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23
Sewerage and Sewage Disposal.—The District is
drained by the dual system. The surface water sewers discharge
at convenient points into the nearest watercourses, and as the
fields adjoining the smaller courses become converted into building
land, suitable sewers and culverts are provided. Where possible
and necessary the surface water sewers are laid at such depths as
will enable the subsoil under cellars and basements to be drained
and connected thereto, thus ensuring dry dwellings and avoiding
any accumulations of stagnant water inside any dwelling house.
The main foul sewers traverse as much as possible the natural
valleys, and run from the higher lands on the east towards the
west, where they join up to the sewers of the Edmonton District
at three points along the boundary between the Southgate and
Edmonton Districts. At each of these points is a specially
designed chamber, entirely constructed underground, for gauging
the quantity of sewage that passes through. By the Edmonton
Local Board Separation Act, 1881, by which Southgate became a
separate District, the Edmonton District is required to receive,
convey, and dispose of the sewage of Southgate, payment being
made according to the quantity ascertained by a monthly system
of gauging. After the separation from Edmonton it was found
that the main sewers were in a very bad condition, and these have
since been reconstructed upon the most approved principles.
Only one length of sewer, apart from culverts, is now constructed
of brickwork, that one being the southern main joining the
Edmonton sewers.
The sewers are laid principally in open trenches, but as their
depth is in some cases as much as 25 feet below the surface, the
driving of short tunnels as headings is occasionally resorted to.
Pymmes Brook is crossed in several places by means of inverted
syphons. These have been constructed with iron pipes from
special designs, which permit the smallest area of sewage being
exposed in the manholes, and have worked satisfactorily. The
sewers are also carried at several points under the New River, and
recently the late New River Company insisted upon a special
system being adopted, by which large cast-iron shield pipes are
forced by means of powerful hydraulic jacks through the clay
under the river, thus forming tunnels in which the sewer pipes
are laid.
In the case of new streets, not a pipe is permitted to be
covered up until the work has been thoroughly inspected and the
foul sewers tested with water. The pipes used have special joints,
are made of the strongest stoneware clays, and laid upon a thick
bed of cement concrete. In addition they are laid to absolutely
straight lines from point to point, and by means of manholes can
be examined and seen through from end to end. At the head of
every branch sewer means are provided by vertical shafts—lampholes
and flushing chambers—through which thousands of gallons