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79
In considering these reports the first thing that strikes us is that the views of the
two Surveyors do not agree. The suggestion of the Surveyor of Lewisham which may
be regarded as the multiplication of the openings in the roadways and the abolition of
interceptors differs most materially from the recommendation of the Surveyor of Shoreditch,
which simply amounts to abolition of interceptors. The former, which provides
for two sets of openings into the sewers, one to act as inlets and the other as outlets,
is theoretically satisfactory, the latter is not so, as no provision is made for additional
inlets. This difference is doubtless determined by the local knowledge possessed by
the two gentlemen in question as to the existing conditions of the sewerage systems of
their respective districts. We direct attention to it as it aptly illustrates the truth of
the opening statement of the Borough Surveyor of Lewisham as to the divergence of
opinion amongst Borough Engineers on the subject of sewer ventilation.
We think it highly probable that the method suggested by the Surveyor of Lewisham
would not be reliable and that the liability to smells in the roadways would remain.
Indeed the Surveyor of Lewisham himself appears to hold a similar opinion, for
he seems to refer to the mitigation of the nuisance as being a partial one. In theory
the openings in the roadways should act as inlets to the sewers, whilst the ventilating
shafts of the house drains should act as outlets. In practice, however, a variety of conditions
affecting the flow of sewage, temperature and barometric pressure would undoubtedly
come into play, and most seriously interfere with the proper action of the
method suggested.
Any method which simply depends upon the ventilating pipes of house drains,
without increasing the number of openings in the roadways, such as appears to be in
the mind of the Borough Surveyor of Shoreditch is hardly likely to satisfactorily ventilate
the public sewers. It is difficult to understand how sufficient movement of air is going
to be produced in the sewers under such a method. All that it can be relied upon
to do is to allow of a certain amount of diffusion of the sewer gas from the outlets
of the vent pipes of the house drains and this diffusion will again be very dependent
upon meteorological conditions.
Sanitarians hold that every possible step should be taken to prevent the impregnation
of dwellings with sewer gas, and there is a very general impression in the public
mind that sewer gas is much more dangerous in its effects than drain emanations.
Certainly the effluvia from well-laid, properly ventilated and intercepted house drains
are as a rule nothing in comparison with those commonly experienced in connection with
public sewers. To dispense with intercepting traps and permit the emission of sewer
gases from ventilation pipes on private premises, would, in our opinion, be a dangerous
and possibly costly experiment. The smells from the sewer ventilators in the roadway
are bad enough at times, but to have similar smells evolved in situations where they
are much more liable to obtain access to dwellings by means of the windows or chimneys,
as is very likely to be the case with the ventilation pipes of house drains which
are not intercepted, is to our minds a short-sighted policy and one which is pretty certain
to be associated with numerous complaints, and there is not much doubt that the
air breathed in the dwellings in Shoreditch would be likely to be distinctly less pure
than it is at present.