The San Francisco call., 1913-07-29
Plans Approved by Public
Works Commission and
Transmitted to Super
visors for Adoption
ESTIMATED COST OF
TUNNEL So, 1894, 1928
Right of Way 1000 Feet in
Length Obtained for
Approach

The hrge engineering feat of pierre
ing Twin peaks with a double track
rapid transit railway tunnel $4,000 feet
in length was advanced a long way
toward actual commencement of con-
strueticn Yesterday when City Engi-
reer ". NJ. Shaughnessy filed with
le Load of works voluminous and
comprehensive report embracing COM
pieta plans and specifications for the
construction of the tunnel and the en-
tire list OF assessments.
The report was approved by the
hoard Of works and transmitted to the
supervisors for adoption
Including acquisitions of land and
easements, the total estimated cost
% the tunnel is s3,994,2S9.23.
Approximately S5 per cent of the as
sessmelt is upon the southwesterly dis
tSict on the farther side of Twin peaks
ridge. and Is per cent on the northeast
erly section, this side of Seventeenth
street.
LARGE SECTION BENEFITED
An area comprising nearly one-sixth
OF the total area of the city, now prac-
ticaIly inaccessible, will be brought into
quick and easy communication with the
business center by means of the tunnel.
The assessment is considered .ex-
fremely low upon individual lots. being
much lower than that for the Stockton
street tunnel and ging less than
cents a square foot.
The tunnel will start at Seventeenth
and Market streets and extend under
Twin peaks to its southwestern portal
half a mile from Ingleside. OF this
$50 feet will be through rock and the
remainder in clay. clay sand and softer
material. Reinforced concrete will be
used throughout but Of very light con-
struction through harG rock
The estimated time given the con-
tractor TO complete the work IS 600
calendar DAYS and a bonus viii be given
or a penalty exacted of.s750 q day as
4 inducement to the contractor to ex-
pedite the work. This method has been
very successful in the Geary street rail-
road work and in the Stockton street
tunnel for inducing prompt action on
the part OF contractors
LONG RIGHT OF WAY
= right of way has been obtained
1900 feet in length and 80 feet wide
for q subway approach to the tunnel
proper. This strip is between Market
and Seventeenth and Hattie and Eigh-
teenth streets. the land and Improve
ments of which have cost the most
substantial part OF the damages.
The right of way has been donated
The main portion of the tunnel
through softer materials will be %
feet wide and 20 felt high. capable Of
carrying a double track electric rail-
way line.
In rock excavation the tunnel is 25
feet wide in the clear and but % feet
high. as it Is unnecessary to have this
section so large.
The general grade of the tunnel is
that high speeds for electric cars can
be made sthrough it.
It is estimated that the time in pass
ing through. including the stop ~at a
subway station at Laguna Honda,
should be less than 10 minutes, so that
the 5000 acres of land at the south
westerly extremity of the tunnel will
be brought nearer to the business CEN
ter OF San Francisco than either Oak
land. Berkeley or Alameda.
EXHAUSTIVE BoRINGs MADE
Exhaustive borings have been made
all along the route. 500 feet apart to
determine the exact nature of the ma
ieriat that will De encountered IN max
ing the bore, so that the contractors
will not have TO bid blindly on the
cost of the work.
All tubing and pipes for electric
wires are carried in the concrete side
walks and inches for operating these
are spaced every 400 feet apart
Similar refuge inches are placed on
each side, so feet apart for the safety
of laborers who may be working in the
tunnel
An elaborate system of ventilating
is to be provided by means of a sepa-
rate compartment on the top OF the
tunnel about five feet high, through
which all the foul air will be extracted
by means of fans. This is superior
to the single opening where cars run
ming at high speed in opposite direc-
tiops mingle the foul with the pure
air
Two stations are provided for-one
in Eureka valley between Eureka and
Diamond streets, and the other at La
guna Honda, about 80 feet below the
surface.
Ample stairways and exits are pro-
vided for both stations, and provision
is made by which elevators may be
installed In the Laguna Honda station.
City Engineer O'Shaughnessy said
Yesterday that this project will have
great influence in stimulating the
growth of San Francisco.
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