Evening public ledger. [volume] (Philadelphia [Pa.]) 1914-1942, 1921-07-26
survey IS STARTED
FOR BRIDGE ROUTE
Sixth and Vine Streets Scene
OF Engineering Prelim-
mary Work
M0DJESKl TELLS OF PLANS


Bridge Commission started q prelimin-
sry survey at Sixth and Vine streets
to determine the actual engineering line
OF the proposed structure.
II has been definitely fixed that the
bridge shall start at Sixth street 31a
rect north Of Race and run easterly to
connect with point near Pearl street
Camden, but the engineers are prc-
vented from marking the course Of the
structure In straight line on account
OF houses and buildings now in tho
path. ''>
Therefore, in order to determine the
actual line IL Is necessary 10 make cal
cuIations from the streets north and
south OF the starting point on this
SIDE and the finishing point in Camden.
When these calculations have been
completed the engineers will know ex-
actly where the center Of tho structure.
will be. In order to connect with the
point selected in Camden It will be
necessary for the b. idgc line to tnkc n
slight southurly angle.
Start Work Early
The engineers started at work Mt o
o'clock this morning and expect to
complete the preliminary survey on this
side of the river today.
Those engaged on the preliminary sur
vey are Charles Elcock, assistant en-
gineer of the commission. John Briggs.
John +. Armstrong and Harold Dixon.
The men were considerably hampcred
In their work today by scores of in
quisitive residents, who were under the
impression that their stores or dwell
fngs were to be torn down. Many
wanted detailed information regarding
the direction OF the structure and some
could not be convinced that their pres
ent business places were sufe.
Ralph Modjcski. chief engineer in
charge Of the designing and building Of
the bridge, today told for tho first time
in detail the actual steps in the laying
OF the foundation and tho construction
OF the great span AS it will take place
during the next five years
Old Story 20 Modieski
Although the bui ding of bridges is BY
this time an old story to Mr.. Modjeski,
he told in n graphic. and at times
dramatic manner. the way In which thu
foundations will be sunk and built. In,
big cables laid and the great slpcr.
structure reared until one of this city <
proudest achievements will have become
an accomplished fact
Much like the weaving of n spider s
web will be large part of the con
structiOn," said Mr.. Mcdjcski and
much in the same way did he weave a
word picture of the engineering work
from the spectacular sinking Of the
caissons on through the various pro-
cesscs as the structure connecting the
two cities and two States will rear
its majestic figure above the Delaware
River.
Although" said Mr.. Modjeski.
contract number one, or the first steD
in building the bridge will be the be-
ginning of test borings for piers and
anchorages to gtnrt August Is. the
actual work Of construction to the
casual observer. will be the sinking v
caissons for the construction of the
main piers and foundations. -
Before this is done, of course. con-
tracts must be let. The firm of pncu-
matte experts to do the work will as
semble plant here and two great Cnis-
sons will be constructed. They will be
about 20 by l4j feet. and before they
are finally in place on rock bottom Of
the river, filed with concrete and sealed.
may attain a depth of ninety feet. This
distance Mt the present time iS probe
matical and must be determined by the
conditions which We encounter at the
bottom OF the river.
HOW N0"k VIII start
eve will first build ways near the
bridge, or it might be possible to use
the shipways of nearby Shipyard.
Here the caissons will be constructed,
and then when they are completed they
will be launched. with or without cerc-
mony, as may be decided.
while the financial status of the
commission will be a deciding factor, it
would be best TO sink the cnissons on
each side of the river at the same time.
Work for sand Hogs
AFTER the caissons are tloatcd, they
are gradually sunk TO the bottom of the
river. ns concrete Is step by step put
into the vessel. At the bottom of the
caisson is chamber where sand hogs.
or caisSOn workmen. will gradually
force the big case 10 rock bottom. While
II is difficult to figure exactly, We might
say for illustration, that the river will
be about forty feet deep at that point.
II may be that we will have to dig
down another forty feet from the bed
sary rock bottom.
'As the caissOn begins to lower IL
the water. more and moro concrete is
poured in. Then, as We get near the
tip. we will build masonry to add tO tn"
lond. To the lay mind no progress will
seem TO be made as This masonry ap-
pears at apparently the same height
above tho water. But the engineer
knows that all the time, the Caisson is
sinking. slowly toward the bottom. Tn"
rate OF sinking has varied from three
inches 10 eleven feet per day, bur it
will probably average about a foot
day;
the bed OF the river the real work OF