The San Francisco call., 1910-04-03

is aggravated by the nonconformity of
the Brannan street sewer grades with
those of the sewers the Brannan street
conduit intersecrs. The latter are
often from one to three feet higher
than the bottom OF the former. In the
tunnel under the south slope Of Rim
con hill there is an Offset of about ID
feet, and the bottom grade for a con-
siderable distance slopes the wrong
way. That under the conditions here
roughly sketched San Francisco has
won the distinction of the most health
full metropolis in America seems to
put heavier debt of gratitude than is
generally acknowledged upon her trade
winds, generous. sunshine and other
climatic blessings.
Despite, then, the many favorable
features in the problem, the board Of
public works and the city engineers
have grappled with a task more for
midable than can be easily realized.
This new system will drain the entire
watershed east of the main ridge that
divides the city into two great slopes
and has its northern limit near Fort
point. The western, or ocean slope. in
addition to the project adopted in 1899
for the Richmond district. and yet to be
completed, will have branches in the
west Richmond, upper Sunset. lower
Sunset and Ocean View districts The
last includes the Lake Merced region,
and extends southwark to the county
line
The drainage and sewerage problem
foT this vast area is still further COM
plicated by the citys peculiar topog-
raphy. Her nature, like her art, is not
yet an unmixed blessing. And this
truth is illustrated, as far as sewer
construction is concerned, by the fact
that the sloping ground, hillsides and
hilltops, which can be easily drained by
orr aytif Hrxxy @f4
the low fiat areas, where it is almost
impossible properly to collect the sew
age without the aid of pumps. The
unanimity of scientific opinion. how
ever, that the ultimate discharge into
the deep waters of the bay or ocean
was the only practical method of sew
age disposal has greatly aided the So
luton.
In general terms the present plans
call for a combined system of storm
water relief outlets, consisting of main
conduits, fed by tributaries carrying
rain water, a certain amount of soil
water entering by leakage, and dilute
sewage.
1t is expected that this sewage will
be rendered quite inoffensive by the
small percentage thereof in the out
flow. In addition to this combined sys-
tenn there will be separate sanitary
systems, disconnected entirely from
the storm water outlets, and discharg-
ing into pumping stations, whence the
sewage will be sent into the principal
relief mains, through which it will be
swept on to the various points of out
fall. And besides this disconnected
system a combination of storm water
and sewage carrying ducts is designed
for districts that have seemed to the
engineers to demand them. Wherever
the condition of the old sewers war
rants they will be retained to supple
ment the new system.
Except the great Division street con-
duit, which is rectangular in shape, all
mains throughout the city will be
either circular or oval, varying from
to about ~ by ~ feet for the latter
These will all be of reinforced SON
crete, and in many instances lined with
vitirified brick. For the supplementary
and sanitary systems ironstone pipe
will be used, ranging from inches to
feet in diameter
This separation system was rendered
necessary in the Yerba Buena and
Mission fat subdistricts by the fact
that much of the surface lies below
city base. And In most of the ocean
slope districts both sewage and storm
water will be intercepted and dis
charged into the ocean at the Point
Lobos outfall, where the oceanward
flow is away from the beach. AS a
large part of this beach is a public
playground it is imperative to keep it
as free as possible from pollution
The main key to the sewage prob
lem presented by this comprehensive