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35
VENTILATION OF SEWERS AND THE
SUGGESTED ABOLITION OF INTERCEPTING
TRAPS.
(Special Report presented to the Council on Felritary 2nd, 1905.)
I have carefully considered the letter of the Town Clerk
of Lewisham, dated December 2nd, 1904, together with the
copy of the Report of the Lewisham Surveyor (Mr. Ernest
van Putten), dated November 4th, 1904, and am of opinion
that the suggestion made therein for the removal of all intercepting
traps, and the repeal of the London County
Council Drainage Bye-laws, with reference to the compulsory
provision of such traps, is one that is fraught with considerable
danger to health, and should, consequently, be
opposed at all costs. I agree that some sewers require
more ventilation than they at present have, and that this
may be accomplished by increasing the number of, and
putting closer together, the ventilating outlets and inlets,
either in the form of open surface grids, in the middle, and
at the level, of the roads (providing the thoroughfares be
fairly wide), or by means of shafts or column ventilators of
suitable calibre and efficient construction : the former method
being, in my opinion and experience, the more satisfactory
from a practical point of view ; indeed, shaft ventilators
alone are useless. The Medical Officer of Health of
Lewisham writes to me that he is not in favour of the abolition
of intercepting traps, but that he is of opinion that as
many houses as possible should assist in ventilating the
sewers by some external form of ventilation taken off at
a point behind the intercepting trap at the sewer end of the
drain.
Sewer-gas and sewer-air must be distinguished one from
the other. The former consists of organic and other gases
(the result of putrefactive and decomposing changes in the
stagnant contents of the sewers), and the latter of practically
atmospheric air (which has gained access into the sewers).
Whatever bacteriologists and chemists (e.g., Dr. Andrews
and Mr. J. Parry Laws, and others) may say about the
harmlessness of sewer air, there can be no difference of
opinion as to the deleterious and dangerous properties of