Evening star. [volume] (Washington, D.C.) 1854-1972, 1882-11-25

when new sewers must be built for that pur-
pose 1t win generally be cheaper. It's cost will
also be favorable in densey inhabited districts
from the circumstance that the proportion of
sewage to rain-water win be greater and there
fore increase the sizes Of the separate sewage
pipes, yet without decreasing those of the rain
water sewers; while the sizes Of the combined
would not vary with the population, because
the quantity OF sewage is less than the guam
tfty within which the amount OF storm water
can be estimated.
"But more important is the fact that in
closely built up sections the surface washings
from slight rains would carry an amount Of de-
composable matter into the rain-water sewers
| which, when it lodges as the flow ceases, will
cause much greater storage OF filth than In
well designed combined sewers which have q
continuous flow, and generally, also, appti-
ances for flushing. In cities which have every
indication OF rapid growth, these points become
OF impo rtance when deciding upon system.
| SEPARATE SYSTEM"
"The separation Of sewage from rain water by
leading them into different channels originated,
| as already mentioned, from causes which were
| mainly financial. Where existing sewers could
be made use Of for rain water conveyance alone.
very much smaller pipes were necessary for
sewage and when proper and complete purif-
| cation Of sewage was very expensive, it was ad-
vantageous to prevent 1t from being OCCASION
ally increased even by small quantity of rain
| washings from the surface.
"The old sewers being Incorporated into the
new system with slight alterations and exten
sions, naturally reduced the cost of the entire
works very materially. 1t was then
thought tn Sa ,s as the sewage was found
pipes, and, on the other hand, many, If not most
OF the large sewers showed accumulations Of
house filth, that the separate system had inhe
rent merits on sanitary grounds.
| among those who are advocating the princi-
pie. there is some disagreement as to the design
by which it will be best accomplished. Several
systems areproposed, the distinguishing features
OF which are briefly described as follows:
| 1.-The ordinary separate system as used in
| England consists Of pipeline extending into
i each house. there to receive the house drainage
/ generally with an admixture Of some rain water
from the yards and back building. The rest Of
the rain water, where it cannot flow off in sur
face channels, is carried off through separate
sewers. These may be quite shallow. as their
only object is to remove the water from the
| surface.
1.-The details OF the former are substantially
IKE those of the combined system. The
only differences are in their shape, which
Is CIRCULAR on account of the regularity of flow,
and their size. which Is very much smaller
The details of the rain-water system are also
substantially like those of the combined. ex-
cepting their depth, and in most cases the
absence Of connections except from street inlets
In shape and size there is no material varia-
ton"
ut appears, therefore, that neither are the
tages great. except in certain cases where puri-
| 1cation is difficult and the pollution of rivers
| feared.
Regarding now the comparative cost the
separate system is said by its advocates. especi-
0tsj those claiming patents, to be much cheaper.
| When rain water can as conveniently and safely
be led off on the surface. there is no need for
| the combined system and its cost, mainly due
to storm-water removal, should not be COM
pared with that Of only part of the separate
| system.
The principle Of separation, therefore. al
though often Ostensibly preferred on sanitary
| grounds, does not necessarily give the system in
this respect any decided advantage over the
combined. except under certain definite cOndi-
| lions. Under all others, preference will depend
| on the cost both of construction and mainte-
nance, which only careful estimate, based on
the local requirements can determine"
''These points, among others, are brought out
prominently by the advocates of the separate
system in arguments to show its great superb
ority over the combined. A close examination,
however, will show that the results obtainable
are IN some points only slightly better and in
Others not necessarily so. A bias is here un-
doubtedly observable. The fact that there are
direct personal interests concerned in several of
the systems brings that out more promi-
nently, and it Is also observable that those
who advocate them exclusively are
generally not concerned in directing,
managing, nor are always thoroughly familiar
with the engineering questions in a large and
pOpulOus city. The advocates OF the separate
| system usually Ignore the practical possibility
| OF making large sewers as perfect sewage car
| rlers as small ones basDg their opinions on per-
feet works in this case and imperfect ones in the
other.
San actual and extensive inspection cannot
but reveal the fact that the above points give
only slight advantages, if at all noticeable over
properly designed and constructed combined
| systems, and also that the latter can readily be
kept as well cleaned as is necessary.
! 'This can be particularly noticed in Frankfort
Hamburg, and the river sewers of London, Lly-
erpO0l, and other English cities, in which the
| air before and during flushing was not found to
| be very Offensive-no more so than in Reading
| Oxford, and other towns using the separate
pipes"
CONCLUSION
"FrOm the foregoing remarks, and mainly
| from the advantages and disadvantages claimed
by the advocates and opponents of the various
| systems as they were stated to me, and to which
| have given such relative Importance and criti-
cisin as my own inspection and examination of
| the works has warranted, several conclusions
can now be drawn.
''The sanitary demands upon system of sew
erage. it is agreed, consist in the prevention Of
decomposition to the greatest possible extent,
and where the latter is unavoidable to decrease
its injurious effects to minimum"
cit can be concluded, from what has been
said, that these demands are fulfilled within
| satisfactory limits by each one of the mentioned
| systems provided they are designed and built
! in as perfect manner as possible, according to
| the principles known to facilitate such removal
and to prevent any evil effects which may arise
| from unpreventable imperfcctions supe-
| riority Of one system over another in
this respect will. then, not depend on
its specific principle as much as on
| the conditions Of the locality where
it is applied and on the care given to It's main
| tenance. misappcation on one hand and
neglect on the other will have a much greater
influence on the sanitary condition Of each sim
gle system than the difference between any two
| systems can have under equally good condi-
tions. 1.-THE factor. therefore, which will
mainly govern preference, is less the sanitary
| value, as frequently asserted, than the cost Of
construction and maintenance. But as also the
cost depends ON the locality, on It's physical
| features, on social requirements, and on the
| value OF ground and materials, 1t is evident
that the criterion for Judging the relative ad-
| vantages of the different systems, both from a
sanitary and financial point Of view, is the
locality itself. And as the conditions presented
by the various cities and places are exceedingly
different, not one particular system will be the