The Chitina leader., 1911-08-05

of the outside pier piles. THESE
short piles were capped longitude
nally with the pier, and a 20 pound
rail was spiked longitudinally with
the cap and made level for its en-
tire length. On this track was a
frame on wheels carrying another
track at right angles to the first
one From a frame carried by the
second track a circular saw was sus-
pended to the shaft arbor with bolts
countersunk on the bottom side of
the saw. A 20 h. p. engine, with the
saw set at the elevation of the pile
cut off had no difficulty in cutting
off the piles 16 feet below the water
surface Three courses of grillage
were pinned together on ways, on
the shore, then launched. completed
and floated into position. guides
were driven, the forms put up ana
the grillage sunk by putting in the
concrete. The greatest variation
from true position in sinking was
one half inch.
The Copper River & Northwestern
railway after crossing the Flag Point
and Round Island channels of the
Copper river, traverses Long Island
in the Copper river delta, for dis
lance of about six miles where 1t
reaches the Hot Cake Channel which
flows along the eastern end of Long
Island.
Thsi channel is a little less than
$50 feet in width with gravel bar
$50 feet wide. 200 feet east of the
east end of Long Island. 1t was
decided to use one 200 foot span
$50 feet of pile trestle and two 200
foot spans for bridging this channel.
AS the $50 foot bar is sufficiently
high that it is always bare at the
time the river freezes, it was thought
pile trestle could be easily main
tanned over it.
Test borings made on this bridge
site in 1908 showed very compact
uncemented sand and gravel for
depth of So feet This material be-
ing so firmly packed that piling
could not be driven to a sufficient
depth for a permanent foundation
and the gravel being so course thai
a jet could not be used successfully
to assist in getting the piling doWL
deep enough in the ground.
AS we did not wish TO go to the
expense of purchasing and installing
a compressor plant in order to use
pneumatic caissons. open caissons or
cribs were designed to be sunk by
dredging through hattchways with
an orange peel bucket, the crib, eX-
cepting the hatchways. being filled
with concrete for weight to assist
in sinking.
In April 1909 camp was establish
ed at this bridge site and actual con-
struction began. There was abou,
ten feet of snow on the ground at
this time and snow storms and Sc
we're winds with drifting snow We're
frequent but the cofferdam of Freis-
tadt steel sheet piling, for abutment
one. was driven and excavation for
this abutment completed in May,
After Nav the weather was such
until September that rapid progress
was made on this work. We tried
to drive piling in the bottom Of abut-
ment one after the excavation was
completed. The greatest penetra-
ton secured was ten feet for the
first few piling driven, and after
driving twelve or fifteen piles the
material became so compact that i
was impossible to secure more than
from two to four feet penetration.
The cribs for the pier foundations
We're erected and sunk without spec
ial difficulty or incident. The great
est difficulty in sinking a crib by
open dredgeing is, that it is prac-
tically impossible to control its po-
ston during the process of sinking
and it is likely TO be considerable
out of its true position when finally
landed
On August 18th we began the
erection of span one and swung the
same on August 18th. In September
the weather became very stormy and
the work from this date till the for
ces were disbanded in November, was
tedious and costly. At the time OF
disbanding the bridge was all COM
plete except riveting a part of the
top laterals and stringer connec-
lions with the floor beams or spans
and 3, painting the entire bridge,
and decking spans 2 and 3. The un-
rivited members were full bolted and
carried light traffic during the win
ter of 1909 and 1910. The work
was all completed during the spring
of 1910. The first coat of paint