(a.) The channels containing sewage should be of enduring and impermeable material, so as to prevent all soakage.
(b.) There should be throughout the channels of the subterranean metropolis a fall or inclination which would suffice to prevent the accumulation of any sewage deposit, with its deleterious influence and ultimate costliness.
(c.) Similar provisions should be used were it but to prevent the creation of the noxious gases which now permeate many houses (especially in the quarters inhabited by the poor) and escape into many streets, courts, and alleys, for until improvements are effected the pent-up sewage and the saturated brickwork of the sewers and older drains must generate such gases.
(d.) No tidal stream should ever receive a flow of sewage, because then the cause of evil is never absent, for the filth comes back with the tide; and as the Thames water constitutes the grand fount of metropolitan consumption, the water companies, with very trifling exceptions, give us back much of our own excrement, mixed with every conceivable, and sometimes noxious, nastiness, with which we may brew, cook, and wash—and drink, if we can. Filtering remedies but a portion of the evil.
Now it would appear that not one of these requirements, the necessity of which is unquestioned and unquestionable, is fully carried out by the present system of sewerage, and hence the need of some new plan in which the defects may be remedied, and the proper principles carried out.
The instructions given by the Court were to the following effect:—
A. The Thames should be kept free from sewage whatever the state of the tide.
B. There should be intercepting drains to carry off the sewage (so keeping the Thames unsoiled by it) wherever practicable.
C. The sewage should be raised by artificial means into a main channel for removal.
D. The intercepting sewers should be so constructed as to secure the largest amount of effective drainage without artificial appliances.