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55
the County of London. It has been realised for some years that the water of
the Thames during the summer does not progressively improve from the outfalls
to Teddington. The improvement which is observed on the early part of the
journey does not continue, but a zone of deteriorating water is reached followed
by some improvement towards Teddington. The low salt content of the bad
water in these upper tidal reaches shows that it is not water which has come up
with the tide from the region of the outfalls of the Council but is rather fresh
water from the non-tidal reaches which has become polluted on its way to the
outfalls and ultimately to the sea. It is this water only which is available for
dilution of the Council's effluent and it is insufficient both in quantity and quality
for this purpose.
"During the summer months (June to September) of this year the flow of
sewage from the Council's outfalls averaged 238.9 million gallons per day (the
average for the last ten years was 273.3 million gallons per day), and it is
estimated that the effluent from other sewage works discharging directly or
indirectly into the Thames below Teddington weir and above the Council's
outfalls averaged 65 million gallons per day, and that the flow of upland water
in this length into the Thames which is not measured would be, perhaps, 15
million gallons per day. The flow of the Thames itself over Teddington weir
averaged 76.7 million gallons per day (June, 129.6 million gallons per day,
July, 73.8 million gallons per day, August, 54.1 million gallons per day,
September, 50 (approximately) million gallons per day.
"The statutory flow in the Thames under the Thames Conservancy Act,
1932, is fixed at 170 million gallons per day, but under powers provided in that
Act the Minister of Health reduced the minimum to 100 million gallons per day
on 22nd June and to 50 million gallons per day on 11th July.
"The result is that during the last four months a quantity of sewage effluent
approximating to 300 million gallons has been discharged each day into the
above-mentioned length of the Thames and has been carried up and down by
the tides, while the flow of upland water tending to drive it down stream was on
occasions as low as 1 /15th of this quantity, while during an average year the
flow of upland water was at least equal to the sewage flow and generally exceeded
it two and three times.
"The Thames has not received a winter scouring by flood water for two
years. As far up as Twickenham at high water it is both dirty and covered with
floating matter—barges are employed in collecting driftwood. The quantity and
quality of the freshwater flow available or permitted do not suffice to remove
all this matter, to remove and oxidise accumulation of foul mud and to purify
the Council's effluent.