387
dotjeriva **JA: 900LWOR
With the low velocity some economy could we think
be effected by substituting concrete for the stone pitching at
the bottom of the channel, and, where the natural side slopes
adait, by constructing the outer bank entirely in made ground.
We find however on laying out the trace for the
catchwater, that the water from a much larger area than the 400 acres originally contemplated might be intercepted. To utilize 400 acres a catchwater about 2 miles long would be required,
while by an additional ½ miles of catchwater picking up the
stream from the Shatin Pass a further area of 600 acres would
be added. And the question arises whether it would not be
advisable to at once construct this additional length of catch-
water.
120010. Ar 10 sadel Jub al
you.
There are 4 alternatives which we would lay before
$900
1. To construct a catchwater as originally proposed to intercept 1¼" rain per hour from 400 acres.
2. To construct a catchwater to intercept 1½" rain per hour from 1,000 acres.
3. To construct a catchwater to intercept a less amount, say 1 inch per hour from 1,000 acres.
4. To construct a catchwater to intercept the water from 400 acres but of such a size that it may afterwards be extended to intercept 1" per hour from 1,000 acres.
We are inclined to favour the adoption of No. 3
for the following reasons:-
It would give in a dry year nearly as much as No.2 and considerably more than No. 1 or No. 4.
It is most probable that it will be necessary to carry out the complete catchwater to the Shatin Pass stream within the next 10 or 15 years (especially as we find the area to the West of site No. 2 of Mr. Gibbs' original report is not so suitable for catchwatering as was originally supposed) and it is probable that in such an out-of-the-way place it will be considerably more costly to construct in two jobs than in one.
It would also have the advantage of definitely
appropriating