximum of -56′ C.D. These trenches were then filled with sand dredged from the harbour bed, dumped by 500 cub. yards hopper barges and mounded with side slopes of 1 in 2 to an elevation of -15′ or -20′ C.D. depending on the exposure to wave action. It was found that this profile remained unaffected by wave action or tidal scour below a depth of 15 feet and the use of sand in place of pell-mell rubble resulted in substantial economy. To protect the sand mound and build up through the zone of wave action up to -3.5′ C.D. granite rubble, roughly graded from 20-lb. to 2-ton stones, was dumped from 100-ton tipping barges. The finished profile of the rubble mound was given a seaward slope of 1 in 1½ with a slope of 1 in 1 on the inner or reclamation side. The top of the mound was levelled off 17 feet wide 3′ 6′′ below chart datum to receive the precast concrete 20-ton foundation blocks of the future reclamation sea-wall.
141. The same methods were adopted for the construction of the nullah at the eastern end of the bay abutting the extensive new installation of the Asiatic Petroleum Co. During dredging operations an unexploded 6′ long 2,000-lb. bomb was picked up in one of the buckets of the dredger. Two draglines levelled the sand-bed of the nullah to a longitudinal grade of 1/400 over the 1,500 feet length with a transverse grade of 1/50 from side walls to centre of the 100 feet width. Invert slabs were of plain precast concrete, 7′ 6′′ square x 9" thick, bedded on a 6" thick mat of 2" crushed stone. On completion of the invert, the gravity section nullah wall of coursed granite-faced mass concrete was built, also on sand, and some 220,000 cub. yards of sand pumped up behind it to an average elevation +17′ C.D. to extend the Oil Company's installation area.
142. At North Point a further contract was let in November 1950, for the construction of 1,000 lineal feet length of sea-wall on the subaqueous foundations referred to in paragraph 139. 15-ton precast concrete foundation blocks were bedded under-water on the rubble mound and from elevation +2.5′ C.D. a gravity wall of mass concrete faced with coursed granite was built.