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Report of the Medical Officer of Health.
149
The replies received from other towns show that in a considerable
proportion such complaints have been received, and
that in the majority of these the surface ventilators are being
closed and shafts erected in their place. That this does away
with the complaints is certain so far as can be ascertained from
the replies received, but whether it is the best means is a difficult
question to answer.
The first desideratum is doubtless to have thoroughly well
laid sewers and frequent flushing of the same. The second, to
have manholes in the roadway where it is of sufficient width, and
there is no doubt that in that position there is less risk to
passers-by as sewer gas is very quickly diluted with fresh air and
has little chance of entering dwelling houses.
If offensive odours are being given off then the sewer at that
part should be flushed and cleansed, as the presence of sewer gas
shows that a deposit has taken place and consequent decomposition.
There is not much use in flushing a sewer at a distance
from such deposit, but the deposit should be located and removed.
In addition to surface ventilators the construction of shafts
as is done at present is the only other alternative, but whether to
supplement the surface ventilators or to take their place must
depend upon circumstances. If the roadway is narrow and the
production and emission of sewer gas is frequent then the surface
ventilators ought to be closed. All dead ends of sewers ought to
be ventilated by means of these shafts, and numerous examples
exist in the Borough of the nuisance having been abated in this
way.
I am, however, of opinion that the more frequent repair,
removal of deposit, and flushing of the main sewers is an absolute
sine qua non, and until this is carried out the generation of sewer
gas will continue and little or no improvement can possibly result.
The smell may be bottled up or discharged at higher levels, but
nothing short of the removal of the causes will be satisfactory
from a sanitary aspect.
Other methods have been suggested for the ventilation of
main sewers, such as a ventilating pipe on the house drain on the
sewer side of the intercepting trap, but this is open to one great