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65
For these, and other reasons, I am of opinion that the water
from Surrey Street wells requires filtration, and that, as soon as an
additional supply has been obtained, the whole of the wells should
be overhauled, their linings examined and probably extended, and
further tests made as to the risk of contamination from adjacent
sewers and drains.
ADDINGTON WELL.—On no occasion has this well been
suspected of conveying disease. Water from this well is usually
extremely satisfactory fiom both a chemical and a bacteriological
standpoint. Unfortunately, however, during recent years it has
been found that the well is subject to intermittent pollution within
24 to 48 hours after excessive rainfalls. For reasons which need
not now be discussed it is believed that this pollution is due to
surface water, which finds its way into a fissure extending over two
miles to the south of the well. Now where surface water finds its
way to-day there is considerable risk in a populous district that
infected sewage may get to-morrow, and it is clear that this risk
is increased by the considerable growth which is taking place in
the population on the gathering ground. 1 have, therefore, no
hesitation in recommending that steps should be taken by sand
filtration or otherwise to purify Addington water before distribution
and thus avoid the risks attendant on the intermittent pollution
which we know to exist.
WADDON B0RE=H0LE.—'1 he report of the Local Government
Board has already been quoted. Taking all the facts into consideration,
and especially our complete ignorance as to the course
of any fissures that may communicate with this well, I am of
opinion that this water should eventually be filtered. The possible
existence of such fissures is, indeed, in all probability, of more
significance than the mere fact that the Waddon site is situated on
bare chalk. Indeed it is probable that less risk attaches to a
gathering ground of uncovered chalk than to one which is partially
covered like that at Warlingham, where in times of heavy rainfall
a large volume of water collects on the overlying impervious
clay, forces its way through some defect in this stratum into
the chalk which is thus undermined, producing more or less defined
underground channels which may carry pollution to some distant
well.
STROUD GREEN WELL. —The site of this well is covered by
many feet of impervious strata, and there is therefore no risk of
contamination from any source of pollution in the immediate
neighbourhood.