follows: When the foundation piles
were driven. S short piling were
driven on each side, three feet clear
of the outside pier piles. These
short piles were capped longitudi
nally with the pier, and a 70 pound
rail was spiked longitudinally with
the cap and made level for its en
tire length. Ca 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 and
the grillage sunk by putting in the
concrete. The greatest variation
from true position in sinking was
one half inch.
The Copper Kiver & Northwestern
railway after crossing the Flag Point
and Round Island channels of the
Copper river, traverses Long Island
in the Copper river delta, for a dis
tance of about six miles where it
reaches the Hot Cake Channel which
flows along the eastern end of Long
Island.
Thsi channel is a little less than
750 feet in width with a gravel bar
150 feet wide. 200 feet east of the
east end of Long Island. It was
decided to use one 200 foot span
150 feet of pile trestle and two 200
foot spans for bridging this channel.
As the 150 foot bar is sufficiently
high that it is always bare at the
time the river freezes, it was thought
a pile trestle could be easily main
tained over it.
Test borings made on this bridge
site in 190S, showed a very compact
uncemented sand and gravel for a
depth of 55 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 tha
a jet could not be used successfully
to assist in getting the piling down
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 wit!',
an orange peel bucket, the crib, ex
cepting the hatchways, being filled
with concrete for weight to assis:
in sinking.
In April ismio camp was ( staouM -
ed at this bridge site and actual con
struction began. There was about
ten feet of snow on the ground at
this time and snow storms and se
vere winds with drifting snow were
frequent but the cofferdam of Freis
tadt steel sheet piling, for abutment
one, was driven and excavation for
this abutment completed in May.
After May 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
tion 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
were erected and sunk without spec-;
ial difficulty or incident. The great- j
est difficulty in sinking a crib by
open dredgeing is, that it is prac
tically impossible to control its po
sition during the process of sinking
and it is likely to be considerable j
out of its true position when finally ]
landed.
On August 13th we began the!
erection of span one and swung the
same on August 19th. In September
the weather became very stormy and
the work from this date till the for-1
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
tions with the floor beams or spans
2 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
was Marine Tocholith and the second
R. I. W.
From the Copper river delta, the
Copper River & Northwestern rail
way follows up the left bank of the
Copper river to a point one-fourth
miles above Childs glacier on the
right bank, and about three miles
below Miles glacier, on the left bank,
where the Copper river is crossed a
second time. This crossing being
necessary to avoid Miles glacier.
This bridge site was located in the
summer of 1907. Assistant Bridge
Engineer A. O. Johnson was sent
here in February, 1908, to continue
the meleorologieal data begun in
1907, prior to which date, no data
covering the river of meleorologieal
conditions were available. Mr. John
son was also instructed to make a
careful profile of the river, make test
borings with a Davis Calyx poiver
drill, and measure out base lines
and set permanent monuments on
them. The drill and a 16 horse pow
er boiler were hauled by team from
mile 9, the end of the track at that
time to the lower end of Childs gla
cier mile 46, and from this point
taken 2 miles to the bridge site
by a cable and the steam winch on
the drill.
The borings subsequently made,
showed nothing but boulders and
cemented sand and gravel in the bed
of the river, after the first 20 feet
in depth. The first 20 feet, the
sand and gravel being loose. The
boulders ranged in size from 1 cubic
foot to 20 cubic yards.
The flow of icebergs from Miles
glacier made any construction in
the main channels of the river an
impossibility during the season of
glacial activity, i. e., from June 1st
to November 1st, and inadvisable at
any time. In 1907, icebergs were
observed passing the bridge site, that
were 20 feet out of the water, and in
190S they were observed in the chan
nel, under the location of the 4 50
foot span, 50x100 feet 8 feet out of
the water, and moving at the rate
of 7.2 miles per hour, notwithstand
ing the fact that they were dragging
on the bottom.
require a rigid lower chord except
the middle panel, so span No. 1 was
designed the same way as spans No
2 and No. 4 for the sake of uniform
ity. On account of the extremely
high winds from September to April,
these spans were designed for a wind
| pressure of 40 pounds per square
foot on the loaded structure, and for
60 pounds per square foot on the
unloaded structure.
The piers were designed with the
top at elevation 16S.02, which would
place bottom of the lower chords
practically 30 feet above extreme
high water, and is ample to clear all
icebergs passing under the bridge.
The great flow of icebergs made
detatched icebreakers necessary at
piers No. 1 and No. 2, pier No. 3 be
ing located out of the heavy ice flow
at any stage of the river. The ice
breakers and all of the piers are ar
mored with r>6 pound rails placed
with the ball out and flush with the
outside of the concrete the rails
being anchored in the concrete with
Johnson corrugated bars 4 feet
longt passed through holes in the
web of the rails at intervals of 2 4
inches and bent inward to the flange.
Designing caissons large enough
to allow ample room for the base of
the piers, gave a total load per
square foot on the foundation of pier
No. 3 of 4.08 tons, by assuming the
almost impossible conditions of two
maximum loaded trains meeting on
February 14th. 1910, and the vibra
tion was not worth considering.
Owing to damage to the temporary
track in the delta by the flood of
February, 1909, we did not reach
the bridge site until April 1st and re
i eeived the last material for one cais
: son on the ground April 24th, 1909.
; The river at this time showed signs
! of beginning to break up, and it was
i deemed unwise to attempt to erect
' more than one caisson on the ice. it
being impossible to hold a caisson in
the river after the glacial ice began
to move, unless it was several feet
in the ground.
i On May 4th, we completed erect
ing caisson No. 1, and although the
| working chamber was not entirely
j caulked, we immediately lowered the
; caisson to the bottom of the river,
and began sinking. At first it was
necessary to run three of the com
' pressors to lower the water in the
working chamber to within one foot
of the cutting edge. We continued
calking while the caisson was being
sunk and in about two weeks had the
working chamber so tight that one
i compressor would supply the air.
The river began breaking up May
7th, and on May 9th, was entirely
; free of ice. but there was no flow
: of glacial ice until June 16, when we
had the cutting edge 10 feet below
! the bed of the river, and the ice did
i no damage of any consequence.
! Previous to the breaking tin of th"
| so large a wave acme down the river
th.at the caisson was washed off the
cribs and carreid 18 feet inshore and
six feet down stream. The cables
by which it was anchored prevented
it from going further down stream,
and a derrick which it wrecked, pre
vented it from going farther inshore.
After this it was jacked into position
and sunk without special incident or
difficulty.
A second rock crusher and con
crete mixing plant was set up on
the north bank of the river, to sup
ply material for pier Xo. 3, and for
abutment Xo. 2. A trestle was buili
from the north shore to the pier, and
the necessary material handled over
that.
We began sinking the caisson for
pier Xo. 3 on July 29th and landed
it August 24tli. with the cutting
edge 50 feet below the surface of
the bar and on boulders and gravel.
At the time the caisson was landed
the cutting edge was 62 feet below
the water surface, and the air pres
sure required was 26.5 pounds per
square inch, or practically the hy
drostatic head. This pier was com
pleted on September 15th.
At the site of pier Xo. 2. an ar
tificial island was built in 14 feet of
water, by taking out over the cable
way, ship loads of gravel in coal
sacks and dumping them at the
proper place. This was begun on th<
1st of September, and fortunatelv the
$1,.',00.000 STEEL BRIDGE, SPANNING THE COPPER RIVER. AT MILES GLACIER.
From our observations the range
from low to high water was found
to be 24 feet, and we were unable
to find any drift to show the water
had ever been any higher than ob
served by us. In 1908, the break
up of the ice in the river took place
on June 7th. On F bruary 19, 1909,
some unknown disturbance took
place in Miles Glacier, and although
the weather was cold, the river rose
20 feet, taking the ice out com
pletely, and doing some damage to
the temporary track across the delta
below. 1 ne ice that froze up after
this flood, was not as thick as it
had been before and the river was
open on May 9th.
After observing the ice flow for
the entire summer of 1908, the foi
lowing span lengths numbered front
the south side of the river, were
decided upon. Span Xo. 1. 400 feet,
span Xo. 2, 300 feet, span Xo. 3, 430
feet, and span Xo. 4. 400 feet This
arrangement places each of the piers
on a bar. and out of the path of the
heaviest flow of ice. In fact, during
190S, no icebergs crossed the site of
either of the piers during daylight.
We decided that we could safe
ly erected spans Xo. 1 and Xo. 2 be
tween April 1st when the wind and
general weather conditions would
not be very severe, and the break
ing up or the river. Span Xo. 3
could possibly be erected in the same
way, but it was uncertain. Span Xo.
4 could be erected on falsework at
any time, except during high water.
As it was important that the bridge
be completed during 1910, span Xo.
3 was designed to erect as a canti
lever, using spans Xo. 2 and Xo. 4
as anchor arms. These two last arms
were to be connected by temporary
members from the top end post pins,
to the same pins in the 450 foot
span, with adjusting wedges, in con
nection with wedges between the end
shoes at the expansion end and cast
iron blocks at the fixed end of the
450 foot span, to hold the outer end
of each half of span Xo. 3 sufficient
ly high, to be able to make the con
nection at the center span. The fix
ed ends of spans Xo. 2 and Xo. 4 are
next to span No. 3. Il was necessary
for spans No. 2 and Xo. 4 each to
have rigid low< r chords if they were
to be used, as anchor spans, and span
Xo. 3 to be erected cantilever would
the pier. This without taking into
consideration the skin friction , or
bouyancy of the portion below water.
As pier No. 3 would have to sustain
the greatest load the matter of sus
taining power of the foundation was
not further considered.
The track reached this bridge site
in October 1908, but for a distance
of approximately 1 miles on the del
ta was lain temporarily on the sur
face of the ground and the severe
weather conditions prevented the con
struetion of the grade that season.
The power house equipment con
sisted of 6, 150 h. p. Erie City, Class
B. horizontal boilers, 4, 14xlG dup
| lex compressors manufactured by the
Chicago Pneumatic Tool Co., each
capable of furnishing 1500 cubic feet
of free air per minute and compres
sing to 50 pounds, 1 Chicago Pneu
matic Tool Co., 10x12x10 compressor
capable of compressing to 125 lbs.,
! 1 Cochrane feed water heater and 1
I Schaife filter, each capable of sup
plying boilers aggregating 1000 h.
p.. and 1, 30 kilowatt Ridgeway dyn
amo with direct connected 50 h. p.
McEwen engine. The filter for the
power house being necessary by the
reason of having to take our water
supply from the Copper river which
carries great quantities of fine silt
in suspension.
We expected to be able to reach
the bridge site March 1st., 1909. in
time to erect caissons No. 1 and No.
2 on the ice and sink them simul
taneously, and if conditions had
had been such that we could have
reached there when we expected to
do so, this would have been done
and the disagreeable and expensive
winte'r work of 1909 and 1910 would
have been avoided.
All the equipment was purchased
self contained in so far as possible,
so as to avoid the delay necessary
to build substantial foundations for
the machines. All the machines were
operated on a foundation consisting
I of 12 inch by 12 inch timbers drift
bolted together and resting on the
surface of the ground, which con
sists of gravel and boulders. The
only precaution taken was that the
i timbers were not allowed to rest
: on filled ground, or in other words,
I the ground was excavated level. The
! compressors were operated almost
! continuously from May 4th, 1909, to
ice we had put across the river a
1 to inch steel wire cable, supported
by towers 100 feet high on each
hank, to deliver concrete and other
supplies to the piers and across the
river by cable trolley. The carrier
was designed and made on the works,
after being advised by two firms
that no carrier was manufactured
which would operate over our length
of span, viz.. 1800 feet. The heav
iest load carried on our cableway
was the man lock, which weighed
5000 pounds.
We also put across the river two
1-inch steel cables resting on sixty
foot towers on each bank, and on
sixty foot double tower on the edges
of the crib above caisson No. 1. Sus
pended from these latter cables, we
carried an 8 inch, double rivited,
flanged end steel pipe, tested for 125
pounds pressure, for supplying com
pressed air to the caissons, and a
foot bridge of 1 inch by 12 inch
planking. We supplied air through
the eight inch pipe to pier No. 3,
a distance of 1300 feet from the
power house, and on the south bank
of the river, with a loss of only one
pound from the indicated pressure
at the power house.
Caisson No. 1 was landed on July
14th. on boulders and gravel, with
the cutting edge 36 feet below the
bed of the river.
Pier No. 1 was completed August
24th, without any serious accidents
from the ice, although it ai one time
broke part of the forms out, and at
another time took out the tower on
the crib, which had been supporting
the cables for carrying our air supply
pipe, just a few minutes after we
had transferred the cables to a new
tower of 12x12 inch timbers, sup
ported by cables slung over the un
finished pier.
Caisson No. 3 was erected in June,
on the pier site, on a bar, before the
river rose. Before the working
chamber was completely caulked the
water in the river began to rise and
tite glaciers became active. The cais
son was anchored to the shore by
long cables reaching as far up the
stream as possible, and in a couple
of days the calking was completed,
the air was turned on and we be
gan lowering. Just as we commenc
ed to lower, an iceberg broke from
■ Miles glacier, three miles away, and
water in the river had fallen so that
the velocity of the current in the
channel had decreased from 9.5 miles
per hour to nearly 7 miles per hour,
and 5 miles per hour over the pier
site, or this method would have been
impossible. Also the tailing of the
river had made it impossible for
icebergs of any size to come in tv r< .
in fact only two or three small on...
struck the island during its construc
tion and the amount of damage was
small. The island was completed
September 12th.
Caisson No. 2 was erected and w
began sinking September 27th, land
ing it November 2nd., with the cut
ting edge at practically the same ele
vation as that of caisson Xo. 1, ov
elevation of 81.95. The material
gone through after the first lu feet
of boulders and loose gravel, (in the
river bed proper, not the island >, was
cemented sand, gravel and boulders.
Freezing weather had begun by
the time we were ready to start
concreting the pier proper, so p
house was built entirely enclosing
the pier and leaving a six foot
.-pace outside of ihe concrete forms
and over the top of the pier. A 2
inch pipe was lain spirally around
the pier approximately 6 feet ver
tically between the coils and two 2'i
n. p boilers used to supply sieam
in order to prevent the concrete
from freezing. The water for mix
'ag co lerete was heated to 110 de
grees Fahr., and the sand an 1 rock
to about 100 degrees Fahr. In this
way as the concrete was taken out
over the cableway in buckets hold
ing 3-4 of a cubic yard, it was put
into the pier at a temperature of
about 70 degrees Fabr.
The material was taken out for the
' abutment foundations by open exca
vation. There were so many boul
ders in the ground that to drive a
coffer dam fi>-.u and excavate inside 1
of it was impossible: therefore, tlie j
excavation was started and a coffer j
dam of 4x10 inch fir pianks was!
driven as the > xcavation was carried
down but at no time was.the bottom
of the coffer dam below the exca
vation, The only objection to this
plan was that it necessitated quite j
a large pumping plant. We had, for!
keeping the water out of these exca- j
rations, two 8-inch, two 6-inch and
one 5-inch centrifugal pumps, besides |
] two ;>-inch boiler feed pumps. If the
i 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
below tne elevation of the water in
the river, at the time the excava
tion was completed.
The boulders taken from the abut
ment excavations on each side of tlio
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 a radius
of one-half mile of the work. Tracks
were built into the pits and the sand
was hatited to the bridge site on
cars. Before the ground froze and
the deep snows came in 1909, a house
was built, and sufficient sand and
crushed rock stored to complete tin/
masonry.
The foundation for all the pier/
and abutments, except pier No. 3,
are cemented sand and gravel, and
boulders from one cubic foot to teit
yards in volume. 1'nder pier No. 3
the boulders are much smaller, and
the sand and gravel while not cemen
ted is firm.
The caissons ror the detached ice
breakers for piers No. 1 and No. 2
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 cais
sons for the piers. The grillage was
fastened together with screw bolts
with the nuts up, in order to remove
I it and have continuous concrete from
'he cutting edge to the top of the
ice breaker. The gravel and boul
ders excavated in sinking these cais
sons was dumped inside the coffer
dams for weight in sinking. On Sep
tember 26th the erection of the eais
1 son for ice breaker No. 1 was com
menced. The water in the river had
fallen to such an extent, at this time,
that the bar was exposed on pier No.
1 and No. 2 anu the icebreakers were
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 during the time of high winds
and consequent drifting snow, tin
temperature was always low. It 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 cais
sons and cofferdams, even then there
were many costly ami 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
■ rected under very trying and costly
conditions. On December 1 4th, the
caisson for ice breaker No. ! was
completed and sinking begun. On
December 2 7th this caisson was land
ed and the sealing of the working
chamber was commenced, which was
completed on December 31.
The erection of the caisson for ice
breaker No. 2 was beitn November 14
and completed January 0. 1910, when
sinking w as begun. Tin* caisson was
landed February 3rd. and the con
creting in i tie working chamber was
completed February ltith.
'I ne sides of these c Nsons W es .
made vertical to simplify framing and
owing to no hatter on the walls, an
excessive skin friction was developed.
On No. 2 with a penetration of 19
feet in the gravel and boulders, it
was impossible to force the cutting
edge any further down, although we
had a load on the caisson which ex
erted a downward pressure of 14 10
pounds per square fi u to the ex
posed sides of tlie ca - n, and had
excavated inside the working cham
ber 2 tg feet below the cutting edge.
Ice breaker caisson No. 1 was sunk
I 9 feet below the surfae of the bar.
On February 14th the removal of
the gravel and boulders used as bal
last in sinking tlte caissons v as be
gun but owing to the severe weather
conditions, poor progress was made
and the last of the ballast and tim
ber grillages were not removed un
til March 22nd, when we attempted
to pump out the cofferdam of No. 1
but found it impossible. Concrete
to the depth of 5 feet was placed in
the water by bottom dumping buck
ets, and on April lltli, was success
fully pumped out, the forms were
built and concreting was commenced
April 13th and completed on April
17th.
The cofferdam No. 2 was filled in
with concrete by tremies through the
water, to within four feet of the stir
face when the forms were built and
concreting was commenced April 25
and completed May 1st.
The entire construction of these
foundations was carried on night and
day requiring two shifts of men In
all capacities.
On January 3rd 1910, false work
for the erection of span No. 1 was
commenced. The ice on the river
at this time was seven feet thick.
One inch steam jets were used to
thaw four holes through the ice at
the point where each pile was to b■>
driven. It only required a few min