The Columbian. [volume] (Bloomsburg, Pa.) 1866-1910, 1894-04-27

viii be manufactured to be very close
dimensions, and it would be a serious
matter, if it did not fit on the mason
ry. | hereby call attention to this
matter as one of the details which re-
quires the utmost care and attention.
With regard to the five river piers,
the dimensions as shown by the filed
and detailed plans, appear to be suf-
ficient, though | think that in stream
like the Susquehanna, subject to
floods and heavy ice, it would be bet
ter to have dressed the faces of its ice
breakers, and rounded the down stream
ends of the piers. The fled plans do
not indicate the character of the pro-
posed foundations, but the detailed
masonry plans and Mr.. Browns YER
bal explanation indicate that No.
(from the South side of the river) will
be located on the rock, the founda-
ton being put in through the medium
of Golfer dam. For the other four
piers my understanding is that it is
proposed to use timber platforms on
the present bed of the river, the plat
form being hoated into place, wooden
sides being built up to exclude the
water, thus forming a caisson, and
the caisson being sunk with the weight
of the masonry built inside of it. On
inquiry am informed that the bot
tom of the river is formed of gravel
and coal dirt, but that no examina-
tons have been made to ascertain
what is below the surface of the
gravel.
1t seems to me that great risk is
being taken, in founding the piers Of
an expensive and important bridge in
the river bottom, without any knowl-
edge of what is below Assuming,
however, that the river bottom is hard
gravel, it will be necessary to protect
the timber bottom with riprap (Which is
not provided for in plans, speciica-
tions or contracts) and distractions
will thus be formed in the river, the
result of which will be to cause the
channels in the river to deepen by
washing. This, it is we'll known, will
occur in the hardest gravel, and in a
few years the bottom of the piers
might be above the rest of the river
bed, with more or less tendency to be
injured with heavy freshets or ice
floods. My opinion is that the found
ations of the piers should be placed
not less than 3 to 4 feet below the
present river bottom except when they
rest on rock. 1t might be found by
examination, that rock could be
reached at reasonable depth below
the river bottom, in which case it
wouldibe advisable 70 use cof'er-dams
and sink to it. The same question
comes up relative to the foundations
of the north abutment. When | was
at the site the excavation had been
made few feet in depth. The ma
terial was hard gravel but with water
flowing freely as if from springs, | WAS
informed that after l left the place
on March goth, the foundation tim
bers were hurried in for fear that
quicksand might be struck. Mr..
Brown, however, said to me that he
had tested the place with bars, and
found several feet of gravel below the
proposed foundation level.
If | were professionally responsible
for the work, | would want to make
more satisfactory examinations before
constructing an abutment for a large
river bridge of that kind, and if there
were any quicksand there, l should
want to know it before putting ma
sonry on it. The south side abutment
| understand is on rock which of
course makes a good foundation. l
have stated that the dimensions ofthe
piers appear to be sufficient, but l re-
greet that | cannot say the same of
the abutments. Take first the north
abutment. The filed plan shown for
the main abutment wall, thickness
at top Of foundation courses of 7 81
and height to the bridge seat of IS
feet. This wall should be II feet
thick of neat work, with correspond
ing increase in width of foundations.
On the same filed drawing, the
wing walls are noted to be feet
thick at the bottom when they should
be II feet thick.
Turning now to the detailed ma
sonry plan for the same abutment, we
find noted a thickness of main wall at
bottom Vcsting on TIMBER of feet
with a height of 2S feet which requires
for strength and stability at bottom a
thickness of IL feet
For the wing walls the thickness is
noted at the bottom in figures as 6
feet, when it should be IL feet. The
required thickness of wall depends on
its height, and the filed and detailed
| Tl1ns do NOT give the San1a HEIGHT