Sessional_Paper_1902 — Page 885

786

10

Application

The sewer starting from F turns to the right on reaching the cross street A B, follows it as far as the street H I, runs down the latter to its intersection with the cross street C D, then along this cross street to K L, and so on. The merit of this arrangement is that each length of sewer in the cross streets A B and CD, presumably those having the least natural fall, is fully flushed, not merely by the sewage from the abutting houses, but from the whole district above.

It may happen that the formation of the ground will permit of a continuous self-cleansing gradient along the streets A B and C D. If such is the case, then it is convenient to make the change of direction of the two sewers, namely, those in the main and cross streets in a common manhole, placing the inverts of the semi- circular channels at the same level. This arrangement offers the additional advantage that, should a stoppage occur in any one street, the overflow will escape by another. Perfect venting, and circulation is moreover secured. A common flush tank, of considerable capacity, may flush the whole system, for by a little arrangement in the manholes a flush say at A might be shunted down any one street or series of streets.

Obviously this arrangement is not universally applicable but it is one which I introduce whenever practicable.

24. It seems possible that this serpentine arrangement might in many cases of serpentine be applied for flushing covered branch drains whenever such are absolutely neces-

covered

<lrains.

sary.

The perennial flow of water from one nullah might be intercepted and passed down through a branch drain to a second nullah and so on.

I have the honour to be,

Sir,

Your obedient Servant,

OSBERT CHADWICK.

Page 885Page 886