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66
House Drainage.
A great many house drains were entirely re-constructed
and a large number repaired. This work was carried out
under the supervision of the Sanitary Inspectors, and
thoroughly tested before being passed. A block plan of each
new drain is prepared by the Inspector upon the completion
of the work, and this is filed and kept for future reference.
This system of keeping graphic records has been in operation
for some years, and constantly proves its value. Increasing
use is being made of heavy cast-iron pipes in place of stoneware,
and there can be no doubt of the advantage of such
construction. A detailed statement of the work done is set
out in the Inspector's Report.
Sewerage and Sewage Disposal.
The drainage of the district is nominally on the dual
system, but the Council's Eaigineor has found that in past
years a number of surface water connections have been made
to the soil sewers, and there is also a considerable influx of
sub-soil water into some of the older ones. The flow of
sewage is therefore considerable after periods of heavy rain.
All surface water not discharging into the soil sewers discharges
into the natural watercourses—the Western district
draining into Dollis Brook, or Brent water-shed, and the
Eastern portion of the district draining into' the Strawberry
Vale, or Lea water-shed.
The district of Finchley is drained by two sewers-, the
higher portion of the district draining into an outfall known
as the "high level" seweir, and the lower portion of the district
draining into a sewer known as the "low level" sewer.
The sewage discharged from the "high level" sewer, after
screening, is mixed with lime and proto-sulphate of iron, and
then passes into settling tanks, where the grosser solids are
deposited. The super-natant liquid is drawn off and treated
on rough filters before passing on to the grass land, and
thence into' the Strawberry Vale Brook. The sludge from the