UNIQUE ENGINEERING AND
CONSTRUCTION FEAT
SECTION OF THE
CIRCULATING
WATER
PUMP HOUSE
FOR
B "
STATION
OF THE
H. K. ELECTRIC
CO., LTD.
new
Bottom Section increased in depth to 26′, and 1,400 tons, being floated into permanent
position where it was sunk on to prepared foundation.
Progress on the erection of the big down to -14.50 in the water by means of amount
two Generating Station at North grabs manipulated by
electrically on an driven scotch Point of the Hongkong Electric Co., tons capacity, and the
derrick cranes, one of 15 the other of 7 tons Ltd., known as "B" Station, is pro- capacity, each equipped with a jib 120 ceeding apace.
feet long.
was
necessary to keep the structure even keel when floating. The walls were, excepting the front one, 18" thick and the temporary thick- ness of the floor 8". There were 5 division walls dividing the length into 6 for the installation of 6
to brace the long walls against water Circulating Water Pumps. These served
pressure while floating. Pipes and valves of 6" and 10" diam. were built into the walls so as to permit of water being put into any of the 6 sections for trimming purpose, and for weighing down the float- when it had been floated ing structure into position.
This In a project of this size located
tedious operation which compartments a took 4 months to along the old waterfront site, it was the blasting of the heavy concrete walls. carry out including expected that difficulties would be what made the work more tedious was encountered in the foundation work. the presence of 12" X 12" RSJ piles The following is a very interesting which were embedded in the concrete of account of how one of these difficulties the sea wall presumably to prevent slid ing. There were 15 such piles which were was met and overcome.
constantly being gripped by the grabs. Each of these had to be cut off in several short lengths by 4 lb. charges of gelignite as they were uncovered. This then gave the grab access
to the loose concrete debris surrounding the piles.
Part of the "B" Station is the Circulat- ing Water Pump House and this has just been installed on the Graham Praya which is in continuation of Mackies Wharf, both of which form the northern boundary of the Generating Station ground.
The Graham Praya, like Mackies Wharf, was formed by the dredging of a channel in the sea bed and depositing therein, from junks and barges, large boulders from 2 to 4 tons in weight up to low tide
Such a method as this made it neces- sary to build the Pump House up to a height of 26 feet as a floating structure and this was accomplished in the following manner.
Construction of this bottom section commenced on 2nd October and on 18th November it was launched and towed over 20th to Mackies Wharf, North Point on November. The floating structure was perfectly watertight.
Between then and 1st May the structure was, while floating, raised to a height of 26 feet and a weight of 1400 tons, the floor being strengthened at а suitable
The Hong Kong & Whampoa Dock Co level. Upon this the granite block faced Ltd. very kindly allowed the Contractors, stage by the addition of a further 22” of
concrete wall was raised to 14 feet above
for what was considered a reasonable low tide.
price, the use of a slipway which was Unfortunately in the middle of the site equipped with a carriage, on over 200 of the Pump House, an old reclamation wheels, running on a rail track and wall ran into the grounds of the Station capable of dealing with a weight of 800 in a southerly direction and this
character.
was tons.
These mounds of rubble precluded the tons on
reinforced concrete. The walls were braced against the mounting water pres- sure by timber struts at suitable places. When the excavation was completed to the designed level the bottom
was soft. Undisturbed samples of the strata obtained and sent to the University for examination and tests. 'The result of the tests showed that good sand available 2'-6" lower and excavation was continued to this level.
were
was
formed on а rubble mound of similar It was decided to build the bottom part of the structure up to a weight of 400 The size this slipway carriage. use of steel sheet piles to form a coffer of this structure was 67'-6" long by 40 dam round the site of the Pump House, in feet wide by 8 feet high on the average. the conventional way, which would have The front wall of the Pump House, by The extra depth was refilled with sand allowed the working area to be pumped reason of its having to accommodate from a granite quarry to a depth of 2'-0" dry. It was therefore decided to surround guides for Screens and Stop Log Gates, in the first instance. It was most desir- the site, so far as it was on land, with was considerably heavier than the back able that the bottom on which the Pump steel sheet piles tied back to concrete wall so the back wall was raised higher House was to rest should be quite level anchor walls and to excavate the site than the level of the other 3 walls by the and plane and this could only be done
67