Cols Nos. 1, 2 and 3.
28.
There are three depressions in the ridge which would form
part of the western boundary of the reservoir, referred to as Cols Nos. 1, 2 and 3, and it has already been pointed out that
a borehole sunk at Col No. 1 failed to reach solid rock at
depth of 150 feet, the surface of the ground being at level 163.
It was not therefore deemed advisable to impound water to a greater depth than level 190, which would involve closing this
gap with a short dam about 40 feet in height.
29. At Col No. 2 weathered rock is exposed at the surface,
the level being about 187, calling for a dam about 15 feet in
height, and at Col No. 3 the surface of the ground is at about
level 184, a dam about 18 feet in height being required.
30.
The main dan would have a maximum height of about 190
feet above the valley bottom its length at road level being
about 940 feet.
Capacity of Reservoir.
31. A diagram prepared from the contoured map indicates that if water were impounded to 190 feet, the reservoir would hold
about 7,400 million gallona. It is not advisable, however, to
draw down the reservoir below level 100 if the scheme is to be
laid out in the most economical manner; the available contents
would therefore be reduced to 6,400 million gallons, or more
than twice the contents of the Jubilee Reservoir.
Catchment Area.
32.
The area draining direct to the reservoir amounts to
4,200 acres, which can be augmented by catchwaters which would
enable a large additional area to contribute to the reservoir.
33.
The extent to which it would be economical to construct
these auxiliary works must be left for future determination,
but it would appear from the contour map that about 8,000 acres
would be the probable limit.