Los Angeles herald., 1892-12-04
LETTER BAG.
MIR. Flynn ON the OutfalI Sewer
Syphon.

MIR. Flynn on the OutfalI Sewer
EDITORS HERALD: In communica-
tion addressed to the council of Los An
geles and signed by several prominent
citizens OF this city, grave doubts are ex-
pressed as to the utility of one of the in.
verted syphons of the outfall sewer.
There is no cause for anxiety about this
syphon or about any other part OF the
design of the outfall sewer.
Flowing to its full capacity the syphon
will have mean velocity of about four
feet per second and discharge of about
32 cubic feet per second. For some
years after the construction of the sewer
the supply of sewage will not be equal
to its full discharging capacity, but
there is more than ample water avail
able at all times to supply the deticien-
cy. There is always water running to
waste in the river below Buena Vista
street bridge, which can be utilized for
this purpose. The sewage will be sold
at Inglewood, and it will be to the in
terest of the official in charge of the
sewer to keepit full at all times, in order
to derive the greatest possible income
from it. The velocity in the sewer
four feet per secono-will be more than
sufficient to keep it clear not only of
sewage silt but even OF heavy sub
stances, such as brickbats, should they
reach the syphone.
As the interior system of city sewers
is built up go will the sewage increase
and the quantity of river water required
diminish, until the sewer is carrying
sewage alone.
This inverted syphon arrangement is
not experimental. Similar syphons are
used in sewerage systems end in irriga-
ton and water works all over the world.
l will quote one instance: In the
Paris sewer system the syphon for con-
veying the sewage from the south to the
north side Of the river Seine is COM
posed of two pipes, each feet inches
has worked satisfactorily.
Hydraulic miners are aware OF the ex-
tensive use of inverted syphons in min
ing, where they are used to- convey
water highly charged with sand and
silt, and they know that so long as they
are given a high velocity they keep
themselves clear of silt deposits.
For nearly six years, under different
administrations, / have been engaged at
different times in the city engineers
Office in almost every detail of design,
specifications and construction Of the
city sewer system. | have seen how
persistent Mr.. Dockweier has been in
impressing on the council the necessity
of adopting route for the outfall sewer
on which the sewage could be utilized
for irrigation purposes, and not uselessly
discharged into the ocean. He sue.
ceeded in convincing the council of this
and he has adopted route and plan
for the outfall sewer which is, in my
opinion, all things considered, the best
tor the interests OF the city. On COM
pletion of the outfall sewer the city will
have at its disposal 80 cubic feet per
second of diluted sewage, which is
equivalent to 1000 miners inches.
There are several irrigation districts in
California where they have expended
several hundred thousand dollars 70
store and convey to their land the
equivalent OF this eupply. The profits
resulting from the sale of the water will
more than repay the whole cost of the
sewer.
The taxpayers Of Los Angeles owe Mr..
Dockweiler q debt of gratitude for
having adopted a route by which the
sewer, inatead Of being a source OF loss
is source OF permanent and increasing
revenue to the city.
p. ]. FLYNN,
Civil and hydraulic engineer.