The Western news. [volume] (Libby, Mont.) 1933-current, 1935-04-25


between San Francisco and Yerba Buena which
had been deemed impossible So the engineers
decided upon two suspension spans In tandem,
anchored In the middle OF the bay to a gigantic
pier It Is 1877 feet long (nearly GO YARDS by
81 feet wide and rises sos feet from the rock
bottom OF the bay nearly twice as large as the
biggest skyscraper In San Francisco. Since the
two spans are anchored to this they actually pull
against each other. The San Francisco anchor
age Is huge mass Of concrete containing g.
600 cubic yards Of cement.
In spinning the cables the entire 10000 miles
ofscable are pulled In place by shuttle wheels
which run over the towers all the way from
San Francisco to the concrete center anchorage
on the west suspension bridge and from the
center anchorage to Yerba Buena on the east
suspension bridge. Spinning the cables Is BY
far the most protracted Job on the bridge and
will require a year. Each piece of wire In the
cable Is approximately two miles long. total
OF 34960 strands must be drawn over the sus
pension towers. EACH cable will exert a pull Of
100000 pounds against Its anchorage In San
Francisco and Yerba Buena Island.
Just as the building of the Bay bridge pre-
SCENTS knotty problems to be solved, so does the
building OF the Golden Gate bridge brink Iup diff
feultIes never before encountered In such work.
of the suspension span, more than twice that OF
any previously attempted and the difficulty OF
erecting foundation for the tower to support
the south span because Of the depth of the
water and the swirling OF the tide In the open
ocean waters at the Golden Gate.
But 1900 feet offshore at a depth of 100 feet
an adequate foundation formation was discoy-
cred although the water here Is constantly tur-
bulenr because of the seven mlle-an-hour tide
which constantly sweeps in and out through the
Golden Gate. AT times breakers 20 feet high
crash over this point. First 1t was necessary 70
level Off the site for this pier by blasting rock
over an area a approximately an acre under
water, after which the rock was dredged up
carried out and dumped In the sea.
Construction of the pier, the first ever attempt
ed In the open ocean swept by the tides, was
made possible only by the erection OF giant
concrete fender, 750 feet In circumference
around, the pier site, an original Idea never be
fore tried This fender Is being built In sections
First a huge steel box Is lowered into place OF
the BOTTOM after which 1t Is boted to adjoining
boxes by deep-sea divers working In complete
darkness. Then concrete Is poured into the boxes
Gradually the structure Is built up until Its toI
rim Is fifteen feet above high water. The cas-
wall of the fender is omitted above elevation
filled with concrete for the pier itself, Is hoatet
into place inside the fender. Then the fende
will be completed, and the builders will hay'
quiet water unaffected by tides inside the fende
In which to complete the pier. The fender VII
serve permanent protection to the pier Whel
the bridge Is completed
Meantime the Marin tower, built on solid roc
above the water lime. was completed ahead 0
program. Its slender steel columns rise above
foundation of concrete embedded In the rock
The tower Is of cellular steel construction. IN
inside being a veritable labyrinth OF chamber
In which even the designer could be lost withou
his charts. Steel ladders connect the hundred
OF chambers from the foundation to the top Q
the tower, TAG feet high
The twin anchorage blocks which support tn
weight Of the worlds longest suspension spa
are enormous solid concrete masses, weighln
Gi0O0 tons each. 80 constructed that they pus
against solid rock when supporting the cable
The cable pull at each anchorage Is 63,0OoU
pounds. but the anchorage block has a resistant
sufficient to support two Golden Gate bridge
Between the piers and the anchorage blocks ~
supporting pylons for the cables and the bridg
Gby Western Newspaper Union.