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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 very satisfactorily.
The sewers are also carried at several points under the New
River, and recently the late New Rivor 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 soil under the river, thus forming tunnels in which the
sewage 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 for flushing are provided
by lamplioles and flushing chambers, through which
thousands of gallons of clean water are systematically delivered
in order to prevent any deposit within the sewers. There are
upwards of 100 of these flushing chambers within the district.
Fortunately, all the sewers may be said to be self-cleansing, and
within an hour or two of any foul matter being discharged into
a drain or sower it is delivered to the Edmonton Sewage Works.
The sewers are ventilated by means of gratings over the
manholes and by upcast shafts; but the gratings intended to be
inlets for fresh air sometimes also discharge foul air, in consequence
of which many of them have been closed in, and extra
upcast shafts erected at points of vantage in their place.
During the past seventeen years no drains of any house have
been permitted to be connected with the sewers unless they have
been provided with a chamber just within the boundary adjoining
the street or road containing a trapped interceptor.
Although the District is scattered over so large an area,
there are very few houses which are not near a sewer, so that
fortunately very few cesspools now exist, and they are becoming
less every year.
In the District there are now 43 miles of foul sewers, and
39½ miles of surface-water sewers, and no less than 39 miles of
these have been constructed during the past eight years.
Sewers.—During the past year a total of 7,230 yards of
sewers were laid as follows :—
New foul sewers 920 yards.
New surface-water sewers 2,981 „
New Estate Sewers.
Foul sewers 1,693 „
Surface-water sewers 1,636 „