399
the present works and make use of the existing main in preference to establishing Water works - carrying out any new, elsewhere or new system.
The works as at present existing supply the wants of the City during the rainy season or from April to October inclusive, What is required is a Reservoir sufficiently large to impound a supply for the dry season or from November to March inclusive during which time probably not a drop of rain may fall.
105,000,800 Gallons would be required to supply 700,000 Gallons per diem for 5 months or per diem say 150 days. From this may be deducted 108,000 Gallons running daily into the Reservoir during the dry season making the quantity required to be impounded 58,000,000 Gallons or allowing 11,200,000 Gallons for evaporation making the total required capacity 100,000,000 Gallons
The present Dam is simply a weir 120 feet long and 10 feet in height - perpendicular on the up side and sloping on the down side, a bank of concrete faced on both sides with Granite, and has a culvert through the centre 3 feet x 2 feet - for the purpose of emptying the Reservoir at any time. All flood waters from the valley have passed over this weir since its construction in 1867 there being at present No other means of exit.
The Dam is built on solid Rock formerly the bed of the stream, and I am informed the rock was level with the foundations of the Dam, no excavation being made in it to receive the Concrete, notwithstanding there appears to be no leak of water under the Dam although there is a certain amount of Leakage when the Reservoir is full through the Dam itself more particularly in the neighbourhood of the Culvert.
I propose to construct a 50 feet embankment behind the present Dam as shown on the accompanying Plan, the intermediate space being worked out to form a Gauge Basin holding about 300,000 Gallons.
The bed of the Reservoir will be formed at the level of the bottom of the present Dam, the average depth of cutting being about 15 feet. The area of the Reservoir has been made as large as practicable the hills rising on all sides from the water side at an angle of in some places 50° and at others being nearly perpendicular
It may be seen that the height of the Bank has been fixed at 50 feet in Consequence of the nature of the ground where it is proposed to construct. The top of the Bank will be level. A Bye wash could not have been formed at a greater height without very heavy labour in cutting into the side of the Hill.
The formation on which the Reservoir will be placed Consists of Boulders of Granite of the Kap class composed apparently of Felspar, and hornblende only, and quarry workers for working up. The Alluvium is apparently of a clayey nature when first cut from the bed of the reservoir, but when dry appears to be somewhat porous, and the...
399
the present works und matte use of the existing main in preference to establishing Water works
-carrying out any new,
Cloewhere or
en system.
The works as at present existing supply the mants
manis Kairy Season of the City during the rainy season or from April to October inclusive, What is required is a Reservoir sufficiently large to impound u supply for the dry season or from November to March inclusive during which time provibly not a drop
of fall.
of rain may of ballons would be required to
105 000. 800
supply 700 000 Gallons per diem for 5 months or
perdiem say 150 days. From this may be deducted 108,000
Gallons ruming daily into the Reservoir during the dry season mating the quantity required to be impounded 58.000 000 Gallons or allowing 11, 200 000 Gallons for evaporation mathing the total required capacity 100 000 000 Gallons
The present Dam is simply a reir 120fect-lony. Existing Dam and 10 feet in height-yourpendicular on the up side and ploping on the down side of M
Stream, Icon- sion of a bank of concrete faced on both pides with. Granite, and has a culvert through the centre 3 feet x 2 feet - for the yourpovve of emplying the Prescrion at ceny time, All flood waters from the valley have passed over this weir price its construction in 1867 there being at present No other means Lexit.
of
The Dam is built on Jolid Rock formerly the bed of the streams, and I am informed the pock.
" oimply Cur-level,
[ for the foundations :
Grove
of the
" the Dam, no excavation beingmade in it to receive The Concrete, notwithstanding there appears to be no Quep of mater under the Dam although there is as of Leakage when the Reservoir is full through the Bum itself more particularly in the neighbourt word of the Culvert-
Certain amount-.
Gauge Ipropvoc
Raisin I propose to construct in 50
- construct is 50 feet ombanttment behind The present-Dam as shown
on the accompanying "Fan the intermediate space being word ou
Gauge Basin holding about 300.000. Gallons.
to of Reservoir The bed of the Reservoir will be formed
a
at the level.
the.
of the bottom of the prevent Dams, the average depth
The area of 15 feet- of cutting being about- 15, Reservoir has been made as large as practicable the hills riving
on all sides from the water side at an angle of in some places 50° and at others being nearly perpendicular
A mice be seen that the height of the Bank has been fixed at 50 feet in Consequence of the nature of the ground where it is proposed loton- Aruct. The Yoye math. A Bye wash could not- have been formed at a greater height-without- very heavy labor in cutting into the side of the Mill
stogical Fermation The formation on which the Reservoir will be placed Consists of Boulders of Granite of the Kap class come pored. appoarently of Felspar, and homblende. only, and quill woelers for working up. The Alluvium is apparently of a clayey nature when first-cut- from the bed of the reservoir,
the reservoir, but other dry appears to be somewhat pourous, and the..
a
No comments yet.
Private notes are available after approval.