Los Angeles daily herald., 1890-01-02
IS b.,
THE INTERIOR SYSTEM OF SEWERS.

THE INTERIOR SYSTEM OF SEWERS.
The interior system OF sewers considered by
the commission is designed on the so-called
separate plan, 4. e.: the storm water and the
sewage are not admitted into the same pipes.
This separation is advised chiefly ON account
OF the difference IN cost OF the two systems
the rainwater and sewage in one and the same
pipes, becau large sewers can be egg g-shaped
so as TO be Just as selfcleaning as small ones
with the same flow Of sewage.
Some OF the most perfect systems In Europe
are constructed on this plan, ana If Ii was not
for the greater cost in this case 1T would be the
preferable system. However, in your city the
hilly portions need sewers, while they are rot
1ncOnven1enced by storm water. IL is only tn 0
parts OF the city located in natural depressions
that suffer from the heavy rains, and they
sheuld be relieved as coon as possible.
Storm drains can, as Il rule, be built shallow,
only deep enough to be below the. surface
They can be built circular instead of egg
shaped, II this Is necessary to reduce the
height. and give greatest capacity for the least
cott OF material. The cost may, therefore, be
reduced below that which would be necessary
If they were to serve as combined sewers.
The sewerage system proper and the storm
water system will be considered separately.
I.-sEwERAaE SYSTEM.
As before stated, the sewers are proportioned
for population of 100000 persons allowing
100 gallons of sewage per day per head, with a
maximum flow of $50 gallons F1om our own
observations of the present water consumption,
it would l OF be prudent to assume less
quantity.
In the present system the flow amounts to
over $50 gallons per head per day at dry times,
while during rains this amount is increased
beyond the capacity OF the present outfall.
This large amount OF water shows that some
of the sewers are not tight and that sub-soil
and rain largely enter them This water must
be prevented from getting into the sewer
already built, as well as into those to be con-
structed hereafter for If this is not done it will
take the place calculated for the sewage and
therefore greatly diminish the capacity of the
system. :.
the sewage az fast as possible into mains and
interce ptors in order to reduce the size of the
numerous branch sewers to minimum, and
to avoid the construction of a great number Of
large sewers. For instance, one 4-foot sewer
will discharge about as much water as six 2-foot
sewers, and will cost much less. 1t Is always
cheaper to concentrate the sewga7 In this man.
may some times be found economical. when
there is yet but little sewage to be carried off,
to construct several smaller sewers in different
streets instead OF a single large one. AS this
Is rather matter of detail, however, the COM
mission leaves it to your City Engineer to de
cide where such procedure can most economi-
cally be adopted.
The interior system will be provided with
several large interceptOrs: One, called the
l'Central. will run along the east bank OF the
Los Ang. les river southerly to Sixth street. and
thence diagonally to a connection with. the
o1tfall sewer near the southwest corner of the
city; one, called the western" will run from
the populated IL districts koutherly along the
west city boundary; and one called the "South-
ern, westerly along the south city boundary
In addition. there should be constructed three
main branches to the Central Interceptor;"
oae, called Mozart Street Main. from Downey
avenue southerly along Workman and Mozart
from the vicinity of First street, soutnwestfsly
along the Hollenbeck Arroyo; and one, Chad
the upper extremifr mifrsnrougn Itde los Reysshile