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9
SECTION C—SANITARY CIRCUMSTANCES.
Water Supply.
Richmond has two separate sources of drinking water:—
(a) From local wells.
(b) From the Metropolitan Water Board.
(a) Richmond Borough Council owns seven wells. One of
them, known as the Terrace Gardens well is 320 feet deep and
reaches two miles of adits in the chalk. From this is obtained a pure
and wholesome water which is softer in character than the supply
obtained from the remainder. These are shallow wells which draw
their water from the ballast covering the London clay.
The water is not filtered but is chlorinated before being passed
into public supply.
Early in 1948 it was found that the two Ham Wells were not
maintaining a wholesome supply and their use was discontinued.
Water from these wells could not be kept under close supervision by
passing it through the Petersham reservoir without laying new mains
and thus incurring heavy expenditure.
The local supply now comes from the deep well, from two
shallow wells in the Old Deer Park and from two shallow wells in
Petersham. Water from all these wells is pumped to the low level
reservoir at Petersham where it undergoes controlled chlorination. It
takes two to four hours to pass through the reservoir and is then
pumped to the high level reservoir in Richmond Park where it remains
for 24 hours before passing into public supply.
Estimations of the amount of free chlorine in the water issuing
from the low level reservoir are carried out every two hours by day
and night by the staff of Petersham Pumping Station. In addition
the free chlorine is continuously recorded by mechanical means at
the Petersham Pumping Station and at the Old Works, Water Lane.
It has been found that, to ensure a safe and wholesome supply dosage
with chlorine must be maintained so as to provide between 0.4 and
0.5 parts per million free chlorine in the water issuing from the low
level reservoir. After 24 hours contact in Richmond Park reservoir
the free chlorine content is reduced to 0.15 p.p.m. and, by the time
is reaches the consumer the free chlorine content is about 0.1 p.p.m.