Hongkong, 26th January, 1904.
Kowloon Waterworks Gravitation Scheme.
Catchwater.
The honourable W. Chatham,
Director of Public Works.
Dear Sir,
We are now about to get out the contract for above and request instructions as to what length of catchwater we should provide for.
In our letter of 14th October, 1901, it was proposed to construct a sufficient length of catchwater to intercept the water from 400 acres, the channel to be of such sectional area and gradient as to carry 12-inch rain per hour from this area, this we estimated could be done for about $40,000.
Since this estimate was made Mr. Chadwick has advised that the catchwater be built of such a gradient as to give a velocity of 5 or 6 feet per second. The Tytan catchwaters on which our estimate was based have a velocity of 10 to 12 feet per second, decreasing the velocity by half would necessitate doubling the sectional area of the channel and consequently at least doubling the cost.
The advantages of the reduced velocity are:-
1. Decreased wear and tear in catchwater and
2. Increased carrying capacity, it being found that with a high velocity a channel did not actually carry the quantity of water which, judging by its sectional area and gradient it was expected it would carry, the wave action set up by the high velocity causing overflow before the channel was actually running full.
With
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The honourable W. Chatham,
Director of Public Works.
Dear Sir,
386
Hongkong, 26th. January, 1904.
Kowloon Waterworks Gravitation Scheme.
Catchwater.
We are now about to get out the contract for above
and request instructions as to what length of catchwater we
should provide for.
In out letter of 14th. October, 1901, it was pro-
posed to construct a sufficient length of catolwater to intercept the water from 400 acres, the channel to be of such sectional area and gradient as to carry 12inch rain per hour from this
area, this we estimated could be done for about $40,000.
Since this estimate was made Mr. Chadwick has
advised that the catchwater be built of such a gradient as to
give a velocity of 5 or 6 feet per second. The Tytan catchwaters
on which our estimate was based have a velocity of 10 to 12 feet
per second, decreasing the veiccity by half would necessitate
doubling the sectional area of the channel and consequently at
least doubling the cost.
The advantages of the reduced veiccity are :-
Decreased wear and tear in catchwater and - Increased carrying capacity, it being found that with a high velocity a channel diä not actually carry the quantity of water which, judging by its
sectional area and gradient it was expected it would carry, the wave action set up by the high velocity causing overflow before
the channel was actually running full.
With
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