The Chitina leader., 1911-08-05

two 5-inch boiler feed pumps. If the
material would not have been very
compact, this method would have
been impossible, on account of the
size of the excavation. and the fact
that it was carried down 16 feet
the river, at the time the excava-
ton was completed
The boulders taken from the abut-
ment excavations on each side of the
river were crushed for use in the
concrete by a Gates gyratory crusher
set up near each excavation. Sand
for the concrete was obtained from
three different pits within radius
of one-half mile of the work Tracks
We're built into the pits and the sand
was hauled to the bridge site on
cars. Before the ground froZe and
the deep SHOWS came in 1909. house
was built. and sufficient sand and
crushed rock stored to complete tho
masonry.
and abutments, except pier No, 3,
are cemented sand and gravel and
boulders from one cubic foot to ten
yards in volume. Under pier No. 8
the boulders are much smaller. and
the sand and gravel while not cemen-
ted is firm.
The calssons Tor the detached ice
breakers for piers No. l and No.
were designed with the idea of not
sinking them over 20 feet below the
bed of the river. They are, therefore,
not built as substantially as the Gals
sons for the piers. The grillage was
fastened together with screw bolts
with the nuts up. in order to remove
it and have continuous concrete from
the cutting edge to the top of the
ice breaker. The gravel and boul-
ders excavated in sinking these Gals
sons was dumped inside the Golfer
dams for weight in sinking. On Sep
TENDER 26th the erection of the Gals
son for ice breaker No. l was COM
| llItuC6u. Inc water Ill Tie river udu
fallen to such an extent. at this time,
that the bar was exposed on pier No.
| l and No. . ana the icebreakers We're
located. The weather condition from
this date until April 1st, 1910, were
very severe the wind velocities rang
ing from sixty to ninety-siX miles per
hour for the greater part of the time
and curing the time of high winds
and consequent drifting snow. tho
temperature was always low 1t was
necessary to build a windbreaker on
the up-river side of both ice breakers
to make it at all possible for men TO
work erecting and calking the Gals
sons and cofferdams, even then there
We're many costly and eXasperating
| Interruptions by the wind breakers
blowing down and having to wait un-
til the velocity of the wind became
| such that it was possible TO put them
! up again. They were always re-
erected under very trying and costly
conditions. On December 1fth. the
caisson for ice breaker No. was
completed and sinking begun On
| December 9th this caisson was land
ed and the sealing of the working
chamber was commenced, which was
/ completed on December 81.
! The erection of the caisson for ice
| breaker No. 2 was beun November IA
and completed January 6, 1910. when
sinking was begun. The caisson was
landed February &rd, and the con-
cretng in the working chamber was
completed February 10th.
Inc sides of these catSsons We're
made vertical to simplify framing and
owing to no batter on the walls. an
excessive skin friction was developed.
! On No. 2 with a penetration of 1879
| feet in the gravel and boulders, it
was impossible TO force the cutting
edge any further down. although we
/ had load on the caisson which eX-
erted downward pressure of 1410
/ pounds per square foot to the eX-
posed sides of the ca - n. and had
! eXcavated inside the working cham
| Der Y feet below the cutting edge.
/ Ice breaker caisson No. / was sunk
| l 9 feet below the surface of the bar.
On February 14th the removal of
the gravel and boulders used as bal
last in sinking the caissons vas be-
gun but owing TO the severe weather
conditions, poor progress was made
and the last of the ballast and tim
Der grillages were not removed un-
til March 22nd. when we attempted
to pump out the cofferdam of No.
but found it impossible. Concrete
to the depth of feet was placed in
the water by bottom dumping buck